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Sample records for cobalt-based oxygen evolving

  1. Nucleation, growth, and repair of a cobalt-based oxygen evolving catalyst.

    PubMed

    Surendranath, Yogesh; Lutterman, Daniel A; Liu, Yi; Nocera, Daniel G

    2012-04-11

    The mechanism of nucleation, steady-state growth, and repair is investigated for an oxygen evolving catalyst prepared by electrodeposition from Co(2+) solutions in weakly basic electrolytes (Co-OEC). Potential step chronoamperometry and atomic force microscopy reveal that nucleation of Co-OEC is progressive and reaches a saturation surface coverage of ca. 70% on highly oriented pyrolytic graphite substrates. Steady-state electrodeposition of Co-OEC exhibits a Tafel slope approximately equal to 2.3 × RT/F. The electrochemical rate law exhibits a first order dependence on Co(2+) and inverse orders on proton (third order) and proton acceptor, methylphosphonate (first order for 1.8 mM ≤ [MeP(i)] ≤ 18 mM and second order dependence for 32 mM ≤ [MeP(i)] ≤ 180 mM). These electrokinetic studies, combined with recent XAS studies of catalyst structure, suggest a mechanism for steady state growth at intermediate MeP(i) concentration (1.8-18 mM) involving a rapid solution equilibrium between aquo Co(II) and Co(III) hydroxo species accompanied with a rapid surface equilibrium involving electrolyte dissociation and deprotonation of surface bound water. These equilibria are followed by a chemical rate-limiting step for incorporation of Co(III) into the growing cobaltate clusters comprising Co-OEC. At higher concentrations of MeP(i) ([MeP(i)] ≥ 32 mM), MePO(3)(2-) equilibrium binding to Co(II) in solution is suggested by the kinetic data. Consistent with the disparate pH profiles for oxygen evolution electrocatalysis and catalyst formation, NMR-based quantification of catalyst dissolution as a function of pH demonstrates functional stability and repair at pH values >6 whereas catalyst corrosion prevails at lower pH values. These kinetic insights provide a basis for developing and operating functional water oxidation (photo)anodes under benign pH conditions. PMID:22394103

  2. Photochemical deposition of cobalt-based oxygen evolving catalyst on a semiconductor photoanode for solar oxygen production

    PubMed Central

    Steinmiller, Ellen M. P.; Choi, Kyoung-Shin

    2009-01-01

    This study describes the photochemical deposition of Co-based oxygen evolution catalysts on a semiconductor photoanode for use in solar oxygen evolution. In the photodeposition process, electron-hole pairs are generated in a semiconductor upon illumination and the photogenerated holes are used to oxidize Co2+ ions to Co3+ ions, resulting in the precipitation of Co3+-based catalysts on the semiconductor surface. Both photodeposition of the catalyst and solar O2 evolution are photo-oxidation reactions using the photogenerated holes. Therefore, photodeposition provides an efficient way to couple oxygen evolution catalysts with photoanodes by naturally placing catalysts at the locations where the holes are most readily available for solar O2 evolution. In this study Co-based catalysts were photochemically deposited as 10–30 nm nanoparticles on the ZnO surface. The comparison of the photocurrent-voltage characteristics of the ZnO electrodes with and without the presence of the Co-based catalyst demonstrated that the catalyst generally enhanced the anodic photocurrent of the ZnO electrode with its effect more pronounced when the band bending is less significant. The presence of Co-based catalyst on the ZnO photoanode also shifted the onset potential of the photocurrent by 0.23 V to the negative direction, closer to the flat band potential. These results demonstrated that the cobalt-based catalyst can efficiently use the photogenerated holes in ZnO to enhance solar O2 evolution. The photodeposition method described in this study can be used as a general route to deposit the Co-based catalysts on any semiconductor electrode with a valence band edge located at a more positive potential than the oxidation potential of Co2+ ions. PMID:19934060

  3. When did oxygenic photosynthesis evolve?

    PubMed

    Buick, Roger

    2008-08-27

    The atmosphere has apparently been oxygenated since the 'Great Oxidation Event' ca 2.4 Ga ago, but when the photosynthetic oxygen production began is debatable. However, geological and geochemical evidence from older sedimentary rocks indicates that oxygenic photosynthesis evolved well before this oxygenation event. Fluid-inclusion oils in ca 2.45 Ga sandstones contain hydrocarbon biomarkers evidently sourced from similarly ancient kerogen, preserved without subsequent contamination, and derived from organisms producing and requiring molecular oxygen. Mo and Re abundances and sulphur isotope systematics of slightly older (2.5 Ga) kerogenous shales record a transient pulse of atmospheric oxygen. As early as ca 2.7 Ga, stromatolites and biomarkers from evaporative lake sediments deficient in exogenous reducing power strongly imply that oxygen-producing cyanobacteria had already evolved. Even at ca 3.2 Ga, thick and widespread kerogenous shales are consistent with aerobic photoautrophic marine plankton, and U-Pb data from ca 3.8 Ga metasediments suggest that this metabolism could have arisen by the start of the geological record. Hence, the hypothesis that oxygenic photosynthesis evolved well before the atmosphere became permanently oxygenated seems well supported. PMID:18468984

  4. When did oxygenic photosynthesis evolve?

    PubMed

    Buick, Roger

    2008-08-27

    The atmosphere has apparently been oxygenated since the 'Great Oxidation Event' ca 2.4 Ga ago, but when the photosynthetic oxygen production began is debatable. However, geological and geochemical evidence from older sedimentary rocks indicates that oxygenic photosynthesis evolved well before this oxygenation event. Fluid-inclusion oils in ca 2.45 Ga sandstones contain hydrocarbon biomarkers evidently sourced from similarly ancient kerogen, preserved without subsequent contamination, and derived from organisms producing and requiring molecular oxygen. Mo and Re abundances and sulphur isotope systematics of slightly older (2.5 Ga) kerogenous shales record a transient pulse of atmospheric oxygen. As early as ca 2.7 Ga, stromatolites and biomarkers from evaporative lake sediments deficient in exogenous reducing power strongly imply that oxygen-producing cyanobacteria had already evolved. Even at ca 3.2 Ga, thick and widespread kerogenous shales are consistent with aerobic photoautrophic marine plankton, and U-Pb data from ca 3.8 Ga metasediments suggest that this metabolism could have arisen by the start of the geological record. Hence, the hypothesis that oxygenic photosynthesis evolved well before the atmosphere became permanently oxygenated seems well supported.

  5. Highly active cobalt phosphate and borate based oxygen evolving catalysts operating in neutral and natural waters

    SciTech Connect

    Esswein, AJ; Surendranath, Y; Reece, SY; Nocera, DG

    2011-02-01

    A high surface area electrode is functionalized with cobalt-based oxygen evolving catalysts (Co-OEC = electrodeposited from pH 7 phosphate, Pi, pH 8.5 methylphosphonate, MePi, and pH 9.2 borate electrolyte, Bi). Co-OEC prepared from MePi and operated in Pi and Bi achieves a current density of 100 mA cm(-2) for water oxidation at 442 and 363 mV overpotential, respectively. The catalyst retains activity in near-neutral pH buffered electrolyte in natural waters such as those from the Charles River (Cambridge, MA) and seawater (Woods Hole, MA). The efficacy and ease of operation of anodes functionalized with Co-OEC at appreciable current density together with its ability to operate in near neutral pH buffered natural water sources bodes well for the translation of this catalyst to a viable renewable energy storage technology.

  6. Homogeneously dispersed multimetal oxygen-evolving catalysts.

    PubMed

    Zhang, Bo; Zheng, Xueli; Voznyy, Oleksandr; Comin, Riccardo; Bajdich, Michal; García-Melchor, Max; Han, Lili; Xu, Jixian; Liu, Min; Zheng, Lirong; García de Arquer, F Pelayo; Dinh, Cao Thang; Fan, Fengjia; Yuan, Mingjian; Yassitepe, Emre; Chen, Ning; Regier, Tom; Liu, Pengfei; Li, Yuhang; De Luna, Phil; Janmohamed, Alyf; Xin, Huolin L; Yang, Huagui; Vojvodic, Aleksandra; Sargent, Edward H

    2016-04-15

    Earth-abundant first-row (3d) transition metal-based catalysts have been developed for the oxygen-evolution reaction (OER); however, they operate at overpotentials substantially above thermodynamic requirements. Density functional theory suggested that non-3d high-valency metals such as tungsten can modulate 3d metal oxides, providing near-optimal adsorption energies for OER intermediates. We developed a room-temperature synthesis to produce gelled oxyhydroxides materials with an atomically homogeneous metal distribution. These gelled FeCoW oxyhydroxides exhibit the lowest overpotential (191 millivolts) reported at 10 milliamperes per square centimeter in alkaline electrolyte. The catalyst shows no evidence of degradation after more than 500 hours of operation. X-ray absorption and computational studies reveal a synergistic interplay between tungsten, iron, and cobalt in producing a favorable local coordination environment and electronic structure that enhance the energetics for OER. PMID:27013427

  7. Homogeneously dispersed, multimetal oxygen-evolving catalysts

    DOE PAGES

    Zhang, Bo; Zheng, Xueli; Voznyy, Oleksandr; Comin, Riccardo; Bajdich, Michal; Garcia-Melchor, Max; Han, Lili; Xu, Jixian; Liu, Min; Zheng, Lirong; et al

    2016-03-24

    Earth-abundant first-row (3d) transition-metal-based catalysts have been developed for the oxygen-evolution reaction (OER); however, they operate at overpotentials significantly above thermodynamic requirements. Density functional theory suggested that non-3d high-valency metals such as tungsten can modulate 3d metal oxides, providing near-optimal adsorption energies for OER intermediates. We developed a room-temperature synthesis to produce gelled oxy-hydroxide materials with an atomically homogeneous metal distribution. These gelled FeCoW oxy-hydroxide exhibits the lowest overpotential (191 mV) reported at 10 mA per square centimeter in alkaline electrolyte. Here, the catalyst shows no evidence of degradation following more than 500 hours of operation. X-ray absorption and computationalmore » studies reveal a synergistic interplay between W, Fe and Co in producing a favorable local coordination environment and electronic structure that enhance the energetics for OER.« less

  8. Catalytic Oxygen Evolution by a Bioinorganic Model of the Photosystem II Oxygen-Evolving Complex

    ERIC Educational Resources Information Center

    Howard, Derrick L.; Tinoco, Arthur D.; Brudvig, Gary W.; Vrettos, John S.; Allen, Bertha Connie

    2005-01-01

    Bioinorganic models of the manganese Mn4 cluster are important not only as aids in understanding the structure and function of the oxygen-evolving complex (OEC), but also in developing artificial water-oxidation catalysts. The mechanism of water oxidation by photosystem II (PSII) is thought to involve the formation of a high-valent terminal Mn-oxo…

  9. Evolving Oxygen Landscape of the Early Atmosphere and Oceans

    NASA Astrophysics Data System (ADS)

    Lyons, T. W.; Reinhard, C. T.; Planavsky, N. J.

    2013-12-01

    The past decade has witnessed remarkable advances in our understanding of oxygen on the early Earth, and a new framework, the topic of this presentation, is now in place to address the controls on spatiotemporal distributions of oxygen and their potential relationships to deep-Earth processes. Recent challenges to the Archean biomarker record have put an added burden on inorganic geochemistry to fingerprint and quantify the early production, accumulation, and variation of biospheric oxygen. Fortunately, a wide variety of techniques now point convincingly to photosynthetic oxygen production and dynamic accumulation well before the canonical Great Oxidation Event (GOE). Recent modeling of sulfur recycling over this interval allows for transient oxygen accumulation in the atmosphere without the disappearance of non-mass-dependent (NMD) sulfur isotope anomalies from the stratigraphic record and further allows for persistent accumulation in the atmosphere well before the permanent disappearance of NMD signals. This recent work suggests that the initial rise of oxygen may have occurred in fits and starts rather than a single step, and that once permanently present in the atmosphere, oxygen likely rose to high levels and then plummeted, in phase with the Paleoproterozoic Lomagundi positive carbon isotope excursion. More than a billion years of oxygen-free conditions in the deep ocean followed and set a challenging course for life, including limited abundances and diversity of eukaryotic organisms. Despite this widespread anoxia, sulfidic (euxinic) conditions were likely limited to productive ocean margins. Nevertheless, euxinia was sufficiently widespread to impact redox-dependent nutrient relationships, particularly the availability of bioessential trace metals critical in the nitrogen cycle, which spawned feedbacks that likely maintained oxygen at very low levels in the ocean and atmosphere and delayed the arrival of animals. Then, in the mid, pre-glacial Neoproterozoic

  10. Cobalt-based nanocatalysts for green oxidation and hydrogenation processes.

    PubMed

    Jagadeesh, Rajenahally V; Stemmler, Tobias; Surkus, Annette-Enrica; Bauer, Matthias; Pohl, Marga-Martina; Radnik, Jörg; Junge, Kathrin; Junge, Henrik; Brückner, Angelika; Beller, Matthias

    2015-06-01

    This protocol describes the preparation of cobalt-based nanocatalysts and their applications in environmentally benign redox processes for fine chemical synthesis. The catalytically active material consists of nanoscale Co3O4 particles surrounded by nitrogen-doped graphene layers (NGrs), which have been prepared by pyrolysis of phenanthroline-ligated cobalt acetate on carbon. The resulting materials have been found to be excellent catalysts for the activation of both molecular oxygen and hydrogen; in all tested reactions, water was the only by-product. By applying these catalysts, green oxidations of alcohols and hydrogenation of nitroarenes for the synthesis of nitriles, esters and amines are demonstrated. The overall time required for catalyst preparation and for redox reactions is 35 h and 10-30 h, respectively.

  11. Hierarchical cobalt-based hydroxide microspheres for water oxidation.

    PubMed

    Zhang, Ye; Cui, Bai; Derr, Olivia; Yao, Zhibo; Qin, Zhaotong; Deng, Xiangyun; Li, Jianbao; Lin, Hong

    2014-03-21

    3D hierarchical cobalt hydroxide carbonate hydrate (Co(CO3)0.5(OH)·0.11H2O) has been synthesized featuring a hollow urchin-like structure by a one-step hydrothermal method at modest temperature on FTO glass substrates. The functionalities of precursor surfactants were isolated and analyzed. A plausible formation mechanism of the spherical urchin-like microclusters has been furnished through time-dependent investigations. Introduction of other transitional metal doping (Cu, Ni) would give rise to a substantial morphological change associated with a surface area drop. The directly grown cobalt-based hydroxide composite electrodes were found to be capable of catalyzing oxygen evolution reaction (OER) under both neutral pH and alkaline conditions. The favorable 3D dendritic morphology and porous structure provide large surface areas and possible defect sites that are likely responsible for their robust electrochemical activity.

  12. Inorganic chemistry. A synthetic Mn₄Ca-cluster mimicking the oxygen-evolving center of photosynthesis.

    PubMed

    Zhang, Chunxi; Chen, Changhui; Dong, Hongxing; Shen, Jian-Ren; Dau, Holger; Zhao, Jingquan

    2015-05-01

    Photosynthetic splitting of water into oxygen by plants, algae, and cyanobacteria is catalyzed by the oxygen-evolving center (OEC). Synthetic mimics of the OEC, which is composed of an asymmetric manganese-calcium-oxygen cluster bound to protein groups, may promote insight into the structural and chemical determinants of biological water oxidation and lead to development of superior catalysts for artificial photosynthesis. We synthesized a Mn4Ca-cluster similar to the native OEC in both the metal-oxygen core and the binding protein groups. Like the native OEC, the synthetic cluster can undergo four redox transitions and shows two magnetic resonance signals assignable to redox and structural isomerism. Comparison with previously synthesized Mn3CaO4-cubane clusters suggests that the fourth Mn ion determines redox potentials and magnetic properties of the native OEC.

  13. Inorganic chemistry. A synthetic Mn₄Ca-cluster mimicking the oxygen-evolving center of photosynthesis.

    PubMed

    Zhang, Chunxi; Chen, Changhui; Dong, Hongxing; Shen, Jian-Ren; Dau, Holger; Zhao, Jingquan

    2015-05-01

    Photosynthetic splitting of water into oxygen by plants, algae, and cyanobacteria is catalyzed by the oxygen-evolving center (OEC). Synthetic mimics of the OEC, which is composed of an asymmetric manganese-calcium-oxygen cluster bound to protein groups, may promote insight into the structural and chemical determinants of biological water oxidation and lead to development of superior catalysts for artificial photosynthesis. We synthesized a Mn4Ca-cluster similar to the native OEC in both the metal-oxygen core and the binding protein groups. Like the native OEC, the synthetic cluster can undergo four redox transitions and shows two magnetic resonance signals assignable to redox and structural isomerism. Comparison with previously synthesized Mn3CaO4-cubane clusters suggests that the fourth Mn ion determines redox potentials and magnetic properties of the native OEC. PMID:25954008

  14. A ligand field chemistry of oxygen generation by the oxygen-evolving complex and synthetic active sites

    PubMed Central

    Betley, Theodore A; Surendranath, Yogesh; Childress, Montana V; Alliger, Glen E; Fu, Ross; Cummins, Christopher C; Nocera, Daniel G

    2007-01-01

    Oxygen–oxygen bond formation and O2 generation occur from the S4 state of the oxygen-evolving complex (OEC). Several mechanistic possibilities have been proposed for water oxidation, depending on the formal oxidation state of the Mn atoms. All fall under two general classifications: the AB mechanism in which nucleophilic oxygen (base, B) attacks electrophilic oxygen (acid, A) of the Mn4Ca cluster or the RC mechanism in which radical-like oxygen species couple within OEC. The critical intermediate in either mechanism involves a metal oxo, though the nature of this oxo for AB and RC mechanisms is disparate. In the case of the AB mechanism, assembly of an even-electron count, high-valent metal-oxo proximate to a hydroxide is needed whereas, in an RC mechanism, two odd-electron count, high-valent metal oxos are required. Thus the two mechanisms give rise to very different design criteria for functional models of the OEC active site. This discussion presents the electron counts and ligand geometries that support metal oxos for AB and RC O–O bond-forming reactions. The construction of architectures that bring two oxygen functionalities together under the purview of the AB and RC scenarios are described. PMID:17971328

  15. Synthetic Model of the Oxygen-Evolving Center: Photosystem II under the Spotlight.

    PubMed

    Yu, Yang; Hu, Cheng; Liu, Xiaohong; Wang, Jiangyun

    2015-09-21

    The oxygen-evolving center (OEC) in photosystem II catalyzes a water splitting reaction. Great efforts have already been made to artificially synthesize the OEC, in order to elucidate the structure-function relationship and the mechanism of the reaction. Now, a new synthetic model makes the best mimic yet of the OEC. This recent study opens up the possibility to study the mechanism of photosystem II and photosynthesis in general for applications in renewable energy and synthetic biology.

  16. Evidence for an oxygen evolving iron–oxo–cerium intermediate in iron-catalysed water oxidation

    PubMed Central

    Codolà, Zoel; Gómez, Laura; Kleespies, Scott T.; Que, Lawrence; Costas, Miquel; Lloret-Fillol, Julio

    2016-01-01

    The non-haem iron complex α-[FeII(CF3SO3)2(mcp)] (mcp = (N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-1,2-cis-diaminocyclohexane) reacts with CeIV to oxidize water to O2, representing an iron-based functional model for the oxygen evolving complex of photosystem II. Here we trap an intermediate, characterized by cryospray ionization high resolution mass spectrometry and resonance Raman spectroscopy, and formulated as [(mcp)FeIV(O) (μ-O)CeIV(NO3)3]+, the first example of a well-characterized inner-sphere complex to be formed in cerium(IV)-mediated water oxidation. The identification of this reactive FeIV–O–CeIV adduct may open new pathways to validate mechanistic notions of an analogous MnV–O–CaII unit in the oxygen evolving complex that is responsible for carrying out the key O–O bond forming step. PMID:25609387

  17. Heat-induced reorganization of the structure of photosystem II membranes: role of oxygen evolving complex.

    PubMed

    Busheva, Mira; Tzonova, Iren; Stoitchkova, Katerina; Andreeva, Atanaska

    2012-12-01

    The sensitivity of the green plants' photosystem II (PSII) to high temperatures is investigated in PSII enriched membranes and in membranes, from which the oxygen evolving complex is removed. Using steady-state 77 K fluorescence and resonance Raman spectroscopy we analyze the interdependency between the temperature-driven changes in structure and energy distribution in the PSII supercomplex. The results show that the heat treatment induces different reduction of the 77 K fluorescence emission in both types of investigated membranes: (i) an additional considerable decrease of the overall fluorescence emission in Tris-washed membranes as compared to the native membranes; (ii) a transition point at 42°C(,) observed only in native membranes; (iii) a sharp reduction of the PSII core fluorescence in Tris-washed membranes at temperatures higher than 50°C; (iv) a 3 nm red-shift of F700 band's maximum in Tris-washed membranes already at 20°C and its further shift by 1 nm at temperature increase. Both treatments intensified their action by increasing the aggregation and dissociation of the peripheral light harvesting complexes. The oxygen-evolving complex, in addition to its main function to produce O(2), increases the thermal stability of PSII core by strengthening the connection between the core and the peripheral antenna proteins and by keeping their structural integrity.

  18. Crystallization of the oxygen-evolving reaction centre of photosystem II in nine different detergent mixtures.

    PubMed

    Adir, N

    1999-04-01

    Oxygen-evolving photosystem II reaction centres (RCII) isolated from both spinach and pea have been crystallized. A single crystal form grew from RCII monomers in the presence of nine different three-component mixtures of non-ionic detergents and heptane-1,2, 3-triol. The crystals grew as hexagonal rods with dimensions of up to 1 x 0.3 x 0.3 mm. The crystals diffracted to a maximum resolution of 6.5 A and belong to a hexagonal space group with unit-cell parameters a = 495, b = 495, c = 115 A, alpha = beta = 90, gamma = 120 degrees. The growth of a single crystal form in the presence of such a large variety of detergents suggests a very limited range of crystal lattice formation sites in the RCII complex. PMID:10089326

  19. A study of QM/Langevin-MD simulation for oxygen-evolving center of photosystem II

    SciTech Connect

    Uchida, Waka; Kimura, Yoshiro; Wakabayashi, Masamitsu; Hatakeyama, Makoto; Ogata, Koji; Nakamura, Shinichiro; Yokojima, Satoshi

    2013-12-10

    We have performed three QM/Langevin-MD simulations for oxygen-evolving complex (OEC) and surrounding residues, which are different configurations of the oxidation numbers on Mn atoms in the Mn{sub 4}O{sub 5}Ca cluster. By analyzing these trajectories, we have observed sensitivity of the change to the configuration of Mn oxidation state on O atoms of carboxyl on three amino acids, Glu354, Ala344, and Glu333. The distances from Mn to O atoms in residues contacting with the Mn{sub 4}O{sub 5}Ca cluster were analyzed for the three trajectories. We found the good correlation of the distances among the simulations. However, the distances with Glu354, Ala344, and Glu333 have not shown the correlation. These residues can be sensitive index of the changes of Mn oxidation numbers.

  20. Spectra from the IRS of Bright Oxygen-Rich Evolved Stars in the SMC

    NASA Astrophysics Data System (ADS)

    Kraemer, Kathleen E.; Sloan, Greg; Wood, Peter

    2016-06-01

    We have used Spitzer's Infrared Spectrograph (IRS) to obtain spectra of stars in the Small Magellanic Cloud (SMC). The targets were chosen from the Point Source Catalog of the Mid-Course Space Experiment (MSX), which detected the 243 brightest infrared sources in the SMC. Our SMC sample of oxygen-rich evolved stars shows more dust than found in previous samples, and the dust tends to be dominated by silicates, with little contribution from alumina. Both results may arise from the selection bias in the MSX sample and our sample toward more massive stars. Additionally, several sources show peculiar spectral features such as PAHs, crystalline silicates, or both carbon-rich and silicate features. The spectrum of one source, MSX SMC 145, is a combination of an ordinary AGB star and a background galaxy at z~0.16, rather than an OH/IR star as previously suggested.

  1. Structural changes of the oxygen-evolving complex in photosystem II during the catalytic cycle.

    PubMed

    Glöckner, Carina; Kern, Jan; Broser, Matthias; Zouni, Athina; Yachandra, Vittal; Yano, Junko

    2013-08-01

    The oxygen-evolving complex (OEC) in the membrane-bound protein complex photosystem II (PSII) catalyzes the water oxidation reaction that takes place in oxygenic photosynthetic organisms. We investigated the structural changes of the Mn4CaO5 cluster in the OEC during the S state transitions using x-ray absorption spectroscopy (XAS). Overall structural changes of the Mn4CaO5 cluster, based on the manganese ligand and Mn-Mn distances obtained from this study, were incorporated into the geometry of the Mn4CaO5 cluster in the OEC obtained from a polarized XAS model and the 1.9-Å high resolution crystal structure. Additionally, we compared the S1 state XAS of the dimeric and monomeric form of PSII from Thermosynechococcus elongatus and spinach PSII. Although the basic structures of the OEC are the same for T. elongatus PSII and spinach PSII, minor electronic structural differences that affect the manganese K-edge XAS between T. elongatus PSII and spinach PSII are found and may originate from differences in the second sphere ligand atom geometry.

  2. Antioxidant Activity of Oxygen Evolving Enhancer Protein 1 Purified from Capsosiphon fulvescens.

    PubMed

    Kim, Eun-Young; Choi, Youn Hee; Lee, Jung Im; Kim, In-Hye; Nam, Taek-Jeong

    2015-06-01

    This study was conducted to determine the antioxidant activity of a protein purified from Capsosiphon fulvescens. The purification steps included sodium acetate (pH 6) extraction and diethylaminoethyl-cellulose, reversed phase Shodex C4P-50 column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that the molecular weight of the purified protein was 33 kDa. The N-terminus and partial peptide amino acid sequence of this protein was identical to the sequence of oxygen evolving enhancer (OEE) 1 protein. The antioxidant activity of the OEE 1 was determined in vitro using a scavenging test with 4 types of reactive oxygen species (ROS), including the 2,2-diphenyl-1-picrylhydrazyl radical, hydroxyl radical, superoxide anion, and hydrogen peroxide (H2 O2 ). OEE 1 had higher H2 O2 scavenging activity, which proved to be the result of enzymatic antioxidants rather than nonenzymatic antioxidants. In addition, OEE 1 showed less H2 O2 -mediated ROS formation in HepG2 cells. In conclusion, this study demonstrates that OEE 1 purified from C. fulvescens is an excellent antioxidant. PMID:25944160

  3. Time-resolved X-Ray Absorption Spectroscopy of a Cobalt-Based Hydrogen Evolution System for Artificial Photosynthesis

    NASA Astrophysics Data System (ADS)

    Moonshiram, Dooshaye; Gimbert, Carolina; Lehmann, Carl; Southworth, Stephen; Llobet, Antoni; Argonne National Laboratory Team; Institut Català d'Investigació Química Collaboration

    2015-03-01

    Production of cost-effective hydrogen gas through solar power is an important challenge of the Department of Energy among other global industry initiatives. In natural photosynthesis, the oxygen evolving complex(OEC) can carry out four-electron water splitting to hydrogen with an efficiency of around 60%. Although, much progress has been carried out in determining mechanistic pathways of the OEC, biomimetic approaches have not duplicated Nature's efficiency in function. Over the past years, we have witnessed progress in developments of light harvesting modules, so called chromophore/catalytic assemblies. In spite of reportedly high catalytic activity of these systems, quantum yields of hydrogen production are below 40 % when using monochromatic light. Proper understanding of kinetics and bond making/breaking steps has to be achieved to improve efficiency of hydrogen evolution systems. This project shows the timing implementation of ultrafast X-ray absorption spectroscopy to visualize in ``real time'' the photo-induced kinetics accompanying a sequence of redox reactions in a cobalt-based molecular photocatalytic system. Formation of a Co(I) species followed by a Co(III) hydride species all the way towards hydrogen evolution is shown through time-resolved XANES.

  4. Light-induced water oxidation at silicon electrodes functionalized with a cobalt oxygen-evolving catalyst.

    PubMed

    Pijpers, Joep J H; Winkler, Mark T; Surendranath, Yogesh; Buonassisi, Tonio; Nocera, Daniel G

    2011-06-21

    Integrating a silicon solar cell with a recently developed cobalt-based water-splitting catalyst (Co-Pi) yields a robust, monolithic, photo-assisted anode for the solar fuels process of water splitting to O(2) at neutral pH. Deposition of the Co-Pi catalyst on the Indium Tin Oxide (ITO)-passivated p-side of a np-Si junction enables the majority of the voltage generated by the solar cell to be utilized for driving the water-splitting reaction. Operation under neutral pH conditions fosters enhanced stability of the anode as compared to operation under alkaline conditions (pH 14) for which long-term stability is much more problematic. This demonstration of a simple, robust construct for photo-assisted water splitting is an important step towards the development of inexpensive direct solar-to-fuel energy conversion technologies.

  5. Light-induced water oxidation at silicon electrodes functionalized with a cobalt oxygen-evolving catalyst

    PubMed Central

    Pijpers, Joep J. H.; Winkler, Mark T.; Surendranath, Yogesh; Buonassisi, Tonio; Nocera, Daniel G.

    2011-01-01

    Integrating a silicon solar cell with a recently developed cobalt-based water-splitting catalyst (Co-Pi) yields a robust, monolithic, photo-assisted anode for the solar fuels process of water splitting to O2 at neutral pH. Deposition of the Co-Pi catalyst on the Indium Tin Oxide (ITO)-passivated p-side of a np-Si junction enables the majority of the voltage generated by the solar cell to be utilized for driving the water-splitting reaction. Operation under neutral pH conditions fosters enhanced stability of the anode as compared to operation under alkaline conditions (pH 14) for which long-term stability is much more problematic. This demonstration of a simple, robust construct for photo-assisted water splitting is an important step towards the development of inexpensive direct solar-to-fuel energy conversion technologies. PMID:21646536

  6. Efficient solar water oxidation using photovoltaic devices functionalized with earth-abundant oxygen evolving catalysts.

    PubMed

    Cristino, Vito; Berardi, Serena; Caramori, Stefano; Argazzi, Roberto; Carli, Stefano; Meda, Laura; Tacca, Alessandra; Bignozzi, Carlo Alberto

    2013-08-21

    Indium tin oxide (ITO) surfaces of triple junction photovoltaic cells were functionalized with oxygen evolving catalysts (OECs) based on amorphous hydrous earth-abundant metal oxides (metal = Fe, Ni, Co), obtained by straightforward Successive Ionic Layer Adsorption and Reaction (SILAR) in an aqueous environment. Functionalization with Fe(iii) oxides gave the best results, leading to photoanodes capable of efficiently splitting water, with photocurrent densities up to 6 ± 1 mA cm(-2) at 0 V vs. the reversible hydrogen electrode (RHE) under AM 1.5 G simulated sunlight illumination. The resulting Solar To Hydrogen (STH) conversion efficiencies, measured in two electrodes configuration, were in the range 3.7-5%, depending on the counter electrode that was employed. Investigations on the stability showed that these photoanodes were able to sustain 120 minutes of continuous illumination with a < 10% photocurrent loss at 0 V vs. RHE. Pristine photoanodic response of the cells could be fully restored by an additional SILAR cycle, evidencing that the observed loss is due to the detachment of the more weakly surface bound catalyst.

  7. Photodamage to the oxygen evolving complex of photosystem II by visible light.

    PubMed

    Zavafer, Alonso; Cheah, Mun Hon; Hillier, Warwick; Chow, Wah Soon; Takahashi, Shunichi

    2015-11-12

    Light damages photosynthetic machinery, primarily photosystem II (PSII), and it results in photoinhibition. A new photodamage model, the two-step photodamage model, suggests that photodamage to PSII initially occurs at the oxygen evolving complex (OEC) by light energy absorbed by manganese and that the PSII reaction center is subsequently damaged by light energy absorbed by photosynthetic pigments due to the limitation of electrons to the PSII reaction center. However, it is still uncertain whether this model is applicable to photodamage to PSII under visible light as manganese absorbs visible light only weakly. In the present study, we identified the initial site of photodamage to PSII upon illumination of visible light using PSII membrane fragments isolated from spinach leaves. When PSII samples were exposed to visible light in the presence of an exogenous electron acceptor, both PSII total activity and the PSII reaction centre activity declined due to photodamage. The supplemental addition of an electron donor to the PSII reaction centre alleviated the decline of the reaction centre activity but not the PSII total activity upon the light exposure. Our results demonstrate that visible light damages OEC prior to photodamage to the PSII reaction center, consistent with two-step photodamage model.

  8. Ammonia Binding in the Second Coordination Sphere of the Oxygen-Evolving Complex of Photosystem II.

    PubMed

    Vinyard, David J; Askerka, Mikhail; Debus, Richard J; Batista, Victor S; Brudvig, Gary W

    2016-08-01

    Ammonia binds to two sites in the oxygen-evolving complex (OEC) of Photosystem II (PSII). The first is as a terminal ligand to Mn in the S2 state, and the second is at a site outside the OEC that is competitive with chloride. Binding of ammonia in this latter secondary site results in the S2 state S = (5)/2 spin isomer being favored over the S = (1)/2 spin isomer. Using electron paramagnetic resonance spectroscopy, we find that ammonia binds to the secondary site in wild-type Synechocystis sp. PCC 6803 PSII, but not in D2-K317A mutated PSII that does not bind chloride. By combining these results with quantum mechanics/molecular mechanics calculations, we propose that ammonia binds in the secondary site in competition with D1-D61 as a hydrogen bond acceptor to the OEC terminal water ligand, W1. Implications for the mechanism of ammonia binding via its primary site directly to Mn4 in the OEC are discussed. PMID:27433995

  9. Artificial synthetic Mn(IV)Ca-oxido complexes mimic the oxygen-evolving complex in photosystem II.

    PubMed

    Chen, Changhui; Zhang, Chunxi; Dong, Hongxing; Zhao, Jingquan

    2015-03-14

    A novel family of heteronuclear Mn(IV)Ca-oxido complexes containing Mn(IV)Ca-oxido cuboidal moieties and reactive water molecules on Ca(2+) have been synthesized and characterized to mimic the oxygen-evolving complex (OEC) of photosystem II (PSII) in nature. PMID:25662151

  10. The role of calcium in the oxygen evolving center of photosystem II

    SciTech Connect

    Latimer, M.J.

    1995-05-01

    The photosynthetic oxygen evolving complex (OEC) contains a cluster of four manganese atoms and requires both Ca and Cl for activity. Ca can be replaced by Sr with retention of activity. The role of Ca in the OEC has been investigated by performing Mn X-ray absorption experiments on Ca-depleted samples of photosystem II (PS II) and on PS II samples depleted of Ca and reconstituted by either Ca or Sr. Mn X-ray K-edge spectra exhibit no significant differences in oxidation state or symmetry between Ca- and Sr-reactivated preparations, but differences are observed in the extended X-ray absorption fine structure (EXAFS). The amplitude of a Fourier transform peak arising from scatterers at distances greater than 3 A is larger for samples reactivated with strontium relative to calcium. Curve-fitting analyses of the EXAFS data using FEFF 5-calculated parameters favor a model where both manganese and calcium (or strontium) scatterers contribute to the {approximately}3 {Angstrom} Fourier peak (Mn-Mn at 3.3{Angstrom} and Mn-Ca(Sr) at 3.4--3.5 {Angstrom}). Possible structural arrangements for a calcium binding site are discussed. Analysis of Mn K-edge spectra from Ca-depleted samples in the S{sub 1}, S{sub 2}, and S{sub 3} states shows an edge shift on the S{sub 1}-S{sub 2} transition, but no edge shift on the S{sub 2}-S{sub 3} transition, supporting a model where the oxidizing equivalent from the S{sub 2} to S{sub 3} transition is stored on a ligand or nearby protein residue rather than on the Mn cluster. Parallels between Ca-depleted and native samples are discussed.

  11. Oxygen-evolving complex of photosystem II: correlating structure with spectroscopy.

    PubMed

    Pokhrel, Ravi; Brudvig, Gary W

    2014-06-28

    Water oxidation at the oxygen-evolving complex (OEC) of photosystem II (PSII) involves multiple redox states called Sn states (n = 0-4). The S1 → S2 redox transition of the OEC has been studied extensively using various forms of spectroscopy, including electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) spectroscopy. In the S2 state, two isomers of the OEC are observed by EPR: a ST = 1/2 form and a ST = 5/2 form. DFT-based structural models of the OEC have been proposed for the two spin isomers in the S2 state, but the factors that determine the stability of one form or the other are not known. Using structural information on the OEC and its surroundings, in conjunction with spectroscopic information available on the S1 → S2 transition for a variety of site-directed mutations, Ca(2+) and Cl(-) substitutions, and small molecule inhibitors, we propose that the hydrogen-bonding network encompassing D1-D61 and the OEC-bound waters plays an important role in stabilizing one spin isomer over the other. In the presence of ammonia, PSII centers can be trapped in either the ST = 5/2 form after a 200 K illumination procedure or an ammonia-altered ST = 1/2 form upon annealing at 273 K. We propose a mechanism for ammonia binding to the OEC in the S2 state that takes into account the hydrogen-binding requirements for ammonia binding and the specificity for binding of ammonia but not methylamine. A discussion regarding the possibility of spin isomers of the OEC in the S1 state, analogous to the spin isomers of the S2 state, is also presented. PMID:24700294

  12. In-Situ Formation of Cobalt-Phosphate Oxygen-Evolving Complex-Anchored Reduced Graphene Oxide Nanosheets for Oxygen Reduction Reaction

    NASA Astrophysics Data System (ADS)

    Zhao, Zhi-Gang; Zhang, Jing; Yuan, Yinyin; Lv, Hong; Tian, Yuyu; Wu, Dan; Li, Qing-Wen

    2013-07-01

    Oxygen conversion process between O2 and H2O by means of electrochemistry or photochemistry has lately received a great deal of attention. Cobalt-phosphate (Co-Pi) catalyst is a new type of cost-effective artificial oxygen-evolving complex (OEC) with amorphous features during photosynthesis. However, can such Co-Pi OEC also act as oxygen reduction reaction (ORR) catalyst in electrochemical processes? The question remains unanswered. Here for the first time we demonstrate that Co-Pi OEC does be rather active for the ORR. Particularly, Co-Pi OEC anchoring on reduced graphite oxide (rGO) nanosheet is shown to possess dramatically improved electrocatalytic activities. Differing from the generally accepted role of rGO as an ``electron reservoir'', we suggest that rGO serves as ``peroxide cleaner'' in enhancing the electrocatalytic behaviors. The present study may bridge the gap between photochemistry and electrochemistry towards oxygen conversion.

  13. In-situ formation of cobalt-phosphate oxygen-evolving complex-anchored reduced graphene oxide nanosheets for oxygen reduction reaction.

    PubMed

    Zhao, Zhi-Gang; Zhang, Jing; Yuan, Yinyin; Lv, Hong; Tian, Yuyu; Wu, Dan; Li, Qing-Wen

    2013-01-01

    Oxygen conversion process between O₂ and H₂O by means of electrochemistry or photochemistry has lately received a great deal of attention. Cobalt-phosphate (Co-Pi) catalyst is a new type of cost-effective artificial oxygen-evolving complex (OEC) with amorphous features during photosynthesis. However, can such Co-Pi OEC also act as oxygen reduction reaction (ORR) catalyst in electrochemical processes? The question remains unanswered. Here for the first time we demonstrate that Co-Pi OEC does be rather active for the ORR. Particularly, Co-Pi OEC anchoring on reduced graphite oxide (rGO) nanosheet is shown to possess dramatically improved electrocatalytic activities. Differing from the generally accepted role of rGO as an "electron reservoir", we suggest that rGO serves as "peroxide cleaner" in enhancing the electrocatalytic behaviors. The present study may bridge the gap between photochemistry and electrochemistry towards oxygen conversion. PMID:23877331

  14. Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

    SciTech Connect

    Liang, W.

    1994-11-01

    X-ray absorption spectroscopy (XAS) was performed on Photosystem II (PSII)-enriched membranes prepared from spinach to explore: (1) the correlation between structure and magnetic spin state of the Mn cluster in the oxygen evolving complex (OEC) in the S{sub 2} state; and (2) the oxidation state changes of the Mn cluster in the flash-induced S-states. The structure of the Mn cluster in the S{sub 2} state with the g{approx}4 electron paramagnetic resonance (EPR) signal (S{sub 2}-g4 state) was compared with that in the S{sub 2} state with multiline signal (S{sub 2}-MLS state) and the S{sub 1} state. The S{sub 2}-g4 state has a higher XAS inflection point energy than that of the S{sub 1} state, indicating the oxidation of Mn in the advance from the S{sub 1} to the S{sub 2}-g4 state. Differences in the edge shape and in the extended X-ray absorption fine structure (EXAFS) show that the structure of the Mn cluster in the S{sub 2}-g4 state is different from that in the S{sub 2}-MLS or the S{sub 1} state. In the S{sub 2}-g4 state, the second shell of backscatterers from the Mn absorber contains two Mn-Mn distances of 2.73 {angstrom} and 2.85 {angstrom}. Very little distance disorder exists in the second shell of the S{sub 1} or S{sub 2}-MLS states. The third shell of the S{sub 2}-g4 state at about 3.3 {angstrom} also contains increased heterogeneity relative to that of the S{sub 2}-MLS or the S{sub 1} state. Various S-states were prepared at room-temperature by saturating, single-turnover flashes. The flash-dependent oscillation in the amplitude of the MLS was used to characterize the S-state composition and to construct {open_quotes}pure{close_quotes} S-state Mn K-edge spectra. The edge position shifts to higher energy by 1.8 eV upon the S{sub 1} {yields} S{sub 2} transition.

  15. Physico-Chemical Conditions in Circumstellar Shells of Evolved Oxygen-Rich M Stars.

    NASA Astrophysics Data System (ADS)

    Slavsky, David Bruce

    1984-12-01

    The physical and chemical conditions in circumstellar shells of evolved oxygen-rich stars have been studied. Time dependent non-equilibrium chemical calculations for several gas phase species (45 in most models) have been performed to determine their radially dependent abundances. The species are formed from the eight elements H, C, N, O, S, Si, Al, and Cl; 135 chemical reactions are included in the reaction set. Since many reaction rates are temperature dependent, the set of chemical rate equations was solved self-consistently with the radially dependent energy equation. The energy equation included contributions from the cooling of the gas due to expansion, heating from gas-grain collisions, and molecular cooling from H(,2), CO, and H(,2)O. The circumstellar chemistry is also affected by ultraviolet radiation. All models include the effects of the ambient interstellar field, and the contributions of chromospheric radiation are included in models employing a restricted set of 17 species. It was found that the total column density through the shell determines two important shell characteristics. Higher densities result in large non-adiabatic contributions to the energy equation, and this work shows that for the highest densities studied, the temperature profile is determined by the non-adiabatic terms. Further, the total column density determines the optical depth through the shell in the UV, which controls the position in the shell where photo-induced chemistry can begin. Certain potentially observable molecules can act as diagnostic probes of certain important properties. Radial abundances of species such as OH, SiO, and SO, which can be formed as a result of H(,2)O dissociation, are diagnostic of the total column density of gas through the shell. Large abundances of hydrogen bearing species such as H(,2)S and NH(,3) are diagnostic of small atomic to molecular hydrogen ratios in the shell. In addition, observations of H(,2)O and other molecules in shells of stars

  16. Biochemical and spectroscopic characterization of a new oxygen-evolving photosystem II core complex from the cyanobacterium Synechocystis PCC 6803.

    PubMed

    Tang, X S; Diner, B A

    1994-04-19

    We describe here a new procedure permitting rapid (12-13 h) isolation of a pure oxygen-evolving photosystem II (PSII) core complex from the cyanobacterium Synechocystis PCC 6803. This procedure involves dodecyl maltoside extraction of thylakoid membranes followed by single-step column chromatography using a weak anion-exchanger. SDS-PAGE and immunoblotting show that the complex consists of five intrinsic membrane proteins (CP47, CP43, D1, D1, and cyt b559), one extrinsic protein (MSP), and one unknown protein with a molecular mass of approximately 26 kDa. A chemical and functional analysis, normalized to 2 molecules of pheophytin a, indicates that this PSII core complex contains 1 photoactive plastoquinone, QA, 4 manganese atoms, 38 chlorophyll a molecules, 1 cytochrome b559, 2 plastoquinone-9, and 9-10 beta-carotenes. The complex exhibits high rates of oxygen evolution, typically 2400-2600 mumol of O2 (mg of Chl)-1 h-1 in the presence of 2,5-dichlorobenzoquinone as an artificial electron acceptor with a pH optimum of 6.5. A strong light minus dark multiline EPR signal, arising from the S2 state of the oxygen-evolving complex (OEC), is observed at 10 K following illumination at 198 K. The determination of the absolute oxygen yield per saturating microsecond flash indicates that essentially all of the PSII centers contain functional oxygen-evolving complexes. This point is further supported by the absence of photoaccumulation, upon room temperature illumination, of the immediate oxidant of the OEC, redox-active tyrosine, YZ.. On the basis of EPR spectra, oxidized minus reduced difference spectra, and SDS-PAGE, the preparation contains on a per mole basis with PSII only trace amounts of PSI (approximately 0.04), cytochrome b6/f complex (< or = 0.01), and ATPase (< or = 0.05). All of these results indicate that this PSII preparation is to date the most highly purified oxygen-evolving core complex from Synechocystis 6803 that retains all of the reaction centers active

  17. XANES, EXAFS and Kbeta spectroscopic studies of the oxygen-evolving complex in Photosystem II

    SciTech Connect

    Robblee, John H.

    2000-12-01

    A key question for the understanding of photosynthetic water oxidation is whether the four oxidizing equivalents necessary to oxidize water to dioxygen are accumulated on the four Mn ions of the oxygen evolving complex (OEC), or whether some ligand-centered oxidations take place before the formation and release of dioxygen during the S{sub 3} {r_arrow} [S{sub 4}] {r_arrow} S{sub 0} transition. Progress in instrumentation and flash sample preparation allowed us to apply Mn K{beta} X-ray emission spectroscopy (Kb XES) to this problem for the first time. The K{beta} XES results, in combination with Mn X-ray absorption near-edge structure (XANES) and electron paramagnetic resonance (EPR) data obtained from the same set of samples, show that the S{sub 2} {r_arrow} S{sub 3} transition, in contrast to the S{sub 0} {r_arrow} S{sub 1} and S{sub 1} {r_arrow} S{sub 2} transitions, does not involve a Mn-centered oxidation. This is rationalized by manganese {mu}-oxo bridge radical formation during the S{sub 2} {r_arrow} S{sub 3} transition. Using extended X-ray absorption fine structure (EXAFS) spectroscopy, the local environment of the Mn atoms in the S{sub 0} state has been structurally characterized. These results show that the Mn-Mn distance in one of the di-{mu}-oxo-bridged Mn-Mn moieties increases from 2.7 {angstrom} in the S{sub 1} state to 2.85 {angstrom} in the S{sub 0} state. Furthermore, evidence is presented that shows three di-{mu}-oxo binuclear Mn{sub 2} clusters may be present in the OEC, which is contrary to the widely held theory that two such clusters are present in the OEC. The EPR properties of the S{sub 0} state have been investigated and a characteristic ''multiline'' signal in the S{sub 0} state has been discovered in the presence of methanol. This provides the first direct confirmation that the native S{sub 0} state is paramagnetic. In addition, this signal was simulated using parameters derived from three possible oxidation states of Mn in the S{sub 0

  18. Identification of oxygen-rich evolved stars by maser surveys and statistical studies on infrared data

    NASA Astrophysics Data System (ADS)

    Yung, Bosco H.-K.

    2013-10-01

    The post-asymptotic giant branch (post-AGB) phase is a short episode in the life of a star with mass between 0.8 to 8 M⊙. It comes after the AGB phase, and before the planetary nebula phase. A rapid change in many physical properties of a star is suggested to happen in this phase, for example the onset of jets. However, a lot of details are still unknown. In this thesis, three major problems are addressed: insufficient samples of post-AGB stars, identification of post-AGB stars, and the true status of a special class of objects called the "water fountains (WFs)". WFs are evolved stars associated with high velocity collimated bipolar jets that can be traced by H2O maser emissions. For the first two problems, new searching criteria are introduced with two new maser surveys on oxygen-rich post-AGB stars. It is necessary to collect more samples of post-AGB stars for further studies. Nonetheless, there has been no systematic searching method because most of the post-AGB stars are dim in optical and near-infrared wavelengths, which increases the difficulty in identification. Maser thus becomes a good alternative tool. In the first survey which focused only on H2O masers, over 200 AGB or post-AGB star candidates have been selected and observed. Those candidates were mainly chosen by new colour criteria with the far-infrared AKARI data. In particular, four characteristic maser sources were found, and they are currently suggested as possible very young post-AGB stars. In the second survey, another 100 objects were observed in OH and/or H2O masers. Three possible high velocity objects were discovered, including a new rare member of WFs. The colour criteria are proved to be quite sensitive in distinguishing post-AGB stars from AGB stars or other types of objects, even though there are still some contamination from young stellar objects. A follow-up study shows that the Q-parameters are effective in isolating objects with spherical or aspherical envelopes, which are also

  19. BIODEGRADATION - MONITORED NATURAL ATTENUATION (MNA) FOR OXYGENATES: HOW IT EVOLVED, WHY IT OCCURS AND STABLE ISOTOPES

    EPA Science Inventory

    The organisms that degrade MtBE under anaerobic conditions are evolved to acquire energy for growth by using molecular hydrogen and carbonate ion to cleave methyl ether bonds. Methyl ether bonds are common in nature and the bond also occurs in MTBE. MTBE in contaminated ground...

  20. Hot corrosion of S-57, 1 cobalt-base alloy

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.

    1977-01-01

    A cobalt base alloy, S-57, was hot corrosion tested in Mach 0.3 burner rig combustion gases at maximum alloy temperatures of 900 and 1000 C. Various salt concentrations were injected into the burner: 0.5, 2, 5, and 10 ppm synthetic sea salt and 4 ppm sodium sulfate (Na2SO4). S-57 underwent accelerated corrosion only under the most severe test conditions, for example, 4 ppm Na2SO4 at 900 C. The process of the accelerated corrosion was primarily sulfidation.

  1. Wear-resistant coatings for cobalt-base alloys

    SciTech Connect

    Cockeram, B.V.

    2000-04-01

    High interfacial stresses and coating failure are expected when a hard coating protects a more-compliant substrate in applications involving high-stress wear contact. Assuming that small differences in stiffness (or modulus) between the coating and substrate are required for a wear-resistant coating in such applications, four approaches have been taken to develop such coatings for cobalt-base alloys. Hardness, scratch adhesion, and nano-indentation testing identified the most promising candidates for cobalt-base alloys: A thin coating with hard Cr{sub 2}N and less-stiff Cr-N(ss) layers; a thick, four-layered coating with a 4{mu}m inner layer of Cr-N(ss)/ 1 {mu}m layer of Cr{sub 2}N/4 {micro}m layer of Cr-N(ss)/1 {micro} outer layer of Cr{sub 2}N; a duplex approach of ion nitriding to harden the subsurface,followed by application of a dual-layered Cr{sub 2}N/Cr-N(ss) coating; and ion nitriding alone. The low scratch adhesion values and high modulus/hardness values indicate that ZrN, TiN, and plasma carburized coatings represent less beneficial approaches. Two different cobalt-base alloys were studied in this work: Haynes 25 and Stellite 3 (Stoody Deloro Stellite). Based on weight change, profilometry measurements, and metallographic and SEM examinations after four-ball wear testing, the thin Cr{sub 2}N/CrN(ss) coated coupons exhibited a significantly lower wear rate than the uncoated Haynes 25 coupons. Of greater importance, the thin Cr{sub 2}N/Cr-N(ss) coatings were adherent on the Stellite 3 intermediate balls and Haynes 25 cups, and prevented the wear of the cobalt-base substrate. based on these results, the thin Cr{sub 2}N/Cr-N(ss) coating was the best coating candidate, and this coating could result in a reduced wear rate and less cobalt wear debris. The ion nitrided coupons exhibited slightly higher wear than the thin Cr{sub 2}N/Cr-N(ss) coated coupons, while the wear of the thin duplex coated coupons was the highest. However, the nitride layer was adherent

  2. Oxygen tolerance of an in silico-designed bioinspired hydrogen-evolving catalyst in water.

    PubMed

    Sit, Patrick H-L; Car, Roberto; Cohen, Morrel H; Selloni, Annabella

    2013-02-01

    Certain bacterial enzymes, the diiron hydrogenases, have turnover numbers for hydrogen production from water as large as 10(4)/s. Their much smaller common active site, composed of earth-abundant materials, has a structure that is an attractive starting point for the design of a practical catalyst for electrocatalytic or solar photocatalytic hydrogen production from water. In earlier work, our group has reported the computational design of [FeFe](P)/FeS(2), a hydrogenase-inspired catalyst/electrode complex, which is efficient and stable throughout the production cycle. However, the diiron hydrogenases are highly sensitive to ambient oxygen by a mechanism not yet understood in detail. An issue critical for practical use of [FeFe](P)/FeS(2) is whether this catalyst/electrode complex is tolerant to the ambient oxygen. We report demonstration by ab initio simulations that the complex is indeed tolerant to dissolved oxygen over timescales long enough for practical application, reducing it efficiently. This promising hydrogen-producing catalyst, composed of earth-abundant materials and with a diffusion-limited rate in acidified water, is efficient as well as oxygen tolerant. PMID:23341607

  3. Crystal structure of the oxygen-evolving complex of photosystem II.

    PubMed

    Barber, James

    2008-03-17

    The oxygen in our atmosphere is derived from and maintained by the water-splitting process of photosynthesis. The enzyme that facilitates this reaction and therefore underpins virtually all life on our planet is known as photosystem II (PSII). It is a multisubunit enzyme embedded in the lipid environment of the thylakoid membranes of plants, algae, and cyanobacteria. Powered by light, PSII catalyzes the chemically and thermodynamically demanding reaction of water splitting. In so doing, it releases molecular oxygen into the atmosphere and provides the reducing equivalents required for the conversion of carbon dioxide into the organic molecules of life. Recently, a fully refined structure of an isolated 700 kDa cyanobacterial dimeric PSII complex was elucidated by X-ray crystallography, which gave organizational and structural details of the 19 subunits (16 intrinsic and 3 extrinsic) that make up each monomer and provided information about the position and protein environments of the many different cofactors it binds. The water-splitting site was revealed as a cluster of four Mn ions and a Ca ion surrounded by amino acid side chains, of which six or seven form direct ligands to the metals. The metal cluster was originally modeled as a cubane-like structure composed of three Mn ions and the Ca (2+) linked by oxo bonds and the fourth Mn attached to the cubane via one of its O atoms. New data from X-ray diffraction and X-ray spectroscopy suggest some alternative arrangements. Nevertheless, all of the models are sufficiently similar to provide a basis for discussing the chemistry by which PSII splits water and makes oxygen.

  4. Modelling the alumina abundance of oxygen-rich evolved stars in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Jones, O. C.; Kemper, F.; Srinivasan, S.; McDonald, I.; Sloan, G. C.; Zijlstra, A. A.

    2014-05-01

    In order to determine the composition of the dust in the circumstellar envelopes of oxygen-rich asymptotic giant branch (AGB) stars, we have computed a grid of MODUST radiative-transfer models for a range of dust compositions, mass-loss rates, dust-shell inner radii and stellar parameters. We compare the resulting colours with the observed oxygen-rich AGB stars from the SAGE-Spec Large Magellanic Cloud (LMC) sample, finding good overall agreement for stars with a mid-infrared excess. We use these models to fit a sample of 37 O-rich AGB stars in the LMC with optically thin circumstellar envelopes, for which 5-35 μm Spitzer infrared spectrograph (IRS) spectra and broad-band photometry from the optical to the mid-infrared are available. From the modelling, we find mass-loss rates in the range ˜8 × 10-8-5 × 10-6 M⊙ yr-1, and we show that a grain mixture consisting primarily of amorphous silicates, with contributions from amorphous alumina and metallic iron, provides a good fit to the observed spectra. Furthermore, we show from dust models that the AKARI [11]-[15] versus [3.2]-[7] colour-colour diagram is able to determine the fractional abundance of alumina in O-rich AGB stars.

  5. CARBON CHEMISTRY IN THE ENVELOPE OF VY CANIS MAJORIS: IMPLICATIONS FOR OXYGEN-RICH EVOLVED STARS

    SciTech Connect

    Ziurys, L. M.; Tenenbaum, E. D.; Pulliam, R. L.; Woolf, N. J.; Milam, S. N. E-mail: emilyt@as.arizona.edu E-mail: nwoolf@as.arizona.edu

    2009-04-20

    Observations of the carbon-bearing molecules CO, HCN, CS, HNC, CN, and HCO{sup +} have been conducted toward the circumstellar envelope of the oxygen-rich red supergiant star, VY Canis Majoris (VY CMa), using the Arizona Radio Observatory (ARO). CO and HCN were also observed toward the O-rich shells of NML Cyg, TX Cam, IK Tau, and W Hya. Rotational transitions of these species at 1 mm, 0.8 mm, and 0.4 mm were measured with the ARO Submillimeter Telescope, including the J = 6 {yields} 5 line of CO at 691 GHz toward TX Cam and W Hya. The ARO 12 m was used for 2 mm and 3 mm observations. Four transitions were observed for HCO{sup +} in VY CMa, the first definitive identification of this ion in a circumstellar envelope. Molecular line profiles from VY CMa are complex, indicating three separate outflows: a roughly spherical flow and separate red- and blueshifted winds, as suggested by earlier observations. Spectra from the other sources appear to trace a single outflow component. The line data were modeled with a radiative transfer code to establish molecular abundances relative to H{sub 2} and source distributions. Abundances for CO derived for these objects vary over an order of magnitude, f {approx} 0.4-5 x 10{sup -4}, with the lower values corresponding to the supergiants. For HCN, a similar range in abundance is found (f {approx} 0.9-9 x 10{sup -6}), with no obvious dependence on the mass-loss rate. In VY CMa, HCO{sup +} is present in all three outflows with f {approx} 0.4-1.6 x 10{sup -8} and a spatial extent similar to that of CO. HNC is found only in the red- and blueshifted components with [HCN]/[HNC] {approx} 150-190, while [CN]/[HCN] {approx} 0.01 in the spherical flow. All three velocity components are traced in CS, which has a confined spatial distribution and f {approx} 2-6 x 10{sup -7}. These observations suggest that carbon-bearing molecules in O-rich shells are produced by a combination of photospheric shocks and photochemistry. Shocks may play a more

  6. Chemical Equilibrium Models for the S3 State of the Oxygen-Evolving Complex of Photosystem II.

    PubMed

    Isobe, Hiroshi; Shoji, Mitsuo; Shen, Jian-Ren; Yamaguchi, Kizashi

    2016-01-19

    We have performed hybrid density functional theory (DFT) calculations to investigate how chemical equilibria can be described in the S3 state of the oxygen-evolving complex in photosystem II. For a chosen 340-atom model, 1 stable and 11 metastable intermediates have been identified within the range of 13 kcal mol(-1) that differ in protonation, charge, spin, and conformational states. The results imply that reversible interconversion of these intermediates gives rise to dynamic equilibria that involve processes with relocations of protons and electrons residing in the Mn4CaO5 cluster, as well as bound water ligands, with concomitant large changes in the cluster geometry. Such proton tautomerism and redox isomerism are responsible for reversible activation/deactivation processes of substrate oxygen species, through which Mn-O and O-O bonds are transiently ruptured and formed. These results may allow for a tentative interpretation of kinetic data on substrate water exchange on the order of seconds at room temperature, as measured by time-resolved mass spectrometry. The reliability of the hybrid DFT method for the multielectron redox reaction in such an intricate system is also addressed.

  7. Substrate water exchange for the oxygen evolving complex in PSII in the S1, S2, and S3 states.

    PubMed

    Siegbahn, Per E M

    2013-06-26

    Detailed mechanisms for substrate water exchange in the oxygen evolving complex in photosystem II have been determined with DFT methods for large models. Existing interpretations of the experimental water exchange results have been quite different. By many groups, these results have been the main argument against the water oxidation mechanism suggested by DFT, in which the oxygen molecule is formed between a bridging oxo and an oxyl radical ligand in the center of the OEC. That mechanism is otherwise in line with most experiments. The problem has been that the mechanism requires a rather fast exchange of a bridging oxo ligand, which is not a common finding for smaller Mn-containing model systems. However, other groups have actually favored a substrate derived oxo ligand partly based on the same experiments. In the present study, three S-states have been studied, and the rates have been well reproduced by the calculations. The surprising experimental finding that water exchange in S1 is slower than the one in S2 is reproduced and explained. The key to this rate difference is the ease by which one of the manganese centers (Mn3) is reduced. This reduction has to occur to release the substrate water from Mn3. The similar rate of the slow exchange in S2 and S3 has been rationalized on the basis of earlier experiments combined with the present calculations. The results strongly support the previous DFT-suggested water oxidation mechanism.

  8. Combinatorial Development of Water Splitting Catalysts Based on the Oxygen Evolving Complex of Photosystem II

    SciTech Connect

    Woodbury, Neal

    2010-03-31

    The use of methods to create large arrays of potential catalysts for the reaction H2O ½ O2 + 2H+ on the anode of an electrolysis system were investigated. This reaction is half of the overall reaction involved in the splitting of water into hydrogen and oxygen gas. This method consisted of starting with an array of electrodes and developing patterned electrochemical approaches for creating a different, defined peptide at each position in the array. Methods were also developed for measuring the rate of reaction at each point in the array. In this way, the goal was to create and then tests many thousands of possible catalysts simultaneously. This type of approach should lead to an ability to optimize catalytic activity systematically, by iteratively designing and testing new libraries of catalysts. Optimization is important to decrease energy losses (over-potentials) associated with the water splitting reaction and thus for the generation of hydrogen. Most of the efforts in this grant period were focused on developing the chemistry and analytical methods required to create pattern peptide formation either using a photolithography approach or an electrochemical approach for dictating the positions of peptide bond formation. This involved testing a large number of different reactions and conditions. We have been able to find conditions that have allowed us to pattern peptide bond formation on both glass slides using photolithographic methods and on electrode arrays made by the company Combimatrix. Part of this effort involved generating novel approaches for performing mass spectroscopy directly from the patterned arrays. We have also been able to demonstrate the ability to measure current at each electrode due to electrolysis of water. This was performed with customized instrumentation created in collaboration with Combimatrix. In addition, several different molecular designs for peptides that bound metals (primarily Mn) were developed and synthesized and metal

  9. Molecular complexity in envelopes of evolved Oxygen-rich stars: IK Tauri and OH231.8+4.2

    NASA Astrophysics Data System (ADS)

    Velilla Prieto, L.; Sánchez Contreras, C.; Cernicharo, J.; Alcolea, J.; Agúndez, M.; Pardo, J. R.; Bujarrabal, V.; Herpin, F.; Menten, K. M.; Wyrowsky, F.

    2013-05-01

    During the late phases of low-intermediate mass (0.1 to 8 solar masses) stars, a significant mass loss is produced creating a gas and dust envelope surrounding the central star. Due to the physical conditions in the envelope, gas is primarily molecular, placing these objects as efficient molecular factories that will enrich the interstellar medium. Observation and study of molecular emission allows deriving physical and chemical properties of these envelopes. As far as today, Oxygen rich objects are not so well studied as their Carbon counterparts, because Carbon chemistry is much more active than Oxygen chemistry. Importance of this work is that the Oxygen rich envelopes are not completely characterized yet. We present preliminary results from our on-going milimiter wavelength survey with the EMIR receivers of the IRAM 30 meters radiotelescope towards the envelopes of two evolved Oxygen rich objects: IK Tauri and OH231.8+4.2. We detect a wealth of lines ranging from few mK to K (with rms ranging from 1 to 3 mK in best cases). Both objects present significant differences in their molecular emission features due to contrast of evolutionary stage and physical properties and both show evidences of different chemical formation processes. Some of the molecules identified are CO, SiO, H_{2}O, NS, HCO^{+}, SO, SO_{2}, SH_{2}, OCS, HCN, HNC, CN, HC_{3}N, CS, H_{2}CO, HNCO, HNCS, SiS, N_{2}H^{+} and a number of isotopologues (bearing ^{13}C, ^{33}S, ^{34}S, ^{17}O, ^{18}O, ^{28}Si, ^{29}Si, ^{30}Si and ^{15}N atoms). Some of the molecules identified represent first detections in Oxygen rich AGB stars. We expect to get a better understanding of the chemistry and structure of these objects, in particular how interaction between AGB (Asymptotic Giant Branch) envelopes and post-AGB winds influences chemistry producing a reformation of molecules through shocked gas reactions. held in Valencia, July 9 - 13, 2012, Eds.: J.C. Guirado, L.M. Lara, V. Quilis, and J. Gorgas.

  10. Geometric and electronic structures of the synthetic Mn₄CaO₄ model compound mimicking the photosynthetic oxygen-evolving complex.

    PubMed

    Shoji, Mitsuo; Isobe, Hiroshi; Shen, Jian-Ren; Yamaguchi, Kizashi

    2016-04-28

    Water oxidation by photosystem II (PSII) converts light energy into chemical energy with the concomitant production of molecular oxygen, both of which are indispensable for sustaining life on Earth. This reaction is catalyzed by an oxygen-evolving complex (OEC) embedded in the huge PSII complex, and its mechanism remains elusive in spite of the extensive studies of the geometric and electronic structures. In order to elucidate the water-splitting mechanism, synthetic approaches have been extensively employed to mimic the native OEC. Very recently, a synthetic complex [Mn4CaO4(Bu(t)COO)8(py)(Bu(t)COOH)2] (1) closely mimicking the structure of the native OEC was obtained. In this study, we extensively examined the geometric, electronic and spin structures of 1 using the density functional theory method. Our results showed that the geometric structure of 1 can be accurately reproduced by theoretical calculations, and revealed many similarities in the ground valence and spin states between 1 and the native OEC. We also revealed two different valence states in the one-electron oxidized state of 1 (corresponding to the S2 state), which lie in the lower and higher ground spin states (S = 1/2 and S = 5/2), respectively. One remarkable difference between 1 and the native OEC is the presence of a non-negligible antiferromagnetic interaction between the Mn1 and Mn4 sites, which slightly influenced their ground spin structures (spin alignments). The major reason causing the difference can be attributed to the short Mn1-O5 and Mn1-Mn4 distances in 1. The introduction of the missing O4 atom and the reorientation of the Ca coordinating ligands improved the Mn1-O5 and Mn1-Mn4 distances comparable to the native OEC. These modifications will therefore be important for the synthesis of further advanced model complexes more closely mimicking the native OEC beyond 1.

  11. Two-step mechanism of photodamage to photosystem II: step 1 occurs at the oxygen-evolving complex and step 2 occurs at the photochemical reaction center.

    PubMed

    Ohnishi, Norikazu; Allakhverdiev, Suleyman I; Takahashi, Shunichi; Higashi, Shoichi; Watanabe, Masakatsu; Nishiyama, Yoshitaka; Murata, Norio

    2005-06-14

    Under strong light, photosystem II (PSII) of oxygenic photosynthetic organisms is inactivated, and this phenomenon is called photoinhibition. In a widely accepted model, photoinhibition is induced by excess light energy, which is absorbed by chlorophyll but not utilized in photosynthesis. Using monochromatic light from the Okazaki Large Spectrograph and thylakoid membranes from Thermosynechococcus elongatus, we observed that UV and blue light inactivated the oxygen-evolving complex much faster than the photochemical reaction center of PSII. These observations suggested that the light-induced damage was associated with a UV- and blue light-absorbing center in the oxygen-evolving complex of PSII. The action spectrum of the primary event in photodamage to PSII revealed the strong effects of UV and blue light and differed considerably from the absorption spectra of chlorophyll and thylakoid membranes. By contrast to the photoinduced inactivation of the oxygen-evolving complex in untreated thylakoid membranes, red light efficiently induced inactivation of the PSII reaction center in Tris-treated thylakoid membranes, and the action spectrum resembled the absorption spectrum of chlorophyll. Our observations suggest that photodamage to PSII occurs in two steps. Step 1 is the light-induced inactivation of the oxygen-evolving complex. Step 2, occurring after step 1 is complete, is the inactivation of the PSII reaction center by light absorbed by chlorophyll. We confirmed our model by illumination of untreated thylakoid membranes with blue and UV light, which inactivated the oxygen-evolving complex, and then with red light, which inactivated the photochemical reaction center.

  12. Structural characterization of photosystem II complex from red alga Porphyridium cruentum retaining extrinsic subunits of the oxygen-evolving complex.

    PubMed

    Bumba, Ladislav; Havelková-Dousová, Helena; Husák, Michal; Vácha, Frantisek

    2004-07-01

    The structure of photosystem II (PSII) complex isolated from thylakoid membranes of the red alga Porphyridium cruentum was investigated using electron microscopy followed by single particle image analysis. The dimeric complexes observed contain all major PSII subunits (CP47, CP43, D1 and D2 proteins) as well as the extrinsic proteins (33 kDa, 12 kDa and the cytochrome c(550)) of the oxygen-evolving complex (OEC) of PSII, encoded by the psbO, psbU and psbV genes, respectively. The single particle analysis of the top-view projections revealed the PSII complex to have maximal dimensions of 22 x 15 nm. The analysis of the side-view projections shows a maximal thickness of the PSII complex of about 9 nm including the densities on the lumenal surface that has been attributed to the proteins of the OEC complex. These results clearly demonstrate that the red algal PSII complex is structurally very similar to that of cyanobacteria and to the PSII core complex of higher plants. In addition, the arrangement of the OEC proteins on the lumenal surface of the PSII complex is consistent to that obtained by X-ray crystallography of cyanobacterial PSII.

  13. Effect of protein modification by malondialdehyde on the interaction between the oxygen-evolving complex 33 kDa protein and photosystem II core proteins.

    PubMed

    Yamauchi, Yasuo; Sugimoto, Yukihiro

    2010-04-01

    Previously we observed that the oxygen-evolving complex 33 kDa protein (OEC33) which stabilizes the Mn cluster in photosystem II (PSII), was modified with malondialdehyde (MDA), an end-product of peroxidized polyunsaturated fatty acids, and the modification increased in heat-stressed plants (Yamauchi et al. 2008). In this study, we examined whether the modification of OEC33 with MDA affects its binding to the PSII complex and causes inactivation of the oxygen-evolving complex. Purified OEC33 and PSII membranes that had been removed of extrinsic proteins of the oxygen-evolving complex (PSIIOEE) of spinach (Spinacia oleracea) were separately treated with MDA. The binding was diminished when both OEC33 and PSIIOEE were modified, but when only OEC33 or PSIIOEE was treated, the binding was not impaired. In the experiment using thylakoid membranes, release of OEC33 from PSII and corresponding loss of oxygen-evolving activity were observed when thylakoid membranes were treated with MDA at 40 degrees C but not at 25 degrees C. In spinach leaves treated at 40 degrees C under light, maximal efficiency of PSII photochemistry (F(v)/F(m) ratio of chlorophyll fluorescence) and oxygen-evolving activity decreased. Simultaneously, MDA contents in heat-stressed leaves increased, and OEC33 and PSII core proteins including 47 and 43 kDa chlorophyll-binding proteins were modified with MDA. In contrast, these changes were to a lesser extent at 40 degrees C in the dark. These results suggest that MDA modification of PSII proteins causes release of OEC33 from PSII and it is promoted in heat and oxidative conditions.

  14. Cobalt-based magnetic nanocomposites: fabrication, fundamentals and applications

    NASA Astrophysics Data System (ADS)

    Wen, Tianlong; Krishnan, Kannan M.

    2011-10-01

    Recently, magnetic nanocomposites (MNC) have aroused significant scientific and technological interests because their properties strongly rely on the interplay between those of the constituent components. Here, using three types of cobalt-based MNCs, we demonstrate how their physical behaviour, including thermal, electrical and magnetic, can be strongly affected by such interplays. First, using Aucore-Coshell nanoparticles (NPs), we demonstrate that their thermal stabilities are critically dependent on various boundaries and they structurally transform from the core-shells to the peanut structures via several intermediate states by a series of energy minimizations including the grain boundaries, Co/Au interface and strain. Second, the microstructures of the MNC are co-determined by the properties of the individual components, which in turn will strongly affect their overall properties. We illustrate this by a careful study of the electron transport in cobalt/poly (3-hexylthiophene, 2, 5-diyl) (P3HT) hybrid thin films, and show that they satisfy a fluctuation-induced tunnelling model that is strongly depended on their microstructures; moreover, a magnetoresistance in these thin films was also observed. Finally, the magnetic properties and phase stability of MNCs can also be strongly altered as a result of this interplay. Three phase transformations are observed in cobalt ferrofluids for T ~ 10-300 K, namely second order magnetic phase transformations (blocked-unblocked transition) at the blocking temperature of the magnetic NP, first order magnetic and structural phase transformations at the solvent melting temperature, TM, and second order premelting transformation at TPM < T < TM. These transformations show specific magnetic signatures in field-cool and zero-field-cool magnetization measurements and are qualitatively in agreement with predictions using M-spectrum theory.

  15. Cryogenic Trapping and Isotope Editing Identify a Protonated Water Cluster as an Intermediate in the Photosynthetic Oxygen-Evolving Reaction.

    PubMed

    Guo, Zhanjun; Barry, Bridgette A

    2016-09-01

    Internal water is known to play a catalytic role in several enzymes. In photosystem II (PSII), water is the substrate. To oxidize water, the PSII Mn4CaO5 cluster or oxygen evolving center (OEC) cycles through five oxidation states, termed Sn states. As reaction products, molecular oxygen is released, and protons are transferred through a ∼25 Å hydrogen-bonded network from the OEC to the thylakoid lumen. Previously, it was reported that a broad infrared band at 2880 cm(-1) is produced during the S1-to-S2 transition and accompanies flash-induced, S state cycling at pH 7.5. Here, we report that when the S2 state is trapped by continuous illumination under cryogenic conditions (190 K), an analogous 2740/2900 cm(-1) band is observed. The frequency depended on the sodium chloride concentration. This band is unambiguously assigned to a normal mode of water by D2(16)O and H2(18)O solvent exchange. Its large, apparent H2(18)O isotope shift, ammonia sensitivity, frequency, and intensity support assignment to a stretching vibration of a hydronium cation, H3O(+), in a small, protonated internal water cluster, nH2O(H3O(+)). Water OH stretching bands, which may be derived from the hydration shell of the hydronium ion, are also identified. Using the 2740 cm(-1) infrared marker, the results of calcium depletion and strontium reconstitution on the protonated water cluster are found to be pH dependent. This change is attributed to protonation of an amino acid side chain and a possible change in nH2O(H3O)(+) localization in the hydrogen-bonding network. These results are consistent with an internal water cluster functioning as a proton acceptor and an intermediate during the S1-to-S2 transition. Our experiments demonstrate the utility of this infrared signal as a novel functional probe in PSII. PMID:27491625

  16. Two-dimensional HYSCORE spectroscopy of superoxidized manganese catalase: a model for the oxygen-evolving complex of photosystem II.

    PubMed

    Coates, Christopher S; Milikisiyants, Sergey; Chatterjee, Ruchira; Whittaker, Mei M; Whittaker, James W; Lakshmi, K V

    2015-04-16

    The solar water-splitting protein complex, photosystem II (PSII), catalyzes one of the most energetically demanding reactions in Nature by using light energy to drive a catalyst capable of oxidizing water. The water oxidation reaction takes place at the tetra-nuclear manganese calcium-oxo (Mn4Ca-oxo) cluster at the heart of the oxygen-evolving complex (OEC) of PSII. Previous studies have determined the magnetic interactions between the paramagnetic Mn4Ca-oxo cluster and its environment in the S2 state of the OEC. The assignments for the electron-nuclear magnetic interactions that were observed in these studies were facilitated by the use of synthetic dimanganese di-μ-oxo complexes. However, there is an immense need to understand the effects of the protein environment on the coordination geometry of the Mn4Ca-oxo cluster in the OEC of PSII. In the present study, we use a proteinaceous model system to examine the protein ligands that are coordinated to the dimanganese catalytic center of manganese catalase from Lactobacillus plantarum. We utilize two-dimensional hyperfine sublevel correlation (2D HYSCORE) spectroscopy to detect the weak magnetic interactions of the paramagnetic dinuclear manganese catalytic center of superoxidized manganese catalase with the nitrogen and proton atoms of the surrounding protein environment. We obtain a complete set of hyperfine interaction parameters for the protons of a water molecule that is directly coordinated to the dinuclear manganese center. We also obtain a complete set of hyperfine and quadrupolar interaction parameters for two histidine ligands as well as a coordinated azide ligand, in azide-treated superoxidized manganese catalase. On the basis of the values of the hyperfine interaction parameters of the dimanganese model, manganese catalase, and those of the S2 state of the OEC of PSII, for the first time, we discuss the impact of a proteinaceous environment on the coordination geometry of multinuclear manganese clusters

  17. Two-dimensional HYSCORE spectroscopy of superoxidized manganese catalase: a model for the oxygen-evolving complex of photosystem II.

    PubMed

    Coates, Christopher S; Milikisiyants, Sergey; Chatterjee, Ruchira; Whittaker, Mei M; Whittaker, James W; Lakshmi, K V

    2015-04-16

    The solar water-splitting protein complex, photosystem II (PSII), catalyzes one of the most energetically demanding reactions in Nature by using light energy to drive a catalyst capable of oxidizing water. The water oxidation reaction takes place at the tetra-nuclear manganese calcium-oxo (Mn4Ca-oxo) cluster at the heart of the oxygen-evolving complex (OEC) of PSII. Previous studies have determined the magnetic interactions between the paramagnetic Mn4Ca-oxo cluster and its environment in the S2 state of the OEC. The assignments for the electron-nuclear magnetic interactions that were observed in these studies were facilitated by the use of synthetic dimanganese di-μ-oxo complexes. However, there is an immense need to understand the effects of the protein environment on the coordination geometry of the Mn4Ca-oxo cluster in the OEC of PSII. In the present study, we use a proteinaceous model system to examine the protein ligands that are coordinated to the dimanganese catalytic center of manganese catalase from Lactobacillus plantarum. We utilize two-dimensional hyperfine sublevel correlation (2D HYSCORE) spectroscopy to detect the weak magnetic interactions of the paramagnetic dinuclear manganese catalytic center of superoxidized manganese catalase with the nitrogen and proton atoms of the surrounding protein environment. We obtain a complete set of hyperfine interaction parameters for the protons of a water molecule that is directly coordinated to the dinuclear manganese center. We also obtain a complete set of hyperfine and quadrupolar interaction parameters for two histidine ligands as well as a coordinated azide ligand, in azide-treated superoxidized manganese catalase. On the basis of the values of the hyperfine interaction parameters of the dimanganese model, manganese catalase, and those of the S2 state of the OEC of PSII, for the first time, we discuss the impact of a proteinaceous environment on the coordination geometry of multinuclear manganese clusters.

  18. Protons bound to the Mn cluster in photosystem II oxygen evolving complex detected by proton matrix ENDOR.

    PubMed

    Yamada, Hiroiku; Mino, Hiroyuki; Itoh, Shigeru

    2007-03-01

    Protons in the vicinity of the oxygen-evolving manganese cluster in photosystem II were studied by proton matrix ENDOR. Six pairs of proton ENDOR signals were detected in both the S(0) and S(2) states of the Mn-cluster. Two pairs of signals that show hyperfine constants of 2.3/2.2 and 4.0 MHz, respectively, disappeared after D(2)O incubation in both states. The signals with 2.3/2.2 MHz hyperfine constants in S(0) and S(2) state multiline disappeared after 3 h of D(2)O incubation in the S(0) and S(1) states, respectively. The signal with 4.0 MHz hyperfine constants in S(0) state multiline disappeared after 3 h of D(2)O incubation in the S(0) state, while the similar signal in S(2) state multiline disappeared only after 24 h of D(2)O incubation in the S(1) state. The different proton exchange rates seem to be ascribable to the change in affinities of water molecules to the variation in oxidation state of the Mn cluster during the water oxidation cycle. Based on the point dipole approximation, the distances between the center of electronic spin of the Mn cluster and the exchangeable protons were estimated to be 3.3/3.2 and 2.7 A, respectively. These short distances suggest the protons belong to the water molecules ligated to the manganese cluster. We propose a model for the binding of water to the manganese cluster based on these results.

  19. X-ray and vibrational spectroscopy of manganese complexes relevant to the oxygen-evolving complex of photosynthesis

    SciTech Connect

    Visser, Hendrik

    2001-05-16

    Manganese model complexes, relevant to the oxygen-evolving complex (OEC) in photosynthesis, were studied with Mn K-edge X-ray absorption near-edge spectroscopy (XANES), Mn Kb X-ray emission spectroscopy (XES), and vibrational spectroscopy. A more detailed understanding was obtained of the influence of nuclearity, overall structure, oxidation state, and ligand environment of the Mn atoms on the spectra from these methods. This refined understanding is necessary for improving the interpretation of spectra of the OEC. Mn XANES and Kb XES were used to study a di-(mu)-oxo and a mono-(mu)-oxo di-nuclear Mn compound in the (III,III), (III,IV), and (IV,IV) oxidation states. XANES spectra show energy shifts of 0.8 - 2.2 eV for 1-electron oxidation-state changes and 0.4 - 1.8 eV for ligand-environment changes. The shifts observed for Mn XES spectra were approximately 0.21 eV for oxidation state-changes and only approximately 0.04 eV for ligand-environment changes. This indicates that Mn Kb XES i s more sensitive to the oxidation state and less sensitive to the ligand environment of the Mn atoms than XANES. These complimentary methods provide information about the oxidation state and the ligand environment of Mn atoms in model compounds and biological systems. A versatile spectroelectrochemical apparatus was designed to aid the interpretation of IR spectra of Mn compounds in different oxidation states. The design, based on an attenuated total reflection device, permits the study of a wide spectral range: 16,700 (600 nm) - 225

  20. Cyclic axial-torsional deformation behavior of a cobalt-base superalloy

    SciTech Connect

    Bonacuse, P.J.; Kalluri, S.

    1992-11-01

    Multiaxial loading, especially at elevated temperature, can cause the inelastic response of a material to differ significantly from that predicted by simple flow rules, i.e., von Mises or Tresca. To quantify some of these differences, the cyclic high-temperature, deformation behavior of a wrought cobalt-based superalloy, Haynes 188, is investigated under combined axial and torsional loads. Haynes 188 is currently used in many aerospace gas turbine and rocket engine applications, e.g., the combustor liner for the T800 turboshaft engine for the RAH-66 Comanche helicopter and the liquid oxygen posts in the main injector of the space shuttle main engine. The deformation behavior of this material is assessed through the examination of hysteresis loops generated from a biaxial fatigue test program. A high-temperature axial, torsional, and combined axial-torsional fatigue data base has been generated on Haynes 188 at 760 C. Cyclic loading tests have been conducted on uniform gauge section tubular specimens in a servohydraulic axial-torsional test rig. Test control and data acquisition were accomplished with a minicomputer. In this paper, the cyclic hardening characteristics and typical hysteresis loops in the axial stress versus axial strain, shear stress versus engineering shear strain, axial strain versus engineering shear strain, and axial stress versus shear stress spaces are presented for cyclic, in-phase and out-of-phase, axial torsional tests. For in-phase tests three different values of the proportionality constant, lambda (ratio of engineering shear strain amplitude to axial strain amplitude), are examined, viz., 0.86, 1.73, and 3.46. In the out-of-phase tests, three different values of the phase angle, phi (between the axial and engineering shear strain waveforms), are studied, viz., 30, 60, and 90 deg with lambda = 1.73.

  1. Inhibition of photosystem II photochemistry by Cr is caused by the alteration of both D1 protein and oxygen evolving complex.

    PubMed

    Ali, Nadia Ait; Dewez, David; Didur, Olivier; Popovic, Radovan

    2006-09-01

    The effect of chromium (Cr) on photosystem II (PSII) electron transport and the change of proteins content within PSII complex were investigated. When Lemna gibba was exposed to Cr during 96 h, growth inhibition was found to be associated with an alteration of the PSII electron transport at both PSII oxidizing and reducing sides. Investigation of fluorescence yields at transients K, J, I, and P suggested for Cr inhibitory effect to be located at the oxygen-evolving complex and Q(A) reduction. Those Cr-inhibitory effects were related to the change of the turnover of PSII D1 protein and the alteration of 24 and 33 kDa proteins of the oxygen-evolving complex. The inhibition of the PSII electron transport and the formation of reactive oxygen species induced by Cr were highly correlated with the decrease in the content of D1 protein and the amount of 24 and 33 kDa proteins. Therefore, functional alteration of PSII activity by Cr was closely related with the structural change within PSII complex. PMID:16969717

  2. Cobalt base superalloy has outstanding properties up to 1478 K (2200 F)

    NASA Technical Reports Server (NTRS)

    Harlow, R. A.; Harf, F. H.; Freche, J. C.

    1974-01-01

    Alloy VM-103 is especially promising for use in applications requiring short time exposure to very high temperatures. Its properties over broad range of temperatures are superior to those of comparable commercial wrought cobalt-base superalloys, L-605 and HS-188.

  3. Photosynthesis. Electronic structure of the oxygen-evolving complex in photosystem II prior to O-O bond formation.

    PubMed

    Cox, Nicholas; Retegan, Marius; Neese, Frank; Pantazis, Dimitrios A; Boussac, Alain; Lubitz, Wolfgang

    2014-08-15

    The photosynthetic protein complex photosystem II oxidizes water to molecular oxygen at an embedded tetramanganese-calcium cluster. Resolving the geometric and electronic structure of this cluster in its highest metastable catalytic state (designated S3) is a prerequisite for understanding the mechanism of O-O bond formation. Here, multifrequency, multidimensional magnetic resonance spectroscopy reveals that all four manganese ions of the catalyst are structurally and electronically similar immediately before the final oxygen evolution step; they all exhibit a 4+ formal oxidation state and octahedral local geometry. Only one structural model derived from quantum chemical modeling is consistent with all magnetic resonance data; its formation requires the binding of an additional water molecule. O-O bond formation would then proceed by the coupling of two proximal manganese-bound oxygens in the transition state of the cofactor. PMID:25124437

  4. Cyclic axial-torsional deformation behavior of a cobalt-base superalloy

    NASA Technical Reports Server (NTRS)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    1992-01-01

    Multiaxial loading, especially at elevated temperature, can cause the inelastic response of a material to differ significantly from that predicted by simple flow rules, i.e., von Mises or Tresca. To quantify some of these differences, the cyclic high-temperature, deformation behavior of a wrought cobalt-based superalloy, Haynes 188, is investigated under combined axial and torsional loads. Haynes 188 is currently used in many aerospace gas turbine and rocket engine applications, e.g., the combustor liner for the T800 turboshaft engine for the RAH-66 Comanche helicopter and the liquid oxygen posts in the main injector of the space shuttle main engine. The deformation behavior of this material is assessed through the examination of hysteresis loops generated from a biaxial fatigue test program. A high-temperature axial, torsional, and combined axial-torsional fatigue data base has been generated on Haynes 188 at 760 C. Cyclic loading tests have been conducted on uniform gauge section tubular specimens in a servohydraulic axial-torsional test rig. Test control and data acquisition were accomplished with a minicomputer. In this paper, the cyclic hardening characteristics and typical hysteresis loops in the axial stress versus axial strain, shear stress versus engineering shear strain, axial strain versus engineering shear strain, and axial stress versus shear stress spaces are presented for cyclic, in-phase and out-of-phase, axial torsional tests. For in-phase tests three different values of the proportionality constant, lambda (ratio of engineering shear strain amplitude to axial strain amplitude), are examined, viz., 0.86, 1.73, and 3.46. In the out-of-phase tests, three different values of the phase angle, phi (between the axial and engineering shear strain waveforms), are studied, viz., 30, 60, and 90 deg with lambda = 1.73. The cyclic hardening behaviors of all the tests conducted on Haynes 188 at 760 C are evaluated using the von Mises equivalent stress

  5. Calcium EXAFS establishes the Mn-Ca cluster in the oxygen-evolving complex of Photosystem II

    SciTech Connect

    Cinco, Roehl M.; McFarlane Holman, Karen L.; Robblee, John H.; Yano, Junko; Pizarro, Shelly A.; Bellacchio, Emanuele; Sauer, Kenneth; Yachandra, Vittal K.

    2002-08-02

    The proximity of Ca to the Mn cluster of the photosynthetic water-oxidation complex is demonstrated by X-ray absorption spectroscopy. We have collected EXAFS data at the Ca K-edge using active PS II membrane samples that contain approximately 2 Ca per 4 Mn. These samples are much less perturbed than previously investigated Sr-substituted samples, which were prepared subsequent to Ca depletion. The new Ca EXAFS clearly shows backscattering from Mn at 3.4 angstroms, a distance that agrees with that surmised from previously recorded Mn EXAFS. This result is also consistent with earlier related experiments at the Sr K-edge, using samples that contained functional Sr, that show Mn is {approx}; 3.5 angstroms distant from Sr. The totality of the evidence clearly advances the notion that the catalytic center of oxygen evolution is a Mn-Ca heteronuclear cluster.

  6. Ta and Ti Anti-passivation Interlayers for Oxygen-Evolving Anodes Produced by Cold Gas Spray

    NASA Astrophysics Data System (ADS)

    Piercy, B.; Allen, C.; Gullá, A. F.

    2015-04-01

    Conventional electrodes for electrochemical oxygen evolution (OER) comprise titanium substrate, an anti-passivation interlayer, and a mixed metal oxide catalyst layer. We report the use of cold gas spray to deposit titanium and tantalum anti-passivation interlayers, directly on titanium, for OER applications. Accelerated electrochemical life tests show that 100% tantalum interlayers exceeded the performance of commercial state-of-the-art electrodes. Microscopy reveals that electrode failure, in the case of 100% tantalum interlayers, is primarily due to catalyst loss; in contrast, the typical failure mode for conventional electrodes of this type is passivation of the titanium substrate. These results highlight the effectiveness of cold gas spray tantalum for extending electrode lifetimes while maximizing catalyst utilization.

  7. Ammonia binding to the oxygen-evolving complex of photosystem II identifies the solvent-exchangeable oxygen bridge (μ-oxo) of the manganese tetramer.

    PubMed

    Pérez Navarro, Montserrat; Ames, William M; Nilsson, Håkan; Lohmiller, Thomas; Pantazis, Dimitrios A; Rapatskiy, Leonid; Nowaczyk, Marc M; Neese, Frank; Boussac, Alain; Messinger, Johannes; Lubitz, Wolfgang; Cox, Nicholas

    2013-09-24

    The assignment of the two substrate water sites of the tetra-manganese penta-oxygen calcium (Mn4O5Ca) cluster of photosystem II is essential for the elucidation of the mechanism of biological O-O bond formation and the subsequent design of bio-inspired water-splitting catalysts. We recently demonstrated using pulsed EPR spectroscopy that one of the five oxygen bridges (μ-oxo) exchanges unusually rapidly with bulk water and is thus a likely candidate for one of the substrates. Ammonia, a water analog, was previously shown to bind to the Mn4O5Ca cluster, potentially displacing a water/substrate ligand [Britt RD, et al. (1989) J Am Chem Soc 111(10):3522-3532]. Here we show by a combination of EPR and time-resolved membrane inlet mass spectrometry that the binding of ammonia perturbs the exchangeable μ-oxo bridge without drastically altering the binding/exchange kinetics of the two substrates. In combination with broken-symmetry density functional theory, our results show that (i) the exchangable μ-oxo bridge is O5 {using the labeling of the current crystal structure [Umena Y, et al. (2011) Nature 473(7345):55-60]}; (ii) ammonia displaces a water ligand to the outer manganese (MnA4-W1); and (iii) as W1 is trans to O5, ammonia binding elongates the MnA4-O5 bond, leading to the perturbation of the μ-oxo bridge resonance and to a small change in the water exchange rates. These experimental results support O-O bond formation between O5 and possibly an oxyl radical as proposed by Siegbahn and exclude W1 as the second substrate water. PMID:24023065

  8. Axial and torsional fatigue behavior of a cobalt-base alloy

    NASA Technical Reports Server (NTRS)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    1991-01-01

    In order to develop elevated temperature multiaxial fatigue life prediction models for the wrought cobalt-base alloy, Haynes 188, a multiaxial fatigue data base is required. To satisfy this need, an elevated temperature experimental program on Haynes 188 consisting of axial, torsional, inphase and out of phase axial-torsional fatigue experiments was designed. Elevated temperature axial and torsional fatigue experiments were conducted under strain control on thin wall tubular specimens of Haynes 188 in air. Test results are given.

  9. Development of wear-resistant coatings for cobalt-base alloys

    SciTech Connect

    Cockeram, B.V.

    1999-10-22

    The level of nuclear plant radiation exposure due to activated cobalt wear debris could potentially be reduced by covering the cobalt-base materials with a wear resistant coating. Laboratory pin-on-disc and rolling contact wear tests were used to evaluate the wear performance of several coatings. Based on the results of these tests, multilayer Cr-nitride coatings and ion nitriding are the most promising approaches.

  10. Mechanisms of the formation of magnetic characteristics of a cobalt-based amorphous magnetically soft alloy under heat treatment in air

    NASA Astrophysics Data System (ADS)

    Skulkina, N. A.; Ivanov, O. A.; Stepanova, E. A.; Shubina, L. N.; Kuznetsov, P. A.; Mazeeva, A. K.

    2015-12-01

    Physical causes of the formation of magnetic characteristics of cobalt-based alloys with a near to zero saturation magnetostriction under heat treatment in air have been studied using the Co-Fe-Ni-Cr-Si-B amorphous magnetically soft alloy as an example. The results of the study have shown the possibility of using the vapor treatment of surfaces of ribbons made of amorphous magnetically soft alloys to determine the sign of magnetostriction. The dependence of the sign of magnetostriction on the structural state of a ribbon, which is produced by the heat treatment, has been experimentally found. It has been established that physical causes of the formation of magnetic characteristics of the cobalt-based alloys are the same as those for iron-based alloys. Changes in the magnetic characteristics after annealing result from the relaxation of quenchinginduced internal stresses, as well as from the effect of stresses induced by hydrogen and oxygen atoms incorporated into the surface of the ribbon in the course of its interaction with water vapor in air and by the formation of an amorphous-crystalline surface layer.

  11. Development of wear-resistant coatings for cobalt-base alloys

    SciTech Connect

    Cockeram, B.V.

    1999-03-01

    The costs and hazards resulting from nuclear plant radiation exposure with activated cobalt wear debris could potentially be reduced by covering the cobalt-base materials with a wear resistant coating. However, the hardnesses of many cobalt-base wear alloys are significantly lower than conventional PVD hard coatings, and mechanical support of the hard coating is a concern. Four approaches have been taken to minimize the hardness differences between the substrate and PVD hard coating: (1) use a thin Cr-nitride hard coating with layers that are graded with respect to hardness, (2) use a thicker, multilayered coating (Cr-nitride or Zr-nitride) with graded layers, (3) use nitriding to harden the alloy subsurface followed by application of a multilayered coating of Cr-nitride, and (4) use of nitriding alone. Since little work has been done on application of PVD hard coatings to cobalt-base alloys, some details on process development and characterization of the coatings is presented. Scratch testing was used to evaluate the adhesion of the different coatings. A bench-top rolling contact test was used to evaluate the wear resistance of the coatings. The test results are discussed, and the more desirable coating approaches are identified.

  12. Correlation between pH dependence of O2 evolution and sensitivity of Mn cations in the oxygen-evolving complex to exogenous reductants.

    PubMed

    Semin, Boris K; Davletshina, Lira N; Rubin, Andrei B

    2015-08-01

    Effects of pH, Ca(2+), and Cl(-) ions on the extraction of Mn cations from oxygen-evolving complex (OEC) in Ca-depleted photosystem II (PSII(-Ca)) by exogenous reductants hydroquinone (H2Q) and H2O2 were studied. Two of 4 Mn cations are released by H2Q and H2O2 at pHs 5.7, 6.5, and 7.5, and their extraction does not depend on the presence of Ca(2+) and Cl(-) ions. One of Mn cations ("resistant" Mn cation) cannot be extracted by H2Q and H2O2 at any pH. Extraction of 4th Mn ion ("flexible" Mn cation) is sensitive to pH, Ca(2+), and Cl(-). This Mn cation is released by reductants at pH 6.5 but not at pHs 5.7 and 7.5. A pH dependence curve of the oxygen-evolving activity in PSII(-Ca) membranes (in the presence of exogenous Ca(2+)) has a bell-shaped form with the maximum at pH 6.5. Thus, the increase in the resistance of flexible Mn cation in OEC to the action of reductants at acidic and alkaline pHs coincides with the decrease in oxygen evolution activity at these pHs. Exogenous Ca(2+) protects the extraction of flexible Mn cation at pH 6.5. High concentration of Cl(-) anions (100 mM) shifts the pH optimum of oxygen evolution to alkaline region (around pH 7.5), while the pH of flexible Mn extraction is also shifted to alkaline pH. This result suggests that flexible Mn cation plays a key role in the water-splitting reaction. The obtained results also demonstrate that only one Mn cation in Mn4 cluster is under strong control of calcium. The change in the flexible Mn cation resistance to exogenous reductants in the presence of Ca(2+) suggests that Ca(2+) can control the redox potential of this cation. PMID:25975707

  13. Crystal structure of oxygen-evolving photosystem II from Thermosynechococcus vulcanus at 3.7-Å resolution

    NASA Astrophysics Data System (ADS)

    Kamiya, Nobuo; Shen, Jian-Ren

    2003-01-01

    Photosystem II (PSII) is a multisubunit membrane protein complex performing light-induced electron transfer and water-splitting reactions, leading to the formation of molecular oxygen. The first crystal structure of PSII from a thermophilic cyanobacterium Thermosynechococcus elongatus was reported recently [Zouni, A., Witt, H. T., Kern, J., Fromme, P., Krauss, N., Saenger, W. & Orth, P. (2001) Nature 409, 739-743)] at 3.8-Å resolution. To analyze the PSII structure in more detail, we have obtained the crystal structure of PSII from another thermophilic cyanobacterium, Thermosynechococcus vulcanus, at 3.7-Å resolution. The present structure was built on the basis of the sequences of PSII large subunits D1, D2, CP47, and CP43; extrinsic 33- and 12-kDa proteins and cytochrome c550; and several low molecular mass subunits, among which the structure of the 12-kDa protein was not reported previously. This yielded much information concerning the molecular interactions within this large protein complex. We also show the arrangement of chlorophylls and cofactors, including two -carotenes recently identified in a region close to the reaction center, which provided important clues to the secondary electron transfer pathways around the reaction center. Furthermore, possible ligands for the Mn-cluster were determined. In particular, the C terminus of D1 polypeptide was shown to be connected to the Mn cluster directly. The structural information obtained here provides important insights into the mechanism of PSII reactions.

  14. Crystal structure of oxygen-evolving photosystem II from Thermosynechococcus vulcanus at 3.7-A resolution.

    PubMed

    Kamiya, Nobuo; Shen, Jian-Ren

    2003-01-01

    Photosystem II (PSII) is a multisubunit membrane protein complex performing light-induced electron transfer and water-splitting reactions, leading to the formation of molecular oxygen. The first crystal structure of PSII from a thermophilic cyanobacterium Thermosynechococcus elongatus was reported recently [Zouni, A., Witt, H. T., Kern, J., Fromme, P., Krauss, N., Saenger, W. & Orth, P. (2001) Nature 409, 739-743)] at 3.8-A resolution. To analyze the PSII structure in more detail, we have obtained the crystal structure of PSII from another thermophilic cyanobacterium, Thermosynechococcus vulcanus, at 3.7-A resolution. The present structure was built on the basis of the sequences of PSII large subunits D1, D2, CP47, and CP43; extrinsic 33- and 12-kDa proteins and cytochrome c550; and several low molecular mass subunits, among which the structure of the 12-kDa protein was not reported previously. This yielded much information concerning the molecular interactions within this large protein complex. We also show the arrangement of chlorophylls and cofactors, including two beta-carotenes recently identified in a region close to the reaction center, which provided important clues to the secondary electron transfer pathways around the reaction center. Furthermore, possible ligands for the Mn-cluster were determined. In particular, the C terminus of D1 polypeptide was shown to be connected to the Mn cluster directly. The structural information obtained here provides important insights into the mechanism of PSII reactions.

  15. Crystal structure of oxygen-evolving photosystem II from Thermosynechococcus vulcanus at 3.7-Å resolution

    PubMed Central

    Kamiya, Nobuo; Shen, Jian-Ren

    2003-01-01

    Photosystem II (PSII) is a multisubunit membrane protein complex performing light-induced electron transfer and water-splitting reactions, leading to the formation of molecular oxygen. The first crystal structure of PSII from a thermophilic cyanobacterium Thermosynechococcus elongatus was reported recently [Zouni, A., Witt, H. T., Kern, J., Fromme, P., Krauss, N., Saenger, W. & Orth, P. (2001) Nature 409, 739–743)] at 3.8-Å resolution. To analyze the PSII structure in more detail, we have obtained the crystal structure of PSII from another thermophilic cyanobacterium, Thermosynechococcus vulcanus, at 3.7-Å resolution. The present structure was built on the basis of the sequences of PSII large subunits D1, D2, CP47, and CP43; extrinsic 33- and 12-kDa proteins and cytochrome c550; and several low molecular mass subunits, among which the structure of the 12-kDa protein was not reported previously. This yielded much information concerning the molecular interactions within this large protein complex. We also show the arrangement of chlorophylls and cofactors, including two β-carotenes recently identified in a region close to the reaction center, which provided important clues to the secondary electron transfer pathways around the reaction center. Furthermore, possible ligands for the Mn-cluster were determined. In particular, the C terminus of D1 polypeptide was shown to be connected to the Mn cluster directly. The structural information obtained here provides important insights into the mechanism of PSII reactions. PMID:12518057

  16. QM/MM study of the S2 to S3 transition reaction in the oxygen-evolving complex of photosystem II

    NASA Astrophysics Data System (ADS)

    Shoji, Mitsuo; Isobe, Hiroshi; Yamaguchi, Kizashi

    2015-09-01

    Catalytic reactions of the proton and electron transfers occurring at the oxygen-evolving complex (OEC) of photosystem II during the S2-S3 transition were investigated by the quantum mechanics/molecular mechanics (QM/MM) methodology. Two favorable reaction pathways were elucidated. Both reactions start by moving the Ca-bound water (W3) to the vacant Mn(III) coordination at the left-opened (L) or right-opened (R) form. The former reaction pathway, in which W3 coordinates to the Mn4 at the S2-L form, has lower activation barriers than the latter. Thus, easier proton transfers from W3 to the Tyr161 phenol anion can be performed.

  17. Nucleotide sequence of psbQ gene for 16-kDa protein of oxygen-evolving complex from Arabidopsis thaliana and regulation of its expression.

    PubMed

    Grover, M; Gaur, T; Kochhar, A; Maheshwari, S C; Tyagi, A K

    1999-06-30

    The psbQ gene encoding a 16-kDa polypeptide of the oxygen-evolving complex of photosystem II has been isolated from Arabidopsis thaliana and characterized. The gene consists of a 28 nucleotide long leader sequence, two introns and three exons encoding a 223-amino-acid precursor polypeptide. The first 75 amino acids act as a transit peptide for the translocation of the polypeptide into the thylakoid lumen. Expression studies show that the gene is light-inducible and expresses only in green tissues with high steady-state mRNA levels in leaves. Using this gene as a probe, restriction fragment length polymorphism between two ecotypes, Columbia and Estland, has also been detected. PMID:10470848

  18. {sup 35}Mn ESE-ENDOR of a mixed valence Mn(III)Mn(IV) complex: Comparison with the Mn cluster of the photosynthetic oxygen-evolving complex

    SciTech Connect

    Randall, D.W.; Sturgeon, B.E.; Ball, J.A.; Lorigan, G.A.; Chan, M.K.; Britt, R.D.; Klein, M.P. |; Armstrong, W.H.

    1995-11-29

    Analysis of {sup 55}Mn electron spin echo-electron nuclear double resonance (ESE-ENDOR) spectra obtained on a dinuclear mixed valence Mn(III)Mn(IV) complex [di-{mu}-oxotetrakis(2, 2`-bipyridine)dimanganese(III,IV)] (1) reveals the hyperfine and nuclear quadrupolar parameters for the spin I=5/2 {sup 55}Mn nucleus of both Mn(III) and Mn(IV) ions. The {sup 55}Mn ESE-ENDOR data obtained on the g = 2 Mn multiline EPR signal of the S{sub 2} state of the photosystem II oxygen-evolving complex demonstrate that this EPR signal cannot arise from a dinuclear Mn(III)-Mn(IV) center. The ENDOR spectra are consistent with a tetranuclear Mn cluster origin for the photosystem II multiline EPR signal. 75 refs., 7 figs., 2 tabs.

  19. Facile electrospinning preparation of phosphorus and nitrogen dual-doped cobalt-based carbon nanofibers as bifunctional electrocatalyst

    NASA Astrophysics Data System (ADS)

    Wang, Zhuang; Zuo, Pengjian; Fan, Liquan; Han, Jianan; Xiong, Yueping; Yin, Geping

    2016-04-01

    A novel electrochemical catalyst of phosphorus and nitrogen dual-doped cobalt-based carbon nanofibers (Cosbnd Nsbnd P-CNFs) is prepared by a facile and cost-effective electrospinning technique. Excellent features of the porous carbon nanofibers with large amounts of Co atoms, N/P-doping effect, abundant pyridinic-N and Cosbnd Nx clusters as catalytic active sites, and the advantages of the structure and composition result in a high catalytic efficiency. In alkaline or acidic media, Cosbnd Nsbnd P-CNFs exhibits remarkable electrocatalytic activities and kinetics for oxygen reduction reaction (ORR), superior methanol tolerance and stability, and a similar four-electron pathway. In addition, Cosbnd Nsbnd P-CNFs also shows excellent performance for hydrogen evolution reaction (HER), offering a low onset potential of -0.216 V and a stable current density of 10 mA cm-2 at potential of -0.248 V. The mechanism of ORR and HER catalytic active site arises from the doping of N/P atoms in the Co-based CNFs, which is responsible for the excellent electrocatalytic performance. Due to the excellent catalytic efficiencies, Cosbnd Nsbnd P-CNFs act as a promising catalyst material for fuel cells and water splitting technologies.

  20. Tyrosyl radicals in dehaloperoxidase: how nature deals with evolving an oxygen-binding globin to a biologically relevant peroxidase.

    PubMed

    Dumarieh, Rania; D'Antonio, Jennifer; Deliz-Liang, Alexandria; Smirnova, Tatyana; Svistunenko, Dimitri A; Ghiladi, Reza A

    2013-11-15

    Dehaloperoxidase (DHP) from Amphitrite ornata, having been shown to catalyze the hydrogen peroxide-dependent oxidation of trihalophenols to dihaloquinones, is the first oxygen binding globin that possesses a biologically relevant peroxidase activity. The catalytically competent species in DHP appears to be Compound ES, a reactive intermediate that contains both a ferryl heme and a tyrosyl radical. By simulating the EPR spectra of DHP activated by H2O2, Thompson et al. (Thompson, M. K., Franzen, S., Ghiladi, R. A., Reeder, B. J., and Svistunenko, D. A. (2010) J. Am. Chem. Soc. 132, 17501-17510) proposed that two different radicals, depending on the pH, are formed, one located on either Tyr-34 or Tyr-28 and the other on Tyr-38. To provide additional support for these simulation-based assignments and to deduce the role(s) that tyrosyl radicals play in DHP, stopped-flow UV-visible and rapid-freeze-quench EPR spectroscopic methods were employed to study radical formation in DHP when three tyrosine residues, Tyr-28, Tyr-34, and Tyr-38, were replaced either individually or in combination with phenylalanines. The results indicate that radicals form on all three tyrosines in DHP. Evidence for the formation of DHP Compound I in several tyrosine mutants was obtained. Variants that formed Compound I showed an increase in the catalytic rate for substrate oxidation but also an increase in heme bleaching, suggesting that the tyrosines are necessary for protecting the enzyme from oxidizing itself. This protective role of tyrosines is likely an evolutionary adaptation allowing DHP to avoid self-inflicted damage in the oxidative environment.

  1. Effect of Chloride Depletion on the Magnetic Properties and the Redox Leveling of the Oxygen-Evolving Complex in Photosystem II.

    PubMed

    Amin, Muhamed; Pokhrel, Ravi; Brudvig, Gary W; Badawi, Ashraf; Obayya, S S A

    2016-05-12

    Chloride is an essential cofactor in the oxygen-evolution reaction that takes place in photosystem II (PSII). The oxygen-evolving complex (OEC) is oxidized in a linear four-step photocatalytic cycle in which chloride is required for the OEC to advance beyond the S2 state. Here, using density functional theory, we compare the energetics and spin configuration of two different states of the Mn4CaO5 cluster in the S2 state: state A with Mn1(3+) and B with Mn4(3+) with and without chloride. The calculations suggest that model B with an S = 5/2 ground state occurs in the chloride-depleted PSII, which may explain the presence of the EPR signal at g = 4.1. Moreover, we use multiconformer continuum electrostatics to study the effect of chloride depletion on the redox potential associated with the S1/S2 and S2/S3 transitions. PMID:27077688

  2. Photocatalytic water oxidation by a mixed-valent Mn(III)₃Mn(IV)O₃ manganese oxo core that mimics the natural oxygen-evolving center.

    PubMed

    Al-Oweini, Rami; Sartorel, Andrea; Bassil, Bassem S; Natali, Mirco; Berardi, Serena; Scandola, Franco; Kortz, Ulrich; Bonchio, Marcella

    2014-10-13

    The functional core of oxygenic photosynthesis is in charge of catalytic water oxidation by a multi-redox Mn(III)/Mn(IV) manifold that evolves through five electronic states (S(i), where i=0-4). The synthetic model system of this catalytic cycle and of its S0→S4 intermediates is the expected turning point for artificial photosynthesis. The tetramanganese-substituted tungstosilicate [Mn(III)3Mn(IV)O3(CH3COO)3(A-α-SiW9O34)](6-)(Mn4POM) offers an unprecedented mimicry of the natural system in its reduced S0 state; it features a hybrid organic-inorganic coordination sphere and is anchored on a polyoxotungstate. Evidence for its photosynthetic properties when combined with [Ru(bpy)3](2+) and S2O8(2-) is obtained by nanosecond laser flash photolysis; its S0→S1 transition within milliseconds and multiple-hole-accumulating properties were studied. Photocatalytic oxygen evolution is achieved in a buffered medium (pH 5) with a quantum efficiency of 1.7%.

  3. The amino-terminal conserved domain of 4-hydroxy-3-methylbut-2-enyl diphosphate reductase is critical for its function in oxygen-evolving photosynthetic organisms.

    PubMed

    Hsieh, Wei-Yu; Hsieh, Ming-Hsiun

    2015-01-01

    4-hydroxy-3-methylbut-2-enyl diphosphate reductase (HDR), also known as isoprenoid synthesis H (IspH) or lysis-tolerant B (LytB), catalyzes the last step of the methylerythritol phosphate pathway to synthesize isopentenyl diphosphate and dimethylallyl diphosphate. The structure and reaction mechanism of IspH have been actively investigated in Escherichia coli but little is known in plants. Compared with the bacterial IspH, cyanobacterial and plant HDRs all contain an extra N-terminal conserved domain (NCD) that is essential for their function. Tyr72 in the NCD and several plant-specific residues around the central active site are critical for Arabidopsis HDR function. These results suggest that the structure and reaction mechanism of HDR/IspH may be different between plants and bacteria. The E. coli IspH is an iron-sulfur protein that is sensitive to oxygen. It is possible that the cyanobacterial HDR may independently evolve from the common ancestor of prokaryotes to obtain the NCD, which may protect the enzyme from high concentration of oxygen during photosynthesis.

  4. Thermal Decomposition of Calcium Perchlorate/Iron-Mineral Mixtures: Implications of the Evolved Oxygen from the Rocknest Eolian Deposit in Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Bruck, A. M.; Sutter, B.; Ming, D. W.; Mahaffy, P.

    2014-01-01

    A major oxygen release between 300 and 500 C was detected by the Mars Curiosity Rover Sample Analysis at Mars (SAM) instrument at the Rocknest eolian deposit. Thermal decomposition of perchlorate (ClO4-) salts in the Rocknest samples are a possible explanation for this evolved oxygen release. Releative to Na-, K-, Mg-, and Fe-perchlorate, the thermal decomposition of Ca-perchlorate in laboratory experiments released O2 in the temperature range (400-500degC) closest to the O2 release temperatures observed for the Rocknest material. Furthermore, calcium perchlorate could have been the source of Cl in the chlorinated-hydrocarbons species that were detected by SAM. Different components in the Martian soil could affect the decomposition temperature of calcium per-chlorate or another oxychlorine species. This interaction of the two components in the soil could result in O2 release temperatures consistent with those detected by SAM in the Rocknest materials. The decomposition temperatures of various alkali metal perchlorates are known to decrease in the presence of a catalyst. The objective of this work is to investigate catalytic interactions on calcium perchlorate from various iron-bearing minerals known to be present in the Rocknest material

  5. Characterization of the Sr(2+)- and Cd(2+)-Substituted Oxygen-Evolving Complex of Photosystem II by Quantum Mechanics/Molecular Mechanics Calculations.

    PubMed

    Pitari, Fabio; Bovi, Daniele; Narzi, Daniele; Guidoni, Leonardo

    2015-09-29

    The Mn4CaO5 cluster in the oxygen-evolving complex is the catalytic core of the Photosystem II (PSII) enzyme, responsible for the water splitting reaction in oxygenic photosynthesis. The role of the redox-inactive ion in the cluster has not yet been fully clarified, although several experimental data are available on Ca2+-depleted and Ca2+-substituted PSII complexes, indicating Sr2+-substituted PSII as the only modification that preserves oxygen evolution. In this work, we investigated the structural and electronic properties of the PSII catalytic core with Ca2+ replaced with Sr2+ and Cd2+ in the S2 state of the Kok−Joliot cycle by means of density functional theory and ab initio molecular dynamics based on a quantum mechanics/ molecular mechanics approach. Our calculations do not reveal significant differences between the substituted and wild-type systems in terms of geometries, thermodynamics, and kinetics of two previously identified intermediate states along the S2 to S3 transition, namely, the open cubane S2 A and closed cubane S2 B conformers. Conversely, our calculations show different pKa values for the water molecule bound to the three investigated heterocations. Specifically, for Cd-substituted PSII, the pKa value is 5.3 units smaller than the respective value in wild type Ca-PSII. On the basis of our results, we conclude that, assuming all the cations sharing the same binding site, the induced difference in the acidity of the binding pocket might influence the hydrogen bonding network and the redox levels to prevent the further evolution of the cycle toward the S3 state.

  6. Orientations of carboxylate groups coupled to the Mn cluster in the photosynthetic oxygen-evolving center as studied by polarized ATR-FTIR spectroscopy.

    PubMed

    Iizasa, Mitsuhiro; Suzuki, Hiroyuki; Noguchi, Takumi

    2010-04-13

    It is essential to clarify the structures and interactions of amino acids surrounding the Mn cluster in photosystem II (PSII) to understand the molecular mechanism of photosynthetic oxygen evolution. In this study, polarized attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was applied for the first time to PSII to investigate the orientation of carboxylate groups coupled to the oxygen-evolving Mn cluster. PSII membranes from spinach were oriented on the surface of a silicon ATR crystal, and flash-induced polarized ATR-FTIR difference spectra for the S(1) --> S(2) transition (S(2)/S(1) spectra) were obtained. The distribution of membrane orientations by mosaic spread was estimated from the semiquinone CO peak in polarized Q(A)(-)/Q(A) difference spectra recorded using the same oriented sample by buffer exchange. The orientations of carboxylate groups coupled to the Mn cluster were estimated from the dichroic ratios of the symmetric COO(-) bands in the polarized S(2)/S(1) ATR-FTIR spectra. We found that most of the carboxylate groups perturbed during the S(1) --> S(2) transition, due to direct ligation to the Mn cluster or though a hydrogen bond network, have orientations in a relatively narrow angle range of 34-48 degrees with respect to the membrane normal. Implications of the obtained orientations and the changes upon formation of S(2) are discussed on the basis of the information from previous FTIR studies and the X-ray structures. The results in this study show that polarized ATR-FTIR difference spectroscopy is a fruitful method for investigating the orientations and their reaction-induced changes in redox cofactors and coupled amino acid side chains in photosynthetic proteins.

  7. Theoretical study on OH{sup −} site and electronic spin state of oxygen-evolving complex in photosystem II at the dark S{sub 1} state

    SciTech Connect

    Hatakeyama, Makoto; Ogata, Koji; Nakamura, Shinichiro; Uchida, Waka

    2013-12-10

    Possible protonation and electronic-spin states of oxygen-evolving complex (OEC) in photosystem II have been investigated by using QM(DFT-UB3LYP)/MM(Amber) calculation, in order to elucidate which OEC state satisfies the known experimental results at the dark stable state (S{sub 1}), i.e. OEC involves Mn{sub 4}(III{sub 2},IV{sub 4})-cluster and a S=0 state as the lowest energy electronic-spin state at S{sub 1}. The configuration of Mn oxidation numbers and the lowest energy spin state within the Mn{sub 4}-cluster depend on the protonation state of one oxo-anion bridging three Mn ions. When all water-ligands and oxo-bridges form H{sub 2}O and O{sup 2−}, respectively, the resulting OEC model involved Mn{sub 4}(III{sub 2},IV{sub 2})-cluster and one S=0 state as the lowest energy spin state. To rationalize the O{sup 2−}-bridge model at S{sub 1} state, a new H{sup +}-release scheme during the H{sub 2}O-splitting reaction is proposed.

  8. Comparison of the manganese oxygen-evolving complex in photosystem II of spinach and Synechococcus sp. with multinuclear manganese model compounds by X-ray absorption spectroscopy

    SciTech Connect

    DeRose, V.J.; Mukerji, I.; Latimer, M.J. ); Yachandra, V.K.; Klein, M.P. ); Sauer, K. Lawrence Berkeley Lab., CA )

    1994-06-15

    The evaluation of Mn X-ray absorption fine structure (EXAFS) studies on the oxygen-evolving complex (OEC) from photosystem II is described for preparations from both spinach and the cyanobacterium Synechococcus sp. poised in the S[sub 1] and S[sub 2] states. In addition to reproducing previous results suggesting the presence of bis([mu]-oxo)-bridged Mn centers in the OEC, a Fourier transform peak due to scatterers at an average distance of > 3 [angstrom] is detected in both types of preparation. In addition, subtle but reproducible changes are found in the relative amplitudes of the Fourier transform peaks due to mainly O ([approximately]1.8 [angstrom]) and Mn ([approximately] 2.7 [angstrom]) neighbors upon cryogenic advance from the S[sub 1] to the S[sub 2] state. Analysis of the peak due to scatterers at [approximately] 3 [angstrom] favors assignment to (per 4 Mn in the OEC) 1-2 heavy atom (Mn, Ca) scatterers at an average distance of 3.3-3.4 [angstrom]. The EXAFS data of several multinuclear Mn model compounds containing such scattering interactions are analyzed and compared with the data for the OEC. Structural models for the OEC are evaluated on the basis of these results. 40 refs., 9 figs., 5 tabs.

  9. Characterization of fabricated cobalt-based alloy/nano bioactive glass composites.

    PubMed

    Bafandeh, Mohammad Reza; Gharahkhani, Raziyeh; Fathi, Mohammad Hossein

    2016-12-01

    In this work, cobalt-based alloy/nano bioactive glass (NBG) composites with 10, 15 and 20wt% NBG were prepared and their bioactivity after immersion in simulated body fluid (SBF) for 1 to 4weeks was studied. Scanning electron microscopy images of two- step sintered composites revealed relatively dense microstructure. The results showed that density of composite samples decreased with increase in NBG amount. The microstructure analysis as well as energy dispersive X-ray analysis (EDX) revealed that small amount of calcium phosphate phases precipitates on the surface of composite samples after 1week immersion in SBF. After 2weeks immersion, considerable amounts of cauliflower-like shaped precipitations were seen on the surface of the composites. Based on EDX analysis, these precipitations were composed mainly from Ca, P and Si. The observed bands in the Fourier transform infrared spectroscopy of immersed composites samples for 4weeks in SBF, were characteristic bands of hydroxyapatite. Therefore it is possible to form hydroxyapatite layer on the surface of composite samples during immersion in SBF. The results indicated that prepared composites unlike cobalt-based alloy are bioactive, promising their possibility for implant applications. PMID:27612763

  10. Characterization of fabricated cobalt-based alloy/nano bioactive glass composites.

    PubMed

    Bafandeh, Mohammad Reza; Gharahkhani, Raziyeh; Fathi, Mohammad Hossein

    2016-12-01

    In this work, cobalt-based alloy/nano bioactive glass (NBG) composites with 10, 15 and 20wt% NBG were prepared and their bioactivity after immersion in simulated body fluid (SBF) for 1 to 4weeks was studied. Scanning electron microscopy images of two- step sintered composites revealed relatively dense microstructure. The results showed that density of composite samples decreased with increase in NBG amount. The microstructure analysis as well as energy dispersive X-ray analysis (EDX) revealed that small amount of calcium phosphate phases precipitates on the surface of composite samples after 1week immersion in SBF. After 2weeks immersion, considerable amounts of cauliflower-like shaped precipitations were seen on the surface of the composites. Based on EDX analysis, these precipitations were composed mainly from Ca, P and Si. The observed bands in the Fourier transform infrared spectroscopy of immersed composites samples for 4weeks in SBF, were characteristic bands of hydroxyapatite. Therefore it is possible to form hydroxyapatite layer on the surface of composite samples during immersion in SBF. The results indicated that prepared composites unlike cobalt-based alloy are bioactive, promising their possibility for implant applications.

  11. The resistance of selected high strength alloys to embrittlement by a hydrogen environment. [iron and cobalt base alloys

    NASA Technical Reports Server (NTRS)

    Benson, R. B., Jr.

    1974-01-01

    Selected high strength iron base and cobalt base alloys were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature. These alloys were strengthened initially by cold working which produced strain induced martensite and fcc mechanical twins in an fcc matrix. Heat treatment of the cobalt base alloy after cold working produced carbide precipitates with retention of an hcp epsilon phase which increased the yield strength level. High strength alloys can be produced which have some resistance to degradation of mechanical properties by a hydrogen environment under certain conditions.

  12. Production of hydrogen in non oxygen-evolving systems: co-produced hydrogen as a bonus in the photodegradation of organic pollutants and hydrogen sulfide

    SciTech Connect

    Sartoretti, C. Jorand; Ulmann, M.; Augustynski, J. ); Linkous, C.A. )

    2000-01-01

    This report was prepared as part of the documentation of Annex 10 (Photoproduction of Hydrogen) of the IEA Hydrogen Agreement. Subtask A of this Annex concerned photo-electrochemical hydrogen production, with an emphasis on direct water splitting. However, studies of non oxygen-evolving systems were also included in view of their interesting potential for combined hydrogen production and waste degradation. Annex 10 was operative from 1 March 1995 until 1 October 1998. One of the collaborative projects involved scientists from the Universities of Geneva and Bern, and the Federal Institute of Technology in Laussane, Switzerland. A device consisting of a photoelectrochemical cell (PEC) with a WO{sub 3} photoanode connected in series with a so-called Grazel cell (a dye sensitized liquid junction photovoltaic cell) was developed and studied in this project. Part of these studies concerned the combination of hydrogen production with degradation of organic pollutants, as described in Chapter 3 of this report. For completeness, a review of the state of the art of organic waste treatment is included in Chapter 2. Most of the work at the University of Geneva, under the supervision of Prof. J. Augustynski, was focused on the development and testing of efficient WO{sub 3} photoanodes for the photoelectrochemical degradation of organic waste solutions. Two types of WO{sub 3} anodes were developed: non transparent bulk photoanodes and non-particle-based transparent film photoanodes. Both types were tested for degradation and proved to be very efficient in dilute solutions. For instance, a solar-to-chemical energy conversion efficiency of 9% was obtained by operating the device in a 0.01M solution of methanol (as compared to about 4% obtained for direct water splitting with the same device). These organic compounds are oxidized to CO{sub 2} by the photocurrent produced by the photoanode. The advantages of this procedure over conventional electrolytic degradation are that much (an

  13. Oxyanion induced variations in domain structure for amorphous cobalt oxide oxygen evolving catalysts, resolved by X-ray pair distribution function analysis.

    PubMed

    Kwon, Gihan; Kokhan, Oleksandr; Han, Ali; Chapman, Karena W; Chupas, Peter J; Du, Pingwu; Tiede, David M

    2015-12-01

    Amorphous thin film oxygen evolving catalysts, OECs, of first-row transition metals show promise to serve as self-assembling photoanode materials in solar-driven, photoelectrochemical `artificial leaf' devices. This report demonstrates the ability to use high-energy X-ray scattering and atomic pair distribution function analysis, PDF, to resolve structure in amorphous metal oxide catalyst films. The analysis is applied here to resolve domain structure differences induced by oxyanion substitution during the electrochemical assembly of amorphous cobalt oxide catalyst films, Co-OEC. PDF patterns for Co-OEC films formed using phosphate, Pi, methylphosphate, MPi, and borate, Bi, electrolyte buffers show that the resulting domains vary in size following the sequence Pi < MPi < Bi. The increases in domain size for CoMPi and CoBi were found to be correlated with increases in the contributions from bilayer and trilayer stacked domains having structures intermediate between those of the LiCoOO and CoO(OH) mineral forms. The lattice structures and offset stacking of adjacent layers in the partially stacked CoMPi and CoBi domains were best matched to those in the LiCoOO layered structure. The results demonstrate the ability of PDF analysis to elucidate features of domain size, structure, defect content and mesoscale organization for amorphous metal oxide catalysts that are not readily accessed by other X-ray techniques. PDF structure analysis is shown to provide a way to characterize domain structures in different forms of amorphous oxide catalysts, and hence provide an opportunity to investigate correlations between domain structure and catalytic activity.

  14. Oxyanion induced variations in domain structure for amorphous cobalt oxide oxygen evolving catalysts, resolved by X-ray pair distribution function analysis

    PubMed Central

    Kwon, Gihan; Kokhan, Oleksandr; Han, Ali; Chapman, Karena W.; Chupas, Peter J.; Du, Pingwu; Tiede, David M.

    2015-01-01

    Amorphous thin film oxygen evolving catalysts, OECs, of first-row transition metals show promise to serve as self-assembling photoanode materials in solar-driven, photoelectrochemical ‘artificial leaf’ devices. This report demonstrates the ability to use high-energy X-ray scattering and atomic pair distribution function analysis, PDF, to resolve structure in amorphous metal oxide catalyst films. The analysis is applied here to resolve domain structure differences induced by oxyanion substitution during the electrochemical assembly of amorphous cobalt oxide catalyst films, Co-OEC. PDF patterns for Co-OEC films formed using phosphate, Pi, methylphosphate, MPi, and borate, Bi, electrolyte buffers show that the resulting domains vary in size following the sequence Pi < MPi < Bi. The increases in domain size for CoMPi and CoBi were found to be correlated with increases in the contributions from bilayer and trilayer stacked domains having structures intermediate between those of the LiCoOO and CoO(OH) mineral forms. The lattice structures and offset stacking of adjacent layers in the partially stacked CoMPi and CoBi domains were best matched to those in the LiCoOO layered structure. The results demonstrate the ability of PDF analysis to elucidate features of domain size, structure, defect content and mesoscale organization for amorphous metal oxide catalysts that are not readily accessed by other X-ray techniques. PDF structure analysis is shown to provide a way to characterize domain structures in different forms of amorphous oxide catalysts, and hence provide an opportunity to investigate correlations between domain structure and catalytic activity. PMID:26634728

  15. Oxyanion Induced Variations in Domain Structure for Amorphous Cobalt Oxide Oxygen Evolving Catalysts, Resolved by X-ray Pair Distribution Function Analysis

    SciTech Connect

    Kwon, Gihan; Kokhan, Oleksandr; Han, Ali; Chapman, Karena W.; Chupas, Peter J.; Du, Pingwu; Tiede, David M.

    2015-12-01

    Amorphous thin film oxygen evolving catalysts, OECs, of first-row transition metals show promise to serve as self-assembling photoanode materials in solar-driven, photoelectrochemical `artificial leaf' devices. This report demonstrates the ability to use high-energy X-ray scattering and atomic pair distribution function analysis, PDF, to resolve structure in amorphous metal oxide catalyst films. The analysis is applied here to resolve domain structure differences induced by oxyanion substitution during the electrochemical assembly of amorphous cobalt oxide catalyst films, Co-OEC. PDF patterns for Co-OEC films formed using phosphate, Pi, methylphosphate, MPi, and borate, Bi, electrolyte buffers show that the resulting domains vary in size following the sequence Pi < MPi < Bi. The increases in domain size for CoMPi and CoBi were found to be correlated with increases in the contributions from bilayer and trilayer stacked domains having structures intermediate between those of the LiCoOO and CoO(OH) mineral forms. The lattice structures and offset stacking of adjacent layers in the partially stacked CoMPi and CoBi domains were best matched to those in the LiCoOO layered structure. The results demonstrate the ability of PDF analysis to elucidate features of domain size, structure, defect content and mesoscale organization for amorphous metal oxide catalysts that are not readily accessed by other X-ray techniques. Finally, PDF structure analysis is shown to provide a way to characterize domain structures in different forms of amorphous oxide catalysts, and hence provide an opportunity to investigate correlations between domain structure and catalytic activity.

  16. Oxyanion Induced Variations in Domain Structure for Amorphous Cobalt Oxide Oxygen Evolving Catalysts, Resolved by X-ray Pair Distribution Function Analysis

    DOE PAGES

    Kwon, Gihan; Kokhan, Oleksandr; Han, Ali; Chapman, Karena W.; Chupas, Peter J.; Du, Pingwu; Tiede, David M.

    2015-12-01

    Amorphous thin film oxygen evolving catalysts, OECs, of first-row transition metals show promise to serve as self-assembling photoanode materials in solar-driven, photoelectrochemical `artificial leaf' devices. This report demonstrates the ability to use high-energy X-ray scattering and atomic pair distribution function analysis, PDF, to resolve structure in amorphous metal oxide catalyst films. The analysis is applied here to resolve domain structure differences induced by oxyanion substitution during the electrochemical assembly of amorphous cobalt oxide catalyst films, Co-OEC. PDF patterns for Co-OEC films formed using phosphate, Pi, methylphosphate, MPi, and borate, Bi, electrolyte buffers show that the resulting domains vary in sizemore » following the sequence Pi < MPi < Bi. The increases in domain size for CoMPi and CoBi were found to be correlated with increases in the contributions from bilayer and trilayer stacked domains having structures intermediate between those of the LiCoOO and CoO(OH) mineral forms. The lattice structures and offset stacking of adjacent layers in the partially stacked CoMPi and CoBi domains were best matched to those in the LiCoOO layered structure. The results demonstrate the ability of PDF analysis to elucidate features of domain size, structure, defect content and mesoscale organization for amorphous metal oxide catalysts that are not readily accessed by other X-ray techniques. Finally, PDF structure analysis is shown to provide a way to characterize domain structures in different forms of amorphous oxide catalysts, and hence provide an opportunity to investigate correlations between domain structure and catalytic activity.« less

  17. Structure, ligands and substrate coordination of the oxygen-evolving complex of photosystem II in the S2 state: a combined EPR and DFT study.

    PubMed

    Lohmiller, Thomas; Krewald, Vera; Navarro, Montserrat Pérez; Retegan, Marius; Rapatskiy, Leonid; Nowaczyk, Marc M; Boussac, Alain; Neese, Frank; Lubitz, Wolfgang; Pantazis, Dimitrios A; Cox, Nicholas

    2014-06-28

    The S2 state of the oxygen-evolving complex of photosystem II, which consists of a Mn4O5Ca cofactor, is EPR-active, typically displaying a multiline signal, which arises from a ground spin state of total spin ST = 1/2. The precise appearance of the signal varies amongst different photosynthetic species, preparation and solvent conditions/compositions. Over the past five years, using the model species Thermosynechococcus elongatus, we have examined modifications that induce changes in the multiline signal, i.e. Ca(2+)/Sr(2+)-substitution and the binding of ammonia, to ascertain how structural perturbations of the cluster are reflected in its magnetic/electronic properties. This refined analysis, which now includes high-field (W-band) data, demonstrates that the electronic structure of the S2 state is essentially invariant to these modifications. This assessment is based on spectroscopies that examine the metal centres themselves (EPR, (55)Mn-ENDOR) and their first coordination sphere ligands ((14)N/(15)N- and (17)O-ESEEM, -HYSCORE and -EDNMR). In addition, extended quantum mechanical models from broken-symmetry DFT now reproduce all EPR, (55)Mn and (14)N experimental magnetic observables, with the inclusion of second coordination sphere ligands being crucial for accurately describing the interaction of NH3 with the Mn tetramer. These results support a mechanism of multiline heterogeneity reported for species differences and the effect of methanol [Biochim. Biophys. Acta, Bioenerg., 2011, 1807, 829], involving small changes in the magnetic connectivity of the solvent accessible outer MnA4 to the cuboidal unit Mn3O3Ca, resulting in predictable changes of the measured effective (55)Mn hyperfine tensors. Sr(2+) and NH3 replacement both affect the observed (17)O-EDNMR signal envelope supporting the assignment of O5 as the exchangeable μ-oxo bridge and it acting as the first site of substrate inclusion.

  18. Three-dimensional electron cryo-microscopy study of the extrinsic domains of the oxygen-evolving complex of spinach: assignment of the PsbO protein.

    PubMed

    Nield, Jon; Balsera, Monica; De Las Rivas, Javier; Barber, J

    2002-04-26

    Three independent three-dimensional reconstructions of the spinach photosystem II-light-harvesting complex supercomplex were derived from single particle analyses of non-stained, vitrified samples imaged by electron microscopy. Each reconstruction was found to differ significantly in the composition of the lumenal oxygen-evolving complex extrinsic proteins. From difference mapping, aided by electron microscopy of negatively stained selectively washed samples, regions of density were assigned to the PsbO and PsbP/PsbQ proteins. Interpretation of the density assigned to the PsbO protein was explored using computer-aided structural predictions. PsbO is calculated to be mainly a beta-protein (38% beta) composed of two domains within an overall elongated shape (Pazos, F., Heredia, P., Valencia, A., and De Las Rivas, J. (2001) Proteins Struct. Funct. Genet. 45, 372-381). The positioning and fitting of the proposed structural model for the PsbO protein within the three-dimensional map indicated that there is a single copy per reaction center. Moreover, the structural model derived for PsbO, together with difference mapping, indicates that this protein stretches across the surface of the reaction center with its N- and C-terminal domains located toward the CP47 and CP43 side, respectively. This structural assignment is discussed in terms of the recent x-ray-derived cyanobacterial model of PSII (Zouni, A., Witt, H.-T., Kern, J., Fromme, P., Krauss, N., Saenger, W., and Orth, P. (2001) Nature 409, 739-743).

  19. The Basic Properties of the Electronic Structure of the Oxygen-evolving Complex of Photosystem II Are Not Perturbed by Ca2+ Removal*

    PubMed Central

    Lohmiller, Thomas; Cox, Nicholas; Su, Ji-Hu; Messinger, Johannes; Lubitz, Wolfgang

    2012-01-01

    Ca2+ is an integral component of the Mn4O5Ca cluster of the oxygen-evolving complex in photosystem II (PS II). Its removal leads to the loss of the water oxidizing functionality. The S2′ state of the Ca2+-depleted cluster from spinach is examined by X- and Q-band EPR and 55Mn electron nuclear double resonance (ENDOR) spectroscopy. Spectral simulations demonstrate that upon Ca2+ removal, its electronic structure remains essentially unaltered, i.e. that of a manganese tetramer. No redistribution of the manganese valence states and only minor perturbation of the exchange interactions between the manganese ions were found. Interestingly, the S2′ state in spinach PS II is very similar to the native S2 state of Thermosynechococcus elongatus in terms of spin state energies and insensitivity to methanol addition. These results assign the Ca2+ a functional as opposed to a structural role in water splitting catalysis, such as (i) being essential for efficient proton-coupled electron transfer between YZ and the manganese cluster and/or (ii) providing an initial binding site for substrate water. Additionally, a novel 55Mn2+ signal, detected by Q-band pulse EPR and ENDOR, was observed in Ca2+-depleted PS II. Mn2+ titration, monitored by 55Mn ENDOR, revealed a specific Mn2+ binding site with a submicromolar KD. Ca2+ titration of Mn2+-loaded, Ca2+-depleted PS II demonstrated that the site is reversibly made accessible to Mn2+ by Ca2+ depletion and reconstitution. Mn2+ is proposed to bind at one of the extrinsic subunits. This process is possibly relevant for the formation of the Mn4O5Ca cluster during photoassembly and/or D1 repair. PMID:22549771

  20. Tuning the Magnetic Properties of Cobalt-Based Metallic Glass Nanocomposites

    NASA Astrophysics Data System (ADS)

    Veligatla, Medha; Das, Santanu; Lee, Won Ki; Hwang, Junyeon; Thumthan, Orathai; Hao, Yaowu; Mukherjee, Sundeep

    2016-01-01

    Temperature-induced variation in magnetic properties for cobalt-based metallic glass was investigated. The formation of metastable nanocrystalline phases prior to complete devitrification and their effect on magnetic properties for Co72B19.2Si4.8Cr4 metallic glass was studied. The nature, shape, and distribution of the intermediate nanocrystalline phases were characterized using transmission electron microscopy and x-ray diffraction. A drastic change in magnetic properties was found in going from a fully amorphous state to different stages of nanocrystallization. The coercivity changes from amorphous soft magnetic state ( H c ~ 0.12 Oe) to a nanocrystalline-dispersed hard magnetic state ( H c ~ 187 Oe), with no significant change in saturation magnetization. This suggests potential use in futuristic magnetic switches, fluxgate sensors, and electromagnetic shielding devices.

  1. Application of Two Cobalt-Based Metal-Organic Frameworks as Oxidative Desulfurization Catalysts.

    PubMed

    Masoomi, Mohammad Yaser; Bagheri, Minoo; Morsali, Ali

    2015-12-01

    Two new porous cobalt-based metal-organic frameworks, [Co6(oba)5(OH)2(H2O)2(DMF)4]n · 5DMF (TMU-10) and [Co3(oba)3(O) (Py)0.5] n · 4DMF · Py (TMU-12) have been synthesized by solvothermal method using a nonlinear dicarboxylate ligand. Under mild reaction conditions, these compounds exhibited good catalytic activity and reusability in oxidative desulfurization (ODS) reaction of model oil which was prepared by dissolving dibenzothiophene (DBT) in n-hexane. FT-IR and Mass analysis showed that the main product of DBT oxidation is its corresponding sulfone, which was adsorbed on the surfaces of catalysts. The activation energy was obtained as 13.4 kJ/mol. PMID:26571113

  2. Life has Evolved to Evolve

    NASA Astrophysics Data System (ADS)

    Deem, Michael

    2006-03-01

    Concomitant with the evolution of biological diversity must have been the evolution of mechanisms that facilitate evolution, due to the essentially infinite complexity of protein sequence space. We describe how evolvability can be an object of Darwinian selection, emphasizing the collective nature of the process. Rapid or dramatic environmental change leads to selection for greater evolvability. The selective pressure for large scale genetic moves, such as DNA exchange, becomes increasingly strong as the environmental conditions become more uncertain. These results demonstrate that evolvability is a selectable trait and allow for the explanation of a large body of experimental results. Many observations within evolutionary biology, heretofore considered evolutionary happenstance or accidents, are explained by selection for evolvability. As specific examaples, we discuss evolution within the immune system and evolution of drug resistant microrganisims.

  3. Water oxidation by amorphous cobalt-based oxides: volume activity and proton transfer to electrolyte bases.

    PubMed

    Klingan, Katharina; Ringleb, Franziska; Zaharieva, Ivelina; Heidkamp, Jonathan; Chernev, Petko; Gonzalez-Flores, Diego; Risch, Marcel; Fischer, Anna; Dau, Holger

    2014-05-01

    Water oxidation in the neutral pH regime catalyzed by amorphous transition-metal oxides is of high interest in energy science. Crucial determinants of electrocatalytic activity were investigated for a cobalt-based oxide film electrodeposited at various thicknesses on inert electrodes. For water oxidation at low current densities, the turnover frequency (TOF) per cobalt ion of the bulk material stayed fully constant for variation of the thickness of the oxide film by a factor of 100 (from about 15 nm to 1.5 μm). Thickness variation changed neither the nanostructure of the outer film surface nor the atomic structure of the oxide catalyst significantly. These findings imply catalytic activity of the bulk hydrated oxide material. Nonclassical dependence on pH was observed. For buffered electrolytes with pKa values of the buffer base ranging from 4.7 (acetate) to 10.3 (hydrogen carbonate), the catalytic activity reflected the protonation state of the buffer base in the electrolyte solution directly and not the intrinsic catalytic properties of the oxide itself. It is proposed that catalysis of water oxidation occurs within the bulk hydrated oxide film at the margins of cobalt oxide fragments of molecular dimensions. At high current densities, the availability of a proton-accepting base at the catalyst-electrolyte interface controls the rate of water oxidation. The reported findings may be of general relevance for water oxidation catalyzed at moderate pH by amorphous transition-metal oxides.

  4. A Cobalt-based Catalyst for CO2 Hydrogenation Under Ambient Conditions

    SciTech Connect

    Jeletic, Matthew S.; Mock, Michael T.; Appel, Aaron M.; Linehan, John C.

    2013-08-07

    Due to the continually rising levels of CO2 in the atmosphere, research into conversion of CO2 into fuels using carbon-neutral energy is currently an important topic in catalysis. Recent research on molecular catalysts has led to improved rates of CO2 conversion to formate, but unfortunately the resulting catalysts are based on precious metals such as iridium, ruthenium and rhodium and require high temperatures and high pressures for catalytic reactivity. Using established thermodynamic properties, a cobalt-based catalyst system has been designed for the catalytic production of formate from CO2 and H2, even at room temperature and one atmosphere of pressure. Using Co(dmpe)2H (dmpe is bis(dimethylphosphino)ethane) as a catalyst in tetrahydrofuran, room temperature turnover frequencies of 3,400 h-1 at 1 atm of 1:1 CO2:H2 and 74,000 h-1 at 20 atm were obtained. These results highlight the value of basic thermodynamic properties in the rational design of catalysts. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle.

  5. Tracking of the organic species during the synthesis of cobalt-based nanoparticles in non-aqueous solution

    NASA Astrophysics Data System (ADS)

    Staniuk, M.; Niederberger, M.; Koziej, D.

    2014-08-01

    In this work we investigate the organic products of the synthesis of Co-based nanoparticles in benzyl alcohol. Our GC and in situ IR studies provide the experimental proofs for the formation of benzaldehyde, toluene and isopropanol in the reaction solution. These organic products can be correlated with formation of cobalt-based nanoparticles with oxidation state from 0 to 3+. These results shine the light on the complexity of organic and inorganic reactions in solution during crystallization of nanoparticles.

  6. MNA of Chlorinated Solvents and Fuel Oxygenates: Why it occurs, how it evolved, and using stable carbon isotopes to predict plume behavior

    EPA Science Inventory

    The organisms that degrade MTBE under anaerobic conditions are evolved to acquire energy for growth by using molecular hydrogen and carbonate ion to cleave methyl ether bonds. Methyl ether bonds are common in nature and the bond also occurs in MTBE. MTBE in contaminated ground...

  7. MNA for Chlorinated Solvents and Fuel Oxygenates: Why It Occurs, How It Evolved, and Using Stable Carbon Isotopes to Predict Plume Behavior

    EPA Science Inventory

    The organisms that degrade MtBE under anaerobic conditions are evolved to acquire energy for growth by using molecular hydrogen and carbonate ion to cleave methyl ether bonds. Methyl ether bonds are common in nature and the bond also occurs in MTBE. MTBE in contaminated ground...

  8. Biodegradation – Monitored Natural Attenuation (MNA) for Oxygenates: How it Evolved, why it Occurs and Using Stable Carbon Isotopes to Predict Plume Behavior

    EPA Science Inventory

    The organisms that degrade MtBE under anaerobic conditions are evolved to acquire energy for growth by using molecular hydrogen and carbonate ion to cleave methyl ether bonds. Methyl ether bonds are common in nature and the bond also occurs in MTBE. MTBE in contaminated ground...

  9. The Detection of Evolved Oxygen from the Rocknest Eolian Bedform Material by the Sample Analysis at Mars(SAM) instrument at the Mars Curiosity Landing Site

    NASA Technical Reports Server (NTRS)

    Sutter, B.; Archer, D.; Ming, D.; Eigenbrode, J. L.; Franz, H.; Glavin, D. P.; McAdam, A.; Mahaffy, P.; Stern, J.; Navarro-Gonzalex, R.; McKay, C.

    2013-01-01

    The Sample Analysis at Mars (SAM) instrument onboard the Curiosity rover detected an O2 gas release from the Rocknest eolain bedform (Fig. 1). The detection of perchlorate (ClO4-) by the Mars Phoenix Lander s Wet Chemistry Laboratory (WCL) [1] suggests that perchlorate is a possible candidate for evolved O2 release detected by SAM. The perchlorate would also serve as a source of chlorine in the chlorinated hydrocarbons detected by the SAM quadrupole mass spectrometer (QMS) and gas chromatography/mass spectrometer (GCMS) [2,3]. Chlorates (ClO3-) [4,5] and/or superoxides [6] may also be sources of evolved O2 from the Rocknest materials. The work objectives are to 1) evaluate the O2 release temperatures from Rocknest materials, 2) compare these O2 release temperatures with a series of perchlorates and chlorates, and 3) evaluate superoxide O2- sources and possible perchlorate interactions with other Rocknest phases during QMS analysis.

  10. Arabidopsis plants lacking PsbQ and PsbR subunits of the oxygen-evolving complex show altered PSII super-complex organization and short-term adaptive mechanisms.

    PubMed

    Allahverdiyeva, Yagut; Suorsa, Marjaana; Rossi, Fabio; Pavesi, Andrea; Kater, Martin M; Antonacci, Alessia; Tadini, Luca; Pribil, Mathias; Schneider, Anja; Wanner, Gerhard; Leister, Dario; Aro, Eva-Mari; Barbato, Roberto; Pesaresi, Paolo

    2013-08-01

    The oxygen-evolving complex of eukaryotic photosystem II (PSII) consists of four extrinsic subunits, PsbO (33 kDa), PsbP (23 kDa), PsbQ (17 kDa) and PsbR (10 kDa), encoded by seven nuclear genes, PsbO1 (At5g66570), PsbO2 (At3g50820), PsbP1 (At1g06680), PsbP2 (At2g30790), PsbQ1 (At4g21280), PsbQ2 (At4g05180) and PsbR (At1g79040). Using Arabidopsis insertion mutant lines, we show that PsbP1, but not PsbP2, is essential for photoautotrophic growth, whereas plants lacking both forms of PsbQ and/or PsbR show normal growth rates. Complete elimination of PsbQ has a minor effect on PSII function, but plants lacking PsbR or both PsbR and PsbQ are characterized by more pronounced defects in PSII activity. Gene expression and immunoblot analyses indicate that accumulation of each of these proteins is highly dependent on the presence of the others, and is controlled at the post-transcriptional level, whereas PsbO stability appears to be less sensitive to depletion of other subunits of the oxygen-evolving complex. In addition, comparison of levels of the PSII super-complex in wild-type and mutant leaves reveals the importance of the individual subunits of the oxygen-evolving complex for the supramolecular organization of PSII and their influence on the rate of state transitions.

  11. Analysis of the Import of Carboxyl-Terminal Truncations of the 23-Kilodalton Subunit of the Oxygen-Evolving Complex Suggests That Its Structure Is an Important Determinant for Thylakoid Transport.

    PubMed Central

    Roffey, R. A.; Theg, S. M.

    1996-01-01

    A series of deletions from the carboxyl terminus of the 23-kD subunit of the photosynthetic oxygen-evolving complex OE23 revealed that these truncations result in various degrees of inhibition of translocation across thylakoid membranes and their subsequent assembly to the oxygen-evolving complex. Import of in vitro translated precursors across the chloroplast envelopes was not inhibited by these truncations. Time-course studies of the import of truncated OE23 precursors into intact chloroplasts revealed that the stromal intermediate was subsequently translocated into the thylakoid lumen, where it was processed to a smaller size and rapidly degraded. In contrast to the full-length OE23 intermediate, the truncated intermediate forms that accumulated in the stroma as a result of de-energization of thylakoid membranes could be found associated with the membrane rather than free in the stroma. Protease digestion experiments revealed that the deletions evidently altered the folded conformation of the protein. These results suggest that the carboxyl-terminal portion of the OE23 precursor is important for the maintenance of an optimal structure for import into thylakoids, implying that the efficient translocation of OE23 requires the protein to be correctly folded. In addition, the rapid degradation of the truncated forms of the processed OE23 within the lumen indicates that a protease (or proteases) active in the lumen can recognize and remove misfolded polypeptides. PMID:12226365

  12. Comparative coarsening kinetics of gamma prime precipitates in nickel and cobalt base superalloys

    NASA Astrophysics Data System (ADS)

    Meher, Subhashish

    The increasing technological need to push service conditions of structural materials to higher temperatures has motivated the development of several alloy systems. Among them, superalloys are an excellent candidate for high temperature applications because of their ability to form coherent ordered precipitates, which enable the retention of high strength close to their melting temperature. The accelerated kinetics of solute diffusion, with or without an added component of mechanical stress, leads to coarsening of the precipitates, and results in microstructural degradation, limiting the durability of the materials. Hence, the coarsening of precipitates has been a classical research problem for these alloys in service. The prolonged hunt for an alternative of nickel base superalloys with superior traits has gained hope after the recent discovery of Co-Al-W based alloys, which readily form high temperature gamma' precipitates, similar to Ni base superalloys. In the present study, coarsening behavior of gamma' precipitates in Co-10Al-10W (at. %) has been carried out at 800°C and 900°C. This study has, for the first time, obtained critical coarsening parameters in cobalt-base alloys. Apart from this, it has incorporated atomic scale compositional information across the gamma/gamma' interfaces into classical Cahn-Hilliard model for a better model of coarsening kinetics. The coarsening study of gamma' precipitates in Ni-14Al-7 Cr (at. %) has shown the importance of temporal evolution of the compositional width of the gamma/gamma' interfaces to the coarsening kinetics of gamma' precipitates. This study has introduced a novel, reproducible characterization method of crystallographic study of ordered phase by coupling of orientation microscopy with atom probe tomography (APT). Along with the detailed analysis of field evaporation behaviors of Ni and Co superalloys in APT, the present study determines the site occupancy of various solutes within ordered gamma' precipitates

  13. Cyclic Axial-Torsional Deformation Behavior of a Cobalt-Base Superalloy

    NASA Technical Reports Server (NTRS)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    1995-01-01

    The cyclic, high-temperature deformation behavior of a wrought cobalt-base super-alloy, Haynes 188, is investigated under combined axial and torsional loads. This is accomplished through the examination of hysteresis loops generated from a biaxial fatigue test program. A high-temperature axial, torsional, and combined axial-torsional fatigue database has been generated on Haynes 188 at 760 C. Cyclic loading tests have been conducted on uniform gage section tubular specimens in a servohydraulic axial-torsional test rig. Test control and data acquisition were accomplished with a minicomputer. The fatigue behavior of Haynes 188 at 760 C under axial, torsional, and combined axial-torsional loads and the monotonic and cyclic deformation behaviors under axial and torsional loads have been previously reported. In this paper, the cyclic hardening characteristics and typical hysteresis loops in the axial stress versus axial strain, shear stress ,versus engineering shear strain, axial strain versus engineering shear strain. and axial stress versus shear stress spaces are presented for cyclic in-phase and out-of-phase axial-torsional tests. For in-phase tests, three different values of the proportionality constant lambda (the ratio of engineering shear strain amplitude to axial strain amplitude, are examined, viz. 0.86, 1.73, and 3.46. In the out-of-phase tests, three different values of the phase angle, phi (between the axial and engineering shear strain waveforms), are studied, viz., 30, 60, and 90 degrees with lambda equals 1.73. The cyclic hardening behaviors of all the tests conducted on Haynes 188 at 760 C are evaluated using the von Mises equivalent stress-strain and the maximum shear stress-maximum engineering shear strain (Tresca) curves. Comparisons are also made between the hardening behaviors of cyclic axial, torsional, and combined in-phase (lambda = 1.73 and phi = 0) and out-of-phase (lambda = 1.73 and phi = 90') axial-torsional fatigue tests. These comparisons

  14. An Assessment of Cumulative Axial and Torsional Fatigue in a Cobalt-Base Superalloy

    NASA Technical Reports Server (NTRS)

    Kalluri, Sreeramesh; Bonacuse, Peter J.

    2010-01-01

    Cumulative fatigue under axial and torsional loading conditions can include both load-order (higMow and low/high) as well as load-type sequence (axial/torsional and torsional/axial) effects. Previously reported experimental studies on a cobalt-base superalloy, Haynes 188 at 538 C, addressed these effects. These studies characterized the cumulative axial and torsional fatigue behavior under high amplitude followed by low amplitude (Kalluri, S. and Bonacuse, P. J., "Cumulative Axial and Torsional Fatigue: An Investigation of Load-Type Sequance Effects," in Multiaxial Fatigue and Deformation: Testing and Prediction, ASTM STP 1387, S. Kalluri, and P. J. Bonacuse, Eds., American Society for Testing and Materials, West Conshohocken, PA, 2000, pp. 281-301) and low amplitude followed by high amplitude (Bonacuse, P. and Kalluri, S. "Sequenced Axial and Torsional Cumulative Fatigue: Low Amplitude Followed by High Amplitude Loading," Biaxial/Multiaxial Fatigue and Fracture, ESIS Publication 31, A. Carpinteri, M. De Freitas, and A. Spagnoli, Eds., Elsevier, New York, 2003, pp. 165-182) conditions. In both studies, experiments with the following four load-type sequences were performed: (a) axial/axial, (b) torsional/torsional, (c) axial/torsional, and (d) torsional/axial. In this paper, the cumulative axial and torsional fatigue data generated in the two previous studies are combined to generate a comprehensive cumulative fatigue database on both the load-order and load-type sequence effects. This comprehensive database is used to examine applicability of the Palmgren-langer-Miner linear damage rule and a nonlinear damage curve approach for Haynes 188 subjected to the load-order and load-type sequencing described above. Summations of life fractions from the experiments are compared to the predictions from both the linear and nonlinear cumulative fatigue damage approaches. The significance of load-order versus load-type sequence effects for axial and torsional loading conditions

  15. Thermodynamic Considerations of Contamination by Alloying Elements of Remelted End-of-Life Nickel- and Cobalt-Based Superalloys

    NASA Astrophysics Data System (ADS)

    Lu, Xin; Matsubae, Kazuyo; Nakajima, Kenichi; Nakamura, Shinichiro; Nagasaka, Tetsuya

    2016-06-01

    Cobalt and nickel are high-value commodity metals and are mostly used in the form of highly alloyed materials. The alloying elements used may cause contamination problems during recycling. To ensure maximum resource efficiency, an understanding of the removability of these alloying elements and the controllability of some of the primary alloying elements is essential with respect to the recycling of end-of-life (EoL) nickel- and cobalt-based superalloys by remelting. In this study, the distribution behaviors of approximately 30 elements that are usually present in EoL nickel- and cobalt-based superalloys in the solvent metal (nickel, cobalt, or nickel-cobalt alloy), oxide slag, and gas phases during the remelting were quantitatively evaluated using a thermodynamic approach. The results showed that most of the alloying elements can be removed either in the slag phase or into the gas phase. However, the removal of copper, tin, arsenic, and antimony by remelting is difficult, and they remain as tramp elements during the recycling. On the other hand, the distribution tendencies of iron, molybdenum, and tungsten can be controlled by changing the remelting conditions. To increase the resource efficiency of recycling, preventing contamination by the tramp elements and identifying the alloying compositions of EoL superalloys are significantly essential, which will require the development of efficient prior alloy-sorting systems and advanced separation technologies.

  16. Thermal cooling effects in the microstructure and properties of cast cobalt-base biomedical alloys

    NASA Astrophysics Data System (ADS)

    Vega Valer, Vladimir

    Joint replacement prosthesis is widely used in the biomedical field to provide a solution for dysfunctional human body joints. The demand for orthopedic knee and hip implants motivate scientists and manufacturers to develop novel materials or to increase the life of service and efficiency of current materials. Cobalt-base alloys have been investigated by various researchers for biomedical implantations. When these alloys contain Chromium, Molybdenum, and Carbon, they exhibit good tribological and mechanical properties, as well as excellent biocompatibility and corrosion resistance. In this study, the microstructure of cast Co-Cr-Mo-C alloy is purposely modified by inducing rapid solidification through fusion welding processes and solution annealing heat treatment (quenched in water at room temperature. In particular the effect of high cooling rates on the athermal phase transformation FCC(gamma)↔HCP(epsilon) on the alloy hardness and corrosion resistance is investigated. The Co-alloy microstructures were characterized using metallography and microscopy techniques. It was found that the as cast sample typically dendritic with dendritic grain sizes of approximately 150 microm and containing Cr-rich coarse carbide precipitates along the interdendritic boundaries. Solution annealing gives rise to a refined microstructure with grain size of 30 microm, common among Co-Cr-Mo alloys after heat treating. Alternatively, an ultrafine grain structure (between 2 and 10 microm) was developed in the fusion zone for specimens melted using Laser and TIG welding methods. When laser surface modification treatments were implemented, the developed solidification microstructure shifted from dendritic to a fine cellular morphology, with possible nanoscale carbide precipitates along the cellular boundaries. In turn, the solidified regions exhibited high hardness values (461.5HV), which exceeds by almost 110 points from the alloy in the as-cast condition. The amount of developed athermal

  17. Replacement of tyrosine D with phenylalanine affects the normal proton transfer pathways for the reduction of P680+ in oxygen-evolving photosystem II particles from Chlamydomonas.

    PubMed

    Jeans, C; Schilstra, M J; Ray, N; Husain, S; Minagawa, J; Nugent, J H A; Klug, D R

    2002-12-31

    We have probed the electrostatics of P680(+) reduction in oxygenic photosynthesis using histidine-tagged and histidine-tagged Y(D)-less Photosystem II cores. We make two main observations: (i) that His-tagged Chlamydomonas cores show kinetics which are essentially identical to those of Photosystem II enriched thylakoid membranes from spinach; (ii) that the microsecond kinetics, previously shown to be proton/hydrogen transfer limited [Schilstra et al. (1998) Biochemistry 37, 3974-3981], are significantly different in Y(D)-less Chlamydomonas particles when compared with both the His-tagged Chlamydomonas particles and the spinach membranes. The oscillatory nature of the kinetics in both Chlamydomonas samples is normal, indicating that S-state cycling is unaffected by either the histidine-tagging or the replacement of tyrosine D with phenylalanine. We propose that the effects on the proton-coupled electron transfers of P680(+) reduction in the absence of Y(D) are likely to be due to pK shifts of residues in a hydrogen-bonded network of amino acids in the vicinity of Y(Z). Tyrosine D is 35 A from Y(Z) and yet has a significant influence on proton-coupled electron transfer events in the vicinity of Y(Z). This finding emphasizes the delicacy of the proton balance that Photosystem II has to achieve during the water splitting process. PMID:12501204

  18. Large-scale QM/MM calculations of the CaMn4O5 cluster in the oxygen-evolving complex of photosystem II: Comparisons with EXAFS structures

    NASA Astrophysics Data System (ADS)

    Shoji, Mitsuo; Isobe, Hiroshi; Nakajima, Takahito; Yamaguchi, Kizashi

    2016-08-01

    Large-scale QM/MM calculations including hydrogen-bonding networks in the oxygen evolving complex (OEC) of photosystem II (PSII) were performed to elucidate the geometric structures of the CaMn4O5 cluster in the key catalytic states (Si (i = 0-3)). The optimized Mn-Mn, Ca-Mn and Mn-O distances by the large-scale QM/MM starting from the high-resolution XRD structure were consistent with those of the EXAFS experiments in the dark stable S1 state by the Berkeley and Berlin groups. The optimized geometrical parameters for other Si (i = 0, 2, 3) states were also consistent with those of EXAFS, indicating the importance of the large-scale QM/MM calculations for the PSII-OEC.

  19. Toward models for the full oxygen-evolving complex of photosystem II by ligand coordination to lower the symmetry of the Mn3CaO4 cubane: demonstration that electronic effects facilitate binding of a fifth metal.

    PubMed

    Kanady, Jacob S; Lin, Po-Heng; Carsch, Kurtis M; Nielsen, Robert J; Takase, Michael K; Goddard, William A; Agapie, Theodor

    2014-10-15

    Synthetic model compounds have been targeted to benchmark and better understand the electronic structure, geometry, spectroscopy, and reactivity of the oxygen-evolving complex (OEC) of photosystem II, a low-symmetry Mn4CaOn cluster. Herein, low-symmetry Mn(IV)3GdO4 and Mn(IV)3CaO4 cubanes are synthesized in a rational, stepwise fashion through desymmetrization by ligand substitution, causing significant cubane distortions. As a result of increased electron richness and desymmetrization, a specific μ3-oxo moiety of the Mn3CaO4 unit becomes more basic allowing for selective protonation. Coordination of a fifth metal ion, Ag(+), to the same site gives a Mn3CaAgO4 cluster that models the topology of the OEC by displaying both a cubane motif and a "dangler" transition metal. The present synthetic strategy provides a rational roadmap for accessing more accurate models of the biological catalyst.

  20. Modelling hourly dissolved oxygen concentration (DO) using dynamic evolving neural-fuzzy inference system (DENFIS)-based approach: case study of Klamath River at Miller Island Boat Ramp, OR, USA.

    PubMed

    Heddam, Salim

    2014-01-01

    In this study, we present application of an artificial intelligence (AI) technique model called dynamic evolving neural-fuzzy inference system (DENFIS) based on an evolving clustering method (ECM), for modelling dissolved oxygen concentration in a river. To demonstrate the forecasting capability of DENFIS, a one year period from 1 January 2009 to 30 December 2009, of hourly experimental water quality data collected by the United States Geological Survey (USGS Station No: 420853121505500) station at Klamath River at Miller Island Boat Ramp, OR, USA, were used for model development. Two DENFIS-based models are presented and compared. The two DENFIS systems are: (1) offline-based system named DENFIS-OF, and (2) online-based system, named DENFIS-ON. The input variables used for the two models are water pH, temperature, specific conductance, and sensor depth. The performances of the models are evaluated using root mean square errors (RMSE), mean absolute error (MAE), Willmott index of agreement (d) and correlation coefficient (CC) statistics. The lowest root mean square error and highest correlation coefficient values were obtained with the DENFIS-ON method. The results obtained with DENFIS models are compared with linear (multiple linear regression, MLR) and nonlinear (multi-layer perceptron neural networks, MLPNN) methods. This study demonstrates that DENFIS-ON investigated herein outperforms all the proposed techniques for DO modelling. PMID:24705953

  1. THE MASS-LOSS RETURN FROM EVOLVED STARS TO THE LARGE MAGELLANIC CLOUD. II. DUST PROPERTIES FOR OXYGEN-RICH ASYMPTOTIC GIANT BRANCH STARS

    SciTech Connect

    Sargent, Benjamin A.; Meixner, M.; Gordon, Karl D.; Srinivasan, S.; Kemper, F.; Woods, Paul M.; Tielens, A. G. G. M.; Speck, A. K.; Matsuura, M.; Bernard, J.-Ph.; Hony, S.; Marengo, M.; Sloan, G. C.

    2010-06-10

    We model multi-wavelength broadband UBVIJHK{sub s} and Spitzer IRAC and MIPS photometry and Infrared Spectrograph spectra from the SAGE and SAGE-Spectroscopy observing programs of two oxygen-rich asymptotic giant branch (O-rich AGB) stars in the Large Magellanic Cloud (LMC) using radiative transfer (RT) models of dust shells around stars. We chose a star from each of the bright and faint O-rich AGB populations found by earlier studies of the SAGE sample in order to derive a baseline set of dust properties to be used in the construction of an extensive grid of RT models of the O-rich AGB stars found in the SAGE surveys. From the bright O-rich AGB population, we chose HV 5715, and from the faint O-rich AGB population we chose SSTISAGE1C J052206.92-715017.6 (SSTSAGE052206). We found the complex indices of refraction of oxygen-deficient silicates from Ossenkopf et al. and a power law with exponential decay grain size distribution like what Kim et al. used but with {gamma} of -3.5, a {sub min} of 0.01 {mu}m, and a {sub 0} of 0.1 {mu}m to be reasonable dust properties for these models. There is a slight indication that the dust around the faint O-rich AGB may be more silica-rich than that around the bright O-rich AGB. Simple models of gas emission suggest a relatively extended gas envelope for the faint O-rich AGB star modeled, consistent with the relatively large dust shell inner radius for the same model. Our models of the data require the luminosity of SSTSAGE052206 and HV 5715 to be {approx}5100 L {sub sun} and {approx}36,000 L {sub sun}, respectively. This, combined with the stellar effective temperatures of 3700 K and 3500 K, respectively, that we find best fit the optical and near-infrared data, suggests stellar masses of {approx}3 M {sub sun} and {approx}7 M {sub sun}. This, in turn, suggests that HV 5715 is undergoing hot-bottom burning and that SSTSAGE052206 is not. Our models of SSTSAGE052206 and HV 5715 require dust shells of inner radius {approx}17 and

  2. Regolith Evolved Gas Analyzer

    NASA Technical Reports Server (NTRS)

    Hoffman, John H.; Hedgecock, Jud; Nienaber, Terry; Cooper, Bonnie; Allen, Carlton; Ming, Doug

    2000-01-01

    The Regolith Evolved Gas Analyzer (REGA) is a high-temperature furnace and mass spectrometer instrument for determining the mineralogical composition and reactivity of soil samples. REGA provides key mineralogical and reactivity data that is needed to understand the soil chemistry of an asteroid, which then aids in determining in-situ which materials should be selected for return to earth. REGA is capable of conducting a number of direct soil measurements that are unique to this instrument. These experimental measurements include: (1) Mass spectrum analysis of evolved gases from soil samples as they are heated from ambient temperature to 900 C; and (2) Identification of liberated chemicals, e.g., water, oxygen, sulfur, chlorine, and fluorine. REGA would be placed on the surface of a near earth asteroid. It is an autonomous instrument that is controlled from earth but does the analysis of regolith materials automatically. The REGA instrument consists of four primary components: (1) a flight-proven mass spectrometer, (2) a high-temperature furnace, (3) a soil handling system, and (4) a microcontroller. An external arm containing a scoop or drill gathers regolith samples. A sample is placed in the inlet orifice where the finest-grained particles are sifted into a metering volume and subsequently moved into a crucible. A movable arm then places the crucible in the furnace. The furnace is closed, thereby sealing the inner volume to collect the evolved gases for analysis. Owing to the very low g forces on an asteroid compared to Mars or the moon, the sample must be moved from inlet to crucible by mechanical means rather than by gravity. As the soil sample is heated through a programmed pattern, the gases evolved at each temperature are passed through a transfer tube to the mass spectrometer for analysis and identification. Return data from the instrument will lead to new insights and discoveries including: (1) Identification of the molecular masses of all of the gases

  3. Biogeochemistry: Oxygen burrowed away

    NASA Astrophysics Data System (ADS)

    Meysman, Filip J. R.

    2014-09-01

    Multicellular animals probably evolved at the seafloor after a rise in oceanic oxygen levels. Biogeochemical model simulations suggest that as these animals started to rework the seafloor, they triggered a negative feedback that reduced global oxygen.

  4. FTIR spectra and normal-mode analysis of a tetranuclear Manganese adamantane-like complex in two electrochemically prepared oxidation states: Relevance to the oxygen-evolving complex of Photosystem II

    SciTech Connect

    Visser, Hendrik; Dube, Christopher E.; Armstrong, William H.; Sauer, Kenneth; Yachandra, Vittal K.

    2002-03-19

    The IR spectra and normal-mode analysis of the adamantane-like compound [Mn4O6(bpea)4]n+ in two oxidation states, MnIV4 and MnIIIMnIV3, that are relevant to the oxygen-evolving complex of photosystem II are presented. Mn-O vibrational modes are identified with isotopic exchange, 16O->18O, of the mono-(mu)-oxo bridging atoms in the complex. IR spectra of the MnIIIMnIV3 species are obtained by electrochemical reduction of the MnIV4 species using a spectroelectrochemical cell, based on attenuated total reflection [Visser et al. Anal Chem 2001, 73, 4374-4378]. A novel method of subtraction is used to reduce background contributions from solvent and ligand modes, and the difference and double-difference spectra are used in identifying Mn-O bridging modes that are sensitive to oxidation state change. Two strong IR bands are observed for the MnIV4 species at 745 and 707 cm-1 and a weaker band at 510 cm-1. Upon reduction, the MnIIIMnIV3 species exhibits two strong IR bands at 745 and 680 cm-1, and several weaker bands are observed in the 510 - 425 cm-1 range. A normal mode analysis is performed to assign all the relevant bridging modes in the oxidized MnIV4 and reduced MnIIIMnIV3 species. The calculated force constants for the MnIV4 species are = 3.15 mdynAngstrom, = 0.55 mdyn/Angstrom, and = 0.20 mdyn/Angstrom. The force constants for the MnIIIMnIV3 species are = 3.10 mdyn/Angstrom, = 2.45 mdyn/Angstrom, = 0.40, and = 0.15 mdyn/Angstrom. This study provides insights for the identification of Mn-O modes in the IR spectra of the photosynthetic oxygen-evolving complex during its catalytic cycle.

  5. Probing the topography of the photosystem II oxygen evolving complex: PsbO is required for efficient calcium protection of the manganese cluster against dark-inhibition by an artificial reductant.

    PubMed

    Popelkova, Hana; Boswell, Nicholas; Yocum, Charles

    2011-12-01

    The photosystem II (PSII) manganese-stabilizing protein (PsbO) is known to be the essential PSII extrinsic subunit for stabilization and retention of the Mn and Cl(-) cofactors in the oxygen evolving complex (OEC) of PSII, but its function relative to Ca(2+) is less clear. To obtain a better insight into the relationship, if any, between PsbO and Ca(2+) binding in the OEC, samples with altered PsbO-PSII binding properties were probed for their potential to promote the ability of Ca(2+) to protect the Mn cluster against dark-inhibition by an exogenous artificial reductant, N,N-dimethylhydroxylamine. In the absence of the PsbP and PsbQ extrinsic subunits, Ca(2+) and its surrogates (Sr(2+), Cd(2+)) shield Mn atoms from inhibitory reduction (Kuntzleman et al., Phys Chem Chem Phys 6:4897, 2004). The results presented here show that PsbO exhibits a positive effect on Ca(2+) binding in the OEC by facilitating the ability of the metal to prevent inhibition of activity by the reductant. The data presented here suggest that PsbO may have a role in the formation of the OEC-associated Ca(2+) binding site by promoting the equilibrium between bound and free Ca(2+) that favors the bound metal.

  6. Computational insights on crystal structures of the oxygen-evolving complex of photosystem II with either Ca²⁺ or Ca²⁺ substituted by Sr²⁺

    DOE PAGES

    Vogt, Leslie; Ertem, Mehmed Z.; Pal, Rhitankar; Brudvig, Gary W.; Batista, Victor S.

    2015-01-15

    The oxygen-evolving complex of photosystem II can function with either Ca²⁺ or Sr²⁺ as the heterocation, but the reason for differing turnover rates remains unresolved despite reported X-ray crystal structures for both forms. Using quantum mechanics/molecular mechanics (QM/MM) calculations, we optimize structures with each cation in both the resting state (S₁) and in a series of reduced states (S₀, S₋₁, and S-₂). Through comparison with experimental data, we determine that X-ray crystal structures with either Ca²⁺ or Sr²⁺ are most consistent with the S-₂ state, Mn₄[III,III,III,II] with O4 and O5 protonated. As expected, the QM/MM models show that Ca²⁺/Sr²⁺ substitutionmore » results in elongation of the heterocation bonds and displaces terminal waters W3 and W4. The optimized structures also show that hydrogen-bonded W5 is displaced in all S states with Sr²⁺ as the heterocation, suggesting that this water may play a critical role during water oxidation.« less

  7. Computational insights on crystal structures of the oxygen-evolving complex of photosystem II with either Ca²⁺ or Ca²⁺ substituted by Sr²⁺

    SciTech Connect

    Vogt, Leslie; Ertem, Mehmed Z.; Pal, Rhitankar; Brudvig, Gary W.; Batista, Victor S.

    2015-01-15

    The oxygen-evolving complex of photosystem II can function with either Ca²⁺ or Sr²⁺ as the heterocation, but the reason for differing turnover rates remains unresolved despite reported X-ray crystal structures for both forms. Using quantum mechanics/molecular mechanics (QM/MM) calculations, we optimize structures with each cation in both the resting state (S₁) and in a series of reduced states (S₀, S₋₁, and S-₂). Through comparison with experimental data, we determine that X-ray crystal structures with either Ca²⁺ or Sr²⁺ are most consistent with the S-₂ state, Mn₄[III,III,III,II] with O4 and O5 protonated. As expected, the QM/MM models show that Ca²⁺/Sr²⁺ substitution results in elongation of the heterocation bonds and displaces terminal waters W3 and W4. The optimized structures also show that hydrogen-bonded W5 is displaced in all S states with Sr²⁺ as the heterocation, suggesting that this water may play a critical role during water oxidation.

  8. Cobalt-based age models of pelagic clay in the South Pacific Gyre

    NASA Astrophysics Data System (ADS)

    Dunlea, Ann G.; Murray, Richard W.; Sauvage, Justine; Pockalny, Robert A.; Spivack, Arthur J.; Harris, Robert N.; D'Hondt, Steven

    2015-09-01

    Dating pelagic clay can be a challenge due to its slow sedimentation rate, post-depositional alteration, and lack of biogenic deposition. Co-based dating techniques have the potential to create age models in pelagic clay under the assumption that the flux of non-detrital Co to the seafloor is spatially and temporally constant, resulting in the non-detrital Co concentrations being inversely proportional to sedimentation rate. We apply a Co-based method to the pelagic clay sequences from Sites U1365, U1366, U1369, and U1370 drilled during Integrated Ocean Drilling Program (IODP) Expedition 329 in the South Pacific Gyre. We distinguished non-detrital Co from detrital Co using multivariate statistical partitioning techniques. We found that the non-detrital flux of Co at Site U1370 is approximately twice as high as that at the other sites, implying that the non-detrital Co flux is not regionally constant. This regional variation reflects the heterogeneous distribution of Co in the water column, as is observed in the present day. We present an improved approach to Co-based age modeling throughout the South Pacific Gyre and determine that the Co-based method can effectively date oxygenated pelagic clay deposited in the distal open ocean, but is less reliable for deposition closer to continents. When extending the method to geologically old sediment, it is important to consider the paleolocation of a given site to ensure these conditions are met.

  9. Evolvable synthetic neural system

    NASA Technical Reports Server (NTRS)

    Curtis, Steven A. (Inventor)

    2009-01-01

    An evolvable synthetic neural system includes an evolvable neural interface operably coupled to at least one neural basis function. Each neural basis function includes an evolvable neural interface operably coupled to a heuristic neural system to perform high-level functions and an autonomic neural system to perform low-level functions. In some embodiments, the evolvable synthetic neural system is operably coupled to one or more evolvable synthetic neural systems in a hierarchy.

  10. Effect of wollastonite ceramics and bioactive glass on the formation of a bonelike apatite layer on a cobalt base alloy.

    PubMed

    Cortés, D A; Medina, A; Escobedo, J C; Escobedo, S; López, M A

    2004-08-01

    A biomimetic method was used to promote a bioactive surface on a cobalt base alloy (ASTM F-75). The metallic substrates were alkali treated and some of the samples were subsequently heat treated. The treated samples were immersed in simulated body fluid (SBF) on granular particles of either bioactive glass or wollastonite. For comparative purposes, no bioactive system was used in some tests. Three different methods were used for the immersion of the samples in SBF: 1) 21 days in SBF, 2) 21 days in 1.5 SBF, and 3) 7 days in SBF followed by 14 days in 1.5 SBF (re-immersion method). A bonelike apatite layer was formed on all the samples placed on wollastonite and bioactive glass particles. The morphology of the apatite layer formed by using the re-immersion method and wollastonite closely resembled the existing bioactive systems. No apatite layer was observed on the samples treated without bioactive material and soaked for 21 days in SBF or 1.5 SBF, apart from the substrates treated by using the re-immersion method. The heat treatment delayed the apatite formation in all the cases studied.

  11. On morphologies, microsegregation, and mechanical behavior of directionally solidified cobalt-base superalloy at medium cooling rate

    NASA Astrophysics Data System (ADS)

    Chu, Shuangjie; Li, Jianguo; Liu, Zhongyuan; Shi, Zhengxing; Fu, Hengzhi

    1994-03-01

    A newly developed experimental setup that can provide a temperature gradient of 1300 K/cm has been used in the research of the morphologies, microsegregation, and mechanical behavior of directionally solidified cobalt-base superalloy (known as K10 in PR China) at medium cooling rates from 38 to 60 K/s. Experimental results show that the primary and secondary dendrite spacings of K10 become less than one-fifth and one-eighth, respectively, of those obtainable with a conventional 100 K/cm temperature gradient and a cooling rate below 1 K/s: the carbides are directionally arrayed and the carbides’ morphology changes from islands of general cast state into worms; microsegregation is almost completely eliminated; the mechanical properties, as can be expected, are greatly superior to those obtainable with 100 K/cm temperature gradient; at 1073 K, creep-rupture strength increases from 167 to 196 MPa; endurance life is raised from 10 to 30 hours; the reduction in area increases from 12 to 52 pct; and the specific elongation increases from 17 to 46 pct. And with the increase of cooling rate, there are always corresponding improvements of mechanical properties of K10. Otherwise, the fractography of superfine columnar structure samples is high-toughness transgranular fracture, with cracks originating at the edge of carbides.

  12. Removal of Ca2+ from the Oxygen-Evolving Complex in Photosystem II Has Minimal Effect on the Mn4O5 Core Structure: A Polarized Mn X-ray Absorption Spectroscopy Study

    DOE PAGES

    Lohmiller, Thomas; Shelby, Megan L.; Long, Xi; Yachandra, Vittal K.; Yano, Junko

    2015-05-19

    We studied Ca2+ -depleted and Ca2+ -reconstituted spinach photosystem II using polarized X-ray absorption spectroscopy of oriented PS II preparations to investigate the structural and functional role of the Ca2+ ion in the Mn4O5Ca cluster of the oxygen-evolving complex (OEC). Samples were prepared by low pH/citrate treatment as one-dimensionally ordered membrane layers and poised in the Ca2+ -depleted S1 (S1') and S2 (S2') states, the S2'YZ• state, at which point the catalytic cycle of water oxidation is inhibited, and the Ca2+ -reconstituted S1 state. Polarized Mn K-edge XANES and EXAFS spectra exhibit pronounced dichroism. Polarized EXAFS data of all statesmore » of Ca2+ -depleted PS II investigated show only minor changes in distances and orientations of the Mn-Mn vectors compared to the Ca2+ -containing OEC, which may be attributed to some loss of rigidity of the core structure. Thus, removal of the Ca2+ ion does not lead to fundamental distortion or rearrangement of the tetranuclear Mn cluster, which indicates that the Ca2+ ion in the OEC is not critical for structural maintenance of the cluster, at least in the S1 and S2 states, but fulfills a crucial catalytic function in the mechanism of the water oxidation reaction. On the basis of this structural information, reasons for the inhibitory effect of Ca2+ removal are discussed, attributing to the Ca2+ ion a fundamental role in organizing the surrounding (substrate) water framework and in proton-coupled electron transfer to YZ• (D1-Tyr161).« less

  13. Magnetic and Electrical Characteristics of Cobalt-Based Amorphous Materials and Comparison to a Permalloy Type Polycrystalline Material

    NASA Technical Reports Server (NTRS)

    Wieserman, William R.; Schwarze, Gene E.; Niedra, Janis M.

    2005-01-01

    Magnetic component designers are always looking for improved soft magnetic core materials to increase the efficiency, temperature rating and power density of transformers, motors, generators and alternators, and energy density of inductors. In this paper, we report on the experimental investigation of commercially available cobalt-based amorphous alloys which, in their processing, were subjected to two different types of magnetic field anneals: A longitudinal magnetic field anneal or a transverse magnetic field anneal. The longitudinal field annealed material investigated was Metglas 2714A. The electrical and magnetic characteristics of this material were investigated over the frequency range of 1 to 200 kHz and temperature range of 23 to 150 C for both sine and square wave voltage excitation. The specific core loss was lower for the square than the sine wave voltage excitation for the same maximum flux density, frequency and temperature. The transverse magnetic field annealed core materials include Metglas 2714AF and Vacuumschmelze 6025F. These two materials were experimentally characterized over the frequency range of 10 to 200 kHz for sine wave voltage excitation and 23 C only. A comparison of the 2174A to 2714AF found that 2714AF always had lower specific core loss than 2714A for any given magnetic flux density and frequency and the ratio of specific core loss of 2714A to 2714AF was dependent on both magnetic flux density and frequency. A comparison was also made of the 2714A, 2714AF, and 6025F materials to two different tape thicknesses of the polycrystalline Supermalloy material and the results show that 2714AF and 6025F have the lowest specific core loss at 100 kHz over the magnetic flux density range of 0.1 to 0.4 Tesla.

  14. Thermal and evolved gas analyzer

    NASA Technical Reports Server (NTRS)

    Williams, M. S.; Boynton, W. V.; James, R. L.; Verts, W. T.; Bailey, S. H.; Hamara, D. K.

    1998-01-01

    The Thermal and Evolved Gas Analyzer (TEGA) instrument will perform calorimetry and evolved gas analysis on soil samples collected from the Martian surface. TEGA is one of three instruments, along with a robotic arm, that form the Mars Volatile and Climate Survey (MVACS) payload. The other instruments are a stereo surface imager, built by Peter Smith of the University of Arizona and a meteorological station, built by JPL. The MVACS lander will investigate a Martian landing site at approximately 70 deg south latitude. Launch will take place from Kennedy Space Center in January, 1999. The TEGA project started in February, 1996. In the intervening 24 months, a flight instrument concept has been designed, prototyped, built as an engineering model and flight model, and tested. The instrument performs laboratory-quality differential-scanning calorimetry (DSC) over the temperature range of Mars ambient to 1400K. Low-temperature volatiles (water and carbon dioxide ices) and the carbonates will be analyzed in this temperature range. Carbonates melt and evolve carbon dioxide at temperatures above 600 C. Evolved oxygen (down to a concentration of 1 ppm) is detected, and C02 and water vapor and the isotopic variations of C02 and water vapor are detected and their concentrations measured. The isotopic composition provides important tests of the theory of solar system formation.

  15. Evidence from FTIR difference spectroscopy that D1-Asp61 influences the water reactions of the oxygen-evolving Mn4CaO5 cluster of photosystem II.

    PubMed

    Debus, Richard J

    2014-05-13

    Understanding the mechanism of photosynthetic water oxidation requires characterizing the reactions of the water molecules that serve as substrate or that otherwise interact with the oxygen-evolving Mn4CaO5 cluster. FTIR difference spectroscopy is a powerful tool for studying the structural changes of hydrogen bonded water molecules. For example, the O-H stretching mode of water molecules having relatively weak hydrogen bonds can be monitored near 3600 cm(-1), the D-O-D bending mode can be monitored near 1210 cm(-1), and highly polarizable networks of hydrogen bonds can be monitored as broad features between 3000 and 2000 cm(-1). The two former regions are practically devoid of overlapping vibrational modes from the protein. In Photosystem II, water oxidation requires a precisely choreographed sequence of proton and electron transfer steps in which proton release is required to prevent the redox potential of the Mn4CaO5 cluster from rising to levels that would prevent its subsequent oxidation. Proton release takes place via one or more proton egress pathways leading from the Mn4CaO5 cluster to the thylakoid lumen. There is growing evidence that D1-D61 is the initial residue of one dominant proton egress pathway. This residue interacts directly with water molecules in the first and second coordination spheres of the Mn4CaO5 cluster. In this study, we explore the influence of D1-D61 on the water reactions accompanying oxygen production by characterizing the FTIR properties of the D1-D61A mutant of the cyanobacterium, Synechocystis sp. PCC 6803. On the basis of mutation-induced changes to the carbonyl stretching region near 1747 cm(-1), we conclude that D1-D61 participates in the same extensive networks of hydrogen bonds that have been identified previously by FTIR studies. On the basis of mutation-induced changes to the weakly hydrogen-bonded O-H stretching region, we conclude that D1-D61 interacts with water molecules that are located near the Cl(-)(1) ion and that

  16. Prokaryote and eukaryote evolvability.

    PubMed

    Poole, Anthony M; Phillips, Matthew J; Penny, David

    2003-05-01

    The concept of evolvability covers a broad spectrum of, often contradictory, ideas. At one end of the spectrum it is equivalent to the statement that evolution is possible, at the other end are untestable post hoc explanations, such as the suggestion that current evolutionary theory cannot explain the evolution of evolvability. We examine similarities and differences in eukaryote and prokaryote evolvability, and look for explanations that are compatible with a wide range of observations. Differences in genome organisation between eukaryotes and prokaryotes meets this criterion. The single origin of replication in prokaryote chromosomes (versus multiple origins in eukaryotes) accounts for many differences because the time to replicate a prokaryote genome limits its size (and the accumulation of junk DNA). Both prokaryotes and eukaryotes appear to switch from genetic stability to genetic change in response to stress. We examine a range of stress responses, and discuss how these impact on evolvability, particularly in unicellular organisms versus complex multicellular ones. Evolvability is also limited by environmental interactions (including competition) and we describe a model that places limits on potential evolvability. Examples are given of its application to predator competition and limits to lateral gene transfer. We suggest that unicellular organisms evolve largely through a process of metabolic change, resulting in biochemical diversity. Multicellular organisms evolve largely through morphological changes, not through extensive changes to cellular biochemistry. PMID:12689728

  17. Oxygen safety

    MedlinePlus

    COPD - oxygen safety; Chronic obstructive pulmonary disease - oxygen safety; Chronic obstructive airways disease - oxygen safety; Emphysema - oxygen safety; Heart failure - oxygen-safety; Palliative care - oxygen safety; ...

  18. REFLECTIONS ON EVOLVING CHANGE.

    PubMed

    Angood, Peter B

    2016-01-01

    Physician leadership is increasingly recognized as pivotal for improved change in health care. Multi-professional care teams, education and leadership are evolving trends that are important for health care's future. PMID:27295737

  19. Analysis of thermoelectric properties of high-temperature complex alloys of nickel-base, iron-base and cobalt-base groups

    NASA Technical Reports Server (NTRS)

    Holanda, R.

    1984-01-01

    The thermoelectric properties alloys of the nickel-base, iron-base, and cobalt-base groups containing from 1% to 25% 106 chromium were compared and correlated with the following material characteristics: atomic percent of the principle alloy constituent; ratio of concentration of two constituents; alloy physical property (electrical resistivity); alloy phase structure (percent precipitate or percent hardener content); alloy electronic structure (electron concentration). For solid-solution-type alloys the most consistent correlation was obtained with electron concentration, for precipitation-hardenable alloys of the nickel-base superalloy group, the thermoelectric potential correlated with hardener content in the alloy structure. For solid-solution-type alloys, no problems were found with thermoelectric stability to 1000; for precipitation-hardenable alloys, thermoelectric stability was dependent on phase stability. The effects of the compositional range of alloy constituents on temperature measurement uncertainty are discussed.

  20. Outcome Study of Cobalt Based Stereotactic Body Radiation Therapy for Patients with Inoperable Stage III Non-small Cell Lung Cancer.

    PubMed

    Wang, Yingjie; Lan, Fengming; Kang, Xiaoli; Shao, Yinjian; Li, Hongqi; Li, Ping; Wu, Weizhang; Wang, Jidong; Chang, Dongshu; Wang, Yong; Xia, Tingyi

    2015-10-01

    Aim of this paper is to retrospectively evaluate the efficacy and toxicity of specialized Body Cobalt based system (BCBS) treatment in the senior patients group (.65 years) with Stage III non-small cell lung carcinoma (NSCLC). A total of 49 patients (41 males and 8 females) with Stage III NSCLC according to UICC TNM classification (6(th) edition) were treated using OUR-QGD™ BCBS which was designed and manufactured in China. Post treatment evaluation with follow-up information was collected from April 2001 to December 2006 in our department. Median age of enrolled patients was 71 years old (65-85). Among those patients, 36 patients were pathologically identified with squamous cell carcinoma, and the other 13 patients were confirmed as adenocarcinoma. All patients were immobilized by vacuum based immobilization mold and then performed slow CT scan without any respiration gating devices. The daily radiation prescription dose was defined at 50% isodose line covering primary lesions and metastatic lymph nodes with doses from 2.5 to 6 Gy in 5 fractions per week according to the tumor stage and internally approved treatment protocols by the Institutional Review Board (IRB). Median daily dose and total delivery dose of 50% isodose line were 4 Gy and 41 Gy, respectively. In this study group, total of 3 patients received neoadjuvant cisplatin-based chemotherapy. Tumor response evaluated 12 weeks after radiation has demonstrated 13 complete responses (26.5%), 21 partial responses (42.9%). The overall survival (OS) rate of 1-year, 2-year and 3-year was 63.3%, 40.8% and 20.4%, respectively. The median and mean survival time was 22 and 24 months. All 49 patients tolerated the treatment well and have completed the planned therapy regiment. Body Cobalt based system treatment of those over 65 years old patients with Stage III NSCLC had reasonable and superior curative effect as well as local control, and at the same time without severe radiation side effects.

  1. Glutamate-354 of the CP43 polypeptide interacts with the oxygen-evolving Mn4Ca cluster of photosystem II: a preliminary characterization of the Glu354Gln mutant.

    PubMed

    Strickler, Melodie A; Hwang, Hong Jin; Burnap, Robert L; Yano, Junko; Walker, Lee M; Service, Rachel J; Britt, R David; Hillier, Warwick; Debus, Richard J

    2008-03-27

    In the recent X-ray crystallographic structural models of photosystem II, Glu354 of the CP43 polypeptide is assigned as a ligand of the O2-evolving Mn4Ca cluster. In this communication, a preliminary characterization of the CP43-Glu354Gln mutant of the cyanobacterium Synechocystis sp. PCC 6803 is presented. The steady-state rate of O2 evolution in the mutant cells is only approximately 20% compared with the wild-type, but the kinetics of O2 release are essentially unchanged and the O2-flash yields show normal period-four oscillations, albeit with lower overall intensity. Purified PSII particles exhibit an essentially normal S2 state multiline electron paramagnetic resonance (EPR) signal, but exhibit a substantially altered S2-minus-S1 Fourier transform infrared (FTIR) difference spectrum. The intensities of the mutant EPR and FTIR difference spectra (above 75% compared with wild-type) are much greater than the O2 signals and suggest that CP43-Glu354Gln PSII reaction centres are heterogeneous, with a minority fraction able to evolve O2 with normal O2 release kinetics and a majority fraction unable to advance beyond the S2 or S3 states. The S2-minus-S1 FTIR difference spectrum of CP43-Glu354Gln PSII particles is altered in both the symmetric and asymmetric carboxylate stretching regions, implying either that CP43-Glu354 is exquisitely sensitive to the increased charge that develops on the Mn4Ca cluster during the S1-->S2 transition or that the CP43-Glu354Gln mutation changes the distribution of Mn(III) and Mn(IV) oxidation states within the Mn4Ca cluster in the S1 and/or S2 states.

  2. Evolvable Neural Software System

    NASA Technical Reports Server (NTRS)

    Curtis, Steven A.

    2009-01-01

    The Evolvable Neural Software System (ENSS) is composed of sets of Neural Basis Functions (NBFs), which can be totally autonomously created and removed according to the changing needs and requirements of the software system. The resulting structure is both hierarchical and self-similar in that a given set of NBFs may have a ruler NBF, which in turn communicates with other sets of NBFs. These sets of NBFs may function as nodes to a ruler node, which are also NBF constructs. In this manner, the synthetic neural system can exhibit the complexity, three-dimensional connectivity, and adaptability of biological neural systems. An added advantage of ENSS over a natural neural system is its ability to modify its core genetic code in response to environmental changes as reflected in needs and requirements. The neural system is fully adaptive and evolvable and is trainable before release. It continues to rewire itself while on the job. The NBF is a unique, bilevel intelligence neural system composed of a higher-level heuristic neural system (HNS) and a lower-level, autonomic neural system (ANS). Taken together, the HNS and the ANS give each NBF the complete capabilities of a biological neural system to match sensory inputs to actions. Another feature of the NBF is the Evolvable Neural Interface (ENI), which links the HNS and ANS. The ENI solves the interface problem between these two systems by actively adapting and evolving from a primitive initial state (a Neural Thread) to a complicated, operational ENI and successfully adapting to a training sequence of sensory input. This simulates the adaptation of a biological neural system in a developmental phase. Within the greater multi-NBF and multi-node ENSS, self-similar ENI s provide the basis for inter-NBF and inter-node connectivity.

  3. Evolvability is inevitable: increasing evolvability without the pressure to adapt.

    PubMed

    Lehman, Joel; Stanley, Kenneth O

    2013-01-01

    Why evolvability appears to have increased over evolutionary time is an important unresolved biological question. Unlike most candidate explanations, this paper proposes that increasing evolvability can result without any pressure to adapt. The insight is that if evolvability is heritable, then an unbiased drifting process across genotypes can still create a distribution of phenotypes biased towards evolvability, because evolvable organisms diffuse more quickly through the space of possible phenotypes. Furthermore, because phenotypic divergence often correlates with founding niches, niche founders may on average be more evolvable, which through population growth provides a genotypic bias towards evolvability. Interestingly, the combination of these two mechanisms can lead to increasing evolvability without any pressure to out-compete other organisms, as demonstrated through experiments with a series of simulated models. Thus rather than from pressure to adapt, evolvability may inevitably result from any drift through genotypic space combined with evolution's passive tendency to accumulate niches.

  4. Cobalt based layered perovskites as cathode material for intermediate temperature Solid Oxide Fuel Cells: A brief review

    NASA Astrophysics Data System (ADS)

    Pelosato, Renato; Cordaro, Giulio; Stucchi, Davide; Cristiani, Cinzia; Dotelli, Giovanni

    2015-12-01

    Nowadays, the cathode is the most studied component in Intermediate Temperature-Solid Oxide Fuel Cells (IT-SOFCs). Decreasing SOFCs operating temperature implies slow oxygen reduction kinetics and large polarization losses. Double perovskites with general formula REBaCo2O5+δ are promising mixed ionic-electronic conductors, offering a remarkable enhancement of the oxygen diffusivity and surface exchange respect to disordered perovskites. In this review, more than 250 compositions investigated in the literature were analyzed. The evaluation was performed in terms of electrical conductivity, Area Specific Resistance (ASR), chemical compatibility with electrolytes and Thermal Expansion Coefficient (TEC). The most promising materials have been identified as those bearing the mid-sized rare earths (Pr, Nd, Sm, Gd). Doping strategies have been analyzed: Sr doping on A site promotes higher electrical conductivity, but worsen ASR and TECs; B-site doping (Fe, Ni, Mn) helps lowering TECs, but is detrimental for the electrochemical properties. A promising boost of the electrochemical activity is obtained by simply introducing a slight Ba under-stoichiometry. Still, the high sensitivity of the electrochemical properties against slight changes in the stoichiometry hamper a conclusive comparison of all the investigated compounds. Opportunities for an improvement of double perovskite cathodes performance is tentatively foreseen in combining together the diverse effective doping strategies.

  5. Submillimeter observations of evolved stars

    SciTech Connect

    Sopka, R.J.; Hildebrand, R.; Jaffe, D.T.; Gatley, I.; Roellig, T.; Werner, M.; Jura, M.; Zuckerman, B.

    1985-07-01

    Broad-band submillimeter observations of the thermal emission from evolved stars have been obtained with the United Kingdom Infrared Telescope on Mauna Kea, Hawaii. These observations, at an effective wavelength of 400 ..mu..m, provide the most direct method for estimating the mass loss rate in dust from these stars and also help to define the long-wavelength thermal spectrum of the dust envelopes. The mass loss rates in dust that we derive range from 10/sup -9/ to 10/sup -6/ M/sub sun/ yr/sup -1/ and are compared with mass loss rates derived from molecular line observations to estimate gas-to-dust ratios in outflowing envelopes. These values are found to be generally compatible with the interstellar gas-to-dust ratio of approx.100 if submillimeter emissivities appropriate to amorphous grain structures are assumed. Our analysis of the spectrum of IRC+10216 confirms previous suggestions that the grain emissivity varies as lambda/sup -1.2/ rather than as lambda/sup -2/ for 10oxygen-rich objects indicates that our submillimeter fluxes for IRC+10011 and NML Cyg are greater than those predicted by previous modeling. This, we argue, is the result of a slower decline in grain emissivity with wavelength than is seen in published silicate grain models. We are not able to distinguish a systematic difference in the dust masses of carbon-rich and oxygen-rich envelopes. We find the largest mass loss rates in dust in the bipolar objects OH 231.8+4.2, CRL 2688, and CRL 618 and in NGC 7027 and VY CMa.

  6. Generalized approximate spin projection calculations of effective exchange integrals of the CaMn4O5 cluster in the S1 and S3 states of the oxygen evolving complex of photosystem II.

    PubMed

    Isobe, H; Shoji, M; Yamanaka, S; Mino, H; Umena, Y; Kawakami, K; Kamiya, N; Shen, J-R; Yamaguchi, K

    2014-06-28

    Full geometry optimizations followed by the vibrational analysis were performed for eight spin configurations of the CaMn4O4X(H2O)3Y (X = O, OH; Y = H2O, OH) cluster in the S1 and S3 states of the oxygen evolution complex (OEC) of photosystem II (PSII). The energy gaps among these configurations obtained by vertical, adiabatic and adiabatic plus zero-point-energy (ZPE) correction procedures have been used for computation of the effective exchange integrals (J) in the spin Hamiltonian model. The J values are calculated by the (1) analytical method and the (2) generalized approximate spin projection (AP) method that eliminates the spin contamination errors of UB3LYP solutions. Using J values derived from these methods, exact diagonalization of the spin Hamiltonian matrix was carried out, yielding excitation energies and spin densities of the ground and lower-excited states of the cluster. The obtained results for the right (R)- and left (L)-opened structures in the S1 and S3 states are found to be consistent with available optical and magnetic experimental results. Implications of the computational results are discussed in relation to (a) the necessity of the exact diagonalization for computations of reliable energy levels, (b) magneto-structural correlations in the CaMn4O5 cluster of the OEC of PSII, (c) structural symmetry breaking in the S1 and S3 states, and (d) the right- and left-handed scenarios for the O-O bond formation for water oxidation.

  7. Generalized approximate spin projection calculations of effective exchange integrals of the CaMn4O5 cluster in the S1 and S3 states of the oxygen evolving complex of photosystem II.

    PubMed

    Isobe, H; Shoji, M; Yamanaka, S; Mino, H; Umena, Y; Kawakami, K; Kamiya, N; Shen, J-R; Yamaguchi, K

    2014-06-28

    Full geometry optimizations followed by the vibrational analysis were performed for eight spin configurations of the CaMn4O4X(H2O)3Y (X = O, OH; Y = H2O, OH) cluster in the S1 and S3 states of the oxygen evolution complex (OEC) of photosystem II (PSII). The energy gaps among these configurations obtained by vertical, adiabatic and adiabatic plus zero-point-energy (ZPE) correction procedures have been used for computation of the effective exchange integrals (J) in the spin Hamiltonian model. The J values are calculated by the (1) analytical method and the (2) generalized approximate spin projection (AP) method that eliminates the spin contamination errors of UB3LYP solutions. Using J values derived from these methods, exact diagonalization of the spin Hamiltonian matrix was carried out, yielding excitation energies and spin densities of the ground and lower-excited states of the cluster. The obtained results for the right (R)- and left (L)-opened structures in the S1 and S3 states are found to be consistent with available optical and magnetic experimental results. Implications of the computational results are discussed in relation to (a) the necessity of the exact diagonalization for computations of reliable energy levels, (b) magneto-structural correlations in the CaMn4O5 cluster of the OEC of PSII, (c) structural symmetry breaking in the S1 and S3 states, and (d) the right- and left-handed scenarios for the O-O bond formation for water oxidation. PMID:24632787

  8. Our evolving universe

    NASA Astrophysics Data System (ADS)

    Longair, Malcolm S.

    Our Evolving Universe is a lucid, non-technical and infectiously enthusiastic introduction to current astronomy and cosmology. Highly illustrated throughout with the latest colour images from the world's most advanced telescopes, it also provides a colourful view of our Universe. Malcolm Longair takes us on a breathtaking tour of the most dramatic recent results astronomers have on the birth of stars, the hunt for black holes and dark matter, on gravitational lensing and the latest tests of the Big Bang. He leads the reader right up to understand the key questions that future research in astronomy and cosmology must answer. A clear and comprehensive glossary of technical terms is also provided. For the general reader, student or professional wishing to understand the key questions today's astronomers and cosmologists are trying to answer, this is an invaluable and inspiring read.

  9. Temperature dependence of the electrode potential of a cobalt-based redox couple in ionic liquid electrolytes for thermal energy harvesting.

    PubMed

    He, Jiangjing; Al-Masri, Danah; MacFarlane, Douglas R; Pringle, Jennifer M

    2016-08-15

    Increasing the application of technologies for harvesting waste heat could make a significant contribution to sustainable energy production. Thermoelectrochemical cells are one such emerging technology, where the thermal response of a redox couple in an electrolyte is used to generate a potential difference across a cell when a temperature gradient exists. The unique physical properties of ionic liquids make them ideal for application as electrolytes in these devices. One of the keys to utilizing these media in efficient thermoelectrochemical cells is achieving high Seebeck coefficients, Se: the thermodynamic quantity that determines the magnitude of the voltage achieved per unit temperature difference. Here, we report the Se and cell performance of a cobalt-based redox couple in a range of different ionic liquids, to investigate the influence of the nature of the IL on the thermodynamics and cell performance of the redox system. The results reported include the highest Se to-date for an IL-based electrolyte. The effect of diluting the different ILs with propylene carbonate is also reported, which results in a significant increase in the output powers and current densities of the device. PMID:27200437

  10. Evolving synergetic interactions.

    PubMed

    Wu, Bin; Arranz, Jordi; Du, Jinming; Zhou, Da; Traulsen, Arne

    2016-07-01

    Cooperators forgo their own interests to benefit others. This reduces their fitness and thus cooperators are not likely to spread based on natural selection. Nonetheless, cooperation is widespread on every level of biological organization ranging from bacterial communities to human society. Mathematical models can help to explain under which circumstances cooperation evolves. Evolutionary game theory is a powerful mathematical tool to depict the interactions between cooperators and defectors. Classical models typically involve either pairwise interactions between individuals or a linear superposition of these interactions. For interactions within groups, however, synergetic effects may arise: their outcome is not just the sum of its parts. This is because the payoffs via a single group interaction can be different from the sum of any collection of two-player interactions. Assuming that all interactions start from pairs, how can such synergetic multiplayer games emerge from simpler pairwise interactions? Here, we present a mathematical model that captures the transition from pairwise interactions to synergetic multiplayer ones. We assume that different social groups have different breaking rates. We show that non-uniform breaking rates do foster the emergence of synergy, even though individuals always interact in pairs. Our work sheds new light on the mechanisms underlying such synergetic interactions. PMID:27466437

  11. Evolving endoscopic surgery.

    PubMed

    Sakai, Paulo; Faintuch, Joel

    2014-06-01

    Since the days of Albukasim in medieval Spain, natural orifices have been regarded not only as a rather repugnant source of bodily odors, fluids and excreta, but also as a convenient invitation to explore and treat the inner passages of the organism. However, surgical ingenuity needed to be matched by appropriate tools and devices. Lack of technologically advanced instrumentation was a strong deterrent during almost a millennium until recent decades when a quantum jump materialized. Endoscopic surgery is currently a vibrant and growing subspecialty, which successfully handles millions of patients every year. Additional opportunities lie ahead which might benefit millions more, however, requiring even more sophisticated apparatuses, particularly in the field of robotics, artificial intelligence, and tissue repair (surgical suturing). This is a particularly exciting and worthwhile challenge, namely of larger and safer endoscopic interventions, followed by seamless and scarless recovery. In synthesis, the future is widely open for those who use together intelligence and creativity to develop new prototypes, new accessories and new techniques. Yet there are many challenges in the path of endoscopic surgery. In this new era of robotic endoscopy, one will likely need a virtual simulator to train and assess the performance of younger doctors. More evidence will be essential in multiple evolving fields, particularly to elucidate whether more ambitious and complex pathways, such as intrathoracic and intraperitoneal surgery via natural orifice transluminal endoscopic surgery (NOTES), are superior or not to conventional techniques.

  12. Communicability across evolving networks

    NASA Astrophysics Data System (ADS)

    Grindrod, Peter; Parsons, Mark C.; Higham, Desmond J.; Estrada, Ernesto

    2011-04-01

    Many natural and technological applications generate time-ordered sequences of networks, defined over a fixed set of nodes; for example, time-stamped information about “who phoned who” or “who came into contact with who” arise naturally in studies of communication and the spread of disease. Concepts and algorithms for static networks do not immediately carry through to this dynamic setting. For example, suppose A and B interact in the morning, and then B and C interact in the afternoon. Information, or disease, may then pass from A to C, but not vice versa. This subtlety is lost if we simply summarize using the daily aggregate network given by the chain A-B-C. However, using a natural definition of a walk on an evolving network, we show that classic centrality measures from the static setting can be extended in a computationally convenient manner. In particular, communicability indices can be computed to summarize the ability of each node to broadcast and receive information. The computations involve basic operations in linear algebra, and the asymmetry caused by time’s arrow is captured naturally through the noncommutativity of matrix-matrix multiplication. Illustrative examples are given for both synthetic and real-world communication data sets. We also discuss the use of the new centrality measures for real-time monitoring and prediction.

  13. Evolving Concepts of Asthma.

    PubMed

    Gauthier, Marc; Ray, Anuradha; Wenzel, Sally E

    2015-09-15

    Our understanding of asthma has evolved over time from a singular disease to a complex of various phenotypes, with varied natural histories, physiologies, and responses to treatment. Early therapies treated most patients with asthma similarly, with bronchodilators and corticosteroids, but these therapies had varying degrees of success. Similarly, despite initial studies that identified an underlying type 2 inflammation in the airways of patients with asthma, biologic therapies targeted toward these type 2 pathways were unsuccessful in all patients. These observations led to increased interest in phenotyping asthma. Clinical approaches, both biased and later unbiased/statistical approaches to large asthma patient cohorts, identified a variety of patient characteristics, but they also consistently identified the importance of age of onset of disease and the presence of eosinophils in determining clinically relevant phenotypes. These paralleled molecular approaches to phenotyping that developed an understanding that not all patients share a type 2 inflammatory pattern. Using biomarkers to select patients with type 2 inflammation, repeated trials of biologics directed toward type 2 cytokine pathways saw newfound success, confirming the importance of phenotyping in asthma. Further research is needed to clarify additional clinical and molecular phenotypes, validate predictive biomarkers, and identify new areas for possible interventions.

  14. Stochastically evolving networks

    NASA Astrophysics Data System (ADS)

    Chan, Derek Y.; Hughes, Barry D.; Leong, Alex S.; Reed, William J.

    2003-12-01

    We discuss a class of models for the evolution of networks in which new nodes are recruited into the network at random times, and links between existing nodes that are not yet directly connected may also form at random times. The class contains both models that produce “small-world” networks and less tightly linked models. We produce both trees, appropriate in certain biological applications, and networks in which closed loops can appear, which model communication networks and networks of human sexual interactions. One of our models is closely related to random recursive trees, and some exact results known in that context can be exploited. The other models are more subtle and difficult to analyze. Our analysis includes a number of exact results for moments, correlations, and distributions of coordination number and network size. We report simulations and also discuss some mean-field approximations. If the system has evolved for a long time and the state of a random node (which thus has a random age) is observed, power-law distributions for properties of the system arise in some of these models.

  15. Evolving endoscopic surgery.

    PubMed

    Sakai, Paulo; Faintuch, Joel

    2014-06-01

    Since the days of Albukasim in medieval Spain, natural orifices have been regarded not only as a rather repugnant source of bodily odors, fluids and excreta, but also as a convenient invitation to explore and treat the inner passages of the organism. However, surgical ingenuity needed to be matched by appropriate tools and devices. Lack of technologically advanced instrumentation was a strong deterrent during almost a millennium until recent decades when a quantum jump materialized. Endoscopic surgery is currently a vibrant and growing subspecialty, which successfully handles millions of patients every year. Additional opportunities lie ahead which might benefit millions more, however, requiring even more sophisticated apparatuses, particularly in the field of robotics, artificial intelligence, and tissue repair (surgical suturing). This is a particularly exciting and worthwhile challenge, namely of larger and safer endoscopic interventions, followed by seamless and scarless recovery. In synthesis, the future is widely open for those who use together intelligence and creativity to develop new prototypes, new accessories and new techniques. Yet there are many challenges in the path of endoscopic surgery. In this new era of robotic endoscopy, one will likely need a virtual simulator to train and assess the performance of younger doctors. More evidence will be essential in multiple evolving fields, particularly to elucidate whether more ambitious and complex pathways, such as intrathoracic and intraperitoneal surgery via natural orifice transluminal endoscopic surgery (NOTES), are superior or not to conventional techniques. PMID:24628672

  16. Evolving paradigms in pharmacovigilance.

    PubMed

    Brewster, Wendy; Gibbs, Trevor; Lacroix, Karol; Murray, Alison; Tydeman, Michael; Almenoff, June

    2006-05-01

    All medicines have adverse effects as well as benefits. The aim of pharmacovigilance is to protect public health by monitoring medicines to identify and evaluate issues and ensure that the overall benefits outweigh the potential risks. The tools and processes used in pharmacovigilance are continually evolving. Increasingly sophisticated tools are being designed to evaluate safety data from clinical trials to enhance the likelihood of detecting safety signals ahead of product registration. Methods include integration of safety data throughout development, meta-analytical techniques, quantitative and qualitative methods for evaluation of adverse event data and graphical tools to explore laboratory and biometric data. Electronic data capture facilitates monitoring of ongoing studies so that it is possible to promptly identify potential issues and manage patient safety. In addition, GSK employs a number of proactive methods for post-marketing signal detection and knowledge management using state-of-the-art statistical and analytical tools. Using these tools, together with safety data collected through pharmacoepidemiologic studies, literature and spontaneous reporting, potential adverse drug reactions can be better identified in marketed products. In summary, the information outlined in this paper provides a valuable benchmark for risk management and pharmacovigilance in pharmaceutical development.

  17. Evolving synergetic interactions

    PubMed Central

    Wu, Bin; Arranz, Jordi; Du, Jinming; Zhou, Da; Traulsen, Arne

    2016-01-01

    Cooperators forgo their own interests to benefit others. This reduces their fitness and thus cooperators are not likely to spread based on natural selection. Nonetheless, cooperation is widespread on every level of biological organization ranging from bacterial communities to human society. Mathematical models can help to explain under which circumstances cooperation evolves. Evolutionary game theory is a powerful mathematical tool to depict the interactions between cooperators and defectors. Classical models typically involve either pairwise interactions between individuals or a linear superposition of these interactions. For interactions within groups, however, synergetic effects may arise: their outcome is not just the sum of its parts. This is because the payoffs via a single group interaction can be different from the sum of any collection of two-player interactions. Assuming that all interactions start from pairs, how can such synergetic multiplayer games emerge from simpler pairwise interactions? Here, we present a mathematical model that captures the transition from pairwise interactions to synergetic multiplayer ones. We assume that different social groups have different breaking rates. We show that non-uniform breaking rates do foster the emergence of synergy, even though individuals always interact in pairs. Our work sheds new light on the mechanisms underlying such synergetic interactions. PMID:27466437

  18. Oxygen Therapy

    MedlinePlus

    Oxygen therapy is a treatment that provides you with extra oxygen. Oxygen is a gas that your body needs to function. Normally, your lungs absorb ... in your home. A different kind of oxygen therapy is called hyperbaric oxygen therapy. It uses oxygen ...

  19. Disgust: Evolved Function and Structure

    ERIC Educational Resources Information Center

    Tybur, Joshua M.; Lieberman, Debra; Kurzban, Robert; DeScioli, Peter

    2013-01-01

    Interest in and research on disgust has surged over the past few decades. The field, however, still lacks a coherent theoretical framework for understanding the evolved function or functions of disgust. Here we present such a framework, emphasizing 2 levels of analysis: that of evolved function and that of information processing. Although there is…

  20. Evolving virtual creatures and catapults.

    PubMed

    Chaumont, Nicolas; Egli, Richard; Adami, Christoph

    2007-01-01

    We present a system that can evolve the morphology and the controller of virtual walking and block-throwing creatures (catapults) using a genetic algorithm. The system is based on Sims' work, implemented as a flexible platform with an off-the-shelf dynamics engine. Experiments aimed at evolving Sims-type walkers resulted in the emergence of various realistic gaits while using fairly simple objective functions. Due to the flexibility of the system, drastically different morphologies and functions evolved with only minor modifications to the system and objective function. For example, various throwing techniques evolved when selecting for catapults that propel a block as far as possible. Among the strategies and morphologies evolved, we find the drop-kick strategy, as well as the systematic invention of the principle behind the wheel, when allowing mutations to the projectile. PMID:17355189

  1. Evolving virtual creatures and catapults.

    PubMed

    Chaumont, Nicolas; Egli, Richard; Adami, Christoph

    2007-01-01

    We present a system that can evolve the morphology and the controller of virtual walking and block-throwing creatures (catapults) using a genetic algorithm. The system is based on Sims' work, implemented as a flexible platform with an off-the-shelf dynamics engine. Experiments aimed at evolving Sims-type walkers resulted in the emergence of various realistic gaits while using fairly simple objective functions. Due to the flexibility of the system, drastically different morphologies and functions evolved with only minor modifications to the system and objective function. For example, various throwing techniques evolved when selecting for catapults that propel a block as far as possible. Among the strategies and morphologies evolved, we find the drop-kick strategy, as well as the systematic invention of the principle behind the wheel, when allowing mutations to the projectile.

  2. 18O/16O in CO2 evolved from goethite during some unusually rapid solid state α-FeOOH to α-Fe2O3 phase transitions: Test of an exchange model for possible use in oxygen isotope analyses of goethite

    NASA Astrophysics Data System (ADS)

    Yapp, Crayton J.

    2015-12-01

    The initial ∼60% of an isothermal vacuum dehydration of goethite can commonly be approximated by first order kinetics. Also, natural goethites contain small amounts of an Fe(CO3)OH component in apparent solid solution. The 18O/16O of CO2 evolved from the Fe(CO3)OH during isothermal vacuum dehydrations is related to the 18O/16O of the goethite by an apparent fractionation factor (αapp) that is, in turn, correlated with a first order rate constant, |m|. A kinetic exchange model predicts that αapp should decrease as |m| increases for a range of |m| that corresponds to relatively slow rates of dehydration. This pattern has been observed in published results. In contrast, for rapid rates of dehydration, αapp is predicted to increase with increasing |m|. Isothermal vacuum dehydrations of two natural goethites had unusually large values of |m| and provided serendipitous tests of this rapid-rate prediction. For these experiments, the measured values of αapp were consistent with patterns of variation predicted by the model. This allowed an estimate of the activation energy (E2) of a model parameter, K2, which is the rate constant for oxygen isotope exchange between CO2 and H2O during the solid-state goethite to hematite phase transition. The estimated value of E2 is only ∼9 kJ/mol. Heterogeneous catalysis tends to decrease the activation energies of gas reactions. Consequently, the inferred value of E2 suggests that goethite and/or hematite catalyze oxygen isotope exchange between CO2 and H2O during the solid-state phase change. Yield, δ13C, and δ18O values are routinely measured for increments of CO2 evolved from the Fe(CO3)OH component during isothermal vacuum dehydration of goethite. Model-predicted values of αapp can be combined with plateau δ18O values of the evolved CO2 to estimate the δ18O of the goethite with a less than optimal, but potentially useful, precision of about ±0.8‰. Therefore, a single analytical procedure (incremental dehydration

  3. Homonuclear Mixed-Valent Cobalt Imidazolate Framework for Oxygen-Evolution Electrocatalysis.

    PubMed

    Flügel, Erik A; Lau, Vincent W-H; Schlomberg, Hendrik; Glaum, Robert; Lotsch, Bettina V

    2016-03-01

    Herein, the synthesis and characterization of the first mixed-valent, purely cobalt-based zeolitic imidazolate framework, Co(II)3Co(III)2(C3H3N2)12 is presented. The material adopts the cubic garnet-type structure and combines high thermal stability of up to 350 °C with excellent chemical stability. Electrochemical characterization showed that the cobalt centres are redox active and efficiently support oxygen evolution, thus rendering this framework a potential candidate for single-site heterogeneous catalysis based on earth-abundant elements.

  4. Homonuclear Mixed-Valent Cobalt Imidazolate Framework for Oxygen-Evolution Electrocatalysis.

    PubMed

    Flügel, Erik A; Lau, Vincent W-H; Schlomberg, Hendrik; Glaum, Robert; Lotsch, Bettina V

    2016-03-01

    Herein, the synthesis and characterization of the first mixed-valent, purely cobalt-based zeolitic imidazolate framework, Co(II)3Co(III)2(C3H3N2)12 is presented. The material adopts the cubic garnet-type structure and combines high thermal stability of up to 350 °C with excellent chemical stability. Electrochemical characterization showed that the cobalt centres are redox active and efficiently support oxygen evolution, thus rendering this framework a potential candidate for single-site heterogeneous catalysis based on earth-abundant elements. PMID:26676066

  5. Spacetimes containing slowly evolving horizons

    SciTech Connect

    Kavanagh, William; Booth, Ivan

    2006-08-15

    Slowly evolving horizons are trapping horizons that are ''almost'' isolated horizons. This paper reviews their definition and discusses several spacetimes containing such structures. These include certain Vaidya and Tolman-Bondi solutions as well as (perturbatively) tidally distorted black holes. Taking into account the mass scales and orders of magnitude that arise in these calculations, we conjecture that slowly evolving horizons are the norm rather than the exception in astrophysical processes that involve stellar-scale black holes.

  6. Natural selection promotes antigenic evolvability.

    PubMed

    Graves, Christopher J; Ros, Vera I D; Stevenson, Brian; Sniegowski, Paul D; Brisson, Dustin

    2013-01-01

    The hypothesis that evolvability - the capacity to evolve by natural selection - is itself the object of natural selection is highly intriguing but remains controversial due in large part to a paucity of direct experimental evidence. The antigenic variation mechanisms of microbial pathogens provide an experimentally tractable system to test whether natural selection has favored mechanisms that increase evolvability. Many antigenic variation systems consist of paralogous unexpressed 'cassettes' that recombine into an expression site to rapidly alter the expressed protein. Importantly, the magnitude of antigenic change is a function of the genetic diversity among the unexpressed cassettes. Thus, evidence that selection favors among-cassette diversity is direct evidence that natural selection promotes antigenic evolvability. We used the Lyme disease bacterium, Borrelia burgdorferi, as a model to test the prediction that natural selection favors amino acid diversity among unexpressed vls cassettes and thereby promotes evolvability in a primary surface antigen, VlsE. The hypothesis that diversity among vls cassettes is favored by natural selection was supported in each B. burgdorferi strain analyzed using both classical (dN/dS ratios) and Bayesian population genetic analyses of genetic sequence data. This hypothesis was also supported by the conservation of highly mutable tandem-repeat structures across B. burgdorferi strains despite a near complete absence of sequence conservation. Diversification among vls cassettes due to natural selection and mutable repeat structures promotes long-term antigenic evolvability of VlsE. These findings provide a direct demonstration that molecular mechanisms that enhance evolvability of surface antigens are an evolutionary adaptation. The molecular evolutionary processes identified here can serve as a model for the evolution of antigenic evolvability in many pathogens which utilize similar strategies to establish chronic infections.

  7. Robustness to Faults Promotes Evolvability: Insights from Evolving Digital Circuits

    PubMed Central

    Nolfi, Stefano

    2016-01-01

    We demonstrate how the need to cope with operational faults enables evolving circuits to find more fit solutions. The analysis of the results obtained in different experimental conditions indicates that, in absence of faults, evolution tends to select circuits that are small and have low phenotypic variability and evolvability. The need to face operation faults, instead, drives evolution toward the selection of larger circuits that are truly robust with respect to genetic variations and that have a greater level of phenotypic variability and evolvability. Overall our results indicate that the need to cope with operation faults leads to the selection of circuits that have a greater probability to generate better circuits as a result of genetic variation with respect to a control condition in which circuits are not subjected to faults. PMID:27409589

  8. Signing Apes and Evolving Linguistics.

    ERIC Educational Resources Information Center

    Stokoe, William C.

    Linguistics retains from its antecedents, philology and the study of sacred writings, some of their apologetic and theological bias. Thus it has not been able to face squarely the question how linguistic function may have evolved from animal communication. Chimpanzees' use of signs from American Sign Language forces re-examination of language…

  9. Evolving Sensitivity Balances Boolean Networks

    PubMed Central

    Luo, Jamie X.; Turner, Matthew S.

    2012-01-01

    We investigate the sensitivity of Boolean Networks (BNs) to mutations. We are interested in Boolean Networks as a model of Gene Regulatory Networks (GRNs). We adopt Ribeiro and Kauffman’s Ergodic Set and use it to study the long term dynamics of a BN. We define the sensitivity of a BN to be the mean change in its Ergodic Set structure under all possible loss of interaction mutations. Insilico experiments were used to selectively evolve BNs for sensitivity to losing interactions. We find that maximum sensitivity was often achievable and resulted in the BNs becoming topologically balanced, i.e. they evolve towards network structures in which they have a similar number of inhibitory and excitatory interactions. In terms of the dynamics, the dominant sensitivity strategy that evolved was to build BNs with Ergodic Sets dominated by a single long limit cycle which is easily destabilised by mutations. We discuss the relevance of our findings in the context of Stem Cell Differentiation and propose a relationship between pluripotent stem cells and our evolved sensitive networks. PMID:22586459

  10. Slippery Texts and Evolving Literacies

    ERIC Educational Resources Information Center

    Mackey, Margaret

    2007-01-01

    The idea of "slippery texts" provides a useful descriptor for materials that mutate and evolve across different media. Eight adult gamers, encountering the slippery text "American McGee's Alice," demonstrate a variety of ways in which players attempt to manage their attention as they encounter a new text with many resonances. The range of their…

  11. Oxygen in demand: How oxygen has shaped vertebrate physiology.

    PubMed

    Dzal, Yvonne A; Jenkin, Sarah E M; Lague, Sabine L; Reichert, Michelle N; York, Julia M; Pamenter, Matthew E

    2015-08-01

    In response to varying environmental and physiological challenges, vertebrates have evolved complex and often overlapping systems. These systems detect changes in environmental oxygen availability and respond by increasing oxygen supply to the tissues and/or by decreasing oxygen demand at the cellular level. This suite of responses is termed the oxygen transport cascade and is comprised of several components. These components include 1) chemosensory detectors that sense changes in oxygen, carbon dioxide, and pH in the blood, and initiate changes in 2) ventilation and 3) cardiac work, thereby altering the rate of oxygen delivery to, and carbon dioxide clearance from, the tissues. In addition, changes in 4) cellular and systemic metabolism alters tissue-level metabolic demand. Thus the need for oxygen can be managed locally when increasing oxygen supply is not sufficient or possible. Together, these mechanisms provide a spectrum of responses that facilitate the maintenance of systemic oxygen homeostasis in the face of environmental hypoxia or physiological oxygen depletion (i.e. due to exercise or disease). Bill Milsom has dedicated his career to the study of these responses across phylogenies, repeatedly demonstrating the power of applying the comparative approach to physiological questions. The focus of this review is to discuss the anatomy, signalling pathways, and mechanics of each step of the oxygen transport cascade from the perspective of a Milsomite. That is, by taking into account the developmental, physiological, and evolutionary components of questions related to oxygen transport. We also highlight examples of some of the remarkable species that have captured Bill's attention through their unique adaptations in multiple components of the oxygen transport cascade, which allow them to achieve astounding physiological feats. Bill's research examining the oxygen transport cascade has provided important insight and leadership to the study of the diverse suite

  12. Removal of Ca2+ from the Oxygen-Evolving Complex in Photosystem II Has Minimal Effect on the Mn4O5 Core Structure: A Polarized Mn X-ray Absorption Spectroscopy Study

    SciTech Connect

    Lohmiller, Thomas; Shelby, Megan L.; Long, Xi; Yachandra, Vittal K.; Yano, Junko

    2015-05-19

    We studied Ca2+ -depleted and Ca2+ -reconstituted spinach photosystem II using polarized X-ray absorption spectroscopy of oriented PS II preparations to investigate the structural and functional role of the Ca2+ ion in the Mn4O5Ca cluster of the oxygen-evolving complex (OEC). Samples were prepared by low pH/citrate treatment as one-dimensionally ordered membrane layers and poised in the Ca2+ -depleted S1 (S1') and S2 (S2') states, the S2'YZ• state, at which point the catalytic cycle of water oxidation is inhibited, and the Ca2+ -reconstituted S1 state. Polarized Mn K-edge XANES and EXAFS spectra exhibit pronounced dichroism. Polarized EXAFS data of all states of Ca2+ -depleted PS II investigated show only minor changes in distances and orientations of the Mn-Mn vectors compared to the Ca2+ -containing OEC, which may be attributed to some loss of rigidity of the core structure. Thus, removal of the Ca2+ ion does not lead to fundamental distortion or rearrangement of the tetranuclear Mn cluster, which indicates that the Ca2+ ion in the OEC is not critical for structural maintenance of the cluster, at least in the S1 and S2 states, but fulfills a crucial catalytic function in the mechanism of the water oxidation reaction. On the basis of this structural information, reasons for the inhibitory effect of Ca2+ removal are discussed, attributing to the Ca2+ ion a fundamental role in organizing the surrounding (substrate) water framework and in proton-coupled electron transfer to YZ• (D1-Tyr161).

  13. Oxygen Therapy

    MedlinePlus

    ... 85-95% pure oxygen. The concentrator runs on electricity or a battery. A concentrator for home usually ... systems deliver 100% oxygen, and do not require electricity. A small canister can be filled from the ...

  14. Oxygen analyzer

    DOEpatents

    Benner, William H.

    1986-01-01

    An oxygen analyzer which identifies and classifies microgram quantities of oxygen in ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen-free nitrogen gas (N.sub.2), and the resulting oxygen quantitatively converted to carbon monoxide (CO) by contact with hot granular carbon (C). Two analysis modes are made possible: (1) rapid determination of total pyrolyzable oxygen obtained by decomposing the sample at 1135.degree. C., or (2) temperature-programmed oxygen thermal analysis obtained by heating the sample from room temperature to 1135.degree. C. as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N.sub.2, ovens used to heat the carbon and/or decompose the sample, and a non-dispersive infrared CO detector coupled to a mini-computer to quantitate oxygen in the decomposition products and control oven heating.

  15. Evolvable Systems for Space Applications

    NASA Technical Reports Server (NTRS)

    Lohn, Jason; Crawford, James; Globus, Al; Hornby, Gregory; Kraus, William; Larchev, Gregory; Pryor, Anna; Srivastava, Deepak

    2003-01-01

    This article surveys the research of the Evolvable System Group at NASA Ames Research Center. Over the past few years, our group has developed the ability to use evolutionary algorithms in a variety of NASA applications ranging from spacecraft antenna design, fault tolerance for programmable logic chips, atomic force field parameter fitting, analog circuit design, and earth observing satellite scheduling. In some of these applications, evolutionary algorithms match or improve on human performance.

  16. Evolvable Hardware for Space Applications

    NASA Technical Reports Server (NTRS)

    Lohn, Jason; Globus, Al; Hornby, Gregory; Larchev, Gregory; Kraus, William

    2004-01-01

    This article surveys the research of the Evolvable Systems Group at NASA Ames Research Center. Over the past few years, our group has developed the ability to use evolutionary algorithms in a variety of NASA applications ranging from spacecraft antenna design, fault tolerance for programmable logic chips, atomic force field parameter fitting, analog circuit design, and earth observing satellite scheduling. In some of these applications, evolutionary algorithms match or improve on human performance.

  17. Evolving Systems and Adaptive Key Component Control

    NASA Technical Reports Server (NTRS)

    Frost, Susan A.; Balas, Mark J.

    2009-01-01

    We propose a new framework called Evolving Systems to describe the self-assembly, or autonomous assembly, of actively controlled dynamical subsystems into an Evolved System with a higher purpose. An introduction to Evolving Systems and exploration of the essential topics of the control and stability properties of Evolving Systems is provided. This chapter defines a framework for Evolving Systems, develops theory and control solutions for fundamental characteristics of Evolving Systems, and provides illustrative examples of Evolving Systems and their control with adaptive key component controllers.

  18. Oxygen analyzer

    DOEpatents

    Benner, W.H.

    1984-05-08

    An oxygen analyzer which identifies and classifies microgram quantities of oxygen in ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen-free nitrogen gas (N/sub 2/), and the resulting oxygen quantitatively converted to carbon monoxide (CO) by contact with hot granular carbon (C). Two analysis modes are made possible: (1) rapid determination of total pyrolyzable obtained by decomposing the sample at 1135/sup 0/C, or (2) temperature-programmed oxygen thermal analysis obtained by heating the sample from room temperature to 1135/sup 0/C as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N/sub 2/, ovens used to heat the carbon and/or decompose the sample, and a non-dispersive infrared CO detector coupled to a mini-computer to quantitate oxygen in the decomposition products and control oven heating.

  19. Evolving Robust Gene Regulatory Networks

    PubMed Central

    Noman, Nasimul; Monjo, Taku; Moscato, Pablo; Iba, Hitoshi

    2015-01-01

    Design and implementation of robust network modules is essential for construction of complex biological systems through hierarchical assembly of ‘parts’ and ‘devices’. The robustness of gene regulatory networks (GRNs) is ascribed chiefly to the underlying topology. The automatic designing capability of GRN topology that can exhibit robust behavior can dramatically change the current practice in synthetic biology. A recent study shows that Darwinian evolution can gradually develop higher topological robustness. Subsequently, this work presents an evolutionary algorithm that simulates natural evolution in silico, for identifying network topologies that are robust to perturbations. We present a Monte Carlo based method for quantifying topological robustness and designed a fitness approximation approach for efficient calculation of topological robustness which is computationally very intensive. The proposed framework was verified using two classic GRN behaviors: oscillation and bistability, although the framework is generalized for evolving other types of responses. The algorithm identified robust GRN architectures which were verified using different analysis and comparison. Analysis of the results also shed light on the relationship among robustness, cooperativity and complexity. This study also shows that nature has already evolved very robust architectures for its crucial systems; hence simulation of this natural process can be very valuable for designing robust biological systems. PMID:25616055

  20. Primordial evolvability: Impasses and challenges.

    PubMed

    Vasas, Vera; Fernando, Chrisantha; Szilágyi, András; Zachár, István; Santos, Mauro; Szathmáry, Eörs

    2015-09-21

    While it is generally agreed that some kind of replicating non-living compounds were the precursors of life, there is much debate over their possible chemical nature. Metabolism-first approaches propose that mutually catalytic sets of simple organic molecules could be capable of self-replication and rudimentary chemical evolution. In particular, the graded autocatalysis replication domain (GARD) model, depicting assemblies of amphiphilic molecules, has received considerable interest. The system propagates compositional information across generations and is suggested to be a target of natural selection. However, evolutionary simulations indicate that the system lacks selectability (i.e. selection has negligible effect on the equilibrium concentrations). We elaborate on the lessons learnt from the example of the GARD model and, more widely, on the issue of evolvability, and discuss the implications for similar metabolism-first scenarios. We found that simple incorporation-type chemistry based on non-covalent bonds, as assumed in GARD, is unlikely to result in alternative autocatalytic cycles when catalytic interactions are randomly distributed. An even more serious problem stems from the lognormal distribution of catalytic factors, causing inherent kinetic instability of such loops, due to the dominance of efficiently catalyzed components that fail to return catalytic aid. Accordingly, the dynamics of the GARD model is dominated by strongly catalytic, but not auto-catalytic, molecules. Without effective autocatalysis, stable hereditary propagation is not possible. Many repetitions and different scaling of the model come to no rescue. Despite all attempts to show the contrary, the GARD model is not evolvable, in contrast to reflexively autocatalytic networks, complemented by rare uncatalyzed reactions and compartmentation. The latter networks, resting on the creation and breakage of chemical bonds, can generate novel ('mutant') autocatalytic loops from a given set of

  1. Appreciating Oxygen

    ERIC Educational Resources Information Center

    Weiss, Hilton M.

    2008-01-01

    Photosynthetic flora and microfauna utilize light from the sun to convert carbon dioxide and water into carbohydrates and oxygen. While these carbohydrates and their derivative hydrocarbons are generally considered to be fuels, it is the thermodynamically energetic oxygen molecule that traps, stores, and provides almost all of the energy that…

  2. Isotopic Analysis and Evolved Gases

    NASA Technical Reports Server (NTRS)

    Swindle, Timothy D.; Boynton, William V.; Chutjian, Ara; Hoffman, John H.; Jordan, Jim L.; Kargel, Jeffrey S.; McEntire, Richard W.; Nyquist, Larry

    1996-01-01

    Precise measurements of the chemical, elemental, and isotopic composition of planetary surface material and gases, and observed variations in these compositions, can contribute significantly to our knowledge of the source(s), ages, and evolution of solar system materials. The analyses discussed in this paper are mostly made by mass spectrometers or some other type of mass analyzer, and address three broad areas of interest: (1) atmospheric composition - isotopic, elemental, and molecular, (2) gases evolved from solids, and (3) solids. Current isotopic data on nine elements, mostly from in situ analysis, but also from meteorites and telescopic observations are summarized. Potential instruments for isotopic analysis of lunar, Martian, Venusian, Mercury, and Pluto surfaces, along with asteroid, cometary and icy satellites, surfaces are discussed.

  3. Speech processing: An evolving technology

    SciTech Connect

    Crochiere, R.E.; Flanagan, J.L.

    1986-09-01

    As we enter the information age, speech processing is emerging as an important technology for making machines easier and more convenient for humans to use. It is both an old and a new technology - dating back to the invention of the telephone and forward, at least in aspirations, to the capabilities of HAL in 2001. Explosive advances in microelectronics now make it possible to implement economical real-time hardware for sophisticated speech processing - processing that formerly could be demonstrated only in simulations on main-frame computers. As a result, fundamentally new product concepts - as well as new features and functions in existing products - are becoming possible and are being explored in the marketplace. As the introductory piece to this issue, the authors draw a brief perspective on the evolving field of speech processing and assess the technology in the the three constituent sectors: speech coding, synthesis, and recognition.

  4. Planets in Evolved Binary Systems

    NASA Astrophysics Data System (ADS)

    Perets, Hagai B.

    2011-03-01

    Exo-planets are typically thought to form in protoplanetary disks left over from protostellar disk of their newly formed host star. However, additional planetary formation and evolution routes may exist in old evolved binary systems. Here we discuss the implications of binary stellar evolution on planetary systems in such environments. In these binary systems stellar evolution could lead to the formation of symbiotic stars, where mass is lost from one star and could be transferred to its binary companion, and may form an accretion disk around it. This raises the possibility that such a disk could provide the necessary environment for the formation of a new, second generation of planets in both circumstellar or circumbinary configurations. Pre-existing first generation planets surviving the post-MS evolution of such systems would be dynamically effected by the mass loss in the systems and may also interact with the newly formed disk. Such planets and/or planetesimals may also serve as seeds for the formation of the second generation planets, and/or interact with them, possibly forming atypical planetary systems. Second generation planetary systems should be typically found in white dwarf binary systems, and may show various observational signatures. Most notably, second generation planets could form in environment which are inaccessible, or less favorable, for first generation planets. The orbital phase space available for the second generation planets could be forbidden (in terms of the system stability) to first generation planets in the pre-evolved progenitor binaries. In addition planets could form in metal poor environments such as globular clusters and/or in double compact object binaries. Observations of exo-planets in such forbidden or unfavorable regions could possibly serve to uniquely identify their second generation character. Finally, we point out a few observed candidate second generation planetary systems, including Gl 86, HD 27442 and all of the

  5. A photoemission study of the effectiveness of nickel, manganese, and cobalt based corrosion barriers for silicon photo-anodes during water oxidation

    NASA Astrophysics Data System (ADS)

    O'Connor, Robert; Bogan, Justin; McCoy, Anthony; Byrne, Conor; Hughes, Greg

    2016-05-01

    Silicon is an attractive material for solar water splitting applications due to its abundance and its capacity to absorb a large fraction of incident solar radiation. However, it has not received as much attention as other materials due to its tendency to oxidize very quickly in aqueous environments, particularly when it is employed as the anode where it drives the oxygen evolution reaction. In recent years, several works have appeared in the literature examining the suitability of thin transition metal oxide films grown on top of the silicon to act as a corrosion barrier. The film should be transparent to solar radiation, allow hole transport from the silicon surface to the electrolyte, and stop the diffusion of oxygen from the electrolyte back to the silicon. In this work, we compare Mn-oxide, Co-oxide, and Ni-oxide thin films grown using physical vapor deposition in order to evaluate which material offers the best combination of photocurrent and corrosion protection. In addition to the electrochemical data, we also present a detailed before-and-after study of the surface chemistry of the films using x-ray photoelectron spectroscopy. This approach allows for a comprehensive analysis of the mechanisms by which the corrosion barriers protect the underlying silicon, and how they degrade during the water oxidation reaction.

  6. Oxygen concentration inside a functioning photosynthetic cell.

    PubMed

    Kihara, Shigeharu; Hartzler, Daniel A; Savikhin, Sergei

    2014-05-01

    The excess oxygen concentration in the photosynthetic membranes of functioning oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on oxygen production rates of cyanobacterial cells. The excess oxygen concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 μM, or four orders of magnitude lower than the oxygen concentration in air-saturated water. Such a low concentration suggests that the first oxygenic photosynthetic bacteria in solitary form could have evolved ∼2.8 billion years ago without special mechanisms to protect them against reactive oxygen species. These mechanisms instead could have been developed during the following ∼500 million years while the oxygen level in the Earth's atmosphere was slowly rising. Excess oxygen concentrations within individual cells of the apomorphic cyanobacteria Synechocystis and Synechococcus are 0.064 and 0.25 μM, respectively. These numbers suggest that intramembrane and intracellular proteins in isolated oxygenic photosynthetic cells are not subjected to excessively high oxygen levels. The situation is different for closely packed colonies of photosynthetic cells. Calculations show that the excess concentration within colonies that are ∼40 μm or larger in diameter can be comparable to the oxygen concentration in air-saturated water, suggesting that species forming colonies require protection against reactive oxygen species even in the absence of oxygen in the surrounding atmosphere.

  7. Oxygen sensing and metabolic homeostasis.

    PubMed

    Palmer, Biff F; Clegg, Deborah J

    2014-11-01

    Oxygen-sensing mechanisms have evolved to maintain cell and tissue homeostasis since the ability to sense and respond to changes in oxygen is essential for survival. The primary site of oxygen sensing occurs at the level of the carotid body which in response to hypoxia signals increased ventilation without the need for new protein synthesis. Chronic hypoxia activates cellular sensing mechanisms which lead to protein synthesis designed to alter cellular metabolism so cells can adapt to the low oxygen environment without suffering toxicity. The master regulator of the cellular response is hypoxia-inducible factor (HIF). Activation of this system under condition of hypobaric hypoxia leads to weight loss accompanied by increased basal metabolic rate and suppression of appetite. These effects are dose dependent, gender and genetic specific, and results in adverse effects if the exposure is extreme. Hypoxic adipose tissue may represent a unified cellular mechanism for variety of metabolic disorders, and insulin resistance in patients with metabolic syndrome.

  8. A Quantitative Approach to Assessing System Evolvability

    NASA Technical Reports Server (NTRS)

    Christian, John A., III

    2004-01-01

    When selecting a system from multiple candidates, the customer seeks the one that best meets his or her needs. Recently the desire for evolvable systems has become more important and engineers are striving to develop systems that accommodate this need. In response to this search for evolvability, we present a historical perspective on evolvability, propose a refined definition of evolvability, and develop a quantitative method for measuring this property. We address this quantitative methodology from both a theoretical and practical perspective. This quantitative model is then applied to the problem of evolving a lunar mission to a Mars mission as a case study.

  9. Pilot Plant Makes Oxygen Difluoride

    NASA Technical Reports Server (NTRS)

    Humphrey, Marshall F.; Lawton, Emil A.

    1989-01-01

    Pilot plant makes oxygen difluoride highly-energetic, space-storable oxidizer not made commercially. Designed to handle reactants, product, and byproduct, most of which highly reactive, corrosive, and toxic. Oxygen difluoride evolves continuously from reactor containing potassium hydroxide in water at 10 degree C. Collection tanks alternated; one filled while other drained to storage cylinder. Excess OF2 and F2 dissipated in combustion of charcoal in burn barrel. Toxic byproduct, potassium fluoride, reacted with calcium hydroxide to form nontoxic calcium fluoride and to regenerate potassium hydroxide. Equipment processes toxic, difficult-to-make substance efficiently and safely.

  10. Magnetic fields around evolved stars

    NASA Astrophysics Data System (ADS)

    Leal-Ferreira, M.; Vlemmings, W.; Kemball, A.; Amiri, N.; Maercker, M.; Ramstedt, S.; Olofsson, G.

    2014-04-01

    A number of mechanisms, such as magnetic fields, (binary) companions and circumstellar disks have been suggested to be the cause of non-spherical PNe and in particular collimated outflows. This work investigates one of these mechanisms: the magnetic fields. While MHD simulations show that the fields can indeed be important, few observations of magnetic fields have been done so far. We used the VLBA to observe five evolved stars, with the goal of detecting the magnetic field by means of water maser polarization. The sample consists in four AGB stars (IK Tau, RT Vir, IRC+60370 and AP Lyn) and one pPN (OH231.8+4.2). In four of the five sources, several strong maser features were detected allowing us to measure the linear and/or circular polarization. Based on the circular polarization detections, we infer the strength of the component of the field along the line of sight to be between ~30 mG and ~330 mG in the water maser regions of these four sources. When extrapolated to the surface of the stars, the magnetic field strength would be between a few hundred mG and a few Gauss when assuming a toroidal field geometry and higher when assuming more complex magnetic fields. We conclude that the magnetic energy we derived in the water maser regions is higher than the thermal and kinetic energy, leading to the conclusion that, indeed, magnetic fields probably play an important role in shaping Planetary Nebulae.

  11. How do drumlin patterns evolve?

    NASA Astrophysics Data System (ADS)

    Ely, Jeremy; Clark, Chris; Spagnolo, Matteo; Hughes, Anna

    2016-04-01

    The flow of a geomorphic agent over a sediment bed creates patterns in the substrate composed of bedforms. Ice is no exception to this, organising soft sedimentary substrates into subglacial bedforms. As we are yet to fully observe their initiation and evolution beneath a contemporary ice mass, little is known about how patterns in subglacial bedforms develop. Here we study 36,222 drumlins, divided into 72 flowsets, left behind by the former British-Irish Ice sheet. These flowsets provide us with 'snapshots' of drumlin pattern development. The probability distribution functions of the size and shape metrics of drumlins within these flowsets were analysed to determine whether behaviour that is common of other patterned phenomena has occurred. Specifically, we ask whether drumlins i) are printed at a specific scale; ii) grow or shrink after they initiate; iii) stabilise at a specific size and shape; and iv) migrate. Our results indicate that drumlins initiate at a minimum size and spacing. After initiation, the log-normal distribution of drumlin size and shape metrics suggests that drumlins grow, or possibly shrink, as they develop. We find no evidence for stabilisation in drumlin length, supporting the idea of a subglacial bedform continuum. Drumlin migration is difficult to determine from the palaeo-record. However, there are some indications that a mixture of static and mobile drumlins occurs, which could potentially lead to collisions, cannibalisation and coarsening. Further images of modern drumlin fields evolving beneath ice are required to capture stages of drumlin pattern evolution.

  12. Recommendation in evolving online networks

    NASA Astrophysics Data System (ADS)

    Hu, Xiao; Zeng, An; Shang, Ming-Sheng

    2016-02-01

    Recommender system is an effective tool to find the most relevant information for online users. By analyzing the historical selection records of users, recommender system predicts the most likely future links in the user-item network and accordingly constructs a personalized recommendation list for each user. So far, the recommendation process is mostly investigated in static user-item networks. In this paper, we propose a model which allows us to examine the performance of the state-of-the-art recommendation algorithms in evolving networks. We find that the recommendation accuracy in general decreases with time if the evolution of the online network fully depends on the recommendation. Interestingly, some randomness in users' choice can significantly improve the long-term accuracy of the recommendation algorithm. When a hybrid recommendation algorithm is applied, we find that the optimal parameter gradually shifts towards the diversity-favoring recommendation algorithm, indicating that recommendation diversity is essential to keep a high long-term recommendation accuracy. Finally, we confirm our conclusions by studying the recommendation on networks with the real evolution data.

  13. Multiscale modelling of evolving foams

    NASA Astrophysics Data System (ADS)

    Saye, R. I.; Sethian, J. A.

    2016-06-01

    We present a set of multi-scale interlinked algorithms to model the dynamics of evolving foams. These algorithms couple the key effects of macroscopic bubble rearrangement, thin film drainage, and membrane rupture. For each of the mechanisms, we construct consistent and accurate algorithms, and couple them together to work across the wide range of space and time scales that occur in foam dynamics. These algorithms include second order finite difference projection methods for computing incompressible fluid flow on the macroscale, second order finite element methods to solve thin film drainage equations in the lamellae and Plateau borders, multiphase Voronoi Implicit Interface Methods to track interconnected membrane boundaries and capture topological changes, and Lagrangian particle methods for conservative liquid redistribution during rearrangement and rupture. We derive a full set of numerical approximations that are coupled via interface jump conditions and flux boundary conditions, and show convergence for the individual mechanisms. We demonstrate our approach by computing a variety of foam dynamics, including coupled evolution of three-dimensional bubble clusters attached to an anchored membrane and collapse of a foam cluster.

  14. Effect of molybdenum plus chromium on the corrosion of iron-, nickel-, and cobalt-base alloys in basaltic lava and simulated magmatic gas at 1150/sup 0/C

    SciTech Connect

    Ehrlich, S.A.; Douglass, D.L.

    1982-06-01

    The compatibility of several binary and ternary alloys in a magma environment was studied. Binary alloys containing molybdenum and ternary alloys containing chromium and molybdenum were exposed to basaltic lava at 1150/sup 0/C for periods of 24 and 96 hours. A cover gas was used to produce oxygen and sulfur fugacities corresponding to those of the gases dissolved in basaltic melts. Three base metals were used. These included iron, nickel, and cobalt. The primary reactions in binary alloys were found to be sulfidation. Oxide scales with a spinel layer formed on ternary alloys. The synergistic effect of molybdenum and chromium additions in ternary alloys exhibited superior corrosion resistance to binary alloys which formed base-metal sulfides down grain-boundaries. Extensive analyses of the reaction products by scanning electron microscopy, X-ray energy dispersive analysis, electron microprobe analysis, and metallography are presented for each alloys. The products formed are discussed with reference to thermodynamic stability diagrams, and the reaction path concept is used to explain some of the corrosion.

  15. Voyages Through Time: Everything Evolves

    NASA Astrophysics Data System (ADS)

    Pendleton, Y. J.; Tarter, J. C.; DeVore, E. K.; O'Sullivan, K. A.; Taylor, S. M.

    2001-12-01

    Evolutionary change is a powerful framework for studying our world and our place therein. It is a recurring theme in every realm of science: over time, the universe, the planet Earth, life, and human technologies all change, albeit on vastly different scales. Evolution offers scientific explanations for the age-old question, "Where did we come from?" In addition, historical perspectives of science show how our understanding has evolved over time. The complexities of all of these systems will never reveal a "finished" story. But it is a story of epic size, capable of inspiring awe and of expanding our sense of time and place, and eminently worthy of investigating. This story is the basis of Voyages Through Time. Voyages Through Time (VTT), provides teachers with not only background science content and pedagogy, but also with materials and resources for the teaching of evolution. The six modules, Cosmic Evolution, Planetary Evolution, Origin of Life, Evolution of Life, Hominid Evolution, and Evolution of Technology, emphasize student inquiry, and promote the nature of science, as recommended in the NSES and BSL. The modules are unified by the overarching theme of evolution and the meta questions: "What is changing?" "What is the rate of change?" and "What is the mechanism of change?" Determination of student outcomes for the project required effective collaboration of scientists, teachers, students and media specialists. The broadest curricula students outcomes are 1) an enjoyment of science, 2) an understanding of the nature of science, especially the understanding of evidence and re-evaluation, and 3) key science content. The curriculum is being developed by the SETI Institute, NASA Ames Research Center, California Academy of Sciences, and San Francisco State University, and is funded by the NSF (IMD 9730693), with support form Hewlett-Packard Company, The Foundation for Microbiology, Combined Federated Charities, NASA Astrobiology Institute, and NASA Fundamental

  16. Options for home oxygen therapy equipment: storage and metering of oxygen in the home.

    PubMed

    McCoy, Robert W

    2013-01-01

    Home oxygen therapy equipment options have increased over the past several decades, in response to innovations in technology, economic pressure from third-party payers, and patient demands. The delivery of oxygen in the home has evolved from packaged gas systems containing 99% United States Pharmacopeia oxygen provided by continuous-flow delivery to intermittent-flow delivery, with oxygen concentrators delivering < 99% oxygen purity. The majority of published papers indicating the value of long-term oxygen therapy have been based on continuous-flow delivery of 99% United States Pharmacopeia oxygen. The lack of research on new home oxygen therapy devices requires more clinical involvement from physician and respiratory therapist to evaluate the performance of oxygen devices used in the home to ensure the patient is provided adequate oxygenation at all activity levels. New standards of care are required to address the need to have consistent titration of long-term oxygen therapy to meet the patient's home needs at all activity levels. Consistent labeling of metering devices on home oxygen equipment will need to be developed by professional medical societies to be implemented by standards organizations that direct industrial manufacturers. Home oxygen therapy will need professionally trained respiratory therapists reimbursed for skills and service to ensure that patients receive optimal benefits from home oxygen equipment to improve patient outcomes and prevent complications and associated costs.

  17. The origin and evolution of oxygenic photosynthesis.

    PubMed

    Blankenship, R E; Hartman, H

    1998-03-01

    The evolutionary developments that led to the ability of photosynthetic organisms to oxidize water to molecular oxygen are discussed. Two major changes from a more primitive non-oxygen-evolving reaction center are required: a charge-accumulating system and a reaction center pigment with a greater oxidizing potential. Intermediate stages are proposed in which hydrogen peroxide was oxidized by the reaction center, and an intermediate pigment, similar to chlorophyll d, was present.

  18. The origin and evolution of oxygenic photosynthesis

    NASA Technical Reports Server (NTRS)

    Blankenship, R. E.; Hartman, H.

    1998-01-01

    The evolutionary developments that led to the ability of photosynthetic organisms to oxidize water to molecular oxygen are discussed. Two major changes from a more primitive non-oxygen-evolving reaction center are required: a charge-accumulating system and a reaction center pigment with a greater oxidizing potential. Intermediate stages are proposed in which hydrogen peroxide was oxidized by the reaction center, and an intermediate pigment, similar to chlorophyll d, was present.

  19. Oxygen saturation targets for preterm infants in the delivery room.

    PubMed

    Vento, Máximo; Aguar, Marta; Brugada, María; Escobar, Javier; Escrig, Raquel; Cubells, Elena; Cernada, María

    2012-04-01

    Fetal life evolves in a low oxygen milieu as compared to the extra-uterine. In the fetal to neonatal transition rapid changes in the oxygen content of the newly born infant occur within a brief period of time. Delivery room care givers should be aware of the slow transition regarding oxygenation, and supply oxygen as needed trying to avoid damage caused by hyper-and-hypoxia. In this regard, titrating oxygen inspiratory fraction against oxygen saturation as measured by pulse oximetry following recent nomogram ranges is a valid method. PMID:22390353

  20. Oxygen-Concentrating Cell

    NASA Technical Reports Server (NTRS)

    Buehler, K.

    1986-01-01

    High-purity oxygen produced from breathing air or from propellantgrade oxygen in oxygen-concentrating cell. Operating economics of concentrator attractive: Energy consumption about 4 Wh per liter of oxygen, slightly lower than conventional electrochemical oxygen extractors.

  1. Evolving Human Alteration of the Carbon Cycle: the Watershed Continuum

    NASA Astrophysics Data System (ADS)

    Kaushal, S.; Delaney Newcomb, K.; Newcomer Johnson, T.; Pennino, M. J.; Smith, R. M.; Beaulieu, J. J.; Belt, K.; Grese, M.; Blomquist, J.; Duan, S.; Findlay, S.; Likens, G.; Mayer, P. M.; Murthy, S.; Utz, R.; Yepsen, M.

    2014-12-01

    Watersheds experiencing land development are constantly evolving, and their biogeochemical signatures are expected to evolve across both space and time in drainage waters. We investigate how land development influences spatial and temporal evolution of the carbon cycle from small streams to major rivers in the Eastern U.S. Along the watershed continuum, we show that there is spatial evolution in: (1) the amount, chemical form, and bioavailability of carbon; (2) carbon retention/release at the reach scale; and (3) ecosystem metabolism of carbon from headwaters to coastal waters. Over shorter time scales, the interaction between land use and climate variability alters magnitude and frequency of carbon "pulses" in watersheds. Amounts and forms of carbon pulses in agricultural and urban watersheds respond similarly to climate variability due to headwater alteration and loss of ecosystem services to buffer runoff and temperature changes. Over longer time scales, land use change has altered organic carbon concentrations in tidal waters of Chesapeake Bay, and there have been increased bicarbonate alkalinity concentrations in rivers throughout the Eastern U.S. due to human activities. In summary, our analyses indicates that the form and reactivity of carbon have evolved over space and time along the watershed continuum with major implications for downstream ecosystem metabolism, biological oxygen demand, carbon dioxide production, and river alkalinization.

  2. What Technology? Reflections on Evolving Services

    ERIC Educational Resources Information Center

    Collins, Sharon

    2009-01-01

    Each year, the members of the EDUCAUSE Evolving Technologies Committee identify and research the evolving technologies that are having--or are predicted to have--the most direct impact on higher education institutions. The committee members choose the relevant topics, write white papers, and present their findings at the EDUCAUSE annual…

  3. BUBBLE DYNAMICS AT GAS-EVOLVING ELECTRODES

    SciTech Connect

    Sides, Paul J.

    1980-12-01

    Nucleation of bubbles, their growth by diffusion of dissolved gas to the bubble surface and by coalescence, and their detachment from the electrode are all very fast phenomena; furthermore, electrolytically generated bubbles range in size from ten to a few hundred microns; therefore, magnification and high speed cinematography are required to observe bubbles and the phenomena of their growth on the electrode surface. Viewing the action from the front side (the surface on which the bubbles form) is complicated because the most important events occur close to the surface and are obscured by other bubbles passing between the camera and the electrode; therefore, oxygen was evolved on a transparent tin oxide "window" electrode and the events were viewed from the backside. The movies showed that coalescence of bubbles is very important for determining the size of bubbles and in the chain of transport processes; growth by diffusion and by coalescence proceeds in series and parallel; coalescing bubbles cause significant fluid motion close to the electrode; bubbles can leave and reattach; and bubbles evolve in a cycle of growth by diffusion and different modes of coalescence. An analytical solution for the primary potential and current distribution around a spherical bubble in contact with a plane electrode is presented. Zero at the contact point, the current density reaches only one percent of its undisturbed value at 30 percent of the radius from that point and goes through a shallow maximum two radii away. The solution obtained for spherical bubbles is shown to apply for the small bubbles of electrolytic processes. The incremental resistance in ohms caused by sparse arrays of bubbles is given by {Delta}R = 1.352 af/kS where f is the void fraction of gas in the bubble layer, a is the bubble layer thickness, k is the conductivity of gas free electrolyte, and S is the electrode area. A densely populated gas bubble layer on an electrode was modeled as a hexagonal array of

  4. Reversible Oxygenation of Oxygen Transport Proteins.

    ERIC Educational Resources Information Center

    Drain, C. M.; Corden, Barry B.

    1987-01-01

    Describes a lecture demonstration which illustrates changes in the visible spectra of oxygen transport proteins upon reversible oxygen binding. Provides a comparison of the physical characteristics of oxygen storage and transport proteins. Reviews essentials for preparation of the materials. (ML)

  5. Interactions between planets and evolved stars

    NASA Astrophysics Data System (ADS)

    Shengbang, Qian; Zhongtao, Han; Fernández Lajús, E.; liying, Zhu; Wenping, Liao; Miloslav, Zejda; Linjia, Li; Voloshina, Irina; Liang, Liu; Jiajia., He

    2016-07-01

    Searching for planetary companions to evolved stars (e.g., white dwarfs (WD) and Cataclysmic Variables (CV)) can provide insight into the interaction between planets and evolved stars as well as on the ultimate fate of planets. We have monitored decades of CVs and their progenitors including some detached WD binaries since 2006 to search for planets orbiting these systems. In the present paper, we will show some observational results of circumbinary planets in orbits around CVs and their progenitors. Some of our findings include planets with the shortest distance to the central evolved binaries and a few multiple planetary systems orbiting binary stars. Finally, by comparing the observational properties of planetary companions to single WDs and WD binaries, the interaction between planets and evolved stars and the ultimate fate of planets are discussed.

  6. Neural mechanisms underlying the evolvability of behaviour

    PubMed Central

    Katz, Paul S.

    2011-01-01

    The complexity of nervous systems alters the evolvability of behaviour. Complex nervous systems are phylogenetically constrained; nevertheless particular species-specific behaviours have repeatedly evolved, suggesting a predisposition towards those behaviours. Independently evolved behaviours in animals that share a common neural architecture are generally produced by homologous neural structures, homologous neural pathways and even in the case of some invertebrates, homologous identified neurons. Such parallel evolution has been documented in the chromatic sensitivity of visual systems, motor behaviours and complex social behaviours such as pair-bonding. The appearance of homoplasious behaviours produced by homologous neural substrates suggests that there might be features of these nervous systems that favoured the repeated evolution of particular behaviours. Neuromodulation may be one such feature because it allows anatomically defined neural circuitry to be re-purposed. The developmental, genetic and physiological mechanisms that contribute to nervous system complexity may also bias the evolution of behaviour, thereby affecting the evolvability of species-specific behaviour. PMID:21690127

  7. Monitoring oxygenation.

    PubMed

    Severinghaus, John W

    2011-06-01

    Cyanosis was used for a century after dentists began pulling teeth under 100% N(2)O in 1844 because brief (2 min) severe hypoxia is harmless. Deaths came with curare and potent anesthetic respiratory arrest. Leland Clark's invention of a polarographic blood oxygen tension electrode (1954) was introduced for transcutaneous PO2 monitoring to adjust PEEP and CPAP PO2 to prevent premature infant blindness from excess O2 (1972). Oximetry for warning military aviators was tried after WW II but not used for routine monitoring until Takuo Aoyagi (1973) discovered an equation to measure SaO2 by the ratio of ratios of red and IR light transmitted through tissue as it changed with arterial pulses. Pulse oximetry (1982) depended on simultaneous technology improvements of light emitting red and IR diodes, tiny cheap solid state sensors and micro-chip computers. Continuous monitoring of airway anesthetic concentration and oxygen also became very common after 1980. Death from anesthesia fell 10 fold between 1985 and 2000 as pulse oximetry became universally used, but no proof of a causative relationship to pulse oximetry exists. It is now assumed that all anesthesiologist became much more aware of the dangers of prolonged hypoxia, perhaps by using the pulse oximeters. PMID:21717228

  8. Quantifying evolvability in small biological networks

    SciTech Connect

    Nemenman, Ilya; Mugler, Andrew; Ziv, Etay; Wiggins, Chris H

    2008-01-01

    The authors introduce a quantitative measure of the capacity of a small biological network to evolve. The measure is applied to a stochastic description of the experimental setup of Guet et al. (Science 2002, 296, pp. 1466), treating chemical inducers as functional inputs to biochemical networks and the expression of a reporter gene as the functional output. The authors take an information-theoretic approach, allowing the system to set parameters that optimise signal processing ability, thus enumerating each network's highest-fidelity functions. All networks studied are highly evolvable by the measure, meaning that change in function has little dependence on change in parameters. Moreover, each network's functions are connected by paths in the parameter space along which information is not significantly lowered, meaning a network may continuously change its functionality without completely losing it along the way. This property further underscores the evolvability of the networks.

  9. Metanetworks of artificially evolved regulatory networks

    NASA Astrophysics Data System (ADS)

    Danacı, Burçin; Erzan, Ayşe

    2016-04-01

    We study metanetworks arising in genotype and phenotype spaces, in the context of a model population of Boolean graphs evolved under selection for short dynamical attractors. We define the adjacency matrix of a graph as its genotype, which gets mutated in the course of evolution, while its phenotype is its set of dynamical attractors. Metanetworks in the genotype and phenotype spaces are formed, respectively, by genetic proximity and by phenotypic similarity, the latter weighted by the sizes of the basins of attraction of the shared attractors. We find that evolved populations of Boolean graphs form tree-like giant clusters in genotype space, while random populations of Boolean graphs are typically so far removed from each other genetically that they cannot form a metanetwork. In phenotype space, the metanetworks of evolved populations are super robust both under the elimination of weak connections and random removal of nodes.

  10. Reliability of genetic networks is evolvable

    NASA Astrophysics Data System (ADS)

    Braunewell, Stefan; Bornholdt, Stefan

    2008-06-01

    Control of the living cell functions with remarkable reliability despite the stochastic nature of the underlying molecular networks—a property presumably optimized by biological evolution. We ask here to what extent the ability of a stochastic dynamical network to produce reliable dynamics is an evolvable trait. Using an evolutionary algorithm based on a deterministic selection criterion for the reliability of dynamical attractors, we evolve networks of noisy discrete threshold nodes. We find that, starting from any random network, reliability of the attractor landscape can often be achieved with only a few small changes to the network structure. Further, the evolvability of networks toward reliable dynamics while retaining their function is investigated and a high success rate is found.

  11. JavaGenes: Evolving Graphs with Crossover

    NASA Technical Reports Server (NTRS)

    Globus, Al; Atsatt, Sean; Lawton, John; Wipke, Todd

    2000-01-01

    Genetic algorithms usually use string or tree representations. We have developed a novel crossover operator for a directed and undirected graph representation, and used this operator to evolve molecules and circuits. Unlike strings or trees, a single point in the representation cannot divide every possible graph into two parts, because graphs may contain cycles. Thus, the crossover operator is non-trivial. A steady-state, tournament selection genetic algorithm code (JavaGenes) was written to implement and test the graph crossover operator. All runs were executed by cycle-scavagging on networked workstations using the Condor batch processing system. The JavaGenes code has evolved pharmaceutical drug molecules and simple digital circuits. Results to date suggest that JavaGenes can evolve moderate sized drug molecules and very small circuits in reasonable time. The algorithm has greater difficulty with somewhat larger circuits, suggesting that directed graphs (circuits) are more difficult to evolve than undirected graphs (molecules), although necessary differences in the crossover operator may also explain the results. In principle, JavaGenes should be able to evolve other graph-representable systems, such as transportation networks, metabolic pathways, and computer networks. However, large graphs evolve significantly slower than smaller graphs, presumably because the space-of-all-graphs explodes combinatorially with graph size. Since the representation strongly affects genetic algorithm performance, adding graphs to the evolutionary programmer's bag-of-tricks should be beneficial. Also, since graph evolution operates directly on the phenotype, the genotype-phenotype translation step, common in genetic algorithm work, is eliminated.

  12. A Stefan problem on an evolving surface

    PubMed Central

    Alphonse, Amal; Elliott, Charles M.

    2015-01-01

    We formulate a Stefan problem on an evolving hypersurface and study the well posedness of weak solutions given L1 data. To do this, we first develop function spaces and results to handle equations on evolving surfaces in order to give a natural treatment of the problem. Then, we consider the existence of solutions for data; this is done by regularization of the nonlinearity. The regularized problem is solved by a fixed point theorem and then uniform estimates are obtained in order to pass to the limit. By using a duality method, we show continuous dependence, which allows us to extend the results to L1 data. PMID:26261364

  13. How the first biopolymers could have evolved.

    PubMed Central

    Abkevich, V I; Gutin, A M; Shakhnovich, E I

    1996-01-01

    In this work, we discuss a possible origin of the first biopolymers with stable unique structures. We suggest that at the prebiotic stage of evolution, long organic polymers had to be compact to avoid hydrolysis and had to be soluble and thus must not be exceedingly hydrophobic. We present an algorithm that generates such sequences for model proteins. The evolved sequences turn out to have a stable unique structure, into which they quickly fold. This result illustrates the idea that the unique three-dimensional native structures of first biopolymers could have evolved as a side effect of nonspecific physicochemical factors acting at the prebiotic stage of evolution. PMID:8570645

  14. Surveying The Digital Landscape: Evolving Technologies 2004. The EDUCAUSE Evolving Technologies Committee

    ERIC Educational Resources Information Center

    EDUCAUSE Review, 2004

    2004-01-01

    Each year, the members of the EDUCAUSE Evolving Technologies Committee identify and research the evolving technologies that are having the most direct impact on higher education institutions. The committee members choose the relevant topics, write white papers, and present their findings at the EDUCAUSE annual conference. This year, under the…

  15. Project Evolve User-Adopter Manual.

    ERIC Educational Resources Information Center

    Joiner, Lee M.

    An adult basic education (ABE) program for mentally retarded young adults between the ages of 14 and 26 years, Project Evolve can provide education agencies for educationally handicapped children with detailed information concerning an innovative program. The manual format was developed through interviews with professional educators concerning the…

  16. The Evolving Leadership Path of Visual Analytics

    SciTech Connect

    Kluse, Michael; Peurrung, Anthony J.; Gracio, Deborah K.

    2012-01-02

    This is a requested book chapter for an internationally authored book on visual analytics and related fields, coordianted by a UK university and to be published by Springer in 2012. This chapter is an overview of the leadship strategies that PNNL's Jim Thomas and other stakeholders used to establish visual analytics as a field, and how those strategies may evolve in the future.

  17. A Course Evolves-Physical Anthropology.

    ERIC Educational Resources Information Center

    O'Neil, Dennis

    2001-01-01

    Describes the development of an online physical anthropology course at Palomar College (California) that evolved from online tutorials. Discusses the ability to update materials on the Web more quickly than in traditional textbooks; creating Web pages that are readable by most Web browsers; test security issues; and clarifying ownership of online…

  18. Hyper massive black holes in evolved galaxies

    NASA Astrophysics Data System (ADS)

    Romero-Cruz, Fernando J.

    2015-09-01

    From the SDSS DR7 we took a sample of 16733 galaxies which do not show all of the emission lines required to classify their activity according to the classical BPT diagram (Baldwin et al. 1981 PASP). Since they do not show these emission lines they are thought to be evolved enough so to host Hyper Massive Black holes. We compared their statistical properties with other galaxies from the SDSS DR7 which do show emission lines and confirmed that their M-sigma relationship correspond to HMBHs (Gutelkin et al. 2009 ApJ) and also that their SFH confirms evolution. We also analyzed them with a new Diagnostic Diagram in the IR (Coziol et al. 2015 AJ) and found that their position in the IR color space (W3W4 vs W2W3) correspond to AGN activity with current low SF, another confirmation of an evolved galaxy. The position of our final sample in the IR diagram is in the same region in which Holm 15A lies, this galaxy is considered to host the most massive BHs in the nearby universe (Lopez-Cruz et al. 2014 ApJL). The morphology of these galaxies (all of them are classified as elliptical) confirms that they are very evolved. We claim that the hyper massive BH lie in galaxies very evolved and with very low SF and without clear AGN activity in the BPT diagram.

  19. Evolving dimensions in medical case reporting

    PubMed Central

    2011-01-01

    Medical case reports (MCRs) have been undervalued in the literature to date. It seems that while case series emphasize what is probable, case reports describe what is possible and what can go wrong. MCRs transfer medical knowledge and act as educational tools. We outline evolving aspects of the MCR in current practice. PMID:21524284

  20. Antibody therapeutics - the evolving patent landscape.

    PubMed

    Petering, Jenny; McManamny, Patrick; Honeyman, Jane

    2011-09-01

    The antibody patent landscape has evolved dramatically over the past 30 years, particularly in areas of technology relating to antibody modification to reduce immunogenicity in humans or improve antibody function. In some cases antibody techniques that were developed in the 1980s are still the subject of patent protection in the United States or Canada.

  1. The Evolving Office of the Registrar

    ERIC Educational Resources Information Center

    Pace, Harold L.

    2011-01-01

    A healthy registrar's office will continue to evolve as it considers student, faculty, and institutional needs; staff talents and expectations; technological opportunities; economic realities; space issues; work environments; and where the strategic plan is taking the institution in support of the mission. Several recognized leaders in the field…

  2. Apollo 16 Evolved Lithology Sodic Ferrogabbro

    NASA Technical Reports Server (NTRS)

    Zeigler, Ryan; Jolliff, B. L.; Korotev, R. L.

    2014-01-01

    Evolved lunar igneous lithologies, often referred to as the alkali suite, are a minor but important component of the lunar crust. These evolved samples are incompatible-element rich samples, and are, not surprisingly, most common in the Apollo sites in (or near) the incompatible-element rich region of the Moon known as the Procellarum KREEP Terrane (PKT). The most commonly occurring lithologies are granites (A12, A14, A15, A17), monzogabbro (A14, A15), alkali anorthosites (A12, A14), and KREEP basalts (A15, A17). The Feldspathic Highlands Terrane is not entirely devoid of evolved lithologies, and rare clasts of alkali gabbronorite and sodic ferrogabbro (SFG) have been identified in Apollo 16 station 11 breccias 67915 and 67016. Curiously, nearly all pristine evolved lithologies have been found as small clasts or soil particles, exceptions being KREEP basalts 15382/6 and granitic sample 12013 (which is itself a breccia). Here we reexamine the petrography and geochemistry of two SFG-like particles found in a survey of Apollo 16 2-4 mm particles from the Cayley Plains 62283,7-15 and 62243,10-3 (hereafter 7-15 and 10-3 respectively). We will compare these to previously reported SFG samples, including recent analyses on the type specimen of SFG from lunar breccia 67915.

  3. Hierarchical construction of an ultrathin layered double hydroxide nanoarray for highly-efficient oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Yang, Qiu; Li, Tian; Lu, Zhiyi; Sun, Xiaoming; Liu, Junfeng

    2014-09-01

    Efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) are essential components of renewable energy technologies, such as solar fuel synthesis and water splitting processes for powering fuel cells. Here, ultrathin NiCoFe layered double hydroxide (LDH) nanoplates, which directly grow on a cobalt-based nanowire array, forming a hierarchical nanoarray structure, are constructed as efficient oxygen evolution electrodes. In alkaline media, the ordered ultrathin hierarchical LDH nanoarray electrode shows dramatically increased catalytic activity compared to that of LDH nanoparticles and pure nanowire arrays due to the small size, large surface area, and high porosity of the NiCoFe LDH nanoarray. Only a small water oxidation overpotential (η) of 257 mV is needed for a current density of 80 mA cm-2 with a Tafel slope of 53 mV per decade. The hierarchical LDH nanoarray also shows excellent structural stability in alkaline media. After continuous testing under a high OER current density (~300 mA cm-2) for 10 h, the sample maintains the ordered hierarchical structure with no significant deactivation of the catalytic properties.Efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) are essential components of renewable energy technologies, such as solar fuel synthesis and water splitting processes for powering fuel cells. Here, ultrathin NiCoFe layered double hydroxide (LDH) nanoplates, which directly grow on a cobalt-based nanowire array, forming a hierarchical nanoarray structure, are constructed as efficient oxygen evolution electrodes. In alkaline media, the ordered ultrathin hierarchical LDH nanoarray electrode shows dramatically increased catalytic activity compared to that of LDH nanoparticles and pure nanowire arrays due to the small size, large surface area, and high porosity of the NiCoFe LDH nanoarray. Only a small water oxidation overpotential (η) of 257 mV is needed for a current density of 80 mA cm-2 with a

  4. Ultrafine Cobalt Catalysts on Covalent Carbon Nitride Frameworks for Oxygenic Photosynthesis.

    PubMed

    Zhang, Guigang; Zang, Shaohong; Lin, Lihua; Lan, Zhi-An; Li, Guosheng; Wang, Xinchen

    2016-01-27

    The rational cooperation of sustainable catalysts with suitable light-harvesting semiconductors to fabricate photosynthetic device/machinery has been regarded as an ideal technique to alleviate the current worldwide energy and environmental issues. Cobalt based species (e.g., Co-Pi, Co3O4, and Co-cubene) have attracted particular attentions because they are earth-abundant, cost-acceptable, and more importantly, it shows comparable water oxidation activities to the noble metal based catalysts (e.g., RuO2, IrO2). In this contribution, we compared two general cocatalysts modification strategies, based on the surface depositing and bulk doping of ultrafine cobalt species into the sustainable graphitic carbon nitride (g-C3N4) polymer networks for oxygenic photosynthesis by splitting water into oxygen, electrons, and protons. The chemical backbone of g-C3N4 does not alter after both engineering modifications; however, in comparison with the bulk doping, the optical and electronic properties of the surface depositing samples are efficiently promoted, and the photocatalytic water oxidation activities are increased owing to much more exposed active sites, reduced overpotential for oxygen evolution and the accelerated interface charge mobility. This paper underlines the advantage of surface engineering to establish efficient advanced polymeric composites for water oxidation, and it opens new insights into the architectural design of binary hybrid photocatalysts with high reactivity and further utilizations in the fields of energy and environment.

  5. Reactive Oxygen Species in Cardiovascular Disease

    PubMed Central

    Sugamura, Koichi; Keaney, John F.

    2011-01-01

    Based on the ‘free-radical theory’ of disease, researchers have been trying to elucidate the role of oxidative stress from free radicals in cardiovascular disease. Considerable data indicate that ROS and oxidative stress are important features of cardiovascular diseases including atherosclerosis, hypertension, and congestive heart failure. However, blanket strategies with antioxidants to ameliorate cardiovascular disease have not generally yielded favorable results. However, our understanding or reactive oxygen species has evolved to the point that we now realize these species have important roles in physiology as well as pathophysiology. Thus, it is overly simplistic to assume a general antioxidant strategy will yield specific effects on cardiovascular disease. Indeed, there are several sources of reactive oxygen species that are known to be active in the cardiovascular system. This review will address our understanding of reactive oxygen species sources in cardiovascular disease and both animal and human data defining how reactive oxygen species contribute to physiology and pathology. PMID:21627987

  6. Living with Oxygen Therapy

    MedlinePlus

    ... page from the NHLBI on Twitter. Living With Oxygen Therapy Oxygen therapy helps many people function better and be ... chronic obstructive pulmonary disease) Although you may need oxygen therapy continuously or for long periods, it doesn' ...

  7. Lunar production of oxygen by electrolysis

    NASA Technical Reports Server (NTRS)

    Keller, Rudolf

    1991-01-01

    Two approaches to prepare oxygen from lunar resources by direct electrolysis are discussed. Silicates can be melted or dissolved in a fused salt and electrolyzed with oxygen evolved at the anode. Direct melting and electrolysis is potentially a very simple process, but high temperatures of 1400-1500 C are required, which aggravates materials problems. Operating temperatures can be lowered to about 1000 C by employing a molten salt flux. In this case, however, losses of electrolyte components must be avoided. Experimentation on both approaches is progressing.

  8. An Evolved Orthogonal Enzyme/Cofactor Pair.

    PubMed

    Reynolds, Evan W; McHenry, Matthew W; Cannac, Fabien; Gober, Joshua G; Snow, Christopher D; Brustad, Eric M

    2016-09-28

    We introduce a strategy that expands the functionality of hemoproteins through orthogonal enzyme/heme pairs. By exploiting the ability of a natural heme transport protein, ChuA, to promiscuously import heme derivatives, we have evolved a cytochrome P450 (P450BM3) that selectively incorporates a nonproteinogenic cofactor, iron deuteroporphyrin IX (Fe-DPIX), even in the presence of endogenous heme. Crystal structures show that selectivity gains are due to mutations that introduce steric clash with the heme vinyl groups while providing a complementary binding surface for the smaller Fe-DPIX cofactor. Furthermore, the evolved orthogonal enzyme/cofactor pair is active in non-natural carbenoid-mediated olefin cyclopropanation. This methodology for the generation of orthogonal enzyme/cofactor pairs promises to expand cofactor diversity in artificial metalloenzymes.

  9. Evolving neural networks through augmenting topologies.

    PubMed

    Stanley, Kenneth O; Miikkulainen, Risto

    2002-01-01

    An important question in neuroevolution is how to gain an advantage from evolving neural network topologies along with weights. We present a method, NeuroEvolution of Augmenting Topologies (NEAT), which outperforms the best fixed-topology method on a challenging benchmark reinforcement learning task. We claim that the increased efficiency is due to (1) employing a principled method of crossover of different topologies, (2) protecting structural innovation using speciation, and (3) incrementally growing from minimal structure. We test this claim through a series of ablation studies that demonstrate that each component is necessary to the system as a whole and to each other. What results is significantly faster learning. NEAT is also an important contribution to GAs because it shows how it is possible for evolution to both optimize and complexify solutions simultaneously, offering the possibility of evolving increasingly complex solutions over generations, and strengthening the analogy with biological evolution. PMID:12180173

  10. Evolving neural models of path integration.

    PubMed

    Vickerstaff, R J; Di Paolo, E A

    2005-09-01

    We use a genetic algorithm to evolve neural models of path integration, with particular emphasis on reproducing the homing behaviour of Cataglyphis fortis ants. This is done within the context of a complete model system, including an explicit representation of the animal's movements within its environment. We show that it is possible to produce a neural network without imposing a priori any particular system for the internal representation of the animal's home vector. The best evolved network obtained is analysed in detail and is found to resemble the bicomponent model of Mittelstaedt. Because of the presence of leaky integration, the model can reproduce the systematic navigation errors found in desert ants. The model also naturally mimics the searching behaviour that ants perform once they have reached their estimate of the nest location. The results support possible roles for leaky integration and cosine-shaped compass response functions in path integration.

  11. Evolved gas analysis of secondary organic aerosols

    SciTech Connect

    Grosjean, D.; Williams, E.L. II; Grosjean, E. ); Novakov, T. )

    1994-11-01

    Secondary organic aerosols have been characterized by evolved gas analysis (EGA). Hydrocarbons selected as aerosol precursors were representative of anthropogenic emissions (cyclohexene, cyclopentene, 1-decene and 1-dodecene, n-dodecane, o-xylene, and 1,3,5-trimethylbenzene) and of biogenic emissions (the terpenes [alpha]-pinene, [beta]-pinene and d-limonene and the sesquiterpene trans-caryophyllene). Also analyzed by EGA were samples of secondary, primary (highway tunnel), and ambient (urban) aerosols before and after exposure to ozone and other photochemical oxidants. The major features of the EGA thermograms (amount of CO[sub 2] evolved as a function of temperature) are described. The usefulness and limitations of EGA data for source apportionment of atmospheric particulate carbon are briefly discussed. 28 refs., 7 figs., 4 tabs.

  12. The evolving definition of systemic arterial hypertension.

    PubMed

    Ram, C Venkata S; Giles, Thomas D

    2010-05-01

    Systemic hypertension is an important risk factor for premature cardiovascular disease. Hypertension also contributes to excessive morbidity and mortality. Whereas excellent therapeutic options are available to treat hypertension, there is an unsettled issue about the very definition of hypertension. At what level of blood pressure should we treat hypertension? Does the definition of hypertension change in the presence of co-morbid conditions? This article covers in detail the evolving concepts in the diagnosis and management of hypertension.

  13. Quantum games on evolving random networks

    NASA Astrophysics Data System (ADS)

    Pawela, Łukasz

    2016-09-01

    We study the advantages of quantum strategies in evolutionary social dilemmas on evolving random networks. We focus our study on the two-player games: prisoner's dilemma, snowdrift and stag-hunt games. The obtained result show the benefits of quantum strategies for the prisoner's dilemma game. For the other two games, we obtain regions of parameters where the quantum strategies dominate, as well as regions where the classical strategies coexist.

  14. How did life survive Earth's great oxygenation?

    PubMed

    Fischer, Woodward W; Hemp, James; Valentine, Joan Selverstone

    2016-04-01

    Life on Earth originated and evolved in anoxic environments. Around 2.4 billion-years-ago, ancestors of Cyanobacteria invented oxygenic photosynthesis, producing substantial amounts of O2 as a byproduct of phototrophic water oxidation. The sudden appearance of O2 would have led to significant oxidative stress due to incompatibilities with core cellular biochemical processes. Here we examine this problem through the lens of Cyanobacteria-the first taxa to observe significant fluxes of intracellular dioxygen. These early oxygenic organisms likely adapted to the oxidative stress by co-opting preexisting systems (exaptation) with fortuitous antioxidant properties. Over time more advanced antioxidant systems evolved, allowing Cyanobacteria to adapt to an aerobic lifestyle and become the most important environmental engineers in Earth history.

  15. Continuous evaluation of evolving behavioral intervention technologies.

    PubMed

    Mohr, David C; Cheung, Ken; Schueller, Stephen M; Hendricks Brown, C; Duan, Naihua

    2013-10-01

    Behavioral intervention technologies (BITs) are web-based and mobile interventions intended to support patients and consumers in changing behaviors related to health, mental health, and well-being. BITs are provided to patients and consumers in clinical care settings and commercial marketplaces, frequently with little or no evaluation. Current evaluation methods, including RCTs and implementation studies, can require years to validate an intervention. This timeline is fundamentally incompatible with the BIT environment, where technology advancement and changes in consumer expectations occur quickly, necessitating rapidly evolving interventions. However, BITs can routinely and iteratively collect data in a planned and strategic manner and generate evidence through systematic prospective analyses, thereby creating a system that can "learn." A methodologic framework, Continuous Evaluation of Evolving Behavioral Intervention Technologies (CEEBIT), is proposed that can support the evaluation of multiple BITs or evolving versions, eliminating those that demonstrate poorer outcomes, while allowing new BITs to be entered at any time. CEEBIT could be used to ensure the effectiveness of BITs provided through deployment platforms in clinical care organizations or BIT marketplaces. The features of CEEBIT are described, including criteria for the determination of inferiority, determination of BIT inclusion, methods of assigning consumers to BITs, definition of outcomes, and evaluation of the usefulness of the system. CEEBIT offers the potential to collapse initial evaluation and postmarketing surveillance, providing ongoing assurance of safety and efficacy to patients and consumers, payers, and policymakers. PMID:24050429

  16. Transistor Level Circuit Experiments using Evolvable Hardware

    NASA Technical Reports Server (NTRS)

    Stoica, A.; Zebulum, R. S.; Keymeulen, D.; Ferguson, M. I.; Daud, Taher; Thakoor, A.

    2005-01-01

    The Jet Propulsion Laboratory (JPL) performs research in fault tolerant, long life, and space survivable electronics for the National Aeronautics and Space Administration (NASA). With that focus, JPL has been involved in Evolvable Hardware (EHW) technology research for the past several years. We have advanced the technology not only by simulation and evolution experiments, but also by designing, fabricating, and evolving a variety of transistor-based analog and digital circuits at the chip level. EHW refers to self-configuration of electronic hardware by evolutionary/genetic search mechanisms, thereby maintaining existing functionality in the presence of degradations due to aging, temperature, and radiation. In addition, EHW has the capability to reconfigure itself for new functionality when required for mission changes or encountered opportunities. Evolution experiments are performed using a genetic algorithm running on a DSP as the reconfiguration mechanism and controlling the evolvable hardware mounted on a self-contained circuit board. Rapid reconfiguration allows convergence to circuit solutions in the order of seconds. The paper illustrates hardware evolution results of electronic circuits and their ability to perform under 230 C temperature as well as radiations of up to 250 kRad.

  17. Continuous Evaluation of Evolving Behavioral Intervention Technologies

    PubMed Central

    Mohr, David C.; Cheung, Ken; Schueller, Stephen M.; Brown, C. Hendricks; Duan, Naihua

    2013-01-01

    Behavioral intervention technologies (BITs) are web-based and mobile interventions intended to support patients and consumers in changing behaviors related to health, mental health, and well-being. BITs are provided to patients and consumers in clinical care settings and commercial marketplaces, frequently with little or no evaluation. Current evaluation methods, including RCTs and implementation studies, can require years to validate an intervention. This timeline is fundamentally incompatible with the BIT environment, where technology advancement and changes in consumer expectations occur quickly, necessitating rapidly evolving interventions. However, BITs can routinely and iteratively collect data in a planned and strategic manner and generate evidence through systematic prospective analyses, thereby creating a system that can “learn.” A methodologic framework, Continuous Evaluation of Evolving Behavioral Intervention Technologies (CEEBIT), is proposed that can support the evaluation of multiple BITs or evolving versions, eliminating those that demonstrate poorer outcomes, while allowing new BITs to be entered at any time. CEEBIT could be used to ensure the effectiveness of BITs provided through deployment platforms in clinical care organizations or BIT marketplaces. The features of CEEBIT are described, including criteria for the determination of inferiority, determination of BIT inclusion, methods of assigning consumers to BITs, definition of outcomes, and evaluation of the usefulness of the system. CEEBIT offers the potential to collapse initial evaluation and postmarketing surveillance, providing ongoing assurance of safety and efficacy to patients and consumers, payers, and policymakers. PMID:24050429

  18. Evolving specialization of the arthropod nervous system

    PubMed Central

    Jarvis, Erin; Bruce, Heather S.; Patel, Nipam H.

    2012-01-01

    The diverse array of body plans possessed by arthropods is created by generating variations upon a design of repeated segments formed during development, using a relatively small “toolbox” of conserved patterning genes. These attributes make the arthropod body plan a valuable model for elucidating how changes in development create diversity of form. As increasingly specialized segments and appendages evolved in arthropods, the nervous systems of these animals also evolved to control the function of these structures. Although there is a remarkable degree of conservation in neural development both between individual segments in any given species and between the nervous systems of different arthropod groups, the differences that do exist are informative for inferring general principles about the holistic evolution of body plans. This review describes developmental processes controlling neural segmentation and regionalization, highlighting segmentation mechanisms that create both ectodermal and neural segments, as well as recent studies of the role of Hox genes in generating regional specification within the central nervous system. We argue that this system generates a modular design that allows the nervous system to evolve in concert with the body segments and their associated appendages. This information will be useful in future studies of macroevolutionary changes in arthropod body plans, especially in understanding how these transformations can be made in a way that retains the function of appendages during evolutionary transitions in morphology. PMID:22723369

  19. The mechanism of Rubisco-catalysed oxygenation.

    PubMed

    Tcherkez, Guillaume

    2016-05-01

    Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the cornerstone of photosynthetic carbon assimilation because it catalyses the fixation of CO2 onto ribulose-1,5-bisphosphate (RuBP). The enzyme also catalyses RuBP oxygenation, thereby evolving phosphoglycolate which is recycled along the photorespiratory pathway. Oxygenation is quantitatively important, because under ordinary gaseous conditions, more than one third of RuBP molecules are oxygenated rather than carboxylated. However, contrary to carboxylation, the chemical mechanism of oxygenation is not well known, and little progress has been made since the early 80s. Here, I review recent experimental data that provide some new insights into the reaction mechanism, and carry out simple calculations of kinetic parameters. Isotope effects suggest that oxygenation is less likely initiated by a redox phenomenon (such as superoxide production) and more likely involves concerted chemical events that imply interactions with protons. A possible energy profile of the reaction is drawn which suggests that the generation of the oxygenated reaction intermediate (peroxide) is irreversible. Possible changes in oxygenation-associated rate constants between Rubisco forms are discussed. PMID:26286702

  20. Low Oxygen Response Mechanisms in Green Organisms

    PubMed Central

    Banti, Valeria; Giuntoli, Beatrice; Gonzali, Silvia; Loreti, Elena; Magneschi, Leonardo; Novi, Giacomo; Paparelli, Eleonora; Parlanti, Sandro; Pucciariello, Chiara; Santaniello, Antonietta; Perata, Pierdomenico

    2013-01-01

    Low oxygen stress often occurs during the life of green organisms, mostly due to the environmental conditions affecting oxygen availability. Both plants and algae respond to low oxygen by resetting their metabolism. The shift from mitochondrial respiration to fermentation is the hallmark of anaerobic metabolism in most organisms. This involves a modified carbohydrate metabolism coupled with glycolysis and fermentation. For a coordinated response to low oxygen, plants exploit various molecular mechanisms to sense when oxygen is either absent or in limited amounts. In Arabidopsis thaliana, a direct oxygen sensing system has recently been discovered, where a conserved N-terminal motif on some ethylene responsive factors (ERFs), targets the fate of the protein under normoxia/hypoxia. In Oryza sativa, this same group of ERFs drives physiological and anatomical modifications that vary in relation to the genotype studied. The microalga Chlamydomonas reinhardtii responses to low oxygen seem to have evolved independently of higher plants, posing questions on how the fermentative metabolism is modulated. In this review, we summarize the most recent findings related to these topics, highlighting promising developments for the future. PMID:23446868

  1. Design of a lunar oxygen production plant

    NASA Technical Reports Server (NTRS)

    Radhakrishnan, Ramalingam

    1990-01-01

    To achieve permanent human presence and activity on the moon, oxygen is required for both life support and propulsion. Lunar oxygen production using resources existing on the moon will reduce or eliminate the need to transport liquid oxygen from earth. In addition, the co-products of oxygen production will provide metals, structural ceramics, and other volatile compounds. This will enable development of even greater self-sufficiency as the lunar outpost evolves. Ilmenite is the most abundant metal-oxide mineral in the lunar regolith. A process involving the reaction of ilmenite with hydrogen at 1000 C to produce water, followed by the electrolysis of this water to provide oxygen and recycle the hydrogen has been explored. The objective of this 1990 Summer Faculty Project was to design a lunar oxygen-production plant to provide 5 metric tons of liquid oxygen per year from lunar soil. The results of this study describe the size and mass of the equipment, the power needs, feedstock quantity and the engineering details of the plant.

  2. Properties of evolved mass-losing stars in the Milky Way and variations in the interstellar dust composition

    SciTech Connect

    Thronson, H.A. Jr.; Latter, W.B.; Black, J.H.; Bally, J.; Hacking, P.

    1987-11-01

    A large sample of evolved carbon-rich and oxygen-rich objects has been studied using data from the IRAS Point Source Catalog. The number density of infrared-emitting carbon stars shows no variation with Galactocentric radius, while the evolved oxygen star volume density can be well fitted by a given law. A law is given for the number of carbon stars; a total is found in the Galaxy of 48,000 highly evolved oxygen stars. The mass-return rate for all evolved stars is found to be 0.35 solar mass/yr, with a small percentage contribution from carbon stars. The mass-loss rates for both types of stars are dominated by the small number of objects with the smallest rates. A mean lifetime of about 200,000 yr is obtained for both carbon and oxygen stars. Main-sequence stars in the mass range of three to five solar masses are the probable precursors of the carbon stars. 53 references.

  3. Properties of evolved mass-losing stars in the Milky Way and variations in the interstellar dust composition

    NASA Technical Reports Server (NTRS)

    Thronson, Harley A., Jr.; Latter, William B.; Black, John H.; Bally, John; Hacking, Perry

    1987-01-01

    A large sample of evolved carbon-rich and oxygen-rich objects has been studied using data from the IRAS Point Source Catalog. The number density of infrared-emitting 'carbon' stars shows no variation with Galactocentric radius, while the evolved 'oxygen' star volume density can be well fitted by a given law. A law is given for the number of carbon stars; a total is found in the Galaxy of 48,000 highly evolved oxygen stars. The mass-return rate for all evolved stars is found to be 0.35 solar mass/yr, with a small percentage contribution from carbon stars. The mass-loss rates for both types of stars are dominated by the small number of objects with the smallest rates. A mean lifetime of about 200,000 yr is obtained for both carbon and oxygen stars. Main-sequence stars in the mass range of three to five solar masses are the probable precursors of the carbon stars.

  4. Artificial oxygen transport protein

    DOEpatents

    Dutton, P. Leslie

    2014-09-30

    This invention provides heme-containing peptides capable of binding molecular oxygen at room temperature. These compounds may be useful in the absorption of molecular oxygen from molecular oxygen-containing atmospheres. Also included in the invention are methods for treating an oxygen transport deficiency in a mammal.

  5. Evolvability Is an Evolved Ability: The Coding Concept as the Arch-Unit of Natural Selection.

    PubMed

    Janković, Srdja; Ćirković, Milan M

    2016-03-01

    Physical processes that characterize living matter are qualitatively distinct in that they involve encoding and transfer of specific types of information. Such information plays an active part in the control of events that are ultimately linked to the capacity of the system to persist and multiply. This algorithmicity of life is a key prerequisite for its Darwinian evolution, driven by natural selection acting upon stochastically arising variations of the encoded information. The concept of evolvability attempts to define the total capacity of a system to evolve new encoded traits under appropriate conditions, i.e., the accessible section of total morphological space. Since this is dependent on previously evolved regulatory networks that govern information flow in the system, evolvability itself may be regarded as an evolved ability. The way information is physically written, read and modified in living cells (the "coding concept") has not changed substantially during the whole history of the Earth's biosphere. This biosphere, be it alone or one of many, is, accordingly, itself a product of natural selection, since the overall evolvability conferred by its coding concept (nucleic acids as information carriers with the "rulebook of meanings" provided by codons, as well as all the subsystems that regulate various conditional information-reading modes) certainly played a key role in enabling this biosphere to survive up to the present, through alterations of planetary conditions, including at least five catastrophic events linked to major mass extinctions. We submit that, whatever the actual prebiotic physical and chemical processes may have been on our home planet, or may, in principle, occur at some time and place in the Universe, a particular coding concept, with its respective potential to give rise to a biosphere, or class of biospheres, of a certain evolvability, may itself be regarded as a unit (indeed the arch-unit) of natural selection.

  6. Evolvability Is an Evolved Ability: The Coding Concept as the Arch-Unit of Natural Selection

    NASA Astrophysics Data System (ADS)

    Janković, Srdja; Ćirković, Milan M.

    2016-03-01

    Physical processes that characterize living matter are qualitatively distinct in that they involve encoding and transfer of specific types of information. Such information plays an active part in the control of events that are ultimately linked to the capacity of the system to persist and multiply. This algorithmicity of life is a key prerequisite for its Darwinian evolution, driven by natural selection acting upon stochastically arising variations of the encoded information. The concept of evolvability attempts to define the total capacity of a system to evolve new encoded traits under appropriate conditions, i.e., the accessible section of total morphological space. Since this is dependent on previously evolved regulatory networks that govern information flow in the system, evolvability itself may be regarded as an evolved ability. The way information is physically written, read and modified in living cells (the "coding concept") has not changed substantially during the whole history of the Earth's biosphere. This biosphere, be it alone or one of many, is, accordingly, itself a product of natural selection, since the overall evolvability conferred by its coding concept (nucleic acids as information carriers with the "rulebook of meanings" provided by codons, as well as all the subsystems that regulate various conditional information-reading modes) certainly played a key role in enabling this biosphere to survive up to the present, through alterations of planetary conditions, including at least five catastrophic events linked to major mass extinctions. We submit that, whatever the actual prebiotic physical and chemical processes may have been on our home planet, or may, in principle, occur at some time and place in the Universe, a particular coding concept, with its respective potential to give rise to a biosphere, or class of biospheres, of a certain evolvability, may itself be regarded as a unit (indeed the arch-unit) of natural selection.

  7. Oxygen Isotopes in Meteorites

    NASA Astrophysics Data System (ADS)

    Clayton, R. N.

    2003-12-01

    types of stellar sources, corresponding to the r-process, s-process, and p-process. Presolar silicon carbide grains, extracted from primitive meteorites, contain molybdenum that has been subject to s-process neutron capture in red-giant stars, resulting in large enrichments of isotopes at masses 95, 96, 97, 98, and severe depletions (up to 100%) of isotopes at masses 92 and 94 (p-process) and 100 (r-process) (Nicolussi et al., 1998). Complementary patterns have been found in whole-rock samples of several meteorites, with >1,000-fold smaller amplitude, suggesting the preservation of a small fraction of the initial isotopic heterogeneity ( Yin et al., 2002; Dauphas et al., 2002). Oxygen is another element for which primordial isotopic heterogeneity might be preserved. This is discussed further below.It would be highly desirable to have samples of oxygen-rich mineral grains that have formed in stellar atmospheres and have recorded the nucleosynthetic processes in individual stars. Similar samples are already available for carbon-rich grains, in the form of SiC and graphite, primarily from asymptotic giant branch (AGB) stars and supernovae (Anders and Zinner, 1993). These presolar grains have provided a wealth of detailed information concerning nucleosynthesis of carbon, nitrogen, silicon, calcium, titanium, and heavier elements (see Chapter 1.02). It is thought that such carbon-rich minerals should form only in environments with C/O>1, as in the late stages of AGB evolution, or in carbon-rich layers of supernovae. By analogy, one would expect to form oxide and silicate minerals in environments with C/O<1, as is common for most stars. Indeed there is evidence in infrared spectra for the formation of Al2O3 (corundum) and silicates, such as olivine (Speck et al., 2000) around evolved oxygen-rich stars. However, searches for such grains in meteorites have yielded only a very small population of corundum grains, a few grains of spinel and hibonite, and no silicates ( Nittler et

  8. Survivability Is More Fundamental Than Evolvability

    PubMed Central

    Palmer, Michael E.; Feldman, Marcus W.

    2012-01-01

    For a lineage to survive over long time periods, it must sometimes change. This has given rise to the term evolvability, meaning the tendency to produce adaptive variation. One lineage may be superior to another in terms of its current standing variation, or it may tend to produce more adaptive variation. However, evolutionary outcomes depend on more than standing variation and produced adaptive variation: deleterious variation also matters. Evolvability, as most commonly interpreted, is not predictive of evolutionary outcomes. Here, we define a predictive measure of the evolutionary success of a lineage that we call the k-survivability, defined as the probability that the lineage avoids extinction for k generations. We estimate the k-survivability using multiple experimental replicates. Because we measure evolutionary outcomes, the initial standing variation, the full spectrum of generated variation, and the heritability of that variation are all incorporated. Survivability also accounts for the decreased joint likelihood of extinction of sub-lineages when they 1) disperse in space, or 2) diversify in lifestyle. We illustrate measurement of survivability with in silico models, and suggest that it may also be measured in vivo using multiple longitudinal replicates. The k-survivability is a metric that enables the quantitative study of, for example, the evolution of 1) mutation rates, 2) dispersal mechanisms, 3) the genotype-phenotype map, and 4) sexual reproduction, in temporally and spatially fluctuating environments. Although these disparate phenomena evolve by well-understood microevolutionary rules, they are also subject to the macroevolutionary constraint of long-term survivability. PMID:22723844

  9. Evolvable circuit with transistor-level reconfigurability

    NASA Technical Reports Server (NTRS)

    Stoica, Adrian (Inventor); Salazar-Lazaro, Carlos Harold (Inventor)

    2004-01-01

    An evolvable circuit includes a plurality of reconfigurable switches, a plurality of transistors within a region of the circuit, the plurality of transistors having terminals, the plurality of transistors being coupled between a power source terminal and a power sink terminal so as to be capable of admitting power between the power source terminal and the power sink terminal, the plurality of transistors being coupled so that every transistor terminal to transistor terminal coupling within the region of the circuit comprises a reconfigurable switch.

  10. Present weather and climate: evolving conditions

    USGS Publications Warehouse

    Hoerling, Martin P; Dettinger, Michael; Wolter, Klaus; Lukas, Jeff; Eischeid, Jon K.; Nemani, Rama; Liebmann, Brant; Kunkel, Kenneth E.

    2013-01-01

    This chapter assesses weather and climate variability and trends in the Southwest, using observed climate and paleoclimate records. It analyzes the last 100 years of climate variability in comparison to the last 1,000 years, and links the important features of evolving climate conditions to river flow variability in four of the region’s major drainage basins. The chapter closes with an assessment of the monitoring and scientific research needed to increase confidence in understanding when climate episodes, events, and phenomena are attributable to human-caused climate change.

  11. The Evolving Theory of Evolutionary Radiations.

    PubMed

    Simões, M; Breitkreuz, L; Alvarado, M; Baca, S; Cooper, J C; Heins, L; Herzog, K; Lieberman, B S

    2016-01-01

    Evolutionary radiations have intrigued biologists for more than 100 years, and our understanding of the patterns and processes associated with these radiations continues to grow and evolve. Recently it has been recognized that there are many different types of evolutionary radiation beyond the well-studied adaptive radiations. We focus here on multifarious types of evolutionary radiations, paying special attention to the abiotic factors that might trigger diversification in clades. We integrate concepts such as exaptation, species selection, coevolution, and the turnover-pulse hypothesis (TPH) into the theoretical framework of evolutionary radiations. We also discuss other phenomena that are related to, but distinct from, evolutionary radiations that have relevance for evolutionary biology.

  12. Evolving Black Holes with Wavy Initial Data

    NASA Astrophysics Data System (ADS)

    Kelly, Bernard; Tichy, Wolfgang; Zlochower, Yosef; Campanelli, Manuela; Whiting, Bernard

    2009-05-01

    In Kelly et al. [Phys. Rev. D v. 76, 024008 (2007)], we presented new binary black-hole initial data adapted to puncture evolutions in numerical relativity. This data satisfies the constraint equations to 2.5 post-Newtonian order, and contains a transverse-traceless ``wavy'' metric contribution, violating the standard assumption of conformal flatness. We report on progress in evolving this data with a modern moving-puncture implementation of the BSSN equations in several numerical codes. We will discuss the effect of the new metric terms on junk radiation and continuity of physical radiation extracted.

  13. Mobile computing acceptance grows as applications evolve.

    PubMed

    Porn, Louis M; Patrick, Kelly

    2002-01-01

    Handheld devices are becoming more cost-effective to own, and their use in healthcare environments is increasing. Handheld devices currently are being used for e-prescribing, charge capture, and accessing daily schedules and reference tools. Future applications may include education on medications, dictation, order entry, and test-results reporting. Selecting the right handheld device requires careful analysis of current and future applications, as well as vendor expertise. It is important to recognize the technology will continue to evolve over the next three years. PMID:11806321

  14. Mobile computing acceptance grows as applications evolve.

    PubMed

    Porn, Louis M; Patrick, Kelly

    2002-01-01

    Handheld devices are becoming more cost-effective to own, and their use in healthcare environments is increasing. Handheld devices currently are being used for e-prescribing, charge capture, and accessing daily schedules and reference tools. Future applications may include education on medications, dictation, order entry, and test-results reporting. Selecting the right handheld device requires careful analysis of current and future applications, as well as vendor expertise. It is important to recognize the technology will continue to evolve over the next three years.

  15. Earth As an Evolving Planetary System

    NASA Astrophysics Data System (ADS)

    Meert, Joseph G.

    2005-05-01

    ``System'' is an overused buzzword in textbooks covering geological sciences. Describing the Earth as a system of component parts is a reasonable concept, but providing a comprehensive framework for detailing the system is a more formidable task. Kent Condie lays out the systems approach in an easy-to-read introductory chapter in Earth as an Evolving Planetary System. In the book, Condie makes a valiant attempt at taking the mélange of diverse subjects in the solid Earth sciences and weaving them into a coherent tapestry.

  16. Oxygen Sensing and Homeostasis.

    PubMed

    Prabhakar, Nanduri R; Semenza, Gregg L

    2015-09-01

    The discovery of carotid bodies as sensory receptors for detecting arterial blood oxygen levels, and the identification and elucidation of the roles of hypoxia-inducible factors (HIFs) in oxygen homeostasis have propelled the field of oxygen biology. This review highlights the gas-messenger signaling mechanisms associated with oxygen sensing, as well as transcriptional and non-transcriptional mechanisms underlying the maintenance of oxygen homeostasis by HIFs and their relevance to physiology and pathology.

  17. Where is the oxygen in protostellar outflows?

    NASA Astrophysics Data System (ADS)

    Kristensen, Lars

    2014-10-01

    Oxygen (O) is the third-most abundant element in the Universe after hydrogen and helium. Despite its high elemental abundance, a good picture of where oxygen is located in low-mass protostellar outflows and jets is missing: we cannot account for > 60% of the oxygen budget in these objects. This hole in our picture means that we currently do not have a good understanding of the dominant cooling processes in outflows jets, despite the fact that [O I] emission at 63 micron is one of the dominant cooling lines, nor how cooling processes evolve with protostellar evolution. To shed light on these processes, we propose to observe the [O I] 63 micron line with SOFIA-GREAT toward five low-mass protostars. As a first step, the velocity-resolved line profile will be decomposed into its constituent components to isolate the relative contributions from the jet and the irradiated outflow. Second, the [O I] line profile will be compared to those of H2O, OH and CO to obtain the relative atomic O abundance with respect to CO, H2O, and OH. Third, the effects of evolution will be examined by observing protostars at different evolutionary stages. These three approaches will allow us to quantify: the oxygen chemistry in warm and hot gas, the relative amounts of material in the outflow and the jet, and finally to start tracing the evolutionary sequence of how feedback evolves with time.

  18. Have plants evolved to self-immolate?

    PubMed

    Bowman, David M J S; French, Ben J; Prior, Lynda D

    2014-01-01

    By definition fire prone ecosystems have highly combustible plants, leading to the hypothesis, first formally stated by Mutch in 1970, that community flammability is the product of natural selection of flammable traits. However, proving the "Mutch hypothesis" has presented an enormous challenge for fire ecologists given the difficulty in establishing cause and effect between landscape fire and flammable plant traits. Individual plant traits (such as leaf moisture content, retention of dead branches and foliage, oil rich foliage) are known to affect the flammability of plants but there is no evidence these characters evolved specifically to self-immolate, although some of these traits may have been secondarily modified to increase the propensity to burn. Demonstrating individual benefits from self-immolation is extraordinarily difficult, given the intersection of the physical environmental factors that control landscape fire (fuel production, dryness and ignitions) with community flammability properties that emerge from numerous traits of multiple species (canopy cover and litter bed bulk density). It is more parsimonious to conclude plants have evolved mechanisms to tolerate, but not promote, landscape fire. PMID:25414710

  19. Evolving resistance to obesity in an insect.

    PubMed

    Warbrick-Smith, James; Behmer, Spencer T; Lee, Kwang Pum; Raubenheimer, David; Simpson, Stephen J

    2006-09-19

    Failure to adapt to a changing nutritional environment comes at a cost, as evidenced by the modern human obesity crisis. Consumption of energy-rich diets can lead to obesity and is associated with deleterious consequences not only in humans but also in many other animals, including insects. The question thus arises whether animals restricted over multiple generations to high-energy diets can evolve mechanisms to limit the deposition of adverse levels of body fat. We show that Plutella xylostella caterpillars reared for multiple generations on carbohydrate-rich foods (either a chemically defined artificial diet or a high-starch Arabidopsis mutant) progressively developed the ability to eat excess carbohydrate without laying it down as fat, providing strong evidence that excess fat storage has a fitness cost. In contrast, caterpillars reared in carbohydrate-scarce environments (a chemically defined artificial diet or a low-starch Arabidopsis mutant) had a greater propensity to store ingested carbohydrate as fat. Additionally, insects reared on the low-starch Arabidopsis mutant evolved a preference for laying their eggs on this plant, whereas those selected on the high-starch Arabidopsis mutant showed no preference. Our results provide an experimental example of metabolic adaptation in the face of changes in the nutritional environment and suggest that changes in plant macronutrient profiles may promote host-associated population divergence.

  20. Collapse of cooperation in evolving games

    PubMed Central

    Stewart, Alexander J.; Plotkin, Joshua B.

    2014-01-01

    Game theory provides a quantitative framework for analyzing the behavior of rational agents. The Iterated Prisoner’s Dilemma in particular has become a standard model for studying cooperation and cheating, with cooperation often emerging as a robust outcome in evolving populations. Here we extend evolutionary game theory by allowing players’ payoffs as well as their strategies to evolve in response to selection on heritable mutations. In nature, many organisms engage in mutually beneficial interactions and individuals may seek to change the ratio of risk to reward for cooperation by altering the resources they commit to cooperative interactions. To study this, we construct a general framework for the coevolution of strategies and payoffs in arbitrary iterated games. We show that, when there is a tradeoff between the benefits and costs of cooperation, coevolution often leads to a dramatic loss of cooperation in the Iterated Prisoner’s Dilemma. The collapse of cooperation is so extreme that the average payoff in a population can decline even as the potential reward for mutual cooperation increases. Depending upon the form of tradeoffs, evolution may even move away from the Iterated Prisoner’s Dilemma game altogether. Our work offers a new perspective on the Prisoner’s Dilemma and its predictions for cooperation in natural populations; and it provides a general framework to understand the coevolution of strategies and payoffs in iterated interactions. PMID:25422421

  1. Caterpillars evolved from onychophorans by hybridogenesis.

    PubMed

    Williamson, Donald I

    2009-11-24

    I reject the Darwinian assumption that larvae and their adults evolved from a single common ancestor. Rather I posit that, in animals that metamorphose, the basic types of larvae originated as adults of different lineages, i.e., larvae were transferred when, through hybridization, their genomes were acquired by distantly related animals. "Caterpillars," the name for eruciforms with thoracic and abdominal legs, are larvae of lepidopterans, hymenopterans, and mecopterans (scorpionflies). Grubs and maggots, including the larvae of beetles, bees, and flies, evolved from caterpillars by loss of legs. Caterpillar larval organs are dismantled and reconstructed in the pupal phase. Such indirect developmental patterns (metamorphoses) did not originate solely by accumulation of random mutations followed by natural selection; rather they are fully consistent with my concept of evolution by hybridogenesis. Members of the phylum Onychophora (velvet worms) are proposed as the evolutionary source of caterpillars and their grub or maggot descendants. I present a molecular biological research proposal to test my thesis. By my hypothesis 2 recognizable sets of genes are detectable in the genomes of all insects with caterpillar grub- or maggot-like larvae: (i) onychophoran genes that code for proteins determining larval morphology/physiology and (ii) sequentially expressed insect genes that code for adult proteins. The genomes of insects and other animals that, by contrast, entirely lack larvae comprise recognizable sets of genes from single animal common ancestors.

  2. Collapse of cooperation in evolving games.

    PubMed

    Stewart, Alexander J; Plotkin, Joshua B

    2014-12-01

    Game theory provides a quantitative framework for analyzing the behavior of rational agents. The Iterated Prisoner's Dilemma in particular has become a standard model for studying cooperation and cheating, with cooperation often emerging as a robust outcome in evolving populations. Here we extend evolutionary game theory by allowing players' payoffs as well as their strategies to evolve in response to selection on heritable mutations. In nature, many organisms engage in mutually beneficial interactions and individuals may seek to change the ratio of risk to reward for cooperation by altering the resources they commit to cooperative interactions. To study this, we construct a general framework for the coevolution of strategies and payoffs in arbitrary iterated games. We show that, when there is a tradeoff between the benefits and costs of cooperation, coevolution often leads to a dramatic loss of cooperation in the Iterated Prisoner's Dilemma. The collapse of cooperation is so extreme that the average payoff in a population can decline even as the potential reward for mutual cooperation increases. Depending upon the form of tradeoffs, evolution may even move away from the Iterated Prisoner's Dilemma game altogether. Our work offers a new perspective on the Prisoner's Dilemma and its predictions for cooperation in natural populations; and it provides a general framework to understand the coevolution of strategies and payoffs in iterated interactions.

  3. Caterpillars evolved from onychophorans by hybridogenesis.

    PubMed

    Williamson, Donald I

    2009-11-24

    I reject the Darwinian assumption that larvae and their adults evolved from a single common ancestor. Rather I posit that, in animals that metamorphose, the basic types of larvae originated as adults of different lineages, i.e., larvae were transferred when, through hybridization, their genomes were acquired by distantly related animals. "Caterpillars," the name for eruciforms with thoracic and abdominal legs, are larvae of lepidopterans, hymenopterans, and mecopterans (scorpionflies). Grubs and maggots, including the larvae of beetles, bees, and flies, evolved from caterpillars by loss of legs. Caterpillar larval organs are dismantled and reconstructed in the pupal phase. Such indirect developmental patterns (metamorphoses) did not originate solely by accumulation of random mutations followed by natural selection; rather they are fully consistent with my concept of evolution by hybridogenesis. Members of the phylum Onychophora (velvet worms) are proposed as the evolutionary source of caterpillars and their grub or maggot descendants. I present a molecular biological research proposal to test my thesis. By my hypothesis 2 recognizable sets of genes are detectable in the genomes of all insects with caterpillar grub- or maggot-like larvae: (i) onychophoran genes that code for proteins determining larval morphology/physiology and (ii) sequentially expressed insect genes that code for adult proteins. The genomes of insects and other animals that, by contrast, entirely lack larvae comprise recognizable sets of genes from single animal common ancestors. PMID:19717430

  4. Evolving resistance to obesity in an insect

    PubMed Central

    Warbrick-Smith, James; Behmer, Spencer T.; Lee, Kwang Pum; Raubenheimer, David; Simpson, Stephen J.

    2006-01-01

    Failure to adapt to a changing nutritional environment comes at a cost, as evidenced by the modern human obesity crisis. Consumption of energy-rich diets can lead to obesity and is associated with deleterious consequences not only in humans but also in many other animals, including insects. The question thus arises whether animals restricted over multiple generations to high-energy diets can evolve mechanisms to limit the deposition of adverse levels of body fat. We show that Plutella xylostella caterpillars reared for multiple generations on carbohydrate-rich foods (either a chemically defined artificial diet or a high-starch Arabidopsis mutant) progressively developed the ability to eat excess carbohydrate without laying it down as fat, providing strong evidence that excess fat storage has a fitness cost. In contrast, caterpillars reared in carbohydrate-scarce environments (a chemically defined artificial diet or a low-starch Arabidopsis mutant) had a greater propensity to store ingested carbohydrate as fat. Additionally, insects reared on the low-starch Arabidopsis mutant evolved a preference for laying their eggs on this plant, whereas those selected on the high-starch Arabidopsis mutant showed no preference. Our results provide an experimental example of metabolic adaptation in the face of changes in the nutritional environment and suggest that changes in plant macronutrient profiles may promote host-associated population divergence. PMID:16968774

  5. Shaping the outflows of evolved stars

    NASA Astrophysics Data System (ADS)

    Mohamed, Shazrene

    2015-08-01

    Both hot and cool evolved stars, e.g., red (super)giants and Wolf-Rayet stars, lose copious amounts of mass, momentum and mechanical energy through powerful, dense stellar winds. The interaction of these outflows with their surroundings results in highly structured and complex circumstellar environments, often featuring knots, arcs, shells and spirals. Recent improvements in computational power and techniques have led to the development of detailed, multi-dimensional simulations that have given new insight into the origin of these structures, and better understanding of the physical mechanisms driving their formation. In this talk, I will discuss three of the main mechanisms that shape the outflows of evolved stars:- interaction with the interstellar medium (ISM), i.e., wind-ISM interactions- interaction with a stellar wind, either from a previous phase of evolution or the wind from a companion star, i.e., wind-wind interactions- and interaction with a companion star that has a weak or insignicant outflow (e.g., a compact companion such as a neutron star or black hole), i.e., wind-companion interactions.I will also highlight the broader implications and impact of these stellar wind interactions for other phenomena, e.g, for symbiotic and X-ray binaries, supernovae and Gamma-ray bursts.

  6. Early formation of evolved asteroidal crust.

    PubMed

    Day, James M D; Ash, Richard D; Liu, Yang; Bellucci, Jeremy J; Rumble, Douglas; McDonough, William F; Walker, Richard J; Taylor, Lawrence A

    2009-01-01

    Mechanisms for the formation of crust on planetary bodies remain poorly understood. It is generally accepted that Earth's andesitic continental crust is the product of plate tectonics, whereas the Moon acquired its feldspar-rich crust by way of plagioclase flotation in a magma ocean. Basaltic meteorites provide evidence that, like the terrestrial planets, some asteroids generated crust and underwent large-scale differentiation processes. Until now, however, no evolved felsic asteroidal crust has been sampled or observed. Here we report age and compositional data for the newly discovered, paired and differentiated meteorites Graves Nunatak (GRA) 06128 and GRA 06129. These meteorites are feldspar-rich, with andesite bulk compositions. Their age of 4.52 +/- 0.06 Gyr demonstrates formation early in Solar System history. The isotopic and elemental compositions, degree of metamorphic re-equilibration and sulphide-rich nature of the meteorites are most consistent with an origin as partial melts from a volatile-rich, oxidized asteroid. GRA 06128 and 06129 are the result of a newly recognized style of evolved crust formation, bearing witness to incomplete differentiation of their parent asteroid and to previously unrecognized diversity of early-formed materials in the Solar System. PMID:19129845

  7. Early formation of evolved asteroidal crust

    NASA Astrophysics Data System (ADS)

    Day, James M. D.; Ash, Richard D.; Liu, Yang; Bellucci, Jeremy J.; Rumble, Douglas, III; McDonough, William F.; Walker, Richard J.; Taylor, Lawrence A.

    2009-01-01

    Mechanisms for the formation of crust on planetary bodies remain poorly understood. It is generally accepted that Earth's andesitic continental crust is the product of plate tectonics, whereas the Moon acquired its feldspar-rich crust by way of plagioclase flotation in a magma ocean. Basaltic meteorites provide evidence that, like the terrestrial planets, some asteroids generated crust and underwent large-scale differentiation processes. Until now, however, no evolved felsic asteroidal crust has been sampled or observed. Here we report age and compositional data for the newly discovered, paired and differentiated meteorites Graves Nunatak (GRA) 06128 and GRA 06129. These meteorites are feldspar-rich, with andesite bulk compositions. Their age of 4.52+/-0.06Gyr demonstrates formation early in Solar System history. The isotopic and elemental compositions, degree of metamorphic re-equilibration and sulphide-rich nature of the meteorites are most consistent with an origin as partial melts from a volatile-rich, oxidized asteroid. GRA 06128 and 06129 are the result of a newly recognized style of evolved crust formation, bearing witness to incomplete differentiation of their parent asteroid and to previously unrecognized diversity of early-formed materials in the Solar System.

  8. Early formation of evolved asteroidal crust.

    PubMed

    Day, James M D; Ash, Richard D; Liu, Yang; Bellucci, Jeremy J; Rumble, Douglas; McDonough, William F; Walker, Richard J; Taylor, Lawrence A

    2009-01-01

    Mechanisms for the formation of crust on planetary bodies remain poorly understood. It is generally accepted that Earth's andesitic continental crust is the product of plate tectonics, whereas the Moon acquired its feldspar-rich crust by way of plagioclase flotation in a magma ocean. Basaltic meteorites provide evidence that, like the terrestrial planets, some asteroids generated crust and underwent large-scale differentiation processes. Until now, however, no evolved felsic asteroidal crust has been sampled or observed. Here we report age and compositional data for the newly discovered, paired and differentiated meteorites Graves Nunatak (GRA) 06128 and GRA 06129. These meteorites are feldspar-rich, with andesite bulk compositions. Their age of 4.52 +/- 0.06 Gyr demonstrates formation early in Solar System history. The isotopic and elemental compositions, degree of metamorphic re-equilibration and sulphide-rich nature of the meteorites are most consistent with an origin as partial melts from a volatile-rich, oxidized asteroid. GRA 06128 and 06129 are the result of a newly recognized style of evolved crust formation, bearing witness to incomplete differentiation of their parent asteroid and to previously unrecognized diversity of early-formed materials in the Solar System.

  9. Netgram: Visualizing Communities in Evolving Networks.

    PubMed

    Mall, Raghvendra; Langone, Rocco; Suykens, Johan A K

    2015-01-01

    Real-world complex networks are dynamic in nature and change over time. The change is usually observed in the interactions within the network over time. Complex networks exhibit community like structures. A key feature of the dynamics of complex networks is the evolution of communities over time. Several methods have been proposed to detect and track the evolution of these groups over time. However, there is no generic tool which visualizes all the aspects of group evolution in dynamic networks including birth, death, splitting, merging, expansion, shrinkage and continuation of groups. In this paper, we propose Netgram: a tool for visualizing evolution of communities in time-evolving graphs. Netgram maintains evolution of communities over 2 consecutive time-stamps in tables which are used to create a query database using the sql outer-join operation. It uses a line-based visualization technique which adheres to certain design principles and aesthetic guidelines. Netgram uses a greedy solution to order the initial community information provided by the evolutionary clustering technique such that we have fewer line cross-overs in the visualization. This makes it easier to track the progress of individual communities in time evolving graphs. Netgram is a generic toolkit which can be used with any evolutionary community detection algorithm as illustrated in our experiments. We use Netgram for visualization of topic evolution in the NIPS conference over a period of 11 years and observe the emergence and merging of several disciplines in the field of information processing systems. PMID:26356538

  10. Environmental stress and evolvability in microbial systems.

    PubMed

    Baquero, F

    2009-01-01

    The sustainability of life on the planet depends on the preservation of the existing microbial systems, which constitutes our major "biological atmosphere". The detection of variations in microbial systems as a result of anthropogenic or natural changes is critical both to detect and assess risks and to programme specific interventions. Changes in microbial systems provokes stress, probably altering the local evolutionary time by changing evolvability (the possibilities of microbes to evolve). Methods should be refined to properly assess diversity in microbial systems. We propose that such diversity estimations should be done on a multi-hierarchical scale, encompassing not only organisms, but sub-cellular entities (e.g. chromosomal domains, plasmids, transposons, integrons, genes, gene modules) and supra-cellular organizations (e.g. clones, populations, communities, ecosystems), applying Hamiltonian criteria of inclusive fitness for the different ensembles. In any of these entities, we can generally identify, in a fractal manner, constant and variable parts. Variation in these entities and ensembles is probably both reduced and increased by environmental stress. Because of that, variation in microbial systems might serve as mirrors or symptoms of the health of the planet. PMID:19220344

  11. The emotion system promotes diversity and evolvability

    PubMed Central

    Giske, Jarl; Eliassen, Sigrunn; Fiksen, Øyvind; Jakobsen, Per J.; Aksnes, Dag L.; Mangel, Marc; Jørgensen, Christian

    2014-01-01

    Studies on the relationship between the optimal phenotype and its environment have had limited focus on genotype-to-phenotype pathways and their evolutionary consequences. Here, we study how multi-layered trait architecture and its associated constraints prescribe diversity. Using an idealized model of the emotion system in fish, we find that trait architecture yields genetic and phenotypic diversity even in absence of frequency-dependent selection or environmental variation. That is, for a given environment, phenotype frequency distributions are predictable while gene pools are not. The conservation of phenotypic traits among these genetically different populations is due to the multi-layered trait architecture, in which one adaptation at a higher architectural level can be achieved by several different adaptations at a lower level. Our results emphasize the role of convergent evolution and the organismal level of selection. While trait architecture makes individuals more constrained than what has been assumed in optimization theory, the resulting populations are genetically more diverse and adaptable. The emotion system in animals may thus have evolved by natural selection because it simultaneously enhances three important functions, the behavioural robustness of individuals, the evolvability of gene pools and the rate of evolutionary innovation at several architectural levels. PMID:25100697

  12. Evolvability of an Optimal Recombination Rate.

    PubMed

    Lobkovsky, Alexander E; Wolf, Yuri I; Koonin, Eugene V

    2015-12-10

    Evolution and maintenance of genetic recombination and its relation to the mutational process is a long-standing, fundamental problem in evolutionary biology that is linked to the general problem of evolution of evolvability. We explored a stochastic model of the evolution of recombination using additive fitness and infinite allele assumptions but no assumptions on the sign or magnitude of the epistasis and the distribution of mutation effects. In this model, fluctuating negative epistasis and predominantly deleterious mutations arise naturally as a consequence of the additive fitness and a reservoir from which new alleles arrive with a fixed distribution of fitness effects. Analysis of the model revealed a nonmonotonic effect of recombination intensity on fitness, with an optimal recombination rate value which maximized fitness in steady state. The optimal recombination rate depended on the mutation rate and was evolvable, that is, subject to selection. The predictions of the model were compatible with the observations on the dependence between genome rearrangement rate and gene flux in microbial genomes.

  13. Collapse of cooperation in evolving games.

    PubMed

    Stewart, Alexander J; Plotkin, Joshua B

    2014-12-01

    Game theory provides a quantitative framework for analyzing the behavior of rational agents. The Iterated Prisoner's Dilemma in particular has become a standard model for studying cooperation and cheating, with cooperation often emerging as a robust outcome in evolving populations. Here we extend evolutionary game theory by allowing players' payoffs as well as their strategies to evolve in response to selection on heritable mutations. In nature, many organisms engage in mutually beneficial interactions and individuals may seek to change the ratio of risk to reward for cooperation by altering the resources they commit to cooperative interactions. To study this, we construct a general framework for the coevolution of strategies and payoffs in arbitrary iterated games. We show that, when there is a tradeoff between the benefits and costs of cooperation, coevolution often leads to a dramatic loss of cooperation in the Iterated Prisoner's Dilemma. The collapse of cooperation is so extreme that the average payoff in a population can decline even as the potential reward for mutual cooperation increases. Depending upon the form of tradeoffs, evolution may even move away from the Iterated Prisoner's Dilemma game altogether. Our work offers a new perspective on the Prisoner's Dilemma and its predictions for cooperation in natural populations; and it provides a general framework to understand the coevolution of strategies and payoffs in iterated interactions. PMID:25422421

  14. Have plants evolved to self-immolate?

    PubMed Central

    Bowman, David M. J. S.; French, Ben J.; Prior, Lynda D.

    2014-01-01

    By definition fire prone ecosystems have highly combustible plants, leading to the hypothesis, first formally stated by Mutch in 1970, that community flammability is the product of natural selection of flammable traits. However, proving the “Mutch hypothesis” has presented an enormous challenge for fire ecologists given the difficulty in establishing cause and effect between landscape fire and flammable plant traits. Individual plant traits (such as leaf moisture content, retention of dead branches and foliage, oil rich foliage) are known to affect the flammability of plants but there is no evidence these characters evolved specifically to self-immolate, although some of these traits may have been secondarily modified to increase the propensity to burn. Demonstrating individual benefits from self-immolation is extraordinarily difficult, given the intersection of the physical environmental factors that control landscape fire (fuel production, dryness and ignitions) with community flammability properties that emerge from numerous traits of multiple species (canopy cover and litter bed bulk density). It is more parsimonious to conclude plants have evolved mechanisms to tolerate, but not promote, landscape fire. PMID:25414710

  15. Evolving MEMS Resonator Designs for Fabrication

    NASA Technical Reports Server (NTRS)

    Hornby, Gregory S.; Kraus, William F.; Lohn, Jason D.

    2008-01-01

    Because of their small size and high reliability, microelectromechanical (MEMS) devices have the potential to revolution many areas of engineering. As with conventionally-sized engineering design, there is likely to be a demand for the automated design of MEMS devices. This paper describes our current status as we progress toward our ultimate goal of using an evolutionary algorithm and a generative representation to produce designs of a MEMS device and successfully demonstrate its transfer to an actual chip. To produce designs that are likely to transfer to reality, we present two ways to modify evaluation of designs. The first is to add location noise, differences between the actual dimensions of the design and the design blueprint, which is a technique we have used for our work in evolving antennas and robots. The second method is to add prestress to model the warping that occurs during the extreme heat of fabrication. In future we expect to fabricate and test some MEMS resonators that are evolved in this way.

  16. X-Ray Spectroscopy of the Photosynthetic Oxygen-Evolving Complex

    SciTech Connect

    Sauer, K.; Yano, J.; Yachandra, V.K.

    2009-05-27

    Water oxidation to dioxygen in photosynthesis is catalyzed by a Mn{sub 4}Ca cluster with O bridging in Photosystem II (PS II) of plants, algae and cyanobacteria. A variety of spectroscopic methods have been applied to analyzing the participation of the complex. X-ray spectroscopy is particularly useful because it is element-specific, and because it can reveal important structural features of the complex with high accuracy and identify the participation of Mn in the redox chemistry. Following a brief history of the application of X-ray spectroscopy to PS II, an overview of newer results will be presented and a description of the present state of our knowledge based on this approach.

  17. Nickel-borate oxygen-evolving catalyst that functions under benign conditions

    PubMed Central

    Dincă, Mircea; Surendranath, Yogesh; Nocera, Daniel G.

    2010-01-01

    Thin catalyst films with electrocatalytic water oxidation properties similar to those of a recently reported Co-based catalyst can be electrodeposited from dilute Ni2+ solutions in borate electrolyte at pH 9.2 (Bi). The Ni-Bi films can be prepared with precise thickness control and operate at modest overpotential providing an alternative to the Co catalyst for applications in solar energy conversion. PMID:20457931

  18. Oxygen-Evolving Porous Glass Plates Containing the Photosynthetic Photosystem II Pigment-Protein Complex.

    PubMed

    Noji, Tomoyasu; Kawakami, Keisuke; Shen, Jian-Ren; Dewa, Takehisa; Nango, Mamoru; Kamiya, Nobuo; Itoh, Shigeru; Jin, Tetsuro

    2016-08-01

    The development of artificial photosynthesis has focused on the efficient coupling of reaction at photoanode and cathode, wherein the production of hydrogen (or energy carriers) is coupled to the electrons derived from water-splitting reactions. The natural photosystem II (PSII) complex splits water efficiently using light energy. The PSII complex is a large pigment-protein complex (20 nm in diameter) containing a manganese cluster. A new photoanodic device was constructed incorporating stable PSII purified from a cyanobacterium Thermosynechococcus vulcanus through immobilization within 20 or 50 nm nanopores contained in porous glass plates (PGPs). PSII in the nanopores retained its native structure and high photoinduced water splitting activity. The photocatalytic rate (turnover frequency) of PSII in PGP was enhanced 11-fold compared to that in solution, yielding a rate of 50-300 mol e(-)/(mol PSII·s) with 2,6-dichloroindophenol (DCIP) as an electron acceptor. The PGP system realized high local concentrations of PSII and DCIP to enhance the collisional reactions in nanotubes with low disturbance of light penetration. The system allows direct visualization/determination of the reaction inside the nanotubes, which contributes to optimize the local reaction condition. The PSII/PGP device will substantively contribute to the construction of artificial photosynthesis using water as the ultimate electron source.

  19. Nickel-borate oxygen-evolving catalyst that functions under benign conditions.

    PubMed

    Dincă, Mircea; Surendranath, Yogesh; Nocera, Daniel G

    2010-06-01

    Thin catalyst films with electrocatalytic water oxidation properties similar to those of a recently reported Co-based catalyst can be electrodeposited from dilute Ni(2+) solutions in borate electrolyte at pH 9.2 (B(i)). The Ni-B(i) films can be prepared with precise thickness control and operate at modest overpotential providing an alternative to the Co catalyst for applications in solar energy conversion.

  20. X-ray spectroscopy of the photosynthetic oxygen-evolving complex

    SciTech Connect

    Sauer, Ken; Yano, Junko; Yachandra, Vittal K

    2007-04-05

    Water oxidation to dioxygen in photosynthesis is catalyzed by a Mn4Ca cluster with O bridging in Photosystem II (PS II) of plants, algae and cyanobacteria. A variety of spectroscopic methods have been applied to analyzing the participation of the complex. X-ray spectroscopy is particularly useful because it is element-specific, and because it can reveal important structural features of the complex with high accuracy and identify the participation of Mn in the redox chemistry. Following a brief history of the application of X-ray spectroscopy to PS II, an overview of newer results will be presented and a description of the present state of our knowledge based on this approach.

  1. Nanostructured Cobalt Oxide Clusters in Mesoporous Silica as Efficient Oxygen-Evolving Catalysts

    SciTech Connect

    Jiao, Feng; Frei, Heinz

    2009-01-01

    The development of integrated artificial photosynthetic systems for the direct conversion of carbon dioxide and water to fuel depends on the availability of efficient and robust catalysts for the chemical transformations. Catalysts need to exhibit turnover frequency (TOF) and density (hence size) commensurate with the solar flux at ground level (1000Wm2, airmass (AM) 1.5)[1]to avoid wasting of incidentsolar photons. For example, a catalyst with a TOF of 100 s1 requires a density of one catalytic site per square nanometer. Catalysts with lower rates or taking up a larger space will require a high-surface-area, nanostructured support that affords tens to hundreds of catalytic sites per square nanometer. Furthermore, catalysts need to operate close to the thermodynamic potential of the redox reaction so that amaximum fraction of the solar photon energy is converted to chemical energy. Stability considerations favor all-inorganic oxide materials, as does avoidance of harsh reaction conditions of pH value or temperature.

  2. X-Ray spectroscopy of the photosynthetic oxygen-evolving complex

    PubMed Central

    Sauer, Kenneth; Yano, Junko; Yachandra, Vittal K.

    2008-01-01

    Water oxidation to dioxygen in photosynthesis is catalyzed by a Mn4Ca cluster with O bridging in Photosystem II (PS II) of plants, algae and cyanobacteria. A variety of spectroscopic methods have been applied to analyzing the participation of the complex. X-ray spectroscopy is particularly useful because it is element-specific, and because it can reveal important structural features of the complex with high accuracy and identify the participation of Mn in the redox chemistry. Following a brief history of the application of X-ray spectroscopy to PS II, an overview of newer results will be presented and a description of the present state of our knowledge based on this approach. PMID:19190720

  3. No surviving evolved companions of the progenitor of SN 1006.

    PubMed

    González Hernández, Jonay I; Ruiz-Lapuente, Pilar; Tabernero, Hugo M; Montes, David; Canal, Ramon; Méndez, Javier; Bedin, Luigi R

    2012-09-27

    Type Ia supernovae are thought to occur when a white dwarf made of carbon and oxygen accretes sufficient mass to trigger a thermonuclear explosion. The accretion could be slow, from an unevolved (main-sequence) or evolved (subgiant or giant) star (the single-degenerate channel), or rapid, as the primary star breaks up a smaller orbiting white dwarf (the double-degenerate channel). A companion star will survive the explosion only in the single-degenerate channel. Both channels might contribute to the production of type Ia supernovae, but the relative proportions of their contributions remain a fundamental puzzle in astronomy. Previous searches for remnant companions have revealed one possible case for SN 1572 (refs 8, 9), although that has been questioned. More recently, observations have restricted surviving companions to be small, main-sequence stars, ruling out giant companions but still allowing the single-degenerate channel. Here we report the results of a search for surviving companions of the progenitor of SN 1006 (ref. 14). None of the stars within 4 arc minutes of the apparent site of the explosion is associated with the supernova remnant, and we can firmly exclude all giant and subgiant stars from being companions of the progenitor. In combination with previous results, our findings indicate that fewer than 20 per cent of type Ia supernovae occur through the single-degenerate channel. PMID:23018963

  4. Evolving hydrothermal systems in the Islas Orcadas fracture zone

    SciTech Connect

    Kimball, K.L.; Spear, F.S.; Gerlach, D.G.

    1985-01-01

    Petrographic and isotopic evidence suggest that the chemical and isotopic composition of fluids responsible for alteration of ultramafic rocks from the Islas Orcadas Fracture Zone evolve with time. Reaction space analyses of high T alterations indicate these reactions release small amounts of Mg, Fe and Si to the fluid. Calculations of equilibrium fluid compositions indicate fluids concentrated in metallic chloride species, suggesting 1) low water/rock ratios (<<1) or 2) reaction of the fluid with other rocks prior to its reaction with the ultramafics. Reaction space analyses of low T alterations show production of larger quantities of metallic species and are compatible with calculated fluid compositions at water/rock=1. In vein mineral separates, high T minerals have lower 87/86Sr and higher Sr than later, lower T minerals, suggesting MORB contamination of the early fluids and more seawater component in late fluids. In samples containing multiple generations of a mineral in one vein, earlier minerals have lower 87/86Sr than later minerals (more seawater at approx. 709.). Oxygen isotopes show MORB affinites.

  5. No surviving evolved companions of the progenitor of SN 1006.

    PubMed

    González Hernández, Jonay I; Ruiz-Lapuente, Pilar; Tabernero, Hugo M; Montes, David; Canal, Ramon; Méndez, Javier; Bedin, Luigi R

    2012-09-27

    Type Ia supernovae are thought to occur when a white dwarf made of carbon and oxygen accretes sufficient mass to trigger a thermonuclear explosion. The accretion could be slow, from an unevolved (main-sequence) or evolved (subgiant or giant) star (the single-degenerate channel), or rapid, as the primary star breaks up a smaller orbiting white dwarf (the double-degenerate channel). A companion star will survive the explosion only in the single-degenerate channel. Both channels might contribute to the production of type Ia supernovae, but the relative proportions of their contributions remain a fundamental puzzle in astronomy. Previous searches for remnant companions have revealed one possible case for SN 1572 (refs 8, 9), although that has been questioned. More recently, observations have restricted surviving companions to be small, main-sequence stars, ruling out giant companions but still allowing the single-degenerate channel. Here we report the results of a search for surviving companions of the progenitor of SN 1006 (ref. 14). None of the stars within 4 arc minutes of the apparent site of the explosion is associated with the supernova remnant, and we can firmly exclude all giant and subgiant stars from being companions of the progenitor. In combination with previous results, our findings indicate that fewer than 20 per cent of type Ia supernovae occur through the single-degenerate channel.

  6. No surviving evolved companions of the progenitor of SN 1006

    NASA Astrophysics Data System (ADS)

    González Hernández, Jonay I.; Ruiz-Lapuente, Pilar; Tabernero, Hugo M.; Montes, David; Canal, Ramon; Méndez, Javier; Bedin, Luigi R.

    2012-09-01

    Type Ia supernovae are thought to occur when a white dwarf made of carbon and oxygen accretes sufficient mass to trigger a thermonuclear explosion. The accretion could be slow, from an unevolved (main-sequence) or evolved (subgiant or giant) star (the single-degenerate channel), or rapid, as the primary star breaks up a smaller orbiting white dwarf (the double-degenerate channel). A companion star will survive the explosion only in the single-degenerate channel. Both channels might contribute to the production of type Ia supernovae, but the relative proportions of their contributions remain a fundamental puzzle in astronomy. Previous searches for remnant companions have revealed one possible case for SN 1572 (refs 8, 9), although that has been questioned. More recently, observations have restricted surviving companions to be small, main-sequence stars, ruling out giant companions but still allowing the single-degenerate channel. Here we report the results of a search for surviving companions of the progenitor of SN 1006 (ref. 14). None of the stars within 4 arc minutes of the apparent site of the explosion is associated with the supernova remnant, and we can firmly exclude all giant and subgiant stars from being companions of the progenitor. In combination with previous results, our findings indicate that fewer than 20 per cent of type Ia supernovae occur through the single-degenerate channel.

  7. Electrochemical Sensing for a Rapidly Evolving World

    NASA Astrophysics Data System (ADS)

    Mullen, Max Robertson

    This dissertation focuses on three projects involving the development of harsh environment gas sensors. The first project discusses the development of a multipurpose oxygen sensor electrode for use in sealing with the common electrolyte yttria stabilized zirconia. The purpose of the sealing function is to produce an internal reference environment maintained by a metal/metal oxide mixture, a criteria for miniaturization of potentiometric oxygen sensing technology. This sensor measures a potential between the internal reference and a sensing environment. The second project discusses the miniaturization of an oxygen sensor and the fabrication of a more generalized electrochemical sensing platform. The third project discusses the discovery of a new mechanism in the electrochemical sensing of ammonia through molecular recognition and the utilization of a sensor taking advantage of the new mechanism. An initial study involving the development of a microwave synthesized La0.8Sr0.2Al0.9Mn0.1O3 sensor electrode material illustrates the ability of the material developed to meet ionic and electronic conducting requirements for effective and Nernstian oxygen sensing. In addition the material deforms plastically under hot isostatic pressing conditions in a similar temperature and pressure regime with yttria stabilized zirconia to produce a seal and survive temperatures up to 1350 °C. In the second project we show novel methods to seal an oxygen environment inside a device cavity to produce an electrochemical sensor body using room temperature plasma-activated bonding and low temperature and pressure assisted plasma-activated bonding with silicon bodies, both in a clean room environment. The evolution from isostatic hot pressing methods towards room temperature complementary metal oxide semiconductor (CMOS) compatible technologies using single crystal silicon substrates in the clean room allows the sealing of devices on a much larger scale. Through this evolution in bonding

  8. Oxygen chemisorption cryogenic refrigerator

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    1987-01-01

    The present invention relates to a chemisorption compressor cryogenic refrigerator which employs oxygen to provide cooling at 60 to 100 K. The invention includes dual vessels containing an oxygen absorbent material, alternately heated and cooled to provide a continuous flow of high pressure oxygen, multiple heat exchangers for precooling the oxygen, a Joule-Thomson expansion valve system for expanding the oxygen to partially liquefy it and a liquid oxygen pressure vessel. The primary novelty is that, while it was believed that once oxygen combined with an element or compound the reaction could not reverse to release gaseous oxygen, in this case oxygen will indeed react in a reversible fashion with certain materials and will do so at temperatures and pressures which make it practical for incorporation into a cryogenic refrigeration system.

  9. The Universal Oxygen Connector.

    PubMed

    Lauer, Mark A; Gombkoto, Rebecca L M

    2006-02-01

    The purpose of this article is to describe the benefits of using the Universal Oxygen Connector. Until now, an oxygen hose was only able to connect to a 22-mm fitting, such as those found on humidifiers used in the recovery room, and oxygen tubing was only able to connect to a Christmas tree type adapter. The Universal Oxygen Connector, manufactured and sold by International Medical, Inc (Burnsville, Minn), was developed to allow the practitioner to attach either a 22-mm oxygen hose, oxygen tubing, or a 15-mm oxygen adapter to the same connector. Patients benefit from the administration of supplemental oxygen in the perioperative period. Supplemental oxygen has been shown to decrease postoperative hypoxemia, infection, and in some cases, nausea and vomiting. As such, oxygen should be administered during transport from the operating room to the recovery room, in the recovery room, and at times during transport to the patient room and in the patient room. Oxygen also should be administered whenever a patient receiving oxygen is transported. Use of the Universal Oxygen Connector decreases material waste, decreases hospital costs, saves time and effort and, most importantly, promotes patient safety by providing a versatile system for oxygen delivery.

  10. Solid state oxygen sensor

    DOEpatents

    Garzon, Fernando H.; Chung, Brandon W.; Raistrick, Ian D.; Brosha, Eric L.

    1996-01-01

    Solid state oxygen sensors are provided with a yttria-doped zirconia as an electrolyte and use the electrochemical oxygen pumping of the zirconia electrolyte. A linear relationship between oxygen concentration and the voltage arising at a current plateau occurs when oxygen accessing the electrolyte is limited by a diffusion barrier. A diffusion barrier is formed herein with a mixed electronic and oxygen ion-conducting membrane of lanthanum-containing perovskite or zirconia-containing fluorite. A heater may be used to maintain an adequate oxygen diffusion coefficient in the mixed conducting layer.

  11. Solid state oxygen sensor

    DOEpatents

    Garzon, F.H.; Chung, B.W.; Raistrick, I.D.; Brosha, E.L.

    1996-08-06

    Solid state oxygen sensors are provided with a yttria-doped zirconia as an electrolyte and use the electrochemical oxygen pumping of the zirconia electrolyte. A linear relationship between oxygen concentration and the voltage arising at a current plateau occurs when oxygen accessing the electrolyte is limited by a diffusion barrier. A diffusion barrier is formed herein with a mixed electronic and oxygen ion-conducting membrane of lanthanum-containing perovskite or zirconia-containing fluorite. A heater may be used to maintain an adequate oxygen diffusion coefficient in the mixed conducting layer. 4 figs.

  12. Bistability of atmospheric oxygen and the Great Oxidation.

    PubMed

    Goldblatt, Colin; Lenton, Timothy M; Watson, Andrew J

    2006-10-12

    The history of the Earth has been characterized by a series of major transitions separated by long periods of relative stability. The largest chemical transition was the 'Great Oxidation', approximately 2.4 billion years ago, when atmospheric oxygen concentrations rose from less than 10(-5) of the present atmospheric level (PAL) to more than 0.01 PAL, and possibly to more than 0.1 PAL. This transition took place long after oxygenic photosynthesis is thought to have evolved, but the causes of this delay and of the Great Oxidation itself remain uncertain. Here we show that the origin of oxygenic photosynthesis gave rise to two simultaneously stable steady states for atmospheric oxygen. The existence of a low-oxygen (less than 10(-5) PAL) steady state explains how a reducing atmosphere persisted for at least 300 million years after the onset of oxygenic photosynthesis. The Great Oxidation can be understood as a switch to the high-oxygen (more than 5 x 10(-3) PAL) steady state. The bistability arises because ultraviolet shielding of the troposphere by ozone becomes effective once oxygen levels exceed 10(-5) PAL, causing a nonlinear increase in the lifetime of atmospheric oxygen. Our results indicate that the existence of oxygenic photosynthesis is not a sufficient condition for either an oxygen-rich atmosphere or the presence of an ozone layer, which has implications for detecting life on other planets using atmospheric analysis and for the evolution of multicellular life.

  13. Evolving spiking networks with variable resistive memories.

    PubMed

    Howard, Gerard; Bull, Larry; de Lacy Costello, Ben; Gale, Ella; Adamatzky, Andrew

    2014-01-01

    Neuromorphic computing is a brainlike information processing paradigm that requires adaptive learning mechanisms. A spiking neuro-evolutionary system is used for this purpose; plastic resistive memories are implemented as synapses in spiking neural networks. The evolutionary design process exploits parameter self-adaptation and allows the topology and synaptic weights to be evolved for each network in an autonomous manner. Variable resistive memories are the focus of this research; each synapse has its own conductance profile which modifies the plastic behaviour of the device and may be altered during evolution. These variable resistive networks are evaluated on a noisy robotic dynamic-reward scenario against two static resistive memories and a system containing standard connections only. The results indicate that the extra behavioural degrees of freedom available to the networks incorporating variable resistive memories enable them to outperform the comparative synapse types. PMID:23614774

  14. Renal cell carcinoma: Evolving and emerging subtypes

    PubMed Central

    Crumley, Suzanne M; Divatia, Mukul; Truong, Luan; Shen, Steven; Ayala, Alberto G; Ro, Jae Y

    2013-01-01

    Our knowledge of renal cell carcinoma (RCC) is rapidly expanding. For those who diagnose and treat RCC, it is important to understand the new developments. In recent years, many new renal tumors have been described and defined, and our understanding of the biology and clinical correlates of these tumors is changing. Evolving concepts in Xp11 translocation carcinoma, mucinous tubular and spindle cell carcinoma, multilocular cystic clear cell RCC, and carcinoma associated with neuroblastoma are addressed within this review. Tubulocystic carcinoma, thyroid-like follicular carcinoma of kidney, acquired cystic disease-associated RCC, and clear cell papillary RCC are also described. Finally, candidate entities, including RCC with t(6;11) translocation, hybrid oncocytoma/chromophobe RCC, hereditary leiomyomatosis and RCC syndrome, and renal angiomyoadenomatous tumor are reviewed. Knowledge of these new entities is important for diagnosis, treatment and subsequent prognosis. This review provides a targeted summary of new developments in RCC. PMID:24364021

  15. Evolving olfactory systems on the fly.

    PubMed

    Ramdya, Pavan; Benton, Richard

    2010-07-01

    The detection of odour stimuli in the environment is universally important for primal behaviours such as feeding, mating, kin interactions and escape responses. Given the ubiquity of many airborne chemical signals and the similar organisation of animal olfactory circuits, a fundamental question in our understanding of the sense of smell is how species-specific behavioural responses to odorants can evolve. Recent comparative genomic, developmental and physiological studies are shedding light on this problem by providing insights into the genetic mechanisms that underlie anatomical and functional evolution of the olfactory system. Here we synthesise these data, with a particular focus on insect olfaction, to address how new olfactory receptors and circuits might arise and diverge, offering glimpses into how odour-evoked behaviours could adapt to an ever-changing chemosensory world.

  16. Evolving unipolar memristor spiking neural networks

    NASA Astrophysics Data System (ADS)

    Howard, David; Bull, Larry; De Lacy Costello, Ben

    2015-10-01

    Neuromorphic computing - brain-like computing in hardware - typically requires myriad complimentary metal oxide semiconductor spiking neurons interconnected by a dense mesh of nanoscale plastic synapses. Memristors are frequently cited as strong synapse candidates due to their statefulness and potential for low-power implementations. To date, plentiful research has focused on the bipolar memristor synapse, which is capable of incremental weight alterations and can provide adaptive self-organisation under a Hebbian learning scheme. In this paper, we consider the unipolar memristor synapse - a device capable of non-Hebbian switching between only two states (conductive and resistive) through application of a suitable input voltage - and discuss its suitability for neuromorphic systems. A self-adaptive evolutionary process is used to autonomously find highly fit network configurations. Experimentation on two robotics tasks shows that unipolar memristor networks evolve task-solving controllers faster than both bipolar memristor networks and networks containing constant non-plastic connections whilst performing at least comparably.

  17. Synchronization in evolving snowdrift game model

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Wu, L.; Zhu, S. Q.

    2009-06-01

    The interaction between the evolution of the game and the underlying network structure with evolving snowdrift game model is investigated. The constructed network follows a power-law degree distribution typically showing scale-free feature. The topological features of average path length, clustering coefficient, degree-degree correlations and the dynamical feature of synchronizability are studied. The synchronizability of the constructed networks changes by the interaction. It will converge to a certain value when sufficient new nodes are added. It is found that initial payoffs of nodes greatly affect the synchronizability. When initial payoffs for players are equal, low common initial payoffs may lead to more heterogeneity of the network and good synchronizability. When initial payoffs follow certain distributions, better synchronizability is obtained compared to equal initial payoff. The result is also true for phase synchronization of nonidentical oscillators.

  18. Hyperhidrosis: evolving concepts and a comprehensive review.

    PubMed

    Vorkamp, Tobias; Foo, Fung Joon; Khan, Sidra; Schmitto, Jan D; Wilson, Paul

    2010-10-01

    Hyperhidrosis (primary or secondary) describes a disorder of excessive sweating. It has a significant negative impact on quality of life and affects nearly 1% of the population living in the United Kingdom (UK). Axillary involvement is the most common affecting 80% of cases. A common link to these disorders is an extreme non-thermoregulatory sympathetic stimulus of exocrine sweat glands, mostly due to emotional stimuli. Non-surgical treatment involves topical medication, iontophoresis and systemic anti-cholinergics. More recently the use of intradermal botulinum toxin has gained popularity. Surgical treatment reserved for severe cases, not responding to conservative management involves local excision, curettage and thoracoscopic sympathectomy. Evolving concepts for treatment, risks and benefits are discussed in the paper herein. PMID:20709287

  19. A local-world evolving hypernetwork model

    NASA Astrophysics Data System (ADS)

    Yang, Guang-Yong; Liu, Jian-Guo

    2014-01-01

    Complex hypernetworks are ubiquitous in the real system. It is very important to investigate the evolution mechanisms. In this paper, we present a local-world evolving hypernetwork model by taking into account the hyperedge growth and local-world hyperedge preferential attachment mechanisms. At each time step, a newly added hyperedge encircles a new coming node and a number of nodes from a randomly selected local world. The number of the selected nodes from the local world obeys the uniform distribution and its mean value is m. The analytical and simulation results show that the hyperdegree approximately obeys the power-law form and the exponent of hyperdegree distribution is γ = 2 + 1/m. Furthermore, we numerically investigate the node degree, hyperedge degree, clustering coefficient, as well as the average distance, and find that the hypernetwork model shares the scale-free and small-world properties, which shed some light for deeply understanding the evolution mechanism of the real systems.

  20. The Evolving Theory of Evolutionary Radiations.

    PubMed

    Simões, M; Breitkreuz, L; Alvarado, M; Baca, S; Cooper, J C; Heins, L; Herzog, K; Lieberman, B S

    2016-01-01

    Evolutionary radiations have intrigued biologists for more than 100 years, and our understanding of the patterns and processes associated with these radiations continues to grow and evolve. Recently it has been recognized that there are many different types of evolutionary radiation beyond the well-studied adaptive radiations. We focus here on multifarious types of evolutionary radiations, paying special attention to the abiotic factors that might trigger diversification in clades. We integrate concepts such as exaptation, species selection, coevolution, and the turnover-pulse hypothesis (TPH) into the theoretical framework of evolutionary radiations. We also discuss other phenomena that are related to, but distinct from, evolutionary radiations that have relevance for evolutionary biology. PMID:26632984

  1. Evolving resistance among Gram-positive pathogens.

    PubMed

    Munita, Jose M; Bayer, Arnold S; Arias, Cesar A

    2015-09-15

    Antimicrobial therapy is a key component of modern medical practice and a cornerstone for the development of complex clinical interventions in critically ill patients. Unfortunately, the increasing problem of antimicrobial resistance is now recognized as a major public health threat jeopardizing the care of thousands of patients worldwide. Gram-positive pathogens exhibit an immense genetic repertoire to adapt and develop resistance to virtually all antimicrobials clinically available. As more molecules become available to treat resistant gram-positive infections, resistance emerges as an evolutionary response. Thus, antimicrobial resistance has to be envisaged as an evolving phenomenon that demands constant surveillance and continuous efforts to identify emerging mechanisms of resistance to optimize the use of antibiotics and create strategies to circumvent this problem. Here, we will provide a broad perspective on the clinical aspects of antibiotic resistance in relevant gram-positive pathogens with emphasis on the mechanistic strategies used by these organisms to avoid being killed by commonly used antimicrobial agents.

  2. Life cycle planning: An evolving concept

    SciTech Connect

    Moore, P.J.R.; Gorman, I.G.

    1994-12-31

    Life-cycle planning is an evolving concept in the management of oil and gas projects. BHP Petroleum now interprets this idea to include all development planning from discovery and field appraisal to final abandonment and includes safety, environmental, technical, plant, regulatory, and staffing issues. This article describes in the context of the Timor Sea, how despite initial successes and continuing facilities upgrades, BHPP came to perceive that current operations could be the victim of early development successes, particularly in the areas of corrosion and maintenance. The search for analogies elsewhere lead to the UK North Sea, including the experiences of Britoil and BP, both of which performed detailed Life of Field studies in the later eighties. These materials have been used to construct a format and content for total Life-cycle plans in general and the social changes required to ensure their successful application in Timor Sea operations and deployment throughout Australia.

  3. Resiliently evolving supply-demand networks

    NASA Astrophysics Data System (ADS)

    Rubido, Nicolás; Grebogi, Celso; Baptista, Murilo S.

    2014-01-01

    The ability to design a transport network such that commodities are brought from suppliers to consumers in a steady, optimal, and stable way is of great importance for distribution systems nowadays. In this work, by using the circuit laws of Kirchhoff and Ohm, we provide the exact capacities of the edges that an optimal supply-demand network should have to operate stably under perturbations, i.e., without overloading. The perturbations we consider are the evolution of the connecting topology, the decentralization of hub sources or sinks, and the intermittence of supplier and consumer characteristics. We analyze these conditions and the impact of our results, both on the current United Kingdom power-grid structure and on numerically generated evolving archetypal network topologies.

  4. Language as an evolving word web.

    PubMed

    Dorogovtsev, S N; Mendes, J F

    2001-12-22

    Human language may be described as a complex network of linked words. In such a treatment, each distinct word in language is a vertex of this web, and interacting words in sentences are connected by edges. The empirical distribution of the number of connections of words in this network is of a peculiar form that includes two pronounced power-law regions. Here we propose a theory of the evolution of language, which treats language as a self-organizing network of interacting words. In the framework of this concept, we completely describe the observed word web structure without any fitting. We show that the two regimes in the distribution naturally emerge from the evolutionary dynamics of the word web. It follows from our theory that the size of the core part of language, the 'kernel lexicon', does not vary as language evolves.

  5. Microbial communities evolve faster in extreme environments

    PubMed Central

    Li, Sheng-Jin; Hua, Zheng-Shuang; Huang, Li-Nan; Li, Jie; Shi, Su-Hua; Chen, Lin-Xing; Kuang, Jia-Liang; Liu, Jun; Hu, Min; Shu, Wen-Sheng

    2014-01-01

    Evolutionary analysis of microbes at the community level represents a new research avenue linking ecological patterns to evolutionary processes, but remains insufficiently studied. Here we report a relative evolutionary rates (rERs) analysis of microbial communities from six diverse natural environments based on 40 metagenomic samples. We show that the rERs of microbial communities are mainly shaped by environmental conditions, and the microbes inhabiting extreme habitats (acid mine drainage, saline lake and hot spring) evolve faster than those populating benign environments (surface ocean, fresh water and soil). These findings were supported by the observation of more relaxed purifying selection and potentially frequent horizontal gene transfers in communities from extreme habitats. The mechanism of high rERs was proposed as high mutation rates imposed by stressful conditions during the evolutionary processes. This study brings us one stage closer to an understanding of the evolutionary mechanisms underlying the adaptation of microbes to extreme environments. PMID:25158668

  6. Evolving circuits in seconds: experiments with a stand-alone board-level evolvable system

    NASA Technical Reports Server (NTRS)

    Stoica, A.; Zebulum, R. S.; Ferguson, M. I.; Keymeulen, D.; Duong, V.; Guo, X.

    2002-01-01

    The purpose of this paper is twofold: first, to illustrate a stand-alone board-level evolvable system (SABLES) and its performance, and second to illustrate some problems that occur during evolution with real hardware in the loop, or when the intention of the user is not completely reflected in the fitness function.

  7. How evolved psychological mechanisms empower cultural group selection.

    PubMed

    Henrich, Joseph; Boyd, Robert

    2016-01-01

    Driven by intergroup competition, social norms, beliefs, and practices can evolve in ways that more effectively tap into a wide variety of evolved psychological mechanisms to foster group-beneficial behavior. The more powerful such evolved mechanisms are, the more effectively culture can potentially harness and manipulate them to generate greater phenotypic variation across groups, thereby fueling cultural group selection. PMID:27561383

  8. Home Oxygen Therapy

    MedlinePlus

    ... important advantage of liquid oxygen is you can transfer some of the liquid oxygen into a smaller, ... from gas stoves, candles, lighted fireplaces, or other heat sources. Don't use any flammable products like ...

  9. Timeline: Cellular Oxygen Sensing.

    PubMed

    Szewczak, Lara

    2016-09-22

    Since the 1950s, researchers have recognized that red blood cell numbers expand or contract as needed, according to the amount of available oxygen. The later discoveries that erythropoietin and VEGF levels adapt to oxygen levels launched a new field aimed at understanding how cells sense and respond to normal- and low-oxygen environments. The 2016 Albert Lasker Basic Medical Research Award recognizes key discoveries about this global oxygen sensing pathway and its impacts on pathogenesis, including cancer and inflammation. PMID:27662095

  10. Oxygen evolution reaction catalysis

    DOEpatents

    Haber, Joel A.; Jin, Jian; Xiang, Chengxiang; Gregoire, John M.; Jones, Ryan J.; Guevarra, Dan W.; Shinde, Aniketa A.

    2016-09-06

    An Oxygen Evolution Reaction (OER) catalyst includes a metal oxide that includes oxygen, cerium, and one or more second metals. In some instances, the cerium is 10 to 80 molar % of the metals in the metal oxide and/or the catalyst includes two or more second metals. The OER catalyst can be included in or on an electrode. The electrode can be arranged in an oxygen evolution system such that the Oxygen Evolution Reaction occurs at the electrode.

  11. Solid state oxygen sensor

    DOEpatents

    Garzon, Fernando H.; Brosha, Eric L.

    1997-01-01

    A potentiometric oxygen sensor is formed having a logarithmic response to a differential oxygen concentration while operating as a Nernstian-type sensor. Very thin films of mixed conducting oxide materials form electrode services while permitting diffusional oxygen access to the interface between the zirconia electrolyte and the electrode. Diffusion of oxygen through the mixed oxide is not rate-limiting. Metal electrodes are not used so that morphological changes in the electrode structure do not occur during extended operation at elevated temperatures.

  12. Active oxygen doctors the evidence

    NASA Astrophysics Data System (ADS)

    Castelló, Ana; Francès, Francesc; Corella, Dolores; Verdú, Fernando

    2009-02-01

    Investigation at the scene of a crime begins with the search for clues. In the case of bloodstains, the most frequently used reagents are luminol and reduced phenolphthalein (or phenolphthalin that is also known as the Kastle-Meyer colour test). The limitations of these reagents have been studied and are well known. Household cleaning products have evolved with the times, and new products with active oxygen are currently widely used, as they are considered to be highly efficient at removing all kinds of stains on a wide range of surfaces. In this study, we investigated the possible effects of these new cleaning products on latent bloodstains that may be left at a scene of a crime. To do so, various fabrics were stained with blood and then washed using cleaning agents containing active oxygen. The results of reduced phenolphthalein, luminol and human haemoglobin tests on the washed fabrics were negative. The conclusion is that these new products alter blood to such an extent that it can no longer be detected by currently accepted methods employed in criminal investigations. This inability to locate bloodstains means that highly important evidence (e.g. a DNA profile) may be lost. Consequently, it is important that investigators are aware of this problem so as to compensate for it.

  13. Biological decontamination by oxygen plasma.

    NASA Astrophysics Data System (ADS)

    Bol'Shakov, A. A.; Cruden, B. A.; Mogul, R.; Rao, M. V. V. S.; Sharma, S. P.; Meyyappan, M.

    2002-10-01

    Oxygen plasma sustained at 13.56 MHz in a standardized reactor with a planar induction coil was used for biological sterilization experiments. Optical emission and mass spectrometry was applied for detection of excited species and ion energy/flux analysis. A plasma mode transition in the ranges of 13-67 Pa and 100-330 W was observed. At higher pressure and lower power, the plasma was in a dim mode (primarily stray capacitive coupling). A primarily inductive bright mode was attained at lower pressure and higher power. This transition was identified using combined diagnostics and then recognized by emission spectroscopy on a scaled down reactor for biological degradation tests. Plasmid DNA removal was 25% more efficient in the bright versus dim mode at the same power. The fast degradation was attributed to photo- and ion-assisted etching by oxygen atoms and perhaps O2 metastable molecules. Volatilization rates of the decomposition products (CO_2, CO, N_2, OH, H) evolving from the Deinococcus radiodurans microbe and polypeptide samples were compared.

  14. Mercury-T: Tidally evolving multi-planet systems code

    NASA Astrophysics Data System (ADS)

    Bolmont, Emeline; Raymond, Sean N.; Leconte, Jeremy; Hersant, Franck; Correia, Alexandre C. M.

    2015-11-01

    Mercury-T calculates the evolution of semi-major axis, eccentricity, inclination, rotation period and obliquity of the planets as well as the rotation period evolution of the host body; it is based on the N-body code Mercury (Chambers 1999, ascl:1201.008). It is flexible, allowing computation of the tidal evolution of systems orbiting any non-evolving object (if its mass, radius, dissipation factor and rotation period are known), but also evolving brown dwarfs (BDs) of mass between 0.01 and 0.08 M⊙, an evolving M-dwarf of 0.1 M⊙, an evolving Sun-like star, and an evolving Jupiter.

  15. Hydrogen production using hydrogenase-containing oxygenic photosynthetic organisms

    DOEpatents

    Melis, Anastasios; Zhang, Liping; Benemann, John R.; Forestier, Marc; Ghirardi, Maria; Seibert, Michael

    2006-01-24

    A reversible physiological process provides for the temporal separation of oxygen evolution and hydrogen production in a microorganism, which includes the steps of growing a culture of the microorganism in medium under illuminated conditions to accumulate an endogenous substrate, depleting from the medium a nutrient selected from the group consisting of sulfur, iron, and/or manganese, sealing the culture from atmospheric oxygen, incubating the culture in light whereby a rate of light-induced oxygen production is equal to or less than a rate of respiration, and collecting an evolved gas. The process is particularly useful to accomplish a sustained photobiological hydrogen gas production in cultures of microorganisms, such as Chlamydomonas reinhardtii.

  16. Hydrogen Production Using Hydrogenase-Containing Oxygenic Photosynthetic Organisms

    DOEpatents

    Melis, A.; Zhang, L.; Benemann, J. R.; Forestier, M.; Ghirardi, M.; Seibert, M.

    2006-01-24

    A reversible physiological process provides for the temporal separation of oxygen evolution and hydrogen production in a microorganism, which includes the steps of growing a culture of the microorganism in medium under illuminated conditions to accumulate an endogenous substrate, depleting from the medium a nutrient selected from the group consisting of sulfur, iron, and/or manganese, sealing the culture from atmospheric oxygen, incubating the culture in light whereby a rate of light-induced oxygen production is equal to or less than a rate of respiration, and collecting an evolved gas. The process is particularly useful to accomplish a sustained photobiological hydrogen gas production in cultures of microorganisms, such as Chlamydomonas reinhardtii.

  17. Oxygen defects in phosphorene.

    PubMed

    Ziletti, A; Carvalho, A; Campbell, D K; Coker, D F; Castro Neto, A H

    2015-01-30

    Surface reactions with oxygen are a fundamental cause of the degradation of phosphorene. Using first-principles calculations, we show that for each oxygen atom adsorbed onto phosphorene there is an energy release of about 2 eV. Although the most stable oxygen adsorbed forms are electrically inactive and lead only to minor distortions of the lattice, there are low energy metastable forms which introduce deep donor and/or acceptor levels in the gap. We also propose a mechanism for phosphorene oxidation involving reactive dangling oxygen atoms and we suggest that dangling oxygen atoms increase the hydrophilicity of phosphorene.

  18. Brain Oxygenation Monitoring.

    PubMed

    Kirkman, Matthew A; Smith, Martin

    2016-09-01

    A mismatch between cerebral oxygen supply and demand can lead to cerebral hypoxia/ischemia and deleterious outcomes. Cerebral oxygenation monitoring is an important aspect of multimodality neuromonitoring. It is increasingly deployed whenever intracranial pressure monitoring is indicated. Although there is a large body of evidence demonstrating an association between cerebral hypoxia/ischemia and poor outcomes, it remains to be determined whether restoring cerebral oxygenation leads to improved outcomes. Randomized prospective studies are required to address uncertainties about cerebral oxygenation monitoring and management. This article describes the different methods of monitoring cerebral oxygenation, their indications, evidence base, limitations, and future perspectives. PMID:27521197

  19. Speciation genetics: current status and evolving approaches

    PubMed Central

    Wolf, Jochen B. W.; Lindell, Johan; Backström, Niclas

    2010-01-01

    The view of species as entities subjected to natural selection and amenable to change put forth by Charles Darwin and Alfred Wallace laid the conceptual foundation for understanding speciation. Initially marred by a rudimental understanding of hereditary principles, evolutionists gained appreciation of the mechanistic underpinnings of speciation following the merger of Mendelian genetic principles with Darwinian evolution. Only recently have we entered an era where deciphering the molecular basis of speciation is within reach. Much focus has been devoted to the genetic basis of intrinsic postzygotic isolation in model organisms and several hybrid incompatibility genes have been successfully identified. However, concomitant with the recent technological advancements in genome analysis and a newfound interest in the role of ecology in the differentiation process, speciation genetic research is becoming increasingly open to non-model organisms. This development will expand speciation research beyond the traditional boundaries and unveil the genetic basis of speciation from manifold perspectives and at various stages of the splitting process. This review aims at providing an extensive overview of speciation genetics. Starting from key historical developments and core concepts of speciation genetics, we focus much of our attention on evolving approaches and introduce promising methodological approaches for future research venues. PMID:20439277

  20. The Evolving Role of Midwives as Laborists.

    PubMed

    DeJoy, Susan A; Sankey, Heather Z; Dickerson, Anissa E; Psaltis, Audrey; Galli, Amy; Burkman, Ronald T

    2015-01-01

    This article examines the history and present state of the midwife as laborist. The role of the midwife and obstetrician laborist/hospitalist is rapidly evolving due to the need to improve patient safety and provide direct care due to reduced resident work hours, as well as practice demands experienced by community providers and other factors. Models under development are customized to meet the needs of different communities and hospitals. Midwives are playing a prominent role in many laborist/hospitalist practices as the first-line hospital provider or as part of a team with physicians. Some models incorporate certified nurse-midwives/certified midwives as faculty to residents and medical students. The midwifery laborist/hospitalist practices at Baystate Medical Center in Springfield, Massachusetts, are presented as an example of how midwives are functioning as laborists. Essential components of a successful midwife laborist program include interdisciplinary planning, delineation of problems the model should solve, establishment of program metrics, clear practice guidelines and role definitions, and a plan for sustained funding. This article is part of a special series of articles that address midwifery innovations in clinical practice, education, interprofessional collaboration, health policy, and global health. PMID:26619374

  1. Are Electronic Cardiac Devices Still Evolving?

    PubMed Central

    Mabo, P.

    2014-01-01

    Summary Objectives The goal of this paper is to review some important issues occurring during the past year in Implantable devices. Methods First cardiac implantable device was proposed to maintain an adequate heart rate, either because the heart’s natural pacemaker is not fast enough, or there is a block in the heart’s electrical conduction system. During the last forty years, pacemakers have evolved considerably and become programmable and allow to configure specific patient optimum pacing modes. Various technological aspects (electrodes, connectors, algorithms diagnosis, therapies, …) have been progressed and cardiac implants address several clinical applications: management of arrhythmias, cardioversion / defibrillation and cardiac resynchronization therapy. Results Observed progress was the miniaturization of device, increased longevity, coupled with efficient pacing functions, multisite pacing modes, leadless pacing and also a better recognition of supraventricular or ventricular tachycardia’s in order to deliver appropriate therapy. Subcutaneous implant, new modes of stimulation (leadless implant or ultrasound lead), quadripolar lead and new sensor or new algorithm for the hemodynamic management are introduced and briefly described. Each times, the main result occurring during the two past years are underlined and repositioned from the history, remaining limitations are also addressed. Conclusion Some important technological improvements were described. Nevertheless, news trends for the future are also considered in a specific session such as the remote follow-up of the patient or the treatment of heart failure by neuromodulation. PMID:25123732

  2. Women and Ischemic Heart Disease: Evolving Knowledge

    PubMed Central

    Shaw, Leslee J.; Bugiardini, Raffaelle; Merz, C. Noel Bairey

    2009-01-01

    Evolving knowledge regarding sex differences in coronary heart disease (CHD) is emerging. Given the lower burden of obstructive coronary artery disease (CAD) and preserved systolic function in women contrasted by higher rates of myocardial ischemia and near-term mortality compared to men, we propose the term ischemic heart disease (IHD) as appropriate for this discussion specific to women, rather than CAD or CHD. This paradoxical difference where women have lower rates of anatomical CAD but more symptoms, ischemia, and outcomes appear linked to coronary reactivity which includes microvascular dysfunction. Novel risk factors can improve the Framingham risk score, including inflammatory markers and reproductive hormones, as well as noninvasive imaging and functional capacity measurements. Risk for women with obstructive CAD is elevated compared to men, yet women are less likely to receive guideline-indicated therapies. In the setting of non-ST elevation acute myocardial infarction, interventional strategies are equally effective in biomarker positive women and men, while conservative management is indicated for biomarker negative women. For women with evidence of ischemia but no obstructive CAD, anti-anginal and anti-ischemic therapies can improve symptoms, endothelial function, and quality of life; however trials evaluating adverse outcomes are needed. We hypothesize that women experience more adverse outcomes compared to men because obstructive CAD remains the current focus of therapeutic strategies. Continued research is indicated to devise therapeutic regimens to improve symptom burden and reduce risk in women with IHD. PMID:19833255

  3. Extreme insular dwarfism evolved in a mammoth.

    PubMed

    Herridge, Victoria L; Lister, Adrian M

    2012-08-22

    The insular dwarfism seen in Pleistocene elephants has come to epitomize the island rule; yet our understanding of this phenomenon is hampered by poor taxonomy. For Mediterranean dwarf elephants, where the most extreme cases of insular dwarfism are observed, a key systematic question remains unresolved: are all taxa phyletic dwarfs of a single mainland species Palaeoloxodon antiquus (straight-tusked elephant), or are some referable to Mammuthus (mammoths)? Ancient DNA and geochronological evidence have been used to support a Mammuthus origin for the Cretan 'Palaeoloxodon' creticus, but these studies have been shown to be flawed. On the basis of existing collections and recent field discoveries, we present new, morphological evidence for the taxonomic status of 'P'. creticus, and show that it is indeed a mammoth, most probably derived from Early Pleistocene Mammuthus meridionalis or possibly Late Pliocene Mammuthus rumanus. We also show that Mammuthus creticus is smaller than other known insular dwarf mammoths, and is similar in size to the smallest dwarf Palaeoloxodon species from Sicily and Malta, making it the smallest mammoth species known to have existed. These findings indicate that extreme insular dwarfism has evolved to a similar degree independently in two elephant lineages.

  4. Evolving Earth Models and Nuclear Explosion Monitoring

    NASA Astrophysics Data System (ADS)

    Wallace, T. C.

    2003-12-01

    One of the most important problems in nuclear explosion monitoring is accurate seismic event location. Traditional location methods rely on estimating travel times in a known Earth model and accounting for heterogeneity through various empirical corrections. The history of location accuracy and precision is closely coupled to evolving theories of the nature of the Earth's interior. LONG SHOT was a 80 Kt explosion conducted on Amchitka Island on October 29, 1965. The travel times recorded from LONG SHOT deviated strongly from a radially symmetric Earth, and in fact showed a pattern consistent a tabular body of relatively high seismic velocity (the subducting North American Plate) validating certain concepts of the then new theory of plate tectonics. Each subsequent advance in conceptual models for the dynamics of the Earth's interior has impacted explosion monitoring. Many of the advances in the theory of the Earth's interior have been spurred by the ideas and work of Don Anderson. These include anelasticity, anisotropy, tomography, the Lehmann discontinuity, and mantle plumes (or lack of). The present state-of-the-art monitoring paradigm incorporates a dynamic Earth model, and the synergy between verification research and basic research on the Earth's interior is quite important.

  5. Evolving Resistance Among Gram-positive Pathogens

    PubMed Central

    Munita, Jose M.; Bayer, Arnold S.; Arias, Cesar A.

    2015-01-01

    Antimicrobial therapy is a key component of modern medical practice and a cornerstone for the development of complex clinical interventions in critically ill patients. Unfortunately, the increasing problem of antimicrobial resistance is now recognized as a major public health threat jeopardizing the care of thousands of patients worldwide. Gram-positive pathogens exhibit an immense genetic repertoire to adapt and develop resistance to virtually all antimicrobials clinically available. As more molecules become available to treat resistant gram-positive infections, resistance emerges as an evolutionary response. Thus, antimicrobial resistance has to be envisaged as an evolving phenomenon that demands constant surveillance and continuous efforts to identify emerging mechanisms of resistance to optimize the use of antibiotics and create strategies to circumvent this problem. Here, we will provide a broad perspective on the clinical aspects of antibiotic resistance in relevant gram-positive pathogens with emphasis on the mechanistic strategies used by these organisms to avoid being killed by commonly used antimicrobial agents. PMID:26316558

  6. Extreme insular dwarfism evolved in a mammoth.

    PubMed

    Herridge, Victoria L; Lister, Adrian M

    2012-08-22

    The insular dwarfism seen in Pleistocene elephants has come to epitomize the island rule; yet our understanding of this phenomenon is hampered by poor taxonomy. For Mediterranean dwarf elephants, where the most extreme cases of insular dwarfism are observed, a key systematic question remains unresolved: are all taxa phyletic dwarfs of a single mainland species Palaeoloxodon antiquus (straight-tusked elephant), or are some referable to Mammuthus (mammoths)? Ancient DNA and geochronological evidence have been used to support a Mammuthus origin for the Cretan 'Palaeoloxodon' creticus, but these studies have been shown to be flawed. On the basis of existing collections and recent field discoveries, we present new, morphological evidence for the taxonomic status of 'P'. creticus, and show that it is indeed a mammoth, most probably derived from Early Pleistocene Mammuthus meridionalis or possibly Late Pliocene Mammuthus rumanus. We also show that Mammuthus creticus is smaller than other known insular dwarf mammoths, and is similar in size to the smallest dwarf Palaeoloxodon species from Sicily and Malta, making it the smallest mammoth species known to have existed. These findings indicate that extreme insular dwarfism has evolved to a similar degree independently in two elephant lineages. PMID:22572206

  7. Tearing Mode Stability of Evolving Toroidal Equilibria

    NASA Astrophysics Data System (ADS)

    Pletzer, A.; McCune, D.; Manickam, J.; Jardin, S. C.

    2000-10-01

    There are a number of toroidal equilibrium (such as JSOLVER, ESC, EFIT, and VMEC) and transport codes (such as TRANSP, BALDUR, and TSC) in our community that utilize differing equilibrium representations. There are also many heating and current drive (LSC and TORRAY), and stability (PEST1-3, GATO, NOVA, MARS, DCON, M3D) codes that require this equilibrium information. In an effort to provide seamless compatibility between the codes that produce and need these equilibria, we have developed two Fortran 90 modules, MEQ and XPLASMA, that serve as common interfaces between these two classes of codes. XPLASMA provides a common equilibrium representation for the heating and current drive applications while MEQ provides common equilibrium and associated metric information needed by MHD stability codes. We illustrate the utility of this approach by presenting results of PEST-3 tearing stability calculations of an NSTX discharge performed on profiles provided by the TRANSP code. Using the MEQ module, the TRANSP equilibrium data are stored in a Fortran 90 derived type and passed to PEST3 as a subroutine argument. All calculations are performed on the fly, as the profiles evolve.

  8. Origins of stereoselectivity in evolved ketoreductases

    PubMed Central

    Noey, Elizabeth L.; Tibrewal, Nidhi; Jiménez-Osés, Gonzalo; Osuna, Sílvia; Park, Jiyong; Bond, Carly M.; Cascio, Duilio; Liang, Jack; Zhang, Xiyun; Huisman, Gjalt W.; Tang, Yi; Houk, Kendall N.

    2015-01-01

    Mutants of Lactobacillus kefir short-chain alcohol dehydrogenase, used here as ketoreductases (KREDs), enantioselectively reduce the pharmaceutically relevant substrates 3-thiacyclopentanone and 3-oxacyclopentanone. These substrates differ by only the heteroatom (S or O) in the ring, but the KRED mutants reduce them with different enantioselectivities. Kinetic studies show that these enzymes are more efficient with 3-thiacyclopentanone than with 3-oxacyclopentanone. X-ray crystal structures of apo- and NADP+-bound selected mutants show that the substrate-binding loop conformational preferences are modified by these mutations. Quantum mechanical calculations and molecular dynamics (MD) simulations are used to investigate the mechanism of reduction by the enzyme. We have developed an MD-based method for studying the diastereomeric transition state complexes and rationalize different enantiomeric ratios. This method, which probes the stability of the catalytic arrangement within the theozyme, shows a correlation between the relative fractions of catalytically competent poses for the enantiomeric reductions and the experimental enantiomeric ratio. Some mutations, such as A94F and Y190F, induce conformational changes in the active site that enlarge the small binding pocket, facilitating accommodation of the larger S atom in this region and enhancing S-selectivity with 3-thiacyclopentanone. In contrast, in the E145S mutant and the final variant evolved for large-scale production of the intermediate for the antibiotic sulopenem, R-selectivity is promoted by shrinking the small binding pocket, thereby destabilizing the pro-S orientation. PMID:26644568

  9. An evolving model of online bipartite networks

    NASA Astrophysics Data System (ADS)

    Zhang, Chu-Xu; Zhang, Zi-Ke; Liu, Chuang

    2013-12-01

    Understanding the structure and evolution of online bipartite networks is a significant task since they play a crucial role in various e-commerce services nowadays. Recently, various attempts have been tried to propose different models, resulting in either power-law or exponential degree distributions. However, many empirical results show that the user degree distribution actually follows a shifted power-law distribution, the so-called Mandelbrot’s law, which cannot be fully described by previous models. In this paper, we propose an evolving model, considering two different user behaviors: random and preferential attachment. Extensive empirical results on two real bipartite networks, Delicious and CiteULike, show that the theoretical model can well characterize the structure of real networks for both user and object degree distributions. In addition, we introduce a structural parameter p, to demonstrate that the hybrid user behavior leads to the shifted power-law degree distribution, and the region of power-law tail will increase with the increment of p. The proposed model might shed some lights in understanding the underlying laws governing the structure of real online bipartite networks.

  10. Regulatory mechanisms link phenotypic plasticity to evolvability

    PubMed Central

    van Gestel, Jordi; Weissing, Franz J.

    2016-01-01

    Organisms have a remarkable capacity to respond to environmental change. They can either respond directly, by means of phenotypic plasticity, or they can slowly adapt through evolution. Yet, how phenotypic plasticity links to evolutionary adaptability is largely unknown. Current studies of plasticity tend to adopt a phenomenological reaction norm (RN) approach, which neglects the mechanisms underlying plasticity. Focusing on a concrete question – the optimal timing of bacterial sporulation – we here also consider a mechanistic approach, the evolution of a gene regulatory network (GRN) underlying plasticity. Using individual-based simulations, we compare the RN and GRN approach and find a number of striking differences. Most importantly, the GRN model results in a much higher diversity of responsive strategies than the RN model. We show that each of the evolved strategies is pre-adapted to a unique set of unseen environmental conditions. The regulatory mechanisms that control plasticity therefore critically link phenotypic plasticity to the adaptive potential of biological populations. PMID:27087393

  11. Gastric cancer: current and evolving treatment landscape.

    PubMed

    Sun, Weijing; Yan, Li

    2016-01-01

    Gastric (including gastroesophageal junction) cancer is the third leading cause of cancer-related death in the world. In China, an estimated 420,000 patients were diagnosed with gastric cancer in 2011, ranking this malignancy the second most prevalent cancer type and resulting in near 300,000 deaths. The treatment landscape of gastric cancer has evolved in recent years. Although systemic chemotherapy is still the mainstay treatment of metastatic disease, the introduction of agents targeting human epidermal growth factor receptor 2 and vascular endothelial growth factor/vascular endothelia growth factor receptor has brought this disease into the molecular and personalized medicine era. The preliminary yet encouraging clinical efficacy observed with immune checkpoint inhibitors, e.g., anti-programmed cell death protein 1/programmed death-ligand 1, will further shape the treatment landscape for gastric cancer. Molecular characterization of patients will play a critical role in developing new agents, as well as in implementing new treatment options for this disease. PMID:27581465

  12. Relatedness influences signal reliability in evolving robots.

    PubMed

    Mitri, Sara; Floreano, Dario; Keller, Laurent

    2011-02-01

    Communication is an indispensable component of animal societies, yet many open questions remain regarding the factors affecting the evolution and reliability of signalling systems. A potentially important factor is the level of genetic relatedness between signallers and receivers. To quantitatively explore the role of relatedness in the evolution of reliable signals, we conducted artificial evolution over 500 generations in a system of foraging robots that can emit and perceive light signals. By devising a quantitative measure of signal reliability, and comparing independently evolving populations differing in within-group relatedness, we show a strong positive correlation between relatedness and reliability. Unrelated robots produced unreliable signals, whereas highly related robots produced signals that reliably indicated the location of the food source and thereby increased performance. Comparisons across populations also revealed that the frequency for signal production-which is often used as a proxy of signal reliability in empirical studies on animal communication-is a poor predictor of signal reliability and, accordingly, is not consistently correlated with group performance. This has important implications for our understanding of signal evolution and the empirical tools that are used to investigate communication.

  13. Exploring Evolving Media Discourse Through Event Cueing.

    PubMed

    Lu, Yafeng; Steptoe, Michael; Burke, Sarah; Wang, Hong; Tsai, Jiun-Yi; Davulcu, Hasan; Montgomery, Douglas; Corman, Steven R; Maciejewski, Ross

    2016-01-01

    Online news, microblogs and other media documents all contain valuable insight regarding events and responses to events. Underlying these documents is the concept of framing, a process in which communicators act (consciously or unconsciously) to construct a point of view that encourages facts to be interpreted by others in a particular manner. As media discourse evolves, how topics and documents are framed can undergo change, shifting the discussion to different viewpoints or rhetoric. What causes these shifts can be difficult to determine directly; however, by linking secondary datasets and enabling visual exploration, we can enhance the hypothesis generation process. In this paper, we present a visual analytics framework for event cueing using media data. As discourse develops over time, our framework applies a time series intervention model which tests to see if the level of framing is different before or after a given date. If the model indicates that the times before and after are statistically significantly different, this cues an analyst to explore related datasets to help enhance their understanding of what (if any) events may have triggered these changes in discourse. Our framework consists of entity extraction and sentiment analysis as lenses for data exploration and uses two different models for intervention analysis. To demonstrate the usage of our framework, we present a case study on exploring potential relationships between climate change framing and conflicts in Africa.

  14. Metapopulation capacity of evolving fluvial landscapes

    NASA Astrophysics Data System (ADS)

    Bertuzzo, Enrico; Rodriguez-Iturbe, Ignacio; Rinaldo, Andrea

    2015-04-01

    The form of fluvial landscapes is known to attain stationary network configurations that settle in dynamically accessible minima of total energy dissipation by landscape-forming discharges. Recent studies have highlighted the role of the dendritic structure of river networks in controlling population dynamics of the species they host and large-scale biodiversity patterns. Here, we systematically investigate the relation between energy dissipation, the physical driver for the evolution of river networks, and the ecological dynamics of their embedded biota. To that end, we use the concept of metapopulation capacity, a measure to link landscape structures with the population dynamics they host. Technically, metapopulation capacity is the leading eigenvalue λM of an appropriate "landscape" matrix subsuming whether a given species is predicted to persist in the long run. λM can conveniently be used to rank different landscapes in terms of their capacity to support viable metapopulations. We study how λM changes in response to the evolving network configurations of spanning trees. Such sequence of configurations is theoretically known to relate network selection to general landscape evolution equations through imperfect searches for dynamically accessible states frustrated by the vagaries of Nature. Results show that the process shaping the metric and the topological properties of river networks, prescribed by physical constraints, leads to a progressive increase in the corresponding metapopulation capacity and therefore on the landscape capacity to support metapopulations—with implications on biodiversity in fluvial ecosystems.

  15. Generative Representations for Evolving Families of Designs

    NASA Technical Reports Server (NTRS)

    Hornby, Gregory S.

    2003-01-01

    Since typical evolutionary design systems encode only a single artifact with each individual, each time the objective changes a new set of individuals must be evolved. When this objective varies in a way that can be parameterized, a more general method is to use a representation in which a single individual encodes an entire class of artifacts. In addition to saving time by preventing the need for multiple evolutionary runs, the evolution of parameter-controlled designs can create families of artifacts with the same style and a reuse of parts between members of the family. In this paper an evolutionary design system is described which uses a generative representation to encode families of designs. Because a generative representation is an algorithmic encoding of a design, its input parameters are a way to control aspects of the design it generates. By evaluating individuals multiple times with different input parameters the evolutionary design system creates individuals in which the input parameter controls specific aspects of a design. This system is demonstrated on two design substrates: neural-networks which solve the 3/5/7-parity problem and three-dimensional tables of varying heights.

  16. How does cognition evolve? Phylogenetic comparative psychology

    PubMed Central

    Matthews, Luke J.; Hare, Brian A.; Nunn, Charles L.; Anderson, Rindy C.; Aureli, Filippo; Brannon, Elizabeth M.; Call, Josep; Drea, Christine M.; Emery, Nathan J.; Haun, Daniel B. M.; Herrmann, Esther; Jacobs, Lucia F.; Platt, Michael L.; Rosati, Alexandra G.; Sandel, Aaron A.; Schroepfer, Kara K.; Seed, Amanda M.; Tan, Jingzhi; van Schaik, Carel P.; Wobber, Victoria

    2014-01-01

    Now more than ever animal studies have the potential to test hypotheses regarding how cognition evolves. Comparative psychologists have developed new techniques to probe the cognitive mechanisms underlying animal behavior, and they have become increasingly skillful at adapting methodologies to test multiple species. Meanwhile, evolutionary biologists have generated quantitative approaches to investigate the phylogenetic distribution and function of phenotypic traits, including cognition. In particular, phylogenetic methods can quantitatively (1) test whether specific cognitive abilities are correlated with life history (e.g., lifespan), morphology (e.g., brain size), or socio-ecological variables (e.g., social system), (2) measure how strongly phylogenetic relatedness predicts the distribution of cognitive skills across species, and (3) estimate the ancestral state of a given cognitive trait using measures of cognitive performance from extant species. Phylogenetic methods can also be used to guide the selection of species comparisons that offer the strongest tests of a priori predictions of cognitive evolutionary hypotheses (i.e., phylogenetic targeting). Here, we explain how an integration of comparative psychology and evolutionary biology will answer a host of questions regarding the phylogenetic distribution and history of cognitive traits, as well as the evolutionary processes that drove their evolution. PMID:21927850

  17. Evolving application of biomimetic nanostructured hydroxyapatite

    PubMed Central

    Roveri, Norberto; Iafisco, Michele

    2010-01-01

    By mimicking Nature, we can design and synthesize inorganic smart materials that are reactive to biological tissues. These smart materials can be utilized to design innovative third-generation biomaterials, which are able to not only optimize their interaction with biological tissues and environment, but also mimic biogenic materials in their functionalities. The biomedical applications involve increasing the biomimetic levels from chemical composition, structural organization, morphology, mechanical behavior, nanostructure, and bulk and surface chemical–physical properties until the surface becomes bioreactive and stimulates cellular materials. The chemical–physical characteristics of biogenic hydroxyapatites from bone and tooth have been described, in order to point out the elective sides, which are important to reproduce the design of a new biomimetic synthetic hydroxyapatite. This review outlines the evolving applications of biomimetic synthetic calcium phosphates, details the main characteristics of bone and tooth, where the calcium phosphates are present, and discusses the chemical–physical characteristics of biomimetic calcium phosphates, methods of synthesizing them, and some of their biomedical applications. PMID:24198477

  18. Speciation genetics: current status and evolving approaches.

    PubMed

    Wolf, Jochen B W; Lindell, Johan; Backström, Niclas

    2010-06-12

    The view of species as entities subjected to natural selection and amenable to change put forth by Charles Darwin and Alfred Wallace laid the conceptual foundation for understanding speciation. Initially marred by a rudimental understanding of hereditary principles, evolutionists gained appreciation of the mechanistic underpinnings of speciation following the merger of Mendelian genetic principles with Darwinian evolution. Only recently have we entered an era where deciphering the molecular basis of speciation is within reach. Much focus has been devoted to the genetic basis of intrinsic postzygotic isolation in model organisms and several hybrid incompatibility genes have been successfully identified. However, concomitant with the recent technological advancements in genome analysis and a newfound interest in the role of ecology in the differentiation process, speciation genetic research is becoming increasingly open to non-model organisms. This development will expand speciation research beyond the traditional boundaries and unveil the genetic basis of speciation from manifold perspectives and at various stages of the splitting process. This review aims at providing an extensive overview of speciation genetics. Starting from key historical developments and core concepts of speciation genetics, we focus much of our attention on evolving approaches and introduce promising methodological approaches for future research venues.

  19. Evolving paradigms in multifocal breast cancer.

    PubMed

    Salgado, Roberto; Aftimos, Philippe; Sotiriou, Christos; Desmedt, Christine

    2015-04-01

    The 7th edition of the TNM defines multifocal breast cancer as multiple simultaneous ipsilateral and synchronous breast cancer lesions, provided they are macroscopically distinct and measurable using current traditional pathological and clinical tools. According to the College of American Pathologists (CAP), the characterization of only the largest lesion is considered sufficient, unless the grade and/or histology are different between the lesions. Here, we review three potentially clinically relevant aspects of multifocal breast cancers: first, the importance of a different intrinsic breast cancer subtype of the various lesions; second, the emerging awareness of inter-lesion heterogeneity; and last but not least, the potential introduction of bias in clinical trials due to the unrecognized biological diversity of these cancers. Although the current strategy to assess the lesion with the largest diameter has clearly its advantages in terms of costs and feasibility, this recommendation may not be sustainable in time and might need to be adapted to be compliant with new evolving paradigms in breast cancer.

  20. Origins and evolvability of the PAX family.

    PubMed

    Paixão-Côrtes, Vanessa R; Salzano, Francisco M; Bortolini, Maria Cátira

    2015-08-01

    The paired box (PAX) family of transcription/developmental genes plays a key role in numerous stages of embryonic development, as well as in adult organogenesis. There is evidence linking the acquisition of a paired-like DNA binding domain (PD) to domestication of a Tc1/mariner transposon. Further duplication/deletion processes led to at least five paralogous metazoan protein groups, which can be classified into two supergroups, PAXB-like or PAXD-like, using ancestral defining structures; the PD plus an octapeptide motif (OP) and a paired-type homeobox DNA binding domain (PTHD), producing the PD-OP-PTHD structure characteristic of the PAXB-like group, whereas an additional domain, the paired-type homeodomain tail (PHT), is present in the PAXD-like group, producing a PD-OP-PTHD-PHT structure. We examined their patterns of distribution in various species, using both available data and new bioinformatic analyses, including vertebrate PAX genes and their shared and specific functions, as well as inter- and intraspecific variability of PAX in primates. These analyses revealed a relatively conserved PAX network, accompanied by specific changes that led to adaptive novelties. Therefore, both stability and evolvability shaped the molecular evolution of this key transcriptional network. PMID:26321496

  1. Evolving role of MRI in Crohn's disease.

    PubMed

    Yacoub, Joseph H; Obara, Piotr; Oto, Aytekin

    2013-06-01

    MR enterography is playing an evolving role in the evaluation of small bowel Crohn's disease (CD). Standard MR enterography includes a combination of rapidly acquired T2 sequence, balanced steady-state acquisition, and contrast enhanced T1-weighted gradient echo sequence. The diagnostic performance of these sequences has been shown to be comparable, and in some respects superior, to other small bowel imaging modalities. The findings of CD on MR enterography have been well described in the literature. New and emerging techniques such as diffusion-weighted imaging (DWI), dynamic contrast enhanced MRI (DCE-MRI), cinematography, and magnetization transfer, may lead to improved accuracy in characterizing the disease. These advanced techniques can provide quantitative parameters that may prove to be useful in assessing disease activity, severity, and response to treatment. In the future, MR enterography may play an increasing role in management decisions for patients with small bowel CD; however, larger studies are needed to validate these emerging MRI parameters as imaging biomarkers. PMID:23712842

  2. Oxygen pressure measurement using singlet oxygen emission

    SciTech Connect

    Khalil, Gamal E.; Chang, Alvin; Gouterman, Martin; Callis, James B.; Dalton, Larry R.; Turro, Nicholas J.; Jockusch, Steffen

    2005-05-15

    Pressure sensitive paint (PSP) provides a visualization of two-dimensional pressure distributions on airfoil and model automobile surfaces. One type of PSP utilizes platinum tetra(pentafluorophenyl)porphine (PtTFPP) dissolved in a fluoro-polymer film. Since the intense 650 nm triplet emission of PtTFPP is quenched by ground state oxygen, it is possible to measure two-dimensional oxygen concentration from the 650 nm emission intensity using a Stern-Volmer-type relationship. This article reports an alternative luminescence method to measure oxygen concentration based on the porphyrin-sensitized 1270 nm singlet oxygen emission, which can be imaged with an InGaAs near infrared camera. This direct measurement of oxygen emission complements and further validates the oxygen measurement based on PtTFPP phosphorescence quenching. Initial success at obtaining a negative correlation between the 650 nm PtTFPP emission and the 1270 nm O{sub 2} emission in solution led us to additional two-dimensional film studies using surfaces coated with PtTFPP, MgTFPP, and H{sub 2}TFPP in polymers in a pressure and temperature controlled chamber.

  3. Oxygen pressure measurement using singlet oxygen emission

    NASA Astrophysics Data System (ADS)

    Khalil, Gamal E.; Chang, Alvin; Gouterman, Martin; Callis, James B.; Dalton, Larry R.; Turro, Nicholas J.; Jockusch, Steffen

    2005-05-01

    Pressure sensitive paint (PSP) provides a visualization of two-dimensional pressure distributions on airfoil and model automobile surfaces. One type of PSP utilizes platinum tetra(pentafluorophenyl)porphine (PtTFPP) dissolved in a fluoro-polymer film. Since the intense 650nm triplet emission of PtTFPP is quenched by ground state oxygen, it is possible to measure two-dimensional oxygen concentration from the 650nm emission intensity using a Stern-Volmer-type relationship. This article reports an alternative luminescence method to measure oxygen concentration based on the porphyrin-sensitized 1270nm singlet oxygen emission, which can be imaged with an InGaAs near infrared camera. This direct measurement of oxygen emission complements and further validates the oxygen measurement based on PtTFPP phosphorescence quenching. Initial success at obtaining a negative correlation between the 650nm PtTFPP emission and the 1270nm O2 emission in solution led us to additional two-dimensional film studies using surfaces coated with PtTFPP, MgTFPP, and H2TFPP in polymers in a pressure and temperature controlled chamber.

  4. Lower mass limit of an evolving interstellar cloud and chemistry in an evolving oscillatory cloud

    NASA Technical Reports Server (NTRS)

    Tarafdar, S. P.

    1986-01-01

    Simultaneous solution of the equation of motion, equation of state and energy equation including heating and cooling processes for interstellar medium gives for a collapsing cloud a lower mass limit which is significantly smaller than the Jeans mass for the same initial density. The clouds with higher mass than this limiting mass collapse whereas clouds with smaller than critical mass pass through a maximum central density giving apparently similar clouds (i.e., same Av, size and central density) at two different phases of its evolution (i.e., with different life time). Preliminary results of chemistry in such an evolving oscillatory cloud show significant difference in abundances of some of the molecules in two physically similar clouds with different life times. The problems of depletion and short life time of evolving clouds appear to be less severe in such an oscillatory cloud.

  5. Hydrogen peroxide and the evolution of oxygenic photosynthesis.

    PubMed

    McKay, C P; Hartman, H

    1991-01-01

    The early atmosphere of the Earth is considered to have been reducing (H2 rich) or neutral (CO2-N2). The present atmosphere by contrast is highly oxidizing (20% O2). The source of this oxygen is generally agreed to have been oxygenic photosynthesis, whereby organisms use water as the electron donor in the production of organic matter, liberating oxygen into the atmosphere. A major question in the evolution of life is how oxygenic photosynthesis could have evolved under anoxic conditions--and also when this capability evolved. It seems unlikely that water would be employed as the electron donor in anoxic environments that were rich in reducing agents such as ferrous or sulfide ions which could play that role. The abiotic production of atmospheric oxidants could have provided a mechanism by which locally oxidizing conditions were sustained within spatially confined habitats thus removing the available reductants and forcing photosynthetic organisms to utilize water as the electron donor. We suggest that atmospheric H2O2 played the key role in inducing oxygenic photosynthesis because as peroxide increased in a local environment, organisms would not only be faced with a loss of reductant, but they would also be pressed to develop the biochemical apparatus (e.g., catalase) that would ultimately be needed to protect against the products of oxygenic photosynthesis. This scenario allows for the early evolution of oxygenic photosynthesis while global conditions were still anaerobic.

  6. Liquefaction and Storage of In-Situ Oxygen on the Surface of Mars

    NASA Technical Reports Server (NTRS)

    Hauser, Daniel M.; Johnson, Wesley L.; Sutherlin, Steven G.

    2016-01-01

    ISRU is currently base-lined for the production of oxygen on the Martian surface in the Evolvable Mars Campaign Over 50 of return vehicle mass is oxygen for propulsion. There are two key cryogenic fluid-thermal technologies that need to be investigated to enable these architectures. High lift refrigeration systems. Thermal Insulation systems, either lightweight vacuum jackets of soft vacuum insulation systems.

  7. Oxygen partial pressure sensor

    DOEpatents

    Dees, D.W.

    1994-09-06

    A method for detecting oxygen partial pressure and an oxygen partial pressure sensor are provided. The method for measuring oxygen partial pressure includes contacting oxygen to a solid oxide electrolyte and measuring the subsequent change in electrical conductivity of the solid oxide electrolyte. A solid oxide electrolyte is utilized that contacts both a porous electrode and a nonporous electrode. The electrical conductivity of the solid oxide electrolyte is affected when oxygen from an exhaust stream permeates through the porous electrode to establish an equilibrium of oxygen anions in the electrolyte, thereby displacing electrons throughout the electrolyte to form an electron gradient. By adapting the two electrodes to sense a voltage potential between them, the change in electrolyte conductivity due to oxygen presence can be measured. 1 fig.

  8. Oxygen partial pressure sensor

    DOEpatents

    Dees, Dennis W.

    1994-01-01

    A method for detecting oxygen partial pressure and an oxygen partial pressure sensor are provided. The method for measuring oxygen partial pressure includes contacting oxygen to a solid oxide electrolyte and measuring the subsequent change in electrical conductivity of the solid oxide electrolyte. A solid oxide electrolyte is utilized that contacts both a porous electrode and a nonporous electrode. The electrical conductivity of the solid oxide electrolyte is affected when oxygen from an exhaust stream permeates through the porous electrode to establish an equilibrium of oxygen anions in the electrolyte, thereby displacing electrons throughout the electrolyte to form an electron gradient. By adapting the two electrodes to sense a voltage potential between them, the change in electrolyte conductivity due to oxygen presence can be measured.

  9. Biogeochemical Modeling of the Second Rise of Oxygen

    NASA Astrophysics Data System (ADS)

    Smith, M. L.; Catling, D.; Claire, M.; Zahnle, K.

    2014-03-01

    The rise of atmospheric oxygen set the tempo for the evolution of complex life on Earth. Oxygen levels are thought to have increased in two broad steps: one step occurred in the Archean ~ 2.45 Ga (the Great Oxidation Event or GOE), and another step occured in the Neoproterozoic ~750-580 Ma (the Neoprotoerozoic Oxygenation Event or NOE). During the NOE, oxygen levels increased from ~1-10% of the present atmospheric level (PAL) (Holland, 2006), to ~15% PAL in the late Neoproterozoic, to ~100% PAL later in the Phanerozoic. Complex life requires O2, so this transition allowed complex life to evolve. We seek to understand what caused the NOE. To explore causes for the NOE, we build upon the biogeochemical model of Claire et al. (2006), which calculates the redox evolution of the atmosphere, ocean, biosphere, and crust in the Archean through to the early Proterozoic. In this model, the balance between oxygenconsuming and oyxgen-producing fluxes evolves over time such that at ~2.4 Ga, the rapidly acting sources of oxygen outweigh the rapidly-acting sinks. Or, in other words, at ~2.4 Ga, the flux of oxygen from organic carbon burial exceeds the sinks of oxygen from reaction with reduced volcanic and metamoprphic gases. The model is able to drive oxygen levels to 1-10% PAL in the Proterozoic; however, the evolving redox fluxes in the model cannot explain how oxygen levels pushed above 1-10% in the late Proterozoic. The authors suggest that perhaps another buffer, such as sulfur, is needed to describe Proterozoic and Phanerozoic redox evolution. Geologic proxies show that in the Proterozoic, up to 10% of the deep ocean may have been sulfidic. With this ocean chemistry, the global sulfur cycle would have worked differently than it does today. Because the sulfur and oxygen cycles interact, the oxygen concentration could have permanently changed due to an evolving sulfur cycle (in combination with evolving redox fluxes associated with other parts of the oxygen cycle and carbon

  10. Early-branching or fast-evolving eukaryotes? An answer based on slowly evolving positions.

    PubMed

    Philippe, H; Lopez, P; Brinkmann, H; Budin, K; Germot, A; Laurent, J; Moreira, D; Müller, M; Le Guyader, H

    2000-06-22

    The current paradigm of eukaryotic evolution is based primarily on comparative analysis of ribosomal RNA sequences. It shows several early-emerging lineages, mostly amitochondriate, which might be living relics of a progressive assembly of the eukaryotic cell. However, the analysis of slow-evolving positions, carried out with the newly developed slow-fast method, reveals that these lineages are, in terms of nucleotide substitution, fast-evolving ones, misplaced at the base of the tree by a long branch attraction artefact. Since the fast-evolving groups are not always the same, depending on which macromolecule is used as a marker, this explains most of the observed incongruent phylogenies. The current paradigm of eukaryotic evolution thus has to be seriously re-examined as the eukaryotic phylogeny is presently best summarized by a multifurcation. This is consistent with the Big Bang hypothesis that all extant eukaryotic lineages are the result of multiple cladogeneses within a relatively brief period, although insufficiency of data is also a possible explanation for the lack of resolution. For further resolution, rare evolutionary events such as shared insertions and/or deletions or gene fusions might be helpful.

  11. Early-branching or fast-evolving eukaryotes? An answer based on slowly evolving positions.

    PubMed Central

    Philippe, H; Lopez, P; Brinkmann, H; Budin, K; Germot, A; Laurent, J; Moreira, D; Müller, M; Le Guyader, H

    2000-01-01

    The current paradigm of eukaryotic evolution is based primarily on comparative analysis of ribosomal RNA sequences. It shows several early-emerging lineages, mostly amitochondriate, which might be living relics of a progressive assembly of the eukaryotic cell. However, the analysis of slow-evolving positions, carried out with the newly developed slow-fast method, reveals that these lineages are, in terms of nucleotide substitution, fast-evolving ones, misplaced at the base of the tree by a long branch attraction artefact. Since the fast-evolving groups are not always the same, depending on which macromolecule is used as a marker, this explains most of the observed incongruent phylogenies. The current paradigm of eukaryotic evolution thus has to be seriously re-examined as the eukaryotic phylogeny is presently best summarized by a multifurcation. This is consistent with the Big Bang hypothesis that all extant eukaryotic lineages are the result of multiple cladogeneses within a relatively brief period, although insufficiency of data is also a possible explanation for the lack of resolution. For further resolution, rare evolutionary events such as shared insertions and/or deletions or gene fusions might be helpful. PMID:10902687

  12. Probing Dust Formation Around Evolved Stars with Near-Infrared Interferometry

    NASA Astrophysics Data System (ADS)

    Sargent, B.; Srinivasan, S.; Riebel, D.; Meixner, M.

    2014-09-01

    Near-infrared interferometry holds great promise for advancing our understanding of the formation of dust around evolved stars. For example, the Magdalena Ridge Observatory Interferometer (MROI), which will be an optical/near-infrared interferometer with down to submilliarcsecond resolution, includes studying stellar mass loss as being of interest to its Key Science Mission. With facilities like MROI, many questions relating to the formation of dust around evolved stars may be probed. How close to an evolved star such as an asymptotic giant branch (AGB) or red supergiant (RSG) star does a dust grain form? Over what temperature ranges will such dust form? How does dust formation temperature and distance from star change as a function of the dust composition (carbonaceous versus oxygen-rich)? What are the ranges of evolved star dust shell geometries, and does dust shell geometry for AGB and RSG stars correlate with dust composition, similar to the correlation seen for planetary nebula outflows? At what point does the AGB star become a post-AGB star, when dust formation ends and the dust shell detaches? Currently we are conducting studies of evolved star mass loss in the Large Magellanic Cloud using photometry from the Surveying the Agents of a Galaxy's Evolution (SAGE; PI: M. Meixner) Spitzer Space Telescope Legacy program. We model this mass loss using the radiative transfer program 2Dust to create our Grid of Red supergiant and Asymptotic giant branch ModelS (GRAMS). For simplicity, we assume spherical symmetry, but 2Dust does have the capability to model axisymmetric, non-spherically-symmetric dust shell geometries. 2Dust can also generate images of models at specified wavelengths. We discuss possible connections of our GRAMS modeling using 2Dust of SAGE data of evolved stars in the LMC and also other data on evolved stars in the Milky Way's Galactic Bulge to near-infrared interferometric studies of such stars. By understanding the origins of dust around evolved

  13. Dust in Interstellar Clouds, Evolved Stars and Supernovae

    SciTech Connect

    Hartquist, T. W.; Van Loo, S.; Caselli, P.; Ashmore, I.; Falle, S. A. E. G.

    2008-09-07

    Outflows of pre-main-sequence stars drive shocks into molecular material within 0.01-1 pc of the young stars. The shock-heated gas emits infrared lines of H{sub 2} and H{sub 2}O and millimeter and submillimeter lines of many species including CO, SiO, H{sub 2}S and HCO{sup +}. Dust grains are important charge carriers and play a large role in coupling the magnetic field and flow of neutral gas. Some understanding of the effects of the dust on the dynamics of oblique shocks began to emerge in the 1990s. However, detailed models of these shocks are required for the calculation of the grain sputtering contribution to gas phase abundances of species producing observed emissions. We are developing such models.Some of the molecular species introduced into the gas phase by sputtering in shocks or by thermally driven desorption in radiatively heated hot cores form on grain surfaces. Recently laboratory studies have begun to contribute to the understanding of surface reactions and thermally driven desorption important for the chemistry of star forming clouds.Dusty plasmas are prevalent in many evolved stars just as well as in star forming regions. Radiation pressure on dust plays a significant role in mass loss from some post-main-sequence stars. The mechanisms leading to the formation of carbonaceous dust in the stellar outflows are similar to those important for soot formation in flames. However, nucleation in oxygen-rich outflows is less well understood and remains a challenging research area.Dust is observed in supernova ejecta that have not passed through the reverse shocks that develop in the interaction of ejecta with ambient media. Dust is detected in high redshift galaxies that are sufficiently young that the only stars that could have produced the dust were so massive that they became supernovae. Consequently, the issue of the survival of dust in strong supernova shocks is of considerable interest.

  14. Robustness and Evolvability of the Human Signaling Network

    PubMed Central

    Kim, Jeong-Rae; Munoz, Amaya Garcia; Kolch, Walter; Cho, Kwang-Hyun

    2014-01-01

    Biological systems are known to be both robust and evolvable to internal and external perturbations, but what causes these apparently contradictory properties? We used Boolean network modeling and attractor landscape analysis to investigate the evolvability and robustness of the human signaling network. Our results show that the human signaling network can be divided into an evolvable core where perturbations change the attractor landscape in state space, and a robust neighbor where perturbations have no effect on the attractor landscape. Using chemical inhibition and overexpression of nodes, we validated that perturbations affect the evolvable core more strongly than the robust neighbor. We also found that the evolvable core has a distinct network structure, which is enriched in feedback loops, and features a higher degree of scale-freeness and longer path lengths connecting the nodes. In addition, the genes with high evolvability scores are associated with evolvability-related properties such as rapid evolvability, low species broadness, and immunity whereas the genes with high robustness scores are associated with robustness-related properties such as slow evolvability, high species broadness, and oncogenes. Intriguingly, US Food and Drug Administration-approved drug targets have high evolvability scores whereas experimental drug targets have high robustness scores. PMID:25077791

  15. S-nitrosylation: integrator of cardiovascular performance and oxygen delivery.

    PubMed

    Haldar, Saptarsi M; Stamler, Jonathan S

    2013-01-01

    Delivery of oxygen to tissues is the primary function of the cardiovascular system. NO, a gasotransmitter that signals predominantly through protein S-nitrosylation to form S-nitrosothiols (SNOs) in target proteins, operates coordinately with oxygen in mammalian cellular systems. From this perspective, SNO-based signaling may have evolved as a major transducer of the cellular oxygen-sensing machinery that underlies global cardiovascular function. Here we review mechanisms that regulate S-nitrosylation in the context of its essential role in "systems-level" control of oxygen sensing, delivery, and utilization in the cardiovascular system, and we highlight examples of aberrant S-nitrosylation that may lead to altered oxygen homeostasis in cardiovascular diseases. Thus, through a bird's-eye view of S-nitrosylation in the cardiovascular system, we provide a conceptual framework that may be broadly applicable to the functioning of other cellular systems and physiological processes and that illuminates new therapeutic promise in cardiovascular medicine.

  16. 42 CFR 414.226 - Oxygen and oxygen equipment.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... only (gaseous or liquid tanks). (iii) Oxygen generating portable equipment only. (iv) Stationary oxygen... stationary oxygen equipment that requires delivery of gaseous or liquid oxygen contents; or (ii) Rents stationary oxygen equipment that requires delivery of gaseous or liquid oxygen contents after the period...

  17. Evolvable Cryogenics (ECRYO) Pressure Transducer Calibration Test

    NASA Technical Reports Server (NTRS)

    Diaz, Carlos E., Jr.

    2015-01-01

    This paper provides a summary of the findings of recent activities conducted by Marshall Space Flight Center's (MSFC) In-Space Propulsion Branch and MSFC's Metrology and Calibration Lab to assess the performance of current "state of the art" pressure transducers for use in long duration storage and transfer of cryogenic propellants. A brief historical narrative in this paper describes the Evolvable Cryogenics program and the relevance of these activities to the program. This paper also provides a review of three separate test activities performed throughout this effort, including: (1) the calibration of several pressure transducer designs in a liquid nitrogen cryogenic environmental chamber, (2) the calibration of a pressure transducer in a liquid helium Dewar, and (3) the calibration of several pressure transducers at temperatures ranging from 20 to 70 degrees Kelvin (K) using a "cryostat" environmental chamber. These three separate test activities allowed for study of the sensors along a temperature range from 4 to 300 K. The combined data shows that both the slope and intercept of the sensor's calibration curve vary as a function of temperature. This homogeneous function is contrary to the linearly decreasing relationship assumed at the start of this investigation. Consequently, the data demonstrates the need for lookup tables to change the slope and intercept used by any data acquisition system. This ultimately would allow for more accurate pressure measurements at the desired temperature range. This paper concludes with a review of a request for information (RFI) survey conducted amongst different suppliers to determine the availability of current "state of the art" flight-qualified pressure transducers. The survey identifies requirements that are most difficult for the suppliers to meet, most notably the capability to validate the sensor's performance at temperatures below 70 K.

  18. Did DNA replication evolve twice independently?

    PubMed

    Leipe, D D; Aravind, L; Koonin, E V

    1999-09-01

    DNA replication is central to all extant cellular organisms. There are substantial functional similarities between the bacterial and the archaeal/eukaryotic replication machineries, including but not limited to defined origins, replication bidirectionality, RNA primers and leading and lagging strand synthesis. However, several core components of the bacterial replication machinery are unrelated or only distantly related to the functionally equivalent components of the archaeal/eukaryotic replication apparatus. This is in sharp contrast to the principal proteins involved in transcription and translation, which are highly conserved in all divisions of life. We performed detailed sequence comparisons of the proteins that fulfill indispensable functions in DNA replication and classified them into four main categories with respect to the conservation in bacteria and archaea/eukaryotes: (i) non-homologous, such as replicative polymerases and primases; (ii) containing homologous domains but apparently non-orthologous and conceivably independently recruited to function in replication, such as the principal replicative helicases or proofreading exonucleases; (iii) apparently orthologous but poorly conserved, such as the sliding clamp proteins or DNA ligases; (iv) orthologous and highly conserved, such as clamp-loader ATPases or 5'-->3' exonucleases (FLAP nucleases). The universal conservation of some components of the DNA replication machinery and enzymes for DNA precursor biosynthesis but not the principal DNA polymerases suggests that the last common ancestor (LCA) of all modern cellular life forms possessed DNA but did not replicate it the way extant cells do. We propose that the LCA had a genetic system that contained both RNA and DNA, with the latter being produced by reverse transcription. Consequently, the modern-type system for double-stranded DNA replication likely evolved independently in the bacterial and archaeal/eukaryotic lineages.

  19. A possible molecular metric for biological evolvability.

    PubMed

    Mittal, Aditya; Jayaram, B

    2012-07-01

    Proteins manifest themselves as phenotypic traits, retained or lost in living systems via evolutionary pressures. Simply put, survival is essentially the ability of a living system to synthesize a functional protein that allows for a response to environmental perturbations (adaptation). Loss of functional proteins leads to extinction. Currently there are no universally applicable quantitative metrics at the molecular level for either measuring 'evolvability' of life or for assessing the conditions under which a living system would go extinct and why. In this work, we show emergence of the first such metric by utilizing the recently discovered stoichiometric margin of life for all known naturally occurring (and functional) proteins. The constraint of having well-defined stoichiometries of the 20 amino acids in naturally occurring protein sequences requires utilization of the full scope of degeneracy in the genetic code, i.e. usage of all codons coding for an amino acid, by only 11 of the 20 amino acids. This shows that the non-availability of individual codons for these 11 amino acids would disturb the fine stoichiometric balance resulting in non-functional proteins and hence extinction. Remarkably, these amino acids are found in close proximity of any given amino acid in the backbones of thousands of known crystal structures of folded proteins. On the other hand, stoichiometry of the remaining 9 amino acids, found to be farther/distal from any given amino acid in backbones of folded proteins, is maintained independent of the number of codons available to synthesize them, thereby providing some robustness and hence survivability.

  20. Evolving Recommendations on Prostate Cancer Screening.

    PubMed

    Brawley, Otis W; Thompson, Ian M; Grönberg, Henrik

    2016-01-01

    Results of a number of studies demonstrate that the serum prostate-specific antigen (PSA) in and of itself is an inadequate screening test. Today, one of the most pressing questions in prostate cancer medicine is how can screening be honed to identify those who have life-threatening disease and need aggressive treatment. A number of efforts are underway. One such effort is the assessment of men in the landmark Prostate Cancer Prevention Trial that has led to a prostate cancer risk calculator (PCPTRC), which is available online. PCPTRC version 2.0 predicts the probability of the diagnosis of no cancer, low-grade cancer, or high-grade cancer when variables such as PSA, age, race, family history, and physical findings are input. Modern biomarker development promises to provide tests with fewer false positives and improved ability to find high-grade cancers. Stockholm III (STHLM3) is a prospective, population-based, paired, screen-positive, prostate cancer diagnostic study assessing a combination of plasma protein biomarkers along with age, family history, previous biopsy, and prostate examination for prediction of prostate cancer. Multiparametric MRI incorporates anatomic and functional imaging to better characterize and predict future behavior of tumors within the prostate. After diagnosis of cancer, several genomic tests promise to better distinguish the cancers that need treatment versus those that need observation. Although the new technologies are promising, there is an urgent need for evaluation of these new tests in high-quality, large population-based studies. Until these technologies are proven, most professional organizations have evolved to a recommendation of informed or shared decision making in which there is a discussion between the doctor and patient. PMID:27249774

  1. Mitochondrial complex III: an essential component of universal oxygen sensing machinery?

    PubMed

    Chandel, Navdeep S

    2010-12-31

    Oxygen is necessary for the survival of mammalian cells. In order to maintain adequate cellular oxygenation, mammals have evolved multiple acute and long-term adaptive responses to hypoxia. These include hypoxic increases in erythropoiesis, pulmonary vasoconstriction and carotid body neurosecretion. Collectively, these responses help maintain oxygen homeostasis as oxygen levels remain scarce. There are multiple effectors proposed to underlie these diverse responses to hypoxia including PHD2, AMPK, NADPH oxidases, and mitochondrial complex III. Here I propose a model wherein complex III is integral to oxygen sensing in regulating diverse response to hypoxia.

  2. Oxygen evolution in the thylakoid-lacking cyanobacterium Gloeobacter violaceus PCC 7421.

    PubMed

    Koyama, Kohei; Suzuki, Hiroyuki; Noguchi, Takumi; Akimoto, Seiji; Tsuchiya, Tohru; Mimuro, Mamoru

    2008-04-01

    The oxygen-evolving reactions of the thylakoid-lacking cyanobacterium Gloeobacter violaceus PCC 7421 were compared with those of Synechocystis sp. PCC 6803. Four aspects were considered: sequence conservation in three extrinsic proteins for oxygen evolution, steady-state oxygen-evolving activity, charge recombination reactions, i.e., thermoluminescence and oscillation patterns of delayed luminescence on a second time scale and delayed fluorescence on the nanosecond time scale at -196 degrees C. Even though there were significant differences between the amino acid sequences of extrinsic proteins in G. violaceus and Synechocystis sp. PCC 6803, the oxygen-evolving activities were similar. The delayed luminescence oscillation patterns and glow curves of thermoluminescence were essentially identical between the two species, and the nanosecond delayed fluorescence spectral profiles and lifetimes were also very similar. These results indicate clearly that even though the oxygen-evolving reactions are carried out in the periplasm by components with altered amino acid sequences, the essential reaction processes for water oxidation are highly conserved. In contrast, we observed significant changes on the reduction side of photosystem II. Based on these data, we discuss the oxygen-evolving activity of G. violaceus. PMID:18298941

  3. Singlet Oxygen Formation during the Charging Process of an Aprotic Lithium-Oxygen Battery.

    PubMed

    Wandt, Johannes; Jakes, Peter; Granwehr, Josef; Gasteiger, Hubert A; Eichel, Rüdiger-A

    2016-06-01

    Aprotic lithium-oxygen (Li-O2 ) batteries have attracted considerable attention in recent years owing to their outstanding theoretical energy density. A major challenge is their poor reversibility caused by degradation reactions, which mainly occur during battery charge and are still poorly understood. Herein, we show that singlet oxygen ((1) Δg ) is formed upon Li2 O2 oxidation at potentials above 3.5 V. Singlet oxygen was detected through a reaction with a spin trap to form a stable radical that was observed by time- and voltage-resolved in operando EPR spectroscopy in a purpose-built spectroelectrochemical cell. According to our estimate, a lower limit of approximately 0.5 % of the evolved oxygen is singlet oxygen. The occurrence of highly reactive singlet oxygen might be the long-overlooked missing link in the understanding of the electrolyte degradation and carbon corrosion reactions that occur during the charging of Li-O2 cells.

  4. Integrated turbomachine oxygen plant

    DOEpatents

    Anand, Ashok Kumar; DePuy, Richard Anthony; Muthaiah, Veerappan

    2014-06-17

    An integrated turbomachine oxygen plant includes a turbomachine and an air separation unit. One or more compressor pathways flow compressed air from a compressor through one or more of a combustor and a turbine expander to cool the combustor and/or the turbine expander. An air separation unit is operably connected to the one or more compressor pathways and is configured to separate the compressed air into oxygen and oxygen-depleted air. A method of air separation in an integrated turbomachine oxygen plant includes compressing a flow of air in a compressor of a turbomachine. The compressed flow of air is flowed through one or more of a combustor and a turbine expander of the turbomachine to cool the combustor and/or the turbine expander. The compressed flow of air is directed to an air separation unit and is separated into oxygen and oxygen-depleted air.

  5. Oxygen ion conducting materials

    DOEpatents

    Vaughey, John; Krumpelt, Michael; Wang, Xiaoping; Carter, J. David

    2005-07-12

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  6. Oxygen ion conducting materials

    DOEpatents

    Carter, J. David; Wang, Xiaoping; Vaughey, John; Krumpelt, Michael

    2004-11-23

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  7. Oxygen ion conducting materials

    DOEpatents

    Vaughey, John; Krumpelt, Michael; Wang, Xiaoping; Carter, J. David

    2003-01-01

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  8. Continuous home oxygen therapy.

    PubMed

    Ortega Ruiz, Francisco; Díaz Lobato, Salvador; Galdiz Iturri, Juan Bautista; García Rio, Francisco; Güell Rous, Rosa; Morante Velez, Fátima; Puente Maestu, Luis; Tàrrega Camarasa, Julia

    2014-05-01

    Oxygen therapy is defined as the therapeutic use of oxygen and consists of administering oxygen at higher concentrations than those found in room air, with the aim of treating or preventing hypoxia. This therapeutic intervention has been shown to increase survival in patients with chronic obstructive pulmonary disease (COPD) and respiratory failure. Although this concept has been extended by analogy to chronic respiratory failure caused by respiratory and non-respiratory diseases, continuous oxygen therapy has not been shown to be effective in other disorders. Oxygen therapy has not been shown to improve survival in patients with COPD and moderate hypoxaemia, nor is there consensus regarding its use during nocturnal desaturations in COPD or desaturations caused by effort. The choice of the oxygen source must be made on the basis of criteria such as technical issues, patient comfort and adaptability and cost. Flow must be adjusted to achieve appropriate transcutaneous oxyhaemoglobin saturation correction.

  9. Extracorporeal membrane oxygenation 2016: an update

    PubMed Central

    Butt, Warwick; MacLaren, Graeme

    2016-01-01

    The use of extracorporeal membrane oxygenation (ECMO) is an important issue for intensivists, critical care nurses, surgeons, cardiologists, and many others. There has been a continued increase in the number of centres performing ECMO. This review examines novel applications and recent trends in the use of ECMO over the last 2 years. These include ECMO to facilitate the safe use of other treatments, changing the timing of initiation, newer equipment and better biocompatibility, and the ability of ECMO programs to essentially choose which cluster of potential complications they are prepared to accept. ECMO continues to evolve, diversify in its applications, and improve in safety. PMID:27158464

  10. Atomic Oxygen Effects

    NASA Technical Reports Server (NTRS)

    Miller, Sharon K. R.

    2014-01-01

    Atomic oxygen, which is the most predominant species in low Earth orbit, is highly reactive and can break chemical bonds on the surface of a wide variety of materials leading to volatilization or surface oxidation which can result in failure of spacecraft materials and components. This presentation will give an overview of how atomic oxygen reacts with spacecraft materials, results of space exposure testing of a variety of materials, and examples of failures caused by atomic oxygen.

  11. Rockets using Liquid Oxygen

    NASA Technical Reports Server (NTRS)

    Busemann, Adolf

    1947-01-01

    It is my task to discuss rocket propulsion using liquid oxygen and my treatment must be highly condensed for the ideas and experiments pertaining to this classic type of rocket are so numerous that one could occupy a whole morning with a detailed presentation. First, with regard to oxygen itself as compared with competing oxygen carriers, it is known that the liquid state of oxygen, in spite of the low boiling point, is more advantageous than the gaseous form of oxygen in pressure tanks, therefore only liquid oxygen need be compared with the oxygen carriers. The advantages of liquid oxygen are absolute purity and unlimited availability at relatively small cost in energy. The disadvantages are those arising from the impossibility of absolute isolation from heat; consequently, allowance must always be made for a certain degree of vaporization and only vented vessels can be used for storage and transportation. This necessity alone eliminates many fields of application, for example, at the front lines. In addition, liquid oxygen has a lower specific weight than other oxygen carriers, therefore many accessories become relatively larger and heavier in the case of an oxygen rocket, for example, the supply tanks and the pumps. The advantages thus become effective only in those cases where definitely scheduled operation and a large ground organization are possible and when the flight requires a great concentration of energy relative to weight. With the aim of brevity, a diagram of an oxygen rocket will be presented and the problem of various component parts that receive particularly thorough investigation in this classic case but which are also often applicable to other rocket types will be referred to.

  12. Cancer and aging. An evolving panorama.

    PubMed

    Balducci, L; Extermann, M

    2000-02-01

    This article illustrates how the nosology of cancer evolves with the patient's age. If the current trends are maintained, 70% of all neoplasms will occur in persons aged 65 years and over by the year 2020, leading to increased cancer-related morbidity among older persons. Cancer control in the older person involves chemoprevention, early diagnosis, and timely and effective treatment that entails both antineoplastic therapy and symptom management. These interventions must be individualized based on a multidimensional assessment that can predict life expectancy and treatment complications and that may evaluate the quality of life of the older person. This article suggests a number of interventions that may improve cancer control in the aged. Public education is needed to illustrate the benefits of health maintenance and early detection of cancer even among older individuals, to create realistic expectations, and to heighten awareness of early symptoms and signs of cancer. Professional education is needed to train students and practitioners in the evaluation and management of the older person. Of special interest is the current initiative of the Hartford Foundation offering combined fellowships in oncology and geriatrics and incorporating principles of geriatric medicine in medical specialty training. Prudent pharmacologic principles must be followed in managing older persons with cytotoxic chemotherapy. These principles include adjusting the dose according to the patient's renal function, using epoietin to maintain hemoglobin levels of 12 g/dL or more, and using hemopoietic growth factors in persons aged 70 years and older receiving cytotoxic chemotherapy of moderate toxicity (e.g., CHOP). To assure uniformity of data, a cooperative oncology group should formulate a geriatric package outlining a common plan for evaluating function and comorbidity. This article also suggests several important areas of research items: Molecular interactions of age and cancer Host

  13. Observational studies of highly evolved cataclysmic variables

    NASA Astrophysics Data System (ADS)

    Uthas, Helena

    2011-05-01

    According to standard evolutionary theory for cataclysmic variables (CVs), angular momentum loss drives CVs to initially evolve from longer to shorter orbital periods until a minimum period is reached (approx 80 min). At roughly this stage, the donors becomes degenerate, expand in size, and the systems move towards longer Porb. Theory predicts that 70% of all CVs should have passed their minimum period and have sub-stellar donors, but until recently, no such systems were known. I present one CV showing evidence of harbouring a sub-dwarf donor, SDSS J1507+52. Due to the system's unusually short Porb of about 65 min, and very high space velocity, two origins for SDSS J1507+52 have been proposed; either the system was formed from a young WD/brown-dwarf binary, or the system is a halo CV. In order to distinguish between these two theories, I present UV spectroscopy and find a metallicity consistent with halo origin. Systems close to Pmin are expected to have low accretion rates. Some of these CVs show absorption in their spectra, implying that the underlying WD is exposed. This yields a rare opportunity to study the WD in a CV. I introduce two new systems showing WD signatures in their light curves and spectra, SDSS J1457+51 and BW Scl. Despite the fact that CVs close to Pmin should be faint, we find systems that are much too bright for their Porb. Such a system is T Pyx - a recurrent nova with an unusually high accretion rate and a photometrically determined Porb < 2 hr. T Pyx is about 2 times brighter than any other CV at its period. However, to confirm its evolutionary status, a more reliable period determination is needed. Here, I present a spectroscopic study, confirming T Pyx as a short-period CV. In this thesis, I discuss what implications these systems may have on the current understanding of CV evolution, and the importance of studying individual systems in general.

  14. The Evolvement of Automobile Steering System Based on TRIZ

    NASA Astrophysics Data System (ADS)

    Zhao, Xinjun; Zhang, Shuang

    Products and techniques pass through a process of birth, growth, maturity, death and quit the stage like biological evolution process. The developments of products and techniques conform to some evolvement rules. If people know and hold these rules, they can design new kind of products and forecast the develop trends of the products. Thereby, enterprises can grasp the future technique directions of products, and make product and technique innovation. Below, based on TRIZ theory, the mechanism evolvement, the function evolvement and the appearance evolvement of automobile steering system had been analyzed and put forward some new ideas about future automobile steering system.

  15. Measuring tissue oxygenation

    NASA Technical Reports Server (NTRS)

    Soyemi, Olusola O. (Inventor); Soller, Babs R. (Inventor); Yang, Ye (Inventor)

    2009-01-01

    Methods and systems for calculating tissue oxygenation, e.g., oxygen saturation, in a target tissue are disclosed. In some embodiments, the methods include: (a) directing incident radiation to a target tissue and determining reflectance spectra of the target tissue by measuring intensities of reflected radiation from the target tissue at a plurality of radiation wavelengths; (b) correcting the measured intensities of the reflectance spectra to reduce contributions thereto from skin and fat layers through which the incident radiation propagates; (c) determining oxygen saturation in the target tissue based on the corrected reflectance spectra; and (d) outputting the determined value of oxygen saturation.

  16. Solid state oxygen sensor

    DOEpatents

    Garzon, F.H.; Brosha, E.L.

    1997-12-09

    A potentiometric oxygen sensor is formed having a logarithmic response to a differential oxygen concentration while operating as a Nernstian-type sensor. Very thin films of mixed conducting oxide materials form electrode services while permitting diffusional oxygen access to the interface between the zirconia electrolyte and the electrode. Diffusion of oxygen through the mixed oxide is not rate-limiting. Metal electrodes are not used so that morphological changes in the electrode structure do not occur during extended operation at elevated temperatures. 6 figs.

  17. Cerebral oxygenation and optimal vascular brain organization

    PubMed Central

    Hadjistassou, Constantinos; Bejan, Adrian; Ventikos, Yiannis

    2015-01-01

    The cerebral vascular network has evolved in such a way so as to minimize transport time and energy expenditure. This is accomplished by a subtle combination of the optimal arrangement of arteries, arterioles and capillaries and the transport mechanisms of convection and diffusion. Elucidating the interaction between cerebral vascular architectonics and the latter physical mechanisms can catalyse progress in treating cerebral pathologies such as stroke, brain tumours, dementia and targeted drug delivery. Here, we show that brain microvascular organization is predicated on commensurate intracapillary oxygen convection and parenchymal diffusion times. Cross-species grey matter results for the rat, cat, rabbit and human reveal very good correlation between the cerebral capillary and tissue mean axial oxygen convective and diffusion time intervals. These findings agree with the constructal principle. PMID:25972435

  18. A Survey and Resource Materials on the Use of Oxygen Supplementation in Fish Culture.

    SciTech Connect

    Colt, John; Orwicz, Kris; Bouck, Gerald R.

    1988-09-01

    Oxygen supplementation is the process by which naturally occurring dissolved oxygen (DO) is supplemented with enriched oxygen to restore or enhance DO levels in water. In aquaculture this is usually done with relatively pure oxygen and the result has significant potential to improve fish health, aid hatchery economic considerations, or both. For example, oxygen supplementation can preclude both hypoxia and gas bubble disease, as well as allow more fish to be reared in the same space or water or both. However, the concepts and technology in oxygen supplementation are evolving rapidly and direct communication with the user groups would foster technology transfer and improve implementation. Therefore we undertook and now report a survey of organizations that either currently use or plan to use oxygen supplementation. Additionally we included various pertinent material, including literature sources, lists of consultants and equipment manufacturers and some current research in oxygen supplementation.

  19. Batteries: Avoiding oxygen

    NASA Astrophysics Data System (ADS)

    Hardwick, Laurence J.

    2016-08-01

    In the development of lithium–air batteries, managing the phase change between gaseous oxygen and crystalline lithium peroxide is a key challenge. Now, a high-performing sealed battery with an oxygen anion-redox electrode is presented that does not involve any gas evolution.

  20. Extracorporeal membrane oxygenation circuitry.

    PubMed

    Lequier, Laurance; Horton, Stephen B; McMullan, D Michael; Bartlett, Robert H

    2013-06-01

    The extracorporeal membrane oxygenation circuit is made of a number of components that have been customized to provide adequate tissue oxygen delivery in patients with severe cardiac and/or respiratory failure for a prolonged period of time (days to weeks). A standard extracorporeal membrane oxygenation circuit consists of a mechanical blood pump, gas-exchange device, and a heat exchanger all connected together with circuit tubing. Extracorporeal membrane oxygenation circuits can vary from simple to complex and may include a variety of blood flow and pressure monitors, continuous oxyhemoglobin saturation monitors, circuit access sites, and a bridge connecting the venous access and arterial infusion limbs of the circuit. Significant technical advancements have been made in the equipment available for short- and long-term extracorporeal membrane oxygenation applications. Contemporary extracorporeal membrane oxygenation circuits have greater biocompatibility and allow for more prolonged cardiopulmonary support time while minimizing the procedure-related complications of bleeding, thrombosis, and other physiologic derangements, which were so common with the early application of extracorporeal membrane oxygenation. Modern era extracorporeal membrane oxygenation circuitry and components are simpler, safer, more compact, and can be used across a wide variety of patient sizes from neonates to adults. PMID:23735989

  1. Oxygen sensitive paper

    NASA Technical Reports Server (NTRS)

    Whidby, J. F.

    1973-01-01

    Paper is impregnated with mixture of methylene blue and ethylenediaminetetraacetic acid. Methylene blue is photo-reduced to leuco-form. Paper is kept isolated from oxygen until ready for use. Paper can be reused by photo-reduction after oxygen exposure.

  2. Oxygen therapy - infants

    MedlinePlus

    ... help breathing than they can get from an oxygen hood or nasal cannula, but do not need a machine to completely ... is not warm enough. Most (but not all) nasal cannulas use cool, dry oxygen. At higher flow rates, this can irritate the ...

  3. Batteries: Avoiding oxygen

    NASA Astrophysics Data System (ADS)

    Hardwick, Laurence J.

    2016-08-01

    In the development of lithium-air batteries, managing the phase change between gaseous oxygen and crystalline lithium peroxide is a key challenge. Now, a high-performing sealed battery with an oxygen anion-redox electrode is presented that does not involve any gas evolution.

  4. Mass Loss from Evolved Stars in the LMC: A Spitzer SAGE View

    NASA Astrophysics Data System (ADS)

    Blum, Robert D.; Volk, K.; Srinivasan, S.; Markwick-Kemper, F.; Meixner, M.; Points, S.; Olsen, K.; Gordon, K.; Engelbracht, C.; For, B.; Block, M.; Misselt, K.; Whitney, B.; Meade, M.; Babler, B.; Indebetouw, R.; Hora, J.; Vijh, U.; Leitherer, C.; Mould, J.; SAGE Team

    2006-12-01

    I will present preliminary results for Evolved Star properties and their mass--loss contribution to the Large Magellanic Cloud (LMC) as viewed from color--magnitude diagrams (CMDs) obtained with the Spitzer space telescope SAGE (Surveying the Agents of a Galaxy's Evolution) survey. These data represent the deepest, widest mid--infrared CMDs of their kind ever produced in the LMC. Combined with the 2MASS survey, the diagrams are used to delineate the evolved stellar populations in the LMC from which we can deduce the relative contributions to the complete mass--loss budget. I will show initial fits to the spectral energy distributions of the LMC stars using dust radiative transfer models and assumptions about the evolved star envelopes guided by existing observations of luminous stars. Owing to the high angular resolution and sensitivity of Spitzer, we can identify essentially all the important mass--loss sources in the galaxy. Indeed, there is strong evidence from the 24 micron channel of Spitzer that previously unexplored, lower luminosity oxygen--rich AGB stars contribute significantly to the mass loss budget. This work has been funded by generous grants from the NASA SST program.

  5. Health-Literate Youth: Evolving Challenges for Health Educators

    ERIC Educational Resources Information Center

    Fetro, Joyce V.

    2010-01-01

    This article presents the author's AAHE Scholar presentation at the 2010 AAHE annual meeting in Indianapolis, Indiana. In her discussion, the author addresses what she sees to be some evolving challenges for health educators working with youth as well as some possible strategies for addressing them. These evolving challenges are: (1) understanding…

  6. Adaptation of Escherichia coli to glucose promotes evolvability in lactose.

    PubMed

    Phillips, Kelly N; Castillo, Gerardo; Wünsche, Andrea; Cooper, Tim F

    2016-02-01

    The selective history of a population can influence its subsequent evolution, an effect known as historical contingency. We previously observed that five of six replicate populations that were evolved in a glucose-limited environment for 2000 generations, then switched to lactose for 1000 generations, had higher fitness increases in lactose than populations started directly from the ancestor. To test if selection in glucose systematically increased lactose evolvability, we started 12 replay populations--six from a population subsample and six from a single randomly selected clone--from each of the six glucose-evolved founder populations. These replay populations and 18 ancestral populations were evolved for 1000 generations in a lactose-limited environment. We found that replay populations were initially slightly less fit in lactose than the ancestor, but were more evolvable, in that they increased in fitness at a faster rate and to higher levels. This result indicates that evolution in the glucose environment resulted in genetic changes that increased the potential of genotypes to adapt to lactose. Genome sequencing identified four genes--iclR, nadR, spoT, and rbs--that were mutated in most glucose-evolved clones and are candidates for mediating increased evolvability. Our results demonstrate that short-term selective costs during selection in one environment can lead to changes in evolvability that confer longer term benefits. PMID:26748670

  7. Loops and autonomy promote evolvability of ecosystem networks.

    PubMed

    Luo, Jianxi

    2014-01-01

    The structure of ecological networks, in particular food webs, determines their ability to evolve further, i.e. evolvability. The knowledge about how food web evolvability is determined by the structures of diverse ecological networks can guide human interventions purposefully to either promote or limit evolvability of ecosystems. However, the focus of prior food web studies was on stability and robustness; little is known regarding the impact of ecological network structures on their evolvability. To correlate ecosystem structure and evolvability, we adopt the NK model originally from evolutionary biology to generate and assess the ruggedness of fitness landscapes of a wide spectrum of model food webs with gradual variation in the amount of feeding loops and link density. The variation in network structures is controlled by linkage rewiring. Our results show that more feeding loops and lower trophic link density, i.e. higher autonomy of species, of food webs increase the potential for the ecosystem to generate heritable variations with improved fitness. Our findings allow the prediction of the evolvability of actual food webs according to their network structures, and provide guidance to enhancing or controlling the evolvability of specific ecosystems.

  8. Atomic Oxygen Textured Polymers

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Rutledge, Sharon K.; Hunt, Jason D.; Drobotij, Erin; Cales, Michael R.; Cantrell, Gidget

    1995-01-01

    Atomic oxygen can be used to microscopically alter the surface morphology of polymeric materials in space or in ground laboratory facilities. For polymeric materials whose sole oxidation products are volatile species, directed atomic oxygen reactions produce surfaces of microscopic cones. However, isotropic atomic oxygen exposure results in polymer surfaces covered with lower aspect ratio sharp-edged craters. Isotropic atomic oxygen plasma exposure of polymers typically causes a significant decrease in water contact angle as well as altered coefficient of static friction. Such surface alterations may be of benefit for industrial and biomedical applications. The results of atomic oxygen plasma exposure of thirty-three (33) different polymers are presented, including typical morphology changes, effects on water contact angle, and coefficient of static friction.

  9. Audit of oxygen therapy.

    PubMed

    Gravil, J H; O'Neill, V J; Stevenson, R D

    1997-06-01

    We audited the use of oxygen in our hospital. Over three days we found 119 patients using oxygen, 21 wearing their mask incorrectly or not at all. The commonest indication was chronic obstructive pulmonary disease. Forty patients had no record of arterial gas analysis. Of those who had, 29 did not require oxygen and the average time from last arterial gas analysis was 5.7 days and only eight patients were being monitored with an oximeter. Taking into account the risk of exacerbating carbon dioxide retention and the problems that arise when discharging a patient who has been receiving oxygen therapy for the duration of their admission, we fee oxygen therapy should only be administered with the knowledge of the arterial gases and with frequent reassessment during therapy.

  10. Acute oxygen therapy.

    PubMed

    Akbar, Fazal; Campbell, Ian Allen

    2004-05-01

    Oxygen therapy is a central part of our clinical practice and is widely used in many pulmonary and non-pulmonary conditions worldwide but it is sometimes used unnecessarily and can be harmful. Optimum use is not only important for patient care but is also sound fiscally because of the expense of oxygen and the cost of devices utilised. This article is aimed both at reviewing available research and guidelines for the use of oxygen and providing knowledge of different administering and monitoring devices and equipment. Various hospital based audits have shown oxygen as being poorly prescribed and inappropriately administered and it is important for everyone involved in patient care to understand the basics of oxygen therapy before optimum practice can be implemented and followed. PMID:15225466

  11. Molecular Evolution of the Oxygen-Binding Hemerythrin Domain

    PubMed Central

    Alvarez-Carreño, Claudia; Becerra, Arturo; Lazcano, Antonio

    2016-01-01

    Background The evolution of oxygenic photosynthesis during Precambrian times entailed the diversification of strategies minimizing reactive oxygen species-associated damage. Four families of oxygen-carrier proteins (hemoglobin, hemerythrin and the two non-homologous families of arthropodan and molluscan hemocyanins) are known to have evolved independently the capacity to bind oxygen reversibly, providing cells with strategies to cope with the evolutionary pressure of oxygen accumulation. Oxygen-binding hemerythrin was first studied in marine invertebrates but further research has made it clear that it is present in the three domains of life, strongly suggesting that its origin predated the emergence of eukaryotes. Results Oxygen-binding hemerythrins are a monophyletic sub-group of the hemerythrin/HHE (histidine, histidine, glutamic acid) cation-binding domain. Oxygen-binding hemerythrin homologs were unambiguously identified in 367/2236 bacterial, 21/150 archaeal and 4/135 eukaryotic genomes. Overall, oxygen-binding hemerythrin homologues were found in the same proportion as single-domain and as long protein sequences. The associated functions of protein domains in long hemerythrin sequences can be classified in three major groups: signal transduction, phosphorelay response regulation, and protein binding. This suggests that in many organisms the reversible oxygen-binding capacity was incorporated in signaling pathways. A maximum-likelihood tree of oxygen-binding hemerythrin homologues revealed a complex evolutionary history in which lateral gene transfer, duplications and gene losses appear to have played an important role. Conclusions Hemerythrin is an ancient protein domain with a complex evolutionary history. The distinctive iron-binding coordination site of oxygen-binding hemerythrins evolved first in prokaryotes, very likely prior to the divergence of Firmicutes and Proteobacteria, and spread into many bacterial, archaeal and eukaryotic species. The later

  12. Laplacian Estrada and normalized Laplacian Estrada indices of evolving graphs.

    PubMed

    Shang, Yilun

    2015-01-01

    Large-scale time-evolving networks have been generated by many natural and technological applications, posing challenges for computation and modeling. Thus, it is of theoretical and practical significance to probe mathematical tools tailored for evolving networks. In this paper, on top of the dynamic Estrada index, we study the dynamic Laplacian Estrada index and the dynamic normalized Laplacian Estrada index of evolving graphs. Using linear algebra techniques, we established general upper and lower bounds for these graph-spectrum-based invariants through a couple of intuitive graph-theoretic measures, including the number of vertices or edges. Synthetic random evolving small-world networks are employed to show the relevance of the proposed dynamic Estrada indices. It is found that neither the static snapshot graphs nor the aggregated graph can approximate the evolving graph itself, indicating the fundamental difference between the static and dynamic Estrada indices. PMID:25822506

  13. Gene Essentiality Is a Quantitative Property Linked to Cellular Evolvability.

    PubMed

    Liu, Gaowen; Yong, Mei Yun Jacy; Yurieva, Marina; Srinivasan, Kandhadayar Gopalan; Liu, Jaron; Lim, John Soon Yew; Poidinger, Michael; Wright, Graham Daniel; Zolezzi, Francesca; Choi, Hyungwon; Pavelka, Norman; Rancati, Giulia

    2015-12-01

    Gene essentiality is typically determined by assessing the viability of the corresponding mutant cells, but this definition fails to account for the ability of cells to adaptively evolve to genetic perturbations. Here, we performed a stringent screen to assess the degree to which Saccharomyces cerevisiae cells can survive the deletion of ~1,000 individual "essential" genes and found that ~9% of these genetic perturbations could in fact be overcome by adaptive evolution. Our analyses uncovered a genome-wide gradient of gene essentiality, with certain essential cellular functions being more "evolvable" than others. Ploidy changes were prevalent among the evolved mutant strains, and aneuploidy of a specific chromosome was adaptive for a class of evolvable nucleoporin mutants. These data justify a quantitative redefinition of gene essentiality that incorporates both viability and evolvability of the corresponding mutant cells and will enable selection of therapeutic targets associated with lower risk of emergence of drug resistance. PMID:26627736

  14. Gene Essentiality Is a Quantitative Property Linked to Cellular Evolvability.

    PubMed

    Liu, Gaowen; Yong, Mei Yun Jacy; Yurieva, Marina; Srinivasan, Kandhadayar Gopalan; Liu, Jaron; Lim, John Soon Yew; Poidinger, Michael; Wright, Graham Daniel; Zolezzi, Francesca; Choi, Hyungwon; Pavelka, Norman; Rancati, Giulia

    2015-12-01

    Gene essentiality is typically determined by assessing the viability of the corresponding mutant cells, but this definition fails to account for the ability of cells to adaptively evolve to genetic perturbations. Here, we performed a stringent screen to assess the degree to which Saccharomyces cerevisiae cells can survive the deletion of ~1,000 individual "essential" genes and found that ~9% of these genetic perturbations could in fact be overcome by adaptive evolution. Our analyses uncovered a genome-wide gradient of gene essentiality, with certain essential cellular functions being more "evolvable" than others. Ploidy changes were prevalent among the evolved mutant strains, and aneuploidy of a specific chromosome was adaptive for a class of evolvable nucleoporin mutants. These data justify a quantitative redefinition of gene essentiality that incorporates both viability and evolvability of the corresponding mutant cells and will enable selection of therapeutic targets associated with lower risk of emergence of drug resistance.

  15. Laplacian Estrada and normalized Laplacian Estrada indices of evolving graphs.

    PubMed

    Shang, Yilun

    2015-01-01

    Large-scale time-evolving networks have been generated by many natural and technological applications, posing challenges for computation and modeling. Thus, it is of theoretical and practical significance to probe mathematical tools tailored for evolving networks. In this paper, on top of the dynamic Estrada index, we study the dynamic Laplacian Estrada index and the dynamic normalized Laplacian Estrada index of evolving graphs. Using linear algebra techniques, we established general upper and lower bounds for these graph-spectrum-based invariants through a couple of intuitive graph-theoretic measures, including the number of vertices or edges. Synthetic random evolving small-world networks are employed to show the relevance of the proposed dynamic Estrada indices. It is found that neither the static snapshot graphs nor the aggregated graph can approximate the evolving graph itself, indicating the fundamental difference between the static and dynamic Estrada indices.

  16. Atomic Oxygen Fluence Monitor

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.

    2011-01-01

    This innovation enables a means for actively measuring atomic oxygen fluence (accumulated atoms of atomic oxygen per area) that has impinged upon spacecraft surfaces. Telemetered data from the device provides spacecraft designers, researchers, and mission managers with real-time measurement of atomic oxygen fluence, which is useful for prediction of the durability of spacecraft materials and components. The innovation is a compact fluence measuring device that allows in-space measurement and transmittance of measured atomic oxygen fluence as a function of time based on atomic oxygen erosion yields (the erosion yield of a material is the volume of material that is oxidized per incident oxygen atom) of materials that have been measured in low Earth orbit. It has a linear electrical response to atomic oxygen fluence, and is capable of measuring high atomic oxygen fluences (up to >10(exp 22) atoms/sq cm), which are representative of multi-year low-Earth orbital missions (such as the International Space Station). The durability or remaining structural lifetime of solar arrays that consist of polymer blankets on which the solar cells are attached can be predicted if one knows the atomic oxygen fluence that the solar array blanket has been exposed to. In addition, numerous organizations that launch space experiments into low-Earth orbit want to know the accumulated atomic oxygen fluence that their materials or components have been exposed to. The device is based on the erosion yield of pyrolytic graphite. It uses two 12deg inclined wedges of graphite that are over a grit-blasted fused silica window covering a photodiode. As the wedges erode, a greater area of solar illumination reaches the photodiode. A reference photodiode is also used that receives unobstructed solar illumination and is oriented in the same direction as the pyrolytic graphite covered photodiode. The short-circuit current from the photodiodes is measured and either sent to an onboard data logger, or

  17. Chromospheric activity of evolved late-type stars - Chromospheric activity in evolved stars

    NASA Astrophysics Data System (ADS)

    Pasquini, L.; Brocato, E.; Pallavicini, R.

    1990-08-01

    Ca II K emission in a homogeneous sample of late-type giants and supergiants is analyzed. The Wilson-Bappu relationship and color-temperature scales are used to construct an H-R diagram which is compared with theoretical evolutionary tracks. It is shown that in spite of the errors involved in the determination of the fundamental stellar parameters, a clear relationship between chromospheric surface activity and stellar mass is present. 5-10 solar mass stars in He burning phase show the highest levels of activity; on the other hand, less massive stars ascending along the Red Giant Branch are extremely quiet. A correlation between surface activity and rotation is found, and it is shown that a knowledge of the stellar evolutionary history is essential for understanding chromospheric emission from evolved stars.

  18. NASA's Space Launch System: An Evolving Capability for Exploration An Evolving Capability for Exploration

    NASA Technical Reports Server (NTRS)

    Creech, Stephen D.; Crumbly, Christopher M.; Robinson, Kimerly F.

    2016-01-01

    A foundational capability for international human deep-space exploration, NASA's Space Launch System (SLS) vehicle represents a new spaceflight infrastructure asset, creating opportunities for mission profiles and space systems that cannot currently be executed. While the primary purpose of SLS, which is making rapid progress towards initial launch readiness in two years, will be to support NASA's Journey to Mars, discussions are already well underway regarding other potential utilization of the vehicle's unique capabilities. In its initial Block 1 configuration, capable of launching 70 metric tons (t) to low Earth orbit (LEO), SLS is capable of propelling the Orion crew vehicle to cislunar space, while also delivering small CubeSat-class spacecraft to deep-space destinations. With the addition of a more powerful upper stage, the Block 1B configuration of SLS will be able to deliver 105 t to LEO and enable more ambitious human missions into the proving ground of space. This configuration offers opportunities for launching co-manifested payloads with the Orion crew vehicle, and a class of secondary payloads, larger than today's CubeSats. Further upgrades to the vehicle, including advanced boosters, will evolve its performance to 130 t in its Block 2 configuration. Both Block 1B and Block 2 also offer the capability to carry 8.4- or 10-m payload fairings, larger than any contemporary launch vehicle. With unmatched mass-lift capability, payload volume, and C3, SLS not only enables spacecraft or mission designs currently impossible with contemporary EELVs, it also offers enhancing benefits, such as reduced risk, operational costs and/or complexity, shorter transit time to destination or launching large systems either monolithically or in fewer components. This paper will discuss both the performance and capabilities of Space Launch System as it evolves, and the current state of SLS utilization planning.

  19. Fiber optic oxygen sensor leak detection system for space applications

    NASA Astrophysics Data System (ADS)

    Kazemi, Alex A.; Goswami, Kish; Mendoza, Edgar A.; Kempen, Lothar U.

    2007-09-01

    This paper describes the successful test of a multi-point fiber optic oxygen sensor system during the static firing of an Evolved Expandable Launch Vehicle (EELV)/Delta IV common booster core (CBC) rocket engine at NASA's Stennis Flight Center. The system consisted of microsensors (optrodes) using an oxygen gas sensitive indicator incorporated onto an optically transparent porous substrate. The modular optoelectronics and multiplexing network system was designed and assembled utilizing a multi-channel opto-electronic sensor readout unit that monitored the oxygen and temperature response of the individual optrodes in real-time and communicated this information via a serial communication port to a remote laptop computer. The sensor packaging for oxygen consisted of two optrodes - one doped with an indicator sensitive to oxygen, and the other doped with an indicator sensitive to temperature. The multichannel oxygen sensor system is fully reversible. It has demonstrated a dynamic response to oxygen gas in the range of 0% to 100% with 0.1% resolution and a response time of <=10 seconds. The sensor package was attached to a custom fiber optic ribbon cable, which was then connected to a fiber optic trunk communications cable (standard telecommunications-grade fiber) that connected to the optoelectronics module. Each board in the expandable module included light sources, photo-detectors, and associated electronics required for detecting oxygen and temperature. The paper illustrates the sensor design and performance data under field deployment conditions.

  20. Oxygen foreshock of Mars

    NASA Astrophysics Data System (ADS)

    Yamauchi, M.; Lundin, R.; Frahm, R. A.; Sauvaud, J.-A.; Holmström, M.; Barabash, S.

    2015-12-01

    Mars Express (MEX) has operated for more than 10 years in the environment of Mars, providing solar wind ion observations from the Analyzer of Space Plasmas and Energetic Atoms experiment's Ion Mass Analyser (IMA). On 21 September 2008, MEX/IMA detected foreshock-like discrete distributions of oxygen ions at around 1 keV in the solar wind attached to the bow shock and this distribution was observed continuously up to more than 2000 km from the bow shock. Foreshock-like protons are also observed but at a shifted location from the oxygen by about 1000 km, at a slightly higher energy, and flowing in a slightly different direction than the oxygen ions. Both protons and oxygen ions are flowing anti-sunward at different angles with respect to the solar wind direction. This is the first time that a substantial amount of planetary oxygen is observed upstream of the bow shock. Although rare, this is not the only IMA observation of foreshock-like oxygen: oxygen ions are sometimes observed for a short period of time (<5 min) inside the foreshock region. These observations suggest a new escape channel for planetary ions through the acceleration in the bow shock-magnetosheath region.

  1. Electrochemical oxygen concentrator as an oxygen compressor

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A solid polymer electrolyte (SPE) oxygen compressor is described which generates pressures of 3000 psi. The SPE is a cation exchange membrane with chemical compatibility, and has the capability of withstanding 5000 psi. Other features of the compressor described include: gasketless sealing, porus plate cell supports, and conductive cooling. Results are presented of a computer program which defines the power of the system as a function of density, temperature, pressure, membrane thickness, and water content.

  2. Females become infertile as the stored sperm's oxygen radicals increase

    PubMed Central

    Reinhardt, Klaus; Ribou, Anne-Cecile

    2013-01-01

    Predicting infertility is central to reproductive biology, medicine and evolutionary biology. In-vitro studies suggest that oxidative sperm damage causes infertility. Oxidative sperm damage can be reduced via two fundamental pathways: the removal of oxygen radicals by antioxidants, or the interference with cell metabolism to reduce the formation of oxygen radicals. Oxidative damage protection of spermatozoa should evolve frequently, especially during female sperm storage. However, in-vivo evidence linking oxidative protection and fertility is rare. We show that the intra-sperm production rate of oxygen radicals and the sperm metabolic rate were reduced in female bedbugs, Cimex lectularius, compared to males, and females laid fertile eggs. Females became infertile when sperm oxygen radicals and sperm metabolic rate increased to male levels. Our results link female fitness to sublethal sperm damage, imply adaptive benefits of interfering with sperm metabolism and offer the hypothesis that polyandry may serve to replace low-quality sperm.

  3. EVOLVE historical and projected orbital debris test environments

    NASA Astrophysics Data System (ADS)

    Krisko, P. H.

    2004-01-01

    The NASA/JSC orbital debris research effort within the Earth's low-altitude regime continues with the upgrade of the debris environment simulation model EVOLVE. Two main contributions to this new version will include a more streamlined structure (transparent to the analyst) and an updated, expanded set of launch/orbital insertion files. The new database includes such improvements as high fidelity launch times and orbital elements, dataderived area-to-mass ratios, and individual object dry mass and physical description. As an additional test of the new code, a version of the Anz-Meador [Adv. Space Res. (2004)] explosive fragmentation model is implemented and the resulting historical and projected LEO environments are compared to those of the US Space Surveillance Network (SSN) Catalog, ORDEM2000, and EVOLVE 4.1 (the current production version of the code) historical and projection periods EVOLVE test historical environments compare well with the catalog and ORDEM2000 environments over the 1-mm and larger size range. However, it should be noted that SRM slag is not included in EVOLVE at this time. Differences between the EVOLVE test and the EVOLVE 4.1 long-term projection environments are traced directly to the modified launch cycle and the chosen form of the Anz-Meador [Adv. Space Res. (2004)] breakup model of this EVOLVE test.

  4. Evolving role of pharmaceutical physicians in the industry: Indian perspective

    PubMed Central

    Patil, Anant; Rajadhyaksha, Viraj

    2012-01-01

    The Indian pharmaceutical industry, like any other industry, has undergone significant change in the last decade. The role of a Medical advisor has always been of paramount importance in the pharmaceutical companies in India. On account of the evolving medical science and the competitive environment, the medical advisor's role is also increasingly becoming critical. In India, with changes in regulatory rules, safety surveillance, and concept of medical liaisons, the role of the medical advisor is evolving continuously and is further likely to evolve in the coming years in important areas like health economics, public private partnerships, and strategic planning. PMID:22347701

  5. Heterogeneous edge weights promote epidemic diffusion in weighted evolving networks

    NASA Astrophysics Data System (ADS)

    Duan, Wei; Song, Zhichao; Qiu, Xiaogang

    2016-08-01

    The impact that the heterogeneities of links’ weights have on epidemic diffusion in weighted networks has received much attention. Investigating how heterogeneous edge weights affect epidemic spread is helpful for disease control. In this paper, we study a Reed-Frost epidemic model in weighted evolving networks. Our results indicate that a higher heterogeneity of edge weights leads to higher epidemic prevalence and epidemic incidence at earlier stage of epidemic diffusion in weighted evolving networks. In addition, weighted evolving scale-free networks come with a higher epidemic prevalence and epidemic incidence than unweighted scale-free networks.

  6. High Selectivity Oxygen Delignification

    SciTech Connect

    Lucian A. Lucia

    2005-11-15

    Project Objective: The objectives of this project are as follows: (1) Examine the physical and chemical characteristics of a partner mill pre- and post-oxygen delignified pulp and compare them to lab generated oxygen delignified pulps; (2) Apply the chemical selectivity enhancement system to the partner pre-oxygen delignified pulps under mill conditions (with and without any predetermined amounts of carryover) to determine how efficiently viscosity is preserved, how well selectivity is enhanced, if strength is improved, measure any yield differences and/or bleachability differences; and (3) Initiate a mill scale oxygen delignification run using the selectivity enhancement agent, collect the mill data, analyze it, and propose any future plans for implementation.

  7. Traveling with Portable Oxygen

    MedlinePlus

    ... is rich in oxygen. At higher altitudes, the atmosphere becomes increasingly thin as a result of decreasing ... breathe a mixture of gases similar to the atmosphere inside a pressurized airplane cabin at cruising altitude. ...

  8. Oxygen and Biological Evolution.

    ERIC Educational Resources Information Center

    Baugh, Mark A.

    1990-01-01

    Discussed is the evolution of aerobic organisms from anaerobic organisms and the accompanying biochemistry that developed to motivate and enable this evolution. Uses of oxygen by aerobic organisms are described. (CW)

  9. Medical Oxygen Safety

    MedlinePlus

    ... near the oxygen. Post No Smoking and No Open Flames signs in and outside the home to remind people not to smoke. Your Source for SAFETY Information NFPA Public Education Division • 1 Batterymarch Park, Quincy, MA 02169 Name ...

  10. Hyperbaric oxygen therapy

    MedlinePlus

    ... units may be available in outpatient centers. The air pressure inside a hyperbaric oxygen chamber is about two and a half times higher than the normal pressure in the ... Air or gas embolism Bone infections ( osteomyelitis ) that have ...

  11. Using oxygen at home

    MedlinePlus

    ... sooner to your house or neighborhood if the power goes out. Keep their phone numbers in a place where you can find them easily. Tell your family, neighbors, and friends that you use oxygen. They can help during an emergency.

  12. Practical procedures: oxygen therapy.

    PubMed

    Olive, Sandra

    Knowing when to start patients on oxygen therapy can save lives, but ongoing assessment and evaluation must be carried out to ensure the treatment is safe and effective. This article outlines when oxygen therapy should be used and the procedures to follow. It also describes the delivery methods applicable to different patient groups, along with the appropriate target saturation ranges, and details relevant nurse competencies.

  13. [Oxygen Leukocyte Larceny].

    PubMed

    Pinto da Costa, Miguel; Pimenta Coelho, Henrique

    2016-05-01

    The authors present a case of a 60-year-old male patient, previously diagnosed with B-cell chronic lymphocytic leukemia, who was admitted to the Emergency Room with dyspnea. The initial evaluation revealed severe anemia (Hgb = 5.0 g/dL) with hyperleukocytosis (800.000/µL), nearly all of the cells being mature lymphocytes, a normal chest X-ray and a low arterial oxygen saturation (89%; pulse oximetry). After red blood cell transfusion, Hgb values rose (9.0 g/dL) and there was a complete reversion of the dyspnea. Yet, subsequent arterial blood gas analysis, without the administration of supplemental oxygen, systematically revealed very low oxygen saturation values (~ 46%), which was inconsistent with the patientâs clinical state and his pulse oximetry values (~ 87%), and these values were not corrected by the administration of oxygen via non-rebreather mask. The investigation performed allowed to establish the diagnosis of oxygen leukocyte larceny, a phenomenon which conceals the true oxygen saturation due to peripheral consumption by leukocytes. PMID:27649020

  14. [Oxygen Leukocyte Larceny].

    PubMed

    Pinto da Costa, Miguel; Pimenta Coelho, Henrique

    2016-05-01

    The authors present a case of a 60-year-old male patient, previously diagnosed with B-cell chronic lymphocytic leukemia, who was admitted to the Emergency Room with dyspnea. The initial evaluation revealed severe anemia (Hgb = 5.0 g/dL) with hyperleukocytosis (800.000/µL), nearly all of the cells being mature lymphocytes, a normal chest X-ray and a low arterial oxygen saturation (89%; pulse oximetry). After red blood cell transfusion, Hgb values rose (9.0 g/dL) and there was a complete reversion of the dyspnea. Yet, subsequent arterial blood gas analysis, without the administration of supplemental oxygen, systematically revealed very low oxygen saturation values (~ 46%), which was inconsistent with the patientâs clinical state and his pulse oximetry values (~ 87%), and these values were not corrected by the administration of oxygen via non-rebreather mask. The investigation performed allowed to establish the diagnosis of oxygen leukocyte larceny, a phenomenon which conceals the true oxygen saturation due to peripheral consumption by leukocytes.

  15. Polarization and studies of evolved star mass loss

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin; Srinivasan, Sundar; Riebel, David; Meixner, Margaret

    2012-05-01

    Polarization studies of astronomical dust have proven very useful in constraining its properties. Such studies are used to constrain the spatial arrangement, shape, composition, and optical properties of astronomical dust grains. Here we explore possible connections between astronomical polarization observations to our studies of mass loss from evolved stars. We are studying evolved star mass loss in the Large Magellanic Cloud (LMC) by using photometry from the Surveying the Agents of a Galaxy's Evolution (SAGE; PI: M. Meixner) Spitzer Space Telescope Legacy program. We use the radiative transfer program 2Dust to create our Grid of Red supergiant and Asymptotic giant branch ModelS (GRAMS), in order to model this mass loss. To model emission of polarized light from evolved stars, however, we appeal to other radiative transfer codes. We probe how polarization observations might be used to constrain the dust shell and dust grain properties of the samples of evolved stars we are studying.

  16. Evolutionary genetics: you are what you evolve to eat.

    PubMed

    Dworkin, Ian; Jones, Corbin D

    2015-04-20

    The evolution of host specialization can potentially limit future evolutionary opportunities. A new study now shows how Drosophila sechellia, specialized on the toxic Morinda fruit, has evolved new nutritional needs influencing its reproduction.

  17. Evolved Stars: Interferometer Baby Food or Staple Diet?

    NASA Astrophysics Data System (ADS)

    Tuthill, Peter

    With their extreme red and infrared luminosities and large apparent diameters, evolved stars have nurtured generations of interferometers (beginning with Michelson's work on Betelgeuse) with unique science programs at attainable resolutions. Furthermore, the inflated photosphere and circumstellar material associated with dying stars presents complex targets with asymmetric structure on many scales encoding a wealth of poorly-understood astrophysics. A brief review the major past milestones and future prospects for interferometry's contribution to studies of circumstellar matter in evolved stars is presented.

  18. 42 CFR 414.226 - Oxygen and oxygen equipment.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... contents (stationary and portable). (ii) Portable equipment only (gaseous or liquid tanks). (iii) Oxygen... equipment that requires delivery of gaseous or liquid oxygen contents; or (ii) Rents stationary oxygen equipment that requires delivery of gaseous or liquid oxygen contents after the period of continuous use...

  19. 42 CFR 414.226 - Oxygen and oxygen equipment.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... contents (stationary and portable). (ii) Portable equipment only (gaseous or liquid tanks). (iii) Oxygen... equipment that requires delivery of gaseous or liquid oxygen contents; or (ii) Rents stationary oxygen equipment that requires delivery of gaseous or liquid oxygen contents after the period of continuous use...

  20. 42 CFR 414.226 - Oxygen and oxygen equipment.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... contents (stationary and portable). (ii) Portable equipment only (gaseous or liquid tanks). (iii) Oxygen... equipment that requires delivery of gaseous or liquid oxygen contents; or (ii) Rents stationary oxygen equipment that requires delivery of gaseous or liquid oxygen contents after the period of continuous use...

  1. Flammability and sensitivity of materials in oxygen-enriched atmospheres; Proceedings of the Fourth International Symposium, Las Cruces, NM, Apr. 11-13, 1989. Volume 4

    NASA Technical Reports Server (NTRS)

    Stoltzfus, Joel M. (Editor); Benz, Frank J. (Editor); Stradling, Jack S. (Editor)

    1989-01-01

    The present volume discusses the ignition of nonmetallic materials by the impact of high-pressure oxygen, the promoted combustion of nine structural metals in high-pressure gaseous oxygen, the oxygen sensitivity/compatibility ranking of several materials by different test methods, the ignition behavior of silicon greases in oxygen atmospheres, fire spread rates along cylindrical metal rods in high-pressure oxygen, and the design of an ignition-resistant, high pressure/temperature oxygen valve. Also discussed are the promoted ignition of oxygen regulators, the ignition of PTFE-lined flexible hoses by rapid pressurization with oxygen, evolving nonswelling elastomers for high-pressure oxygen environments, the evaluation of systems for oxygen service through the use of the quantitative fault-tree analysis, and oxygen-enriched fires during surgery of the head and neck.

  2. Origin and Evolution of Europa's Oxygen Exosphere

    NASA Astrophysics Data System (ADS)

    Oza, Apurva V.; Leblanc, Francois; Schmidt, Carl; Johnson, Robert E.

    2016-10-01

    Europa's icy surface is constantly bombarded by sulfur and oxygen ions originating from the Io plasma torus. The momentum transferred to molecules in Europa's surface results in the sputtering of water ice, populating a water product exosphere. We simulate Europa's neutral exosphere using a ballistic 3D Monte Carlo routine and find that the O2 exosphere, while global, is not uniformly symmetric in Europa local time. The O2 exosphere, sourced at a rate of ~ 5 kg/s with a disk-averaged column density of NO2 ~ 2.5 x 1014 O2/cm2, preferentially accumulates towards Europa's dusk. These dawn-dusk atmospheric inhomogeneities escalate as the surface-bounded O2 dissociates into an atomic O corona via electron impact. The inhomogeneities persist and evolve throughout the satellite's orbit, implying a diurnal cycle of the exosphere, recently evidenced by a detailed HST oxygen aurorae campaign (Roth et al. 2016). We conclude that the consistently observed 50% increase in FUV auroral emission from dusk to dawn is principally driven by the day-to-night thermal diffusion of O2 coupled with the Coriolis acceleration. This leads to a dawn-to-dusk gradient, peaking at Europa's leading hemisphere. This exospheric oxygen cycle, dependent on both orbital longitude and magnetic latitude, is fundamentally due to the bulk-sputtering vector changing with respect to the subsolar and subjovian points throughout the orbit. In principle, a similar mechanism should be present at other tidally-locked, rapidly orbiting satellite exospheres.

  3. canEvolve: A Web Portal for Integrative Oncogenomics

    PubMed Central

    Yan, Zhenyu; Wang, Xujun; Cao, Qingyi; Munshi, Nikhil C.; Li, Cheng

    2013-01-01

    Background & Objective Genome-wide profiles of tumors obtained using functional genomics platforms are being deposited to the public repositories at an astronomical scale, as a result of focused efforts by individual laboratories and large projects such as the Cancer Genome Atlas (TCGA) and the International Cancer Genome Consortium. Consequently, there is an urgent need for reliable tools that integrate and interpret these data in light of current knowledge and disseminate results to biomedical researchers in a user-friendly manner. We have built the canEvolve web portal to meet this need. Results canEvolve query functionalities are designed to fulfill most frequent analysis needs of cancer researchers with a view to generate novel hypotheses. canEvolve stores gene, microRNA (miRNA) and protein expression profiles, copy number alterations for multiple cancer types, and protein-protein interaction information. canEvolve allows querying of results of primary analysis, integrative analysis and network analysis of oncogenomics data. The querying for primary analysis includes differential gene and miRNA expression as well as changes in gene copy number measured with SNP microarrays. canEvolve provides results of integrative analysis of gene expression profiles with copy number alterations and with miRNA profiles as well as generalized integrative analysis using gene set enrichment analysis. The network analysis capability includes storage and visualization of gene co-expression, inferred gene regulatory networks and protein-protein interaction information. Finally, canEvolve provides correlations between gene expression and clinical outcomes in terms of univariate survival analysis. Conclusion At present canEvolve provides different types of information extracted from 90 cancer genomics studies comprising of more than 10,000 patients. The presence of multiple data types, novel integrative analysis for identifying regulators of oncogenesis, network analysis and ability

  4. Late Archean Surface Ocean Oxygenation (Invited)

    NASA Astrophysics Data System (ADS)

    Kendall, B.; Reinhard, C.; Lyons, T. W.; Kaufman, A. J.; Anbar, A. D.

    2009-12-01

    Oxygenic photosynthesis must have evolved by 2.45-2.32 Ga, when atmospheric oxygen abundances first rose above 0.001% present atmospheric level (Great Oxidation Event; GOE). Biomarker evidence for a time lag between the evolution of cyanobacterial oxygenic photosynthesis and the GOE continues to be debated. Geochemical signatures from sedimentary rocks (redox-sensitive trace metal abundances, sedimentary Fe geochemistry, and S isotopes) represent an alternative tool for tracing the history of Earth surface oxygenation. Integrated high-resolution chemostratigraphic profiles through the 2.5 Ga Mt. McRae Shale (Pilbara Craton, Western Australia) suggest a ‘whiff’ of oxygen in the surface environment at least 50 M.y. prior to the GOE. However, the geochemical data from the Mt. McRae Shale does not uniquely constrain the presence or extent of Late Archean ocean oxygenation. Here, we present high-resolution chemostratigraphic profiles from 2.6-2.5 Ga black shales (upper Campbellrand Subgroup, Kaapvaal Craton, South Africa) that provide the earliest direct evidence for an oxygenated ocean water column. On the slope beneath the Campbellrand - Malmani carbonate platform (Nauga Formation), a mildly oxygenated water column (highly reactive iron to total iron ratios [FeHR/FeT] ≤ 0.4) was underlain by oxidizing sediments (low Re and Mo abundances) or mildly reducing sediments (high Re but low Mo abundances). After drowning of the carbonate platform (Klein Naute Formation), the local bottom waters became anoxic (FeHR/FeT > 0.4) and intermittently sulphidic (pyrite iron to highly reactive iron ratios [FePY/FeHR] > 0.8), conducive to enrichment of both Re and Mo in sediments, followed by anoxic and Fe2+-rich (ferruginous) conditions (high FeT, FePY/FeHR near 0). Widespread surface ocean oxygenation is suggested by Re enrichment in the broadly correlative Klein Naute Formation and Mt. McRae Shale, deposited ~1000 km apart in the Griqualand West and Hamersley basins

  5. Optical oxygen concentration monitor

    DOEpatents

    Kebabian, P.

    1997-07-22

    A system for measuring and monitoring the concentration of oxygen uses as a light source an argon discharge lamp, which inherently emits light with a spectral line that is close to one of oxygen`s A-band absorption lines. In a preferred embodiment, the argon line is split into sets of components of shorter and longer wavelengths by a magnetic field of approximately 2,000 Gauss that is parallel to the light propagation from the lamp. The longer wavelength components are centered on an absorption line of oxygen and thus readily absorbed, and the shorter wavelength components are moved away from that line and minimally absorbed. A polarization modulator alternately selects the set of the longer wavelength, or upshifted, components or the set of the shorter wavelength, or downshifted, components and passes the selected set to an environment of interest. After transmission over a path through that environment, the transmitted optical flux of the argon line varies as a result of the differential absorption. The system then determines the concentration of oxygen in the environment based on the changes in the transmitted optical flux between the two sets of components. In alternative embodiments modulation is achieved by selectively reversing the polarity of the magnetic field or by selectively supplying the magnetic field to either the emitting plasma of the lamp or the environment of interest. 4 figs.

  6. Atomic oxygen stimulated outgassing

    NASA Technical Reports Server (NTRS)

    Linton, Roger C.; Reynolds, John M.

    1991-01-01

    The passive Long Duration Exposure Facility (LDEF) Experiment A0034, Atomic Oxygen Simulated Outgassing, consisted of two identical one-sixth tray modules, exposing selected thermal control coatings to atomic oxygen and the combined space environment on the leading edge and, for reference, to the relative wake environment on the trailing edge. Optical mirrors were included adjacent to the thermal coatings for deposition of outgassing products. Ultraviolet grade windows and metal covers were provided for additional assessment of the effects of the various environmental factors. Preliminary results indicate that orbital atomic oxygen is both a degrading and a optically restorative factor in the thermo-optical properties of selected thermal coatings. There is evidence of more severe optical degradation on collector mirrors adjacent to coatings that were exposed to the RAM-impinging atomic oxygen. This evidence of atomic oxygen stimulated outgassing is discussed in relation to alternative factors that could affect degradation. The general effects of the space environment on the experiment hardware as well as the specimens are discussed.

  7. OXYGEN POISONING IN MAMMALS.

    PubMed

    Binger, C A; Faulkner, J M; Moore, R L

    1927-04-30

    1. Oxygen in concentrations of over 70 per cent of an atmosphere is poisonous to dogs, rabbits, guinea pigs and mice. 2. The poisonous effects manifest themselves in drowsiness, anorexia, loss of weight, increasing dyspnea, cyanosis and death from oxygen want. 3. The cause of oxygen want is a destructive lesion of the lungs. 4. The lesion may be characterized grossly as an hemorrhagic edema. Microscopically there is to be seen in varying degrees of intensity (a) capillary engorgement with hemorrhage, (b) the presence of interstitial and intraalveolar serum, (c) hypertrophy and desquamation of alveolar cells, (d) interstitial and alveolar infiltration of mononuclear cells. 5. The type of tissue reaction is not characteristic of an infectious process and no organisms have been recovered at autopsy from the heart's blood or from lung puncture. 6. The poisonous effects of inhalations of oxygen-rich mixtures do not appear to be related to impurities in the oxygen, nor are they related to faulty ventilation, excessive moisture or increased carbon dioxide in the atmosphere of the chambers in which the experimental animals were confined. PMID:19869294

  8. A novel electrocatalyst for oxygen evolution reaction based on rational anchoring of cobalt carbonate hydroxide hydrate on multiwall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhang, Yuxia; Xiao, Qingqing; Guo, Xin; Zhang, Xiaoxue; Xue, Yifei; Jing, Lin; Zhai, Xue; Yan, Yi-Ming; Sun, Kening

    2015-03-01

    Cobalt carbonate hydroxide hydrate (CCHH) nanosheets have been densely and strongly anchored onto mildly oxidized multiwalled carbon nanotubes with the assistance of diethylenetriamine (DETA). The resulted hybrid (CCHH/MWCNT) is used as high efficient electrocatalyst for water oxidation with an extremely low onset potential of ∼1.47 V vs. RHE and an overpotential of 285 mV to achieve a current density of 10 mA cm-2 in 1.0 mol L-1 KOH. The CCHH/MWCNT electrode affords a Tafel slope of 51 mV/decade and an exchange current density of 2.5 × 10-7 A cm-2. Moreover, the CCHH/MWCNT catalyst delivers a high faradic efficiency of 95% and possesses remarkable stability for long-term electrolysis of water. By contrast, neither MWCNT nor CCHH exhibits apparent catalytical activity towards water oxidation. Importantly, we demonstrate that DETA plays crucial role in determining the morphology, structure of the CCHH/MWCNT, therefore resulting in an enhanced performance for water oxidation. This work not only provides a novel cobalt-based electrocatalyst for oxygen evolution, but also offers a useful and viable approach to deliberately synthesize functional nanocomposites for applications in energy conversion and storage.

  9. Monolithic solid electrolyte oxygen pump

    DOEpatents

    Fee, Darrell C.; Poeppel, Roger B.; Easler, Timothy E.; Dees, Dennis W.

    1989-01-01

    A multi-layer oxygen pump having a one-piece, monolithic ceramic structure affords high oxygen production per unit weight and volume and is thus particularly adapted for use as a portable oxygen supply. The oxygen pump is comprised of a large number of small cells on the order of 1-2 millimeters in diameter which form the walls of the pump and which are comprised of thin, i.e., 25-50 micrometers, ceramic layers of cell components. The cell components include an air electrode, an oxygen electrode, an electrolyte and interconnection materials. The cell walls form the passages for input air and for exhausting the oxygen which is transferred from a relatively dilute gaseous mixture to a higher concentration by applying a DC voltage across the electrodes so as to ionize the oxygen at the air electrode, whereupon the ionized oxygen travels through the electrolyte and is converted to oxygen gas at the oxygen electrode.

  10. Spitzer SAGE Survey of the Large Magellanic Cloud. II. Evolved Stars and Infrared Color-Magnitude Diagrams

    NASA Astrophysics Data System (ADS)

    Blum, R. D.; Mould, J. R.; Olsen, K. A.; Frogel, J. A.; Werner, M.; Meixner, M.; Markwick-Kemper, F.; Indebetouw, R.; Whitney, B.; Meade, M.; Babler, B.; Churchwell, E. B.; Gordon, K.; Engelbracht, C.; For, B.-Q.; Misselt, K.; Vijh, U.; Leitherer, C.; Volk, K.; Points, S.; Reach, W.; Hora, J. L.; Bernard, J.-P.; Boulanger, F.; Bracker, S.; Cohen, M.; Fukui, Y.; Gallagher, J.; Gorjian, V.; Harris, J.; Kelly, D.; Kawamura, A.; Latter, W. B.; Madden, S.; Mizuno, A.; Mizuno, N.; Nota, A.; Oey, M. S.; Onishi, T.; Paladini, R.; Panagia, N.; Perez-Gonzalez, P.; Shibai, H.; Sato, S.; Smith, L.; Staveley-Smith, L.; Tielens, A. G. G. M.; Ueta, T.; Van Dyk, S.; Zaritsky, D.

    2006-11-01

    Color-magnitude diagrams (CMDs) are presented for the Spitzer SAGE (Surveying the Agents of a Galaxy's Evolution) survey of the Large Magellanic Cloud (LMC). IRAC and MIPS 24 μm epoch 1 data are presented. These data represent the deepest, widest mid-infrared CMDs of their kind ever produced in the LMC. Combined with the Two Micron All Sky Survey, the diagrams are used to delineate the evolved stellar populations in the LMC, as well as Galactic foreground and extragalactic background populations. Some 32,000 evolved stars brighter than the tip of the red giant branch are identified. Of these, approximately 17,500 are classified as oxygen-rich, 7000 as carbon-rich, and another 1200 as ``extreme'' asymptotic giant branch (AGB) stars. Brighter members of the latter group have been called ``obscured'' AGB stars in the literature owing to their dusty circumstellar envelopes. A large number (1200) of luminous oxygen-rich AGB stars/M supergiants are also identified. Finally, there is strong evidence from the 24 μm MIPS channel that previously unexplored, lower luminosity oxygen-rich AGB stars contribute significantly to the mass-loss budget of the LMC (1200 such sources are identified).

  11. Neurological oxygen toxicity.

    PubMed

    Farmery, Scott; Sykes, Oliver

    2012-10-01

    SCUBA diving has several risks associated with it from breathing air under pressure--nitrogen narcosis, barotrauma and decompression sickness (the bends). Trimix SCUBA diving involves regulating mixtures of nitrogen, oxygen and helium in an attempt to overcome the risks of narcosis and decompression sickness during deep dives, but introduces other potential hazards such as hypoxia and oxygen toxicity convulsions. This study reports on a seizure during the ascent phase, its potential causes and management and discusses the hazards posed to the diver and his rescuer by an emergency ascent to the surface.

  12. The Appropriate Use of Oxygen

    PubMed Central

    Lubin, Stan

    1988-01-01

    The scientific evidence for the efficacy of oxygen therapy in acute hypoxemia is limited. In chronic hypoxemia continuous oxygen therapy appears to decrease mortality. Current indications for oxygen treatment are PaO2 less than 60 in acute hypoxemia and less than 55 in chronic hypoxemia. Physical and physiological hazards of oxygen are reviewed. Three syndromes of pulmonary oxygen toxicity are described: tracheobronchitis, adult respiratory distress syndrome, and bronchopulmonary dysplasia. PMID:21253258

  13. Plant hemoglobins: a molecular fossil record for the evolution of oxygen transport.

    PubMed

    Hoy, Julie A; Robinson, Howard; Trent, James T; Kakar, Smita; Smagghe, Benoit J; Hargrove, Mark S

    2007-08-01

    The evolution of oxygen transport hemoglobins occurred on at least two independent occasions. The earliest event led to myoglobin and red blood cell hemoglobin in animals. In plants, oxygen transport "leghemoglobins" evolved much more recently. In both events, pentacoordinate heme sites capable of inert oxygen transfer evolved from hexacoordinate hemoglobins that have unrelated functions. High sequence homology between hexacoordinate and pentacoordinate hemoglobins in plants has poised them for potential structural analysis leading to a molecular understanding of this important evolutionary event. However, the lack of a plant hexacoordinate hemoglobin structure in the exogenously ligand-bound form has prevented such comparison. Here we report the crystal structure of the cyanide-bound hexacoordinate hemoglobin from barley. This presents the first opportunity to examine conformational changes in plant hexacoordinate hemoglobins upon exogenous ligand binding, and reveals structural mechanisms for stabilizing the high-energy pentacoordinate heme conformation critical to the evolution of reversible oxygen binding hemoglobins.

  14. Plant Hemoglobins: A Molecular Fossil Record for the Evolutin of Oxygen Transport

    SciTech Connect

    Hoy,J.; Robinson, H.; Trent, lll, J.; Kakar, S.; Smagghe, B.; Hargrove, M.

    2007-01-01

    The evolution of oxygen transport hemoglobins occurred on at least two independent occasions. The earliest event led to myoglobin and red blood cell hemoglobin in animals. In plants, oxygen transport 'leghemoglobins' evolved much more recently. In both events, pentacoordinate heme sites capable of inert oxygen transfer evolved from hexacoordinate hemoglobins that have unrelated functions. High sequence homology between hexacoordinate and pentacoordinate hemoglobins in plants has poised them for potential structural analysis leading to a molecular understanding of this important evolutionary event. However, the lack of a plant hexacoordinate hemoglobin structure in the exogenously ligand-bound form has prevented such comparison. Here we report the crystal structure of the cyanide-bound hexacoordinate hemoglobin from barley. This presents the first opportunity to examine conformational changes in plant hexacoordinate hemoglobins upon exogenous ligand binding, and reveals structural mechanisms for stabilizing the high-energy pentacoordinate heme conformation critical to the evolution of reversible oxygen binding hemoglobins.

  15. Measuring and comparing evolvability and constraint in multivariate characters.

    PubMed

    Hansen, T F; Houle, D

    2008-09-01

    The Lande equation forms the basis for our understanding of the short-term evolution of quantitative traits in a multivariate context. It predicts the response to selection as the product of an additive genetic variance matrix and a selection gradient. The selection gradient approximates the force and direction of selection, and the genetic variance matrix quantifies the role of the genetic system in evolution. Attempts to understand the evolutionary significance of the genetic variance matrix are hampered by the fact that the majority of the methods used to characterize and compare variance matrices have not been derived in an explicit theoretical context. We use the Lande equation to derive new measures of the ability of a variance matrix to allow or constrain evolution in any direction in phenotype space. Evolvability captures the ability of a population to evolve in the direction of selection when stabilizing selection is absent. Conditional evolvability captures the ability of a population to respond to directional selection in the presence of stabilizing selection on other trait combinations. We then derive measures of character autonomy and integration from these evolvabilities. We study the properties of these measures and show how they can be used to interpret and compare variance matrices. As an illustration, we show that divergence of wing shape in the dipteran family Drosophilidae has proceeded in directions that have relatively high evolvabilities.

  16. The fitness and functionality of culturally evolved communication systems.

    PubMed

    Fay, Nicolas; Garrod, Simon; Roberts, Leo

    2008-11-12

    This paper assesses whether human communication systems undergo the same progressive adaptation seen in animal communication systems and concrete artefacts. Four experiments compared the fitness of ad hoc sign systems created under different conditions when participants play a graphical communication task. Experiment 1 demonstrated that when participants are organized into interacting communities, a series of signs evolve that enhance individual learning and promote efficient decoding. No such benefits are found for signs that result from the local interactions of isolated pairs of interlocutors. Experiments 2 and 3 showed that the decoding benefits associated with community evolved signs cannot be attributed to superior sign encoding or detection. Experiment 4 revealed that naive overseers were better able to identify the meaning of community evolved signs when compared with isolated pair developed signs. Hence, the decoding benefits for community evolved signs arise from their greater residual iconicity. We argue that community evolved sign systems undergo a process of communicative selection and adaptation that promotes optimized sign systems. This results from the interplay between sign diversity and a global alignment constraint; pairwise interaction introduces a range of competing signs and the need to globally align on a single sign-meaning mapping for each referent applies selection pressure.

  17. The fitness and functionality of culturally evolved communication systems.

    PubMed

    Fay, Nicolas; Garrod, Simon; Roberts, Leo

    2008-11-12

    This paper assesses whether human communication systems undergo the same progressive adaptation seen in animal communication systems and concrete artefacts. Four experiments compared the fitness of ad hoc sign systems created under different conditions when participants play a graphical communication task. Experiment 1 demonstrated that when participants are organized into interacting communities, a series of signs evolve that enhance individual learning and promote efficient decoding. No such benefits are found for signs that result from the local interactions of isolated pairs of interlocutors. Experiments 2 and 3 showed that the decoding benefits associated with community evolved signs cannot be attributed to superior sign encoding or detection. Experiment 4 revealed that naive overseers were better able to identify the meaning of community evolved signs when compared with isolated pair developed signs. Hence, the decoding benefits for community evolved signs arise from their greater residual iconicity. We argue that community evolved sign systems undergo a process of communicative selection and adaptation that promotes optimized sign systems. This results from the interplay between sign diversity and a global alignment constraint; pairwise interaction introduces a range of competing signs and the need to globally align on a single sign-meaning mapping for each referent applies selection pressure. PMID:18799421

  18. How Hierarchical Topics Evolve in Large Text Corpora.

    PubMed

    Cui, Weiwei; Liu, Shixia; Wu, Zhuofeng; Wei, Hao

    2014-12-01

    Using a sequence of topic trees to organize documents is a popular way to represent hierarchical and evolving topics in text corpora. However, following evolving topics in the context of topic trees remains difficult for users. To address this issue, we present an interactive visual text analysis approach to allow users to progressively explore and analyze the complex evolutionary patterns of hierarchical topics. The key idea behind our approach is to exploit a tree cut to approximate each tree and allow users to interactively modify the tree cuts based on their interests. In particular, we propose an incremental evolutionary tree cut algorithm with the goal of balancing 1) the fitness of each tree cut and the smoothness between adjacent tree cuts; 2) the historical and new information related to user interests. A time-based visualization is designed to illustrate the evolving topics over time. To preserve the mental map, we develop a stable layout algorithm. As a result, our approach can quickly guide users to progressively gain profound insights into evolving hierarchical topics. We evaluate the effectiveness of the proposed method on Amazon's Mechanical Turk and real-world news data. The results show that users are able to successfully analyze evolving topics in text data.

  19. The value of monitoring to control evolving populations

    PubMed Central

    Fischer, Andrej; Mustonen, Ville

    2015-01-01

    Populations can evolve to adapt to external changes. The capacity to evolve and adapt makes successful treatment of infectious diseases and cancer difficult. Indeed, therapy resistance has become a key challenge for global health. Therefore, ideas of how to control evolving populations to overcome this threat are valuable. Here we use the mathematical concepts of stochastic optimal control to study what is needed to control evolving populations. Following established routes to calculate control strategies, we first study how a polymorphism can be maintained in a finite population by adaptively tuning selection. We then introduce a minimal model of drug resistance in a stochastically evolving cancer cell population and compute adaptive therapies. When decisions are in this manner based on monitoring the response of the tumor, this can outperform established therapy paradigms. For both case studies, we demonstrate the importance of high-resolution monitoring of the target population to achieve a given control objective, thus quantifying the intuition that to control, one must monitor. PMID:25587136

  20. How Hierarchical Topics Evolve in Large Text Corpora.

    PubMed

    Cui, Weiwei; Liu, Shixia; Wu, Zhuofeng; Wei, Hao

    2014-12-01

    Using a sequence of topic trees to organize documents is a popular way to represent hierarchical and evolving topics in text corpora. However, following evolving topics in the context of topic trees remains difficult for users. To address this issue, we present an interactive visual text analysis approach to allow users to progressively explore and analyze the complex evolutionary patterns of hierarchical topics. The key idea behind our approach is to exploit a tree cut to approximate each tree and allow users to interactively modify the tree cuts based on their interests. In particular, we propose an incremental evolutionary tree cut algorithm with the goal of balancing 1) the fitness of each tree cut and the smoothness between adjacent tree cuts; 2) the historical and new information related to user interests. A time-based visualization is designed to illustrate the evolving topics over time. To preserve the mental map, we develop a stable layout algorithm. As a result, our approach can quickly guide users to progressively gain profound insights into evolving hierarchical topics. We evaluate the effectiveness of the proposed method on Amazon's Mechanical Turk and real-world news data. The results show that users are able to successfully analyze evolving topics in text data. PMID:26356942

  1. A slowly evolving host moves first in symbiotic interactions

    NASA Astrophysics Data System (ADS)

    Damore, James; Gore, Jeff

    2011-03-01

    Symbiotic relationships, both parasitic and mutualistic, are ubiquitous in nature. Understanding how these symbioses evolve, from bacteria and their phages to humans and our gut microflora, is crucial in understanding how life operates. Often, symbioses consist of a slowly evolving host species with each host only interacting with its own sub-population of symbionts. The Red Queen hypothesis describes coevolutionary relationships as constant arms races with each species rushing to evolve an advantage over the other, suggesting that faster evolution is favored. Here, we use a simple game theoretic model of host- symbiont coevolution that includes population structure to show that if the symbionts evolve much faster than the host, the equilibrium distribution is the same as it would be if it were a sequential game where the host moves first against its symbionts. For the slowly evolving host, this will prove to be advantageous in mutualisms and a handicap in antagonisms. The model allows for symbiont adaptation to its host, a result that is robust to changes in the parameters and generalizes to continuous and multiplayer games. Our findings provide insight into a wide range of symbiotic phenomena and help to unify the field of coevolutionary theory.

  2. The origin of atmospheric oxygen on Earth: the innovation of oxygenic photosynthesis.

    PubMed

    Dismukes, G C; Klimov, V V; Baranov, S V; Kozlov, Y N; DasGupta, J; Tyryshkin, A

    2001-02-27

    The evolution of O(2)-producing cyanobacteria that use water as terminal reductant transformed Earth's atmosphere to one suitable for the evolution of aerobic metabolism and complex life. The innovation of water oxidation freed photosynthesis to invade new environments and visibly changed the face of the Earth. We offer a new hypothesis for how this process evolved, which identifies two critical roles for carbon dioxide in the Archean period. First, we present a thermodynamic analysis showing that bicarbonate (formed by dissolution of CO(2)) is a more efficient alternative substrate than water for O(2) production by oxygenic phototrophs. This analysis clarifies the origin of the long debated "bicarbonate effect" on photosynthetic O(2) production. We propose that bicarbonate was the thermodynamically preferred reductant before water in the evolution of oxygenic photosynthesis. Second, we have examined the speciation of manganese(II) and bicarbonate in water, and find that they form Mn-bicarbonate clusters as the major species under conditions that model the chemistry of the Archean sea. These clusters have been found to be highly efficient precursors for the assembly of the tetramanganese-oxide core of the water-oxidizing enzyme during biogenesis. We show that these clusters can be oxidized at electrochemical potentials that are accessible to anoxygenic phototrophs and thus the most likely building blocks for assembly of the first O(2) evolving photoreaction center, most likely originating from green nonsulfur bacteria before the evolution of cyanobacteria.

  3. Atomic Oxygen Task

    NASA Technical Reports Server (NTRS)

    Hadaway, James B.

    1997-01-01

    This report details work performed by the Center for Applied Optics (CAO) at the University of Alabama in Huntsville (UAH) on the contract entitled 'Atomic Oxygen Task' for NASA's Marshall Space Flight Center (contract NAS8-38609, Delivery Order 109, modification number 1). Atomic oxygen effects on exposed materials remain a critical concern in designing spacecraft to withstand exposure in the Low Earth Orbit (LEO) environment. The basic objective of atomic oxygen research in NASA's Materials & Processes (M&P) Laboratory is to provide the solutions to material problems facing present and future space missions. The objective of this work was to provide the necessary research for the design of specialized experimental test configurations and development of techniques for evaluating in-situ space environmental effects, including the effects of atomic oxygen and electromagnetic radiation on candidate materials. Specific tasks were performed to address materials issues concerning accelerated environmental testing as well as specifically addressing materials issues of particular concern for LDEF analysis and Space Station materials selection.

  4. Optical oxygen concentration monitor

    DOEpatents

    Kebabian, Paul

    1997-01-01

    A system for measuring and monitoring the concentration of oxygen uses as a light source an argon discharge lamp, which inherently emits light with a spectral line that is close to one of oxygen's A-band absorption lines. In a preferred embodiment, the argon line is split into sets of components of shorter and longer wavelengths by a magnetic field of approximately 2000 Gauss that is parallel to the light propagation from the lamp. The longer wavelength components are centered on an absorption line of oxygen and thus readily absorbed, and the shorter wavelength components are moved away from that line and minimally absorbed. A polarization modulator alternately selects the set of the longer wavelength, or upshifted, components or the set of the shorter wavelength, or downshifted, components and passes the selected set to an environment of interest. After transmission over a path through that environment, the transmitted optical flux of the argon line varies as a result of the differential absorption. The system then determines the concentration of oxygen in the environment based on the changes in the transmitted optical flux between the two sets of components. In alternative embodiments modulation is achieved by selectively reversing the polarity of the magnetic field or by selectively supplying the magnetic field to either the emitting plasma of the lamp or the environment of interest.

  5. The Oxygen Flask Method

    ERIC Educational Resources Information Center

    Boulton, L. H.

    1973-01-01

    Discusses application of Schoniger's method of quantitative organic elemental analysis in teaching of qualitative analysis of the halogens, nitrogen, sulphur, and phosphorus. Indicates that the oxygen flask method is safe and suitable for both high school and college courses because of simple apparatus requirements. (CC)

  6. Oxygen transport by hemoglobin.

    PubMed

    Mairbäurl, Heimo; Weber, Roy E

    2012-04-01

    Hemoglobin (Hb) constitutes a vital link between ambient O2 availability and aerobic metabolism by transporting oxygen (O2) from the respiratory surfaces of the lungs or gills to the O2-consuming tissues. The amount of O2 available to tissues depends on the blood-perfusion rate, as well as the arterio-venous difference in blood O2 contents, which is determined by the respective loading and unloading O2 tensions and Hb-O2-affinity. Short-term adjustments in tissue oxygen delivery in response to decreased O2 supply or increased O2 demand (under exercise, hypoxia at high altitude, cardiovascular disease, and ischemia) are mediated by metabolically induced changes in the red cell levels of allosteric effectors such as protons (H(+)), carbon dioxide (CO2), organic phosphates, and chloride (Cl(-)) that modulate Hb-O2 affinity. The long-term, genetically coded adaptations in oxygen transport encountered in animals that permanently are subjected to low environmental O2 tensions commonly result from changes in the molecular structure of Hb, notably amino acid exchanges that alter Hb's intrinsic O2 affinity or its sensitivity to allosteric effectors. Structure-function studies of animal Hbs and human Hb mutants illustrate the different strategies for adjusting Hb-O2 affinity and optimizing tissue oxygen supply.

  7. The Oxygen Cycle.

    ERIC Educational Resources Information Center

    Swant, Gary D.

    Produced for primary grades, this booklet provides study of the oxygen-carbon dioxide cycle in nature. Line drawings, a minimum amount of narrative, and a glossary of terms make up its content. The booklet is designed to be used as reading material, a coloring book, or for dramatic arts with students acting out parts of the cycle. This work was…

  8. FUEL OXYGENATES HEALTH ISSUES

    EPA Science Inventory

    Oxygenates (e.g., methyl tertiary butyl ether [MTBE], ethanol) are required in certain areas of the United States by the 1990 Clean Air Act Amendments. MTBE and ethanol have also been used to increase octane ratings in U.S. gasoline since the 1970s. In 1996 alone, 10 billion Kg...

  9. Calibration Of Oxygen Monitors

    NASA Technical Reports Server (NTRS)

    Zalenski, M. A.; Rowe, E. L.; Mcphee, J. R.

    1988-01-01

    Readings corrected for temperature, pressure, and humidity of air. Program for handheld computer developed to ensure accuracy of oxygen monitors in National Transonic Facility, where liquid nitrogen stored. Calibration values, determined daily, based on entries of data on barometric pressure, temperature, and relative humidity. Output provided directly in millivolts.

  10. Evolving mobile robots able to display collective behaviors.

    PubMed

    Baldassarre, Gianluca; Nolfi, Stefano; Parisi, Domenico

    2003-01-01

    We present a set of experiments in which simulated robots are evolved for the ability to aggregate and move together toward a light target. By developing and using quantitative indexes that capture the structural properties of the emerged formations, we show that evolved individuals display interesting behavioral patterns in which groups of robots act as a single unit. Moreover, evolved groups of robots with identical controllers display primitive forms of situated specialization and play different behavioral functions within the group according to the circumstances. Overall, the results presented in the article demonstrate that evolutionary techniques, by exploiting the self-organizing behavioral properties that emerge from the interactions between the robots and between the robots and the environment, are a powerful method for synthesizing collective behavior. PMID:14556687

  11. Synthesis of Evolving Cells for Reconfigurable Manufacturing Systems

    NASA Astrophysics Data System (ADS)

    Padayachee, J.; Bright, G.

    2014-07-01

    The concept of Reconfigurable Manufacturing Systems (RMSs) was formulated due to the global necessity for production systems that are able to economically evolve according to changes in markets and products. Technologies and design methods are under development to enable RMSs to exhibit transformable system layouts, reconfigurable processes, cells and machines. Existing factory design methods and software have not yet advanced to include reconfigurable manufacturing concepts. This paper presents the underlying group technology framework for the design of manufacturing cells that are able to evolve according to a changing product mix by mechanisms of reconfiguration. The framework is based on a Norton- Bass forecast and time variant BOM models. An adaptation of legacy group technology methods is presented for the synthesis of evolving cells and two optimization problems are presented within this context.

  12. Evolving Lorentzian wormholes supported by phantom matter and cosmological constant

    SciTech Connect

    Cataldo, Mauricio; Campo, Sergio del; Minning, Paul; Salgado, Patricio

    2009-01-15

    In this paper we study the possibility of sustaining an evolving wormhole via exotic matter made of phantom energy in the presence of a cosmological constant. We derive analytical evolving wormhole geometries by supposing that the radial tension of the phantom matter, which is negative to the radial pressure, and the pressure measured in the tangential directions have barotropic equations of state with constant state parameters. In this case the presence of a cosmological constant ensures accelerated expansion of the wormhole configurations. More specifically, for positive cosmological constant we have wormholes which expand forever and, for negative cosmological constant we have wormholes which expand to a maximum value and then recollapse. At spatial infinity the energy density and the pressures of the anisotropic phantom matter threading the wormholes vanish; thus these evolving wormholes are asymptotically vacuum {lambda}-Friedmann models with either open or closed or flat topologies.

  13. Evolving Systems: An Outcome of Fondest Hopes and Wildest Dreams

    NASA Technical Reports Server (NTRS)

    Frost, Susan A.; Balas, Mark J.

    2012-01-01

    New theory is presented for evolving systems, which are autonomously controlled subsystems that self-assemble into a new evolved system with a higher purpose. Evolving systems of aerospace structures often require additional control when assembling to maintain stability during the entire evolution process. This is the concept of Adaptive Key Component Control that operates through one specific component to maintain stability during the evolution. In addition, this control must often overcome persistent disturbances that occur while the evolution is in progress. Theoretical results will be presented for Adaptive Key Component control for persistent disturbance rejection. An illustrative example will demonstrate the Adaptive Key Component controller on a system composed of rigid body and flexible body modes.

  14. Topology of Coronal Fields from Evolving Magnetofrictional Models

    NASA Astrophysics Data System (ADS)

    DeRosa, Marc L.; Cheung, M.

    2012-05-01

    The evolving magnetofrictional (MF) scheme enables the construction of time-dependent models of the active region coronal magnetic field in response to photospheric driving. When advancing such models, only the magnetic induction is solved, during which the velocity at each point is assumed to be oriented parallel to the Lorentz force. This leads to the field to evolve toward a force-free state. We present results from an evolving MF model of NOAA AR11158 using driving from time sequences of SDO/HMI data. Utilizing this simulation, we investigate changes in magnetic configurations and topology, including the number of null points, evolution of quasi-separatrix layers, and the time-history of total and free magnetic energies as well as relative helicity. This work seeks to elucidate the relation(s) between topological and energetic properties of the AR.

  15. Hybridization Reveals the Evolving Genomic Architecture of Speciation

    PubMed Central

    Kronforst, Marcus R.; Hansen, Matthew E.B.; Crawford, Nicholas G.; Gallant, Jason R.; Zhang, Wei; Kulathinal, Rob J.; Kapan, Durrell D.; Mullen, Sean P.

    2014-01-01

    SUMMARY The rate at which genomes diverge during speciation is unknown, as are the physical dynamics of the process. Here, we compare full genome sequences of 32 butterflies, representing five species from a hybridizing Heliconius butterfly community, to examine genome-wide patterns of introgression and infer how divergence evolves during the speciation process. Our analyses reveal that initial divergence is restricted to a small fraction of the genome, largely clustered around known wing-patterning genes. Over time, divergence evolves rapidly, due primarily to the origin of new divergent regions. Furthermore, divergent genomic regions display signatures of both selection and adaptive introgression, demonstrating the link between microevolutionary processes acting within species and the origin of species across macroevolutionary timescales. Our results provide a uniquely comprehensive portrait of the evolving species boundary due to the role that hybridization plays in reducing the background accumulation of divergence at neutral sites. PMID:24183670

  16. The evolved basis and adaptive functions of cognitive distortions.

    PubMed

    Gilbert, P

    1998-12-01

    This paper explores common cognitive distortions from the perspective of evolutionary psychology. It is suggested that cognitive distortions are natural consequences of using fast track defensive algorithms that are sensitive to threat. In various contexts, especially those of threat, humans evolved to think adaptively rather than logically. Hence cognitive distortions are not strictly errors in brain functioning and it can be useful to inform patients that 'negative thinking' may be dysfunctional but is a reflection of basic brain design and not personal irrationality. The evolved nature of cognitive distortions has been implicit in cognitive therapy from its early days (Beck, 1963; Ellis, 1962) but has not been fully articulated in what is now known about evolved mental processes. Many forms of cognitive distortion can be seen to use the (previously) adaptive heuristic of better safe than sorry.

  17. Active Printed Materials for Complex Self-Evolving Deformations

    NASA Astrophysics Data System (ADS)

    Raviv, Dan; Zhao, Wei; McKnelly, Carrie; Papadopoulou, Athina; Kadambi, Achuta; Shi, Boxin; Hirsch, Shai; Dikovsky, Daniel; Zyracki, Michael; Olguin, Carlos; Raskar, Ramesh; Tibbits, Skylar

    2014-12-01

    We propose a new design of complex self-evolving structures that vary over time due to environmental interaction. In conventional 3D printing systems, materials are meant to be stable rather than active and fabricated models are designed and printed as static objects. Here, we introduce a novel approach for simulating and fabricating self-evolving structures that transform into a predetermined shape, changing property and function after fabrication. The new locally coordinated bending primitives combine into a single system, allowing for a global deformation which can stretch, fold and bend given environmental stimulus.

  18. Active printed materials for complex self-evolving deformations.

    PubMed

    Raviv, Dan; Zhao, Wei; McKnelly, Carrie; Papadopoulou, Athina; Kadambi, Achuta; Shi, Boxin; Hirsch, Shai; Dikovsky, Daniel; Zyracki, Michael; Olguin, Carlos; Raskar, Ramesh; Tibbits, Skylar

    2014-12-18

    We propose a new design of complex self-evolving structures that vary over time due to environmental interaction. In conventional 3D printing systems, materials are meant to be stable rather than active and fabricated models are designed and printed as static objects. Here, we introduce a novel approach for simulating and fabricating self-evolving structures that transform into a predetermined shape, changing property and function after fabrication. The new locally coordinated bending primitives combine into a single system, allowing for a global deformation which can stretch, fold and bend given environmental stimulus.

  19. The cartography of pain: the evolving contribution of pain maps.

    PubMed

    Schott, Geoffrey D

    2010-09-01

    Pain maps are nowadays widely used in clinical practice. This article aims to critically review the fundamental principles that underlie the mapping of pain, to analyse the evolving iconography of pain maps and their sometimes straightforward and sometimes contentious nature when used in the clinic, and to draw attention to some more recent developments in mapping pain. It is concluded that these maps are intriguing and evolving cartographic tools which can be used for depicting not only the spatial features but also the interpretative or perceptual components and accompaniments of pain.

  20. The history of extracorporeal oxygenators.

    PubMed

    Lim, M W

    2006-10-01

    Extracorporeal oxygenators are artificial devices that substitute for anatomical lungs by delivering oxygen to, and extracting carbon dioxide from, blood. They were first conceptualised by the English scientist Robert Hooke (1635-1703) and developed into practical extracorporeal oxygenators by French and German experimental physiologists in the 19th century. Indeed, most of the extracorporeal oxygenators used until the late 1970s were derived from von Schroder's 1882 bubble oxygenator and Frey and Gruber's 1885 film oxygenator. As there is no intervening barrier between blood and oxygen, these are called 'direct contact' oxygenators; they contributed significantly to the development and practice of cardiac surgery till the 1980s. Membrane extracorporeal oxygenators introduce a gas-permeable interface between blood and oxygen. This greatly decreased the blood trauma of direct-contact extracorporeal oxygenators, and enabled extracorporeal oxygenators to be used in longer-term applications such as the intensive therapy of respiratory distress syndrome; this was demonstrably beneficial for neonates but less so for older patients. Much work since the 1960s focused on overcoming the gas exchange handicap of the membrane barrier, leading to the development of high-performance microporous hollow-fibre oxygenators that eventually replaced direct-contact oxygenators in cardiac theatres. PMID:16978315

  1. The history of extracorporeal oxygenators.

    PubMed

    Lim, M W

    2006-10-01

    Extracorporeal oxygenators are artificial devices that substitute for anatomical lungs by delivering oxygen to, and extracting carbon dioxide from, blood. They were first conceptualised by the English scientist Robert Hooke (1635-1703) and developed into practical extracorporeal oxygenators by French and German experimental physiologists in the 19th century. Indeed, most of the extracorporeal oxygenators used until the late 1970s were derived from von Schroder's 1882 bubble oxygenator and Frey and Gruber's 1885 film oxygenator. As there is no intervening barrier between blood and oxygen, these are called 'direct contact' oxygenators; they contributed significantly to the development and practice of cardiac surgery till the 1980s. Membrane extracorporeal oxygenators introduce a gas-permeable interface between blood and oxygen. This greatly decreased the blood trauma of direct-contact extracorporeal oxygenators, and enabled extracorporeal oxygenators to be used in longer-term applications such as the intensive therapy of respiratory distress syndrome; this was demonstrably beneficial for neonates but less so for older patients. Much work since the 1960s focused on overcoming the gas exchange handicap of the membrane barrier, leading to the development of high-performance microporous hollow-fibre oxygenators that eventually replaced direct-contact oxygenators in cardiac theatres.

  2. Emergency oxygen: What? Who? When?

    PubMed

    Starr, L M

    1994-01-01

    1. While the need for oxygen to support ill or injured clients is well established, confusion exists about oxygen devices and legal and training requirements. 2. The FDA recognizes both emergency and prescription oxygen. Emergency devices may be used legally by a non-health care workplace first aider who has completed a course in oxygen administration. Training sources for oxygen administration training are identified. 3. Workplace first aiders may assist a client and occupational health nurse by administering emergency oxygen. The appropriate use of these devices for cases of cardiac distress/arrest, shock, COPD, and hyperventilation is reviewed. PMID:8147981

  3. Evolving in thin air--lessons from the llama fetus in the altiplano.

    PubMed

    Llanos, Aníbal J; Riquelme, Raquel A; Herrera, Emilio A; Ebensperger, Germán; Krause, Bernardo; Reyes, Roberto V; Sanhueza, Emilia M; Pulgar, Víctor M; Behn, Claus; Cabello, Gertrudis; Parer, Julian T; Giussani, Dino A; Blanco, Carlos E; Hanson, Mark A

    2007-09-30

    Compared with lowland species, fetal life for mammalian species whose mothers live in high altitude is demanding. For instance, fetal llamas have to cope with the low fetal arterial PO2 of all species, but also the likely superimposition of hypoxia as a result of the decreased oxygen environment in which the mother lives in the Andean altiplano. When subjected to acute hypoxia the llama fetus responds with an intense peripheral vasoconstriction mediated by alpha-adrenergic mechanisms plus high plasma concentrations of catecholamines and neuropeptide Y (NPY). Endothelial factors such as NO and endothelin-1 also play a role in the regulation of local blood flows. Unlike fetuses of lowland species such as the sheep, the llama fetus shows a profound cerebral hypometabolic response to hypoxia, decreasing cerebral oxygen consumption, Na-K-ATPase activity and temperature, and resulting in an absence of seizures and apoptosis in neural cells. These strategies may have evolved to prevent hypoxic injury to the brain or other organs in the face of the persistent hypobaric hypoxia of life in the Andean altiplano.

  4. Co-evolution of eukaryotes and ocean oxygenation in the Neoproterozoic era

    NASA Astrophysics Data System (ADS)

    Lenton, Timothy M.; Boyle, Richard A.; Poulton, Simon W.; Shields-Zhou, Graham A.; Butterfield, Nicholas J.

    2014-04-01

    The Neoproterozoic era (about 1,000 to 542 million years ago) was a time of turbulent environmental change. Large fluctuations in the carbon cycle were associated with at least two severe -- possible Snowball Earth -- glaciations. There were also massive changes in the redox state of the oceans, culminating in the oxygenation of much of the deep oceans. Amid this environmental change, increasingly complex life forms evolved. The traditional view is that a rise in atmospheric oxygen concentrations led to the oxygenation of the ocean, thus triggering the evolution of animals. We argue instead that the evolution of increasingly complex eukaryotes, including the first animals, could have oxygenated the ocean without requiring an increase in atmospheric oxygen. We propose that large eukaryotic particles sank quickly through the water column and reduced the consumption of oxygen in the surface waters. Combined with the advent of benthic filter feeding, this shifted oxygen demand away from the surface to greater depths and into sediments, allowing oxygen to reach deeper waters. The decline in bottom-water anoxia would hinder the release of phosphorus from sediments, potentially triggering a potent positive feedback: phosphorus removal from the ocean reduced global productivity and ocean-wide oxygen demand, resulting in oxygenation of the deep ocean. That, in turn, would have further reinforced eukaryote evolution, phosphorus removal and ocean oxygenation.

  5. Research at the Crossroads: How Intellectual Initiatives across Disciplines Evolve

    ERIC Educational Resources Information Center

    Frost, Susan H.; Jean, Paul M.; Teodorescu, Daniel; Brown, Amy B.

    2004-01-01

    How do intellectual initiatives across disciplines evolve? This qualitative case study of 11 interdisciplinary research initiatives at Emory University identifies key factors in their development: the passionate commitments of scholarly leaders, the presence of strong collegial networks, access to timely and multiple resources, flexible practices,…

  6. The Evolving Status of Photojournalism Education. ERIC Digest.

    ERIC Educational Resources Information Center

    Cookman, Claude

    Noting that new technologies are resulting in extensive changes in the field of photojournalism, both as it is practiced and taught, this Digest reviews this rapidly evolving field of education and professional practice. It discusses what digital photography is; the history of digital photography; how digital photography has changed…

  7. Coevolution Drives the Emergence of Complex Traits and Promotes Evolvability

    PubMed Central

    Zaman, Luis; Meyer, Justin R.; Devangam, Suhas; Bryson, David M.; Lenski, Richard E.; Ofria, Charles

    2014-01-01

    The evolution of complex organismal traits is obvious as a historical fact, but the underlying causes—including the role of natural selection—are contested. Gould argued that a random walk from a necessarily simple beginning would produce the appearance of increasing complexity over time. Others contend that selection, including coevolutionary arms races, can systematically push organisms toward more complex traits. Methodological challenges have largely precluded experimental tests of these hypotheses. Using the Avida platform for digital evolution, we show that coevolution of hosts and parasites greatly increases organismal complexity relative to that otherwise achieved. As parasites evolve to counter the rise of resistant hosts, parasite populations retain a genetic record of past coevolutionary states. As a consequence, hosts differentially escape by performing progressively more complex functions. We show that coevolution's unique feedback between host and parasite frequencies is a key process in the evolution of complexity. Strikingly, the hosts evolve genomes that are also more phenotypically evolvable, similar to the phenomenon of contingency loci observed in bacterial pathogens. Because coevolution is ubiquitous in nature, our results support a general model whereby antagonistic interactions and natural selection together favor both increased complexity and evolvability. PMID:25514332

  8. Evolving Nature of Sexual Orientation and Gender Identity

    ERIC Educational Resources Information Center

    Jourian, T. J.

    2015-01-01

    This chapter discusses the historical and evolving terminology, constructs, and ideologies that inform the language used by those who are lesbian, gay, bisexual, and same-gender loving, who may identify as queer, as well as those who are members of trans* communities from multiple and intersectional perspectives.

  9. Optimists' Creed: Brave New Cyberlearning, Evolving Utopias (Circa 2041)

    ERIC Educational Resources Information Center

    Burleson, Winslow; Lewis, Armanda

    2016-01-01

    This essay imagines the role that artificial intelligence innovations play in the integrated living, learning and research environments of 2041. Here, in 2041, in the context of increasingly complex wicked challenges, whose solutions by their very nature continue to evade even the most capable experts, society and technology have co-evolved to…

  10. Does evolving the future preclude learning from it?

    PubMed

    Dowrick, Peter W

    2014-08-01

    Despite its considerable length, this article proposes a theory of human behavioral science that eschews half the evidence. There is irony in the title "Evolving the Future" when the featured examples of intentional change represent procedures that build slowly on the past. Has an opportunity been missed, or is an evolutionary perspective simply incompatible with learning from the future? PMID:25162866

  11. Hip Hop Is Now: An Evolving Youth Culture

    ERIC Educational Resources Information Center

    Taylor, Carl; Taylor, Virgil

    2007-01-01

    Emerging from Rap music, Hip Hop has become a lifestyle to many modern youth around the world. Embodying both creativity and controversy, Hip Hop mirrors the values, violence, and hypocrisy of modern culture. The authors dispel some of the simplistic views that surround this evolving youth movement embraced by millions of young people who are…

  12. The Evolving Military Learner Population: A Review of the Literature

    ERIC Educational Resources Information Center

    Ford, Kate; Vignare, Karen

    2015-01-01

    This literature review examines the evolving online military learner population with emphasis on current generation military learners, who are most frequently Post-9/11 veterans. The review synthesizes recent scholarly and grey literature on military learner demographics and attributes, college experiences, and academic outcomes against a backdrop…

  13. Towards Evolving Electronic Circuits for Autonomous Space Applications

    NASA Technical Reports Server (NTRS)

    Lohn, Jason D.; Haith, Gary L.; Colombano, Silvano P.; Stassinopoulos, Dimitris

    2000-01-01

    The relatively new field of Evolvable Hardware studies how simulated evolution can reconfigure, adapt, and design hardware structures in an automated manner. Space applications, especially those requiring autonomy, are potential beneficiaries of evolvable hardware. For example, robotic drilling from a mobile platform requires high-bandwidth controller circuits that are difficult to design. In this paper, we present automated design techniques based on evolutionary search that could potentially be used in such applications. First, we present a method of automatically generating analog circuit designs using evolutionary search and a circuit construction language. Our system allows circuit size (number of devices), circuit topology, and device values to be evolved. Using a parallel genetic algorithm, we present experimental results for five design tasks. Second, we investigate the use of coevolution in automated circuit design. We examine fitness evaluation by comparing the effectiveness of four fitness schedules. The results indicate that solution quality is highest with static and co-evolving fitness schedules as compared to the other two dynamic schedules. We discuss these results and offer two possible explanations for the observed behavior: retention of useful information, and alignment of problem difficulty with circuit proficiency.

  14. Do Infants Possess an Evolved Spider-Detection Mechanism?

    ERIC Educational Resources Information Center

    Rakison, David H.; Derringer, Jaime

    2008-01-01

    Previous studies with various non-human animals have revealed that they possess an evolved predator recognition mechanism that specifies the appearance of recurring threats. We used the preferential looking and habituation paradigms in three experiments to investigate whether 5-month-old human infants have a perceptual template for spiders that…

  15. A Conceptual Framework for Evolving, Recommender Online Learning Systems

    ERIC Educational Resources Information Center

    Peiris, K. Dharini Amitha; Gallupe, R. Brent

    2012-01-01

    A comprehensive conceptual framework is developed and described for evolving recommender-driven online learning systems (ROLS). This framework describes how such systems can support students, course authors, course instructors, systems administrators, and policy makers in developing and using these ROLS. The design science information systems…

  16. Today`s control systems evolved from early pioneers` dreams

    SciTech Connect

    Smith, D.J.

    1996-04-01

    In the last 100 years, power plant controls have evolved from manual operation and simple instruments to automatic state-of-the-art computerized control systems using smart instruments. This article traces the evolution of controls. The topics of the article include early control systems, developments in the early 20th century, Bailey controls, and developments in the late 20th century.

  17. You 3.0: The Most Important Evolving Technology

    ERIC Educational Resources Information Center

    Tamarkin, Molly; Bantz, David A.; Childs, Melody; diFilipo, Stephen; Landry, Stephen G.; LoPresti, Frances; McDonald, Robert H.; McGuthry, John W.; Meier, Tina; Rodrigo, Rochelle; Sparrow, Jennifer; Diggs, D. Teddy; Yang, Catherine W.

    2010-01-01

    That technology evolves is a given. Not as well understood is the impact of technological evolution on each individual--on oneself, one's skill development, one's career, and one's relationship with the work community. The authors believe that everyone in higher education will become an IT worker and that IT workers will be managing a growing…

  18. The Evolving Understanding of the Construct of Intellectual Disability

    ERIC Educational Resources Information Center

    Schalock, Robert L.

    2011-01-01

    This article addresses two major areas concerned with the evolving understanding of the construct of intellectual disability. The first part of the article discusses current answers to five critical questions that have revolved around the general question, "What is Intellectual Disability?" These five are what to call the phenomenon, how to…

  19. Evolving Strategies for Cancer and Autoimmunity: Back to the Future

    PubMed Central

    Lane, Peter J. L.; McConnell, Fiona M.; Anderson, Graham; Nawaf, Maher G.; Gaspal, Fabrina M.; Withers, David R.

    2014-01-01

    Although current thinking has focused on genetic variation between individuals and environmental influences as underpinning susceptibility to both autoimmunity and cancer, an alternative view is that human susceptibility to these diseases is a consequence of the way the immune system evolved. It is important to remember that the immunological genes that we inherit and the systems that they control were shaped by the drive for reproductive success rather than for individual survival. It is our view that human susceptibility to autoimmunity and cancer is the evolutionarily acceptable side effect of the immune adaptations that evolved in early placental mammals to accommodate a fundamental change in reproductive strategy. Studies of immune function in mammals show that high affinity antibodies and CD4 memory, along with its regulation, co-evolved with placentation. By dissection of the immunologically active genes and proteins that evolved to regulate this step change in the mammalian immune system, clues have emerged that may reveal ways of de-tuning both effector and regulatory arms of the immune system to abrogate autoimmune responses whilst preserving protection against infection. Paradoxically, it appears that such a detuned and deregulated immune system is much better equipped to mount anti-tumor immune responses against cancers. PMID:24782861

  20. Institutional Change of Universities as a Problem of Evolving Boundaries

    ERIC Educational Resources Information Center

    Vakkuri, Jarmo

    2004-01-01

    This paper examines institutional change in universities from the perspective of the notion of "boundaries". The paper asks: how can some of the most important regulatory and administrative changes in universities be understood in the framework of evolving boundaries? Two areas are studied empirically. First, the third mission of universities is…

  1. Tensions inherent in the evolving role of the infection preventionist

    PubMed Central

    Conway, Laurie J.; Raveis, Victoria H.; Pogorzelska-Maziarz, Monika; Uchida, May; Stone, Patricia W.; Larson, Elaine L.

    2014-01-01

    Background The role of infection preventionists (IPs) is expanding in response to demands for quality and transparency in health care. Practice analyses and survey research have demonstrated that IPs spend a majority of their time on surveillance and are increasingly responsible for prevention activities and management; however, deeper qualitative aspects of the IP role have rarely been explored. Methods We conducted a qualitative content analysis of in-depth interviews with 19 IPs at hospitals throughout the United States to describe the current IP role, specifically the ways that IPs effect improvements and the facilitators and barriers they face. Results The narratives document that the IP role is evolving in response to recent changes in the health care landscape and reveal that this progression is associated with friction and uncertainty. Tensions inherent in the evolving role of the IP emerged from the interviews as 4 broad themes: (1) expanding responsibilities outstrip resources, (2) shifting role boundaries create uncertainty, (3) evolving mechanisms of influence involve trade-offs, and (4) the stress of constant change is compounded by chronic recurring challenges. Conclusion Advances in implementation science, data standardization, and training in leadership skills are needed to support IPs in their evolving role. PMID:23880116

  2. An Evolved Wavelet Library Based on Genetic Algorithm

    PubMed Central

    Vaithiyanathan, D.; Seshasayanan, R.; Kunaraj, K.; Keerthiga, J.

    2014-01-01

    As the size of the images being captured increases, there is a need for a robust algorithm for image compression which satiates the bandwidth limitation of the transmitted channels and preserves the image resolution without considerable loss in the image quality. Many conventional image compression algorithms use wavelet transform which can significantly reduce the number of bits needed to represent a pixel and the process of quantization and thresholding further increases the compression. In this paper the authors evolve two sets of wavelet filter coefficients using genetic algorithm (GA), one for the whole image portion except the edge areas and the other for the portions near the edges in the image (i.e., global and local filters). Images are initially separated into several groups based on their frequency content, edges, and textures and the wavelet filter coefficients are evolved separately for each group. As there is a possibility of the GA settling in local maximum, we introduce a new shuffling operator to prevent the GA from this effect. The GA used to evolve filter coefficients primarily focuses on maximizing the peak signal to noise ratio (PSNR). The evolved filter coefficients by the proposed method outperform the existing methods by a 0.31 dB improvement in the average PSNR and a 0.39 dB improvement in the maximum PSNR. PMID:25405225

  3. Coevolution drives the emergence of complex traits and promotes evolvability.

    PubMed

    Zaman, Luis; Meyer, Justin R; Devangam, Suhas; Bryson, David M; Lenski, Richard E; Ofria, Charles

    2014-12-01

    The evolution of complex organismal traits is obvious as a historical fact, but the underlying causes--including the role of natural selection--are contested. Gould argued that a random walk from a necessarily simple beginning would produce the appearance of increasing complexity over time. Others contend that selection, including coevolutionary arms races, can systematically push organisms toward more complex traits. Methodological challenges have largely precluded experimental tests of these hypotheses. Using the Avida platform for digital evolution, we show that coevolution of hosts and parasites greatly increases organismal complexity relative to that otherwise achieved. As parasites evolve to counter the rise of resistant hosts, parasite populations retain a genetic record of past coevolutionary states. As a consequence, hosts differentially escape by performing progressively more complex functions. We show that coevolution's unique feedback between host and parasite frequencies is a key process in the evolution of complexity. Strikingly, the hosts evolve genomes that are also more phenotypically evolvable, similar to the phenomenon of contingency loci observed in bacterial pathogens. Because coevolution is ubiquitous in nature, our results support a general model whereby antagonistic interactions and natural selection together favor both increased complexity and evolvability.

  4. Evolvability suppression to stabilize far-sighted adaptations.

    PubMed

    Altenberg, Lee

    2005-01-01

    The opportunistic character of adaptation through natural selection can lead to evolutionary pathologies--situations in which traits evolve that promote the extinction of the population. Such pathologies include imprudent predation and other forms of habitat overexploitation, or the tragedy of the commons, adaptation to temporally unreliable resources, cheating and other antisocial behavior, infectious pathogen carrier states, parthenogenesis, and cancer, an intraorganismal evolutionary pathology. It is known that hierarchical population dynamics can protect a population from invasion by pathological genes. Can it also alter the genotype so as to prevent the generation of such genes in the first place, that is, suppress the evolvability of evolutionary pathologies? A model is constructed in which one locus controls the expression of the pathological trait, and a series of modifier loci exist that can prevent the expression of this trait. It is found that multiple evolvability checkpoint genes can evolve to prevent the generation of variants that cause evolutionary pathologies. The consequences of this finding are discussed.

  5. The Evolving Theme of Teaching Multicultural Art Education. Monograph Series.

    ERIC Educational Resources Information Center

    La Pierre, Sharon Greenleaf, Ed.; Ballengee-Morris, Christine, Ed.

    This publication, sponsored by the U.S. Society of Education through Art (USSEA) as a forum of past presidents involving audience participation, aims to stimulate dialogue on the evolving theme of teaching multicultural issues and what affects student learning. Session participants were past presidents of the USSEA who prepared written statements…

  6. The Evolving Significance of Race: Living, Learning, and Teaching

    ERIC Educational Resources Information Center

    Hughes, Sherick A., Ed.; Berry, Theodorea Regina, Ed.

    2012-01-01

    Individuals are living, learning, and teaching by questioning how to address race in a society that consistently prefers to see itself as colorblind, a society claiming to seek a "post-racial" existence. This edited volume offers evidence of the evolving significance of race from a diverse group of male and female contributors self-identifying as…

  7. 42 CFR 414.226 - Oxygen and oxygen equipment.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... different for stationary oxygen equipment than for portable oxygen equipment, the flow rate for the stationary equipment is used. (ii) If the prescribed flow rate is different for the patient at rest than for... amounts are separately calculated for the following items: (i) Stationary oxygen equipment and...

  8. High pressure oxygen furnace

    DOEpatents

    Morris, D.E.

    1992-07-14

    A high temperature high pressure oxygen furnace having a hybrid partially externally heated construction is disclosed. A metallic bar fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized, the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum). The disclosed alloy is fabricated into 11/4 inch bar stock and has a length of about 17 inches. This bar stock is gun drilled for over 16 inches of its length with 0.400 inch aperture to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the bar is provided with a small support aperture into which both a support and a thermocouple can be inserted. The closed end of the gun drilled bar is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior. 5 figs.

  9. High pressure oxygen furnace

    DOEpatents

    Morris, Donald E.

    1992-01-01

    A high temperature high pressure oxygen furnace having a hybrid partially externally heated construction is disclosed. A metallic bar fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized (the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum). The disclosed alloy is fabricated into 11/4 inch bar stock and has a length of about 17 inches. This bar stock is gun drilled for over 16 inches of its length with 0.400 inch aperture to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the bar is provided with a small support aperture into which both a support and a thermocouple can be inserted. The closed end of the gun drilled bar is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior.

  10. Integrated oxygen recovery system

    NASA Technical Reports Server (NTRS)

    Lee, M. Gene; Davenport, Ronald J.

    1993-01-01

    Life Systems has conceptualized an innovative Integrated Oxygen Recovery System (IORS) applicable to advanced mission air revitalization. The IORS provides the capability to electrochemically generate metabolic oxygen (O2) and recover O2 from the space habitat atmosphere via a carbon dioxide (CO2) reduction process within a single assembly. To achieve this capability, the IORS utilizes a Solid Metal Cathode (SMC) water electrolysis unit that simultaneously serves as the Sabatier CO2 reduction reactor. The IORS enables two major life support systems currently baselined in closed loop air revitalization systems to be combined into one smaller, less complex system. This concept reduces fluidic and electrical interface requirements and eliminates a hydrogen (H2) interface. Life Systems is performing an evaluation of the IORS process directed at demonstrating performance and quantifying key physical characteristics including power, weight, and volume. The results of the checkout, shakedown, and initial parametric tests are summarized.

  11. Integrated oxygen recovery system

    NASA Technical Reports Server (NTRS)

    Lee, M. Gene; Davenport, Ronald J.

    1993-01-01

    Life Systems has conceptualized an innovative Integrated Oxygen Recovery System (IORS) applicable to advanced mission air revitalization. The IORS provides the capability to electrochemically generate metabolic oxygen (O2) and recover O2 from the space habitat atmosphere via a carbon dioxide (CO2) reduction process within a single assembly. To achieve this capability, the IORS utilizes a Solid Metal Cathode (SMC) water electrolysis unit that simultaneously serves as the Sabatier CO2 reduction reactor. The IORS enables two major life support systems currently baselined in closed loop air revitalization systems to be combined into one smaller, less complex system. This concept reduces fluidic and electrical interface requirements and eliminates a hydrogen (H2) interface. Life Systems is performing an evaluation of the IORS process directed at demonstrating performance and quantifying key physical characteristics including power, weight, and volume. Technical progress achieved during the first two months of the program is summarized.

  12. Oxygen Transport Ceramic Membranes

    SciTech Connect

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-08-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In the previous research, the reference point of oxygen occupancy was determined and verified. In the current research, the oxygen occupancy was investigated at 1200 C as a function of oxygen activity and compared with that at 1000 C. The cause of bumps at about 200 C was also investigated by using different heating and cooling rates during TGA. The fracture toughness of LSFT and dual phase membranes at room temperature is an important mechanical property. Vicker's indentation method was used to evaluate this toughness. Through this technique, a K{sub Ic} (Mode-I Fracture Toughness) value is attained by means of semi-empirical correlations between the indentation load and the length of the cracks emanating from the corresponding Vickers indentation impression. In the present investigation, crack propagation behavior was extensively analyzed in order to understand the strengthening mechanisms involved in the non-transforming La based ceramic composites. Cracks were generated using Vicker's indenter and used to identify and evaluate the toughening mechanisms involved. Preliminary results of an electron microscopy study of the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appear to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. Modeling of the isotopic transients on operating membranes (LSCrF-2828 at 900 C) and a ''frozen'' isotope profile have been analyzed in conjunction with a 1-D model to reveal the gradient in oxygen diffusivity through the membrane under conditions of high chemical gradients.

  13. Oxygen Transport Ceramic Membranes

    SciTech Connect

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-02-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. The in situ electrical conductivity and Seebeck coefficient measurements were made on LSFT at 1000 and 1200 C over the oxygen activity range from air to 10{sup -15} atm. The electrical conductivity measurements exhibited a p to n type transition at an oxygen activity of 1 x 10{sup -10} at 1000 C and 1 x 10{sup -6} at 1200 C. Thermogravimetric studies were also carried out over the same oxygen activities and temperatures. Based on the results of these measurements, the chemical and mechanical stability range of LSFT were determined and defect structure was established. The studies on the fracture toughness of the LSFT and dual phase membranes exposed to air and N{sub 2} at 1000 C was done and the XRD and SEM analysis of the specimens were carried out to understand the structural and microstructural changes. The membranes that are exposed to high temperatures at an inert and a reactive atmosphere undergo many structural and chemical changes which affect the mechanical properties. A complete transformation of fracture behavior was observed in the N{sub 2} treated LSFT samples. Further results to investigate the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appear to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. Recent results on transient kinetic data are presented. The 2-D modeling of oxygen movement has been undertaken in order to fit isotope data. The model is used to study ''frozen'' profiles in patterned or composite membranes.

  14. Fuel cell oxygen electrode

    DOEpatents

    Shanks, H.R.; Bevolo, A.J.; Danielson, G.C.; Weber, M.F.

    An oxygen electrode for a fuel cell utilizing an acid electrolyte has a substrate of an alkali metal tungsten bronze of the formula: A/sub x/WO/sub 3/ where A is an alkali metal and x is at least 0.2, which is covered with a thin layer of platinum tungsten bronze of the formula: Pt/sub y/WO/sub 3/ where y is at least 0.8.

  15. Transport properties of oxygen

    NASA Technical Reports Server (NTRS)

    Roder, H. M.

    1983-01-01

    Tables of viscosity, thermal conductivity, and thermal diffusivity of oxygen as a function of temperature and pressure from the triple point to 320 K and at pressures to 100 MPa are presented. Auxiliary tables in engineering units are also given. Viscosity and thermal conductivity are calculated from published correlations. Density and specific heat at constant pressure, required to calculate thermal diffusivity, are obtained from an equation of state. The Prandtl number can be obtained quite easily from the values tabulated.

  16. Electrocatalyst for oxygen reduction

    NASA Technical Reports Server (NTRS)

    Swette, L. L. (Inventor)

    1971-01-01

    The performance and costs of an electrochemical catalyst as compared to a pure platinum catalyst is evaluated. The catalysts are used to reduce oxygen in low temperature alkaline fuel cells. The electrochemical catalyst is composed of silver and platinum and is dispersed in a resinous inert binder to provide a cell electrode. The results indicate the electrochemical catalyst is superior structurally to the platinum one for high current density operation, and is at least as active as the platinum catalyst in other operations.

  17. Fuel cell oxygen electrode

    DOEpatents

    Shanks, Howard R.; Bevolo, Albert J.; Danielson, Gordon C.; Weber, Michael F.

    1980-11-04

    An oxygen electrode for a fuel cell utilizing an acid electrolyte has a substrate of an alkali metal tungsten bronze of the formula: A.sub.x WO.sub.3 where A is an alkali metal and x is at least 0.2, which is covered with a thin layer of platinum tungsten bronze of the formula: Pt.sub.y WO.sub.3 where y is at least 0.8.

  18. Evolvable mathematical models: A new artificial Intelligence paradigm

    NASA Astrophysics Data System (ADS)

    Grouchy, Paul

    We develop a novel Artificial Intelligence paradigm to generate autonomously artificial agents as mathematical models of behaviour. Agent/environment inputs are mapped to agent outputs via equation trees which are evolved in a manner similar to Symbolic Regression in Genetic Programming. Equations are comprised of only the four basic mathematical operators, addition, subtraction, multiplication and division, as well as input and output variables and constants. From these operations, equations can be constructed that approximate any analytic function. These Evolvable Mathematical Models (EMMs) are tested and compared to their Artificial Neural Network (ANN) counterparts on two benchmarking tasks: the double-pole balancing without velocity information benchmark and the challenging discrete Double-T Maze experiments with homing. The results from these experiments show that EMMs are capable of solving tasks typically solved by ANNs, and that they have the ability to produce agents that demonstrate learning behaviours. To further explore the capabilities of EMMs, as well as to investigate the evolutionary origins of communication, we develop NoiseWorld, an Artificial Life simulation in which interagent communication emerges and evolves from initially noncommunicating EMM-based agents. Agents develop the capability to transmit their x and y position information over a one-dimensional channel via a complex, dialogue-based communication scheme. These evolved communication schemes are analyzed and their evolutionary trajectories examined, yielding significant insight into the emergence and subsequent evolution of cooperative communication. Evolved agents from NoiseWorld are successfully transferred onto physical robots, demonstrating the transferability of EMM-based AIs from simulation into physical reality.

  19. Atmospheric Oxygen Photoabsorption

    NASA Technical Reports Server (NTRS)

    Slanger, Tom G.

    1996-01-01

    The work conducted on this grant was devoted to various aspects of the photophysics and photochemistry of the oxygen molecule. Predissociation linewidths were measured for several vibrational levels in the O2(B3 Sigma(sub u)(sup -)) state, providing good agreement with other groups working on this important problem. Extensive measurements were made on the loss kinetics of vibrationally excited oxygen, where levels between v = 5 and v = 22 were investigated. Cavity ring-down spectroscopy was used to measure oscillator strengths in the oxygen Herzberg bands. The great sensitivity of this technique made it possible to extend the known absorption bands to the dissociation limit as well as providing many new absorption lines that seem to be associated with new O2 transitions. The literature concerning the Herzberg band strengths was evaluated in light of our new measurements, and we made recommendations for the appropriate Herzberg continuum cross sections to be used in stratospheric chemistry. The transition probabilities for all three Herzberg band systems were re-evaluated, and we are recommending a new set of values.

  20. Evolution of Oxygenic Photosynthesis

    NASA Astrophysics Data System (ADS)

    Fischer, Woodward W.; Hemp, James; Johnson, Jena E.

    2016-06-01

    The origin of oxygenic photosynthesis was the most important metabolic innovation in Earth history. It allowed life to generate energy and reducing power directly from sunlight and water, freeing it from the limited resources of geochemically derived reductants. This greatly increased global primary productivity and restructured ecosystems. The release of O2 as an end product of water oxidation led to the rise of oxygen, which dramatically altered the redox state of Earth's atmosphere and oceans and permanently changed all major biogeochemical cycles. Furthermore, the biological availability of O2 allowed for the evolution of aerobic respiration and novel biosynthetic pathways, facilitating much of the richness we associate with modern biology, including complex multicellularity. Here we critically review and synthesize information from the geological and biological records for the origin and evolution of oxygenic photosynthesis. Data from both of these archives illustrate that this metabolism first appeared in early Paleoproterozoic time and, despite its biogeochemical prominence, is a relatively late invention in the context of our planet's history.