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Sample records for alpha-active iridium isotopes

  1. Discovery of tantalum, rhenium, osmium, and iridium isotopes

    SciTech Connect

    Robinson, R.; Thoennessen, M.

    2012-09-15

    Currently, thirty-eight tantalum, thirty-eight rhenium, thirty-nine osmium, and thirty-eight iridium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  2. Iridium isotope ratio measurements by negative thermal ionization mass spectrometry and atomic weight of iridium

    NASA Astrophysics Data System (ADS)

    Walczyk, Thomas; Heumann, Klaus G.

    1993-02-01

    A technique of negative thermal ionization mass spectrometry (NTI-MS) for the precise iridium isotope ratio determination is presented. IrO-2 and IrO-3 ions are formed in a double-filament (Pt) ion source using (NH4)2IrCl6 as a sample compound. The IrO-2 ion current always exceeds the IrO-3 current by a factor of about 50-300 depending on the filament temperature and the oxygen gas introduced into the ion source. IrO-3 ion currents of more than 10-11 A can be obtained at the detector side from 100 ng iridium samples. The relative standard deviation of the 191Ir/193 ratio determination is 0.06%, which is much better than the data quoted in past literature. From such data the atomic weight of iridium could be calculated to be 192.21661 ± 0.00029. This value is a great improvement when compared with the iridium atomic weight of 192.22 ± 0.03 recommended by IUPAC. Additionally, an NTI-MS technique has been developed which allows the simultaneous measurement of iridium and osmium isotope ratio from osmiridium samples without any chemical separation. The iridium isotope ratios of three osmiridium samples agree well with the ratios determined from the hexachloroiridate compound. The direct 187Os/186OS determination from osmiridium samples opens the possibility of studying the evolution of osmium in the Earth's mantle due to the radioactive decay of 187Re into 187Os.

  3. Characterization of Tank 48H Samples for Alpha Activity and Actinide Isotopics

    SciTech Connect

    Hobbs, D.T.; Coleman, C.J.; Hay, M.S.

    1995-12-04

    This document reports the total alpha activity and actinide isotopic results for samples taken from Tank 48H prior to the addition of sodium tetraphenylborate and MST in Batch {number_sign}1 of the ITP process. This information used to determine the quantity of MST for Batch {number_sign}1 of the ITP process and the total actinide content in the tank for dose calculations.

  4. Anion effects to deliver enhanced iridium catalysts for hydrogen isotope exchange processes.

    PubMed

    Kennedy, Alan R; Kerr, William J; Moir, Rory; Reid, Marc

    2014-10-28

    Synthesis of a series of iridium(I) complexes of the type [(COD)Ir(IMes)(PPh3)]X (X = BF4, OTf, and BArF) has been established. Application of these species in mild hydrogen isotope exchange processes revealed more efficient catalysis and, further, a wider solvent scope when employing larger, more weakly coordinating counterions. PMID:25208265

  5. Formic acid dehydrogenation with bioinspired iridium complexes: a kinetic isotope effect study and mechanistic insight.

    PubMed

    Wang, Wan-Hui; Xu, Shaoan; Manaka, Yuichi; Suna, Yuki; Kambayashi, Hide; Muckerman, James T; Fujita, Etsuko; Himeda, Yuichiro

    2014-07-01

    Highly efficient hydrogen generation from dehydrogenation of formic acid is achieved by using bioinspired iridium complexes that have hydroxyl groups at the ortho positions of the bipyridine or bipyrimidine ligand (i.e., OH in the second coordination sphere of the metal center). In particular, [Ir(Cp*)(TH4BPM)(H2 O)]SO4 (TH4BPM: 2,2',6,6'-tetrahydroxyl-4,4'-bipyrimidine; Cp*: pentamethylcyclopentadienyl) has a high turnover frequency of 39 500 h(-1) at 80 °C in a 1 M aqueous solution of HCO2 H/HCO2 Na and produces hydrogen and carbon dioxide without carbon monoxide contamination. The deuterium kinetic isotope effect study clearly indicates a different rate-determining step for complexes with hydroxyl groups at different positions of the ligands. The rate-limiting step is β-hydrogen elimination from the iridium-formate intermediate for complexes with hydroxyl groups at ortho positions, owing to a proton relay (i.e., pendent-base effect), which lowers the energy barrier of hydrogen generation. In contrast, the reaction of iridium hydride with a proton to liberate hydrogen is demonstrated to be the rate-determining step for complexes that do not have hydroxyl groups at the ortho positions.

  6. Refining Radchem Detectors: Iridium

    NASA Astrophysics Data System (ADS)

    Arnold, C. W.; Bredeweg, T. A.; Vieira, D. J.; Bond, E. M.; Jandel, M.; Rusev, G.; Moody, W. A.; Ullmann, J. L.; Couture, A. J.; Mosby, S.; O'Donnell, J. M.; Haight, R. C.

    2013-10-01

    Accurate determination of neutron fluence is an important diagnostic of nuclear device performance, whether the device is a commercial reactor, a critical assembly or an explosive device. One important method for neutron fluence determination, generally referred to as dosimetry, is based on exploiting various threshold reactions of elements such as iridium. It is possible to infer details about the integrated neutron energy spectrum to which the dosimetry sample or ``radiochemical detector'' was exposed by measuring specific activation products post-irradiation. The ability of radchem detectors like iridium to give accurate neutron fluence measurements is limited by the precision of the cross-sections in the production/destruction network (189Ir-193Ir). The Detector for Advanced Neutron Capture Experiments (DANCE) located at LANSCE is ideal for refining neutron capture cross sections of iridium isotopes. Recent results from a measurement of neutron capture on 193-Ir are promising. Plans to measure other iridium isotopes are underway.

  7. Chromium-Isotope and iridium-Abundance Measurements for Late Eocene Impact-Derived Spherule Deposits

    NASA Astrophysics Data System (ADS)

    Kyte, F. T.; Shukolyukov, A.; Hildebrand, A. R.; Lugmair, G. W.; Hanova, J.

    2004-05-01

    The late Eocene (approx. 35 Ma) was a time of multiple large body impacts superimposed within an interval of dust accretion. At least two spherule layers are preserved in deep sea sediments: North American microtektites and the slightly older cpx spherules. The two largest impact structures in the Cenozoic, the 45 km Chesapeake Bay structure and the 100 km Popigai structure, are indicated as the respective spherule sources. Enhanced 3He concentrations extending across a 3 m.y. duration in upper Eocene sediments from the Massignano quarry in Italy indicate accretion of <50 micron dust over this time interval. To characterize one of the impactors we have analyzed splits from the 125-250 micron cpx spherules from ODP 709C, and two fractions from the Massignano layer. Splits of each sample were analyzed for minor and trace elements by instrumental activation analysis (INAA) including Ir, Cr, Fe, Ni, and Co. Additional splits were analyzed for their Cr-isotopic composition, using thermal ionization mass spectrometry. Significant concentrations of Ir were found in all samples, with the highest levels in the Massignano coarse sample and the lowest in the 709C sample. In all cases, element/Ir ratios are much higher than in chondritic meteorites; this may reflect elemental fractionation due to preferential concentration of Cr in spinel growing in the impact fireball. The Cr-isotopic compositions of the 709C and Massignano coarse samples are both non-terrestrial with a positive epsilon 53, indicating a 53Cr/52Cr ratio higher than in terrestrial materials. Microprobe surveys showed that the Massignano samples had significant fine grained oxide grains (mixed with the spherules in the coarse sample) that were not Ni- or Cr-rich, including Ti-rich spinels (likely terrestrial contaminants). In contrast, the ODP 709C sample is a pure extract of generally well-preserved cpx spherules composed of clinopyroxene in a glass matrix. Both the Massignano coarse and the 709C cpx samples

  8. Carbon isotope curve and iridium anomaly in the Albian-Cenomanian paleoceanic deposits of the Eastern Kamchatka

    NASA Astrophysics Data System (ADS)

    Savelyev, D. P.; Savelyeva, O. L.; Palechek, T. N.; Pokrovsky, B. G.

    2012-04-01

    determined contents of carbon and oxygen stable isotopes in limestones and have compared the received results to isotope curves of other regions. In studied section the curve of d13C is characterized by a clearly expressed positive shift at the level of the lower carbonaceous bed. Below it and in the overlapping stratum of siliceous limestone (1 cm thickness) d13C has the values of 1.9-2.1 pro mille and above it d13C increases up to 2.5-3 pro mille. The precise d13C maximum after a sharp shift is correlatable with the form of a d13C curve of the Middle Cenomanian Tethyan sections. Accordingly, it is possible to assert, that the lower carbonaceous bed was formed during the mid-Cenomanian anoxic event (MCE). Gradual increase of d13C in the upper part of our section is similar to change of d13C in Upper Cenomanian fragments of Tethyan sections, i.e. the lower carbonaceous bed corresponds to anoxic event at the Cenomanian/Turonian boundary (OAE2). Neutron activation analysis indicates increased up to 9 ppb concentration of Ir at the bottom of the lower carbonaceous bed (inorganic part of the sample was analyzed comprising 46% of the bulk rock). This anomaly correlates in the studied section with a positive shift of d13C. Taking into account radiolarian age data this allows to correlate the anomaly with the MCE. A source of iridium and other elements of the platinum group could be basalts and hyaloclastites from the eruptions during the sedimentation period. Anoxic conditions promoted deposit enrichment in ore elements. This work was supported by the RFBR (No. 10-05-00065).

  9. Iridium in natural waters

    SciTech Connect

    Anbar, A.D.; Wasserburg, G.J.; Papanastassiou, D.A.

    1996-09-13

    Iridium, commonly used as a tracer of extraterrestrial material, was measured in rivers, oceans, and an estuarine environment. The concentration of iridium in the oceans ranges from 3.0 ({+-}1.3) x 10{sup 8} to 5.7 ({+-}0.8) x 10{sup 8} atoms per kilogram. Rivers contain from 17.4 ({+-}0.9) x 10{sup 8} to 92.9 ({+-}2.2) x 10{sup 8} atoms per kilogram and supply more dissolved iridium to the oceans than do extraterrestrial sources. In the Baltic Sea, {approximately}75% of riverine iridium is removed from solution. Iron-manganese oxyhydroxides scavenge iridium under oxidizing conditions, but anoxic environments are not a major sink for iridium. The ocean residence time of iridium is between 2 x 10{sup 3} and 2 x 10{sup 4} years. 32 refs., 3 figs., 1 tab.

  10. Scientists use GEANIE to Study Isotopes of Iridium and Europium to Improve Radiochemical Diagnostics in Nuclear Devices

    SciTech Connect

    Becker, J A; Nelson, R

    2002-11-21

    Radiochemical diagnostics play an important role in helping scientists understand the detonation of a nuclear device. Sometimes some elements or isotopes are inserted as radiochemical detectors at various locations in the nuclear device. During the detonation of the device, these detectors are subjected for a short time to the intense flux of neutrons emitted through fission and possibly through fusion of light elements (usually deuterium and tritium). After the detonation, the radiochemical detectors and their long-lived activation products are retrieved from the area where the underground explosion took place. These radiochemical samples are analyzed to extract information about how the device operated. A large amount of such radiochemical data exist from past nuclear-device tests.

  11. Processing of Iridium and Iridium Alloys

    SciTech Connect

    Ohriner, Evan Keith

    2008-01-01

    Iridium and its alloys have been considered to be difficult to fabricate due to their high melting temperatures, limited ductility, sensitivity to impurity content, and chemical properties. The variety of processing methods used for iridium and its alloys are reviewed, including purification, melting, forming, joining, and powder metallurgy techniques. Also included are coating and forming by the methods of electroplating, chemical and physical vapor deposition, and melt particle deposition.

  12. Low energy cyclotron production and cyclometalation chemistry of iridium-192.

    PubMed

    Langille, G; Yang, H; Zeisler, S K; Hoehr, C; Storr, T; Andreoiu, C; Schaffer, P

    2016-09-01

    This work demonstrates the labelling of a novel class of iridium lumophore with radioiridium, as proof-of-feasibility for producing and using the medically useful isotope iridium-192. Natural osmium was electroplated onto silver target backings in basic media and irradiated for up to two hours with ≤20μA of 12.8MeV protons. A range of iridium isotopes were generated, characterized and quantified using γ-spectroscopy methods. The target material was removed from the backings via oxidative dissolution with hydrogen peroxide, and the iridium radioisotopes isolated using an anion exchange resin. Both no-carrier-added as well as carrier-added formulations were then used in subsequent cyclometalation reactions. PMID:27344003

  13. Iridium Interfacial Stack (IRIS)

    NASA Technical Reports Server (NTRS)

    Spry, David James (Inventor)

    2015-01-01

    An iridium interfacial stack ("IrIS") and a method for producing the same are provided. The IrIS may include ordered layers of TaSi.sub.2, platinum, iridium, and platinum, and may be placed on top of a titanium layer and a silicon carbide layer. The IrIS may prevent, reduce, or mitigate against diffusion of elements such as oxygen, platinum, and gold through at least some of its layers.

  14. Prestimulus EEG alpha activity reflects temporal expectancy.

    PubMed

    Min, Byoung-Kyong; Park, Jin Young; Kim, Eun Joo; Kim, Joong Il; Kim, Jae-Jin; Park, Hae-Jeong

    2008-06-27

    Since prestimulus EEG alpha activity has recently been considered to convey prestimulus top-down processing, we investigated whether prestimulus alpha activity reflects temporal expectancy of upcoming stimulation even under the non-classical contingent negative variation (CNV) paradigm. EEG was recorded from 16 subjects performing a color and a shape discrimination task manipulated with constant and variable inter-stimulus interval (ISI) conditions. The power of oscillatory activity was investigated by convolving the EEG signals with Morlet wavelets. The constant ISI condition yielded significantly shorter reaction times than the variable ISI condition, indicating more efficient preparation for upcoming stimuli during the constant ISI. We found significantly higher prestimulus alpha activity in the constant ISI condition than in the variable ISI condition, but no significant CNV even in the constant ISI condition. Such a reflection of temporal expectancy in the prestimulus alpha activity corroborates that the prestimulus top-down mental state for preparing upcoming task-performance is considerably reflected in the prestimulus ongoing alpha activity. PMID:18486342

  15. Iridium: failures & successes

    NASA Astrophysics Data System (ADS)

    Christensen, CarissaBryce; Beard, Suzette

    2001-03-01

    This paper will provide an overview of the Iridium business venture in terms of the challenges faced, the successes achieved, and the causes of the ultimate failure of the venture — bankruptcy and system de-orbit. The paper will address technical, business, and policy issues. The intent of the paper is to provide a balanced and accurate overview of the Iridium experience, to aid future decision-making by policy makers, the business community, and technical experts. Key topics will include the history of the program, the objectives and decision-making of Motorola, the market research and analysis conducted, partnering strategies and their impact, consumer equipment availability, and technical issues — target performance, performance achieved, technical accomplishments, and expected and unexpected technical challenges. The paper will use as sources trade media and business articles on the Iridium program, technical papers and conference presentations, Wall Street analyst's reports, and, where possible, interviews with participants and close observers.

  16. Laser spectroscopy of iridium monoboride

    NASA Astrophysics Data System (ADS)

    Ye, Jianjun; Pang, H. F.; Wong, A. M.-Y.; Leung, J. W.-H.; Cheung, A. S.-C.

    2008-04-01

    High resolution laser induced fluorescence spectrum of IrB in the spectral region between 545 and 610nm has been recorded and analyzed. Reacting laser-ablated iridium atoms with 1% B2H6 seeded in argon produced the IrB molecule. This is the first experimental observation of the IrB molecule. Four vibronic transition bands, (v,0) with v =0-3 of an electronic transition system, have been observed. Spectra of all four isotopic molecules, Ir191B10, Ir193B10, Ir191B11, and Ir193B11, were recorded. Isotopic relationships confirmed the carrier of the spectra and the vibrational quantum number assignment. Preliminary analysis of rotational lines showed that these vibronic bands are with Ω'=2 and Ω″=3. The electronic transition identified is assigned as the [16.5]Π23-XΔ33 system. Partially resolved hyperfine structure which conforms to the Hund's case aβ coupling scheme has been observed and analyzed. The bond length r0 of the lower XΔ33 state of IrB was determined to be 1.7675Å.

  17. Method for refining contaminated iridium

    DOEpatents

    Heshmatpour, B.; Heestand, R.L.

    1982-08-31

    Contaminated iridium is refined by alloying it with an alloying agent selected from the group consisting of manganese and an alloy of manganese and copper, and then dissolving the alloying agent from the formed alloy to provide a purified iridium powder.

  18. Method for refining contaminated iridium

    DOEpatents

    Heshmatpour, Bahman; Heestand, Richard L.

    1983-01-01

    Contaminated iridium is refined by alloying it with an alloying agent selected from the group consisting of manganese and an alloy of manganese and copper, and then dissolving the alloying agent from the formed alloy to provide a purified iridium powder.

  19. Laser Spectroscopy of Iridium Monochloride

    NASA Astrophysics Data System (ADS)

    Linton, Colan; Adam, Allan G.; Foran, Samantha; Ma, Tongmei; Steimle, Timothy

    2016-06-01

    Iridium monochloride (IrCl) molecules have been produced in the gas phase using laser ablation sources at the University of New Brunswick (UNB) and Arizona State University (ASU). Low resolution laser induced fluorescence (LIF) spectra, obtained at UNB using a pulsed dye laser, showed three bands at 557, 545 and 534 nm which appeared to form an upper state vibrational progression. Dispersed fluorescence (DF) spectra, obtained by exciting each band at its band head frequency, showed a ground state vibrational progression extending from v=0 to 6. High resolution spectra (FWHM=0.006 wn), taken using a cw ring dye laser, showed resolved rotational lines, broadened by unresolved Ir (I=3/2) hyperfine structure, in both the 193Ir35Cl and 191Ir35Cl isotopologues. Vibrational assignments of 0-0, 1-0 and 2-0 for the three bands were determined from the isotope structure and the rotational analysis showed the transition to be ^3Φ_4 - ^3Φ_4, similar to that previously observed in IrF. Higher resolution spectra (FWHM=0.001 wn) of the 1-0 band, obtained at ASU, showed resolved hyperfine structure from which the magnetic and quadrupole hyperfine parameters in the ground and excited states were determined. The interpretation of the hyperfine parameters in terms of the electron configurations will be presented along with a comparison of the properties of IrCl and IrF.

  20. Miniature Neutron-Alpha Activation Spectrometer

    NASA Astrophysics Data System (ADS)

    Rhodes, Edgar; Holloway, James Paul; He, Zhong; Goldsten, John

    2002-10-01

    We are developing a miniature neutron-alpha activation spectrometer for in-situ analysis of chem-bio samples, including rocks, fines, ices, and drill cores, suitable for a lander or Rover platform for Mars or outer-planet missions. In the neutron-activation mode, penetrating analysis will be performed of the whole sample using a γ spectrometer and in the α-activation mode, the sample surface will be analyzed using Rutherford-backscatter and x-ray spectrometers. Novel in our approach is the development of a switchable radioactive neutron source and a small high-resolution γ detector. The detectors and electronics will benefit from remote unattended operation capabilities resulting from our NEAR XGRS heritage and recent development of a Ge γ detector for MESSENGER. Much of the technology used in this instrument can be adapted to portable or unattended terrestrial applications for detection of explosives, chemical toxins, nuclear weapons, and contraband.

  1. Solar abundance of iridium

    PubMed Central

    Drake, Stephen; Aller, Lawrence H.

    1976-01-01

    By a method of spectrum synthesis, which yields log gfA, where g is the statistical weight of the lower level, f is the oscillator strength, and A is the abundance, an attempt is made to deduce the solar iridium abundance from one relatively unblended, but fairly weak IrI line, λ 3220.78 Å. If the Corliss-Bozman f-value for this line is adopted, we find log A(Ir) = 0.82 on the scale log A(H) = 12.00. The discordance with the value found from carbonaceous chondrites may arise from faulty f-values or from difficulties arising from line blending in this far ultraviolet domain of the solar spectrum. PMID:16578735

  2. Mononuclear iridium dinitrogen complexes bonded to zeolite HY

    SciTech Connect

    Yang, Dong; Chen, Mingyang; Martinez-Macias, Claudia; Dixon, David A.; Gates, Bruce C.

    2014-11-07

    In this study, the adsorption of N2 on structurally well-defined dealuminated HY zeolite-supported iridium diethylene complexes was investigated. Iridium dinitrogen complexes formed when the sample was exposed to N2 in H2 at 298 K, as shown by infrared spectra recorded with isotopically labeled N2. Four supported species formed in various flowing gases: Ir(N2), Ir(N2)(N2), Ir(C2H5)(N2), and Ir(H)(N2). Their interconversions are summarized in a reaction network, showing, for example, that, in the presence of N2, Ir(N2) was the predominant dinitrogen species at temperatures of 273-373 K. Ir(CO)(N2) formed transiently in flowing CO, and in the presence of H2, rather stable iridium hydride complexes formed. Here, four structural models of each iridium complex bonded at the acidic sites of the zeolite were employed in a computational investigation, showing that the calculated vibrational frequencies agree well with experiment when full calculations are done at the level of density functional theory, independent of the size of the model of the zeolite.

  3. Hydridomethyl iridium complex

    DOEpatents

    Bergman, Robert G.; Buchanan, J. Michael; Stryker, Jeffrey M.; Wax, Michael J.

    1989-01-01

    A process for functionalizing methane comprising: (a) reacting methane with a hydridoalkyl metal complex of the formula: CpIr[P(R.sub.1).sub.3 ]H(R.sub.2) wherein Cp represents a cyclopentadienyl or alkylcyclopentadienyl radical having from 1 to 5 carbon atoms; Ir represents an iridium atom; P represents a phosphorus atom; R.sub.1 represents an alkyl group; R.sub.2 represents an alkyl group having at least two carbon atoms; and H represents a hydrogen atom, in the presence of a liquid alkane R.sub.3 H having at least three carbon atoms to form a hydridomethyl complex of the formula: CpIr[P(R.sub.1).sub.3 ]HMe where Me represents a methyl radical. (b) reacting said hydridomethyl complex with an organic halogenating agent such as a tetrahalomethane or a haloform of the formulas: CX'X"X'"X"" or CHX'X"X'"; wherein X', X", X"', and X"" represent halogens selected from bromine, iodine and chlorine, to halomethyl complex of step (a) having the formula: CpIr[P(R.sub.1).sub.3 ]MeX: (c) reacting said halomethyl complex with a mercuric halide of the formula HgX.sub.2 to form a methyl mercuric halide of the formula HgMeX; and (d) reacting said methyl mercuric halide with a molecular halogen of the formula X.sub.2 to form methyl halide.

  4. A novel self-guided approach to alpha activity training.

    PubMed

    van Boxtel, Geert J M; Denissen, Ad J M; Jäger, Mark; Vernon, David; Dekker, Marian K J; Mihajlović, Vojkan; Sitskoorn, Margriet M

    2012-03-01

    Fifty healthy participants took part in a double-blind placebo-controlled study in which they were either given auditory alpha activity (8-12Hz) training (N=18), random beta training (N=12), or no training at all (N=20). A novel wireless electrode system was used for training without instructions, involving water-based electrodes mounted in an audio headset. Training was applied approximately at central electrodes. Post-training measurement using a conventional full-cap EEG system revealed a 10% increase in alpha activity at posterior sites compared to pre-training levels, when using the conventional index of alpha activity and a non-linear regression fit intended to model individual alpha frequency. This statistically significant increase was present only in the group that received the alpha training, and remained evident at a 3 month follow-up session, especially under eyes open conditions where an additional 10% increase was found. In an exit interview, approximately twice as many participants in the alpha training group (53%) mentioned that the training was relaxing, compared to those in either the beta (20%) or no training (21%) control groups. Behavioural measures of stress and relaxation were indicative of effects of alpha activity training but failed to reach statistical significance. These results are discussed in terms of a lack of statistical power. Overall, results suggest that self-guided alpha activity training using this novel system is feasible and represents a step forward in the ease of instrumental conditioning of brain rhythms.

  5. Mononuclear iridium dinitrogen complexes bonded to zeolite HY

    DOE PAGES

    Yang, Dong; Chen, Mingyang; Martinez-Macias, Claudia; Dixon, David A.; Gates, Bruce C.

    2014-11-07

    In this study, the adsorption of N2 on structurally well-defined dealuminated HY zeolite-supported iridium diethylene complexes was investigated. Iridium dinitrogen complexes formed when the sample was exposed to N2 in H2 at 298 K, as shown by infrared spectra recorded with isotopically labeled N2. Four supported species formed in various flowing gases: Ir(N2), Ir(N2)(N2), Ir(C2H5)(N2), and Ir(H)(N2). Their interconversions are summarized in a reaction network, showing, for example, that, in the presence of N2, Ir(N2) was the predominant dinitrogen species at temperatures of 273-373 K. Ir(CO)(N2) formed transiently in flowing CO, and in the presence of H2, rather stable iridiummore » hydride complexes formed. Here, four structural models of each iridium complex bonded at the acidic sites of the zeolite were employed in a computational investigation, showing that the calculated vibrational frequencies agree well with experiment when full calculations are done at the level of density functional theory, independent of the size of the model of the zeolite.« less

  6. Iridium material for hydrothermal oxidation environments

    DOEpatents

    Hong, Glenn T.; Zilberstein, Vladimir A.

    1996-01-01

    A process for hydrothermal oxidation of combustible materials in which, during at least a part of the oxidation, corrosive material is present and makes contact with at least a portion of the apparatus over a contact area on the apparatus. At least a portion of the contact surface area comprises iridium, iridium oxide, an iridium alloy, or a base metal overlaid with an iridium coating. Iridium has been found to be highly resistant to environments encountered in the process of hydrothermal oxidation. Such environments typically contain greater than 50 mole percent water, together with oxygen, carbon dioxide, and a wide range of acids, bases and salts. Pressures are typically about 27.5 to about 1000 bar while temperatures range as high as 800.degree. C.

  7. Electronic Structure of Iridium Clusters on Graphene

    NASA Astrophysics Data System (ADS)

    Barker, Bradford A.; Bradley, Aaron J.; Ugeda, Miguel M.; Coh, Sinisa; Zettl, Alex; Crommie, Michael F.; Cohen, Marvin L.; Louie, Steven G.

    2015-03-01

    Graphene was predicted to exhibit non-trivial Z2 topology, but its exceedingly weak spin-orbit coupling prevented this from being observed. Previous theoretical work has proposed enhancing the spin-orbit coupling strength by depositing individual adatoms adsorbed onto the surface of graphene. We show experimental evidence that the iridium adatoms cluster, with a cluster size of at least two atoms. We investigate through theoretical calculations the orientation of the iridium dimers on graphene, contrast the electronic structure of iridium dimers with iridium monomers, and compare the theoretical iridium dimer electronic structure calculations with the experimental results determined via scanning tunneling spectroscopy. This work was supported by NSF Grant No. DMR10-1006184 and U.S. DOE under Contract No. DE-AC02-05CH11231. Computational resources have been provided by DOE at LBNL's NERSC facility.

  8. Lucid dreaming and alpha activity: a preliminary report.

    PubMed

    Ogilvie, R D; Hunt, H T; Tyson, P D; Lucescu, M L; Jeakins, D B

    1982-12-01

    10 good dream recallers spent 2 nights in the sleep lab during which they were awakened 4 times per night from REM sleep, twice during their highest alpha activity in REM, and twice during low REM alpha. 5 were given alpha feedback training prior to sleep onset. Arousals from high alpha REM sleep yielded significantly higher lucidity ratings. Alpha feedback had no effect upon lucidity or REM alpha levels. Similarities between lucid dreams and meditative phenomena are discussed. PMID:7162915

  9. Lucid dreaming and alpha activity: a preliminary report.

    PubMed

    Ogilvie, R D; Hunt, H T; Tyson, P D; Lucescu, M L; Jeakins, D B

    1982-12-01

    10 good dream recallers spent 2 nights in the sleep lab during which they were awakened 4 times per night from REM sleep, twice during their highest alpha activity in REM, and twice during low REM alpha. 5 were given alpha feedback training prior to sleep onset. Arousals from high alpha REM sleep yielded significantly higher lucidity ratings. Alpha feedback had no effect upon lucidity or REM alpha levels. Similarities between lucid dreams and meditative phenomena are discussed.

  10. On the dissolution of iridium by aluminum.

    SciTech Connect

    Hewson, John C.

    2009-08-01

    The potential for liquid aluminum to dissolve an iridium solid is examined. Substantial uncertainties exist in material properties, and the available data for the iridium solubility and iridium diffusivity are discussed. The dissolution rate is expressed in terms of the regression velocity of the solid iridium when exposed to the solvent (aluminum). The temperature has the strongest influence in the dissolution rate. This dependence comes primarily from the solubility of iridium in aluminum and secondarily from the temperature dependence of the diffusion coefficient. This dissolution mass flux is geometry dependent and results are provided for simplified geometries at constant temperatures. For situations where there is negligible convective flow, simple time-dependent diffusion solutions are provided. Correlations for mass transfer are also given for natural convection and forced convection. These estimates suggest that dissolution of iridium can be significant for temperatures well below the melting temperature of iridium, but the uncertainties in actual rates are large because of uncertainties in the physical parameters and in the details of the relevant geometries.

  11. Cortical alpha activity predicts the confidence in an impending action

    PubMed Central

    Kubanek, Jan; Hill, N. Jeremy; Snyder, Lawrence H.; Schalk, Gerwin

    2015-01-01

    When we make a decision, we experience a degree of confidence that our choice may lead to a desirable outcome. Recent studies in animals have probed the subjective aspects of the choice confidence using confidence-reporting tasks. These studies showed that estimates of the choice confidence substantially modulate neural activity in multiple regions of the brain. Building on these findings, we investigated the neural representation of the confidence in a choice in humans who explicitly reported the confidence in their choice. Subjects performed a perceptual decision task in which they decided between choosing a button press or a saccade while we recorded EEG activity. Following each choice, subjects indicated whether they were sure or unsure about the choice. We found that alpha activity strongly encodes a subject's confidence level in a forthcoming button press choice. The neural effect of the subjects' confidence was independent of the reaction time and independent of the sensory input modeled as a decision variable. Furthermore, the effect is not due to a general cognitive state, such as reward expectation, because the effect was specifically observed during button press choices and not during saccade choices. The neural effect of the confidence in the ensuing button press choice was strong enough that we could predict, from independent single trial neural signals, whether a subject was going to be sure or unsure of an ensuing button press choice. In sum, alpha activity in human cortex provides a window into the commitment to make a hand movement. PMID:26283892

  12. Resting alpha activity predicts learning ability in alpha neurofeedback

    PubMed Central

    Wan, Feng; Nan, Wenya; Vai, Mang I.; Rosa, Agostinho

    2014-01-01

    Individuals differ in their ability to learn how to regulate the brain activity by neurofeedback. This study aimed to investigate whether the resting alpha activity can predict the learning ability in alpha neurofeedback. A total of 25 subjects performed 20 sessions of individualized alpha neurofeedback and the learning ability was assessed by three indices respectively: the training parameter changes between two periods, within a short period and across the whole training time. It was found that the resting alpha amplitude measured before training had significant positive correlations with all learning indices and could be used as a predictor for the learning ability prediction. This finding would help the researchers in not only predicting the training efficacy in individuals but also gaining further insight into the mechanisms of alpha neurofeedback. PMID:25071528

  13. Tracking variations in the alpha activity in an electroencephalogram

    NASA Technical Reports Server (NTRS)

    Prabhu, K. S.

    1971-01-01

    The problem of tracking Alpha voltage variations in an electroencephalogram is discussed. This problem is important in encephalographic studies of sleep and effects of different stimuli on the brain. Very often the Alpha voltage is tracked by passing the EEG signal through a bandpass filter centered at the Alpha frequency, which hopefully will filter out unwanted noise from the Alpha activity. Some alternative digital techniques are suggested and their performance is compared with the standard technique. These digital techniques can be used in an environment where an electroencephalograph is interfaced with a small digital computer via an A/D convertor. They have the advantage that statistical statements about their variability can sometimes be made so that the effect sought can be assessed correctly in the presence of random fluctuations.

  14. Salt passivation during anodic iridium dissolution in chloride melts

    SciTech Connect

    Saltykova, N.A.; Pechorskaya, L.S.; Baraboshkin, A.N.; Kotovskii, S.N.; Kosikhin, L.T.

    1986-11-01

    Anodic iridium dissolution in chloride melts at 500-700/sup 0/C was studied by potentiostatic, potentiodynamic, and galvanostatic techniques. It was found that an iridium anode is passivated by hexachloroiridates, first by the iridium (III) salt and at more positive potentials by the iridium (IV) salt. Values for anode resistance during passivation by salt films were calculated. It was shown that the morphology of the dissolving anode surface is determined by the value of polarization.

  15. IRIDIUM (R): A Lockheed transition to commercial space

    NASA Technical Reports Server (NTRS)

    Tadano, Thomas N.

    1995-01-01

    At Lockheed Missiles & Space Company, the IRIDIUM commercial space program is dramatically revolutionizing spacecraft development and manufacturing processes to reduce cost while maintaining quality and reliability. This report includes the following sections: an overview of the IRIDIUM system, the Lockheed IRIDIUM project and challenges; cycle-time reduction through production reorganization; and design for manufacturing and quality.

  16. The kinetics and mechanism of the organo-iridium catalysed racemisation of amines.

    PubMed

    Stirling, Matthew J; Mwansa, Joseph M; Sweeney, Gemma; Blacker, A John; Page, Michael I

    2016-08-01

    The dimeric iodo-iridium complex [IrCp*I2]2 (Cp* = pentamethylcyclopentadiene) is an efficient catalyst for the racemisation of secondary and tertiary amines at ambient and higher temperatures with a low catalyst loading. The racemisation occurs with pseudo-first-order kinetics and the corresponding four rate constants were obtained by monitoring the time dependence of the concentrations of the (R) and (S) enantiomers starting with either pure (R) or (S) and show a first-order dependence on catalyst concentration. Low temperature (1)H NMR data is consistent with the formation of a 1 : 1 complex with the amine coordinated to the iridium and with both iodide anions still bound to the metal-ion, but at the higher temperatures used for kinetic studies binding is weak and so no saturation zero-order kinetics are observed. A cross-over experiment with isotopically labelled amines demonstrates the intermediate formation of an imine which can dissociate from the iridium complex. Replacing the iodides in the catalyst by other ligands or having an amide substituent in Cp* results in a much less effective catalysts for the racemisation of amines. The rate constants for a deuterated amine yield a significant primary kinetic isotope effect kH/kD = 3.24 indicating that hydride transfer is involved in the rate-limiting step.

  17. Half-sandwich iridium complexes for homogeneous water-oxidation catalysis.

    PubMed

    Blakemore, James D; Schley, Nathan D; Balcells, David; Hull, Jonathan F; Olack, Gerard W; Incarvito, Christopher D; Eisenstein, Odile; Brudvig, Gary W; Crabtree, Robert H

    2010-11-17

    Iridium half-sandwich complexes of the types Cp*Ir(N-C)X, [Cp*Ir(N-N)X]X, and [CpIr(N-N)X]X are catalyst precursors for the homogeneous oxidation of water to dioxygen. Kinetic studies with cerium(IV) ammonium nitrate as primary oxidant show that oxygen evolution is rapid and continues over many hours. In addition, [Cp*Ir(H(2)O)(3)]SO(4) and [(Cp*Ir)(2)(μ-OH)(3)]OH can show even higher turnover frequencies (up to 20 min(-1) at pH 0.89). Aqueous electrochemical studies on the cationic complexes having chelate ligands show catalytic oxidation at pH > 7; conversely, at low pH, there are no oxidation waves up to 1.5 V vs NHE for the complexes. H(2)(18)O isotope incorporation studies demonstrate that water is the source of oxygen atoms during cerium(IV)-driven catalysis. DFT calculations and kinetic experiments, including kinetic-isotope-effect studies, suggest a mechanism for homogeneous iridium-catalyzed water oxidation and contribute to the determination of the rate-determining step. The kinetic experiments also help distinguish the active homogeneous catalyst from heterogeneous nanoparticulate iridium dioxide.

  18. Iridium emissions from Hawaiian volcanoes

    NASA Technical Reports Server (NTRS)

    Finnegan, D. L.; Zoller, W. H.; Miller, T. M.

    1988-01-01

    Particle and gas samples were collected at Mauna Loa volcano during and after its eruption in March and April, 1984 and at Kilauea volcano in 1983, 1984, and 1985 during various phases of its ongoing activity. In the last two Kilauea sampling missions, samples were collected during eruptive activity. The samples were collected using a filterpack system consisting of a Teflon particle filter followed by a series of 4 base-treated Whatman filters. The samples were analyzed by INAA for over 40 elements. As previously reported in the literature, Ir was first detected on particle filters at the Mauna Loa Observatory and later from non-erupting high temperature vents at Kilauea. Since that time Ir was found in samples collected at Kilauea and Mauna Loa during fountaining activity as well as after eruptive activity. Enrichment factors for Ir in the volcanic fumes range from 10,000 to 100,000 relative to BHVO. Charcoal impregnated filters following a particle filter were collected to see if a significant amount of the Ir was in the gas phase during sample collection. Iridium was found on charcoal filters collected close to the vent, no Ir was found on the charcoal filters. This indicates that all of the Ir is in particulate form very soon after its release. Ratios of Ir to F and Cl were calculated for the samples from Mauna Loa and Kilauea collected during fountaining activity. The implications for the KT Ir anomaly are still unclear though as Ir was not found at volcanoes other than those at Hawaii. Further investigations are needed at other volcanoes to ascertain if basaltic volcanoes other than hot spots have Ir enrichments in their fumes.

  19. Iridium-catalyzed enantioselective polyene cyclization.

    PubMed

    Schafroth, Michael A; Sarlah, David; Krautwald, Simon; Carreira, Erick M

    2012-12-19

    A highly enantioselective polycyclization method has been developed using the combination of Lewis acid activation with iridium-catalyzed allylic substitution. This strategy relies on direct use of branched, racemic allylic alcohols and furnishes a diverse and unique set of carbo- and heteropolycyclic ring systems in good yields and ≥99% ee. PMID:23193947

  20. Note: electrochemical etching of sharp iridium tips.

    PubMed

    Lalanne, Jean-Benoît; Paul, William; Oliver, David; Grütter, Peter H

    2011-11-01

    We describe an etching procedure for the production of sharp iridium tips with apex radii of 15-70 nm, as determined by scanning electron microscopy, field ion microscopy, and field emission measurements. A coarse electrochemical etch followed by zone electropolishing is performed in a relatively harmless calcium chloride solution with high success rate.

  1. Osmium-191/iridium-191m radionuclide

    DOEpatents

    Knapp, Jr., Furn F.; Butler, Thomas A.; Brihaye, Claude

    1987-01-01

    A generator system to provide iridium-191m for clinical imaging applications comprises an activated carbon adsorbent loaded with a compound containing the parent nuclide, osmium-191. The generator, which has a shelf-life in excess of two weeks and does not require a scavenger column, can be eluted with physiologically compatible saline.

  2. Iridium-192 Production for Cancer Treatment

    SciTech Connect

    Rostelato, M.E.C.M.; Silva, C.P.G.; Rela, P.R.; Zeituni, C.A.; Lepki, V.; Feher, A.

    2004-10-05

    The purpose of this work is to settle a laboratory for Iridium -192 sources production, that is, to determine a wire activation method and to build a hot cell for the wires manipulation, quality control and packaging. The paper relates, mainly, the wire activation method and its quality control. The wire activation is carried out in our nuclear reactor, IEA- R1m.

  3. Iridium-catalyzed enantioselective polyene cyclization.

    PubMed

    Schafroth, Michael A; Sarlah, David; Krautwald, Simon; Carreira, Erick M

    2012-12-19

    A highly enantioselective polycyclization method has been developed using the combination of Lewis acid activation with iridium-catalyzed allylic substitution. This strategy relies on direct use of branched, racemic allylic alcohols and furnishes a diverse and unique set of carbo- and heteropolycyclic ring systems in good yields and ≥99% ee.

  4. Osmium-191/iridium-191m radionuclide

    DOEpatents

    Knapp, F.F. Jr.; Butler, T.A.; Brihaye, C.

    1985-08-26

    A generator system to provide iridium-191m for clinical imaging applications comprises an activated carbon adsorbent loaded with a compound containing the parent nuclide, osmium-191. The generator, which has a shelf-life in excess of two weeks and does not require a scavenger column, can be eluted with physiologically compatible saline. 4 figs. 3 tabs.

  5. Iridium-Coated Rhenium Combustion Chamber

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.; Tuffias, Robert H.; Rosenberg, Sanders D.

    1994-01-01

    Iridium-coated rhenium combustion chamber withstands operating temperatures up to 2,200 degrees C. Chamber designed to replace older silicide-coated combustion chamber in small rocket engine. Modified versions of newer chamber could be designed for use on Earth in gas turbines, ramjets, and scramjets.

  6. Iridium-Catalyzed Selective Isomerization of Primary Allylic Alcohols.

    PubMed

    Li, Houhua; Mazet, Clément

    2016-06-21

    This Account presents the development of the iridium-catalyzed isomerization of primary allylic alcohols in our laboratory over the past 8 years. Our initial interest was driven by the long-standing challenge associated with the development of a general catalyst even for the nonasymmetric version of this seemingly simple chemical transformation. The added value of the aldehyde products and the possibility to rapidly generate molecular complexity from readily accessible allylic alcohols upon a redox-economical isomerization reaction were additional sources of motivation. Certainly influenced by the success story of the related isomerization of allylic amines, most catalysts developed for the selective isomerization of allylic alcohols were focused on rhodium as a transition metal of choice. Our approach has been based on the commonly accepted precept that hydrogenation and isomerization are often competing processes, with the latter being usually suppressed in favor of the former. The cationic iridium complexes [(Cy3P)(pyridine)Ir(cod)]X developed by Crabtree (X = PF6) and Pfaltz (X = BArF) are usually considered as the most versatile catalysts for the hydrogenation of allylic alcohols. Using molecular hydrogen to generate controlled amounts of the active form of these complexes but performing the reaction in the absence of molecular hydrogen enabled deviation from the typical hydrogenation manifold and favored exclusively the isomerization of allylic alcohols into aldehydes. Isotopic labeling and crossover experiments revealed the intermolecular nature of the process. Systematic variation of the ligand on the iridium center allowed us to identify the structural features beneficial for catalytic activity. Subsequently, three generations of chiral catalysts have been investigated and enabled us to reach excellent levels of enantioselectivity for a wide range of 3,3-disubstituted aryl/alkyl and alkyl/alkyl primary allylic alcohols leading to β-chiral aldehydes. The

  7. Spatial correspondence of brain alpha activity component in fMRI and EEG

    NASA Astrophysics Data System (ADS)

    Jeong, Jeong-Won; Kim, Sung-Heon; Singh, Manbir

    2005-04-01

    This paper presents a new approach to investigate the spatial correlation of brain alpha activity in functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). To avoid potential problems of simultaneous fMRI and EEG acquisitions in imaging brain alpha activity, data from each modality were acquired separately under a "three conditions" setup where one of the conditions involved closing eyes and relaxing, thus making it conducive to generation of alpha activity. The other two conditions -- eyes open in a lighted room or engaged in a mental arithmetic task, were designed to attenuate alpha activity. Using the Mixture Density Independent Component Analysis (MD-ICA) that incorporates flexible non-linearity functions into the conventional ICA framework, we could identify the spatiotemporal components of fMRI activations and EEG activities associated with the alpha rhythm. The sources of the individual EEG alpha activity component were localized by a Maximum Entropy (ME) method that solves an inverse problem in the framework of a classical four-sphere head model. The resulting dipole sources of EEG alpha activity were spatially transformed to 3D MRIs of the subject and compared to fMRI ICA-determined alpha activity maps.

  8. Application of the Iridium Satellite System to Aeronautical Communications

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.; Meza, Mike; Gupta, Om

    2008-01-01

    The next generation air transportation system will require greater air-ground communications capacity to accommodate more air traffic with increased safety and efficiency. Communications will remain primarily terrestrially based, but satellite communications will have an increased role. Inmarsat s aeronautical services have been approved and are in use for aeronautical safety communications provided by geostationary satellites. More recently the approval process for the Iridium low earth orbit constellation is nearing completion. The current Iridium system will be able to provide basic air traffic services communications suitable for oceanic, remote and polar regions. The planned second generation of the Iridium system, called Iridium NEXT, will provide enhanced capabilities and enable a greater role in the future of aeronautical communications. This paper will review the potential role of satellite communications in the future of air transportation, the Iridium approval process and relevant system testing, and the potential role of Iridium NEXT.

  9. Ultrasonic detection of laminar-type defects in iridium alloy blanks

    SciTech Connect

    Cook, K.V.; Cunningham, R.A. Jr.; Simpson, W.A. Jr.; McClung, R.W.

    1986-07-01

    Encapsulated isotopic heat sources for use in generating electrical power for space applications require flight-quality hardware material. Iridium is the chosen material for such applications, and Oak Ridge National Laboratory has been the prime supplier of iridium alloy forming blanks 52 mm in diameter by 0.66 mm thick (1.0 by 0.026 in.). Prior to the work reported here, these blanks were ultrasonically examined by using 0.9-mm-diam (0.035-in.) simulated flaw standards. However, as a result of this effort, the sensitivity of our ultrasonic pulse-echo test system has been increased. The improved ultrasonic test system permits blank inspection at the 0.5-mm-diam (0.020-in.) simulated flaw detection level. This test system was successfully demonstrated on the initial blanks provided via an improved processing route (consumable arc-melting, extruding, and rolling). The equipment modification and/or selection and the specific focused search unit immersion technique developed to provide this capability are described. The improved flaw detection capability also provides data maps of a common type of defect in iridium (delaminations).

  10. Iridium-coated rhenium thrusters by CVD

    NASA Technical Reports Server (NTRS)

    Harding, J. T.; Kazaroff, J. M.; Appel, M. A.

    1989-01-01

    Operation of spacecraft thrusters at increased temperature reduces propellant requirements. Inasmuch as propellant comprises the bulk of a satellite's mass, even a small percentage reduction makes possible a significant enhancement of the mission in terms of increased payload. Because of its excellent high temperature strength, rhenium is often the structural material of choice. It can be fabricated into free-standing shapes by chemical vapor deposition (CVD) onto an expendable mandrel. What rhenium lacks is oxidation resistance, but this can be provided by a coating of iridium, also by CVD. This paper describes the process used by Ultramet to fabricate 22-N (5-lbf) and, more recently, 445-N (100-lbf) Ir/Re thrusters; characterizes the CVD-deposited materials; and summarizes the materials effects of firing these thrusters. Optimal propellant mixture ratios can be employed because the materials withstand an oxidizing environment up to the melting temperature of iridium, 2400 C (4350 F).

  11. Iridium-coated rhenium thrusters by CVD

    NASA Technical Reports Server (NTRS)

    Harding, John T.; Kazaroff, John M.; Appel, Marshall A.

    1988-01-01

    Operation of spacecraft thrusters at increased temperature reduces propellant requirements. Inasmuch as propellant comprises the bulk of a satellite's mass, even a small percentage reduction makes possible a significant enhancement of the mission in terms of increased payload. Because of its excellent high temperature strength, rhenium is often the structural material of choice. It can be fabricated into free-standing shapes by chemical vapor deposition (CVD) onto an expendable mandrel. What rhenium lacks is oxidation resistance, but this can be provided by a coating of iridium, also by CVD. This paper describes the process used by Ultramet to fabricate 22-N (5-lbf) and, more recently, 445-N (100-lbf) Ir/Re thrusters; characterizes the CVD-deposited materials; and summarizes the materials effects of firing these thrusters. Optimal propellant mixture ratios can be employed because the materials withstand an oxidizing environment up to the meltimg temperature of iridium, 2400 C (4350 F).

  12. Handling System for Iridium-192 Seeds

    NASA Technical Reports Server (NTRS)

    Carpenter, W.; Wodicka, D.

    1973-01-01

    A complete system is proposed for safe handling of iridium-192 seeds used to internally irradiate malignant growths. A vibratory hopper feeds the seeds onto a transport system for deposit in a magazine or storage area. A circular magazine consisting of segmented plastic tubing with holes in the walls to accommodate the seeds seems feasible. The magazine is indexed to stop and release a seed for calibration and deposition.

  13. Assessment of alpha activity of building materials commonly used in West Bengal, India.

    PubMed

    Ghosh, Dipak; Deb, Argha; Bera, Sukumar; Sengupta, Rosalima; Patra, Kanchan Kumar

    2008-02-01

    This paper, reports for the first time, an extensive study of alpha activity of all widely used building materials (plaster of Paris, stone chips, marble, white cement, mosaic stone, limestone, sand, granite, cement brick, asbestos, red brick, cement tile, ceramic tile and ceramics) in West Bengal, India. The alpha activities have been measured using Solid State Nuclear Track Detector (SSNTD), a very sensitive detector for alpha particles. The samples were collected from local markets of Kolkata. The measured average alpha activities ranged from 22.7+/-2.5 to 590.6+/-16.8Bqkg(-1). The alpha activity of ceramic tiles was highest and provides additional data to estimate the effect of environmental radiation exposure on human health.

  14. Iridium Abundances across the Ordovician-Silurian Stratotype

    NASA Astrophysics Data System (ADS)

    Wilde, Pat; Berry, William B. N.; Quinby-Hunt, Mary S.; Orth, Charles J.; Quintana, Leonard R.; Gilmore, James S.

    1986-07-01

    Chemostratigraphic analyses in the Ordovician-Silurian boundary stratotype section, bracketing a major extinction event in the graptolitic shale section at Dob's Linn, Scotland, show persistently high iridium concentrations of 0.050 to 0.250 parts per billion. There is no iridium concentration spike in the boundary interval or elsewhere in the 13 graptolite zones examined encompassing about 20 million years. Iridium correlated with chromium, both elements showing a gradual decrease with time into the middle part of the Lower Silurian. The chromium-iridium ratio averages about 106. Paleogeographic and geologic reconstructions coupled with the occurrence of ophiolites and other deep crustal rocks in the source area suggest that the high iridium and chromium concentrations observed in the shales result from terrestrial erosion of exposed upper mantle ultramafic rocks rather than from a cataclysmic extraterrestrial event.

  15. Iridium/Rhenium Parts For Rocket Engines

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.; Harding, John T.; Wooten, John R.

    1991-01-01

    Oxidation/corrosion of metals at high temperatures primary life-limiting mechanism of parts in rocket engines. Combination of metals greatly increases operating temperature and longevity of these parts. Consists of two transition-element metals - iridium and rhenium - that melt at extremely high temperatures. Maximum operating temperature increased to 2,200 degrees C from 1,400 degrees C. Increases operating lifetimes of small rocket engines by more than factor of 10. Possible to make hotter-operating, longer-lasting components for turbines and other heat engines.

  16. Validation of EXAFS Analysis of Iridium Compounds

    NASA Astrophysics Data System (ADS)

    Feiters, M. C.; Longo, A.; Banerjee, D.; van der Ham, C. J. M.; Hetterscheid, D. G. H.

    2016-05-01

    Results of iridium L3 edge EXAFS measurements of compounds relevant for water oxidation catalysis are compared to those of other structural techniques. The structural results from EXAFS for the Ir compounds investigated here compare well to those of other structural techniques. Multiple scattering contributions are important in the coordinated Cp* and NHC ligands as well as in the IrCl6 unit and the IrO2 rutile structure. NHC is relatively weak compared to Ir, Cl, and even Cp* and O, and often out of phase with the other contributions.

  17. Measurement of natural radioactivity in chemical fertilizer and agricultural soil: evidence of high alpha activity.

    PubMed

    Ghosh, Dipak; Deb, Argha; Bera, Sukumar; Sengupta, Rosalima; Patra, Kanchan Kumar

    2008-02-01

    People are exposed to ionizing radiation from the radionuclides that are present in different types of natural sources, of which phosphate fertilizer is one of the most important sources. Radionuclides in phosphate fertilizer belonging to 232Th and 238U series as well as radioisotope of potassium (40K) are the major contributors of outdoor terrestrial natural radiation. The study of alpha activity in fertilizers, which is the first ever in West Bengal, has been performed in order to determine the effect of the use of phosphate fertilizers on human health. The data have been compared with the alpha activity of different types of chemical fertilizers. The measurement of alpha activity in surface soil samples collected from the cultivated land was also performed. The sampling sites were randomly selected in the cultivated land in the Midnapore district, which is the largest district in West Bengal. The phosphate fertilizer is widely used for large agricultural production, mainly potatoes. The alpha activities have been measured using solid-state nuclear track detectors (SSNTD), a very sensitive detector for alpha particles. The results show that alpha activity of those fertilizer and soil samples varies from 141 Bq/kg to 2,589 Bq/kg and from 109 Bq/kg to 660 Bq/kg, respectively. These results were used to estimate environmental radiation exposure on human health contributed by the direct application of fertilizers.

  18. Iridium wire grid polarizer fabricated using atomic layer deposition.

    PubMed

    Weber, Thomas; Käsebier, Thomas; Szeghalmi, Adriana; Knez, Mato; Kley, Ernst-Bernhard; Tünnermann, Andreas

    2011-10-25

    In this work, an effective multistep process toward fabrication of an iridium wire grid polarizer for UV applications involving a frequency doubling process based on ultrafast electron beam lithography and atomic layer deposition is presented. The choice of iridium as grating material is based on its good optical properties and a superior oxidation resistance. Furthermore, atomic layer deposition of iridium allows a precise adjustment of the structural parameters of the grating much better than other deposition techniques like sputtering for example. At the target wavelength of 250 nm, a transmission of about 45% and an extinction ratio of 87 are achieved.

  19. Iridium anomaly approximately synchronous with terminal eocene extinctions

    SciTech Connect

    Alvarez, W.; Asaro, F.; Michel, H.V.; Alvarez, L.W.

    1982-05-21

    An iridium anomaly has been found in coincidence with the known microtektite level in cores from Deep Sea Drilling Project site 149 in the Caribbean Sea. The iridium was probably not in the microtektites but deposited simultaneously with them; this could occur if the iridium was deposited from a dust cloud resulting from a bolide impact, as suggested for the anomaly associated with the Cretaceous-Tertiary boundary. Other workers have deduced that the microtektites are part of the North American strewn tektite field, which is dated at about 34 million years before present, and that the microtektite horizon in deep-sea cores is synchronous with the extinction of five radiolarian species. Mass extinctions also occur in terrestrial mammals within 4 million years of this time. The iridium anomaly and the tektites and microtektites are supportive of a major bolide impact about 34 million years ago.

  20. Iridium anomaly approximately synchronous with terminal eocene extinctions.

    PubMed

    Alvarez, W; Asaro, F; Michel, H V; Alvarez, L W

    1982-05-21

    An iridium anomaly has been found in coincidence with the known microtektite level in cores from Deep Sea Drilling Project site 149 in the Caribbean Sea. The iridium was probably not in the microtektites but deposited simultaneously with them; this could occur if the iridium was deposited from a dust cloud resulting from a bolide impact, as suggested for the anomaly associated with the Cretaceous-Tertiary boundary. Other workers have deduced that the microtektites are part of the North American strewn tektite field, which is dated at about 34 million years before present, and that the microtektite horizon in deep-sea cores is synchronous with the extinction of five radiolarian species. Mass extinctions also occur in terrestrial mammals within 4 million years of this time. The iridium anomaly and the tektites and microtektites are supportive of a major bolide impact about 34 million years ago.

  1. Acute radiodermatitis from occupational exposure to iridium 192

    SciTech Connect

    Becker, J.; Rosen, T. )

    1989-12-01

    Industrial radiography using the man-made radioisotope iridium 192 is commonplace in the southern states. Despite established procedures and safeguards, accidental exposure may result in typical acute radiodermatitis. We have presented a clinical example of this phenomenon.9 references.

  2. Membrane-disrupting iridium(iii) oligocationic organometallopeptides.

    PubMed

    Salvadó, Iria; Gamba, Ilaria; Montenegro, Javier; Martínez-Costas, José; Brea, Jose Manuel; Loza, María Isabel; Vázquez López, Miguel; Vázquez, M Eugenio

    2016-09-21

    A series of oligoarginine peptide derivatives containing cyclometallated iridium(iii) units display remarkable cytotoxicity, comparable to that of cisplatin. In vitro studies with unilamellar vesicles support a membrane-disrupting mechanism of action.

  3. Scattering effects on the dosimetry of iridium-192

    SciTech Connect

    Serago, C.F. Department of Radiation Oncology, University of Miami, Miami, Florida ); Houdek, P.V. ); Pisciotta, V. ); Schwade, J.G. ); Abitbol, A.A.; Lewin, A.A. Department of Radiation Oncology, University of Miami, Miami, Florida ); Poole, D.O. ); Marcial-Vega, V. )

    1991-11-01

    Dosimetry calculations for iridium-192 sources generally assume that a sufficient medium surrounds both the iridium source(s) and the point of calculation so that full scattering conditions exist. In several clinical applications the iridium sources may be anatomically located so that the full scattering requirement is not satisfied. To assess the magnitude of this problem, relative measurements were made with a small ionization chamber in phantoms near air and lung-equivalent interfaces. Dose reduction caused by decreasing the volume of scattering material near these interfaces was then evaluated for a few clinical applications. The results show that reductions on the order of 8% may be expected at the interface with minimal dose reduction within the volume of the implant itself. In addition, the results indicate the verification of source strength of iridium sources in phantom require phantom dimensions determined by the source-chamber separation distance.

  4. Iridium anomaly approximately synchronous with terminal eocene extinctions.

    PubMed

    Alvarez, W; Asaro, F; Michel, H V; Alvarez, L W

    1982-05-21

    An iridium anomaly has been found in coincidence with the known microtektite level in cores from Deep Sea Drilling Project site 149 in the Caribbean Sea. The iridium was probably not in the microtektites but deposited simultaneously with them; this could occur if the iridium was deposited from a dust cloud resulting from a bolide impact, as suggested for the anomaly associated with the Cretaceous-Tertiary boundary. Other workers have deduced that the microtektites are part of the North American strewn tektite field, which is dated at about 34 million years before present, and that the microtektite horizon in deep-sea cores is synchronous with the extinction of five radiolarian species. Mass extinctions also occur in terrestrial mammals within 4 million years of this time. The iridium anomaly and the tektites and microtektites are supportive of a major bolide impact about 34 million years ago. PMID:17819180

  5. GPS/GNSS Interference from Iridium Data Transmitters

    NASA Astrophysics Data System (ADS)

    Berglund, H. T.; Blume, F.; Estey, L.; White, S.

    2011-12-01

    The Iridium satellite communication system broadcasts in the 1610 to 1626.5 MHz band. The L1 frequencies broadcast by GPS, Galileo and GLONASS satellites are 1575.42 MHz, 1575.42 MHz and 1602 MHz + n × 0.5625 MHz, respectively (each GLONASS satellite uses a unique frequency). The proximity of the Iridium frequency band with the L1 frequencies of the GPS, Galileo and GLONASS systems leaves GNSS receivers susceptible to interference from Iridium data transmissions. Interference from Iridium transmissions can cause cycle slips and loss of lock on the carrier and code phases, thereby degrading the quality of GNSS observations and position estimates. In 2008, UNAVCO staff members observed that the percent of slips vs. the number of observations increased as the distance between a GPS choke ring antenna (TRM29659.00) and an Iridium antenna decreased. From those observations they suggested that Iridium antennas and GPS antennas should be separated by >30 m to minimize cycle slips caused by the interference from Iridium data transmissions. A second test conducted in 2009 using a newer Trimble GNSS choke ring antenna (TRM59800.00) showed similar results to the previous test despite the wider frequency range of the newer antenna. More recent testing conducted to investigate the response of new receiver models to iridium transmissions has shown that many GNSS enabled models, when combined with GNSS enabled antennas, have increased sensitivity to interference when compared to older GPS-only models. The broader frequency spectrum of the Low Noise Amplifiers (LNA) installed in many newer GNSS antennas can increase the impact of near-band RF interference on tracking performance. Our testing has shown that the quality of data collected at sites collocated with iridium communications is highly degraded for antenna separations exceeding 100m. Using older GPS antenna models (e.g. TRM29659.00) with newer GNSS enabled receivers can reduce this effect. To mitigate the effects that

  6. Improvements in manufacture of iridium alloy materials

    NASA Astrophysics Data System (ADS)

    Ohriner, E. K.

    1992-10-01

    Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTG's). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecraft. This hardware was fabricated from small, 500-g drop-cast ingots. Porosity in these ingots and the resulting defects in the rolled sheets caused rejection of about 30 percent of the product. An improved manufacturing process was developed with the goal of substantially reducing the level of defects in the rolled sheets. The ingot size is increased to 10 kg and is produced by vacuum arc remelting. In addition, the ingot is hot extruded prior to rolling. Since implementation of the process in 1989, the average rate of rejection of the product has been reduced to below 10 percent.

  7. Improvements in manufacture of iridium alloy materials

    SciTech Connect

    Ohriner, E.K.

    1992-08-01

    Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecraft. This hardware was fabricated from small, 500-g drop-cast ingots. Porosity in these ingots and the resulting defects in the rolled sheets caused rejection of about 30% of the product. An improved manufacturing process was developed with the goal of substantially reducing the level of defects in the rolled sheets. The ingot size is increased to 10 kg and is produced by vacuum arc remelting. In addition, the ingot is hot extruded prior to rolling. Since implementation of the process in 1989, the average rate of rejection of the product has been reduced to below 10%.

  8. Improvements in manufacture of iridium alloy materials

    SciTech Connect

    Ohriner, E.K.

    1992-01-01

    Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecraft. This hardware was fabricated from small, 500-g drop-cast ingots. Porosity in these ingots and the resulting defects in the rolled sheets caused rejection of about 30% of the product. An improved manufacturing process was developed with the goal of substantially reducing the level of defects in the rolled sheets. The ingot size is increased to 10 kg and is produced by vacuum arc remelting. In addition, the ingot is hot extruded prior to rolling. Since implementation of the process in 1989, the average rate of rejection of the product has been reduced to below 10%.

  9. Iridium{reg_sign} worldwide personal communication system

    SciTech Connect

    Helm, J.

    1997-01-01

    The IRIDIUM system is a personal worldwide communication system designed to support portable, low power subscriber units through the use of a constellation of satellites in low earth polar orbit. The satellites are networked together to form a system which provides continuous line-of-sight communications between the IRIDIUM system and any point within 30 km of the earth{close_quote}s surface. The system architecture and operation are described. {copyright} {ital 1997 American Institute of Physics.}

  10. PURIFICATION OF IRIDIUM BY ELECTRON BEAM MELTING

    SciTech Connect

    Ohriner, Evan Keith

    2008-01-01

    The purification of iridium metal by electron beam melting has been characterized for 48 impurity elements. Chemical analysis was performed by glow discharge mass spectrographic (GDMS) analysis for all elements except carbon, which was analyzed by combustion. The average levels of individual elemental impurities in the starting powder varied from 37 g/g to 0.02 g/g. The impurity elements Li, Na, Mg, P, S, Cl, K, Ca, Mn, Co, Ni, Cu, Zn, As, Pd, Ag, Cd, Sn, Sb, Te, Ba, Ce, Tl, Pb, and Bi were not detectable following the purification. No significant change in concentration of the elements Ti, V, Zr, Nb, Mo, and Re was found. The elements B, C, Al, Si, Cr, Fe, Ru, Rh, and Pt were partially removed by vaporization during electron beam melting. Langmuir's equation for ideal vaporization into a vacuum was used to calculate for each impurity element the expected ratio of impurity content after melting to that before melting. Equilibrium vapor pressures were calculated using Henry's law, with activity coefficients obtained from published data for the elements Fe, Ti, and Pt. Activity coefficients were estimated from enthalpy data for Al, Si, V, Cr, Mn, Co, Ni, Zr, Nb, Mo, and Hf and an ideal solution model was used for the remaining elements. The melt temperature was determined from measured iridium weight loss. Excellent agreement was found between measured and calculated impurity ratios for all impurity elements. The results are consistent with some localized heating of the melt pool due to rastering of the electron beam, with an average vaporization temperature of 3100 K as compared to a temperature of 2965 K calculated for uniform heating of the melt pool. The results are also consistent with ideal mixing in the melt pool.

  11. Solvent-Dependent Structure of Iridium Dihydride Complexes: Different Geometries at Low and High Dielectricity of the Medium.

    PubMed

    Polukeev, Alexey V; Marcos, Rocío; Ahlquist, Mårten S G; Wendt, Ola F

    2016-03-14

    The hydride iridium pincer complex [(PCyP)IrH2] (PCyP=cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane, 1) reveals remarkably solvent-dependent hydride chemical shifts, isotope chemical shifts, JHD and T1(min), with rHH increasing upon moving to more polar medium. The only known example of such behaviour (complex [(POCOP)IrH2], POCOP=2,6-(tBu2PO)2C6H3) was explained by the coordination of a polar solvent molecule to the iridium (J. Am. Chem. Soc. 2006, 128, 17114). Based on the existence of an agostic bond between α-C-H and iridium in 1 in all solvents, we argue that the coordination of solvent can be rejected. DFT calculations revealed that the structures of 1 and [(POCOP)IrH2] depend on the dielectric permittivity of the medium and these compounds adopt trigonal-bipyramidal geometries in non-polar media and square-pyramidal geometries in polar media. PMID:26880293

  12. Iridium NEXT: A Global access for your sensor needs

    NASA Astrophysics Data System (ADS)

    Gupta, O. P.; Fish, C. S.

    2010-12-01

    The operational Iridium constellation is comprised of 66 satellites, used to primarily provide worldwide voice and data coverage to satellite phones, pagers and integrated transceivers. The satellites are in low Earth orbit at 781 km and inclination of 86.4 deg, resulting in unprecedented 24/7 coverage and real-time visibility of the entire globe. Recently, through funding from the National Science Foundation (NSF), Iridium has been utilized by the Johns Hopkins University Applied Physics Laboratory (APL), with help from The Boeing Company, as an infrastructure for a comprehensive network for space environment measurements. Known as the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), the Iridium-based system provides real-time magnetic field measurements using the satellites as part of a new observation network to forecast weather in space. In February 2007, Iridium announced Iridium NEXT, a novel design for a second-generation satellite constellation. Anticipated to begin launching in 2015, Iridium NEXT will maintain the existing Iridium constellation architecture of 66 cross-linked satellite LEO covering 100 percent of the globe. In the spirit of AMPERE, for commercial, government, and scientific organizations Iridium NEXT also plans to offer new earth and space observation opportunities through hosted hosted payloads on the 66 Iridium NEXT satellite network. To provide seamless support and access to this latest innovation in payload transportation, Iridium NEXT has teamed with Space Dynamics Laboratory - Utah State University which has delivered thousands of successful sensors and subsystems for over 400 space borne and aircraf based payloads. One such innovation called SensorPOD will offer unique benefits such as unprecedented spatial and temporal coverage, real-time relay of data to and from up to 5 Kg payloads in space, and access to space at a fraction of the cost of a dedicated missions such as 3U or larger Cubesats. In this

  13. Iridium complexes demonstrating broadband emission through controlled geometric distortion and applications thereof

    DOEpatents

    Li, Jian; Turner, Eric

    2016-04-12

    Iridium compounds and their uses are disclosed herein. For example, carbazole containing iridium compounds are disclosed. The compounds are useful in many devices, including, but not limited to, electroluminescent devices.

  14. DETERMINATION OF HETEROGENEOUS ELECTRON TRANSFER RATE CONSTANTS AT MICROFABRICATED IRIDIUM ELECTRODES. (R825511C022)

    EPA Science Inventory

    There has been an increasing use of both solid metal and microfabricated iridium electrodes as substrates for various types of electroanalysis. However, investigations to determine heterogeneous electron transfer rate constants on iridium, especially at an electron beam evapor...

  15. Sounds elicit relative left frontal alpha activity in 2-month-old infants

    PubMed Central

    Mai, Xiaoqin; Xu, Lin; Li, Mingyan; Shao, Jie; Zhao, Zhengyan; Lamm, Connie; Fox, Nathan A.; Nelson, Charles A.; Lozoff, Betsy

    2015-01-01

    As one kind of sounds, human voices are important for language acquisition and human-infant relations. Human voices have positive effects on infants, e.g., soothe infants and evoke an infant's smile. Increased left relative to right frontal alpha activity as assessed by the electroencephalogram (EEG) is considered to reflect approach-related emotions. In the present study, we recorded the EEG in thirty-eight 2-month-old infants during a baseline period and then while they listened to sounds, i.e., human voices. Infants displayed increased relative left frontal alpha activity in response to sounds compared to the baseline condition. These results suggest that sounds can elicit relative left frontal activity in young infants, and that this approach-related emotion presents early in life. PMID:25242501

  16. Accessory proteins for DNA polymerase alpha activity with single-strand DNA templates.

    PubMed Central

    Lamothe, P; Baril, B; Chi, A; Lee, L; Baril, E

    1981-01-01

    Three forms of DNA polymerase alpha [DNA nucleotidyltransferase (DNA-directed), EC 2.7.7.7] were partially purified from the combined nuclear extract and postmicrosomal supernatant solution of synchronized HeLa cells. These enzymes, designated DNA polymerases alpha 1, alpha 2, and alpha 3, on the basis of their order of elution from DEAE-Bio-Gel, differ in their abilities to utilize single-strand DNA templates. DNA polymerase alpha 2 has equal catalytic activities with activated and single-strand DNAs as template-primers. DNA polymerase alpha 1 has only partial catalytic activity with single-strand DNA templates, and DNA polymerase alpha 3 is essentially inactive with this template. Successive steps of hydrophobic affinity chromatography and phosphocellulose chromatography of DNA polymerase alpha 2 resolved the polymerase alpha activity and two protein factors (C1 and C2) that are required for its catalytic activity with a DNA template-primer that contains extended single-strand regions. In the absence of the factors, DNA polymerase alpha activity is measurable with activated but not single-strand DNA templates. In the presence of the C1 and C2 factors DNA polymerase alpha activity with single-strand DNA templates is restored to about 75% of the catalytic activity of DNA polymerase alpha 2 with this template. Images PMID:6946421

  17. Characterization of Platinum and Iridium Oxyhydrate Surface Layers from Platinum and Iridium Foils.

    PubMed

    Johnson, Benjamin; Ranjan, Chinmoy; Greiner, Mark; Arrigo, Rosa; Schuster, Manfred Erwin; Höpfner, Britta; Gorgoi, Mihaela; Lauermann, Iver; Willinger, Marc; Knop-Gericke, Axel; Schlögl, Robert

    2016-07-01

    Platinum and iridium polycrystalline foils were oxidized electrochemically through anodization to create thin platinum and iridium hydrous oxide layers, which were analyzed through laboratory photoelectron spectroscopy during heating and time series (temperature-programmed spectroscopy). The films contain oxygen in the form of bound oxides, water, and hydroxides and were investigated by depth profiling with high-energy photoelectron spectroscopy. The Pt films are unstable and begin to degrade immediately after removal from the electrolyte to form core-shell structures with a metallic inner core and a hydrous oxide outer shell almost devoid of Pt. However, evidence was found for metastable intermediate states of degradation; therefore, it may be possible to manufacture PtOx phases with increased stability. Heating the film to even 100 °C causes accelerated degradation, which shows that stoichiometric oxides such as PtO2 or PtO are not the active species in the electrolyte. The Ir films exhibit increased stability and higher surface Ir content, and gentle heating at low temperatures leads to a decrease in defect density. Although both layers are based on noble metals, their surface structures are markedly different. The complexity of such hydrous oxide systems is discussed in detail with the goal of identifying the film composition more precisely. PMID:27226255

  18. Iridium oxide-polymer nanocomposite electrode materials for water oxidation.

    PubMed

    Lattach, Youssef; Rivera, Juan Francisco; Bamine, Tahya; Deronzier, Alain; Moutet, Jean-Claude

    2014-08-13

    Nanocomposite anode materials for water oxidation have been readily synthesized by electrodeposition of iridium oxide nanoparticles into poly(pyrrole-alkylammonium) films, previously deposited onto carbon electrodes by oxidative electropolymerization of a pyrrole-alkylammonium monomer. The nanocomposite films were characterized by electrochemistry, transmission electron microscopy, and atomic force microscopy. They showed an efficient electrocatalytic activity toward the oxygen evolution reaction. Data from Tafel plots have demonstrated that the catalytic activity of the iridium oxide nanoparticles is maintained following their inclusion in the polymer matrix. Bulk electrolysis of water at carbon foam modified electrodes have shown that the iridium oxide-polymer composite presents a higher catalytic activity and a better operational stability than regular oxide films.

  19. Experimental determination of the solubility of iridium in silicate melts: Preliminary results

    NASA Technical Reports Server (NTRS)

    Borisov, Alexander; Dingwell, Donald B.; Oneill, Hugh ST.C.; Palme, Herbert

    1992-01-01

    Little is known of the geochemical behavior of iridium. Normally this element is taken to be chalcophile and/or siderophile so that during planetary differentiation processes, e.g., core formation, iridium is extracted from silicate phases into metallic phases. Experimental determination of the metal/silicate partition coefficient of iridium is difficult simply because it is so large. Also there are no data on the solubility behavior of iridium in silicate melts. With information on the solubility of iridium in silicate melts it is possible, in combination with experimental data for Fe-Ir alloys, to calculate the partition coefficient between a metallic phase and a silicate melt.

  20. Synthesis of new heteroscorpionate iridium(I) and iridium(III) complexes.

    PubMed

    Roa, A E; Campos, J; Paneque, M; Salazar, V; Otero, A; Lara-Sánchez, A; Rodríguez, A M; López-Solera, I; Gómez, M V

    2015-04-21

    The reactivity of different heteroscorpionate ligands based on bis(pyrazol-1-yl)methane, with different iridium-(i) and -(iii) precursors is reported. The reaction of the heteroscorpionate lithium salts "Li(bdmpza)", [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate], "Li(bdmpzdta)" [bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate] and "Li(S)-mbpam" [(S)-mbpam = (S)-(-)-N-α-methylbenzyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate] with 1 equivalent of [IrCl3(THF)3] in THF for 18 h affords high yields of neutral and anionic heteroscorpionate chloride iridium complexes [IrCl2(bdmpza)(THF)] (), [Li(THF)4][IrCl3(bdmpzdta)] () and [IrCl2{(S)-mbpam})(THF)] (). Solution of complex in acetonitrile at room temperature leads to complex [IrCl2{(S)-mbpam})(NCCH3)] (). Complexes and were isolated as enantiopure compounds. The reaction of the lithium salt "Li(bdmpza)" with [IrCl(η(4)-CH2[double bond, length as m-dash]C(Me)C(Me)[double bond, length as m-dash]CH2)]2 in THF for 18 h gave the Ir(i) complex [Ir(bdmpza)(η(4)-CH2[double bond, length as m-dash]C(Me)C(Me)[double bond, length as m-dash]CH2)] (). The reaction of complex with CO (2 atm) at room temperature leads to a new complex of Ir(iii), [Ir(bdmpza)(k(2)-CH2C(Me)[double bond, length as m-dash]C(Me)CH2)(CO)] (). Treatment of heteroscorpionate ligand precursors "Li(bdmpza)" and "Li(bdmpzdta)" with [IrCp*Cl2]2 in THF yielded the iridium(iii) complexes [Ir2Cp*2Cl2(bdmpzx)] (x = a , x = dta ). These complexes have helical chirality due to the demands of the fixed pyrazole rings. The stereoisomerism and the self-assembly processes of these helicates have been studied in some detail in solution by NMR spectroscopy and in the solid state by X-ray diffraction. Mixtures of M- and P-handed enantiomers were obtained. Complex undergoes a decarboxylation process initiated by the HCl generated in the previous step leading to the known ionic complex [IrClCp*(bdmpm)][IrCl3Cp*] [bdmpm = bis(3,5-dimethylpyrazol-1-yl)methane] (). The

  1. Synthesis of new heteroscorpionate iridium(I) and iridium(III) complexes.

    PubMed

    Roa, A E; Campos, J; Paneque, M; Salazar, V; Otero, A; Lara-Sánchez, A; Rodríguez, A M; López-Solera, I; Gómez, M V

    2015-04-21

    The reactivity of different heteroscorpionate ligands based on bis(pyrazol-1-yl)methane, with different iridium-(i) and -(iii) precursors is reported. The reaction of the heteroscorpionate lithium salts "Li(bdmpza)", [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate], "Li(bdmpzdta)" [bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate] and "Li(S)-mbpam" [(S)-mbpam = (S)-(-)-N-α-methylbenzyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate] with 1 equivalent of [IrCl3(THF)3] in THF for 18 h affords high yields of neutral and anionic heteroscorpionate chloride iridium complexes [IrCl2(bdmpza)(THF)] (), [Li(THF)4][IrCl3(bdmpzdta)] () and [IrCl2{(S)-mbpam})(THF)] (). Solution of complex in acetonitrile at room temperature leads to complex [IrCl2{(S)-mbpam})(NCCH3)] (). Complexes and were isolated as enantiopure compounds. The reaction of the lithium salt "Li(bdmpza)" with [IrCl(η(4)-CH2[double bond, length as m-dash]C(Me)C(Me)[double bond, length as m-dash]CH2)]2 in THF for 18 h gave the Ir(i) complex [Ir(bdmpza)(η(4)-CH2[double bond, length as m-dash]C(Me)C(Me)[double bond, length as m-dash]CH2)] (). The reaction of complex with CO (2 atm) at room temperature leads to a new complex of Ir(iii), [Ir(bdmpza)(k(2)-CH2C(Me)[double bond, length as m-dash]C(Me)CH2)(CO)] (). Treatment of heteroscorpionate ligand precursors "Li(bdmpza)" and "Li(bdmpzdta)" with [IrCp*Cl2]2 in THF yielded the iridium(iii) complexes [Ir2Cp*2Cl2(bdmpzx)] (x = a , x = dta ). These complexes have helical chirality due to the demands of the fixed pyrazole rings. The stereoisomerism and the self-assembly processes of these helicates have been studied in some detail in solution by NMR spectroscopy and in the solid state by X-ray diffraction. Mixtures of M- and P-handed enantiomers were obtained. Complex undergoes a decarboxylation process initiated by the HCl generated in the previous step leading to the known ionic complex [IrClCp*(bdmpm)][IrCl3Cp*] [bdmpm = bis(3,5-dimethylpyrazol-1-yl)methane] (). The

  2. Homogeneous and heterogenized iridium water oxidation catalysts

    NASA Astrophysics Data System (ADS)

    Macchioni, Alceo

    2014-10-01

    The development of an efficient catalyst for the oxidative splitting of water into molecular oxygen, protons and electrons is of key importance for producing solar fuels through artificial photosynthesis. We are facing the problem by means of a rational approach aimed at understanding how catalytic performance may be optimized by the knowledge of the reaction mechanism of water oxidation and the fate of the catalytic site under the inevitably harsh oxidative conditions. For the purposes of our study we selected iridium water oxidation catalysts, exhibiting remarkable performance (TOF > 5 s-1 and TON > 20000). In particular, we recently focused our attention on [Cp*Ir(N,O)X] (N,O = 2-pyridincarboxylate; X = Cl or NO3) and [IrCl(Hedta)]Na water oxidation catalysts. The former exhibited a remarkable TOF whereas the latter showed a very high TON. Furthermore, [IrCl(Hedta)]Na was heterogenized onto TiO2 taking advantage of the presence of a dandling -COOH functionality. The heterogenized catalyst maintained approximately the same catalytic activity of the homogeneous analogous with the advantage that could be reused many times. Mechanistic studies were performed in order to shed some light on the rate-determining step and the transformation of catalysts when exposed to "oxidative stress". It was found that the last oxidative step, preceding oxygen liberation, is the rate-determining step when a small excess of sacrificial oxidant is used. In addition, several intermediates of the oxidative transformation of the catalyst were intercepted and characterized by NMR, X-Ray diffractometry and ESI-MS.

  3. Mercury Underpotential Deposition to Determine Iridium and Iridium Oxide Electrochemical Surface Areas

    DOE PAGES

    Alia, Shaun M.; Hurst, Katherine E.; Kocha, Shyam S.; Pivovar, Bryan S.

    2016-06-02

    Determining the surface areas of electrocatalysts is critical for separating the key properties of area-specific activity and electrochemical surface area from mass activity. Hydrogen underpotential deposition and carbon monoxide oxidation are typically used to evaluate iridium (Ir) surface areas, but are ineffective on oxides and can be sensitive to surface oxides formed on Ir metals. Mercury underpotential deposition is presented in this study as an alternative, able to produce reasonable surface areas on Ir and Ir oxide nanoparticles, and able to produce similar surface areas prior to and following characterization in oxygen evolution. Reliable electrochemical surface areas allow for comparativemore » studies of different catalyst types and the characterization of advanced oxygen evolution catalysts. Lastly, they also enable the study of catalyst degradation in durability testing, both areas of increasing importance within electrolysis and electrocatalysis.« less

  4. Occurrence of natural radioactivity in public water supplies in Germany: (238)U, (234)U, (235)U, (228)RA, (226)RA, (222)RN, (210)PB, (210)PO and gross alpha activity concentrations.

    PubMed

    Beyermann, M; Bünger, T; Schmidt, K; Obrikat, D

    2010-09-01

    The Federal Office for Radiation Protection performed a representative survey on the radiological quality of drinking water in Germany. The aim of this study was to determine regional variations of natural radionuclide concentrations and to estimate radiation exposures caused by drinking water consumption. The study includes analyses of the natural radionuclides (238)U, (234)U, (235)U, (228)Ra, (226)Ra, (222)Rn, (210)Pb, (210)Po and of gross alpha activity concentrations in drinking water from 564 public water supplies. This represents 3 % of all German water supplies providing about 37 Mio. inhabitants. Results on ranges, medians and distributions of radionuclide concentrations of drinking water as well as age-dependent ingestion and inhalation doses estimated for members of the public are presented. Generally, the dose due to uranium isotopes is negligibly low. Radiation exposures are predominantly caused by (222)Rn, (228)Ra, (210)Po and (210)Pb. The ingestion dose deduced for adults (>17 a) and infants (0-1 a) is dominated by (222)Rn and (228)Ra, respectively. A gross alpha activity analysis procedure using liquid scintillation counting has been tested. Measured gross alpha activities values were found to be well related to the summarised activities of (238)U, (234)U, (226)Ra and (210)Po.

  5. Iridium-catalyzed enantioselective hydrogenation of unsaturated heterocyclic acids.

    PubMed

    Song, Song; Zhu, Shou-Fei; Pu, Liu-Yang; Zhou, Qi-Lin

    2013-06-01

    Spiral binding: A highly enantioselective hydrogenation of unsaturated heterocyclic acids has been developed by using chiral iridium/spirophosphino oxazoline catalysts (see scheme; BArF(-) =tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, Boc=tert-butoxycarbonyl). This reaction provided an efficient method for the preparation of optically active heterocyclic acids with excellent enantioselectivities. PMID:23610004

  6. The Iridium (tm) system: Personal communications anytime, anyplace

    NASA Technical Reports Server (NTRS)

    Hatlelid, John E.; Casey, Larry

    1993-01-01

    The Iridium system is designed to provide handheld personal communications between diverse locations around the world at any time and without prior knowledge of the location of the personal units. This paper provides an overview of the system, the services it provides, its operation, and an overview of the commercial practices and relatively high volume satellite production techniques which will make the system cost effective. A constellation of 66 satellites will provide an orbiting, spherical-shell, infrastructure for this global calling capability. The satellites act as tall cellular towers and allow convenient operation for portable handheld telephones. The system will provide a full range of services including voice, paging, data, geolocation, and fax capabilities. Motorola is a world leader in the production of high volume, high quality, reliable telecommunications hardware. One of Iridium's goals is to apply these production techniques to high reliability space hardware. Concurrent engineering, high performance work teams, advanced manufacturing technologies, and improved assembly and test methods are some of the techniques that will keep the Iridium system cost effective. Mobile, global, flexible personal communications are coming that will allow anyone to call or receive a call from/to anyplace at anytime. The Iridium system will provide communications where none exist today. This connectivity will allow increased information transfer, open new markets for various business endeavors, and in general increase productivity and development.

  7. Iridium Aluminide Coats For Protection Against Ox idation

    NASA Technical Reports Server (NTRS)

    Kaplan, Richard B.; Tuffias, Robert H.; La Ferla, Raffaele; Jang, Qin

    1996-01-01

    Iridium aluminide coats investigated for use in protecting some metallic substrates against oxidation at high temperatures. Investigation prompted by need for cost-effective anti-oxidation coats for walls of combustion chambers in rocket engines. Also useful in special terrestrial applications like laboratory combustion chambers and some chemical-processing chambers.

  8. The Iridium (tm) system: Personal communications anytime, anyplace

    NASA Astrophysics Data System (ADS)

    Hatlelid, John E.; Casey, Larry

    The Iridium system is designed to provide handheld personal communications between diverse locations around the world at any time and without prior knowledge of the location of the personal units. This paper provides an overview of the system, the services it provides, its operation, and an overview of the commercial practices and relatively high volume satellite production techniques which will make the system cost effective. A constellation of 66 satellites will provide an orbiting, spherical-shell, infrastructure for this global calling capability. The satellites act as tall cellular towers and allow convenient operation for portable handheld telephones. The system will provide a full range of services including voice, paging, data, geolocation, and fax capabilities. Motorola is a world leader in the production of high volume, high quality, reliable telecommunications hardware. One of Iridium's goals is to apply these production techniques to high reliability space hardware. Concurrent engineering, high performance work teams, advanced manufacturing technologies, and improved assembly and test methods are some of the techniques that will keep the Iridium system cost effective. Mobile, global, flexible personal communications are coming that will allow anyone to call or receive a call from/to anyplace at anytime. The Iridium system will provide communications where none exist today. This connectivity will allow increased information transfer, open new markets for various business endeavors, and in general increase productivity and development.

  9. Achieving Zero Stress in Iridium, Chromium, and Nickle Thin Films

    NASA Technical Reports Server (NTRS)

    Broadway, David M.; Weimer, Jeffrey; Gurgew, Danielle; Lis, Tomasz; Ramsey, Brian D.; O'Dell, Stephen L.; Ames, A.; Bruni, R.

    2015-01-01

    We examine a method for achieving zero intrinsic stress in thin films of iridium, chromium, and nickel deposited by magnetron sputter deposition. The examination of the stress in these materials is motivated by efforts to advance the optical performance of light-weight x-ray space telescopes into the regime of sub-arc second resolution that rely on control of the film stress to values within 10-100 MPa. A characteristic feature of the intrinsic stress behavior in chromium and nickel is their sensitivity to the magnitude and sign of the intrinsic stress with argon gas pressure, including the existence of a critical pressure that results in zero film stress. This critical pressure scales linearly with the film's density. While the effect of stress reversal with argon pressure has been previously reported by Hoffman and others for nickel and chromium, we have discovered a similar behavior for iridium. Additionally, we have identified zero stress in iridium shortly after island coalescence. This feature of film growth is used for achieving a total internal stress of -2.89 MPa for a 15.8 nm thick iridium film. The surface roughness of this low-stress film was examined using scanning probe microscopy (SPM) and x-ray reflectivity (XRR) at CuKa and these results presented and discussed.

  10. Magnetostratigraphy, Late devonian iridium anomaly, and impact hypotheses

    SciTech Connect

    Hurley, N.F.; Van der Voo, R. )

    1990-04-01

    Paleomagnetism, sedimentology, and fine-scale stratigraphy have been integrated to explain the origin of an iridium anomaly in the Late Devonian of Western Australia. Thermal demagnetization experiments were carried out on 93 specimens of marginal-slope limestone form the northern Canning Basin. Samples are from a condensed sequence of deep-water (> 100 m) Frutexites microstromatolites. Frutexites is a shrublike cyanobacterial organism that probably precipitated hematite, or a metastable precursor, from sea water. When plotted within the microstratigraphic framework for the study area, the observed characteristic directions from the sampled interval (14.5 cm thick) are in five discrete, layer-parallel, normal- and reversed-polarity zones. The measured northeast-southwest declinations and shallow inclinations probably record Late Devonian magnetostratigraphy on a centimetre scale. The Frutexites bed studied there occurs close to the Frasnian/Famennian (Late Devonian) boundary, a time of mass extinction of a wide variety of marine organisms throughout the world. Anomalously high iridium concentrations observed in the Frutexites bed have suggested to some authors that the mass extinction was caused by meteorite impact. This study concludes that iridium, which is present over the span of five layer-parallel magnetic reversals, was concentrated over a long period of time by biologic processes. Thus, the Canning Basin iridium anomaly may be unrelated to meteorite impact.

  11. Utilization of Low Bandwidth Iridium Modems for Polar Seismology

    NASA Astrophysics Data System (ADS)

    Parker, T.

    2012-12-01

    Transmission of realtime seismic data is a desirable goal when a rapid response is needed. However, for many science applications sample waveform data, system state of health, and the ability to command and control the seismic station are operationally adequate. Determining the optimal telemetry requirements for a remote polar seismic experiment requires balancing science objective against the expensive, over-subscribed support available in the polar environments? For example there is a significant difference in the resources needed for a permanent "monitoring" effort versus a short-term experiment. We will describe IRIS/PASSCAL's successful approach to utilizing Iridium telemetry for short-term seismic experiments and suggest viable use of an Iridium RUDICs system for higher data-rate, permanent seismic stations such as a monitoring scenario. Most seismic stations are configured to record at a rate that exceeds twice the data rate of a single Iridium Internet modem. The power requirement to run continuous Iridium telemetry better than doubles that of a standalone seismic station. Doubling station power roughly doubles station logistics by requiring an increased number of support flights for installation and service. The tradeoffs between desirable and adequate telemetry requirements and the ramifications these requirements have on support services must be considered for a successful seismic station. We describe two Iridium telemetry systems, developed by the IRIS/PASSCAL Polar Program, for use with seismic stations in Antarctica and the Arctic. The first system uses an inexpensive Iridium 9602 modem based device and short burst data (SBD) transmission to monitor station performance, provide some command and control, and return a small amount of representative seismic data. Power requirements for this SBD system are approximately 10Ah per year for a daily message. The second system uses an Iridium 9522b modem based device the DOD RUDICs system for a 2400 Baud

  12. Structure, electrochemical properties and capacitance performance of polypyrrole electrodeposited onto 1-D crystals of iridium complex

    NASA Astrophysics Data System (ADS)

    Wysocka-Żołopa, Monika; Winkler, Krzysztof

    2015-12-01

    Composites of polypyrrole and one-dimensional iridium complex crystals [(C2H5)4N]0.55[IrCl2(CO)2] were prepared by in situ two-step electrodeposition. Initially, iridium complex crystals were formed during [IrCl2(CO)2]- complex oxidation. Next, pyrrole was electropolymerized on the surface of the iridium needles. The morphology of the composite was investigated by scanning and transmission electron microscopy. At positive potentials, the iridium complex crystals and the polypyrrole were oxidized. In aprotic solvents, oxidation of the iridium complex crystals resulted in their dissolution. In water containing tetra(n-butyl)ammonium chlorides, the 1-D iridium complex crystals were reversibly oxidized. The product of the iridium complex oxidation remained on the electrode surface in crystalline form. The iridium complex needles significantly influenced the redox properties of the polymer. The polypyrrole involved electrode processes become more reversible in presence of crystals of iridium complex. The current of polypyrrole oxidation was higher compared to that of pure polypyrrole and the capacitance properties of the polymer were significantly enhanced. A specific capacitance as high as 590 F g-1 was obtained for a composite of polypyrrole and 1-D crystals of the iridium complex in water containing tetra(n-butyl)ammonium chloride. This value is approximately twice as high as the capacitance of the pure polymer deposited onto the electrode surface.

  13. Special Form Testing of Sealed Source Encapsulation for High-Alpha-Activity Actinide Materials

    SciTech Connect

    Martinez, Oscar A

    2016-01-01

    In the United States all transportation of radioactive material is regulated by the U.S. Department of Transportation (DOT). Beginning in 2008 a new type of sealed-source encapsulation package was developed and tested by Oak Ridge National Laboratory (ORNL). These packages contain high-alpha-activity actinides and are regulated and transported in accordance with the requirements for DOT Class 7 hazardous material. The DOT provides specific regulations pertaining to special form encapsulation designs. The special form designation indicates that the encapsulated radioactive contents have a very low probability of dispersion even when subjected to significant structural events. The special form designs have been shown to simplify the delivery, transport, acceptance, and receipt processes. It is intended for these sealed-source encapsulations to be shipped to various facilities making it very advantageous for them to be certified as special form. To this end, DOT Certificates of Competent Authority (CoCAs) have been sought for the design suitable for containing high-alpha-activity actinide materials. This design consists of the high-alpha-activity material encapsulated within a triangular zirconia canister, referred to as a ZipCan, tile that is then enclosed by a spherical shell. The spherical shell design, with ZipCan tile inside, was tested for compliance with the special form regulations found in 49 CFR 173.469. The spherical enclosure was subjected to 9-m impact, 1 m percussion, and 10-minute thermal tests at the Packaging Evaluation Facility located at the National Transportation Research Center in Knoxville, TN USA and operated by ORNL. Before and after each test, the test units were subjected to a helium leak check and a bubble test. The ZipCan tiles and core were also subjected to the tests required for ISO 2919:2012(E), including a Class IV impact test and heat test and subsequently subjected to helium leakage rate tests [49 CFR 173.469(a)(4)(i)]. The impact

  14. Simulation of dose distribution for iridium-192 brachytherapy source type-H01 using MCNPX

    NASA Astrophysics Data System (ADS)

    Purwaningsih, Anik

    2014-09-01

    Dosimetric data for a brachytherapy source should be known before it used for clinical treatment. Iridium-192 source type H01 was manufactured by PRR-BATAN aimed to brachytherapy is not yet known its dosimetric data. Radial dose function and anisotropic dose distribution are some primary keys in brachytherapy source. Dose distribution for Iridium-192 source type H01 was obtained from the dose calculation formalism recommended in the AAPM TG-43U1 report using MCNPX 2.6.0 Monte Carlo simulation code. To know the effect of cavity on Iridium-192 type H01 caused by manufacturing process, also calculated on Iridium-192 type H01 if without cavity. The result of calculation of radial dose function and anisotropic dose distribution for Iridium-192 source type H01 were compared with another model of Iridium-192 source.

  15. Simulation of dose distribution for iridium-192 brachytherapy source type-H01 using MCNPX

    SciTech Connect

    Purwaningsih, Anik

    2014-09-30

    Dosimetric data for a brachytherapy source should be known before it used for clinical treatment. Iridium-192 source type H01 was manufactured by PRR-BATAN aimed to brachytherapy is not yet known its dosimetric data. Radial dose function and anisotropic dose distribution are some primary keys in brachytherapy source. Dose distribution for Iridium-192 source type H01 was obtained from the dose calculation formalism recommended in the AAPM TG-43U1 report using MCNPX 2.6.0 Monte Carlo simulation code. To know the effect of cavity on Iridium-192 type H01 caused by manufacturing process, also calculated on Iridium-192 type H01 if without cavity. The result of calculation of radial dose function and anisotropic dose distribution for Iridium-192 source type H01 were compared with another model of Iridium-192 source.

  16. Short term integrative meditation improves resting alpha activity and stroop performance.

    PubMed

    Fan, Yaxin; Tang, Yi-Yuan; Tang, Rongxiang; Posner, Michael I

    2014-12-01

    Our previous research showed that short term meditation training reduces the time to resolve conflict in the flanker task. Studies also show that resting alpha increases with long term meditation practice. The aim of this study is to determine whether short term meditation training both increases resting alpha activity and reduces the time to resolve conflict in the Stroop task and whether these two effects are related. Forty-three Chinese undergraduates were randomly assigned an experiment group given 5 days meditation training using integrative body-mind training (IBMT) and a relaxation training control. After training, only the IBMT group showed decreased conflict reaction time (RT), and increased resting mean alpha power. Moreover, the higher the enhancement of resting alpha power, the stronger the improvement of conflict RT. The results indicate that short term meditation diffusely enhances alpha and improves the ability to deal with conflict and moreover these two effects are positively related.

  17. Medial profrontal cortex and anterior cingulate cortex in the generation of alpha activity induced by transcendental meditation: a magnetoencephalographic study.

    PubMed

    Yamamoto, Shin; Kitamura, Yoshihiro; Yamada, Norihito; Nakashima, Yoshihiko; Kuroda, Shigetoshi

    2006-02-01

    Previous EEG studies have shown that transcendental meditation (TM) increases frontal and central alpha activity. The present study was aimed at identifying the source of this alpha activity using magnetoencephalography (MEG) and electroencephalography (EEG) simultaneously on eight TM practitioners before, during, and after TM. The magnetic field potentials corresponding to TM-induced alpha activities on EEG recordings were extracted, and we attempted to localize the dipole sources using the multiple signal classification (MUSIC) algorithm, equivalent current dipole source analysis, and the multiple spatio-temporal dipole model. Since the dipoles were mapped to both the medial prefrontal cortex (mPFC) and anterior cingulate cortex (ACC), it is suggested that the mPFC and ACC play an important role in brain activity induced by TM.

  18. Circularly polarised phosphorescent photoluminescence and electroluminescence of iridium complexes

    PubMed Central

    Li, Tian-Yi; Jing, Yi-Ming; Liu, Xuan; Zhao, Yue; Shi, Lin; Tang, Zhiyong; Zheng, You-Xuan; Zuo, Jing-Lin

    2015-01-01

    Nearly all the neutral iridium complexes widely used as dopants in PhOLEDs are racemic mixtures; however, this study observed that these complexes can be separated into stable optically active Λ and ∆ isomers and that their chirality is an intrinsic property. The circularly polarised phosphorescent photoluminescence (CPPPL) signals of Λ/Δ isomers are perfect mirror images with opposite polarisation and equal intensity exhibiting a “handedness” for the polarisation. For the first time, we applied the Λ/Δ iridium isomers as emitters in OLEDs, and the circularly polarised phosphorescent electroluminescence (CPPEL) spectra reveal completely positive or negative broad peaks consistent with the CPPPL spectra. The results demonstrate that the Λ/Δ isomers have potential application for 3D OLEDs because they can exhibit high efficiency and luminance, and 3D display technology based on circularly polarised light is the most comfortable for the eyes. PMID:26446521

  19. Olefin hydroaryloxylation catalyzed by pincer-iridium complexes.

    PubMed

    Haibach, Michael C; Guan, Changjian; Wang, David Y; Li, Bo; Lease, Nicholas; Steffens, Andrew M; Krogh-Jespersen, Karsten; Goldman, Alan S

    2013-10-01

    Aryl alkyl ethers, which are widely used throughout the chemical industry, are typically produced via the Williamson ether synthesis. Olefin hydroaryloxylation potentially offers a much more atom-economical alternative. Known acidic catalysts for hydroaryloxylation, however, afford very poor selectivity. We report the organometallic-catalyzed intermolecular hydroaryloxylation of unactivated olefins by iridium "pincer" complexes. These catalysts do not operate via the hidden Brønsted acid pathway common to previously developed transition-metal-based catalysts. The reaction is proposed to proceed via olefin insertion into an iridium-alkoxide bond, followed by rate-determining C-H reductive elimination to yield the ether product. The reaction is highly chemo- and regioselective and offers a new approach to the atom-economical synthesis of industrially important ethers and, potentially, a wide range of other oxygenates. PMID:24028199

  20. Processing and properties of iridium alloys for space power applications

    SciTech Connect

    Ohriner, E.K.

    1994-12-31

    Iridium alloys are used as fuel cladding in radioisotope thermoelectric generators due to their high-melting point, high- temperature strength, and oxidation and corrosion resistance. Although iridium has a face-centered cubic crystal structure, it undergoes a distinct ductile-to-brittle transition characteristic of many body-centered cubic metals. Improved ductility in the alloys is achieved through material purification and controlled alloy additions at the parts per million (ppm) level. A vacuum arc remelt operation produces a nearly defect-free casting, which is further processed to sheet products. A change in processing from drop castings of small arc-melted buttons to large arc-remelted ingots has substantially improved product yields. The effects of processing changes on alloy microstructure, sheet textures, oxidation effects, high-strain-rate ductility, and fabricability are discussed.

  1. Iridium alloy clad vent set manufacturing qualification studies

    SciTech Connect

    Ulrich, G.B. )

    1991-01-10

    Qualification studies have been successfully conducted to demonstrate iridium alloy Clad Vent Set (CVS) manufacturing readiness for the General Purpose Heat Source (GPHS) program at the Oak Ridge Y-12 Plant. These studies were joint comparison evaluations of both the Y-12 Plant and EG G Mound Applied Technologies, Inc. (EG G-MAT) products. Note: EG G-MAT formerly manufactured the iridium alloy CVS. The comparison evaluations involved work in a number of areas; however, only the CVS cup metallurgical evalution will be presented here. The initial metallurgical comparisons in conjunction with follow-up metallurgical work showed the Y-12 Plant CVS product to be comparable to the fully qualified (for Galileo and Ulysses missions) EG G-MAT product. This allowed the Y-12 Plant to commence pilot production of CVS components for potential use in the CRAF and CASSINI missions.

  2. Photoswitchable azobenzene-appended iridium(iii) complexes.

    PubMed

    Pérez-Miqueo, J; Altube, A; García-Lecina, E; Tron, A; McClenaghan, N D; Freixa, Z

    2016-09-21

    Iridium(iii) cyclometalated complexes have been used as models to study the effect that extended conjugation and substitution pattern has on the photochromic behavior of azobenzene-appended 2-phenylpyridyl (ppy) ligands. For this purpose four azobenzene-containing ppy ligands were synthesized. With these ligands, nine iridium(iii) complexes containing up to three appended azobenzenes were synthesized. Analysis of their photochromic behaviour by means of UV-vis and (1)H-NMR spectroscopy permitted us to conclude that the light-induced trans-to-cis isomerization of the azobenzene was strongly inhibited upon coordination to the Ir(iii) cation when the electronic conjugation was extended along the whole ligand. The use of an aliphatic spacer unit (either -CH2- or -OCH2-) between the azobenzene and the ppy fragment of the ligand sufficed to disrupt the electronic communication, and obtain photochromic organometallic complexes. PMID:27460186

  3. Iridium-Doped Ruthenium Oxide Catalyst for Oxygen Evolution

    NASA Technical Reports Server (NTRS)

    Valdez, Thomas I.; Narayan, Sri R.; Billings, Keith J.

    2011-01-01

    NASA requires a durable and efficient catalyst for the electrolysis of water in a polymer-electrolyte-membrane (PEM) cell. Ruthenium oxide in a slightly reduced form is known to be a very efficient catalyst for the anodic oxidation of water to oxygen, but it degrades rapidly, reducing efficiency. To combat this tendency of ruthenium oxide to change oxidation states, it is combined with iridium, which has a tendency to stabilize ruthenium oxide at oxygen evolution potentials. The novel oxygen evolution catalyst was fabricated under flowing argon in order to allow the iridium to preferentially react with oxygen from the ruthenium oxide, and not oxygen from the environment. Nanoparticulate iridium black and anhydrous ruthenium oxide are weighed out and mixed to 5 18 atomic percent. They are then heat treated at 300 C under flowing argon (in order to create an inert environment) for a minimum of 14 hours. This temperature was chosen because it is approximately the creep temperature of ruthenium oxide, and is below the sintering temperature of both materials. In general, the temperature should always be below the sintering temperature of both materials. The iridium- doped ruthenium oxide catalyst is then fabricated into a PEM-based membrane- electrode assembly (MEA), and then mounted into test cells. The result is an electrolyzer system that can sustain electrolysis at twice the current density, and at the same efficiency as commercial catalysts in the range of 100-200 mA/sq cm. At 200 mA/sq cm, this new system operates at an efficiency of 85 percent, which is 2 percent greater than commercially available catalysts. Testing has shown that this material is as stable as commercially available oxygen evolution catalysts. This means that this new catalyst can be used to regenerate fuel cell systems in space, and as a hydrogen generator on Earth.

  4. THE ATOMIC WEIGHTS COMMISSION AND ISOTOPIC ABUNDANCE RATIO DETERMINATIONS.

    SciTech Connect

    HOLDEN, N.E.

    2005-08-07

    Following Thomson's discovery of stable isotopes in non-radioactive chemical elements, the derivation of atomic weight values from mass spectrometric measurements of isotopic abundance ratios moved very slowly. Forty years later, only 3 1/2 % of the recommended values were based on mass spectrometric measurements and only 38% in the first half century. It might be noted that two chemical elements (tellurium and mercury) are still based on chemical measurements, where the atomic weight value calculated from the relative isotopic abundance measurement either agrees with the value from the chemical measurement or the atomic weight value calculated from the relative isotopic abundance measurement falls within the uncertainty of the chemical measurement of the atomic weight. Of the 19 chemical elements, whose atomic weight is based on non-corrected relative isotopic abundance measurements, five of these are two isotope systems (indium, iridium, lanthanum, lutetium and tantalum) and one is a three-isotope system (oxygen).

  5. Rockot Launch Vehicle Commercial Operations for Grace and Iridium Program

    NASA Astrophysics Data System (ADS)

    Viertel, Y.; Kinnersley, M.; Schumacher, I.

    2002-01-01

    The GRACE mission and the IRIDIUM mission on ROCKOT launch vehicle are presented. Two identical GRACE satellites to measure in tandem the gravitational field of the earth with previously unattainable accuracy - it's called the Gravity Research and Climate Experiment, or and is a joint project of the U.S. space agency, NASA and the German Centre for Aeronautics and Space Flight, DLR. In order to send the GRACE twins into a 500x500 km , 89deg. orbit, the Rockot launch vehicle was selected. A dual launch of two Iridium satellites was scheduled for June 2002 using the ROCKOT launch vehicle from Plesetsk Cosmodrome in Northern Russia. This launch will inject two replacement satellites into a low earth orbit (LEO) to support the maintenance of the Iridium constellation. In September 2001, Eurockot successfully carried out a "Pathfinder Campaign" to simulate the entire Iridium mission cycle at Plesetsk. The campaign comprised the transport of simulators and related equipment to the Russian port-of-entry and launch site and also included the integration and encapsulation of the simulators with the actual Rockot launch vehicle at Eurockot's dedicated launch facilities at Plesetsk Cosmodrome. The pathfinder campaign lasted four weeks and was carried out by a joint team that also included Khrunichev, Russian Space Forces and Eurockot personnel on the contractors' side. The pathfinder mission confirmed the capability of Eurockot Launch Services to perform the Iridium launch on cost and on schedule at Plesetsk following Eurockot's major investment in international standard preparation, integration and launch facilities including customer facilities and a new hotel. In 2003, Eurockot will also launch the Japanese SERVI'S-1 satellite for USEF. The ROCKOT launch vehicle is a 3 stage liquid fuel rocket whose first 2 stages have been adapted from the Russian SS-19. A third stage, called "Breeze", can be repeatedly ignited and is extraordinarily capable of manoeuvre. Rockot can place

  6. Evaluation of Molybdenum as a Surrogate for Iridium in the GPHS Weld Development

    SciTech Connect

    Stine, Andrew Martin; Pierce, Stanley W.; Moniz, Paul F.

    2015-10-17

    The welding equipment used for welding iridium containers (clads) at Los Alamos National Laboratory is twenty five years old and is undergoing an upgrade. With the upgrade, there is a requirement for requalification of the welding process, and the opportunity for process improvement. Testing of the new system and requalification will require several welds on iridium test parts and clads, and any efforts to improve the process will add to the need for iridium parts. The extreme high cost of iridium imposes a severe limitation on the extent of test welding that can be done. The 2 inch diameter, 0.027 inch thick, iridium blank disc that the clad cup is formed from, is useful for initial weld trials, but it costs $5000. The development clad sets needed for final tests and requalification cost $15,000 per set. A solution to iridium cost issue would be to do the majority of the weld development on a less expensive surrogate metal with similar weld characteristics. One such metal is molybdenum. Since its melting index (melting temperature x thermal conductivity) is closest to iridium, welds on molybdenum should be similar in size for a given weld power level. Molybdenum is inexpensive; a single 2 inch molybdenum disc costs only $9. In order to evaluate molybdenum as a surrogate for iridium, GTA welds were first developed to provide full penetration on 0.030 inch thick molybdenum discs at speeds of 20, 25, and 30 inches per minute (ipm). These weld parameters were then repeated on the standard 0.027 inch thick iridium blanks. The top surface and bottom surface (root) width and grain structure of the molybdenum and iridium welds were compared, and similarities were evident between the two metals. Due to material and thickness differences, the iridium welds were approximately 35% wider than the molybdenum welds. A reduction in iridium weld current of 35% produce welds slightly smaller than the molybdenum welds yet showed that current could be scaled according to molybdenum/iridium

  7. Selection of the appropriate radionuclide source for the efficiency calibration in methods of determining gross alpha activity in water.

    PubMed

    Corbacho, J A; Zapata-García, D; Montaña, M; Fons, J; Camacho, A; Guillén, J; Serrano, I; Baeza, A; Llauradó, M; Vallés, I

    2016-01-01

    Measuring the gross alpha activity in water samples is a rapid, straightforward way of determining whether the water might contain a radionuclide concentration whose consumption would imply a total indicative dose (TID) greater than some reference limit - currently set at 0.1 mSv/y in Europe. There are several methods used for such measurements. Two of them are desiccation with the salts being deposited on a planchet, and coprecipitation. The main advantage of these two methods is their ease of implementation and low cost of preparing the source to measure. However, there is considerable variability in the selection of the most suitable radioactive reference standard against which to calculate the water's gross alpha activity. The goal of this paper is to propose the most appropriate reference radionuclides to use as standards in determining gross alpha activities with these two methods, taking into account the natural radioactive characteristics of a wide range of waters collected at different points in Spain. Thus, the results will be consistent with each other and representative of the sum of alpha activities of all the alpha-emitters contained in a sample. PMID:26397746

  8. Development and Testing of High Surface Area Iridium Anodes for Molten Oxide Electrolysis

    NASA Technical Reports Server (NTRS)

    Shchetkovskiy, Anatoliy; McKechnie, Timothy; Sadoway, Donald R.; Paramore, James; Melendez, Orlando; Curreri, Peter A.

    2010-01-01

    Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400-1600?C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form? process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

  9. Development and Testing of High Surface Area Iridium Anodes for Molten Oxide Electrolysis

    NASA Technical Reports Server (NTRS)

    Shchetkovskiy, Anatoliy; McKechnie, Timothy; Sadoway, Donald R.; Paramore, James; Melendez, Orlando; Curreri, Peter A.

    2010-01-01

    Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400-1600 C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

  10. Development of a bioluminescence resonance energy transfer (BRET) for monitoring estrogen receptor alpha activation

    NASA Astrophysics Data System (ADS)

    Michelini, Elisa; Mirasoli, Mara; Karp, Matti; Virta, Marko; Roda, Aldo

    2004-06-01

    Estrogen receptor (ER) is a ligand-activated transcriptional factor, able to dimerize after activation and to bind specific DNA sequences (estrogen response elements), thus activating gene target transcription. Since ER homo- and hetero-dimerization (giving a-a and a-b isoforms) is a fundamental step for receptor activation, we developed an assay for detecting compounds that induce human ERa homo-dimerization based on bioluminescence resonance energy transfer (BRET). BRET is a non-radiative energy transfer, occurring between a luminescent donor and a fluorescent acceptor, that strictly depends on the closeness between the two proteins and can therefore be used for studying protein-protein interactions. We cloned ERa coding sequence in frame with either a variant of the green fluorescent protein (enhanced yellow fluorescent protein, EYFP) or Renilla luciferase (RLuc). Upon ERa homo-dimerization, BRET process takes place in the presence of the RLuc substrate coelenterazine resulting in EYFP emission at its characteristic wavelength. The ER alpha-Rluc and ER alpha-EYFP fusion proteins were cloned, then the occurrence of BRET in the presence of ER alpha activators was assayed both in vivo, within cells, and in vitro, with purified fusion proteins.

  11. Iridium-based double perovskites for efficient water oxidation in acid media

    NASA Astrophysics Data System (ADS)

    Diaz-Morales, Oscar; Raaijman, Stefan; Kortlever, Ruud; Kooyman, Patricia J.; Wezendonk, Tim; Gascon, Jorge; Fu, W. T.; Koper, Marc T. M.

    2016-08-01

    The development of active, cost-effective and stable oxygen-evolving catalysts is one of the major challenges for solar-to-fuel conversion towards sustainable energy generation. Iridium oxide exhibits the best available compromise between catalytic activity and stability in acid media, but it is prohibitively expensive for large-scale applications. Therefore, preparing oxygen-evolving catalysts with lower amounts of the scarce but active and stable iridium is an attractive avenue to overcome this economical constraint. Here we report on a class of oxygen-evolving catalysts based on iridium double perovskites which contain 32 wt% less iridium than IrO2 and yet exhibit a more than threefold higher activity in acid media. According to recently suggested benchmarking criteria, the iridium double perovskites are the most active catalysts for oxygen evolution in acid media reported until now, to the best of our knowledge, and exhibit similar stability to IrO2.

  12. Iridium-based double perovskites for efficient water oxidation in acid media

    PubMed Central

    Diaz-Morales, Oscar; Raaijman, Stefan; Kortlever, Ruud; Kooyman, Patricia J.; Wezendonk, Tim; Gascon, Jorge; Fu, W. T.; Koper, Marc T. M.

    2016-01-01

    The development of active, cost-effective and stable oxygen-evolving catalysts is one of the major challenges for solar-to-fuel conversion towards sustainable energy generation. Iridium oxide exhibits the best available compromise between catalytic activity and stability in acid media, but it is prohibitively expensive for large-scale applications. Therefore, preparing oxygen-evolving catalysts with lower amounts of the scarce but active and stable iridium is an attractive avenue to overcome this economical constraint. Here we report on a class of oxygen-evolving catalysts based on iridium double perovskites which contain 32 wt% less iridium than IrO2 and yet exhibit a more than threefold higher activity in acid media. According to recently suggested benchmarking criteria, the iridium double perovskites are the most active catalysts for oxygen evolution in acid media reported until now, to the best of our knowledge, and exhibit similar stability to IrO2. PMID:27498694

  13. Iridium-based double perovskites for efficient water oxidation in acid media.

    PubMed

    Diaz-Morales, Oscar; Raaijman, Stefan; Kortlever, Ruud; Kooyman, Patricia J; Wezendonk, Tim; Gascon, Jorge; Fu, W T; Koper, Marc T M

    2016-01-01

    The development of active, cost-effective and stable oxygen-evolving catalysts is one of the major challenges for solar-to-fuel conversion towards sustainable energy generation. Iridium oxide exhibits the best available compromise between catalytic activity and stability in acid media, but it is prohibitively expensive for large-scale applications. Therefore, preparing oxygen-evolving catalysts with lower amounts of the scarce but active and stable iridium is an attractive avenue to overcome this economical constraint. Here we report on a class of oxygen-evolving catalysts based on iridium double perovskites which contain 32 wt% less iridium than IrO2 and yet exhibit a more than threefold higher activity in acid media. According to recently suggested benchmarking criteria, the iridium double perovskites are the most active catalysts for oxygen evolution in acid media reported until now, to the best of our knowledge, and exhibit similar stability to IrO2. PMID:27498694

  14. Sensitized near-infrared emission from ytterbium(III) via direct energy transfer from iridium(III) in a heterometallic neutral complex.

    PubMed

    Mehlstäubl, Marita; Kottas, Gregg S; Colella, Silvia; De Cola, Luisa

    2008-05-14

    A tetrametallic iridium-ytterbium complex has been synthesised that shows sensitized near-infrared emission (lambda(max) = 976 nm) upon excitation of the iridium unit in the visible region (400 nm) due to efficient energy transfer from the iridium units to the Yb(III) ion. The iridium phosphorescence is quenched nearly quantitatively while the ytterbium ion emits brightly in the NIR.

  15. Iridium: Global OTH data communications for high altitude scientific ballooning

    NASA Astrophysics Data System (ADS)

    Denney, A.

    beneficial points provided by the Iridium platform include pure global accessibility (as well as polar), cost effectiveness because it is available as a COTS (Commercially Off The Shelf) technology, reliability in that the equipment must operate in extreme conditions (near space), integration and development time into current systems must be minimized. As a bonus Motorola and NAL Research Corporation are developing SBD (Short Burst Data) into the Iridium network. This may lead the way to a global IP (Internet Protocol) node based ballooning platform. The Iridium satellite data modems employ the Iridium Low-Earth Orbit (LEO) satellite network. The scope of this paper is to introduce an OTH communications alternative, albeit not necessarily a primary one, to existing ballooning platforms using COTS based emerging technologies. Design aspects, characteristics, actual flight testing statistics, principles of the Iridium modems and communication paths are described including payload and support instrumentation interfacing. Not limited to high altitude ballooning, the Iridium communications platform opens a new era in remote commanding and data retrieval.

  16. The solubility of hydrogen in rhodium, ruthenium, iridium and nickel.

    NASA Technical Reports Server (NTRS)

    Mclellan, R. B.; Oates, W. A.

    1973-01-01

    The temperature variation of the solubility of hydrogen in rhodium, ruthenium, iridium, and nickel in equilibrium with H2 gas at 1 atm pressure has been measured by a technique involving saturating the solvent metal with hydrogen, quenching, and analyzing in resultant solid solutions. The solubilities determined are small (atom fraction of H is in the range from 0.0005 to 0.00001, and the results are consistent with the simple quasi-regular model for dilute interstitial solid solutions. The relative partial enthalpy and excess entropy of the dissolved hydrogen atoms have been calculated from the solubility data and compared with well-known correlations between these quantities.

  17. Levitation of iridium and liquid mercury by ultrasound.

    PubMed

    Xie, W J; Cao, C D; Lü, Y J; Wei, B

    2002-09-01

    Single-axis acoustic levitation of the heaviest solid (iridium, rho=22.6 g cm(-3)) and liquid (mercury, rho=13.6 g cm(-3) on the Earth is achieved by greatly enhancing both the levitation force and stability through optimizing the geometric parameters of the levitator. The acoustically levitated Pb-Sn eutectic alloy melt (rho=8.5 g cm(-3)) is highly undercooled by up to 38 K, which results in a microstructural transition of "lamellae-broken lamellae-dendrites." The drastic enhancement of levitation capability indicates a broader application range of single-axis acoustic levitation. PMID:12225198

  18. Determination of iridium in mafic rocks by atomic absorption

    USGS Publications Warehouse

    Grimaldi, F.S.; Schnepfe, M.M.

    1970-01-01

    Iridium is determined in mineralized mafic rocks by atomic absorption after fire-assay concentration into a gold bead. Interelement interferences in the atomic-absorption determination are removed and Ir sensitivity is increased by buffering the solutions with a mixture of copper and sodium sulphates. Substantial amounts of Ag, Al, Au, Bi, Ca, Cd, Co, Cr, Fe, Ho, Hg, K, La, Mg, Mn, Mo, Ni, Pb, Te, Ti, V, Y, Zn and platinum metals can be tolerated in the atomic-absorption determination. The sensitivity and detection limits are 3.2 and 0.25 ppm of Ir, respectively. ?? 1970.

  19. Intercalation of graphene on iridium with sodium atoms

    NASA Astrophysics Data System (ADS)

    Rut'kov, E. V.; Gall', N. R.

    2015-06-01

    It has been shown that sodium atoms deposited on the surface of graphene atop iridium at T ≤ 850 K diffuse under the graphene layer into an intercalated state and accumulate there in significant concentrations ˜(2-3) × 1014 atoms cm-2. The release of the atoms from under the graphene "carpet" takes place upon destruction of the layer at T ≥ 1800 K. The physical nature of the differences in the processes of release of atoms of different alkali metals from under graphene has been discussed.

  20. Luminescent cyclometallated iridium(III) complexes having acetylide ligands

    SciTech Connect

    Thompson, Mark E.; Bossi, Alberto; Djurovich, Peter Ivan

    2014-09-02

    The present invention relates to phosphorescent (triplet-emitting) organometallic materials. The phosphorescent materials of the present invention comprise Ir(III)cyclometallated alkynyl complexes for use as triplet light-emitting materials. The Ir(III)cyclometallated alkynyl complexes comprise at least one cyclometallating ligand and at least one alkynyl ligand bonded to the iridium. Also provided is an organic light emitting device comprising an anode, a cathode and an emissive layer between the anode and the cathode, wherein the emissive layer comprises a Ir(III)cyclometallated alkynyl complex as a triplet emitting material.

  1. Measurements of the hard-x-ray reflectivity of iridium

    SciTech Connect

    Romaine, S.; Bruni, R.; Gorenstein, P.; Zhong, Z

    2007-01-10

    In connection with the design of a hard-x-ray telescope for the Constellation X-Ray Observatory we measured the reflectivity of an iridium-coated zerodur substrate as a function of angle at 55, 60, 70, and 80 keV at the National Synchrotron Light Source of Brookhaven National Laboratory. The optical constants were derived from the reflectivity data. The real component of the index of refraction is in excellent agreement with theoretical values at all four energies. However, the imaginary component, which is related to the mass attenuation coefficient, is 50% to 70% larger at 55, 60, and 70 keV than theoretical values.

  2. Dosimetric characterization of the M-15 high-dose-rate Iridium-192 brachytherapy source using the AAPM and ESTRO formalism.

    PubMed

    Ho Than, Minh-Tri; Munro Iii, John J; Medich, David C

    2015-05-08

    The Source Production & Equipment Co. (SPEC) model M-15 is a new Iridium-192 brachytherapy source model intended for use as a temporary high-dose-rate (HDR) brachytherapy source for the Nucletron microSelectron Classic afterloading system. The purpose of this study is to characterize this HDR source for clinical application by obtaining a complete set of Monte Carlo calculated dosimetric parameters for the M-15, as recommended by AAPM and ESTRO, for isotopes with average energies greater than 50 keV. This was accomplished by using the MCNP6 Monte Carlo code to simulate the resulting source dosimetry at various points within a pseudoinfinite water phantom. These dosimetric values next were converted into the AAPM and ESTRO dosimetry parameters and the respective statistical uncertainty in each parameter also calculated and presented. The M-15 source was modeled in an MCNP6 Monte Carlo environment using the physical source specifications provided by the manufacturer. Iridium-192 photons were uniformly generated inside the iridium core of the model M-15 with photon and secondary electron transport replicated using photoatomic cross-sectional tables supplied with MCNP6. Simulations were performed for both water and air/vacuum computer models with a total of 4 × 109 sources photon history for each simulation and the in-air photon spectrum filtered to remove low-energy photons belowδ = 10 keV. Dosimetric data, including D·(r,θ), gL(r), F(r,θ), φan(r), and φ-an, and their statistical uncertainty were calculated from the output of an MCNP model consisting of an M-15 source placed at the center of a spherical water phantom of 100 cm diameter. The air kerma strength in free space, SK, and dose rate constant, Λ, also was computed from a MCNP model with M-15 Iridium-192 source, was centered at the origin of an evacuated phantom in which a critical volume containing air at STP was added 100 cm from the source center. The reference dose rate, D·(r0,θ0) ≡ D· (1cm

  3. Dynamic high-temperature characterization of an iridium alloy in tension

    SciTech Connect

    Song, Bo; Nelson, Kevin; Jin, Helena; Lipinski, Ronald J.; Bignell, John; Ulrich, G. B.; George, E. P.

    2015-09-01

    Iridium alloys have been utilized as structural materials for certain high-temperature applications, due to their superior strength and ductility at elevated temperatures. The mechanical properties, including failure response at high strain rates and elevated temperatures of the iridium alloys need to be characterized to better understand high-speed impacts at elevated temperatures. A DOP-26 iridium alloy has been dynamically characterized in compression at elevated temperatures with high-temperature Kolsky compression bar techniques. However, the dynamic high-temperature compression tests were not able to provide sufficient dynamic high-temperature failure information of the iridium alloy. In this study, we modified current room-temperature Kolsky tension bar techniques for obtaining dynamic tensile stress-strain curves of the DOP-26 iridium alloy at two different strain rates (~1000 and ~3000 s-1) and temperatures (~750°C and ~1030°C). The effects of strain rate and temperature on the tensile stress-strain response of the iridium alloy were determined. The DOP-26 iridium alloy exhibited high ductility in stress-strain response that strongly depended on both strain rate and temperature.

  4. Analysis and Consequences of the Iridium 33-Cosmos 2251 Collision

    NASA Technical Reports Server (NTRS)

    Anz-Meador, P. D.; Liou, Jer-Chi

    2010-01-01

    The collision of Iridium 33 and Cosmos 2251, on 10 February 2009, was the first known unintentional hypervelocity collision in space of intact satellites. Iridium 33 was an active commercial telecommunications satellite, while Cosmos 2251 was a derelict communication satellite of the Strela-2M class. The collision occurred at a relative velocity of 11.6 km/s at an altitude of approximately 790 km over the Great Siberian Plain and near the northern apex of Cosmos 2251 s orbit. This paper describes the physical and orbital characteristics of the relevant spacecraft classes and reports upon our analysis of the resulting debris clouds size, mass, area-to-mass ratio, and relative velocity/directionality distributions. We compare these distributions to those predicted by the NASA breakup model and notable recent fragmentation events; in particular, we compare the area-to-mass ratio distribution for each spacecraft to that exhibited by the FY-1C debris cloud for the purpose of assessing the relative contribution of modern aerospace materials to debris clouds resulting from energetic collisions. In addition, we examine the long-term consequences of this event for the low Earth orbit (LEO) environment. Finally, we discuss "lessons learned", which may be incorporated into NASA s environmental models.

  5. Single step radiolytic synthesis of iridium nanoparticles onto graphene oxide

    NASA Astrophysics Data System (ADS)

    Rojas, J. V.; Molina Higgins, M. C.; Toro Gonzalez, M.; Castano, C. E.

    2015-12-01

    In this work a new approach to synthesize iridium nanoparticles on reduced graphene oxide is presented. The nanoparticles were directly deposited and grown on the surface of the carbon-based support using a single step reduction method through gamma irradiation. In this process, an aqueous isopropanol solution containing the iridium precursor, graphene oxide, and sodium dodecyl sulfate was initially prepared and sonicated thoroughly to obtain a homogeneous dispersion. The samples were irradiated with gamma rays with energies of 1.17 and 1.33 MeV emitted from the spontaneous decay of the 60Co irradiator. The interaction of gamma rays with water in the presence of isopropanol generates highly reducing species homogeneously distributed in the solution that can reduce the Ir precursor down to a zero valence state. An absorbed dose of 60 kGy was used, which according to the yield of reducing species is sufficient to reduce the total amount of precursor present in the solution. This novel approach leads to the formation of 2.3 ± 0.5 nm Ir nanoparticles distributed along the surface of the support. The oxygenated functionalities of graphene oxide served as nucleation sites for the formation of Ir nuclei and their subsequent growth. XPS results revealed that the interaction of Ir with the support occurs through Irsbnd O bonds.

  6. Analysis of Abrasive Blasting of DOP-26 Iridium Alloy

    SciTech Connect

    Ohriner, Evan Keith; Zhang, Wei; Ulrich, George B

    2012-01-01

    The effects of abrasive blasting on the surface geometry and microstructure of DOP-26 iridium alloy (Ir-0.3% W-0.006% Th 0.005% Al) have been investigated. Abrasive blasting has been used to control emissivity of components operating at elevated temperature. The effects of abrasive blasting conditions on surface morphology were investigated both experimentally and by numerical modeling. The simplified model, based on finite element analysis of a single angular particle impacting on Ir alloy disk, calculates the surface deformation and residual strain distribution. The experimental results and modeling results both indicate that the surface geometry is not sensitive to the abrasive blast process conditions of nozzle pressure and standoff distance considered in this study. On the other hand, the modeling results suggest that the angularity of the abrasive particle has an important role in determining surface geometry, which in turn, affects the emissivity. Abrasive blasting causes localized surface strains and localized recrystallization, but it does not affect grain size following extended exposure at elevated temperature. The dependence of emissivity of the DOP-26 alloy on mean surface slope follows a similar trend to that reported for pure iridium.

  7. Iridium anomaly in the Cretaceous section of the Eastern Kamchatka

    NASA Astrophysics Data System (ADS)

    Savelyev, Dmitry; Savelyeva, Olga

    2010-05-01

    The origin of iridium anomalies is widely discussed with regard to massive fauna and flora extinction at several geologic boundaries. Two hypotheses are most popular, cosmogenic and volcanogenic. Anomalies of iridium are known at many stratigraphic levels, both at the geologic series borders and within geologic series. Our studies revealed increased content of iridium in a section of Cretaceous oceanic deposits on the Kamchatsky Mys Peninsula (Eastern Kamchatka, Russia). The investigated section (56°03.353´N, 163°00.376´E) includes interbedded jaspers and siliceous limestones overlaying pillow-basalts. These deposits belong to the Smagin Formation of the Albian-Cenomanian age. In the middle and upper parts of the section two beds of black carbonaceous rocks with sapropelic organic matter were observed. Their formation marked likely episodes of oxygen depletion of oceanic intermediate water (oceanic anoxic events). Our geochemical studies revealed an enrichment of the carbonaceous beds in a number of major and trace elements (Al2O3, TiO2, FeO, MgO, K2O, P2O5, Cu, Zn, Ni, Cr, V, Mo, Ba, Y, Zr, Nb, REE, U, Au, Pt etc.) in comparison with associating jaspers and limestones. There are likely different sources which contributed to the enrichment. It is possible however to correlate the excess of Al, Ti, Zr, Nb with volcanogenic admixture, which is absent in limestones and jaspers. A possible source of the volcanogenic material was local volcanism as suggested by the close association of the investigated section with volcanic rocks (basaltic lavas and hyaloclastites). The basalts of the Smagin Formation were previously proposed to originate during Cretaceous activity of the Hawaiian mantle plume (Portnyagin et al., Geology, 2008). Neutron activation analysis indicated increased up to 9 ppb concentration of Ir at the bottom of the lower carbonaceous bed (inorganic part of the sample was analyzed comprising 46% of the bulk rock). In other samples Ir content was below

  8. Formylated chloro-bridged iridium(III) dimers as OLED materials: opening up new possibilities.

    PubMed

    Wong, Michael Y; Xie, Guohua; Tourbillon, Clarisse; Sandroni, Martina; Cordes, David B; Slawin, Alexandra M Z; Samuel, Ifor D W; Zysman-Colman, Eli

    2015-05-14

    In this study, a series of four formyl-substituted chloro-bridged iridium(iii) dimers were prepared. Their absorption, photophysical and electrochemical properties were studied in dichloromethane solution. It was found that as the formyl content increased on the cyclometalating ligands, emission unexpectedly became brighter. Organic light-emitting diodes (OLEDs) were fabricated using each of these iridium dimers as the emitter. The OLED fabricated using the brightest of the series, 2b, as the dopant afforded a decent external quantum efficiency (EQE) of 2.6%. This suggests that chloro-bridged iridium dimers are potential candidates as solid-state emitters.

  9. Sub-Chronic Oral Exposure to Iridium (III) Chloride Hydrate in Female Wistar Rats: Distribution and Excretion of the Metal

    PubMed Central

    Iavicoli, Ivo; Fontana, Luca; Bergamaschi, Antonio; Conti, Marcelo Enrique; Pino, Anna; Mattei, Daniela; Bocca, Beatrice; Alimonti, Alessandro

    2012-01-01

    Iridium tissue distribution and excretion in female Wistar rats following oral exposure to iridium (III) chloride hydrate in drinking water (from 1 to 1000 ng/ml) in a sub-chronic oral study were determined. Samples of urine, feces, blood and organs (kidneys, liver, lung, spleen and brain) were collected at the end of exposure. The most prominent fractions of iridium were retained in kidney and spleen; smaller amounts were found in lungs, liver and brain. Iridium brain levels were lower than those observed in other tissues but this finding can support the hypothesis of iridium capability to cross the blood brain barrier. The iridium kidney levels rose significantly with the administered dose. At the highest dose, important amounts of the metal were found in serum, urine and feces. Iridium was predominantly excreted via feces with a significant linear correlation with the ingested dose, which is likely due to low intestinal absorption of the metal. However, at the higher doses iridium was also eliminated through urine. These findings may be useful to help in the understanding of the adverse health effects, particularly on the immune system, of iridium dispersed in the environment as well as in identifying appropriate biological indices of iridium exposure. PMID:22942873

  10. Analysis and Implications of the Iridium 33-Cosmos 2251 Collision

    NASA Astrophysics Data System (ADS)

    Kelso, T. S.

    On 2009 February 10, Iridium 33--an operational US communications satellite in low-Earth orbit--was struck and destroyed by Cosmos 2251--a long-defunct Russian communications satellite. This is the first time since the dawn of the Space Age that two satellites have collided in orbit. To better understand the circumstances of this event and the ramifications for avoiding similar events in the future, this paper provides a detailed analysis of the predictions leading up to the collision, using various data sources, and looks in detail at the collision, the evolution of the debris clouds, and the long-term implications for satellite operations. The only publicly available system available to satellite operators for screening for close approaches, SOCRATES, did predict this close approach, but it certainly wasn't the closest approach predicted for the week of February 10. In fact, at the time of the collision, SOCRATES ranked this close approach 152 of the 11,428 within 5 km of any payload. A detailed breakdown is provided to help understand the limitations of screening for close approaches using the two-line orbital element sets. Information is also provided specifically for the Iridium constellation to provide an understanding of how these limitations affect decision making for satellite operators. Post-event analysis using high-accuracy orbital data sources will be presented to show how that information might have been used to prevent this collision, had it been available and used. Analysis of the collision event, along with the distribution of the debris relative to the original orbits, will be presented to help develop an understanding of the geometry of the collision and the near-term evolution of the resulting debris clouds. Additional analysis will be presented to show the long-term evolution of the debris clouds, including orbital lifetimes, and estimate the increased risk for operations conducted by Iridium and other satellite operators in the low-Earth orbit

  11. Iridium-catalyst-based autonomous bubble-propelled graphene micromotors with ultralow catalyst loading.

    PubMed

    Wang, Hong; Sofer, Zdeněk; Eng, Alex Yong Sheng; Pumera, Martin

    2014-11-10

    A novel concept of an iridium-based bubble-propelled Janus-particle-type graphene micromotor with very high surface area and with very low catalyst loading is described. The low loading of Ir catalyst (0.54 at %) allows for fast motion of graphene microparticles with high surface area of 316.2 m(2)  g(-1). The micromotor was prepared with a simple and scalable method by thermal exfoliation of iridium-doped graphite oxide precursor composite in hydrogen atmosphere. Oxygen bubbles generated from the decomposition of hydrogen peroxide at the iridium catalytic sites provide robust propulsion thrust for the graphene micromotor. The high surface area and low iridium catalyst loading of the bubble-propelled graphene motors offer great possibilities for dramatically enhanced cargo delivery. PMID:25293511

  12. Iridium-alloy processing experience in FY 1990

    SciTech Connect

    Ohriner, E.K.

    1991-11-01

    Iridium-alloy blanks and foil are produced at the Oak Ridge National Laboratory for use as fuel cladding material in radioisotope thermoelectric generators for space power sources. Until 1984, the material was produced from small, 500-g drop castings. A new process has been developed in which consumable electrodes of about 10 kg are melted, extruded, and then rolled to produce the sheet products. The work performed during FY 1990 included the consumable-electrode arc melting of four ingots and the extruding and rolling to sheet of four billets. Significant improvements made in the extruding and arc-melting processes during FY 1989 have been demonstrated to dramatically increase the rate of blank acceptance in nondestructive evaluations. Efforts to improve the rolling practice and to better characterize intermetallic particle distributions in the sheet are also described.

  13. Iridium-alloy processing experience in FY 1989

    SciTech Connect

    Ohriner, E.K.

    1990-11-01

    Iridium-alloy blanks and foil are produced at the Oak Ridge National Laboratory for use as fuel cladding material in radioisotope thermoelectric generators for space power sources. Until 1984, the material was produced from small 500-g drop castings. A new process has been developed in which consumable electrodes of about 10 kg are arc melted, extruded, and then rolled to produce the sheet products. The work performed during FY 1989 included the arc melting of three electrodes and the extruding and rolling to sheet of three billets. Significant improvements have been made in the extruding and arc-melting processes. Preliminary results show that these improvements have had an important effect in increasing the rate of blank acceptance in nondestructive evaluations. 4 refs., 33 figs., 11 tabs.

  14. Comparative modelling of chemical ordering in palladium-iridium nanoalloys

    SciTech Connect

    Davis, Jack B. A.; Johnston, Roy L.; Rubinovich, Leonid; Polak, Micha

    2014-12-14

    Chemical ordering in “magic-number” palladium-iridium nanoalloys has been studied by means of density functional theory (DFT) computations, and compared to those obtained by the Free Energy Concentration Expansion Method (FCEM) using derived coordination dependent bond energy variations (CBEV), and by the Birmingham Cluster Genetic Algorithm using the Gupta potential. Several compositions have been studied for 38- and 79-atom particles as well as the site preference for a single Ir dopant atom in the 201-atom truncated octahedron (TO). The 79- and 38-atom nanoalloy homotops predicted for the TO by the FCEM/CBEV are shown to be, respectively, the global minima and competitive low energy minima. Significant reordering of minima predicted by the Gupta potential is seen after reoptimisation at the DFT level.

  15. Iridium abundance maxima in the Upper Cenomanian extinction interval

    NASA Astrophysics Data System (ADS)

    Orth, C. J.; Attrep, M., Jr.; Mao, X. Y.; Kauffman, E. G.; Diner, R.

    1988-04-01

    Two iridium abundance peaks, both 0.11 ppb (whole-rock basis) over a local background of 0.017 ppb, have been found in Middle Cretaceous marine rocks near Pueblo, Colorado. They occur just below the 92-million-year-old Cenomanian-Turonian (C-T) stage boundary. No other peaks were found in 45 meters of strata (about 2.5 million years of deposition) above and below the boundary interval. The broad lower peak straddles the first in a series of extinctions of benthic and nektonic macrobiota which comprise the C-T extinction event. The sharp upper peak occurs stratigraphically about 1.2 meters above the lower peak. The excess Ir might be from meteoroid impacts.

  16. Iridium abundance maxima in the Upper Cenomanian extinction interval

    NASA Technical Reports Server (NTRS)

    Orth, C. J.; Attrep, M., Jr.; Mao, X. Y.; Kauffman, E. G.; Diner, R.

    1988-01-01

    Two iridium abundance peaks, both 0.11 ppb (whole-rock basis) over a local background of 0.017 ppb, have been found in Middle Cretaceous marine rocks near Pueblo, Colorado. They occur just below the 92-million-year-old Cenomanian-Turonian (C-T) stage boundary. No other peaks were found in 45 meters of strata (about 2.5 million years of deposition) above and below the boundary interval. The broad lower peak straddles the first in a series of extinctions of benthic and nektonic macrobiota which comprise the C-T extinction event. The sharp upper peak occurs stratigraphically about 1.2 meters above the lower peak. The excess Ir might be from meteoroid impacts.

  17. Intercalation of graphene on iridium with samarium atoms

    NASA Astrophysics Data System (ADS)

    Afanas'eva, E. Yu.; Rut'kov, E. V.; Gall, N. R.

    2016-07-01

    Intercalation of graphene on Ir (111) with Sm atoms is studied by methods of thermal desorption spectroscopy and thermionic emission. It is shown that adsorption of samarium at T = 300 K on graphene to concentrations of N ≤ 6 × 1014 atoms cm-2 followed by heating of the substrate leads to practically complete escape of adsorbate underneath the graphene layer. At N > 6 × 1014 atoms cm-2 and increasing temperature, a fraction of adsorbate remains on graphene in the form of two-dimensional "gas" and samarium islands and are desorbed in the range of temperatures of 1000-1200 K. Samarium remaining under the graphene is desorbed from the surface in the temperature range 1200-2150 K. Model conceptions for the samarium-graphene-iridium system in a wide temperature range are developed.

  18. Inhibition of Beta-Amyloid Fibrillation by Luminescent Iridium(III) Complex Probes

    PubMed Central

    Lu, Lihua; Zhong, Hai-Jing; Wang, Modi; Ho, See-Lok; Li, Hung-Wing; Leung, Chung-Hang; Ma, Dik-Lung

    2015-01-01

    We report herein the application of kinetically inert luminescent iridium(III) complexes as dual inhibitors and probes of beta-amyloid fibrillogenesis. These iridium(III) complexes inhibited Aβ1–40 peptide aggregation in vitro, and protected against Aβ-induced cytotoxicity in neuronal cells. Furthermore, the complexes differentiated between the aggregated and unaggregated forms of Aβ1–40 peptide on the basis of their emission response. PMID:26419607

  19. Synthesis of a chloro protected iridium nitrido complex.

    PubMed

    Sieh, Daniel; Schöffel, Julia; Burger, Peter

    2011-10-01

    Intramolecular activation processes of vulnerable ligand C-H bonds frequently limit the thermal stability and accessibility of late transition metal complexes with terminal metal nitrido units. In this study chloro substitution of the 2,6-ketimine N-aryl substituents (2,6-C(6)H(3)R(2), R = Cl) of the pyridine, diimine ligand is probed to increase the stability of square-planar iridium nitrido compounds. The thermal stability of iridium azido precursor and nitrido compounds was studied by a combination of thermoanalytical methods (DTG/MS and DSC) and were compared to the results for the related complexes with 2,6-dialkyl substituted N-aryl groups (R = Me, iPr). The investigations were complemented by DFT calculations, which allowed us to unravel details of the thermal decomposition pathways and provided mechanistic insights of further conversion steps and fluctional processes. The DTG/MS and DSC measurements revealed two different types of thermolysis pathways for the azido compounds. For the complexes with R = Cl and iPr substituents, two well-separated exothermic processes were observed. The first moderately exothermic loss of N(2) is followed by a second, strongly exothermic transformation. This contrasts the experimental results for the compound with 2,6-dimethyl substituents (R = Me), where both steps proceed concurrently in the same temperature range. The separation of the two thermal steps in the 2,6-dichloro substituted derivative allowed us to develop a protocol for the isolation of the highly insoluble nitrido complex, which was characterized by UV/vis, IR-spectroscopy and elemental analysis. Its constitution was further confirmed by reaction with silanes, which gave the corresponding silyl amido complexes.

  20. Dynamic High-Temperature Characterization of an Iridium Alloy in Compression at High Strain Rates

    SciTech Connect

    Song, Bo; Nelson, Kevin; Lipinski, Ronald J.; Bignell, John L.; Ulrich, G. B.; George, E. P.

    2014-06-01

    Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-temperature high-strain-rate performance are needed for understanding high-speed impacts in severe elevated-temperature environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain-rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. Current high-temperature Kolsky compression bar techniques are not capable of obtaining satisfactory high-temperature high-strain-rate stress-strain response of thin iridium specimens investigated in this study. We analyzed the difficulties encountered in high-temperature Kolsky compression bar testing of thin iridium alloy specimens. Appropriate modifications were made to the current high-temperature Kolsky compression bar technique to obtain reliable compressive stress-strain response of an iridium alloy at high strain rates (300 – 10000 s-1) and temperatures (750°C and 1030°C). Uncertainties in such high-temperature high-strain-rate experiments on thin iridium specimens were also analyzed. The compressive stress-strain response of the iridium alloy showed significant sensitivity to strain rate and temperature.

  1. In vitro electrical properties for iridium oxide versus titanium nitride stimulating electrodes.

    PubMed

    Weiland, James D; Anderson, David J; Humayun, Mark S

    2002-12-01

    Stimulating electrode materials must be capable of supplying high-density electrical charge to effectively activate neural tissue. Platinum is the most commonly used material for neural stimulation. Two other materials have been considered: iridium oxide and titanium nitride. This study directly compared the electrical characteristics of iridium oxide and titanium nitride by fabricating silicon substrate probes that differed only in the material used to form the electrode. Electrochemical measurements indicated that iridium oxide had lower impedance and a higher charge storage capacity than titanium nitride, suggesting better performance as a stimulating electrode. Direct measurement of the electrode potential in response to a biphasic current pulse confirmed that iridium oxide uses less voltage to transfer the same amount of charge, therefore using less power. The charge injection limit for titanium nitride was 0.87 mC/cm2, contradicting other reports estimating that titanium nitride was capable of injecting 22 mC/cm2. Iridium oxide charge storage was 4 mC/cm2, which is comparable to other published values for iridium oxide. Electrode efficiency will lead to an overall more efficient and effective device.

  2. Detailed correlation of type III radio bursts with H alpha activity. I - Active region of 22 May 1970.

    NASA Technical Reports Server (NTRS)

    Kuiper, T. B. H.; Pasachoff, J. M.

    1973-01-01

    Comparison of observations of type III impulsive radio bursts made at the Clark Lake Radio Observatory with high-spatial-resolution cinematographic observations taken at the Big Bear Solar Observatory. Use of the log-periodic radio interferometer makes it possible to localize the radio emission uniquely. This study concentrates on the particularly active region close to the limb on May 22, 1970. Sixteen of the 17 groups were associated with some H alpha activity, 11 of them with the start of such activity.

  3. Evaluation of oxide-coated iridium-rhenium chambers

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.

    1994-01-01

    Iridium-coated rhenium (Ir-Re) provides long life operation of radiation-cooled rockets at temperatures up to 2200 C. Ceramic oxide coatings could be used to increase Ir-Re rocket lifetimes and allow operation in highly oxidizing environments. Ceramic oxide coatings promise to serve as both thermal and diffusion barriers for the iridium layer. Seven ceramic oxide-coated Ir-Re, 22-N rocket chambers were tested with gaseous hydrogen/gaseous oxygen (GHz/G02) propellants. Five chambers had thick (over 10 mils), monolithic coatings of either hafnia (HfO2) or zirconia (ZrO2). Two chambers had coatings with thicknesses less than 5 mils. One of these chambers had a thin-walled coating of ZrO2 infiltrated with sol gel HfO2. The other chamber had a coating composed of an Ir-oxide composite. The purpose of this test program was to assess the ability of the oxide coatings to withstand the thermal shock of combustion initiation, adhere under repeated thermal cycling, and operate in aggressively oxidizing environments. All of the coatings survived the thermal shock of combustion and demonstrated operation at mixture ratios up to 11. Testing the Ir-oxide composite-coated chamber included over 29 min at mixture ratio 16. The thicker walled coatings provided the larger temperature drops across the oxide layer (up to 570 C), but were susceptible to macrocracking and eventual chipping at a stress concentrator. The cracks apparently resealed during firing, under compression of the oxide layer. The thinner walled coatings did not experience the macrocracking and chipping of the chambers that was seen with the thick, monolithic coatings. However, burn-throughs in the throat region did occur in both of the thin-walled chambers at mixture ratios well above stoichiometric. The burn-throughs were probably the result of oxygen diffusion through the oxide coating that allowed the underlying Ir and Re layers to be oxidized. The results of this test program indicated that the thin-walled oxide

  4. Evaluation of oxide-coated iridium-rhenium chambers

    NASA Astrophysics Data System (ADS)

    Reed, Brian D.

    1994-03-01

    Iridium-coated rhenium (Ir-Re) provides long life operation of radiation-cooled rockets at temperatures up to 2200 C. Ceramic oxide coatings could be used to increase Ir-Re rocket lifetimes and allow operation in highly oxidizing environments. Ceramic oxide coatings promise to serve as both thermal and diffusion barriers for the iridium layer. Seven ceramic oxide-coated Ir-Re, 22-N rocket chambers were tested with gaseous hydrogen/gaseous oxygen (GHz/G02) propellants. Five chambers had thick (over 10 mils), monolithic coatings of either hafnia (HfO2) or zirconia (ZrO2). Two chambers had coatings with thicknesses less than 5 mils. One of these chambers had a thin-walled coating of ZrO2 infiltrated with sol gel HfO2. The other chamber had a coating composed of an Ir-oxide composite. The purpose of this test program was to assess the ability of the oxide coatings to withstand the thermal shock of combustion initiation, adhere under repeated thermal cycling, and operate in aggressively oxidizing environments. All of the coatings survived the thermal shock of combustion and demonstrated operation at mixture ratios up to 11. Testing the Ir-oxide composite-coated chamber included over 29 min at mixture ratio 16. The thicker walled coatings provided the larger temperature drops across the oxide layer (up to 570 C), but were susceptible to macrocracking and eventual chipping at a stress concentrator. The cracks apparently resealed during firing, under compression of the oxide layer. The thinner walled coatings did not experience the macrocracking and chipping of the chambers that was seen with the thick, monolithic coatings. However, burn-throughs in the throat region did occur in both of the thin-walled chambers at mixture ratios well above stoichiometric. The burn-throughs were probably the result of oxygen diffusion through the oxide coating that allowed the underlying Ir and Re layers to be oxidized. The results of this test program indicated that the thin-walled oxide

  5. Luminescent Iridium(III) Complex Labeled DNA for Graphene Oxide-Based Biosensors.

    PubMed

    Zhao, Qingcheng; Zhou, Yuyang; Li, Yingying; Gu, Wei; Zhang, Qi; Liu, Jian

    2016-02-01

    There has been growing interest in utilizing highly photostable iridium(III) complexes as new luminescent probes for biotechnology and life science. Herein, iridium(III) complex with carboxyl group was synthesized and activated with N-hydroxysuccinimide, followed by tagging to the amino terminate of single-stranded DNA (ssDNA). The Ir-ssDNA probe was further combined with graphene oxide (GO) nanosheets to develop a GO-based biosensor for target ssDNA detection. The quenching efficiency of GO, and the photostability of iridium(III) complex and GO-Ir-ssDNA biosensor, were also investigated. On the basis of the high luminescence quenching efficiency of GO toward iridium(III) complex, the GO-Ir-ssDNA biosensor exhibited minimal background signals, while strong emission was observed when Ir-ssDNA desorbed from GO nanosheets and formed a double helix with the specific target, leading to a high signal-to-background ratio. Moreover, it was found that luminescent intensities of iridium(III) complex and GO-Ir-ssDNA biosensor were around 15 and 3 times higher than those of the traditional carboxyl fluorescein (FAM) dye and the GO-FAM-ssDNA biosensor after UV irradiation, respectively. Our study suggested the sensitive and selective Ir-ssDNA probe was suitable for the development of highly photostable GO-based detection platforms, showing promise for application beyond the OLED (organic light emitting diode) area. PMID:26753824

  6. Design, analysis, and fabrication of oxide-coated iridium/rhenium combustion chambers

    NASA Astrophysics Data System (ADS)

    Jang, Q.; Tuffias, R. H.; Laferla, R.; Ghoniem, N. M.

    1993-11-01

    Iridium-coated rhenium (Ir/Re) combustion chambers provide high temperature, oxidation-resistant operation for radiation-cooled liquid-fueled rocket engines. A 22-N (5-lb(sub f)) chamber has been operated for 15 hours at 2200 C (4000 F) using nitrogen tetroxide/monomethyl hydrazine (NTO/MMH) propellant, with negligible internal erosion. The oxidation resistance of these chambers could be further increased by the addition of refractory oxide coatings, providing longer life and/or operation in more oxidizing and higher temperature environments. The oxide coatings would serve as a thermal and diffusion barrier for the iridium coating, lowering the temperature of the iridium layer while also preventing the ingress of oxygen and egress of iridium oxides. This would serve to slow the failure mechanisms of Ir/Re chambers, namely the diffusion of rhenium to the inner surface and the oxidation of iridium. Such protection could extend chamber lifetimes by tens or perhaps hundreds of hours, and allow chamber operation on stoichiometric or higher mixture ratio oxygen/hydrogen (O2/H2) propellant. Extensive thermomechanical, thermochemical, and mass transport modeling was performed as a key material/structure design tool. Based on the results of these analyses, several 22-N oxide-coated Ir/Re chambers were fabricated and delivered to NASA Lewis Research Center for hot-fire testing.

  7. Electrodeposition of platinum-iridium alloy nanowires for hermetic packaging of microelectronics.

    PubMed

    Petrossians, Artin; Whalen, John J; Weiland, James D; Mansfeld, Florian

    2012-01-01

    An electrodeposition technique was applied for fabrication of dense platinum-iridium alloy nanowires as interconnect structures in hermetic microelectronic packaging to be used in implantable devices. Vertically aligned arrays of platinum-iridium alloy nanowires with controllable length and a diameter of about 200 nm were fabricated using a cyclic potential technique from a novel electrodeposition bath in nanoporous aluminum oxide templates. Ti/Au thin films were sputter deposited on one side of the alumina membranes to form a base material for electrodeposition. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to characterize the morphology and the chemical composition of the nanowires, respectively. SEM micrographs revealed that the electrodeposited nanowires have dense and compact structures. EDS analysis showed a 60:40% platinum-iridium nanowire composition. Deposition rates were estimated by determining nanowire length as a function of deposition time. High Resolution Transmission Electron Microscopy (HRTEM) images revealed that the nanowires have a nanocrystalline structure with grain sizes ranging from 3 nm to 5 nm. Helium leak tests performed using a helium leak detector showed leak rates as low as 1 × 10(-11) mbar L s(-1) indicating that dense nanowires were electrodeposited inside the nanoporous membranes. Comparison of electrical measurements on platinum and platinum-iridium nanowires revealed that platinum-iridium nanowires have improved electrical conductivity.

  8. Design, analysis, and fabrication of oxide-coated iridium/rhenium combustion chambers

    NASA Technical Reports Server (NTRS)

    Jang, Q.; Tuffias, R. H.; Laferla, R.; Ghoniem, N. M.

    1993-01-01

    Iridium-coated rhenium (Ir/Re) combustion chambers provide high temperature, oxidation-resistant operation for radiation-cooled liquid-fueled rocket engines. A 22-N (5-lb(sub f)) chamber has been operated for 15 hours at 2200 C (4000 F) using nitrogen tetroxide/monomethyl hydrazine (NTO/MMH) propellant, with negligible internal erosion. The oxidation resistance of these chambers could be further increased by the addition of refractory oxide coatings, providing longer life and/or operation in more oxidizing and higher temperature environments. The oxide coatings would serve as a thermal and diffusion barrier for the iridium coating, lowering the temperature of the iridium layer while also preventing the ingress of oxygen and egress of iridium oxides. This would serve to slow the failure mechanisms of Ir/Re chambers, namely the diffusion of rhenium to the inner surface and the oxidation of iridium. Such protection could extend chamber lifetimes by tens or perhaps hundreds of hours, and allow chamber operation on stoichiometric or higher mixture ratio oxygen/hydrogen (O2/H2) propellant. Extensive thermomechanical, thermochemical, and mass transport modeling was performed as a key material/structure design tool. Based on the results of these analyses, several 22-N oxide-coated Ir/Re chambers were fabricated and delivered to NASA Lewis Research Center for hot-fire testing.

  9. Toward the Digital Electrochemical Recognition of Cobalt, Iridium, Nickel, and Iron Ion Collisions by Catalytic Amplification.

    PubMed

    Dick, Jeffrey E; Bard, Allen J

    2016-07-13

    We report the electrochemical detection of femtomolar amounts of cobalt, iridium, nickel, and iron ions in solution by electrocatalyst formation and amplification. The metal oxides of these ions can be formed electrochemically and can catalyze the oxidation of water. Alternatively, the reduction of metal ions to metals, such as the reduction of IrCl6(3-) to iridium, is capable of electrocatalytically reducing protons to molecular hydrogen, as shown previously with Pt. These events, which manifest themselves in amperometry, correspond to the formation of electrocatalytic nuclei on the electrode surface, capable of electrocatalytically oxidizing water or reducing protons. An analysis of the frequency of anodic blips compared to theory implies that the requirement for water oxidation is 10 ± 1 ions of cobalt, 13 ± 4 ions of iridium, and 11 ± 3 ions of nickel. A similar analysis for iridium reduction and the corresponding catalytic reduction of protons implies that 6 ± 2 ions of iridium are required for proton reduction. These numbers are confirmed in an analysis of the time of first nucleation event, i.e. the time at which the first blip on the amperometric i-t experiment occurs. We further show that the anodic blips in detecting nickel increase in intensity upon increasing amounts of iron ions in solution to a ratio of Ni/Fe of ∼5, surprisingly close to that for bulk electrocatalysts of Ni-Fe. PMID:27295309

  10. Meteoric smoke fallout over the Holocene epoch revealed by iridium and platinum in Greenland ice.

    PubMed

    Gabrielli, Paolo; Barbante, Carlo; Plane, John M C; Varga, Anita; Hong, Sungmin; Cozzi, Giulio; Gaspari, Vania; Planchon, Frédéric A M; Cairns, Warren; Ferrari, Christophe; Crutzen, Paul; Cescon, Paolo; Boutron, Claude F

    2004-12-23

    An iridium anomaly at the Cretaceous/Tertiary boundary layer has been attributed to an extraterrestrial body that struck the Earth some 65 million years ago. It has been suggested that, during this event, the carrier of iridium was probably a micrometre-sized silicate-enclosed aggregate or the nanophase material of the vaporized impactor. But the fate of platinum-group elements (such as iridium) that regularly enter the atmosphere via ablating meteoroids remains largely unknown. Here we report a record of iridium and platinum fluxes on a climatic-cycle timescale, back to 128,000 years ago, from a Greenland ice core. We find that unexpectedly constant fallout of extraterrestrial matter to Greenland occurred during the Holocene, whereas a greatly enhanced input of terrestrial iridium and platinum masked the cosmic flux in the dust-laden atmosphere of the last glacial age. We suggest that nanometre-sized meteoric smoke particles, formed from the recondensation of ablated meteoroids in the atmosphere at altitudes >70 kilometres, are transported into the winter polar vortices by the mesospheric meridional circulation and are preferentially deposited in the polar ice caps. This implies an average global fallout of 14 +/- 5 kilotons per year of meteoric smoke during the Holocene.

  11. Earth's Radiation Imbalance from a Constellation of 66 Iridium Satellites

    NASA Astrophysics Data System (ADS)

    Chiu, J. C.; Wiscombe, W. J.

    2012-04-01

    The Earth Radiation Imbalance (ERI) at the top of the atmosphere is the primary driving force for climate change. If ERI is not zero, then Earth's temperature, both oceanic and atmospheric, will change gradually over time, tending toward a new steady state. The best estimates of current ERI from climate models range from 0.4 to 0.9 W/m2 (the imbalance being caused mainly by increasing CO2), but current satellite systems do not have the accuracy to measure ERI to even one significant digit. In this paper, we will describe a proposed constellation of 66 Earth radiation budget instruments, to be hosted on Iridium satellites. This system represents a quantum leap over current systems in several ways, in particular in providing ERI to at least one significant digit, thus enabling a crucial test of climate models. Because of its 24/7 coverage, the system will also provide ERI at three-hourly time scales without requiring extrapolations from narrowband geostationary instruments. This would allow studies of ERI's response to fast-evolving phenomena like dust storms and hurricanes. This offers a new, synoptic view of Earth radiation budget that will transform it from a monthly average into a dynamical variable alongside standard meteorological variables like temperature and pressure.

  12. High-Temperature Oxidation Behavior of Iridium-Rhenium Alloys

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.

    1995-01-01

    The life-limiting mechanism for radiation-cooled rockets made from iridium-coated rhenium (Ir/Re) is the diffusion of Re into the Ir layer and the subsequent oxidation of the resulting Ir-Re alloy from the inner surface. In a previous study, a life model for Ir/Re rockets was developed. It incorporated Ir-Re diffusion and oxidation data to predict chamber lifetimes as a function of temperature and oxygen partial pressure. Oxidation testing at 1540 deg C suggested that a 20-wt percent Re concentration at the inner wall surface should be established as the failure criterion. The present study was performed to better define Ir-oxidation behavior as a function of Re concentration and to supplement the data base for the life model. Samples ranging from pure Ir to Ir-40 wt percent Re (Ir-40Re) were tested at 1500 deg C, in two different oxygen environments. There were indications that the oxidation rate of the Ir-Re alloy increased significantly when it went from a single-phase solid solution to a two-phase mixture, as was suggested in previous work. However, because of testing anomalies in this study, there were not enough dependable oxidation data to definitively raise the Ir/Re rocket failure criterion from 20-wt percent Re to a Re concentration corresponding to entry into the two-phase region.

  13. High Strain Rate Tensile Testing of DOP-26 Iridium

    SciTech Connect

    Schneibel, Joachim H; Carmichael Jr, Cecil Albert; George, Easo P

    2007-11-01

    The iridium alloy DOP-26 was developed through the Radioisotope Power Systems Program in the Office of Nuclear Energy of the Department of Energy. It is used for clad vent set cups containing radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for spacecraft. This report describes mechanical testing results for DOP-26. Specimens were given a vacuum recrystallization anneal of 1 hour at 1375 C and tested in tension in orientations parallel and perpendicular to the rolling direction of the sheet from which they were fabricated. The tests were performed at temperatures ranging from room temperature to 1090 C and strain rates ranging from 1 x 10{sup -3} to 50 s{sup -1}. Room temperature testing was performed in air, while testing at elevated temperatures was performed in a vacuum better than 1 x 10{sup -4} Torr. The yield stress (YS) and the ultimate tensile stress (UTS) decreased with increasing temperature and increased with increasing strain rate. Between 600 and 1090 C, the ductility showed a slight increase with increasing temperature. Within the scatter of the data, the ductility did not depend on the strain rate. The reduction in area (RA), on the other hand, decreased with increasing strain rate. The YS and UTS values did not differ significantly for the longitudinal and transverse specimens. The ductility and RA values of the transverse specimens were marginally lower than those of the longitudinal specimens.

  14. Evaluated Iridium, Yttrium, and Thulium Cross Sections and Integral Validation Against Critical Assembly and Bethe Sphere Measurements

    SciTech Connect

    Chadwick, M.B. Frankle, S.; Trellue, H.; Talou, P.; Kawano, T.; Young, P.G.; MacFarlane, R.E.; Wilkerson, C.W.

    2007-12-15

    We describe new dosimetry (radiochemical) ENDF evaluations for yttrium, iridium, and thulium. These LANL2006 evaluations were based upon measured data and on nuclear model cross section calculations. In the case of iridium and yttrium, new measurements using the GEANIE gamma-ray detector at LANSCE were used to infer (n,xn) cross sections, the measurements being augmented by nuclear model calculations using the GNASH code. The thulium isotope evaluations were based on GNASH calculations and older measurements. The evaluated cross section data are tested through comparisons of simulations with measurements of reaction rates in critical assemblies and in Bethe sphere (sometimes called Wyman sphere) integral experiments. Two types of Bethe sphere experiments were studied - a LiD experiment that had a significant component of 14 MeV neutrons, and a LiD-U experiment that additionally had varying amounts of fission neutrons depending upon the location. These simulations were performed with the MCNP code using continuous energy Monte Carlo, and because the neutron fluences can be modeled fairly accurately by MCNP at different locations in these assemblies, the comparisons provide a valuable validation test of the accuracy of the evaluated cross sections and their energy dependencies. The MCNP integral reaction rate validation testing for the three detectors yttrium, iridium, and thulium, in the LANL2006 database is summarized as follows: (1) (n,2n)near 14 MeV: In 14 MeV-dominated locations (the LiD Bethe spheres and the outer regions of the LiD-U Bethe spheres), the (n,2n) products are modeled very well for all three detectors, suggesting that the evaluated {sup 89}Y(n,2n), {sup 191}Ir(n,2n), and {sup 169}Tm(n,2n) cross sections are accurate to better than about 5% near 14 MeV; (2) (n,2n)near threshold: In locations that have a significant number of fission spectrum neutrons or downscattered neutrons from 14 MeV inelastic scattering (the central regions of the Li

  15. Isotopic Biogeochemistry

    NASA Technical Reports Server (NTRS)

    Hayes, J. M.

    1985-01-01

    An overview is provided of the biogeochemical research. The funding, productivity, personnel and facilities are reviewed. Some of the technical areas covered are: carbon isotopic records; isotopic studies of banded iron formations; isotope effects in microbial systems; studies of organic compounds in ancient sediments; and development in isotopic geochemistry and analysis.

  16. Facilitation and inhibition in attention: Functional dissociation of pre-stimulus alpha activity, P1, and N1 components.

    PubMed

    Slagter, H A; Prinssen, S; Reteig, L C; Mazaheri, A

    2016-01-15

    Attention--the ability to attend to some things while ignoring others - can be best described as an emergent property of many neural mechanisms, facilitatory and inhibitory, working together to resolve competition for processing resources and control of behavior. Previous EEG and MEG studies examining the neural mechanisms underlying facilitation and inhibition of stimulus processing typically used paradigms requiring alternating shifts of attention in the spatial domain, with stimuli occurring at both attended and unattended locations. These studies generally observed greater pre-stimulus alpha oscillations over task-irrelevant vs. relevant posterior regions and bilateral attentional modulations of early sensory processing. In contrast, in the current series of experiments, participants continuously attended to only one hemifield and stimuli were only presented at the attended location, affording us an opportunity to elucidate the inhibitory and facilitatory effects of attention in the brain in a context in which spatial relevance was fixed. We found that continuous attention to one hemifield did not modulate prestimulus alpha activity in ipsilateral regions but did result in a perfectly lateralized P1 attention effect to ipsilateral posterior regions. Moreover, we found a bilateral N1 effect. These findings suggest that pre-stimulus alpha activity, the P1 and the N1 reflect qualitatively different aspects of attention; While pre-stimulus alpha-band activity may reflect a top-down inhibitory mechanism that critically depends on functional competition between task-relevant and irrelevant sensory regions, the ipsilateral P1 effect may reflect stimulus-triggered blocking of sensory processing in irrelevant networks, and the N1 effect facilitation of task-relevant processing.

  17. Identification of an iridium(III) complex with anti-bacterial and anti-cancer activity

    PubMed Central

    Lu, Lihua; Liu, Li-Juan; Chao, Wei-chieh; Zhong, Hai-Jing; Wang, Modi; Chen, Xiu-Ping; Lu, Jin-Jian; Li, Ruei-nian; Ma, Dik-Lung; Leung, Chung-Hang

    2015-01-01

    Group 9 transition metal complexes have been widely explored as therapeutic agents due to their unique geometry, their propensity to undergo ligand exchanges with biomolecules and their diverse steric and electronic properties. These metal complexes can offer distinct modes of action in living organisms compared to carbon-based molecules. In this study, we investigated the antimicrobial and anti-proliferative abilities of a series of cyclometallated iridium(III) complexes. The iridium(III) complex 1 inhibited the growth of S. aureus with MIC and MBC values of 3.60 and 7.19 μM, respectively, indicating its potent bactericidal activity. Moreover, complex 1 also exhibited cytotoxicity against a number of cancer cell lines, with particular potency against ovarian, cervical and melanoma cells. This cyclometallated iridium(III) complex is the first example of a substitutionally-inert, Group 9 organometallic compound utilized as a direct and selective inhibitor of S. aureus. PMID:26416333

  18. Near-Infrared Phosphorescent Iridium(III) Benzonorrole Complexes Possessing Pyridine-based Axial Ligands.

    PubMed

    Maurya, Yogesh Kumar; Ishikawa, Takahiro; Kawabe, Yasunori; Ishida, Masatoshi; Toganoh, Motoki; Mori, Shigeki; Yasutake, Yuhsuke; Fukatsu, Susumu; Furuta, Hiroyuki

    2016-06-20

    Novel near-infrared phosphorescent iridium(III) complexes based on benzo-annulated N-linked corrole analogue (termed as benzonorrole) were synthesized. The structures of the complexes revealed octahedral coordination geometries involving an organometallic iridium-carbon bond with two external axial ligands. Interestingly, the iridium(III) complex exhibits near-infrared phosphorescence at room temperature at wavelengths beyond 900 nm. The significant redshift of the emission, as compared to the corrole congener, is originated from the ligand-centered triplet character. The fine-tuning of the photophysical properties of the complexes was achieved by introducing electron-donating and electron-withdrawing substituents on the axial pyridine ligands. PMID:27249778

  19. Preparation of iridium targets by electrodeposition for neutron capture cross section measurements

    DOE PAGES

    Bond, Evelyn M.; Moody, W. Allen; Arnold, Charles; Bredeweg, Todd A.; Jandel, Marian; Rusev, Gencho Y.

    2016-03-01

    Here, the preparation of 191Ir and 193Ir electrodeposits for neutron capture cross-section measurements at the detector for advanced neutron capture experiments located at the at Los Alamos Neutron Science Center is described. The electrodeposition of iridium in the desired thickness of 0.4–1 mg/cm2 is challenging. Better yields and thicknesses were obtained using electrodeposition from isopropyl alcohol solutions than from ammonium sulfate solutions. 191Ir and 193Ir targets were initially prepared using the standard single-sided electrodeposition cell. Iridium electrodepositions using a double-sided electrodeposition cell were developed and were optimized, resulting in thick, uniform iridium deposits. LA UR 15-22475.

  20. Preparation of iridium targets by electrodeposition for neutron capture cross section measurements

    SciTech Connect

    Bond, Evelyn M.; Moody, W. Allen; Arnold, Charles; Bredeweg, Todd A.; Jandel, Marian; Rusev, Gencho Y.

    2015-11-18

    Here, the preparation of 191Ir and 193Ir electrodeposits for neutron capture cross-section measurements at the detector for advanced neutron capture experiments located at the at Los Alamos Neutron Science Center is described. The electrodeposition of iridium in the desired thickness of 0.4–1 mg/cm2 is challenging. Better yields and thicknesses were obtained using electrodeposition from isopropyl alcohol solutions than from ammonium sulfate solutions. 191Ir and 193Ir targets were initially prepared using the standard single-sided electrodeposition cell. Iridium electrodepositions using a double-sided electrodeposition cell were developed and were optimized, resulting in thick, uniform iridium deposits. LA UR 15-22475.

  1. Grain-boundary cavitation and weld-underbead cracking in DOP-26 iridium alloy

    SciTech Connect

    Mosley, W.C. Jr.

    1983-01-01

    Plutonium-238 oxide fuel pellets for the General Purpose Heat Source Radioisotopic thermoelectric generators to be used on the NASA Galileo Mission to Jupiter and the International Solar Polar Mission are produced and encapsulated in DOP-26 iridium alloy at the Savannah River Plant. DOP-26 iridium alloy was developed at the Oak Ridge National Laboratory and contains nominally 0.3 weight-percent tungsten, 60-ppM thorium and 50-ppM aluminum. Underbead cracks occasionally occur in the girth weld on the iridium alloy cladding in the area where the gas tungsten arc is quenched. A variety of electron beam techniques have been used to determine the cause of cracking. Results are discussed. (WHK)

  2. Heterogeneous Catalysis for Water Oxidation by an Iridium Complex Immobilized on Bipyridine-Periodic Mesoporous Organosilica.

    PubMed

    Liu, Xiao; Maegawa, Yoshifumi; Goto, Yasutomo; Hara, Kenji; Inagaki, Shinji

    2016-07-01

    Heterogenization of metal-complex catalysts for water oxidation without loss of their catalytic activity is important for the development of devices simulating photosynthesis. In this study, efficient heterogeneous iridium complexes for water oxidation were prepared using bipyridine-bridged periodic mesoporous organosilica (BPy-PMO) as a solid chelating ligand. The BPy-PMO-based iridium catalysts (Ir-BPy-PMO) were prepared by postsynthetic metalation of BPy-PMO and characterized through physicochemical analyses. The Ir-BPy-PMOs showed high catalytic activity for water oxidation. The turnover frequency (TOF) values for Ir-BPy-PMOs were one order of magnitude higher than those of conventional heterogeneous iridium catalysts. The reusability and stability of Ir-BPy-PMO were also examined, and detailed characterization was conducted using powder X-ray diffraction, nitrogen adsorption, (13) C DD MAS NMR spectroscopy, TEM, and XAFS methods. PMID:27168492

  3. Selective DNA purine base photooxidation by bis-terdentate iridium(III) polypyridyl and cyclometalated complexes.

    PubMed

    Jacques, Alexandre; Kirsch-De Mesmaeker, Andrée; Elias, Benjamin

    2014-02-01

    Two bis-terdentate iridium(III) complexes with polypyridyl and cyclometalated ligands have been prepared and characterized. Their spectroscopic and electrochemical properties have been studied, and a photophysical scheme addressing their properties is proposed. Different types of excited states have been considered to account for the deactivation processes in each complex. Interestingly, in the presence of mono- or polynucleotides, a photoinduced electron-transfer process from a DNA purine base (i.e., guanine or adenine) to the excited complex is shown through luminescence quenching experiments. For the first time, this work reports evidence for selective DNA purine bases oxidation by excited iridium(III) bis-terdentate complexes.

  4. High-strain-rate, high-temperature biaxial testing of DOP-26 iridium

    SciTech Connect

    George, T.G.

    1988-05-01

    High-strain-rate biaxial punch tests were performed on DOP-26 (Ir-0.3 wt.% tungsten) iridium-alloy disc given annealing and aging heat treatments. Test temperatures ranged between 600 and 1440/degree/C, and punch velocity was held constant at 45 m/s. Three types of samples were evaluated: Z-batch old-process discs, B-batch old-process discs, and B-batch new-process discs. The results indicate that batch-to-batch variations in ductility are significant and that new-process iridium is slightly more ductile than old-process material. 12 refs., 43 figs., 26 tabs.

  5. Thermocouples of molybdenum and iridium alloys for more stable vacuum-high temperature performance

    NASA Technical Reports Server (NTRS)

    Morris, J. F. (Inventor)

    1978-01-01

    Thermocouples providing stability and performance reliability in systems involving high temperatures and vacuums by employing a bimetallic thermocouple sensor are described. Each metal of the sensor is selected from a group of metals comprising molybdenum and iridium and alloys containing only those two metals. The molybdenum, iridium thermocouple sensor alloys provide bare metal thermocouple sensors having advantageous vapor pressure compatibility and performance characteristics. The compatibility and physical characteristics of the thermocouple sensor alloys result in improved emf, temperature properties and thermocouple hot junction performance.

  6. Donor-Flexible Nitrogen Ligands for Efficient Iridium-Catalyzed Water Oxidation Catalysis.

    PubMed

    Navarro, Miquel; Li, Mo; Müller-Bunz, Helge; Bernhard, Stefan; Albrecht, Martin

    2016-05-10

    A pyridylideneamide ligand with variable donor properties owing to a pronounced zwitterionic and a neutral diene-type resonance structure was used as a dynamic ligand at a Cp* iridium center to facilitate water oxidation catalysis, a reaction that requires the stabilization of a variety of different iridium oxidation states and that is key for developing an efficient solar fuel device. The ligand imparts high activity (nearly three-fold increase of turnover frequency compared to benchmark systems), and exceptionally high turnover numbers, which indicate a robust catalytic cycle and little catalyst degradation.

  7. New Iridium Complex Coordinated with Tetrathiafulvalene Substituted Triazole-pyridine Ligand: Synthesis, Photophysical and Electrochemical Properties.

    PubMed

    Niu, Zhi-Gang; Xie, Hui; He, Li-Rong; Li, Kai-Xiu; Xia, Qing; Wu, Dong-Min; Li, Gao-Nan

    2016-01-01

    A new iridium(III) complex based on the triazole-pyridine ligand with tetrathiafulvalene unit, [Ir(ppy)2(L)]PF6 (1), has been synthesized and structurally characterized. The absorption spectra, luminescent spectra and electrochemical behaviors of L and 1 have been investigated. Complex 1 is found to be emissive at room temperature with maxima at 481 and 510 nm. The broad and structured emission bands are suggested a mixing of 3LC (3π-π*) and 3CT (3MLCT) excited states. The influence of iridium ion coordination on the redox properties of the TTF has also been investigated by cyclic voltammetry. PMID:27333555

  8. Iridium {mu}-imido/amido A-frame complexes

    SciTech Connect

    Ye, Changqing; Sharp, P.R.

    1995-01-04

    The reaction of Ir{sub 2}Cl{sub 2}(CO){sub 2}({mu}-dppm){sub 2}(dppm=bis(diphenylphosphino)methane) with 2 equiv of LiNHR yields Ir{sub 2}({mu}-NR)(CO){sub 2}({mu}-dppm){sub 2}, (1) (R=p-tolyl,Ph,p-BrC{sub 6}H{sub 4}), or its tautomer Ir{sub 2}({mu}-NHR)(CO){sub 2}({mu}-dppm)-({mu}-dppm-H), (2) (dppm-H = bis(diphenylphosphino)methanide; R= Et, Bu{sup 5}). NMR data suggest that (1) (R=p-tolyl, Ph, p-BrC{sub 6}H{sub 4}) are in equilibrium with small amounts of (2) in polar solvents. An X-ray structural determination of (1) (R = p-tolyl) shows that the imido nitrogen atom links two iridium atoms at the apex of an A-frame complex. A very short N-C distance in the imido group suggests extensive N-lone pair donation to the tolyl ring. Crystals of (1) (R = p-tolyl) from benzene are tetragonal (P4{sub 3}) with a = 21.337(1) {Angstrom},c = 14.478-(2) {Angstrom}, and Z = 4. With the exception of R=p-NO{sub 2}C{sub 6}H{sub 4}, p-BrC{sub 6}H{sub 4}, and Et, the complexes react with 1 equiv of CO at ambient temperature to form Ir{sub 2}(CO){sub 3}({mu}-dppm){sub 2} as the major metal containing product. For R = Et, the reaction generates the unstable isocyanate complex Ir{sub 2}(CO){sub 4}({mu}-dppm){sub 2} and amine except for the p-NO{sub 2}C{sub 6}H{sub 4} complex, which gives a complex mixture of products.

  9. Metal-ligand cooperation in catalytic intramolecular hydroamination: a computational study of iridium-pyrazolato cooperative activation of aminoalkenes.

    PubMed

    Tobisch, Sven

    2012-06-01

    The present study comprehensively explores diverse mechanistic pathways for intramolecular hydroamination of prototype 2,2-dimethyl-4-penten-1-amine by Cp*Ir chloropyrazole (1; Cp*=pentamethylcyclopentadienyl) in the presence of KOtBu base with the aid of density functional theory (DFT) calculations. The most accessible mechanistic pathway for catalytic turnover commences from Cp*Ir pyrazolato (Pz) substrate adduct 2⋅S, representing the catalytically competent compound and proceeds via initial electrophilic activation of the olefin C=C bond by the metal centre. It entails 1) facile and reversible anti nucleophilic amine attack on the iridium-olefin linkage; 2) Ir-C bond protonolysis via stepwise transfer of the ammonium N-H proton at the zwitterionic [Cp*IrPz-alkyl] intermediate onto the metal that is linked to turnover-limiting, reductive, cycloamine elimination commencing from a high-energy, metastable [Cp*IrPz-hydrido-alkyl] species; and 3) subsequent facile cycloamine liberation to regenerate the active catalyst species. The amine-iridium bound 2 a⋅S likely corresponds to the catalyst resting state and the catalytic reaction is expected to proceed with a significant primary kinetic isotope. This study unveils the vital role of a supportive hydrogen-bonded network involving suitably aligned β-basic pyrazolato and cycloamido moieties together with an external amine molecule in facilitating metal protonation and reductive elimination. Cooperative hydrogen bonding thus appears pivotal for effective catalysis. The mechanistic scenario is consonant with catalyst performance data and furthermore accounts for the variation in performance for [Cp*IrPz] compounds featuring a β- or γ-basic pyrazolato unit. As far as the route that involves amine N-H bond activation is concerned, a thus far undocumented pathway for concerted amidoalkene → cycloamine conversion through olefin protonation by the pyrazole N-H concurrent with N-C ring closure is disclosed as a

  10. Iridium(I) Compounds as Prospective Anticancer Agents: Solution Chemistry, Antiproliferative Profiles and Protein Interactions for a Series of Iridium(I) N-Heterocyclic Carbene Complexes.

    PubMed

    Gothe, Yvonne; Marzo, Tiziano; Messori, Luigi; Metzler-Nolte, Nils

    2016-08-22

    A series of structurally related mono- and bis-NHC-iridium(I) (NHC: N-heterocyclic carbene) complexes have been investigated for their suitability as potential anticancer drugs. Their spectral behaviour in aqueous buffers under physiological-like conditions and their cytotoxicity against the cancer cell lines MCF-7 and HT-29 are reported. Notably, almost all complexes exhibit significant cytotoxic effects towards both cancer cell lines. In general, the cationic bis-carbene complexes show higher stability and greater anticancer activity than their neutral mono-carbene analogues with IC50 values in the high nanomolar range. Furthermore, to gain initial mechanistic insight, the interactions of these iridium(I)-NHC complexes with two model proteins, namely lysozyme and cytochrome c, were explored by HR-ESI-MS analyses. The different protein metalation patterns of the complexes can be roughly classified into two distinct groups. Those interactions give us a first idea about the possible mechanism of action of this class of compounds. Overall, our findings show that iridium(I)-NHC complexes represent very interesting candidates for further development as new metal-based anticancer drugs.

  11. Iridium(I) Compounds as Prospective Anticancer Agents: Solution Chemistry, Antiproliferative Profiles and Protein Interactions for a Series of Iridium(I) N-Heterocyclic Carbene Complexes.

    PubMed

    Gothe, Yvonne; Marzo, Tiziano; Messori, Luigi; Metzler-Nolte, Nils

    2016-08-22

    A series of structurally related mono- and bis-NHC-iridium(I) (NHC: N-heterocyclic carbene) complexes have been investigated for their suitability as potential anticancer drugs. Their spectral behaviour in aqueous buffers under physiological-like conditions and their cytotoxicity against the cancer cell lines MCF-7 and HT-29 are reported. Notably, almost all complexes exhibit significant cytotoxic effects towards both cancer cell lines. In general, the cationic bis-carbene complexes show higher stability and greater anticancer activity than their neutral mono-carbene analogues with IC50 values in the high nanomolar range. Furthermore, to gain initial mechanistic insight, the interactions of these iridium(I)-NHC complexes with two model proteins, namely lysozyme and cytochrome c, were explored by HR-ESI-MS analyses. The different protein metalation patterns of the complexes can be roughly classified into two distinct groups. Those interactions give us a first idea about the possible mechanism of action of this class of compounds. Overall, our findings show that iridium(I)-NHC complexes represent very interesting candidates for further development as new metal-based anticancer drugs. PMID:27443984

  12. The growth of graphite phase on an iridium field electron emitter

    NASA Astrophysics Data System (ADS)

    Bernatskii, D. P.; Pavlov, V. G.

    2016-06-01

    The growth of graphite on the surface of an iridium tip in pyrolysis of benzene to give a ribbed crystal has been found by the methods of field electron and desorption microscopy. The formation of a graphite crystal results in the electric field factor increasing. The adsorption of alkali metals on the surface of graphite is accompanied by the intercalation effect.

  13. Catalytic cleavage of ether C-O bonds by pincer iridium complexes.

    PubMed

    Haibach, Michael C; Lease, Nicholas; Goldman, Alan S

    2014-09-15

    The development of efficient catalytic methods to cleave the relatively unreactive C-O bonds of ethers remains an important challenge in catalysis. Building on our group's recent work, we report the dehydroaryloxylation of aryl alkyl ethers using pincer iridium catalysts. This method represents a rare fully atom-economical method for ether C-O bond cleavage. PMID:25060043

  14. Single orientation graphene synthesized on iridium thin films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Dangwal Pandey, A.; Krausert, K.; Franz, D.; Grânäs, E.; Shayduk, R.; Müller, P.; Keller, T. F.; Noei, H.; Vonk, V.; Stierle, A.

    2016-08-01

    Heteroepitaxial iridium thin films were deposited on (0001) sapphire substrates by means of molecular beam epitaxy, and subsequently, one monolayer of graphene was synthesized by chemical vapor deposition. The influence of the growth parameters on the quality of the Ir films, as well as of graphene, was investigated systematically by means of low energy electron diffraction, x-ray reflectivity, x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and atomic force microscopy. Our study reveals (111) oriented iridium films with high crystalline quality and extremely low surface roughness, on which the formation of large-area epitaxial graphene is achieved. The presence of defects, like dislocations, twins, and 30° rotated domains in the iridium films is also discussed. The coverage of graphene was found to be influenced by the presence of 30° rotated domains in the Ir films. Low iridium deposition rates suppress these rotated domains and an almost complete coverage of graphene was obtained. This synthesis route yields inexpensive, air-stable, and large-area graphene with a well-defined orientation, making it accessible to a wider community of researchers for numerous experiments or applications, including those which use destructive analysis techniques or irreversible processes. Moreover, this approach can be used to tune the structural quality of graphene, allowing a systematic study of the influence of defects in various processes like intercalation below graphene.

  15. Comparative assessment of iridium oxide and platinum alloy wires using an in vitro glial scar assay.

    PubMed

    Ereifej, Evon S; Khan, Saida; Newaz, Golam; Zhang, Jinsheng; Auner, Gregory W; VandeVord, Pamela J

    2013-12-01

    The long-term effect of chronically implanted electrodes is the formation of a glial scar. Therefore, it is imperative to assess the biocompatibility of materials before employing them in neural electrode fabrication. Platinum alloy and iridium oxide have been identified as good candidates as neural electrode biomaterials due to their mechanical and electrical properties, however, effect of glial scar formation for these two materials is lacking. In this study, we applied a glial scarring assay to observe the cellular reactivity to platinum alloy and iridium oxide wires in order to assess the biocompatibility based on previously defined characteristics. Through real-time PCR, immunostaining and imaging techniques, we will advance the understanding of the biocompatibility of these materials. Results of this study demonstrate iridium oxide wires exhibited a more significant reactive response as compared to platinum alloy wires. Cells cultured with platinum alloy wires had less GFAP gene expression, lower average GFAP intensity, and smaller glial scar thickness. Collectively, these results indicated that platinum alloy wires were more biocompatible than the iridium oxide wires.

  16. A pH Sensor Based on a Stainless Steel Electrode Electrodeposited with Iridium Oxide

    ERIC Educational Resources Information Center

    Martinez, C. C. M.; Madrid, R. E.; Felice, C. J.

    2009-01-01

    A simple procedure to make an iridium oxide (IrO[subscript 2]) electrodeposited pH sensor, that can be used in a chemical, biomedical, or materials laboratory, is presented here. Some exercises, based on this sensor, that can be used to teach important concepts in the field of biomedical, biochemical, tissue, or materials engineering, are also…

  17. Potential contributions to space geodesy from the IridiumNEXT constellation

    NASA Astrophysics Data System (ADS)

    Gunter, B. C.; Encarnação, J.; Ditmar, P.; Klees, R.

    2012-12-01

    The IridiumNEXT constellation will soon replace the existing Iridium satellite telecommunication network, with initial launches set to start in 2015. In addition to the primary task of providing global telecommunication services, each IridiumNEXT satellite will also carry a hosted payload that will provide both private and public institutions the opportunity to place an instrument suite on one or all of constellation's satellites. This creates the possibility to gather continuous, global observations of Earth over the entire 15 year projected mission lifetime. Access to such a platform creates the potential to investigate many of Earth's highly dynamic processes at a spatiotemporal resolution that is simply not possible from single-satellite missions. Space geodesy is one the numerous fields that would benefit from such a mission. Precise orbits of the IridiumNEXT satellites derived through an on-board GNSS receiver (plus accelerometers and star cameras) have the potential to observe the large-scale, high-frequency variations in Earth's gravity field at time scales as short as one day. Additional positioning data from ground-based laser ranging stations would help improve the orbit determination, in addition to providing the necessary link to improve estimates of geocenter motion and reference frames. In this presentation, we will analyze the expected geodetic science returns from such a mission and will discuss the instrumental requirements needed to achieve these objectives.

  18. Luminescent Iridium Complexes Used in Light-Emitting Electrochemical Cells (LEECs).

    PubMed

    Henwood, Adam F; Zysman-Colman, Eli

    2016-08-01

    Cationic iridium(III) complexes represent the single largest class of emitters used in light emitting electrochemical cells (LEECs). In this chapter, we highlight the state-of-the-art emitters in terms of efficiency and stability in LEEC devices, highlighting blue, green, yellow/orange, red and white devices, and provide an outlook to the future of LEECs. PMID:27573388

  19. A neutron activation analysis of iridium concentration in Yamato carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Yabushita, S.; Wada, K.; Moriyama, H.; Takeuchi, K.

    1988-09-01

    Iridium concentration in extra-terrestrial bodies is an important quantity in relation to Ir-rich geological layers. Ir concentration of a Yamato carbonaceous chondrite (Y-793321) has been measured by a neutron activation method. The measurement yields a value (0.57±0.06) μg per gramme for the chondrite.

  20. Iridium complexes of new NCP pincer ligands: catalytic alkane dehydrogenation and alkene isomerization.

    PubMed

    Jia, Xiangqing; Zhang, Lei; Qin, Chuan; Leng, Xuebing; Huang, Zheng

    2014-09-28

    Iridium complexes of novel NCP pincer ligands containing pyridine and phosphinite arms have been synthesized. One Ir complex shows good catalytic activity for alkane dehydrogenation, and all complexes are highly active for olefin isomerization. A combination of the Ir complex and a (PNN)Fe pincer complex catalyzes the formation of linear alkylboronates selectively from internal olefins via sequential olefin isomerization-hydroboration.

  1. Arctic Ocean Communications: Performance Of High-Data Transmission Over The Iridium System

    NASA Astrophysics Data System (ADS)

    Wilkinson, J.; Valcic, L.; Doble, M. J.; Maksym, T. L.; Robst, J.

    2014-12-01

    The Iridium satellite communications service was launched over 15 years ago, and it is presently the "go to" service for transmitting data and voice from the polar regions. However there is very little information available regarding the metrics associated with the throughput of data via this system. During a recent campaign we released over 30 "dial-up" iridium enabled drifting buoys in a relatively small region of the Arctic Ocean. Over the past 6 months relatively large amounts of data have now been routinely downloaded (every hour) from these systems. Each platform, as well as the base station in the UK, independently monitored the throughput of data and here we present an analysis of the metrics (download speed, drop outs, power consumption etc.) associated with the transmission of data through the Iridium system. As the role of autonomous platforms in the polar region increases there is a greater need to better understand the issues associated with data transfer. Iridium is a vital component of any autonomous system and therefore the information presented here will be of value to the technological, scientific and engineering communities.

  2. Report of Iridium/{sup 238}PuO{sub 2} Compatibility Test

    SciTech Connect

    Taylor, D.H.

    2001-08-09

    This study indicates that the chemical purity of the fuel used presently to fabricate fueled clad vent sets will not present any special problems to the performance of the fueled clad vent sets as intended. However, cation impurities in the fuel can have a deleterious effect on the iridium cladding and vents and should be minimized as much as practical.

  3. Testing and evaluation of oxide-coated iridium/rhenium chambers

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.

    1993-01-01

    Iridium-coated rhenium provides long life operation of radiation-cooled rockets at temperatures up to 2200 C. Ceramic oxide coatings could be used to increase iridium/rhenium rocket lifetimes and allow operation in highly oxidizing environments. Ceramic oxide coatings promise to serve as both thermal and diffusion barriers for the iridium layer. Seven ceramic oxide-coated iridium/rhenium, 22 N rocket chambers were tested on gaseous hydrogen/gaseous oxygen propellants. Five chambers had thick (over 10 mils), monolithic coatings of either hafnia or zirconia. Two chambers had coatings with thicknesses less than 5 mils. One of these chambers had a thin-walled coating of zirconia infiltrated with sol gel hafnia. The other chamber had a coating composed of an iridium/oxide composite. The purpose of this test program was to assess the ability of the oxide coatings to withstand the thermal shock of combustion initiation, adhere under repeated thermal cycling, and operate in aggressively oxidizing environments. All of the coatings survived the thermal shock of combustion and demonstrated operation at mixture ratios up to 11. The iridium/oxide composite coated chamber included testing for over 29 minutes at mixture ratio 16. The thicker-walled coatings provided the larger temperature drops across the oxide layer (up to 570 C), but were susceptible to macrocracking and eventual chipping at a stress concentrator. The cracks apparently resealed during firing, under compression of the oxide layer. The thinner-walled coatings did not experience the macrocracking and chipping of the chambers seen with the thick, monolithic coatings. However, burnthroughs in the throat region did occur in both of the thin-walled chambers at mixture ratios well above stochiometric. The burn-throughs were probably the result of oxygen-diffusion through the oxide coating that allowed the underlying iridium and rhenium layers to be oxidized. The results of this test program indicated that the thin

  4. High temperature reactive ion etching of iridium thin films with aluminum mask in CF4/O2/Ar plasma

    NASA Astrophysics Data System (ADS)

    Yeh, Chia-Pin; Lisker, Marco; Kalkofen, Bodo; Burte, Edmund P.

    2016-08-01

    Reactive ion etching (RIE) technology for iridium with CF4/O2/Ar gas mixtures and aluminum mask at high temperatures up to 350 °C was developed. The influence of various process parameters such as gas mixing ratio and substrate temperature on the etch rate was studied in order to find optimal process conditions. The surface of the samples after etching was found to be clean under SEM inspection. It was also shown that the etch rate of iridium could be enhanced at higher process temperature and, at the same time, very high etching selectivity between aluminum etching mask and iridium could be achieved.

  5. Iridium and Spherules in Late Eocene Impact Deposits

    NASA Technical Reports Server (NTRS)

    Kyte, F. T.; Liu, S.

    2002-01-01

    We have been independently examining the Ir (FTK) and spherule (SL) contents of recently discovered late Eocene impact deposits from the south Atlantic and western Indian oceans. These include ODP Sites 1090 [14,15], 709 [lo], and 699 [Liu in prep.]. Iridium abundances at these sites are within the typical range reported for late Eocene deposits, with peak concentrations between 100 and 1000 pg/g. In Table 1 we present estimated net Ir fluences (in ng Ir/cm ) for these and nine other sites. Although there are fewer sites than the K/T boundary, the average of 9 ng Ir/cm2 is probably a good estimate of the late Eocene global flux. This is enough Ir for a 6 km comet (assuming 250 ng/g Ir, p=1.5), is sufficient to produce the Popigai or Chesapeake Bay structures, and is 16% of the flux estimated for the K/T boundary (55 ng/cm2 [ 161). Figure 1 shows the relative abundances of Ir, glassy microtektites and cpx-bearing spherules in sediments from Sites 699 and 1090, which are separated by only 3100 km. Although these two sites have similar Ir anomalies, the abundances of spherules are quite different. Site 1090 has well-defined peaks for both types of spherules, with a peak of 562 cpx spheruledg, while Site 699 contains only a few glassy microtektites and no cpx spherules. While the different abundances of spherules may reflect a heterogeneous distribution of spherules on the Earth s surface, an equally likely cause of this difference may be differential preservation of spherules in the sediment. recovered are only a trace residue of the initial impact deposit. Earlier work found 0.22 ng/g Ir in glassy microtektites from Site 689 [17], an insufficient concentration to support 0.16 ng/g in the bulk sediment at this site. We measured 15 ng/g Ir in a group of 95 cpx spherules from Site 1090 with sizes from 63 to -200 pm, a set typical of the size distribution at this site. Although this is a significant concentration it also cannot support the Ir peak. We presently lack

  6. Testing of electroformed deposited iridium/powder metallurgy rhenium rockets

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.; Dickerson, Robert

    1996-01-01

    High-temperature, oxidation-resistant chamber materials offer the thermal margin for high performance and extended lifetimes for radiation-cooled rockets. Rhenium (Re) coated with iridium (Ir) allow hours of operation at 2200 C on Earth-storable propellants. One process for manufacturing Ir/Re rocket chambers is the fabrication of Re substrates by powder metallurgy (PM) and the application of Ir coatings by using electroformed deposition (ED). ED Ir coatings, however, have been found to be porous and poorly adherent. The integrity of ED Ir coatings could be improved by densification after the electroforming process. This report summarizes the testing of two 22-N, ED Ir/PM Re rocket chambers that were subjected to post-deposition treatments in an effort to densify the Ir coating. One chamber was vacuum annealed, while the other chamber was subjected to hot isostatic pressure (HIP). The chambers were tested on gaseous oxygen/gaseous hydrogen propellants, at mixture ratios that simulated the oxidizing environments of Earth-storable propellants. ne annealed ED Ir/PM Re chamber was tested for a total of 24 firings and 4.58 hr at a mixture ratio of 4.2. After only 9 firings, the annealed ED Ir coating began to blister and spall upstream of the throat. The blistering and spalling were similar to what had been experienced with unannealed, as-deposited ED Ir coatings. The HIP ED Ir/PM Re chamber was tested for a total of 91 firings and 11.45 hr at mixture ratios of 3.2 and 4.2. The HIP ED Ir coating remained adherent to the Re substrate throughout testing; there were no visible signs of coating degradation. Metallography revealed, however, thinning of the HIP Ir coating and occasional pores in the Re layer upstream of the throat. Pinholes in the Ir coating may have provided a path for oxidation of the Re substrate at these locations. The HIP ED Ir coating proved to be more effective than vacuum annealed and as-deposited ED Ir. Further densification is still required to

  7. Simulated Microgravity Reduces TNF-Alpha Activity, Suppresses Glucose Uptake and Enhances Arginine Flux in Pancreatic Islets of Langerhans

    NASA Technical Reports Server (NTRS)

    Tobin, Brian W.; Leeper-Woodford, Sandra K.; Hashemi, Brian B.; Smith, Scott M.; Sams, Clarence F.; Paloski, W. H. (Technical Monitor)

    2000-01-01

    The present studies were designed to determine effects of microgravity upon lipopolysaccharide (LPS) stimulated tumor necrosis factor alpha (TNF - alpha) activity and indices of insulin and fuel homeostasis of pancreatic islets of Langerhans. Islets (1726+/-117,150 u IEU) from Wistar Furth rats were treated as: 1) HARV (High Aspect Ratio Vessel cell culture) , 2) HARV plus LPS 3) static culture, 4) static culture plus LPS TNF-alpha (L929 cytotoxicity assay) was significantly increased in LPS-induced HARV and static cultures, yet the increase was more pronounced in the static culture group (p<0.05). A decrease in insulin concentration was demonstrated in the LPS stimulated HARV culture (p<0.05). We observed a greater glucose concentration and increased disappearance of arginine in islets cultured in HARVs. While nitrogenous compound analysis indicated a ubiquitous reliance upon glutamine in all experimental groups, arginine was converted to ornithine at a two-fold greater rate in the islets cultured in the HARV microgravity paradigm (p<0.05). These studies demonstrate alterations in LPS induced TNF-alpha production of pancreatic islets of Langerhans, favoring a lesser TNF activity in the HARV paradigm. These alterations in fuel homeostasis may be promulgated by gravity averaged cell culture methods or by three dimensional cell assembly.

  8. Identification of an iridium-containing compound with a formal oxidation state of IX.

    PubMed

    Wang, Guanjun; Zhou, Mingfei; Goettel, James T; Schrobilgen, Gary J; Su, Jing; Li, Jun; Schlöder, Tobias; Riedel, Sebastian

    2014-10-23

    One of the most important classifications in chemistry and within the periodic table is the concept of formal oxidation states. The preparation and characterization of compounds containing elements with unusual oxidation states is of great interest to chemists. The highest experimentally known formal oxidation state of any chemical element is at present VIII, although higher oxidation states have been postulated. Compounds with oxidation state VIII include several xenon compounds (for example XeO4 and XeO3F2) and the well-characterized species RuO4 and OsO4 (refs 2-4). Iridium, which has nine valence electrons, is predicted to have the greatest chance of being oxidized beyond the VIII oxidation state. In recent matrix-isolation experiments, the IrO4 molecule was characterized as an isolated molecule in rare-gas matrices. The valence electron configuration of iridium in IrO4 is 5d(1), with a formal oxidation state of VIII. Removal of the remaining d electron from IrO4 would lead to the iridium tetroxide cation ([IrO4](+)), which was recently predicted to be stable and in which iridium is in a formal oxidation state of IX. There has been some speculation about the formation of [IrO4](+) species, but these experimental observations have not been structurally confirmed. Here we report the formation of [IrO4](+) and its identification by infrared photodissociation spectroscopy. Quantum-chemical calculations were carried out at the highest level of theory that is available today, and predict that the iridium tetroxide cation, with a Td-symmetrical structure and a d(0) electron configuration, is the most stable of all possible [IrO4](+) isomers. PMID:25341786

  9. Identification of an iridium-containing compound with a formal oxidation state of IX

    NASA Astrophysics Data System (ADS)

    Wang, Guanjun; Zhou, Mingfei; Goettel, James T.; Schrobilgen, Gary J.; Su, Jing; Li, Jun; Schlöder, Tobias; Riedel, Sebastian

    2014-10-01

    One of the most important classifications in chemistry and within the periodic table is the concept of formal oxidation states. The preparation and characterization of compounds containing elements with unusual oxidation states is of great interest to chemists. The highest experimentally known formal oxidation state of any chemical element is at present VIII, although higher oxidation states have been postulated. Compounds with oxidation state VIII include several xenon compounds (for example XeO4 and XeO3F2) and the well-characterized species RuO4 and OsO4 (refs 2, 3, 4). Iridium, which has nine valence electrons, is predicted to have the greatest chance of being oxidized beyond the VIII oxidation state. In recent matrix-isolation experiments, the IrO4 molecule was characterized as an isolated molecule in rare-gas matrices. The valence electron configuration of iridium in IrO4 is 5d1, with a formal oxidation state of VIII. Removal of the remaining d electron from IrO4 would lead to the iridium tetroxide cation ([IrO4]+), which was recently predicted to be stable and in which iridium is in a formal oxidation state of IX. There has been some speculation about the formation of [IrO4]+ species, but these experimental observations have not been structurally confirmed. Here we report the formation of [IrO4]+ and its identification by infrared photodissociation spectroscopy. Quantum-chemical calculations were carried out at the highest level of theory that is available today, and predict that the iridium tetroxide cation, with a Td-symmetrical structure and a d0 electron configuration, is the most stable of all possible [IrO4]+ isomers.

  10. Highly Active Iridium/Iridium Tin/Tin Oxide Heterogeneous Nanoparticles as Alternative Electrocatalysts for the Ethanol Oxidation Reaction

    SciTech Connect

    Du W.; Su D.; Wang Q.; Saxner D.; Deskins N.A.; Krzanowski J.E.; Frenkel A.I.; Teng X.

    2011-08-03

    Ethanol is a promising fuel for low-temperature direct fuel cell reactions due to its low toxicity, ease of storage and transportation, high-energy density, and availability from biomass. However, the implementation of ethanol fuel cell technology has been hindered by the lack of low-cost, highly active anode catalysts. In this paper, we have studied Iridium (Ir)-based binary catalysts as low-cost alternative electrocatalysts replacing platinum (Pt)-based catalysts for the direct ethanol fuel cell (DEFC) reaction. We report the synthesis of carbon supported Ir{sub 71}Sn{sub 29} catalysts with an average diameter of 2.7 {+-} 0.6 nm through a 'surfactant-free' wet chemistry approach. The complementary characterization techniques, including aberration-corrected scanning transmission electron microscopy equipped with electron energy loss spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy, are used to identify the 'real' heterogeneous structure of Ir{sub 71}Sn{sub 29}/C particles as Ir/Ir-Sn/SnO{sub 2}, which consists of an Ir-rich core and an Ir-Sn alloy shell with SnO{sub 2} present on the surface. The Ir{sub 71}Sn{sub 29}/C heterogeneous catalyst exhibited high electrochemical activity toward the ethanol oxidation reaction compared to the commercial Pt/C (ETEK), PtRu/C (Johnson Matthey) as well as PtSn/C catalysts. Electrochemical measurements and density functional theory calculations demonstrate that the superior electro-activity is directly related to the high degree of Ir-Sn alloy formation as well as the existence of nonalloyed SnO{sub 2} on surface. Our cross-disciplinary work, from novel 'surfactant-free' synthesis of Ir-Sn catalysts, theoretical simulations, and catalytic measurements to the characterizations of 'real' heterogeneous nanostructures, will not only highlight the intriguing structure-property correlations in nanosized catalysts but also have a transformative impact on the commercialization of DEFC

  11. Negative thermal ion mass spectrometry of osmium, rhenium, and iridium

    NASA Technical Reports Server (NTRS)

    Creaser, R. A.; Papanastassiou, D. A.; Wasserburg, G. J.

    1991-01-01

    This paper describes a technique for obtaining, in a conventional surface ionization mass spectrometer, intense ion beams of negatively charged oxides of Os, Re, and Ir by thermal ionization. It is shown that the principal ion species of these ions are OsO3(-), ReO4(-), and IrO2(-), respectively. For Re-187/Os-187 studies, this technique offers the advantage of isotopic analyses without prior chemical separation of Re from Os.

  12. Determination of surface coverage of catalysts: Temperature programmed experiments on platinum and iridium sponge catalysts after low temperature ammonia oxidation

    SciTech Connect

    Broek, A.C.M. van den; Grondelle, J. van; Santen, R.A. van

    1999-07-25

    The activity of iridium and platinum sponge catalysts was studied in the low temperature gas phase oxidation of ammonia with oxygen. Under the reaction conditions used, iridium was found to be more active and more selective to nitrogen than platinum. Furthermore it was established from activity measurements that both catalysts lose activity as a function of time on stream due to inhibition of the surface by reaction intermediates. The used catalysts were studied by XPS and temperature programmed techniques. It was found that the surface of the catalysts had a high coverage of NH and OH and some additional NH{sub 2}. It seems most likely that the reaction mechanism proceeds through a stepwise dehydrogenation of the ammonia molecule. It appears that the last dehydrogenation step (NH by OH to N and water) is the rate determining step. The high selectivity of iridium to nitrogen can be explained by the higher activity of iridium in dissociating NO.

  13. (210)Po in drinking water, its potential health effects, and inadequacy of the gross alpha activity MCL.

    PubMed

    Seiler, Ralph

    2016-10-15

    Polonium-210 ((210)Po) is a naturally-occurring, carcinogenic member of the (238)U decay series and the granddaughter of (210)Pb. It has a half life of 138.4days and is rarely found in drinking water at levels exceeding 5mBq/L because it strongly binds to aquifer sediment. When the current US Maximum Contaminant Level (MCL) covering (210)Po was promulgated in December 2000, very little was known about its occurrence and the processes responsible for mobilizing it. More is now known about the processes that mobilize (210)Po from sediments and a review of recent occurrence data show that it may not be as rare in the US as the US Environmental Protection Agency (USEPA) thought in 2000. Worldwide, only about 2200 analyses for (210)Po in drinking water were identified, with activities exceeding 500mBq/L being found only in Finland, India, Sweden, and the US. The median of 400 (210)Po analyses from the US is 4.75mBq/L and >10% of the samples exceed 500mBq/L. Current compliance-monitoring regulations in the US essentially guarantee that (210)Po contamination will not be detected except in very contaminated wells. Major problems with the US Gross Alpha Activity MCL include the volatility of (210)Po and extended holding times and sample-compositing methods that can allow the majority of (210)Po in a sample bottle to decay before analysis. In light of new information, the radionuclide rule should be changed and direct measurements of (210)Po should be made in all public-water supply wells to rule out its presence. Much of the important biological and toxicological research on (210)Po is more than four decades old and new laboratory research using modern tools is needed. Biological and epidemiological investigations of known contaminated areas are needed to assess the effect (210)Po exposure is having on animals and humans consuming the water.

  14. Uncoupling protein-2 up-regulation and enhanced cyanide toxicity are mediated by PPAR{alpha} activation and oxidative stress

    SciTech Connect

    Zhang, X.; Li, L.; Prabhakaran, K.; Zhang, L.; Leavesley, H.B.; Borowitz, J.L.; Isom, G.E.

    2007-08-15

    Uncoupling protein 2 (UCP-2) is an inner mitochondrial membrane proton carrier that modulates mitochondrial membrane potential ({delta}{psi}{sub m}) and uncouples oxidative phosphorylation. We have shown that up-regulation of UCP-2 by Wy14,643, a selective peroxisome proliferator-activated receptor-{alpha} (PPAR{alpha}) agonist, enhances cyanide cytotoxicity. The pathway by which Wy14,643 up-regulates UCP-2 was determined in a dopaminergic cell line (N27 cells). Since dopaminergic mesencephalic cells are a primary brain target of cyanide, the N27 immortalized mesencephalic cell was used in this study. Wy14,643 produced a concentration- and time-dependent up-regulation of UCP-2 that was linked to enhanced cyanide-induced cell death. MK886 (PPAR{alpha} antagonist) or PPAR{alpha} knock-down by RNA interference (RNAi) inhibited PPAR{alpha} activity as shown by the peroxisome proliferator response element-luciferase reporter assay, but only partially decreased up-regulation of UCP-2. The role of oxidative stress as an alternative pathway to UCP-2 up-regulation was determined. Wy14,643 induced a rapid surge of ROS generation and loading cells with glutathione ethyl ester (GSH-EE) or pre-treatment with vitamin E attenuated up-regulation of UCP-2. On the other hand, RNAi knockdown of PPAR{alpha} did not alter ROS generation, suggesting a PPAR{alpha}-independent component to the response. Co-treatment with PPAR{alpha}-RNAi and GSH-EE blocked both the up-regulation of UCP-2 by Wy14,643 and the cyanide-induced cell death. It was concluded that a PPAR{alpha}-mediated pathway and an oxidative stress pathway independent of PPAR{alpha} mediate the up-regulation of UCP-2 and subsequent increased vulnerability to cyanide-induced cytotoxicity.

  15. Excimer laser deinsulation of Parylene-C on iridium for use in an activated iridium oxide film-coated Utah electrode array

    PubMed Central

    Yoo, Je-Min; Negi, Sandeep; Tathireddy, Prashant; Solzbacher, Florian; Song, Jong-In; Rieth, Loren W.

    2013-01-01

    Implantable microelectrodes provide a measure to electrically stimulate neurons in the brain and spinal cord and record their electrophysiological activity. A material with a high charge capacity such as activated or sputter-deposited iridium oxide film (AIROF or SIROF) is used as an interface. The Utah electrode array (UEA) uses SIROF for its interface material with neural tissue and oxygen plasma etching (OPE) with an aluminium foil mask to expose the active area, where the interface between the electrode and neural tissue is formed. However, deinsulation of Parylene-C using OPE has limitations, including the lack of uniformity in the exposed area and reproducibility. While the deinsulation of Parylene-C using an excimer laser is proven to be an alternative for overcoming the limitations, the iridium oxide (IrOx) suffers from fracture when high laser fluence (>1000 mJ/cm2) is used. Iridium (Ir), which has a much higher fracture resistance than IrOx, can be deposited before excimer laser deinsulation and then the exposed Ir film area can be activated by electrochemical treatment to acquire the AIROF. Characterisation of the laser-ablated Ir film and AIROF by surface analysis (X-ray photoelectron spectroscopy, scanning electron microscope, and atomic force microscope) and electrochemical analysis (electrochemical impedance spectroscopy, and cyclic voltammetry) shows that the damage on the Ir film induced by laser irradiation is significantly less than that on SIROF, and the AIROF has a high charge storage capacity. The results show the potential of the laser deinsulation technique for use in high performance AIROF-coated UEA fabrication. PMID:23458659

  16. Isotope separation

    DOEpatents

    Bartlett, Rodney J.; Morrey, John R.

    1978-01-01

    A method and apparatus is described for separating gas molecules containing one isotope of an element from gas molecules containing other isotopes of the same element in which all of the molecules of the gas are at the same electronic state in their ground state. Gas molecules in a gas stream containing one of the isotopes are selectively excited to a different electronic state while leaving the other gas molecules in their original ground state. Gas molecules containing one of the isotopes are then deflected from the other gas molecules in the stream and thus physically separated.

  17. Anodically Electrodeposited Iridium Oxide Films (AEIROF) from Alkaline Solutions for Electrochromic Display Devices

    NASA Astrophysics Data System (ADS)

    Yamanaka, Kazusuke

    1989-04-01

    Anodically electrodeposited iridium oxide films from alkaline solutions were investigated for application to electrochromic devices. Micro-crystalline (diameter: 15Å) films obtained by the electrolysis of aqueous alkaline solutions containing iridium chloride, oxalic acid and potassium carbonate showed good electrochromic reaction reversibility. The coloration efficiency of the films was about one third that of typical evaporated tungsten oxide films, and the response rate measured by the amount of injected charge was about double. The cycle lives of the cells, composed of electrodeposited films, 1M H3PO4-NaOH (pH{=}3˜ 5), and an activated carbon cloth, were more than 8× 106 with a 0.6 V, 1 Hz continuous square wave.

  18. The treatment of malignant diseases in Romania using stainless steel encapsulated iridium-192 sources

    NASA Astrophysics Data System (ADS)

    Stanef, I.; Matache, G.; Ciocǎltei, V.; Gheorghiev, G.

    1994-01-01

    Iridium-192 sources supplied by the Institute for Nuclear Physics and Engineering have been used in Romanian radiotherapy clinics since 1980. The source assembly is sealed in a protective stainless steel sheath which satisfies the requirements of international standards. Since this sheath acts as a filter to change the characteristic spectrum it has been necessary to determine experimentally an accurate value of the specific gamma-ray constant. Some clinical aspects of the complex treatment of carcinomas with iridium-192 are reviewed. Results of the calculation of the dose distribution around single and multiple sources are given for different applications in the treatment of carcinomas of the vaginal and uterine cervix, oral cavity, rectum and vagina.

  19. Iridium-bearing sublimates at a hot-spot volcano (Piton de la Fournaise, Indian Ocean)

    SciTech Connect

    Toutain, J.P. ); Meyer, G.

    1989-12-01

    Sublimates and incrustations derived upon the cooling of volcanic gases have been collected on various sites (Piton de la Fournaise, Poas, Momotombo, Etna, Ardoukoba and Erta-Ale). They have been analyzed for Ir and other volatile elements (Se, As, Cu, Au, Ag, Pb, Tl) by means of instrumental neutron activation analysis (INAA) and proton induced X-Ray emission (PIXE). Among the investigated volcanoes, only Piton de la Fournaise is found to release detectable amounts of iridium. Ir in Piton de la Fournaise sublimates is associated with F-minerals. This confirms its gaseous transport as a volatile fluoride compound. Iridium seems to be preferentialy released by hot-spot type volcanoes, and its detection in Piton de la Fournaise sublimates provides a positive argument in favor of a volcanic hypothesis to explain the KTB events.

  20. First Applications of DoD Iridium RUDICS in the NSF Polar Programs

    NASA Astrophysics Data System (ADS)

    Valentic, T.; Stehle, R.

    2008-12-01

    We will present the first deployment and application of the new Iridium RUDICS service to remote instrumentation projects within the National Science Foundation's polar programs. The rise of automated observing networks has increased the demand for real-time connectivity to remote instruments, not only for immediate access to data, but to also interrogate health and status. Communicating with field sites in the polar regions is complicated by the remoteness from existing infrastructure, low temperatures and limited connection options. Sites located above 78° latitude are not able to see geostationary satellites, leaving the Iridium constellation as the only one that provide a direct connection. Some others, such as Orbcomm, only provide a store-and-forward service. Iridium is often used as a dial up modem to establish a PPP connection to the Internet with data files transferred via FTP. On low-bandwidth, high-latency networks like Iridium (2400bps with ping times of seconds), this approach is time consuming and inefficient. The dial up time alone takes upwards of a minute, and standard TCP/IP and FTP protocols are hampered by the long latencies. Minimizing transmission time is important for reducing battery usage and connection costs. The new Iridium RUDICS service can be used for more efficient transfers. RUDICS is an acronym for "Router-based Unstructured Digital Inter-working Connectivity Solution" and provides a direct connection between an instrument in the field and a server on the Internet. After dialing into the Iridium gateway, a socket connection is opened to a registered port on a user's server. Bytes sent to or from the modem appear at the server's socket. The connection time is reduced to about 10 seconds because the modem training and PPP negotiation stages are eliminated. The remote device does not need to have a full TCP/IP stack, allowing smaller instruments such as data loggers to directly handle the data transmission. Alternative protocols can

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

    PubMed

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

    2010-10-14

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

  2. Research of remote control for Chinese Antarctica Telescope based on iridium satellite communication

    NASA Astrophysics Data System (ADS)

    Xu, Lingzhe; Yang, Shihai

    2010-07-01

    Astronomers are ever dreaming of sites with best seeing on the Earth surface for celestial observation, and the Antarctica is one of a few such sites only left owing to the global air pollution. However, Antarctica region is largely unaccessible for human being due to lacking of fundamental living conditions, travel facilities and effective ways of communication. Worst of all, the popular internet source as a general way of communication scarcely exists there. Facing such a dilemma and as a solution remote control and data transmission for telescopes through iridium satellite communication has been put forward for the Chinese network Antarctic Schmidt Telescopes 3 (AST3), which is currently under all round research and development. This paper presents iridium satellite-based remote control application adapted to telescope control. The pioneer work in China involves hardware and software configuration utilizing techniques for reliable and secure communication, which is outlined in the paper too.

  3. Surface studies of iridium-alloy grain boundaries associated with weld cracking

    SciTech Connect

    Mosley, W.C.

    1982-01-01

    Plutonium-238 oxide fuel pellets for the General Purpose Heat Source (GPHS) Radioisotopic Thermoelectric Generators to be used on the NASA Galileo Mission to Jupiter and the International Solar Polar Mission are produced and encapsulated in iridium alloy at the Savannah River Plant (SRP). Underbead cracks occasionally occur in the girth weld on the iridium-alloy-clad vent sets in the region where the gas tungsten arc is quenched. Grain-boundary structures and compositions were characterized by scanning electron microscopy/x-ray energy spectroscopy, electron microprobe analysis and scanning Auger microprobe analysis to determine the cause of weld quench area cracking. Results suggest that weld quench area cracking may be caused by gas porosity or liquation in the grain boundaries.

  4. The activity of platinum, iridium and rhodium drug complexes against Leishmania donovani.

    PubMed

    Croft, S L; Neal, R A; Craciunescu, D G; Certad-Fombona, G

    1992-03-01

    The activities of twenty seven Platinum, Rhodium and Iridium drug complexes were determined against Leishmania donovani amastigotes in mouse peritoneal macrophages in vitro. Eight compounds showed antileishmanial activity of which only three, Rh(III)-mepacrine, Ir(III) pyrrolidine dithiocarbamate and Ir(III) diethyl dithiocarbamate had ED50 values of less than 1 microM. The two Iridium complexes produced, respectively, a 50% and 39% suppression of L. donovani amastigotes in the liver of BALB/c mice following the subcutaneous administration of 200 mg/kg for 5 consecutive days. Ultrastructural studies suggest that the amastigote kinetoplast-mitochondrion complex is the primary site of action of the Ir and Rh complexes. PMID:1598504

  5. Strongly improved electrochemical cycling durability by adding iridium to electrochromic nickel oxide films.

    PubMed

    Wen, Rui-Tao; Niklasson, Gunnar A; Granqvist, Claes G

    2015-05-13

    Anodically colored nickel oxide (NiO) thin films are of much interest as counter electrodes in tungsten oxide based electrochromic devices such as "smart windows" for energy-efficient buildings. However, NiO films are prone to suffering severe charge density degradation upon prolonged electrochemical cycling, which can lead to insufficient device lifetime. Therefore, a means to improve the durability of NiO-based films is an important challenge at present. Here we report that the incorporation of a modest amount of iridium into NiO films [Ir/(Ir + Ni) = 7.6 atom %] leads to remarkable durability, exceeding 10000 cycles in a lithium-conducting electrolyte, along with significantly improved optical modulation during extended cycling. Structure characterization showed that the face-centered-cubic-type NiO structure remained after iridium addition. Moreover, the crystallinity of these films was enhanced upon electrochemical cycling. PMID:25919917

  6. Rhodium(i), rhodium(iii) and iridium(iii) carbaporphyrins.

    PubMed

    Adiraju, Venkata A K; Ferrence, Gregory M; Lash, Timothy D

    2016-09-21

    Treatment of a benzocarbaporphyrin with [Rh(CO)2Cl]2 in refluxing dichloromethane gave a rhodium(i) dicarbonyl complex, and further reaction in refluxing pyridine afforded an organometallic rhodium(iii) derivative. The carbaporphyrin also reacted with [Ir(COD)Cl]2 and pyridine in refluxing p-xylene to generate a related iridium(iii) compound. These novel metalated porphyrinoids retained strongly diatropic characteristics and were fully characterized by XRD. PMID:27529466

  7. Iridium complexes of new NCP pincer ligands: catalytic alkane dehydrogenation and alkene isomerization.

    PubMed

    Jia, Xiangqing; Zhang, Lei; Qin, Chuan; Leng, Xuebing; Huang, Zheng

    2014-09-28

    Iridium complexes of novel NCP pincer ligands containing pyridine and phosphinite arms have been synthesized. One Ir complex shows good catalytic activity for alkane dehydrogenation, and all complexes are highly active for olefin isomerization. A combination of the Ir complex and a (PNN)Fe pincer complex catalyzes the formation of linear alkylboronates selectively from internal olefins via sequential olefin isomerization-hydroboration. PMID:25101950

  8. Solvent free selective dehydrogenation of indolic and carbazolic molecules with an iridium pincer catalyst.

    PubMed

    Brayton, Daniel F; Jensen, Craig M

    2014-06-01

    A previously known iridium POCOP pincer catalyst was found to selectively dehydrogenate the heterocyclic portion of several indolic and carbazolic molecules. These molecules were found to have an "activity window" (172-178 °C) upon which only the heterocyclic ring underwent dehydrogenation. All reactions were run solvent free, yields for selected substrates were excellent, and the products were isolated by either distillation or alumina plug filtration. PMID:24763968

  9. Electrochemical and chemical routes to hydride loss from an iridium dihydride.

    PubMed

    Walden, A G; Kumar, A; Lease, N; Goldman, A S; Miller, A J M

    2016-06-14

    With a view towards replacing sacrificial hydrogen acceptors in alkane dehydrogenation catalysis, electrochemical methods for oxidative activation of a pincer-ligated iridium hydride intermediate were explored. A 1H(+)/2e(-) oxidation process was observed in THF solvent, with net hydride loss leading to a reactive cationic intermediate that can be trapped by chloride. Analogous reactivity was observed with the concerted hydride transfer reagent Ph3C(+), connecting chemical and electrochemical hydride loss pathways. PMID:26979786

  10. Selective Aromatic C–H Hydroxylation Enabled by η6-Coordination to Iridium(III)

    PubMed Central

    D'Amato, Erica M.; Neumann, Constanze N.; Ritter, Tobias

    2016-01-01

    We report an aromatic C–H hydroxylation protocol in which the arene is activated through η6-coordination to an iridium(III) complex. η6-Coordination of the arene increases its electrophilicity and allows for high positional selectivity of hydroxylation at the site of least electron density. Through investigation of intermediate η5-cyclohexadienyl adducts and arene exchange reactions, we evaluate incorporation of arene π-activation into a catalytic cycle for C–H functionalization. PMID:26877574

  11. Branch-Selective Alkene Hydroarylation by Cooperative Destabilization: Iridium-Catalyzed ortho-Alkylation of Acetanilides.

    PubMed

    Crisenza, Giacomo E M; Sokolova, Olga O; Bower, John F

    2015-12-01

    An iridium(I) catalyst system, modified with the wide-bite-angle and electron-deficient bisphosphine d(F) ppb (1,4-bis(di(pentafluorophenyl)phosphino)butane) promotes highly branch-selective hydroarylation reactions between diverse acetanilides and aryl- or alkyl-substituted alkenes. This provides direct and ortho-selective access to synthetically challenging anilines, and addresses long-standing issues associated with related Friedel-Crafts alkylations. PMID:26490739

  12. Transformation of a Cp*-iridium(III) precatalyst for water oxidation when exposed to oxidative stress.

    PubMed

    Zuccaccia, Cristiano; Bellachioma, Gianfranco; Bortolini, Olga; Bucci, Alberto; Savini, Arianna; Macchioni, Alceo

    2014-03-17

    The reaction of [Cp*Ir(bzpy)NO3 ] (1; bzpy=2-benzoylpyridine, Cp*=pentamethylcyclopentadienyl anion), a competent water-oxidation catalyst, with several oxidants (H2 O2 , NaIO4 , cerium ammonium nitrate (CAN)) was studied to intercept and characterize possible intermediates of the oxidative transformation. NMR spectroscopy and ESI-MS techniques provided evidence for the formation of many species that all had the intact Ir-bzpy moiety and a gradually more oxidized Cp* ligand. Initially, an oxygen atom is trapped in between two carbon atoms of Cp* and iridium, which gives an oxygen-Ir coordinated epoxide, whereas the remaining three carbon atoms of Cp* are involved in a η(3) interaction with iridium (2 a). Formal addition of H2 O to 2 a or H2 O2 to 1 leads to 2 b, in which a double MeCOH functionalization of Cp* is present with one MeCOH engaged in an interaction with iridium. The structure of 2 b was unambiguously determined in the solid state and in solution by X-ray single-crystal diffractometry and advanced NMR spectroscopic techniques, respectively. Further oxidation led to the opening of Cp* and transformation of the diol into a diketone with one carbonyl coordinated at the metal (2 c). A η(3) interaction between the three non-oxygenated carbons of "ex-Cp*" and iridium is also present in both 2 b and 2 c. Isolated 2 b and mixtures of 2 a-c species were tested in water-oxidation catalysis by using CAN as sacrificial oxidant. They showed substantially the same activity than 1 (turnover frequency values ranged from 9 to 14 min(-1) ). PMID:24523138

  13. An iridium abundance anomaly at the palynological cretaceous-tertiary boundary in northern new Mexico.

    PubMed

    Orth, C J; Gilmore, J S; Knight, J D; Pillmore, C L; Tschudy, R H; Fassett, J E

    1981-12-18

    An iridium abundance anomaly, with concentrations up to 5000 parts per trillion over a background level of 4 to 20 parts per trillion, has been located in sedimentary rocks laid down under freshwater swamp conditions in the Raton Basin of northeastern New Mexico. The anomaly occurs at the base of a coal bed, at the same stratigraphic position at which several well-known species of Cretaceous-age pollen became extinct.

  14. Branch-Selective Alkene Hydroarylation by Cooperative Destabilization: Iridium-Catalyzed ortho-Alkylation of Acetanilides

    PubMed Central

    Crisenza, Giacomo E M; Sokolova, Olga O; Bower, John F

    2015-01-01

    An iridium(I) catalyst system, modified with the wide-bite-angle and electron-deficient bisphosphine dFppb (1,4-bis(di(pentafluorophenyl)phosphino)butane) promotes highly branch-selective hydroarylation reactions between diverse acetanilides and aryl- or alkyl-substituted alkenes. This provides direct and ortho-selective access to synthetically challenging anilines, and addresses long-standing issues associated with related Friedel–Crafts alkylations. PMID:26490739

  15. Transformation of a Cp*-iridium(III) precatalyst for water oxidation when exposed to oxidative stress.

    PubMed

    Zuccaccia, Cristiano; Bellachioma, Gianfranco; Bortolini, Olga; Bucci, Alberto; Savini, Arianna; Macchioni, Alceo

    2014-03-17

    The reaction of [Cp*Ir(bzpy)NO3 ] (1; bzpy=2-benzoylpyridine, Cp*=pentamethylcyclopentadienyl anion), a competent water-oxidation catalyst, with several oxidants (H2 O2 , NaIO4 , cerium ammonium nitrate (CAN)) was studied to intercept and characterize possible intermediates of the oxidative transformation. NMR spectroscopy and ESI-MS techniques provided evidence for the formation of many species that all had the intact Ir-bzpy moiety and a gradually more oxidized Cp* ligand. Initially, an oxygen atom is trapped in between two carbon atoms of Cp* and iridium, which gives an oxygen-Ir coordinated epoxide, whereas the remaining three carbon atoms of Cp* are involved in a η(3) interaction with iridium (2 a). Formal addition of H2 O to 2 a or H2 O2 to 1 leads to 2 b, in which a double MeCOH functionalization of Cp* is present with one MeCOH engaged in an interaction with iridium. The structure of 2 b was unambiguously determined in the solid state and in solution by X-ray single-crystal diffractometry and advanced NMR spectroscopic techniques, respectively. Further oxidation led to the opening of Cp* and transformation of the diol into a diketone with one carbonyl coordinated at the metal (2 c). A η(3) interaction between the three non-oxygenated carbons of "ex-Cp*" and iridium is also present in both 2 b and 2 c. Isolated 2 b and mixtures of 2 a-c species were tested in water-oxidation catalysis by using CAN as sacrificial oxidant. They showed substantially the same activity than 1 (turnover frequency values ranged from 9 to 14 min(-1) ).

  16. (210)Po in drinking water, its potential health effects, and inadequacy of the gross alpha activity MCL.

    PubMed

    Seiler, Ralph

    2016-10-15

    Polonium-210 ((210)Po) is a naturally-occurring, carcinogenic member of the (238)U decay series and the granddaughter of (210)Pb. It has a half life of 138.4days and is rarely found in drinking water at levels exceeding 5mBq/L because it strongly binds to aquifer sediment. When the current US Maximum Contaminant Level (MCL) covering (210)Po was promulgated in December 2000, very little was known about its occurrence and the processes responsible for mobilizing it. More is now known about the processes that mobilize (210)Po from sediments and a review of recent occurrence data show that it may not be as rare in the US as the US Environmental Protection Agency (USEPA) thought in 2000. Worldwide, only about 2200 analyses for (210)Po in drinking water were identified, with activities exceeding 500mBq/L being found only in Finland, India, Sweden, and the US. The median of 400 (210)Po analyses from the US is 4.75mBq/L and >10% of the samples exceed 500mBq/L. Current compliance-monitoring regulations in the US essentially guarantee that (210)Po contamination will not be detected except in very contaminated wells. Major problems with the US Gross Alpha Activity MCL include the volatility of (210)Po and extended holding times and sample-compositing methods that can allow the majority of (210)Po in a sample bottle to decay before analysis. In light of new information, the radionuclide rule should be changed and direct measurements of (210)Po should be made in all public-water supply wells to rule out its presence. Much of the important biological and toxicological research on (210)Po is more than four decades old and new laboratory research using modern tools is needed. Biological and epidemiological investigations of known contaminated areas are needed to assess the effect (210)Po exposure is having on animals and humans consuming the water. PMID:27369089

  17. Neutron activation determination of iridium, gold, platinum, and silver in geologic samples

    USGS Publications Warehouse

    Millard, H.T.

    1987-01-01

    Low-level methods for the determination of iridium and other noble metals have become increasingly important in recent years due to interest in locating abundance anomalies associated with the Cretaceous and Tertiary (K-T) boundary. Typical iridium anomalies are in the range of 1 to 100 ??g/kg (ppb). Thus methods with detection limits near 0.1 ??g/kg should be adequate to detect K-T boundary anomalies. Radiochemical neutron activation analysis methods continue to be required although instrumental neutron activation analysis techniques employing elaborate gamma-counters are under development. In the procedure developed in this study samples irradiated in the epithermal neutron facility of the U. S. Geological Survey TRIGA Reactor (Denver, Colorado) are treated with a mini-fire assay technique. The iridium, gold, and silver are collected in a 1-gram metallic lead button. Primary contaminants at this stage are arsenic and antimony. These can be removed by heating the button with a mixture of sodium perioxide and sodium hydroxide. The resulting 0.2-gram lead bead is counted in a Compton suppression spectrometer. Carrier yields are determined by reirradiation of the lead beads. This procedure has been applied to the U.S.G.S. Standard Rock PCC-1 and samples from K-T boundary sites in the Western Interior of North America. ?? 1987 Akade??miai Kiado??.

  18. Synthesis and Electroluminescent Property of New Orange Iridium Compounds for Flexible White Organic Light Emitting Diodes.

    PubMed

    Lee, Ho Won; Jeong, Hyunjin; Kim, Young Kwan; Ha, Yunkyoung

    2015-10-01

    Recently, white organic light-emitting diodes (OLEDs) have aroused considerable attention because they have the potential of next-generation flexible displays and white illuminated applications. White OLED applications are particularly heading to the industry but they have still many problems both materials and manufacturing. Therefore, we proposed that the new iridium compounds of orange emitters could be demonstrated and also applied to flexible white OLEDs for verification of potential. First, we demonstrated the chemical properties of new orange iridium compounds. Secondly, conventional two kinds of white phosphorescent OLEDs were fabricated by following devices; indium-tin oxide coated glass substrate/4,4'-bis[N-(napthyl)-N-phenylamino]biphenyl/N,N'-dicarbazolyl-3,5-benzene doped with blue and new iridium compounds for orange emitting 8 wt%/1,3,5-tris[N-phenylbenzimidazole-2-yl]benzene/lithium quinolate/aluminum. In addition, we fabricated white OLEDs using these emitters to verify the potential on flexible substrate. Therefore, this work could be proposed that white light applications can be applied and could be extended to additional research on flexible applications. PMID:26726407

  19. Consumable arc-melting, extruding, and rolling process for iridium sheet

    SciTech Connect

    Heestand, R.L.; Copeland, G.L.; Martin, M.M.

    1986-06-01

    An iridium alloy has been used as cladding for the /sup 238/PuO/sub 2/ fuel in radioisotope thermoelectric generators (RTGs) for recent interplanetary spacecraft such as Voyagers 1 and 2 and will be used for the Galileo and Ulysses spacecraft. The iridium alloy sheet for the fuel cladding used on these missions was fabricated by hot and cold rolling of arc-melted and drop-cast 0.5-kg ingots. Upon completion of production for these spacecraft, an opportunity was taken to conduct process improvement studies that would increase processing batch sizes, develop a more uniform product, decrease rejections due to internal delaminations and surface defects, and reduce costs. The studies to scale up and improve the fabrication process are described. In the new process, iridium is electron beam melted, alloyed by arc melting, and then consumable arc melted to form a cylindrical ingot of approximately 7 kg for extrusion. The ingot is extruded to sheet bar and hot and cold rooled into sheet. Sheet evaluated from the first two ingots showed 100% acceptance with no defects on inspection. An improved uniformity of microstructure was obtained, and chemistry was controlled within specification limits.

  20. Grain Growth Behavior, Tensile Impact Ductility, and Weldability of Cerium-Doped Iridium Alloys

    SciTech Connect

    McKamey, C.G.

    2002-05-28

    An iridium alloy doped with small amounts of cerium and thorium is being developed as a potential replacement for the iridium-based DOP-26 alloy (doped with thorium only) that is currently used by the National Aeronautics and Space Administration (NASA) for cladding and post-impact containment of the radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for interplanetary spacecraft. This report summarizes results of studies conducted to date under the Iridium Alloy Characterization and Development subtask of the Radioisotope Power System Materials Production and Technology Program to characterize the properties of the iridium-based alloy (designated as DOP-40) containing both cerium and thorium. Included within this report are data on grain growth of sheet material in vacuum and low-pressure oxygen environments, grain growth in vacuum of the clad vent set cup material, weldability, and the effect of grain size and test temperature on tensile properties. Where applicable, data for the DOP-26 alloy are included for comparison. Both grain size and grain-boundary cohesion affect the ductility of iridium alloys. In this study it was found that cerium and thorium, when added together, refine grain size more effectively than when thorium is added by itself (especially at high temperatures). In addition, the effect of cerium additions on grain-boundary cohesion is similar to that of thorium. Mechanical testing at both low ({approx} 10{sup -3}s{sup -1}) and high ({approx} 10{sup -3}s{sup -1}) strain rates showed that the Ce/Th-doped alloys have tensile ductilities that are as good or better than the DOP-26 alloy. The general conclusion from these studies is that cerium can be used to replace some of the radioactive thorium currently used in DOP-26 while maintaining or improving its metallurgical properties. The current DOP-26 alloy meets all requirements for cladding the radioactive fuel in the RTG heat source, but the

  1. Alpha-decay of light protactinium isotopes

    SciTech Connect

    Faestermann, T.; Gillitzer, A.; Hartel, K.; Henning, W.; Kienle, P.

    1987-12-10

    Light protactinium isotopes have been produced with /sup 204/Pb (/sup 19/F,xn) reactions. ..cap alpha..-activities with E/sub ..cap alpha../ = 9.90(5) MeV, T/sub 1/2/ = 53(10) ns and E/sub ..cap alpha../ = 9.65(5) MeV, T/sub 1/2/ = 0.78(16) ..mu..s could be attributed to the previously unobserved nuclei /sup 219/Pa and /sup 220/Pa with the help of excitation functions. The peak cross sections for the 4n and 3n evaporation channels are on the order of 10 ..mu..b. The decay energies as well as the halflives fit well into the systematics of these nuclei close to the magic neutron number N = 126. /sup 219/Pa is the shortest lived nuclide known with directly measured halflife.

  2. Visualization of Zn²⁺ ions in live zebrafish using a luminescent iridium(III) chemosensor.

    PubMed

    Ma, Dik-Lung; He, Hong-Zhang; Zhong, Hai-Jing; Lin, Sheng; Chan, Daniel Shiu-Hin; Wang, Liang; Lee, Simon Ming-Yuen; Leung, Chung-Hang; Wong, Chun-Yuen

    2014-08-27

    A novel luminescent cyclometalated iridium(III) complex-based chemosensor (1) bearing a zinc-specific receptor, tris(2-pyridylmethyl)amine, and the 3-phenyl-1H-pyrazole ligand has been designed and synthesized. Upon the addition of Zn(2+) ions to a solution of iridium(III) complex 1, a pronounced luminescence color change from blue to green can be observed, which may be attributed to the suppression of photoinduced electron transfer upon complexation of complex 1 with Zn(2+) ions. The interaction of iridium(III) complex 1 with Zn(2+) ions was investigated by UV-vis absorption titration, emission titration, and (1)H NMR titration. Furthermore, the iridium(III) complex 1 exhibited good selectivity for Zn(2+) over 13 other common metal ions, including K(+), Ag(+), Na(+), Ni(2+), Fe(3+), Hg(2+), Cd(2+), Mg(2+), Ca(2+), Cu(2+), Mn(2+), Co(2+), and Pb(2+) ions. The practical application of the iridium(III) complex 1 in visualizing intracellular Zn(2+) distribution in live zebrafish was also demonstrated.

  3. Iridium contents in the Late Cretaceous-Early Tertiary clays in relation to the K/T boundary, North Jordan

    NASA Astrophysics Data System (ADS)

    Abboud, Iyad Ahmed

    2016-06-01

    The mineralogy, lithology, and geochemistry of five discrete laminations across the K/T boundary of clayey shale at the Yarmouk River area, Jordan, were examined. There were no marked changes in the mineralogy of the clayey shale within the K/T boundary. This outcrop consists of more than 100 m of Maastrichtian oil shale overlying about 20 m limestone. Marly limestone included many clay laminations from organic and volcanic origins, which are considered an evidence of the K/T boundary through detected iridium anomalies. Any of these particular lamellae range from 2 mm to 5 mm in thickness. Smectite was the predominant clay mineral in smectitic shale laminations. It was located at eight meters above the K/T boundary and includes some anomalous concentrations of iridium and traces of other elements. The analysis of geochemical platinum group at the K/T boundary clays showed anomalous enrichments of iridium, compared with other carbonate rocks as a result of weathering processes of oil shale, or through concentration from weathering of basalt flows, but not pointing to an impact process. The clays in late Maastrichtian have Ir-Sc prevailed anomalies and synchronize with increasing of terrigenous and volcanogenic traced elements. Kaolin, smectite, and volkonskoite were the dominant clay minerals at the K/T boundary with high concentrations of iridium. The concentration levels of iridium in some laminations of the Yarmouk sediments ranged between 1.6 and 7.8 ppb.

  4. Transuranium isotopes

    SciTech Connect

    Hoffman, D.C.

    1985-12-01

    The needs of the research community for the production of transuranium isotopes, the quantities required, the continuity of production desired, and what a new steady state neutron source would have to provide to satisfy these needs are discussed. Examples of past frontier research which need these isotopes as well as an outline of the proposed Large Einsteinium Activation Program, LEAP, which requires roughly ten times the current production of /sup 254/Es are given. 15 refs., 5 figs., 4 tabs.

  5. Isotopic Paleoclimatology

    NASA Astrophysics Data System (ADS)

    Bowen, R.

    Paleotemperature scales were calculated by H. C. Urey and others in the 1950s to assess past temperatures, and later work using the stable isotopes of oxygen, hydrogen, and carbon employed standards such as Peedee belemnite (PDB) and Standard Mean Ocean Water (SMOW). Subsequently, subjects as diverse as ice volume and paleotemperatures, oceanic ice and sediment cores, Pleistocene/Holocene climatic changes, and isotope chronostratigraphy extending back to the Precambrian were investigated.

  6. Isotopic chirality

    SciTech Connect

    Floss, H.G.

    1994-12-01

    This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.

  7. Iridium nanoparticles supported on hierarchical porous N-doped carbon: an efficient water-tolerant catalyst for bio-alcohol condensation in water

    NASA Astrophysics Data System (ADS)

    Liu, Di; Chen, Xiufang; Xu, Guoqiang; Guan, Jing; Cao, Quan; Dong, Bo; Qi, Yunfei; Li, Chunhu; Mu, Xindong

    2016-02-01

    Nitrogen-doped hierarchical porous carbons were synthesized successfully by a controllable one-pot method using glucose and dicyandiamide as carbon source and nitrogen source via hydrothermal carbonization process. The nitrogen-doped materials, possessing high nitrogen content (up to 7 wt%), large surface area (>320 m2 g-1) and excellent hierarchical nanostructure, were employed as catalyst supports for immobilization of iridium nanoparticles for bio-alcohol condensation in water. The introduction of nitrogen atoms into the carbon framework significantly improved iridium nanoparticles dispersion and stabilization. The novel iridium catalysts exhibited superior catalytic activity in the aqueous phase condensation of butanol, offering high butanol conversion of 45% with impressive 2-ethylhexanol selectivity of 97%. The heterogeneous catalysts had great advantages of easy recovery and high catalytic stability. The outstanding catalytic performance could be attributed to excellent dispersion of iridium nanoparticles, stronger iridium-support interactions and interaction of nitrogen species with alcohol substrates.

  8. Iridium nanoparticles supported on hierarchical porous N-doped carbon: an efficient water-tolerant catalyst for bio-alcohol condensation in water

    PubMed Central

    Liu, Di; Chen, Xiufang; Xu, Guoqiang; Guan, Jing; Cao, Quan; Dong, Bo; Qi, Yunfei; Li, Chunhu; Mu, Xindong

    2016-01-01

    Nitrogen-doped hierarchical porous carbons were synthesized successfully by a controllable one-pot method using glucose and dicyandiamide as carbon source and nitrogen source via hydrothermal carbonization process. The nitrogen-doped materials, possessing high nitrogen content (up to 7 wt%), large surface area (>320 m2 g−1) and excellent hierarchical nanostructure, were employed as catalyst supports for immobilization of iridium nanoparticles for bio-alcohol condensation in water. The introduction of nitrogen atoms into the carbon framework significantly improved iridium nanoparticles dispersion and stabilization. The novel iridium catalysts exhibited superior catalytic activity in the aqueous phase condensation of butanol, offering high butanol conversion of 45% with impressive 2-ethylhexanol selectivity of 97%. The heterogeneous catalysts had great advantages of easy recovery and high catalytic stability. The outstanding catalytic performance could be attributed to excellent dispersion of iridium nanoparticles, stronger iridium-support interactions and interaction of nitrogen species with alcohol substrates. PMID:26912370

  9. Development of U.S. Government General Technical Requirements for UAS Flight Safety Systems Utilizing the Iridium Satellite Constellation

    NASA Technical Reports Server (NTRS)

    Murray, Jennifer; Birr, Richard

    2010-01-01

    This slide presentation reviews the development of technical requirements for Unmanned Aircraft Systems (UAS) utilization of the Iridium Satellite Constellation to provide flight safety. The Federal Aviation Authority (FAA) required an over-the-horizon communication standard to guarantee flight safety before permitting widespread UAS flights in the National Air Space (NAS). This is important to ensure reliable control of UASs during loss-link and over-the-horizon scenarios. The core requirement was to utilize a satellite system to send GPS tracking data and other telemetry from a flight vehicle down to the ground. Iridium was chosen as the system because it is one of the only true satellite systems that has world wide coverage, and the service has a highly reliable link margin. The Iridium system, the flight modems, and the test flight are described.

  10. Techniques for Achieving Zero Stress in Thin Films of Iridium, Chromium, and Nickel

    NASA Technical Reports Server (NTRS)

    Broadway, David M.; O'Dell, Stephen L.; Ramsey, Brian D.; Weimer, Jeffrey

    2015-01-01

    We examine techniques for achieving zero intrinsic stress in thin films of iridium, chromium, and nickel deposited by magnetron sputter deposition. The intrinsic stress is further correlated to the microstructural features and physical properties such as surface roughness and optical density at a scale appropriate to soft X-ray wavelengths. The examination of the stress in these materials is motivated by efforts to advance the optical performance of light-weight X-ray space telescopes into the regime of sub-arcsecond resolution through various deposition techniques that rely on control of the film stress to values within 10-100 MPa. A characteristic feature of the intrinsic stress behavior in chromium and nickel is their sensitivity to the magnitude and sign of the intrinsic stress with argon gas pressure and deposition rate, including the existence of a critical argon process pressure that results in zero film stress which scales linearly with the atomic mass of the sputtered species. While the effect of stress reversal with argon pressure has been previously reported by Hoffman and others for nickel and chromium, we report this effect for iridium. In addition to stress reversal, we identify zero stress in the optical functioning iridium layer shortly after island coalescence for low process pressures at a film thickness of approximately 35nm. The measurement of the low values of stress during deposition was achieved with the aid of a sensitive in-situ instrument capable of a minimum detectable level of stress, assuming a 35nm thick film, in the range of 0.40-6.0 MPa for <111> oriented crystalline silicon substrate thicknesses of 70-280 microns, respectively.

  11. Efficient light harvesting and energy transfer in a red phosphorescent iridium dendrimer.

    PubMed

    Cho, Yang-Jin; Hong, Seong Ahn; Son, Ho-Jin; Han, Won-Sik; Cho, Dae Won; Kang, Sang Ook

    2014-12-15

    A series of red phosphorescent iridium dendrimers of the type [Ir(btp)2(pic-PCn)] (Ir-Gn; n = 0, 1, 2, and 3) with two 2-(benzo[b]thiophen-2-yl)pyridines (btp) and 3-hydroxypicolinate (pic) as the cyclometalating and ancillary ligands were prepared in good yields. Dendritic generation was grown at the 3 position of the pic ligand with 4-(9H-carbazolyl)phenyl dendrons connected to 3,5-bis(methyleneoxy)benzyloxy branches (PCn; n = 0, 2, 4, and 8). The harvesting photons on the PCn dendrons followed by efficient energy transfer to the iridium center resulted in high red emissions at ∼600 nm by metal-to-ligand charge transfer. The intensity of the phosphorescence gradually increased with increasing dendrimer generation. Steady-state and time-resolved spectroscopy were used to investigate the energy-transfer mechanism. On the basis of the fluorescence quenching rate constants of the PCn dendrons, the energy-transfer efficiencies for Ir-G1, Ir-G2, and Ir-G3 were 99, 98, and 96%, respectively. The energy-transfer efficiency for higher-generation dendrimers decreased slightly because of the longer distance between the PC dendrons and the core iridium(III) complex, indicating that energy transfer in Ir-Gn is a Förster-type energy transfer. Finally, the light-harvesting efficiencies for Ir-G1, Ir-G2, and Ir-G3 were determined to be 162, 223, and 334%, respectively.

  12. Cyclometalated iridium(III) complexes for phosphorescence sensing of biological metal ions.

    PubMed

    You, Youngmin; Cho, Somin; Nam, Wonwoo

    2014-02-17

    Phosphorescence signaling provides a valuable alternative to conventional bioimaging based on fluorescence. The benefits of using phosphorescent molecules include improved sensitivity and capabilities for effective elimination of background signals by time-gated acquisition. Cyclometalated Ir(III) complexes are promising candidates for facilitating phosphorescent bioimaging because they provide synthetic versatility and excellent phosphorescence properties. In this Forum Article, we present our recent studies on the development of phosphorescence sensors for the detection of metal ions based on cyclometalated iridium(III) complexes. The constructs contained cyclometalating (C^N) ligands with the electron densities and band-gap energies of the C^N ligand structures systematically varied. Receptors that chelated zinc, cupric, and chromium ions were tethered to the ligands to create phosphorescence sensors. The alterations in the C^N ligand structures had a profound influence on the phosphorescence responses to metal ions. Mechanistic studies suggested that the phosphorescence responses could be explained on the basis of the modulation of photoinduced electron transfer (PeT) from the receptor to the photoexcited iridium species. The PeT behaviors strictly adhered to the Rehm-Weller principle, and the occurrence of PeT was located in the Marcus-normal region. It is thus anticipated that improved responses will be obtainable by increasing the excited-state reduction potential of the iridium(III) complexes. Femtosecond transient absorption experiments provided evidence for the presence of an additional photophysical mechanism that involved metal-ion-induced alteration of the intraligand charge-transfer (ILCT) transition state. Utility of the mechanism by PeT and ILCT has been demonstrated for the phosphorescence sensing of biologically important transition-metal ions. In particular, the phosphorescence zinc sensor could report the presence of intracellular zinc pools by

  13. Intercalated samarium as an agent enabling the intercalation of oxygen under a monolayer graphene film on iridium

    NASA Astrophysics Data System (ADS)

    Afanas'eva, E. Yu.; Rut'kov, E. V.; Gall', N. R.

    2016-06-01

    Using thermal desorption time-of-flight mass spectrometry and thermionic methods, it is shown that oxygen does not intercalate under a graphene monolayer grown correctly on iridium, at least at temperatures of T = 300-400 K and exposures below 12000 L. However, if the graphene film on iridium is preliminary intercalated with samarium atoms (up to coverage of θSm = 0.2-0.45), the penetration of oxygen atoms under the graphene film is observed. The oxygen atoms in the intercalated state are chemically bonded to samarium atoms and remain under graphene up to high temperatures (~2150 K).

  14. Stereodivergent α-allylation of linear aldehydes with dual iridium and amine catalysis.

    PubMed

    Krautwald, Simon; Schafroth, Michael A; Sarlah, David; Carreira, Erick M

    2014-02-26

    We describe the fully stereodivergent, dual catalytic α-allylation of linear aldehydes. The reaction proceeds via direct iridium-catalyzed substitution of racemic allylic alcohols with enamines generated in situ. The use of an Ir(P,olefin) complex and a diarylsilyl prolinol ether as catalysts in the presence of dimethylhydrogen phosphate as the promoter proved to be crucial for achieving high enantio- and diastereoselectivity (>99% ee, up to >20:1 dr). The utility of the method is demonstrated in a concise enantioselective synthesis of the antidepressant (-)-paroxetine. PMID:24506196

  15. Palynological and iridium anomalies at Cretaceous-Tertiary boundary, south-central Saskatchewan

    USGS Publications Warehouse

    Nichols, D.J.; Jarzen, D.M.; Orth, C.J.; Oliver, P.Q.

    1986-01-01

    The Cretaceous-Tertiary boundary in south-central Saskatchewan is marked by coincident anomalies in abundance of iridium and fern spores at the extinction level of a suite of Cretaceous pollen taxa. Evidence of disruption of the terrestrial flora includes the fern-spore abundance anomaly and local extinction of as much as 30 percent of angiosperm species. The reorganized earliest Tertiary flora is made up largely of surviving species that assumed new roles of dominance. Persistence of climatically sensitive taxa across the boundary indicates that if paleoclimate was altered by the terminal Cretaceous event, it returned quickly to the pre-event condition.

  16. Catalytic dehydrogenation of cycloalkanes to arenes by a dihydrido iridium P-C-P pincer complex

    SciTech Connect

    Gupta, M.; Hagen, C.; Cramer, R.E.; Jensen, C.M.; Kaska, W.C.

    1997-01-29

    We recently found that the iridium P-C-P pincer complex IrH{sub 2}[C{sub 6}H{sub 3}-2,6-(CH{sub 2}-PBu{sup T}{sub 2}){sub 2}] (1) is a highly active, homogeneous catalyst for the transfer dehydrogenation of cyclooctane with unusual long-term stability at temperatures as high as 200 {degree}C. This reactivity has now been extended to the catalytic transfer dehydrogenation of cycloalkanes to arenes. We report this novel catalytic activity as well as the results of an X-ray structure determination of 1. 15 refs., 1 fig., 1 tab.

  17. Salvage irradiation of oropharynx and mobile tongue about /sup 192/iridium brachytherapy in Centre Alexis Vautrin

    SciTech Connect

    Langlois, D.; Hoffstetter, S.; Malissard, L.; Pernot, M.; Taghian, A.

    1988-05-01

    Between 1972 and 1984, 123 patients were treated using /sup 192/Iridium afterloading techniques for recurrence or new cancer of the tongue or oropharynx arising in previously irradiated tissues. The actuarial local control was 67% at 2 years and 59% at 5 years. Local control of the tumor was achieved in the majority of these patients, the actuarial survival was only 48% at 2 years and 24% at 5 years. Twenty-eight patients developed mucosal necrosis. We analyzed prognostic factors for survival, local control, and complication. We proposed a selection for this salvage therapy.

  18. Iridium/Copper Co-catalyzed Anti-Stereoselective Ring Opening of Oxabenzonorbornadienes with Grignard Reagents.

    PubMed

    Cheng, Guo; Yang, Wen; Li, Yue; Yang, Dingqiao

    2016-09-01

    Cooperative catalysis has been widely considered as one of the most powerful strategies to improve synthetic efficiency. A new iridium/copper cocatalyst was developed for the ring-opening reaction of oxabenzonorbornadienes with a wide variety of Grignard reagents, which afforded the corresponding anti-2-substituted 1,2-dihydronaphthalen-1-ols in high yields (up to 99% yield) under mild conditions. The effects of catalyst loading, Lewis acid, Grignard reagent loading, and reaction temperature on the yield were investigated. To the best of our knowledge, it represents the first example of ring-opening reactions of oxabicyclic alkenes with Grignard reagent nucleophiles in a trans-stereoselective manner. PMID:27455165

  19. Theoretical studies on the photophysical properties of some Iridium (III) complexes used for OLED

    NASA Astrophysics Data System (ADS)

    Urinda, Sharmistha; Das, Goutam; Pramanik, Anup; Sarkar, Pranab

    2016-09-01

    The structural and photophysical properties of four heteroleptic Iridium (III) complexes, based on 1-phenylpyrazole ligand, have been investigated theoretically. The effect of chemical substitution on the absorption and the emission spectra of the complexes has been studied and compared with the experimental data. We observe a significant structural change in the lowest triplet excited state as compared to the ground singlet state. We compute the emission wavelength of the complexes by considering the spin-orbit coupling. Using these understandings, we predict two new complexes having deeper blue emission which are supposed to be better efficient OLED materials.

  20. Electrogenerated chemiluminescence from heteroleptic iridium(III) complexes with multicolor emission.

    PubMed

    Zhou, Yuyang; Gao, Hongfang; Wang, Xiaomei; Qi, Honglan

    2015-02-16

    Electrogenerated chemiluminescence (ECL) with different emission colors is important in the development of multichannel analytical techniques. In this report, five new heteroleptic iridium(III) complexes were synthesized, and their photophysical, electrochemical, and ECL properties were studied. Here, 2-(2,4-difluorophenyl)pyridine (dfppy, complex 1), 2-phenylbenzo[d]thiazole (bt, complex 2), and 2-phenylpyridine (ppy, complex 3) were used as the main ligands to tune the emission color, while avobenzone (avo) was used as the ancillary ligand. For comparison, complexes 4 and 5 with 2-phenylpyridine and 2-phenylbenzo[d]thiazole as the main ligand, respectively, and acetyl acetone (acac) as the ancillary ligand were also synthesized. All five iridium(III) complexes had strong intraligand absorption bands (π–π*) in the UV region (below 350 nm) and a featureless MLCT (d−π*) transition in the visible 400–500 nm range. Multicolored emissions were observed for these five iridium(III) complexes, including green, orange, and red for complexes 4, 5, 2, 1, 3, respectively. Density functional theory calculations indicate that the electronic density of the highest occupied molecular orbital is entirely located on the C^N ligands and the iridium atom, while the formation of the lowest unoccupied molecular orbital (LUMO) is complicated. The LUMO is mainly assigned to the ancillary ligand for complexes 1 and 3 but to the C^N ligand for complexes 2, 4, and 5. Cyclic voltammetry studies showed that all these complexes have a reversible oxidation wave, but no reduction waves were found in the electrochemical windows of CH2Cl2. The E1/2(ox) values of these complexes ranged from 0.642 to 0.978 V for complexes 3, 4, 2, 5, 1, (in increasing order) and are all lower than that of Ru(bpy)3(2+). Most importantly, when using tripropylamine as a coreactant, complexes 1–5 exhibited intense ECL signals with an emission wavelength centered at 616, 580, 663, 536, and 569 nm, respectively

  1. Flexible, high-density microphotodiode array with integrated sputtered iridium oxide electrodes for retinal stimulation

    NASA Astrophysics Data System (ADS)

    Yang, Frank; Chang, Mao-Yen; Yang, Chung-Hua; Teng, Chih-Ciao; Fan, Long-Sheng

    2016-01-01

    To assess the charge-injection capacity of the sputtered iridium oxide film (SIROF) electrode on the retinal CMOS image sensor (CIS) chip, a polyimide-based flex device was designed and fabricated to package the retinal CIS chip. The polyimide-flex-based packaging process keeps the surface of photosensors clean, and the measured connection resistance meets the packaging requirement of the low-power retinal CIS chip. The in vitro experimental results show that the small SIROF electrodes can provide a biphasic charge injection per phase of 3.9 nC/ph to achieve the stimulation threshold at a polarization potential of -0.44 V.

  2. Iridium Complexes and Clusters in Dealuminated Zeolite HY: Distribution between Crystalline and Impurity Amorphous Regions

    SciTech Connect

    Martinez-Macias, Claudia; Xu, Pinghong; Hwang, Son-Jong; Lu, Jing; Chen, Cong-Yan; Browning, Nigel D.; Gates, Bruce C.

    2014-07-08

    Dealuminated zeolite HY was used to support Ir(CO)2 complexes formed from Ir(CO)2(C5H7O2). Infrared and X-ray absorption spectra and atomic-resolution electron microscopy images identify these complexes, and the images and 27Al NMR spectra identify impurity amorphous regions in the zeolite where the iridium is more susceptible to aggregation than in the crystalline regions. The results indicate a significant stability limitation of metal in amorphous impurity regions of zeolites.

  3. Iridium-Catalyzed Asymmetric Ring-Opening of Oxabenzonorbornadienes with N-Substituted Piperazine Nucleophiles.

    PubMed

    Yang, Wen; Luo, Renshi; Yang, Dingqiao

    2015-01-01

    Iridium-catalyzed asymmetric ring-opening of oxabenzonorbornadienes with N-substituted piperazines was described. The reaction afforded the corresponding ring-opening products in high yields and moderate enantioselectivities in the presence of 2.5 mol % [Ir(COD)Cl]₂ and 5.0 mol % (S)-p-Tol-BINAP. The effects of various chiral bidentate ligands, catalyst loading, solvent, and temperature on the yield and enantioselectivity were also investigated. A plausible mechanism was proposed to account for the formation of the corresponding trans-ring opened products based on the X-ray structure of product 2i. PMID:26633315

  4. Relationship between mass extinction and iridium across the Cretaceous-Paleogene boundary in New Jersey

    USGS Publications Warehouse

    Miller, K.G.; Sherrell, Robert M.; Browning, J.V.; Field, M.P.; Gallagher, W.; Olsson, R.K.; Sugarman, P.J.; Tuorto, S.; Wahyudi, H.

    2010-01-01

    We directly link iridium (Ir) anomalies in New Jersey to the mass extinction of marine plankton marking the Cretaceous-Paleogene (K-Pg) boundary. We confirm previous reports of an Ir anomaly 20 cm below the extinction of Cretaceous macrofauna (the "Pinna" bed) with new results from a muddy sand section from Tighe Park, Freehold, New Jersey (United States), but we also show that Ir anomalies correlate with marine mass extinctions at three other clay-rich New Jersey sections. Thus, we attribute the anomaly at Freehold to the downward movement of Ir and reaffirm the link between impact and mass extinction. ?? 2010 Geological Society of America.

  5. Iridium/N-heterocyclic carbene-catalyzed C–H borylation of arenes by diisopropylaminoborane

    PubMed Central

    Igarashi, Takuya

    2016-01-01

    Summary Catalytic C–H borylation of arenes has been widely used in organic synthesis because it allows the introduction of a versatile boron functionality directly onto simple, unfunctionalized arenes. We report herein the use of diisopropylaminoborane as a boron source in C–H borylation of arenes. An iridium(I) complex with 1,3-dicyclohexylimidazol-2-ylidene is found to efficiently catalyze the borylation of arenes and heteroarenes. The resulting aminoborylated products can be converted to the corresponding boronic acid derivatives simply by treatment with suitable diols or diamines. PMID:27340457

  6. Stereodivergent α-allylation of linear aldehydes with dual iridium and amine catalysis.

    PubMed

    Krautwald, Simon; Schafroth, Michael A; Sarlah, David; Carreira, Erick M

    2014-02-26

    We describe the fully stereodivergent, dual catalytic α-allylation of linear aldehydes. The reaction proceeds via direct iridium-catalyzed substitution of racemic allylic alcohols with enamines generated in situ. The use of an Ir(P,olefin) complex and a diarylsilyl prolinol ether as catalysts in the presence of dimethylhydrogen phosphate as the promoter proved to be crucial for achieving high enantio- and diastereoselectivity (>99% ee, up to >20:1 dr). The utility of the method is demonstrated in a concise enantioselective synthesis of the antidepressant (-)-paroxetine.

  7. Iridium-catalyzed intermolecular dehydrogenative silylation of polycyclic aromatic compounds without directing groups.

    PubMed

    Murai, Masahito; Takami, Keishi; Takai, Kazuhiko

    2015-03-16

    This study describes the iridium-catalyzed intermolecular dehydrogenative silylation of C(sp(2))-H bonds of polycyclic aromatic compounds without directing groups. The reaction produced various arylsilanes through both Si-H and C-H bond activation, with hydrogen as the sole byproduct. Reactivity was affected by the electronic nature of the aromatic compounds, and silylation of electron-deficient and polycyclic aromatic compounds proceeded efficiently. Site-selectivity was controlled predominantly by steric factors. Therefore, the current functionalization proceeded with opposite chemo- and site-selectivity compared to that observed for general electrophilic functionalization of aromatic compounds.

  8. Iridium(III)-Catalyzed Regioselective Intermolecular Unactivated Secondary Csp(3) -H Bond Amidation.

    PubMed

    Xiao, Xinsheng; Hou, Cheng; Zhang, Zhenhui; Ke, Zhuofeng; Lan, Jianyong; Jiang, Huanfeng; Zeng, Wei

    2016-09-19

    For the first time, a highly regioselective intermolecular sulfonylamidation unactivated secondary Csp(3) -H bond has been achieved using Ir(III) catalysts. The introduced N,N'-bichelating ligand plays a crucial role in enabling iridium-nitrene insertion into a secondary Csp(3) -H bond via an outer-sphere pathway. Mechanistic studies and density functional theory (DFT) calculations demonstrated that a two-electron concerted nitrene insertion was involved in this Csp(3) -H amidation process. This method tolerates a broad range of linear and branched-chain N-alkylamides, and provides efficient access to diverse γ-sulfonamido-substituted aliphatic amines. PMID:27561950

  9. Sizeable Kane-Mele-like spin orbit coupling in graphene decorated with iridium clusters

    NASA Astrophysics Data System (ADS)

    Qin, Yuyuan; Wang, Siqi; Wang, Rui; Bu, Haijun; Wang, Xuefeng; Wang, Xinran; Song, Fengqi; Wang, Baigeng; Wang, Guanghou

    2016-05-01

    The spin-orbit coupling strength of graphene can be enhanced by depositing iridium nanoclusters. Weak localization is intensely suppressed near zero fields after the cluster deposition, rather than changing to weak anti-localization. Fitting the magnetoresistance gives the spin relaxation time, which increases by two orders with the application of a back gate. The spin relaxation time is found to be proportional to the electronic elastic scattering time, demonstrating the Elliot-Yafet spin relaxation mechanism. A sizeable Kane-Mele-like coupling strength of over 5.5 meV is determined by extrapolating the temperature dependence to zero.

  10. ISOTOPE SEPARATORS

    DOEpatents

    Bacon, C.G.

    1958-08-26

    An improvement is presented in the structure of an isotope separation apparatus and, in particular, is concerned with a magnetically operated shutter associated with a window which is provided for the purpose of enabling the operator to view the processes going on within the interior of the apparatus. The shutier is mounted to close under the force of gravity in the absence of any other force. By closing an electrical circuit to a coil mouated on the shutter the magnetic field of the isotope separating apparatus coacts with the magnetic field of the coil to force the shutter to the open position.

  11. 60-watt isotopic heat source for terrestrial applications

    NASA Astrophysics Data System (ADS)

    Brittain, Wayne M.

    1995-01-01

    A sealed isotopic heat source (IHS) with a nominal thermal inventory of 60 watts is being developed by the U.S. Department of Energy (DOE) for use in remote terrestrial applications that require isotopic power for electrical power generation. Emphasis is on use in radioisotope thermoelectric generators (RTGs) and dynamic cycle power units. The selected IHS design incorporates technologies developed for prior space and terrestrial IHSs to minimize development cost and span time. A General Purpose Heat Source (GPHS) Fueled Clad (FC), comprised of a plutonium-238 enriched pressed-plutonia pellet contained within a vented iridium clad, is the source for thermal energy. The GPHS FC technology was developed by DOE for use in space RTGs. The GPHS FC is, in turn, enclosed within a three-layer cladding system similar to that developed by DOE for earlier terrestrial heat sources. The cladding system provides for retention of the helium gas generated by the decay of the isotopic fuel and containment of the isotopic fuel under normal operating and accident conditions. Test hardware is currently being fabricated and safety demonstration testing is scheduled to be completed in early 1995.

  12. Iridium-catalyzed dehydrogenative decarbonylation of primary alcohols with the liberation of syngas.

    PubMed

    Olsen, Esben P K; Madsen, Robert

    2012-12-01

    A new iridium-catalyzed reaction in which molecular hydrogen and carbon monoxide are cleaved from primary alcohols in the absence of any stoichiometric additives has been developed. The dehydrogenative decarbonylation was achieved with a catalyst generated in situ from [Ir(coe)(2)Cl](2) (coe = cyclooctene) and racemic 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (rac-BINAP) in a mesitylene solution saturated with water. A catalytic amount of lithium chloride was also added to improve the catalyst turnover. The reaction has been applied to a variety of primary alcohols and gives rise to products in good to excellent yields. Ethers, esters, imides, and aryl halides are stable under the reaction conditions, whereas olefins are partially saturated. The reaction is believed to proceed by two consecutive organometallic transformations that are catalyzed by the same iridium(I)-BINAP species. First, dehydrogenation of the primary alcohol to the corresponding aldehyde takes place, which is then followed by decarbonylation to the product with one less carbon atom. PMID:23108889

  13. Blue light emission from cyclometallated iridium (III) cyano complexes: Syntheses, crystal structures, and photophysical properties

    SciTech Connect

    Sanner, Robert D.; Cherepy, Nerine J.; Young, Jr., Victor G.

    2015-11-02

    In this study, we describe the synthesis and crystal structures of four iridium compounds containing the 2-(4,6-difluorophenyl)pyridyl ligand. Cleavage of dichloro-bridged iridium(III) dimers with phosphorus ligands leads to (46dfppy)2Ir(L)(Cl) where L = PPh3 or P(OPh)3. Treatment of the chloro compounds with cyanide forms the cyano complexes (46dfppy)2Ir(L)(CN). All complexes exhibit a trans effect in their molecular structures due to the phosphorus ligands, with the phosphite having a greater effect than the phosphine. With L = PPh3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.24), quantum yield of 0.66 ± 0.15 and 4.5 ± 0.5 μs decay time is measured. For L = P(OPh)3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.21), quantum yield of 0.65 ± 0.15 and 2.9 ± 0.3 μs decay time is measured.

  14. Blue light emission from cyclometallated iridium (III) cyano complexes: Syntheses, crystal structures, and photophysical properties

    DOE PAGES

    Sanner, Robert D.; Cherepy, Nerine J.; Young, Jr., Victor G.

    2015-11-02

    In this study, we describe the synthesis and crystal structures of four iridium compounds containing the 2-(4,6-difluorophenyl)pyridyl ligand. Cleavage of dichloro-bridged iridium(III) dimers with phosphorus ligands leads to (46dfppy)2Ir(L)(Cl) where L = PPh3 or P(OPh)3. Treatment of the chloro compounds with cyanide forms the cyano complexes (46dfppy)2Ir(L)(CN). All complexes exhibit a trans effect in their molecular structures due to the phosphorus ligands, with the phosphite having a greater effect than the phosphine. With L = PPh3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.24), quantum yield of 0.66 ± 0.15 and 4.5 ± 0.5 μs decay timemore » is measured. For L = P(OPh)3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.21), quantum yield of 0.65 ± 0.15 and 2.9 ± 0.3 μs decay time is measured.« less

  15. The kinetics and mechanism of the organo-iridium-catalysed enantioselective reduction of imines.

    PubMed

    Stirling, Matthew J; Sweeney, Gemma; MacRory, Kerry; Blacker, A John; Page, Michael I

    2016-04-14

    The iridium complex of pentamethylcyclopentadiene and (S,S)-1,2-diphenyl-N'-tosylethane-1,2-diamine is an effective catalyst for the asymmetric transfer hydrogenation of imine substrates under acidic conditions. Using the Ir catalyst and a 5 : 2 ratio of formic acid : triethylamine as the hydride source for the asymmetric transfer hydrogenation of 1-methyl-3,4-dihydroisoquinoline and its 6,7-dimethoxy substituted derivative, in either acetonitrile or dichloromethane, shows unusual enantiomeric excess (ee) profiles for the product amines. The reactions initially give predominantly the (R) enantiomer of the chiral amine products with >90% ee but which then decreases significantly during the reaction. The decrease in ee is not due to racemisation of the product amine, but because the rate of formation of the (R)-enantiomer follows first-order kinetics whereas that for the (S)-enantiomer is zero-order. This difference in reaction order explains the change in selectivity as the reaction proceeds - the rate formation of the (R)-enantiomer decreases exponentially with time while that for the (S)-enantiomer remains constant. A reaction scheme is proposed which requires rate-limiting hydride transfer from the iridium hydride to the iminium ion for the first-order rate of formation of the (R)-enantiomer amine and rate-limiting dissociation of the product for the zero-order rate of formation of the (S)-enantiomer.

  16. Treatment of carcinoma of the penis by iridium 192 wire implant

    SciTech Connect

    Daly, N.J.; Douchez, J.; Combes, P.F.

    1982-07-01

    Since 1971, a group of 22 adult patients with squamous cell carcinoma of the penis have been treated by iridium 192 wire implants. There were 6 T1 tumors, 14 T2 tumors and 2 T3; only one patient (T3) presented with local failure after implant. Local necrosis occurred in 2 patients without local tumoral recurrence, but was sufficient enough to warrant amputation. Thus 19/22 (86%) patients were locally cured with penile conservation. In these patients the most frequent posttherapeutic complication is chronic urethral stenosis (9/19 patients, 47%) requiring repeated instrumental dilations. Four patients presented with initial inguinal mestastatic nodes; only one was cured by radiosurgical treatment. Among patients without metastatic nodes at the time of diagnosis, none had delayed metastatic nodes. Three patients died of nodal evolution, 5 patients died of intercurrent disease without evidence of disease and 14 are now alive and NED. It appears that iridium 192 wire implant is the most effective conservative treatment of invasive squamous cell carcinoma of the penis; however, these results confirm that no particular treatment is required for inguinal nodal areas for patients who initially present with no disease.

  17. [Brachytherapy in France: current situation and economic outlook due to the unavailability of iridium wires].

    PubMed

    Le Vu, B; Boucher, S

    2014-10-01

    In 2013, about 6000 patients were treated with brachytherapy, the number diminishing by 2.6% per year since 2008. Prostate, breast and gynecological cancers are the most common types of cancers. Since 2008, the number of brachytherapy facilities has decreased by 18%. In medicoeconomic terms, brachytherapy faces many problems: the coding system is outdated; brachytherapy treatments cost as much as internal radiation; fees do not cover costs; since iridium wire has disappeared from the market, the technique will be transferred to more expensive high-speed or pulse dose rates. The French financing grid based on the national study of costs lags behind changes in such treatments and in the best of cases, hospitals resorting to alternatives such as in-hospital brachytherapy are funded at 46% of their additional costs. Brachytherapy is a reference technique. With intense pressure on hospital pricing, financing brachytherapy facilities will become even more problematic as a consequence of the disappearance of iridium 192 wires. The case of brachytherapy illustrates the limits of the French financing system and raises serious doubts as to its responsiveness. PMID:25195115

  18. Iridium- and Osmium-decorated Reduced Graphenes as Promising Catalysts for Hydrogen Evolution.

    PubMed

    Lim, Chee Shan; Sofer, Zdeněk; Toh, Rou Jun; Eng, Alex Yong Sheng; Luxa, Jan; Pumera, Martin

    2015-06-22

    Renewable energy sources are highly sought after as a result of numerous worldwide problems concerning the environment and the shortage of energy. Currently, the focus in the field is on the development of catalysts that are able to provide water splitting catalysis and energy storage for the hydrogen evolution reaction (HER). While platinum is an excellent material for HER catalysis, it is costly and rare. In this work, we investigated the electrocatalytic abilities of various graphene-metal hybrids to replace platinum for the HER. The graphene materials were doped with 4f metals, namely, iridium, osmium, platinum and rhenium, as well as 3d metals, namely, cobalt, iron and manganese. We discovered that a few hybrids, in particular iridium- and osmium-doped graphenes, have the potential to become competent electrocatalysts owing to their low costs and-more importantly-to their promising electrochemical performances towards the HER. One of the more noteworthy observations of this work is the superiority of these two hybrids over MoS2 , a well-known electrocatalyst for the HER. PMID:25908556

  19. Iridium-191 angiocardiography for the detection and quantitation of left-to-right shunting

    SciTech Connect

    Treves, S.; Cheng, C.; Samuel, A.; Lambrecht, R.; Babchyck, B.; Zimmerman, R.; Norwood, W.

    1980-12-01

    An osmium-191 ..-->.. iridium-191 generator that can deliver multiple doses of Ir-191m for first-pass radionuclide angiography has been developed. Iridium-191m has a physical half-life of 4.96 sec and decays with emission of 65-keV and 129-keV photons in 58 and 30% abundance, respectively. Using a gamma camera, Ir-191m radionuclide angiography was carried out, in dogs and ten patients, for the detection and quantitation of left-to-right shunting. In a one-year-old patient, 25 mCi of Ir-191m results in a whole-body radiation absorbed dose of 35 mrad. Multiple Ir-191m angiograms can be performed, seconds to minutes apart, without interference from background. The 15.4-day half-life of Os-191 permits transportation of the generator to centers far from the production facility. With the low radiation dose, high information density, and the ability to repeat studies with Ir-191m, clinical use of radionuclide angiography should be expanded.

  20. Electron-beam processing of kilogram quantities of iridium for radioisotope thermoelectric generator applications

    SciTech Connect

    Huxford, T.J.; Ohriner, E.K.

    1992-01-01

    Iridium alloys are used as fuel-cladding materials in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyagers I and 2, Galilee, and Ulysses spacecraft. An integral part of the production of iridium-sheet metal involves electron-beam (EB) processing. These processes include the degassing of powder-pressed compacts followed by multiple meltings in order to purify 500-g buttons of Ir-0.3% W alloy. Starting in 1972 and continuing into 1992, our laboratory EB processing was Performed (ca. 1970) in a 60-kW (20 kV at 3 A), two-gun system. In 1991, a new 150-kW EB gun facility was installed to complement the older unit. This paper describes how the newly installed system was qualified for production of RTG developmental work is discussed that will potentially improve the existing process by utilizing the capabilities of the new EB system.

  1. Electron-beam processing of kilogram quantities of iridium for radioisotope thermoelectric generator applications

    SciTech Connect

    Huxford, T.J.; Ohriner, E.K.

    1992-12-31

    Iridium alloys are used as fuel-cladding materials in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyagers I and 2, Galilee, and Ulysses spacecraft. An integral part of the production of iridium-sheet metal involves electron-beam (EB) processing. These processes include the degassing of powder-pressed compacts followed by multiple meltings in order to purify 500-g buttons of Ir-0.3% W alloy. Starting in 1972 and continuing into 1992, our laboratory EB processing was Performed (ca. 1970) in a 60-kW (20 kV at 3 A), two-gun system. In 1991, a new 150-kW EB gun facility was installed to complement the older unit. This paper describes how the newly installed system was qualified for production of RTG developmental work is discussed that will potentially improve the existing process by utilizing the capabilities of the new EB system.

  2. Earth Radiation Imbalance from a Constellation of 66 Iridium Satellites: Technological Aspects

    NASA Technical Reports Server (NTRS)

    Wiscombe, W.; Chiu, C. J-Y.

    2012-01-01

    Iridium Communications Inc. is launching a new generation of polar orbiting communication satellites in 2015-2017. Iridium will provide a hosted payload bay on each of the 66 satellites (plus 6 in-space spares). This offers the potential for a paradigm shift in the way we measure Earth radiation imbalance from space, as well as massive cost savings. Because the constellation provides 24/7 global coverage, there is no need to account for diurnal cycle via extrapolations from uncalibrated narrowband geostationary imagers. And the spares can be rolled over to view the Sun and deep space, then transfer their calibration to the other members of the constellation during the frequent cross-overs. In part using simulations of the constellation viewing realistic Earth scenes, this presentation will address the technological aspects of such a constellation: (1) the calibration strategy; (2) the highly-accurate and stable radiometers for measuring outgoing flux; and (3) the GRACE-inspired algorithms for representing the outgoing flux field in spherical harmonics and thus achieving rv500-km spatial resolution and two-hour temporal resolution.

  3. High-Performance Computer Modeling of the Cosmos-Iridium Collision

    SciTech Connect

    Olivier, S; Cook, K; Fasenfest, B; Jefferson, D; Jiang, M; Leek, J; Levatin, J; Nikolaev, S; Pertica, A; Phillion, D; Springer, K; De Vries, W

    2009-08-28

    This paper describes the application of a new, integrated modeling and simulation framework, encompassing the space situational awareness (SSA) enterprise, to the recent Cosmos-Iridium collision. This framework is based on a flexible, scalable architecture to enable efficient simulation of the current SSA enterprise, and to accommodate future advancements in SSA systems. In particular, the code is designed to take advantage of massively parallel, high-performance computer systems available, for example, at Lawrence Livermore National Laboratory. We will describe the application of this framework to the recent collision of the Cosmos and Iridium satellites, including (1) detailed hydrodynamic modeling of the satellite collision and resulting debris generation, (2) orbital propagation of the simulated debris and analysis of the increased risk to other satellites (3) calculation of the radar and optical signatures of the simulated debris and modeling of debris detection with space surveillance radar and optical systems (4) determination of simulated debris orbits from modeled space surveillance observations and analysis of the resulting orbital accuracy, (5) comparison of these modeling and simulation results with Space Surveillance Network observations. We will also discuss the use of this integrated modeling and simulation framework to analyze the risks and consequences of future satellite collisions and to assess strategies for mitigating or avoiding future incidents, including the addition of new sensor systems, used in conjunction with the Space Surveillance Network, for improving space situational awareness.

  4. Establishment of the platinum-iridium kilogram mass standards at NMIJ after the Extraordinary Calibrations

    NASA Astrophysics Data System (ADS)

    Mizushima, Shigeki; Fujii, Kenichi

    2016-04-01

    The Bureau International des Poids et Mesures has carried out calibrations of the platinum-iridium kilogram mass standards by referencing the international prototype of the kilogram for the first time since the third periodic verification of national prototypes of the kilogram was carried out in 1988-92. This calibration campaign was designated ‘Extraordinary Calibrations’ in the second phase, in which two platinum-iridium kilogram mass standards of the National Metrology Institute of Japan were calibrated with a standard uncertainty of 3.5 μg. By adding these new calibration data into our data sets from 1991, we established our mass unit with a standard uncertainty of 3.3 μg by least-squares analysis using an exponential model, which is useful for compensating for mass increase after cleaning the mass standards. Moreover, it was found that our established mass unit following the Extraordinary Calibrations shifted against our previously maintained mass unit by  -20.8 μg as of the beginning of 2015. The analysis with a linear model revealed that the amount of mass increase over time of some standards was significantly smaller than that suggested at the third periodic verification of national prototypes of the kilogram. The analysis with the exponential model gave an exponent of 0.217 with a standard uncertainty of 0.057. This suggests that the mass increase due to surface contamination cannot be explained by a diffusion-limited process.

  5. Determination of the amount of physical adsorption of water vapour on platinum-iridium surfaces

    NASA Astrophysics Data System (ADS)

    Mizushima, S.; Ueda, K.; Ooiwa, A.; Fujii, K.

    2015-08-01

    This paper presents the measurement of the physical adsorption of water vapour on platinum-iridium surfaces using a vacuum mass comparator. This value is of importance for redefining the kilogram, which will be realized under vacuum in the near future. Mirror-polished artefacts, consisting of a reference artefact and a test artefact, were manufactured for this experiment. The surface area difference between the reference and test artefacts was 226.2 cm2. This surface area difference was approximately 3.2 times the geometric surface area of the prototype of the kilogram made of platinum-iridium (71.7 cm2). The measurement results indicate that the amount of physical adsorption at a relative humidity of 50% is 0.0129 μg cm{{-}2} , with a standard uncertainty of 0.0016 μg cm{{-}2} . This value is 0.03 to 0.16 times that observed in other studies.

  6. Results of an Iridium-Based Data Communication System Providing Internet Access to Polar Expeditions

    NASA Astrophysics Data System (ADS)

    Mohammad, A.; Frost, V.; Braaten, D.

    2003-12-01

    The Polar Radar for Ice Sheet Measurements (PRISM) Project at the University of Kansas has developed and field-tested a versatile communications system for use by researchers in high-latitude Polar Regions. The PRISM project is developing advanced intelligent remote sensing technology that involves radar systems, an autonomous rover, and communications systems to measure detailed ice sheet characteristics, and to determine bed conditions (frozen or wet) below active ice sheets in both Greenland and Antarctica. We also have a very strong public outreach and educational program aimed at K-12 educators and students that requires data, voice and video feeds from Polar field locations in near real time. Hence, PRISM requires a robust communications system for use in the field between a base camp and the mobile remote sensing system, and from the field back to the University of Kansas and onto the Internet. The communication system that has been developed is truly mobile and is relatively inexpensive. We initially considered various satellite services during the design phase of this project. The two feasible options for high-latitude locations were Iridium, with its low-bit-rate service (2.4 Kb/s), and Inmarsat/Intelsat with broadband service. We selected the Iridium option for testing and development because it provided coverage in both Antarctica and Greenland. To achieve higher capacity communications, the multilink point-to-point protocol (MLPPP) implemented in Linux was tuned to operate efficiently over the Iridium satellite system. This mechanism combines multiple channels to obtain a seamless data connection with a capacity equal to the sum of the individual link rates. We used four Iridium modems to obtain an aggregate capacity of about 9.6 Kb/s. Standard Internet protocols (TCP/IP) were then used to provide end-to-end connectivity. The communications system field experiments were conducted at the NorthGRIP ice core drilling camp in Greenland (75° 06' N, 42° 20

  7. Characterization of sputtered iridium oxide thin films on planar and laser micro-structured platinum thin film surfaces for neural stimulation applications

    NASA Astrophysics Data System (ADS)

    Thanawala, Sachin

    Electrical stimulation of neurons provides promising results for treatment of a number of diseases and for restoration of lost function. Clinical examples include retinal stimulation for treatment of blindness and cochlear implants for deafness and deep brain stimulation for treatment of Parkinsons disease. A wide variety of materials have been tested for fabrication of electrodes for neural stimulation applications, some of which are platinum and its alloys, titanium nitride, and iridium oxide. In this study iridium oxide thin films were sputtered onto laser micro-structured platinum thin films by pulsed-DC reactive sputtering of iridium metal in oxygen-containing atmosphere, to obtain high charge capacity coatings for neural stimulation applications. The micro-structuring of platinum films was achieved by a pulsed-laser-based technique (KrF excimer laser emitting at lambda=248nm). The surface morphology of the micro-structured films was studied using different surface characterization techniques. In-vitro biocompatibility of these laser micro-structured films coated with iridium oxide thin films was evaluated using cortical neurons isolated from rat embryo brain. Characterization of these laser micro-structured films coated with iridium oxide, by cyclic voltammetry and impedance spectroscopy has revealed a considerable decrease in impedance and increase in charge capacity. A comparison between amorphous and crystalline iridium oxide thin films as electrode materials indicated that amorphous iridium oxide has significantly higher charge capacity and lower impedance making it preferable material for neural stimulation application. Our biocompatibility studies show that neural cells can grow and differentiate successfully on our laser micro-structured films coated with iridium oxide. This indicates that reactively sputtered iridium oxide (SIROF) is biocompatible.

  8. Application of AirCell Cellular AMPS Network and Iridium Satellite System Dual Mode Service to Air Traffic Management

    NASA Technical Reports Server (NTRS)

    Shamma, Mohammed A.

    2004-01-01

    The AirCell/Iridium dual mode service is evaluated for potential applications to Air Traffic Management (ATM) communication needs. The AirCell system which is largely based on the Advanced Mobile Phone System (AMPS) technology, and the Iridium FDMA/TDMA system largely based on the Global System for Mobile Communications(GSM) technology, can both provide communication relief for existing or future aeronautical communication links. Both have a potential to serve as experimental platforms for future technologies via a cost effective approach. The two systems are well established in the entire CONUS and globally hence making it feasible to utilize in all regions, for all altitudes, and all classes of aircraft. Both systems have been certified for air usage. The paper summarizes the specifications of the AirCell/Iridium system, as well as the ATM current and future links, and application specifications. the paper highlights the scenarios, applications, and conditions under which the AirCell/Iridium technology can be suited for ATM Communication.

  9. A Hexakis Terpyridine-Fullerene Ligand in Six-Fold Ruthenium, Iridium, and Iron Complexes: Synthesis and Electrochemical Properties.

    PubMed

    Yan, Weibo; Réthoré, Céline; Menning, Sebastian; Brenner-Weiß, Gerald; Muller, Thierry; Pierrat, Philippe; Bräse, Stefan

    2016-08-01

    An unprecedented straightforward route to six-fold terpyridine ligands around C60 , the latter being regioselectively functionalized in pseudo-octahedral positions using a six-fold Bingel reaction, is reported. Ruthenium, iridium, and iron complexes have been synthesized, and unambiguously characterized by NMR, MS, and cyclic voltammetry. PMID:27189254

  10. Enhancement of activity of RuSex electrocatalyst by modification with nanostructured iridium towards more efficient reduction of oxygen

    NASA Astrophysics Data System (ADS)

    Dembinska, Beata; Kiliszek, Malgorzata; Elzanowska, Hanna; Pisarek, Marcin; Kulesza, Pawel J.

    2013-12-01

    Electrocatalytic activity of carbon (Vulcan XC-72) supported selenium-modified ruthenium, RuSex/C, nanoparticles for reduction of oxygen was enhanced through intentional decoration with iridium nanostructures (dimensions, 2-3 nm). The catalytic materials were characterized in oxygenated 0.5 mol dm-3 H2SO4 using cyclic and rotating ring disk voltammetric techniques as well as using transmission electron microscopy and scanning electron microscopy equipped with X-ray dispersive analyzer. Experiments utilizing gas diffusion electrode aimed at mimicking conditions existing in the low-temperature fuel cell. Upon application of our composite catalytic system, the reduction of oxygen proceeded at more positive potentials, and higher current densities were observed when compared to the behavior of the simple iridium-free system (RuSex/C) investigated under the analogous conditions. The enhancement effect was more pronounced than that one would expect from simple superposition of voltammetric responses for the oxygen reduction at RuSex/C and iridium nanostructures studied separately. Nanostructured iridium acted here as an example of a powerful catalyst for the reduction of H2O2 (rather than O2) and, when combined with such a moderate catalyst as ruthenium-selenium (for O2 reduction), it produced an integrated system of increased electrocatalytic activity in the oxygen reduction process. The proposed system retained its activity in the presence of methanol that could appear in a cathode compartment of alcohol fuel cell.

  11. Thinking Problems of the Present Collision Warning Work by Analyzing the Intersection Between Cosmos 2251 and Iridium 33

    NASA Astrophysics Data System (ADS)

    Wang, R. L.; Liu, W.; Yan, R. D.; Gong, J. C.

    2013-08-01

    After Cosmos 2251 and Iridium 33 collision breakup event, the institutions at home and abroad began the collision warning analysis for the event. This paper compared the results from the different research units and discussed the problems of the current collision warning work, then gave the suggestions of further study.

  12. Type B investigation of the iridium contamination event at the High Flux Isotope Reactor on September 7, 1993

    SciTech Connect

    Not Available

    1994-03-01

    On the title date, at ORNL, area radiation alarms sounded during a routine transfer of a shielding cask (containing 60 Ci{sup 192}Ir) from the HFIR pool side to a transport truck. Small amounts of Ir were released from the cask onto the reactor bay floor. The floor was cleaned, and the cask was shipped to a hot cell at Building 3047 on Oct. 3, 1993. The event was caused by rupture of one of the Ir target rods after it was loaded into the cask for normal transport operations; the rupture was the result of steam generation in the target rod soon after it was placed in the cask (water had entered the target rod through a tiny defect in a weld while it was in the reactor under pressure). While the target rods were in the reactor and reactor pool, there was sufficient cooling to prevent steam generation; when the target rod was loaded into the dry transport cask, the temperature increased enough to result in boiling of the trapped water and produced high enough pressure to result in rupture. The escaping steam ejected some of the Ir pellets. The event was reported as Occurrence Report Number ORO--MMES-X10HFIR-1993-0030, dated Sept. 8, 1993. Analysis indicated that the following conditions were probable causes: less than adequate welding procedures, practices, or techniques, material controls, or inspection methods, or combination thereof, could have led to weld defects, affecting the integrity of target rod IR-75; less than adequate secondary containment in the cask allowed Ir pellets to escape.

  13. CEOS: A Small, Low Cost Spectrometer for Use on the Iridium NEXT Constellation

    NASA Astrophysics Data System (ADS)

    Murphy, S. D.; Slagowski, S.; Greenbaum, A.; Landis, D.; Mustard, J. F.; Chance, K.

    2012-12-01

    As part of the proposed GEOScan sensor payload to be placed onboard the Iridium NEXT constellation; a small, low cost spectrometer will be included. The Compact Earth Observing Spectrometer (CEOS) is an ultraviolet-visible and near infrared (UV/VIS/NIR) optical spectrometer ideally suited for detailed earth observations. CEOS is derived from a spectrometer originally designed for NASA's O/OREOS mission, a CubeSat launched in November 2010 that is still performing extended science operations. It is also slated to be the key science payload component of VIOLET, a CubeSat mission designed to characterize the spectral characteristics of the upper atmosphere. The CEOS has several unique design elements that allow for high performance over a broad range of environmental conditions. The CEOS design allows for a range of customizations to tune the instrument performance for a wide range of science applications. The baseline instrument provides 200-1000 nm spectral coverage with 1 nm FWHM optical resolution, which is ideal for wide variety of science objectives. However by simply exchanging gratings in the instrument, it can be customized for narrower spectral range with significantly higher resolution. The CEOS instrument will also add a significant feature to allow for more detailed earth science observations. The optical portion of the spectrometer will be augmented with a second optical path designed to measure spectra from 1000 - 2000 nm. This will make the finished instrument capable of detailed spectral measurements from 200 - 2000 nm, covering the ultraviolet through near-infrared. The instrument will be designed to allow the independent operation of both the UV/VIS and NIR portions of the instrument to provide flexibility in science data product volumes. We will describe the design of this spectrometer as well as discuss the details of its design heritage. In addition to Iridium NEXT, we will describe other platforms that this spectrometer may be suited for. We

  14. Migration of Single Iridium Atoms and Tri-iridium Clusters on MgO Surfaces. Aberration-Corrected STEM Imaging and ab-initio Calculations

    SciTech Connect

    Han, Chang W.; Iddir, Hakim; Uzun, Alper; Curtiss, Larry A.; Browning, Nigel D.; Gates, Bruce C.; Ortalan, Volkan

    2015-11-06

    To address the challenge of fast, direct atomic-scale visualization of the diffusion of atoms and clusters on surfaces, we used aberration-corrected scanning transmission electron microscopy (STEM) with high scan speeds (as little as ~0.1 s per frame) to visualize the diffusion of (1) a heavy atom (Ir) on the surface of a support consisting of light atoms, MgO(100), and (2) an Ir3 cluster on MgO(110). Sequential Z-contrast images elucidate the diffusion mechanisms, including the hopping of Ir1 and the rotational migration of Ir3 as two Ir atoms remain anchored to the surface. Density functional theory (DFT) calculations provided estimates of the diffusion energy barriers and binding energies of the iridium species to the surfaces. The results show how the combination of fast-scan STEM and DFT calculations allow real-time visualization and fundamental understanding of surface diffusion phenomena pertaining to supported catalysts and other materials.

  15. Iridium abundance maxima at the latest Ordovician mass extinction horizon, Yangtze Basin, China: Terrestrial or extraterrestrial

    SciTech Connect

    Kun Wang; Chatterton, B.D.E. ); Attrep, M. Jr; Orth, C.J. )

    1992-01-01

    Neutron activation analyses of the Chinese Ordovician/Silurian (O/S) boundary sections at two distant localities in the Yangtze Basin, spanning the horizon of a major latest Ordovician global extinction event, show the maxima of iridium abundances to be coincident with the extinction horizon at the base of the graptolite Glyptograptus persculputs zone. The 0.23 ppb Ir maximum in the Yichang type section is almost as large as the late Eocene impact Ir anomaly. However, the authors have observed that the Ir abundances in the Chinese sections are closely correlated with the sedimentation rates, and therefore have concluded that Ir maxima do not indicate a cataclysmic extraterrestrial impact at this extinction level.

  16. Iridium Oxide Nanotube Electrodes for Highly Sensitive and Prolonged Intracellular Measurement of Action Potentials

    PubMed Central

    Lin, Ziliang Carter; Xie, Chong; Osakada, Yasuko; Cui, Yi; Cui, Bianxiao

    2014-01-01

    Intracellular recording of action potentials is important to understand electrically-excitable cells. Recently, vertical nanoelectrodes have been developed to achieve highly sensitive, minimally invasive, and large scale intracellular recording. It has been demonstrated that the vertical geometry is crucial for the enhanced signal detection. Here we develop nanoelectrodes made up of nanotubes of iridium oxide. When cardiomyocytes are cultured upon those nanotubes, the cell membrane not only wraps around the vertical tubes but also protrudes deep into the hollow center. We show that this geometry enhances cell-electrode coupling and results in measuring much larger intracellular action potentials. The nanotube electrodes afford much longer intracellular access and are minimally invasive, making it possible to achieve stable recording up to an hour in a single session and more than 8 days of consecutive daily recording. This study suggests that the electrode performance can be significantly improved by optimizing the electrode geometry. PMID:24487777

  17. Anion-Anion Bonding and Topology in Ternary Iridium Tin Selenides

    NASA Astrophysics Data System (ADS)

    Trump, Benjamin; Tutmaher, Jake; McQueen, Tyrel

    Iridium compounds have been under intense scrutiny due to strong relativistic effects (spin-orbit coupling) which have comparable energy scales to crystal field stabilization and electron correlations, which could lead to non-trivial behavior. Here we report the synthesis, characterization, and physical properties of two new, and one known, Ir-Sn-Se compounds. Resistivity, specific heat, and magnetization measurements show that all three have insulating and diamagnetic behavior, indicative of low spin 5d6 Ir3+. Furthermore, electronic structures calculations on Ir2Sn3Se3 show a single, spherical, non-spin-orbit split valence band that supports mobile p-type carriers, and imply that Ir2Sn3Se3 is topologically non-trivial under tensile strain, due to inversion of Ir- d and Se- p states. Work supported by NSF, Division of Materials Research (DMR), Solid State Chemistry (SSMC), CAREER Grant under Award DMR-1253562, and the ICDD Ludo Frevel Crystallography Scholarship.

  18. Catalytic dehydroaromatization of n-alkanes by pincer-ligated iridium complexes

    NASA Astrophysics Data System (ADS)

    Ahuja, Ritu; Punji, Benudhar; Findlater, Michael; Supplee, Carolyn; Schinski, William; Brookhart, Maurice; Goldman, Alan S.

    2011-02-01

    Aromatic hydrocarbons are among the most important building blocks in the chemical industry. Benzene, toluene and xylenes are obtained from the high temperature thermolysis of alkanes. Higher alkylaromatics are generally derived from arene-olefin coupling, which gives branched products—that is, secondary alkyl arenes—with olefins higher than ethylene. The dehydrogenation of acyclic alkanes to give alkylaromatics can be achieved using heterogeneous catalysts at high temperatures, but with low yields and low selectivity. We present here the first catalytic conversion of n-alkanes to alkylaromatics using homogeneous or molecular catalysts—specifically ‘pincer’-ligated iridium complexes—and olefinic hydrogen acceptors. For example, the reaction of n-octane affords up to 86% yield of aromatic product, primarily o-xylene and secondarily ethylbenzene. In the case of n-decane and n-dodecane, the resulting alkylarenes are exclusively unbranched (that is, n-alkyl-substituted), with selectivity for the corresponding o-(n-alkyl)toluene.

  19. Formation of C-C Bonds via Iridium-Catalyzed Hydrogenation and Transfer Hydrogenation.

    PubMed

    Bower, John F; Krische, Michael J

    2011-01-01

    The formation of C-C bonds via catalytic hydrogenation and transfer hydrogenation enables carbonyl and imine addition in the absence of stoichiometric organometallic reagents. In this review, iridium-catalyzed C-C bond-forming hydrogenations and transfer hydrogenations are surveyed. These processes encompass selective, atom-economic methods for the vinylation and allylation of carbonyl compounds and imines. Notably, under transfer hydrogenation conditions, alcohol dehydrogenation drives reductive generation of organoiridium nucleophiles, enabling carbonyl addition from the aldehyde or alcohol oxidation level. In the latter case, hydrogen exchange between alcohols and π-unsaturated reactants generates electrophile-nucleophile pairs en route to products of hydro-hydroxyalkylation, representing a direct method for the functionalization of carbinol C-H bonds. PMID:21822399

  20. Iridium-catalyzed hydrogen production from monosaccharides, disaccharide, cellulose, and lignocellulose.

    PubMed

    Li, Yang; Sponholz, Peter; Nielsen, Martin; Junge, Henrik; Beller, Matthias

    2015-03-01

    Hydrogen constitutes an important feedstock for clean-energy technologies as well as for production of bulk and fine chemicals. Hence, the development of novel processes to convert easily available biomass into H2 is of general interest. Herein, we demonstrate a one-pot protocol hydrogen generation from monosaccharides, disaccharide, and extremely demanding cellulose and lignocellulose substrates by using a pincer-type iridium catalyst. Applying ppm amounts of this catalyst, hydrogen is produced at temperatures lower than 120 °C. More specifically, catalyst turnover numbers (TONs) for lignocellulose from bamboo reached up to about 3000. Interestingly, even (used) cigarette filters, which are composed of cellulose acetate, produce hydrogen under optimized conditions.

  1. Iridium Catalyzed Dehydrogenation of Substituted Amine Boranes: Kinetics, Thermodynamics and Implications for Hydrogen Storage.

    SciTech Connect

    Dietrich, Brandon L.; Goldberg, Karen I.; Heinekey, D. M.; Autrey, Thomas; Linehan, John C.

    2008-10-06

    Dehydrogenation of ammonia borane (AB) and methylamine-borane (MeAB) is catalyzed efficiently by the iridium pincer complex (η3-1,3-(OPtBu2)2C6H3)Ir(H)2 (1). With MeAB and with MeAB/AB mixtures, rapid release of one equivalent of H2 is observed to yield soluble oligomeric products at rates similar to those previously reported for the dehydrogenation of AB catalyzed by 1. The rapid dehydrogenation reaction has allowed the experimental determination of the reaction enthalpy (ΔH) for the dehydrogenation of AB, MeAB, and AB/MeAB mixtures by calorimetry. The reactions are significantly more exothermic than suggested by some computational studies. This work was supported by the U.S. Department of Energy (DOE) as part of the Center of Excellence for Chemical Hydrogen Storage. PNNL is operated by Battelle for DOE.

  2. Activity and Durability of Iridium Nanoparticles in the Oxygen Evolution Reaction

    DOE PAGES

    Alia, Shaun M.; Rasimick, Brian; Ngo, Chilan; Neyerlin, K. C.; Kocha, Shyam S.; Pylypenko, Svitlana; Xu, Hui; Pivovar, Bryan S.

    2016-07-15

    Unsupported iridium (Ir) nanoparticles, that serve as standard oxygen evolution reaction (OER) catalysts in acidic electrolyzers, were investigated for electrochemical performance and durability in rotating disk electrode (RDE) half-cells. Fixed potential holds and potential cycling were applied to probe the durability of Ir nanoparticles, and performance losses were found to be driven by particle growth (coarsening) at moderate potential (1.4 to 1.6 V) and Ir dissolution at higher potential (>/=1.8 V). Several different commercially available samples were evaluated and standardized conditions for performance comparison are reported. In conclusion, the electrocatalyst RDE results have also been compared to results obtained formore » performance and durability in electrolysis cells.« less

  3. Ascent of dinosaurs linked to an iridium anomaly at the Triassic-Jurassic boundary.

    PubMed

    Olsen, P E; Kent, D V; Sues, H-D; Koeberl, C; Huber, H; Montanari, A; Rainforth, E C; Fowell, S J; Szajna, M J; Hartline, B W

    2002-05-17

    Analysis of tetrapod footprints and skeletal material from more than 70 localities in eastern North America shows that large theropod dinosaurs appeared less than 10,000 years after the Triassic-Jurassic boundary and less than 30,000 years after the last Triassic taxa, synchronous with a terrestrial mass extinction. This extraordinary turnover is associated with an iridium anomaly (up to 285 parts per trillion, with an average maximum of 141 parts per trillion) and a fern spore spike, suggesting that a bolide impact was the cause. Eastern North American dinosaurian diversity reached a stable maximum less than 100,000 years after the boundary, marking the establishment of dinosaur-dominated communities that prevailed for the next 135 million years.

  4. Iridium-catalyzed reductive carbon-carbon bond cleavage reaction on a curved pyridylcorannulene skeleton.

    PubMed

    Tashiro, Shohei; Yamada, Mihoko; Shionoya, Mitsuhiko

    2015-04-27

    The cleavage of CC bonds in π-conjugated systems is an important method for controlling their shape and coplanarity. An efficient way for the cleavage of an aromatic CC bond in a typical buckybowl corannulene skeleton is reported. The reaction of 2-pyridylcorannulene with a catalytic amount of IrCl3 ⋅n H2 O in ethylene glycol at 250 °C resulted in a structural transformation from the curved corannulene skeleton to a strain-free flat benzo[ghi]fluoranthene skeleton through a site-selective CC cleavage reaction. This cleavage reaction was found to be driven by both the coordination of the 2-pyridyl substituent to iridium and the relief of strain in the curved corannulene skeleton. This finding should facilitate the design of carbon nanomaterials based on CC bond cleavage reactions.

  5. Iridium-Catalyzed, Hydrosilyl-Directed Borylation of Unactivated Alkyl C-H Bonds.

    PubMed

    Larsen, Matthew A; Cho, Seung Hwan; Hartwig, John

    2016-01-27

    We report the iridium-catalyzed borylation of primary and secondary alkyl C-H bonds directed by a Si-H group to form alkylboronate esters site selectively. The reactions occur with high selectivity at primary C-H bonds γ to the hydrosilyl group to form primary alkyl bisboronate esters. In the absence of such primary C-H bonds, the borylation occurs selectively at a secondary C-H bond γ to the hydrosilyl group, and these reactions of secondary C-H bonds occur with high diastereoselectivity. The hydrosilyl-containing alkyl boronate esters formed by this method undergo transformations selectively at the carbon-boron or carbon-silicon bonds of these products under distinct conditions to give the products of amination, oxidation, and arylation.

  6. Conodont survival and low iridium abundances across the Permian-Triassic boundary in South China

    SciTech Connect

    Clark, D.L.; Wang, C.Y.; Orth, C.J.; Gilmore, J.S.

    1986-08-29

    The Permian-Triassic sedimentary sequence of China includes one of the most complete and fossiliferous Paleozoic-Mesozoic boundaries known. Closely spaced sampling across the boundary, which is an important extinction event for most organisms, has produced good conodont faunas that show little diversity change. A drop in conodont abundance is the only apparent response to the extinction event. A low concentration of iridium in the boundary clay (0.002 part per billion +/- 20 percent), as well as in samples immediately below and above, that range form 0.004 to 0.034 part per billion do not support the proposal of an extraterrestrial impact event at this boundary in China. 21 references, 2 tables.

  7. Noisy CO oxidation on Iridium(111) surfaces. Experiments explained by theory under realistic assumptions

    NASA Astrophysics Data System (ADS)

    Wehner, S.; Cisternas, J.; Descalzi, O.; Küppers, J.

    2014-01-01

    Noise is an everywhere phenomenon. Its influence could be described theoretically quite easily, but is hard to measure in an experiment. Catalytic reactions on surfaces can be described by nonlinear reaction-diffusion equations. For one of such surface reactions - CO oxidation on Iridium(111) surfaces - the probability distribution of CO2 rates around the mean value - showing the influence of noise - could be measured directly in a ultra high vacuum (UHV) experiment. This opens the way to address such a fundamental phenomenon like noise by all three modern methods of physics - experimental, computational and analytical. We show the measured effect of colored noise on a bistable surface reaction and explain all observations directly with the underlying theoretical description - the Langmuir-Hinshelwood reaction scheme - by solving the equations under realistic assumptions. It is a great pleasure to dedicate this work to Prof. Dr. Helmut R. Brand on the occasion of his 60th birthday.

  8. Formation of C–C Bonds via Iridium-Catalyzed Hydrogenation and Transfer Hydrogenation

    PubMed Central

    Bower, John F.; Krische, Michael J.

    2011-01-01

    The formation of C–C bonds via catalytic hydrogenation and transfer hydrogenation enables carbonyl and imine addition in the absence of stoichiometric organometallic reagents. In this review, iridium-catalyzed C–C bond-forming hydrogenations and transfer hydrogenations are surveyed. These processes encompass selective, atom-economic methods for the vinylation and allylation of carbonyl compounds and imines. Notably, under transfer hydrogenation conditions, alcohol dehydrogenation drives reductive generation of organoiridium nucleophiles, enabling carbonyl addition from the aldehyde or alcohol oxidation level. In the latter case, hydrogen exchange between alcohols and π-unsaturated reactants generates electrophile–nucleophile pairs en route to products of hydro-hydroxyalkylation, representing a direct method for the functionalization of carbinol C–H bonds. PMID:21822399

  9. Hot rocket plume experiment - Survey and conceptual design. [of rhenium-iridium bipropellants

    NASA Technical Reports Server (NTRS)

    Millard, Jerry M.; Luan, Taylor W.; Dowdy, Mack W.

    1992-01-01

    Attention is given to a space-borne engine plume experiment study to fly an experiment which will both verify and quantify the reduced contamination from advanced rhenium-iridium earth-storable bipropellant rockets (hot rockets) and provide a correlation between high-fidelity, in-space measurements and theoretical plume and surface contamination models. The experiment conceptual design is based on survey results from plume and contamination technologists throughout the U.S. With respect to shuttle use, cursory investigations validate Hitchhiker availability and adaptability, adequate remote manipulator system (RMS) articulation and dynamic capability, acceptable RMS attachment capability, adequate power and telemetry capability, and adequate flight altitude and attitude/orbital capability.

  10. Anodic Deposition of a Robust Iridium-Based Water-Oxidation Catalyst from Organometallic Precursors

    SciTech Connect

    Blakemore, James D; Schley, Nathan D; Olack, G.; Incarvito, Christopher D; Brudvig, Gary W; Crabtree, Robert H

    2011-01-01

    Artificial photosynthesis, modeled on natural light-driven oxidation of water in Photosystem II, holds promise as a sustainable source of reducing equivalents for producing fuels. Few robust water-oxidation catalysts capable of mediating this difficult four-electron, four-proton reaction have yet been described. We report a new method for generating an amorphous electrodeposited material, principally consisting of iridium and oxygen, which is a robust and long-lived catalyst for water oxidation, when driven electrochemically. The catalyst material is generated by a simple anodic deposition from Cp*Ir aqua or hydroxo complexes in aqueous solution. This work suggests that organometallic precursors may be useful in electrodeposition of inorganic heterogeneous catalysts.

  11. Spin-orbit coupled jeff=1/2 iridium moments on the geometrically frustrated fcc lattice

    DOE PAGES

    Cook, A. M.; Matern, S.; Hickey, C.; Aczel, A. A.; Paramekanti, A.

    2015-07-01

    Motivated by experiments on La2ZnIrO6 and La2MgIrO6, we study the magnetism of spin-orbit coupled jeff = 1/2 iridium moments on the three-dimensional geometrically-frustrated face-centered cubic lattice. The symmetry-allowed nearest-neighbor interaction includes Heisenberg, Kitaev, and symmetric off-diagonal exchange. Using Luttinger-Tisza and Monte Carlo simulations, we find a rich variety of orders, including collinear A-type antiferromagnetism, collinear stripe order with moments along the {111}-direction, and incommensurate non-coplanar spirals, and determine their magnetic ordering transition temperatures. We argue that thermodynamic data on these iridates underscore the presence of a dominant Kitaev exchange, and suggest a possible resolution to the puzzle of why La2ZnIrO6,more » but not La2MgIrO6, exhibits 'weak' ferromagnetism.« less

  12. Nd2K2IrO7 and Sm2K2IrO7: Iridium(VI) Oxides Prepared under Ambient Pressure

    SciTech Connect

    Mugavero, III, S.; Smith, M; Yoon, W; zur Loye, H

    2009-01-01

    The most-oxidized iridium oxides known to date are prepared in a hydroxide flux under normal pressure. They contain iridium centers exclusively in the +VI oxidation state and are characterized crystallographically. The picture shows the structure of the Ln2K2IrO7 (Ln=Nd, Sm) and its structural components: IrO6 octahedra (black), KO10 polyhedra (beige), LnO10 polyhedra (blue).

  13. Method of making a long life high current density cathode from tungsten and iridium powders using a quaternary compound as the impregnant

    SciTech Connect

    Branovich, L.E.; Smith, B.; Freemen, G.L.; Eckart, D.W.

    1990-09-18

    This patent describes a method of making a long life high current density cathode. It is suitable for operation in microwave devices. It is made from tungsten and iridium powders using a quaternary compound including barium, oxygen, a metal selected from the group consisting of osmium, iridium, rhodium, and rhenium, and a metal selected from the group consisting of strontium, calcium, scandium, and titanium as the impregnant.

  14. Bond Fission and Non-Radiative Decay in Iridium(III) Complexes.

    PubMed

    Zhou, Xiuwen; Burn, Paul L; Powell, Benjamin J

    2016-06-01

    We investigate the role of metal-ligand bond fission in the nonradiative decay of excited states in iridium(III) complexes with applications in blue organic light-emitting diodes (OLEDs). We report density functional theory (DFT) calculations of the potential energy surfaces upon lengthening an iridium-nitrogen (Ir-N) bond. In all cases we find that for bond lengths comparable to those of the ground state the lowest energy state is a triplet with significant metal-to-ligand change transfer character ((3)MLCT). But, as the Ir-N bond is lengthened there is a sudden transition to a regime where the lowest excited state is a triplet with significant metal centered character ((3)MC). Time-dependent DFT relativistic calculations including spin-orbit coupling perturbatively show that the radiative decay rate from the (3)MC state is orders of magnitude slower than that from the (3)MLCT state. The calculated barrier height between the (3)MLCT and (3)MC regimes is clearly correlated with previously measured nonradiative decay rates, suggesting that thermal population of the (3)MC state is the dominant nonradiative decay process at ambient temperature. In particular, fluorination both drives the emission of these complexes to a deeper blue color and lowers the (3)MLCT-(3)MC barrier. If the Ir-N bond is shortened in the (3)MC state another N atom is pushed away from the Ir, resulting in the breaking of this bond, suggesting that once the Ir-N bond breaks the damage to the complex is permanent-this will have important implications for the lifetimes of devices using this type of complex as the active material. The consequences of these results for the design of more efficient blue phosphors for OLED applications are discussed. PMID:27175618

  15. Cationic iridium(III) complexes with two carbene-based cyclometalating ligands: cis versus trans isomers.

    PubMed

    Monti, Filippo; La Placa, Maria Grazia I; Armaroli, Nicola; Scopelliti, Rosario; Grätzel, Michael; Nazeeruddin, Mohammad Khaja; Kessler, Florian

    2015-03-16

    A series of cationic iridium(III) complexes with two carbene-based cyclometalating ligands and five different N^N bipyridine and 1,10-phenanthroline ancillary ligands is presented. For the first time--in the frame of a rarely studied class of bis(heteroleptic) iridium complexes with two carbene-based cyclometalating ligands--a pair of cis and trans isomers has been isolated. All complexes (trans-1-5 and cis-3) were characterized by (1)H NMR, (13)C NMR, (31)P NMR, and HRMS (ESI-TOF); in addition, crystal structures of cis-3 and trans-4 are reported and discussed. Cyclic voltammetric studies show that the whole series exhibits highly reversible oxidation and reduction processes, suggesting promising potential for optoelectronic applications. Ground-state DFT and TD-DFT calculations nicely predict the blue shift experimentally observed in the room-temperature absorption and emission spectra of cis-3, compared to the trans complexes. In CH3CN, cis-3 displays a 4-fold increase in photoluminescence quantum yield (PLQY) with respect to trans-3, as a consequence of drastically slower nonradiative rate constant. By contrast, at 77 K, the emission properties of all the compounds, including the cis isomer, are much more similar, with a pronounced hypsochromic shift for the trans complexes. A similar behavior is found in solid state (1% w/w poly(methyl methacrylate) matrix), with all complexes displaying PLQY of ∼70-80%, comparable emission lifetimes (τ ≈ 1.3 μs), and a remarkable rigidochromic shift. To rationalize the more pronounced nonradiative deactivation (and smaller PLQY) observed for photoexcited trans complexes, comparative temperature-dependent emission studies in the range of 77-450 K for cis-3 and trans-3 were made in propylene glycol, showing that solvation effects are primarily responsible for the observed behavior.

  16. Charged bis-cyclometalated iridium(III) complexes with carbene-based ancillary ligands.

    PubMed

    Monti, Filippo; Kessler, Florian; Delgado, Manuel; Frey, Julien; Bazzanini, Federico; Accorsi, Gianluca; Armaroli, Nicola; Bolink, Henk J; Ortí, Enrique; Scopelliti, Rosario; Nazeeruddin, Md Khaja; Baranoff, Etienne

    2013-09-16

    Charged cyclometalated (C(^)N) iridium(III) complexes with carbene-based ancillary ligands are a promising family of deep-blue phosphorescent compounds. Their emission properties are controlled primarily by the main C(^)N ligands, in contrast to the classical design of charged complexes where N(^)N ancillary ligands with low-energy π* orbitals, such as 2,2'-bipyridine, are generally used for this purpose. Herein we report two series of charged iridium complexes with various carbene-based ancillary ligands. In the first series the C(^)N ligand is 2-phenylpyridine, whereas in the second one it is 2-(2,4-difluorophenyl)-pyridine. One bis-carbene (:C(^)C:) and four different pyridine-carbene (N(^)C:) chelators are used as bidentate ancillary ligands in each series. Synthesis, X-ray crystal structures, and photophysical and electrochemical properties of the two series of complexes are described. At room temperature, the :C(^)C: complexes show much larger photoluminescence quantum yields (ΦPL) of ca. 30%, compared to the N(^)C: analogues (around 1%). On the contrary, all of the investigated complexes are bright emitters in the solid state both at room temperature (1% poly(methyl methacrylate) matrix, ΦPL 30-60%) and at 77 K. Density functional theory calculations are used to rationalize the differences in the photophysical behavior observed upon change of the ancillary ligands. The N(^)C:-type complexes possess a low-lying triplet metal-centered ((3)MC) state mainly deactivating the excited state through nonradiative processes; in contrast, no such state is present for the :C(^)C: analogues. This finding is supported by temperature-dependent excited-state lifetime measurements made on representative N(^)C: and :C(^)C: complexes.

  17. Sol-Gel Deposition of Iridium Oxide for Biomedical Micro-Devices

    PubMed Central

    Nguyen, Cuong M.; Rao, Smitha; Yang, Xuesong; Dubey, Souvik; Mays, Jeffrey; Cao, Hung; Chiao, Jung-Chih

    2015-01-01

    Flexible iridium oxide (IrOx)-based micro-electrodes were fabricated on flexible polyimide substrates using a sol-gel deposition process for utilization as integrated pseudo-reference electrodes for bio-electrochemical sensing applications. The fabrication method yields reliable miniature on-probe IrOx electrodes with long lifetime, high stability and repeatability. Such sensors can be used for long-term measurements. Various dimensions of sol-gel iridium oxide electrodes including 1 mm × 1 mm, 500 μm × 500 μm, and 100 μm × 100 μm were fabricated. Sensor longevity and pH dependence were investigated by immersing the electrodes in hydrochloric acid, fetal bovine serum (FBS), and sodium hydroxide solutions for 30 days. Less pH dependent responses, compared to IrOx electrodes fabricated by electrochemical deposition processes, were measured at 58.8 ± 0.4 mV/pH, 53.8 ± 1.3 mV/pH and 48 ± 0.6 mV/pH, respectively. The on-probe IrOx pseudo-reference electrodes were utilized for dopamine sensing. The baseline responses of the sensors were higher than the one using an external Ag/AgCl reference electrode. Using IrOx reference electrodes integrated on the same probe with working electrodes eliminated the use of cytotoxic Ag/AgCl reference electrode without loss in sensitivity. This enables employing such sensors in long-term recording of concentrations of neurotransmitters in central nervous systems of animals and humans. PMID:25686309

  18. Osmium, ruthenium, iridium and uranium in silicates and chromite from the eastern Bushveld Complex, South Africa

    USGS Publications Warehouse

    Gijbels, R.h.; Millard, H.T.; Desborough, G.A.; Bartel, A.J.

    1974-01-01

    Osmium, ruthenium, iridium and uranium contents were determined in eight ortho pyroxene, seven plagioclase, and three chromite mineral separates from the eastern Bushveld Complex. Neutron activation analysis was used to measure the platinum metals, and uranium was determined by a fission track technique. The platinum metals were found to be present within each mine??ral in the proportions Os:Ru:Ir = 1:7:1, while the concentrations of these metals in the minerals are in the ratios orthopyroxene:plagioclase:chromite = 1:16:700. The concentration of uranium was found to range from 11 to 66 ppb (parts per billion) and not to vary significantly from mineral to mineral. The data for the platinum metals are consistent with a model in which the eastern Bushveld Complex was formed by the fractional crystallization of two separately injected magmas. A computer fit of this model to these data indicates that the initial concentrations of Os, Ru and Ir in the first magma were 0.24, 2.0 and 0.21 ppb and in the second magma were 0.16, 1.1 and 0.18 ppb, respectively. The fit also yields the distribution coefficients for the partitioning between the liquid and cumulus orthopyroxene, cumulus plagioclase and cumulus chromite. These coefficients (mineral/liquid) for osmium are 4.5, 66 and 2700; for ruthenium, they are 5, 65 and 2700; and for iridium, they are 4, 60 and 1600. To make this fit, it was necessary to hypothesize the existence of two types of chromite: one type with a large distribution coefficient, presumably formed as a cumulus phase at high temperature, and another, more prevalent type with a smaller distribution coefficient, which may have been formed by postcumulus growth at a lower temperature. This hypothesis is supported by data for coexisting chromite-silicate pairs, which indicate that the chromite grains expelled these platinum metals as they cooled. ?? 1974.

  19. Mobility of iridium in terrestrial environments: Implications for the interpretation of impact-related mass-extinctions

    NASA Astrophysics Data System (ADS)

    Martín-Peinado, F. J.; Rodríguez-Tovar, F. J.

    2010-08-01

    Traditionally, iridium has been considered an element of low mobility, but its behavior is still debated. Ir concentration in a soil affected by a catastrophic mining spill in 1998 that covered the soil with a layer of tailings offers the opportunity to analyse an exceptional Ir-bearing horizon 10 years after deposition. This has enabled comparisons with the values of past Ir-bearing horizons associated to impact-related mass-extinction events. Iridium concentration in the tailings (0.349 ppm) was 5-fold higher than the anomaly in the K-Pg at The Moody Creek Mine section (the highest values obtained from terrestrial sections). The oxidative weathering of the tailings caused the release of Ir and infiltration into the soil. Iridium distribution in depth indicates redistribution throughout the profile in relation to the change in the physico-chemical properties of the soil. With regard to the background concentration in the soil (0.056 ppm), anomalous values of Ir (0.129 ppm) can be detected to 11 cm below the layer of tailings. The correlation analysis between the Ir concentration and the main properties and constituents of the soils indicated a significant correlation with sulfur, iron, clay content, and pH. Selective extractions were made to study the forms in which Ir can be mobilized in the soil. The residual/insoluble fraction was >90% of the total Ir concentration in soil. Soluble-in-water concentration of Ir (1.5% of total) was detected in the uppermost 2-3 cm of the soil, which were directly affected by the leaching of acidic waters coming from the oxidation of the pyrite tailings. Iridium retention in the affected part of the soil reached 9% of the total Ir concentration; this retention could be related to the amorphous iron forms dissolved by the oxalic-oxalate extraction. However, according to our research, original Ir abundance could be secondarily modified, and then a direct analysis of the iridium values recorded in sediments could induce

  20. Alpha-emitting isotopes and chromium in a coastal California aquifer

    USGS Publications Warehouse

    Densmore, Jill N.; Izbicki, John A.; Murtaugh, Joseph M.; Swarzenski, Peter W.; Bullen, Thomas D.

    2014-01-01

    The unadjusted 72-h gross alpha activities in water from two wells completed in marine and alluvial deposits in a coastal southern California aquifer 40 km north of San Diego were 15 and 25 picoCuries per liter (pCi/L). Although activities were below the Maximum Contaminant Level (MCL) of 15 pCi/L, when adjusted for uranium activity; there is concern that new wells in the area may exceed MCLs, or that future regulations may limit water use from the wells. Coupled well-bore flow and depth-dependent water-quality data collected from the wells in 2011 (with analyses for isotopes within the uranium, actinium, and thorium decay-chains) show gross alpha activity in marine deposits is associated with decay of naturally-occurring 238U and its daughter 234U. Radon activities in marine deposits were as high as 2230 pCi/L. In contrast, gross alpha activities in overlying alluvium within the Piedra de Lumbre watershed, eroded from the nearby San Onofre Hills, were associated with decay of 232Th, including its daughter 224Ra. Radon activities in alluvium from Piedra de Lumbre of 450 pCi/L were lower than in marine deposits. Chromium VI concentrations in marine deposits were less than the California MCL of 10 μg/L (effective July 1, 2014) but δ53Cr compositions were near zero and within reported ranges for anthropogenic chromium. Alluvial deposits from the nearby Las Flores watershed, which drains a larger area having diverse geology, has low alpha activities and chromium as a result of geologic and geochemical conditions and may be more promising for future water-supply development.

  1. Development of a luminescent G-quadruplex-selective iridium(III) complex for the label-free detection of adenosine

    PubMed Central

    Lu, Lihua; Zhong, Hai-Jing; He, Bingyong; Leung, Chung-Hang; Ma, Dik-Lung

    2016-01-01

    A panel of six luminescent iridium(III) complexes were synthesized and evaluated for their ability to act as G-quadruplex-selective probes. The novel iridium(III) complex 1 was found to be highly selective for G-quadruplex DNA, and was employed for the construction of a label-free G-quadruplex-based adenosine detection assay in aqueous solution. Two different detection strategies were investigated for adenosine detection, and the results showed that initial addition of adenosine to the adenosine aptamer gave superior results. The assay exhibited a linear response for adenosine in the concentration range of 5 to 120 μM (R2 = 0.992), and the limit of detection for adenosine was 5 μM. Moreover, this assay was highly selective for adenosine over other nucleosides, and exhibited potential use for biological sample analysis. PMID:26778273

  2. Development of a luminescent G-quadruplex-selective iridium(III) complex for the label-free detection of adenosine

    NASA Astrophysics Data System (ADS)

    Lu, Lihua; Zhong, Hai-Jing; He, Bingyong; Leung, Chung-Hang; Ma, Dik-Lung

    2016-01-01

    A panel of six luminescent iridium(III) complexes were synthesized and evaluated for their ability to act as G-quadruplex-selective probes. The novel iridium(III) complex 1 was found to be highly selective for G-quadruplex DNA, and was employed for the construction of a label-free G-quadruplex-based adenosine detection assay in aqueous solution. Two different detection strategies were investigated for adenosine detection, and the results showed that initial addition of adenosine to the adenosine aptamer gave superior results. The assay exhibited a linear response for adenosine in the concentration range of 5 to 120 μM (R2 = 0.992), and the limit of detection for adenosine was 5 μM. Moreover, this assay was highly selective for adenosine over other nucleosides, and exhibited potential use for biological sample analysis.

  3. Dicarba-closo-dodecarborane-containing half-sandwich complexes of ruthenium, osmium, rhodium and iridium: biological relevance and synthetic strategies.

    PubMed

    Barry, Nicolas P E; Sadler, Peter J

    2012-04-21

    This review describes how the incorporation of dicarba-closo-dodecarboranes into half-sandwich complexes of ruthenium, osmium, rhodium and iridium might lead to the development of a new class of compounds with applications in medicine. Such a combination not only has unexplored potential in traditional areas such as Boron Neutron Capture Therapy agents, but also as pharmacophores for the targeting of biologically important proteins and the development of targeted drugs. The synthetic pathways used for the syntheses of dicarba-closo-dodecarboranes-containing half-sandwich complexes of ruthenium, osmium, rhodium and iridium are also reviewed. Complexes with a wide variety of geometries and characteristics can be prepared. Examples of addition reactions on the metal centre, B-H activation, transmetalation reactions and/or direct formation of metal-metal bonds are discussed (103 references).

  4. Solution-processable deep red-emitting supramolecular phosphorescent polymer with novel iridium complex for organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Liang, Aihui; Huang, Gui; Wang, Zhiping; Wu, Wenjin; Zhong, Yu; Zhao, Shan

    2016-07-01

    A novel bis(dibenzo-24-crown-8)-functionalized iridium complex with an emission peak at 665 nm was synthesized. Several deep red-emitting supramolecualr phosphorescent polymers (SPPs) as a class of solutionprocessable electroluminescent (EL) emitters were formed by utilizing the efficient non-bonding self-assembly between the resulting iridium complex and bis(dibenzylammonium)-tethered monomers. These SPPs show an intrinsic glass transition with a T g of ca. 90 °C. The photophysical and electroluminescent properties are strongly dependent on the hosts' structures of the supramolecular phosphorescent polymers. The polymer light-emitting diode based on SPP3 displayed a maximal external quantum efficiency (EQE) of 2.14% ph·el-1 and the Commission Internationale de L'Eclairage (CIE) coordinates of (0.70, 0.29).

  5. Solution-processable deep red-emitting supramolecular phosphorescent polymer with novel iridium complex for organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Liang, Aihui; Huang, Gui; Wang, Zhiping; Wu, Wenjin; Zhong, Yu; Zhao, Shan

    2016-09-01

    A novel bis(dibenzo-24-crown-8)-functionalized iridium complex with an emission peak at 665 nm was synthesized. Several deep red-emitting supramolecualr phosphorescent polymers (SPPs) as a class of solutionprocessable electroluminescent (EL) emitters were formed by utilizing the efficient non-bonding self-assembly between the resulting iridium complex and bis(dibenzylammonium)-tethered monomers. These SPPs show an intrinsic glass transition with a T g of ca. 90 °C. The photophysical and electroluminescent properties are strongly dependent on the hosts' structures of the supramolecular phosphorescent polymers. The polymer light-emitting diode based on SPP3 displayed a maximal external quantum efficiency (EQE) of 2.14% ph·el-1 and the Commission Internationale de L'Eclairage (CIE) coordinates of (0.70, 0.29).

  6. Luminescence switch-on assay of interferon-gamma using a G-quadruplex-selective iridium(III) complex.

    PubMed

    Lin, Sheng; He, Bingyong; Yang, Chao; Leung, Chung-Hang; Mergny, Jean-Louis; Ma, Dik-Lung

    2015-11-18

    In this study, we synthesized a series of 9 luminescent iridium(III) complexes and studied their ability to function as luminescent probes for G-quadruplex DNA. The iridium(III) complex 8 [Ir(pbtz)2(dtbpy)]PF6 (where pbtz = 2-phenylbenzo[d]thiazole; dtbpy = 4,4'-di-tert-butyl-2,2'-bipyridine) showed high selectivity for G-quadruplex DNA over single-stranded and double-stranded DNA, and was subsequently utilized for the development of a label-free oligonucleotide-based assay for interferon-gamma (IFN-γ), an important biomarker for a range of immune and infectious diseases, in aqueous solution. We further demonstrated that this assay could monitor IFN-γ levels even in the presence of cellular debris. This assay represents the first G-quadruplex-based assay for IFN-γ detection described in the literature.

  7. Diastereo- and enantioselective iridium-catalyzed allylation of cyclic ketone enolates: synergetic effect of ligands and barium enolates.

    PubMed

    Chen, Wenyong; Chen, Ming; Hartwig, John F

    2014-11-12

    We report asymmetric allylic alkylation of barium enolates of cyclic ketones catalyzed by a metallacyclic iridium complex containing a phosphoramidite ligand derived from (R)-1-(2-naphthyl)ethylamine. The reaction products contain adjacent quaternary and tertiary stereocenters. This process demonstrates that unstabilized cyclic ketone enolates can undergo diastereo- and enantioselective Ir-catalyzed allylic substitution reactions with the proper choice of enolate countercation. The products of these reactions can be conveniently transformed to various useful polycarbocyclic structures.

  8. Highly regio- and enantioselective synthesis of N-substituted 2-pyridones: iridium-catalyzed intermolecular asymmetric allylic amination.

    PubMed

    Zhang, Xiao; Yang, Ze-Peng; Huang, Lin; You, Shu-Li

    2015-02-01

    The first iridium-catalyzed intermolecular asymmetric allylic amination reaction with 2-hydroxypyridines has been developed, thus providing a highly efficient synthesis of enantioenriched N-substituted 2-pyridone derivatives from readily available starting materials. This protocol features a good tolerance of functional groups in both the allylic carbonates and 2-hydroxypyridines, thereby delivering multifunctionalized heterocyclic products with up to 98% yield and 99% ee. PMID:25504907

  9. Iridium-catalysed dehydrocoupling of aryl phosphine-borane adducts: synthesis and characterisation of high molecular weight poly(phosphinoboranes).

    PubMed

    Paul, Ursula S D; Braunschweig, Holger; Radius, Udo

    2016-06-30

    The thermal dehydrogenative coupling of aryl phosphine-borane adducts with iridium complexes bearing a bis(phosphinite) pincer ligand is reported. This catalysis produces high molecular weight poly(phosphinoboranes) [ArPH-BH2]n (Ar = Ph, (p)Tol, Mes). Furthermore, we investigated the reactivity of these pincer complexes towards primary phosphines and their respective borane adducts on a stoichiometric scale. PMID:27320239

  10. Rapid selective electrocatalytic reduction of carbon dioxide to formate by an iridium pincer catalyst immobilized on carbon nanotube electrodes.

    PubMed

    Kang, Peng; Zhang, Sheng; Meyer, Thomas J; Brookhart, Maurice

    2014-08-11

    An iridium pincer dihydride catalyst was immobilized on carbon nanotube-coated gas diffusion electrodes (GDEs) by using a non-covalent binding strategy. The as-prepared GDEs are efficient, selective, durable, gas permeable electrodes for electrocatalytic reduction of CO2 to formate. High turnover numbers (ca. 54,000) and turnover frequencies (ca. 15 s(-1)) were enabled by the novel electrode architecture in aqueous solutions saturated in CO2 with added HCO3(-).

  11. Spectroscopic characterization of alumina-supported bis(allyl)iridium complexes : site-isolation, reactivity, and decomposition studies.

    SciTech Connect

    Trovitch, R. J.; Guo, N.; Janicke, M. T.; Li, H.; Marshall, C. L.; Miller, J. T.; Sattelberger, A. P.; John, K. D.; Baker, R. T.; LANL; Univ. of Ottawa

    2010-01-01

    The covalent attachment of tris(allyl)iridium to partially dehydroxylated ?-alumina is found to proceed via surface hydroxyl group protonation of one allyl ligand to form an immobilized bis(allyl)iridium moiety, (?AlO)Ir(allyl)2, as characterized by CP-MAS 13C NMR, inductively coupled plasma-mass spectrometry, and Ir L3 edge X-ray absorption spectroscopy. Extended X-ray absorption fine-structure (EXAFS) measurements taken on unsupported Ir(allyl)3 and several associated tertiary phosphine addition complexes suggest that the ?3-allyl ligands generally account for an Ir-C coordination number of 2 rather than 3, with an average Ir-C distance of 2.16 A. Using this knowledge, combined EXAFS and X-ray absorption near-edge structure studies reveal that a small amount of Ir0 is also formed upon reaction of Ir(allyl)3 with the surface. It was found that the addition of either 2,6-dimethylphenyl isocyanide or carbon monoxide to the supported complex allows spectroscopic identification of the supported bis(allyl)iridium complexes, (?AlO)Ir(allyl)2(CNAr) [Ar = 2,6-(CH3)2C6H4] and (?AlO)Ir(allyl)2(CO)2, respectively. Although samples of the supported bis(allyl)iridium complex are active for the dehydrogenation of cyclohexane to benzene at temperatures between 180 and 220C, in situ temperature-programmed reaction XAFS and continuous-flow reactor studies suggest that Ir0 nanoparticles, rather than a well-defined Ir3+ complex, are responsible for the observed activity.

  12. Secondary interactions or ligand scrambling? Subtle steric effects govern the iridium(I) coordination chemistry of phosphoramidite ligands.

    PubMed

    Osswald, Tina; Rüegger, Heinz; Mezzetti, Antonio

    2010-01-25

    The like and unlike isomers of phosphoramidite (P*) ligands are found to react differently with iridium(I), which is a key to explaining the apparently inconsistent results obtained by us and other research groups in a variety of catalytic reactions. Thus, the unlike diastereoisomer (aR,S,S)-[IrCl(cod)(1 a)] (2 a; cod=1,5-cyclooctadiene, 1 a=(aR,S,S)-(1,1'-binaphthalene)-2,2'-diyl bis(1-phenylethyl)phosphoramidite) forms, upon chloride abstraction, the monosubstituted complex (aR,S,S)-[Ir(cod)(1,2-eta-1 a,kappaP)](+) (3 a), which contains a chelating P* ligand that features an eta(2) interaction between a dangling phenyl group and iridium. Under analogous conditions, the like analogue (aR,R,R)-1 a' gives the disubstituted species (aR,R,R)-[Ir(cod)(1 a',kappaP)(2)](+) (4 a') with monodentate P* ligands. The structure of 3 a was assessed by a combination of X-ray and NMR spectroscopic studies, which indicate that it is the configuration of the binaphthol moiety (and not that of the dangling benzyl N groups) that determines the configuration of the complex. The effect of the relative configuration of the P* ligand on its iridium(I) coordination chemistry is discussed in the context of our preliminary catalytic results and of apparently random results obtained by other groups in the iridium(I)-catalyzed asymmetric allylic alkylation of allylic acetates and in rhodium(I)-catalyzed asymmetric cycloaddition reactions. Further studies with the unlike ligand (aS,R,R)-(1,1'-binaphthalene)-2,2'-diyl bis{[1-(1-naphthalene-1-yl)ethyl]phosphoramidite} (1 b) showed a yet different coordination mode, that is, the eta(4)-arene-metal interaction in (aS,R,R)-[Ir(cod)(1,2,3,4-eta-1 b,kappaP)](+) (3 b).

  13. Spectroscopic characterization of alumina-supported bis(allyl)iridium complexes: site-isolation, reactivity, and decomposition studies.

    PubMed

    Trovitch, Ryan J; Guo, Neng; Janicke, Michael T; Li, Hongbo; Marshall, Christopher L; Miller, Jeffrey T; Sattelberger, Alfred P; John, Kevin D; Baker, R Thomas

    2010-03-01

    The covalent attachment of tris(allyl)iridium to partially dehydroxylated gamma-alumina is found to proceed via surface hydroxyl group protonation of one allyl ligand to form an immobilized bis(allyl)iridium moiety, (=AlO)Ir(allyl)(2), as characterized by CP-MAS (13)C NMR, inductively coupled plasma-mass spectrometry, and Ir L(3) edge X-ray absorption spectroscopy. Extended X-ray absorption fine-structure (EXAFS) measurements taken on unsupported Ir(allyl)(3) and several associated tertiary phosphine addition complexes suggest that the eta(3)-allyl ligands generally account for an Ir-C coordination number of 2 rather than 3, with an average Ir-C distance of 2.16 A. Using this knowledge, combined EXAFS and X-ray absorption near-edge structure studies reveal that a small amount of Ir(0) is also formed upon reaction of Ir(allyl)(3) with the surface. It was found that the addition of either 2,6-dimethylphenyl isocyanide or carbon monoxide to the supported complex allows spectroscopic identification of the supported bis(allyl)iridium complexes, (=AlO)Ir(allyl)(2)(CNAr) [Ar = 2,6-(CH(3))(2)C(6)H(4)] and (=AlO)Ir(allyl)(2)(CO)(2), respectively. Although samples of the supported bis(allyl)iridium complex are active for the dehydrogenation of cyclohexane to benzene at temperatures between 180 and 220 degrees C, in situ temperature-programmed reaction XAFS and continuous-flow reactor studies suggest that Ir(0) nanoparticles, rather than a well-defined Ir(3+) complex, are responsible for the observed activity. PMID:20112918

  14. Iridium-Catalyzed Allylic Amination Route to α-Aminoboronates: Illustration of the Decisive Role of Boron Substituents

    PubMed Central

    Touchet, Sabrina; Molander, Gary A.; Carboni, Bertrand; Bouillon, Alexandre

    2012-01-01

    The development of a new route to α-aminoboronates using an iridium-catalyzed allylic amination on boronated substrates is described. Unlike the boronate group, the trifluoroborato substituent was found to govern the regioselectivity exclusively in favor of branched products. The transformation of an allylic substitution product into an α-aminoboronic ester in an efficient way validated the implementation of this approach. PMID:22350584

  15. Using iridium films to compensate for piezo-electric materials processing stresses in adjustable x-ray optics

    NASA Astrophysics Data System (ADS)

    Ames, A.; Bruni, R.; Cotroneo, V.; Johnson-Wilke, R.; Kester, T.; Reid, P.; Romaine, S.; Tolier-McKinstry, S.; Wilke, R. H. T.

    2015-09-01

    Adjustable X-ray optics represent a potential enabling technology for simultaneously achieving large effective area and high angular resolution for future X-ray Astronomy missions. The adjustable optics employ a bimorph mirror composed of a thin (1.5 μm) film of piezoelectric material deposited on the back of a 0.4 mm thick conical mirror segment. The application of localized electric fields in the piezoelectric material, normal to the mirror surface, result in localized deformations in mirror shape. Thus, mirror fabrication and mounting induced figure errors can be corrected, without the need for a massive reaction structure. With this approach, though, film stresses in the piezoelectric layer, resulting from deposition, crystallization, and differences in coefficient of thermal expansion, can distort the mirror. The large relative thickness of the piezoelectric material compared to the glass means that even 100MPa stresses can result in significant distortions. We have examined compensating for the piezoelectric processing related distortions by the deposition of controlled stress chromium/iridium films on the front surface of the mirror. We describe our experiments with tuning the product of the chromium/iridium film stress and film thickness to balance that resulting from the piezoelectric layer. We also evaluated the repeatability of this deposition process, and the robustness of the iridium coating.

  16. Method of making a cathode from tungsten and iridium powders using a strontium peroxide containing material as the impregnant

    SciTech Connect

    Branovich, L.E.; Freeman, G.L.; Smith, B.

    1988-11-25

    This invention relates in general to a method of making a long-life high-current-density cathode and in particular, to a method of making such a cathode from a mixture of tungsten and iridium powders using a strontium peroxide containing material as the impregnant. The general object of this invention is to provide an improved method of making a long life high current density cathode. A more specific object of the invention is to provide such a method in which lower temperatures can be used than were used in S.N. 204,327 for the impregnation of the tungsten-iridium billet. It has now been found that the aforementioned objects can be attained by a method that uses a strontium peroxide-containing material as the impregnant. More particularly, according to the invention, a suitable porous billet of tungsten, or tungsten-iridium, or tungsten-osmium or tungsten-rhodium is impregnated with a strontium peroxide containing material in a hydrogen atmosphere and slowly heated to above 215 C to decompose the strontium peroxide, SrO/sub 2/ to form strontium oxide, SrO, and oxygen, O/sub 2/.

  17. Structural characterization and comparison of iridium, platinum and gold/palladium ultra-thin film coatings for STM of biomolecules

    SciTech Connect

    Sebring, R.; Arendt, P.; Imai, B.; Bradbury, E.M.; Gatewood, J.; Panitz, J.; Yau, P.

    1997-10-30

    Scanning tunneling microscopy (STM) is capable of atomic resolution and is ideally suited for imaging surfaces with uniform work function. A biological sample on a conducting substrate in air does not meet this criteria and requires a conductive coating for stable and reproducible STM imaging. In this paper, the authors describe the STM and transmission electron microscopy (TEM) characterization of ultra-thin ion-beam sputtered films of iridium and cathode sputtered gold/palladium and platinum films on highly ordered pyrolytic graphite (HOPG) which were developed for use as biomolecule coatings. The goals were the development of metal coatings sufficiently thin and fine grained that 15--20 {angstrom} features of biological molecules could be resolved using STM, and the development of a substrate/coating system which would allow complementary TEM information to be obtained for films and biological molecules. The authors demonstrate in this paper that ion-beam sputtered iridium on highly ordered pyrolytic graphite (HOPG) has met both these goals. The ion-beam sputtered iridium produced a very fine grained (< 10 {angstrom}) continuous film at 5--6 {angstrom} thickness suitable for stable air STM imaging. In comparison, cathode sputtered platinum produced 16 {angstrom} grains with the thinnest continuous film at 15 {angstrom} thickness, and the sputtered gold/palladium produced 25 {angstrom} grains with the thinnest continuous film at 18 {angstrom} thickness.

  18. Method for separating isotopes

    DOEpatents

    Jepson, B.E.

    1975-10-21

    Isotopes are separated by contacting a feed solution containing the isotopes with a cyclic polyether wherein a complex of one isotope is formed with the cyclic polyether, the cyclic polyether complex is extracted from the feed solution, and the isotope is thereafter separated from the cyclic polyether.

  19. Stable isotope studies

    SciTech Connect

    Ishida, T.

    1992-01-01

    The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs.

  20. Isotope separation by photochromatography

    DOEpatents

    Suslick, K.S.

    1975-10-03

    A photochromatographic method for isotope separation is described. An isotopically mixed molecular species is adsorbed on an adsorptive surface, and the adsorbed molecules are irradiated with radiation of a predetermined wavelength which will selectively excite desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thus separate them from the undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes. (BLM)

  1. Isotope separation by photochromatography

    DOEpatents

    Suslick, Kenneth S.

    1977-01-01

    An isotope separation method which comprises physically adsorbing an isotopically mixed molecular species on an adsorptive surface and irradiating the adsorbed molecules with radiation of a predetermined wavelength which will selectively excite a desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thereby separate them from the unexcited undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes.

  2. Relationship between an iridium anomaly and the North American microtektite layer in core RC9--58 from the Caribbean Sea

    SciTech Connect

    Glass, B.P.; DuBois, D.L.; Ganapathy, R.

    1982-11-15

    In a previous publication, an iridium anomaly was reported in core RC9--58 from the Caribbean Sea, about 30 cm below the peak abundance of North American microtektites. In order to determine more precisely the relationship between the iridium anomaly and the North American microtektite layer, we searched for microtektites in the samples that were used for the iridium studies. We found that the North American microtektite layer is actually two layers, with the peak abundances separated by 25 cm. The upper layer consists of 'normal' North American microtektites and the lower layer consists of previously described clinopyroxene-bearing spherules. The iridium anomaly was found to correlate with the lower layer. Although the two layers appear to be the result of two separate events, several lines of evidence suggest that they were produced by a single event. The separation into two layers may have been produced by differential settling in the sediment due to density variations. The correlation between the iridium anomaly and the North American microtektite layer supports the terrestrial impact origin for tektites.

  3. Mechanistic Insights into the Formation of Dodecanethiolate-Stabilized Magnetic Iridium Nanoparticles: Thiosulfate vs Thiol Ligands

    PubMed Central

    2015-01-01

    The synthesis of stable and isolable iridium nanoparticles with an average core size of ∼1.2 ± 0.3 nm was achieved by employing sodium S-dodecylthiosulfate as a ligand precursor during the modified Brust–Schiffrin reaction. Transmission electron microscopy (TEM) of the isolated Ir nanoparticles revealed a high degree of monodispersity. Further characterizations with 1H NMR, FT-IR, UV–vis spectroscopy, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) confirmed that the synthesized Ir nanoparticles are stabilized by dodecanethiolate ligands produced upon the adsorption/cleavage of S-dodecylthiosulfate on the growing Ir nanoparticle surface. By comparison, synthetic attempts employing dodecanethiol as a stabilizing ligand led to the formation of Ir-thiolate species (Ir(SR)3) as an intermediate and Ir-hydroxide species at the completion of reaction. Mechanistic investigations of these two reactions using S-dodecylthiosulfate and dodecanethiol provided deeper understandings on the novelty of thiosulfate ligands, which allow the successful formation of stable thiolate-capped Ir nanoparticles. Moreover, these Ir nanoparticles were shown to have strong magnetic properties. PMID:25018790

  4. A vapor-pressure study of the systems formed by polonium with palladium and iridium

    SciTech Connect

    Abakumou, A.S.; Khokhlou, A.D.; Malysheu, M.L.; Reznikova, N.F.

    1985-11-01

    Direct thermal vacuum synthesis shows that polonium vapor does not react with iridium when they are heated together to 1000/sup 0/C. Polonium vapor begins to be absorbed appreciably by palladium at 340-350/sup 0/C. The radiotensimetric method has been used in examining the thermal stabilities of polonium-palladium comounds, which has shown that there are three intermetallides PdPo, Pd/sub 2/Po, and Pd/sub 3/Po, which dissociate to release elemental polonium. The dissociation temperature increases as the polonium content of the compound decreases and is in the range 390-700/sup 0/C. The temperature dependence of the polonium vapor pressure in the dissociation is described by the following: PdPo log P /SUB Pa/ = (7.31 + or - 0.08) -- (4520 + or -40)/T, and at 460580/sup 0/C, ..delta..H = 86.3 + or - 0.7 kJ/mol; Pd/sub 2/Po log P /SUB Pa/ = (7.42 + or - 0.01) -- (6080 + or 10)/T at 725900/sup 0/C, ..delta..H = 116 + or - 0.2 kJ/mol; Pd/sub 3/Po log P /SUB Pa/ = (9.18 + or - 0.01) -- (8620 + or 1000/sup 0/C, ..delta..H = 164 + or - 1 kJ/mol. The properties of these compounds are compared with those of the corresponding tellurides and of the polonium-nickel and poloniumplatinum systems.

  5. Plastic Straining of Iridium Alloy DOP-26 During Cup Sizing Operations

    SciTech Connect

    Ohriner, Evan Keith; Ulrich, George B; Sabau, Adrian S

    2007-09-01

    DOP-26 iridium alloy cups are used for fuel cladding for radioisotope power systems. The cups are deep drawn and recrystallized prior to final fabrication operations. This study characterizes the plastic deformation of cups during a sizing operation following the recrystallization heat treatment. The purpose of the sizing operation is to achieve the specified roundness, diameter, and radius dimensions of the cup. The operation introduces various levels of plastic strain in the cup. Plastic strain can be a cause of inhomogeneous or abnormal grain growth during subsequent exposure to elevated temperature during the service life of the fueled clad. This is particularly true in the case of cups which have irregularities in the cup walls from the deep drawing operations. Diameter and roundness measurements were made on two cups both before and after sizing. Plastic strain levels were calculated using the ABAQUSTM finite element software. The calculated plastic strain levels in both cups were below 0.025, a value shown to be below the critical strain for abnormal grain growth during a simulated service exposure. The calculated maximum plastic strain was found to increase with increased applied sizing load and was not sensitive to the input value for the clearance between the cup and the sizing die. The calculated geometry of the sized cups was in good agreement with the measurements on the finished cups.

  6. UV/ozone cleaning of platinum/iridium kilogram mass prototypes

    NASA Astrophysics Data System (ADS)

    Berry, James; Downes, Stephen; Davidson, Stuart

    2010-08-01

    Platinum-iridium (Pt/Ir) kilogram mass prototypes are known to gain contamination from the environment in which they are stored. The current method of cleaning these mass prototypes is called nettoyage-lavage and involves the physical rubbing of a kilogram with a chamois leather cloth soaked in a solvent followed by removal of any solvent residue using a jet of steam water. The manual nature of the technique means the effectiveness of the cleaning process is reliant on the human operative. An alternative cleaning method involving exposure to ultraviolet light and ozone (UV/O3) has been tested on Pt/Ir foils and kilogram mass prototypes. The changes to the surface of the Pt/Ir foils as a result of this process have been quantified using x-ray photoelectron spectroscopy and have shown a clear reduction in the quantity of carbonaceous contamination. Variation of the UV intensity, ozone concentration and exposure duration enabled the optimum cleaning conditions to be established. The UV/O3 cleaning method was then used to clean two Pt/Ir kilogram mass prototypes and gravimetric weighing of the kilograms before and after cleaning gave the amount of contamination removed. These gravimetric weighing results demonstrated that UV/O3 cleaning was as effective as the nettoyage-lavage process.

  7. En route to phosphonato iridium(i) complexes: the decisive effect of an intramolecular hydrogen bond.

    PubMed

    Passarelli, Vincenzo; Pérez-Torrente, Jesús J; Oro, Luis A

    2016-01-21

    Pentacoordinated iridium(i) complexes of formula IrCl(SiNP)(tfbb) (1) and IrCl(HNP)2(tfbb) (2) (SiNP = SiMe2{N(4-C6H4CH3)PPh2}2; HNP = NH(4-C6H4CH3)PPh2) have been prepared and fully characterised. Both feature a distorted square pyramidal coordination polyhedron at the metal centre in the solid state and are fluxional in solution. Their reaction with trimethyl phosphite yields the derivatives [Ir(SiNP){P(OMe)3}(tfbb)]Cl ([3]Cl) and Ir{PO(OMe)2}(HNP)2(tfbb) (4). The course of the reaction between IrCl(HNP)2(tfbb) (2) and trimethyl phosphite was elucidated by NMR spectroscopy and DFT calculations, showing that the intermediate [Ir(HNP)2{P(OMe)3}(tfbb)](+) ((5+)) forms and further reacts with the chloride anion yielding the phosphonato derivative 4 and methyl chloride. The decisive role of the N-H group in the formation of the phosphonato ligand has been established by IR and NMR spectroscopic measurements and by DFT calculations.

  8. Elastic, magnetic and electronic properties of iridium phosphide Ir2P.

    PubMed

    Wang, Pei; Wang, Yonggang; Wang, Liping; Zhang, Xinyu; Yu, Xiaohui; Zhu, Jinlong; Wang, Shanmin; Qin, Jiaqian; Leinenweber, Kurt; Chen, Haihua; He, Duanwei; Zhao, Yusheng

    2016-01-01

    Cubic (space group: Fmm) iridium phosphide, Ir2P, has been synthesized at high pressure and high temperature. Angle-dispersive synchrotron X-ray diffraction measurements on Ir2P powder using a diamond-anvil cell at room temperature and high pressures (up to 40.6 GPa) yielded a bulk modulus of B0 = 306(6) GPa and its pressure derivative B0' = 6.4(5). Such a high bulk modulus attributed to the short and strongly covalent Ir-P bonds as revealed by first - principles calculations and three-dimensionally distributed [IrP4] tetrahedron network. Indentation testing on a well-sintered polycrystalline sample yielded the hardness of 11.8(4) GPa. Relatively low shear modulus of ~64 GPa from theoretical calculations suggests a complicated overall bonding in Ir2P with metallic, ionic, and covalent characteristics. In addition, a spin glass behavior is indicated by magnetic susceptibility measurements. PMID:26905444

  9. Radiation control in the intensive care unit for high intensity iridium-192 brain implants

    SciTech Connect

    Sewchand, W.; Drzymala, R.E.; Amin, P.P.; Salcman, M.; Salazar, O.M.

    1987-04-01

    A bedside lead cubicle was designed to minimize the radiation exposure of intensive care unit staff during routine interstitial brain irradiation by removable, high intensity iridium-192. The cubicle shields the patient without restricting intensive care routines. The design specifications were confirmed by exposure measurements around the shield with an implanted anthropomorphic phantom simulating the patient situation. The cubicle reduces the exposure rate around an implant patient by as much as 90%, with the exposure level not exceeding 0.1 mR/hour/mg of radium-equivalent /sup 192/Ir. Evaluation of data accumulated for the past 3 years has shown that the exposure levels of individual attending nurses are 0.12 to 0.36 mR/mg of radium-equivalent /sup 192/Ir per 12-hour shift. The corresponding range for entire nursing teams varies between 0.18 and 0.26. A radiation control index (exposure per mg of radium-equivalent /sup 192/Ir per nurse-hour) is thus defined for individual nurses and nursing teams; this index is a significant guide to the planning of nurse rotations for brain implant patients with various /sup 192/Ir loads. The bedside shield reduces exposure from /sup 192/Ir implants by a factor of about 20, as expected, and the exposure from the lower energy radioisotope iodine-125 is barely detectable.

  10. Radiation control in the intensive care unit for high intensity iridium-192 brain implants.

    PubMed

    Sewchand, W; Drzymala, R E; Amin, P P; Salcman, M; Salazar, O M

    1987-04-01

    A bedside lead cubicle was designed to minimize the radiation exposure of intensive care unit staff during routine interstitial brain irradiation by removable, high intensity iridium-192. The cubicle shields the patient without restricting intensive care routines. The design specifications were confirmed by exposure measurements around the shield with an implanted anthropomorphic phantom simulating the patient situation. The cubicle reduces the exposure rate around an implant patient by as much as 90%, with the exposure level not exceeding 0.1 mR/hour/mg of radium-equivalent 192Ir. Evaluation of data accumulated for the past 3 years has shown that the exposure levels of individual attending nurses are 0.12 to 0.36 mR/mg of radium-equivalent 192Ir per 12-hour shift. The corresponding range for entire nursing teams varies between 0.18 and 0.26. A radiation control index (exposure per mg of radium-equivalent 192Ir per nurse-hour) is thus defined for individual nurses and nursing teams; this index is a significant guide to the planning of nurse rotations for brain implant patients with various 192Ir loads. The bedside shield reduces exposure from 192Ir implants by a factor of about 20, as expected, and the exposure from the lower energy radioisotope iodine-125 is barely detectable.

  11. Elastic, magnetic and electronic properties of iridium phosphide Ir2P

    DOE PAGES

    Wang, Pei; Wang, Yonggang; Wang, Liping; Zhang, Xinyu; Yu, Xiaohui; Zhu, Jinlong; Wang, Shanmin; Qin, Jiaqian; Leinenweber, Kurt; Chen, Haihua; et al

    2016-02-24

    Cubic (space group: Fm3¯m) iridium phosphide, Ir2P, has been synthesized at high pressure and high temperature. Angle-dispersive synchrotron X-ray diffraction measurements on Ir2P powder using a diamond-anvil cell at room temperature and high pressures (up to 40.6 GPa) yielded a bulk modulus of B0 = 306(6) GPa and its pressure derivative B0'= 6.4(5). Such a high bulk modulus attributed to the short and strongly covalent Ir-P bonds as revealed by first – principles calculations and three-dimensionally distributed [IrP4] tetrahedron network. Indentation testing on a well–sintered polycrystalline sample yielded the hardness of 11.8(4) GPa. Relatively low shear modulus of ~64 GPamore » from theoretical calculations suggests a complicated overall bonding in Ir2P with metallic, ionic, and covalent characteristics. Additionally, a spin glass behavior is indicated by magnetic susceptibility measurements.« less

  12. Long life testing of oxide-coated iridium/rhenium rockets

    NASA Astrophysics Data System (ADS)

    Reed, Brian D.

    1995-09-01

    22-N class rockets, composed of a rhenium (Re) substrate, an iridium (Ir) coating, and an additional composite coating consisting of Ir and a ceramic oxide, were tested on gaseous oxygen/gaseous hydrogen (GO2/GH2) propellants. Two rockets were tested, one for nearly 39 hours at a nominal mixture ratio (MR) of 4.6 and chamber pressure (Pc) of 469 kPa, and the other for over 13 hours at a nominal MR of 5.8 and 621 kPa Pc. Four additional Ir/Re rockets, with a composite Ir-oxide coating fabricated using a modified process, were also tested, including one for 1.3 hours at a nominal MR of 16.7 and Pc of 503 kPa. The long lifetimes demonstrated on low MR GO2/GH2 suggest greatly extended chamber lifetimes (tens of hours) in the relatively low oxidizing combustion environments of Earth storable propellants. The oxide coatings could also serve as a protective coating in the near injector region, where a still-mixing flowfield may cause degradation of the Ir layer. Operation at MR close to 17 suggests that oxide-coated Ir/Re rockets could be used in severely oxidizing combustion environments, such as high MR GO2/GH2, oxygen/hydrocarbon, and liquid gun propellants.

  13. Synthesis, Structure, and Conformational Dynamics of Rhodium and Iridium Complexes of Dimethylbis(2-pyridyl)borate†

    PubMed Central

    Pennington-Boggio, Megan K.; Conley, Brian L.; Richmond, Michael G.; Williams, Travis J.

    2014-01-01

    Rhodium(I) and Iridium(I) borate complexes of the structure [Me2B(2-py)2]ML2 (L2 = (tBuNC)2, (CO)2, (C2H4)2, cod, dppe) were prepared and structurally characterized (cod = 1,5-cyclooctadiene; dppe = 1,2-diphenylphosphinoethane). Each contains a boat-configured chelate ring that participates in a boat-to-boat ring flip. Computational evidence shows that the ring flip proceeds through a transition state that is near planarity about the chelate ring. We observe an empirical, quantitative correlation between the barrier of this ring flip and the π acceptor ability of the ancillary ligand groups on the metal. The ring flip barrier correlates weakly to the Tolman and Lever ligand parameterization schemes, apparently because these combine both σ and π effects while we propose that the ring flip barrier is dominated by π bonding. This observation is consistent with metal-ligand π interactions becoming temporarily available only in the near-planar transition state of the chelate ring flip and not the boat-configured ground state. Thus, this is a first-of-class observation of metal-ligand π bonding governing conformational dynamics. PMID:25435645

  14. Insights into the oxidative dehydrogenation of amines with nanoparticulate iridium oxide.

    PubMed

    Hammond, Ceri; Schümperli, Martin T; Hermans, Ive

    2013-09-23

    The aerobic oxidation of amines offers a promising route towards many versatile chemical compounds. Within this contribution, we extend our previous investigations of iridium oxide-catalyzed alcohol oxidation to amine substrates. In addition to demonstrating the versatility of this catalyst, particular attention is focused on the mechanisms of the reaction. Herein, we demonstrate that although amines are oxidized slower than the corresponding alcohols, the catalyst has a preference for amine substrates, and oxidizes various amines at turnover frequencies greater than other systems found in the open literature. Furthermore, the competition between double amine dehydrogenation, to yield the corresponding nitrile, and amine-imine coupling, to yield the corresponding coupled imine, has been found to arise from a competitive reaction pathway, and stems from an effect of substrate-to-metal ratio. Finally, the mechanism responsible for the formation of N-benzylidene-1-phenylmethanamine was examined, and attributed to the coupling of free benzyl amine substrate and benzaldehyde, formed in situ through hydrolysis of the primary reaction product, benzyl imine. PMID:23939827

  15. Global iridium anomaly, mass extinction, and redox change at the Devonian-Carboniferous boundary

    SciTech Connect

    Wang, K. Univ. of Calgary, Alberta ); Attrep, M. Jr.; Orth, C.J. )

    1993-12-01

    Iridium abundance anomalies have been found on a global scale in the Devonian-Carboniferous (D-C) boundary interval, which records one of the largest Phanerozoic mass-extinction events, an event that devastated many groups of living organisms, such as plants, ammonoids, trilobites, conodonts, fish, foraminiferans, brachiopods, and ostracodes. At or very close to the D-C boundary, there exists a geographically widespread black-shale interval, and Ir abundances reach anomalous maxima of 0.148 ppb (Montagne Noire, France), 0.138 ppb (Alberta, Canada) 0.140 ppb (Carnic Alps, Austria), 0.156 ppb (Guangxi, China), 0.258 ppb (Guizhou, China), and 0.250 ppb (Oklahoma). The discovery of global D-C Ir anomalies argues for an impact-extinction model. However, nonchondritic ratios of Ir to other important elements and a lack of physical evidence (shocked quartz, microtektites) do not support such a scenario. The fact that all Ir abundance maxima are at sharp redox boundaries in these sections leads us to conclude that the Ir anomalies likely resulted from a sudden change in paleo-redox conditions during deposition and/or early diagenesis. 36 refs., 2 figs., 1 tab.

  16. CO2 hydrogenation catalyzed by iridium complexes with a proton-responsive ligand

    DOE PAGES

    Onishi, Naoya; Xu, Shaoan; Manaka, Yuichi; Suna, Yuki; Wang, Wan -Hui; Muckerman, James T.; Fujita, Etsuko; Himeda, Yuichiro

    2015-02-18

    In this study, the catalytic cycle for the production of formic acid by CO₂ hydrogenation and the reverse reaction has received renewed attention because they are viewed as offering a viable scheme for hydrogen storage and release. In this Forum Article, CO₂ hydrogenation catalyzed by iridium complexes bearing N^N-bidentate ligands is reported. We describe how a ligand containing hydroxyl groups as proton-responsive substituents enhances catalytic performance by an electronic effect of the oxyanions and a pendent-base effect through secondary coordination sphere interaction. In particular, [(Cp*IrCl)₂(TH2BPM)]Cl₂ (Cp* = pentamethyl cyclopentadienyl, TH2BPM = 4,4',6,6'-tetrahydroxy-2,2'-bipyrimidine) promotes enormously the catalytic hydrogenation of CO₂ bymore » these synergistic effects under atmospheric pressure and at room temperature. Additionally, newly designed complexes with azole-type ligands are applied to CO₂ hydrogenation. The catalytic efficiencies of the azole-type complexes are much higher than that of the unsubstituted bipyridine complex [Cp*Ir(bpy)(OH₂)]SO₄. Furthermore, the introduction of one or more hydroxyl groups into ligands such as 2-pyrazolyl-6-hydroxypyridine, 2-pyrazolyl-4,6-dihydroxyl pyrimidine, and 4-pyrazolyl-2,6-dihydroxyl pyrimidine enhanced catalytic activity. It is clear that the incorporation of electron-donating hydroxyl groups into proton-responsive ligands is effective for promoting the hydrogenation of CO₂.« less

  17. An iridium-rich iron micrometeorite with silicate inclusions from the Moon

    NASA Technical Reports Server (NTRS)

    Jolliff, Bradley L.; Korotev, Randy L.; Haskin, Larry A.

    1993-01-01

    We have found a 0.1 mg iron micrometeorite containing meteoritic silicate inclusions in an agglutinate from 2-2.5 cm deep in regolith core 60014. The metal is 93 percent iron, 6.5 percent nickel, 0.5 percent cobalt, approximately 150 ppm iridium, and less than 2 ppm gold. Although the Ir concentration is higher than that reported previously for any iron meteorite group, it lies on the extrapolation to low Ni and high Ir concentrations of several meteorite groups on Ni,Ir plots (groups 2C,D,E, and 3AB,E,F). Tiny, subrounded silicate inclusions comprise low-Ca pyroxene (En83), olivine (FO80), and albitic and potassic feldspars, as mixtures of minerals or glasses. Minor phases include oldhamite (CaS) and, tentatively, hercynite (FeAl2O4). The inclusions have pyroxene FeO/MnO of approximately 25 and olivine FeO/MnO of 40-60. In comparison with known iron meteorites, the inclusions are most similar to those in type 2E, e.g., Weekeroo Station, Colomera, and Kodaikanal. As far as we know, this is the first observation of an iron meteorite with silicate inclusions from a lunar sample. No metal fragments with meteoritic, nonmetallic inclusions were reported in several previous, exhaustive studies of soil particles.

  18. The Decomposition of Hydrazine in the Gas Phase and over an Iridium Catalyst

    SciTech Connect

    Schmidt, Michael W.; Gordon, Mark S.

    2013-09-30

    Hydrazine is an important rocket fuel, used as both a monopropellant and a bipropellant. This paper presents theoretical results to complement the extensive experimental studies of the gas phase and Ir catalyzed decompositions involved in the monopropellant applications of hydrazine. Gas phase electronic structure theory calculations that include electron correlation predict that numerous molecular and free radical reactions occur within the same energy range as the basic free radical pathways: NN bond breaking around 65 kcal/mol and NH bond breaking around 81 kcal/mol. The data suggest that a revision to existing kinetics modeling is desirable, based on the energetics and the new elementary steps reported herein. A supported Ir-6 octahedron model for the Shell 405 Iridium catalyst used in thrusters was developed. Self-Consistent Field and electron correlation calculations (with core potentials and associated basis sets) find a rich chemistry for hydrazine on this catalyst model. The model catalyst provides dramatically lower NN and NH bond cleavage energies and an even smaller barrier to breaking the NH bond by NH2 abstractions. Thus, the low temperature decomposition over the catalyst is interpreted in terms of consecutive NH2 abstractions to produce ammonia and nitrogen. The higher temperature channel, which has hydrogen and nitrogen products, may be due to a mixture of two mechanisms. These two mechanisms are successive NH cleavages with surface H + H recombinations, and the same type of assisted H-2 eliminations found to occur in the gas phase part of this study.

  19. CO2 hydrogenation catalyzed by iridium complexes with a proton-responsive ligand

    SciTech Connect

    Onishi, Naoya; Xu, Shaoan; Manaka, Yuichi; Suna, Yuki; Wang, Wan -Hui; Muckerman, James T.; Fujita, Etsuko; Himeda, Yuichiro

    2015-02-18

    In this study, the catalytic cycle for the production of formic acid by CO₂ hydrogenation and the reverse reaction has received renewed attention because they are viewed as offering a viable scheme for hydrogen storage and release. In this Forum Article, CO₂ hydrogenation catalyzed by iridium complexes bearing N^N-bidentate ligands is reported. We describe how a ligand containing hydroxyl groups as proton-responsive substituents enhances catalytic performance by an electronic effect of the oxyanions and a pendent-base effect through secondary coordination sphere interaction. In particular, [(Cp*IrCl)₂(TH2BPM)]Cl₂ (Cp* = pentamethyl cyclopentadienyl, TH2BPM = 4,4',6,6'-tetrahydroxy-2,2'-bipyrimidine) promotes enormously the catalytic hydrogenation of CO₂ by these synergistic effects under atmospheric pressure and at room temperature. Additionally, newly designed complexes with azole-type ligands are applied to CO₂ hydrogenation. The catalytic efficiencies of the azole-type complexes are much higher than that of the unsubstituted bipyridine complex [Cp*Ir(bpy)(OH₂)]SO₄. Furthermore, the introduction of one or more hydroxyl groups into ligands such as 2-pyrazolyl-6-hydroxypyridine, 2-pyrazolyl-4,6-dihydroxyl pyrimidine, and 4-pyrazolyl-2,6-dihydroxyl pyrimidine enhanced catalytic activity. It is clear that the incorporation of electron-donating hydroxyl groups into proton-responsive ligands is effective for promoting the hydrogenation of CO₂.

  20. Iridium Oxide Coatings with Templated Porosity as Highly Active Oxygen Evolution Catalysts: Structure-Activity Relationships.

    PubMed

    Bernicke, Michael; Ortel, Erik; Reier, Tobias; Bergmann, Arno; Ferreira de Araujo, Jorge; Strasser, Peter; Kraehnert, Ralph

    2015-06-01

    Iridium oxide is the catalytic material with the highest stability in the oxygen evolution reaction (OER) performed under acidic conditions. However, its high cost and limited availability demand that IrO2 is utilized as efficiently as possible. We report the synthesis and OER performance of highly active mesoporous IrO2 catalysts with optimized surface area, intrinsic activity, and pore accessibility. Catalytic layers with controlled pore size were obtained by soft-templating with micelles formed from amphiphilic block copolymers poly(ethylene oxide)-b-poly(butadiene)-b-poly(ethylene oxide). A systematic study on the influence of the calcination temperature and film thickness on the morphology, phase composition, accessible surface area, and OER activity reveals that the catalytic performance is controlled by at least two independent factors, that is, accessible surface area and intrinsic activity per accessible site. Catalysts with lower crystallinity show higher intrinsic activity. The catalyst surface area increases linearly with film thickness. As a result of the templated mesopores, the pore surface remains fully active and accessible even for thick IrO2 films. Even the most active multilayer catalyst does not show signs of transport limitations at current densities as high as 75 mA cm(-2) . PMID:25958795

  1. Local structure of Iridium organometallic catalysts covalently bonded to carbon nanotubes.

    NASA Astrophysics Data System (ADS)

    Blasco, J.; Cuartero, V.; Subías, G.; Jiménez, M. V.; Pérez-Torrente, J. J.; Oro, L. A.; Blanco, M.; Álvarez, P.; Blanco, C.; Menéndez, R.

    2016-05-01

    Hybrid catalysts based on Iridium N-heterocyclic carbenes anchored to carbon nanotubes (CNT) have been studied by XAFS spectroscopy. Oxidation of CNT yields a large amount of functional groups, mainly hydroxyl groups at the walls and carboxylic groups at the tips, defects and edges. Different kinds of esterification reactions were performed to functionalize oxidized CNT with imidazolium salts. Then, the resulting products were reacted with an Ir organometallic compound to form hybrid catalysts efficient in hydrogen transfer processes. XANES spectroscopy agree with the presence of Ir(I) in these catalysts and the EXAFS spectra detected differences in the local structure of Ir atoms between the initial Ir organometallic compound and the Ir complexes anchored to the CNT. Our results confirm that the halide atom, present in the Ir precursor, was replaced by oxygen from -OH groups at the CNT wall in the first coordination shell of Ir. The lability of this group accounts for the good recyclability and the good efficiency shown by these hybrid catalysts.

  2. Weldability of DOP-26 iridium alloy: Effects of welding gas and alloy composition

    NASA Astrophysics Data System (ADS)

    Ohriner, Evan K.; Goodwin, Gene M.; Frederick, D. A.

    1992-01-01

    The DOP-26 iridium alloy, containing 2000- to 4000-ppm W, 30- to 90-ppm Th, and 20- to 80-ppm Al by weight, is used as a cladding material. The closure weld on the fueled clad is performed by gas-tungsten-arc (GTA) welding, which under certain conditions results in hot cracking of the fusion zone. The effects of variations in the chemical composition of the alloy and in the welding gas atmosphere on the welding behavior are evaluated using the Sigmajig test. In this test, sheet materials are welded in an argon atmosphere with measured levels of applied stress to determine a threshold stress for hot cracking. The threshold stress for cracking of DOP-26 alloy increases by a factor of two as the thorium content is decreased from 94 to 37 ppm. There is no effect on threshold cracking stress for variations in oxygen content of the argon welding atmosphere from 10 to 2000 ppm or for variations in water vapor content from 10 to 1000 ppm.

  3. High-level ab initio computations of the absorption spectra of organic iridium complexes.

    PubMed

    Plasser, Felix; Dreuw, Andreas

    2015-02-12

    The excited states of fac-tris(phenylpyridinato)iridium [Ir(ppy)3] and the smaller model complex Ir(C3H4N)3 are computed using a number of high-level ab initio methods, including the recently implemented algebraic diagrammatic construction method to third-order ADC(3). A detailed description of the states is provided through advanced analysis methods, which allow a quantification of different charge transfer and orbital relaxation effects and give extended insight into the many-body wave functions. Compared to the ADC(3) benchmark an unexpected striking difference of ADC(2) is found for Ir(C3H4N)3, which derives from an overstabilization of charge transfer effects. Time-dependent density functional theory (TDDFT) using the B3LYP functional shows an analogous but less severe error for charge transfer states, whereas the ωB97 results are in good agreement with ADC(3). Multireference configuration interaction computations, which are in reasonable agreement with ADC(3), reveal that static correlation does not play a significant role. In the case of the larger Ir(ppy)3 complex, results at the TDDFT/B3LYP and TDDFT/ωB97 levels of theory are presented. Strong discrepancies between the two functionals, which are found with respect to the energies, characters, as well as the density of the low lying states, are discussed in detail and compared to experiment. PMID:25584785

  4. Elastic, magnetic and electronic properties of iridium phosphide Ir2P

    PubMed Central

    Wang, Pei; Wang, Yonggang; Wang, Liping; Zhang, Xinyu; Yu, Xiaohui; Zhu, Jinlong; Wang, Shanmin; Qin, Jiaqian; Leinenweber, Kurt; Chen, Haihua; He, Duanwei; Zhao, Yusheng

    2016-01-01

    Cubic (space group: Fmm) iridium phosphide, Ir2P, has been synthesized at high pressure and high temperature. Angle-dispersive synchrotron X-ray diffraction measurements on Ir2P powder using a diamond-anvil cell at room temperature and high pressures (up to 40.6 GPa) yielded a bulk modulus of B0 = 306(6) GPa and its pressure derivative B0′ = 6.4(5). Such a high bulk modulus attributed to the short and strongly covalent Ir-P bonds as revealed by first – principles calculations and three-dimensionally distributed [IrP4] tetrahedron network. Indentation testing on a well–sintered polycrystalline sample yielded the hardness of 11.8(4) GPa. Relatively low shear modulus of ~64 GPa from theoretical calculations suggests a complicated overall bonding in Ir2P with metallic, ionic, and covalent characteristics. In addition, a spin glass behavior is indicated by magnetic susceptibility measurements. PMID:26905444

  5. Osmium-191/iridium-191m radionuclide generator using an oxalato osmate parent complex

    SciTech Connect

    Packard, A.B.; Treves, S.T.; O'Brien, G.M.; Lim, K.S.

    1987-10-01

    A new osmium-191/iridium-191m (/sup 191/Os//sup 191/mIr) radionuclide generator has been developed that offers high /sup 191/mIr yield (greater than 20%/ml) and low /sup 191/Os breakthrough (less than 5 X 10(-4)%/ml) when eluted with a solution of 0.001 M oxalic acid and 0.9% (normal) saline. This is the first /sup 191/Os//sup 191/mIr generator that combines the advantages of high /sup 191/mIr yield, extremely low /sup 191/Os breakthrough, and an eluate that does not require buffering prior to injection. These improvements in performance were accomplished through use of the chelate transdioxobisoxalatoosmate(VI) as the parent complex on the generator. The clinical result of the combination of higher yield and lower breakthrough is a 100-fold decrease in the estimated patient radiation dose compared with the same study performed with technetium-99m (/sup 99m/Tc), and the injectable eluate makes the generator easier to use. Acute and subacute toxicity studies performed on this generator eluate have shown no adverse effects attributable to the eluate.

  6. Iridium Oxide Coatings with Templated Porosity as Highly Active Oxygen Evolution Catalysts: Structure-Activity Relationships.

    PubMed

    Bernicke, Michael; Ortel, Erik; Reier, Tobias; Bergmann, Arno; Ferreira de Araujo, Jorge; Strasser, Peter; Kraehnert, Ralph

    2015-06-01

    Iridium oxide is the catalytic material with the highest stability in the oxygen evolution reaction (OER) performed under acidic conditions. However, its high cost and limited availability demand that IrO2 is utilized as efficiently as possible. We report the synthesis and OER performance of highly active mesoporous IrO2 catalysts with optimized surface area, intrinsic activity, and pore accessibility. Catalytic layers with controlled pore size were obtained by soft-templating with micelles formed from amphiphilic block copolymers poly(ethylene oxide)-b-poly(butadiene)-b-poly(ethylene oxide). A systematic study on the influence of the calcination temperature and film thickness on the morphology, phase composition, accessible surface area, and OER activity reveals that the catalytic performance is controlled by at least two independent factors, that is, accessible surface area and intrinsic activity per accessible site. Catalysts with lower crystallinity show higher intrinsic activity. The catalyst surface area increases linearly with film thickness. As a result of the templated mesopores, the pore surface remains fully active and accessible even for thick IrO2 films. Even the most active multilayer catalyst does not show signs of transport limitations at current densities as high as 75 mA cm(-2) .

  7. Closed-shell and open-shell square-planar iridium nitrido complexes

    NASA Astrophysics Data System (ADS)

    Scheibel, Markus G.; Askevold, Bjorn; Heinemann, Frank W.; Reijerse, Edward J.; de Bruin, Bas; Schneider, Sven

    2012-07-01

    Coupling reactions of nitrogen atoms represent elementary steps to many important heterogeneously catalysed reactions, such as the Haber-Bosch process or the selective catalytic reduction of NOx to give N2. For molecular nitrido (and related oxo) complexes, it is well established that the intrinsic reactivity, for example nucleophilicity or electrophilicity of the nitrido (or oxo) ligand, can be attributed to M-N (M-O) ground-state bonding. In recent years, nitrogen (oxygen)-centred radical reactivity was ascribed to the possible redox non-innocence of nitrido (oxo) ligands. However, unequivocal spectroscopic characterization of such transient nitridyl {M=N•} (or oxyl {M-O•}) complexes remained elusive. Here we describe the synthesis and characterization of the novel, closed-shell and open-shell square-planar iridium nitrido complexes [IrN(Lt-Bu)]+ and [IrN(Lt-Bu)] (Lt-Bu=N(CHCHP-t-Bu2)2). Spectroscopic characterization and quantum chemical calculations for [IrN(Lt-Bu)] indicate a considerable nitridyl, {Ir=N•}, radical character. The clean formation of IrI-N2 complexes via binuclear coupling is rationalized in terms of nitrido redox non-innocence in [IrN(Lt-Bu)].

  8. Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes

    PubMed Central

    2016-01-01

    Summary Bearing the versatility of N-heterocyclic carbene (NHC) ligands, here density functional theory (DFT) calculations unravel the capacity of coordination of a deprotonated NHC ligand (pNHC) to generate a doubly C2,N3-bridged dinuclear complex. Here, in particular the discussion is based on the combination of the deprotonated 1-arylimidazol (aryl = mesityl (Mes)) with [M(cod)(μ-Cl)] (M = Ir, Rh) generated two geometrical isomers of complex [M(cod){µ-C3H2N2(Mes)-κC2,κN3}]2). The latter two isomers display conformations head-to-head (H-H) and head-to-tail (H-T) of C S and C 2 symmetry, respectively. The isomerization from the H-H to the H-T conformation is feasible, whereas next substitutions of the cod ligand by CO first, and PMe3 later confirm the H-T coordination as the thermodynamically preferred. It is envisaged the exchange of the metal, from iridium to rhodium, confirming here the innocence of the nature of the metal for such arrangements of the bridging ligands. PMID:26877814

  9. Elastic, magnetic and electronic properties of iridium phosphide Ir2P.

    PubMed

    Wang, Pei; Wang, Yonggang; Wang, Liping; Zhang, Xinyu; Yu, Xiaohui; Zhu, Jinlong; Wang, Shanmin; Qin, Jiaqian; Leinenweber, Kurt; Chen, Haihua; He, Duanwei; Zhao, Yusheng

    2016-02-24

    Cubic (space group: Fmm) iridium phosphide, Ir2P, has been synthesized at high pressure and high temperature. Angle-dispersive synchrotron X-ray diffraction measurements on Ir2P powder using a diamond-anvil cell at room temperature and high pressures (up to 40.6 GPa) yielded a bulk modulus of B0 = 306(6) GPa and its pressure derivative B0' = 6.4(5). Such a high bulk modulus attributed to the short and strongly covalent Ir-P bonds as revealed by first - principles calculations and three-dimensionally distributed [IrP4] tetrahedron network. Indentation testing on a well-sintered polycrystalline sample yielded the hardness of 11.8(4) GPa. Relatively low shear modulus of ~64 GPa from theoretical calculations suggests a complicated overall bonding in Ir2P with metallic, ionic, and covalent characteristics. In addition, a spin glass behavior is indicated by magnetic susceptibility measurements.

  10. Molecular organization of a water-insoluble iridium(III) complex in mixed monolayers.

    PubMed

    Giner-Casares, Juan J; Pérez-Morales, Marta; Bolink, Henk J; Muñoz, Eulogia; de Miguel, Gustavo; Martín-Romero, María T; Camacho, Luis

    2007-11-01

    In this work, organized mixed monolayers containing a cationic water-insoluble iridium(III) complex, Ir-dye, [Ir(ppy)(2)(tmphen)]PF(6), (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline, and ppy = 2-phenylpyridine), and an anionic lipid matrix, DMPA, dimyristoyl-phosphatidic acid, with different molar proportions, were formed by the co-spreading method at the air-water interface. The presence of the dye at the interface, as well as the molecular organization of the mixed films, is deduced from surface techniques such as pi-A isotherms, Brewster angle microscopy (BAM) and reflection spectroscopy. The results obtained remark the formation of an equimolar mixed film, Ir-dye/DMPA = 1:1. BAM images reveal a whole homogeneous monolayer, with gradually increasing reflectivity along the compression process up to reaching the collapse of this equimolecular monolayer at pi approximately equal to 37 mNm(-1). Increasing the molar ratio of DMPA in the mixture, the excess of lipid molecules organizes themselves forming dark flower-like domains of pure DMPA at high surface pressures, coexisting with the mixed Ir-dye/DMPA = 1:1 monolayer. On the other hand, unstable mixed monolayers are obtained by using an initial dye surface concentration higher than the equimolecular one. These mixed Langmuir monolayers have been successfully transferred onto solid substrates by the LB (Langmuir-Blodgett) technique. PMID:17618641

  11. Molecular organization of a water-insoluble iridium(III) complex in mixed monolayers.

    PubMed

    Giner-Casares, Juan J; Pérez-Morales, Marta; Bolink, Henk J; Muñoz, Eulogia; de Miguel, Gustavo; Martín-Romero, María T; Camacho, Luis

    2007-11-01

    In this work, organized mixed monolayers containing a cationic water-insoluble iridium(III) complex, Ir-dye, [Ir(ppy)(2)(tmphen)]PF(6), (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline, and ppy = 2-phenylpyridine), and an anionic lipid matrix, DMPA, dimyristoyl-phosphatidic acid, with different molar proportions, were formed by the co-spreading method at the air-water interface. The presence of the dye at the interface, as well as the molecular organization of the mixed films, is deduced from surface techniques such as pi-A isotherms, Brewster angle microscopy (BAM) and reflection spectroscopy. The results obtained remark the formation of an equimolar mixed film, Ir-dye/DMPA = 1:1. BAM images reveal a whole homogeneous monolayer, with gradually increasing reflectivity along the compression process up to reaching the collapse of this equimolecular monolayer at pi approximately equal to 37 mNm(-1). Increasing the molar ratio of DMPA in the mixture, the excess of lipid molecules organizes themselves forming dark flower-like domains of pure DMPA at high surface pressures, coexisting with the mixed Ir-dye/DMPA = 1:1 monolayer. On the other hand, unstable mixed monolayers are obtained by using an initial dye surface concentration higher than the equimolecular one. These mixed Langmuir monolayers have been successfully transferred onto solid substrates by the LB (Langmuir-Blodgett) technique.

  12. A promising phosphorescent heteroleptic iridium complex with carbazole-functionalized substituent: Synthesis, photophysical and electroluminescent performances

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Zang, Tienan; Yu, Lianshui; Zhang, Dongyu; Lu, Gonghao; Chi, Haijun; Xiao, Guoyong; Dong, Yan; Cui, Zheng; Zhang, Zhiqiang; Hu, Zhizhi

    2012-12-01

    A promising heteroleptic iridium complex with carbazole-functionalized substituent, i.e., (cbbt)2Ir(acac), in which cbbt was 2-(4-(4-(9H-carbazol-9-yl)butoxy)phenyl)benzo[d]thiazole and acac acetylacetonate, was designed, synthesized and structurally characterized. The complex emitted intensely orange phosphorescence upon photoexcitation with high luminescent quantum efficiency (0.30), short triplet lifetime (0.15 μs) and high decomposition temperature (310 °C). The electronic properties of (cbbt)2Ir(acac) were also examined according to the density functional theory calculations. Organic light-emitting diodes using (cbbt)2Ir(acac) as doped emitter exhibited orange electrophosphorescence with prominent performances. An extremely high brightness of 17,910 cd m-2 at a high voltage (17 V) and a maximum luminance efficiency of 25.5 cd A-1 were achieved. More importantly, those devices exhibited low efficiency roll-off of 30-35% from 10 to 100 mA cm-2, which was probably attributed to the short triplet lifetime of (cbbt)2Ir(acac).

  13. BOWIEITE: A NEW RHODIUM-IRIDIUM-PLATINUM SULFIDE IN PLATINUM-ALLOY NUGGETS, GOODNEWS BAY, ALASKA.

    USGS Publications Warehouse

    Desborough, George A.; Criddle, Alan J.

    1984-01-01

    Bowieite (Rh,Ir,Pt)//2S//3, a new mineral species, is found in three nuggets of platinum from Goodnews Bay, Alaska. In linearly polarized reflected light, and compared to the host, higher reflecting white platinum-iridium alloy, bowieite is pale gray to pale gray-brown; neither bireflectance nor reflectance pleochroism is apparent. With polars crossed, its anisotropic rotation tints vary from gray to dark brown. Luminance values (relative to the CIE illuminant C) for R//1 and R//2, computed from full spectral data for the most bireflectant grain, are 45. 8% and 48. 2% in air, and 30. 5% and 33. 0% in oil, respectively. VHN//1//0//0 1288 (858 to 1635). Bowieite is orthorhombic, space group Pnca, with a 8. 454(7) -8. 473(8), b 5. 995(1)-6. 002(7), c 6. 143(1)-6. 121(8) A, Z equals 4. Some grains that are 2. 6 to 3. 8 atomic % metal-deficient occur as an optically coherent rim on bowieite; the rim and the bowieite grain are not optically continuous.

  14. Assessment of density functional methods for reaction energetics: iridium-catalyzed water oxidation as case study.

    PubMed

    Kazaryan, Andranik; Baerends, Evert Jan

    2013-04-01

    We investigate basis set convergence for a series of density functional theory (DFT) functionals (both hybrid and nonhybrid) and compare to coupled-cluster with single and double excitations and perturbative triples [CCSD(T)] benchmark calculations. The case studied is the energetics of the water oxidation reaction by an iridium-oxo complex. Complexation energies for the reactants and products complexes as well as the transition state (TS) energy are considered. Contrary to the expectation of relatively weak basis set dependence for DFT, the basis set effects are large, for example, more than 10 kcal mol(-1) difference from converged basis for the activation energy with "small" basis sets (DZ/6-31G** for Ir/other atoms, or SVP) and still more than 6 kcal mol(-1) for def2-TZVPP/6-31G**. Inclusion of the dispersion correction in DFT-D3 schemes affects the energies of reactant complex (RC), TS, and product complex (PC) by almost the same amount; it significantly improves the complexation energy (the formation of RC), but has little effect on the activation energy with respect to RC. With converged basis, some pure GGAs (PBE-D3, BP86-D3) as well as the hybrid functional B3LYP-D3 are very accurate compared to benchmark CCSD(T) calculations.

  15. [sub 193]Ir Moessbauer study of chloro(carbonyl)bis-(triphenylphosphine)(buckminsterfullerene)iridium

    SciTech Connect

    Vertes, A.; Gal, M. ); Wagner, F.E. ); Tuczek, F.; Guetlich, P. )

    1993-09-29

    The authors have measured the Moessbauer spectrum of the adduct of chlorocarbonylbis(triphenylphosphine)iridium (CCTI) with buckminsterfullerene (C[sub 60]) and, for comparison, remeasured the spectra of both the parent compound CCTI and its adduct with tetracyanoethylene, CCTI-TCNE. Moessbauer spectra of the [sup 193]Ir 73 keV [gamma]-transition were taken at 4.2 K. The source was metallic [sup 193]Os, which, being hexagonal, exhibits a quadrupole splitting of about 0.48 mm/s. The individual lines of the quadrupole doublets of the studied samples are therefore not simple Lorentzians; this circumstance is taken into account in the fitting procedure. The full widths at half-maximum of the individual superimposed Lorentzian lines obtained by the least-squares fits are between 0.75 and 0.79 mm s[sup [minus]1] and thus but slightly larger than the natural line width of 0.60 mm s[sup [minus]1].

  16. Long Life Testing of Oxide-Coated Iridium/Rhenium Rockets

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.

    1995-01-01

    22-N class rockets, composed of a rhenium (Re) substrate, an iridium (Ir) coating, and an additional composite coating consisting of Ir and a ceramic oxide, were tested on gaseous oxygen/gaseous hydrogen (GO2/GH2) propellants. Two rockets were tested, one for nearly 39 hours at a nominal mixture ratio (MR) of 4.6 and chamber pressure (Pc) of 469 kPa, and the other for over 13 hours at a nominal MR of 5.8 and 621 kPa Pc. Four additional Ir/Re rockets, with a composite Ir-oxide coating fabricated using a modified process, were also tested, including one for 1.3 hours at a nominal MR of 16.7 and Pc of 503 kPa. The long lifetimes demonstrated on low MR GO2/GH2 suggest greatly extended chamber lifetimes (tens of hours) in the relatively low oxidizing combustion environments of Earth storable propellants. The oxide coatings could also serve as a protective coating in the near injector region, where a still-mixing flowfield may cause degradation of the Ir layer. Operation at MR close to 17 suggests that oxide-coated Ir/Re rockets could be used in severely oxidizing combustion environments, such as high MR GO2/GH2, oxygen/hydrocarbon, and liquid gun propellants.

  17. Iridium Complexes with Terdentate Ligands: Cyclometalated vs. Polypyridine Analogues; Hybrid vs. ``Pure'' DFT

    NASA Astrophysics Data System (ADS)

    Ravaglia, Marcella; Garavelli, Marco; Polson, Matthew; Scandola, Franco

    2007-12-01

    The present investigation has a twofold aim. In the first place, the ground-state spectroscopic features of three IrIII polypyridyl complexes were studied by computational means, in order to elucidate the nature of their UV-visible spectra and electrochemical behaviour. Coincidentally, the limited but variegated set of molecules was employed to analyse how different exchange-correlation functionals model the properties of interest in the presence of transition metal atoms. These iridium complexes involve various terdentate ligands: a N∧N∧N bonded ttpy derivative (ttpy = 4'-tolyl-2:2',6':2″-terpyridine), a C∧N∧C bonded dppy derivative (dppy = 2,6-diphenyl-pyridine), a C∧N∧N pbp derivative (pbp = 6-phenyl-2:2'-bipyridine). The axially-symmetric-homoleptic or heteroleptic-arrangement gives the low-lying excited states of these molecules a unique directional nature. Analysis of the electronic transitions calculated by first-principle method based on time-dependent density functional theory (TDDFT) gives insight on their steady-state visible absorption bands. The comparison of generalised-gradient approximation (GGA) functionals (BLYP and G96LYP) with hybrid GGA functionals (B3LYP and PBE0) values the consequences of the nonlocal Hartree-Fock exchange embedded in the latter.

  18. Metal-Ligand Cooperativity in a Methandiide-Derived Iridium Carbene Complex.

    PubMed

    Weismann, Julia; Waterman, Rory; Gessner, Viktoria H

    2016-03-01

    The synthesis, electronic structure, and reactivity of the first Group 9 carbene complex, [Cp*IrL] [L=C(Ph2 PS)(SO2 Ph)] (2), based on a dilithio methandiide are reported. Spectroscopic as well as computational studies have shown that, despite using a late transition-metal precursor, sufficient charge transfer occurred from the methandiide to the metal, resulting in a stable, nucleophilic carbene species with pronounced metal-carbon double-bond character. The potential of this iridium complex in the activation of a series of E-H bonds by means of metal-ligand cooperation has been tested. These studies have revealed distinct differences in the reactivity of 2 compared to a previously reported ruthenium analogue. Whereas attempts to activate the O-H bond in different phenol derivatives resulted in ligand cleavage, H-H and Si-H activation as well as dehydrogenation of isopropanol have been accomplished. These reactions are driven by the transformation of the carbene to an alkyl ligand. Contrary to a previously reported ruthenium carbene system, the dihydrogen activation has been found to proceed by a stepwise mechanism, with the activation first taking place solely at the metal. The activated products further reacted to afford a cyclometalated complex through liberation of the activated substrates. In the case of triphenylsilane, cyclometalation could thus be induced by a substoichiometric (i.e., catalytic) amount of silane. PMID:26748420

  19. Mixed N-Heterocyclic Carbene-Bis(oxazolinyl)borato Rhodium and Iridium Complexes in Photochemical and Thermal Oxidative Addition Reactions

    SciTech Connect

    Xu, Songchen; Manna, Kuntal; Ellern, Arkady; Sadow, Aaron D

    2014-12-08

    In order to facilitate oxidative addition chemistry of fac-coordinated rhodium(I) and iridium(I) compounds, carbene–bis(oxazolinyl)phenylborate proligands have been synthesized and reacted with organometallic precursors. Two proligands, PhB(OxMe2)2(ImtBuH) (H[1]; OxMe2 = 4,4-dimethyl-2-oxazoline; ImtBuH = 1-tert-butylimidazole) and PhB(OxMe2)2(ImMesH) (H[2]; ImMesH = 1-mesitylimidazole), are deprotonated with potassium benzyl to generate K[1] and K[2], and these potassium compounds serve as reagents for the synthesis of a series of rhodium and iridium complexes. Cyclooctadiene and dicarbonyl compounds {PhB(OxMe2)2ImtBu}Rh(η4-C8H12) (3), {PhB(OxMe2)2ImMes}Rh(η4-C8H12) (4), {PhB(OxMe2)2ImMes}Rh(CO)2 (5), {PhB(OxMe2)2ImMes}Ir(η4-C8H12) (6), and {PhB(OxMe2)2ImMes}Ir(CO)2 (7) are synthesized along with ToMM(η4-C8H12) (M = Rh (8); M = Ir (9); ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate). The spectroscopic and structural properties and reactivity of this series of compounds show electronic and steric effects of substituents on the imidazole (tert-butyl vs mesityl), effects of replacing an oxazoline in ToM with a carbene donor, and the influence of the donor ligand (CO vs C8H12). The reactions of K[2] and [M(μ-Cl)(η2-C8H14)2]2 (M = Rh, Ir) provide {κ4-PhB(OxMe2)2ImMes'CH2}Rh(μ-H)(μ-Cl)Rh(η2-C8H14)2 (10) and {PhB(OxMe2)2ImMes}IrH(η3-C8H13) (11). In the former compound, a spontaneous oxidative addition of a mesityl ortho-methyl to give a mixed-valent dirhodium species is observed, while the iridium compound forms a monometallic allyl hydride. Photochemical reactions of dicarbonyl compounds 5 and 7 result in C–H bond oxidative addition providing the compounds {κ4-PhB(OxMe2)2ImMes'CH2}RhH(CO) (12) and {PhB(OxMe2)2ImMes}IrH(Ph)CO (13). In 12, oxidative addition results in cyclometalation of the mesityl ortho-methyl similar to 10, whereas the iridium compound reacts with the benzene solvent to give a rare crystallographically characterized cis

  20. Electrochemical isotope effect and lithium isotope separation.

    PubMed

    Black, Jay R; Umeda, Grant; Dunn, Bruce; McDonough, William F; Kavner, Abby

    2009-07-29

    A large electrochemical isotopic effect is observed upon the electrodeposition of lithium from solutions of propylene carbonate producing isotopically light metal deposits. The magnitude of fractionation is controlled by the applied overpotential and is largest close to equilibrium. Calculated partition function ratios for tetrahedrally coordinated lithium complexes and metallic lithium predict an equilibrium fractionation close to that measured experimentally.

  1. METHOD OF ISOTOPE CONCENTRATION

    DOEpatents

    Spevack, J.S.

    1957-04-01

    An isotope concentration process is described which consists of exchanging, at two or more different temperature stages, two isotopes of an element between substances that are physically separate from each other and each of which is capable of containing either of the isotopes, and withdrawing from a point between at least two of the temperatare stages one of the substances containing an increased concentration of the desired isotope.

  2. Mechanochemical Iridium(III)-Catalyzed C-H Bond Amidation of Benzamides with Sulfonyl Azides under Solvent-Free Conditions in a Ball Mill.

    PubMed

    Hermann, Gary N; Becker, Peter; Bolm, Carsten

    2016-03-01

    Mechanochemical conditions have been applied to an iridium(III)-catalyzed C-H bond amidation process for the first time. In the absence of solvent, the mechanochemical activation enables the formation of an iridium species that catalyzes the ortho-selective amidation of benzamides with sulfonyl azides as the nitrogen source. As the reaction proceeds in the absence of organic solvents without external heating and yields the desired products in excellent yields within short reaction times, this method constitutes a powerful, fast, and environmentally benign alternative to the common solvent-based standard approaches.

  3. A Highly Selective and Non-Reaction Based Chemosensor for the Detection of Hg2+ Ions Using a Luminescent Iridium(III) Complex

    PubMed Central

    Wang, Modi; Liu, Li-Juan; Leung, Chung-Hang; Ma, Dik-Lung

    2013-01-01

    We report herein a novel luminescent iridium(III) complex with two hydrophobic carbon chains as a non-reaction based chemosensor for the detection of Hg2+ ions in aqueous solution (<0.002% of organic solvent attributed to the probe solution). Upon the addition of Hg2+ ions, the emission intensity of the complex was significantly enhanced and this change could be monitored by the naked eye under UV irradiation. The iridium(III) complex shows high specificity for Hg2+ ions over eighteen other cations. The system is capable of detecting micromolar levels of Hg2+ ions, which is within the range of many chemical systems. PMID:23533670

  4. Superconductivity in Ca10(Ir4As8)(Fe2As2)5 with Square-Planar Coordination of Iridium

    PubMed Central

    Kudo, Kazutaka; Mitsuoka, Daisuke; Takasuga, Masaya; Sugiyama, Yuki; Sugawara, Kento; Katayama, Naoyuki; Sawa, Hiroshi; Kubo, Hiroaki S.; Takamori, Kenta; Ichioka, Masanori; Fujii, Tatsuo; Mizokawa, Takashi; Nohara, Minoru

    2013-01-01

    We report the unprecedented square-planar coordination of iridium in the iron iridium arsenide Ca10(Ir4As8)(Fe2As2)5. This material experiences superconductivity at 16 K. X-ray photoemission spectroscopy and first-principles band calculation suggest Ir(II) oxidation state, which yields electrically conductive Ir4As8 layers. Such metallic spacer layers are thought to enhance the interlayer coupling of Fe2As2, in which superconductivity emerges, thus offering a way to control the superconducting transition temperature. PMID:24173038

  5. Water-Soluble Iridium-NHC-Phosphine Complexes as Catalysts for Chemical Hydrogen Batteries Based on Formate.

    PubMed

    Horváth, Henrietta; Papp, Gábor; Szabolcsi, Roland; Kathó, Ágnes; Joó, Ferenc

    2015-09-21

    Molecular hydrogen, obtained by water electrolysis or photocatalytic water splitting, can be used to store energy obtained from intermittent sources such as wind and solar power. The storage and safe transportation of H2 , however, is an open and central question in such a hydrogen economy. Easy-to-synthesize, water-soluble iridium-N-heterocyclic carbene-phosphine (Ir(I) -NHC-phosphine) catalysts show unprecedented high catalytic activity in dehydrogenation of aqueous sodium formate. Fast reversible generation and storage of hydrogen can be achieved with these catalysts by a simple decrease or increase in the hydrogen pressure, respectively.

  6. Water-Soluble Iridium-NHC-Phosphine Complexes as Catalysts for Chemical Hydrogen Batteries Based on Formate.

    PubMed

    Horváth, Henrietta; Papp, Gábor; Szabolcsi, Roland; Kathó, Ágnes; Joó, Ferenc

    2015-09-21

    Molecular hydrogen, obtained by water electrolysis or photocatalytic water splitting, can be used to store energy obtained from intermittent sources such as wind and solar power. The storage and safe transportation of H2 , however, is an open and central question in such a hydrogen economy. Easy-to-synthesize, water-soluble iridium-N-heterocyclic carbene-phosphine (Ir(I) -NHC-phosphine) catalysts show unprecedented high catalytic activity in dehydrogenation of aqueous sodium formate. Fast reversible generation and storage of hydrogen can be achieved with these catalysts by a simple decrease or increase in the hydrogen pressure, respectively. PMID:26289830

  7. Virus-templated iridium oxide-gold hybrid nanowires for electrochromic application

    NASA Astrophysics Data System (ADS)

    Nam, Yoon Sung; Park, Heechul; Magyar, Andrew P.; Yun, Dong Soo; Pollom, Thomas S.; Belcher, Angela M.

    2012-05-01

    A highly porous electrode comprised of biologically templated iridium oxide-gold (IrO2-Au) hybrid nanowires is introduced for electrochromic applications. A filamentous M13 virus is genetically engineered to display IrO2-binding peptides on the viral surface and used as a template for the self-assembly of IrO2 nanoclusters into a nanowire. The open porous morphology of the prepared nanowire film facilitates ion transport. Subsequently, the redox kinetics of the IrO2 nanowires seems to be limited by the electric resistance of the nanowire film. To increase the electron mobility in the nanowires, gold nanoparticles are chemically linked to the virus prior to the IrO2 mineralization, forming a gold nanostring structure along the long axis of the virus. The resulting IrO2-Au hybrid nanowires exhibit a switching time of 35 ms for coloration and 25 ms for bleaching with a transmission change of about 30.5% at 425 nm. These values represent almost an order of magnitude faster switching responses than those of an IrO2 nanowire film having the similar optical contrast. This work shows that genetically engineered viruses can serve as versatile templates to co-assemble multiple functional molecules, enabling control of the electrochemical properties of nanomaterials.A highly porous electrode comprised of biologically templated iridium oxide-gold (IrO2-Au) hybrid nanowires is introduced for electrochromic applications. A filamentous M13 virus is genetically engineered to display IrO2-binding peptides on the viral surface and used as a template for the self-assembly of IrO2 nanoclusters into a nanowire. The open porous morphology of the prepared nanowire film facilitates ion transport. Subsequently, the redox kinetics of the IrO2 nanowires seems to be limited by the electric resistance of the nanowire film. To increase the electron mobility in the nanowires, gold nanoparticles are chemically linked to the virus prior to the IrO2 mineralization, forming a gold nanostring

  8. Isotope reference materials

    USGS Publications Warehouse

    Coplen, Tyler B.

    2010-01-01

    Measurement of the same isotopically homogeneous sample by any laboratory worldwide should yield the same isotopic composition within analytical uncertainty. International distribution of light element isotopic reference materials by the International Atomic Energy Agency and the U.S. National Institute of Standards and Technology enable laboratories to achieve this goal.

  9. Statistical clumped isotope signatures.

    PubMed

    Röckmann, T; Popa, M E; Krol, M C; Hofmann, M E G

    2016-08-18

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules.

  10. Statistical clumped isotope signatures

    PubMed Central

    Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

  11. Statistical clumped isotope signatures

    NASA Astrophysics Data System (ADS)

    Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.

    2016-08-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules.

  12. Statistical clumped isotope signatures.

    PubMed

    Röckmann, T; Popa, M E; Krol, M C; Hofmann, M E G

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

  13. Cosmic ray isotopes

    NASA Technical Reports Server (NTRS)

    Stone, E. C.

    1973-01-01

    The isotopic composition of cosmic rays is studied in order to develop the relationship between cosmic rays and stellar processes. Cross section and model calculations are reported on isotopes of H, He, Be, Al and Fe. Satellite instrument measuring techniques separate only the isotopes of the lighter elements.

  14. Enantioselective hydrogenation. III. Methyl pyruvate hydrogenation catalyzed by alkaloid-modified iridium

    SciTech Connect

    Simons, K.E.; Johnston, P.; Plum, H.; Wells, P.B.; Ibbotson, A.

    1994-12-01

    Enantioselective hydrogenation of methyl pyruvate, MeCOCOOMe to methyl lactate, MeCH(OH)COOMe, is catalyzed in solution at room temperature by supported iridium catalysts modified with cinchona alkaloids. Modification with cinchonidine or quinine yields R-lactate in excess, whereas modification with cinchonine or quinidine favors S-lactate formation. Ir/SiO{sub 2} catalysts (20%) calcined at 393 to 573 K and reduced at 523 to 593 K were highly active for racemic hydrogenation in the absence of a modifier (rates typically 1.8 mol h{sup -1} g{sub cat}{sup -1}) and were comparably active when modified with cinchonidine but gave an enantiomeric excess of about 30%. Use of higher calcination or reduction temperatures led to substantially inferior activity and selectivity. The high rates recorded for both racemic and enantioselective reactions are dependent on the catalysts being activated before use by a procedure involving exposure of the catalyst to air after the initial reduction. Use of a Cl-free precursor gave an Ir/SiO{sub 2} catalyst (20%) of superior activity but inferior enantioselectivity. Ir/CaCO{sub 3} (5%) was more active for racemic hydrogenation than for enantioselective hydrogenation, but provided the highest value of the enantiomeric excess 39%. Kinematics of reaction are reported. Exchange of H for D in 10,11-dihydrocinchonidine at room temperature over Ir/CaCO{sub 3} occurred in the quinoline moiety but not in the quinuclidine ring system, indicating that the alkaloid was adsorbed to the Ir surface via the interaction of its {pi}-electron system. For both silica-supported and calcium carbonate-supported Ir, the presence of chloride ion in the catalyst was advantageous for the achievement of enantioselectivity. 25 refs., 2 figs., 3 tabs.

  15. Laminar iridium coating produced by pulse current electrodeposition from chloride molten salt

    NASA Astrophysics Data System (ADS)

    Zhu, Li'an; Bai, Shuxin; Zhang, Hong; Ye, Yicong

    2013-10-01

    Due to the unique physical and chemical properties, Iridium (Ir) is one of the most promising oxidation-resistant coatings for refractory materials above 1800 °C in aerospace field. However, the Ir coatings prepared by traditional methods are composed of columnar grains throughout the coating thickness. The columnar structure of the coating is considered to do harm to its oxidation resistance. The laminar Ir coating is expected to have a better high-temperature oxidation resistance than the columnar Ir coating does. The pulse current electrodeposition, with three independent parameters: average current density (Jm), duty cycle (R) and pulse frequency (f), is considered to be a promising method to fabricate layered Ir coating. In this study, laminar Ir coatings were prepared by pulse current electrodeposition in chloride molten salt. The morphology, roughness and texture of the coatings were determined by scanning electron microscope (SEM), profilometer and X-ray diffraction (XRD), respectively. The results showed that the laminar Ir coatings were composed of a nucleation layer with columnar structure and a growth layer with laminar structure. The top surfaces of the laminar Ir coatings consisted of cauliflower-like aggregates containing many fine grains, which were separated by deep grooves. The laminar Ir coating produced at the deposition condition of 20 mA/cm2 (Jm), 10% (R) and 6 Hz (f) was quite smooth (Ra 1.01 ± 0.09 μm) with extremely high degree of preferred orientation of <1 1 1>, and its laminar structure was well developed with clear boundaries and uniform thickness of sub-layers.

  16. A nonemissive iridium(III) complex that specifically lights-up the nuclei of living cells.

    PubMed

    Li, Chunyan; Yu, Mengxiao; Sun, Yun; Wu, Yongquan; Huang, Chunhui; Li, Fuyou

    2011-07-27

    A nonemissive cyclometalated iridium(III) solvent complex, without conjugation with a cell-penetrating molecular transporter, [Ir(ppy)(2)(DMSO)(2)](+)PF(6)(-) (LIr1), has been developed as a first reaction-based fluorescence-turn-on agent for the nuclei of living cells. LIr1 can rapidly and selectively light-up the nuclei of living cells over fixed cells, giving rise to a significant luminescence enhancement (200-fold), and shows very low cytotoxicity at the imaging concentration (incubation time <10 min, LIr1 concentration 10 μM). More importantly, in contrast to the reported nuclear stains that are based on luminescence enhancement through interaction with nucleic acids, complex LIr1 as a nuclear stain has a reaction-based mode of action, which relies on its rapid reaction with histidine/histidine-containing proteins. Cellular uptake of LIr1 has been investigated in detail under different conditions, such as at various temperatures, with hypertonic treatment, and in the presence of metabolic and endocytic inhibitors. The results have indicated that LIr1 permeates the outer and nuclear membranes of living cells through an energy-dependent entry pathway within a few minutes. As determined by an inductively coupled plasma atomic emission spectroscopy (ICP-AEC), LIr1 is accumulated in the nuclei of living cells and converted into an intensely emissive adduct. Such novel reaction-based nuclear staining for visualizing exclusively the nuclei of living cells with a significant luminescence enhancement may extend the arsenal of currently available fluorescent stains for specific staining of cellular compartments.

  17. Consideration of Lower Allowable Impact Temperature for DOP-26 Iridium Alloy Fueled Clads

    NASA Astrophysics Data System (ADS)

    Skrabek, Emanuel A.

    2005-02-01

    The current DOE General Purpose Heat Source (GPHS) was developed specifically for a SiGe Radioisotope Thermoelectric Generator (RTG) which was to be launched on a Space Shuttle. In such a launch, if the final stage of the deployed spacecraft failed to ignite, the spacecraft and RTG would reenter the atmosphere after about three months in a Shuttle parking orbit. The indium alloy clad containing the radioisotope fuel would have then been at about 1300° C for the entire time on orbit. This would lead to some grain growth in the clad material, which would tend to decrease its ductility. Due to these constraints, it was concluded by the heat source community that safety considerations would require that the clads be maintained at a temperature of at least 930° C through impact. The safety testing for the GPHS RTG programs was therefore conducted with these conditions as guides. Within this set of guidelines, the heat source was shown to be able to safely handle all credible launch and reentry accident events in these missions. Currently proposed missions plan to use different power conversion systems and launch scenarios that are able to utilize much lower operating temperatures. Imposing the high operating and impact temperatures required by the SiGe RTG onto these new systems would lead to unnecessary added design complexity and probably a less robust system. If the heat source is operated so that the iridium alloy clads are generally maintained at less than 1000° C, essentially no grain growth would be experienced over normal mission lifetimes, and the clads would stay more ductile and able to safely withstand the resulting lower impact temperatures. Therefore DOE has embarked on a study to determine the lowest safe operating and impact temperatures for the GPHS. This paper presents the historical background and some preliminary results of this study.

  18. Highly effective water oxidation catalysis with iridium complexes through the use of NaIO4.

    PubMed

    Codolà, Zoel; Cardoso, João M S; Royo, Beatriz; Costas, Miquel; Lloret-Fillol, Julio

    2013-05-27

    Exceptional water oxidation (WO) turnover frequencies (TOF=17,000 h(-1)), and turnover numbers (TONs) close to 400,000, the largest ever reported for a metal-catalyzed WO reaction, have been found by using [Cp*Ir(III)(NHC)Cl2] (in which NHC=3-methyl-1-(1-phenylethyl)-imidazoline-2-ylidene) as the pre-catalyst and NaIO4 as oxidant in water at 40 °C. The apparent TOF for [Cp*Ir(III)(NHC)X2] (1X, in which X stands for I (1I), Cl (1Cl), or triflate anion (1OTf)) and [(Cp*-NHCMe)Ir(III)I2] (2) complexes, is kept constant during almost all of the O2 evolution reaction when using NaIO4 as oxidant. The TOF was found to be dependent on the ligand and on the anion (TOF ranging from ≈600 to ≈1100 h(-1) at 25 °C). Degradation of the complexes by oxidation of the organic ligands upon reaction with NaIO4 has been investigated. (1)H NMR, ESI-MS, and dynamic light-scattering measurements (DLS) of the reaction medium indicated that the complex undergoes rapid degradation, even at low equivalents of oxidant, but this process takes place without formation of nanoparticles. Remarkably, three-month-old solution samples of oxidized pre-catalysts remain equally as active as freshly prepared solutions. A UV/Vis feature band at λmax =405 nm is observed in catalytic reaction solutions only when O2 evolves, which may be attributed to a resting state iridium speciation, most probably Ir-oxo species with an oxidation state higher than IV.

  19. Five-year clinical and angiographic follow-up after intracoronary iridium-192 radiation therapy

    SciTech Connect

    Condado, Jose A.; Waksman, Ron; Saucedo, Jorge F.; Bhargava, Balram; Lansky, Alexandra J.; Calderas, Carlos; Gurdiel, Orlando; Gonzalez, Juan; Fadoul, Merche; Parra, Bogart; Iturria, Isabel; Amezaga, Bingen

    2002-06-01

    Background: Ionizing gamma radiation has been shown to reduce neointimal formation and the incidence of restenosis after balloon angioplasty and stenting in clinical trials. However, the long-term effects of this therapy are unknown. The first cohort of patients to receive intracoronary gamma radiation after balloon angioplasty for the prevention of restenosis have completed a 5-year angiographic and clinical follow-up. The outcome of these patients is presented and discussed. Methods: Twenty-one patients with unstable angina (22 arteries) underwent standard balloon angioplasty. Intracoronary radiation therapy was performed immediately after the intervention using an Iridium-192 source wire hand-delivered to the angioplasty site. All patients were followed clinically and Quantitative Coronary Analysis (QCA) was performed at 6, 24, 36 and 60 months. Results: Target lesion revascularization occurred in six lesions, three of which were total occlusions (two early within 30 days and one occurred at 2 years), and one patient had a myocardial infarction attributable to a nontarget vessel. Serial QCA detected a binary restenosis rate of 28.6% (n=6) at 6 months. The late loss (0.29 mm) and loss index (0.25) remained low at 2, 3 and 5 years. Angiographic complications included four aneurysms (two procedure related and two occurring within 3 months). At 2 years, only one aneurysm increased in size (46 vs. 27 mm{sup 2}); and at 3 and 5 years, all aneurysms remained unchanged. No other angiographic complications were observed. Conclusion: The early clinical and angiographic effects of intracoronary gamma radiation were maintained at 5 years without further increase in the aneurysm formation or apparent new adverse effects related to the radiation therapy between 2 and 5 years.

  20. Electrochemical detection of catecholamine release using planar iridium oxide electrodes in nanoliter microfluidic cell culture volumes.

    PubMed

    Ges, Igor A; Currie, Kevin P M; Baudenbacher, Franz

    2012-04-15

    Release of neurotransmitters and hormones by calcium regulated exocytosis is a fundamental cellular/molecular process that is disrupted in a variety of psychiatric, neurological, and endocrine disorders. Therefore, this area represents a relevant target for drug and therapeutic development, efforts that will be aided by novel analytical tools and devices that provide mechanistically rich data with increased throughput. Toward this goal, we have electrochemically deposited iridium oxide (IrOx) films onto planar thin film platinum electrodes (20 μm×300 μm) and utilized these for quantitative detection of catecholamine release from adrenal chromaffin cells trapped in a microfluidic network. The IrOx electrodes show a linear response to norepinephrine in the range of 0-400 μM, with a sensitivity of 23.1±0.5 mA/M mm(2). The sensitivity of the IrOx electrodes does not change in the presence of ascorbic acid, a substance commonly found in biological samples. A replica molded polydimethylsiloxane (PDMS) microfluidic device with nanoliter sensing volumes was aligned and sealed to a glass substrate with the sensing electrodes. Small populations of chromaffin cells were trapped in the microfluidic device and stimulated by rapid perfusion with high potassium (50mM) containing Tyrode's solution at a flow rate of 1 nL/s. Stimulation of the cells produced a rapid increase in current due to oxidation of the released catecholamines, with an estimated maximum concentration in the cell culture volume of ~52 μM. Thus, we demonstrate the utility of an integrated microfluidic network with IrOx electrodes for real-time quantitative detection of catecholamines released from small populations of chromaffin cells. PMID:22398270

  1. Characterization of Iridium Coated Rhenium Used in High-Temperature, Radiation-Cooled Rocket Thrusters

    NASA Technical Reports Server (NTRS)

    Stulen, R. H.; Boehme, D. R.; Clift, W. M.; McCarty, K. F.

    1990-01-01

    Materials used for radiation-cooled rocket thrusters must be capable of surviving under extreme conditions of high-temperatures and oxidizing environments. While combustion efficiency is optimized at high temperatures, many refractory metals are unsuitable for thruster applications due to rapid material loss from the formation of volatile oxides. This process occurs during thruster operation by reaction of the combustion products with the material surface. Aerojet Technical Systems has developed a thruster cone chamber constructed of Re coated with Ir on the inside surface where exposure to the rocket exhaust occurs. Re maintains its structural integrity at high temperature and the Ir coating is applied as an oxidation barrier. Ir also forms volatile oxide species (IrO2 and IrO3) but at a considerably slower rate than Re. In order to understand the performance limits of Ir-coated Re thrusters, we are investigating the interdiffusion and oxidation kinetics of Ir/Re. The formation of iridium and rhenium oxides has been monitored in situ by Raman spectroscopy during high temperature exposure to oxygen. For pure Ir, the growth of oxide films as thin as approximately 200 A could be easily detected and the formation of IrO2 was observed at temperatures as low as 600 C. Ir/Re diffusion test specimens were prepared by magnetron sputtering of Ir on Re substrates. Concentration profiles were determined by sputter Auger depth profiles of the heat treated specimens. Significant interdiffusion was observed at temperatures as low as 1000 C. Measurements of the activation energy suggest that below 1350 C, the dominant diffusion path is along defects, most likely grain boundaries, rather than bulk diffusion through the grains. The phases that form during interdiffusion have been examined by x ray diffraction. Analysis of heated test specimens indicates that the Ir-Re reaction produces a solid solution phase of Ir dissolved in the HCP structure of Re.

  2. Iridium, platinum and rhodium baseline concentration in lichens from Tierra del Fuego (South Patagonia, Argentina).

    PubMed

    Pino, Anna; Alimonti, Alessandro; Conti, Marcelo Enrique; Bocca, Beatrice

    2010-10-01

    Lichen samples of Usnea barbata were used as possible biomonitors of the atmospheric background level of iridium (Ir), platinum (Pt) and rhodium (Rh) in the remote region of Tierra del Fuego (South Patagonia, Argentina). Lichens were collected in 2006 at 53 sites covering 7 different areas of the region (24 transplanted lichens of the northern region and 29 native lichen samples of the central-southern region). A microwave acidic digestion procedure was used to mineralize the samples and a sector field inductively coupled plasma mass spectrometry method was developed to quantify the elements. The study of the influence of interferences on analyte signals and a quality control procedure were carried out. The analytical protocol was further applied to evaluate Ir, Pt and Rh bioaccumulation in lichens. The detection limits obtained were 0.010 ng g⁻¹, 0.013 ng g⁻¹ and 0.030 ng g⁻¹ for Ir, Pt and Rh, respectively. Recoveries at different fortification levels were between 96.3% and 106% and precision was 3.3% on average. The metals concentration (as dry weight) spanned the following ranges: Ir, <0.010-1.011 ng g⁻¹; Pt, 0.016-2.734 ng g⁻¹; and Rh, 0.063-1.298 ng g⁻¹. Data on 7 areas were similar suggesting that no specific source, for example traffic or anthropogenic activity, influenced directly the metal concentrations in Tierra del Fuego. Values detected are more likely influenced by the long-range atmospheric transport of these pollutants and, in comparison with densely populated areas in the world, they can represent the baseline for low impacted areas.

  3. ISOTOPE CONVERSION DEVICE

    DOEpatents

    Wigner, E.P.; Young, G.J.; Ohlinger, L.A.

    1957-12-01

    This patent relates to nuclear reactors of tbe type utilizing a liquid fuel and designed to convert a non-thermally fissionable isotope to a thermally fissionable isotope by neutron absorption. A tank containing a reactive composition of a thermally fissionable isotope dispersed in a liquid moderator is disposed within an outer tank containing a slurry of a non-thermally fissionable isotope convertible to a thermally fissionable isotope by neutron absorption. A control rod is used to control the chain reaction in the reactive composition and means are provided for circulating and cooling the reactive composition and slurry in separate circuits.

  4. Isotopically controlled semiconductors

    SciTech Connect

    Haller, Eugene E.

    2001-12-21

    Semiconductor bulk crystals and multilayer structures with controlled isotopic composition have attracted much scientific and technical interest in the past few years. Isotopic composition affects a large number of physical properties, including phonon energies and lifetimes, bandgaps, the thermal conductivity and expansion coefficient and spin-related effects. Isotope superlattices are ideal media for self-diffusion studies. In combination with neutron transmutation doping, isotope control offers a novel approach to metal-insulator transition studies. Spintronics, quantum computing and nanoparticle science are emerging fields using isotope control.

  5. Osmium Isotopic Composition of the Sumbar Cretaceous- Tertiary Boundary, Turkmenia

    NASA Astrophysics Data System (ADS)

    Meisel, T.; Krahenbuhl, U.; Nazarov, M. A.

    1992-07-01

    Turekian (1982) propagated the use of the osmium isotopic composition as a cosmic indicator for the origin of the high osmium (and iridium) layers at the K/T boundaries. He did not consider the osmium isotopic signature of the terrestrial mantle, which also has a chondritic evolution of the Re-Os system. Osmium cannot serve alone as an infallible indicator of the impact theory, but interesting results can be obtained from their investigation. Different K/T boundary section have been analyzed so far for ^187Os/^186Os. An overview of the values is presented in the table. Boundary Clay layer Os ratio Reference Stevns Klint fish clay 1.66 Luck and Turekian, 1983 Woodside Creek 1.12 Lichte et al., 1986 Raton Basin 1.23 Kraehenbuehl et al., 1988 Raton Basin (several) 1.15-1.23 Esser and Turekian, 1989 Sumbar (0-1 cm) 1.16 This work We obtained a complete marine section of the K/T boundary in southern Turkmenia (decribed by Alekseyev, 1988). It shows a very high Ir concentration (66 ppb) at the boundary layer and a remarkable Ir enrichment over crustal rocks continuing up to 30 cm above the boundary. Our aim of this investigation is to analyze several samples from above and below the boundary for the ^187Os/^186Os ratio to obtain a complete picture of the isotopic evolution of the section. We want to evaluate mixing of Os with chondritic ratios with Os from upper crustal rocks. Another goal is to investigate a mobilization of Os. So far only one sample has been analyzed with NTI-MS after fire assay digestion of the sample. The sample 0 to 1 cm has an ^187Os/^186Os ratio of 1.162 +- 13, which is quite low. We expect an even lower value for the boundary clay (0 cm) itself not taking into account a contribution of radiogenic osmium from the decay of terrestrial rhenium. This might put this K/T boundary section closest of all to the present day chondritic value (approx. 1.05). Further analysis will be presented at the meeting. References Alekseyev A. S., Nazarov M. A

  6. Determination of plutonium content in high burnup pressurized water reactor fuel samples and its use for isotope correlations for isotopic composition of plutonium.

    PubMed

    Joe, Kihsoo; Jeon, Young-Shin; Han, Sun-Ho; Lee, Chang-Heon; Ha, Yeong-Keong; Song, Kyuseok

    2012-06-01

    The content of plutonium isotopes in high burnup pressurized water reactor fuel samples was examined using both alpha spectrometry and mass spectrometry after anion exchange separation. The measured values were compared with results calculated by the ORIGEN-2 code. On average, the ratios (m/c) of the measured values (m) over the calculated values (c) were 1.22±0.16 for (238)Pu, 1.02±0.14 for (239)Pu, 1.08±0.06 for (240)Pu, 1.06±0.16 for (241)Pu, and 1.13±0.08 for (242)Pu. Using the Pu data obtained in this work, correlations were derived between the alpha activity ratios of (238)Pu/((239)Pu+(240)Pu), the alpha specific activities of Pu, and the atom % abundances of the Pu isotopes. Using these correlations, the atom % abundances of the plutonium isotopes in the target samples were calculated. These calculated results agreed within a range from 2 to 8% of the experimentally derived values according to the isotopes of plutonium.

  7. Oxidation and β-Alkylation of Alcohols Catalysed by Iridium(I) Complexes with Functionalised N-Heterocyclic Carbene Ligands.

    PubMed

    Jiménez, M Victoria; Fernández-Tornos, Javier; Modrego, F Javier; Pérez-Torrente, Jesús J; Oro, Luis A

    2015-12-01

    The borrowing hydrogen methodology allows for the use of alcohols as alkylating agents for CC bond forming processes offering significant environmental benefits over traditional approaches. Iridium(I)-cyclooctadiene complexes having a NHC ligand with a O- or N-functionalised wingtip efficiently catalysed the oxidation and β-alkylation of secondary alcohols with primary alcohols in the presence of a base. The cationic complex [Ir(NCCH3 )(cod)(MeIm(2- methoxybenzyl))][BF4 ] (cod=1,5-cyclooctadiene, MeIm=1-methylimidazolyl) having a rigid O-functionalised wingtip, shows the best catalyst performance in the dehydrogenation of benzyl alcohol in acetone, with an initial turnover frequency (TOF0 ) of 1283 h(-1) , and also in the β-alkylation of 2-propanol with butan-1-ol, which gives a conversion of 94 % in 10 h with a selectivity of 99 % for heptan-2-ol. We have investigated the full reaction mechanism including the dehydrogenation, the cross-aldol condensation and the hydrogenation step by DFT calculations. Interestingly, these studies revealed the participation of the iridium catalyst in the key step leading to the formation of the new CC bond that involves the reaction of an O-bound enolate generated in the basic medium with the electrophilic aldehyde.

  8. Oxidation and β-Alkylation of Alcohols Catalysed by Iridium(I) Complexes with Functionalised N-Heterocyclic Carbene Ligands.

    PubMed

    Jiménez, M Victoria; Fernández-Tornos, Javier; Modrego, F Javier; Pérez-Torrente, Jesús J; Oro, Luis A

    2015-12-01

    The borrowing hydrogen methodology allows for the use of alcohols as alkylating agents for CC bond forming processes offering significant environmental benefits over traditional approaches. Iridium(I)-cyclooctadiene complexes having a NHC ligand with a O- or N-functionalised wingtip efficiently catalysed the oxidation and β-alkylation of secondary alcohols with primary alcohols in the presence of a base. The cationic complex [Ir(NCCH3 )(cod)(MeIm(2- methoxybenzyl))][BF4 ] (cod=1,5-cyclooctadiene, MeIm=1-methylimidazolyl) having a rigid O-functionalised wingtip, shows the best catalyst performance in the dehydrogenation of benzyl alcohol in acetone, with an initial turnover frequency (TOF0 ) of 1283 h(-1) , and also in the β-alkylation of 2-propanol with butan-1-ol, which gives a conversion of 94 % in 10 h with a selectivity of 99 % for heptan-2-ol. We have investigated the full reaction mechanism including the dehydrogenation, the cross-aldol condensation and the hydrogenation step by DFT calculations. Interestingly, these studies revealed the participation of the iridium catalyst in the key step leading to the formation of the new CC bond that involves the reaction of an O-bound enolate generated in the basic medium with the electrophilic aldehyde. PMID:26493780

  9. Cyclometalated Iridium(III) Complexes as Two-Photon Phosphorescent Probes for Specific Mitochondrial Dynamics Tracking in Living Cells.

    PubMed

    Jin, Chengzhi; Liu, Jiangping; Chen, Yu; Zeng, Leli; Guan, Ruilin; Ouyang, Cheng; Ji, Liangnian; Chao, Hui

    2015-08-17

    Five cyclometalated iridium(III) complexes with 2-phenylimidazo[4,5-f][1,10]phenanthroline derivatives (IrL1-IrL5) were synthesized and developed to image and track mitochondria in living cells under two-photon (750 nm) excitation, with two-photon absorption cross-sections of 48.8-65.5 GM at 750 nm. Confocal microscopy and inductive coupled plasma-mass spectrometry (ICP-MS) demonstrated that these complexes selectively accumulate in mitochondria within 5 min, without needing additional reagents for membrane permeabilization, or replacement of the culture medium. In addition, photobleaching experiments and luminescence measurements confirmed the photostability of these complexes under continuous laser irradiation and physiological pH resistance. Moreover, results using 3D multicellular spheroids demonstrate the proficiency of these two-photon luminescent complexes in deep penetration imaging. Two-photon excitation using such novel complexes of iridium(III) for exclusive visualization of mitochondria in living cells may substantially enhance practical applications of bioimaging and tracking.

  10. Interstitial radiation therapy for carcinoma of the penis using iridium 192 wires: the Henri Mondor experience (1970-1979)

    SciTech Connect

    Mazeron, J.J.; Langlois, D.; Lobo, P.A.; Huart, J.A.; Calitchi, E.; Lusinchi, A.; Raynal, M.; Le Bourgeois, J.P.; Abbou, C.C.; Pierquin, B.

    1984-10-01

    From 1970 to 1979, a group of 50 patients was treated for squamous cell carcinoma of the penis by interstitial irradiation using an afterloading technique and iridium 192 wires. The group included 9 patients with T1 tumors, 27 with T2 tumors, and 14 with T3 tumors. Forty-five patients presented with no metastatic inguinal nodes (NO), 3 patients with N1 nodes, and 2 patients had N3 nodes. After treatment, 11 patients (1 T1, 6 T2 and 4 T3) developed local recurrences. Three patients developed post-therapeutic necrosis which necessitated partial amputation in 2 cases. Eight patients developed post-therapeutic urethral stenosis, which required surgical treatment in three of the cases. Twenty-one percent of the patients died of their disease. The authors advocate interstitial irradiation using iridium 192 wires for the treatment of non-infiltrating or moderately infiltrating squamous cell carcinoma of the penis in which the largest dimension does no exceed 4 cm. When regular follow-up can be assurred, it is reasonable to forgo prophylactic treatment of the inguinal nodes in patients presenting without groin metastasis.

  11. Inhibition of the p53/hDM2 protein-protein interaction by cyclometallated iridium(III) compounds

    PubMed Central

    Liu, Li-Juan; He, Bingyong; Miles, Jennifer A.; Wang, Wanhe; Mao, Zhifeng; Che, Weng Ian; Lu, Jin-Jian; Chen, Xiu-Ping; Wilson, Andrew J.; Ma, Dik-Lung; Leung, Chung-Hang

    2016-01-01

    Inactivation of the p53 transcription factor by mutation or other mechanisms is a frequent event in tumorigenesis. One of the major endogenous negative regulators of p53 in humans is hDM2, a ubiquitin E3 ligase that binds to p53 causing proteasomal p53 degradation. In this work, a library of organometallic iridium(III) compounds were synthesized and evaluated for their ability to disrupt the p53/hDM2 protein-protein interaction. The novel cyclometallated iridium(III) compound 1 [Ir(eppy)2(dcphen)](PF6) (where eppy = 2-(4-ethylphenyl)pyridine and dcphen = 4, 7-dichloro-1, 10-phenanthroline) blocked the interaction of p53/hDM2 in human amelanotic melanoma cells. Finally, 1 exhibited anti-proliferative activity and induced apoptosis in cancer cell lines consistent with inhibition of the p53/hDM2 interaction. Compound 1 represents the first reported organometallic p53/hDM2 protein-protein interaction inhibitor. PMID:26883110

  12. Phosphorescent light-emitting iridium complexes serve as a hypoxia-sensing probe for tumor imaging in living animals

    NASA Astrophysics Data System (ADS)

    Takeuchi, Toshiyuki; Zhang, Shaojuan; Negishi, Kazuya; Yoshihara, Toshitada; Hosaka, Masahiro; Tobita, Seiji

    2010-02-01

    Iridium complex, a promising organic light-emitting diode material for next generation television and computer displays, emits phosphorescence. Phosphorescence is quenched by oxygen. We used this oxygen-quenching feature for imaging tumor hypoxia. Red light-emitting iridium complex Ir(btp)2(acac) (BTP) presented hypoxia-dependent light emission in culture cell lines, whose intensity was in parallel with hypoxia-inducible factor (HIF)-1 expression. BTP was further applied to imaging five nude mouse-transplanted tumors. All tumors presented a bright BTP-emitting image as early as 5 min after the injection. The BTP-dependent tumor image peaked at 1 to 2 h after the injection, and was then removed from tumors within 24 h. The minimal BTP image recognition size was at least 2 mm in diameter. By morphological examination and phosphorescence lifetime measurement, BTP is presumed to localize to the tumor cells, not to stay in the tumor microvessels by binding to albumin. The primary problem on suse of luminescent probe for tumor imaging is its weak penetrance to deep tissues from the skin surface. Since BTP is easily modifiable, we made BTP analogues with a longer excitation/emission wavelength to improve the tissue penetrance. One of them, BTPHSA, displayed 560/720 wavelength, and depicted its clear imaging from tumors transplanted over 6-7 mm deep from the skin surface. We suggest that BTP analogues have a vast potential for imaging hypoxic lesions such as tumor tissues.

  13. Efficient and tunable white-light emission of metal–organic frameworks by iridium-complex encapsulation

    PubMed Central

    Sun, Chun-Yi; Wang, Xin-Long; Zhang, Xiao; Qin, Chao; Li, Peng; Su, Zhong-Min; Zhu, Dong-Xia; Shan, Guo-Gang; Shao, Kui-Zhan; Wu, Han; Li, Jing

    2013-01-01

    Metal–organic frameworks (MOFs) are well known for their tunable structure and porosity. Many studies have shown they are promising for various important applications, for which their performance can be further enhanced by encapsulating functional species, such as luminescent guest molecules, within the frameworks. Although numerous MOFs are luminescent, very few emit white light and their quantum yield is usually low. Here we report a strategy to achieve efficient white-light emission by encapsulating an iridium complex in the MOF cavity. A mesoporous blue-emitting MOF is prepared as host to encapsulate a yellow-emitting iridium complex, [Ir(ppy)2(bpy)]+. The resultant composites emit bright white light with good colour quality (for example, Commission International de I’Eclairage coordinates, colour-rendering index and correlated colour temperature of (0.31, 0.33), 84.5 and 5409 K, respectively), and high quantum yield up to 115 °C. This strategy may open new perspectives for developing high-performance energy-saving solid-state lighting materials. PMID:24212250

  14. Silica nanoparticles for micro-particle imaging velocimetry: fluorosurfactant improves nanoparticle stability and brightness of immobilized iridium(III) complexes.

    PubMed

    Lewis, David J; Dore, Valentina; Rogers, Nicola J; Mole, Thomas K; Nash, Gerard B; Angeli, Panagiota; Pikramenou, Zoe

    2013-11-26

    To establish highly luminescent nanoparticles for monitoring fluid flows, we examined the preparation of silica nanoparticles based on immobilization of a cyclometalated iridium(III) complex and an examination of the photophysical studies provided a good insight into the Ir(III) microenvironment in order to reveal the most suitable silica nanoparticles for micro particle imaging velocimetry (μ-PIV) studies. Iridium complexes covalently incorporated at the surface of preformed silica nanoparticles, [Ir-4]@Si500-Z, using a fluorinated polymer during their preparation, demonstrated better stability than those without the polymer, [Ir-4]@Si500, as well as an increase in steady state photoluminescence intensity (and therefore particle brightness) and lifetimes which are increased by 7-fold compared with nanoparticles with the same metal complex attached covalently throughout their core, [Ir-4]⊂Si500. Screening of the nanoparticles in fluid flows using epi-luminescence microscopy also confirm that the brightest, and therefore most suitable particles for microparticle imaging velocimetry (μ-PIV) measurements are those with the Ir(III) complex immobilized at the surface with fluorosurfactant, that is [Ir-4]@Si500-Z. μ-PIV studies demonstrate the suitability of these nanoparticles as nanotracers in microchannels.

  15. Cyclometalated iridium complex-based label-free photoelectrochemical biosensor for DNA detection by hybridization chain reaction amplification.

    PubMed

    Li, Chunxiang; Wang, Hongyang; Shen, Jing; Tang, Bo

    2015-04-21

    Photoactive material is the most crucial factor which intimately determines analytical performances of the photoelectrochemical sensor. On the basis of the high affinity of dipyrido [3,2-a:2',3'-c] phenazine (dppz) with DNA helix, a novel photoactive intercalator, [(ppy)2Ir(dppz)](+)PF6(-)(ppy = 2-phenylpyridine and dppz = dipyrido [3,2-a:2',3'-c] phenazine) was prepared and characterized by UV-vis absorption spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. The photoelectrochemical properties of the as-prepared iridium(III) complex immobilized on the ITO electrode was investigated. Either cathodic or anodic photocurrent generation can be observed when triethanolamine (TEOA) or dissolved O2 is used as a sacrificial electron donor/acceptor, respectively. The probable photocurrent-generation mechanisms are speculated. A highly sensitive iridium(III) complex-based photoelectrochemical sensor was proposed for DNA detection via hybridization chain reaction (HCR) signal amplification. Under optimal conditions, the biosensor was found to be linearly proportional to the logarithm of target DNA concentration in the range from 0.025 to 100 pmol L(-1) with a detection limit of 9.0 fmol L(-1) (3σ). Moreover, the proposed sensor displayed high selectivity and good reproducibility, demonstrating efficient and stable photoelectric conversion ability of the Ir(III) complex. PMID:25816127

  16. Uranium and strontium isotopes in Boulder Zone waters, South Florida

    SciTech Connect

    Cowart, J.B. . Dept. of Geology)

    1993-03-01

    The Boulder Zone of southern peninsular Florida, which is at a depth of approximately 1,000 m, is a cavernous, dolomitized zone which contains anomalously cool water which appears to be of marine composition. Samples of this water, as they have become available, have been analyzed for uranium concentration, U-234/U-238 alpha activity ratio, and, in a few cases, Sr-87/Sr-86 ratio and concentration. Boulder Zone samples collected in the vicinity of Ft. Lauderdale have analyzed values of the above mentioned parameters which are virtually indistinguishable from those of sea water. In a fan-like radial pattern, the uranium concentrations decrease and the U-234/U-238 activity ratios increase away from the apex at Ft. Lauderdale. It has been hypothesized by others that the Ft. Lauderdale area is the location on land that is nearest to an intake area where sea water moves into the Boulder Zone. The isotopic and concentration values reported here are consistent with this hypothesis. Waters collected from well located near the Atlantic coast north of Ft. Lauderdale do not display the same U and Sr isotopic pattern as those in the remainder of south Florida. This may be due to increased mixing between water bearing units which have been fractured and/or faulted by the extention of a flexure which has been postulated in the northern part of the study area.

  17. Enantioselective allylic substitution of cinnamyl esters catalyzed by iridium-chiral aryl phosphite complex: conspicuous change in the mechanistic spectrum by a countercation and solvent.

    PubMed

    Kinoshita, Naosumi; Marx, Karsten H; Tanaka, Kiyoshi; Tsubaki, Kazunori; Kawabata, Takeo; Yoshikai, Naohiko; Nakamura, Eiichi; Fuji, Kaoru

    2004-11-12

    Iridium-catalyzed asymmetric allylic alkylation of monoaryl substrates 4-6 with chiral phosphites 1-3 has been investigated. Although branched isomers were formed with high regioselectivities, the enantioselectivities of these products were remarkably influenced by solvents, countercations, and additives (ZnCl(2) and LiCl).

  18. Charge injection properties of iridium oxide films produced on Ti-6Al-4V alloy substrates by ion-beam mixing techniques

    SciTech Connect

    Williams, J.M. ); Lee, I-S.; Buchanan, R.A. )

    1991-10-01

    The charge injection capabilities of iridium oxide films, as produced on Ti6Al-4V alloy substrates by ion beam mixing techniques, have been investigated. Iridium oxide is a valence change oxide, and therefore has high values of charge injection density upon voltage cycling in electrolytes. Because of this property, iridium oxide films are useful as working elements in neural prostheses. Iridium films of three thicknesses, produced by sputter deposition followed by ion beam mixing, were tested in cyclic voltammetry out to 1000 cycles or more. Two surface preparations, mechanical polishing and an acid passivation treatment, were also used as controls. Surface analysis was primarily by Rutherford backscattering spectrometry. Both the ion- beam mixing and the acid pretreatment increased the lifetimes of films, in comparison with the mechanically polished standards. Reductions in charge injection capability, when they occurred, were attributed to loss of Ir from the films, and there was a close correlation between the charge injection density and the Ir inventory. 13 refs., 5 figs.

  19. Synthesis of 2H-Azirines by Iridium-Catalyzed Decarboxylative Ring Contraction of Isoxazol-5(4H)-ones.

    PubMed

    Okamoto, Kazuhiro; Shimbayashi, Takuya; Yoshida, Masato; Nanya, Atsushi; Ohe, Kouichi

    2016-06-13

    A phosphine-free iridium-catalyzed reaction of isoxazol-5(4H)-ones (isoxazolones) has been developed, and affords 2H-azirines through decarboxylation and ring contraction. This method provides an efficient and environmentally benign protocol which could replace the conventional approaches used to synthesize 2H-azirines. PMID:27125870

  20. Dynamic High-temperature Testing of an Iridium Alloy in Compression at High-strain Rates: Dynamic High-temperature Testing

    SciTech Connect

    Song, B.; Nelson, K.; Lipinski, R.; Bignell, J.; Ulrich, G.; George, E. P.

    2014-08-21

    Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-strain -rate performance are needed for understanding high-speed impacts in severe environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain -rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. In our study, we analyzed the difficulties encountered in high-temperature Kolsky bar testing of thin iridium alloy specimens in compression. We made appropriate modifications using the current high-temperature Kolsky bar technique in order to obtain reliable compressive stress–strain response of an iridium alloy at high-strain rates (300–10 000 s-1) and temperatures (750 and 1030°C). The compressive stress–strain response of the iridium alloy showed significant sensitivity to both strain rate and temperature.

  1. Dynamic High-temperature Testing of an Iridium Alloy in Compression at High-strain Rates: Dynamic High-temperature Testing

    DOE PAGES

    Song, B.; Nelson, K.; Lipinski, R.; Bignell, J.; Ulrich, G.; George, E. P.

    2014-08-21

    Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-strain -rate performance are needed for understanding high-speed impacts in severe environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain -rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. In our study, we analyzed the difficulties encountered in high-temperature Kolsky bar testing of thin iridium alloy specimens in compression. We made appropriate modifications using themore » current high-temperature Kolsky bar technique in order to obtain reliable compressive stress–strain response of an iridium alloy at high-strain rates (300–10 000 s-1) and temperatures (750 and 1030°C). The compressive stress–strain response of the iridium alloy showed significant sensitivity to both strain rate and temperature.« less

  2. Synthesis of 2H-Azirines by Iridium-Catalyzed Decarboxylative Ring Contraction of Isoxazol-5(4H)-ones.

    PubMed

    Okamoto, Kazuhiro; Shimbayashi, Takuya; Yoshida, Masato; Nanya, Atsushi; Ohe, Kouichi

    2016-06-13

    A phosphine-free iridium-catalyzed reaction of isoxazol-5(4H)-ones (isoxazolones) has been developed, and affords 2H-azirines through decarboxylation and ring contraction. This method provides an efficient and environmentally benign protocol which could replace the conventional approaches used to synthesize 2H-azirines.

  3. Required treatment margin for coronary endovascular brachytherapy with iridium-192 seed ribbon

    SciTech Connect

    Giap Huan

    2002-03-01

    Purpose: Preliminary clinical trials (SCRIPPS I, WRIST and Gamma 1) employing catheter-based endovascular brachytherapy (EVBT) with iridium-192 (Ir-192) seeds show promising results in reducing restenosis after coronary intervention. Failure analysis of these studies showed a significant number of restenosis at the treatment margin called ''edge effect.'' The objective of this study is to investigate the factors that contribute to the adequacy of treatment margin. Methods and materials: The factors contributing to the margins are penumbra effect at the end of the seed train, uncertainty in target localization, longitudinal seed movement during cardiac cycle and barotrauma due to stent deployment. The magnitudes of the penumbra effect, which refers to the tapering off the prescribed isodose line near the ends of the source train, were calculated for various source lengths of Ir-192 seed ribbon using AAPM TG-43 algorithm. Uncertainty in target localization refers to the fact that the visual estimation of proximal and distal extent of the injury is not accurate, and this can be obtained by comparing the 'estimate' from the interventional cardiologist with careful review of the cine-angiogram. Longitudinal seed movements relative to the coronary vessel during the cardiac cycle were determined by frame-by-frame reviewing cine-angiograms of 30 patients. The proximal and distal source points were measured in reference to branching vessels during the contrast phase of the cine-angiogram. The maximum proximal and distal longitudinal movement was captured and source displacement was measured from the closest proximal and distal branching vessel. Barotrauma, additional injury to the vessel arising from the stent deployment balloon, was obtained by reviewing specifications from commercially available stent delivery systems. Results: The penumbra effect ranges from 3.9 to 4.5 mm for 6-22 Ir-192 seed ribbons. The uncertainty in target localization is within 3 mm for our

  4. Synthesis, structural characterization, and ligand replacement reactions of gem-dithiolato-bridged rhodium and iridium complexes.

    PubMed

    Rivas, Angel B; Gascón, José M; Lahoz, Fernando J; Balana, Ana I; Pardey, Alvaro J; Oro, Luis A; Pérez-Torrente, Jesús J

    2008-07-01

    The reaction of gem-dithiol compounds R 2C(SH) 2 (R = Bn (benzyl), (i) Pr; R 2 = -(CH 2) 4-) with dinuclear rhodium or iridium complexes containing basic ligands such as [M(mu-OH)(cod)] 2 and [M(mu-OMe)(cod)] 2, or the mononuclear [M(acac)(cod)] (M = Rh, Ir, cod = 1,5-cyclooctadiene) in the presence of a external base, afforded the dinuclear complexes [M 2(mu-S 2CR 2)(cod) 2] ( 1- 4). The monodeprotonation of 1,1-dimercaptocyclopentane gave the mononuclear complex [Rh(HS 2Cptn)(cod)] ( 5) that is a precursor for the dinuclear compound [Rh 2(mu-S 2Cptn)(cod) 2] ( 6). Carbonylation of the diolefin compounds gave the complexes [Rh 2(mu-S 2CR 2)(CO) 4] ( 7- 9), which reacted with P-donor ligands to stereoselectively produce the trans isomer of the disubstituted complexes [Rh 2(mu-S 2CR 2)(CO) 2(PR' 3) 2] (R' = Ph, Cy (cyclohexyl)) ( 10- 13) and [Rh 2(mu-S 2CBn 2)(CO) 2{P(OR') 3} 2] (R' = Me, Ph) ( 14- 15). The substitution process in [Rh 2(mu-S 2CBn 2)(CO) 4] ( 7) by P(OMe) 3 has been studied by spectroscopic means and the full series of substituted complexes [Rh 2(mu-S 2CBn 2)(CO) 4- n {P(OR) 3} n ] ( n = 1, 4) has been identified in solution. The cis complex [Rh 2(mu-S 2CBn 2)(CO) 2(mu-dppb)] ( 16) was obtained by reaction of 7 with the diphosphine dppb (1,4-bis(diphenylphosphino)butane). The molecular structures of the diolefinic dinuclear complexes [Rh 2(mu-S 2CR 2)(cod) 2] (R = Bn ( 1), (i) Pr ( 2); R 2 = -(CH 2) 4- ( 6)) and that of the cis complex 16 have been studied by X-ray diffraction. PMID:18507456

  5. Volcanic ash layers in blue ice fields (Beardmore Glacier Area, Antarctica): Iridium enrichments

    NASA Technical Reports Server (NTRS)

    Koeberl, Christian

    1988-01-01

    samples, including Ir. Iridium determinations were made using INAA, with synthetical and natural (meteorite) standards. These findings are discussed.

  6. Synthesis, characterization and chemistry of platinum and iridium nanoparticles in solution and nanoporous silicas

    NASA Astrophysics Data System (ADS)

    Jagassar, Parbatee Samaroo

    This project focuses on the synthesis of catalytically-active, transition-metal nanoparticles, their adsorption into porous Vycor glass (PVG), the removal of the poly(vinylpyrrolidone) (PVP) surfactant employed in their synthesis and their chemistry with Ru(II) diimine complexes. Platinum and iridium nanoparticles with a narrow size distribution were prepared by the alcohol reduction method with poly(vinylpyrrolidone) (PVP) as the size limiting surfactant. PVP/Pt nanoparticles adsorb into PVG and as much as 46 ± 4% of the PVP can be removed without further nanoparticle aggregation. XANES spectra show that removal of the PVP surfactant occurs without oxidation of the Pt nanoparticle. EXAFS of the adsorbed Pt nanoparticles after removal of the PVP yield a Pt-Pt bond length of 2.74 ± 0.01 Å which is slightly shorter than the Pt-Pt bond length measured in Pt foil, 2.78 Å. We have shown that the Pt nanoparticles, both the stripped and the unstripped of PVP in porous Vycor glass, does not influence their reactivity with either the [Ru(bpy)2 dpp]2+ or the [Ru(bpy)2ppz]2+ complexes. The addition of PVP/Pt or PVP/Ir nanoparticles to aqueous-ethanol solutions of [Ru(bpy)2ppz]2+ (ppz denotes 4,7-phenanthro-lino-5:6,5'6'pyrazine) leads to the spontaneous aggregation of the nanoparticles about the complex. A comparison of the aggregation about different Ru(II) diimines indicates aggregation initiates at the heteroleptic ligand. Although initiating at the ppz ligand, continued aggregation of the nanoparticles about the complex dilutes the specificity of the initial interaction leading to larger aggregates of differing shape. TEM analyses of the aggregates indicate the volume occupied by the individual nanoparticles is a small fraction of the total volume of the aggregate suggesting a somewhat open structure interlaced with the solvent. Correlating TEM analyses of the aggregation with the electronic spectra of the solutions reveals a new absorption assigned to the formation

  7. Earth Radiation Imbalance from a Constellation of 66 Iridium Satellites: Climate Science Aspects

    NASA Technical Reports Server (NTRS)

    Wiscombe, W.; Chiu, CJ. Y.

    2012-01-01

    The "global warming hiatus" since the 1998 El Nino, highlighted by Meehl et al., and the resulting "missing energy" problem highlighted by Trenberth et al., has opened the door to a more fundamental view of climate change than mere surface air temperature. That new view is based on two variables which are strongly correlated: the rate of change of ocean heat content d(OHC)/dt; and Earth Radiation Imbalance (ERI) at the top of the atmosphere, whose guesstimated range is 0.4 to 0.9 Watts per square meters (this imbalance being mainly due to increasing CO2). The Argo float array is making better and better measurements of OHC. But existing satellite systems cannot measure ERI to even one significant digit. So, climate model predictions of ERI are used in place of real measurements of it, and the satellite data are tuned to the climate model predictions. Some oceanographers say "just depend on Argo for understanding the global warming hiatus and the missing energy", but we don't think this is a good idea because d(OHC)/dt and ERI have different time scales and are never perfectly correlated. We think the ERB community needs to step up to measuring ERI correctly, just as oceanographers have deployed Argo to measure OHC correctly. This talk will overview a proposed constellation of 66 Earth radiation budget instruments, hosted on Iridium satellites, that will actually be able to measure ERI to at least one significant digit, thus enabling a crucial test of climate models. This constellation will also be able to provide ERI at two-hourly time scales and 500-km spatial scales without extrapolations from uncalibrated narrowband geostationary instruments, using the highly successful methods of GRACE to obtain spatial resolution. This high time resolution would make ERI a synoptic variable like temperature, and allow studies of ERI's response to fast-evolving phenomena like dust storms and hurricanes and even brief excursions of Total Solar Irradiance. Time permitting, we

  8. Hybrid isotope separation scheme

    DOEpatents

    Maya, Jakob

    1991-01-01

    A method of yielding selectively a desired enrichment in a specific isotope including the steps of inputting into a spinning chamber a gas from which a scavenger, radiating the gas with a wave length or frequency characteristic of the absorption of a particular isotope of the atomic or molecular gas, thereby inducing a photochemical reaction between the scavenger, and collecting the specific isotope-containing chemical by using a recombination surface or by a scooping apparatus.

  9. Hybrid isotope separation scheme

    DOEpatents

    Maya, J.

    1991-06-18

    A method is described for yielding selectively a desired enrichment in a specific isotope including the steps of inputting into a spinning chamber a gas from which a scavenger, radiating the gas with a wave length or frequency characteristic of the absorption of a particular isotope of the atomic or molecular gas, thereby inducing a photochemical reaction between the scavenger, and collecting the specific isotope-containing chemical by using a recombination surface or by a scooping apparatus. 2 figures.

  10. HYDROGEN ISOTOPE TARGETS

    DOEpatents

    Ashley, R.W.

    1958-08-12

    The design of targets for use in the investigation of nuclear reactions of hydrogen isotopes by bombardment with accelerated particles is described. The target con struction eomprises a backing disc of a metal selected from the group consisting of molybdenunn and tungsten, a eoating of condensed titaniunn on the dise, and a hydrogen isotope selected from the group consisting of deuterium and tritium absorbed in the coatiag. The proeess for preparing these hydrogen isotope targets is described.

  11. PRINCIPAL ISOTOPE SELECTION REPORT

    SciTech Connect

    K. D. Wright

    1998-08-28

    Utilizing nuclear fuel to produce power in commercial reactors results in the production of hundreds of fission product and transuranic isotopes in the spent nuclear fuel (SNF). When the SNF is disposed of in a repository, the criticality analyses could consider all of the isotopes, some principal isotopes affecting criticality, or none of the isotopes, other than the initial loading. The selected set of principal isotopes will be the ones used in criticality analyses of the SNF to evaluate the reactivity of the fuel/waste package composition and configuration. This technical document discusses the process used to select the principal isotopes and the possible affect that these isotopes could have on criticality in the SNF. The objective of this technical document is to discuss the process used to select the principal isotopes for disposal criticality evaluations with commercial SNF. The principal isotopes will be used as supporting information in the ''Disposal Criticality Analysis Methodology Topical Report'' which will be presented to the United States Nuclear Regulatory Commission (NRC) when approved by the United States Department of Energy (DOE) Office of Civilian Radioactive Waste Management (OCRWM).

  12. Isotopically engineered semiconductors

    NASA Astrophysics Data System (ADS)

    Haller, E. E.

    1995-04-01

    Scientific interest, technological promise, and increased availability of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This review of mostly recent activities begins with an introduction to some past classical experiments which have been performed on isotopically controlled semiconductors. A review of the natural isotopic composition of the relevant elements follows. Some materials aspects resulting in part from the high costs of enriched isotopes are discussed next. Raman spectroscopy studies with a number of isotopically pure and deliberately mixed Ge bulk crystals show that the Brillouin-zone-center optical phonons are not localized. Their lifetime is almost independent of isotopic disorder, leading to homogeneous Raman line broadening. Studies with short period isotope superlattices consisting of alternating layers of n atomic planes of 70Ge and 74Ge reveal a host of zone-center phonons due to Brillouin-zone folding. At n≳40 one observes two phonon lines at frequencies corresponding to the bulk values of the two isotopes. In natural diamond, isotope scattering of the low-energy phonons, which are responsible for the thermal conductivity, is very strongly affected by small isotope disorder. Isotopically pure 12C diamond crystals exhibit thermal conductivities as high as 410 W cm-1 K-1 at 104 K, leading to projected values of over 2000 W cm-1 K-1 near 80 K. The changes in phonon properties with isotopic composition also weakly affect the electronic band structures and the lattice constants. The latter isotope dependence is most relevant for future standards of length based on crystal lattice constants. Capture of thermal neutrons by isotope nuclei followed by nuclear decay produces new elements, resulting in a very large number of possibilities for isotope selective doping of semiconductors. This neutron transmutation of isotope nuclei, already used

  13. Photochemistry of Dihydrido(hydrotris(3,5-dimethylpyrazolyl)borato)(Z-cyclooctene)iridium. Synthetic Intermediates and Mechanism of the Photochemical Formation of Hydridophenyl(hydrotris(3,5-dimethylpyrazolyl)borato)(trimethyl phosphite)iridium.

    PubMed

    Ferrari, Arlen; Polo, Eleonora; Rüegger, Heinz; Sostero, Silvana; Venanzi, Luigi M.

    1996-03-13

    The photolysis of a benzene solution of [Tp(Me2)IrH(2)(COE)], 1 (Tp(Me2) = hydrotris(3,5-dimethylpyrazolyl)borate, COE = Z-cyclooctene), in the presence of P(OMe)(3), gives the stable novel complex [Tp(Me2)IrH(C(6)H(5))(P(OMe)(3))], 3a. The photochemical syntheses of [Tp(Me2)IrH(2)(P(OMe)(3))], from 1 and P(OMe)(3) in diethyl ether, and [Tp(Me2)IrH(2)(CH(2)=CHCOO(t)Bu)], from 1 in tert-butyl acrylate, are also reported. The above reactions and several experiments using C(6)D(6) and P(OCD(3))(3) show that, in all cases, the primary photoproduct is the 16-electron, five-coordinate iridium(III) intermediate {Tp(Me2)IrH(2)}, 6a, produced by loss of COE from 1. The above experiments also allow the postulation of a mechanistic pathway for the formation of 3a which involves the oxidative addition of an aromatic C-H bond by 6a. Furthemore, the photochemical reaction of 1 in the presence of P(OCD(3))(3) shows that, under the reaction conditions used, oxidative addition of C-H bonds of P(OMe)(3) and of coordinated Tp(Me2)-ligands, presumably, to the intermediates 6a and {Tp(Me2)IrH(C(6)H(5))}, also occurs. Thus, coordinatively unsaturated iridium(III) species readily activate C-H bonds.

  14. Intracellular Cadmium Isotope Fractionation

    NASA Astrophysics Data System (ADS)

    Horner, T. J.; Lee, R. B.; Henderson, G. M.; Rickaby, R. E.

    2011-12-01

    Recent stable isotope studies into the biological utilization of transition metals (e.g. Cu, Fe, Zn, Cd) suggest several stepwise cellular processes can fractionate isotopes in both culture and nature. However, the determination of fractionation factors is often unsatisfactory, as significant variability can exist - even between different organisms with the same cellular functions. Thus, it has not been possible to adequately understand the source and mechanisms of metal isotopic fractionation. In order to address this problem, we investigated the biological fractionation of Cd isotopes within genetically-modified bacteria (E. coli). There is currently only one known biological use or requirement of Cd, a Cd/Zn carbonic anhydrase (CdCA, from the marine diatom T. weissfloggii), which we introduce into the E. coli genome. We have also developed a cleaning procedure that allows for the treating of bacteria so as to study the isotopic composition of different cellular components. We find that whole cells always exhibit a preference for uptake of the lighter isotopes of Cd. Notably, whole cells appear to have a similar Cd isotopic composition regardless of the expression of CdCA within the E. coli. However, isotopic fractionation can occur within the genetically modified E. coli during Cd use, such that Cd bound in CdCA can display a distinct isotopic composition compared to the cell as a whole. Thus, the externally observed fractionation is independent of the internal uses of Cd, with the largest Cd isotope fractionation occurring during cross-membrane transport. A general implication of these experiments is that trace metal isotopic fractionation most likely reflects metal transport into biological cells (either actively or passively), rather than relating to expression of specific physiological function and genetic expression of different metalloenzymes.

  15. Discovery of the krypton isotopes

    SciTech Connect

    Heim, M.; Fritsch, A.; Schuh, A.; Shore, A.; Thoennessen, M.

    2010-07-15

    Thirty-two krypton isotopes have been observed so far and the discovery of these isotopes is discussed here. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  16. Iridium Cyclometalated Complexes in Host-Guest Chemistry: A Strategy for Maximizing Quantum Yield in Aqueous Media.

    PubMed

    Alrawashdeh, Lubna R; Cronin, Michael P; Woodward, Clifford E; Day, Anthony I; Wallace, Lynne

    2016-07-01

    The weaker emission typically seen for iridium(III) cyclometalated complexes in aqueous medium can be reversed via encapsulation in cucurbit[10]uril (Q[10]). The Q[10] cavity is shown to effectively maximize quantum yields for the complexes, compared to any other medium. This may provide significant advantages for a number of sensor applications. NMR studies show that the complexes are accommodated similarly within the host molecule, even with cationic substituents attached to the ppy ligands, indicating that the hydrophobic effect is the dominant driving force for binding. Cavity-encapsulated 1:1 host-guest species dominate the emission, but 1:2 species are also indicated, which also give some enhancement of intensity. Results demonstrate that the enhancement is due primarily to much lower rates of nonradiative decay but also suggest that the encapsulation can cause a change in character of the emitting state.

  17. Hydrogen Photogeneration Promoted by Efficient Electron Transfer from Iridium Sensitizers to Colloidal MoS2 Catalysts

    NASA Astrophysics Data System (ADS)

    Yuan, Yong-Jun; Yu, Zhen-Tao; Liu, Xiao-Jie; Cai, Jian-Guang; Guan, Zhong-Jie; Zou, Zhi-Gang

    2014-02-01

    We report the utilization of colloidal MoS2 nanoparticles (NPs) for multicomponent photocatalytic water reduction systems in cooperation with a series of cyclometalated Ir(III) sensitizers. The effects of the particle size and particle dispersion of MoS2 NPs catalyst, reaction solvent and the concentration of the components on hydrogen evolution efficiency were investigated. The MoS2 NPs exhibited higher catalytic performance than did other commonly used water reduction catalysts under identical experiment conditions. The introduction of the carboxylate anchoring groups in the iridium complexes allows the species to be favorably chem-adsorbed onto the MoS2 NPs surface to increase the electron transfer, resulting in enhancement of hydrogen evolution relative to the non-attached systems. The highest apparent quantum yield, which was as high as 12.4%, for hydrogen evolution, was obtained (λ = 400 nm).

  18. Iridium Short Burst Data: Two-Way, Robust, Reliable, Low Power Communications for Oceanographic Data Transmission Applications

    NASA Astrophysics Data System (ADS)

    Roggenstein, E. B.; Hensley, W.

    2011-12-01

    Over the past two hundred years, water level observations in coastal areas have been used to help mariners navigate oceans and estuaries, cartographers develop nautical charts, government agencies regulate boundaries, and scientists gain a better understanding of various physical processes in the ocean. As technology has progressed the latency in providing these data to the user has been reduced. The National Oceanic and Atmospheric Administration's (NOAA) Center for Operational Oceanographic Products and Services (CO-OPS) provides near real-time oceanographic and meteorological data to support navigation, coastal managers, and storm surge and tsunami warning programs. CO-OPS maintains the National Water Level Observation Network (NWLON), a system of over 200 stations for the coastal United States, Great Lakes, Caribbean islands, and Pacific island territories. CO-OPS also supports the NOAA Physical Oceanographic Real Time Systems° (PORTS), which are currently operating in 21 US ports. With an expanding role in Arctic and Alaska support, CO-OPS has identified a need for a robust and reliable data communications pathway to supplement the existing Geostationary Operational Environmental Systems (GOES) network, which has limitations at high latitudes. Iridium satellite Short Burst Data (SBD) services offer a global coverage, including remote Arctic regions outside of GOES coverage. Previous testing conducted by CO-OPS has shown a great potential for the SBD service including continuous near-real-time 6 minute data transmissions from two CO-OPS test water level stations located in Guam, with >99.9% data return. Also, successful transmissions of hourly wave statistics were demonstrated with a with a test system that employed a Nortek Acoustic Wave and Current (AWAC) instrument in Chesapeake Bay were accomplished. Data transmissions involved a buoy-mounted SIM-less SBD modem. Independent of location, data can be transmitted from a remote instrument platform to Iridium

  19. Hydrogen Photogeneration Promoted by Efficient Electron Transfer from Iridium Sensitizers to Colloidal MoS2 Catalysts

    PubMed Central

    Yuan, Yong-Jun; Yu, Zhen-Tao; Liu, Xiao-Jie; Cai, Jian-Guang; Guan, Zhong-Jie; Zou, Zhi-Gang

    2014-01-01

    We report the utilization of colloidal MoS2 nanoparticles (NPs) for multicomponent photocatalytic water reduction systems in cooperation with a series of cyclometalated Ir(III) sensitizers. The effects of the particle size and particle dispersion of MoS2 NPs catalyst, reaction solvent and the concentration of the components on hydrogen evolution efficiency were investigated. The MoS2 NPs exhibited higher catalytic performance than did other commonly used water reduction catalysts under identical experiment conditions. The introduction of the carboxylate anchoring groups in the iridium complexes allows the species to be favorably chem-adsorbed onto the MoS2 NPs surface to increase the electron transfer, resulting in enhancement of hydrogen evolution relative to the non-attached systems. The highest apparent quantum yield, which was as high as 12.4%, for hydrogen evolution, was obtained (λ = 400 nm). PMID:24509729

  20. Iridium Cyclometalated Complexes in Host-Guest Chemistry: A Strategy for Maximizing Quantum Yield in Aqueous Media.

    PubMed

    Alrawashdeh, Lubna R; Cronin, Michael P; Woodward, Clifford E; Day, Anthony I; Wallace, Lynne

    2016-07-01

    The weaker emission typically seen for iridium(III) cyclometalated complexes in aqueous medium can be reversed via encapsulation in cucurbit[10]uril (Q[10]). The Q[10] cavity is shown to effectively maximize quantum yields for the complexes, compared to any other medium. This may provide significant advantages for a number of sensor applications. NMR studies show that the complexes are accommodated similarly within the host molecule, even with cationic substituents attached to the ppy ligands, indicating that the hydrophobic effect is the dominant driving force for binding. Cavity-encapsulated 1:1 host-guest species dominate the emission, but 1:2 species are also indicated, which also give some enhancement of intensity. Results demonstrate that the enhancement is due primarily to much lower rates of nonradiative decay but also suggest that the encapsulation can cause a change in character of the emitting state. PMID:27315543

  1. Stepwise versus pseudo-concerted two-electron-transfer in a triarylamine-iridium dipyrrin-naphthalene diimide triad.

    PubMed

    Klein, Johannes H; Sunderland, Travis L; Kaufmann, Christina; Holzapfel, Marco; Schmiedel, Alexander; Lambert, Christoph

    2013-10-14

    A triad based on triarylamine donors, an iridium dipyrrin sensitiser and a naphthalene diimide acceptor is investigated using fs-pump-probe spectroscopy at two different pump wavelengths. Excitation of the naphthalene diimide induces a stepwise electron transfer process that yields within ca. 100 ps a charge separated state with 50-60% quantum yield in which one triarylamine is oxidised and the imide is reduced. Although being in the Marcus normal region, this state has a lifetime of 580 ns in MeCN. Excitation at the dipyrrin ligand centred absorption directly produces the charge separated state within ca. 1 ns however without formation of an intermediate. This pseudo-concerted two-electron transfer step was analysed with the help of a model dyad and a modified triad and is interpreted to be caused by inverted electron transfer rates. Although being much slower the latter process has a quantum yield of practically 100%. PMID:23959428

  2. The use of organolithium reagents for the synthesis of 4-aryl-2-phenylpyridines and their corresponding iridium(iii) complexes.

    PubMed

    Davidson, Ross; Hsu, Yu-Ting; Batchelor, Thomas; Yufit, Dmitry; Beeby, Andrew

    2016-07-28

    A versatile palladium-free route for the synthesis of 4-aryl-substituted phenylpyridines (ppy), starting from tert-butyl 4-oxopiperidine-1-carboxylate, is reported. Reaction with an aryllithium, followed by trifluoroacetic acid dehydration/deprotection and oxidation with 2-iodoylbenzoic acid and finally phenylation, gave 4 ligands (L(1-4)H): 2,4-diphenylpyridine, 4-(4-methoxyphenyl)-2-phenylpyridine, 2-phenyl-4-(o-tolyl)pyridine and 4-mesityl-2-phenylpyridine. These ligands were coordinated to iridium to give the corresponding Ir(L)2(A) complexes (Ir1-7), where A = ancillary ligand acetylacetate or 2-picolinate. This was used to demonstrate that, through a combination of ancillary ligand choice and torsional twisting between the 4-aryl substituents of the ppy ligands, it is possible to tune the phosphorescent emission of the complexes in the range 502-560 nm. PMID:27346376

  3. Luminescent Rhenium(I) and Iridium(III) Polypyridine Complexes as Biological Probes, Imaging Reagents, and Photocytotoxic Agents.

    PubMed

    Lo, Kenneth Kam-Wing

    2015-12-15

    Although the interactions of transition metal complexes with biological molecules have been extensively studied, the use of luminescent transition metal complexes as intracellular sensors and bioimaging reagents has not been a focus of research until recently. The main advantages of luminescent transition metal complexes are their high photostability, long-lived phosphorescence that allows time-resolved detection, and large Stokes shifts that can minimize the possible self-quenching effect. Also, by the use of transition metal complexes, the degree of cellular uptake can be readily determined using inductively coupled plasma mass spectrometry. For more than a decade, we have been interested in the development of luminescent transition metal complexes as covalent labels and noncovalent probes for biological molecules. We argue that many transition metal polypyridine complexes display triplet charge transfer ((3)CT) emission that is highly sensitive to the local environment of the complexes. Hence, the biological labeling and binding interactions can be readily reflected by changes in the photophysical properties of the complexes. In this laboratory, we have modified luminescent tricarbonylrhenium(I) and bis-cyclometalated iridium(III) polypyridine complexes of general formula [Re(bpy-R(1))(CO)3(py-R(2))](+) and [Ir(ppy-R(3))2(bpy-R(4))](+), respectively, with reactive functional groups and used them to label the amine and sulfhydryl groups of biomolecules such as oligonucleotides, amino acids, peptides, and proteins. Additionally, using a range of biological substrates such as biotin, estradiol, and indole, we have designed luminescent rhenium(I) and iridium(III) polypyridine complexes as noncovalent probes for biological receptors. The interesting results generated from these studies have prompted us to investigate the possible applications of luminescent transition metal complexes in intracellular systems. Thus, in the past few years, we have developed an interest

  4. Safety of /sup 125/iodine and /sup 192/iridium implants to the canine carotid artery: preliminary report

    SciTech Connect

    Fee, W.E. Jr.; Goffinet, D.R.; Guthaner, D.; Fajardo, L.F.; Handen, C.

    1985-03-01

    Thirty-nine healthy dogs underwent a simulated radical neck dissection followed by implantation of either /sup 125/Iodine or /sup 192/Iridium in various dose regimes randomized prospectively from 3,000 to 30,000 rad. Bilateral selective carotid angiography was performed immediately postoperatively and at six months and one year. No significant effects occurred to the animals who received 15,000 rad /sup 125/I or 6,000 rad /sup 192/Ir. In the higher dosed animals the /sup 125/I treated group fared better than the /sup 192/Ir treated group, probably due to the lower dose rate delivery. All surviving animals will be maintained an additional year to determine the late effects of brachytherapy irradiation to the carotid artery.

  5. Selective iridium-catalyzed alkylation of (hetero)aromatic amines and diamines with alcohols under mild reaction conditions.

    PubMed

    Blank, Benoît; Michlik, Stefan; Kempe, Rhett

    2009-01-01

    A P,N-ligand-coordinated iridium complex has been employed as an efficient catalyst for the selective monoalkylation of (hetero)aromatic amines with alcohols. A significant improvement of this alkylation method has been achieved, such that it can be performed at a temperature of 70 degrees C and with catalyst loadings as low as 0.1 mol % Ir, while still affording excellent yields of secondary amines. Furthermore, the high selectivity of this catalyst for the monoalkylation of aromatic amino functions has been successfully exploited for the alkylation of diamines in both symmetric and nonsymmetric fashions, providing a novel and very efficient synthetic tool for the preparation of N,N'-dialkylated aromatic diamines.

  6. Detecting isotopic ratio outliers

    SciTech Connect

    Bayne, C.K.; Smith, D.H.

    1985-01-01

    An alternative method is proposed for improving isotopic ratio estimates. This method mathematically models pulse-count data and uses iterative reweighted Poisson regression to estimate model parameters to calculate the isotopic ratios. This computer-oriented approach provides theoretically better methods than conventional techniques to establish error limits and to identify outliers. 6 refs., 3 figs., 3 tabs.

  7. (Carbon isotope fractionation inplants)

    SciTech Connect

    O'Leary, M.H.

    1990-01-01

    The objectives of this research are: To develop a theoretical and experimental framework for understanding isotope fractionations in plants; and to develop methods for using this isotope fractionation for understanding the dynamics of CO{sub 2} fixation in plants. Progress is described.

  8. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a...,” and “osmium,” or any abbreviation to mark or describe all or part of an industry product if such... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  9. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a...,” and “osmium,” or any abbreviation to mark or describe all or part of an industry product if such... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  10. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a...,” and “osmium,” or any abbreviation to mark or describe all or part of an industry product if such... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  11. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a...,” and “osmium,” or any abbreviation to mark or describe all or part of an industry product if such... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  12. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a...,” and “osmium,” or any abbreviation to mark or describe all or part of an industry product if such... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  13. Absorbed dose simulations in near-surface regions using high dose rate Iridium-192 sources applied for brachytherapy

    NASA Astrophysics Data System (ADS)

    Moura, E. S.; Zeituni, C. A.; Sakuraba, R. K.; Gonçalves, V. D.; Cruz, J. C.; Júnior, D. K.; Souza, C. D.; Rostelato, M. E. C. M.

    2014-02-01

    Brachytherapy treatment with Iridium-192 high dose rate (HDR) sources is widely used for various tumours and it could be developed in many anatomic regions. Iridium-192 sources are inserted inside or close to the region that will be treated. Usually, the treatment is performed in prostate, gynaecological, lung, breast and oral cavity regions for a better clinical dose coverage compared with other techniques, such as, high energy photons and Cobalt-60 machines. This work will evaluate absorbed dose distributions in near-surface regions around Ir-192 HDR sources. Near-surface dose measurements are a complex task, due to the contribution of beta particles in the near-surface regions. These dose distributions should be useful for non-tumour treatments, such as keloids, and other non-intracavitary technique. For the absorbed dose distribution simulations the Monte Carlo code PENELOPE with the general code penEasy was used. Ir-192 source geometry and a Polymethylmethacrylate (PMMA) tube, for beta particles shield were modelled to yield the percentage depth dose (PDD) on a cubic water phantom. Absorbed dose simulations were realized at the central axis to yield the Ir-192 dose fall-off along central axis. The results showed that more than 99.2% of the absorbed doses (relative to the surface) are deposited in 5 cm depth but with slower rate at higher distances. Near-surface treatments with Ir-192 HDR sources yields achievable measurements and with proper clinical technique and accessories should apply as an alternative for treatment of lesions where only beta sources were used.

  14. Red- and green-emitting iridium(III) complexes for a dual barometric and temperature-sensitive paint.

    PubMed

    Fischer, Lorenz H; Stich, Matthias I J; Wolfbeis, Otto S; Tian, Nan; Holder, Elisabeth; Schäferling, Michael

    2009-10-19

    A new dual luminescent sensitive paint for barometric pressure and temperature (T) is presented. The green-emitting iridium(III) complex [Ir(ppy)(2)(carbac)] (ppy=2-phenylpyridine; carbac=1-(9H-carbazol-9-yl)-5,5-dimethylhexane-2,4-dione) was applied as a novel probe for T along with the red-emitting complex [Ir(btpy)(3)], (btpy=2-(benzo[b]thiophene-2-yl)pyridine) which functions as a barometric (in fact oxygen-sensitive) probe. Both iridium complexes were dissolved in different polymer materials to achieve optimal responses. The probe [Ir(ppy)(2)(carbac)] was dispersed in gas-blocking poly(acrylonitrile) microparticles in order to suppress any quenching of its luminescence by oxygen. The barometric probe [Ir(btpy)(3)], in turn, was incorporated in a cellulose acetate butyrate film which exhibits good permeability for oxygen. The effects of temperature on the response of the oxygen probe can be corrected by simultaneous optical determination of T, as the poly(acrylonitrile) microparticles containing the temperature indicator are incorporated into the film. The phosphorescent signals of the probes for T and barometric pressure, respectively, can be separated by optical filters due to the approximately 75 nm difference in their emission maxima. The dual sensor is applicable to luminescence lifetime imaging of T and barometric pressure. It is the first luminescent dual sensor material for barometric pressure/T based exclusively on the use of Ir(III) complexes in combination with luminescence lifetime imaging.

  15. Possible world-wide middle miocene iridium anomaly and its relationship to periodicity of impacts and extinctions

    NASA Technical Reports Server (NTRS)

    Asaro, F.; Alvarez, W.; Michel, H. V.; Alvarez, L. W.; Anders, Mark H.; Montanari, A.; Kennett, James P.

    1988-01-01

    In a study of one million years of Middle Miocene sediment deposition in ODP Hole 689B in the Weddell Sea near Antarctica, a single iridium (Ir) anomaly of 44 (+ or - 10) x 10 to the 12th gram Ir per gram rock (ppt) was observed in core 6H, section 3, 50 to 60 cm, after background contributions associated with manganese precipitates and clay are subtracted. The ODP Hole 689B is 10,000 km away from another site, DSDP Hole 588B in the Tasman Sea north of New Zealand, where a single Ir anomaly of 144 + or - 7 ppt over a background of 11 ppt was found in an earlier study of 3 million years of deposition. From chemical measurements the latter deposition was thought to be impact-related. Ir measurements were made, following neutron activation, with the Iridium Coincidence Spectrometer. The age vs depth calibration curves given in the DSDP and ODP preliminary reports indicate the ages of the Iranomalies are identical, 11.7 million years, but the absolute and relative uncertainties in the curves are not known. Based on the newest age data the age estimate is 10 million years. As the Ir was deposited at the two sites at about the same time and they are one quarter of the way around the world from each other it seems likely that the deposition was world-wide. The impact of a large asteroid or comet could produce the wide distribution, and this data is supportive of the impact relationship deduced for Deep Sea Drilling Project (DSDP) 588B from the chemical evidence. If the surface densities of Ir at the two sites are representative of the world-wide average, the diameter of a Cl type asteroid containing the necessary Ir would be 3 + or - 1 km, which is large enough to cause world-wide darkness and hence extinctions although the latter point is disputed.

  16. Laser isotope separation

    DOEpatents

    Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Boyer, Keith; Greiner, Norman R.

    1988-01-01

    A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.

  17. Photochemical isotope separation

    DOEpatents

    Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Greiner, Norman R.; Boyer, Keith

    1987-01-01

    A process for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium.

  18. Photochemical isotope separation

    DOEpatents

    Robinson, C.P.; Jensen, R.J.; Cotter, T.P.; Greiner, N.R.; Boyer, K.

    1987-04-28

    A process is described for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium. 8 figs.

  19. Laser isotope separation

    DOEpatents

    Robinson, C.P.; Reed, J.J.; Cotter, T.P.; Boyer, K.; Greiner, N.R.

    1975-11-26

    A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light is described. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.

  20. Meteoritic Sulfur Isotopic Analysis

    NASA Technical Reports Server (NTRS)

    Thiemens, Mark H.

    1996-01-01

    Funds were requested to continue our program in meteoritic sulfur isotopic analysis. We have recently detected a potential nucleosynthetic sulfur isotopic anomaly. We will search for potential carriers. The documentation of bulk systematics and the possible relation to nebular chemistry and oxygen isotopes will be explored. Analytical techniques for delta(sup 33), delta(sup 34)S, delta(sup 36)S isotopic analysis were improved. Analysis of sub milligram samples is now possible. A possible relation between sulfur isotopes and oxygen was detected, with similar group systematics noted, particularly in the case of aubrites, ureilites and entstatite chondrites. A possible nucleosynthetic excess S-33 has been noted in bulk ureilites and an oldhamite separate from Norton County. High energy proton (approximately 1 GeV) bombardments of iron foils were done to experimentally determine S-33, S-36 spallogenic yields for quantitation of isotopic measurements in iron meteorites. Techniques for measurement of mineral separates were perfected and an analysis program initiated. The systematic behavior of bulk sulfur isotopes will continue to be explored.

  1. Isotopically controlled semiconductors

    SciTech Connect

    Haller, Eugene E.

    2006-06-19

    The following article is an edited transcript based on the Turnbull Lecture given by Eugene E. Haller at the 2005 Materials Research Society Fall Meeting in Boston on November 29, 2005. The David Turnbull Lectureship is awarded to recognize the career of a scientist who has made outstanding contributions to understanding materials phenomena and properties through research, writing, and lecturing, as exemplified by the life work of David Turnbull. Haller was named the 2005 David Turnbull Lecturer for his 'pioneering achievements and leadership in establishing the field of isotopically engineered semiconductors; for outstanding contributions to materials growth, doping and diffusion; and for excellence in lecturing, writing, and fostering international collaborations'. The scientific interest, increased availability, and technological promise of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This article reviews results obtained with isotopically controlled semiconductor bulk and thin-film heterostructures. Isotopic composition affects several properties such as phonon energies, band structure, and lattice constant in subtle, but, for their physical understanding, significant ways. Large isotope-related effects are observed for thermal conductivity in local vibrational modes of impurities and after neutron transmutation doping. Spectacularly sharp photoluminescence lines have been observed in ultrapure, isotopically enriched silicon crystals. Isotope multilayer structures are especially well suited for simultaneous self- and dopant-diffusion studies. The absence of any chemical, mechanical, or electrical driving forces makes possible the study of an ideal random-walk problem. Isotopically controlled semiconductors may find applications in quantum computing, nanoscience, and spintronics.

  2. ISOTOPE SEPARATING APPARATUS

    DOEpatents

    Kudravetz, M.K.; Greene, H.B.

    1958-09-16

    This patent relates to control systems for a calutron and, in particular, describes an electro-mechanical system for interrupting the collection of charged particles when the ratio between the two isotopes being receivcd deviates from a predetermined value. One embodiment of the invention includes means responsive to the ratio between two isotopes being received for opening a normally closed shutter over the receiver entrance when the isotope ratio is the desired value. In another form of the invention the collection operation is interrupted by changing the beam accelerating voltage to deflect the ion beam away from the receiver.

  3. Carbon isotope techniques

    SciTech Connect

    Coleman, D.C. ); Fry, B. )

    1991-01-01

    This book is a hands-on introduction to using carbon isotope tracers in experimental biology and ecology. It is a bench-top reference with protocols for the study of plants, animals, and soils. The {sup 11}C, {sup 12}C, {sup 13}C, and {sup 14}C carbon isotopes are considered and standard techniques are described by established authors. The compilation includes the following features: specific, well-established, user-oriented techniques; carbon cycles in plants, animals, soils, air, and water; isotopes in ecological research; examples and sample calculations.

  4. New iridium catalysts for the selective alkylation of amines by alcohols under mild conditions and for the synthesis of quinolines by acceptor-less dehydrogenative condensation.

    PubMed

    Ruch, Susanne; Irrgang, Torsten; Kempe, Rhett

    2014-10-01

    A novel family of iridium catalysts stabilised by P,N-ligands have been introduced. The ligands are based on imidazo[1,5-b]pyridazin-7-amines and can be synthesised with a broad variety of substitution patterns. The catalysts were synthesised quantitatively from the protonated ligands and a commercially available iridium precursor. The catalysts mediate the alkylation of amines by alcohols under mild conditions (70 °C). In addition, the synthesis of quinolines from secondary or primary alcohols and amino alcohols is reported. This sustainable synthesis proceeds through the liberation of two equivalents of water and two equivalents of dihydrogen. The investigations indicate that catalysts suitable for hydrogen autotransfer or borrowing hydrogen chemistry might also be suitable for acceptor-less dehydrogenative condensation reactions. PMID:25186522

  5. A Label-Free Luminescent Switch-On Assay for ATP Using a G-Quadruplex-Selective Iridium(III) Complex

    PubMed Central

    Wang, Modi; Mak, Tsun-Yin; Chan, Daniel Shiu-Hin; Tang, Fung-Kit; Leung, Chung-Hang; Kwan, Hiu-Yee; Yu, Zhiling; Ma, Dik-Lung

    2013-01-01

    We report herein the G-quadruplex-selective property of a luminescent cyclometallated iridium(III) complex for the detection of adenosine-5′-triphosphate (ATP) in aqueous solution. The ATP-binding aptamer was employed as the ATP recognition unit, while the iridium(III) complex was used to monitor the formation of the G-quadruplex structure induced by ATP. The sensitivity and fold enhancement of the assay were higher than those of the previously reported assay using the organic dye crystal violet as a fluorescent probe. This label-free luminescent switch-on assay exhibits high sensitivity and selectivity towards ATP with a limit of detection of 2.5 µM. PMID:24204723

  6. Regioselective borylation of porphyrins by C-H bond activation under iridium catalysis to afford useful building blocks for porphyrin assemblies.

    PubMed

    Hata, Hiroshi; Yamaguchi, Shigeru; Mori, Goro; Nakazono, Satomi; Katoh, Taisuke; Takatsu, Keishi; Hiroto, Satoru; Shinokubo, Hiroshi; Osuka, Atsuhiro

    2007-07-01

    Highly regioselective and efficient borylation of a variety of porphyrins has been achieved by reaction with bis(pinacolato)diboron through C-H bond activation under iridium catalysis on the basis of the synthetic protocol developed by Miyaura, Hartwig, and Smith. A boryl group can be selectively introduced at sterically uncongested positions in the peripheral aryl groups of porphyrin substrates whose peripheral beta-positions are sterically hindered. Curiously, beta substituents adjacent to the aryl group to be borylated have unexpectedly large effects on the regioselectivity, because the iridium catalyst can discriminate between subtle steric differences. Chemoselective borylation was also achieved for several functionalized porphyrins. This borylation protocol can be applied to various monomeric and oligomeric functional porphyrins, hence offering an efficient route to elaborate multiporphyrin-based molecular constructs.

  7. Osmium Isotopic Composition of the K/T Boundary Sediments from Sumbar: A Progress Report

    NASA Astrophysics Data System (ADS)

    Meisel, T.; Krahenbuhl, U.; Nazarov, M. A.

    1993-07-01

    Osmium isotope measurements have been performed on the boundary clay at different Cretaceous-Tertiary boundary (KTB) sites [1-5] since [6] suggested that Os isotopes are an indicator of an extraterrestrial component. The debate over "impact vs. volcanic" could not be resolved, but an isotope ratio close to chondritic could be demonstrated. The study of the distribution of iridium in the stratigraphy of the KTB cannot distinguish the contribution of chondritic and/or terrestrial Ir respectively, whereas the Os isotopes allow us to better constrain a mixing model. The ^187Os/^186Os ratio of the continental crust and chondritic reservoirs differ by at least 10-30 times. Assuming certain parameters, we should be able to calculate the proportion of the reservoirs making up the sediments of the KTB section. We studied a complete section of the KTB of Sumbar, Turkmenistan [7], for its Os isotopic composition. In the section 0-30 cm above the boundary clay, the ^187Os/^186Os ratio increases from 1.15 to 1.47, whereas the Ir concentration decreases from 66 to 1.4 ng/g or 66 to 4.7 ng/g on a carbonate-free basis respectively. Calculations show that the chondritic component makes up 9% at the boundary layer and decreases down to 0.6% at +30 cm. The data cannot be simply explained by varying admixtures of a chondritic component to a sediment of constant Os concentration and isotopic signature. To explain the Os ratios completely it is necessary to consider a mixture of four components (extraterrestrial, ejecta material, local terrigeneous, and carbonacous sediments) with certain assumptions: (1) The extraterrestrial source is chondritic in its Os and Re content and has an initial Os isotope ratio of 1.12 at 65 Ma (time of impact), which is above the average for normal chondrites but is within the range measured so far (e.g., Murray). (2) The ejecta material has a higher Os concentration (0.2 ng/g) than the sediments and is only present in the first 5 cm of the sequence above

  8. Dramatic Enhancement of Power Conversion Efficiency in Polymer Solar Cells by Conjugating Very Low Ratio of Triplet Iridium Complexes to PTB7.

    PubMed

    Qian, Min; Zhang, Ran; Hao, Jingyu; Zhang, Wenjun; Zhang, Qin; Wang, Jianpu; Tao, Youtian; Chen, Shufen; Fang, Junfeng; Huang, Wei

    2015-06-17

    Various low ratios of triplet iridium complexes (0, 0.5, 1, 1.5, 2.5, and 5 mol%) are conjugated to the backbone of the famous champion donor polymer PTB7. At the same conditions, the power conversion efficiency for polymer containing 1% of Ir increases by 45%, 39%, and 31% in three batches of devices compared with control Ir-free PTB7.

  9. Conversion of carbohydrate biomass to γ-valerolactone by using water-soluble and reusable iridium complexes in acidic aqueous media.

    PubMed

    Deng, Jin; Wang, Yan; Pan, Tao; Xu, Qing; Guo, Qing-Xiang; Fu, Yao

    2013-07-01

    Mild-mannered manipulation: A catalytic method for the conversion of carbohydrate biomass to γ-valerolactone in acidic aqueous media has been developed. The water-soluble iridium complexes were observed to be extremely catalytically active for providing γ-valerolactone in high yields with high TONs. The homogeneous catalysts can also be recycled and reused by applying a simple phase separation process. PMID:23757330

  10. Design of a water-soluble hybrid nanocomposite of CdTe quantum dots and an iridium complex for photoinduced charge transfer.

    PubMed

    Wang, Yu; Li, Steve; Kershaw, Stephen V; Hetsch, Frederik; Tam, Anthony Y Y; Shan, Guangcun; Susha, Andrei S; Ko, Chi-Chiu; Wing-Wah Yam, Vivian; Lo, Kenneth K W; Rogach, Andrey L

    2012-07-16

    We report the use of an organo-iridium dye conjugated with a water-soluble copolyethylenimine polymer, allowing the hybrid material to be used in combination with thioacid-coated CdTe quantum dots in an aqueous medium. When they are combined, hot carrier cooling observed in the pure quantum-dot case is heavily suppressed indicating fast (ps) electron transfer on a timescale that competes with non-radiative (Auger) relaxation. PMID:22499537

  11. A click chemistry approach to 5,5'-disubstituted-3,3'-bisisoxazoles from dichloroglyoxime and alkynes: luminescent organometallic iridium and rhenium bisisoxazole complexes.

    PubMed

    van der Peet, Phillip L; Connell, Timothy U; Gunawan, Christian; White, Jonathan M; Donnelly, Paul S; Williams, Spencer J

    2013-07-19

    5,5'-Disubstituted-3,3'-bisisoxazoles are prepared in one step by the dropwise addition of aqueous potassium hydrogen carbonate to a mixture of dichloroglyoxime and terminal alkynes. The reaction exhibits a striking preference for the 5,5'-disubstituted 3,3'-bisisoxazole over the 4,5'-regioisomer. Organometallic iridium and rhenium bisisoxazole complexes are luminescent with emission wavelengths varying depending upon the identity of the 5,5'-substituent (phenyl, butyl).

  12. Plasma isotope separation methods

    SciTech Connect

    Grossman, M.W. ); Shepp, T.A. )

    1991-12-01

    Isotope separation has many important industrial, medical, and research applications. Large-scale processes have typically utilized complex cascade systems; for example, the gas centrifuge. Alternatively, high single-stage enrichment processes (as in the case of the calutron) are very energy intensive. Plasma-based methods being developed for the past 15 to 20 years have attempted to overcome these two drawbacks. In this review, six major types of isotope separation methods which involve plasma phenomena are discussed. These methods are: plasma centrifuge, AVLIS (atomic vapor laser isotope separation), ion wave, ICR (ion-cyclotron resonance), calutron, and gas discharge. The emphasis of this paper is to describe the plasma phenomena in these major categories. An attempt was made to include enough references so that more detailed study or evaluation of a particular method could readily be pursued. A brief discussion of isotope separation using mass balance concepts is also carried out.

  13. Stable isotopes in mineralogy

    USGS Publications Warehouse

    O'Neil, J.R.

    1977-01-01

    Stable isotope fractionations between minerals are functions of the fundamental vibrational frequencies of the minerals and therefore bear on several topics of mineralogical interest. Isotopic compositions of the elements H, C, O, Si, and S can now be determined routinely in almost any mineral. A summary has been made of both published and new results of laboratory investigations, analyses of natural materials, and theoretical considerations which bear on the importance of temperature, pressure, chemical composition and crystal structure to the isotopic properties of minerals. It is shown that stable isotope studies can sometimes provide evidence for elucidating details of crystal structure and can be a powerful tool for use in tracing the reaction paths of mineralogical reactions. ?? 1977 Springer-Verlag.

  14. Isotopically controlled semiconductors

    SciTech Connect

    Haller, E.E.

    2004-11-15

    A review of recent research involving isotopically controlled semiconductors is presented. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, can be considered the most important one for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples. Manuel Cardona, the longtime editor-in-chief of Solid State Communications has been and continues to be one of the major contributors to this field of solid state physics and it is a great pleasure to dedicate this review to him.

  15. Perchlorate isotope forensics.

    PubMed

    Böhlke, John Karl; Sturchio, Neil C; Gu, Baohua; Horita, Juske; Brown, Gilbert M; Jackson, W Andrew; Batista, Jacimaria; Hatzinger, Paul B

    2005-12-01

    Perchlorate has been detected recently in a variety of soils, waters, plants, and food products at levels that may be detrimental to human health. These discoveries have generated considerable interest in perchlorate source identification. In this study, comprehensive stable isotope analyses (37Cl/35Cl and 18O/17O/16O) of perchlorate from known synthetic and natural sources reveal systematic differences in isotopic characteristics that are related to the formation mechanisms. In addition, isotopic analyses of perchlorate extracted from groundwater and surface water demonstrate the feasibility of identifying perchlorate sources in contaminated environments on the basis of this technique. Both natural and synthetic sources of perchlorate have been identified in water samples from some perchlorate occurrences in the United States by the isotopic method. PMID:16316196

  16. Rare Isotope Accelerators

    NASA Astrophysics Data System (ADS)

    Savard, Guy

    2002-04-01

    The next frontier for low-energy nuclear physics involves experimentation with accelerated beams of short-lived radioactive isotopes. A new facility, the Rare Isotope Accelerator (RIA), is proposed to produce large amount of these rare isotopes and post-accelerate them to energies relevant for studies in nuclear physics, astrophysics and the study of fundamental interactions at low energy. The basic science motivation for this facility will be introduced. The general facility layout, from the 400 kW heavy-ion superconducting linac used for production of the required isotopes to the novel production and extraction schemes and the highly efficient post-accelerator, will be presented. Special emphasis will be put on a number of technical breakthroughs and recent R&D results that enable this new facility.

  17. Perchlorate isotope forensics

    USGS Publications Warehouse

    Böhlke, J.K.; Sturchio, N.C.; Gu, B.; Horita, J.; Brown, G.M.; Jackson, W.A.; Batista, J.; Hatzinger, P.B.

    2005-01-01

    Perchlorate has been detected recently in a variety of soils, waters, plants, and food products at levels that may be detrimental to human health. These discoveries have generated considerable interest in perchlorate source identification. In this study, comprehensive stable isotope analyses ( 37Cl/35Cl and 18O/17O/ 16O) of perchlorate from known synthetic and natural sources reveal systematic differences in isotopic characteristics that are related to the formation mechanisms. In addition, isotopic analyses of perchlorate extracted from groundwater and surface water demonstrate the feasibility of identifying perchlorate sources in contaminated environments on the basis of this technique. Both natural and synthetic sources of perchlorate have been identified in water samples from some perchlorate occurrences in the United States by the isotopic method. ?? 2005 American Chemical Society.

  18. (4-Chloro-acetanilido-κ(2)N,O)bis-[2-(pyridin-2-yl)phenyl-κ(2)C(1),N]iridium(III).

    PubMed

    Sun, Lijun; Zhang, Songlin; Song, Qijun

    2013-02-01

    In the neutral mononuclear iridium(III) title compound, [Ir(C(8)H(7)ClNO)(C(11)H(8)N)(2)], the Ir(III) atom adopts an octa-hedral geometry, and is coordinated by two 2-phenyl-pyridyl ligands and one anionic 4-chloro-acetanilide ligand. The 2-phenyl-pyridyl ligands are arranged in a cis-C,C' and cis-N,N' fashion. Each 2-phenyl-pyridyl ligand forms a five-membered ring with the Ir(III) atom. The 2-phenyl-pyridyl planes are perpendicular to each other [dihedral angle = 89.9 (1)°]. The Ir-C and Ir-N bond lengths are comparable to those reported for related iridium(III) 2-phenyl-pyridyl complexes. The remaining two coordination sites are occupied by the amidate N and O atoms, which form a four-membered ring with the iridium atom (Ir-N-C-O). The amidate plane is nearly perpendicular to both 2-phenyl-pyridyl ligands [dihedral angles = 87.8 (2) and 88.3 (2)°]. PMID:23424440

  19. Methods of isotopic geochronology

    NASA Astrophysics Data System (ADS)

    Gorokhov, I. M.; Levchenkov, O. A.

    Papers are presented on such topics as the age of the chemical elements; the age of meteorites, the moon, and the earth; isotopic ages of the most ancient terrestrial formations; and the Archean evolution of Enderby Land in the Antarctic as evidenced by isotopic dating. Consideration is also given to a uranium-lead geochronology technique for investigating Precambrian ore deposits, a Pb-Pb technique of zircon dating, and the potentials and limitations of Sm-Nd geochronology.

  20. The isotopic distribution conundrum.

    PubMed

    Valkenborg, Dirk; Mertens, Inge; Lemière, Filip; Witters, Erwin; Burzykowski, Tomasz

    2012-01-01

    Although access to high-resolution mass spectrometry (MS), especially in the field of biomolecular MS, is becoming readily available due to recent advances in MS technology, the accompanied information on isotopic distribution in high-resolution spectra is not used at its full potential, mainly because of lack of knowledge and/or awareness. In this review, we give an insight into the practical problems related to calculating the isotopic distribution for large biomolecules, and present an overview of methods for the calculation of the isotopic distribution. We discuss the key events that triggered the development of various algorithms and explain the rationale of how and why the various isotopic-distribution calculations were performed. The review is focused around the developmental stages as briefly outlined below, starting with the first observation of an isotopic distribution. The observations of Beynon in the field of organic MS that chlorine appeared in a mass spectrum as two variants with odds 3:1 lie at the basis of the first wave of algorithms for the calculation of the isotopic distribution, based on the atomic composition of a molecule. From here on, we explain why more complex biomolecules such as peptides exhibit a highly complex isotope pattern when assayed by MS, and we discuss how combinatorial difficulties complicate the calculation of the isotopic distribution on computers. For this purpose, we highlight three methods, which were introduced in the 1980s. These are the stepwise procedure introduced by Kubinyi, the polynomial expansion from Brownawell and Fillippo, and the multinomial expansion from Yergey. The next development was instigated by Rockwood, who suggested to decompose the isotopic distribution in terms of their nucleon count instead of the exact mass. In this respect, we could claim that the term "aggregated" isotopic distribution is more appropriate. Due to the simplification of the isotopic distribution to its aggregated counterpart

  1. Radioactive isotope production for medical applications using Kharkov electron driven subcritical assembly facility.

    SciTech Connect

    Talamo, A.; Gohar, Y.; Nuclear Engineering Division

    2007-05-15

    , the parent isotopes with high reaction rate were explicitly modeled in the calculations. For the nuclides with a very high capture microscopic cross section, such as iridium, rhenium, and samarium, their specific activities are reduced by a factor of 30 when the self-shielding effect is included. Four irradiation locations were considered in the analyses to maximize the medical isotope production rate. The results show the self-shield effect reduces the specific activity values and changes the irradiation location for obtaining the maximum possible specific activity. The axial and radial distributions of the specific activity were used to define the irradiation sample size for producing each isotope.

  2. Oxygen Isotopes in Meteorites

    NASA Astrophysics Data System (ADS)

    Clayton, R. N.

    2003-12-01

    Oxygen isotope abundance variations in meteorites are very useful in elucidating chemical and physical processes that occurred during the formation of the solar system (Clayton, 1993). On Earth, the mean abundances of the three stable isotopes are 16O: 99.76%, 17O: 0.039%, and 18O: 0.202%. It is conventional to express variations in abundances of the isotopes in terms of isotopic ratios, relative to an arbitrary standard, called SMOW (for standard mean ocean water), as follows:The isotopic composition of any sample can then be represented by one point on a "three-isotope plot," a graph of δ17O versus δ18O. It will be seen that such plots are invaluable in interpreting meteoritic data. Figure 1 shows schematically the effect of various processes on an initial composition at the center of the diagram. Almost all terrestrial materials lie along a "fractionation" trend; most meteoritic materials lie near a line of "16O addition" (or subtraction). (4K)Figure 1. Schematic representation of various isotopic processes shown on an oxygen three-isotope plot. Almost all terrestrial materials plot along a line of "fractionation"; most primitive meteoritic materials plot near a line of "16O addition." The three isotopes of oxygen are produced by nucleosynthesis in stars, but by different nuclear processes in different stellar environments. The principal isotope, 16O, is a primary isotope (capable of being produced from hydrogen and helium alone), formed in massive stars (>10 solar masses), and ejected by supernova explosions. The two rare isotopes are secondary nuclei (produced in stars from nuclei formed in an earlier generation of stars), with 17O coming primarily from low- and intermediate-mass stars (<8 solar masses), and 18O coming primarily from high-mass stars (Prantzos et al., 1996). These differences in type of stellar source result in large observable variations in stellar isotopic abundances as functions of age, size, metallicity, and galactic location ( Prantzos

  3. Contrasting Anticancer Activity of Half-Sandwich Iridium(III) Complexes Bearing Functionally Diverse 2-Phenylpyridine Ligands

    PubMed Central

    2015-01-01

    We report the synthesis, characterization, and antiproliferative activity of 15 iridium(III) half-sandwich complexes of the type [(η5-Cp*)Ir(2-(R′-phenyl)-R-pyridine)Cl] bearing either an electron-donating (−OH, −CH2OH, −CH3) or electron-withdrawing (−F, −CHO, −NO2) group at various positions on the 2-phenylpyridine (2-PhPy) chelating ligand giving rise to six sets of structural isomers. The X-ray crystal structures of [(η5-Cp*)Ir(2-(2′-fluorophenyl)pyridine)Cl] (1) and [(η5-Cp*)Ir(2-(4′-fluorophenyl)pyridine)Cl] (2) exhibit the expected “piano-stool” configuration. DFT calculations showed that substituents caused only localized effects on the electrostatic potential surface of the chelating 2-PhPy ligand of the complexes. Hydrolysis of all complexes is rapid, but readily reversed by addition of NaCl. The complexes show preferential binding to 9-ethylguanine over 9-methyladenine and are active catalysts for the oxidation of NADH to NAD+. Antiproliferative activity experiments in A2780 ovarian, MCF-7 breast, A549 lung, and HCT116 colon cancer cell lines showed IC50 values ranging from 1 to 89 μM, with the most potent complex, [(η5-Cp*)Ir(2-(2′-methylphenyl)pyridine)Cl] (13) (A2780 IC50 = 1.18 μM), being 10× more active than the parent, [(η5-Cp*)Ir(2-phenylpyridine)Cl], and 2× more active than [(η5-CpxPh)Ir(2-phenylpyridine)Cl]. Intriguingly, contrasting biological activities are observed between structural isomers despite exhibiting similar chemical reactivity. For pairs of structural isomers both the nature and position of the functional group can affect the hydrophobicity of the complex. An increase in hydrophobicity resulted in enhanced cellular-iridium accumulation in A2780 ovarian cells, which generally gave rise to an increase in potency. The structural isomers [(η5-Cp*)Ir(2-(4′-fluorophenyl)pyridine)Cl] (2) and [(η5-Cp*)Ir(2-phenyl-5-fluoropyridine)Cl] (4) preferentially localized in the cytosol > membrane and particulate

  4. Molecular models of site-isolated cobalt, rhodium, and iridium catalysts supported on zeolites: Ligand bond dissociation energies

    DOE PAGES

    Chen, Mingyang; Serna, Pedro; Lu, Jing; Gates, Bruce C.; Dixon, David A.

    2015-09-28

    The chemistry of zeolite-supported site-isolated cobalt, rhodium, and iridium complexes that are essentially molecular was investigated with density functional theory (DFT) and the results compared with experimentally determined spectra characterizing rhodium and iridium species formed by the reactions of Rh(C2H4)2(acac) and Ir(C2H4)2(acac) (acac = acetylacetonate) with acidic zeolites such as dealuminated HY zeolite. The experimental results characterize ligand exchange reactions and catalytic reactions of adsorbed ligands, including olefin hydrogenation and dimerization. Two molecular models were used to characterize various binding sites of the metal complexes in the zeolites, and the agreement between experimental and calculated infrared frequencies and metal-ligand distancesmore » determined by extended X-ray absorption fine structure spectroscopy was generally very good. The calculated structures and energies indicate a metal-support-oxygen (M(I)-O) coordination number of two for most of the supported complexes and a value of three when the ligands include the radicals C2H5 or H. The results characterizing various isomers of the supported metal complexes incorporating hydrocarbon ligands indicate that some carbene and carbyne ligands could form. Ligand bond dissociation energies (LDEs) are reported to explain the observed reactivity trends. The experimental observations of a stronger M-CO bond than M-(C2H4) bond for both Ir and Rh match the calculated LDEs, which show that the single-ligand LDEs of the mono and dual-ligand complexes for CO are similar to 12 and similar to 15 kcal/mol higher in energy (when the metal is Rh) and similar to 17 and similar to 20 kcal/mol higher (when the metal is Ir) than the single-ligand LDEs of the mono and dual ligand complexes for C2H4, respectively. The results provide a foundation for the prediction of the catalytic properties of numerous supported metal complexes, as summarized in detail here.« less

  5. Molecular models of site-isolated cobalt, rhodium, and iridium catalysts supported on zeolites: Ligand bond dissociation energies

    SciTech Connect

    Chen, Mingyang; Serna, Pedro; Lu, Jing; Gates, Bruce C.; Dixon, David A.

    2015-09-28

    The chemistry of zeolite-supported site-isolated cobalt, rhodium, and iridium complexes that are essentially molecular was investigated with density functional theory (DFT) and the results compared with experimentally determined spectra characterizing rhodium and iridium species formed by the reactions of Rh(C2H4)2(acac) and Ir(C2H4)2(acac) (acac = acetylacetonate) with acidic zeolites such as dealuminated HY zeolite. The experimental results characterize ligand exchange reactions and catalytic reactions of adsorbed ligands, including olefin hydrogenation and dimerization. Two molecular models were used to characterize various binding sites of the metal complexes in the zeolites, and the agreement between experimental and calculated infrared frequencies and metal-ligand distances determined by extended X-ray absorption fine structure spectroscopy was generally very good. The calculated structures and energies indicate a metal-support-oxygen (M(I)-O) coordination number of two for most of the supported complexes and a value of three when the ligands include the radicals C2H5 or H. The results characterizing various isomers of the supported metal complexes incorporating hydrocarbon ligands indicate that some carbene and carbyne ligands could form. Ligand bond dissociation energies (LDEs) are reported to explain the observed reactivity trends. The experimental observations of a stronger M-CO bond than M-(C2H4) bond for both Ir and Rh match the calculated LDEs, which show that the single-ligand LDEs of the mono and dual-ligand complexes for CO are similar to 12 and similar to 15 kcal/mol higher in energy (when the metal is Rh) and similar to 17 and similar to 20 kcal/mol higher (when the metal is Ir) than the single-ligand LDEs of the mono and dual ligand complexes for C2H4, respectively. The results provide a foundation for the prediction

  6. Manipulating the Excited States of Cyclometalated Iridium Complexes with β-Ketoiminate and β-Diketiminate Ligands.

    PubMed

    Radwan, Yousf K; Maity, Ayan; Teets, Thomas S

    2015-07-20

    A series of cyclometalated iridium complexes with β-ketoiminate and β-diketiminate ligands are described. Two different cyclometalating (C^N) ligands-2-phenylpridine (ppy) and 2-phenylbenzothiazole (bt)-are used in concert with three different ancillary (LX) ligands-a phenyl-substituted β-ketoiminate (acNac(Me)), a phenyl-substituted β-diketiminate (NacNac(Me)), and a fluorinated version of the β-diketiminate (NacNac(CF3))-to furnish a suite of six complexes. The complexes are prepared by metathesis reactions of chloro-bridged dimers [Ir(C^N)2(μ-Cl)]2 with potassium or lithium salts of the ancillary LX ligand. Four of the complexes are characterized by X-ray crystallography, and all six were subjected to in-depth optical and electrochemical interrogation. Cyclic voltammetry shows both reduction and oxidation waves, with the latter strongly dependent on the identity of the LX ligand. The complexes are all luminescent, with the nature of the emissive excited state and the quantum yield (Φ) dependent on the identity of both the C^N and LX ligands. Whereas the complexes Ir(ppy)2(NacNac(Me)) and Ir(ppy)2(acNac(Me)) are weakly luminescent (Φ ≈ 0.01), the complexes Ir(bt)2(NacNac(Me)) and Ir(bt)2(acNac(Me)) are strongly luminescent, with the latter's quantum efficiency (Φ = 0.82) among the highest ever observed for cyclometalated iridium complexes. Fluorination of the NacNac ligand gives rise to completely disparate emission behavior suggestive of a NacNac-centered emissive state. The results described here, in comparison with previous groups' studies on acetylacetonate (acac) analogues, suggest that the weaker-field NacNac and acNac ligands raise the energy of the metal-centered HOMO, with energy of the HOMO increasing in the order NacNac(CF3) < acNac(Me) < NacNac(Me). PMID:26158354

  7. A magnetism-based approach to examining spin-orbit coupling effects in solid systems of isolated iridium octahedra

    NASA Astrophysics Data System (ADS)

    Phelan, Brendan F.

    This thesis explores the relative strengths of Spin-Orbit Coupling (SOC) in several perovskite-like systems that feature uninterrupted arrays of isolated IrO6 octahedra. Iridate compounds are particularly interesting to the community due to their relevance to emergent material properties such as insulating antiferromagnets, superconductors, and topological insulators. Recently literature has pointed to a complex interaction between SOC and crystal field splitting (CFS) in d5 metals. I utilize a straightforward, magnetic approach to determine the relative strengths of SOC vs CFS by chemically modifying structure and oxidation state. This contrasts with other work where advanced spectroscopic measurements are utilized to probe energy levels within a single compound. The focus of this study lies in two main methodologies: 1) Tracking the evolution of the Ir magnetic moment on progressing from 5 d5 Ir4+ to 5d 4 Ir5+ oxidation states that are clearly best described by a transition from a J=1/2 to a J=0 Ir magnetic state. In these cases, the evolution of the magnetic susceptibility shows the dominance of spin-orbit coupling in determining the magnetic properties of a material with highly isolated IrO6 octahedra. 2) Distorting J=0 Ir5+ systems where there is no emergence of an enhanced magnetic moment in the series on increasing the structural distortions, as would have been the case for significant crystal field splitting that reinforces the notion that spin-orbit coupling is the dominant force in determining the magnetism of iridium-oxygen octahedra in perovskite-like structures. The organization of this thesis is as follows: Chapter 1 presents a brief introduction to solid-state chemistry, iridates, and magnetism. Chapter 2 is an overview of experimental methodology and instrumentation. Chapter 3, presents a study of tuning the oxidation state of a new structure type: SrxLa11-xIr4O24. Chapter 4 presents a structural tuning of the Ir5+ system: Ba 2-xSrxYIrO6. Finally

  8. Physicochemical isotope anomalies

    SciTech Connect

    Esat, T.M.

    1988-06-01

    Isotopic composition of refractory elements can be modified, by physical processes such as distillation and sputtering, in unexpected patterns. Distillation enriches the heavy isotopes in the residue and the light isotopes in the vapor. However, current models appear to be inadequate to describe the detailed mass dependence, in particular for large fractionations. Coarse- and fine-grained inclusions from the Allende meteorite exhibit correlated isotope effects in Mg both as mass-dependent fractionation and residual anomalies. This isotope pattern can be duplicated by high temperature distillation in the laboratory. A ubiquitous property of meteoritic inclusions for Mg as well as for most of the other elements, where measurements exist, is mass-dependent fractionation. In contrast, terrestrial materials such as microtektites, tektite buttons as well as lunar orange and green glass spheres have normal Mg isotopic composition. A subset of interplanetary dust particles labelled as chondritic aggregates exhibit excesses in {sup 26}Mg and deuterium anomalies. Sputtering is expected to be a dominant mechanism in the destruction of grains within interstellar dust clouds. An active proto-sun as well as the present solar-wind and solar-flare flux are of sufficient intensity to sputter significant amounts of material. Laboratory experiments in Mg show widespread isotope effects including residual {sup 26}Mg excesses and mass dependent fractionation. It is possible that the {sup 26}Mg excesses in interplanetary dust is related to sputtering by energetic solar-wind particles. The implication if the laboratory distillation and sputtering effects are discussed and contrasted with the anomalies in meteoritic inclusions the other extraterrestrial materials the authors have access to.

  9. Transportation of medical isotopes

    SciTech Connect

    Nielsen, D.L.

    1997-11-19

    A Draft Technical Information Document (HNF-1855) is being prepared to evaluate proposed interim tritium and medical isotope production at the Fast Flux Test Facility (FFTF). This assessment examines the potential health and safety impacts of transportation operations associated with the production of medical isotopes. Incident-free and accidental impacts are assessed using bounding source terms for the shipment of nonradiological target materials to the Hanford Site, the shipment of irradiated targets from the FFTF to the 325 Building, and the shipment of medical isotope products from the 325 Building to medical distributors. The health and safety consequences to workers and the public from the incident-free transportation of targets and isotope products would be within acceptable levels. For transportation accidents, risks to works and the public also would be within acceptable levels. This assessment is based on best information available at this time. As the medical isotope program matures, this analysis will be revised, if necessary, to support development of a final revision to the Technical Information Document.

  10. Separation of sulfur isotopes

    DOEpatents

    DeWitt, Robert; Jepson, Bernhart E.; Schwind, Roger A.

    1976-06-22

    Sulfur isotopes are continuously separated and enriched using a closed loop reflux system wherein sulfur dioxide (SO.sub.2) is reacted with sodium hydroxide (NaOH) or the like to form sodium hydrogen sulfite (NaHSO.sub.3). Heavier sulfur isotopes are preferentially attracted to the NaHSO.sub.3, and subsequently reacted with sulfuric acid (H.sub.2 SO.sub.4) forming sodium hydrogen sulfate (NaHSO.sub.4) and SO.sub.2 gas which contains increased concentrations of the heavier sulfur isotopes. This heavy isotope enriched SO.sub.2 gas is subsequently separated and the NaHSO.sub.4 is reacted with NaOH to form sodium sulfate (Na.sub.2 SO.sub.4) which is subsequently decomposed in an electrodialysis unit to form the NaOH and H.sub.2 SO.sub.4 components which are used in the aforesaid reactions thereby effecting sulfur isotope separation and enrichment without objectionable loss of feed materials.

  11. Isotope geochemistry. Biological signatures in clumped isotopes of O₂.

    PubMed

    Yeung, Laurence Y; Ash, Jeanine L; Young, Edward D

    2015-04-24

    The abundances of molecules containing more than one rare isotope have been applied broadly to determine formation temperatures of natural materials. These applications of "clumped" isotopes rely on the assumption that isotope-exchange equilibrium is reached, or at least approached, during the formation of those materials. In a closed-system terrarium experiment, we demonstrate that biological oxygen (O2) cycling drives the clumped-isotope composition of O2 away from isotopic equilibrium. Our model of the system suggests that unique biological signatures are present in clumped isotopes of O2—and not formation temperatures. Photosynthetic O2 is depleted in (18)O(18)O and (17)O(18)O relative to a stochastic distribution of isotopes, unlike at equilibrium, where heavy-isotope pairs are enriched. Similar signatures may be widespread in nature, offering new tracers of biological and geochemical cycling.

  12. Isotope geochemistry. Biological signatures in clumped isotopes of O₂.

    PubMed

    Yeung, Laurence Y; Ash, Jeanine L; Young, Edward D

    2015-04-24

    The abundances of molecules containing more than one rare isotope have been applied broadly to determine formation temperatures of natural materials. These applications of "clumped" isotopes rely on the assumption that isotope-exchange equilibrium is reached, or at least approached, during the formation of those materials. In a closed-system terrarium experiment, we demonstrate that biological oxygen (O2) cycling drives the clumped-isotope composition of O2 away from isotopic equilibrium. Our model of the system suggests that unique biological signatures are present in clumped isotopes of O2—and not formation temperatures. Photosynthetic O2 is depleted in (18)O(18)O and (17)O(18)O relative to a stochastic distribution of isotopes, unlike at equilibrium, where heavy-isotope pairs are enriched. Similar signatures may be widespread in nature, offering new tracers of biological and geochemical cycling. PMID:25908819

  13. Metallurgical Evaluation of Grit Blasted Versus Non-Grit Blasted Iridium Alloy Clad Vent Set Cup Surfaces

    SciTech Connect

    Ulrich, George B; Longmire, Hu Foster

    2010-02-01

    Metallurgical evaluations were conducted to determine what, if any, grain size differences exist between grit blasted and non-grit blasted DOP-26 iridium alloy cup surfaces and if grit blasting imparts sufficient compressive cold work to induce abnormal grain growth during subsequent temperature exposures. Metallographic measurements indicated that grit blasting cold worked the outside cup surface to a depth of approximately 19 {micro}m. Subsequent processing through the air burn-off (635 C/4h) and vacuum outgassing (1250 C/1h) operations was found to uniformly recrystallize the cold worked surface to produce grains with an average diameter of approximately 8.5 {micro}m (American Society for Testing and Materials (ASTM) grain size number 11). Follow-on heat treatments at 1375 C, 1500 C, and 1900 C for durations ranging from 1 min to 70 h yielded uniform grain sizes and no abnormal grain growth from grit blasting. Abnormal grain growth was noted at the 1500 C and 1900 C heat treatments in areas of cold work from excessive clamping during sample preparation.

  14. Effects of Molecular Oxygen, Solvent, and Light on Iridium-Photoredox/Nickel Dual-Catalyzed Cross-Coupling Reactions.

    PubMed

    Oderinde, Martins S; Varela-Alvarez, Adrian; Aquila, Brian; Robbins, Daniel W; Johannes, Jeffrey W

    2015-08-01

    In order to achieve reproducibility during iridium-photoredox and nickel dual-catalyzed sp(3)-sp(2) carbon-carbon bond-forming reactions, we investigated the role that molecular oxygen (O2), solvent and light-source (CF lamp or blue LED) play in a variety of Ir-photoredox mediated transformations. The presence of O2 was discovered to be important for catalyst activation when air-stable Ni(II) precatalysts were used in DMF under CF lamp irradiation; however, O2 was not required for catalysis when conducted with Ni(COD)2 in the same reaction system. O2 is believed to promote rapid reduction of the Ni(II) precatalyst by Ir(II) to Ni(0). In addition to O2, the effects that solvent and light-source have on the dual-catalyzed decarboxylative cross-coupling reactions will be discussed. These findings have enabled us to develop a more robust dual-catalyzed decarboxylative cross-coupling protocol.

  15. Iridium Concentrations and Abundances of Meteoritic Ejecta from the Eltanin Impact in Sediment Cores from Polarstern Expedition ANT XII/4

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.

    2002-01-01

    The abundances of meteoritic ejecta from the Eltanin asteroid impact have been examined in several sediment cores recovered by the FS Polarstern during expedition ANT XII/4 using elemental concentrations of iridium and weights of coarse ejecta debris. Three cores with well-preserved impact deposits, PS204-1, PS2708-1, and PS2709-1, each contain Ir and ejecta fluences similar to those found in USNS Eltanin core E13-4. Small Ir anomalies and traces of ejecta were found in cores PS2706-1 and PS2710-1, but since these cores lack well-defined deposits, these are considered to be reworked and not representative of the fallout. No evidence of ejecta was found in cores PS2802-1 and PS2705-1. These results confirm earlier speculation that the Eltanin impact resulted in deposits of ejecta with up to 1 gram/sq centimeter of depris over a wide area of the ocean floor. However, there are sill large uncertainties over the actual regional or global extent of this unique sediment deposit.

  16. Iridium and trace element measurements from the Cretaceous-Tertiary boundary, site 752, Broken Ridge, Indian Ocean

    NASA Technical Reports Server (NTRS)

    Schuraytz, B. C.; O'Connell, S.; Sharpton, V. L.

    1991-01-01

    Fourteen samples spanning a 2.5 m interval that includes the Cretaceous-Tertiary (K/T) boundary from Hole 752B near the crest of Broken Ridge in the eastern Indian Ocean were studied in order to search for anomalous enrichments of iridium (Ir) and shock-metamorphosed quartz grains. No allogenic quartz grains larger than 10 microns were observed, hence the presence of quartz containing diagnostic evidence of shock-metamorphism could not be confirmed. Two Ir anomalies of 2.2 +/- 0.6 and 2.0 +/- 0.4 parts per billion (ppb) were measured in samples of dark green ash-bearing chalk at depths of 357.93 and 358.80 m below seafloor, respectively. These samples containing anomalous enrichments of Ir were taken from approximately 82 cm above and 5 cm below the extinction level of Globotruncanids. Our results are consistent with those of Michel et al., who observe elevated concentrations of Ir at these depths in addition to a larger Ir anomaly associated with the extinction level of Globotruncanids.

  17. Blue Electrogenerated Chemiluminescence from Water-Soluble Iridium Complexes Containing Sulfonated Phenylpyridine or Tetraethylene Glycol Derivatized Triazolylpyridine Ligands.

    PubMed

    Kerr, Emily; Doeven, Egan H; Barbante, Gregory J; Connell, Timothy U; Donnelly, Paul S; Wilson, David J D; Ashton, Trent D; Pfeffer, Frederick M; Francis, Paul S

    2015-10-12

    Incorporating phenylpyridine- and triazolylpyridine-based ligands decorated with methylsulfonate or tetraethylene glycol (TEG) groups, a series of iridium(III) complexes has been created for green and blue electrogenerated chemiluminescence under analytically useful aqueous conditions, with tri-n-propylamine as a coreactant. The relative electrochemiluminescence (ECL) intensities of the complexes were dependent on the sensitivity of the photodetector over the wavelength range and the pulse time of the applied electrochemical potential. In terms of the integrated area of corrected ECL spectra, with a pulse time of 0.5 s, the intensities of the Ir(III) complexes were between 18 and 102 % that of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine). However, when the intensities were measured with a typical bialkali photomultiplier tube, the signal of the most effective blue emitter, [Ir(df-ppy)2 (pt-TEG)](+) (df-ppy=2-(2,4-difluorophenyl)pyridine anion, pt-TEG=1-(2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethyl)-4-(2-pyridyl)-1,2,3-triazole), was over 1200 % that of the orange-red emitter [Ru(bpy)3 ](2+) . A combined experimental and theoretical investigation of the electrochemical and spectroscopic properties of the Ir(III) complexes indicated that the greater intensity from [Ir(df-ppy)2 (pt-TEG)](+) relative to those of the other Ir(III) complexes resulted from a combination of many factors, rather than being significantly favored in one area.

  18. Blue Electrogenerated Chemiluminescence from Water-Soluble Iridium Complexes Containing Sulfonated Phenylpyridine or Tetraethylene Glycol Derivatized Triazolylpyridine Ligands.

    PubMed

    Kerr, Emily; Doeven, Egan H; Barbante, Gregory J; Connell, Timothy U; Donnelly, Paul S; Wilson, David J D; Ashton, Trent D; Pfeffer, Frederick M; Francis, Paul S

    2015-10-12

    Incorporating phenylpyridine- and triazolylpyridine-based ligands decorated with methylsulfonate or tetraethylene glycol (TEG) groups, a series of iridium(III) complexes has been created for green and blue electrogenerated chemiluminescence under analytically useful aqueous conditions, with tri-n-propylamine as a coreactant. The relative electrochemiluminescence (ECL) intensities of the complexes were dependent on the sensitivity of the photodetector over the wavelength range and the pulse time of the applied electrochemical potential. In terms of the integrated area of corrected ECL spectra, with a pulse time of 0.5 s, the intensities of the Ir(III) complexes were between 18 and 102 % that of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine). However, when the intensities were measured with a typical bialkali photomultiplier tube, the signal of the most effective blue emitter, [Ir(df-ppy)2 (pt-TEG)](+) (df-ppy=2-(2,4-difluorophenyl)pyridine anion, pt-TEG=1-(2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethyl)-4-(2-pyridyl)-1,2,3-triazole), was over 1200 % that of the orange-red emitter [Ru(bpy)3 ](2+) . A combined experimental and theoretical investigation of the electrochemical and spectroscopic properties of the Ir(III) complexes indicated that the greater intensity from [Ir(df-ppy)2 (pt-TEG)](+) relative to those of the other Ir(III) complexes resulted from a combination of many factors, rather than being significantly favored in one area. PMID:26334026

  19. Iridium oxide pH sensor for biomedical applications. Case urea-urease in real urine samples.

    PubMed

    Prats-Alfonso, Elisabet; Abad, Llibertat; Casañ-Pastor, Nieves; Gonzalo-Ruiz, Javier; Baldrich, Eva

    2013-01-15

    This work demonstrates the implementation of iridium oxide films (IROF) grown on silicon-based thin-film platinum microelectrodes, their utilization as a pH sensor, and their successful formatting into a urea pH sensor. In this context, Pt electrodes were fabricated on Silicon by using standard photolithography and lift-off procedures and IROF thin films were growth by a dynamic oxidation electrodeposition method (AEIROF). The AEIROF pH sensor reported showed a super-Nerstian (72.9±0.9mV/pH) response between pH 3 and 11, with residual standard deviation of both repeatability and reproducibility below 5%, and resolution of 0.03 pH units. For their application as urea pH sensors, AEIROF electrodes were reversibly modified with urease-coated magnetic microparticles (MP) using a magnet. The urea pH sensor provided fast detection of urea between 78μM and 20mM in saline solution, in sample volumes of just 50μL. The applicability to urea determination in real urine samples is discussed.

  20. Cationic mono and dicarbonyl pincer complexes of rhodium and iridium to assess the donor properties of PCcarbeneP ligands.

    PubMed

    Smith, Joel D; Logan, Jessamyn R; Doyle, Lauren E; Burford, Richard J; Sugawara, Shun; Ohnita, Chiho; Yamamoto, Yohsuke; Piers, Warren E; Spasyuk, Denis M; Borau-Garcia, Javier

    2016-08-01

    The donor properties of five different PCcarbeneP ligands are assessed by evaluation of the CO stretching frequencies in iridium(i) and rhodium(i) carbonyl cations. The ligands feature dialkyl phosphine units (R = (i)Pr or (t)Bu) linked to the central benzylic carbon by either an ortho-phenylene bridge, or a 2,3-benzo[b]thiophene linker; in the former, substituent patterns on the phenyl linker are varied. The carbonyl complexes are synthesized from the (PCcarbeneP)M-Cl starting materials via abstraction of the chlorides in the presence of CO gas. In addition to the expected mono carbonyl cations, products with two carbonyl ligands are produced, and for the rhodium example, a novel product in which the second carbonyl ligand adds reversibly across the Rh[double bond, length as m-dash]C bond to give an η(2) ketene moiety was characterized. The IR data for the complexes shows the 2,3-benzo[b]thiophene linked system to be the poorest overall donor, while the phenyl bridged ligands incorporating electron donating dialkyl amino groups para to the anchoring carbene are very strongly donating pincer arrays. PMID:27465584

  1. Efficient red electroluminescent devices with sterically hindered phosphorescent platinum(II) Schiff base complexes and iridium complex codopant.

    PubMed

    Zhou, Liang; Kwong, Chun-Lam; Kwok, Chi-Chung; Cheng, Gang; Zhang, Hongjie; Che, Chi-Ming

    2014-10-01

    Sterically hindered platinum(II) Schiff base complexes were prepared. Complex 4, which displays red emission with a quantum yield of 0.29 in a thin film and a self-quenching rate constant of 1×10(-7) dm(3) mol(-1)  s(-1), was used to fabricate organic light-emitting diodes with single or double emissive layers (EMLs). An iridium(III) complex with a wide band gap was codoped into the electron-dominant EML to act as a deep electron trapper, and red-light-emitting devices with the highest current, power, and external quantum efficiencies of 20.43 cd A(-1) 18.33 Lm W(-1), and 11.7%, respectively, were fabricated. A high current efficiency and EQE of up to 14.69 cd A(-1) and 8.3%, respectively, were achieved at a high brightness of 1000 cd m(-2). The significant delay of efficiency roll-off is attributed to the bulky 3D structure of the norbornene moiety at the periphery of the Schiff base ligand of 4 and to the new device design strategy. The fabricated device had a projected lifetime (LT50) of 18,000 h.

  2. A study of the electrochemical behavior in tungsten and caustic solutions and platinum/iridium in chloride solutions, informal report

    SciTech Connect

    Vitus, C.M.; Isaacs, H.S.; Schroeder, V.

    1994-11-22

    Platinum/iridium and tungsten wires were electronically etched in chloride and caustic solution, respectively, to produce tips with high aspect ratio. A direct relationship between the meniscus and the aspect ratio of etched tips was established. Scanning electron micrographs indicated that higher aspect ratios were obtained by changing the geometry of the meniscus during the etch either by an increase in the applied a.c. voltage or with the addition of a nonpolar layer above the electrolytic solution during the etching process. Above the breakdown voltage, two possible mechanisms appeared to control the etching process by expediting chemical dissolution: cavitation and sparking. Cavitation caused erosion due to the force of evolved gases against the electrode and sparking attacked the surface by vaporizing the metal. Sparking commenced on both wires near 24V. This voltage corresponded to a minimum in the plot of total etch time versus voltage. From light emission studies, sparking on Pt/Ir was associated with the ionization of Pt, Ir, Ca, and Cl. A compositional analysis of insoluble black particles produced during a.c. and d.c. etching of Pt/Ir revealed Pt and Ir as the major constituents of the product. The sparking process was shown to have a potential use in micromachining.

  3. Azo-Based Iridium(III) Complexes as Multicolor Phosphorescent Probes to Detect Hypoxia in 3D Multicellular Tumor Spheroids

    PubMed Central

    Sun, Lingli; Li, Guanying; Chen, Xiang; Chen, Yu; Jin, Chengzhi; Ji, Liangnian; Chao, Hui

    2015-01-01

    Hypoxia is an important characteristic of malignant solid tumors and is considered as a possible causative factor for serious resistance to chemo- and radiotherapy. The exploration of novel fluorescent probes capable of detecting hypoxia in solid tumors will aid tumor diagnosis and treatment. In this study, we reported the design and synthesis of a series of “off-on” phosphorescence probes for hypoxia detection in adherent and three-dimensional multicellular spheroid models. All of the iridium(III) complexes incorporate an azo group as an azo-reductase reactive moiety to detect hypoxia. Reduction of non-phosphorescent probes Ir1-Ir8 by reductases under hypoxic conditions resulted in the generation of highly phosphorescent corresponding amines for detection of hypoxic regions. Moreover, these probes can penetrate into 3D multicellular spheroids over 100 μm and image the hypoxic regions. Most importantly, these probes display a high selectivity for the detection of hypoxia in 2D cells and 3D multicellular spheroids. PMID:26423609

  4. Histidine-iridium(III) coordination-based peptide luminogenic cyclization and cyclo-RGD peptides for cancer-cell targeting.

    PubMed

    Ma, Xiaochuan; Jia, Junli; Cao, Rui; Wang, Xiaobo; Fei, Hao

    2014-12-24

    In the field of peptide drug discovery, structural constraining and fluorescent labeling are two sought-after techniques important for both basic research and pharmaceutical development. In this work, we describe an easy-to-use approach for simultaneous peptide cyclization and luminescent labeling based on iridium(III)-histidine coordination (Ir-HH cyclization). Using a series of model peptides with histidine flanking each terminus, the binding activity and reaction kinetics of Ir-HH cyclization of different ring sizes were characterized. In the series, Ir-HAnH (n = 2, 3) with moderate ring sizes provides appropriate flexibility and proper distance between histidines for cyclic formation, which leads to the best binding affinity and structural stability in physiological conditions, as compared to other Ir-HH-cyclized peptides with smaller (n = 0, 1) or larger (n = 4, 5) ring sizes. Ir-HRGDH, an Ir-HH-cyclized peptide containing integrin targeting motif Arg-Gly-Asp (RGD), showed better targeting affinity than its linear form and enhanced membrane permeability in comparison with fluorescein-labeled cyclic RGDyK peptide. Cell death inducing peptide KLA-linked Ir-HRGDH (Ir-HRGDH-KLA) showed dramatically enhanced cytotoxicity and high selectivity for cancer cells versus noncancer cells. These data demonstrate that the method conveniently combines structural constraining of peptides with luminescent imaging capabilities, which facilitates functional and intracellular characterization of potential peptide-based drug leads, thus introducing a new tool to meet emerging needs in medicinal research.

  5. Design and Synthesis of Pyrimidine-Based Iridium(III) Complexes with Horizontal Orientation for Orange and White Phosphorescent OLEDs.

    PubMed

    Cui, Lin-Song; Liu, Yuan; Liu, Xiang-Yang; Jiang, Zuo-Quan; Liao, Liang-Sheng

    2015-05-27

    Two phosphorescent Ir(III) complexes Ir(ppm)2(acac) and Ir(dmppm)2(acac) were synthesized and characterized with emission ranged at 584/600 nm and high photoluminescence quantum yields (PLQYs) of 0.90/0.92, respectively. The angle-dependent PL spectra analysis reveals that the two orange iridium(III) complexes embodied horizontal orientation property. The high photoluminescence quantum yield and high horizontal dipoles ratio determine their excellent device performance. The devices based on Ir(ppm)2(acac) and Ir(dmppm)2(acac) achieved efficiencies of 26.8% and 28.2%, respectively, which can be comparable to the best orange phosphorescent devices reported in the literature. Furthermore, with the introduction of FIrpic as sky-blue emitter, phosphorescent two-element white organic light-emitting devices (OLEDs) have been realized with external quantum efficiencies (EQEs) as high as 25%, which are the highest values among the reported two-element white OLEDs. PMID:25943159

  6. Tuning the Emission of Cationic Iridium (III) Complexes Towards the Red Through Methoxy Substitution of the Cyclometalating Ligand

    PubMed Central

    Hasan, Kamrul; Bansal, Ashu K.; Samuel, Ifor D.W.; Roldán-Carmona, Cristina; Bolink, Henk J.; Zysman-Colman, Eli

    2015-01-01

    The synthesis, characterization and evaluation in solid-state devices of a series of 8 cationic iridium complexes bearing different numbers of methoxy groups on the cyclometallating ligands are reported. The optoelectronic characterization showed a dramatic red shift in the absorption and the emission and a reduction of the electrochemical gap of the complexes when a methoxy group was introduced para to the Ir-C bond. The addition of a second or third methoxy group did not lead to a significant further red shift in these spectra. Emission maxima over the series ranged from 595 to 730 nm. All complexes possessing a motif with a methoxy group at the 3-position of the cyclometalating ligands showed very short emission lifetimes and poor photoluminescence quantum yields whereas complexes having a methoxy group at the 4-position were slightly blue shifted compared to the unsubstituted parent complexes, resulting from the inductively electron withdrawing nature of this directing group on the Ir-C bond. Light-emitting electrochemical cells were fabricated and evaluated. These deep red emitters generally showed poor performance with electroluminescence mirroring photoluminescence. DFT calculations accurately modelled the observed photophysical and electrochemical behavior of the complexes and point to an emission from a mixed charge transfer state. PMID:26179641

  7. Development of biosensor for phenolic compounds containing PPO in β-cyclodextrin modified support and iridium nanoparticles.

    PubMed

    da Silva, Cristiano P; Franzoi, Ana C; Fernandes, Suellen C; Dupont, Jairton; Vieira, Iolanda C

    2013-04-10

    A biosensor based on the iridium nanoparticles dispersed in ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (Ir-BMI·PF6) and a celery (Apium graveolens) extract as a source of polyphenol oxidase (PPO) was constructed. A modified support based on β-cyclodextrin (β-CDEP) was used for enzyme immobilization. The behavior of phenolic compounds was investigated by square-wave voltammetry and rutin was selected by presenting the greatest signal. The best performance was obtained with a composition of 70:10:10:10% (w/w/w/w) of the graphite powder:β-CDEP:Nujol:Ir-BMI·PF6 composition, a PPO concentration of 500unitsmL(-1), in 0.1M phosphate buffer solution (pH 6.0) with frequency, pulse amplitude and scan increment at 100Hz, 60mV, and 3.0mV, respectively. Under optimized conditions, the cathodic currents increased linearly for the rutin concentration range of 1.3×10(-7)-2.0×10(-6)M with a detection limit of 7.9×10(-8)M. This sensor demonstrated acceptable repeatability and reproducibility and the results for the rutin recovery ranged from 92.8 to 103.4%. A relative error of 0.7% was obtained in the rutin determination in simulated samples.

  8. Development of a fast and sensitive glucose biosensor using iridium complex-doped electrospun optical fibrous membrane.

    PubMed

    Zhou, Cuisong; Shi, Yalin; Ding, Xiaodong; Li, Ming; Luo, Jiaojiao; Lu, Zhiyun; Xiao, Dan

    2013-01-15

    Polystyrene electrospun optical fibrous membrane (EOF) was fabricated using a one-step electrospinning technique, functionalized with glucose oxidases (GOD/EOF), and used as a quick and highly sensitive optical biosensor. Because of the doped iridium complex, the fibrous membrane emitted yellow luminescence (562 nm) when excited at 405 nm. Its luminescence was significantly enhanced with the presence of extremely low concentration glucose. The detection limit was of 1.0 × 10(-10) M (S/N = 3), superior to that of reported glucose biosensor with 1.2 × 10(-10) M. A linear range between the relative intensity increase and the logarithm of glucose concentration was exhibited from 3.0 × 10(-10) M to 1.3 × 10(-4) M, which was much wider than reported results. Notably, the response time was less than 1 s. These high sensitivity and fast response were attributed to the high surface-area-to-volume of the porous fibrous membrane, the efficient GOD biocatalyst reaction on the fibers surface, as well as the fast electron or energy transfer between dissolved oxygen and the optical fibrous membrane. PMID:23215003

  9. New method for the measurement of osmium isotopes applied to a New Zealand Cretaceous/Tertiary boundary shale

    USGS Publications Warehouse

    Lichte, F.E.; Wilson, S.M.; Brooks, R.R.; Reeves, R.D.; Holzbecher, J.; Ryan, D.E.

    1986-01-01

    The determination of osmium content and isotopic abundances in geological materials has received increasing attention in recent years following the proposal of Alvarez et al.1 that mass extinctions at the end of the Cretaceous period were caused by the impact of a large (???10km) meteorite which left anomalously high iridium levels as a geochemical signature in the boundary shales. Here we report a new and simple method for measuring osmium in geological materials, involving fusion of the sample with sodium peroxide, distillation of the osmium as the tetroxide using perchloric acid, extraction into chloroform, and absorption of the chloroform extract onto graphite powder before instrumental neutron activation analysis. In a variant of this technique, the chloroform extract is back-extracted into an aqueous phase and the osmium isotopes are determined by plasma-source mass spectrometry (ICPMS). We have used this method on the Woodside Creek (New Zealand) Cretaceous/Tertiary boundary clay and have obtained the first osmium content (6g ng g-1) for this material. The 187Os/186Os ratio is 1.12??0.16, showing a typical non-crustal signature. This combined distillation-extraction- ICPMS method will prove to be useful for measuring osmium isotopes in other geological materials. ?? 1986 Nature Publishing Group.

  10. Isotope separation apparatus

    DOEpatents

    Arnush, Donald; MacKenzie, Kenneth R.; Wuerker, Ralph F.

    1980-01-01

    Isotope separation apparatus consisting of a plurality of cells disposed adjacent to each other in an evacuated container. A common magnetic field is established extending through all of the cells. A source of energetic electrons at one end of the container generates electrons which pass through the cells along the magnetic field lines. Each cell includes an array of collector plates arranged in parallel or in tandem within a common magnetic field. Sets of collector plates are disposed adjacent to each other in each cell. Means are provided for differentially energizing ions of a desired isotope by applying energy at the cyclotron resonant frequency of the desired isotope. As a result, the energized desired ions are preferentially collected by the collector plates.

  11. Chlorine Isotope Variation in Eucrites

    NASA Astrophysics Data System (ADS)

    Barrett, T. J.; Barnes, J. J.; Anand, M.; Franchi, I. A.; Greenwood, R. C.; Charlier, B. L. A.; Grady, M. M.

    2016-08-01

    We present Cl isotopic compositions for several eucrites with a wide range of petrological and geochemical histories. Our results include some of the heaviest chlorine isotopic compositions recorded so far in the solar system.

  12. Atomic Weights and Isotopic Compositions

    National Institute of Standards and Technology Data Gateway

    SRD 144 Atomic Weights and Isotopic Compositions (Web, free access)   The atomic weights are available for elements 1 through 111, and isotopic compositions or abundances are given when appropriate.

  13. Nonbiological fractionation of iron isotopes

    NASA Technical Reports Server (NTRS)

    Anbar, A. D.; Roe, J. E.; Barling, J.; Nealson, K. H.

    2000-01-01

    Laboratory experiments demonstrate that iron isotopes can be chemically fractionated in the absence of biology. Isotopic variations comparable to those seen during microbially mediated reduction of ferrihydrite are observed. Fractionation may occur in aqueous solution during equilibration between inorganic iron complexes. These findings provide insight into the mechanisms of iron isotope fractionation and suggest that nonbiological processes may contribute to iron isotope variations observed in sediments.

  14. DEEP WATER ISOTOPIC CURRENT ANALYZER

    DOEpatents

    Johnston, W.H.

    1964-04-21

    A deepwater isotopic current analyzer, which employs radioactive isotopes for measurement of ocean currents at various levels beneath the sea, is described. The apparatus, which can determine the direction and velocity of liquid currents, comprises a shaft having a plurality of radiation detectors extending equidistant radially therefrom, means for releasing radioactive isotopes from the shaft, and means for determining the time required for the isotope to reach a particular detector. (AEC)

  15. Method for separating boron isotopes

    DOEpatents

    Rockwood, Stephen D.

    1978-01-01

    A method of separating boron isotopes .sup.10 B and .sup.11 B by laser-induced selective excitation and photodissociation of BCl.sub.3 molecules containing a particular boron isotope. The photodissociation products react with an appropriate chemical scavenger and the reaction products may readily be separated from undissociated BCl.sub.3, thus effecting the desired separation of the boron isotopes.

  16. Forensic Stable Isotope Biogeochemistry

    NASA Astrophysics Data System (ADS)

    Cerling, Thure E.; Barnette, Janet E.; Bowen, Gabriel J.; Chesson, Lesley A.; Ehleringer, James R.; Remien, Christopher H.; Shea, Patrick; Tipple, Brett J.; West, Jason B.

    2016-06-01

    Stable isotopes are being used for forensic science studies, with applications to both natural and manufactured products. In this review we discuss how scientific evidence can be used in the legal context and where the scientific progress of hypothesis revisions can be in tension with the legal expectations of widely used methods for measurements. Although this review is written in the context of US law, many of the considerations of scientific reproducibility and acceptance of relevant scientific data span other legal systems that might apply different legal principles and therefore reach different conclusions. Stable isotopes are used in legal situations for comparing samples for authenticity or evidentiary considerations, in understanding trade patterns of illegal materials, and in understanding the origins of unknown decedents. Isotope evidence is particularly useful when considered in the broad framework of physiochemical processes and in recognizing regional to global patterns found in many materials, including foods and food products, drugs, and humans. Stable isotopes considered in the larger spatial context add an important dimension to forensic science.

  17. Sulfur isotopic data

    SciTech Connect

    Rye, R.O.

    1987-01-01

    Preliminary sulfur isotope data have been determined for samples of the Vermillion Creek coal bed and associated rocks in the Vermillion Creek basin and for samples of evaporites collected from Jurassic and Triassic formations that crop out in the nearby Uinta Mountains. The data are inconclusive, but it is likely that the sulfur in the coal was derived from the evaporites.

  18. Isotope fractionation studies of molybdenum

    NASA Astrophysics Data System (ADS)

    Wieser, M. E.; de Laeter, J. R.; Varner, M. D.

    2007-08-01

    Mass spectrometric studies of the isotopic composition of molybdenum have become an active area of research in stable isotope geochemistry, biogeochemistry and cosmochemistry. The redox chemistry of Mo, together with its proclivity for covalent bonding, indicates its importance in isotope fractionation studies such as palaeoceanography. The measurement of the magnitude of isotope fractionation of Mo in natural systems is a challenging task, in that natural fractionation has to be carefully distinguished from chemical and instrumental isotope fractionation. An ion exchange chemical separation procedure has been developed with high efficiency and low blank, to ensure that the isobaric elements Zr and Ru are removed from the samples before mass spectrometric analysis. The isotope fractionation resulting from this procedure is 0.14[per mille sign] per u. The isotopic composition of Mo of a Laboratory Standard has been measured by positive and negative thermal ionization mass spectrometry (P-TIMS and N-TIMS, respectively), to give an isotope fractionation of 6.4[per mille sign] and 0.5[per mille sign] per u, respectively, with respect to the absolute isotope abundances of Mo. In both cases the lighter isotopes are enhanced with respect to the heavier isotopes. An ascorbic acid activator has enabled the sensitivity of P-TIMS to be improved as compared to traditional methods. The same experiment was repeated using a multiple collector-inductively coupled plasma-mass spectrometer (MC-ICP-MS) to give an isotope fractionation of approximately 17.0[per mille sign] per u. In this case the heavier isotopes are enhanced with respect to the lighter isotopes. The strengths and weaknesses of these three mass spectrometric techniques are evaluated. We conclude that MC-ICP-MS is the optimum mass spectrometric method for accurately measuring the isotope fractionation of Mo in natural materials, provided chemical and instrumental isotope fractionation can be resolved from naturally

  19. Iridium-mediated C-S bond activation and transformation: organoiridium(III) thioether, thiolato, sulfinato and thiyl radical compounds. Synthesis, mechanistic, spectral, electrochemical and theoretical aspects.

    PubMed

    Das, Ujjwal; Ghorui, Tapas; Adhikari, Basab; Roy, Sima; Pramanik, Shuvam; Pramanik, Kausikisankar

    2015-05-14

    An attractive methodology, single-electron transfer (SET) reductive cleavage of the C-S bond mediated by a metal in the presence of the external stimuli PPh3, has been applied to the kinetically inert IrCl3 in order to synthesize the thiolato complex [Ir(III)(L(S))Cl(PPh3)2] 3 from precursor thioether complexes [Ir(III)(L(SR))Cl2(PPh3)] (R = alkyl) 2. The aforesaid cleavage process in association with (arene)C-H activation furnishes a new class of organosulfur compounds of iridium(III). The thiolato chelate 3 displays a reversible oxidative wave at 0.75 V vs. Ag/AgCl signifying its remarkable nucleophilic character. The high electron density on the thiolato-S vis-à-vis superior nucleophilicity can be envisaged through the formation of a number of S-centered derivatives. This observation has been corroborated with the nature of HOMO in 3, which assumes 49% of S(3p). Notably, the facile oxidative nature of 3 makes it an apposite precursor for metal-stabilized thiyl radical species. Indeed, iridium(III)-stabilized 3˙(+) can be generated by chemical/electrochemical means. The axial EPR spectra with g ∼ 2.0 along with theoretical analysis of SOMO (S(3p) 24% + Ph(π) 43% + d(yz) 15%) and spin density (ρ(S) = +0.543, ρ(Ph) = +0.315, ρ(Ir) = +0.151) of one-electron oxidized 3˙(+) validate the iridium-stabilized thiyl radical description. This observation suggests that the CNS coordination mode in thiophenolato complex 3 is redox-active. Complex 3 is very prone to S-centered oxidation under normal aerobic conditions to yield metallosulfoxide [Ir(III)(L(SO2))Cl(PPh3)2] 4. The enhanced nucleophilicity of thiolato-S can also be manifested via the smooth S-C bond making process with alkyl halides (R'X, R' = Me and allyl; X = Br, I) and subsequent formation of thioether complexes of type [Ir(III)(L(SR'))ClX(PPh3)] 5. The organosulfur compounds of iridium(III) exhibit rich spectral properties including luminescence and the origin of these transitions is scrutinized with

  20. Iridium-catalyzed ortho-selective C-H silylation of aromatic compounds directed toward the synthesis of π-conjugated molecules with Lewis acid-base interaction.

    PubMed

    Wakaki, Takayuki; Kanai, Motomu; Kuninobu, Yoichiro

    2015-04-01

    We successfully developed an iridium-catalyzed ortho-selective C-H silylation of aromatic compounds. The reaction exhibited a wide substrate scope, and a variety of π-conjugated molecules were synthesized in good to excellent yields, even in gram scale. Several silyl groups could also be introduced into the products. The experimental results indicated that the regioselectivity could be controlled by a Lewis acid-base interaction between the Lewis acidic silicon atoms of fluorinated hydrosilanes and the Lewis basic nitrogen atoms of aromatic compounds.