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

Science.gov (United States)

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) ). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Welding of iridium heat source capsule components

International Nuclear Information System (INIS)

Mustaleski, T.M.; Yearwood, J.C.; Burgan, C.E.; Green, L.A.

1991-01-01

Interplanetary spacecraft have long used radioisotope thermoelectric generators (RTG) to produce power for instrumentation. These RTG produce electrical energy from the heat generated through the radioactive decay of plutonium-238. The plutonium is present as a ceramic pellet of plutonium oxide. The pellet is encapsulated in a containment shell of iridium. Iridium is the material of choice for these capsules because of its compatibility with the plutonium dioxide. The high-energy beam welding (electron beam and laser) processes used in the fabrication of the capsules has not been published. These welding procedures were originally developed at the Mound Laboratories and have been adapted for use at the Oak Ridge Y-12 Plant. The work involves joining of thin material in small sizes to exacting tolerances. There are four different electron beam welds on each capsule, with one procedure being used in three locations. There is also a laser weld used to seal the edges of a sintered frit assembly. An additional electron beam weld is also performed to seal each of the iridium blanks in a stainless steel waster sheet prior to forming. In the transfer of these welding procedures from one facility to another, a number of modifications were necessary. These modifications are discussed in detail, as well as the inherent problems in making welds in material which is only 0.005 in. thick. In summary, the paper discusses the welding of thin components of iridium using the high energy beam processes. While the peculiarities of iridium are pertinent to the discussion, much of the information is of general interest to the users of these processes. This is especially true of applications involving thin materials and high-precision assemblies

Enantiomeric separation of iridium (III) complexes using HPLC chiral stationary phases based on amylose derivatives

International Nuclear Information System (INIS)

Kim, Hee Eun; Seo, Na Hyeon; Hyun, Myung Ho

2016-01-01

Cyclometalated iridium (III) complexes formed with three identical cyclometalating (C-N) ligands (homoleptic) or formed with two cyclometalating (C-N) ligands and one ancillary (LX) ligand (heteroleptic) have been known as highly phosphorescent materials and, thus, they have been utilized as efficient phosphorescent dopants in organic light emitting diodes (OLEDs) 1–3 or as effective phosphorescent chemosensors. 4–7 Cylometalated iridium (III) complexes are chiral compounds consisting of lambda (Λ, left-handed) and delta (Δ, right-handed) isomers. Racemic cyclometa- lated iridium (III) complexes emit light with no net polarization, but optically active cyclometalated iridium (III) complexes emit circularly polarized light. 8,9 Circularly polarized light can be used in various fields including highly efficient three dimensional electronic devices, photo nic devices for optical data storage, biological assays, and others. 8,9 In order to obtain optically active cylometalated iridium (III) complexes and to determine the enantiomeric composition of optically active cylometalated iridium (III) complexes, liquid chromatogr aphic enantiomer separation method on chiral stationary phases (CSPs) has been used. For example, Okamoto and coworkers first reported the high performance liquid chromatographic (HPLC) direct enantiomeric separation of two homoleptic cylometalated iridium (III) complexes on immobilized amylose tris(3,5- dimethylphenylcarbamate) (Chiralpak IA), coated cellulose tris(3,5-dimethylphenylcarbamate) (Chiralc el OD), and coated cellulose tris(4-methylbenzoate) (Chiralce l OJ). 10 Supercritical fluid chromatography (SFC) was also used by Bernhard and coworkers for the enantiomeric separation of cylometalated iridium (III) complexes on coated amylose tris(3,5-dimethylphenylcarbamate) (Chiralpak AD-H). 8 However, the general use of the HPLC method for the direct enantiomeric separation of homoleptic

Enantiomeric separation of iridium (III) complexes using HPLC chiral stationary phases based on amylose derivatives

Energy Technology Data Exchange (ETDEWEB)

Kim, Hee Eun; Seo, Na Hyeon; Hyun, Myung Ho [Dept. of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan (Korea, Republic of)

2016-12-15

Cyclometalated iridium (III) complexes formed with three identical cyclometalating (C-N) ligands (homoleptic) or formed with two cyclometalating (C-N) ligands and one ancillary (LX) ligand (heteroleptic) have been known as highly phosphorescent materials and, thus, they have been utilized as efficient phosphorescent dopants in organic light emitting diodes (OLEDs) 1–3 or as effective phosphorescent chemosensors. 4–7 Cylometalated iridium (III) complexes are chiral compounds consisting of lambda (Λ, left-handed) and delta (Δ, right-handed) isomers. Racemic cyclometa- lated iridium (III) complexes emit light with no net polarization, but optically active cyclometalated iridium (III) complexes emit circularly polarized light. 8,9 Circularly polarized light can be used in various fields including highly efficient three dimensional electronic devices, photo nic devices for optical data storage, biological assays, and others. 8,9 In order to obtain optically active cylometalated iridium (III) complexes and to determine the enantiomeric composition of optically active cylometalated iridium (III) complexes, liquid chromatogr aphic enantiomer separation method on chiral stationary phases (CSPs) has been used. For example, Okamoto and coworkers first reported the high performance liquid chromatographic (HPLC) direct enantiomeric separation of two homoleptic cylometalated iridium (III) complexes on immobilized amylose tris(3,5- dimethylphenylcarbamate) (Chiralpak IA), coated cellulose tris(3,5-dimethylphenylcarbamate) (Chiralc el OD), and coated cellulose tris(4-methylbenzoate) (Chiralce l OJ). 10 Supercritical fluid chromatography (SFC) was also used by Bernhard and coworkers for the enantiomeric separation of cylometalated iridium (III) complexes on coated amylose tris(3,5-dimethylphenylcarbamate) (Chiralpak AD-H). 8 However, the general use of the HPLC method for the direct enantiomeric separation of homoleptic.

Impedance analysis of nanostructured iridium oxide electrocatalysts

International Nuclear Information System (INIS)

Sunde, Svein; Lervik, Ingrid Anne; Tsypkin, Mikhail; Owe, Lars-Erik

2010-01-01

Impedance data were collected for nanostructured iridium oxide (NIROF) at potentials below those at which the oxygen evolution reaction commences. The measurements included thin oxide films covered by a protective Nafion TM layer and thicker composite Nafion TM -oxide electrodes. The time constants for the low-frequency diffusion process were approximately the same for both types of electrodes, indicating diffusion in individual particles in the porous electrode rather than across the film. The diffusion process involves trapping of the diffusion species. The impedance data indicated that there were no significant variations in conductivity of the oxides with potential, as opposed to what appears to be the case for anodically formed iridium oxide films (AIROF). This is interpreted to reflect differences in electronic structure between NIROF and AIROF.

Balancing activity, stability and conductivity of nanoporous core-shell iridium/iridium oxide oxygen evolution catalysts

Energy Technology Data Exchange (ETDEWEB)

Kim, Yong-Tae; Lopes, Pietro Papa; Park, Shin-Ae; Lee, A-Yeong; Lim, Jinkyu; Lee, Hyunjoo; Back, Seoin; Jung, Yousung; Danilovic, Nemanja; Stamenkovic, Vojislav; Erlebacher, Jonah; Snyder, Joshua; Markovic, Nenad M.

2017-11-13

The selection of oxide materials for catalyzing the Oxygen Evolution Reaction in acid-based electrolyzers must be guided by the proper balance between activity, stability and conductivity – a challenging mission of great importance for delivering affordable and environmentally friendly hydrogen. Here we report that the highly conductive nanoporous architecture of an iridium oxide shell on a metallic iridium core, formed through the fast dealloying of osmium from an Ir25Os75 alloy, exhibits an exceptional balance between oxygen evolution activity and stability as quantified by the Activity-Stability FactorASF. Based on this metric, the nanoporous Ir/IrO2 morphology of dealloyed Ir25Os75 shows a factor of ~30 improvement ASFrelative to conventional Ir-based oxide materials and a ~8 times improvement over dealloyed Ir25Os75 nanoparticles due to optimized stability and conductivity, respectively. We propose that the Activity-Stability FactorASF is the key “metric” for determining the technological relevance of oxide-based anodic water electrolyzer catalysts.

Iridium: failures & successes

Science.gov (United States)

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.

Iridium Interfacial Stack (IRIS)

Science.gov (United States)

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.

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

Energy Technology Data Exchange (ETDEWEB)

Dangwal Pandey, A., E-mail: arti.pandey@desy.de; Grånäs, E.; Shayduk, R.; Noei, H.; Vonk, V. [Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg (Germany); Krausert, K.; Franz, D.; Müller, P.; Keller, T. F.; Stierle, A., E-mail: andreas.stierle@desy.de [Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg (Germany); Fachbereich Physik, Universität Hamburg, D-22607 Hamburg (Germany)

2016-08-21

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.

Crystal structure of an iridium(III complex of the [C(dppm2] PCP pincer ligand system and its conjugate CH acid form

Directory of Open Access Journals (Sweden)

Christian Reitsamer

2018-05-01

Full Text Available After the successful creation of the newly designed PCP carbodiphosphorane (CDP ligand [Reitsamer et al. (2012. Dalton Trans. 41, 3503–3514; Stallinger et al. (2007. Chem. Commun. pp. 510–512], the treatment of this PCP pincer system with the transition metal iridium and further the analysis of the structures by single-crystal diffraction and by NMR spectroscopy were of major interest. Two different iridium complexes, namely (bis{[(diphenylphosphanylmethyl]diphenylphosphanylidene}methane-κ3P,C,P′carbonylchloridohydridoiridium(III chloride dichloromethane trisolvate, [IrIII(CO{C(dppm2-κ3P,C,P′}ClH]Cl·3CH2Cl2 (1 and the closely related (bis{[(diphenylphosphanylmethyl]diphenylphosphanylidene}methanide(1+-κ3P,C,P′carbonylchloridohydridoiridium(III dichloride–hydrochloric acid–water (1/2/5.5, [IrIII(CO{CH(dppm2-κ3P,C,P′ClH]Cl}2 (2, have been designed and both complexes show a slightly distorted octahedral coordinated IrIII centre. The PCP pincer ligand system is arranged in a meridional manner, the CO ligand is located trans to the central PCP carbon and a hydride and chloride are located perpendicular above and below the P2C2 plane. With an Ir—CCDP distance of 2.157 (5 Å, an Ir—CO distance of 1.891 (6 Å and a quite short C—O distance of 1.117 (7 Å, complex 1 presents a strong carbonyl bond. Complex 2, the corresponding CH acid of 1, shows an additionally attached proton at the carbodiphosphorane carbon atom located antiperiplanar to the hydride of the metal centre. In comparison with complex 1, the Ir—CCDP distance of 2.207 (3 Å is lengthened and the Ir—C—O values indicate a weaker trans influence of the central carbodiphosphorane carbon atom.

An iron-57 Moessbauer spectroscopic study of titania-supported iron- and iron-iridium catalysts

International Nuclear Information System (INIS)

Berry, F.J.; Jobson, S.

1992-01-01

57 Fe Moessbauer spectroscopy shows that titania-supported iron is reduced by treatment in hydrogen at significantly lower temperatures than corresponding silica- and alumina-supported catalysts. The metallic iron formed under hydrogen at 600deg C is partially converted to carbide by treatment in carbon monoxide and hydrogen. In contrast to its alumina- and silica-supported counterparts, the remainder of the titania-supported iron is unchanged by this gaseous mixture. The 57 Fe Moessbauer spectra of EXAFS show that iron and iridium in the titania-supported iron-iridium catalysts are reduced in hydrogen at even lower temperatures and, after treatment at 600deg C, are predominantly present as the iron-iridium alloy. The treatment of these reduced catalysts in carbon monoxide and hydrogen is shown by Moessbauer spectroscopy and EXAFS to induce the segregation of iron from the iron-iridium alloy and its conversion to iron oxide. (orig.)

Trapping interference effects of arsenic, antimony and bismuth hydrides in collection of selenium hydride within iridium-modified transversally-heated graphite tube atomizer

Energy Technology Data Exchange (ETDEWEB)

Furdikova, Zuzana [Department of Environmental Chemistry and Technology, Faculty of Chemistry, Brno University of Technology, Purkynova 118, CZ-61200 Brno (Czech Republic); Institute of Analytical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Veveri 97, CZ-60200, Brno (Czech Republic); Docekal, Bohumil [Institute of Analytical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Veveri 97, CZ-60200, Brno (Czech Republic)], E-mail: docekal@iach.cz

2009-04-15

Interference effects of co-generated hydrides of arsenic, antimony and bismuth on trapping behavior of selenium hydride (analyte) within an iridium-modified, transversely heated graphite tube atomizer (THGA) were investigated. A twin-channel hydride generation system was used for independent separate generation and introduction of analyte and interferent hydrides, i.e. in a simultaneous and/or sequential analyte-interferent and interferent-analyte mode of operation. The influence of the analyte and modifier mass, interferent amount, trapping temperature and composition of the gaseous phase was studied. A simple approach for the elimination of mutual interference effects by modification of the gaseous phase with oxygen in a substoichiometric ratio to chemically generated hydrogen is proposed and the suppression of these interference effects is demonstrated. A hypothesis on the mechanism of trapping and mutual interference effects is drawn.

Dynamic high-temperature characterization of an iridium alloy in tension

Energy Technology Data Exchange (ETDEWEB)

Song, Bo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Nelson, Kevin [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Jin, Helena [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Lipinski, Ronald J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bignell, John [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ulrich, G. B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); George, E. P. [Ruhr Univ., Bochum (Germany)

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.

Synthesis and structural studies of Cp{sup *} rhodium and Cp{sup *} iridium complexes of picolinic hydrazine ligand

Energy Technology Data Exchange (ETDEWEB)

Palepu, Narasinga Rao; Kollipara, Mohan Rao [Centre for Advanced Studies in Chemistry, North-Eastern Hill University, Shillong (India); Kaminsky Werner [Dept. of Chemistry, University of Washington, Seattle (United States)

2017-01-15

A series of Cp{sup *}Rh and Cp{sup *}Ir complexes of picolinic hydrazine ligand are synthesized and characterized. Picolinic hydrazine has yielded only dinuclear complexes in the case of rhodium metal whereas both mono and dinuclear complexes with iridium metal. Iridium complexes are formed as quaternary salts by the migration of the N–H proton onto the adjacent amine group of the hydrazine after binding to the metal. Picolinic hydrazine acts as nitrogen and oxygen donor ligand in the form of bi and tetradentate bonding modes.

The role of iridium in the work-function behavior of dilute-solution tungsten, iridium alloys

International Nuclear Information System (INIS)

D'Cruz, L.A.

1991-01-01

Requirements of thermionic electrode materials have emphasized the need for substantial improvements in microstructural stability, strength and creep resistance at service temperatures in excess of 2,500K. This study utilized both chemical alloying and mechanical alloying procedures for the addition of iridium to submicron W powder followed by cold compaction and sintering. The shrinkage characteristics and microstructural development were studied in iridium-added tungsten compacts with a range of additive levels. An electron-emission study was subsequently carried out in order to evaluate the work-function behavior of the consolidated alloys. The work function was obtained from current-emission measurements from the electrode surface under UHV conditions in the temperature range of 1,800 to 2,500K using a Vacuum Emission Vehicle (VEV). The data show that the magnitude of the work function in these alloys varied with temperature and was sensitive to sub-surface iridium content

Effective Area and Charge Density of Iridium Oxide Neural Electrodes

International Nuclear Information System (INIS)

Harris, Alexander R.; Paolini, Antonio G.; Wallace, Gordon G.

2017-01-01

The effective electrode area and charge density of iridium metal and anodically activated iridium has been measured by optical and electrochemical techniques. The degree of electrode activation could be assessed by changes in electrode colour. The reduction charge, activation charge, number of activation pulses and charge density were all strongly correlated. Activated iridium showed slow electron transfer kinetics for reduction of a dissolved redox species. At fast voltammetric scan rates the linear diffusion electroactive area was unaffected by iridium activation. At slow voltammetric scan rates, the steady state diffusion electroactive area was reduced by iridium activation. The steady state current was consistent with a ring electrode geometry, with lateral resistance reducing the electrode area. Slow electron transfer on activated iridium would require a larger overpotential to reduce or oxidise dissolved species in tissue, limiting the electrodes charge capacity but also reducing the likelihood of generating toxic species in vivo.

Experimental and Theoretical Mechanistic Investigation of the Iridium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols

DEFF Research Database (Denmark)

Olsen, Esben Paul Krogh; Singh, Thishana; Harris, Pernille

2015-01-01

The mechanism for the iridium-BINAP catalyzed dehydrogenative decarbonylation of primary alcohols with the liberation of molecular hydrogen and carbon monoxide was studied experimentally and computationally. The reaction takes place by tandem catalysis through two catalytic cycles involving...... cycles. One carbon monoxide ligand was shown to remain coordinated to iridium throughout the reaction, and release of carbon monoxide was suggested to occur from a dicarbonyl complex. IrH2Cl(CO)(rac-BINAP) was also synthesized and detected in the dehydrogenation of benzyl alcohol. In the same experiment......, IrHCl2(CO)(rac-BINAP) was detected from the release of HCl in the dehydrogenation and subsequent reaction with IrCl(CO)(rac-BINAP). This indicated a substitution of chloride with the alcohol to form a square planar iridium alkoxo complex that could undergo a beta-hydride elimination. A KIE of 1...

Production of iridium-alloy clad vent sets for the Cassini mission to Saturn

International Nuclear Information System (INIS)

Helle, K.J.; Moore, J.P.

1995-01-01

Martin Marietta Energy Systems, Inc., has successfully produced the iridium-alloy clad vent sets required for encapsulation of plutonia for the National Aeronautics and Space Administration Cassini mission to Saturn. Numerous improvements were made to the manufacturing process in various areas including dye-penetrant examination of cups, foil part stamping, chemical analysis, tungsten fixturing for laser welding, and enhanced inspections at high magnification. In addition, systems were initiated to ensure process control, and a detailed quality and technical surveillance program was prepared and followed to detect any incipient production problem early in the process so that corrective action could be taken immediately. The quality of the resulting iridium components has been high, and production yields have been above 90%. During the course of the production campaign for the Cassini mission, worker efficiencies lowered production costs, and further cost reductions are possible if operations are consolidated into a single area and bare-forming of the iridium alloys cups can be qualified for flight-quality clad vent sets

User-friendly aerobic reductive alkylation of iridium(III) porphyrin chloride with potassium hydroxide: scope and mechanism.

Science.gov (United States)

Zuo, Huiping; Liu, Zhipeng; Yang, Wu; Zhou, Zhikuan; Chan, Kin Shing

2015-12-21

Alkylation of iridium 5,10,15,20-tetrakistolylporphyrinato carbonyl chloride, Ir(ttp)Cl(CO) (1), with 1°, 2° alkyl halides was achieved to give (ttp)Ir-alkyls in good yields under air and water compatible conditions by utilizing KOH as the cheap reducing agent. The reaction rate followed the order: RCl < RBr < RI (R = alkyl), and suggests an SN2 pathway by [Ir(I)(ttp)](-). Ir(ttp)-adamantyl was obtained under N2 when 1-bromoadamantane was utilized, which could only undergo bromine atom transfer pathway. Mechanistic investigations reveal a substrate dependent pathway of SN2 or halogen atom transfer.

Problems associated with iridium-192 wire implants

International Nuclear Information System (INIS)

Arnott, S.J.; Law, J.; Ash, D.; Flynn, A.; Paine, C.H.; Durrant, K.R.; Barber, C.D.; Dixon-Brown, A.

1985-01-01

Three incidents are reported, from different radiotherapy centres, in which an implanted iridium-192 wire remained in the tissues of a patient after withdrawal of the plastic tubing in which it was contained. In each case the instrument used to cut the wire had probably formed a hook on the end of the wire which caused it to catch in the tissues. Detailed recommendations are made for avoiding such incidents in the future, the most important of which is that the patient should be effectively monitored after the supposed removal of all radioactive sources. (author)

Synthesis of benzimidazoles via iridium-catalyzed acceptorless dehydrogenative coupling.

Science.gov (United States)

Sun, Xiang; Lv, Xiao-Hui; Ye, Lin-Miao; Hu, Yu; Chen, Yan-Yan; Zhang, Xue-Jing; Yan, Ming

2015-07-21

Iridium-catalyzed acceptorless dehydrogenative coupling of tertiary amines and arylamines has been developed. A number of benzimidazoles were prepared in good yields. An iridium-mediated C-H activation mechanism is suggested. This finding represents a novel strategy for the synthesis of benzimidazoles.

Analytical evaluation of atomic form factors: Application to Rayleigh scattering

Energy Technology Data Exchange (ETDEWEB)

Safari, L., E-mail: laleh.safari@ist.ac.at [IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg (Austria); Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Santos, J. P. [Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação (LIBPhys-UNL), Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Amaro, P. [Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação (LIBPhys-UNL), Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg (Germany); Jänkälä, K. [Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Fratini, F. [Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Institute of Atomic and Subatomic Physics, TU Wien, Stadionallee 2, 1020 Wien (Austria); Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG (Brazil)

2015-05-15

Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wave functions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.

Weldability of general purpose heat source new-process iridium

International Nuclear Information System (INIS)

Kanne, W.R.

1987-01-01

Weldability tests on General Purpose Heat Source (GPHS) iridium capsules showed that a new iridium fabrication process reduced susceptibility to underbead cracking. Seventeen capsules were welded (a total of 255 welds) in four categories and the number of cracks in each weld was measured

Synthesis and characterization of low-valence actinide phosphide tellurides and ternary selenium-halide iridium complexes; Synthese und Charakterisierung niedervalenter Actinoidphosphidtelluride und ternaerer Selen-Halogenid-Komplexe des Iridiums

Energy Technology Data Exchange (ETDEWEB)

Stolze, Karoline

2016-04-07

The thesis on the synthesis and characterization of low-valence actinide phosphide tellurides and ternary selenium-halide iridium complexes includes two parts: a description of the experimental synthesis of UPTe and U2PTe2O and ThPTe and the synthesis of selenium-chloride iridium complexes and selenium-bromide iridium complexes. The characterization included X-ray diffraction and phase studies.

Synthesis and crystal structure of the iridium(I) carbene complex with a pair of hydrogen wing tips

Energy Technology Data Exchange (ETDEWEB)

Huang, H.-Y.; Chen, Z.-M.; Wang, Y.; Wu, E.-M.; Wang, G. [Jiangsu Institute of Nuclear Medicine, Ministry of Health, Key Laboratory of Molecular Nuclear Medicine (China); Jiang, M.-J., E-mail: jmj16888@126.com [Nanjing Medical University, Affiliated Wuxi Peoples Hospital, Wuxi Institute of Translational Medicine, Department of Clinical Laboratory Science (China)

2016-12-15

The iridium(I) cyclooctadiene complex with two (3-tert-butylimidazol-2-ylidene) ligands [(H-Im{sup t}Bu){sub 2}Ir(COD)]{sup +}PF{sub 6}{sup −} (C{sub 22}H{sub 32}PF{sub 6}IrN{sub 4}) has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal atom, which is coordinated by two H-Im{sup t}Bu ligands and one cyclooctadiene group. The new iridium carbene complex has a pair of hydrogen wing tips. The Ir−C{sub carbene} bond lengths are 2.066(5) and 2.052(5) Å, and the bond angle C−Ir−C between these bonds is 95.54(19)°. The dihedral angle between two imidazol-2-ylidene rings is 86.42°.

Laser welding parameters for manufacturing iridium-192 (Ir-192) source

International Nuclear Information System (INIS)

Anung Pujiyanto; Moch Subechi; Hotman Lubis; Diandono KY

2013-01-01

Number of cervical cancer patients in Indonesia is growing every year. One of cervical cancer treatment was fairly effective use brachytherapy treatment with radioisotope sources of iridium-192. Manufacturing of iridium sources for brachytherapy can be done by incorporating the iridium-192 into stainless steel microcapsules then welding using laser welder which the quality of the welding of iridium source (Ir-192) was determined by the welding parameters such as full power, energy frequency, average power and speed. Based on the result of leakage test using pressure -20 inch Hg and tensile test 2.5 bar showed the welding parameters III and IV did not have leakage and damaged. So that parameters III and IV are recommended to be applied to Ir-192 HDR's source. (author)

Iridium catalyzed growth of vertically aligned CNTs by APCVD

International Nuclear Information System (INIS)

Sahoo, R.K.; Jacob, C.

2014-01-01

Highlights: • Growth of uniform-diameter vertically-aligned multi-walled CNTs by APCVD. • Use of high melting point low carbon solubility iridium nanoparticles as catalyst. • Optimization of growth time for uniform sized, uniformly aligned CNTs. • Growth model for the various features in the vertically aligned CNTs is proposed. - Abstract: Vertically aligned carbon nanotubes (VA-CNTs) have been synthesized using high temperature catalyst nanoparticles of iridium. The catalyst layer was prepared by DC sputtering. Particle density, circularity and average particle size of the catalyst were analyzed using field emission scanning electron microscopy. The alignment, morphology and the length of the as-grown CNTs were analyzed using field-emission scanning electron microscopy. High resolution transmission electron microscopy was carried out to observe the layers of graphitic stacking which form the carbon nanotubes. Micro Raman measurement was used for the analysis of the graphitic crystallinity of the as-grown carbon nano structures. Effects of growth time variation on growth morphology and alignment have been studied. The alignment has been explained on the basis of the crowding effect of the neighboring nanoparticles

Iridium catalyzed growth of vertically aligned CNTs by APCVD

Energy Technology Data Exchange (ETDEWEB)

Sahoo, R.K.; Jacob, C., E-mail: cxj14_holiday@yahoo.com

2014-07-01

Highlights: • Growth of uniform-diameter vertically-aligned multi-walled CNTs by APCVD. • Use of high melting point low carbon solubility iridium nanoparticles as catalyst. • Optimization of growth time for uniform sized, uniformly aligned CNTs. • Growth model for the various features in the vertically aligned CNTs is proposed. - Abstract: Vertically aligned carbon nanotubes (VA-CNTs) have been synthesized using high temperature catalyst nanoparticles of iridium. The catalyst layer was prepared by DC sputtering. Particle density, circularity and average particle size of the catalyst were analyzed using field emission scanning electron microscopy. The alignment, morphology and the length of the as-grown CNTs were analyzed using field-emission scanning electron microscopy. High resolution transmission electron microscopy was carried out to observe the layers of graphitic stacking which form the carbon nanotubes. Micro Raman measurement was used for the analysis of the graphitic crystallinity of the as-grown carbon nano structures. Effects of growth time variation on growth morphology and alignment have been studied. The alignment has been explained on the basis of the crowding effect of the neighboring nanoparticles.

Simultaneous iridium catalysed oxidation and enzymatic reduction employing orthogonal reagents

NARCIS (Netherlands)

Mutti, Francesco G.; Orthaber, Andreas; Schrittwieser, Joerg H.; Vries, Johannes G. de; Pietschnig, Rudolf; Kroutil, Wolfgang

2010-01-01

An iridium catalysed oxidation was coupled concurrently to an asymmetric biocatalytic reduction in one-pot; thus it was shown for the first time that iridium- and alcohol dehydrogenase-catalysed redox reactions are compatible. As a model system racemic chlorohydrins were transformed to

pH-sensor properties of electrochemically grown iridium oxide

NARCIS (Netherlands)

Olthuis, Wouter; Robben, M.A.M.; Bergveld, Piet; Bos, M.; van der Linden, W.E.

1990-01-01

The open-circuit potential of an electrochemically grown iridium oxide film is measured and shows a pH sensitivity between −60 and −80 mV/pH. This sensitivity is found to depend on the state of oxidation of the iridium oxide film; for a higher state of oxidation (or more of the oxide in the high

Influence of the atomic structure on the quantum state of sputtered Ir atoms

International Nuclear Information System (INIS)

Bastiaansen, J.; Philipsen, V.; Lievens, P.; Silverans, R.E.; Vandeweert, E.

2004-01-01

The probability of the ejection of a neutral atom in a specific quantum state after keV-ion beam sputtering is often interpreted in terms of the interaction between the atomic states of the escaping atom and the electronic states of the solid. In this work, we examined this interplay in the sputtering of iridium as this element has--unlike the elements employed in previous investigations--a complex atomic structure due to strong configuration interactions. Double-resonant two-photon laser ionization is used to probe the sputtered Ir atoms yielding information about the probability for an ejected atom to populate a specific atomic state and its escape velocity. The qualitative features of the corresponding population partition and state-selective velocity distributions show the influence of the excitation energy and the electronic structure of the different atomic states. A comparison is made between the experimental data and predictions from the resonant electron transfer description

Screening the collision risk of the Iridium 33 - Cosmos 2251 Clouds

OpenAIRE

Rossi, Alessandro; Valsecchi, Giovanni Battista

2011-01-01

More than 10 years ago, in Rossi, Valsecchi and Farinella (Nature, 1999), it was shown how a near polar multi-plane constellation such as Iridium is particularly at risk of a collisional cascade if one of its satellites is first accidentally fragmented. Those results are recalled and actualized in the light of the real collision of February 2009, between Iridium 33 and Cosmos 2251. The collision risk, for the remaining Iridium satellites, arising from the two clouds of fragments generated by ...

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

Science.gov (United States)

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 oriented crystalline silicon substrate thicknesses of 70-280 microns, respectively.

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

Science.gov (United States)

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.

pH sensors based on iridium oxide

International Nuclear Information System (INIS)

Tarlov, M.J.; Kreider, K.G.; Semancik, S.; Huang, P.

1990-03-01

Results are presented on the pH-potential response of dc magnetron reactively sputtered iridium oxide films. The films exhibit a nearly Nernstian response to pH, no hysteresis effects, and minimal response to ionic interferences. Sensitivity to certain redox species is observed, however. In addition, methods are discussed for preparing model iridium oxide sensor surfaces for ultrahigh vacuum surface analytical studies. Stoichiometric IrO 2 -like surfaces are shown to be relatively inert to gas phase water. However, hydroxylation of IrO 2 -like surfaces can be induced by rf water plasma treatment. 17 refs., 5 figs

Iridium Oxide pH Sensor Based on Stainless Steel Wire for pH Mapping on Metal Surface

Science.gov (United States)

Shahrestani, S.; Ismail, M. C.; Kakooei, S.; Beheshti, M.; Zabihiazadboni, M.; Zavareh, M. A.

2018-03-01

A simple technique to fabricate the iridium oxide pH sensor is useful in several applications such as medical, food processing and engineering material where it is able to detect the changes of pH. Generally, the fabrication technique can be classified into three types: electro-deposition iridium oxide film (EIrOF), activated iridium oxide film (AIROF) and sputtering iridium oxide film (SIROF). This study focuses on fabricating electrode, calibration and test. Electro-deposition iridium oxide film is a simple and effective method of fabricating this kind of sensor via cyclic voltammetry process. The iridium oxide thick film was successfully electrodeposited on the surface of stainless steel wire with 500 cycles of sweep potential. A further analysis under FESEM shows detailed image of iridium oxide film which has cauliflower-liked microstructure. EDX analysis shows the highest element present are iridium and oxygen which concluded that the process is successful. The iridium oxide based pH sensor has shown a good performance in comparison to conventional glass pH sensor when it is being calibrated in buffer solutions with 2, 4, 7 and 9 pH values. The iridium oxide pH sensor is specifically designed to measure the pH on the surface of metal plate.

Adsorption and the initial stages of samarium condensation on iridium coated by graphite monolayer

International Nuclear Information System (INIS)

Abdullaev, R.M.; Tontegode, A.Ya.; Yusifov, F.K.

1978-01-01

Adsorption and the initial stages of vacuum samarium condensation on iridium coated by graphite monolayer (valent-saturated neutral substrate) were studied by the thermodesorption mass-spectrometry and thermoemission methods, and were compared with samarium adsorption and condensation on iridium. Desorption heat of samarium atoms with thin coating of Ir-C, equal to E approximately 1.9 eV has been determined. For desorption with Ir E is approximately 6 eV. Such a great difference in desorption heats is connected with the reduction of covalent constituent of adsorption bond in a neutral substrate. Samarium on Ir-C is found to be condensated in two states: loosely bound and tightly bound which sharply differ in properties. The tightly bound state is characterized by abnormally low vapour pressure. Possible nature of this state is discussed. Double effect on the condensation of the substrate valent saturation is noted. On the one hand, the reduction of the particle bond with the substrate decreases their concentration on the surface, preventing condensation. On the other hand, the release of the valent eloctrons of adatous brings about strong lateral interaction between them, which in its turn, promotes condensation during eased migration on the neutral substrate

Development of iridium coated x-ray mirrors for astronomical applications

Science.gov (United States)

Döhring, Thorsten; Probst, Anne-Catherine; Emmerich, Florian; Stollenwerk, Manfred; Stehlíková, Veronika; Friedrich, Peter; Damm, Christine

2017-08-01

Future space-based X-ray observatories need to be very lightweight for launcher mass constraints. Therefore they will use a reduced mirror thickness, which results in the additional requirement of low coating stress to avoid deformation of the initial precisely shaped mirror substrates. Due to their excellent reflection properties iridium coatings are sometimes applied for grazing incidence mirrors in astronomical X-ray telescopes. At Aschaffenburg University of Applied Sciences the coating of thin iridium films by an RF-magnetron sputtering technique is under development. The work is embedded in collaborations with the Max-Planck-Institute for Extraterrestrial Physics in Germany, the Czech Technical University in Prague, the Osservatorio Astronomico di Brera in Italy, the German Leibniz Institute for Solid State and Materials Research in Dresden, and the French Institute Fresnel. Sputtering with different parameters leads to iridium films with different properties. The current work is focused on the microstructure of the iridium coatings to study the influence of the substrate and of the argon gas pressure on the thin film growing process. Correlations between coating density, surface micro-roughness, the crystalline structure of the iridium layers, and the expected reflectivity of the X-ray mirror as well as coating stress effects are presented and discussed. The final goal of the project is to integrate the produced prototype mirrors into an X-ray telescope module. On a longer timescale measurements of the mirror modules optical performance are planned at the X-ray test facility PANTER.

Prototyping iridium coated mirrors for x-ray astronomy

Science.gov (United States)

Döhring, Thorsten; Probst, Anne-Catherine; Stollenwerk, Manfred; Emmerich, Florian; Stehlíková, Veronika; Inneman, Adolf

2017-05-01

X-ray astronomy uses space-based telescopes to overcome the disturbing absorption of the Earth's atmosphere. The telescope mirrors are operating at grazing incidence angles and are coated with thin metal films of high-Z materials to get sufficient reflectivity for the high-energy radiation to be observed. In addition the optical payload needs to be light-weighted for launcher mass constrains. Within the project JEUMICO, an acronym for "Joint European Mirror Competence", the Aschaffenburg University of Applied Sciences and the Czech Technical University in Prague started a collaboration to develop mirrors for X-ray telescopes. The X-ray telescopes currently developed within this Bavarian- Czech project are of Lobster eye type optical design. Corresponding mirror segments use substrates of flat silicon wafers which are coated with thin iridium films, as this material is promising high reflectivity in the X-ray range of interest. The deposition of the iridium films is based on a magnetron sputtering process. Sputtering with different parameters, especially by variation of the argon gas pressure, leads to iridium films with different properties. In addition to investigations of the uncoated mirror substrates the achieved surface roughness has been studied. Occasional delamination of the iridium films due to high stress levels is prevented by chromium sublayers. Thereby the sputtering parameters are optimized in the context of the expected reflectivity of the coated X-ray mirrors. In near future measurements of the assembled mirror modules optical performances are planned at an X-ray test facility.

Measurements of iridium and the meteoric impact hypothesis at cretaceous end

International Nuclear Information System (INIS)

Sircilli Neto, F.

1986-12-01

Both instrumental and radiochemical neutron activation analysis methods were developed for trace-element determination, such as iridium and gold, for application in cosmochemistry. The magnitude of the determined concentrations is in the range of parts per billion. In the instrumental method 1.5 grams of sample were submitted to irradiation by 10 13 thermal neutrons.cm -2 .s -1 during 32 hours. The gamma spectrometry is carried out with 10 to 12 hours counting time after 40 days of decay. In the radiochemical analysis a method of radiochemical separation of noble metals based on tellurium coprecipitation is implanted for iridium and gold determinations. As an application of the instrumental neutron activation analysis, preliminary iridium concentrations are measured for the first time in sedimentary rocks collected in the Brazilian territory. These techniques for determinations of iridium will be useful to check the asteroid impact hypothesis, which is supposed to be the cause of the great Cretaceous/Tertiary mass extinction, using samples collected in the South Hemisphere. (Author) [pt

Welding iridium heat-source capsules for space missions

International Nuclear Information System (INIS)

Kanne, W.R. Jr.

1982-03-01

A remote computer-controlled welding station was developed to encapsulate radioactive PuO 2 in iridium. Weld quench cracking caused an interruption in production of capsules for upcoming space missions. Hot crack sensitivity of the DOP-26 iridium alloy was associated with low melting constituents in the grain boundaries. The extent of cracking was reduced but could not be eliminated by changes to the welding operation. An ultrasonic test was developed to detect underbead cracks exceeding a threshold size. Production was continued using the ultrasonic test to reject capsules with detectable cracks

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

Energy Technology Data Exchange (ETDEWEB)

Sebring, R.; Arendt, P.; Imai, B.; Bradbury, E.M.; Gatewood, J. [Los Alamos National Lab., NM (United States); Panitz, J. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Physics and Astronomy; Yau, P. [Univ. of California, Davis, CA (United States)

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.

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

Science.gov (United States)

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. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of iridium on the reactivity of LaFeO3 base perovskites

DEFF Research Database (Denmark)

Kindermann, L.; Das, D.; Bahadur, D.

1998-01-01

The influence of iridium on the reactivity of powder mixtures made of perovskites and 8 mol% yttria stabilized zirconia (8 YSZ) is reported. Iridium is added to the perovskites of the composition (La0.6M0.4)(z)Fe0.8TM0.2O3-delta (M = Sr, Ca; TM = Mn, Co; z = 0.90, 1.00) via the gaseous phase....... Iridium is present in the perovskite lattice as Ir4+ replacing iron as is evident from XRD and TEM/EDX results. Compatibility studies carried out at 1000 degrees C demonstrate that iridium has considerable influence on the reactivity. The results are discussed with respect to the stability...... of the perovskites, thermodynamic activities, Ir(IV)-O bonding, tolerance factor and oxygen migration....

Reverse saturable absorption (RSA) in fluorinated iridium derivatives

Science.gov (United States)

Ferry, Michael J.; O'Donnell, Ryan M.; Bambha, Neal; Ensley, Trenton R.; Shensky, William M.; Shi, Jianmin

2017-08-01

The photophysical properties of cyclometallated iridium compounds are beneficial for nonlinear optical (NLO) applications, such as the design of reverse saturable absorption (RSA) materials. We report on the NLO characterization of a family of compounds of the form [Ir(pbt)2(LX)], where pbt is 2-phenylbenzothiazole and LX is a beta-diketonate ligand. In particular, we investigate the effects of trifluoromethylation on compound solubility and photophysics compared to the parent acetylacetonate (acac) version. The NLO properties, such as the singlet and triplet excited-state cross sections, of these compounds were measured using the Z-scan technique. The excited-state lifetimes were determined from visible transient absorption spectroscopy.

Angular absorption of iridium - ICW12 needles: practical considerations

International Nuclear Information System (INIS)

Szymczyk, W.; Lesiak, J.

1984-01-01

An analysis was made of two potential sources of error in Ir 192 dosimetry: the effect of angular absorption and the differences in the ionization constants found in literature. Corrections for selfabsorption in the ICW12 iridium source were determined from measurements and calculations. It was found that the decrease in the dose caused by the angular absorption in the central therapeutic area of a typical implantation can exceed 5 percent. The need for employing the concept of ''constant exposure rate'' is stressed as well as that for using angular absorption in the form of absorption. 13 refs., 6 figs., 1 tab. (author)

Postimpact examinations of three DOP 4 iridium shells from simulant fuel sphere assemblies

International Nuclear Information System (INIS)

Cramer, E.M.; Hecker, S.S.

1975-12-01

Three fuel sphere assemblies, with thoria in doped iridium containment shells, were examined after a simulated earth impact from an aborted orbital mission of a multihundred-watt thermoelectric heat source. The extent of deformation of each unit was measured. Damage to the containment shells was minimal in comparison to that in undoped iridium. Metallographic sections from critical areas indicated that superficial grain boundary cracking in weld zones and microscopic cracking in regions of maximum diameter had occurred in addition to local thinning and coining. The improved properties of the doped iridium are attributed to the retention of a small grain size and to an additional fracture resistance over iridium of a comparable grain size, imparted by either a change in grain boundary chemistry or the flow characteristics of the doped material

Growth and characterization of iridium dioxide nanorods

International Nuclear Information System (INIS)

Chen, R.S.; Huang, Y.S.; Liang, Y.M.; Tsai, D.S.; Tiong, K.K.

2004-01-01

Conductive iridium dioxide (IrO 2 ) nanorods have been successfully grown on the Si(1 0 0) substrates via metalorganic chemical vapor deposition (MOCVD). A wedge-shaped morphology and naturally formed sharp tips are observed for IrO 2 nanorods using field-emission scanning electron microscopy (FESEM). High-resolution transmission electron microscopy (TEM) image and electron diffraction pattern show the growth of IrO 2 nanorods preferentially along c-axis. Structure and composition of IrO 2 nanorods have also been characterized using the techniques of Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. It is noted that the IrO 2 nanorods are self-mediated instead of the conventional vapor-liquid-solid (VLS) approach or catalyst-mediated method

Production of iridium-192 radiation sources: Indian Experience

International Nuclear Information System (INIS)

Sastry, K.V.S.; Kolhe, O.T.; Nagarja, P.S.; Paramr, Y.D.

2002-01-01

Board of Radiation and Isotope Technology (BRIT), a unit under the Department of Atomic Energy is fabricating and supplying Ir-192 industrial radiography sources for various models of radiography cameras for use in the industry for non-destructive testing. Basically these sources are fabricated by encapsulating the required quantity of the activity in stainless steel 316 L capsules using Tungsten Inert gas welding process and crimping/attaching to the respective pigtail assemblies of the radiography cameras. The inactive iridium pellets are irradiated in the DHRUVA reactor at a flux on 1.8 X 10 14 n/cm 2 /sec. The performance classification of these source encapsulation for various conditions of normal and accidental nature are tested by subjecting the prototype sources as per the standard laid down by the regulatory authority, Atomic Energy Regulatory Board, in India. The sources are fabricated as per the national and international standards. Activity of the sources varies from 37O GBq (10 Ci ) to 2.96 TBq (80 Ci ) source strength depending on the requirement of the user. The specific activity of the Ir-192 sources supplied is around 7.4 TBq/gm (200 Ci/gm ). Quality control /Assurance for the manufacture of the source begins from the procurement of the raw material and ends with the finished source. Ir- 192 in the form of -0.3 mm diameter (0.1 mm dia wire of Ir-25 % and Pt-75% sheathed in pure platinum of 0.1 mm thick) is being supplied for use in the treatment of cancer of cervix, tongue etc. by brachytherapy. This is supplied in lengths of 50 cm / 100 cm with 37 - 185 GBq/cm ( 1-5 mCi/cm) activity. Annually 925 TBq (25 kCi) of Ir-192 for industrial radiography and about 60 meters of wire for brachytherapy are being fabricated and supplied. Because of the quality of these sources BRIT not only caters to the Indian industry but also is able to export sources to the third world countries. (Author)

Synthesis and Luminescence Properties of Iridium(III Azide- and Triazole-Bisterpyridine Complexes

Directory of Open Access Journals (Sweden)

Timothy W. Schmidt

2013-07-01

Full Text Available We describe here the synthesis of azide-functionalised iridium(III bisterpyridines using the “chemistry on the complex” strategy. The resulting azide-complexes are then used in the copper(I-catalysed azide-alkyne Huisgen 1,3-dipolar cycloaddition “click chemistry” reaction to from the corresponding triazole-functionalised iridium(III bisterpyridines. The photophysical characteristics, including lifetimes, of these compounds were also investigated. Interestingly, oxygen appears to have very little effect on the lifetime of these complexes in aqueous solutions. Unexpectedly, sodium ascorbate acid appears to quench the luminescence of triazole-functionalised iridium(III bisterpyridines, but this effect can be reversed by the addition of copper(II sulfate, which is known to oxidize ascorbate under aerobic conditions. The results demonstrate that iridium(III bisterpyridines can be functionalized for use in “click chemistry” facilitating the use of these photophysically interesting complexes in the modification of polymers or surfaces, to highlight just two possible applications.

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

Energy Technology Data Exchange (ETDEWEB)

Song, Bo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Experimental Environment Simulation Dept.; Nelson, Kevin [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials Dept.; Lipinski, Ronald J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Nuclear Fuel Cycle Technology Dept.; Bignell, John L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Structural and Thermal Analysis Dept.; Ulrich, G. B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Radioisotope Power Systems Program; George, E. P. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Radioisotope Power Systems Program

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.

A slow atomic diffusion process in high-entropy glass-forming metallic melts

Science.gov (United States)

Chen, Changjiu; Wong, Kaikin; Krishnan, Rithin P.; Embs, Jan P.; Chathoth, Suresh M.

2018-04-01

Quasi-elastic neutron scattering has been used to study atomic relaxation processes in high-entropy glass-forming metallic melts with different glass-forming ability (GFA). The momentum transfer dependence of mean relaxation time shows a highly collective atomic transport process in the alloy melts with the highest and lowest GFA. However, a jump diffusion process is the long-range atomic transport process in the intermediate GFA alloy melt. Nevertheless, atomic mobility close to the melting temperature of these alloy melts is quite similar, and the temperature dependence of the diffusion coefficient exhibits a non-Arrhenius behavior. The atomic mobility in these high-entropy melts is much slower than that of the best glass-forming melts at their respective melting temperatures.

Atomic structure of graphene supported heterogeneous model catalysts

International Nuclear Information System (INIS)

Franz, Dirk

2017-04-01

Graphene on Ir(111) forms a moire structure with well defined nucleation centres. Therefore it can be utilized to create hexagonal metal cluster lattices with outstanding structural quality. At diffraction experiments these 2D surface lattices cause a coherent superposition of the moire cell structure factor, so that the measured signal intensity scales with the square of coherently scattering unit cells. This artificial signal enhancement enables the opportunity for X-ray diffraction to determine the atomic structure of small nano-objects, which are hardly accessible with any experimental technique. The uniform environment of every metal cluster makes the described metal cluster lattices on graphene/Ir(111) an attractive model system for the investigation of catalytic, magnetic and quantum size properties of ultra-small nano-objects. In this context the use of x-rays provides a maximum of flexibility concerning the possible sample environments (vacuum, selected gases, liquids, sample temperature) and allows in-situ/operando measurements. In the framework of the present thesis the structure of different metal clusters grown by physical vapor deposition in an UHV environment and after gas exposure have been investigated. On the one hand the obtained results will explore many aspects of the atomic structure of these small metal clusters and on the other hand the presented results will proof the capabilities of the described technique (SXRD on cluster lattices). For iridium, platinum, iridium/palladium and platinum/rhodium the growth on graphene/Ir(111) of epitaxial, crystalline clusters with an ordered hexagonal lattice arrangement has been confirmed using SXRD. The clusters nucleate at the hcp sites of the moire cell and bind via rehybridization of the carbon atoms (sp"2 → sp"3) to the Ir(111) substrate. This causes small displacements of the substrate atoms, which is revealed by the diffraction experiments. All metal clusters exhibit a fcc structure, whereupon

Atomic structure of graphene supported heterogeneous model catalysts

Energy Technology Data Exchange (ETDEWEB)

Franz, Dirk

2017-04-15

Graphene on Ir(111) forms a moire structure with well defined nucleation centres. Therefore it can be utilized to create hexagonal metal cluster lattices with outstanding structural quality. At diffraction experiments these 2D surface lattices cause a coherent superposition of the moire cell structure factor, so that the measured signal intensity scales with the square of coherently scattering unit cells. This artificial signal enhancement enables the opportunity for X-ray diffraction to determine the atomic structure of small nano-objects, which are hardly accessible with any experimental technique. The uniform environment of every metal cluster makes the described metal cluster lattices on graphene/Ir(111) an attractive model system for the investigation of catalytic, magnetic and quantum size properties of ultra-small nano-objects. In this context the use of x-rays provides a maximum of flexibility concerning the possible sample environments (vacuum, selected gases, liquids, sample temperature) and allows in-situ/operando measurements. In the framework of the present thesis the structure of different metal clusters grown by physical vapor deposition in an UHV environment and after gas exposure have been investigated. On the one hand the obtained results will explore many aspects of the atomic structure of these small metal clusters and on the other hand the presented results will proof the capabilities of the described technique (SXRD on cluster lattices). For iridium, platinum, iridium/palladium and platinum/rhodium the growth on graphene/Ir(111) of epitaxial, crystalline clusters with an ordered hexagonal lattice arrangement has been confirmed using SXRD. The clusters nucleate at the hcp sites of the moire cell and bind via rehybridization of the carbon atoms (sp{sup 2} → sp{sup 3}) to the Ir(111) substrate. This causes small displacements of the substrate atoms, which is revealed by the diffraction experiments. All metal clusters exhibit a fcc structure

Incorporation of iridium into electrodeposited rhenium–nickel alloys

International Nuclear Information System (INIS)

Cohen Sagiv, Maayan; Eliaz, Noam; Gileadi, Eliezer

2013-01-01

Rhenium (Re), a refractory metal that has gained significant recognition as a high performance engineering material, is mostly used in military, aircraft and aerospace applications, as well as for catalysis in the petrochemical industry. However, its performance at high temperature in humid air is limited by the formation of rhenium heptoxide (Re 2 O 7 ), which penetrates the grain boundaries and causes brittleness. Improvement of this is being sought through the incorporation of iridium (Ir) into Re deposits. To this end, suitable plating baths for Re–Ir–Ni coatings were developed. These alloys were deposited from different aqueous solutions on copper substrates under galvanostatic conditions, in a three-electrode cell. The plating bath consisted of iridium tri-chloride, ammonium perrhenate and nickel sulfamate as the electroactive species, and citric acid as the complexing agent. The effects of bath composition and operating conditions on the Faradaic efficiency (FE), partial current densities, as well as on the thickness of the coatings and their composition were studied. Re–Ir–Ni coatings as thick as 18 μm, with Re-content as high as 73 at.% and Ir-content as high as 29 at.%, were obtained, using different plating baths. A mechanism of the electrochemical process was suggested. It was found that both an HCP Ir 0.4 Re 0.6 phase and an HCP Ni phase with nanometric crystallites were formed, possibly together with a hexagonal nickel hydride (Ni 2 H) phase

Antiferromagnetic iridium-manganese intermediate layers for perpendicular recording media (invited)

Science.gov (United States)

Srinivasan, Kumar; Piramanayagam, S. N.; Sbiaa, Rachid; Kay, Yew Seng; Tan, Hang Khume; Wong, Seng Kai

2009-04-01

Current generation of cobalt-oxide-based perpendicular magnetic recording media uses single or dual ruthenium intermediate layers in order to grow crystallographically textured, and magnetically isolated granular media. In this work, the potential advantages of an antiferromagnetic iridium-manganese intermediate layer directly under the recording layer are highlighted. Owing to its close lattice matching with hexagonal cobalt, iridium-manganese which has the L12, or AuCu3-type crystal structure, can support the heteroepitaxial growth of the cobalt-based recording layer. In one of the media schemes described here, (111) textured iridium-manganese thin film was grown on 7.5 nm thick ruthenium layer. On the iridium-manganese as segregation layer, the Co-oxide-based magnetic recording layer showed perpendicular texture with Δθ50 below 4°, coercivity of over 4000 Oe alongside magnetic exchange decoupling, average grain sizes of 6 nm with distributions under 14%, and improved thermal stability. Measurements of the anisotropy constant did not show any significant change and even an IrMn capping layer was observed to improve the thermal stability. The possible mechanisms through which the IrMn layer could affect the thermal stability are hypothesized. The initial layers of the magnetic recording layer on IrMn segregation layers also showed exchange-decoupled and segregated grains, which is unlike that observed on Ru segregation layers. In a second media scheme, (111) textured iridium-manganese thin film was grown on a crystalline soft magnetic underlayer belonging on top of amorphous soft underlayers. In this scheme, partial pinning of the soft underlayer due to exchange-bias interaction with the IrMn layer was observed. This scheme offers the possibility to reduce the intermediate layer thickness, thus improve media writability, and with further optimization, could potentially facilitate the approach toward 1 Tbits/in.2.

Colorimetric and luminescent bifunctional iridium(III) complexes for the sensitive recognition of cyanide ions

Science.gov (United States)

Chen, Xiudan; Wang, Huili; Li, Jing; Hu, Wenqin; Li, Mei-Jin

2017-02-01

Two new cyclometalated iridium(III) complexes [(ppy)2Irppz]Cl (1) and [(ppy)2Irbppz]Cl (2) (where ppy = 2-phenylpyridine, ppz = 4,7-phenanthrolino-5,6:5,6-pyrazine, bppz = 2.3-di-2-pyridylpyrazine), were designed and synthesized. The structure of [(ppy)2Irppz]Cl was determined by single crystal X-ray diffraction. Their photophysical properties were also studied. This kind of complexes could coordinate with Cu2 +, the photoluminescence (PL) of the complex was quenched, and the color changed from orange-red to green. The forming M-Cu (M: complexes 1 and 2) ensemble could be further utilized as a colorimetric and emission ;turn-on; bifunctional detection for CN-, especially for complex 1-Cu2 + showed a high sensitivity toward CN- with a limit of diction is 97 nM. Importantly, this kind of iridium(III) complexes shows a unique recognition of cyanide ions over other anions which makes it an eligible sensing probe for cyanide ions.

Development of an Iridium-192 seed for use in ophthalmic brachytherapy

International Nuclear Information System (INIS)

Mattos, Fabio R.; Rostelato, Maria Elisa C.M.; Zeituni, Carlos; Moura, Joao A.; Costa, Osvaldo L.; Feher, Anselmo; Moura, Eduardo S.; Souza, Carla D.; Peleias Junior, Fernando S.

2011-01-01

The Institute for Energy and Nuclear Research (IPEN), in partnership with the School or Medicine (UNIFESP), created a project that aims to develop and implement an ophthalmic therapeutic treatment for cancer with Iridium-192 seeds. The School of Medicine treats many cancer cases in the SUS (Brazilian Public Health System), and brachytherapy group of IPEN has extensive experience in prototype sources. The seed to be manufactured will perform as follows: a core of Iridium-192 is packaged inside small cylindrical seeds consist of a titanium capsule of 0.8 mm outer diameter, 0.05 mm wall thickness and 4 5 mm in length. The core is an alloy of platinum-iridium (20/80) of 3.0 mm in length and 0.3 mm in diameter. Material analysis, neutron activation and activity measurements were carried out. (author)

Intermittent contact atomic force microscopy in electrochemical environment

Energy Technology Data Exchange (ETDEWEB)

Haering, P; Koetz, R [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Siegenthaler, H [Bern Univ., Bern (Switzerland)

1997-06-01

In situ measurements with Atomic Force Microscopy may cause surface modifications due to the tip-surface interactions. As an alternative and less destructive method, Intermittent Contact Atomic Force Microscopy (ICAFM) has been tested in an electrolytic environment. In the ICAFM mode the tip is not constantly in contact with the surface under investigation but is tapping onto the surface with a certain frequency. A commercial Park Scientific Instruments Microscopy has been modified to enable in situ experiment with ICAFM. It was possible to image iridium oxide films with ICAFM in the electrolytic environment without any noticeable surface modifications. (author) 3 figs., 4 refs.

A preliminary study of factors affecting the calibration stability of the iridium versus iridium-40 percent rhodium thermocouple

Science.gov (United States)

Ahmed, Shaffiq; Germain, Edward F.; Daryabeigi, Kamran; Alderfer, David W.; Wright, Robert E.

1987-01-01

An iridium versus iridium-40% rhodium thermocouple was studied. Problems associated with the use of this thermocouple for high temperature applications (up to 2000 C) were investigated. The metallurgical studies included X-ray, macroscopic, resistance, and metallographic studies. The thermocouples in the as-received condition from the manufacturer revealed large amounts of internal stress caused by cold working during manufacturing. The thermocouples also contained a large amount of inhomogeneities and segregations. No phase transformations were observed in the alloy up to 1100 C. It was found that annealing the thermocouple at 1800 C for two hours, and then at 1400 C for 2 to 3 hours yielded a fine grain structure, relieving some of the strains, and making the wire more ductile. It was also found that the above annealing procedure stabilized the thermal emf behavior of the thermocouple for application below 1800 C (an improvement from + or - 1% to + or - 0.02% within the range of the test parameters used).

Microindentation hardness evaluation of iridium alloy clad vent set cups

International Nuclear Information System (INIS)

Ulrich, G.B.; DeRoos, L.F.; Stinnette, S.E.

1993-01-01

An iridium alloy, DOP-26, is used as cladding for 238 PuO 2 fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration's Cassini mission to Saturn. Wrought/ground/stress relieved blanks are warm formed into CVS cups. These cups are then annealed to recrystallize the material for subsequent fabrication/assembly operations as well as for final use. One of the cup manufacturing certification requirements is to test for Vickers microindentation hardness. New microindentation hardness specification limits, 210 to 310 HV, have been established for a test load of 1000 grams-force (gf). The original specification limits, 250 to 350 HV, were for 200 gf testing. The primary reason for switching to a higher test load was to reduce variability in the test data. The DOP-26 alloy exhibits microindentation hardness load dependence, therefore, new limits were needed for 1000 gf testing. The new limits were established by testing material from 15 CVS cups using 200 gf and 1000 gf loads and then statistically analyzing the data. Additional work using a Knoop indenter and a 10 gf load indicated that the DOP-26 alloy grain boundaries have higher hardnesses than the grain interiors

Microindentation hardness evaluation of iridium alloy clad vent set cups

International Nuclear Information System (INIS)

Ulrich, G.B.; DeRoos, L.F.; Stinnette, S.E.

1992-01-01

An iridium alloy, DOP-26, is used as cladding for 238 PuO 2 fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration's Cassini mission to Saturn. Wrought/ground/stress relieved blanks are warm formed into CVS cups. These cups are then annealed to recrystallize the material for subsequent fabrication/assembly operations as well as for final use. One of the cup manufacturing certification requirements is to test for Vickers microindentation hardness. New microindentation hardness specification limits, 210 to 310 HV, have been established for a test load of 1000 grams-force (gf). The original specification limits, 250 to 350 HV, were for 200 gf testing. The primary reason for switching to a higher test load was to reduce variability in the test data. The DOP-26 alloy exhibits microindentation hardness load dependence, therefore, new limits were needed for 1000 gf testing. The new limits were established by testing material from 15 CVS cups using 200 gf and 1000 gf loads and then statistically analyzing the data. Additional work using a Knoop indenter and a 10 gf load indicated that the DOP-26 alloy grain boundaries have higher hardnesses than the grain interiors

Study and development of an Iridium-192 seed for use in ophthalmic cancer

International Nuclear Information System (INIS)

Mattos, Fabio Rodrigues de

2013-01-01

Even ocular tumors are not among the cases with a higher incidence, they affect the population, especially children. The Institute of Energy and Nuclear Research (IPEN-CNEN/SP) in partnership with Escola Paulista de Medicina (UNIFESP), created a project to develop and implement a alternative treatment for ophthalmic cancer that use brachytherapy iridium-192 seeds. The project arose by reason of the Escola Paulista treat many cancer cases within the Unified Health System (SUS) and the research experience of sealed radioactive sources group at IPEN. The methodology was developed from the available infrastructure and the experience of researchers. The prototype seed presents with a core (192-iridium alloy of iridium-platinum) of 3.0 mm long sealed by a capsule of titanium of 0.8 mm outside diameter, 0.05 mm wall thickness and 4,5mm long. This work aims to study and develop a seed of iridium-192 from a platinum-iridium alloy. No study on the fabrication of these seeds was found in available literature. It was created a methodology that involved: characterization of the material used in the core, creation of device for neutron activation irradiation and and seed sealing tests. As a result, proved the feasibility of the method. As a suggestion for future work, studies regarding metrology and dosimetry of these sources and improvement of the methodology should be carried out, for future implementation in national scope. (author)

Phosphorescent systems based on iridium(III) complexes

NARCIS (Netherlands)

Ulbricht, C.

2009-01-01

Phosphorescent iridium(III)-based complexes are experiencing a growing interest in a number of research fields. Aside from lighting and display technologies (i.e. OLEDs and LECs), they find use in various applications such as biolabeling, sensors, solar cells and water splitting. In particular, the

Iridium Catalysis: Reductive Conversion of Glucan to Xylan

DEFF Research Database (Denmark)

Pedersen, Martin Jæger; Madsen, Robert; Clausen, Mads Hartvig

2018-01-01

By using iridium catalysed dehydrogenative decarbonylation, we converted a partly protected cellobioside into a fully protected xylobioside. We demonstrate good yields with two different aromatic ester protecting groups. The resulting xylobioside was directly used as glycosyl donor in further...

Iridium: Global OTH data communications for high altitude scientific ballooning

Science.gov (United States)

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.

3,9-Dithia-6-azaundecane-appended Iridium (III) Complex for the Selective Detection of Hg2+ in Aqueous Acetonitrile

International Nuclear Information System (INIS)

Ann, Jee Hye; Li, Yinan; Hyun, Myung Ho

2012-01-01

Detection of mercuric ion (Hg 2+ ) originated from natural or industrial sources is very important because it is extremely toxic even at low levels and causes serious environmental and health problems. Consequently, many efforts have been devoted to the development of sensitive chemosensors for the detection of Hg 2+ . For example, various fluorescent chemosensors based on rhodamine, nitrobenzoxadiazole, fluorescein, boradiazaindacene (BODIPY), dansyl, pyrene, or other fluorophores have been developed for the selective detection of Hg 2+ . While various fluorescent chemosensors for the selective detection of Hg 2+ have been developed, phosphorescent chemosensors for the selective detection of Hg 2+ are relatively rare. Among various phosphors, iridium (III) complexes with sulfur containing cyclometalated ligands have been used as phosphorescent chemosensors for the selective detection of Hg 2+ . Azacrown ether-appended iridium (III) complex developed in our laboratory has also been utilized as a phosphorescent chemosensor for the selective detection of Hg 2+ . As an another iridium (III) complex-based phosphorescent chemosensors for the selective detection of Hg 2+ , in this study, we wish to prepare iridium (III) complex containing two 3,9-dithia-6-azaundecane units as chelating ligands for metal ions. Some fluorophores containing 3,9-dithia-6-azaundecane unit have been successfully applied for the selective detection of Hg 2+ . In this instance, iridium (III) complex containing two 3,9-dithia-6-azaundecane units is expected to be useful as a phosphorescent chemosensor for the selective detection of Hg 2+ . Iridium (III) complex containing two 3,9-dithia-6-azaundecane units was prepared starting from 2-phenylpyridine according to the procedure shown in Scheme 1. 2-Phenylpyridine was transformed into chloride bridged dimeric iridium complex, [(ppy) 2 IrCl] 2 , via the reported procedure. By treating [(ppy) 2 IrCl] 2 with 4,4'-bis(bromomethyl)-2,2'-bipyridine, which

Network flexibility of the IRIDIUM (R) Global Mobile Satellite System

Science.gov (United States)

Hutcheson, Jonathan; Laurin, Mala

1995-01-01

The IRIDIUM system is a global personal communications system supported by a constellation of 66 low earth orbit (LEO) satellites and a collection of earth-based 'gateway' switching installations. Like traditional wireless cellular systems, coverage is achieved by a grid of cells in which bandwidth is reused for spectral efficiency. Unlike any cellular system ever built, the moving cells can be shared by multiple switching facilities. Noteworthy features of the IRIDIUM system include inter-satellite links, a GSM-based telephony architecture, and a geographically controlled system access process. These features, working in concert, permit flexible and reliable administration of the worldwide service area by gateway operators. This paper will explore this unique concept.

Atomic beam formed by the vaporization of a high velocity pellet

International Nuclear Information System (INIS)

Foster, C.A.; Hendricks, C.D.

1974-01-01

A description of an atomic beam formed by vaporizing an electrostatically accelerated high velocity pellet is given. Uniformly sized droplets of neon will be formed by the mechanical disintegration of liquid jet and frozen by adiabatic vaporization in vacuum. The pellets produced will be charged and accelerated by contacting a needle held at high potential. The accelerated pellets will be vaporized forming a pulse of mono-energetic atoms. The advantages are that a wide range of energies will be possible. The beam will be mono-energetic. The beam is inheretly pulsed, allowing a detailed time of flight velocity distribution measurement. The beam will have a high instantaneous intensity. The beam will be able to operate into an ultra high vacuum chamber

Diphosphinoazine Rhodium(I) and Iridium(I) Complexes

Czech Academy of Sciences Publication Activity Database

Pošta, Martin; Čermák, Jan; Vojtíšek, P.; Císařová, I.

2006-01-01

Roč. 71, č. 2 (2006), s. 197-206 ISSN 0010-0765 R&D Projects: GA ČR(CZ) GA203/01/0554; GA ČR(CZ) GA203/99/M037 Institutional research plan: CEZ:AV0Z40720504 Keywords : diphosphinoazines * rhodium complexes * iridium complexes Subject RIV: CC - Organic Chemistry Impact factor: 0.881, year: 2006

Development of Iridium Solid-state Reference Electrode for the Water Chemistry Status Measurement in Nuclear Power Plants

International Nuclear Information System (INIS)

Ku, Heekwon; Lim, Dongseok; Cho, Jaeseon

2013-01-01

The result of ECP measurement of piping material in nuclear power plant at low temperature using the developed iridium (SSRE) reference electrode is approximately -0.370V. Based on the various results of this study, the developed iridium (SSRE) reference electrode can be applied to the water chemistry environments of nuclear power plant. Various metallic materials used in a nuclear power plant have been exposed to a variety of water chemistry environments and the corrosion of metallic materials occurs due to the reactions between metal structures and water chemistry environments. Therefore, the management of the water chemistry factors is needed to prevent corrosion. The chemical factors affecting the corrosion are pH and Electrochemical Corrosion Potential (ECP). The world-wide studies suggest that ECP and pH are effective indicators for preventing the material damage from water chemistry condition. ECP and pH should be measured as the reference electrodes, and should show stable potential characteristics with fast responses. In this study, the iridium reference electrodes using a solid-state metal oxide electrode has been developed to measure effective indicators such as ECP and pH. The iridium (SSRE) reference electrode for the ECP measurement in water chemistry environment of nuclear power plants has been developed. A calibration for water chemistry measurement was performed by potential measurement of iridium (SSRE) reference electrode with Ag/AgCl (SSRE) reference electrode. The result exhibited a stable potential for 117 hours and a super-Nernst ian response with 63.12mV/p H. In this study, the iridium (SSRE) reference electrode shows super-Nernst ian characteristic and it may be caused by the property of electrolytically coated iridium oxide. Considering the long-term stability of the developed electrode, it is possible to apply as a reference electrode through calibration procedure

An Analysis of the FY-1C, Iridium 33, and Cosmos 2251 Fragments

Science.gov (United States)

Liou, J.-C.

2014-01-01

The beginning of the year 2013 marks the sixth anniversary of the destruction of the Fengyun-1C (FY-1C) weather satellite as the result of an anti-satellite test conducted by China in January 2007 and the fourth anniversary of the accidental collision between Cosmos 2251 and the operational Iridium 33 in February 2009. These two events represent the worst satellite breakups in history. A total of 5579 fragments have been cataloged by the U.S. Space Surveillance Network (SSN), and almost 5000 of them were still in orbit in January 2013. In addition to these cataloged objects, hundreds of thousands (or more) of fragments down to the millimeter size regime were also generated during the breakups. These fragments are too small to be tracked by the SSN, but are large enough to be a safety concern for human space activities and robotic missions in low Earth orbit (LEO, the region below 2000 km altitude). Like their cataloged siblings, many of them remain in orbit today. These two breakup events dramatically changed the landscape of the orbital debris environment in LEO. The spatial density of the cataloged population in January 2013 is shown as the top blue curve. The combined FY-1C, Iridium 33, and Cosmos 2251 fragments (black curve) account for about 50 percent of the cataloged population below an altitude of 1000 km. They are also responsible for the concentrations at 770 km and 850 km, altitudes at which the collisions occurred. The effects of the FY-1C, Iridium 33, and Cosmos 2251 fragments will continue to be felt for decades to come. For example, approximately half of the generated FY-1C fragments will remain in orbit 20 years from now. In general, the Iridium 33 and Cosmos 2251 fragments will decay faster than the FY-1C fragments because of their lower altitudes. Of the Iridium 33 and Cosmos 2251 fragments, the former have much shorter orbital lifetimes than the latter, because lightweight composite materials were heavily used in the construction of the Iridium

Iridium Sulfide and Ir Promoted Mo Based Catalysts.

Czech Academy of Sciences Publication Activity Database

Vít, Zdeněk

2007-01-01

Roč. 322, - (2007), s. 142-151 ISSN 0926-860X R&D Projects: GA ČR(CZ) GA104/06/0870 Institutional research plan: CEZ:AV0Z40720504 Keywords : iridium sulfide * IrMo catalyst * hydrodesulfurization Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.166, year: 2007

Synthesis of Fluoroalkoxy Substituted Arylboronic Esters by Iridium-Catalyzed Aromatic C–H Borylation

KAUST Repository

Batool, Farhat

2015-08-17

The preparation of fluoroalkoxy arylboronic esters by iridium-catalyzed aromatic C–H borylation is described. The fluoroalkoxy groups employed include trifluoromethoxy, difluoromethoxy, 1,1,2,2-tetrafluoroethoxy, and 2,2-difluoro-1,3-benzodioxole. The borylation reactions were carried out neat without the use of a glovebox or Schlenk line. The regioselectivities available through the iridium-catalyzed C–H borylation are complementary to those obtained by the electrophilic aromatic substitution reactions of fluoroalkoxy arenes. Fluoroalkoxy arylboronic esters can serve as versatile building blocks.

Synthesis of Fluoroalkoxy Substituted Arylboronic Esters by Iridium-Catalyzed Aromatic C–H Borylation

KAUST Repository

Batool, Farhat; Parveen, Shehla; Emwas, Abdul-Hamid M.; Sioud, Salim; Gao, Xin; Munawar, Munawar A.; Chotana, Ghayoor A.

2015-01-01

The preparation of fluoroalkoxy arylboronic esters by iridium-catalyzed aromatic C–H borylation is described. The fluoroalkoxy groups employed include trifluoromethoxy, difluoromethoxy, 1,1,2,2-tetrafluoroethoxy, and 2,2-difluoro-1,3-benzodioxole. The borylation reactions were carried out neat without the use of a glovebox or Schlenk line. The regioselectivities available through the iridium-catalyzed C–H borylation are complementary to those obtained by the electrophilic aromatic substitution reactions of fluoroalkoxy arenes. Fluoroalkoxy arylboronic esters can serve as versatile building blocks.

A first-principles study of oxygen adsorption on Ir(111) surface

Energy Technology Data Exchange (ETDEWEB)

Gao, Hengjiao, E-mail: gaohengjiao@163.com; Xiong, Yuqing, E-mail: xiongyq@hotmail.com; Liu, Xiaoli, E-mail: shantianzi@126.com; Zhao, Dongcai, E-mail: zhaodongc@163.com; Feng, Yudong, E-mail: yudong_feng@sina.com; Wang, Lanxi, E-mail: wanglanxi@live.com; Wang, Jinxiao, E-mail: coldwind716@gmail.com

2016-12-15

Highlights: • Adsorption of oxygen on Ir(111) surface was studied by density functional theory. • The most stable adsorption site was determined by adsorption energy calculation. • Adsorption of oxygen at bridge and top site on Ir surface was the most stable ones. • Interaction of O 2p and Ir 5d orbits is relatively strong and formed hybridization. - Abstract: In order to understand deposition mechanism of iridium thin film by atomic layer deposition, the adsorption of oxygen on Ir(111) surface was studied by use of density functional theory and a periodical slab model. By calculating the adsorption energy and structure of oxygen at four adsorption sites (top, bridge, fcc-hollow and hcp-hollow) on Ir(111) surface, the most stable adsorption site was determined. On this basis, the banding mechanism of O and Ir atoms was studied by density of states of oxygen and iridium atoms. Oxygen adsorbed at hcp(parallel) site on Ir(111) surface was the most stable one according to the adsorption energy calculation results. Orbital charge analysis indicate that charge transferred from 5p and 5d orbit to 2p orbit of adsorbed O atoms, and 6s orbit of iridium atoms. Meanwhile, density of state study indicated that adsorption of oxygen on Ir(111) surface is mainly due to the interaction between 2p orbit of O atoms and 5d orbit of iridium atoms.

Development and characterisation of iridium-192 seeds for brachytherapy treatment of ocular tumors

International Nuclear Information System (INIS)

Peleias Jr, F.S.; Zeituni, C.A.; Souza, C.D.; Rostelato, M.E.CM.; Mattos, F.R.; Banega, M.A.G.; Rodrigues, B.T.; Tiezzi, R.; Oliveira, T.B.; Feher, A.; Moura, J.A.; Costa, O.L.

2014-01-01

Even ocular tumors are not amongst the cases with a high incidence, they affect the population, particularly children. The Institute of Energy and Nuclear Research (IPEN-CNEN/SP) in partnership with Escola Paulista de Medicina (UNIFESP), created a project to develop an alternative treatment for ophthalmic cancer that uses iridium-192 seeds in brachytherapy. This work aims to study and develop a seed of iridium-192 from a platinum-iridium alloy The prototype seed has a 3.0 mm long core sealed by a titanium capsule of 0.8 mm of outer diameter, 0.05 mm of wall thickness and 4.5 mm long. We developed a methodology that covered: characterisation of the material used in the core, creation of a device for neutron activation of the cores and leakage tests. The results show that this methodology is feasible. As a suggestion for future work, studies regarding metrology and dosimetry of these sources should be carried out. (authors)

Preparation and determination of kerma for Iridium 192 sources of low dose rate for brachytherapy

International Nuclear Information System (INIS)

Tendilla, J.I.; Tovar M, V.; Mitsoura, E.; Aguilar H, F.; Alanis M, J.

2000-01-01

The practice of Brachytherapy with Iridium-192 sources of low dose rate (0.4 - 0.8 Gy/h) is a technique used in the treatment of diverse illnesses. in this work the preparation, quality control and calibration are presented in terms of kerma in air of Iridium-192 using as target these recycled Iridium-Platinum wires. The targets were obtained as decayed sources of different radio therapeutical centers in the country and they were characterized by Scanning electron microscopy in order to determine their chemical composition. Subsequently it was developed an experimental design to establish the effect of neutron flux, geometrical array and irradiation time over the activity and percentage of the sources homogeneity. The homogeneity was determined by auto radiography and by Gamma spectroscopy. Once the optimal irradiation conditions were established, it is determined the apparent activity and kerma in air using a well type ionization chamber with traceability to a primary laboratory. Iridium-192 sources were obtained with an average homogeneity 96 %, apparent activity 282.129 ± 0.531 M Bq and kerma in air 0.03200 ± 0.00006 m Gy m/h A. (Author)

Synthesis and electrophosphorescence of iridium complexes containing benzothiazole-based ligands.

Science.gov (United States)

Liu, Di; Ren, Huicai; Deng, Lijun; Zhang, Ting

2013-06-12

Four heteroleptic bis-cyclometalated iridium(III) complexes containing 2-aryl-benzothiazole ligands, in which the aryl is dibenzofuran-2-yl [Ir(O-bt)2(acac)], dibenzothiophene-2-yl [Ir(S-bt)2(acac)], dibenzothiophene-S,S-dioxide-2-yl [Ir(SO2-bt)2(acac)] and 4-(diphenylphosphoryl)phenyl [Ir(PO-bt)2(acac)], have been synthesized and characterized for use in organic light-emitting diodes (OLEDs). These complexes emit bright yellow (551 nm) to orange-red (598 nm) phosphorescence at room temperature, the peak wavelengths of which can be finely tuned depending upon the electronic properties of the aryl group in the 2-position of benzothiazole. The strong electron-withdrawing aryls such as dibenzothiophene-S,S-dioxide2-yl and 4-(diphenylphosphoryl)phenyl caused bathochromatic shift of the iridium complex phosphorescence. These iridium complexes were used as doped emitters to fabricate yellow to orange-red OLEDs and good performance was obtained. In particular, a maximum luminance efficiency of 58.4 cd A(-1) (corresponding to 30.6 lm W(-1) and 19%) with CIE coordinates of (0.45, 0.52) was achieved for Ir(O-bt)2(acac)-based yellow device. Furthermore, the yellow emitting Ir(S-bt)2(acac) was used to fabricate two-element white OLED that exhibited a high efficiency of 32.4 cd A(-1) with CIE coordinates of (0.28, 0.44).

Interstitial curietherapy with iridium 192 applied to small cancers of the rectum

International Nuclear Information System (INIS)

Papillon, J.; Montbarbon, J.F.; Gerard, J.P.

1975-01-01

Intracavity irradiation aimed at curing cancers of the rectum mainly calls on contact radiotherapy but also on interstitial curietherapy. Iridium curietherapy has replaced radium-therapy owing to the better homogeneousness of its action and precise method of assay. It uses a 2 pronged fork containing 2 iridium wires which can be very simply placed in position. It is applied on the one hand to the base of the ulcerated tumour, after abrasion by contactotherapy and on the other hand as a method of prophylactic irradiation after exeresis of a malignant or degenerated polyp where the scar is badly adapted to contactotherapy [fr

Electrogenerated chemiluminescence of a cationic cyclometalated iridium complex–Nafion modified electrode in neutral aqueous solution

International Nuclear Information System (INIS)

Dong, YongPing; Ni, ZiYue; Zhang, Jing; Tong, BiHai; Chu, XiangFeng

2013-01-01

Electrogenerated chemiluminescence (ECL) of a cationic cyclometalated iridium complex, [(pqcm) 2 Ir(bpy)](PF 6 ) (1, pqcmH=2-phenyl-quinoline-4-carboxylic acid methyl ester, bpy=2,2′-bipyridine), was investigated at a bare glassy carbon electrode in CH 3 CN solution and 4 ECL peaks were observed. Then, the ECL of the iridium complex was studied in neutral phosphate buffer solution (PBS) by immobilizing it on a glassy carbon electrode. Two closely located ECL peaks were obtained at 1.07 and 1.40 V when the potential was scanned from −3.00 V to 2.20 V, while only one broad ECL peak located around −2.0 V was obtained when the potential was scanned from 2.20 V to −3.00 V. In the presence of oxalate, one ECL peak located around 1.22 V could be obtained except the broad ECL peak located at −2.00 V. The ECL peak at positive potential range was enhanced more than one magnitude in the presence of Nafion and was nearly 5-times higher than that of Ru(bpy) 3 2+ –Nafion modified electrode, suggesting that the synthesized iridium complex has great application potential in ECL detection. The ECL spectra of iridium complex were identical to its photoluminescence spectrum, indicating the same metal-to-ligand charge transfer (MLCT) excited states. The mechanisms of ECL were proposed based on the experimental results. The present ECL sensor gave a linear response for the oxalate concentration from 1.0×10 −6 to 1.0×10 −4 mol L −1 with a detection limit (S/N=3) of 9.1×10 −7 mol L −1 . -- Graphical abstract: Electrochemiluminescence (ECL) of immobilized novel cationic cyclometalated iridium complex in neutral phosphate buffer solution is reported for the first time. The intensity of iridium complex ECL is 5-times higher than that of Ru(bpy) 3 2+ ECL. Highlights: ► Cationic cyclometalated iridium complex was modified on a bare electrode. ► Electrochemiluminescence (ECL) of the modified electrode was studied. ► The ECL intensity is higher than that of Ru

A projector of iridium 192 wires: motivations and preliminary studies

International Nuclear Information System (INIS)

Cosset, J.M.; Gerbaulet, A.; Chassagne, D.

1979-01-01

Though the majority of procedures involved in curietherapy with Iridium 192 wires cause very few problems concerning radiation protection, this is not true in all cases: in elderly of debilitated patients, young children, or when using special techniques (curietherapy for prostate of bladder cancers for example). In these cases, the need for frequent treatment exposes the therapists to increased doses. The projector of Iridium 192 wires was conceived in order to reduce this irradiated hazard. A simple manipulation places the radioactive wires in a lead container during treatment, and then replaces them in the right position after therapy. This apparatus appears to offer the possibility of: an almost total protection of the therapists, and thus an opportunity for enlarging the indications for curietherapy; an improved quality of treatment to the patient during the application [fr

Asymmetric Hydrogenation of Quinoxalines Catalyzed by Iridium/PipPhos

NARCIS (Netherlands)

Mrsic, Natasa; Jerphagnon, Thomas; Minnaard, Adriaan J.; Feringa, Ben L.; de Vries, Johannes G.

2009-01-01

A catalyst made in situ from the (cyclooctadiene)iridium chloride dimer, [Ir(COD)Cl](2), and the monodentate phosphoramidite ligand (S)-PipPhos was used in the enantioselective hydrogenation of 2- and 2,6-substituted quinoxalines. In the presence of piperidine hydrochloride as additive full

3,9-Dithia-6-azaundecane-appended Iridium (III) Complex for the Selective Detection of Hg{sup 2+} in Aqueous Acetonitrile

Energy Technology Data Exchange (ETDEWEB)

Ann, Jee Hye; Li, Yinan; Hyun, Myung Ho [Pusan National Univ., Busan (Korea, Republic of)

2012-10-15

Detection of mercuric ion (Hg{sup 2+}) originated from natural or industrial sources is very important because it is extremely toxic even at low levels and causes serious environmental and health problems. Consequently, many efforts have been devoted to the development of sensitive chemosensors for the detection of Hg{sup 2+}. For example, various fluorescent chemosensors based on rhodamine, nitrobenzoxadiazole, fluorescein, boradiazaindacene (BODIPY), dansyl, pyrene, or other fluorophores have been developed for the selective detection of Hg{sup 2+}. While various fluorescent chemosensors for the selective detection of Hg{sup 2+} have been developed, phosphorescent chemosensors for the selective detection of Hg{sup 2+} are relatively rare. Among various phosphors, iridium (III) complexes with sulfur containing cyclometalated ligands have been used as phosphorescent chemosensors for the selective detection of Hg{sup 2+}. Azacrown ether-appended iridium (III) complex developed in our laboratory has also been utilized as a phosphorescent chemosensor for the selective detection of Hg{sup 2+}. As an another iridium (III) complex-based phosphorescent chemosensors for the selective detection of Hg{sup 2+}, in this study, we wish to prepare iridium (III) complex containing two 3,9-dithia-6-azaundecane units as chelating ligands for metal ions. Some fluorophores containing 3,9-dithia-6-azaundecane unit have been successfully applied for the selective detection of Hg{sup 2+}. In this instance, iridium (III) complex containing two 3,9-dithia-6-azaundecane units is expected to be useful as a phosphorescent chemosensor for the selective detection of Hg{sup 2+}. Iridium (III) complex containing two 3,9-dithia-6-azaundecane units was prepared starting from 2-phenylpyridine according to the procedure shown in Scheme 1. 2-Phenylpyridine was transformed into chloride bridged dimeric iridium complex, [(ppy){sub 2}IrCl]{sub 2}, via the reported procedure. By treating [(ppy){sub 2}Ir

Experimental Estimation of the Lifetime of Atoms Formed by π+ and π- Mesons

International Nuclear Information System (INIS)

Afanas'ev, L.G.; Gorchakov, O.E.; Chvyrov, A.S.

1994-01-01

Based on observation of 272±49 atoms formed by π + and π - mesons an estimation of the atom lifetime in the ground state is obtained: τ=(2.9 -2.1 +∞ )·10 -15 s or τ>0.6·10 -15 s at 90% confidence level. Atoms were produced in inclusive pTa interactions at 70 GeV. 18 refs., 1 fig., 1 tab

Assessment of radiation exposure of personnel during clinical application of radioactive iridium

Energy Technology Data Exchange (ETDEWEB)

Dworakowski, M; Krystman-Mazgajska, E; Wysopolski, J [Instytut Onkologii, Warsaw (Poland); Centralne Lab. Ochrony Radiologicznej, Warsaw (Poland))

1975-01-01

The authors describe the results of measurements of doses and the evaluation of radiation exposure of the personnel of the Department of General Oncology working with application of radioactive iridium for interstitial and superficial treatment of neoplasma. The doses were measured by the photographic method simultaneously at six sites of the body: on the forehead, left side of the chest, 4th fingers of both hands, and on the left and right sides of the trunk at the level of gonads. The authors believe that introduction of iridium in place of radium will improve the conditions of work from the standpoint of protection against radioactivity.

Mixed N-Heterocyclic Carbene-Bis(oxazolinyl)borato Rhodium and Iridium Complexes in Photochemical and Thermal Oxidative Addition Reactions

Energy Technology Data Exchange (ETDEWEB)

Xu, Songchen [Ames Laboratory; Manna, Kuntal [Ames Laboratory; Ellern, Arkady [Ames Laboratory; Sadow, Aaron D [Ames Laboratory

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

Closed-shell and open-shell square-planar iridium nitrido complexes

Science.gov (United States)

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)].

Enantioselective synthesis of almorexant via iridium-catalysed intramolecular allylic amidation

NARCIS (Netherlands)

Fananas Mastral, Martin; Teichert, Johannes F.; Fernandez-Salas, Jose Antonio; Heijnen, Dorus; Feringa, Ben L.

2013-01-01

An enantioselective synthesis of almorexant, a potent antagonist of human orexin receptors, is presented. The chiral tetrahydroisoquinoline core structure was prepared via iridium-catalysed asymmetric intramolecular allylic amidation. Further key catalytic steps of the synthesis include an oxidative

Interstitial hyperthermia and iridium-192 treatment alone vs. interstitial iridium-192 treatment/hyperthermia and low dose cisplatinum infusion in the treatment of locally advanced head and neck malignancies

International Nuclear Information System (INIS)

Schreiber, David P.; Overett, Thomas K.

1995-01-01

Purpose: To determine whether the addition of low dose platinum infusional chemotherapy adds to the effectiveness of interstitial hyperthermia/iridium-192 management of locally advanced head and neck malignancies. Methods and Materials: From 1987 to 1993, 36 patients with locally advanced head and neck malignancies were treated locally with interstitial hyperthermia and iridium-192 as part or all of their management. Twenty-two of the above-mentioned patients also received low dose infusional cisplatinum chemotherapy at 20 mg/M 2 per day during the time of the implant. No patient received greater than 100 mg/M 2 total dose. Implant times ranged from 38.5 to 134 h and total doses delivered with the radiation implants ranged from 15 to 39.9 Gy. Average implant volume was 50 cc. Twenty-three patients received external beam irradiation supplementation in a dose range from 25.2 to 64 Gy. Results: Median follow-up for the entire group was 8, months with 7 months for the chemotherapy group vs. 12 months for the no-chemotherapy group. Freedom from relapse rates for the chemotherapy group vs. the no-chemotherapy group were 70% at 41 months vs. 63% at 60 months, p not significant (p = NS). Overall survival by Life Table Analysis was 28% for the chemotherapy group at 41 months vs. 31% for the no-chemotherapy group at 60 months (p = NS). Complete response (CR) rates were 93% for the chemotherapy group vs. 86% for the no-chemotherapy group. Seven patients in the chemotherapy group had recurrent disease and four patients in the no-chemotherapy group were being treated for recurrent disease. Complication rates were similar in both groups, with two patients in the chemotherapy arm requiring hyperbaric oxygen treatments and one patient in the no-chemotherapy arm requiring hyperbaric oxygen treatments (for soft tissue necrosis). Conclusion: It appears that low dose platinum infusional chemotherapy can be added safely to patients receiving interstitial iridium-192 implants along with

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

International Nuclear Information System (INIS)

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

Determination of iridium in the Bering Sea and Arctic Ocean seawaters by anion exchange preconcentration-neutron activation analysis

International Nuclear Information System (INIS)

Li Shihong; Mao Xueying; Chai Zhifang

2004-01-01

Anion exchange method is investigated to separate and enrich iridium in seawater by radiotracer 192 Ir. The adsorption of Ir in the resin increases with the decreasing acidity in the 0.05-1.2 mol/L HCl media, The recovery of iridium in pH=1.5 seawater reaches 89% by a single anion-exchange column. The polyethylene container of acidity of pH=1.5 are suitable for storing trace Ir in seawater. An anion exchange preconcentration-neutron activation analysis procedure is developed to determine iridium in seawaters sampled from the Bering Sea and Arctic Ocean at different depth. The reagent blank value of the whole procedures is (0.18-0.20) x 10 -12 g Ir. The iridium concentrations in the Bering Sea and Arctic Ocean seawater samples are (0.85-3.58) x 10 -12 g/L (0-3504 m) and (1.26-1.97) x 10 -12 g/L (25-1900 m), respectively

[New calculation algorithms in brachytherapy for iridium 192 treatments].

Science.gov (United States)

Robert, C; Dumas, I; Martinetti, F; Chargari, C; Haie-Meder, C; Lefkopoulos, D

2018-05-18

Since 1995, the brachytherapy dosimetry protocols follow the methodology recommended by the Task Group 43. This methodology, which has the advantage of being fast, is based on several approximations that are not always valid in clinical conditions. Model-based dose calculation algorithms have recently emerged in treatment planning stations and are considered as a major evolution by allowing for consideration of the patient's finite dimensions, tissue heterogeneities and the presence of high atomic number materials in applicators. In 2012, a report from the American Association of Physicists in Medicine Radiation Therapy Task Group 186 reviews these models and makes recommendations for their clinical implementation. This review focuses on the use of model-based dose calculation algorithms in the context of iridium 192 treatments. After a description of these algorithms and their clinical implementation, a summary of the main questions raised by these new methods is performed. Considerations regarding the choice of the medium used for the dose specification and the recommended methodology for assigning materials characteristics are especially described. In the last part, recent concrete examples from the literature illustrate the capabilities of these new algorithms on clinical cases. Copyright © 2018 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.

Iridium/Bipyridine-Catalyzed ortho-Selective C-H Borylation of Phenol and Aniline Derivatives.

Science.gov (United States)

Li, Hong-Liang; Kanai, Motomu; Kuninobu, Yoichiro

2017-11-03

An iridium-catalyzed ortho-selective C-H borylation of phenol and aniline derivatives has been successfully developed. Iridium/bipyridine-catalyzed C-H borylation generally occurred at the meta- and para-positions of aromatic substrates. Introduction of an electron-withdrawing substituent on the bipyridine-type ligand and a methylthiomethyl group on the hydroxy and amino groups of the phenol and aniline substrates, however, dramatically altered the regioselectivity, affording exclusively ortho-borylated products. The reaction proceeded in good to excellent yields with good functional group tolerance. C-H borylation was applied to the synthesis of a calcium receptor modulator.

Fragmentation of neutral carbon clusters formed by high velocity atomic collision

International Nuclear Information System (INIS)

Martinet, G.

2004-05-01

The aim of this work is to understand the fragmentation of small neutral carbon clusters formed by high velocity atomic collision on atomic gas. In this experiment, the main way of deexcitation of neutral clusters formed by electron capture with ionic species is the fragmentation. To measure the channels of fragmentation, a new detection tool based on shape analysis of current pulse delivered by semiconductor detectors has been developed. For the first time, all branching ratios of neutral carbon clusters are measured in an unambiguous way for clusters size up to 10 atoms. The measurements have been compared to a statistical model in microcanonical ensemble (Microcanonical Metropolis Monte Carlo). In this model, various structural properties of carbon clusters are required. These data have been calculated with Density Functional Theory (DFT-B3LYP) to find the geometries of the clusters and then with Coupled Clusters (CCSD(T)) formalism to obtain dissociation energies and other quantities needed to compute fragmentation calculations. The experimental branching ratios have been compared to the fragmentation model which has allowed to find an energy distribution deposited in the collision. Finally, specific cluster effect has been found namely a large population of excited states. This behaviour is completely different of the atomic carbon case for which the electron capture in the ground states predominates. (author)

Triazole-pyridine ligands: a novel approach to chromophoric iridium arrays

NARCIS (Netherlands)

Juríček, M.; Felici, M.; Contreras-Carballada, P.; Lauko, J.; Bou, S.R.; Kouwer, P.H.J.; Brouwer, A.M.; Rowan, A.E.

2011-01-01

We describe a novel modular approach to a series of luminescent iridium complexes bearing triazole-pyridine-derived ligands that were conveniently prepared by using "click" chemistry. One, two or three triazole-pyridine units were effectively built into the heteroaromatic macromolecule using

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

International Nuclear Information System (INIS)

Millard, H.T.

1986-01-01

Low-level methods for the determination of iridium and other noble metals have been important in recent years due to interest in locating abundance anomalies associated with the Cretaceous/Tertiary (K/T) boundary. Typical iridium anomalies are in the range of 1 to 100 ppb. Thus methods with detection limits near 0.1 ppb 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 employed in this study samples irradiated in the epithermal neutron facility of the U.S. Geological Survey TRIGA Reactor 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 peroxide 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. (author)

Effect of the substituents on the photophysical, electrochemical and electroluminescence properties of OLED dopant Iridium bis(2-phenylbenzothiozolato- N,C2')(acetylacetonate)

Science.gov (United States)

Ivanov, P.; Tomova, R.; Petrova, P.

2014-12-01

The effect of two substituents: clorine and 1,3-diphenylpropane-1,3-dionate, placed on different position in the molecule of Iridium (III) bis(2-phenylbenzothiozolato-N,C2')- (acetylacetonate) (bt)2Ir(acac), on its electrochemical behaviour, photophysical and electroluminescence properties were investigated. Three complexes (bt)2Ir(acac), Iridium (III) bis[2-(4-chlorophenyl)benzothiazolato-N,C2']-acetylacetonate (Clbt)2Ir(acac), in which the Cl atom was introduced on the 4-position in the benzothiazole ring, and the new Iridium (Ill) bis[2 -phenylbenzothiazolato -N,C2'] -(1,3 -diphenylpropane-1,3 -dionate) (bt)2Ir(dbm), where ancillary acetylacetonate ligand was replaced by 1,3-diphenylpropane-1,3-dionate, were synthesized and characterised by 1H-NMR and elemental analysis. The HOMO/LUMO energy levels of the complexes were determined by cyclic voltammetry (CV) and their properties were established by UV-Visible and fluorescence spectroscopy. The application of (Clbt)2Ir(acac), (bt)2Ir(bsm) and (bt)2Ir(acac) as dopants in hole transporting layer (HTL) of Organic light- emitting diodes(OLEDs). It was found that with respect to the reference (bt)2Ir(acac): both LUMO and HOMO of the substituted complexes were shifted to more positive values accordingly with 0.23 and 0.19 eV for (Clbt)2Ir(acac) and 0.14 and 0.12 eV for (bt)2Ir(dbm). OLEDs doped with 1 w% of the complexes irradiated the warm white light with Commission internationale de l'eclairage (CIE) coordinates: 0.24;0.38 for (Clbt)2Ir(acac), 0.30;0.44 for (bt)2Ir(acac) and 0.28;0.46 for (bt)2Ir(dbm). Devices doped with 10 w% of all complexes irradiated in the yellow orange region of the spectrum.

Phosphorescent Organic Light-Emitting Devices: Working Principle and Iridium Based Emitter Materials

Directory of Open Access Journals (Sweden)

Emil J. W. List

2008-08-01

Full Text Available Even though organic light-emitting device (OLED technology has evolved to a point where it is now an important competitor to liquid crystal displays (LCDs, further scientific efforts devoted to the design, engineering and fabrication of OLEDs are required for complete commercialization of this technology. Along these lines, the present work reviews the essentials of OLED technology putting special focus on the general working principle of single and multilayer OLEDs, fluorescent and phosphorescent emitter materials as well as transfer processes in host materials doped with phosphorescent dyes. Moreover, as a prototypical example of phosphorescent emitter materials, a brief discussion of homo- and heteroleptic iridium(III complexes is enclosed concentrating on their synthesis, photophysical properties and approaches for realizing iridium based phosphorescent polymers.

Extrahepatic bile duct carcinoma treated by intraluminal irradiation with iridium-192 wire

International Nuclear Information System (INIS)

Ikeda, Hiro; Kuroda, Tomosumi; Uchida, Hideo

1980-01-01

A 57-year-old male with obstructive jaundice was diagnosed extrahepatic bile duct carcinoma at bifurcation by percutaneous transhepatic cholangiography (PTC). He was treated 3,300 rad of external irradiation and then intraluminal irradiation using the Iridium-192 wire by two times with the aid of PTC internal drainage, each was given by the dose of 1,600 rad at 5 mm inside the tumor from the PTC-tube. He had been well for about 1 year and then died because of ascites and cachexia. Autopsy revealed only microscopic tumor cells remaining around the common duct below the cystic junction. It was confirmed that intraluminal irradiation using the Iridium-192 wire was potentially curable and easily applicable to the bile duct carcinoma. (author)

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

Directory of Open Access Journals (Sweden)

Chia-Pin Yeh

2016-08-01

Full Text Available 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.

Nuclear resonance scattering study of iridates, iridium and antimony based pyrochlores

International Nuclear Information System (INIS)

Alexeev, P.

2017-04-01

This thesis shows the first synchrotron-based Moessbauer spectroscopy studies on iridium containing compounds and first vibrational spectroscopy on Sb containing compounds carried out at the P01 beamline of PETRA III. In this context, two types of X-ray monochromators have been developed: a monochromator for 73 keV photons with medium energy resolution, and a high-resolution backscattering monochromator based on a sapphire crystal. The monochromator for 73 keV X-rays is the key instrument for hyperfine spectroscopy on Iridium compounds, while the sapphire backscattering monochromator is purposed to vibrational spectroscopy on any Moessbauer resonances with the transition energies in the 20-50 keV range. Additionally, the signal detection for nuclear resonance scattering experiments at the beamline was significantly improved during this work, inspired by the high energies and low lifetimes of the employed resonances. The first synchrotron-based hyperfine spectroscopy on Iridium-containing compounds was demonstrated by NRS on 73 keV resonance in "1"9"3Ir. The results can be interpreted by dynamical theory of nuclear resonance scattering. In this work, special emphasis is set onto the electronic and magnetic properties of Ir nuclei in IrO_2 and in Ruddlesden-Popper (RP) phases of strontium iridates Sr_n_+_1Ir_nO_3_n_+_1 (n=0,1). These systems are well-suited for studies with X-ray scattering techniques, since the scattered signal contains vast information about the widely tunable crystallographic and electronic structure of these systems; furthermore, studies with X-rays are less limited by absorption from iridium as it is the case for neutron scattering experiments. The hyperfine parameters in IrO_2, SrIrO_3 and Sr_2IrO_4 have been measured via Nuclear Forward Scattering for the first time. Using the dynamical theory of NRS, the temperature and magnetic field dependence of the electric field gradient and magnetic hyperfine field on Ir nucleus have been determined for

Nuclear resonance scattering study of iridates, iridium and antimony based pyrochlores

Energy Technology Data Exchange (ETDEWEB)

Alexeev, P.

2017-04-15

This thesis shows the first synchrotron-based Moessbauer spectroscopy studies on iridium containing compounds and first vibrational spectroscopy on Sb containing compounds carried out at the P01 beamline of PETRA III. In this context, two types of X-ray monochromators have been developed: a monochromator for 73 keV photons with medium energy resolution, and a high-resolution backscattering monochromator based on a sapphire crystal. The monochromator for 73 keV X-rays is the key instrument for hyperfine spectroscopy on Iridium compounds, while the sapphire backscattering monochromator is purposed to vibrational spectroscopy on any Moessbauer resonances with the transition energies in the 20-50 keV range. Additionally, the signal detection for nuclear resonance scattering experiments at the beamline was significantly improved during this work, inspired by the high energies and low lifetimes of the employed resonances. The first synchrotron-based hyperfine spectroscopy on Iridium-containing compounds was demonstrated by NRS on 73 keV resonance in {sup 193}Ir. The results can be interpreted by dynamical theory of nuclear resonance scattering. In this work, special emphasis is set onto the electronic and magnetic properties of Ir nuclei in IrO{sub 2} and in Ruddlesden-Popper (RP) phases of strontium iridates Sr{sub n+1}Ir{sub n}O{sub 3n+1} (n=0,1). These systems are well-suited for studies with X-ray scattering techniques, since the scattered signal contains vast information about the widely tunable crystallographic and electronic structure of these systems; furthermore, studies with X-rays are less limited by absorption from iridium as it is the case for neutron scattering experiments. The hyperfine parameters in IrO{sub 2}, SrIrO{sub 3} and Sr{sub 2}IrO{sub 4} have been measured via Nuclear Forward Scattering for the first time. Using the dynamical theory of NRS, the temperature and magnetic field dependence of the electric field gradient and magnetic hyperfine field

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

NARCIS (Netherlands)

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

1999-01-01

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

Low-Stress Iridium Coatings for Thin-Shell X-Ray Telescopes, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — We propose to develop and commercialize a new type of low-stress iridium (Ir) X-ray mirror coating technology that can be used for the construction of...

Intercalating cobalt between graphene and iridium (111): Spatially dependent kinetics from the edges

Science.gov (United States)

Vlaic, Sergio; Rougemaille, Nicolas; Kimouche, Amina; Burgos, Benito Santos; Locatelli, Andrea; Coraux, Johann

2017-10-01

Using low-energy electron microscopy, we image in real time the intercalation of a cobalt monolayer between graphene and the (111) surface of iridium. Our measurements reveal that the edges of a graphene flake represent an energy barrier to intercalation. Based on a simple description of the growth kinetics, we estimate this energy barrier and find small, but substantial, local variations. These local variations suggest a possible influence of the graphene orientation with respect to its substrate and of the graphene edge termination on the energy value of the barrier height. Besides, our measurements show that intercalated cobalt is energetically more favorable than cobalt on bare iridium, indicating a surfactant role of graphene.

The effect of surface depletion on the work function of arc-melted dilute solution tungsten-iridium alloys

International Nuclear Information System (INIS)

D'Cruz, L.A.; Bosch, D.R.; Jacobson, D.L.

1991-01-01

The requirements of thermionic electrode materials have emphasized the need for substantial improvements in microstructural stability, strength, and creep resistance at service temperature in excess of 2,500K. The present work extends an earlier study of the effective work function trends of a series of dilute solution tungsten, iridium alloys with iridium contents of 1, 3, and 5 wt%. Since the lifetime of candidate electrode materials is an important consideration, the present work attempts to evaluate the repeatability of the work function trends in these alloys. The effective work function was obtained from measurements of the current emitted from the electrode surface under UHV conditions in the temperature range of 1,800-2,500K using a Vacuum Emission Vehicle (VEV). The data generated in this work have been compared with data obtained in earlier studies performed on these alloys. It was found that the magnitude of the effective work function of these alloys was affected by changes in the subsurface iridium concentration. Furthermore, these alloys exhibited a dependence of the work function on temperature, after prolonged exposure to elevated temperatures. Such a temperature dependence can be explained by diffusion-controlled changes in the coverage of an iridium monolayer on the surface. It is proposed that the significant difference in effective work function trends obtained after prolonged exposure to elevated temperatures is a direct consequence of changes in the coverage of an iridium-rich monolayer on the electrode surface. The constitution of such a surface layer, however, would be governed by composition changes in the subsurface regions of the electrode caused thermally-activated transport processes

Dose determination in breast tumor in brachytherapy using Iridium-192

International Nuclear Information System (INIS)

Okuno, S.F.

1984-01-01

Thermoluminescent dosimetry studies in vivo and in vitro aiming to determing radiation dose in the breast tumor, in brachytherapy using Iridium-192 was done. The correlation between radiation doses in tumor and external surface of the breast was investigated for correcting the time interval of radiation source implantation. (author) [pt

Study of neutron deficient iridium isotopes by using laser spectroscopy; Etude des noyaux d'iridium deficients en neutrons par spectroscopie laser

Energy Technology Data Exchange (ETDEWEB)

Verney, D

2000-12-19

Resonance ionization spectroscopy was performed on neutron deficient iridium isotopes {sup 182-189}Ir, {sup 186}Ir{sup m} and stable isotopes {sup 191,193}Ir. Hyperfine spectra were recorded from the optical transition at 351,7 nm between the 5d{sup 7}6s{sup 2} {sup 4}F{sub 9/2} ground state and the 5d{sup 7}6s6p {sup 6}F{sub 11/2} excited state. Radioactive iridium isotopes were obtained from {beta}{sup +}/EC decay of radioactive mercury nuclei deposited on a graphite substrate. The radioactive mercury nuclei were produced at the ISOLDE facility at CERN through spallation reactions, by bombarding a molten lead target with the 1 GeV proton beam delivered by the PS-Booster. Magnetic dipole moments and spectroscopic quadrupole moments were extracted from the hyperfine spectra. The mean square charge radius variations, as deduced from the measured isotopic shift, show a sharp change between {sup 187}Ir and {sup 186}Ir{sup g}, accompanied by a sudden increase in deformation: from {beta}2 {approx} 0,16 to {beta}2 > 0, 2. These results were analysed in the framework of an axial rotor plus one or two quasiparticles. The wave functions of the osmium and platinum cores which are used in order to describe the iridium nuclei were calculated from the HF+BCS method with the Skyrme SIII effective interaction. The cores were constrained to take the deformation parameters extracted from the isotopic shift measurements. One shows then that this sudden deformation change corresponds also to a change in the proton state that describes the odd nuclei ground state or that participates in the coupling with the neutron in odd-odd nuclei. This state is identified with the {pi}3/2{sup +}[402] orbital for the smaller deformations nuclei and with the {pi}1/2{sup -}[541] orbital stemming from the h{sub 9/2} subshell for bigger deformations nuclei. (author)

Eletrodeposição de irídio em tubo de grafite como modificador químico permanente em espectrometria de absorção atômica Electrodeposition of iridium in graphite tube as permanent chemical modifier in atomic absorption spectrometry

Directory of Open Access Journals (Sweden)

Juliana Naozuka

2003-12-01

Full Text Available A tubular electrochemical flow-cell for iridium deposition on the inner surface of pyrolytic graphite tube for permanent chemical modification is proposed. A transversal heated graphite tube was used as working electrode, a cylindrical piece of graphite inserted into the graphite tube as auxiliary electrode, and a micro Ag/AgCl(sat as reference electrode. Iridium solution in 1.0 mol L-1 HCl, flowing at 0.55 mL min-1 for 60 min was used to perform the electrochemical modification. The applied potential to the flow-cell was - 0.700 V vs Ag/AgCl. Scanning electron microscopy images were taken for thermal and electrochemical modified graphite surface in order to evaluate the iridium distribution. Selenium hydride trapping was used to verify the performance of the proposed permanent chemical modifier.

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

Science.gov (United States)

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.

Dosimetry of wires and single ribbons of Iridium 192

International Nuclear Information System (INIS)

Mazzucco, L.D.

1998-01-01

The objective of this work is in order to present in table formats the dosimetry of wires and single ribbons of Iridium with lengths 1-12 cm for each one linear source along the bisector which is perpendicular at tissue sources (water) computed for linear activity 1 mCi/cm in the case of wires, and 1 mCi/seed for ribbons. The above tables are of direct use, adaptable at particular cases so they facilitate logarithmic graphics of doses in function of the distance for interpolation and use in the treatments planning. It was shown that for two sources with identical linear activity and total length, one of the equidistant seeds at 1 cm (ribbon) and one wire on the other hand, the differences in dose rates in near positions can be about the 15% so corroborating that it is not possible to use wire tables for seeds neither vice versa. Moreover it was elaborated tables of practical direct use for dose rate in water at c Gy/hr for wires and Ribbons 1-12 cm length and from 0.5-10 cm of distance in the perpendicular bisector at the Iridium implant. (Author)

Quantitative characterization of the atomic-scale structure of oxyhydroxides in rusts formed on steel surfaces

International Nuclear Information System (INIS)

Saito, M.; Suzuki, S.; Kimura, M.; Suzuki, T.; Kihira, H.; Waseda, Y.

2005-01-01

Quantitative X-ray structural analysis coupled with anomalous X-ray scattering has been used for characterizing the atomic-scale structure of rust formed on steel surfaces. Samples were prepared from rust layers formed on the surfaces of two commercial steels. X-ray scattered intensity profiles of the two samples showed that the rusts consisted mainly of two types of ferric oxyhydroxide, α-FeOOH and γ-FeOOH. The amounts of these rust components and the realistic atomic arrangements in the components were estimated by fitting both the ordinary and the environmental interference functions with a model structure calculated using the reverse Monte Carlo simulation technique. The two rust components were found to be the network structure formed by FeO 6 octahedral units, the network structure itself deviating from the ideal case. The present results also suggest that the structural analysis method using anomalous X-ray scattering and the reverse Monte Carlo technique is very successful in determining the atomic-scale structure of rusts formed on the steel surfaces

The asymmetric rotator model applied to odd-mass iridium isotopes

International Nuclear Information System (INIS)

Piepenbring, R.

1980-04-01

The method of inversion of the eigenvalue problem previously developed for nuclei with axial symmetry is extended to asymmetric equilibrium shapes. This new approach of the asymmetric rotator model is applied to the odd-mass iridium isotopes. A satisfactory and coherent description of the observed energy spectra is obtained, especially for the lighter isotopes

Synthesis, structure, redox and spectra of green iridium complexes ...

Indian Academy of Sciences (India)

Reactions of IrCl3 ⋅ H2O with the ligands, 2-[(phenylamino)phenylazo]pyridine (HL1a) and 2-[(-tolylamino)phenylazo]pyridine (HL1b) produce [Ir(L1)2]Cl (L1 = L1a, [1]Cl and L1 = L1b, [2]Cl) along with many unidentified products. The iridium complexes have been characterized by various techniques such as X-ray ...

Development of accurate mass spectrometric routine and reference methods for the determination of trace amounts of iridium and rhodium in photographic emulsionsf

NARCIS (Netherlands)

Krystek, Petra; Heumann, Klaus G.

1999-01-01

For the determination of trace amounts of iridium and rhodium in photographic emulsions different sample treatment procedures were coupled with inductively coupled plasma mass spectrometry (ICP-MS) and, for iridium, also with negative thermal ionisation isotope dilution mass spectrometry (NTI-IDMS)

Oxygen Sensing by the Hybrid Langmuir-Blodgett Films of Iridium(III Complexes and Synthetic Saponite on the Basis of Energy Transfer

Directory of Open Access Journals (Sweden)

Hisako Sato

2017-09-01

Full Text Available An ultra-thin hybrid film of amphiphilic iridium(III complexes and synthetic saponite was manipulated by means of the modified Langmuir-Blodgett method. In the film deposited onto a quartz substrate, the external mixed molecular layer of amphiphilic iridium(III complexes was reinforced by the inner layer of exfoliated synthetic saponite. As components of the molecular layer, two iridium(III complexes were used: [Ir(dfppy2(dc9bpy]+ (dfppyH = 2-(4′,6′-difluorophenyl pyridine; dc9bpy = 4,4′-dinonyl-2,2′-bipyridine (denoted as DFPPY and [Ir(piq2(dc9bpy]+ (piqH = 1-phenyisoquinoline denoted as PIQ. The emission spectra from the films changed from blue to red maxima with the decrease of a ratio of DFPPY/PIQ due to the energy transfer from excited DFPPY to PIQ. The intensity of red decreased with the increase of oxygen pressure through the quenching of excited iridium(III complexes, promising a possibility as an oxygen-sensing film.

Iridium anomaly in the cretaceous-paleogene boundary at Højerup (Stevns Klint, Denmark and Woodside Creek (New Zealand: The question of an enormous proportion of extraterrestrial component

Directory of Open Access Journals (Sweden)

Premović Pavle I.

2012-01-01

Full Text Available The Cretaceous-Paleogene boundary clays at Højerup and Woodside Creek show anomalous enrichments of iridium compared with the marine sedimentary rocks. For the average iridium content of 465 ppb in CI chondrite the estimate of the carbonaceous chondritic proportions in the decarbonated iridium-rich boundary layers, based on the integrated iridium fluencies, is about 26% at Højerup and 65% at Woodside Creek. These proportions are most likely too high due to a significant Ir influx from the nearby marine or continental site to these sections.

A colorimetric and luminescent dual-modal assay for Cu(II ion detection using an iridium(III complex.

Directory of Open Access Journals (Sweden)

Dik-Lung Ma

Full Text Available A novel iridium(III complex-based chemosensor bearing the 5,6-bis(salicylideneimino-1,10-phenanthroline ligand receptor was developed, which exhibited a highly sensitive and selective color change from colorless to yellow and a visible turn-off luminescence response upon the addition of Cu(II ions. The interactions of this iridium(III complex with Cu2+ ions and thirteen other cations have been investigated by UV-Vis absorption titration, emission titration, and 1H NMR titration.

Mechanistic investigation of the iridium-catalysed alkylation of amines with alcohols

DEFF Research Database (Denmark)

Fristrup, Peter; Tursky, Matyas; Madsen, Robert

2012-01-01

where the intermediate aldehyde stays coordinated to the iridium catalyst and reacts with the amine to give a hemiaminal which is also bound to the catalyst. Dehydration to the imine and reduction to the product amine also takes place without breaking the coordination to the catalyst. The fact...

BOWIEITE: A NEW RHODIUM-IRIDIUM-PLATINUM SULFIDE IN PLATINUM-ALLOY NUGGETS, GOODNEWS BAY, ALASKA.

Science.gov (United States)

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.

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

Science.gov (United States)

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.

Electro-catalytic oxidation of ethanol on platinum-iridium mixtures supported on glassy carbon

International Nuclear Information System (INIS)

Rodriguez, Henry; Hoyos Bibian

2004-01-01

Electro-catalytic oxidation of ethanol on platinum-iridium mixtures supported on glassy carbon was studied, in acid media at different temperatures and concentrations. During the maturation time of deposited iridium, the surface is covered by an irreversible oxide formation, which affects the behavior of the catalytic mixture. The Pt 7 0 Ir 3 0 and Pt 9 0 Ir 1 0 mixtures seem to be a little more active than the Pt/C electrode at potentials below 800 mV (vs. HRE). In all electrodes appears two reactions: partial ethanol oxidation to produce acetaldehyde (main path of reaction at low temperatures and high electrode coverage with ethanol adsorption residues) and the total oxidation to carbon dioxide which is considerable at potential above 800 mV and it is increased with increasing temperature

Grain Growth and Precipitation Behavior of Iridium Alloy DOP-26 During Long Term Aging

Energy Technology Data Exchange (ETDEWEB)

Pierce, Dean T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Muralidharan, Govindarajan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Fox, Ethan E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cox, Victoria A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Geer, Tom [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-05-01

The influence of long term aging on grain growth and precipitate sizes and spatial distribution in iridium alloy DOP-26 was studied. Samples of DOP-26 were fabricated using the new process, recrystallized for 1 hour (h) at 1375 C, then aged at either 1300, 1400, or 1500 C for times ranging from 50 to 10,000 h. Grain size measurements (vertical and horizontal mean linear intercept and horizontal and vertical projection) and analyses of iridium-thorium precipitates (size and spacing) were made on the longitudinal, transverse, and rolling surfaces of the as-recrystallized and aged specimens from which the two-dimensional spatial distribution and mean sizes of the precipitates were obtained. The results obtained from this study are intended to provide input to grain growth models.

Interaction of an iridium-clad RTG heat source unit with a simulated terrestrial environment

International Nuclear Information System (INIS)

Patterson, J.H.; Herrera, B.; Nelson, G.B.; Matlack, G.M.; Waterbury, G.R.

1976-02-01

An iridium-clad, 100-W 238 PuO 2 sphere, a prototype for the multihundred-watt radioisotope thermoelectric generator, was exposed for 1 y to a simulated temperate humid climate in an environmental test chamber containing sandy soil. The hot sphere sank into the soil after the first rain, then gradually acquired a hard crust around it as a result of the rainwater reacting with the hot soil during successive rains. Time and temperature profiles of the sphere were recorded during the weekly rains, and the air and rainwater that percolated through the soil were monitored for plutonium. No plutonium was released from the sphere. Aside from the crust formation, very little reaction occurred between the hot iridium shell and the soil

Efficiency Control in Iridium Complex-Based Phosphorescent Light-Emitting Diodes

Directory of Open Access Journals (Sweden)

Boucar Diouf

2012-01-01

Full Text Available Key factors to control the efficiency in iridium doped red and green phosphorescent light emitting diodes (PhOLEDs are discussed in this review: exciton confinement, charge trapping, dopant concentration and dopant molecular structure. They are not independent from each other but we attempt to present each of them in a situation where its specific effects are predominant. A good efficiency in PhOLEDs requires the triplet energy of host molecules to be sufficiently high to confine the triplet excitons within the emitting layer (EML. Furthermore, triplet excitons must be retained within the EML and should not drift into the nonradiative levels of the electron or hole transport layer (resp., ETL or HTL; this is achieved by carefully choosing the EML’s adjacent layers. We prove how reducing charge trapping results in higher efficiency in PhOLEDs. We show that there is an ideal concentration for a maximum efficiency of PhOLEDs. Finally, we present the effects of molecular structure on the efficiency of PhOLEDs using red iridium complex dopant with different modifications on the ligand to tune its highest occupied molecular orbital (HOMO and lowest unoccupied molecular orbital (LUMO energies.

Influence of the profile of Iridium-192 wire in measurements of quality control for use in brachytherapy

International Nuclear Information System (INIS)

Costa, Osvaldo L.; Zeituni, Carlos A.; Rostelato, Maria Elisa C.M.; Moura, Joao A.; Feher, Anselmo; Moura, Eduardo S.; Souza, Carla D.; Somessari, Samir L.; Peleias Junior, Fernando S.; Mattos, Fabio R.

2013-01-01

Brachytherapy is a method used in the treatment of cancerous tumors, by ionizing radiation produced by sources, introduced into the tumor area, this method seeks a more direct to the tumor, thereby maximizing the radiation dose to diseased tissue, while minimizing the dose to healthy tissues. One of the radionuclides used in brachytherapy is iridium-192. The Radiation Technology Center (CTR), of the Nuclear and Energy Research Institute (IPEN), has produced commercially, since 1998, iridium-192 wires used in low dose rate (LDR) brachytherapy. To produce this radionuclides, firstly an iridium-platinum wire is irradiated in the nuclear reactor IEA-R1 for 30 hours, with a neutron flux of 5x 10 13 n cm -2 s -1 , the wire is left to decay by 30 days to remove the main contaminants, and then goes through a quality control, before being sent to the hospital. In this quality control is checked the radiation homogeneity along each centimeter of the wire. To implement this procedure, is used a device, consisting of an ionization chamber, surrounded by a lead shield, with a samol 1 cm wide slit, linked to the ionization chamber is a voltage source, and a Keithley 617 electrometer, 2 minutes is the range used to measure the charge by the electrometer. The iridium wire is considered in accordance, when there is no variation higher than 5%, between the average measures and the maximum and minimum values. However, due to design features of the measurement system, the wire may appear to the detector through the slit in larger sizes than the ideal, improperly influencing the final quality control. This paper calculates the difference in size of these variations in profile, and their influence on the final count, it compares the actual values obtained, and describes the improvements, made in quality control procedures, that provided more accurate measurement data, analyzes the results, and suggests changes in devices, aimed at further improving the quality control of iridium-192

COUPLED ATOMIZATION AND SPRAY MODELLING IN THE SPRAY FORMING PROCESS USING OPENFOAM

DEFF Research Database (Denmark)

Gjesing, Rasmus; Hattel, Jesper Henri; Fritsching, Udo

2009-01-01

The paper presents a numerical model capable of simulating the atomization, break-up and in-flight spray phenomena in the spray forming process. The model is developed and implemented in the freeware code openFOAM. The focus is on studying the coupling effect of the melt break-up phenomena...

Synthesis and optoelectronic properties of oxadiazole-functionalized iridium complexes in the poly(vinylcarbazole)-hosted devices

International Nuclear Information System (INIS)

Wu Zhonglian; Luo Cuiping; Jiang Changyun; Zhu Meixiang; Cao, Yong; Zhu Weiguo

2008-01-01

A class of oxadiazole-functionalized iridium complexes was used as phosphor emitters in poly (vinylcarbazole)-hosted devices. Efficient green electrophosphorescences were achieved in the devices with a maximum luminance efficiency of 9.3 cd/A at 10.6 mA/cm 2 and brightness of 3882 cd/m 2 at 92.1 mA/cm 2 . More importantly, the iridium complexes-doped devices exhibited a low turn-on voltage of 7.0 V and an applied voltage of 9.2 V at 500 cd/m 2 . The good optoelectronic properties of the complexes were attributed to the enhanced electron-injection and transport properties resulting from the effect of oxadiazole ligands in the complexes

16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

Science.gov (United States)

2010-01-01

... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Misuse of the words âplatinum,â âiridium,â... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a) It is unfair or deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium...

Iridium emissions from Hawaiian volcanoes

International Nuclear Information System (INIS)

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

Iridium emissions from Hawaiian volcanoes

Science.gov (United States)

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.

Iridium containing honeycomb Delafossites by topotactic cation exchange.

Science.gov (United States)

Roudebush, John H; Ross, K A; Cava, R J

2016-06-07

We report the structure and magnetic properties of two new iridium-based honeycomb Delafossite compounds, Cu3NaIr2O6 and Cu3LiIr2O6, formed by a topotactic cation exchange reaction. The starting materials Na2IrO3 and Li2IrO3, which are based on layers of IrO6 octahedra in a honeycomb lattice separated by layers of alkali ions, are transformed to the title compounds by a topotactic exchange reaction through heating with CuCl below 450 °C; higher temperature reactions cause decomposition. The new compounds display dramatically different magnetic behavior from their parent compounds - Cu3NaIr2O6 has a ferromagnetic like magnetic transition at 10 K, while Cu3LiIr2O6 retains the antiferromagnetic transition temperature of its parent compound but displays significantly stronger dominance of antiferromagnetic coupling between spins. These results reveal that a surprising difference in the magnetic interactions between the magnetic Ir ions has been induced by a change in the non-magnetic interlayer species. A combination of neutron and X-ray powder diffraction is used for the structure refinement of Cu3NaIr2O6 and both compounds are compared to their parent materials.

Regio- and Enantioselective N-Allylations of Imidazole, Benzimidazole, and Purine Heterocycles Catalyzed by Single-Component Metallacyclic Iridium Complexes

Science.gov (United States)

Stanley, Levi M.

2010-01-01

Highly regio- and enantioselective iridium-catalyzed N-allylations of benzimidazoles, imidazoles, and purines have been developed. N-Allylated benzimidazoles and imidazoles were isolated in high yields (up to 97%) with high branched-to-linear selectivity (up to 99:1) and enantioselectivity (up to 98% ee) from the reactions of benzimidazole and imidazole nucleophiles with unsymmetrical allylic carbonates in the presence of single component, ethylene-bound, metallacyclic iridium catalysts. N-Allylated purines were also obtained in high yields (up to 91%) with high N9:N7 selectivity (up to 96:4), high branched-to-linear selectivity (98:2), and high enantioselectivity (up to 98% ee) under similar conditions. The reactions encompass a range of benzimidazole, imidazole, and purine nucleophiles, as well as a variety of unsymmetrical aryl, heteroaryl, and aliphatic allylic carbonates. Competition experiments between common amine nucleophiles and the heterocyclic nitrogen nucleophiles studied in this work illustrate the effect of nucleophile pKa on the rate of iridium-catalyzed N-allylation reactions. Kinetic studies on the allylation of benzimidazole catalyzed by metallacyclic iridium-phosphoramidite complexes, in combination with studies on the deactivation of these catalysts in the presence of heterocyclic nucleophiles, provide insight into the effects of the structure of the phosphoramidite ligands on the stability of the metallacyclic catalysts. The data obtained from these studies has led to the development of N-allylations of benzimidazoles and imidazoles in the absence of an exogenous base. PMID:19480431

High-Performance Computer Modeling of the Cosmos-Iridium Collision

Energy Technology Data Exchange (ETDEWEB)

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.

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

Energy Technology Data Exchange (ETDEWEB)

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.

Thermally induced atomic diffusion at the interface between release agent coating and mould substrate in a glass moulding press

Energy Technology Data Exchange (ETDEWEB)

Masuda, Jun; Fukase, Yasushi [Toshiba Machine Co., Ltd, Ooka 2068-3, Numazu-Shi, Shizuoka-Ken, 410-8510 (Japan); Yan Jiwang; Zhou Tianfeng; Kuriyagawa, Tsunemoto, E-mail: yanjw@pm.mech.tohoku.ac.jp [Department of Mechanical Systems and Design, Graduate School of Engineering, Tohoku University, Aoba 6-6-01, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

2011-06-01

In a glass moulding press (GMP) for refractive/diffractive hybrid lenses, to improve the service life of nickel-phosphorus (Ni-P) plated moulds, it is necessary to control the diffusion of constituent elements from the mould into the release agent coating. In this study, diffusion phenomena of constituents of Ni-P plating are investigated for two types of release agent coatings, iridium-platinum (Ir-Pt) and iridium-rhenium (Ir-Re), by cross-sectional observation, compositional analysis and stress measurements. The results show that Ni atoms in the plating layer flow from regions of compressive stress to regions of tensile stress. In the case of the Ir-Pt coated mould, the diffusion of Ni is promoted from the grain boundaries between the Ni and Ni{sub 3}P phases in the plating towards the surface of the Ir-Pt coating. However, in the Ir-Re coated mould, the diffusion of Ni is suppressed because the diffusion coefficient of Ni in the Ir-Re alloy is smaller than that in the Ir-Pt alloy, although the stress state is similar in both cases. By controlling the diffusion of Ni atoms, the use of Ir-Re alloy as a release agent coating for Ni-P plated moulds is expected to lead to a high degree of durability.

Asymmetric hydrogenation of quinolines catalyzed by iridium complexes of monodentate BINOL-derived phosphoramidites

NARCIS (Netherlands)

Mrsic, Natasa; Lefort, Laurent; Boogers, Jeroen A. F.; Minnaard, Adriaan J.; Feringa, Ben L.; de Vries, Johannes G.; Mršić, Nataša

The monodentate BINOL-derived phosphoramidite PipPhos is used as ligand for the iridium-catalyzed asymmetric hydrogenation of 2- and 2,6-substituted quinolines. If tri-ortho-tolylphosphine and/or chloride salts are used as additives enantioselectivities are strongly enhanced up to 89%. NMR indicates

Iridium-192 implants in the treatment of tonsillar region malignancies

International Nuclear Information System (INIS)

Puthawala, A.A.; Syed, A.M.; Gates, T.C.

1985-01-01

A total of 127 patients with histologically proved diagnosis of carcinoma of the tonsillar region and soft palate were treated over the past ten years utilizing interstitial iridium-192 implants. Eighty patients were treated for primary tumors and 47 patients for either recurrent or persistent tumors after definitive irradiation and/or surgery. All patients with primary tumors were treated by a combination of external megavoltage irradiation and interstitial iridium-192 implants, whereas patients with recurrent tumors were treated by interstitial implants alone. In the primary group, 95% of patients with T1 and T2 lesions and 79% with T3 and T4 lesions achieved complete local tumor control. The three-year absolute disease-free survival rate was 72%. Seventy-five percent local tumor control was obtained in patients with recurrent disease, with two-year absolute disease-free survival of 42%. Treatment-related complications such as soft-tissue necrosis or osteoradionecrosis occurred in 6% of patients in the primary group and 23% in recurrent group. This treatment regimen offers an excellent locoregional control with no significant functional or esthetic impairment. Most patients with primary lesions who fail this regimen can be salvaged by surgery or reirradiation using interstitial implants

Implantation of the maxillary antrum for delivery of iridium brachytherapy and microwave induced hyperthermia

International Nuclear Information System (INIS)

Coughlin, C.T.; Wong, T.Z.; Geurkink, N.

1985-01-01

A 63 year-old male was referred tp Dartmouth in March 1984 for a locally advanced recurrent squamous cell carcinoma of the left maxillary antrum. This had been initially diagnosed in January 1983 by a Caldwell-Luc procedure and had failed partial resection, external radiation therapy, and multiagent chemotherapy. Our initial evaluation revealed disease replacing the left maxillary antrum, extending into the pterygomaxillary fossa, the lateral aspect of the superior alveloar ridge, and into the soft palate. He was taken to the operating room and under general anesthesia was implanted the 7 catheters through this tumor volume. Two days later a therapeutic (>42 0 C for 1 hour) hyperthermia treatment was administered followed by iridium placement. A second heating was performed upon removal of the iridium and was accomplished without major side effects. Thermometry data and follow-up are presented

Separation of rhodium(III and iridium(IV chlorido species by quaternary diammonium centres hosted on silica microparticles

Directory of Open Access Journals (Sweden)

A. Majavu

2017-12-01

Full Text Available Silica gel was functionalized with six different quaternary diammonium centres derived from ethylenediamine (EDA, tetramethylenediamine (TMDA, hexamethylenediamine (HMDA, 1,8-diaminooctane (OMDA, 1,10-diaminodecane (DMDA and 1,12-diaminododecane (DDMDA to produce Si-QUAT EDA, Si-QUAT TMDA, Si-QUAT HMDA, Si-QUAT OMDA, Si-QUAT DMDA and Si-QUAT DDMDA, respectively. The synthesized silica-based resins were characterized by means of FTIR, XPS, SEM, BET surface area, thermogravimetric analysis and elemental analysis. The materials were used to investigate the adsorption and separation of [RhCl5(H2O]2− and [IrCl6]2−. Batch studies (equilibrium and kinetic studies were conducted to study the adsorption of [RhCl5(H2O]2− and [IrCl6]2− onto Si-QUAT EDA, Si-QUAT TMDA, Si-QUAT HMDA, Si-QUAT OMDA, Si-QUAT DMDA and Si-QUAT DDMDA using single metal aqueous solutions. The Freundlich isotherm confirmed multilayer adsorption and the Freundlich constant (kf displayed the following ascending order; Si-QUAT EDA, Si-QUAT TMDA, Si-QUAT HMDA, Si-QUAT OMDA and Si-QUAT DMDA, and a decrease in kf for Si-QUAT DDMDA. Kinetic studies suggest a pseudo-first order kinetic model. Column studies were also conducted for a binary mixture of these metal ion chlorido species ([RhCl5(H2O]2− and [IrCl6]2−. The iridium loading capacities increased as the carbon spacer between the diammonium centres increased in the following order; Si-QUAT EDA, Si-QUAT TMDA, Si-QUAT HMDA, Si-QUAT OMDA and Si-QUAT DMDA (4.56 mg/g, 6.88 mg/g, 14.63 mg/g, 19.01 mg/g and 29.35 mg/g, respectively. It was observed that the iridium loading capacity of Si-QUAT DDMDA decreased to 8.90 mg/g. This paper presents iridium-specific materials that could be applied in solutions of secondary PGMs sources containing rhodium and iridium as well as in feed solutions from ore processing. Keywords: Silica gel, Quaternary diammonium centres, Rhodium, Iridium, Separation

Iridium-Knife: Another knife in radiation oncology.

Science.gov (United States)

Milickovic, Natasa; Tselis, Nikolaos; Karagiannis, Efstratios; Ferentinos, Konstantinos; Zamboglou, Nikolaos

Intratarget dose escalation with superior conformity is a defining feature of three-dimensional (3D) iridium-192 ( 192 Ir) high-dose-rate (HDR) brachytherapy (BRT). In this study, we analyzed the dosimetric characteristics of interstitial 192 Ir HDR BRT for intrathoracic and cerebral malignancies. We examined the dose gradient sharpness of HDR BRT compared with that of linear accelerator-based stereotactic radiosurgery and stereotactic body radiation therapy, usually called X-Knife, to demonstrate that it may as well be called a Knife. Treatment plans for 10 patients with recurrent glioblastoma multiforme or intrathoracic malignancies, five of each entity, treated with X-Knife (stereotactic radiosurgery for glioblastoma multiforme and stereotactic body radiation therapy for intrathoracic malignancies) were replanned for simulated HDR BRT. For 3D BRT planning, we used identical structure sets and dose prescription as for the X-Knife planning. The indices for qualitative treatment plan analysis encompassed planning target volume coverage, conformity, dose falloff gradient, and the maximum dose-volume limits to different organs at risk. Volume coverage in HDR plans was comparable to that calculated for X-Knife plans with no statistically significant difference in terms of conformity. The dose falloff gradient-sharpness-of the HDR plans was considerably steeper compared with the X-Knife plans. Both 3D 192 Ir HDR BRT and X-Knife are effective means for intratarget dose escalation with HDR BRT achieving at least equal conformity and a steeper dose falloff at the target volume margin. In this sense, it can reasonably be argued that 3D 192 Ir HDR BRT deserves also to be called a Knife, namely Iridium-Knife. Copyright © 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

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

Science.gov (United States)

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.

A label-free luminescent switch-on assay for ATP using a G-quadruplex-selective iridium(III) complex.

Science.gov (United States)

Leung, Ka-Ho; Lu, Lihua; 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.

A label-free luminescent switch-on assay for ATP using a G-quadruplex-selective iridium(III complex.

Directory of Open Access Journals (Sweden)

Ka-Ho Leung

Full Text Available 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.

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

Science.gov (United States)

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.

Iridium Coating Deposited by Double Glow Plasma Technique — Effect of Glow Plasma on Structure of Coating at Single Substrate Edge

International Nuclear Information System (INIS)

Wu Wangping; Chen Zhaofeng; Liu Yong

2012-01-01

Double glow plasma technique has a high deposition rate for preparing iridium coating. However, the glow plasma can influence the structure of the coating at the single substrate edge. In this study, the iridium coating was prepared by double glow plasma on the surface of single niobium substrate. The microstructure of iridium coating at the substrate edge was observed by scanning electron microscopy. The composition of the coating was confirmed by energy dispersive spectroscopy and X-ray diffraction. There was a boundary between the coating and the substrate edge. The covered area for the iridium coating at the substrate edge became fewer and fewer from the inner area to the outer flange-area. The bamboo sprout-like particles on the surface of the substrate edge were composed of elemental niobium. The substrate edge was composed of the Nb coating and there was a transition zone between the Ir coating and the Nb coating. The interesting phenomenon of the substrate edge could be attributed to the effects of the bias voltages and the plasma cloud in the deposition chamber. The substrate edge effect could be mitigated or eliminated by adding lots of small niobium plates around the substrate in a deposition process. (plasma technology)

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

International Nuclear Information System (INIS)

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

1990-01-01

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

76 FR 46313 - Notice of Issuance of Final Determination Concerning Iridium Satellite Telephones

Science.gov (United States)

2011-08-02

... modulates them into radio streams that communicate with the Iridium gateway network infrastructure using a... (DSP) cores, made in China, and two radio frequency (RF) backend chips, made in Taiwan. The bill of... marking of a cellular phone. CBP found that a digital mobile telephone was substantially transformed in...

Beating Homogeneous Nucleation and Tuning Atomic Ordering in Glass-Forming Metals by Nanocalorimetry.

Science.gov (United States)

Zhao, Bingge; Yang, Bin; Abyzov, Alexander S; Schmelzer, Jürn W P; Rodríguez-Viejo, Javier; Zhai, Qijie; Schick, Christoph; Gao, Yulai

2017-12-13

In this paper, the amorphous Ce 68 Al 10 Cu 20 Co 2 (atom %) alloy was in situ prepared by nanocalorimetry. The high cooling and heating rates accessible with this technique facilitate the suppression of crystallization on cooling and the identification of homogeneous nucleation. Different from the generally accepted notion that metallic glasses form just by avoiding crystallization, the role of nucleation and growth in the crystallization behavior of amorphous alloys is specified, allowing an access to the ideal metallic glass free of nuclei. Local atomic configurations are fundamentally significant to unravel the glass forming ability (GFA) and phase transitions in metallic glasses. For this reason, isothermal annealing near T g from 0.001 s to 25,000 s following quenching becomes the strategy to tune local atomic configurations and facilitate an amorphous alloy, a mixed glassy-nanocrystalline state, and a crystalline sample successively. On the basis of the evolution of crystallization enthalpy and overall latent heat on reheating, we quantify the underlying mechanism for the isothermal nucleation and crystallization of amorphous alloys. With Johnson-Mehl-Avrami method, it is demonstrated that the coexistence of homogeneous and heterogeneous nucleation contributes to the isothermal crystallization of glass. Heterogeneous rather than homogeneous nucleation dominates the isothermal crystallization of the undercooled liquid. For the mixed glassy-nanocrystalline structure, an extraordinary kinetic stability of the residual glass is validated, which is ascribed to the denser packed interface between amorphous phase and ordered nanocrystals. Tailoring the amorphous structure by nanocalorimetry permits new insights into unraveling GFA and the mechanism that correlates local atomic configurations and phase transitions in metallic glasses.

Solid-state electrochromic cell with anodic iridium oxide film electrodes

International Nuclear Information System (INIS)

Dautremont-Smith, W.C.; Beni, G.; Schiavone, L.M.; Shay, J.L.

1979-01-01

A new solid-state electrochromic cell has been fabricated using an anodic iridium oxide film (AIROF) display electrode. The cell has the symmetric sandwich structure AIROFvertical-barNafionvertical-barAIROF, with the Nafion solid electrolyte opacified by an in situ precipitation technique. A symmetric square-wave voltage of 1.5 V amplitude produces clearly perceivable color changes from pale to dark blue-gray in approx. =1 sec when viewed in diffuse reflection. Good open-circuit optical memory is exhibited:

Extrahepatic bile duct carcinoma treated by intraluminal irradiation with iridium-192 wire. Report of a case

Energy Technology Data Exchange (ETDEWEB)

Ikeda, H; Kuroda, T; Uchida, H [Osaka Univ. (Japan). Faculty of Medicine

1980-08-01

A 57-year-old male with obstructive jaundice was diagnosed extrahepatic bile duct carcinoma at bifurcation by percutaneous transhepatic cholangiography (PTC). He was treated 3,300 rad of external irradiation and then intraluminal irradiation using the Iridium-192 wire by two times with the aid of PTC internal drainage, each was given by the dose of 1,600 rad at 5 mm inside the tumor from the PTC-tube. He had been well for about 1 year and then died because of ascites and cachexia. Autopsy revealed only microscopic tumor cells remaining around the common duct below the cystic junction. It was confirmed that intraluminal irradiation using the Iridium-192 wire was potentially curable and easily applicable to the bile duct carcinoma.

Effect of the lead screen in the radiographic image using iridium 192 as a source

International Nuclear Information System (INIS)

Garate Rojas, M.

1983-01-01

It's presented the effect of the lead screen in the image obtained on an impressionable film used in industrial gammagraphy. The source used was Iridium 192 and the tests were simulated like a real inspection. (E.G.) [pt

The effects of aluminum or scandium on the toughness, density and ...

African Journals Online (AJOL)

The effects of the substitution of aluminum or scandium on the density, toughness as well as the stability of the phases formed by such an addition on platinum, iridium, rhodium and palladium metals were evaluated with the density functional quantum mechanical calculation methods. All the metals had four atoms per ...

Role of string-like collective atomic motion on diffusion and structural relaxation in glass forming Cu-Zr alloys

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hao [International Center for New-Structured Materials (ICNSM), Zhejiang University and Laboratory of New-Structured Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada); Zhong, Cheng; Wang, Xiaodong; Cao, Qingping; Jiang, Jian-Zhong, E-mail: jiangjz@zju.edu.cn, E-mail: jack.douglas@nist.gov [International Center for New-Structured Materials (ICNSM), Zhejiang University and Laboratory of New-Structured Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Douglas, Jack F., E-mail: jiangjz@zju.edu.cn, E-mail: jack.douglas@nist.gov [Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Zhang, Dongxian [State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027 (China)

2015-04-28

We investigate Cu-Zr liquid alloys using molecular dynamics simulation and well-accepted embedded atom method potentials over a wide range of chemical composition and temperature as model metallic glass-forming (GF) liquids. As with other types of GF materials, the dynamics of these complex liquids are characterized by “dynamic heterogeneity” in the form of transient polymeric clusters of highly mobile atoms that are composed in turn of atomic clusters exhibiting string-like cooperative motion. In accordance with the string model of relaxation, an extension of the Adam-Gibbs (AG) model, changes in the activation free energy ΔG{sub a} with temperature of both the Cu and Zr diffusion coefficients D, and the alpha structural relaxation time τ{sub α} can be described to a good approximation by changes in the average string length, L. In particular, we confirm that the strings are a concrete realization of the abstract “cooperatively rearranging regions” of AG. We also find coexisting clusters of relatively “immobile” atoms that exhibit predominantly icosahedral local packing rather than the low symmetry packing of “mobile” atoms. These two distinct types of dynamic heterogeneity are then associated with different fluid structural states. Glass-forming liquids are thus analogous to polycrystalline materials where the icosahedrally packed regions correspond to crystal grains, and the strings reside in the relatively disordered grain boundary-like regions exterior to these locally well-ordered regions. A dynamic equilibrium between localized (“immobile”) and wandering (“mobile”) particles exists in the liquid so that the dynamic heterogeneity can be considered to be type of self-assembly process. We also characterize changes in the local atomic free volume in the course of string-like atomic motion to better understand the initiation and propagation of these fluid excitations.

Phosphorescence Imaging of Living Cells with Amino Acid-Functionalized Tris(2-phenylpyridine)iridium(III) Complexes

NARCIS (Netherlands)

Steunenberg, P.; Ruggi, A.; Berg, van den N.S.; Buckle, T.; Kuil, J.; Leeuwen, van F.W.B.; Velders, A.H.

2012-01-01

A series of nine luminescent cyclometalated octahedral iridium(III) tris(2-phenylpyridine) complexes has been synthesized, functionalized with three different amino acids (glycine, alanine, and lysine), on one, two, or all three of the phenylpyridine ligands. All starting complexes and final

Laser-assisted atom-atom collisions

International Nuclear Information System (INIS)

Roussel, F.

1984-01-01

The basic layer-assisted atom-atom collision processes are reviewed in order to get a simpler picture of the main physical facts. The processes can be separated into two groups: optical collisions where only one atom is changing state during the collision, the other acting as a spectator atom, and radiative collisions where the states of the two atoms are changing during the collision. All the processes can be interpreted in terms of photoexcitation of the quasimolecule formed during the collisional process. (author)

Sterically directed iridium-catalyzed hydrosilylation of alkenes in the presence of alkynes.

Science.gov (United States)

Muchnij, Jill A; Kwaramba, Farai B; Rahaim, Ronald J

2014-03-07

A selective iridium catalyzed hydrosilylation of alkenes in the presence of more reactive alkynes is described. By utilizing [IrCl(COD)]2 in the presence of excess COD, hydrosilylation of alkenes and alkynes with ethynylsilanes is achieved with good chemo- and regioselectivity. This approach goes against the traditional reactivity trends of platinum and rhodium catalysts and allows access to highly substituted silicon alkyne tethers.

Electron beam welding of iridium heat source capsules

International Nuclear Information System (INIS)

Mustaleski, T.M.; Yearwood, J.C.; Burgan, C.E.; Green, L.A.

1991-01-01

The development of the welding procedures for the production of DOP-26 iridium alloy cups for heat source encapsulation is described. All the final assembly welds were made using the electron beam welding process. The welding of the 0.13-mm weld shield required the use of computer controlled X-Y table and a run-off tab. Welding of the frit vent to the cup required that a laser weld be made to hold the frit assembly edges together for the final electron beam weld. Great care is required in tooling design and beam placement to achieve acceptable results. Unsuccessful attempts to use laser beam welding for heat shield butt weld are discussed

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

Directory of Open Access Journals (Sweden)

Cuong M. Nguyen

2015-02-01

Full Text Available 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.

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

Science.gov (United States)

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

STM studies of an atomic-scale gate electrode formed by a single charged vacancy in GaAs

Science.gov (United States)

Lee, Donghun; Daughton, David; Gupta, Jay

2009-03-01

Electric-field control of spin-spin interactions at the atomic level is desirable for the realization of spintronics and spin-based quantum computation. Here we demonstrate the realization of an atomic-scale gate electrode formed by a single charged vacancy on the GaAs(110) surface[1]. We can position these vacancies with atomic precision using the tip of a home-built, low temperature STM. Tunneling spectroscopy of single Mn acceptors is used to quantify the electrostatic field as a function of distance from the vacancy. Single Mn acceptors are formed by substituting Mn adatoms for Ga atoms in the first layer of the p-GaAs(110) surface[2]. Depending on the distance, the in-gap resonance of single Mn acceptors can shift as much as 200meV. Our data indicate that the electrostatic field decays according to a screened Coulomb potential. The charge state of the vacancy can be switched to neutral, as evidenced by the Mn resonance returning to its unperturbed position. Reversible control of the local electric field as well as charged states of defects in semiconductors can open new insights such as realizing an atomic-scale gate control and studying spin-spin interactions in semiconductors. http://www.physics.ohio-state.edu/sim jgupta [1] D. Lee and J.A. Gupta (in preparation) [2] D. Kitchen et al., Nature 442, 436-439 (2006)

Ammonia synthesis in the presence of rhodium-ruthenium-iridium carbonyl clusters

International Nuclear Information System (INIS)

Fedoseev, I.V.; Solov'ev, N.V.

2007-01-01

Researches in the field of platinum metal coordination compounds, where nitrogen enters as a ligand in coordination sphere of metal, are discussed. Results of experiments on the ammonia synthesis during the CO+N 2 mixture passing through alkali solution containing mixture of carbonyl clusters of rhodium, ruthenium and iridium at atmospheric pressure are given. Technique of the experiment and steps of assumed reactions of nitrogen fixation by Rh, Ir and Ru carbonyl clusters are demonstrated [ru

Ionic double layer of atomically flat gold formed on mica templates

International Nuclear Information System (INIS)

Chilcott, Terry C.; Wong, Elicia L.S.; Coster, Hans G.L.; Coster, Adelle C.F.; James, Michael

2009-01-01

Electrical impedance spectroscopy characterisations of gold surfaces formed on mica templates in contact with potassium chloride electrolytes were performed at the electric potential of zero charge over a frequency range of 6 x 10 -3 to 100 x 10 3 Hz. They revealed constant-phase-angle (CPA) behaviour with a frequency exponent value of 0.96 for surfaces that were also characterised as atomically flat using atomic force microscopy (AFM). As the frequency exponent value was only marginally less than unity, the CPA behaviour yielded a realistic estimate for the capacitance of the ionic double layer. The retention of the CPA behaviour was attributed to specific adsorption of chloride ions which was detected as an adsorption conductance element in parallel with the CPA impedance element. Significant variations in the ionic double layer capacitance as well as the adsorption conductance were observed for electrolyte concentrations ranging from 33 μM to 100 mM, but neither of these variations correlated with concentration. This is consistent with the electrical properties of the interface deriving principally from the inner or Stern region of the double layer.

Determination of iridium at low levels (sub ng g-1) in geological materials by neutron activation analysis

International Nuclear Information System (INIS)

Morcelli, Claudia Petronilho Ribeiro

1999-01-01

The analysis of the platinum group elements (PGE: Ru, Rh, Pd, Os, Ir and Pt) in geological materials is difficult, due to the low concentrations of these elements (ng g -1 or sub ng g -1 ) and their heterogeneous distribution in many geological matrices. The determination of PGE has attracted great interest due not only to the increasing utilization of these elements in modern industry, but also to the information that these elements can provide on mantle processes. The determination of very low amounts of iridium is particularly important on account of some anomalous concentrations of iridium in sedimentary rock samples, related to the impact of an extraterrestrial object responsible for extinctions at the Cretaceous-Tertiary (K-T) boundary. In the present paper, a radiochemical neutron activation method for the determination of iridium in geological materials is presented. The procedure consisted of thermal neutron irradiation of about 500 mg of the sample, followed by sintering with sodium peroxide, precipitation with tellurium and high resolution gamma-ray spectrometry with a hyper-pure Ge detector. The accuracy and precision of the procedure were evaluated by analysis of the certified reference material SARM-7 (South Africa Bureau of Standards) and W-1 (USGS). The detection limit for the analytical conditions employed was 0.004 ng g -1 . The procedure was applied to the reference materials TDB-1 and WGB-1 (CANMET), which present provisional values for Ir, and to the reference materials GXR-3, GXR-5 and GXR- 6 (USGS), which do not present information values for Ir. This work is a contribution to Ir values in these reference materials. As an example of application of the method to real samples, the developed procedure was employed in the determination of iridium in basalts from Parana basin, collected in Bom Guara do Sul, Santa Catarina, provided by the Geosciences Institute of the University of Campinas. (author)

High-efficiency red-light emission from polyfluorenes grafted with cyclometalated iridium complexes and charge transport moiety.

Science.gov (United States)

Chen, Xiwen; Liao, Jin-Long; Liang, Yongmin; Ahmed, M O; Tseng, Hao-En; Chen, Show-An

2003-01-22

We report a new route for the design of electroluminescent polymers by grafting high-efficiency phosphorescent organometallic complexes as dopants and charge transport moieties onto alky side chains of fully conjugated polymers for polymer light-emitting diodes (PLED) with single layer/single polymers. The polymer system studied involves polyfluorene (PF) as the base conjugated polymer, carbazole (Cz) as the charge transport moiety and a source for green emission by forming an electroplex with the PF main chain, and cyclometalated iridium (Ir) complexes as the phosphorescent dopant. Energy transfer from the green Ir complex or an electroplex formed between the fluorene main chain and side-chain carbazole moieties, in addition to that from the PF main chain, to the red Ir complex can significantly enhance the device performance, and a red light-emitting device with the high efficiency 2.8 cd/A at 7 V and 65 cd/m2, comparable to that of the same Ir complex-based OLED, and a broad-band light-emitting device containing blue, green, and red peaks (2.16 cd/A at 9 V) are obtained.

238Pu fuel form activities, March 1-September 30, 1985

International Nuclear Information System (INIS)

1986-01-01

The SRP portion of this report summarizes production 238 PuO 2 fuel forms for use in radioisotopic thermoelectric generators (RTG's) in the Plutonium Fuel Form (PuFF) Facility at the Savannah River Plant. The PuFF Facility began producing iridium-encapsulated, 62.5-watt 238 PuO 2 right circular cylinders for GPHS (General Purpose Heat Source) RTG's in June 1980; this program was completed in December 1983. The PuFF Facility has been placed in a production readiness mode of operation pending funding of additional heat source programs

Iridium-Catalyzed Asymmetric Intramolecular Allylic Amidation : Enantioselective Synthesis of Chiral Tetrahydroisoquinolines and Saturated Nitrogen Heterocycles

NARCIS (Netherlands)

Teichert, Johannes F.; Fañanás-Mastral, Martín; Feringa, Bernard

2011-01-01

For the first time iridium catalysis has been used for the synthesis of chiral tetrahydroisoquinolines with excellent yields and high enantioselectivities (see scheme; cod=1,5-cyclooctadiene, DBU=1,8-diazabicyclo[5.4.0]undec-7-ene). These products are important chiral building blocks for the

Density and glass forming ability in amorphous atomic alloys: The role of the particle softness

International Nuclear Information System (INIS)

Douglass, Ian; Hudson, Toby; Harrowell, Peter

2016-01-01

A key property of glass forming alloys, the anomalously small volume difference with respect to the crystal, is shown to arise as a direct consequence of the soft repulsive potentials between metals. This feature of the inter-atomic potential is demonstrated to be responsible for a significant component of the glass forming ability of alloys due to the decrease in the enthalpy of fusion and the associated depression of the freezing point.

Density and glass forming ability in amorphous atomic alloys: The role of the particle softness

Energy Technology Data Exchange (ETDEWEB)

Douglass, Ian; Hudson, Toby; Harrowell, Peter [School of Chemistry, University of Sydney, Sydney, NSW (Australia)

2016-04-14

A key property of glass forming alloys, the anomalously small volume difference with respect to the crystal, is shown to arise as a direct consequence of the soft repulsive potentials between metals. This feature of the inter-atomic potential is demonstrated to be responsible for a significant component of the glass forming ability of alloys due to the decrease in the enthalpy of fusion and the associated depression of the freezing point.

Effect of component substitution on the atomic dynamics in glass-forming binary metallic melts

Science.gov (United States)

Nowak, B.; Holland-Moritz, D.; Yang, F.; Voigtmann, Th.; Evenson, Z.; Hansen, T. C.; Meyer, A.

2017-08-01

We investigate the substitution of early transition metals (Zr, Hf, and Nb) in Ni-based binary glass-forming metallic melts and the impact on structural and dynamical properties by using a combination of neutron scattering, electrostatic levitation (ESL), and isotopic substitution. The self-diffusion coefficients measured by quasielastic neutron scattering (QENS) identify a sluggish diffusion as well as an increased activation energy by almost a factor of 2 for Hf35Ni65 compared to Zr36Ni64 . This finding can be explained by the locally higher packing density of Hf atoms in Hf35Ni65 compared to Zr atoms in Zr36Ni64 , which has been derived from interatomic distances by analyzing the measured partial structure factors. Furthermore, QENS measurements of liquid Hf35Ni65 prepared with 60Ni , which has a vanishing incoherent scattering cross section, have demonstrated that self-diffusion of Hf is slowed down compared to the concentration weighted self-diffusion of Hf and Ni. This implies a dynamical decoupling between larger Hf and smaller Ni atoms, which can be related to a saturation effect of unequal atomic nearest-neighbor pairs, that was observed recently for Ni-rich compositions in Zr-Ni metallic melts. In order to establish a structure-dynamics relation, measured partial structure factors have been used as an input for mode-coupling theory (MCT) of the glass transition to calculate self-diffusion coefficients for the different atomic components. Remarkably, MCT can reproduce the increased activation energy for Hf35Ni65 as well as the dynamical decoupling between Hf and Ni atoms.

Fragmentation of neutral carbon clusters formed by high velocity atomic collision; Fragmentation d'agregats de carbone neutres formes par collision atomique a haute vitesse

Energy Technology Data Exchange (ETDEWEB)

Martinet, G

2004-05-01

The aim of this work is to understand the fragmentation of small neutral carbon clusters formed by high velocity atomic collision on atomic gas. In this experiment, the main way of deexcitation of neutral clusters formed by electron capture with ionic species is the fragmentation. To measure the channels of fragmentation, a new detection tool based on shape analysis of current pulse delivered by semiconductor detectors has been developed. For the first time, all branching ratios of neutral carbon clusters are measured in an unambiguous way for clusters size up to 10 atoms. The measurements have been compared to a statistical model in microcanonical ensemble (Microcanonical Metropolis Monte Carlo). In this model, various structural properties of carbon clusters are required. These data have been calculated with Density Functional Theory (DFT-B3LYP) to find the geometries of the clusters and then with Coupled Clusters (CCSD(T)) formalism to obtain dissociation energies and other quantities needed to compute fragmentation calculations. The experimental branching ratios have been compared to the fragmentation model which has allowed to find an energy distribution deposited in the collision. Finally, specific cluster effect has been found namely a large population of excited states. This behaviour is completely different of the atomic carbon case for which the electron capture in the ground states predominates. (author)

Installing an additional emission quenching pathway in the design of iridium(III)-based phosphorogenic biomaterials for bioorthogonal labelling and imaging.

Science.gov (United States)

Li, Steve Po-Yam; Yip, Alex Man-Hei; Liu, Hua-Wei; Lo, Kenneth Kam-Wing

2016-10-01

We report the synthesis, characterization, photophysical and electrochemical behaviour and biological labelling applications of new phosphorogenic bioorthogonal probes derived from iridium(III) polypyridine complexes containing a 1,2,4,5-tetrazine moiety. In contrast to common luminescent cyclometallated iridium(III) polypyridine complexes, these tetrazine complexes are almost non-emissive due to effective Förster resonance energy transfer (FRET) and/or photoinduced electron transfer (PET) from the excited iridium(III) polypyridine unit to the appended tetrazine moiety. However, they exhibited significant emission enhancement upon reacting with (1R,8S,9s)-bicyclo[6.1.0]non-4-yn-9-ylmethanol (BCN-OH) (ca. 19.5-121.9 fold) and BCN-modified bovine serum albumin (BCN-BSA) (ca. 140.8-1133.7 fold) as a result of the conversion of the tetrazine unit to a non-quenching pyridazine derivative. The complexes were applied to image azide-modified glycans in live cells using a homobifunctional crosslinker, 1,13-bis((1R,8S,9s)-bicyclo[6.1.0]non-4-yn-9-ylmethyloxycarbonylamino)-4,7,10-trioxatridecane (bis-BCN). Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of solute atoms on glass-forming ability for Fe–Y–B alloy: An ab initio molecular dynamics study

International Nuclear Information System (INIS)

Han, J.J.; Wang, W.Y.; Liu, X.J.; Wang, C.P.; Hui, X.D.; Liu, Z.K.

2014-01-01

The glass-forming abilities of Fe 78 B 22 , Fe 70 Y 6 B 24 , Fe 72 Y 6 B 22 and Fe 72.5 Y 3.5 B 24 alloys were characterized comprehensively using ab initio molecular dynamics simulations. The calculated results were correlated with the properties and atomic structures. It was found that the Fe 72 Y 6 B 22 alloy consists of both the most stable and the least deformed body centered cubic atomic packing structures in the supercooled liquid and glassy states. It was observed that the local compositions in the Fe 72 Y 6 B 22 alloy significantly deviate from the compositions of stable crystalline phases, indicating that the Fe 72 Y 6 B 22 alloy has the best glass-forming ability among the alloys studied. However, Fe 72 Y 6 B 22 alloy has two flaws in terms of glass-forming ability, i.e. relatively large atomic diffusivity and insufficiently close atomic packing. The best performance in these two aspects is observed in the Fe 72.5 Y 3.5 B 24 alloy. Thus, the theoretical study predicts that the best glass former for the Fe–Y–B system is within the compositional range of 22–24 at.% B and 3.5–6 at.% Y

Complexes of rhodium (I) and iridium (I) with mixed phosphorus-oxygen and phosphorus-nitrogen glands

International Nuclear Information System (INIS)

Meintjies, E.; Singleton, E.; Schmutzler, R.; Sell, M.

1985-01-01

A series of four- and five-coordinate rhodium(I) and iridium(I) complexes of the type [MCl(cod)L] and [M(COD)L 2 ] sup(+)[M = Rh or Ir;cod = cycloocta-1,5-diene; L = P(C 6 H 4 OMe-o) 3 ,PMe 2 (C 6 H 4 OMe-o), PPh 2 (C 6 H 4 OMe-o),PPh 2 -(C 6 H 4 NMe 2 -o),PMe(C 6 H 4 OMe-o) 2 and PPh 2 (C 6 H 4 OPr sup(i)-o)] have been prepared from the reactions of [(MCl(cod)) 2 ] (M = Rh or Ir) with the appropriate stoichiometric amount of L in diethyl ether or methanol solution. N.m.r. evidence ( 1 H and 13 C) is presented for non-chelation in the case of the ether ligands and chelation for the amine ligand. Thus, the complexes [MCl(cod)L](L = ether ligand) are mononuclear square-planar species, whereas the amine ligand chelates to the metal atom, and a distorted trigonal bipyramidal structure is proposed. Attempts at displacing cod from the complexes [MCl(cod)L] with these ether and amine ligands, or with small phosphines, were unsuccessful. However, treatment of [MCl(cod)[P(C 6 H 4 OMe-o) 3

Study and development of an Iridium-192 seed for use in ophthalmic cancer; Estudo e desenvolvimento de uma semente de iridio-192 para aplicacao em cancer oftalmico

Energy Technology Data Exchange (ETDEWEB)

Mattos, Fabio Rodrigues de

2013-07-01

Even ocular tumors are not among the cases with a higher incidence, they affect the population, especially children. The Institute of Energy and Nuclear Research (IPEN-CNEN/SP) in partnership with Escola Paulista de Medicina (UNIFESP), created a project to develop and implement a alternative treatment for ophthalmic cancer that use brachytherapy iridium-192 seeds. The project arose by reason of the Escola Paulista treat many cancer cases within the Unified Health System (SUS) and the research experience of sealed radioactive sources group at IPEN. The methodology was developed from the available infrastructure and the experience of researchers. The prototype seed presents with a core (192-iridium alloy of iridium-platinum) of 3.0 mm long sealed by a capsule of titanium of 0.8 mm outside diameter, 0.05 mm wall thickness and 4,5mm long. This work aims to study and develop a seed of iridium-192 from a platinum-iridium alloy. No study on the fabrication of these seeds was found in available literature. It was created a methodology that involved: characterization of the material used in the core, creation of device for neutron activation irradiation and and seed sealing tests. As a result, proved the feasibility of the method. As a suggestion for future work, studies regarding metrology and dosimetry of these sources and improvement of the methodology should be carried out, for future implementation in national scope. (author)

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

Science.gov (United States)

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…

Substrate-induced antiferromagnetism of ultrathin iron overlayers on the iridium and rhodium (001) surfaces

Czech Academy of Sciences Publication Activity Database

Máca, František; Kudrnovský, Josef; Drchal, Václav; Turek, Ilja; Bengone, O.; Redinger, J.

2009-01-01

Roč. 11, - (2009), s. 38-40 ISSN 1642-6037 R&D Projects: GA ČR GA202/07/0456; GA MŠk OC09028 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z20410507 Keywords : iridium * rhodium * iron * magnetismus in thin layers * density functional calculations Subject RIV: BM - Solid Matter Physics ; Magnetism

Efficient near-infrared emission of π-extended cyclometalated iridium complexes based on pyrene in solution-processed polymer light-emitting diode

Science.gov (United States)

Liu, Yu; Hao, Zhaoran; Meng, Fanyuan; Wang, Pu; Yang, Liang; Wang, Yafei; Pei, Yong; Su, Shijian

2018-05-01

A novel iridium complex grafting hole-transporting triphenylamine (TPA) unit onto cyclometalated ligand, namely t-BuPyrPyTPA)2Ir(acac), was successfully synthesized and characterized. The photophysical, electrochemical and DFT/TD-DFT calculation, as well as electroluminescence properties of this iridium complex were fully investigated. Meanwhile, the PLEDs employing (t-BuPyrPyTPA)2Ir(acac) as dopant presented stable NIR emission peaked at 697 nm and a shoulder at 764 nm with a highest external quantum efficiency (EQE) of 0.56% at 4 wt% dopant concentration. These results demonstrate that expanding the conjugation length of the ligand is an effective way to achieve NIR emission.

Single step radiolytic synthesis of iridium nanoparticles onto graphene oxide

International Nuclear Information System (INIS)

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

2015-01-01

Graphical abstract: - Highlights: • Ir nanoparticles were synthesized through a single step gamma irradiation process. • Homogeneously distributed Ir nanoparticles on graphene oxide are ∼2.3 nm in size. • Ir−O bonds evidenced the interaction of the nanoparticles with the support. - Abstract: 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 60 Co 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 Ir−O bonds.

Direct determination of lead in human urine and serum samples by electrothermal atomic absorption spectrometry and permanent modifiers

International Nuclear Information System (INIS)

Andrada, Daniel; Pinto, Frederico G.; Magalhaes, Cristina Goncalves; Nunes, Berta R.; Silva, Jose Bento Borba da; Franco, Milton B.

2006-01-01

The object of the present study was the development of alternative methods for the direct determination of lead in undigested samples of human urine and serum by electrothermal atomic absorption spectrometry (ETAAS). Thus, some substances have been investigated to act as chemical modifiers. Volumes of 20 μL of diluted samples, 1 + 1, v/v for urine and 1 + 4, v/v for serum, with HNO 3 1% v/v and 0.02% v/v of cetyl trimethyl ammonium chloride (CTAC) were prepared directly in the autosampler cups and placed into the graphite furnace. For modifiers in solutions 10 μL were used. Pyrolysis and atomization temperature curves were used in all optimizations in the matrixes diluted as exposed. For urine with permanent iridium (500 μg), the best pyrolysis and atomization temperatures were 900 and 1600 deg C, respectively, with a characteristic mass of 12 pg (recommended of 10 pg), with symmetrical absorption pulses and corrected background. Spiked urine samples presented recoveries between 86 and 112% for Ir permanent. The analysis results of certified urine samples are in agreement with certified values (95% of confidence) for two levels of the metal. For serum, good results were obtained with the mixture of Zr+Rh or Ir+Rh as permanent modifiers, with characteristic masses of 9.8 and 8.1 pg, respectively. Recoveries from spiked serum samples varied between 98.6 and 100.1% (Ir+Rh) and between 93.9 and 105.2% (Zr+Rh). In both recovery studies, the relative standard deviation (n=3) was lower than 7%. Calibration for both samples were made with aqueous calibration curves and presented r 2 higher than 0.99. The limits of detection were 0.7 μg L -1 for serum samples, with Zr+Rh permanent, and 1.0 μg L -1 for urine with iridium permanent. (author)

Direct determination of lead in human urine and serum samples by electrothermal atomic absorption spectrometry and permanent modifiers

Directory of Open Access Journals (Sweden)

Andrada Daniel

2006-01-01

Full Text Available The object of the present study was the development of alternative methods for the direct determination of lead in undigested samples of human urine and serum by electrothermal atomic absorption spectrometry (ET AAS. Thus, some substances have been investigated to act as chemical modifiers. Volumes of 20 µL of diluted samples, 1 + 1, v/v for urine and 1 + 4, v/v for serum, with HNO3 1% v/v and 0.02% v/v of cetil trimethyl ammonium chloride (CTAC were prepared directly in the autosampler cups and placed into the graphite furnace. For modifiers in solutions 10 µL were used. Pyrolysis and atomization temperature curves were used in all optimizations in the matrixes diluted as exposed. For urine with permanent iridium (500 µg, the best pyrolysis and atomization temperatures were 900 and 1600 ºC, respectively, with a characteristic mass of 12 pg (recommended of 10 pg, with symmetrical absorption pulses and corrected background. Spiked urine samples presented recoveries between 86 and 112% for Ir permanent. The analysis results of certified urine samples are in agreement with certified values (95% of confidence for two levels of the metal. For serum, good results were obtained with the mixture of Zr+Rh or Ir+Rh as permanent modifiers, with characteristic masses of 9.8 and 8.1 pg, respectively. Recoveries from spiked serum samples varied between 98.6 and 100.1% (Ir+Rh and between 93.9 and 105.2% (Zr+Rh. In both recovery studies, the relative standard deviation (n=3 was lower than 7%. Calibration for both samples were made with aqueous calibration curves and presented r² higher than 0.99. The limits of detection were 0.7 µg L-1 for serum samples, with Zr+Rh permanent, and 1.0 µg L-1 for urine with iridium permanent.

A calorimetric particle detector using an iridium superconducting phase transition thermometer

International Nuclear Information System (INIS)

Frank, M.; Dummer, D.; Cooper, S.; Igalson, J.; Proebst, F.; Seidel, W.

1994-01-01

We report on a calorimetric particles detector consisting of an 18.3 g silicon crystal and an iridium superconducting phase transition thermometer. The cryogenic calorimeter and the associated apparatus are described in detail. The pulses from irradiation with an α-particle source have a large unexpected overshoot in addition to the component expected from a naive thermal model. The pulse height spectrum displays an energy resolution of 1 percent FWHM at 6 MeV and good linearity. The noise, electrothermal feedback, and position dependence are discussed. (orig.)

Muscle invasive bladder cancer treated by transurethral resection, followed by external beam radiation and interstitial iridium-192

NARCIS (Netherlands)

A. Wijnmaalen (Arendjan); P.A. Helle (Peter); P.C.M. Koper (Peter); P.P. Jansen (Peter); P. Hanssens (Patrick); C.G.G. Boeken Kruger (Cornelis); W.L.J. van Putten (Wim)

1997-01-01

textabstractPurpose: To evaluate the results of transurethral resection (TUR), external beam radiotherapy (EBRT), and interstitial radiation (IRT) with iridium-192, using the afterloading technique in patients with muscle invasive bladder cancer. Methods and Materials: From May 1989 until September

Hydrogenation of ethene catalyzed by Ir atom deposited on γ-Al2O3(001) surface: From ab initio calculations

International Nuclear Information System (INIS)

Chen, Yongchang; Sun, Zhaolin; Song, Lijuan; Li, Qiang; Xu, Ming

2012-01-01

Ethene hydrogenation reaction, catalyzed by an iridium atom adsorbed on γ-Al 2 O 3 (001) surface, is studied via ab initio calculations based on density functional theory (DFT). The catalyzed reaction process and activation energy are compared with the counterparts of a reaction occurs in vacuum condition. It is found that the activation energy barrier is substantially lowered by the adsorbed Ir atom on the γ-Al 2 O 3 (001). The catalyzed reaction is modeled in two steps: (1) Hydrogen molecular dissolution and then bonded with C 2 H 4 molecular. (2) Desorption of the C 2 H 6 molecular from the surface. -- Highlights: ► The ethene hydrogenation reaction is simulated with nudged elastic band methods. ► The catalytic effect of the Ir atom on γ-Al 2 O 3 (001) surface is modeled. ► Details of the catalytic reaction are exhibited.

238Pu fuel form processes. Final report, January-September 1983

International Nuclear Information System (INIS)

Mosley, W.C.; Taylor, D.H.

1983-01-01

Progress is reported on the following: analytical studies of weld-quench cracking in DOP-26 iridium alloy, iridium/ 238 PuO 2 compatibility test, surface area measurements of 238 PuO 2 using the Blaine air permeability apparatus, and helium release from 238 PuO 2

Proposed measurement of the imaginary component of atomic form factor for medium Z-elements in regions exhibiting significant discrepancies

International Nuclear Information System (INIS)

De Jonge, M.; Dhal, B.B.; Tran, C.Q.; Barnea, Z.; Chantler, C.T.

2000-01-01

Full text: Discrepancies in measurements of the complex atomic form factor in regions of medium Z are alarmingly high for such a fundamental problem. The consequence of this is that any experiment reliant on the Beer-Lambert absorption law that uses the tabulated absorption coefficients assumes an immediate experimental uncertainty of 2-10%, depending on the element and the energy under consideration. We have begun to address this state of affairs in the medium Z-region through a series of precise determinations of attenuation coefficients. We will elaborate on a proposed method of measuring the atomic form factor to 0.2% absolute accuracy

Organic Light-Emitting Diodes Using Multifunctional Phosphorescent Dendrimers with Iridium-Complex Core and Charge-Transporting Dendrons

Science.gov (United States)

Tsuzuki, Toshimitsu; Shirasawa, Nobuhiko; Suzuki, Toshiyasu; Tokito, Shizuo

2005-06-01

We report a novel class of light-emitting materials for use in organic light-emitting diodes (OLEDs): multifunctional phosphorescent dendrimers that have a phosphorescent core and dendrons based on charge-transporting building blocks. We synthesized first-generation and second-generation dendrimers consisting of a fac-tris(2-phenylpyridine)iridium [Ir(ppy)3] core and hole-transporting phenylcarbazole-based dendrons. Smooth amorphous films of these dendrimers were formed by spin-coating them from solutions. The OLEDs using the dendrimer exhibited bright green or yellowish-green emission from the Ir(ppy)3 core. The OLEDs using the film containing a mixture of the dendrimer and an electron-transporting material exhibited higher efficiency than those using the neat dendrimer film. The external quantum efficiency of OLEDs using the film containing a mixture of the first-generation dendrimer and an electron-transporting material was as high as 7.6%.

A highly selective and non-reaction based chemosensor for the detection of Hg2+ ions using a luminescent iridium(III complex.

Directory of Open Access Journals (Sweden)

Daniel Shiu-Hin Chan

Full Text Available We report herein a novel luminescent iridium(III complex with two hydrophobic carbon chains as a non-reaction based chemosensor for the detection of Hg(2+ ions in aqueous solution (<0.002% of organic solvent attributed to the probe solution. Upon the addition of Hg(2+ 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 Hg(2+ ions over eighteen other cations. The system is capable of detecting micromolar levels of Hg(2+ ions, which is within the range of many chemical systems.

Muscle invasive bladder cancer treated by transurethral resection, followed by external beam radiation and interstitial iridium-192

International Nuclear Information System (INIS)

Wijnmaalen, Arendjan; Helle, Peter A.; Koper, Peter C.M.; Jansen, Peter P.; Hanssens, Patrick E.J.; Boeken Kruger, Cornelis G.G.; Putten, Wim L.J. van

1996-01-01

Purpose: In our center interstitial radiation has played an important role in the treatment of bladder cancer patients for over 40 years. Radium needles, that were initially used, were replaced by caesium needles in 1983, whereas the afterloading iridium wire technique was adopted in 1989. Patients with solitary tumors (T1, T2 and T3) with a surface diameter of < 5 cm are considered for interstitial radiation. In this study we report on the results of the afterloading iridium wire technique in patients with muscle invasive bladder cancer. Materials and Methods: From May 1989 to September 1993 interstitial radiation using iridium wires was part of the treatment in 46 patients with muscle invasive bladder cancer (37 T2, 9 T3). The mean age was 67 years. After transurethral resection of all visible tumor (if possible), in most cases 40 Gy (20 x 2.0 Gy, midplane dose) external beam radiation was delivered to the true pelvis, followed by 30 Gy interstitial radiation using iridium-192 wires covering the tumor area in the bladder. Results: After a median follow-up of 26 months, bladder relapses occurred in 7 patients. In 5 of them the tumor relapsed in the initial area, in 1 patient elsewhere in the bladder and in 1 patient tumor recurred in and outside the initial site. Recurrence was superficial (T1) in 4 patients. A relapse in the urethra was found once. Metastases developed in 13 patients, in 8 without bladder relapse. During the observation period 17 patients died, 13 due to bladder cancer. The actuarial bladder relapse-free survival at 4 years was 74% and 82% for T2 and T3 tumors, respectively. The actuarial distant metastases-free survival was 65% for both categories. No serious toxicity was recorded. Conclusion: In a selected group of patients with muscle invasive bladder cancer transurethral resection in combination with external beam and interstitial radiation provides an excellent opportunity to preserve the bladder with a high chance of success. Development of

Detection of triglyceride using an iridium nano-particle catalyst based amperometric biosensor.

Science.gov (United States)

Liao, Wei-Yin; Liu, Chung-Chiun; Chou, Tse-Chuan

2008-12-01

The detection and quantification of triglyceride (TG) using an iridium nano-particle modified carbon based biosensor was successfully carried out in this study. The detection procedures were based on the electrochemical detection of enzymatically produced NADH. TG was hydrolyzed by lipase and the glycerol produced was catalytically oxidized by NAD-dependent glycerol dehydrogenase producing NADH in a solution containing NAD(+). Glyceryl tributyrate, a short chain triglyceride, was chosen as the substrate for the evaluation of this TG biosensor in bovine serum and human serum. A linear response to glyceryl tributyrate in the concentration range of 0 to 10 mM and a sensitivity of 7.5 nA mM(-1) in bovine serum and 7.0 nA mM(-1) in human serum were observed experimentally. The potential interference of species such as uric acid (UA) and ascorbic acid (AA) was assessed. The incorporation of a selected surfactant and an increase in the incubation temperature appeared to enhance the performance of this biosensor. The conditions for the determination of TG levels in bovine serum using this biosensor were optimized, with sunflower seed oil being used as an analyte to simulate the detection of TG in blood. The experimental results demonstrated that this iridium nano-particle modified working electrode based biosensor provided a relatively simple means for the accurate determination of TG in serum.

New cyclometalated Iridium(III) beta-dicetone complex as phosphorescent dopant in Organic light emitting devices

Science.gov (United States)

Ivanov, P.; Petrova, P.; Stanimirov, S.; Tomova, R.

2017-01-01

A new Bis[4-(benzothiazolato-N,C2‧-2-yl)-N,N-dimethylaniline]Iridium(III) acetylacetonate (Me2N-bt) 2Ir(acac) was synthesized and identified by 1H NMR and elemental analysis. The application of the new compound as a dopant in the hole transporting layer (HTL) of Organic light emitting diode (OLED) structure: HTL/EL/ETL, where HTL was N,N’-bis(3-methylphenyl)-N,N’-diphenylbenzidine (TPD), incorporated in Poly(N-vinylcarbazole) (PVK) matrix, EL - electroluminescent layer of Bis(8-hydroxy-2-methylquinoline)-(4-phenylpheno-xy)aluminum (BAlq) and ETL - electron-transporting layer of Tris-(8-hydroxyquinoline) aluminum (Alq3) or Bis[2-(2-benzothiazoly) phenolato]zinc (Zn(btz)2). We established that the electroluminescent spectra of OLEDs at different concentrations of the dopant were basically the sum of the greenish-blue emission of BAlq and yellowish-green emission of Ir complex. It was found that with increasing of the dopant concentration the relative electroluminescent intensity of Iridium complex emission increased and this of BAlq decreased and as a result the fine tuning of OLED color was observed.

Nanocomposites of iridium oxide and conducting polymers as electroactive phases in biological media.

Science.gov (United States)

Moral-Vico, J; Sánchez-Redondo, S; Lichtenstein, M P; Suñol, C; Casañ-Pastor, N

2014-05-01

Much effort is currently devoted to implementing new materials in electrodes that will be used in the central nervous system, either for functional electrostimulation or for tests on nerve regeneration. Their main aim is to improve the charge capacity of the electrodes, while preventing damaging secondary reactions, such as peroxide formation, occurring while applying the electric field. Thus, hybrids may represent a new generation of materials. Two novel hybrid materials are synthesized using three known biocompatible materials tested in the neural system: polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) (PEDOT) and iridium oxide (IrO2). In particular, PPy-IrO2 and PEDOT-IrO2 hybrid nanocomposite materials are prepared by chemical polymerization in hydrothermal conditions, using IrO2 as oxidizing agent. The reaction yields a significant ordered new hybrid where the conducting polymer is formed around the IrO2 nanoparticles, encapsulating them. Scanning electron microscopy and backscattering techniques show the extent of the encapsulation. Both X-ray photoelectron and Fourier transform infrared spectroscopies identify the components of the phases, as well as the absence of impurities. Electrochemical properties of the final phases in powder and pellet form are evaluated by cyclic voltammetry. Biocompatibility is tested with MTT toxicity tests using primary cultures of cortical neurons grown in vitro for 6 and 9days. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Destabilization of the 6H-SrIrO3 polymorph through partial substitution of zinc and lithium

DEFF Research Database (Denmark)

Bremholm, Martin; K. Kim, Cindi; Hirai, Daigo

2012-01-01

We report on the destabilization of the 6H-SrIrO3 polymorph through partial substitutions of zinc and lithium for iridium to form perovskites. The perovskites crystallize in the orthorhombic space group Pbnm: SrIr1−xZnxO3 is found for 0.25 ≤ x ≤ 0.33, while SrIr1−xLixO3 is found only for x = 0...... show Curie–Weiss behavior, with relatively large temperature independent contributions, and that the iridium atoms have low effective moments, 0.52 to 1.08 μB per Ir. The resistivity of SrIr0.67Zn0.33O3, characterized by Mott variable range hopping type semiconducting behavior, indicates...

Oxidation of iridium coating on rhenium coated graphite at elevated temperature in stagnated air

International Nuclear Information System (INIS)

Huang, Yongle; Bai, Shuxin; Zhang, Hong; Ye, Yicong

2015-01-01

Highlights: • Continuous and dense Ir coatings were prepared on graphite by electrodepostion. • The purification of the as-prepared Ir coating was higher than about 99.98%. • The Ir/Re/C specimen kept integrity without significant failures after oxidation. • The average oxidation rate of the Ir coating was about 0.219 mg/(cm 2 min). • Penetrating holes at gains boundaries resulted in the failure of the Ir coating. - Abstract: Continuous and dense iridium coatings were prepared on the rhenium coated graphite specimens by electrodeposition. The iridium/rhenium coated graphite (Ir/Re/C) specimens were oxidized at elevated temperatures in stagnated air for 3600 s. The purification of the as-prepared Ir coating was higher than about 99.98% with the main impurity elements Si, Al, Fe and Ru. After oxidation, the Ir/Re/C specimens kept integrity without significant failures and the average oxidation rate was about 0.219 mg/(cm 2 min). Pores were found at the grain boundaries and concentrated to penetrating holes with the growth of Ir grains, which resulted in disastrous failures of the Ir coating

Oxidation of iridium coating on rhenium coated graphite at elevated temperature in stagnated air

Energy Technology Data Exchange (ETDEWEB)

Huang, Yongle; Bai, Shuxin, E-mail: NUDT_MSE_501@163.com; Zhang, Hong; Ye, Yicong

2015-02-15

Highlights: • Continuous and dense Ir coatings were prepared on graphite by electrodepostion. • The purification of the as-prepared Ir coating was higher than about 99.98%. • The Ir/Re/C specimen kept integrity without significant failures after oxidation. • The average oxidation rate of the Ir coating was about 0.219 mg/(cm{sup 2} min). • Penetrating holes at gains boundaries resulted in the failure of the Ir coating. - Abstract: Continuous and dense iridium coatings were prepared on the rhenium coated graphite specimens by electrodeposition. The iridium/rhenium coated graphite (Ir/Re/C) specimens were oxidized at elevated temperatures in stagnated air for 3600 s. The purification of the as-prepared Ir coating was higher than about 99.98% with the main impurity elements Si, Al, Fe and Ru. After oxidation, the Ir/Re/C specimens kept integrity without significant failures and the average oxidation rate was about 0.219 mg/(cm{sup 2} min). Pores were found at the grain boundaries and concentrated to penetrating holes with the growth of Ir grains, which resulted in disastrous failures of the Ir coating.

Strong ligand field effects of blue phosphorescent mono-cyclometalated iridium(III) complexes

International Nuclear Information System (INIS)

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

2010-01-01

A series of mono-cyclometalated blue phosphorescent iridium(III) complexes with two phosphines trans to each other and two cis-ancillary ligands, such as Ir(F 2 Meppy)(PPhMe 2 ) 2 (H)(Cl), [Ir(F 2 Meppy)(PPhMe 2 ) 2 (H)(NCMe)] + and Ir(F 2 Meppy)(PPhMe 2 ) 2 -(H)(CN), [F 2 Meppy = 2-(2',4'-difluorophenyl)-4-methyl-pyridine] were synthesized and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. We investigate the electron-withdrawing capabilities of ancillary ligands using the DFT and TD-DFT calculations on the ground and excited states of the three complexes to gain insight into the factors responsible for the emission color change and the different luminescence efficiency. Reducing the molecular weight of phosphine ligand with PPhMe 2 leads to a strategy of the efficient deep blue organic light-emitting devices (OLED) by thermal processing instead of the solution processing. The electron-withdrawing difluoro group substituted on the phenyl ring and the cyano strong field ancillary ligand in the trans position to the carbon atom of phenyl ring increased HOMO-LUMO gap and achieved the hypsochromic shift in emission color. As a result, the maximum emission spectra of Ir(F 2 Meppy)(PPhMe 2 ) 2 (H)(Cl), [Ir(F 2 Meppy)(PPhMe 2 ) 2 (H)-(NCMe)] + and Ir(F 2 Meppy)(PPh-Me 2 ) 2 (H)(CN) were in the ranges of 446, 440, 439 nm, respectively.

A study on the relationship between iridium concentration in hen eggshell and iridium-enriched feed by NAA

International Nuclear Information System (INIS)

Yang Gaochuang; Mao Xueying; Wang Jinchun; Lu Yali; Ouyang Hong; Zhang Zhaohui; Chai Zhifang

2001-01-01

Four hens were fed by adding ammonium hexachloroiridate into their forage. After two weeks, Ir concentration in three fractions (eggshell, albumen, egg yolk) of their eggs were measured by instrumental neutron activation analysis (INAA). Ir was present in all the three parts of the eggs. Further, the highest concentration of Ir was found in the egg yolk fraction, about 10 times higher than that in the eggshell and albumen. Moreover, the longer the Ir-containing feed was used, the higher the Ir concentration in the egg fractions was. After 4-6 day feeding, the Ir concentration became stable. The experimental results indicated that the Ir concentration was about 2-7 x 10 -10 g/g in the eggshell fraction compared to 5.6 x 10 -7 g/g in feed. Therefore, the ratio from the feed over the eggshell via gastrointestinal pathway was estimated to be about 0.08%. The new result is useful to evaluate the iridium-enriched eggshell fossils of dinosauria and to interpret the origin of the mass extinction of dinosauria at the end of Cretaceous. (author)

Small-angle scattering of ions or atoms by atomic hydrogen

International Nuclear Information System (INIS)

Franco, V.

1982-01-01

A theory for small-angle scattering of arbitrary medium- or high-energy atoms or ions by atomic hydrogen is described. Results are obtained in terms of the known closed-form and easily calculable Glauber-approximation scattering amplitudes for electron-hydrogen collisions and for collisions between the nucleus (treated as one charged particle) of the ion or atom and the hydrogen atom, and in terms of the transition form factor of the arbitrary ion or atom. Applications are made to the angular differential cross sections for the excitation of atomic hydrogen to its n = 2 states by singly charged ground-state helium ions having velocities of roughly between 1/2 and 1 a.u. The differential cross sections are obtained in terms of electron-hydrogen amplitudes and the known He + ground-state form factor. Comparisons are made with other calculations and with recent measurements. The results are in good agreement with the data. It is seen that the effect of the He + electron is to produce significant constructive interference at most energies

Separation of gold, palladium and platinum in chromite by anion exchange chromatography for inductively coupled plasma atomic emission spectrometric analysis

International Nuclear Information System (INIS)

Choi, Kwang Soon; Lee, Chang Heon; Park, Yeong Jae; Joe, Kih Soo; Kim, Won Ho

2001-01-01

A study has been carried out on the separation of gold, iridium, palladium, rhodium, ruthenium and platinum in chromite samples and their quantitative determination using inductively coupled plasma atomic emission spectrometry (ICP-AES). The dissolution condition of the minerals by fusion with sodium peroxide was optimized and chromatographic elution behavior of the rare metals was investigated by anion exchange chromatography. Spectral interference of chromium, a matrix of the minerals, was investigated on determination of gold. Chromium interfered on determination of gold at the concentration of 500 mg/L and higher. Gold plus trace amounts of iridium, palladium, rhodium and ruthenium, which must be preconcentrated before ICP-AES was separated by anion exchange chromatography after reducing Cr(VI) to Cr(III) by H 2 O 2 . AuCl - 4 retained on the resin column was selectively eluted with acetone- HNO 3 -H 2 O as an eluent. In addition, iridium, palladium, rhodium and ruthenium remaining on the resin column were eluted as a group with concentrated HCl. However, platinum was eluted with concentrated HNO 3 . The recovery yield of gold with acetone-HNO 3 -H 2 O was 100.7 ± 2.0 % , and the yields of palladium and platinum with concentrated HCl and HNO 3 were 96.1 ± 1.8% and 96.6 ± 1.3%, respectively. The contents of gold and platinum in a Mongolian chromite sample were 32.6 ± 2.2 μg/g and 1.6 ± 0.14 μg/g, respectively. Palladium was not detected

Probing the mer- to fac-isomerization of tris-cyclometallated homo- and heteroleptic (C,N)3 Iridium(III) complexes

NARCIS (Netherlands)

McDonald, A.R.; Lutz, M.; von Chrzanowski, L.S.; van Klink, G.P.M.; Spek, A.L.; van Koten, G.

2008-01-01

We have developed techniques which allow for covalent tethering, via a “hetero” cyclometallating ligand, of heteroleptic tris-cyclometallated iridium(III) complexes to polymeric supports (for application in light-emitting diode technologies). This involved the selective synthesis and thorough

The form of electron-atom excitation amplitudes at high momentum transfers in the Faddeev-Watson approximation

International Nuclear Information System (INIS)

Catalan, G.; Roberts, M.J.

1979-01-01

A form of the off-shell Coulomb T matrix, which has a well defined on-shell limit, is used in the Faddeev-Watson multiple-scattering expansion for a direct three-body collision process. Using the excitation of atomic hydrogen by electron impact as an example, approximations to the second-order terms, which are valid for high momentum transfers of the incident electron, are derived. It is shown how the resulting asymptotic behaviour of the second-order Faddeev-Watson approximation is related to the high momentum transfer limit of the second Born approximation. The results are generalised to the excitation of more complex atoms. The asymptotic forms of the Faddeev-Watson and Born approximations are compared with other theories and with measurements of differential cross sections and angular correlation parameters for the excitation of H(2p) and He(2 1 P). The results indicate that the Faddeev-Watson approximation converges more rapidly at high momentum transfers than does the Born approximation. (author)

Single Pot Selective Hydrogenation of Furfural to 2-Methylfuran Over Carbon Supported Iridium Catalysts

KAUST Repository

Date, Nandan S; Hengne, Amol Mahalingappa; Huang, Kuo-Wei; Chikate, Rajeev C.; Rode, C. V.

2018-01-01

Various iridium supported carbon catalysts were prepared and screened for direct hydrogenation of furfural (FFR) to 2-methyl furan (2-MF). Amongest these, 5% Ir/C showed excellent results with complete FFR conversion and highest selectivity of 95% to 2-MF at very low H2 pressure of 100 psig. Metallic (Iro) and oxide ( IrO2) phases of Ir catalyzed first step hydrogenation involving FFR to FAL and subsequent hydrogenation to 2-MF,respecively. This was confirmed by XPS analysis and some controlled experiments. At low temperature of 140 oC, almost equal selectivities of FAL (42%) and 2-MF (43%) were observed, while higher temperature (220oC) favored selective hydrodeoxygenation. At optimized temperature, 2-MF formed selectively while higher pressure and higher catalyst loading favored ring hydrogenation of furfural rather than side chain hydrogenation. With combination of several control experimental results and detailed catalyst characterization, a plausible reaction pathway has been proposed for selective formation of 2-MF. The selectivity to various other products in FFR hydrogenation can be manipulated by tailoring the reaction conditions over the same catalyst.

Single Pot Selective Hydrogenation of Furfural to 2-Methylfuran Over Carbon Supported Iridium Catalysts

KAUST Repository

Date, Nandan S

2018-03-20

Various iridium supported carbon catalysts were prepared and screened for direct hydrogenation of furfural (FFR) to 2-methyl furan (2-MF). Amongest these, 5% Ir/C showed excellent results with complete FFR conversion and highest selectivity of 95% to 2-MF at very low H2 pressure of 100 psig. Metallic (Iro) and oxide ( IrO2) phases of Ir catalyzed first step hydrogenation involving FFR to FAL and subsequent hydrogenation to 2-MF,respecively. This was confirmed by XPS analysis and some controlled experiments. At low temperature of 140 oC, almost equal selectivities of FAL (42%) and 2-MF (43%) were observed, while higher temperature (220oC) favored selective hydrodeoxygenation. At optimized temperature, 2-MF formed selectively while higher pressure and higher catalyst loading favored ring hydrogenation of furfural rather than side chain hydrogenation. With combination of several control experimental results and detailed catalyst characterization, a plausible reaction pathway has been proposed for selective formation of 2-MF. The selectivity to various other products in FFR hydrogenation can be manipulated by tailoring the reaction conditions over the same catalyst.

Reversible switching of the sol- gel transition with ultrasound in rhodium(I) and iridium(I) coordination networks

NARCIS (Netherlands)

Paulusse, J.M.J.; Beek, van D.J.M.; Sijbesma, R.P.

2007-01-01

Reversible coordination networks were prepared by combining diphenylphosphinite telechelic polytetrahydrofuran (2) with [RhCl(COD)]2 or [IrCl(COD)]2 in chloroform. Both systems resulted in stable gels at concentrations above 50 and 30 g/L for the rhodium(I) and iridium(I) networks, respectively. The

Synthesis of a red electrophosphorescent heteroleptic iridium complex and its application in efficient polymer light-emitting diodes

International Nuclear Information System (INIS)

Zhang Xiuju; Xu Yunhua; Sun Yiheng; Shi Huahong; Zhu Xuhui; Cao Yong

2007-01-01

The preparation and characterization of a heteroleptic iridium complex [2-(benzo[b]thiophen-2-yl)pyridine]Ir(III)[2-(4H-1,2,4-triazol-3-yl) pyridine] [(Btp) 2 Ir(PZ)] were reported (2-(benzo[b]thiophen-2-yl)pyridine = Btp; 2-(4H-1,2,4-triazol-3-yl)pyridine = PZ). Electrophosphorescence was investigated in the device structure [indium-tin-oxide (ITO)/poly(ethlenedioxythiophene) (PEDOT)/poly(vinylcarbazole)(PVK)/Poly(9,9-dioctylfluorenyl-2,7-diyl) end capped with dimethylphenyl (PFO): (Btp) 2 Ir(PZ)/Ba/Al] by using this iridium complex as guest and PFO as host. The red electrophosphorescent devices showed a peak emission at approximately 604 nm and shoulder at 654 nm with the Commission International de'Eclairage (CIE) coordinates of (0.64, 0.35) and external quantum efficiency of 7.7% at a doping concentration of 8 wt.% without an electron-transporting material in the emitting layer

Activity of ruthenium, rhodium, iridium-ruthenium and iridium-rhodium adsorbed catalysts in dehydrogenation of formic acid

Energy Technology Data Exchange (ETDEWEB)

Mikhailov, V A; Zubovich, I A [Yaroslavskij Politekhnicheskij Inst. (USSR)

1977-04-01

The activity of Ru-, Rh- (Ir+nRu)- and (Ir+nRn) catalysts on sugar carbon and silicon dioxide in decomposition of HCOOH was studied. The catalyst activity increases in the series Iratoms interact with Ru(Rh), and variable-composition structures are formed.

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

Science.gov (United States)

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.

Recovery from Iridium-192 flakes of a radioactive source for industrial use after a radiation incident

International Nuclear Information System (INIS)

Cruz, W.H.; Zapata, L.A.

2013-01-01

The Iridium-192 ( 192 Ir) is the most used and ideal for industrial radiography applications, especially in petrochemical plants and pipelines and provides better contrast sensitivity for thick (25.4 mm). This source has constructive sealed double encapsulation, the internal capsule containing stainless steel to radioactive material in the form of flakes and welded with TIG process. The radiological incident happened at a gas station fuel sales in circumstances in which there was a homogeneity test welds a tank, the flakes or Ir-192 fell off his ponytail and left scattered over an area of 2 m 2 , some fell flat areas and other land so collected in lead shielding and metal container and ground source. Full recovery of the leaflets was performed at the Division of radioactive waste management (GRRA) gaining a total of 22 flakes with no radiation risk to staff performance and installation and the conclusion was reached that the misapplicaion of TIG welding was the main cause the incident. (author)

Electronic structure of atoms: atomic spectroscopy information system

International Nuclear Information System (INIS)

Kazakov, V V; Kazakov, V G; Kovalev, V S; Meshkov, O I; Yatsenko, A S

2017-01-01

The article presents a Russian atomic spectroscopy, information system electronic structure of atoms (IS ESA) (http://grotrian.nsu.ru), and describes its main features and options to support research and training. The database contains over 234 000 records, great attention paid to experimental data and uniform filling of the database for all atomic numbers Z, including classified levels and transitions of rare earth and transuranic elements and their ions. Original means of visualization of scientific data in the form of spectrograms and Grotrian diagrams have been proposed. Presentation of spectral data in the form of interactive color charts facilitates understanding and analysis of properties of atomic systems. The use of the spectral data of the IS ESA together with its functionality is effective for solving various scientific problems and training of specialists. (paper)

Electronic structure of atoms: atomic spectroscopy information system

Science.gov (United States)

Kazakov, V. V.; Kazakov, V. G.; Kovalev, V. S.; Meshkov, O. I.; Yatsenko, A. S.

2017-10-01

The article presents a Russian atomic spectroscopy, information system electronic structure of atoms (IS ESA) (http://grotrian.nsu.ru), and describes its main features and options to support research and training. The database contains over 234 000 records, great attention paid to experimental data and uniform filling of the database for all atomic numbers Z, including classified levels and transitions of rare earth and transuranic elements and their ions. Original means of visualization of scientific data in the form of spectrograms and Grotrian diagrams have been proposed. Presentation of spectral data in the form of interactive color charts facilitates understanding and analysis of properties of atomic systems. The use of the spectral data of the IS ESA together with its functionality is effective for solving various scientific problems and training of specialists.

UV-light promoted C-H bond activation of benzene and fluorobenzenes by an iridium(i) pincer complex.

Science.gov (United States)

Hauser, Simone A; Emerson-King, Jack; Habershon, Scott; Chaplin, Adrian B

2017-03-28

Iridium(i) carbonyl complex [Ir(2,6-(P t Bu 2 CH 2 ) 2 C 6 H 3 )(CO)] undergoes reversible C-H bond activation of benzene and a series of fluorobenzenes on UV irradiation. Exclusive ortho-selectivity is observed in reactions of fluorobenzene and 1,2-difluorobenzene.

UV-light promoted C–H bond activation of benzene and fluorobenzenes by an iridium(i) pincer complex

OpenAIRE

Hauser, Simone A.; Emerson-King, Jack; Habershon, Scott; Chaplin, Adrian B.

2017-01-01

Iridium(I) carbonyl complex [Ir(2,6-(PtBu2CH2)2C6H3)(CO)] undergoes reversible C–H bond activation of benzene and a series of fluorobenzenes on UV irradiation. Exclusive ortho-selectivity is observed in reactions of fluorobenzene and 1,2-difluorobenzene.\\ud \\ud

Grain growth behavior and high-temperature high-strain-rate tensile ductility of iridium alloy DOP-26

International Nuclear Information System (INIS)

McKamey, C.G.; Gubbi, A.N.; Lin, Y.; Cohron, J.W.; Lee, E.H.; George, E.P.

1998-04-01

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 new-process iridium-based DOP-26 alloy used for the Cassini space mission. This alloy was developed at Oak Ridge National Laboratory (ORNL) in the early 1980's and is currently used by 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. Included within this report are data generated on grain growth in vacuum or low-pressure oxygen environments; a comparison of grain growth in vacuum of the clad vent set cup material with sheet material; effect of grain size, test temperature, and oxygen exposure on high-temperature high-strain-rate tensile ductility; and grain growth in vacuum and high-temperature high-strain-rate tensile ductility of welded DOP-26. The data for the new-process material is compared to available old-process data

Electrochemistry of transition metal complex catalysts Part 10. Intra- and intermolecular electrochemically activated C-H addition to the central metal atom of a P-C-P-pincer iridium complex

International Nuclear Information System (INIS)

Novak, Filip; Speiser, Bernd; Mohammad, Hani A.Y.; Mayer, Hermann A.

2004-01-01

The electrochemical properties of a promising catalyst for C-H bond activation are investigated. This P-C-P-pincer complex of iridium exhibits an intramolecular C-H oxidative addition at room temperature, which becomes enhanced upon oxidation. The reaction product is detected by cyclic voltammetry. Mechanistic, kinetic, and thermodynamic information is extracted from experiments in combination with digital simulation. Multicycle voltammograms and voltammograms of mixtures consistently suggest an extended square scheme as the electrode reaction mechanism. The unsubstituted parent compound shows a more complex redox behavior including a coupled ECE sequence. Intermolecular C-H activation by reaction of the complex in the presence of cyclooctane is indicated by characteristic changes in the cyclic voltammograms

Hybrid white organic light-emitting devices based on phosphorescent iridium-benzotriazole orange-red and fluorescent blue emitters

Energy Technology Data Exchange (ETDEWEB)

Xia, Zhen-Yuan, E-mail: xiazhenyuan@hotmail.com [Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237 (China); Su, Jian-Hua [Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237 (China); Chang, Chi-Sheng; Chen, Chin H. [Display Institute, Microelectronics and Information Systems Research Center, National Chiao Tung University, Hsinchu, Taiwan 300 (China)

2013-03-15

We demonstrate that high color purity or efficiency hybrid white organic light-emitting devices (OLEDs) can be generated by integrating a phosphorescent orange-red emitter, bis[4-(2H-benzotriazol-2-yl)-N,N-diphenyl-aniline-N{sup 1},C{sup 3}] iridium acetylacetonate, Ir(TBT){sub 2}(acac) with fluorescent blue emitters in two different emissive layers. The device based on deep blue fluorescent material diphenyl-[4-(2-[1,1 Prime ;4 Prime ,1 Double-Prime ]terphenyl-4-yl-vinyl)-phenyl]-amine BpSAB and Ir(TBT){sub 2}(acac) shows pure white color with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.33,0.30). When using sky-blue fluorescent dopant N,N Prime -(4,4 Prime -(1E,1 Prime E)-2,2 Prime -(1,4-phenylene)bis(ethene-2,1-diyl) bis(4,1-phenylene))bis(2-ethyl-6-methyl-N-phenylaniline) (BUBD-1) and orange-red phosphor with a color-tuning phosphorescent material fac-tris(2-phenylpyridine) iridium (Ir(ppy){sub 3} ), it exhibits peak luminance yield and power efficiency of 17.4 cd/A and 10.7 lm/W, respectively with yellow-white color and CIE color rendering index (CRI) value of 73. - Highlights: Black-Right-Pointing-Pointer An iridium-based orange-red phosphor Ir(TBT){sub 2}(acac) was applied in hybrid white OLEDs. Black-Right-Pointing-Pointer Duel- and tri-emitter WOLEDs were achieved with either high color purity or efficiency performance. Black-Right-Pointing-Pointer Peak luminance yield of tri-emitter WOLEDs was 17.4 cd/A with yellow-white color and color rendering index (CRI) value of 73.

Studies of high-level radioactive waste form performance at Japan Atomic Energy Research Institute

International Nuclear Information System (INIS)

Banba, Tsunetaka; Kamizono, Hiroshi; Mitamura, Hisayoshi

1992-02-01

The recent studies of high-level radioactive waste form at Japan Atomic Energy Research Institute can be classified into the following three categories; (1) Study on the leaching behavior of the nuclear waste glass placing the focus on the alteration layer and the chemical composition of leachant for the prediction of the long-term corrosion of the waste glass. (2) Study on the radiation (alpha-radiation) effects which have relation to the long-term stability of the nuclear waste glass. (3) Study on the long-term self-irradiation damage of a SYNROC waste form using a curium-doped sample. In the present report, the recent results corresponding to the above categories are described. (author)

Influence of iridium doping in MgB2 superconducting wires

DEFF Research Database (Denmark)

Grivel, Jean-Claude

2018-01-01

MgB2 wires with iridium doping were manufactured using the in-situ technique in a composite Cu-Nb sheath. Reaction was performed at 700°C, 800°C or 900°C for 1h in argon atmosphere. A maximum of about 1.5 at.% Ir replaces Mg in MgB2. The superconducting transition temperature is slightly lowered...... by Ir doping. The formation of IrMg3 and IrMg4 secondary phase particles is evidenced, especially for a nominal stoichiometry with 2.0 at.% Ir doping. The critical current density and accommodation field of the wires are strongly dependent on the Ir content and are generally weakened in the presence...

Studies of glass waste form performance at Japan Atomic Energy Research Institute

International Nuclear Information System (INIS)

Banba, Tsunetaka; Kamizono, Hiroshi; Nakayama, Shinichi; Tashiro, Shingo

1989-08-01

The recent studies of glass waste form performance at Japan Atomic Energy Research Institute can be classified into the following three categories; (1) Study on the volatilization of radionuclides from the waste glass, which is necessary to estimate the safety in relation to operation of a storage facility. (2) Study on the radiation (alpha-radiation) effects which have relation to the long-term stability of the waste glass. (3) Study on the leaching behavior of actinides under the repository conditions, which is necessary to predict the long-term release rate of radionuclides from the waste glass. In the present report, the recent results corresponding to the above categories are described. (author)

Atomic hydrogen in the Orion star-forming region

International Nuclear Information System (INIS)

Chromey, F.R.; Elmegreen, B.G.; Elmegreen, D.M.

1989-01-01

A large-scale survey of atomic hydrogen in Orion reveals low-density material with a total mass comparable to that in dense molecular clouds. The atomic gas is sufficiently dense that it can shield the molecular material from photodissociative radiation and provide a pressure link to the low-density intercloud medium. An excess of H I emission comes from photodissociation fronts near the bright stars and from a giant shell in the Orion Belt region. This shell may have caused the apparent bifurcation between the Orion A and B clouds, and the associated pressures may have induced peculiar motions and star formation in NGC 2023 and 2024. 49 refs

An iridium abundance anomaly at the palynological Cretaceous-Tertiary boundary in northern New Mexico

Science.gov (United States)

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

1981-01-01

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. Copyright ?? 1981 AAAS.

Atomic Scale Investigation of Structural Properties and Glass Forming Ability of Ti100- x Al x Metallic Glasses

Science.gov (United States)

Tahiri, M.; Hasnaoui, A.; Sbiaai, K.

2018-06-01

In this work, we employed molecular dynamics (MD) simulations to study Ti-Al metallic glasses (MGs) using the embedded atom method (EAM) potential to model the atomic interaction with different compositions. The results showed evidence of the metallic glass formation induced by the split occurring in the second peak of the radial distribution function (RDF) curves implying both Ti and Al atoms. The common neighbor analysis (CNA) method confirmed the presence of the icosahedral clusters with a maximum amount observed for an alloy with 75 pct of Al. Analysis of coordination numbers (CNs) indicated that the total CNs are nearly unchanged in these systems. Finally, Voronoi tessellation analyses (VTA) showed a higher value of the number of icosahedral units at Ti25Al75 composition. This specific composition represents a nearby peritectic point localized at a low melting point in the Ti-Al binary phase diagram. The glass forming ability (GFA) becomes important when the fraction of Al increases by forming and connecting "icosahedral-like" clusters (12-coordinated and 13-coordinated ) and by playing a main role in the structure stability of the Ti-Al MGs.

Atomic Scale Investigation of Structural Properties and Glass Forming Ability of Ti100-x Al x Metallic Glasses

Science.gov (United States)

Tahiri, M.; Hasnaoui, A.; Sbiaai, K.

2018-03-01

In this work, we employed molecular dynamics (MD) simulations to study Ti-Al metallic glasses (MGs) using the embedded atom method (EAM) potential to model the atomic interaction with different compositions. The results showed evidence of the metallic glass formation induced by the split occurring in the second peak of the radial distribution function (RDF) curves implying both Ti and Al atoms. The common neighbor analysis (CNA) method confirmed the presence of the icosahedral clusters with a maximum amount observed for an alloy with 75 pct of Al. Analysis of coordination numbers (CNs) indicated that the total CNs are nearly unchanged in these systems. Finally, Voronoi tessellation analyses (VTA) showed a higher value of the number of icosahedral units at Ti25Al75 composition. This specific composition represents a nearby peritectic point localized at a low melting point in the Ti-Al binary phase diagram. The glass forming ability (GFA) becomes important when the fraction of Al increases by forming and connecting "icosahedral-like" clusters (12-coordinated and 13-coordinated ) and by playing a main role in the structure stability of the Ti-Al MGs.

Strong ligand field effects of blue phosphorescent mono-cyclometalated iridium(III) complexes

Energy Technology Data Exchange (ETDEWEB)

Ham, Ho Wan [Department of Information Display, Hongik University, Seoul, 121-791 (Korea, Republic of); Jung, Kyung Yoon [International Design School for Advanced Studies, Hongik University, Seoul 121-791 (Korea, Republic of); Kim, Young Sik, E-mail: youngkim@hongik.ac.k [Department of Information Display, Hongik University, Seoul, 121-791 (Korea, Republic of)

2010-09-01

A series of mono-cyclometalated blue phosphorescent iridium(III) complexes with two phosphines trans to each other and two cis-ancillary ligands, such as Ir(F{sub 2}Meppy)(PPhMe{sub 2}){sub 2}(H)(Cl), [Ir(F{sub 2}Meppy)(PPhMe{sub 2}){sub 2}(H)(NCMe)]{sup +} and Ir(F{sub 2}Meppy)(PPhMe{sub 2}){sub 2}-(H)(CN), [F{sub 2}Meppy = 2-(2',4'-difluorophenyl)-4-methyl-pyridine] were synthesized and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. We investigate the electron-withdrawing capabilities of ancillary ligands using the DFT and TD-DFT calculations on the ground and excited states of the three complexes to gain insight into the factors responsible for the emission color change and the different luminescence efficiency. Reducing the molecular weight of phosphine ligand with PPhMe{sub 2} leads to a strategy of the efficient deep blue organic light-emitting devices (OLED) by thermal processing instead of the solution processing. The electron-withdrawing difluoro group substituted on the phenyl ring and the cyano strong field ancillary ligand in the trans position to the carbon atom of phenyl ring increased HOMO-LUMO gap and achieved the hypsochromic shift in emission color. As a result, the maximum emission spectra of Ir(F{sub 2}Meppy)(PPhMe{sub 2}){sub 2}(H)(Cl), [Ir(F{sub 2}Meppy)(PPhMe{sub 2}){sub 2}(H)-(NCMe)]{sup +} and Ir(F{sub 2}Meppy)(PPh-Me{sub 2}){sub 2} (H)(CN) were in the ranges of 446, 440, 439 nm, respectively.

Microstructural features and heat flow analysis of atomized and spray-formed Al-Fe-V-Si alloy

International Nuclear Information System (INIS)

Srivastava, A.K.; Ranganathan, S.; Ojha, S.N.

1998-01-01

Microstructural features of rapidly solidified powders and preforms of Al 80 Fe 10 V 4 Si 6 alloy produced by spray forming process have been studied. The atomization and spray deposition were carried out using a confined gas atomization process and the microstructural features were characterized using scanning electron microscopy and transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The microstructure of a wide size range of atomized powders invariably revealed cellular and dendritic morphology. The extent of dendritic region and the dendritic arm spacing were observed to increase with power particle size. The TEM investigations indicated the presence of ultrafine second-phase particles in the intercellular or interdendritic regions. In contrast, the spray deposits of the alloy showed considerable variation in microstructure and size and dispersion of the second-phase particles at specific distances from the deposit-substrate interface and the exterior regions of the deposit. Nevertheless, considerable homogeneity was observed in the microstructure toward the center of the spray deposit. The formation and distribution of a cubic phase α-Al(Fe, V)Si has been characterized in both atomized powders and spray deposits. A one-dimensional heat flow model has been used to analyze the evolution of microstructure during atomization and also during spray deposition processing of this alloy. The results indicate that thermal history of droplets in the spray on deposition surface and their solidification behavior considerably influence the microstructural features of the spray deposits

Osmium-191 → iridium-191m radionuclide generator: development and clinical application. Progress report, March 1, 1981-February 28, 1982

International Nuclear Information System (INIS)

Treves, S.; Cheng, C.

1981-01-01

A prototype osmium-191 (T 1/2 = 16 days) → iridium-191m (T 1/2 = 4.9 seconds) generator designed for first pass radionuclide angiography was developed in our laboratory (Os-191 → Ir-191m). Our generator had 14 to 20% Ir-191m yield and a 1 to 3 x 10 -3 % Os-191 breakthrough. Iridium-191m decays with emission of a 65 and a 129 keV photon in 50% and 25% abundance respectively. This radionuclide is advantageous for angiography since it provides higher photon flux and results in much lower radiation dose to the patient than Tc-99m. One objective of this research is to improve the Os-191 → Ir-191m generator for first pass radionuclide angiography at an increase in the Ir-191m yield and a decrease in the Os-191 breakthrough. In addition, we would like to develop an Os-191 → Ir-191m generator for continuous infusion which will be used for ECG gated blood pool ventriculography, venography, and arteriography. Another approach will be to develop a carrier free Os-191 → Ir-191m generator in combination with organic or inorganic exchangers. Iridium-191m from our current generator has been employed successfully in two patient studies for the quantitation left-to-right shunting and the measurement of right and left ventricular ejection fractions. These types of studies will be expanded and further evaluated

A study on the relationship between iridium concentration in hen eggs and the iridium-enriched feed stuff by INAA

International Nuclear Information System (INIS)

Yang Gaochuang; Mao Xueying; Lu Yali; Ouyang Hong; Wang Jinchun; Zhang Zhaohui; Chai Zhifang

2000-01-01

Several hens were fed by adding ammonium chloroiridate into their forage. After two weeks, the Ir concentration in three fractions (eggshell, albumen, egg yolk) of their eggs were measured by INAA. Ir was found in all of the three parts. However, the highest concentration of Ir was found in the egg yolk fraction, which was about 10 times higher than that in the eggshell and albumen. Moreover, the longer the Ir-containing feed stuff was used, the higher the Ir concentration in the egg fractions was. After 7-8 days feeding, it kept stable. On the other hand, as soon as adding the Ir-containing additives were stopped, the Ir concentration in the egg fractions fell down quickly. The experimental results indicated that the ratio from the feedstuff to the eggshell via gastrointestinal pathway to be about 0.07 percent. The new result might be beneficial to explain the iridium-enriched dinosaur eggshell fossils and to interpret the origin of the mass extinct event of dinosaur occurred at the end of Cretaceous

Highly efficient and heavily-doped organic light-emitting devices based on an orange phosphorescent iridium complex

International Nuclear Information System (INIS)

Zhou, Shunliang; Wang, Qi; Li, Ming; Lu, Zhiyun; Yu, Junsheng

2014-01-01

Heavily doped and highly efficient phosphorescent organic light-emitting devices (PhOLEDs) had been fabricated by utilizing an orange iridium complex, bis[2-(3′,5′-di-tert-butylbiphenyl-4-yl)benzothiazolato-N,C 2' ]iridium(III) (acetylacetonate) [(tbpbt) 2 Ir(acac)], as a phosphor. When the doping concentration of [(tbpbt) 2 Ir(acac)] reached as high as 15 wt%, the PhOLEDs exhibited a power efficiency, current efficiency, and external quantum efficiency of 24.5 lm/W, 32.1 cd/A, 15.7%, respectively, implying a promising quenching-resistant characteristics of this novel phosphor. Furthermore, the efficient white PhOLEDs had been obtained by employing (tbpbt) 2 Ir(acac) as a self-host orange emitter, indicating that (tbpbt) 2 Ir(acac) could serve as a promising phosphor to fabricate white organic light-emitting devices with simplified manufacturing process. - Highlights: • Efficient phosphorescent devices were fabricated. • Optimized phosphor doping ratio reached as high as 15 wt%. • The results proved a promising quench-resistant property of the phosphor. • Efficient white devices based on this phosphor as self-host layer had been realized

Highly efficient and heavily-doped organic light-emitting devices based on an orange phosphorescent iridium complex

Energy Technology Data Exchange (ETDEWEB)

Zhou, Shunliang; Wang, Qi [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China); Li, Ming [College of Chemistry, Sichuan University, Chengdu, 610064 (China); Lu, Zhiyun, E-mail: luzhiyun@scu.edu.cn [College of Chemistry, Sichuan University, Chengdu, 610064 (China); Yu, Junsheng, E-mail: jsyu@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)

2014-10-15

Heavily doped and highly efficient phosphorescent organic light-emitting devices (PhOLEDs) had been fabricated by utilizing an orange iridium complex, bis[2-(3′,5′-di-tert-butylbiphenyl-4-yl)benzothiazolato-N,C{sup 2'}]iridium(III) (acetylacetonate) [(tbpbt){sub 2}Ir(acac)], as a phosphor. When the doping concentration of [(tbpbt){sub 2}Ir(acac)] reached as high as 15 wt%, the PhOLEDs exhibited a power efficiency, current efficiency, and external quantum efficiency of 24.5 lm/W, 32.1 cd/A, 15.7%, respectively, implying a promising quenching-resistant characteristics of this novel phosphor. Furthermore, the efficient white PhOLEDs had been obtained by employing (tbpbt){sub 2}Ir(acac) as a self-host orange emitter, indicating that (tbpbt){sub 2}Ir(acac) could serve as a promising phosphor to fabricate white organic light-emitting devices with simplified manufacturing process. - Highlights: • Efficient phosphorescent devices were fabricated. • Optimized phosphor doping ratio reached as high as 15 wt%. • The results proved a promising quench-resistant property of the phosphor. • Efficient white devices based on this phosphor as self-host layer had been realized.

High-efficiency and heavily doped organic light-emitting devices based on quench-resistant red iridium complex

Energy Technology Data Exchange (ETDEWEB)

Wang, Qi [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China); Yu, Junsheng, E-mail: jsyu@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China); Zhao, Juan; Wang, Jun [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China); Li, Ming [College of Chemistry, Sichuan University, Chengdu 610064 (China); Lu, Zhiyun, E-mail: luzhiyun@scu.edu.cn [College of Chemistry, Sichuan University, Chengdu 610064 (China)

2013-02-15

Highly efficient red phosphorescent organic light-emitting devices had been fabricated using a new iridium complex, bis[2-(9,9-dimethyl-9H-fluoren-2-yl) benzothiazolato-N,C{sup 2'}]iridium(III) (acetylacetonate) [(fbt){sub 2}Ir(acac)] as phosphor. With a high doping concentration of 15 wt%, the device exhibited a maximum luminance efficiency, power efficiency and external quantum efficiency (EQE) of 35.2 cd/A, 21.3 lm/W, 18.2%, respectively, indicating an excellent quench-resistant property of (fbt){sub 2}Ir(acac). The results are appealing towards the development of 'easy-to-make' OLEDs. It has been demonstrated that the high efficiency arises from more balanced charge carriers in the emissive layer. - Highlight: Black-Right-Pointing-Pointer We obtained efficient OLEDs based on newly synthesized quench-resistant phosphor. Black-Right-Pointing-Pointer Peak performance was obtained with 15 wt% (fbt){sub 2}Ir(acac) doped device. Black-Right-Pointing-Pointer Our devices gave one of the best performance among heavily-doped red devices. Black-Right-Pointing-Pointer Balanced carrier transport is crucial for the high performance of our devices.

Thermal hydraulic modelling of the Mo and Iridium irradiation facilities of the RA10 reactor

International Nuclear Information System (INIS)

Gramajo, M.; García, J.; Marcel, C.P.

2013-01-01

The RA-10 reactor is a multipurpose, open pool research reactor. The core consists of a rectangular array of MTR type fuel. The produced thermal power is 30 MW which is extracted by the refrigeration system via an ascendant flow through the core. The core reflector is D 2 O contained in a watertight tank. The design of the reactor includes a number of out-core facilities which are meant to be used for industrial, medical and research purposes. Among all the facilities, the most important ones are the Molybdenum and Iridium ones which we modeled in this work. During the normal operation of the reactor, the manipulation and the on-line extraction of the irradiation facilities is foreseen. Therefore the study of the head loss during the normal operation as well as during the extraction maneuvers plays a relevant role in the design and safety analysis. In this work a CFD commercial code is use dto perform the calculations needed to guarantee the design requirements.In addition, a full detailed geometric model for both, the Molybdenum and Iridium facilities,is used to perform the required simulations. The obtained results allow to evaluating the thermal-hydraulic performance of the proposed facilities designs. (author)

Synthesis and green electrophosphorescence of a novel cyclometalated iridium complex in polymer light-emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Wu Lilan [Department of Chemistry, National Cheng Kung University, Tainan, Taiwan 70101 (China); Tsai Sunghao [Institute of Electro-Optical Science and Engineering, National Cheng Kung University, Tainan, Taiwan 70101 (China); Guo Tzungfang [Institute of Electro-Optical Science and Engineering, National Cheng Kung University, Tainan, Taiwan 70101 (China); Yang Chenghsien [Carbon Nanocapsules Research Department, Nano-Powder and Thin Film Technology Center, ITRI South, Tainan, Taiwan 709 (China)]. E-mail: jasonyang0606@yahoo.com.tw; Sun, I-W. [Department of Chemistry, National Cheng Kung University, Tainan, Taiwan 70101 (China)]. E-mail: iwsun@mail.ncku.edu.tw

2007-10-15

Abstact: In this paper, we synthesized a new complex bis(dibenzo[f,h]quinolinato-N,C {sup 2'}) iridium(III) acetylactonate ((DBQ){sub 2}Ir(acac)) having a longer conjugate system than bis(2-phenylpyridinato-N,C {sup 2'}) iridium(III) acetylacetonate ((PPY){sub 2}Ir(acac)). Interestingly (DBQ){sub 2}Ir(acac) emits at the same wavelength as (photoluminescence of 530 nm) (PPY){sub 2}Ir(acac). A high-efficiency electrophosphorescent polymer light-emitting diodes was constructed by using (DBQ){sub 2}Ir(acac) as the dopant, and a blend of poly(vinylcarbazole) (PVK) with 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazol (PBD) as the host material. The electroluminescence efficiency of 9.5 cd/A is reported for the device doped with 3 wt% of (DBQ){sub 2}Ir(acac). In this device, the emission from the PVK or PBD host was effectively inhibited with the using (DBQ){sub 2}Ir(acac) . Emission from the dopant molecules in such devices involve localization of the injected electron and hole on the metal-organic center. This can occur by a variety of mechanisms, including Foerster and Dexter energy transfer from the host transport material to the dopant, and direct trapping of both electrons and holes on the metal-organic center.

Preparation and determination of kerma for Iridium 192 sources of low dose rate for brachytherapy; Preparacion y determinacion del kerma de fuentes de iridio-192 de baja tasa de dosis para braquiterapia

Energy Technology Data Exchange (ETDEWEB)

Tendilla, J.I.; Tovar M, V.; Mitsoura, E.; Aguilar H, F.; Alanis M, J. [Instituto Nacional de Investigaciones Nucleares, C.P. 52045-1, Salazar, Esrado de Mexico, D.F. (Mexico)

2000-07-01

The practice of Brachytherapy with Iridium-192 sources of low dose rate (0.4 - 0.8 Gy/h) is a technique used in the treatment of diverse illnesses. in this work the preparation, quality control and calibration are presented in terms of kerma in air of Iridium-192 using as target these recycled Iridium-Platinum wires. The targets were obtained as decayed sources of different radio therapeutical centers in the country and they were characterized by Scanning electron microscopy in order to determine their chemical composition. Subsequently it was developed an experimental design to establish the effect of neutron flux, geometrical array and irradiation time over the activity and percentage of the sources homogeneity. The homogeneity was determined by auto radiography and by Gamma spectroscopy. Once the optimal irradiation conditions were established, it is determined the apparent activity and kerma in air using a well type ionization chamber with traceability to a primary laboratory. Iridium-192 sources were obtained with an average homogeneity 96 %, apparent activity 282.129 {+-} 0.531 M Bq and kerma in air 0.03200 {+-} 0.00006 m Gy m/h A. (Author)

Direct electrocatalytic reduction of coenzyme NAD{sup +} to enzymatically-active 1,4-NADH employing an iridium/ruthenium-oxide electrode

Energy Technology Data Exchange (ETDEWEB)

Ullah, Nehar, E-mail: nehar.ullah@mail.mcgill.ca; Ali, Irshad; Omanovic, Sasha

2015-01-15

A thermally prepared iridium/ruthenium-oxide coating (Ir{sub 0.8}Ru{sub 0.2}-oxide) formed on a titanium substrate was investigated as a possible electrode for direct electrochemical regeneration of enzymatically-active 1,4-NADH from its oxidized form NAD{sup +}, at various electrode potentials, in a batch electrochemical reactor. The coating surface was characterized by ‘cracked mud’ morphology, yielding a high surface roughness. The NADH regeneration results showed that the percentage of enzymatically-active 1,4-NADH present in the product mixture (i.e. recovery) is strongly dependent on the electrode potential, reaching a maximum (88%) at −1.70 V vs. MSE. The relatively high recovery was explained on the basis of availability of adsorbed ‘active’ hydrogen (H{sub ads}) on the Ir/Ru-oxide surface, i.e. on the basis of electrochemical hydrogenation. - Highlights: • Ir{sub 0.8}Ru{sub 0.2}-oxide coating was formed thermally on a Ti substrate. • Electrochemical regeneration of enzymatically-active 1,4-NADH was investigated. • The 1,4-NADH recovery percentage is strongly dependent on the electrode potential. • A highest recovery, 88%, was obtained at −1.70 V vs. MSE. • The NADH regeneration process involved electrochemical hydrogenation.

Lewis Base Activation of Silyl Acetals: Iridium-Catalyzed Reductive Horner-Wadsworth-Emmons Olefination.

Science.gov (United States)

Dakarapu, Udaya Sree; Bokka, Apparao; Asgari, Parham; Trog, Gabriela; Hua, Yuanda; Nguyen, Hiep H; Rahman, Nawal; Jeon, Junha

2015-12-04

A Lewis base promoted deprotonative pronucleophile addition to silyl acetals has been developed and applied to the iridium-catalyzed reductive Horner-Wadsworth-Emmons (HWE) olefination of esters and the chemoselective reduction of the resulting enoates. Lewis base activation of silyl acetals generates putative pentacoordinate silicate acetals, which fragment into aldehydes, silanes, and alkoxides in situ. Subsequent deprotonative metalation of phosphonate esters followed by HWE with aldehydes furnishes enoates. This operationally convenient, mechanistically unique protocol converts the traditionally challenging aryl, alkenyl, and alkynyl esters to homologated enoates at room temperature within a single vessel.

Distinct atomic structures of the Ni-Nb metallic glasses formed by ion beam mixing

International Nuclear Information System (INIS)

Tai, K. P.; Wang, L. T.; Liu, B. X.

2007-01-01

Four Ni-Nb metallic glasses are obtained by ion beam mixing and their compositions are measured to be Ni 77 Nb 23 , Ni 55 Nb 45 , Ni 31 Nb 69 , and Ni 15 Nb 85 , respectively, suggesting that a composition range of 23-85 at. % of Nb is favored for metallic glass formation in the Ni-Nb system. Interestingly, diffraction analyses show that the structure of the Nb-based Ni 31 Nb 69 metallic glass is distinctly different from the structure of the Nb-based Ni 15 Nb 85 metallic glass, as the respective amorphous halos are located at 2θ≅38 and 39 deg. To explore an atomic scale description of the Ni-Nb metallic glasses, an n-body Ni-Nb potential is first constructed with an aid of the ab initio calculations and then applied to perform the molecular dynamics simulation. Simulation results determine not only the intrinsic glass forming range of the Ni-Nb system to be within 20-85 at. % of Nb, but also the exact atomic positions in the Ni-Nb metallic glasses. Through a statistical analysis of the determined atomic positions, a new dominant local packing unit is found in the Ni 15 Nb 85 metallic glass, i.e., an icositetrahedron with a coordination number to be around 14, while in Ni 31 Nb 69 metallic glasses, the dominant local packing unit is an icosahedron with a coordination number to be around 12, which has been reported for the other metallic glasses. In fact, with increasing the irradiation dose, the Ni 31 Nb 69 metallic glasses are formed through an intermediate state of face-centered-cubic-solid solution, whereas the Ni 15 Nb 85 metallic glass is through an intermediate state of body-centered-cubic-solid solution, suggesting that the structures of the constituent metals play an important role in governing the structural characteristics of the resultant metallic glasses

Mono and dinuclear iridium, rhodium and ruthenium complexes containing chelating carboxylato pyrazine ligands: Synthesis, molecular structure and electrochemistry

Czech Academy of Sciences Publication Activity Database

Govindaswamy, P.; Therrien, B.; Süss-Fink, G.; Štěpnička, P.; Ludvík, Jiří

2007-01-01

Roč. 692, č. 8 (2007), s. 1661-1671 ISSN 0022-328X R&D Projects: GA MŠk LC510; GA MŠk(CZ) LC06070 Institutional research plan: CEZ:AV0Z40400503 Keywords : dinuclear complexes * iridium * rhodium * ruthenium * electrochemistry Subject RIV: CG - Electrochemistry Impact factor: 2.168, year: 2007

Ligand-Centred Reactivity of Bis(picolyl)amine Iridium: Sequential Deprotonation, Oxidation and Oxygenation of a "Non-Innocent" Ligand

Czech Academy of Sciences Publication Activity Database

Tejel, C.; del Río, M. P.; Ciriano, M. A.; Reijerse, E. J.; Hartl, F.; Záliš, Stanislav; Hetterscheid, D. G. H.; Tsichlis i Spithas, N.; de Bruin, B.

2009-01-01

Roč. 15, č. 44 (2009), s. 11878-11889 ISSN 0947-6539 R&D Projects: GA MŠk OC 139; GA AV ČR KAN100400702 Institutional research plan: CEZ:AV0Z40400503 Keywords : bis(picolyl)amine * iridium * ligand radical * oxygenation Subject RIV: CG - Electrochemistry Impact factor: 5.382, year: 2009

Trapping of hydride forming elements within miniature electrothermal devices. Part 2. Investigation of collection of arsenic and selenium hydrides on a surface and in a cavity of a graphite rod

International Nuclear Information System (INIS)

Docekal, Bohumil

2004-01-01

The interaction of arsenic and selenium hydrides with bare and modified graphite was investigated by atomic absorption spectrometry and by radiotracer technique using 75 Se radionuclide in a laboratory made brass cylindrical chamber equipped with a vertical quartz tube torch for supporting miniature hydrogen diffusion flame atomizer. Strong interaction was observed at elevated temperatures above 800 deg. C. In contrast to the very often-reported data for conventional graphite tube atomizers, this high temperature interaction was also accompanied by a pronounced trapping of analytes at elevated temperatures close to 1100-1200 deg. C when modified graphite was used. Comparing modifiers tested (Ir, Pt and Rh), iridium appeared the only useful permanent modifier. Among various graphite-rod traps designed, the most efficient trapping of analytes was achieved in a graphite cavity. The net selenium trapping efficiencies of approximately 53% and 70% were found by radiotracer technique for the iridium-treated graphite surface and the iridium-treated graphite cavity, respectively. In contrast to the molybdenum surface, bare graphite did not exhibit any significant trapping effect. Trapping isotherms obtained at different temperatures displayed non-linear course in the range up to the upper limit of the analytical relevance of 100 ng of an analyte, indicating a limited trapping capacity of the modified graphite surface and the same trapping mechanism at low and elevated temperatures applied (300-1300 deg. C). Radiography experiments with 75 Se radiotracer showed that a major part of selenium was collected within the small cavity of the graphite rod and that selenium was also deposited after the trapping and vaporization steps in the trap chamber and on the quartz tube wall of the burner. Complementary experiments performed with the conventional transversally heated graphite tube and with bare and thermally shielded injection capillaries for hydride introduction, showed that

Methods of forming single source precursors, methods of forming polymeric single source precursors, and single source precursors formed by such methods

Science.gov (United States)

Fox, Robert V.; Rodriguez, Rene G.; Pak, Joshua J.; Sun, Chivin; Margulieux, Kelsey R.; Holland, Andrew W.

2014-09-09

Methods of forming single source precursors (SSPs) include forming intermediate products having the empirical formula 1/2{L.sub.2N(.mu.-X).sub.2M'X.sub.2}.sub.2, and reacting MER with the intermediate products to form SSPs of the formula L.sub.2N(.mu.-ER).sub.2M'(ER).sub.2, wherein L is a Lewis base, M is a Group IA atom, N is a Group IB atom, M' is a Group IIIB atom, each E is a Group VIB atom, each X is a Group VIIA atom or a nitrate group, and each R group is an alkyl, aryl, vinyl, (per)fluoro alkyl, (per)fluoro aryl, silane, or carbamato group. Methods of forming polymeric or copolymeric SSPs include reacting at least one of HE.sup.1R.sup.1E.sup.1H and MER with one or more substances having the empirical formula L.sub.2N(.mu.-ER).sub.2M'(ER).sub.2 or L.sub.2N(.mu.-X).sub.2M'(X).sub.2 to form a polymeric or copolymeric SSP. New SSPs and intermediate products are formed by such methods.

Investigation of the atomic interface structure of mesotaxial Si/CoSi2(100) layers formed by high-dose implantation

International Nuclear Information System (INIS)

Bulle-Lieuwma, C.W.T.; Jong, A.F. de; Vandenhoudt, D.E.W.

1991-01-01

Aligned mesotaxial films of CoSi 2 in monocrystalline (100) oriented Si substrates have been formed by high-dose ion implantation of Co, followed by a high temperature treatment. The atomic structures of both the lower and upper Si/CoSi 2 (100) interfaces of the buried CoSi 2 layer have been investigated by high-resolution electron microscopy (HREM) combined with image simulations. A domain-like structure is observed consisting of areas with different interfaces. In order to derive the atomic configuration, image simulations of different proposed models are presented. By comparing simulated images and HREM images, two different atomic structure models for the Si/CoSi 2 (100) interface have been found. In the first model the interfacial Co atoms are six-fold coordinated and the tetrahedral coordination and bond lengths of silicon atoms are everywhere maintained. In the second model we found evidence for a 2 x 1 interface reconstruction, involving a difference in composition. The interfacial Co atoms are seven-fold coordinated. It is shown that the boundaries between the domains are associated with interfacial dislocations of edge-type with Burgers vectors b a/4 inclined and b = a/2 parallel to the interfacial plane. (author)

Atomic physics

International Nuclear Information System (INIS)

Armbruster, P.; Beyer, H.; Bosch, F.; Dohmann, H.D.; Kozhuharov, C.; Liesen, D.; Mann, R.; Mokler, P.H.

1984-01-01

The heavy ion accelerator UNILAC is well suited to experiments in the field of atomic physics because, with the aid of high-energy heavy ions atoms can be produced in exotic states - that is, heavy atoms with only a few electrons. Also, in close collisions of heavy ions (atomic number Z 1 ) and heavy target atoms (Z 2 ) short-lived quasi-atomic 'superheavy' systems will be formed - huge 'atoms', where the inner electrons are bound in the field of the combined charge Z 1 + Z 2 , which exceeds by far the charge of the known elements (Z <= 109). Those exotic or transient superheavy atoms delivered from the heavy ion accelerator make it possible to study for the first time in a terrestrial laboratory exotic, but fundamental, processes, which occur only inside stars. Some of the basic research carried out with the UNILAC is discussed. This includes investigation of highly charged heavy atoms with the beam-foil method, the spectroscopy of highly charged slow-recoil ions, atomic collision studies with highly ionised, decelerated ions and investigations of super-heavy quasi-atoms. (U.K.)

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

Science.gov (United States)

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.

Production of the sealed gamma-radiation sources of with iridium-192 radionuclide at the WWR-K research reactor

International Nuclear Information System (INIS)

Petukhov, V.K.; Chernayev, V.P.; Chabeyev, N.T.; Ermakov, E.L.; Chakrov, P.V.

2005-01-01

Full text: Conversion orientation of the WWR-K research reactor activity was established after renewal of its operation in 1997. A priority in reactor works was determined in the decision of tasks of practical use of nuclear technologies in a national economy in the next directions: in an industry, public health services and agriculture. The items of prime tasks: development and introduction of radiation technologies and manufacturing of radioisotopes for industry. This task included both scientific and technical program in the list of works of the Republican goals. At the WWR-K reactor within the framework of the this task solution the works on pilot production of the sealed sources of radioactive radiations (SSRR) with Ir-192 radionuclide for an industry of Republic of Kazakhstan were made. Organizational questions related to the Kazakhstan authority body and the regulating documentation were solved the first of all. The second stage was the development of the techniques of creating of devices providing an samples irradiation in reactor, control of sources sealing, measurements of the equivalent radiation doze from sources and high-quality support of SSRR manufacture over all technological way. At the third stage was made a little quantity SSRR with Ir-192 radionuclide, such as GIID-A1 (G6), for 'TEKOPS-660' Gammaray Projectors. This work served as experimental check of the decisions correctness, and has allowed to remove those lacks, to find out which it was possible only during direct manufacturing of radioactive sources. During performance of all these works the following was carried out: development and release of the documents and specifications regulating work on SSRR manufacture at the Institute of Nuclear Physics; personnel preparation and certification; preparation and equipment providing of reactor hot chambers by additional devices for work with irradiated iridium samples; development and manufacturing of the devices for iridium samples irradiation in

Cationic polyhydrido cluster complexes. Crystal and molecular structures of (Ir3(Ph2P(CH2)3PPh2)3(H)7(CO))2+ and (Ir3(Ph2P(CH2)2(2-py))3(H)7)2+

International Nuclear Information System (INIS)

Hsienhau Wang; Casalnuovo, A.L.; Johnson, B.J.; Mueting, A.M.; Pignolet, L.H.

1988-01-01

Two new cationic polyhydrido cluster complexes of iridium have been synthesized and characterized by single-crystal x-ray diffraction and by ir and 1 H and 31 P NMR spectroscopy (Ir 3 (dppp) 3 (H) 7 (CO)) 2+ (2) and (Ir3 (PN) 3 (H) 7)2+ (5), where dppp = 1,3-bis(diphenylphosphino)propane and PN = 1-(2-pyridyl)-2-(diphenylphosphino)ethane, were synthesized by the reaction of CO with (Ir 3 (dppp) 3 (H) 7 ) 2+ (1) in CH 2 Cl 2 solution and H 2 with (Ir(PN)(COD)) + (4) in CH 3 OH solution, respectively. Crystal structures for both compounds is reported. The hydride positions were not located in the crystal structure analyses but were deduced from structural and 1 H NMR data. The molecular structure of 2 consists of a bilateral triangle of three iridium atoms with a carbonyl at the vertex and a chelating dppp ligand on each iridium atom. 1 H NMR data with use of acetone-d 6 as solvent showed that 2 possesses four doubly bridging hydrides and three terminal hydrides, yielding C 1 symmetry. The molecular structure of 5 consists of an approximately equilateral triangle of three iridium atoms (average Ir-Ir distance 2.746 (1) angstrom) with one PN ligand chelated to each iridium atom. 1 H NMR analysis, with use of CD 2 Cl 2 as solvent, showed that 5 has one triply bridging hydride and six terminal hydrides, giving C 3 symmetry. (Ir 3 (dppp) 3 (H) 7 (CH 3 C 6 H 4 NC)) 2+ (3) a complex structurally analogous to 2, was synthesized from 1 and p-tolyl isocyanide in CH 2 Cl 2 solution and characterized by ir and 1 H and 31 P NMR spectroscopy. 44 refs., 3 figs., 3 tabs

Experimental realization of suspended atomic chains composed of different atomic species

International Nuclear Information System (INIS)

Bettini, Jefferson; Ugarte, Daniel; Sato, Fernando; Galvao, Douglas Soares; Coura, Pablo Zimmerman; Dantas, Socrates de Oliveira

2006-01-01

We report high resolution transmission electron microscopy (HRTEM) and molecular dynamics results of the first experimental test of suspended atomic chains composed of different atomic species formed from spontaneous stretching of metallic nanowires. (author)

Solid-phase extraction of iridium from soil and water samples by using activated carbon cloth prior to its spectrophotometric determination.

Science.gov (United States)

Ozkantar, Nebiye; Yilmaz, Erkan; Soylak, Mustafa; Tuzen, Mustafa

2015-08-01

A solid-phase extraction method for separation and preconcentration of Ir(IV) ion by using activated carbon cloth (ACC) has been presented. Ir(IV) as their 1-(2-pyridylazo) 2-naphtol (PAN) chelate was adsorbed on ACC at pH 2.0 and was eluted from ACC with acidic dimethylformamide (DMF). The Ir(IV) concentration was determined at 536 nm as Ir(IV)-PAN complex by using UV-vis spectrophotometer. The analytical parameters including pH, sample and eluent flow rates, amount of PAN, eluent type, concentration, and sample volume were optimized. The effects of foreign ions on the recoveries of iridium were also investigated. The preconcentration factor was calculated as 60. The limit of detection (LOD) and the limit of quantification (LOQ) of the method were found as 0.039 and 0.129 μg L(-1), respectively. The method was applied to soil and water samples for iridium determination.

Cationic Heteroleptic Cyclometalated Iridium Complexes with 1-Pyridylimidazo[1,5-alpha]pyridine Ligands: Exploitation of an Efficient Intersystem Crossing

Czech Academy of Sciences Publication Activity Database

Volpi, G.; Garino, C.; Salassa, L.; Fiedler, Jan; Hardcastle, K.; Gobetto, R.; Nervi, C.

2009-01-01

Roč. 15, č. 26 (2009), s. 6415-6427 ISSN 0947-6539 R&D Projects: GA MŠk OC 140; GA MŠk LC510 Institutional research plan: CEZ:AV0Z40400503 Keywords : density functional calculation * fluorescence * intersystem crossing * iridium * phosphorescence Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.382, year: 2009

The production and investigation of cold antihydrogen atoms

International Nuclear Information System (INIS)

Pittner, H.

2005-04-01

This work reports on experiments in which antihydrogen atoms have been produced in cryogenic Penning traps from antiproton and positron plasmas by two different methods and on experiments that have been carried out subsequently in order to investigate the antihydrogen atoms. By the first method antihydrogen atoms have been formed during the process of positron cooling of antiprotons in so called nested Penning traps and detected via a field ionization method. A measurement of the state distribution has revealed that the antihydrogen atoms are formed in highly excited states. This suggests along with the high production rate that the antihydrogen atoms are formed by three-body recombination processes and subsequent collisional deexcitations. However current theory cannot yet account for the measured state distribution. Typical radii of the detected antihydrogen atoms lie in the range between 0.4 μm and 0.15 μm. The deepest bound antihydrogen atoms have radii below 0.1 μm.The kinetic energy of the weakest bound antihydrogen atoms has been measured to about 200 meV. By the second method antihydrogen atoms have been synthesized in charge-exchange processes. Lasers are used to produce a Rydberg cesium beam within the cryogenic Penning trap that collides with trapped positrons so that Rydberg positronium atoms are formed via charge-exchange reactions. The Rydberg positronium atoms that collide with nearby stored antiprotons form antihydrogen atoms in charge-exchange reactions. So far, 14±4 antihydrogen atoms have been detected background-free via a field-ionization method. The antihydrogen atoms produced via the two-step charge-exchange mechanism are expected to have a temperature of 4.2 K, the temperature of the antiprotons from which they are formed

Enantiopure Ferrocene-Based Planar-Chiral Iridacycles: Stereospecific Control of Iridium-Centred Chirality.

Science.gov (United States)

Arthurs, Ross A; Ismail, Muhammad; Prior, Christopher C; Oganesyan, Vasily S; Horton, Peter N; Coles, Simon J; Richards, Christopher J

2016-02-24

Reaction of [IrCp*Cl2 ]2 with ferrocenylimines (Fc=NAr, Ar=Ph, p-MeOC6 H4 ) results in ferrocene C-H activation and the diastereoselective synthesis of half-sandwich iridacycles of relative configuration Sp *,RIr *. Extension to (S)-2-ferrocenyl-4-(1-methylethyl)oxazoline gave highly diastereoselective control over the new elements of planar chirality and metal-based pseudo-tetrahedral chirality, to give both neutral and cationic half-sandwich iridacycles of absolute configuration Sc ,Sp ,RIr . Substitution reactions proceed with retention of configuration, with the planar chirality controlling the metal-centred chirality through an iron-iridium interaction in the coordinatively unsaturated cationic intermediate. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Methods of forming single source precursors, methods of forming polymeric single source precursors, and single source precursors and intermediate products formed by such methods

Science.gov (United States)

Fox, Robert V.; Rodriguez, Rene G.; Pak, Joshua J.; Sun, Chivin; Margulieux, Kelsey R.; Holland, Andrew W.

2012-12-04

Methods of forming single source precursors (SSPs) include forming intermediate products having the empirical formula 1/2{L.sub.2N(.mu.-X).sub.2M'X.sub.2}.sub.2, and reacting MER with the intermediate products to form SSPs of the formula L.sub.2N(.mu.-ER).sub.2M'(ER).sub.2, wherein L is a Lewis base, M is a Group IA atom, N is a Group IB atom, M' is a Group IIIB atom, each E is a Group VIB atom, each X is a Group VIIA atom or a nitrate group, and each R group is an alkyl, aryl, vinyl, (per)fluoro alkyl, (per)fluoro aryl, silane, or carbamato group. Methods of forming polymeric or copolymeric SSPs include reacting at least one of HE.sup.1R.sup.1E.sup.1H and MER with one or more substances having the empirical formula L.sub.2N(.mu.-ER).sub.2M'(ER).sub.2 or L.sub.2N(.mu.-X).sub.2M'(X).sub.2 to form a polymeric or copolymeric SSP. New SSPs and intermediate products are formed by such methods.

Dosimetry of wires and single ribbons of Iridium 192; Dosimetria de alambres y ribbons individuales de Iridio-192

Energy Technology Data Exchange (ETDEWEB)

Mazzucco, L.D. [Centro Medico Nuclear S.R.L. San Juan (Argentina)

1998-12-31

The objective of this work is in order to present in table formats the dosimetry of wires and single ribbons of Iridium with lengths 1-12 cm for each one linear source along the bisector which is perpendicular at tissue sources (water) computed for linear activity 1 mCi/cm in the case of wires, and 1 mCi/seed for ribbons. The above tables are of direct use, adaptable at particular cases so they facilitate logarithmic graphics of doses in function of the distance for interpolation and use in the treatments planning. It was shown that for two sources with identical linear activity and total length, one of the equidistant seeds at 1 cm (ribbon) and one wire on the other hand, the differences in dose rates in near positions can be about the 15% so corroborating that it is not possible to use wire tables for seeds neither vice versa. Moreover it was elaborated tables of practical direct use for dose rate in water at c Gy/hr for wires and Ribbons 1-12 cm length and from 0.5-10 cm of distance in the perpendicular bisector at the Iridium implant. (Author)

High-latitude poynting flux from combined Iridium and SuperDARN data

Directory of Open Access Journals (Sweden)

C. L. Waters

2004-09-01

Full Text Available Field-aligned currents convey stress between the magnetosphere and ionosphere, and the associated low altitude magnetic and electric fields reflect the flow of electromagnetic energy to the polar ionosphere. We introduce a new technique to measure the global distribution of high latitude Poynting flux, S||, by combining electric field estimates from the Super Dual Auroral Radar Network (SuperDARN with magnetic perturbations derived using magnetometer data from the Iridium satellite constellation. Spherical harmonic methods are used to merge the data sets and calculate S|| for any magnetic local time (MLT from the pole to 60° magnetic latitude (MLAT. The effective spatial resolutions are 2° MLAT, 2h MLT, and the time resolution is about one hour due to the telemetry rate of the Iridium magnetometer data. The technique allows for the assessment of high-latitude net S|| and its spatial distribution on one hour time scales with two key advantages: (1 it yields the net S|| including the contribution of neutral winds; and (2 the results are obtained without recourse to estimates of ionosphere conductivity. We present two examples, 23 November 1999, 14:00-15:00 UT, and 11 March 2000, 16:00-17:00 UT, to test the accuracy of the technique and to illustrate the distributions of S|| that it gives. Comparisons with in-situ S|| estimates from DMSP satellites show agreement to a few mW/m2 and in the locations of S|| enhancements to within the technique's resolution. The total electromagnetic energy flux was 50GW for these events. At auroral latitudes, S|| tends to maximize in the morning and afternoon in regions less than 5° in MLAT by two hours in MLT having S||=10 to 20mW/m2 and total power up to 10GW. The power poleward of the Region 1 currents is about one-third of the total power, indicating significant energy flux over the polar cap.

Rhodium, iridium and nickel complexes with a 1,3,5-triphenylbenzene tris-MIC ligand. Study of the electronic properties and catalytic activities

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Carmen Mejuto

2015-12-01

Full Text Available The coordination versatility of a 1,3,5-triphenylbenzene-tris-mesoionic carbene ligand is illustrated by the preparation of complexes with three different metals: rhodium, iridium and nickel. The rhodium and iridium complexes contained the [MCl(COD] fragments, while the nickel compound contained [NiCpCl]. The preparation of the tris-MIC (MIC = mesoionic carbene complex with three [IrCl(CO2] fragments, allowed the estimation of the Tolman electronic parameter (TEP for the ligand, which was compared with the TEP value for a related 1,3,5-triphenylbenzene-tris-NHC ligand. The electronic properties of the tris-MIC ligand were studied by cyclic voltammetry measurements. In all cases, the tris-MIC ligand showed a stronger electron-donating character than the corresponding NHC-based ligands. The catalytic activity of the tri-rhodium complex was tested in the addition reaction of arylboronic acids to α,β-unsaturated ketones.

Cyclometalated Iridium(III) Carbene Phosphors for Highly Efficient Blue Organic Light-Emitting Diodes.

Science.gov (United States)

Chen, Zhao; Wang, Liqi; Su, Sikai; Zheng, Xingyu; Zhu, Nianyong; Ho, Cheuk-Lam; Chen, Shuming; Wong, Wai-Yeung

2017-11-22

Five deep blue carbene-based iridium(III) phosphors were synthesized and characterized. Interestingly, one of them can be fabricated into deep blue, sky blue and white organic light-emitting diodes (OLEDs) through changing the host materials and exciton blocking layers. These deep and sky blue devices exhibit Commission Internationale de l'Éclairage (CIE) coordinates of (0.145, 0.186) and (0.152, 0.277) with external quantum efficiency (EQE) of 15.2% and 9.6%, respectively. The EQE of the deep blue device can be further improved up to 19.0% by choosing a host with suitable energy level of its lowest unoccupied molecular orbital (LUMO).

Atomic nucleus and elementary particles

International Nuclear Information System (INIS)

Zakrzewski, J.

1976-01-01

Negatively charged leptons and hadrons can be incorporated into atomic shells forming exotic atoms. Nucleon resonances and Λ hyperons can be considered as constituents of atomic nuclei. Information derived from studies of such exotic systems enriches our knowledge of both the interactions of elementary particles and of the structure of atomic nuclei. (author)

Systematics of atom-atom collision strengths at high speeds

International Nuclear Information System (INIS)

Gillespie, G.H.; Inokuti, M.

1980-01-01

The collision strengths for atom-atom collisions at high speeds are calculated in the first Born approximation. We studied four classes of collisions, distinguished depending upon whether each of the collision partners becomes excited or not. The results of numerical calculations of the collision strengths are presented for all neutral atoms with Z< or =18. The calculations are based on atomic form factors and incoherent scattering functions found in the literature. The relative contribution of each class of collision processes to the total collision cross section is examined in detail. In general, inelastic processes dominate for low-Z atoms, while elastic scattering is more important for large Z. Other systematics of the collision strengths are comprehensively discussed. The relevant experimental literature has been surveyed and the results of this work for the three collision systems H-He, He-He, and H-Ar are compared with the data for electron-loss processes. Finally, suggestions are made for future work in measurements of atom-atom and ion-atom collision cross sections

mer-Bis[3,5-difluoro-2-(2-pyridylphenyl-κ2C1,N]{5-(2-pyridyl-κN-3-[3-(4-vinylbenzyloxyphenyl]-1,2,4-triazol-1-ido}iridium(III methanol solvate

Directory of Open Access Journals (Sweden)

Peter G. Jones

2010-01-01

Full Text Available In the title compound, [Ir(C11H6F2N2(C22H17N4O]·CH3OH, the coordination at iridium is essentially octahedral, but with distortions associated with the bite angles of the ligands [76.25 (9–80.71 (12°] and the differing trans influences of C and N ligands [Ir—N = 2.04 Å (average trans to N but 2.14 Å trans to C]. All three bidentate ligands have coordinating ring systems that are almost coplanar [interplanar angles = 1.7 (1–3.8 (2°]. The vinylbenzyl group is disordered over two positions with occupations of 0.653 (4 and 0.347 (4. The methanol solvent molecule is involved in a classical O—H...N hydrogen bond to a triazole N atom.

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

Science.gov (United States)

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.

Crystal structures of fac-trichloridotris(trimethylphosphane-κPrhodium(III monohydrate and fac-trichloridotris(trimethylphosphane-κPrhodium(III methanol hemisolvate: rhodium structures that are isotypic with their iridium analogs

Directory of Open Access Journals (Sweden)

Joseph S. Merola

2015-02-01

Full Text Available The crystal structures of two solvates of fac-trichloridotris(trimethylphosphane-κPrhodium(III are reported, i.e. one with water in the crystal lattice, fac-[RhCl3(Me3P3]·H2O, and one with methanol in the crystal lattice, fac-[RhCl3(Me3P3]·0.5CH3OH. These rhodium compounds exhibit distorted octahedral coordination spheres at the metal and are isotypic with the analogous iridium compounds previously reported by us [Merola et al. (2013. Polyhedron, 54, 67–73]. Comparison is made between the rhodium and iridium compounds, highlighting their isostructural relationships.

The behavior of various chemical forms of nickel in graphite furnace atomic absorption spectrometry under different chemical modification approaches

International Nuclear Information System (INIS)

Kowalewska, Zofia

2012-01-01

Various organic and inorganic Ni forms were investigated using graphite furnace atomic absorption spectrometry. Experiments without chemical modification showed a wide range of characteristic mass values for Ni (from 6.7 to 29 pg) and the importance of interaction with graphite. With the aim of achieving signal unification of organic Ni forms, different ways of chemical modification were tested. Some rules that govern the behavior of Ni were found and confirmed a significant role of the organic component of the analyte molecule in the analytical process. The application of air as an internal furnace gas in the pyrolysis phase and the Pd modifier injected with the sample solution improved the signal of porphyrins, while the application of iodine and methyltrioctylammonium chloride was required for organic compounds containing oxygen-bound Ni atoms. The Ni signal was strongly diminished when an aqueous solution containing hydrochloric acid was measured with the Pd modifier injected over the sample. Using the developed analytical methods, the range of characteristic mass values for various Ni forms totally dissolved in organic or aqueous solution was 6.5–7.9 pg. - Highlights: ► Some rules that govern behavior of organic Ni forms during GFAAS analysis were found. ► Interaction with graphite can significantly influence evaporation of porphyrins. ► Determination of Ni in form of porphyrins needs Pd organic modifier and air ashing. ► Determination of Ni in O-bound organic compounds needs pretreatment with I2+MTOACl. ► Chemical modification for GFAAS determination of Ni in HCl-containing solution.

Hydrogen transfer reduction of polyketones catalyzed by iridium complexes: a novel route towards more biocompatible materials.

Science.gov (United States)

Milani, Barbara; Crottib, Corrado; Farnetti, Erica

2008-09-14

Transfer hydrogenation from 2-propanol to CO/4-methylstyrene and CO/styrene polyketones was catalyzed by [Ir(diene)(N-N)X] (N-N = nitrogen chelating ligand; X = halogen) in the presence of a basic cocatalyst. The reactions were performed using dioxane as cosolvent, in order to overcome problems due to low polyketone solubility. The polyalcohols were obtained in yields up to 95%, the conversions being markedly dependent on the nature of the ligands coordinated to iridium as well as on the experimental conditions.

Breakup of relativistic π+π- atoms in matter

International Nuclear Information System (INIS)

Afanasyev, L.G.; Tarasov, A.V.

1996-01-01

The relativistic motion of atoms formed by π+ and π- mesons in matter is considered. Exact analytic expressions for the form factors of hydrogenlike atoms for discrete-discrete transitions are obtained in a form convenient for numerical calculations. The total and transition cross sections for the interaction of π+π- atoms with matter are calculated in the Born approximation. The evolution of atomic-state populations is treated in terms of kinetic equations. The method of calculation makes it possible to obtain the populations of discrete atomic states, as well as the probability of transitions to the continuous spectrum (ionization). The proposed method yields the first experimental estimate of the lifetime of the π+π- atom

Atom chips: mesoscopic physics with cold atoms

International Nuclear Information System (INIS)

Krueger, P.; Wildermuth, S.; Hofferberth, S.; Haller, E.; GAllego Garcia, D.; Schmiedmayer, J.

2005-01-01

Full text: Cold neutral atoms can be controlled and manipulated in microscopic potentials near surfaces of atom chips. These integrated micro-devices combine the known techniques of atom optics with the capabilities of well established micro- and nanofabrication technology. In analogy to electronic microchips and integrated fiber optics, the concept of atom chips is suitable to explore the domain of mesoscopic physics with matter waves. We use current and charge carrying structures to form complex potentials with high spatial resolution only microns from the surface. In particular, atoms can be confined to an essentially one-dimensional motion. In this talk, we will give an overview of our experiments studying the manipulation of both thermal atoms and BECs on atom chips. First experiments in the quasi one-dimensional regime will be presented. These experiments profit from strongly reduced residual disorder potentials caused by imperfections of the chip fabrication with respect to previously published experiments. This is due to our purely lithographic fabrication technique that proves to be advantageous over electroplating. We have used one dimensionally confined BECs as an ultra-sensitive probe to characterize these potentials. These smooth potentials allow us to explore various aspects of the physics of degenerate quantum gases in low dimensions. (author)

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

International Nuclear Information System (INIS)

Millard, H.T. Jr.

1987-01-01

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-free 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 peroxide 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 was 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. (author)

Coupling of Electron Transfer and Bond Dissociation Processes in Dinuclear Complexes with Rhodium and Iridium Reaction Centers Bridged by 2,2'-Bipyrimidine

Czech Academy of Sciences Publication Activity Database

Kaim, W.; Reinhardt, R.; Greulich, S.; Sieger, M.; Klein, A.; Fiedler, Jan

2001-01-01

Roč. 66, č. 2 (2001), s. 291-306 ISSN 0010-0765 R&D Projects: GA MŠk OC D15.10 Institutional research plan: CEZ:AV0Z4040901 Keywords : EPR spectroscopy * iridium complexes * rhodium complexes Subject RIV: CG - Electrochemistry Impact factor: 0.778, year: 2001

Effect of chemical modification on behavior of various organic vanadium forms during analysis by electrothermal atomic absorption spectrometry

International Nuclear Information System (INIS)

Kowalewska, Zofia

2007-01-01

The behavior of various organic V forms dissolved in xylene during analysis by electrothermal atomic absorption spectrometry (ETAAS) was compared. The investigated analyte forms included compounds with vanadium at the oxidation state III, IV or V, as well as N, O or S atoms in molecules. Another group consisted of petroleum products containing naturally-occurring V species. Although the characteristic mass determined under different analytical conditions was in the very wide range from 11 up to 55 pg, some rules of V behavior were found. In the case of porphyrins and petroleum products, the application of Pd as a chemical modifier (xylene solution of Pd(II) acetylacetonate) seemed to be crucial. It was shown that Pd must be introduced to a furnace together with a sample. Pd injected and thermally pretreated before the sample injection was less effective for porphyrins and the petroleum products, but it increased signals of V compounds containing O as donor atom. The iodine pretreatment followed by the methyltrioctylammonium chloride (MTOACl) pretreatment was advantageous for these V forms. The air ashing in a graphite tube appeared to be important to improve decomposition of the petroleum products. No significant influence of the V oxidation state on the analytical signal was observed. The behavior of V contained in two Conostan oil standards, the single-element and the S21 multielement standard, was different in many situations. Probably, the joint action of other elements is responsible for this effect. In general, chemical modification was applied in the work for two reasons: to reduce the V volatility (in some cases losses at about 300 deg. C were observed) and to enhance the atomization efficiency. For routine analysis air ashing, modification by Pd introduced into the furnace together with the sample solution and petroleum products with known V content as standard is recommended. Using this procedure the characteristic mass varied from 16 to 19 pg for

Mixed-metal cluster chemistry. 28. Core enlargement of tungsten-iridium clusters with alkynyl, ethyndiyl, and butadiyndiyl reagents.

Science.gov (United States)

Dalton, Gulliver T; Viau, Lydie; Waterman, Susan M; Humphrey, Mark G; Bruce, Michael I; Low, Paul J; Roberts, Rachel L; Willis, Anthony C; Koutsantonis, George A; Skelton, Brian W; White, Allan H

2005-05-02

Reaction of [WIr3(mu-CO)3(CO)8(eta-C5Me5)] (1c) with [W(C[triple bond]CPh)(CO)3(eta-C5H5)] afforded the edge-bridged tetrahedral cluster [W2Ir3(mu4-eta2-C2Ph)(mu-CO)(CO)9(eta-C5H5)(eta-C5Me5)] (3) and the edge-bridged trigonal-bipyramidal cluster [W3Ir3(mu4-eta2-C2Ph)(mu-eta2-C=CHPh)(Cl)(CO)8(eta-C5Me5)(eta-C5H5)2] (4) in poor to fair yield. Cluster 3 forms by insertion of [W(C[triple bond]CPh)(CO)3(eta-C5H5)] into Ir-Ir and W-Ir bonds, accompanied by a change in coordination mode from a terminally bonded alkynyl to a mu4-eta2 alkynyl ligand. Cluster 4 contains an alkynyl ligand interacting with two iridium atoms and two tungsten atoms in a mu4-eta2 fashion, as well as a vinylidene ligand bridging a W-W bond. Reaction of [WIr3(CO)11(eta-C5H5)] (1a) or 1c with [(eta-C5H5)(CO)2 Ru(C[triple bond]C)Ru(CO)2(eta-C5H5)] afforded [Ru2WIr3(mu5-eta2-C2)(mu-CO)3(CO)7(eta-C5H5)2(eta-C5R5)] [R = H (5a), Me (5c)] in low yield, a structural study of 5a revealing a WIr3 butterfly core capped and spiked by Ru atoms; the diruthenium ethyndiyl precursor has undergone Ru-C scission, with insertion of the C2 unit into a W-Ir bond of the cluster precursor. Reaction of [W2Ir2(CO)10(eta-C5H5)2] with the diruthenium ethyndiyl reagent gave [RuW2Ir2{mu4-eta2-(C2C[triple bond]C)Ru(CO)2(eta-C5H5)}(mu-CO)2(CO)6(eta-C5H5)3] (6) in low yield, a structural study of 6 revealing a butterfly W2Ir2 unit capped by a Ru(eta-C5H5) group resulting from Ru-C scission; the terminal C2 of a new ruthenium-bound butadiyndiyl ligand has been inserted into the W-Ir bond. Reaction between 1a, [WIr3(CO)11(eta-C5H4Me)] (1b), or 1c and [(eta-C5H5)(CO)3W(C[triple bond]CC[triple bond]C)W(CO)3(eta-C5H5)] afforded [W2Ir3{mu4-eta2-(C2C[triple bond]C)W(CO)3(eta-C5H5)}(mu-CO)2(CO)2(eta-C5H5)(eta-C5R5)] [R = H (7a), Me (7c); R5 = H4Me (7b)] in good yield, a structural study of 7c revealing it to be a metallaethynyl analogue of 3.

Self-forming Al oxide barrier for nanoscale Cu interconnects created by hybrid atomic layer deposition of Cu–Al alloy

Energy Technology Data Exchange (ETDEWEB)

Park, Jae-Hyung; Han, Dong-Suk; Kang, You-Jin [Division of Nanoscale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Shin, So-Ra; Park, Jong-Wan, E-mail: jwpark@hanyang.ac.kr [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

2014-01-15

The authors synthesized a Cu–Al alloy by employing alternating atomic layer deposition (ALD) surface reactions using Cu and Al precursors, respectively. By alternating between these two ALD surface chemistries, the authors fabricated ALD Cu–Al alloy. Cu was deposited using bis(1-dimethylamino-2-methyl-2-butoxy) copper as a precursor and H{sub 2} plasma, while Al was deposited using trimethylaluminum as the precursor and H{sub 2} plasma. The Al atomic percent in the Cu–Al alloy films varied from 0 to 15.6 at. %. Transmission electron microscopy revealed that a uniform Al-based interlayer self-formed at the interface after annealing. To evaluate the barrier properties of the Al-based interlayer and adhesion between the Cu–Al alloy film and SiO{sub 2} dielectric, thermal stability and peel-off adhesion tests were performed, respectively. The Al-based interlayer showed similar thermal stability and adhesion to the reference Mn-based interlayer. Our results indicate that Cu–Al alloys formed by alternating ALD are suitable seed layer materials for Cu interconnects.

Self-forming Al oxide barrier for nanoscale Cu interconnects created by hybrid atomic layer deposition of Cu–Al alloy

International Nuclear Information System (INIS)

Park, Jae-Hyung; Han, Dong-Suk; Kang, You-Jin; Shin, So-Ra; Park, Jong-Wan

2014-01-01

The authors synthesized a Cu–Al alloy by employing alternating atomic layer deposition (ALD) surface reactions using Cu and Al precursors, respectively. By alternating between these two ALD surface chemistries, the authors fabricated ALD Cu–Al alloy. Cu was deposited using bis(1-dimethylamino-2-methyl-2-butoxy) copper as a precursor and H 2 plasma, while Al was deposited using trimethylaluminum as the precursor and H 2 plasma. The Al atomic percent in the Cu–Al alloy films varied from 0 to 15.6 at. %. Transmission electron microscopy revealed that a uniform Al-based interlayer self-formed at the interface after annealing. To evaluate the barrier properties of the Al-based interlayer and adhesion between the Cu–Al alloy film and SiO 2 dielectric, thermal stability and peel-off adhesion tests were performed, respectively. The Al-based interlayer showed similar thermal stability and adhesion to the reference Mn-based interlayer. Our results indicate that Cu–Al alloys formed by alternating ALD are suitable seed layer materials for Cu interconnects

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

Science.gov (United States)

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.

Electron-beam welding of thorium-doped iridium alloy sheets

International Nuclear Information System (INIS)

David, S.A.; Liu, C.T.; Hudson, J.D.

1979-04-01

Modified iridium alloys containing 100 ppM Th were found to be very susceptible to hot-cracking during gas tungsten-arc and electron-beam welding. However, the electron-beam welding process showed greater promise of success in welding these alloys, in particular Ir--0.3% W doped with 200 ppM Th and 50 ppM Al. The weldability of this particular alloy was extremely sensitive to the welding parameters, such as beam focus condition and welding speed, and the resulting fusion zone structure. At low speed successful electron-beam welds were made over a narrow range of beam focus conditions. However, at high speeds successful welds can be made over an extended range of focus conditions. The fusion zone grain structure is a strong function of welding speed and focus condition, as well. In the welds that showed hot-cracking, a region of positive segregation of thorium was identified at the fusion boundary. This highly thorium-segregated region seems to act as a potential source for the nucleation of a liquation crack, which later grows as a centerline crack

An important atomic process in the CVD growth of graphene: Sinking and up-floating of carbon atom on copper surface

International Nuclear Information System (INIS)

Li, Yingfeng; Li, Meicheng; Gu, TianSheng; Bai, Fan; Yu, Yue; Trevor, Mwenya; Yu, Yangxin

2013-01-01

By density functional theory (DFT) calculations, the early stages of the growth of graphene on copper (1 1 1) surface are investigated. At the very first time of graphene growth, the carbon atom sinks into subsurface. As more carbon atoms are adsorbed nearby the site, the sunken carbon atom will spontaneously form a dimer with one of the newly adsorbed carbon atoms, and the formed dimer will up-float on the top of the surface. We emphasize the role of the co-operative relaxation of the co-adsorbed carbon atoms in facilitating the sinking and up-floating of carbon atoms. In detail: when two carbon atoms are co-adsorbed, their co-operative relaxation will result in different carbon–copper interactions for the co-adsorbed carbon atoms. This difference facilitates the sinking of a single carbon atom into the subsurface. As a third carbon atom is co-adsorbed nearby, it draws the sunken carbon atom on top of the surface, forming a dimer. Co-operative relaxations of the surface involving all adsorbed carbon atoms and their copper neighbors facilitate these sinking and up-floating processes. This investigation is helpful for the deeper understanding of graphene synthesis and the choosing of optimal carbon sources or process.

Radiation dose evaluation for hypothetical accident with transport package containing Iridium-192 source

International Nuclear Information System (INIS)

Trontl, K.; Bace, M.; Pevec, D.

2002-01-01

The aim of this paper is to evaluate dose rates for a hypothetical accident with transport package containing Iridium-192 source and to design additional shielding necessary for the safe unloading of the container, assuming that during the unloading process the whole contents of a radioactive source is unshielded and that the operation is going to take place at the site where a working area exists in the vicinity of the unloading location. Based on the calculated radiation dose rates, a single arrangement of the additional concrete shields necessary for reduction of the gamma dose rates to the permitted level is proposed. The proposed solution is optimal considering safety on one hand and costs on the other.(author)

Iridium-191m radionuclide angiocardiography detection and quantitation of left-to-rigth shunts

International Nuclear Information System (INIS)

Treves, S.; Fujii, A.; Cheng, C.; Kuruc, A.

1983-01-01

The purpose of this study was to determine whether Iridium-191m (Ir-191m) could replace Technetium-99m (Tc-99m) in the detection and quantitation of left-to-right shunts. It was demonstrated that Ir-191m radionuclide angiography is a safe, rapid, and accurate method for the detection and quantitation of left-to-right shunts with very low radiation dose to the patient. It is also possible with this radiotracer to evaluate other aspects of the anatomy and physiology of the circulation such as ventricular function, patency of major vessels, renal and cerebral perfusion. Further improvements on 0s-191 production, generator design and gamma cameras would expand the use of this ultrashort-lived radionuclide

Investigating the atomic level influencing factors of glass forming ability in NiAl and CuZr metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Sedighi, Sina; Kirk, Donald Walter; Singh, Chandra Veer, E-mail: chandraveer.singh@utoronto.ca; Thorpe, Steven John [Department of Materials Science and Engineering, University of Toronto, Room 140, 184 College Street, Toronto, Ontario M5S 3E4 (Canada)

2015-09-21

Bulk metallic glasses are a relatively new class of amorphous metal alloy which possess unique mechanical and magnetic properties. The specific concentrations and combinations of alloy elements needed to prevent crystallization during melt quenching remains poorly understood. A correlation between atomic properties that can explain some of the previously identified glass forming ability (GFA) anomalies of the NiAl and CuZr systems has been identified, with these findings likely extensible to other transition metal–transition metal and transition metal–metalloid (TM–M) alloy classes as a whole. In this work, molecular dynamics simulation methods are utilized to study thermodynamic, kinetic, and structural properties of equiatomic CuZr and NiAl metallic glasses in an attempt to further understand the underlying connections between glass forming ability, nature of atomic level bonding, short and medium range ordering, and the evolution of structure and relaxation properties in the disordered phase. The anomalous breakdown of the fragility parameter as a useful GFA indicator in TM–M alloy systems is addressed through an in-depth investigation of bulk stiffness properties and the evolution of (pseudo)Gruneisen parameters over the quench domain, with the efficacy of other common glass forming ability indicators similarly being analyzed through direct computation in respective CuZr and NiAl systems. Comparison of fractional liquid-crystal density differences in the two systems revealed 2-3 times higher values for the NiAl system, providing further support for its efficacy as a general purpose GFA indicator.

Influence of oxidation state on the pH dependence of hydrous iridium oxide films

International Nuclear Information System (INIS)

Steegstra, Patrick; Ahlberg, Elisabet

2012-01-01

Many electrochemical reactions taking place in aqueous solution consume or produce protons. The pH in the diffusion layer can therefore be significantly altered during the reaction and there is a need for in situ pH measurements tracing this near surface pH. In the present paper the rotating ring disc technique was used to measure near surface pH changes during oxygen reduction, utilising hydrous iridium oxide as the pH sensing probe. Before such experiments a good understanding of the pH sensing properties of these films is required and the impact of the oxidation state of the film on the pH sensing properties was investigated as well as the influence of solution redox species. The pH sensitivity (depicted by dE/dpH) was found to depend on the average oxidation state of the film in a manner resembling the cyclic voltammetry response. In all cases the pH response is “supernernstian” with more than one proton per electron. The origin of this behaviour is discussed in the context of acid-base properties of the film and the existence of both hydrous and anhydrous oxide phases. The pH response depends also on the redox properties of the solution but can be optimised for various purposes by conditioning the film at different potentials. This was clearly illustrated by adding hydrogen peroxide, an intermediate in the oxygen reduction reaction, to the solution. It was shown that hydrous iridium oxide can be used as a reliable in situ pH sensor provided that care is taken to optimise the oxidation state of the film.

Bibliographies on radiation chemistry. 9. Metal ions and complexes. Part A: Cobalt, rhodium, iridium

Energy Technology Data Exchange (ETDEWEB)

Hoffman, M Z; Ross, A B

1986-01-01

The one-electron oxidation and reduction of metal ions and complexes can yield species in unusual oxidation states, and ligand-radicals coordinated to the central metal. These often unstable species can be mechanistically important intermediates in thermal, photochemical, and electrochemical reactions involving metal-containing substances. Their generation via radiolysis provides an alternate means of characterizing them using kinetic and spectroscopic techniques. We hope these bibliographies on the radiation chemistry of metal ions and complexes, presented according to periodic groups, will prove useful to researchers in metallo-redox chemistry. These bibliographies contain only primary literature sources; reviews are not included. However, a list of general review articles on the radiation chemistry of metal ions and complexes is presented here in the first section which covers cobalt, rhodium and iridium, Group 9 in the new IUPAC notation. Additional parts of the bibliography are planned, covering other periodic groups. Part A of the bibliography was prepared by a search of the Radiation Chemistry Data Center Bibliographic Data Base (RCDCbib) through January 1986 for papers on rhodium, iridium and cobalt compounds, and radiolysis (both continuous and pulsed). Papers in which the use of metal compounds was incidental to the primary objective of the study were excluded. Excluded also were publications in unrefereed and obscure sources such as meeting proceedings, internal reports, dissertations, and patents. The majority of the studies in the resultant compilation deal with experiments performed on solutions, mainly aqueous, although a substantial fraction is devoted to solid-state esr measurements. The references are listed in separate sections for each of the metals, and are presented in approximate chronological order.

A Many-Atom Cavity QED System with Homogeneous Atom-Cavity Coupling

OpenAIRE

Lee, Jongmin; Vrijsen, Geert; Teper, Igor; Hosten, Onur; Kasevich, Mark A.

2013-01-01

We demonstrate a many-atom-cavity system with a high-finesse dual-wavelength standing wave cavity in which all participating rubidium atoms are nearly identically coupled to a 780-nm cavity mode. This homogeneous coupling is enforced by a one-dimensional optical lattice formed by the field of a 1560-nm cavity mode.

Synthesis and structure of (tricarbollide)iodide iridium complex [(eta-1-(BuNH)-N-t-1,7,9-C3B8H10)IrI2](2)

Czech Academy of Sciences Publication Activity Database

Loginov, D.A.; Miloserdov, A.M.; Starikova, ZA.; Holub, Josef; Kudinov, AR.

2013-01-01

Roč. 62, č. 5 (2013), s. 1268-1271 ISSN 1066-5285 Institutional support: RVO:61388980 Keywords : iridium * metallacarboranes * tricarbollide Subject RIV: CA - Inorganic Chemistry Impact factor: 0.509, year: 2013

Magnetic atom optics: mirrors, guides, traps, and chips for atoms

Energy Technology Data Exchange (ETDEWEB)

Hinds, E.A.; Hughes, I.G. [Sussex Centre for Optical and Atomic Physics, University of Sussex, Brighton (United Kingdom)

1999-09-21

For the last decade it has been possible to cool atoms to microkelvin temperatures ({approx}1 cm s{sup -1}) using a variety of optical techniques. Light beams provide the very strong frictional forces required to slow atoms from room temperature ({approx}500 m s{sup -1}). However, once the atoms are cold, the relatively weak conservative forces of static electric and magnetic fields play an important role. In our group we have been studying the interaction of cold rubidium atoms with periodically magnetized data storage media. Here we review the underlying principles of the forces acting on atoms above a suitably magnetized substrate or near current-carrying wires. We also summarize the status of experiments. These structures can be used as smooth or corrugated reflectors for controlling the trajectories of cold atoms. Alternatively, they may be used to confine atoms to a plane, a line, or a dot and in some cases to reach the quantum limit of confinement. Atoms levitated above a magnetized surface can be guided electrostatically by wires deposited on the surface. The flow and interaction of atoms in such a structure may form the basis of a new technology, 'integrated atom optics' which might ultimately be capable of realizing a quantum computer. (author)

Atomic bonding between metal and graphene

KAUST Repository

Wang, Hongtao; Feng, Qiong; Cheng, Yingchun; Yao, Yingbang; Wang, Qingxiao; Li, Kun; Schwingenschlö gl, Udo; Zhang, Xixiang; Yang, Wei

2013-01-01

and graphene, agreeing well with density functional theory studies. Single Cr atoms are located in the valleys of a zigzag edge, and few-atom ensembles preferentially form atomic chains by self-assembly. Low migration barriers lead to rich dynamics of metal

High-latitude poynting flux from combined Iridium and SuperDARN data

Directory of Open Access Journals (Sweden)

C. L. Waters

2004-09-01

Full Text Available Field-aligned currents convey stress between the magnetosphere and ionosphere, and the associated low altitude magnetic and electric fields reflect the flow of electromagnetic energy to the polar ionosphere. We introduce a new technique to measure the global distribution of high latitude Poynting flux, S_||, by combining electric field estimates from the Super Dual Auroral Radar Network (SuperDARN with magnetic perturbations derived using magnetometer data from the Iridium satellite constellation. Spherical harmonic methods are used to merge the data sets and calculate S_|| for any magnetic local time (MLT from the pole to 60° magnetic latitude (MLAT. The effective spatial resolutions are 2° MLAT, 2h MLT, and the time resolution is about one hour due to the telemetry rate of the Iridium magnetometer data. The technique allows for the assessment of high-latitude net S_|| and its spatial distribution on one hour time scales with two key advantages: (1 it yields the net S_|| including the contribution of neutral winds; and (2 the results are obtained without recourse to estimates of ionosphere conductivity. We present two examples, 23 November 1999, 14:00-15:00 UT, and 11 March 2000, 16:00-17:00 UT, to test the accuracy of the technique and to illustrate the distributions of S_|| that it gives. Comparisons with in-situ S_|| estimates from DMSP satellites show agreement to a few mW/m² and in the locations of S_|| enhancements to within the technique's resolution. The total electromagnetic energy flux was 50GW for these events. At auroral latitudes, S_|| tends to maximize in the morning and afternoon in regions less than 5° in MLAT by two hours in MLT having S_||=10 to 20mW/m² and total power up to 10GW. The power poleward of the Region 1 currents is about one

Atomic bomb and leukemia

Energy Technology Data Exchange (ETDEWEB)

Ichimaru, M; Tomonaga, M; Amenomori, T; Matsuo, T [Nagasaki Univ. (Japan). School of Medicine

1991-12-01

Characteristic features of the leukemia among atomic bomb survivors were studied. Dose estimates of atomic bomb radiation were based on T65D, but the new dosimetry system DS86 was used for some analyses. The ratio of a single leukemia type to all leukemias was highest for chronic myelogenous leukemia (CML) in Hiroshima, and the occurrence of CML was thought to be most characteristic to atomic bomb radiation induced leukemia. The threshold of CML occurrence in Hiroshima is likely to be between 0.5{approx}0.09 Gy. However, the threshold of acute leukemia appears to be nearly 1 Gy. In the distribution of acute myeloid leukemia (AML) subtypes by French-American-British classification, there was no M3 case in 1 Gy or more group, although several atypical AML cases of survivors were observed. Although aplastic anemia has not increased as a late effect of the atomic bomb radiation exposure, many atypical leukemia or other myeloproliferative diseases who had been diagnosed as aplastic anemia or its related diseases have been experienced among atomic bomb survivors. Chromosome study was conducted using colony forming cells induced by hemopoietic stem cells of peripheral blood of proximal survivors. Same chromosome aberrations were observed in colony forming cells and peripheral T-cells in several atomic bomb survivors. (author).

Atomic bomb and leukemia

International Nuclear Information System (INIS)

Ichimaru, M.; Tomonaga, M.; Amenomori, T.; Matsuo, T.

1991-01-01

Characteristic features of the leukemia among atomic bomb survivors were studied. Dose estimates of atomic bomb radiation were based on T65D, but the new dosimetry system DS86 was used for some analyses. The ratio of a single leukemia type to all leukemias was highest for chronic myelogenous leukemia (CML) in Hiroshima, and the occurrence of CML was thought to be most characteristic to atomic bomb radiation induced leukemia. The threshold of CML occurrence in Hiroshima is likely to be between 0.5∼0.09 Gy. However, the threshold of acute leukemia appears to be nearly 1 Gy. In the distribution of acute myeloid leukemia (AML) subtypes by French-American-British classification, there was no M3 case in 1 Gy or more group, although several atypical AML cases of survivors were observed. Although aplastic anemia has not increased as a late effect of the atomic bomb radiation exposure, many atypical leukemia or other myeloproliferative diseases who had been diagnosed as aplastic anemia or its related diseases have been experienced among atomic bomb survivors. Chromosome study was conducted using colony forming cells induced by hemopoietic stem cells of peripheral blood of proximal survivors. Same chromosome aberrations were observed in colony forming cells and peripheral T-cells in several atomic bomb survivors. (author)

Assessment of density functional theory for bonds formed between rare gases and open-shell atoms: a computational study of small molecules containing He, Ar, Kr and Xe.

Science.gov (United States)

Bertolus, Marjorie; Major, Mohamed; Brenner, Valérie

2012-01-14

The validity of the description of the DFT approximations currently implemented in plane wave DFT codes (LDA, GGA, meta-GGA, hybrid, GGA + empirical dispersion correction) for interactions between rare gases and open-shell atoms which form materials is poorly known. We have performed a first assessment of the accuracy of these functionals for the description of the bonds formed by helium, argon, krypton and xenon with various open-shell atoms. This evaluation has been done on model molecular systems for which precise experimental data are available and reference post-Hartree-Fock calculations (CCSD(T) using large basis sets) are feasible. The results show that when the rare gas atom shares density with the neighbouring atoms, the GGA functionals yield good geometries and qualitatively correct binding energies, even if these are quite significantly overestimated. The use of hybrid functionals enables us to obtain good geometries and satisfactory binding energies. For compounds in which the rare gas atom forms weak dispersive-like bonding, the accuracy yielded by the various functionals is not as good. No functional gives satisfactory binding energies for all the compounds investigated. Several GGA and hybrid functionals yield correct geometries, even if some isomers are not obtained. One GGA functional (PBE) yields qualitatively correct results for the compounds of the three rare gases and several hybrid functionals give satisfactory energies for He compounds. The addition of an empirical dispersive correction improves the results on association compounds, but several isomers are not found.

Assessment of density functional theory for bonds formed between rare gases and open-shell atoms: a computational study of small molecules containing He, Ar, Kr and Xe

International Nuclear Information System (INIS)

Bertolus, Marjorie; Major, Mohamed; Brenner, Valerie

2012-01-01

The validity of the description of the DFT approximations currently implemented in plane wave DFT codes (LDA, GGA, meta-GGA, hybrid, GGA + empirical dispersion correction) for interactions between rare gases and open-shell atoms which form materials is poorly known. We have performed a first assessment of the accuracy of these functionals for the description of the bonds formed by helium, argon, krypton and xenon with various open-shell atoms. This evaluation has been done on model molecular systems for which precise experimental data are available and reference post-Hartree-Fock calculations (CCSD(T) using large basis sets) are feasible. The results show that when the rare gas atom shares density with the neighbouring atoms, the GGA functionals yield good geometries and qualitatively correct binding energies, even if these are quite significantly overestimated. The use of hybrid functionals enables us to obtain good geometries and satisfactory binding energies. For compounds in which the rare gas atom forms weak dispersive-like bonding, the accuracy yielded by the various functionals is not as good. No functional gives satisfactory binding energies for all the compounds investigated. Several GGA and hybrid functionals yield correct geometries, even if some isomers are not obtained. One GGA functional (PBE) yields qualitatively correct results for the compounds of the three rare gases and several hybrid functionals give satisfactory energies for He compounds. The addition of an empirical dispersive correction improves the results on association compounds, but several isomers are not found. (authors)

Elementary Atom Interaction with Matter

OpenAIRE

Mrowczynski, Stanislaw

1998-01-01

The calculations of the elementary atom (the Coulomb bound state of elementary particles) interaction with the atom of matter, which are performed in the Born approximation, are reviewed. We first discuss the nonrelativistic approach and then its relativistic generalization. The cross section of the elementary atom excitation and ionization as well as the total cross section are considered. A specific selection rule, which applies for the atom formed as positronium by particle-antiparticle pa...

The atomic conflict

International Nuclear Information System (INIS)

Mez, L.

1981-01-01

This book provides a general view at the atomic programmes of several countries and makes an attempt to unmask the atomic industrial combines with their interlockings. The governments role is analysed as well as the atomic policy of the parties, union-trades and associations. Then, the anti-atomic movements in those countries, their forms of resistance, the resonance and the alternative proposals are presented. The countries concerned are Australia, the FRG, COMECON, Danmark, the EG, Finland, France, Great Britain, Ireland, Japan, the Netherlands, Norway, Austria, Sweden, Switzerland, Spain and the USA. For the pocket book version, Lutz Mez adds an updating epilogue which continues with the developments until springtime 1981. (orig./HP) [de

Atom lithography of Fe

NARCIS (Netherlands)

Sligte, te E.; Smeets, B.; van der Stam, K.M.R.; Herfst, R.W.; Straten, van der P.; Beijerinck, H.C.W.; Leeuwen, van K.A.H.

2004-01-01

Direct write atom lithography is a technique in which nearly resonant light is used to pattern an atom beam. Nanostructures are formed when the patterned beam falls onto a substrate. We have applied this lithography scheme to a ferromagnetic element, using a 372 nm laser light standing wave to

Toward the Atomic-Level Mass Analysis of Biomolecules by the Scanning Atom Probe.

Science.gov (United States)

Nishikawa, Osamu; Taniguchi, Masahiro

2017-04-01

In 1994, a new type of atom probe instrument, named the scanning atom probe (SAP), was proposed. The unique feature of the SAP is the introduction of a small extraction electrode, which scans over a specimen surface and confines the high field, required for field evaporation of surface atoms in a small space, between the specimen and the electrode. Thus, the SAP does not require a sharp specimen tip. This indicates that the SAP can mass analyze the specimens which are difficult to form in a sharp tip, such as organic materials and biomolecules. Clean single wall carbon nanotubes (CNT), made by high-pressure carbon monoxide process are found to be the best substrates for biomolecules. Various amino acids and dipeptide biomolecules were successfully mass analyzed, revealing characteristic clusters formed by strongly bound atoms in the specimens. The mass analysis indicates that SAP analysis of biomolecules is not only qualitative, but also quantitative.

Multi-center vs. two-center bonding within the hetero-polyanion in Eu{sub 2}GaPt{sub 2} and its prototype Ca{sub 2}SiIr{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster (Germany); Borrmann, Horst; Grin, Yuri [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Dresden (Germany)

2017-11-17

The compound Eu{sub 2}GaPt{sub 2} was synthesized from the elements in a sealed tantalum tube. Its Ca{sub 2}SiIr{sub 2}-type crystal structure was refined from single-crystal X-ray diffraction data: space group C2/c, a = 9.8775(6), b = 5.8621(6), c = 7.9677(5) Aa, β = 102.257(4) , R{sub F} = 0.039, 1344 observed reflections, and 25 variable parameters. The platinum (iridium) atoms in Eu{sub 2}GaPt{sub 2} and Ca{sub 2}SiIr{sub 2} form linear chains of dumbbells [2c(Pt-Pt) or 2c(Ir-Ir) bonds, respectively]. These chains are interconnected to 2D polyanions in Eu{sub 2}GaPt{sub 2} by the gallium atoms forming 4c(Ga-Pt-Ga-Pt) or by silicon atoms forming 2c(Si-Ir) bonds in Ca{sub 2}SiIr{sub 2}. The polyanion bonds to the europium (calcium) matrix via the pseudo lone-pairs at the gallium (silicon) atoms. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Structural evidence for the partially oxidized dipyrromethene and dipyrromethanone forms of the cofactor of porphobilinogen deaminase: structures of the Bacillus megaterium enzyme at near-atomic resolution

International Nuclear Information System (INIS)

Azim, N.; Deery, E.; Warren, M. J.; Wolfenden, B. A. A.; Erskine, P.; Cooper, J. B.; Coker, A.; Wood, S. P.; Akhtar, M.

2014-01-01

The enzyme porphobilinogen deaminase (PBGD; hydroxymethylbilane synthase; EC 2.5.1.61) catalyses a key early step in the biosynthesis of tetrapyrroles in which four molecules of the monopyrrole porphobilinogen are condensed to form a linear tetrapyrrole. Two near-atomic resolution structures of PBGD from B. megaterium are reported that demonstrate the time-dependent accumulation of partially oxidized forms of the cofactor, including one that possesses a tetrahedral C atom in the terminal pyrrole ring. The enzyme porphobilinogen deaminase (PBGD; hydroxymethylbilane synthase; EC 2.5.1.61) catalyses an early step of the tetrapyrrole-biosynthesis pathway in which four molecules of the monopyrrole porphobilinogen are condensed to form a linear tetrapyrrole. The enzyme possesses a dipyrromethane cofactor, which is covalently linked by a thioether bridge to an invariant cysteine residue (Cys241 in the Bacillus megaterium enzyme). The cofactor is extended during the reaction by the sequential addition of the four substrate molecules, which are released as a linear tetrapyrrole product. Expression in Escherichia coli of a His-tagged form of B. megaterium PBGD has permitted the X-ray analysis of the enzyme from this species at high resolution, showing that the cofactor becomes progressively oxidized to the dipyrromethene and dipyrromethanone forms. In previously solved PBGD structures, the oxidized cofactor is in the dipyromethenone form, in which both pyrrole rings are approximately coplanar. In contrast, the oxidized cofactor in the B. megaterium enzyme appears to be in the dipyrromethanone form, in which the C atom at the bridging α-position of the outer pyrrole ring is very clearly in a tetrahedral configuration. It is suggested that the pink colour of the freshly purified protein is owing to the presence of the dipyrromethene form of the cofactor which, in the structure reported here, adopts the same conformation as the fully reduced dipyrromethane form

Atomic switch: atom/ion movement controlled devices for beyond von-neumann computers.

Science.gov (United States)

Hasegawa, Tsuyoshi; Terabe, Kazuya; Tsuruoka, Tohru; Aono, Masakazu

2012-01-10

An atomic switch is a nanoionic device that controls the diffusion of metal ions/atoms and their reduction/oxidation processes in the switching operation to form/annihilate a conductive path. Since metal atoms can provide a highly conductive channel even if their cluster size is in the nanometer scale, atomic switches may enable downscaling to smaller than the 11 nm technology node, which is a great challenge for semiconductor devices. Atomic switches also possess novel characteristics, such as high on/off ratios, very low power consumption and non-volatility. The unique operating mechanisms of these devices have enabled the development of various types of atomic switch, such as gap-type and gapless-type two-terminal atomic switches and three-terminal atomic switches. Novel functions, such as selective volatile/nonvolatile, synaptic, memristive, and photo-assisted operations have been demonstrated. Such atomic switch characteristics can not only improve the performance of present-day electronic systems, but also enable development of new types of electronic systems, such as beyond von- Neumann computers. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly efficient and concentration-insensitive organic light-emitting devices based on self-quenching-resistant orange–red iridium complex

Energy Technology Data Exchange (ETDEWEB)

Qi, Yige; Wang, Xu [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China); Li, Ming [College of Chemistry, Sichuan University, Chengdu 610064 (China); Lu, Zhiyun, E-mail: luzhiyun@scu.edu.cn [College of Chemistry, Sichuan University, Chengdu 610064 (China); Yu, Junsheng, E-mail: jsyu@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)

2014-11-15

Orange–red phosphorescent organic light-emitting devices (PHOLEDs) with high efficiency and concentration insensitivity based on a novel iridium complex, bis[2-(biphenyl-4-yl)benzothiazole-N,C{sup 2}′]iridium(III) (acetylacetonate) [(4Phbt){sub 2}Ir(acac)], were fabricated. With the heavily doped emissive layer (EML) of 4,4′-N,N′-dicarbazolylbiphenyl (CBP): (4Phbt){sub 2}Ir(acac) in a wide and easily controlled dopant concentration range from 12 wt% to 24 wt%, a maximum power efficiency of 29 lm/W and an external quantum efficiency of >16% of the PHOLEDs were obtained, implying the insensitivity of electroluminescence (EL) properties to doping concentration. Meanwhile, a maximum power efficiency of 5.0 lm/W was achieved from a non-doped device with neat (4Phbt){sub 2}Ir(acac) as the EML, indicating a superior property of self-quenching resistance. The mechanism of direct exciton formation, in which exciton-formation regions are distributed throughout the EML, is responsible for the significant alleviation of triplet–triplet annihilation and superior EL performance. - Highlights: • Highly efficient and concentration-insensitive PHOLEDs were obtained. • The high efficiency of non-doped PHOLEDs indicated a quenching-resistant property. • The independence of EL spectra on doping concentration was observed. • The heavily doped devices were dominated by mechanism of direct exciton formation.

The correlation between fragility, density, and atomic interaction in glass-forming liquids.

Science.gov (United States)

Wang, Lijin; Guan, Pengfei; Wang, W H

2016-07-21

The fragility that controls the temperature-dependent viscous properties of liquids as the glass transition is approached, in various glass-forming liquids with different softness of the repulsive part of atomic interactions at different densities, is investigated by molecular dynamic simulations. We show that the landscape of fragility in purely repulsive systems can be separated into three regions denoted as RI, RII, and RIII, respectively, with qualitatively disparate dynamic behaviors: RI which can be described by "softness makes strong glasses," RII where fragility is independent of softness and can only be tuned by density, and RIII with constant fragility, suggesting that density plays an unexpected role for understanding the repulsive softness dependence of fragility. What is more important is that we unify the long-standing inconsistence with respect to the repulsive softness dependence of fragility by observing that a glass former can be tuned more fragile if nonperturbative attraction is added into it. Moreover, we find that the vastly dissimilar influences of attractive interaction on fragility could be estimated from the structural properties of related zero-temperature glasses.

Atomic switches: atomic-movement-controlled nanodevices for new types of computing

International Nuclear Information System (INIS)

Hino, Takami; Hasegawa, Tsuyoshi; Terabe, Kazuya; Tsuruoka, Tohru; Nayak, Alpana; Ohno, Takeo; Aono, Masakazu

2011-01-01

Atomic switches are nanoionic devices that control the diffusion of metal cations and their reduction/oxidation processes in the switching operation to form/annihilate a metal atomic bridge, which is a conductive path between two electrodes in the on-state. In contrast to conventional semiconductor devices, atomic switches can provide a highly conductive channel even if their size is of nanometer order. In addition to their small size and low on-resistance, their nonvolatility has enabled the development of new types of programmable devices, which may achieve all the required functions on a single chip. Three-terminal atomic switches have also been developed, in which the formation and annihilation of a metal atomic bridge between a source electrode and a drain electrode are controlled by a third (gate) electrode. Three-terminal atomic switches are expected to enhance the development of new types of logic circuits, such as nonvolatile logic. The recent development of atomic switches that use a metal oxide as the ionic conductive material has enabled the integration of atomic switches with complementary metal-oxide-semiconductor (CMOS) devices, which will facilitate the commercialization of atomic switches. The novel characteristics of atomic switches, such as their learning and photosensing abilities, are also introduced in the latter part of this review. (topical review)

Syntheses of the hexahydroindene cores of indanomycin and stawamycin by combinations of iridium-catalyzed asymmetric allylic alkylations and intramolecular Diels-Alder reactions.

Science.gov (United States)

Gärtner, Martin; Satyanarayana, Gedu; Förster, Sebastian; Helmchen, Günter

2013-01-02

Short and concise syntheses of the hexahydroindene cores of the antibiotics indanomycin (X-14547 A) and stawamycin are presented. Key methods used are an asymmetric iridium-catalyzed allylic alkylation, a modified Julia olefination, a Suzuki-Miyaura coupling, and an intramolecular Diels-Alder reaction. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Blue phosphorescent mono-cyclometalated iridium(III) complexes

International Nuclear Information System (INIS)

Ham, Ho Wan; Yang, Yoon A; Kim, Young Sik

2010-01-01

New deep blue phosphorescent iridium(III) complexes comprised of one cyclometalate, two phosphines trans to each other and two cis-ancillary ligands, such as Ir(F 2 Meppy)(PPh 2 Me) 2 (H)(Cl), Ir(F 2 Meppy)(PPh 2 Me) 2 (H)(NCMe) + , and Ir(F 2 Meppy)(PPh 2 Me) 2 (H)(CN), [F 2 Meppy = 2-(2', 4'- difluorophenyl)-4-methyl-pyridine] were synthesized and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. We investigated the strong field effects of ancillary ligands to gain insight into the factors responsible for the emission color change and the different luminescence efficiency. Reducing the molecular weight of the phosphine ligand with PPh 2 Me leads to more efficient deep-blue organic light-emitting devices (OLED) by thermal processing instead of through solution processing. The electron-withdrawing difluoro group substituted on the phenyl ring, the electron-donating methyl group on the pyridyl ring, and the cyano strong field ancillary ligand increased the HOMO-LUMO gap and achieved a hypsochromic shift in the emission color. As a result, the maximum emission spectra of Ir(F 2 Meppy)-(PPh 2 Me) 2 (H)(Cl), Ir(F 2 Meppy)(PPh 2 Me) 2 (H)(NCMe) + , and Ir(F 2 Meppy)(PPh 2 Me) 2- (H)(CN) were in the ranges of 440.5, 437, 436 nm, respectively.

Phosphorescent light-emitting iridium complexes serve as a hypoxia-sensing probe for tumor imaging in living animals

Science.gov (United States)

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.

Serendipitous preparation of fac-(acetonitrile-κNtrichlorido[(1,2,5,6-η-cycloocta-1,5-diene]iridium(III

Directory of Open Access Journals (Sweden)

David M. Morris

2015-04-01

Full Text Available A reaction between [(CODIrCl]2 (COD is cycloocta-1,5-diene, HCl and indene failed to provide the hoped for chloridoindenyliridium dimer, but instead produced the title compound, [IrCl3(CH3CN(C8H12], which is an octahedral complex of iridium(III with a chelating cycloocta-1,5-diene ligand, three chloride ligands in a fac arrangement, and one acetonitrile ligand. Attempts to devise a rational synthesis for the title compound were unsuccessful.

Hydrogen-like atom in laser field: Invariant atomic parameters in the ground state

International Nuclear Information System (INIS)

Bondarev, I.V.; Kuten, S.A.

1994-07-01

The invariant atomic parameters (dynamical vector and tensor polarizabilities) of hydrogen-like atom in the ground 1S 1/2 state are calculated analytically by means of the Laplace transform of the radial Schroedinger equation. The obtained analytical expressions have been written in the compact form as a sum of linear and squared combinations of Gauss hypergeometric functions 2 F 1 . The frequency dependence of the invariant atomic parameters is analyzed. (author). 24 refs, 1 fig

Development of a new osmium-191: Iridium-191m radionuclide generator: Final report

International Nuclear Information System (INIS)

Treves, S.; Packard, A.B.

1986-01-01

The use of iridium-191m (T/sub 1/2/ = 5s) for first-pass radionuclide angiography offers the potential advantages of lower patient radiation dose and the ability to obtain repeated studies without interference from the previously administered radioisotope. These potential advantages have been offset by the absence of satisfactory 191 Os-/sup 191m/Ir generators. The goal of this project was, therefore, the development of an 191 Os-/sup 191m/Ir generator that would be suitable for clinical use. This goal was first sought through modifications of an existing 191 Os-/sup 191m/Ir generator design (i.e., changes in the ion exchange material and eluent) but these changes did not lead to the required improvements. A new approach was then undertaken in which different chemical forms of the 191 Os parent were evaluated in prototype generators. The complex trans-dioxobisoxalatoosmate (VI) led to a generator with higher /sup 191m/Ir yield (25 to 30%/mL) and lower 191 Os breakthrough ( -4 %) with a more physiologically compatible eluent than had been previously achieved. Toxicity studies were conducted on the eluate and an IND subsequently obtained. While this is not a final solution to the problem of developing a clinically acceptable 191 Os-/sup 191m/Ir generator, the ''oxalate'' generator is the most significant improvement of the 191 Os-/sup 191m/Ir generator to date and will be used in an expanded program of clinical studies. 16 refs., 16 tabs

Atomic spectrometry based on metallic tube atomizers heated by flame: Innovative strategies from fundamentals to analysis

International Nuclear Information System (INIS)

Arruda, Marco Aurelio Zezzi; Figueiredo, Eduardo Costa

2009-01-01

This review describes recent developments in atomic absorption spectrometry using metallic tube atomizers heated by flames. Sample introduction in spray or gaseous form is emphasized, describing some proposed systems for this task and the fundamentals involved in each context. The latest challenges and future possibilities for use of metallic tubes in atomic/mass spectrometry are also considered.

(Pyridine-2-aldoximato-κ2N,N′bis[2-(pyridin-2-ylphenyl-κ2C1,N]iridium(III

Directory of Open Access Journals (Sweden)

Bimal Chandra Singh

2013-03-01

Full Text Available In the title complex, [Ir(C11H8N2(C6H5N2O], the octahedrally coordinated IrIII atom is bonded to two 2-(pyridin-2-ylphenyl ligands, through two phenyl C and two pydidine N atoms, and to one pyridine-2-aldoxime ligand through a pyridine N and an oxime N atom. The oxime O atom of the aldoxime unit forms intermolecular C—H...O hydrogen bonds, which result in a two-dimensional hydrogen-bonded polymeric network parallel to (100. C—H...π interactions are also observed.

Nanoscale investigation on Pseudomonas aeruginosa biofilm formed on porous silicon using atomic force microscopy.

Science.gov (United States)

Kannan, Ashwin; Karumanchi, Subbalakshmi Latha; Krishna, Vinatha; Thiruvengadam, Kothai; Ramalingam, Subramaniam; Gautam, Pennathur

2014-01-01

Colonization of surfaces by bacterial cells results in the formation of biofilms. There is a need to study the factors that are important for formation of biofilms since biofilms have been implicated in the failure of semiconductor devices and implants. In the present study, the adhesion force of biofilms (formed by Pseudomonas aeruginosa) on porous silicon substrates of varying surface roughness was quantified using atomic force microscopy (AFM). The experiments were carried out to quantify the effect of surface roughness on the adhesion force of biofilm. The results show that the adhesion force increased from 1.5 ± 0.5 to 13.2 ± 0.9 nN with increase in the surface roughness of silicon substrate. The results suggest that the adhesion force of biofilm is affected by surface roughness of substrate. © 2014 Wiley Periodicals, Inc.

Neutron capture cross sections of rhodium, thulium, iridium, and gold between 0.5 and 3.0 MeV

International Nuclear Information System (INIS)

Joly, S.; Voignier, J.; Grenier, G.; Drake, D.M.; Nilsson, L.

1979-01-01

Measurements of the neutron capture cross sections of rhodium, thulium, gold, and iridium were carried out in the 0.5- to 3.0-MeV energy range. The cross sections are deduced from the capture gamma-ray spectra recorded by a NaI spectrometer consisting of central and annulus detectors. Time-of-flight techniques are used to improve the signal-to-background ratio. When comparison is possible, the present results are found to be in general agreement with the previous data. 5 figures, 3 tables

Stereodivergent-at-metal synthesis of [60]fullerene hybrids

Energy Technology Data Exchange (ETDEWEB)

Marco-Martinez, Juan; Vidal, Sara; Fernandez, Israel; Filippone, Salvatore [Departamento de Quimica Organica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid (Spain); Martin, Nazario [Departamento de Quimica Organica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid (Spain); IMDEA-Nanociencia, C/Faraday, Universidad Autonoma de Madrid (Spain)

2017-02-13

Chiral fullerene-metal hybrids with complete control over the four stereogenic centers, including the absolute configuration of the metal atom, have been synthesized for the first time. The stereochemistry of the four chiral centers formed during [60]fullerene functionalization is the result of both the chiral catalysts employed and the diastereoselective addition of the metal complexes used (iridium, rhodium, or ruthenium). DFT calculations underpin the observed configurational stability at the metal center, which does not undergo an epimerization process. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Limited external irradiation and interstitial 192iridium implant in the treatment of squamous cell carcinoma of the tonsillar region

International Nuclear Information System (INIS)

Puthawala, A.A.; Syed, A.M.; Eads, D.L.; Neblett, D.; Gillin, L.; Gates, T.C.

1985-01-01

Between January 1976 and March 1982, 80 patients with histologically proven diagnosis of squamous cell carcinoma of the tonsillar region were treated with definitive radiotherapy. Sixty-five (81%) of these patients had locally advanced tumors (Stage III and IV); 49% of patients had clinically palpable cervical lymphadenopathy. All patients received a combined external megavoltage and interstitial irradiation. The dose of external irradiation was limited to 4500-5000 cGy over 41/2 to 51/2 weeks. This was followed by interstitial 192 iridium implants to doses of 2000-2500 cGy in 50-60 hours for T1, T2 lesions and 3000-4000 cGy in 60-100 hours for T3, T4 lesions. The neck masses were also separately implanted to deliver additional doses of 2000-4000 cGy in 50-80 hours. Overall local tumor control was observed in 84% of patients with a minimum follow-up period of 2 years. An absolute 3-year disease free survival of the entire group was 72%. Treatment related complications such as soft tissue necrosis or osteoradionecrosis occurred in 6% (5/80) of patients. The salvage of neck failures and local failures was possible in 78 and 38% of patients, respectively, either by surgery or by re-irradiation employing interstitial 192 iridium implants. Functional and esthetic integrity was well preserved in most cases

Generation of atom-photon entangled states in atomic Bose-Einstein condensate via electromagnetically induced transparency

International Nuclear Information System (INIS)

Kuang Leman; Zhou Lan

2003-01-01

In this paper, we present a method to generate continuous-variable-type entangled states between photons and atoms in atomic Bose-Einstein condensate (BEC). The proposed method involves an atomic BEC with three internal states, a weak quantized probe laser, and a strong classical coupling laser, which form a three-level Λ-shaped BEC system. We consider a situation where the BEC is in electromagnetically induced transparency with the coupling laser being much stronger than the probe laser. In this case, the upper and intermediate levels are unpopulated, so that their adiabatic elimination enables an effective two-mode model involving only the atomic field at the lowest internal level and the quantized probe laser field. Atom-photon quantum entanglement is created through laser-atom and interatomic interactions, and two-photon detuning. We show how to generate atom-photon entangled coherent states and entangled states between photon (atom) coherent states and atom-(photon-) macroscopic quantum superposition (MQS) states, and between photon-MQS and atom-MQS states

Atomic collisions research with excited atomic species

International Nuclear Information System (INIS)

Hoogerland, M.D.; Gulley, R.J.; Colla, M.; Lu, W.; Milic, D.; Baldwin, K.G.H.; Buckman, S.J.

1999-01-01

Measurements and calculations of fundamental atomic collision and spectroscopic properties such as collision cross sections, reaction rates, transition probabilities etc. underpin the understanding and operation of many plasma and gas-discharge-based devices and phenomena, for example plasma processing and deposition. In almost all cases the complex series of reactions which sustains the discharge or plasma, or produces the reactive species of interest, has a precursor electron impact excitation, attachment, dissociation or ionisation event. These processes have been extensively studied in a wide range of atomic and molecular species and an impressive data base of collision cross sections and reaction rates now exists. However, most of these measurements are for collisions with stable atomic or molecular species which are initially in their ground electronic state. Relatively little information is available for scattering from excited states or for scattering from unstable molecular radicals. Examples of such species would be metastable excited rare gases, which are often used as buffer gases, or CF 2 radicals formed by electron impact dissociation in a CF 4 plasma processing discharge. We are interested in developing experimental techniques which will enable the quantitative study of such exotic atomic and molecular species. In this talk I would like to outline one such facility which is being used for studies of collisions with metastable He(2 3 S) atoms

Coherent radiation from atoms and a channeled particle

International Nuclear Information System (INIS)

Epp, V.; Sosedova, M.A.

2013-01-01

Highlights: ► Impact of coherent atoms vibrations on radiation of a channeled particle is studied. ► Resonant amplification of atomic radiation is possible under certain conditions. ► Radiation of vibrating atoms forms an intense narrow peak in angular distribution. ► Radiation of atoms on resonance conditions is higher than that of channeled particle. -- Abstract: A new mechanism of radiation emitted at channeling of a relativistic charged particle in a crystal is studied. The superposition of coherent radiation from atoms, which are excited to vibrate in the crystal lattice by a channeled charged particle, with the ordinary channeling radiation is considered. It is shown that the coherent radiation from a chain of oscillating atoms forms a resonance peak on the tail of radiation emitted by the channeled particle

Real-Time Verification of a High-Dose-Rate Iridium 192 Source Position Using a Modified C-Arm Fluoroscope

Energy Technology Data Exchange (ETDEWEB)

Nose, Takayuki, E-mail: nose-takayuki@nms.ac.jp [Department of Radiation Oncology, Nippon Medical School Tamanagayama Hospital, Tama (Japan); Chatani, Masashi [Department of Radiation Oncology, Osaka Rosai Hospital, Sakai (Japan); Otani, Yuki [Department of Radiology, Kaizuka City Hospital, Kaizuka (Japan); Teshima, Teruki [Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka (Japan); Kumita, Shinichirou [Department of Radiology, Nippon Medical School Hospital, Tokyo (Japan)

2017-03-15

Purpose: High-dose-rate (HDR) brachytherapy misdeliveries can occur at any institution, and they can cause disastrous results. Even a patient's death has been reported. Misdeliveries could be avoided with real-time verification methods. In 1996, we developed a modified C-arm fluoroscopic verification of an HDR Iridium 192 source position prevent these misdeliveries. This method provided excellent image quality sufficient to detect errors, and it has been in clinical use at our institutions for 20 years. The purpose of the current study is to introduce the mechanisms and validity of our straightforward C-arm fluoroscopic verification method. Methods and Materials: Conventional X-ray fluoroscopic images are degraded by spurious signals and quantum noise from Iridium 192 photons, which make source verification impractical. To improve image quality, we quadrupled the C-arm fluoroscopic X-ray dose per pulse. The pulse rate was reduced by a factor of 4 to keep the average exposure compliant with Japanese medical regulations. The images were then displayed with quarter-frame rates. Results: Sufficient quality was obtained to enable observation of the source position relative to both the applicators and the anatomy. With this method, 2 errors were detected among 2031 treatment sessions for 370 patients within a 6-year period. Conclusions: With the use of a modified C-arm fluoroscopic verification method, treatment errors that were otherwise overlooked were detected in real time. This method should be given consideration for widespread use.

Blue phosphorescent mono-cyclometalated iridium(III) complexes

Energy Technology Data Exchange (ETDEWEB)

Ham, Ho Wan; Yang, Yoon A; Kim, Young Sik [Hongik University, Seoul (Korea, Republic of)

2010-12-15

New deep blue phosphorescent iridium(III) complexes comprised of one cyclometalate, two phosphines trans to each other and two cis-ancillary ligands, such as Ir(F{sub 2}Meppy)(PPh{sub 2}Me){sub 2}(H)(Cl), Ir(F{sub 2}Meppy)(PPh{sub 2}Me){sub 2}(H)(NCMe){sup +}, and Ir(F{sub 2}Meppy)(PPh{sub 2}Me){sub 2}(H)(CN), [F{sub 2}Meppy = 2-(2', 4'- difluorophenyl)-4-methyl-pyridine] were synthesized and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. We investigated the strong field effects of ancillary ligands to gain insight into the factors responsible for the emission color change and the different luminescence efficiency. Reducing the molecular weight of the phosphine ligand with PPh{sub 2}Me leads to more efficient deep-blue organic light-emitting devices (OLED) by thermal processing instead of through solution processing. The electron-withdrawing difluoro group substituted on the phenyl ring, the electron-donating methyl group on the pyridyl ring, and the cyano strong field ancillary ligand increased the HOMO-LUMO gap and achieved a hypsochromic shift in the emission color. As a result, the maximum emission spectra of Ir(F{sub 2}Meppy)-(PPh{sub 2}Me){sub 2}(H)(Cl), Ir(F{sub 2}Meppy)(PPh{sub 2}Me){sub 2}(H)(NCMe){sup +}, and Ir(F{sub 2}Meppy)(PPh{sub 2}Me){sub 2-}(H)(CN) were in the ranges of 440.5, 437, 436 nm, respectively.

Atom optics in the time domain

Science.gov (United States)

Arndt, M.; Szriftgiser, P.; Dalibard, J.; Steane, A. M.

1996-05-01

Atom-optics experiments are presented using a time-modulated evanescent light wave as an atomic mirror in the trampoline configuration, i.e., perpendicular to the direction of the atomic free fall. This modulated mirror is used to accelerate cesium atoms, to focus their trajectories, and to apply a ``multiple lens'' to separately focus different velocity classes of atoms originating from a point source. We form images of a simple two-slit object to show the resolution of the device. The experiments are modelled by a general treatment analogous to classical ray optics.

Atom probe tomography of intermetallic phases and interfaces formed in dissimilar joining between Al alloys and steel

International Nuclear Information System (INIS)

Lemmens, B.; Springer, H.; Duarte, M.J.; De Graeve, I.; De Strycker, J.; Raabe, D.; Verbeken, K.

2016-01-01

While Si additions to Al are widely used to reduce the thickness of the brittle intermetallic seam formed at the interface during joining of Al alloys to steel, the underlying mechanisms are not clarified yet. The developed approach for the site specific atom probe tomography analysis revealed Si enrichments at grain and phase boundaries between the θ (Fe 4 Al 13 ) and η (Fe 2 Al 5 ) phase, up to about ten times that of the concentration in Al. The increase in Si concentration could play an important role for the growth kinetics of the intermetallic phases formed for example in hot-dip aluminizing of steel. - Highlights: •Si additions to Al reduce thickness of intermetallic seam in joining with steel. •Approach developed for the site specific APT analysis of the intermetallic seam •Si enrichment at grain and phase boundaries possibly affects growth of intermetallics.

Isotopes and atomic weights

International Nuclear Information System (INIS)

Zhang Qinglian

1990-01-01

A review of the chemical and mass spectrometric methods of determining the atomic weights of elements is presented. A, special discussion is devoted to the calibration of the mass spectrometer with highly enriched isotopes. It is illustrated by the recent work on europium. How to choose the candidate element for new atomic weight determination forms the last section of the article

The correlation between fragility, density, and atomic interaction in glass-forming liquids

Energy Technology Data Exchange (ETDEWEB)

Wang, Lijin; Guan, Pengfei, E-mail: pguan@csrc.ac.cn [Beijing Computational Science Research Center, Beijing 100193 (China); Wang, W. H. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2016-07-21

The fragility that controls the temperature-dependent viscous properties of liquids as the glass transition is approached, in various glass-forming liquids with different softness of the repulsive part of atomic interactions at different densities, is investigated by molecular dynamic simulations. We show that the landscape of fragility in purely repulsive systems can be separated into three regions denoted as R{sub I,} R{sub II}, and R{sub III}, respectively, with qualitatively disparate dynamic behaviors: R{sub I} which can be described by “softness makes strong glasses,” R{sub II} where fragility is independent of softness and can only be tuned by density, and R{sub III} with constant fragility, suggesting that density plays an unexpected role for understanding the repulsive softness dependence of fragility. What is more important is that we unify the long-standing inconsistence with respect to the repulsive softness dependence of fragility by observing that a glass former can be tuned more fragile if nonperturbative attraction is added into it. Moreover, we find that the vastly dissimilar influences of attractive interaction on fragility could be estimated from the structural properties of related zero-temperature glasses.

The correlation between fragility, density, and atomic interaction in glass-forming liquids

International Nuclear Information System (INIS)

Wang, Lijin; Guan, Pengfei; Wang, W. H.

2016-01-01

The fragility that controls the temperature-dependent viscous properties of liquids as the glass transition is approached, in various glass-forming liquids with different softness of the repulsive part of atomic interactions at different densities, is investigated by molecular dynamic simulations. We show that the landscape of fragility in purely repulsive systems can be separated into three regions denoted as R I, R II , and R III , respectively, with qualitatively disparate dynamic behaviors: R I which can be described by “softness makes strong glasses,” R II where fragility is independent of softness and can only be tuned by density, and R III with constant fragility, suggesting that density plays an unexpected role for understanding the repulsive softness dependence of fragility. What is more important is that we unify the long-standing inconsistence with respect to the repulsive softness dependence of fragility by observing that a glass former can be tuned more fragile if nonperturbative attraction is added into it. Moreover, we find that the vastly dissimilar influences of attractive interaction on fragility could be estimated from the structural properties of related zero-temperature glasses.

Synthesis, photophysical and electrochemical properties, and protein-binding studies of luminescent cyclometalated iridium(III) bipyridine estradiol conjugates.

Science.gov (United States)

Lo, Kenneth Kam-Wing; Zhang, Kenneth Yin; Chung, Chi-Keung; Kwok, Karen Ying

2007-01-01

A new series of luminescent cyclometalated iridium(III) bipyridine estradiol conjugates [Ir(N-C)2(N-N)](PF6) (N-N = 5-(4-(17alpha-ethynylestradiolyl)phenyl)-2,2'-bipyridine, bpy-est, HN-C = 2-phenylpyridine, Hppy (1 a), 1-phenylpyrazole, Hppz (2 a), 7,8-benzoquinoline, Hbzq (3 a), 2-phenylquinoline, Hpq (4 a), 2-((1,1'-biphenyl)-4-yl)benzothiazole, Hbsb (5 a); N-N = 4-(N-(6-(4-(17alpha-ethynylestradiolyl)benzoylamino)hexyl)aminocarbonyl)-4'-methyl-2,2'-bipyridine, bpy-C6-est, HN-C = Hppy (1 b), Hppz (2 b), Hbzq (3 b), Hpq (4 b), Hbsb (5 b)) was synthesized, characterized, and their photophysical and electrochemical properties studied. Upon photoexcitation, all the complexes displayed intense and long-lived emission in fluid solutions at 298 K and in low-temperature glass. The emission of complexes 1 a-3 a and 1 b-3 b was assigned to a triplet metal-to-ligand charge-transfer ((3)MLCT) (dpi(Ir)-->pi*(bpy-est and N-C-)) state mixed with some triplet intraligand ((3)IL) (pi-->pi*) (N-C- and N-N) character. However, the emissive states of the pq- and bsb- complexes 4 a, 4 b, 5 a, and 5 b showed substantial (3)IL (pi-->pi*) (pq-/bsb-) character. The lipophilicity of all the complexes was determined by reversed-phase HPLC. Upon binding to estrogen receptor alpha, all of these iridium(III) estradiol conjugates exhibited emission enhancement and lifetime extension, rendering them a novel series of luminescent probes for this receptor.

Oxidation of ruthenium thin films using atomic oxygen

Energy Technology Data Exchange (ETDEWEB)

McCoy, A.P.; Bogan, J.; Brady, A.; Hughes, G.

2015-12-31

In this study, the use of atomic oxygen to oxidise ruthenium thin films is assessed. Atomic layer deposited (ALD) ruthenium thin films (~ 3 nm) were exposed to varying amounts of atomic oxygen and the results were compared to the impact of exposures to molecular oxygen. X-ray photoelectron spectroscopy studies reveal substantial oxidation of metallic ruthenium films to RuO{sub 2} at exposures as low as ~ 10{sup 2} L at 575 K when atomic oxygen was used. Higher exposures of molecular oxygen resulted in no metal oxidation highlighting the benefits of using atomic oxygen to form RuO{sub 2}. Additionally, the partial oxidation of these ruthenium films occurred at temperatures as low as 293 K (room temperature) in an atomic oxygen environment. - Highlights: • X-ray photoelectron spectroscopy study of the oxidation of Ru thin films • Oxidation of Ru thin films using atomic oxygen • Comparison between atomic oxygen and molecular oxygen treatments on Ru thin films • Fully oxidised RuO{sub 2} thin films formed with low exposures to atomic oxygen.

Atom and Bond Fukui Functions and Matrices: A Hirshfeld-I Atoms-in-Molecule Approach.

Science.gov (United States)

Oña, Ofelia B; De Clercq, Olivier; Alcoba, Diego R; Torre, Alicia; Lain, Luis; Van Neck, Dimitri; Bultinck, Patrick

2016-09-19

The Fukui function is often used in its atom-condensed form by isolating it from the molecular Fukui function using a chosen weight function for the atom in the molecule. Recently, Fukui functions and matrices for both atoms and bonds separately were introduced for semiempirical and ab initio levels of theory using Hückel and Mulliken atoms-in-molecule models. In this work, a double partitioning method of the Fukui matrix is proposed within the Hirshfeld-I atoms-in-molecule framework. Diagonalizing the resulting atomic and bond matrices gives eigenvalues and eigenvectors (Fukui orbitals) describing the reactivity of atoms and bonds. The Fukui function is the diagonal element of the Fukui matrix and may be resolved in atom and bond contributions. The extra information contained in the atom and bond resolution of the Fukui matrices and functions is highlighted. The effect of the choice of weight function arising from the Hirshfeld-I approach to obtain atom- and bond-condensed Fukui functions is studied. A comparison of the results with those generated by using the Mulliken atoms-in-molecule approach shows low correlation between the two partitioning schemes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Atomic spectral-product representations of molecular electronic structure: metric matrices and atomic-product composition of molecular eigenfunctions.

Science.gov (United States)

Ben-Nun, M; Mills, J D; Hinde, R J; Winstead, C L; Boatz, J A; Gallup, G A; Langhoff, P W

2009-07-02

Recent progress is reported in development of ab initio computational methods for the electronic structures of molecules employing the many-electron eigenstates of constituent atoms in spectral-product forms. The approach provides a universal atomic-product description of the electronic structure of matter as an alternative to more commonly employed valence-bond- or molecular-orbital-based representations. The Hamiltonian matrix in this representation is seen to comprise a sum over atomic energies and a pairwise sum over Coulombic interaction terms that depend only on the separations of the individual atomic pairs. Overall electron antisymmetry can be enforced by unitary transformation when appropriate, rather than as a possibly encumbering or unnecessary global constraint. The matrix representative of the antisymmetrizer in the spectral-product basis, which is equivalent to the metric matrix of the corresponding explicitly antisymmetric basis, provides the required transformation to antisymmetric or linearly independent states after Hamiltonian evaluation. Particular attention is focused in the present report on properties of the metric matrix and on the atomic-product compositions of molecular eigenstates as described in the spectral-product representations. Illustrative calculations are reported for simple but prototypically important diatomic (H(2), CH) and triatomic (H(3), CH(2)) molecules employing algorithms and computer codes devised recently for this purpose. This particular implementation of the approach combines Slater-orbital-based one- and two-electron integral evaluations, valence-bond constructions of standard tableau functions and matrices, and transformations to atomic eigenstate-product representations. The calculated metric matrices and corresponding potential energy surfaces obtained in this way elucidate a number of aspects of the spectral-product development, including the nature of closure in the representation, the general redundancy or

Passivation and alloying element retention in gas atomized powders

Science.gov (United States)

Heidloff, Andrew J.; Rieken, Joel R.; Anderson, Iver E.

2017-12-05

A method for gas atomization of a titanium alloy, nickel alloy, or other alumina (Al.sub.2O.sub.3)-forming alloy wherein the atomized particles are exposed as they solidify and cool in a very short time to multiple gaseous reactive agents for the in-situ formation of a passivation reaction film on the atomized particles wherein the reaction film retains a precursor halogen alloying element that is subsequently introduced into a microstructure formed by subsequent thermally processing of the atomized particles to improve oxidation resistance.

NMR paves the way for atomic level descriptions of sparsely populated, transiently formed biomolecular conformers.

Science.gov (United States)

Sekhar, Ashok; Kay, Lewis E

2013-08-06

The importance of dynamics to biomolecular function is becoming increasingly clear. A description of the structure-function relationship must, therefore, include the role of motion, requiring a shift in paradigm from focus on a single static 3D picture to one where a given biomolecule is considered in terms of an ensemble of interconverting conformers, each with potentially diverse activities. In this Perspective, we describe how recent developments in solution NMR spectroscopy facilitate atomic resolution studies of sparsely populated, transiently formed biomolecular conformations that exchange with the native state. Examples of how this methodology is applied to protein folding and misfolding, ligand binding, and molecular recognition are provided as a means of illustrating both the power of the new techniques and the significant roles that conformationally excited protein states play in biology.

Hydride generation – in-atomizer collection of Pb in a quartz trap-and-atomizer device for atomic absorption spectrometry – an interference study

Energy Technology Data Exchange (ETDEWEB)

Novotný, Pavel [Institute of Analytical Chemistry of the ASCR, v.v.i., Veveří 97, 602 00 Brno (Czech Republic); High School in Hořice, Husova 1414, 508 01 Hořice (Czech Republic); Kratzer, Jan, E-mail: jkratzer@biomed.cas.cz [Institute of Analytical Chemistry of the ASCR, v.v.i., Veveří 97, 602 00 Brno (Czech Republic)

2013-01-01

Interferences of selected hydride forming elements (As, Sb, Bi, Se and Sn) on lead determination by hydride generation atomic absorption spectrometry were extensively studied in both on-line atomization and preconcentration (collection) modes. The commonly used on-line atomization mode was found free of significant interferences, whereas strong interference from Bi was observed when employing the preconcentration mode with plumbane collection in a quartz trap-and-atomizer device. Interference of Bi seems to take place in the preconcentration step. Interference of Bi in the collection mode cannot be reduced by increased hydrogen radical amount in the trap and/or the atomizer. - Highlights: ► Interference study on Pb determination by in-atomizer trapping was performed for the first time. ► Bi was found as a severe interferent in the preconcentration mode (Pb:Bi ratio 1:100). ► No interference was found in the on-line atomization (no preconcentration). ► Bi interference occurs during preconcentration.

On the atomic displacement fields of small interstitial dislocation loops

International Nuclear Information System (INIS)

Zhou, Z.; Dudarev, S.L.; Jenkins, M.L.; Sutton, A.P.; Kirk, M.A.

2005-01-01

The atomic displacement fields of dislocation loops of size 1-5 nm formed by self-interstitial atoms in α-Fe have been calculated using isotropic elasticity theory and anisotropic elasticity theory, and compared with atomic simulations for loops formed by 43-275 self-interstitial atoms. The atomic displacements predicted by anisotropic elasticity theory were in good agreement with those given by the atomistic simulations at distances greater than 3 nm from the loop plane, but the displacements predicted by isotropic elasticity theory showed significant discrepancies at distances up to 15 nm

Silicene on metal substrates: A first-principles study on the emergence of a hierarchy of honeycomb structures

International Nuclear Information System (INIS)

Kaltsas, D.; Tsetseris, L.; Dimoulas, A.

2014-01-01

Experimental studies have reported several types of Si monolayer structures that are formed on metal surfaces. These structures typically show the topology of a honeycomb bonding network, but differ in terms of corrugation and surface coverage. Using first-principles calculations, we identify atomic-scale mechanisms that underlie the appearance of different configurations as coverage increases during Si deposition on silver. The key point is that any extra Si adatoms that land on preformed silicene films can be incorporated in the honeycomb network and form bonds with underlying Ag atoms. As a result, the corrugation profile changes, giving rise to varying overlayer geometries. We also show that the same set of mechanisms control the appearance of silicene films on an iridium substrate. The results address available experimental data, but also probe the stability and properties of silicene wetting films that have not been observed yet.

Transpapillary iridium-192 wire in the treatment of malignant bile duct obstruction

International Nuclear Information System (INIS)

Levitt, M.D.; Laurence, B.H.; Cameron, F.; Klemp, P.F.B.

1988-01-01

Twenty four patients with malignant bile duct obstruction were treated with intraluminal radiotherapy using iridium-192 wire inserted through an endoscopically placed nasobiliary catheter. Biliary drainage after treatment was maintained by an endoprosthesis. The median dose of intraluminal radiotherapy was 6000 cGy; two patients with cholangiocarcinoma were given a second course because of disease extension; four patients with pancreatic carcinoma received additional external irradiation (3000 cGy). There was one early death from a cerebrovascular accident (30 day mortality, 4.2%). Cholangitis (30%) was the major early complication and stent blockage (40%) the major late complication; there were no complications directly attributable to radiotherapy. The median survival for patients with pancreatic carcinoma was 250 days and for cholangiocarcinoma, 300 days. This method is technically feasible and may prove safer than the transhepatic technique. The ability of intraluminal irradiation to improve palliation or lengthen survival in patients with malignant bile duct obstruction remains uncertain. (author)

Transpapillary iridium-192 wire in the treatment of malignant bile duct obstruction

Energy Technology Data Exchange (ETDEWEB)

Levitt, M D; Laurence, B H; Cameron, F; Klemp, P F.B.

1988-02-01

Twenty four patients with malignant bile duct obstruction were treated with intraluminal radiotherapy using iridium-192 wire inserted through an endoscopically placed nasobiliary catheter. Biliary drainage after treatment was maintained by an endoprosthesis. The median dose of intraluminal radiotherapy was 6000 cGy; two patients with cholangiocarcinoma were given a second course because of disease extension; four patients with pancreatic carcinoma received additional external irradiation (3000 cGy). There was one early death from a cerebrovascular accident (30 day mortality, 4.2%). Cholangitis (30%) was the major early complication and stent blockage (40%) the major late complication; there were no complications directly attributable to radiotherapy. The median survival for patients with pancreatic carcinoma was 250 days and for cholangiocarcinoma, 300 days. This method is technically feasible and may prove safer than the transhepatic technique. The ability of intraluminal irradiation to improve palliation or lengthen survival in patients with malignant bile duct obstruction remains uncertain.

Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes

Directory of Open Access Journals (Sweden)

Albert Poater

2016-01-01

Full Text Available 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 CS and C2 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.

High-dose rate iridium-192 brachytherapy with flexible applicator. A trial toward decrease of stress during treatment and improvement of quality of life

International Nuclear Information System (INIS)

Inoue, Keiji; Kasahara, Kotaro; Karashima, Takashi; Inoue, Yuichiro; Kariya, Shinji; Inomata, Taisuke; Yoshida, Shoji; Shuin, Taro

2001-01-01

We tried to improve the materials and methods of high-dose rate Iridium-192 brachytherapy for localized prostate cancer and evaluated the stress during the treatment in 20 patients with whom the therapy was performed. Rigid applicators made of stainless steel of 1.6 mm in diameter were indwelt with a template as usual for 30 hours in 14 patients (group A). Flexible applicators made of polyoxymethylene rosin (POM) of 2.0 mm in diameter were indwelt without a template for 30 hours after the applicator insertion in 6 patients (group B). We made inquiries about lumbago, inconvenience and necessity of assistant help and sleep in the course of therapy, and urinary incontinence and erectile function after the course of therapy as the QOL. The stress during the course of therapy in the patients of group B was obviously less than that of group A. There were no significant differences in urinary incontinence and erectile function after the course of therapy between group A and B. In this study, our trial successfully reduced the stress during the course of therapy in the patients with localized prostate cancer in the course of high-dose rate Iridium-192 brachytherapy. (author)

High-dose rate iridium-192 brachytherapy with flexible applicator. A trial toward decrease of stress during treatment and improvement of quality of life

Energy Technology Data Exchange (ETDEWEB)

Inoue, Keiji; Kasahara, Kotaro; Karashima, Takashi; Inoue, Yuichiro; Kariya, Shinji; Inomata, Taisuke; Yoshida, Shoji; Shuin, Taro [Kochi Medical School, Nankoku (Japan)

2001-07-01

We tried to improve the materials and methods of high-dose rate Iridium-192 brachytherapy for localized prostate cancer and evaluated the stress during the treatment in 20 patients with whom the therapy was performed. Rigid applicators made of stainless steel of 1.6 mm in diameter were indwelt with a template as usual for 30 hours in 14 patients (group A). Flexible applicators made of polyoxymethylene rosin (POM) of 2.0 mm in diameter were indwelt without a template for 30 hours after the applicator insertion in 6 patients (group B). We made inquiries about lumbago, inconvenience and necessity of assistant help and sleep in the course of therapy, and urinary incontinence and erectile function after the course of therapy as the QOL. The stress during the course of therapy in the patients of group B was obviously less than that of group A. There were no significant differences in urinary incontinence and erectile function after the course of therapy between group A and B. In this study, our trial successfully reduced the stress during the course of therapy in the patients with localized prostate cancer in the course of high-dose rate Iridium-192 brachytherapy. (author)

Effective oscillator strength distributions of spherically symmetric atoms for calculating polarizabilities and long-range atom–atom interactions

Energy Technology Data Exchange (ETDEWEB)

Jiang, Jun, E-mail: phyjiang@yeah.net [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Cheng, Yongjun, E-mail: cyj83mail@gmail.com [School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Academy of Fundamental and Interdisciplinary Science, Harbin Institute of Technology, Harbin 150080 (China); Bromley, M.W.J., E-mail: brom@physics.uq.edu.au [School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4075 (Australia)

2015-01-15

Effective oscillator strength distributions are systematically generated and tabulated for the alkali atoms, the alkaline-earth atoms, the alkaline-earth ions, the rare gases and some miscellaneous atoms. These effective distributions are used to compute the dipole, quadrupole and octupole static polarizabilities, and are then applied to the calculation of the dynamic polarizabilities at imaginary frequencies. These polarizabilities can be used to determine the long-range C{sub 6}, C{sub 8} and C{sub 10} atom–atom interactions for the dimers formed from any of these atoms and ions, and we present tables covering all of these combinations.

Effective oscillator strength distributions of spherically symmetric atoms for calculating polarizabilities and long-range atom–atom interactions

International Nuclear Information System (INIS)

Jiang, Jun; Mitroy, J.; Cheng, Yongjun; Bromley, M.W.J.

2015-01-01

Effective oscillator strength distributions are systematically generated and tabulated for the alkali atoms, the alkaline-earth atoms, the alkaline-earth ions, the rare gases and some miscellaneous atoms. These effective distributions are used to compute the dipole, quadrupole and octupole static polarizabilities, and are then applied to the calculation of the dynamic polarizabilities at imaginary frequencies. These polarizabilities can be used to determine the long-range C 6 , C 8 and C 10 atom–atom interactions for the dimers formed from any of these atoms and ions, and we present tables covering all of these combinations

Atomic-scale observation of hydrogen-induced crack growth by atom-probe FIM

International Nuclear Information System (INIS)

Kuk, Y.; Pickering, H.W.; Sakurai, T.

1980-01-01

Formation and propagation of a microcrack due to hydrogen in a Fe-0.29 wt.% Ti alloy was observed at the atomic scale by field ion microscopy. A microcrack (-20 nm in length) formed and became noticeably large when the tip was heated at 950 0 C in the presence of about 1 torr of Hg. Propagation was reported several times by reheating, until a portion of the tip ruptured and became detached from the tip. Compositional analysis, performed in situ using a high performance atom-probe, identified atomic hydrogen in quantity and some hydrogen molecules and FEH in the crack, but not elsewhere on the surface

Reactions of atomic oxygen with the chlorate ion and the perchlorate ion

Science.gov (United States)

Anan'ev, Vladimir; Miklin, Mikhail; Kriger, Ludmila

2014-06-01

The reactions of the chlorate ion with atomic oxygen formed under photolysis of the nitrate ion introduced to potassium chlorate crystal by co-crystallization were studied by optical and infrared absorption spectroscopy. The perchlorate ion was found to form in solids as product of addition reaction of singlet atomic oxygen, formed under dissociation of the peroxynitrite ion - the product of isomerization of the excited nitrate ion. Triplet atomic oxygen does not react with the chlorate ion. The atomic oxygen formed under photolysis of the nitrate ion introduced to potassium perchlorate crystal by co-crystallization does not react with the perchlorate ion.

The brachytherapy with low dose-rate iridium for prostate cancer

International Nuclear Information System (INIS)

Momma, Tetsuo; Saito, Shiro; Ohki, Takahiro; Satoh, Hiroyuki; Toya, Kazuhito; Dokiya, Takushi; Murai, Masaru

2000-01-01

Brachytherapy as an option for the treatment of prostate cancer has been commonly performed in USA. As the permanent seeding of the radioactive materials is strictly restricted by the law in Japan, brachytherapy must be performed by the temporary implant. This treatment has been performed at a few facilities in Japan mostly using high dose-rate iridium. Only our facility has been using low dose-rate iridium (LDR-Ir) for prostate cancer. This study evaluates the clinical results of the treatment. Since December 1997 to December 1999, 26 patients with histologically diagnosed as prostate cancer (Stage B, 92%; Stage C, 8%) underwent brachytherapy. Twenty-two patients received brachytherapy alone, three were treated with a combination of brachytherapy and external beam radiotherapy (ERT) and one was treated with a combination of brachytherapy and neoadjuvant endocrine therapy. Patients ranged in age from 61 to 84 (median 76) years old. Treatment was initiated with perineal needle placement. From 10 to 14 needles were placed through the holes on the template which was fixed to the stabilizer of the transrectal ultrasound probe. After the needle placement, CT scan was performed to draw distribution curves for the treatment planning. LDR-Ir wires were introduced to the sheath and indwelled during the time calculated from dosimetry. Peripheral dose was 70 Gy for the monotherapy of brachytherapy. For the combination therapy, 40 Gy was given by brachytherapy and 36 Gy with ERT afterwards. LDR-Ir wires were removed after completion of the radiation and patients were followed with serum PSA level and annual biopsy. During 2 to 26 (median 12) months follow-up, 8 out of 9 patients with initial PSA level above 20 ng/ml showed PSA failure. All 13 patients with initial PSA level lower than 20 ng/ml were free from PSA failure. Eight out of 11 patients with Gleason's score 7 or higher showed PSA failure, and all 14 patients (including three patients with combined therapy) with

Intra-operative placement of catheters for interstitial microwave-induced hyperthermia and iridium brachytherapy

International Nuclear Information System (INIS)

Coughlin, C.T.; Wong, T.Z.; Strohbehn, J.W.; Colacchio, T.A.; Belch, R.Z.; Sutton, J.E. Jr.; Douple, E.B.

1984-01-01

The authors have previously described a system for delivery of microwave-induced hyperthermia utilizing flexible coaxial cables that are modified to serve as microwave antennas. These small (--1.6mm o.d.) antennas ae introduced into 2mm o.d. nylon catheters implanted in the tumor. This system has been further modified for use in the treatment of surgically unresectible abdominal, pelvic, and head and neck tumors. The modifications are described that were used to treat two pelvic, one upper abdominal, and one base of tongue tumor. The nylon catheters are implanted during surgery. After a short recovery period, the microwave antennas are inserted and the tumor region is heated for --1hr. The antennas are removed, iridium-192 seeds are placed in the catheters, 2800 - 5000 rad (CGy) doses are delivered, followed by a 1hr hyperthermia treatment. The temperature distributions and future applications are discussed

Microstructural evolution and magnetic properties of ultrafine solute-atom particles formed in a Cu75-Ni20-Fe5 alloy on isothermal annealing

Science.gov (United States)

Kim, Jun-Seop; Takeda, Mahoto; Bae, Dong-Sik

2016-12-01

Microstructural features strongly affect magnetism in nano-granular magnetic materials. In the present work we have investigated the relationship between the magnetic properties and the self-organized microstructure formed in a Cu75-Ni20-Fe5 alloy comprising ferromagnetic elements and copper atoms. High resolution transmission electron microscopy (HRTEM) observations showed that on isothermal annealing at 873 K, nano-scale solute (Fe,Ni)-rich clusters initially formed with a random distribution in the Cu-rich matrix. Superconducting quantum interference device (SQUID) measurements revealed that these ultrafine solute clusters exhibited super-spinglass and superparamagnetic states. On further isothermal annealing the precipitates evolved to cubic or rectangular ferromagnetic particles and aligned along the directions of the copper-rich matrix. Electron energy-band calculations based on the first-principle Korringa-Kohn-Rostocker (KKR) method were also implemented to investigate both the electronic structure and the magnetic properties of the alloy. Inputting compositions obtained experimentally by scanning transmission electron microscopy-electron dispersive X-ray spectroscopy (STEM-EDS) analysis, the KKR calculation confirmed that ferromagnetic precipitates (of moment 1.07μB per atom) formed after annealing for 2 × 104 min. Magneto-thermogravimetric (MTG) analysis determined with high sensitivity the Curie temperatures and magnetic susceptibility above room temperature of samples containing nano-scale ferromagnetic particles.

Droplet Breakup Mechanisms in Air-blast Atomizers

Science.gov (United States)

Aliabadi, Amir Abbas; Taghavi, Seyed Mohammad; Lim, Kelly

2011-11-01

Atomization processes are encountered in many natural and man-made phenomena. Examples are pollen release by plants, human cough or sneeze, engine fuel injectors, spray paint and many more. The physics governing the atomization of liquids is important in understanding and utilizing atomization processes in both natural and industrial processes. We have observed the governing physics of droplet breakup in an air-blast water atomizer using a high magnification, high speed, and high resolution LASER imaging technique. The droplet breakup mechanisms are investigated in three major categories. First, the liquid drops are flattened to form an oblate ellipsoid (lenticular deformation). Subsequent deformation depends on the magnitude of the internal forces relative to external forces. The ellipsoid is converted into a torus that becomes stretched and disintegrates into smaller drops. Second, the drops become elongated to form a long cylindrical thread or ligament that break up into smaller drops (Cigar-shaped deformation). Third, local deformation on the drop surface creates bulges and protuberances that eventually detach themselves from the parent drop to form smaller drops.

Atomic form factors, incoherent scattering functions, and photon scattering cross sections

International Nuclear Information System (INIS)

Hubbell, J.H.; Veigele, W.J.; Briggs, E.A.; Brown, R.T.; Cromer, D.T.; Howerton, R.J.

1975-01-01

Tabulations are presented of the atomic form factor, F (α,Z), and the incoherent scattering function, S (x,Z), for values of x (=sin theta/2)/lambda) from 0.005 A -1 to 10 9 A -1 , for all elements A=1 to 100. These tables are constructed from available state-of-the-art theoretical data, including the Pirenne formulas for Z=1, configuration-into action results by Brown using Brown-Fontana and Weiss correlated wavefunctions for Z=2 to 6 non-relativistic Hartree-Fock results by Cromer for Z=7 to 100 and a relativistic K-shell analytic expression for F (x,Z) by Bethe Levinger for x>10 A -1 for all elements Z=2 to 100. These tabulated values are graphically compared with available photon scattering angular distribution measurements. Tables of coherent (Rayleigh) and incoherent (Compton) total scattering cross sections obtained by nummerical integration over combinations of F 2 (x,Z) with the Thomson formula and S (x,Z) with the Klum-Nishina Formual, respectively, are presented for all elements Z=1 to 100, for photon energies 100 eV (lambda=124 A) to 100 MeV (0.000124 A). The incoherent scattering cross sections also include the radiative and double-Compton corrections as given by Mork. Similar tables are presented for the special cases of terminally-bonded hydrogen and for the H 2 molecule, interpolated and extrapolated from values calculated by Stewart et al., and by Bentley and Stewart using Kolos-Roothaan wavefunctions

X-ray holography with an atomic scatterer

Energy Technology Data Exchange (ETDEWEB)

Mityureva, A.A.; Smirnov, V.V., E-mail: valery_smirnov@mail.ru

2016-08-15

X-ray holography scheme with reference scatterer consisting of heavy atom as reference center and its link to an object consisting of several light atoms and using controlled variation of the alignment is represented. The scheme can reproduce an object in three dimensions with atomic resolution. The distorting factors of reconstruction are considered. - Highlights: • X-ray holography scheme with a reference wave formed by atomic scatterer. • 3D object reconstruction with atomic resolution from the set of holograms. • Simple formula for the distorting factor in reconstruction.

The labeling of unsaturated gamma-hydroxybutyric acid by heavy isotopes of hydrogen: iridium complex-mediated H/D exchange by C-H bond activation vs reduction by boro-deuterides/tritides

Czech Academy of Sciences Publication Activity Database

Marek, Aleš; Pedersen, M. H. F.; Vogensen, S. B.; Clausen, R. P.; Frolund, B.; Elbert, Tomáš

2016-01-01

Roč. 59, č. 12 (2016), s. 476-483 ISSN 0362-4803 Institutional support: RVO:61388963 Keywords : C-H activation * borotritides * hydrogen/deuterium exchange * iridium catalyst * tritium-labeled gamma-hydroxybutyric acid Subject RIV: CC - Organic Chemistry Impact factor: 1.745, year: 2016

Division of atomic physics

International Nuclear Information System (INIS)

Kroell, S.

1994-01-01

The Division of Atomic Physics, Lund Institute of Technology (LTH), is responsible for the basic physics teaching in all subjects at LTH and for specialized teaching in Optics, Atomic Physics, Atomic and Molecular Spectroscopy and Laser Physics. The Division has research activities in basic and applied optical spectroscopy, to a large extent based on lasers. It is also part of the Physics Department, Lund University, where it forms one of eight divisions. Since the beginning of 1980 the research activities of our division have been centred around the use of lasers. The activities during the period 1991-1992 is described in this progress reports

Complexes of rhodium (I) and iridium (I) with mixed phosphorus-oxygen and phosphorus-nitrogen glands

Energy Technology Data Exchange (ETDEWEB)

Meintjies, E.; Singleton, E.; Schmutzler, R.; Sell, M.

1985-09-01

A series of four- and five-coordinate rhodium(I) and iridium(I) complexes of the type (MCl(cod)L) and (M(COD)L/sub 2/) sup(+)(M = Rh or Ir;cod = cycloocta-1,5-diene; L = P(C/sub 6/H/sub 4/OMe-o)/sub 3/, PMe/sub 2/(C/sub 6/H/sub 4/OMe-o), PPh/sub 2/(C/sub 6/H/sub 4/OMe-o), PPh/sub 2/-(C/sub 6/H/sub 4/NMe/sub 2/-o), PMe(C/sub 6/H/sub 4/OMe-o)/sub 2/ and PPh/sub 2/(C/sub 6/H/sub 4/OPr sup(i)-o)) have been prepared from the reactions of ((MCl(cod))/sub 2/) (M = Rh or Ir) with the appropriate stoichiometric amount of L in diethyl ether or methanol solution. N.M.R. evidence (/sup 1/H and /sup 13/C) is presented for non-chelation in the case of the ether ligands and chelation for the amine ligand. Thus, the complexes (MCl(cod)L)(L = ether ligand) are mononuclear square-planar species, whereas the amine ligand chelates to the metal atom, and a distorted trigonal bipyramidal structure is proposed. Attempts at displacing cod from the complexes (MCl(cod)L) with these ether and amine ligands, or with small phosphines, were unsuccessful. However, treatment of (MCl(cod)(P(C/sub 6/H/sub 4/OMe-o)/sub 3/))(M = Rh or Ir) with carbon monoxide gave (MCl(CO)/sub 2/ (P(C/sub 6/H/sub 4/OMe-o)/sub 3/)). In contrast, a disproportionation product, (RhCl(CNBu sup(t)/sub 2/(PPh/sub 2/ (C/sub 6/H/sub 4/OPr sup(i)-o))/sub 2/), was obtained from treatment of (RhCl(cod)(PPh/sub 2/(C/sub 6/H/sub 4/OPr sup(i)-o))) with t-butyl isocyanide. N.M.R. data (/sup 1/H and /sup 13/C) for the complexes are described.

Multielectron effects in atomic processes

International Nuclear Information System (INIS)

Amusia, M.Ya.; Chernysheva, L.V.

1999-01-01

One demonstrates a prominent role of electron collectivization in atoms and quasi-atomic formations. Paper discusses in detail the approximation of random phases with exchange enabling to take account of these effects. One points out the necessity to go outside the terms of the approximation when studying some processes via combination of the approximation with the theory of disturbances. The results of the recently conducted estimations of cross sections of photoionization of atomic iodine and of its positive and negative ions, Xe + single-electron photoionization, resonance-amplified emission of photons in electron collisions with atoms and quasi-atomic formations, non-dipole corrections to the angular distribution of photoelectrons, probabilities of two electron transitions where the whole amount of energy releases in the form of one photon, illustrate the role of the collective effects [ru

Empirical atom model of Vegard's law

International Nuclear Information System (INIS)

Zhang, Lei; Li, Shichun

2014-01-01

Vegard's law seldom holds true for most binary continuous solid solutions. When two components form a solid solution, the atom radii of component elements will change to satisfy the continuity requirement of electron density at the interface between component atom A and atom B so that the atom with larger electron density will expand and the atom with the smaller one will contract. If the expansion and contraction of the atomic radii of A and B respectively are equal in magnitude, Vegard's law will hold true. However, the expansion and contraction of two component atoms are not equal in most situations. The magnitude of the variation will depend on the cohesive energy of corresponding element crystals. An empirical atom model of Vegard's law has been proposed to account for signs of deviations according to the electron density at Wigner–Seitz cell from Thomas–Fermi–Dirac–Cheng model

Fundamentals in hadronic atom theory

CERN Document Server

Deloff, A

2003-01-01

Hadronic atoms provide a unique laboratory for studying hadronic interactions essentially at threshold. This text is the first book-form exposition of hadronic atom theory with emphasis on recent developments, both theoretical and experimental. Since the underlying Hamiltonian is a non-self-adjoined operator, the theory goes beyond traditional quantum mechanics and this book covers topics that are often glossed over in standard texts on nuclear physics. The material contained here is intended for the advanced student and researcher in nuclear, atomic or elementary-particle physics. A good know

A mitochondrial targeted two-photon iridium(III) phosphorescent probe for selective detection of hypochlorite in live cells and in vivo.

Science.gov (United States)

Li, Guanying; Lin, Qian; Sun, Lingli; Feng, Changsheng; Zhang, Pingyu; Yu, Bole; Chen, Yu; Wen, Ya; Wang, Hui; Ji, Liangnian; Chao, Hui

2015-01-01

Endogenous hypochlorite ion (ClO(-)) is a highly reactive oxygen species (ROS) that is produced from hydrogen peroxide and chloride ions catalyzed by myeloperoxidase (MPO). And mitochondrion is one of the major sources of ROS including ClO(-). In the present work, a two-photon phosphorescent probe for ClO(-) in mitochondria was developed. An iridium(III) complex bearing a diaminomaleonitrile group as ClO(-) reactive moiety specifically responded to ClO(-) over other ions and ROSs. When the probe was reacted with ClO(-) to form an oxidized carboxylate product, a significant enhancement in phosphorescence intensity was observed under one-photon (402 nm) and two-photon (750 nm) excitation, with a two-photon absorption cross-section of 78.1 GM at 750 nm. More importantly, ICP-MS results and cellular images co-stained with Mito-tracker Green demonstrated that this probe possessed high specificity for mitochondria. This probe was applied in the one- and two-photon imaging of ClO(-) in vitro and in vivo. The results suggested endotoxin lipopolysaccharide (LPS) induced ClO(-) mostly generated in the liver of zebrafish. Copyright © 2015 Elsevier Ltd. All rights reserved.

Ultratrace determination of tin by hydride generation in-atomizer trapping atomic absorption spectrometry

Energy Technology Data Exchange (ETDEWEB)

Průša, Libor [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic); Charles University in Prague, Faculty of Science, Department of Analytical Chemistry, Hlavova 8, Prague 2, CZ 128 43 Czech Republic (Czech Republic); Dědina, Jiří [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic); Kratzer, Jan, E-mail: jkratzer@biomed.cas.cz [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic)

2013-12-04

Graphical abstract: -- Highlights: •In-atomizer trapping HG-AAS was optimized for Sn. •A compact quartz trap-and-atomizer device was employed. •Generation, preconcentration and atomization steps were investigated in detail. •Hundred percent preconcentration efficiency for tin was reached. •Routine analytical method was developed for Sn determination (LOD of 0.03 ng mL{sup −1} Sn). -- Abstract: A quartz multiatomizer with its inlet arm modified to serve as a trap (trap-and-atomizer device) was employed to trap tin hydride and subsequently to volatilize collected analyte species with atomic absorption spectrometric detection. Generation, atomization and preconcentration conditions were optimized and analytical figures of merit of both on-line atomization as well as preconcentration modes were quantified. Preconcentration efficiency of 95 ± 5% was found. The detection limits reached were 0.029 and 0.14 ng mL{sup −1} Sn, respectively, for 120 s preconcentration period and on-line atomization mode without any preconcentration. The interference extent of other hydride forming elements (As, Se, Sb and Bi) on tin determination was found negligible in both modes of operation. The applicability of the developed preconcentration method was verified by Sn determination in a certified reference material as well as by analysis of real samples.

Interaction of epitaxial silicene with overlayers formed by exposure to Al atoms and O2 molecules.

Science.gov (United States)

Friedlein, R; Van Bui, H; Wiggers, F B; Yamada-Takamura, Y; Kovalgin, A Y; de Jong, M P

2014-05-28

As silicene is not chemically inert, the study and exploitation of its electronic properties outside of ultrahigh vacuum environments require the use of insulating capping layers. In order to understand if aluminum oxide might be a suitable encapsulation material, we used high-resolution synchrotron photoelectron spectroscopy to study the interactions of Al atoms and O2 molecules, as well as the combination of both, with epitaxial silicene on thin ZrB2(0001) films grown on Si(111). The deposition of Al atoms onto silicene, up to the coverage of about 0.4 Al per Si atoms, has little effect on the chemical state of the Si atoms. The silicene-terminated surface is also hardly affected by exposure to O2 gas, up to a dose of 4500 L. In contrast, when Al-covered silicene is exposed to the same dose, a large fraction of the Si atoms becomes oxidized. This is attributed to dissociative chemisorption of O2 molecules by Al atoms at the surface, producing reactive atomic oxygen species that cause the oxidation. It is concluded that aluminum oxide overlayers prepared in this fashion are not suitable for encapsulation since they do not prevent but actually enhance the degradation of silicene.

Ifluence of the collisions of electrons and ions with atoms and molecules on the dynamic form-factors of bounded many-particle systems

International Nuclear Information System (INIS)

Yakimenko, I.P.; Zagorodny, A.G.

1980-01-01

The kinetic theory of fluctuations is used to investigate the influence of the collisions of charged particles with atoms and molecules on the dynamic form-factors of semi-infinite weakly ionized plasma. It is shown that the collisions between the electrons and neutral particles and the diffuse processes connected with them lead to a much increased influence of the boundary on correlations in a plasma [ru

Laser control of atomic beam motion and applications

International Nuclear Information System (INIS)

Balykin, V.I.; Letokhov, V.S.

1987-01-01

The authors present the results of an experimental investigation of the control of atomic beam motion by the light pressure of laser radiation. Collimation, focusing and reflection of the atomic beam are considered. Collimation of the atomic beam is achieved by the interaction of laser radiation with atoms, when the light pressure force depends only on the atom's velocity. A similar regime of atomic beam interaction with radiation was performed with transversal irradiation of a beam by the axis-symmetrical field. The axis-symmetrical field was formed by laser radiation reflected from the conical mirror surface of a reflecting axicon. The axis of the atomic beam coincided with that of the axicon. The collimation regime was reached under negative detuning of the laser radiation frequency from the atomic transition frequency by a value equal to several homogeneous widths. With positive detuning by the same value the regime of beam decollimation was observed. The density of atoms on the beam axis was changed by 10 3 times, when the collimation regime was replaced by that of decollimation. Focusing of the atomic beam was achieved by light pressure dependent on the atomic coordinate. Focusing was performed within the field configuration formed by divergent laser Gaussian beams propagating in the direction +- X, +- Y of a Cartesian coordinate system. Waists of the laser beams were an equal distance from the atomic beam axis. With an atomic beam propagating along the z axis, expressions for local distance and a formula for the laser lens were obtained. Focusing of the atomic beam was experimentally accomplished, and the image of the atomic beam was received. In this work they also investigated reflection of the atomic beam by laser radiation. The possibility of creating the optics of a neutral atomic beam is shown

Isolating and moving single atoms using silicon nanocrystals

Science.gov (United States)

Carroll, Malcolm S.

2010-09-07

A method is disclosed for isolating single atoms of an atomic species of interest by locating the atoms within silicon nanocrystals. This can be done by implanting, on the average, a single atom of the atomic species of interest into each nanocrystal, and then measuring an electrical charge distribution on the nanocrystals with scanning capacitance microscopy (SCM) or electrostatic force microscopy (EFM) to identify and select those nanocrystals having exactly one atom of the atomic species of interest therein. The nanocrystals with the single atom of the atomic species of interest therein can be sorted and moved using an atomic force microscope (AFM) tip. The method is useful for forming nanoscale electronic and optical devices including quantum computers and single-photon light sources.

Atoms in Flight: The Remarkable Connections between Atomic and Hadronic Physics

Energy Technology Data Exchange (ETDEWEB)

Brodsky, Stanley J.; /SLAC

2012-02-16

Atomic physics and hadron physics are both based on Yang Mills gauge theory; in fact, quantum electrodynamics can be regarded as the zero-color limit of quantum chromodynamics. I review a number of areas where the techniques of atomic physics provide important insight into the theory of hadrons in QCD. For example, the Dirac-Coulomb equation, which predicts the spectroscopy and structure of hydrogenic atoms, has an analog in hadron physics in the form of light-front relativistic equations of motion which give a remarkable first approximation to the spectroscopy, dynamics, and structure of light hadrons. The renormalization scale for the running coupling, which is unambiguously set in QED, leads to a method for setting the renormalization scale in QCD. The production of atoms in flight provides a method for computing the formation of hadrons at the amplitude level. Conversely, many techniques which have been developed for hadron physics, such as scaling laws, evolution equations, and light-front quantization have equal utility for atomic physics, especially in the relativistic domain. I also present a new perspective for understanding the contributions to the cosmological constant from QED and QCD.

Quantum Phases of Atom-Molecule Mixtures of Fermionic Atoms

Science.gov (United States)

Lopez, Nicolas; Tsai, Shan-Wen

2009-11-01

Cold atom experiments have observed atom-molecule mixtures by tuning the interactions between particles.footnotetextM.L. Olsen, J. D. Perreault, T. D. Cumby, and D. S. Jin, Phys. Rev. A 80, 030701(R) (2009) We study many particle interactions by examaning a simple model that describes the destruction of fermionic atom pairs to form single bosonic molecules and vice versa. A set of functional Renomalization Group equationsfootnotetextR. Shankar, Rev. Mod. Phys., Vol 66 No. 1, January 1994^,footnotetextS.W. Tsai, A.H. Castro Neto, R. Shankar, D.K. Campbell, Phys. Rev. B 72, 054531 (2005) describing these processes are set up and solved numerically. The Self Energy of the fermions are attained as a function of frequency and we search for frequency dependent instabilities that could denote a transition from a disordered liquid to a BCS phase. (Financial support from NSF DMR-084781 and UC-Lab Fees Research Program.)

Iridium Clusters Encapsulated in Carbon Nanospheres as Nanocatalysts for Methylation of (Bio)Alcohols.

Science.gov (United States)

Liu, Qiang; Xu, Guoqiang; Wang, Zhendong; Liu, Xiaoran; Wang, Xicheng; Dong, Linlin; Mu, Xindong; Liu, Huizhou

2017-12-08

C-H methylation is an attractive chemical transformation for C-C bonds construction in organic chemistry, yet efficient methylation of readily available (bio)alcohols in water using methanol as sustainable C1 feedstock is limited. Herein, iridium nanocatalysts encapsulated in yolk-shell-structured mesoporous carbon nanospheres (Ir@YSMCNs) were synthesized for this transformation. Monodispersed Ir clusters (ca. 1.0 nm) were encapsulated in situ and spatially isolated within YSMCNs by a silica-assisted sol-gel emulsion strategy. A selection of (bio)alcohols (19 examples) was selectively methylated in aqueous phase with good-to-high yields over the developed Ir@YSMCNs. The improved catalytic efficiencies in terms of activity and selectivity together with the good stability and recyclability were contributable to the ultrasmall Ir clusters with oxidation chemical state as a consequence of the confinement effect of YSMCNs with interconnected nanostructures. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chain formation of metal atoms

DEFF Research Database (Denmark)

Bahn, Sune Rastad; Jacobsen, Karsten Wedel

2001-01-01

The possibility of formation of single-atomic chains by manipulation of nanocontacts is studied for a selection of metals (Ni, Pd, Pt, Cu, Ag, Au). Molecular dynamics simulations show that the tendency for chain formation is strongest for Au and Pt. Density functional theory calculations indicate...... that the metals which form chains exhibit pronounced many-atom interactions with strong bonding in low coordinated systems....

The relation of double peaks, observed in quartz hydride atomizers, to the fate of free analyte atoms in the determination of arsenic and selenium by atomic absorption spectrometry

International Nuclear Information System (INIS)

D'Ulivo, Alessandro; Dedina, Jiri

2002-01-01

The mechanism at the origin of double peaks formation in quartz hydride atomizers were investigated by continuous flow hydride generation atomic absorption spectrometry. Arsenic and selenium were used as model analytes. The effect of atomization mode (flame-in-gas-shield (FIGS), miniature diffusion flame and double flame (DF)) and some experimental parameters as oxygen supply rate for microflame and the distance from atomization to free atoms detection point, were investigated on the shape of both analytical signals and calibration graphs. Rollover of calibration graphs and double peak formation are strictly related each to the other and could be observed only in FIGS atomizer mode under some particular conditions. A mechanism based on incomplete atomization of hydrides cannot explain the collected experimental evidences because the microflame of FIGS is able to produce quantitative atomization of large amount of hydrides even at supply rate of oxygen close to extinction threshold of microflame. The heterogeneous gas-solid reactions between finely dispersed particles, formed by free atom recombination, and the free atoms in the gaseous phase are at the origin of double peak formation

Light exotic atoms in liquid and gaseous hydrogen and deuterium. Atom anti pp, theory and experiment

International Nuclear Information System (INIS)

Markushin, V.E.

1980-01-01

Considered are the de-eXcitation, absorption and Stark mixing processes in light exotic atoms formed in liquid and gaseous hydrogen (deuteriUm) and presented is the new method of the cascade calculations. Atom anti pp is studied in detail, calculated are: the populations of atomic levels, the absorption probabilities, and the X-rays yields. The present-day experimental data are discussed and it is concluded that all of them (but one result), can be easily reconciled with each other and with the theory

Atomic hydrogen storage method and apparatus

Science.gov (United States)

Woollam, J. A. (Inventor)

1980-01-01

Atomic hydrogen, for use as a fuel or as an explosive, is stored in the presence of a strong magnetic field in exfoliated layered compounds such as molybdenum disulfide or an elemental layer material such as graphite. The compounds maintained at liquid helium temperatures and the atomic hydrogen is collected on the surfaces of the layered compound which are exposed during delamination (exfoliation). The strong magnetic field and the low temperature combine to prevent the atoms of hydrogen from recombining to form molecules.

The labeling of unsaturated γ-hydroxybutyric acid by heavy isotopes of hydrogen: iridium complex-mediated H/D exchange by C─H bond activation vs reduction by boro-deuterides/tritides.

Science.gov (United States)

Marek, Aleš; Pedersen, Martin H F; Vogensen, Stine B; Clausen, Rasmus P; Frølund, Bente; Elbert, Tomáš

2016-10-01

3-Hydroxycyclopent-1-ene-1-carboxylic acid (HOCPCA (1)) is a potent ligand for high-affinity γ-hydroxybutyric acid binding sites in the central nervous system. Various approaches to the introduction of a hydrogen label onto the HOCPCA skeleton are reported. The outcomes of the feasible C─H activation of olefin carbon (C-2) by iridium catalyst are compared with the reduction of the carbonyl group (C-3) by freshly prepared borodeuterides. The most efficient iridium catalysts proved to be Kerr bulky phosphine N-heterocyclic species providing outstanding deuterium enrichment (up to 91%) in a short period of time. The highest deuterium enrichment (>99%) was achieved through the reduction of ketone precursor 2 by lithium trimethoxyborodeuteride. Hence, analogical conditions were used for the tritiation experiment. [ 3 H]-HOCPCA selectively labeled on the position C-3 was synthetized with radiochemical purity >99%, an isolated yield of 637 mCi and specific activity = 28.9 Ci/mmol. Copyright © 2016 John Wiley & Sons, Ltd.

Laser-induced fluorescence line narrowing in atomic vapors

International Nuclear Information System (INIS)

Meier, T.; Schuessler, H.A.

1983-01-01

The use of highly monochromatic light allows the selective excitation of atoms in vapors if excitation and detection of the fluorescence is carried out collinearly. The atoms capable of absorbing light then form an atomic beam of well defined velocity along the direction of the laser beam, but no velocity selection occurs perpendicular to it. The potential of the technique for Doppler-free atomic spectroscopy and for the study of excited atom collisions is demonstrated using the Na D 1 line as an example

Reversible Interconversion between 2,5-Dimethylpyrazine and 2,5-Dimethylpiperazine by Iridium-Catalyzed Hydrogenation/Dehydrogenation for Efficient Hydrogen Storage.

Science.gov (United States)

Fujita, Ken-Ichi; Wada, Tomokatsu; Shiraishi, Takumi

2017-08-28

A new hydrogen storage system based on the hydrogenation and dehydrogenation of nitrogen heterocyclic compounds, employing a single iridium catalyst, has been developed. Efficient hydrogen storage using relatively small amounts of solvent compared with previous systems was achieved by this new system. Reversible transformations between 2,5-dimethylpyrazine and 2,5-dimethylpiperazine, accompanied by the uptake and release of three equivalents of hydrogen, could be repeated almost quantitatively at least four times without any loss of efficiency. Furthermore, hydrogen storage under solvent-free conditions was also accomplished. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Attitudes and treatment outcome of breast conservation therapy for stage I and II breast cancer using peroperative iridium-192 implant boost to the tumour bed

International Nuclear Information System (INIS)

Deo, S.V.S.; Shukla, N.K.; Mohanti, B.K.; Chawla, S.; Julka, P.K.; Rath, G.K.; Raina, V.

2001-01-01

Breast conservation therapy for early breast cancer is an established but grossly under-utilized treatment option in India for various reasons. Breast conservation therapy was offered to 200 suitable breast cancer patients between June 1993 and June 1998. Fifty-one patients (25%) opted for breast conservation and the remaining preferred mastectomy. In patients agreeing to conservation therapy, surgery was performed first along with peroperative implantation of iridium-192 to deliver a boost. Whole breast irradiation of 45 Gy was delivered 3-4 weeks after the boost. Cosmesis was assessed at the end of 6 months from completion of therapy. The main reason for refusal of breast conservation therapy was fear of recurrence in the remaining breast (60%). There were no loco-regional failures in our study at a median follow up of 42 months; one patient experienced a systemic relapse. Cosmesis was good to excellent in 80% of patients. Breast conservation therapy using peroperative iridium-192 implant provides excellent loco-regional disease control and cosmesis. The results of our study indicate that patient preference for mastectomy is an important reason for the under-utilization of breast conservation therapy in India. Copyright (2001) Blackwell Science Pty Ltd

New iridium complex as additive to the spiro-OMeTAD in perovskite solar cells with enhanced stability

Directory of Open Access Journals (Sweden)

Laura Badia

2014-08-01

Full Text Available A new iridium complex, IrCp*Cl(PyPyz[TFSI], has been synthesized and used as additive for the hole transporter material, spiro-OMeTAD, in perovskite solar cells. The cells prepared with this Ir additive present higher efficiency than reference cells, and similar to cells prepared with Co additive. We have determined that the presence of metal complexes as additives decreases the recombination rate, as it has been observed by impedance spectroscopy. Very interestingly, while the efficiency after 3 months decreases by 22% and 70% for reference cell and cell with Co additive, respectively, the efficiency of devices containing the Ir additive is only decreased by a 4%.

/sup 238/Pu fuel-form processes. Quarterly report, October-December 1981

Energy Technology Data Exchange (ETDEWEB)

1982-05-01

Progress in the Savannah River /sup 238/Pu Fuel Form Program is summarized. Work during this period concentrated on the extensive cracking of the /sup 238/PuO/sub 2/ fuel form prior to encapsulation in the iridium containment shell for heat sources. This cracking results in increased recycle cost and decreased production efficiency. To better understand this cracking, Savannah River Laboratory (SRL) has made an extensive review of the development of /sup 238/PuO/sub 2/ fuel forms from small-scale Multi-hundred Watt (MHW) pellets through the current GPHS full-scale pellet production. Historically, /sup 238/PuO/sub 2/ fuel has almost always been uncracked after hot pressing in a graphite die, but has emerged cracked and fragile from the final heat-treatment furnace. The cracking tendency depends on the microstructure of the fuel form and on the hot pressing conditions used to fabricate it. In general, a microstructure of large intershard porosity is more desirable because it allows internal gas to escape more readily and it can absorb more reoxidation strain. Studies of the GPHS microstructure showed that the internal structures of typical GPHS Pellets fabricated at LANL and in the PEF differed significantly. The LANL pellets had severe density gradients and were extensively cracked.

Second CERN group produces cold atoms of antihydrogen

CERN Document Server

Levi-Goss, Barbara

2003-01-01

A new experiment, by CERN's ATRAP collaboration, which introduced a technique for determining the quantum state in which antihydrogen atoms are formed was discussed. To make antihydrogen, antiprotons were taken from CERN's Antiproton Decelerator, further slowed down, and trapped with a configuration of electric fields. The evidence gathered confirmed that the H over bar atoms formed in the experiment occupy highly excited Rydberg states. (Edited abstract) 5 Refs.

Reactions of newly formed fission products in the gas phase

International Nuclear Information System (INIS)

Strickert, R.G.

1976-01-01

A dynamic gas-flow system was constructed which stopped fission products in the gas phase and rapidly separated (in less than 2 sec) volatile compounds from non-volatile ones. The filter assembly designed and used was shown to stop essentially all non-volatile fission products. Between 5 percent and 20 percent of tellurium fission-product isotopes reacted with several hydrocarbon gases to form volatile compounds, which passed through the filter. With carbon monoxide gas, volatile tellurium compound(s) (probably TeCO) were also formed with similar efficiencies. The upper limits for the yields of volatile compounds formed between CO and tin and antimony fission products were shown to be less than 0.3 percent, so tellurium nuclides, not their precursors, reacted with CO. It was found that CO reacted preferentially with independently produced tellurium atoms; the reaction efficiency of beta-produced atoms was only 27 +- 3 percent of that of the independently formed atoms. The selectivity, which was independent of the over-all reaction efficiency, was shown to be due to reaction of independently formed atoms in the gas phase. The gas phase reactions are believed to occur mainly at thermal energies because of the independence of the yield upon argon moderator mole-fraction (up to 80 percent). It was shown in some experiments that about one-half of the TeCO decomposed in passing through a filter and that an appreciable fraction (approximately 20 percent) of the tellurium atoms deposited on the filter reacted agin with CO. Other tellurium atoms on the filter surface (those formed by beta decay and those formed independently but not reacting in the gas phase) also reacted with CO, but probably somewhat less efficiently than atoms formed by TeCO decomposition. No evidence was found for formation of TeCO as a direct result of beta-decay

Atom-by-atom assembly

International Nuclear Information System (INIS)

Hla, Saw Wai

2014-01-01

Atomic manipulation using a scanning tunneling microscope (STM) tip enables the construction of quantum structures on an atom-by-atom basis, as well as the investigation of the electronic and dynamical properties of individual atoms on a one-atom-at-a-time basis. An STM is not only an instrument that is used to ‘see’ individual atoms by means of imaging, but is also a tool that is used to ‘touch’ and ‘take’ the atoms, or to ‘hear’ their movements. Therefore, the STM can be considered as the ‘eyes’, ‘hands’ and ‘ears’ of the scientists, connecting our macroscopic world to the exciting atomic world. In this article, various STM atom manipulation schemes and their example applications are described. The future directions of atomic level assembly on surfaces using scanning probe tips are also discussed. (review article)

Theoretical study on the electronic structures and phosphorescent properties of a series of iridium(III) complexes with the different positional N-substitution in the pyridyl moiety

Energy Technology Data Exchange (ETDEWEB)

Han, Deming; Hao, Fengqi [School of Life Science and Technology, Changchun University of Science and Technology, Changchun 130022 (China); Tian, Jian [Clean Energy Technology Laboratory, Changchun University of Science and Technology, Changchun 130022 (China); Pang, Chunying; Li, Jingmei [School of Life Science and Technology, Changchun University of Science and Technology, Changchun 130022 (China); Zhao, Lihui, E-mail: zhaolihui@yahoo.com [School of Life Science and Technology, Changchun University of Science and Technology, Changchun 130022 (China); Zhang, Gang [State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023 (China)

2015-03-15

The geometry structures, electronic structures, absorption and phosphorescent properties of a series of iridium(III) complexes with the different N-substitution cyclometalating ligand and the same benzyldiphenylphosphine auxiliary ligand have been theoretically investigated by using the density functional theory method. The lowest energy absorption wavelengths are located at 378 nm for A, 430 nm for B, 411 nm for C, 436 nm for D, and 394 nm for E. The introduction of N atom substitution at 1-, 2-, 3-, and 4-positions on the pyridyl moiety of complex A leads to an obvious redshifted absorption. The lowest energy emissions for complexes A–E are localized at 450, 409, 438, 483, and 429 nm, respectively, simulated in CH{sub 2}Cl{sub 2} medium at M052X level. Ionization potential and electron affinity have been calculated to evaluate the injection abilities of holes and electrons into these complexes. For complex C, the calculated results showed that it can possibly possess the larger radiative decay rate (k{sub r}) value than those of other four complexes. It is anticipated that the theoretical studies can provide valuable information for designing new phosphorescent metal complexes of organic light-emitting diodes. - Highlights: • Five Ir(III) complexes have been theoretically investigated. • The effect of N-substitution cyclometalating ligand has been studied. • The complex C possibly possesses the largest radiative decay rate value.

The optical model in atomic physics

International Nuclear Information System (INIS)

McCarthy, I.E.

1978-01-01

The optical model for electron scattering on atoms has quite a short history in comparison with nuclear physics. The main reason for this is that there were insufficient data. Angular distribution for elastic and some inelastic scattering have now been measured for the atoms which exist in gaseous form at reasonable temperatures, inert gases, hydrogen, alkalies and mercury being the main ones out in. The author shows that the optical model makes sense in atomic physics by considering its theory and recent history. (orig./AH) [de

Highly Simplified Reddish Orange Phosphorescent Organic Light-Emitting Diodes Incorporating a Novel Carrier- and Exciton-Confining Spiro-Exciplex-Forming Host for Reduced Efficiency Roll-off.

Science.gov (United States)

Xu, Ting; Zhang, Ye-Xin; Wang, Bo; Huang, Chen-Chao; Murtaza, Imran; Meng, Hong; Liao, Liang-Sheng

2017-01-25

A novel exciplex-forming host is applied so as to design highly simplified reddish orange light-emitting diodes (OLEDs) with low driving voltage, high efficiency, and an extraordinarily low efficiency roll-off, by combining N,N-10-triphenyl-10H-spiro [acridine-9,9'-fluoren]-3'-amine (SAFDPA) with 4,7-diphenyl-1,10-phenanthroline (Bphen) doped with trivalent iridium complex bis(2-methyldibenzo[f,h]quinoxaline) (acetylacetonate)iridium(III) (Ir(MDQ) 2 (acac)). The reddish orange OLEDs achieve a strikingly high power efficiency (PE) of 31.80 lm/W with an ultralow threshold voltage of 2.24 V which is almost equal to the triplet energy level of the phosphorescent reddish orange emitting dopant. The power efficiency of the device with the exciplex-forming host is enhanced, achieving 36.2% mainly owing to the lower operating voltage by the novel exciplex forming cohost, compared with the reference device (23.54 lm/W). Moreover, the OLEDs show extraordinarily low current efficiency (CE) roll-off to 1.41% at the brightness from 500 to 5000 cd/m 2 with a maximal CE of 32.87 cd/A (EQE max = 11.01%). The devices display a good reddish orange color (CIE of (0.628, 0.372) at 500 cd/m 2 ) nearly without color shift with increasing brightness. Co-host architecture phosphorescent OLEDs show a simpler device structure, lower working voltage, and a better efficiency and stability than those of the reference devices without the cohost architecture, which helps to simplify the OLED structure, lower the cost, and popularize OLED technology.

Analytic cross sections for collisions of H, H2, He and Li atoms and ions with atoms and molecules. 3

International Nuclear Information System (INIS)

Ito, Rinsuke; Tabata, Tatsuo; Shirai, Toshizo; Phaneuf, R.A.

1995-07-01

Analytic expressions fitted to Barnett's recommended data are given for the collision cross sections of H, H 2 , He, and Li atoms and ions colliding with atoms and molecules. The collisions treated are ionization collisions, charge-production collisions, electron-loss collisions, and electron detachment collisions. The analytic expressions use the semiempirical functional forms proposed by Green and McNeal and some modified forms to make it possible not only to interpolate but also to extrapolate the recommended data. (author)

Four-parameter analytical local model potential for atoms

International Nuclear Information System (INIS)

Fei, Yu; Jiu-Xun, Sun; Rong-Gang, Tian; Wei, Yang

2009-01-01

Analytical local model potential for modeling the interaction in an atom reduces the computational effort in electronic structure calculations significantly. A new four-parameter analytical local model potential is proposed for atoms Li through Lr, and the values of four parameters are shell-independent and obtained by fitting the results of X a method. At the same time, the energy eigenvalues, the radial wave functions and the total energies of electrons are obtained by solving the radial Schrödinger equation with a new form of potential function by Numerov's numerical method. The results show that our new form of potential function is suitable for high, medium and low Z atoms. A comparison among the new potential function and other analytical potential functions shows the greater flexibility and greater accuracy of the present new potential function. (atomic and molecular physics)

Ultrafine Iridium Oxide Nanorods Synthesized by Molten Salt Method toward Electrocatalytic Oxygen and Hydrogen Evolution Reactions

International Nuclear Information System (INIS)

Ahmed, Jahangeer; Mao, Yuanbing

2016-01-01

Highlights: • Ultrafine iridium oxide nanorods were synthesized by a molten salt method at 650 °C. • They show enhanced electrocatalytic activity to oxygen and hydrogen evolution reactions. • These results are comparable with, and in most cases, higher than reported data in the literature. • This study reports a novel synthetic process for IrO_2 but also a high efficient IrO_2 nanostructure. • These IrO_2 NRs are expected to serve as a benchmark to develop active electrocatalysts. - Abstract: Ultrafine iridium oxide nanorods (IrO_2 NRs) were successfully synthesized using a molten salt method at 650 °C. The structural and morphological characterizations of these IrO_2 NRs were carried out by powder X-ray diffraction, Raman spectroscopy and electron microscopic techniques. Compared to commercial IrO_2 nanoparticles (IrO_2 NPs) and previous reports, these IrO_2 NRs show enhanced electrocatalytic activity to oxygen and hydrogen evolution reactions by passing either N_2 or O_2 gas in a 0.5 M KOH electrolyte before electrochemical measurements, including cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Specifically, the current densities from the as-synthesized IrO_2 NRs and commercial IrO_2 NPs were measured in 0.5 M KOH electrolyte to be 70 and 58 (OER, deaerated, at 0.6 V versus Ag/AgCl), 71 and 61 (OER, O_2, from −0.10 to 1.0 V versus Ag/AgCl at 50 mV/s), and 25 and 14 (HER, deaerated, at −1.4 V versus Ag/AgCl) mA/cm"2, respectively. These results are comparable with, and in most cases, higher than reported data in the literature. Therefore, the current study reports not only a novel synthetic process for IrO_2 but also a high efficient IrO_2 nanostructure, and it is expected that these IrO_2 NRs can serve as a benchmark in the development of active OER and HER (photo)electrocatalysts for various applications.

Possible world-wide middle miocene iridium anomaly and its relationship to periodicity of impacts and extinctions

Science.gov (United States)

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.

Atomic Act amended

International Nuclear Information System (INIS)

Drabova, D.

2002-01-01

In the paper by the chairwoman of the Czech nuclear regulatory authority, the history of Czech nuclear legislation is outlined, the reasons for the amendment of the Atomic Act (Act No. 18/1997) are explained, and the amendments themselves are highlighted. The Act No. 13/2002 of 18 December 2001 is reproduced from the official Collection of Acts of the Czech Republic in the facsimile form. The following acts were thereby amended: Atomic Act No. 18/1997, Metrology Act No. 505/1990, Public Health Protection Act No. 258/2000, and Act No. 2/1969 on the Establishment of Ministries and Other Governmental Agencies of the Czech Republic. (P.A.)

Atomic size effect on critical cooling rate and glass formation

International Nuclear Information System (INIS)

Jalali, Payman; Li Mo

2005-01-01

Atomic size effect on critical cooling rate and glass formability in a model binary system is investigated using molecular dynamics simulation. To isolate atomic size effect from the rest of the factors that critically influence the glass formation, a hard sphere model is employed in conjunction with a newly developed densification method. The glass formability is defined as a set of optimal conditions that result in the slowest cooling rate of the glass-forming liquid. Critical cooling rates are identified from extensive molecular dynamics simulations. A kinetic glass-forming diagram is mapped out that marks the boundary between the glass-forming regions and competing crystalline phases in terms of the parameters of the atomic size ratio and alloy concentration. It is found that the potency of the atomic size difference on glass formation is influenced greatly by the competing metastable and equilibrium crystalline phases in the system, and the kinetic processes leading to the formation of these phases. The mechanisms of the atomic size effect on topological instability of crystal packing and glass formation are discussed

Interaction of epitaxial silicene with overlayers formed by exposure to Al atoms and O{sub 2} molecules

Energy Technology Data Exchange (ETDEWEB)

Friedlein, R.; Yamada-Takamura, Y. [Japan Advanced Institute of Science and Technology, School of Materials Science, Nomi, Ishikawa 923-1292 (Japan); Van Bui, H.; Wiggers, F. B.; Kovalgin, A. Y.; Jong, M. P. de, E-mail: M.P.deJong@utwente.nl [MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede (Netherlands)

2014-05-28

As silicene is not chemically inert, the study and exploitation of its electronic properties outside of ultrahigh vacuum environments require the use of insulating capping layers. In order to understand if aluminum oxide might be a suitable encapsulation material, we used high-resolution synchrotron photoelectron spectroscopy to study the interactions of Al atoms and O{sub 2} molecules, as well as the combination of both, with epitaxial silicene on thin ZrB{sub 2}(0001) films grown on Si(111). The deposition of Al atoms onto silicene, up to the coverage of about 0.4 Al per Si atoms, has little effect on the chemical state of the Si atoms. The silicene-terminated surface is also hardly affected by exposure to O{sub 2} gas, up to a dose of 4500 L. In contrast, when Al-covered silicene is exposed to the same dose, a large fraction of the Si atoms becomes oxidized. This is attributed to dissociative chemisorption of O{sub 2} molecules by Al atoms at the surface, producing reactive atomic oxygen species that cause the oxidation. It is concluded that aluminum oxide overlayers prepared in this fashion are not suitable for encapsulation since they do not prevent but actually enhance the degradation of silicene.

Highly sensitive and interference-free determination of bismuth in environmental samples by electrothermal vaporization atomic fluorescence spectrometry after hydride trapping on iridium-coated tungsten coil

International Nuclear Information System (INIS)

Liu Rui; Wu Peng; Xu Kailai; Lv Yi; Hou Xiandeng

2008-01-01

Bismuthine was on-line trapped on tungsten coil and subsequently electrothermally vaporized for the determination by atomic fluorescence spectrometry (AFS). Several noble metals, including Pd, Rh, Pt, and Ir, were explored as permanent chemical modifier for tungsten coil on-line trapping. Investigation showed that Ir gave the best performance, in which bismuthine was on-line trapped on Ir-coated tungsten coil at 560 o C, and then released at 1550 o C for subsequent transfer to AFS by a mixture of Ar and H 2 . Under optimum instrumental conditions, the trapping efficiency was found to be 73 ± 3%. With 120 s (12 mL sample volume) trapping time, a limit of detection (LOD) of 4 ng L -1 was obtained, compared to conventional hydride generation AFS (0.09 μg L -1 ); the LOD can be lowered down to 1 ng L -1 by increasing the trapping time to 480 s. The LOD was found to be better or at least comparable to literature levels involving on-line trapping and some other sophisticated instrumental methods such as ICP-MS and GF-AAS. A comprehensive interference study involving conventional hydride-forming elements and some transition metals was carried out, and the result showed that the gas phase interference from other hydride-forming elements was largely reduced, thanks to the use of on-line tungsten coil trapping. Finally, the proposed method was applied to the determination of bismuth in several biological and environmental standard reference materials, and a t-test shows that the analytical results by the proposed method have no significant difference from the certified values at the confidence level of 95%

The influence of different cyclometalated ligand substituents and ancillary ligand on the phosphorescent properties of iridium(III) complexes

Energy Technology Data Exchange (ETDEWEB)

Zhang, Qing; Li, Yuanyuan; Wang, Xin; Wang, Li, E-mail: chemwangl@henu.edu.cn; Zhang, Jinglai, E-mail: zhangjinglai@henu.edu.cn

2016-07-01

Four iridium(III) complexes, (dfpmpy){sub 2}Ir(pic), (1), (dfpmpy){sub 2}Ir(EO{sub 2}-pic) (2), (dfpmpy){sub 2}Ir(pic-N-O) (3), and (dfpmpy){sub 2}Ir(EO{sub 2}-pic-N-O) (4) (dfpmpy = 2-(2,4-difluorophenyl)-4-methylpyridine, pic = picolinic acid, EO{sub 2}-pic = 4-(2-ethoxyethoxy) picolinic acid, pic-N-O = picolinic acid N-oxide, and EO{sub 2}-pic-N-O = 4-(2-ethoxyethoxy) picolinic acid N-oxide) are investigated by means of the density functional theory/time-dependent density functional theory (DFT/TD-DFT) to explore the influence of the ancillary ligand on the electronic structures, phosphorescent properties, and organic light-emitting diode (OLED) performance. Employing pic-N-O and EO{sub 2}-pic-N-O as the ancillary ligands would decrease the vertical energy and result in the red-shifted wavelength. Then, other four iridium(III) complexes (2a-2d) (See Scheme 1) are designed by introduction of the phenyl and −CHO substituents on the pyridine ring and phenyl ring of complex 2, respectively. As compared with complex 2, theoretical results show that newly designed complexes 2a-2c might be potential candidates for blue-emitting phosphors with better/comparable quantum yield and Δλ. Moreover, the performance of complexes 2a and 2c, i.e., introducing phenyl on the para-position of pyridine ring and phenyl ring in dfpmpy ligand, are better than that of 2b. - Highlights: • The structure-property relationship of Ir(III) complexes are investigated. • The effect of different substituents/positions on properties is explored. • Do the emissions follow the Kasha or non-Kasha scenario? • Newly possible blue-emitting Ir(III) complexes are theoretically designed.

High atomic weight isotope separator

International Nuclear Information System (INIS)

Book, D.L.

1978-01-01

A continuously operating device is described which separates one isotopic species of a given element from a mixture. The given element is vaporized and formed into a neutral beam containing the isotopes desired to be separated. The plasma is accelerated through a laser beam which is formed by two separate lasers which operate in the continuous wave mode in which the beams are as nearly as possible in the same beam path. The two laser output beams excite and ionize the isotope of interest while leaving the remaining atoms unaffected. The ionized isotopes are then separated from the beam by an electrostatic deflection technique and the unaffected atoms continue on in their path and are directed to a recovery device

Fluorine atom subsurface diffusion and reaction in photoresist

International Nuclear Information System (INIS)

Greer, Frank; Fraser, D.; Coburn, J.W.; Graves, David B.

2003-01-01

Kinetic studies of fluorine and deuterium atoms interacting with an OiR 897 10i i-line photoresist (PR) are reported. All experiments were conducted at room temperature. Films of this PR were coated on quartz-crystal microbalance (QCM) substrates and exposed to alternating fluxes of these atoms in a high vacuum apparatus. Mass changes of the PR were observed in situ and in real time during the atom beam exposures using the QCM. A molecular-beam sampled differentially pumped quadrupole mass spectrometer (QMS) was used to measure the species desorbing from the PR surface during the F and D atom exposures. During the D atom exposures, hydrogen abstraction and etching of the PR was observed, but no DF formation was detected. However, during the F atom exposures, the major species observed to desorb from the surface was DF, formed from fluorine abstraction of deuterium from the photoresist. No evidence of film etching or fluorine self-abstraction was observed. The film mass increased during F atom exposure, evidently due to the replacement of D by F in the film. The rate of DF formation and mass uptake were both characterized by the same kinetics: An initially rapid step declining exponentially with time (e -t/τ ), followed by a much slower step following inverse square root of time (t -1/2 ) kinetics. The initially rapid step was interpreted as surface abstraction of D by F to form DF, which desorbs, with subsequent F impacting the surface inserted into surface C dangling bonds. The slower step was interpreted as F atoms diffusing into the fluorinated photoresist, forming DF at the boundary of the fluorinated carbon layer. The t -1/2 kinetics of this step are interpreted to indicate that F diffusion through the fluorinated carbon layer is much slower than the rate of F abstraction of D to form DF, or the rate of F insertion into the carbon dangling bonds left behind after DF formation. A diffusion-limited growth model was formulated, and the model parameters are

Oxidation of MoS2 by thermal and hyperthermal atomic oxygen

International Nuclear Information System (INIS)

Cross, J.B.; Martin, J.A.; Pope, L.E.; Koontz, S.L.

1989-01-01

The present study shows that, at 1.5 eV O-atom translational energy, SO 2 is generated and outgases from an anhydrous MoS 2 surface with a reactivity nearly that of kapton. The reaction of atomic oxygen with MoS 2 has little or no translational energy barrier; i.e., thermally generated atomic oxygen reacts as readily as that having 1.5 eV of translational energy. It is also shown that water present in the flowing afterglow apparatus used to study thermal O-atom reactivity formed sulfates on the MoS 2 surface and that the sulfate is most likely in the form of sulfuric acid. These results imply that water dumps or outgasing in low earth orbit have the potential of forming sulfuric acid covered surfaces on MoS 2 lubricants. Friction measurements show a high initial friction coefficient (0.2) for O-atom exposed MoS 2 surfaces which drops to the normal low value (0.05) after several cycles of operation

An iridium oxide microelectrode for monitoring acute local pH changes of endothelial cells.

Science.gov (United States)

Ng, Shu Rui; O'Hare, Danny

2015-06-21

pH sensors were fabricated by anodically electrodepositing iridium oxide films (AEIROFs) onto microelectrodes on chips and coated with poly(ethyleneimine) (PEI) for mechanical stability. These demonstrate super-Nernstian response to pH from pH 4.0 to 7.7 in chloride-free phosphate buffer. The surface of the chip was coated with fibronectin for the attachment of porcine aortic endothelial cells (PAECs). The working capability of the pH sensor for monitoring acute local pH changes was investigated by stimulating the PAECs with thrombin. Our results show that thrombin induced acute extracellular acidification of PAECs and dissolution of fibronectin, causing the local pH to decrease. The use of PD98059, a mitogen-activated protein kinase (MAPK) inhibitor, reduced extracellular acidification and an increase in local pH was observed. This study shows that our pH sensors can facilitate the investigation of acute cellular responses to stimulation by monitoring the real-time, local pH changes of cells attached to the sensors.

Organometallic rhodium(III) and iridium(III) cyclopentadienyl complexes with curcumin and bisdemethoxycurcumin co-ligands.

Science.gov (United States)

Pettinari, Riccardo; Marchetti, Fabio; Pettinari, Claudio; Condello, Francesca; Petrini, Agnese; Scopelliti, Rosario; Riedel, Tina; Dyson, Paul J

2015-12-21

A series of half-sandwich cyclopentadienyl rhodium(III) and iridium(III) complexes of the type [Cp*M(curc/bdcurc)Cl] and [Cp*M(curc/bdcurc)(PTA)][SO3CF3], in which Cp* = pentamethylcyclopentadienyl, curcH = curcumin and bdcurcH = bisdemethoxycurcumin as O^O-chelating ligands, and PTA = 1,3,5-triaza-7-phosphaadamantane, is described. The X-ray crystal structures of three of the complexes, i.e. [Cp*Rh(curc)(PTA)][SO3CF3] (5), [Cp*Rh(bdcurc)(PTA)][SO3CF3] (6) and [Cp*Ir(bdcurc)(PTA)][SO3CF3] (8), confirm the expected "piano-stool" geometry. With the exception of 5, the complexes are stable under pseudo-physiological conditions and are moderately cytotoxic to human ovarian carcinoma (A2780 and A2780cisR) cells and also to non-tumorigenic human embryonic kidney (HEK293) cells, but lack the cancer cell selectivity observed for related arene ruthenium(II) complexes.

Atomic bonding between metal and graphene

KAUST Repository

Wang, Hongtao

2013-03-07

To understand structural and chemical properties of metal-graphene composites, it is crucial to unveil the chemical bonding along the interface. We provide direct experimental evidence of atomic bonding between typical metal nano structures and graphene, agreeing well with density functional theory studies. Single Cr atoms are located in the valleys of a zigzag edge, and few-atom ensembles preferentially form atomic chains by self-assembly. Low migration barriers lead to rich dynamics of metal atoms and clusters under electron irradiation. We demonstrate no electron-instigated interaction between Cr clusters and pristine graphene, though Cr has been reported to be highly reactive to graphene. The metal-mediated etching is a dynamic effect between metal clusters and pre-existing defects. The resolved atomic configurations of typical nano metal structures on graphene offer insight into modeling and simulations on properties of metal-decorated graphene for both catalysis and future carbon-based electronics. © 2013 American Chemical Society.

Magnetic trapping of cold bromine atoms.

Science.gov (United States)

Rennick, C J; Lam, J; Doherty, W G; Softley, T P

2014-01-17

Magnetic trapping of bromine atoms at temperatures in the millikelvin regime is demonstrated for the first time. The atoms are produced by photodissociation of Br2 molecules in a molecular beam. The lab-frame velocity of Br atoms is controlled by the wavelength and polarization of the photodissociation laser. Careful selection of the wavelength results in one of the pair of atoms having sufficient velocity to exactly cancel that of the parent molecule, and it remains stationary in the lab frame. A trap is formed at the null point between two opposing neodymium permanent magnets. Dissociation of molecules at the field minimum results in the slowest fraction of photofragments remaining trapped. After the ballistic escape of the fastest atoms, the trapped slow atoms are lost only by elastic collisions with the chamber background gas. The measured loss rate is consistent with estimates of the total cross section for only those collisions transferring sufficient kinetic energy to overcome the trapping potential.

Optical orientation of atoms in plasma

Energy Technology Data Exchange (ETDEWEB)

Zhitnikov, R

1979-06-01

The results are summed up of experimental work on the optical orientation of atoms in a plasma conducted by the Atomic Radiospectroscopy Group at the AN SSSR Physical Technology Institute. The main methods of forming and observing the optical orientation of atoms in a helium plasma and an alkali metal plasma are described in detail. A quantum mechanical explanation is given of all observed phenomena. The most significant results include the discovery of the effect of the optical orientation of atoms in a plasma on the plasma optical and electrical properties, such as electric conductivity, emitted light intensity, ionization degree, and electron density. The phenomenon applies generally and is inherent to plasmas of different chemical compositions, at the optical orientation of atoms of different elements. The methods are indicated of the practical application of the phenomenon in designing principally new precision quantum magnetometers.

Formation of fast exotic atoms by radiative Coulomb capture

International Nuclear Information System (INIS)

Chatterjee, L.; Das, G.; Chakravorty, A.; Goswami, R.; Mondal, S.K.

1993-01-01

Interesting surprises in some exotic atom kinetics have been reported recently. These involve muonic atom transfer cross sections, nuclear pion capture and the q 1s effect in μCF. These can be explained if the exotic atom population contains a contributing fast component. Such fast atoms can be formed by radiative continuum to bound transitions of fast (keV) muons or pions. Cross sections for formation of such fast pionic and muonic atoms and their velocity distributions are reported. The possibility of these processes competing with the thermalisation channels and contributing effectively to the exotic atom population discussed. (orig.)

Extending the accuracy of the SNAP interatomic potential form

Science.gov (United States)

Wood, Mitchell A.; Thompson, Aidan P.

2018-06-01

The Spectral Neighbor Analysis Potential (SNAP) is a classical interatomic potential that expresses the energy of each atom as a linear function of selected bispectrum components of the neighbor atoms. An extension of the SNAP form is proposed that includes quadratic terms in the bispectrum components. The extension is shown to provide a large increase in accuracy relative to the linear form, while incurring only a modest increase in computational cost. The mathematical structure of the quadratic SNAP form is similar to the embedded atom method (EAM), with the SNAP bispectrum components serving as counterparts to the two-body density functions in EAM. The effectiveness of the new form is demonstrated using an extensive set of training data for tantalum structures. Similar to artificial neural network potentials, the quadratic SNAP form requires substantially more training data in order to prevent overfitting. The quality of this new potential form is measured through a robust cross-validation analysis.

Copper Benzenetricarboxylate Metal-Organic Framework Nucleation Mechanisms on Metal Oxide Powders and Thin Films formed by Atomic Layer Deposition.

Science.gov (United States)

Lemaire, Paul C; Zhao, Junjie; Williams, Philip S; Walls, Howard J; Shepherd, Sarah D; Losego, Mark D; Peterson, Gregory W; Parsons, Gregory N

2016-04-13

Chemically functional microporous metal-organic framework (MOF) crystals are attractive for filtration and gas storage applications, and recent results show that they can be immobilized on high surface area substrates, such as fiber mats. However, fundamental knowledge is still lacking regarding initial key reaction steps in thin film MOF nucleation and growth. We find that thin inorganic nucleation layers formed by atomic layer deposition (ALD) can promote solvothermal growth of copper benzenetricarboxylate MOF (Cu-BTC) on various substrate surfaces. The nature of the ALD material affects the MOF nucleation time, crystal size and morphology, and the resulting MOF surface area per unit mass. To understand MOF nucleation mechanisms, we investigate detailed Cu-BTC MOF nucleation behavior on metal oxide powders and Al2O3, ZnO, and TiO2 layers formed by ALD on polypropylene substrates. Studying both combined and sequential MOF reactant exposure conditions, we find that during solvothermal synthesis ALD metal oxides can react with the MOF metal precursor to form double hydroxy salts that can further convert to Cu-BTC MOF. The acidic organic linker can also etch or react with the surface to form MOF from an oxide metal source, which can also function as a nucleation agent for Cu-BTC in the mixed solvothermal solution. We discuss the implications of these results for better controlled thin film MOF nucleation and growth.

When two are better than one: bright phosphorescence from non-stereogenic dinuclear iridium(III) complexes.

Science.gov (United States)

Daniels, Ruth E; Culham, Stacey; Hunter, Michael; Durrant, Marcus C; Probert, Michael R; Clegg, William; Williams, J A Gareth; Kozhevnikov, Valery N

2016-04-28

A new family of eight dinuclear iridium(iii) complexes has been prepared, featuring 4,6-diarylpyrimidines L(y) as bis-N^C-coordinating bridging ligands. The metal ions are also coordinated by a terminal N^C^N-cyclometallating ligand L(X) based on 1,3-di(2-pyridyl)benzene, and by a monodentate chloride or cyanide. The general formula of the compounds is {IrL(X)Z}2L(y) (Z = Cl or CN). The family comprises examples with three different L(X) ligands and five different diarylpyrimidines L(y), of which four are diphenylpyrimidines and one is a dithienylpyrimidine. The requisite proligands have been synthesised via standard cross-coupling methodology. The synthesis of the complexes involves a two-step procedure, in which L(X)H is reacted with IrCl3·3H2O to form dinuclear complexes of the form [IrL(X)Cl(μ-Cl)]2, followed by treatment with the diarylpyrimidine L(y)H2. Crucially, each complex is formed as a single compound only: the strong trans influence of the metallated rings dictates the relative disposition of the ligands, whilst the use of symmetrically substituted tridentate ligands eliminates the possibility of Λ and Δ enantiomers that are obtained when bis-bidentate units are linked through bridging ligands. The crystal structure of one member of the family has been obtained using a synchrotron X-ray source. All of the complexes are very brightly luminescent, with emission maxima in solution varying over the range 517-572 nm, according to the identity of the ligands. The highest-energy emitter is the cyanide derivative whilst the lowest is the complex with the dithienylpyrimidine. The trends in both the absorption and emission energies as a function of ligand substituent have been rationalised accurately with the aid of TD-DFT calculations. The lowest-excited singlet and triplet levels correlate with the trend in the HOMO-LUMO gap. All the complexes have quantum yields that are close to unity and phosphorescence lifetimes - of the order of 500 ns - that are

Phase and group velocities for Lamb waves in DOP-26 iridium alloy sheet

International Nuclear Information System (INIS)

Simpson, W.A.; McGuire, D.J.

1994-07-01

The relatively coarse grain structure of iridium weldments limits the ultrasonic inspection of these structures to frequencies in the low megahertz range. As the material thickness is nominally 0.635 mm for clad vent set capsules, the low frequencies involved necessarily entail the generation of Lamb waves m the specimen. These waves are, of course, dispersive and detailed knowledge of both the phase and group velocities is required in order to determine accurately the location of flaws detected using Lamb waves. Purpose of this study is to elucidate the behavior of Lamb waves propagating in the capsule alloy and to quantify the velocities so that accurate flaw location is ensured. We describe a numerical technique for computing the phase velocities of Lamb waves (or of any other type of guided wave) and derive the group velocities from this information. A frequency-domain method is described for measuring group velocity when multiple Lamb modes are present and mutually interfering in the time domain, and experimental confirmation of the group velocity is presented for the capsule material

Shuttling single metal atom into and out of a metal nanoparticle.

Science.gov (United States)

Wang, Shuxin; Abroshan, Hadi; Liu, Chong; Luo, Tian-Yi; Zhu, Manzhou; Kim, Hyung J; Rosi, Nathaniel L; Jin, Rongchao

2017-10-10

It has long been a challenge to dope metal nanoparticles with a specific number of heterometal atoms at specific positions. This becomes even more challenging if the heterometal belongs to the same group as the host metal because of the high tendency of forming a distribution of alloy nanoparticles with different numbers of dopants due to the similarities of metals in outmost electron configuration. Herein we report a new strategy for shuttling a single Ag or Cu atom into a centrally hollow, rod-shaped Au 24 nanoparticle, forming AgAu 24 and CuAu 24 nanoparticles in a highly controllable manner. Through a combined approach of experiment and theory, we explain the shuttling pathways of single dopants into and out of the nanoparticles. This study shows that the single dopant is shuttled into the hollow Au 24 nanoparticle either through the apex or side entry, while shuttling a metal atom out of the Au 25 to form the Au 24 nanoparticle occurs mainly through the side entry.Doping a metal nanocluster with heteroatoms dramatically changes its properties, but it remains difficult to dope with single-atom control. Here, the authors devise a strategy to dope single atoms of Ag or Cu into hollow Au nanoclusters, creating precise alloy nanoparticles atom-by-atom.

Radiofrequency-dressed-state potentials for neutral atoms

DEFF Research Database (Denmark)

Hofferberth, S.; Lesanovsky, Igor; Fischer, B.

2006-01-01

Potentials for atoms can be created by external fields acting on properties such as magnetic moment, charge, polarizability, or by oscillating fields that couple internal states. The most prominent realization of the latter is the optical dipole potential formed by coupling ground and electronica......Potentials for atoms can be created by external fields acting on properties such as magnetic moment, charge, polarizability, or by oscillating fields that couple internal states. The most prominent realization of the latter is the optical dipole potential formed by coupling ground...... and electronically excited states of an atom with light. Here, we present an extensive experimental analysis of potentials derived from radiofrequency (RF) coupling of electronic ground states. The coupling is magnetic and the vector character allows the design of versatile microscopic state-dependent potential...... landscapes. Compared with standard magnetic trapping, we find no additional heating or (collisional) loss up to densities of 1015 atoms cm-3. We demonstrate robust evaporative cooling in RF potentials, which allows easy production of Bose-Einstein condensates in complex potentials. Altogether, this makes RF...

Topological Fractional Pumping with Alkaline-Earth-Like Atoms in Synthetic Lattices

Science.gov (United States)

Taddia, Luca; Cornfeld, Eyal; Rossini, Davide; Mazza, Leonardo; Sela, Eran; Fazio, Rosario

2017-06-01

Alkaline-earth(-like) atoms, trapped in optical lattices and in the presence of an external gauge field, can form insulating states at given fractional fillings. We will show that, by exploiting these properties, it is possible to realize a topological fractional pump. Our analysis is based on a many-body adiabatic expansion, on simulations with time-dependent matrix product states, and, for a specific form of atom-atom interaction, on an exactly solvable model of fractional pump. The numerical simulations allow us to consider a realistic setup amenable of an experimental realization. As a further consequence, the measure of the center-of-mass shift of the atomic cloud would constitute the first measurement of a many-body Chern number in a cold-atom experiment.

Atomic energy control board. History backgrounder

International Nuclear Information System (INIS)

1986-10-01

The Atomic Energy Control Board (AECB) is a regulatory agency set up by the Government of Canada under the Atomic Energy Control Act of 1946 to assist the Government in its efforts to make provision for the control and supervision of the development, application and use of atomic energy and to enable Canada to participate effectively in measures of international control of atomic energy. It is also responsible for the administration of the Nuclear Liability Act, including the designation of nuclear installations and the prescription of basic insurance to be carried by the operators of such nuclear installations. An overview is presented of the AECB's evolution in chronological form, its major current activities, and some of the challenges expected in the next decade

Long-range interactions among three alkali-metal atoms

International Nuclear Information System (INIS)

Marinescu, M.; Starace, A.F.

1996-01-01

The long-range asymptotic form of the interaction potential surface for three neutral alkali-metal atoms in their ground states may be expressed as an expansion in inverse powers of inter-nuclear distances. The first leading powers are proportional to the dispersion coefficients for pairwise atomic interactions. They are followed by a term responsible for a three body dipole interaction. The authors results consist in evaluation of the three body dipole interaction coefficient between three alkali-metal atoms. The generalization to long-range n atom interaction terms will be discussed qualitatively

Development and application of an iridium tracer for tracking tailings in the central Red Sea

International Nuclear Information System (INIS)

Schnier, C.; Fanger, H.U.

1983-01-01

In order to investigate the distribution of disposed tailings, the element iridium was applied as a tracer during the prepilot mining test in the Red Sea 1979. In the sediment matrix, Ir can be detected in quantities as small as 25 x 10 -12 g by means of neutron activation analysis. The tracer was obtained by melting down a mixture of 50 kg quartz and 1 kg IrO 2 , then grinding and pulverizing the material to an appropriate grain size distribution. An amount of 480 m 3 tracer-added tailings was disposed in a depth of 400 m close to the Atlantis II deep. Subsequently, in the period 1 month to 2 1/2 years later, 32 sediment samples were taken from the deposition area and analysed for Ir. The Ir concentration observed were surprisingly low and give only vague indications of the spreading of the tailings. (orig.) [de

Postoperative irradiation of endometrial cancer by iridium afterloading technique

International Nuclear Information System (INIS)

Kucera, H.; Weghaupt, K.

1988-01-01

From 1981 to 1986 708 patients were operated and postoperativly treated by total hysterectomy, bilateral salpingo-oophorectomy and postoperative vaginal irradiation with high-dose-afterloading (iridium 192). A percutaneous irradiation (cobalt 60) was done in stage I cases only when myometrial infiltration was deep. Highly differentiated tumors with infiltration of the first and second thirth of the myometrium were treated by vaginal irradiation alone. Poorly differentiated tumors with infiltration of the second and third thirth of the myometrium were treated by vaginal and percutaneous irradiation. A group of 125 cases with good prognosis and with postoperative vaginal irradiation alone had the same five-year-survival of 83% as a group of 152 cases with bad prognosis treated by vaginal and percutaneous irrradiation. This result shows clearly the importance of additional irradiation of the pelvis in cases with bad prognosis factors. The incidence of radiation side effect in all 708 cases was: cystitis 4.6%, proctitis 5.2%, vaginal or rectal ulcera 1.4% and fistulas 0.2%. Cases with vaginal irradiation alone and with the optimal intravaginal fraction dose of 700 cGy (twice) had the lowest level of side effects: cystitis 3.8% proctitis 2.1%, vaginal necrosis 0.7%, no further severe complications. None of the patients with postoperative vaginal irradiation alone had a vaginal recurrence. The incidence of recurrences in 708 patients was 1.6%. All recurrence cases in stage I (0.7%) had bad prognosis factors and were treated with vaginal and percutaneous irradiation. (orig./MG) [de

Sequences of measures on atomic subalgebras of P(N) | Aizpuru ...

African Journals Online (AJOL)

Sequences of measures on atomic subalgebras of P(N). Antonio Aizpuru, Antonio Gutierrez-D´avila. Abstract. A vector form of Phillips' theorem, for atomic Boolean algebras with countably many atoms, is given. As a consequence we obtain a new characterization of weak compact sets of σ-additive measures. Quaestiones ...

Optical orientation of atoms in plasma

International Nuclear Information System (INIS)

Zhitnikov, R.

1979-01-01

The results are summed up of experimental work on the optical orientation of atoms in a plasma conducted by the Atomic Radiospectroscopy Group at the AN SSSR Physical Technology Institute. The main methods of forming and observing the optical orientation of atoms in a helium plasma and an alkali metal plasma are described in detail. A quantum mechanical explanation is given of all observed phenomena. The most significant results include the discovery of the effect of the optical orientation of atoms in a plasma on the plasma optical and electrical properties, such as electric conductivity, emitted light intensity, ionization degree, and electron density. The phenomenon applies generally and is inherent to plasmas of different chemical compositions, at the optical orientation of atoms of different elements. The methods are indicated of the practical application of the phenomenon in designing principally new precision quantum magnetometers. (J.U.)

Thermal stability of atom configurations around Er atoms doped in InP by OMVPE

International Nuclear Information System (INIS)

Ofuchi, Hironori; Ito, Takashi; Kawamoto, Takeshi; Tabuchi, Masao; Fujiwara, Yasufumi; Takeda, Yoshikazu

1999-01-01

It has been found that there is a threshold growth temperature between 550 deg C and 580 deg C for the change of local structure around Er atoms in InP doped Er atoms grown by organometallic vapor phase epitaxy (OMVPE). To understand whether the structure change is induced at the growing surface or during the growth as an in situ annealing, the thermal stability of the local structures around the Er atoms doped in InP by the OMVPE at 530 deg C has been investigated by the extended X-ray absorption fine structure (EXAFS). The EXAFS analysis revealed that the local structure around the Er atoms, which existed substitutionally on In sites in the InP lattice, was stable against the post-growth annealing even for 1 h at 650 deg C. Therefore, it is concluded that the local structures are formed on the growth front, and not in the volume of InP by thermal annealing during or after the growth. (author)

Atom Probe Analysis of Ex Situ Gas-Charged Stable Hydrides.

Science.gov (United States)

Haley, Daniel; Bagot, Paul A J; Moody, Michael P

2017-04-01

In this work, we report on the atom probe tomography analysis of two metallic hydrides formed by pressurized charging using an ex situ hydrogen charging cell, in the pressure range of 200-500 kPa (2-5 bar). Specifically we report on the deuterium charging of Pd/Rh and V systems. Using this ex situ system, we demonstrate the successful loading and subsequent atom probe analysis of deuterium within a Pd/Rh alloy, and demonstrate that deuterium is likely present within the oxide-metal interface of a native oxide formed on vanadium. Through these experiments, we demonstrate the feasibility of ex situ hydrogen analysis for hydrides via atom probe tomography, and thus a practical route to three-dimensional imaging of hydrogen in hydrides at the atomic scale.

Investigation of chemical modifiers for the direct determination of arsenic in fish oil using high-resolution continuum source graphite furnace atomic absorption spectrometry.

Science.gov (United States)

Pereira, Éderson R; de Almeida, Tarcísio S; Borges, Daniel L G; Carasek, Eduardo; Welz, Bernhard; Feldmann, Jörg; Campo Menoyo, Javier Del

2016-04-01

High-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) has been applied for the development of a method for the determination of total As in fish oil samples using direct analysis. The method does not use any sample pretreatment, besides dilution with 1-propanole, in order to decrease the oil viscosity. The stability and sensitivity of As were evaluated using ruthenium and iridium as permanent chemical modifiers and palladium added in solution over the sample. The best results were obtained with ruthenium as the permanent modifier and palladium in solution added to samples and standard solutions. Under these conditions, aqueous standard solutions could be used for calibration for the fish oil samples diluted with 1-propanole. The pyrolysis and atomization temperatures were 1400 °C and 2300 °C, respectively, and the limit of detection and characteristic mass were 30 pg and 43 pg, respectively. Accuracy and precision of the method have been evaluated using microwave-assisted acid digestion of the samples with subsequent determination by HR-CS GF AAS and ICP-MS; the results were in agreement (95% confidence level) with those of the proposed method. Copyright © 2015 Elsevier B.V. All rights reserved.

Neutron activation analysis in geochemical characterization of Jurassic-Cretaceous sedimentary rocks from the Nordvik Peninsula

Czech Academy of Sciences Publication Activity Database

Mizera, Jiří; Řanda, Zdeněk; Košťák, M.

2010-01-01

Roč. 284, č. 1 (2010), s. 211-219 ISSN 0236-5731 Institutional research plan: CEZ:AV0Z10480505 Keywords : Jurassic-Cretaceous boundary * Nordvik Peninsula * Iridium anomaly Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 0.777, year: 2010

Equiatomic indides REIrIn (RE=La, Pr, Nd, Er-Yb). Crystal and electronic structure

Energy Technology Data Exchange (ETDEWEB)

Zaremba, Nazar [Ivan Franko National Univ. of Lviv (Ukraine). Dept. of Inorganic Chemistry; Technische Univ. Muenchen, Garching (Germany). Fakultaet fuer Chemie; Muts, Ihor; Zaremba, Vasyl [Ivan Franko National Univ. of Lviv (Ukraine). Dept. of Inorganic Chemistry; Hlukhyy, Viktor [Technische Univ. Muenchen, Garching (Germany). Fakultaet fuer Chemie; Stein, Sebastian; Rodewald, Ute C.; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Pavlyuk, Volodymyr [Ivan Franko National Univ. of Lviv (Ukraine). Dept. of Inorganic Chemistry; Czestochowa Jan Dlugosz Univ., Czestochowa (Poland). Inst. of Chemistry, Environmental Protection and Biotechnology

2017-10-01

The equiatomic rare earth iridium indides REIrIn (RE=La, Pr, Nd, Er-Yb) were synthesized by reaction of the elements in induction or muffle furnaces and were characterized through X-ray powder patterns. The structures of LaIr{sub 0.86}In{sub 1.14}, PrIr{sub 0.89}In{sub 1.11}, NdIr{sub 0.94}In{sub 1.06}, ErIrIn (all ZrNiAl type, P anti 62m), and YbIrIn (TiNiSi type, Pnma) were refined from single crystal X-ray diffractometer data. Refinements of the occupancy parameters revealed small degrees of solid solutions with indium substitution on the iridium sites. Chemical bonding analyses and electronic structure calculations indicate the dominance of metallic bonding in addition to partial ionic interactions between the cations and polyanions, as well as covalent contributions between the indium and iridium atoms.

Massive stars formed in atomic hydrogen reservoirs: H i observations of gamma-ray burst host galaxies

DEFF Research Database (Denmark)

Michałowski, M. J.; Gentile, G.; Hjorth, J.

2015-01-01

to be the fuel of star formation. Moreover, optical spectroscopy of GRB afterglows implies that the molecular phase constitutes only a small fraction of the gas along the GRB line of sight. Here we report the first ever 21 cm line observations of GRB host galaxies, using the Australia Telescope Compact Array......, implying high levels of atomic hydrogen (HI), which suggests that the connection between atomic gas and star formation is stronger than previously thought. In this case, it is possible that star formation is directly fuelled by atomic gas (or that the H1-to-H2 conversion is very efficient, which rapidly...... exhaust molecular gas), as has been theoretically shown to be possible. This can happen in low-metallicity gas near the onset of star formation because cooling of gas (necessary for star formation) is faster than the H1-to-H2 conversion. Indeed, large atomic gas reservoirs, together with low molecular gas...

Pentamethylcyclopentadienyl-rhodium and iridium complexes containing (N^N and N^O) bound chloroquine analogue ligands: synthesis, characterization and antimalarial properties.

Science.gov (United States)

Ekengard, Erik; Kumar, Kamlesh; Fogeron, Thibault; de Kock, Carmen; Smith, Peter J; Haukka, Matti; Monari, Magda; Nordlander, Ebbe

2016-03-07

The synthesis and characterization of twenty new pentamethylcyclopentadienyl-rhodium and iridium complexes containing N^N and N^O-chelating chloroquine analogue ligands are described. The in vitro antimalarial activity of the new ligands as well as the complexes was evaluated against the chloroquine sensitive (CQS) NF54 and the chloroquine resistant (CQR) Dd2 strains of Plasmodium falciparum. The antimalarial activity was found to be good to moderate; although all complexes are less active than artesunate, some of the ligands and complexes showed better activity than chloroquine (CQ). In particular, rhodium complexes were found to be considerably more active than iridium complexes against the CQS NF54 strain. Salicylaldimine Schiff base ligands having electron-withdrawing groups (F, Cl, Br, I and NO2) in para position of the salicyl moiety and their rhodium complexes showed good antiplasmodial activity against both the CQS-NF54 and the CQR-Dd2 strains. The crystal structures of (η(5)-pentamethylcyclopentadienyl){N(1)-(7-chloroquinolin-4-yl)-N(2)-(pyridin-2-ylmethyl)ethane-1,2-diamine)} chlororhodium(III) chloride and (η(5)-pentamethylcyclopentadienyl){(4-chloro-2-(((2-((7-chloroquinolin-4-yl)amino)ethyl)imino)methyl)phenolate)}chlororhodium(III) chloride are reported. The crystallization of the amino-pyridyl complex (η(5)-pentamethylcyclopentadienyl){(N(1)-(7-chloroquinolin-4-yl)-N(2)-(pyridin-2-ylmethyl)ethane-1,2-diamine)}chloroiridium(III) chloride in acetone resulted in the formation of the imino-pyridyl derivative (η(5)-pentamethylcyclopentadienyl){(N1-(7-chloroquinolin-4-yl)-N2-(pyridin-2-ylmethylene)ethane-1,2-diamine)}chloroiridium(III) chloride, the crystal structure of which is also reported.

Synthesis of Fischer carbene complexes of iridium by C-H bond activation of methyl and cyclic ethers: Evidence for reversible {alpha}-hydrogen migration

Energy Technology Data Exchange (ETDEWEB)

Luecke, H.F.; Arndtsen, B.A.; Burger, P.; Bergman, R.G. [Lawrence Berkeley Lab., CA (United States)]|[Univ. of California, Berkeley, CA (United States)

1996-03-13

We report here a mild and versatile route to Fischer carbene complexes of iridium via the activation of C-H bonds of methyl and cyclic ethers, along with our preliminary studies of this rare family of carbene complexes. Theoretical studies suggest that {alpha}-hydrogen migrations can be kinetically favorable if a coordinatively unsaturated species can be accessed. Thus, the lability of the triflate ligand presumably facilitates this process. Further evidence for the rapidity, as well as reversibility, of this rearrangement was obtained by NMR analysis. 20 refs.

Reactivity Control of Rhodium Cluster Ions by Alloying with Tantalum Atoms.

Science.gov (United States)

Mafuné, Fumitaka; Tawaraya, Yuki; Kudoh, Satoshi

2016-02-18

Gas phase, bielement rhodium and tantalum clusters, RhnTam(+) (n + m = 6), were prepared by the double laser ablation of Rh and Ta rods in He carrier gas. The clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He and were subjected to collisions with NO and He at room temperature. The product species were observed by mass spectrometry, demonstrating that the NO molecules were sequentially adsorbed on the RhnTam(+) clusters to form RhnTam(+)NxOx (x = 1, 2, 3, ...) species. In addition, oxide clusters, RhnTam(+)O2, were also observed, suggesting that the NO molecules were dissociatively adsorbed on the cluster, the N atoms migrated on the surface to form N2, and the N2 molecules were released from RhnTam(+)N2O2. The reactivity, leading to oxide formation, was composition dependent: oxide clusters were dominantly formed for the bielement clusters containing both Rh and Ta atoms, whereas such clusters were hardly formed for the single-element Rhn(+) and Tam(+) clusters. DFT calculations indicated that the Ta atoms induce dissociation of NO on the clusters by lowering the dissociation energy, whereas the Rh atoms enable release of N2 by lowering the binding energy of the N atoms on the clusters.

Storage ring to investigate cold unidimensional atomic collisions

International Nuclear Information System (INIS)

Marcassa, L. G.; Caires, A. R. L.; Nascimento, V. A.; Dulieu, O.; Weiner, J.; Bagnato, V. S.

2005-01-01

In this paper we employ a circulating ring of trapped atoms, that we have named the atomotron, to study cold collisions. The atomotron is obtained from a conventional magneto-optical trap when the two pairs of normally retroreflecting Gaussian laser beams in the x-y plane are slightly offset. Circulating stable atomic orbits then form a racetrack geometry in this plane. The circulating atom flux behaves similarly to an atomic beam with an average tangential velocity much greater than the transverse components, and is therefore suitable for one-dimensional atomic collision studies. Using the atomotron, we have investigated the polarization dependence of ultracold photoassociation collisions between Rb atoms circulating in the racetrack. The ability to investigate collisions in ultracold circulating atomic rings reveals alignment and orientation properties that are averaged away in ordinary three-dimensional magneto-optical trap collision processes

Collisional destruction of fast hydrogen Rydberg atoms

International Nuclear Information System (INIS)

King, M.R.

1984-01-01

A new modulated electric field technique was developed to study Rydberg atom destruction processes in a fast beam. The process of destruction of a band of Rydberg atom destruction of a band of Rydberg atoms through the combined processes of ionization, excitation, and deexcitation was studied for collisions with gas targets. Rydberg atoms of hydrogen were formed by electron capture, and detected by field ionization. The modulated field technique described proved to be an effective technique for producing a large signal for accurate cross section measurements. The independent particle model for Rydberg atom destruction processes was found to hold well for collisions with molecular nitrogen, argon, and carbon dioxide. The resonances in the cross sections for the free electron scattering with these targets were found to also occur in Rydberg destruction. Suggestions for future investigations of Rydberg atom collision processes in the fast beam regime are given

Polarization-dependent atomic dipole traps behind a circular aperture for neutral-atom quantum computing

International Nuclear Information System (INIS)

Gillen-Christandl, Katharina; Copsey, Bert D.

2011-01-01

The neutral-atom quantum computing community has successfully implemented almost all necessary steps for constructing a neutral-atom quantum computer. We present computational results of a study aimed at solving the remaining problem of creating a quantum memory with individually addressable sites for quantum computing. The basis of this quantum memory is the diffraction pattern formed by laser light incident on a circular aperture. Very close to the aperture, the diffraction pattern has localized bright and dark spots that can serve as red-detuned or blue-detuned atomic dipole traps. These traps are suitable for quantum computing even for moderate laser powers. In particular, for moderate laser intensities (∼100 W/cm 2 ) and comparatively small detunings (∼1000-10 000 linewidths), trap depths of ∼1 mK and trap frequencies of several to tens of kilohertz are achieved. Our results indicate that these dipole traps can be moved by tilting the incident laser beams without significantly changing the trap properties. We also explored the polarization dependence of these dipole traps. We developed a code that calculates the trapping potential energy for any magnetic substate of any hyperfine ground state of any alkali-metal atom for any laser detuning much smaller than the fine-structure splitting for any given electric field distribution. We describe details of our calculations and include a summary of different notations and conventions for the reduced matrix element and how to convert it to SI units. We applied this code to these traps and found a method for bringing two traps together and apart controllably without expelling the atoms from the trap and without significant tunneling probability between the traps. This approach can be scaled up to a two-dimensional array of many pinholes, forming a quantum memory with single-site addressability, in which pairs of atoms can be brought together and apart for two-qubit gates for quantum computing.

Simulations of atomic-scale sliding friction

DEFF Research Database (Denmark)

Sørensen, Mads Reinholdt; Jacobsen, Karsten Wedel; Stoltze, Per

1996-01-01

Simulation studies of atomic-scale sliding friction have been performed for a number of tip-surface and surface-surface contacts consisting of copper atoms. Both geometrically very simple tip-surface structures and more realistic interface necks formed by simulated annealing have been studied....... Kinetic friction is observed to be caused by atomic-scale Stick and slip which occurs by nucleation and subsequent motion of dislocations preferably between close-packed {111} planes. Stick and slip seems ro occur in different situations. For single crystalline contacts without grain boundaries...... pinning of atoms near the boundary of the interface and is therefore more easily observed for smaller contacts. Depending on crystal orientation and load, frictional wear can also be seen in the simulations. In particular, for the annealed interface-necks which model contacts created by scanning tunneling...

Atom-surface potentials and atom interferometry

International Nuclear Information System (INIS)

Babb, J.F.

1998-01-01

Long-range atom-surface potentials characterize the physics of many actual systems and are now measurable spectroscopically in deflection of atomic beams in cavities or in reflection of atoms in atomic fountains. For a ground state, spherically symmetric atom the potential varies as -1/R 3 near the wall, where R is the atom-surface distance. For asymptotically large distances the potential is weaker and goes as -1/R 4 due to retardation arising from the finite speed of light. This diminished interaction can also be interpreted as a Casimir effect. The possibility of measuring atom-surface potentials using atomic interferometry is explored. The particular cases studied are the interactions of a ground-state alkali-metal atom and a dielectric or a conducting wall. Accurate descriptions of atom-surface potentials in theories of evanescent-wave atomic mirrors and evanescent wave-guided atoms are also discussed. (author)

Bremsstrahlung in atom-atom collisions

International Nuclear Information System (INIS)

Amus'ya, M.Y.; Kuchiev, M.Y.; Solov'ev, A.V.

1985-01-01

It is shown that in the collision of a fast atom with a target atom when the frequencies are on the order of the potentials or higher, there arises bremsstrahlung comparable in intensity with the bremsstrahlung emitted by an electron with the same velocity in the field of the target atom. The mechanism by which bremsstrahlung is produced in atom-atom collisions is elucidated. Results of specific calculations of the bremsstrahlung spectra are given for α particles and helium atoms colliding with xenon

Decaying Dark Atom Constituents and Cosmic Positron Excess

DEFF Research Database (Denmark)

Belotsky, K.; Khlopov, M.; Kouvaris, C.

2014-01-01

We present a scenario where dark matter is in the form of dark atoms that can accommodate the experimentally observed excess of positrons in PAMELA and AMS-02 while being compatible with the constraints imposed on the gamma-ray ux from Fermi/LAT. This scenario assumes that the dominant component...... of dark matter is in the form of a bound state between a helium nucleus and a -2 particle and a small component is in the form of a WIMP-like dark atom compatible with direct searches in underground detectors. One of the constituents of this WIMP-like state is a +2 metastable particle with a mass of 1 Te...... baryons in the universe to be close to -3....

Explanation of the Hund's rule for atomic spectra

International Nuclear Information System (INIS)

Muftakhova, F.I.; Zilberman, L.A.

1982-01-01

An original formula for electrostatic interaction in many-electron atoms, based on a new mathematical method, related by recoupling a matrix of n vector coupling momenta and its permutation properties, is given in general form. Hund's rule for atomic spectra-like maximum probability of couple momentum of l 2 configuration in the LS term of lsup(n) configuration is explained. Also, non-competence of exchange interaction notion for d and f atoms is based on mentioned formula. (Auth.)

Optical ferris wheel for ultracold atoms

Science.gov (United States)

Franke-Arnold, S.; Leach, J.; Padgett, M. J.; Lembessis, V. E.; Ellinas, D.; Wright, A. J.; Girkin, J. M.; Ohberg, P.; Arnold, A. S.

2007-07-01

We propose a versatile optical ring lattice suitable for trapping cold and quantum degenerate atomic samples. We demonstrate the realisation of intensity patterns from pairs of Laguerre-Gauss (exp(iℓө) modes with different ℓ indices. These patterns can be rotated by introducing a frequency shift between the modes. We can generate bright ring lattices for trapping atoms in red-detuned light, and dark ring lattices suitable for trapping atoms with minimal heating in the optical vortices of blue-detuned light. The lattice sites can be joined to form a uniform ring trap, making it ideal for studying persistent currents and the Mott insulator transition in a ring geometry.

Empirical atom model of Vegard's law

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lei, E-mail: zhleile2002@163.com [Materials Department, College of Electromechanical Engineering, China University of Petroleum, Qingdao 266555 (China); School of Electromechanical Automobile Engineering, Yantai University, Yantai 264005 (China); Li, Shichun [Materials Department, College of Electromechanical Engineering, China University of Petroleum, Qingdao 266555 (China)

2014-02-01

Vegard's law seldom holds true for most binary continuous solid solutions. When two components form a solid solution, the atom radii of component elements will change to satisfy the continuity requirement of electron density at the interface between component atom A and atom B so that the atom with larger electron density will expand and the atom with the smaller one will contract. If the expansion and contraction of the atomic radii of A and B respectively are equal in magnitude, Vegard's law will hold true. However, the expansion and contraction of two component atoms are not equal in most situations. The magnitude of the variation will depend on the cohesive energy of corresponding element crystals. An empirical atom model of Vegard's law has been proposed to account for signs of deviations according to the electron density at Wigner–Seitz cell from Thomas–Fermi–Dirac–Cheng model.

Theory of direct scattering of neutral and charged atoms

Science.gov (United States)

Franco, V.

1979-01-01

The theory for direct elastic and inelastic collisions between composite atomic systems formulated within the framework of the Glauber approximation is presented. It is shown that the phase-shift function is the sum of a point Coulomb contribution and of an expression in terms of the known electron-hydrogen-atom and proton-hydrogen-atom phase shift function. The scattering amplitude is reexpressed, the pure Coulomb scattering in the case of elastic collisions between ions is isolated, and the exact optical profile function is approximated by a first-order expansion in Glauber theory which takes into account some multiple collisions. The approximate optical profile function terms corresponding to interactions involving one and two electrons are obtained in forms of Meijer G functions and as a one-dimensional integral, and for collisions involving one or two neutral atoms, the scattering amplitude is further reduced to a simple closed-form expression.

Electrochemical Dissolution of Iridium and Iridium Oxide Particles in Acidic Media: Transmission Electron Microscopy, Electrochemical Flow Cell Coupled to Inductively Coupled Plasma Mass Spectrometry, and X-ray Absorption Spectroscopy Study.

Science.gov (United States)

Jovanovič, Primož; Hodnik, Nejc; Ruiz-Zepeda, Francisco; Arčon, Iztok; Jozinović, Barbara; Zorko, Milena; Bele, Marjan; Šala, Martin; Šelih, Vid Simon; Hočevar, Samo; Gaberšček, Miran

2017-09-13

Iridium-based particles, regarded as the most promising proton exchange membrane electrolyzer electrocatalysts, were investigated by transmission electron microscopy and by coupling of an electrochemical flow cell (EFC) with online inductively coupled plasma mass spectrometry. Additionally, studies using a thin-film rotating disc electrode, identical location transmission and scanning electron microscopy, as well as X-ray absorption spectroscopy have been performed. Extremely sensitive online time-and potential-resolved electrochemical dissolution profiles revealed that Ir particles dissolve well below oxygen evolution reaction (OER) potentials, presumably induced by Ir surface oxidation and reduction processes, also referred to as transient dissolution. Overall, thermally prepared rutile-type IrO 2 particles are substantially more stable and less active in comparison to as-prepared metallic and electrochemically pretreated (E-Ir) analogues. Interestingly, under OER-relevant conditions, E-Ir particles exhibit superior stability and activity owing to the altered corrosion mechanism, where the formation of unstable Ir(>IV) species is hindered. Due to the enhanced and lasting OER performance, electrochemically pre-oxidized E-Ir particles may be considered as the electrocatalyst of choice for an improved low-temperature electrochemical hydrogen production device, namely a proton exchange membrane electrolyzer.

Analytic cross sections for collisions of H, H2, He and Li atoms and ions with atoms and molecules, 1

International Nuclear Information System (INIS)

Ito, Rinsuke; Tabata, Tatsuo; Shirai, Toshizo; Phaneuf, R.A.

1993-06-01

Analytic expressions fitted to Barnett's recommended data are given for the cross sections of the following reactions: (1) electron capture by H, H + , H 2 + , He + , and He 2+ colliding with atoms, molecules, and ions and (2) electron capture into excited states by H + , He + , and He 2+ colliding with atoms and molecules. The latter category includes cross sections for photon emission due to electron capture. The expressions use the semiempirical functional forms proposed by Green and McNeal and some modified forms to make it possible not only to interpolate but also to extrapolate the recommended data. (author)

High-fidelity Rydberg quantum gate via a two-atom dark state

DEFF Research Database (Denmark)

Petrosyan, David; Motzoi, Felix; Saffman, Mark

2017-01-01

We propose a two-qubit gate for neutral atoms in which one of the logical state components adiabatically follows a two-atom dark state formed by the laser coupling to a Rydberg state and a strong, resonant dipole-dipole exchange interaction between two Rydberg excited atoms. Our gate exhibits...

Atomic hydrogen storage. [cryotrapping and magnetic field strength

Science.gov (United States)

Woollam, J. A. (Inventor)

1980-01-01

Atomic hydrogen, for use as a fuel or as an explosive, is stored in the presence of a strong magnetic field in exfoliated layered compounds such as molybdenum disulfide or an elemental layer material such as graphite. The compound is maintained at liquid temperatures and the atomic hydrogen is collected on the surfaces of the layered compound which are exposed during delamination (exfoliation). The strong magnetic field and the low temperature combine to prevent the atoms of hydrogen from recombining to form molecules.

Complex operator method of the hydrogen atom

International Nuclear Information System (INIS)

Jiang, X.

1989-01-01

Frequently the hydrogen atom eigenvalue problem is analytically solved by solving a radial wave equation for a particle in a Coulomb field. In this article, complex coordinates are introduced, and an expression for the energy levels of the hydrogen atom is obtained by means of the algebraic solution of operators. The form of this solution is in accord with that of the analytical solution

The Star Formation Rate Efficiency of Neutral Atomic-Dominated Hydrogen Gas in the Ooutskirts of Star-Forming Galaxies From z approx. 1 to z approx. 3

Science.gov (United States)

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

2016-01-01

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

On the size and structure of helium snowballs formed around charged atoms and clusters of noble gases.

Science.gov (United States)

Bartl, Peter; Leidlmair, Christian; Denifl, Stephan; Scheier, Paul; Echt, Olof

2014-09-18

Helium nanodroplets doped with argon, krypton, or xenon are ionized by electrons and analyzed in a mass spectrometer. HenNgx(+) ions containing up to seven noble gas (Ng) atoms and dozens of helium atoms are identified; the high resolution of the mass spectrometer combined with advanced data analysis make it possible to unscramble contributions from isotopologues that have the same nominal mass but different numbers of helium or Ng atoms, such as the magic He20(84)Kr2(+) and the isobaric, nonmagic He41(84)Kr(+). Anomalies in these ion abundances reveal particularly stable ions; several intriguing patterns emerge. Perhaps most astounding are the results for HenAr(+), which show evidence for three distinct, solid-like solvation shells containing 12, 20, and 12 helium atoms. This observation runs counter to the common notion that only the first solvation shell is solid-like but agrees with calculations by Galli et al. for HenNa(+) [J. Phys. Chem. A 2011, 115, 7300] that reveal three shells of icosahedral symmetry. HenArx(+) (2 ≤ x ≤ 7) ions appear to be especially stable if they contain a total of n + x = 19 atoms. A sequence of anomalies in the abundance distribution of HenKrx(+) suggests that rings of six helium atoms are inserted into the solvation shell each time a krypton atom is added to the ionic core, from Kr(+) to Kr3(+). Previously reported strong anomalies at He12Kr2(+) and He12Kr3(+) [Kim , J. H.; et al. J. Chem. Phys. 2006, 124, 214301] are attributed to a contamination. Only minor local anomalies appear in the distributions of HenXex(+) (x ≤ 3). The distributions of HenKr(+) and HenXe(+) show strikingly similar, broad features that are absent from the distribution of HenAr(+); differences are tentatively ascribed to the very different fragmentation dynamics of these ions.

Charge-state-distributions of foil-excited heavy Rydberg atoms

International Nuclear Information System (INIS)

Faibis, A.; Kanter, E.P.; Koenig, W.; Zabransky, B.J.

1985-01-01

Studies of foil-excited fast (MeV/amu) heavy ions have demonstrated large yields of high Rydberg atoms formed in such beams. Further experiments have suggested a strong target-thickness dependence of the yields of such atoms. These results have been puzzling in view of the supposed short mean free paths of such atoms in solids. In an effort to better understand these results, the authors have measured the yields of Rydberg atoms (napprox.100-200) in foil-excited 32 S ions at an incident energy of 125 MeV

Iridium catalysed synthesis of piperazines from diols

DEFF Research Database (Denmark)

Nordstrøm, Lars Ulrik Rubæk; Madsen, Robert

2007-01-01

A green and atom-economical method has been developed for the synthesis of piperazines by cyclocondensation of diols and amines in aqueous media in the presence of a catalytic amount of [Cp*IrCl2]2....

Magnetic scattering of neutrons by atoms

International Nuclear Information System (INIS)

Stassis, C.; Deckman, H.W.

1976-01-01

The magnetic scattering of neutrons by an atom or ion possessing both a spin and orbital magnetic moment is examined. For an atom in the 1sup(n) electronic configuration the magnetic scattering amplitude is determined by matrix elements of even-order electric and odd-order magnetic multipoles, whose order of multipolarity k is less than or equal to 21 + 1. The calculation of the matrix elements of these multipoles is separated into evaluating radial matrix elements and matrix elements of the Racah tensors Wsup(0,k) and Wsup(1,k') where k is an even integar less than or equal to 21. The calculation of the matrix elements of these tensors is considerably simplified by selection rules based on the groups Sp(41 + 2), R(21 + 1), R(3) and in the case of f-electrons, the special group G 2 . It is shown that, in the case of elastic scattering by an atom or an ion whose state is a single Russell-Saunders state, the magnetic scattering amplitude can be written in the conventional form p(q)qsub(m).sigma. General expressions for the amplitude p(q) as well as the elastic magnetic form factor are obtained. The evaluation of the coherent magnetic scattering amplitude by an atom in a magnetic field is discussed, and the small-q approximation to the elastic magnetic scattering is considered. The formation is illustrated for the important case of d- and f-electrons. The generalization of the formalism to the case of mixed atomic configurations is examined in some detail. (author)

Instrumental measurement of iridium abundances in the part-per-trillion range following neutron activation

International Nuclear Information System (INIS)

Alvarez, L.W.; Asaro, F.; Goulding, F.S.; Landis, D.A.; Madden, N.W.; Malone, D.F.

1988-01-01

An automated gamma-ray coincidence spectrometer has been constructed which, following neutron activation, can measure iridium (Ir) abundances of the order of 25 parts-per-trillion (ppt) in rock samples 500 times more rapidly than previously possible by instrumental techniques used at the Lawrence Berkeley Laboratory. Twin intrinsic Ge gamma-ray detectors count coincidences between the 316.5 and 468.1 keV gamma rays of 192 Ir, and together with a mineral-oil-based Compton suppression shield provide a sensitivity of 50 ppt Ir in 7 minute measurements of 100 mg limestone samples subsequent to irradiation in the University of Missouri reactor. Over 3000 samples have been measured, and in collaboration with many geologists and paleontologists from around the world, anomalous amounts of Ir have been detected in rocks with approximate ages of 12, 39, 67, 91, 150 and 3500 million years. Modifications are nearly complete to measure ten other elements very important to geochemical studies simultaneously (in the singles rather than the coincidence mode) with the Ir measurements

Accelerated ions as a tool in atomic physics

International Nuclear Information System (INIS)

Hansteen, J.M.

1977-01-01

Some of the aspects of atomic physics which are being brought into focus by the construction and completion of a new generation of heavy-ion accelerators are dealt with. Various types of processes occurring in the overlapping electron clouds are visualised in an elementary way, using among others, some recent observations on the formation of quasi-molecules and quasi-atoms. Phenomena connected with the inner electron shells in superheavy atoms are touched upon, in particular those processes possibly leading to the production of positrons. In such cases the crucial importance of an atomic Coulomb excitation mechanism is stressed. In conclusion the view is emphasized that inner shell ionization phenomena in heavy ion collisions form a bridge between processes originating respectively from nuclear and atomic physics. (Auth.)

Deep Atomic Binding (DAB) Hypothesis: A New Approach of Fission Product Chemistry

International Nuclear Information System (INIS)

Ajlouni, Abdul-Wali M.S.

2006-01-01

Former studies assumed that, after fission process occurs, the highly ionized new born atoms (20-22 positive charge), ionize the media in which they pass through before becoming stable atoms in a manner similar to 4-MeV ?-particles. Via ordinary chemical reactions with the surroundings, each stable atom has a probability to form chemical compound. Since there are about 35 different elemental atoms created through fission processes, a large number of chemical species were suggested to be formed. But, these suggested chemical species were not found in the environment after actual releases of FP during accidents like TMI (USA, 1979), and Chernobyl (former USSR, 1986), also the models based on these suggested reactions and species could not interpret the behavior of these actual species. It is assumed here that the ionization states of the new born atoms and the long term high temperature were not dealt with in an appropriate way and they were the reasons of former models failure. Our new approach of Deep Atomic Binding (DAB) based on the following: 1-The new born atoms which are highly ionized, 10-12 electrons associated with each nucleus, having a large probability to create bonds between them to form molecules. These bonds are at the L, or M shells, and we call it DAB. 2-The molecules stay in the reactor at high temperatures for long periods, so they undergo many stages of composition and decomposition to form giant molecules. By applying DAB approach, field data from Chernobyl, TMI and nuclear detonations could be interpreted with a wide coincidence resulted. (author)

Atomically resolved tissue integration.

Science.gov (United States)

Karlsson, Johan; Sundell, Gustav; Thuvander, Mattias; Andersson, Martin

2014-08-13

In the field of biomedical technology, a critical aspect is the ability to control and understand the integration of an implantable device in living tissue. Despite the technical advances in the development of biomaterials, the elaborate interplay encompassing materials science and biology on the atomic level is not very well understood. Within implantology, anchoring a biomaterial device into bone tissue is termed osseointegration. In the most accepted theory, osseointegration is defined as an interfacial bonding between implant and bone; however, there is lack of experimental evidence to confirm this. Here we show that atom probe tomography can be used to study the implant-tissue interaction, allowing for three-dimensional atomic mapping of the interface region. Interestingly, our analyses demonstrated that direct contact between Ca atoms and the implanted titanium oxide surface is formed without the presence of a protein interlayer, which means that a pure inorganic interface is created, hence giving experimental support to the current theory of osseointegration. We foresee that this result will be of importance in the development of future biomaterials as well as in the design of in vitro evaluation techniques.

Atomic-orbital expansion model for describing ion-atom collisions at intermediate and low energies

International Nuclear Information System (INIS)

Lin, C.D.; Fritsch, W.

1983-01-01

In the description of inelastic processes in ion-atom collisions at moderate energies, the semiclassical close-coupling method is well established as the standard method. Ever since the pioneering work on H + + H in the early 60's, the standard procedure is to expand the electronic wavefunction in terms of molecular orbitals (MO) or atomic orbitals (AO) for describing collisions at, respectively, low or intermediate velocities. It has been recognized since early days that traveling orbitals are needed in the expansions in order to represent the asymptotic states in the collisions correctly. While the adoption of such traveling orbitals presents no conceptual difficulties for expansions using atomic orbitals, the situation for molecular orbitals is less clear. In recent years, various forms of traveling MO's have been proposed, but conflicting results for several well-studied systems have been reported

Matterwave interferometric velocimetry of cold Rb atoms

Science.gov (United States)

Carey, Max; Belal, Mohammad; Himsworth, Matthew; Bateman, James; Freegarde, Tim

2018-03-01

We consider the matterwave interferometric measurement of atomic velocities, which forms a building block for all matterwave inertial measurements. A theoretical analysis, addressing both the laboratory and atomic frames and accounting for residual Doppler sensitivity in the beamsplitter and recombiner pulses, is followed by an experimental demonstration, with measurements of the velocity distribution within a 20 ?K cloud of rubidium atoms. Our experiments use Raman transitions between the long-lived ground hyperfine states, and allow quadrature measurements that yield the full complex interferometer signal and hence discriminate between positive and negative velocities. The technique is most suitable for measurement of colder samples.

Global iridium anomaly, mass extinction, and redox change at the Devonian-Carboniferous boundary

Energy Technology Data Exchange (ETDEWEB)

Wang, K. (Geological Survey of Canada, Calgary, Alberta (Canada) Univ. of Calgary, Alberta (Canada)); Attrep, M. Jr.; Orth, C.J. (Los Alamos National Lab., NM (United States))

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.

High speed atom source

International Nuclear Information System (INIS)

Hoshino, Hitoshi.

1990-01-01

In a high speed atom source, since the speed is not identical between ions and electrons, no sufficient neutralizing effect for ionic rays due to the mixing of the ionic rays and the electron rays can be obtained failing to obtain high speed atomic rays at high density. In view of the above, a speed control means is disposed for equalizing the speed of ions forming ionic rays and the speed of electrons forming electron rays. Further, incident angle of the electron rays and/or ionic rays to a magnet or an electrode is made variable. As a result, the relative speed between the ions and the electrons to the processing direction is reduced to zero, in which the probability of association between the ions and the electrons due to the coulomb force is increased to improve the neutralizing efficiency to easily obtain fine and high density high speed electron rays. Further, by varying the incident angle, a track capable of obtaining an ideal mixing depending on the energy of the neutralized ionic rays is formed. Since the high speed electron rays has such high density, they can be irradiated easily to the minute region of the specimen. (N.H.)

Identification of unknown sample using NAA, EDXRF, XRD techniques

International Nuclear Information System (INIS)

Dalvi, Aditi A.; Swain, K.K.; Chavan, Trupti; Remya Devi, P.S.; Wagh, D.N.; Verma, R.

2015-01-01

Analytical Chemistry Division (ACD), Bhabha Atomic Research Centre (BARC) receives samples from law enforcement agencies such as Directorate of Revenue Intelligence, Customs for analysis. Five unknown grey powdered samples were received for identification and were suspected to be Iridium (Ir). Identification of unknown sample is always a challenging task and suitable analytical techniques have to be judiciously utilized for arriving at the conclusion. Qualitative analysis was carried out using Jordan Valley, EX-3600 M Energy dispersive X-ray fluorescence (EDXRF) spectrometer at ACD, BARC. A SLP series LEO Si (Li) detector (active area: 30 mm 2 ; thickness: 3.5 mm; resolution: 140 eV at 5.9 keV of Mn K X-ray) was used during the measurement and only characteristic X-rays of Ir (Lα: 9.17 keV and Lβ: 10.70 keV) was seen in the X-ray spectrum. X-ray diffraction (XRD) measurement results indicated that the Ir was in the form of metal. To confirm the XRD data, neutron activation analysis (NAA) was carried out by irradiating samples and elemental standards (as comparator) in graphite reflector position of Advanced Heavy Water Reactor Critical Facility (AHWR CF) reactor, BARC, Mumbai. After suitable decay period, gamma activity measurements were carried out using 45% HPGe detector coupled to 8 k multi channel analyzer. Characteristic gamma line at 328.4 keV of the activation product 194 Ir was used for quantification of iridium and relative method of NAA was used for concentration calculations. NAA results confirmed that all the samples were Iridium metal. (author)

Neutron activation analysis in geochemical characterization of Jurassic-Cretaceous sedimentary rocks from the Nordvik Peninsula

Czech Academy of Sciences Publication Activity Database

Mizera, Jiří; Řanda, Z.; Košťák, M.

2010-01-01

Roč. 284, č. 1 (2010), s. 211-219 ISSN 0236-5731 Institutional research plan: CEZ:AV0Z30460519 Keywords : Jurassic-Cretaceous boundary * Nordvik Peninsula * Iridium anomaly Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders OBOR OECD: Geology Impact factor: 0.777, year: 2010

Thermal decomposition of silane to form hydrogenated amorphous Si

Science.gov (United States)

Strongin, M.; Ghosh, A.K.; Wiesmann, H.J.; Rock, E.B.; Lutz, H.A. III

Hydrogenated amorphous silicon is produced by thermally decomposing silane (SiH/sub 4/) or other gases comprising H and Si, at elevated temperatures of about 1700 to 2300/sup 0/C, in a vacuum of about 10/sup -8/ to 10/sup -4/ torr. A gaseous mixture is formed of atomic hydrogen and atomic silicon. The gaseous mixture is deposited onto a substrate to form hydrogenated amorphous silicon.

Crystal structure of chlorido(dimethyl sulfoxide-κSbis[4-(pyridin-2-ylbenzaldehyde-κ3C2,N]iridium(III acetonitrile monosolvate

Directory of Open Access Journals (Sweden)

Andrew J. Peloquin

2017-09-01

Full Text Available The title compound, [IrCl(C12H8NO2{(CH32SO}]·H3CCN or [IrCl(fppy2(DMSO]·H3CCN [where fppy is 4-(pyridin-2-ylbenzaldehyde and DMSO is dimethyl sulfoxide], is a mononuclear iridium(III complex including two fppy ligands, a sulfur-coordinating DMSO ligand, and one terminal chloride ligand that define a distorted octahedral coordination sphere. The complex crystallizes from 1:1 DMSO–acetonitrile as an acetonitrile solvate. In the crystal, weak C—H...O and C—H...N hydrogen-bonding interactions between adjacent complexes and between the acetonitrile solvent and the complex consolidate the packing.

Ionization of Rydberg atoms by the kicks of half-cycle pulses

Indian Academy of Sciences (India)

Rydberg atom; half-cycle pulses; ionization; quantum mechanical model. ... packet which represents a non-stationary quantum state formed by coherent ...... Wetzels, Impulsive interactions of half cycle pulse radiation with Rydberg atoms, Ph.D.

Chemical forms of radioiodine

International Nuclear Information System (INIS)

Tachikawa, Enzo

1979-01-01

Release of radioiodine built-up during reactor operations presents a potential problem from the standpoint of environmental safety. Among the chemical forms of radioiodine, depending upon the circumstances, organic iodides cast a most serious problem because of its difficulties in the trapping and because of its stability compared to other chemical forms. Furthermore, pellet-cladding interaction (PCl) fuel failures in LWR fuel rods are believed to be stress corrosion cracks caused by embrittling fission product species, radioiodine. To deal with these problems, knowledge is required on the chemical behaviors of radioiodine in and out of fuels, as well as the release behaviors from fuels. Here a brief review is given of these respects, in aiming at clearing-up the questions still remaining unknown. The data seem to indicate that radioiodine exists as a combined form in fuels. upon heating slightly irradiated fuels, the iodine atoms are released in a chemical form associated with uranium atoms. Experiments, however, as needed with specimen of higher burnup, where the interactions of radioiodine with metallic fission products could be favored. The dominant release mechanism of radioiodine under normal operating temperatures will be diffusion to grain boundaries leading to open surfaces. Radiation-induced internal traps, however, after the rate of diffusion significantly. The carbon sources of organic iodides formed under various conditions and its formation mechanisms have also been considered. (author)

Atom Skimmers and Atom Lasers Utilizing Them

Science.gov (United States)

Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.

2005-01-01

Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

THE ATOMIC WEIGHT OF ANTIMONY

Institute of Scientific and Technical Information of China (English)

张青莲; 钱秋宇; 赵墨田

1989-01-01

With enriched antimony isotopes of 99.224 atom% 121Sb and 99.528 atom% 123Sb, twotracer solutions were prepared, whose antimony content was ascertained by the isotopicdilution analysis utilizing an accurately assayed laboratory standard. Mass spectrometricmeasurements were made on a Finnigan MAT- 261 instrument to find the ratio of masses121 and 123. Five synthetic mixtures formed from the tracers served to determine thecorrection factor of mass discrimination. The isotopic abundances thus found for the anti-mony in the mineral stibnite together with the known nuclidic masses yield an accurateatomic weight of antimony as 121 .7575± 0 .0009.

Noble gas atoms as chemical impurities in silicon

International Nuclear Information System (INIS)

Tkachev, V.D.; Mudryi, A.V.; Minaev, N.S.

1984-01-01

The behaviour of noble gas atoms implanted in silicon is studied by the luminescence method. The energy position of Moessbauer-type luminescence bands with zero-phonon lines 1.0148, 1.0120, 1.0097, 1.0048 eV and others connected with implanted atoms of neon, helium, argon, krypton, respectively, indicates the formation of deep energy levels in the forbidden gap of silicon. Implantation of the noble gas isotopes confirms their participation in formation processes of the luminescence centers in silicon. The temperature range of existence and the symmetry of defects incorporating the noble gas atoms are found. It is noted that noble gas atoms form impurity complexes with deep energy levels and their behaviour in crystals does not differ from that of main doped or residual technological impurity atoms. (author)

Absorptive form factors for high-energy electron diffraction

International Nuclear Information System (INIS)

Bird, D.M.; King, Q.A.

1990-01-01

The thermal diffuse scattering contribution to the absorptive potential in high-energy electron diffraction is calculated in the form of an absorptive contribution to the atomic form factor. To do this, the Einstein model of lattice vibrations is used, with isotropic Debye-Waller factors. The absorptive form factors are calculated as a function of scattering vector s and temperature factor M on a grid which enables polynomial interpolation of the results to be accurate to better than 2% for much of the ranges 0≤Ms 2 ≤6 and 0≤M≤2 A 2 . The computed values, together with an interpolation routine, have been incorporated into a Fortran subroutine which calculates both the real and absorptive form factors for 54 atomic species. (orig.)

A new atomic model

International Nuclear Information System (INIS)

Petrescu, Florian Ion

2012-01-01

The movement of an electron around the atomic nucleus has today a great importance in many engineering fields. Electronics, aeronautics, micro and nanotechnology, electrical engineering, optics, lasers, nuclear power, computing, equipment and automation, telecommunications, genetic engineering, bioengineering, special processing, modern welding, robotics, energy and electromagnetic wave field is today only a few of the many applications of electronic engineering. This book presents, shortly, a new and original relation (20 and 20') who determines the radius with that, the electron is running around the nucleus of an atom. One utilizes, two times the Lorenz relation, the Niels Bohr generalized equation, and a mass relation, which was deduced from the kinematics energy relation written in two modes: classical and Coulombian. Equalizing the mass relation with Lorenz relation one obtains a form which is a relation between the squared electron speed (v 2 ) and the radius (r). The second relation between v 2 and r was obtained by equalizing the mass of Bohr equation and the mass of Lorenz relation. For a Bohr energetically level (n=a constant value), one determines now two energetically below levels, which form an electronic layer. The author realizes by this a new atomic model, or a new quantum theory, which explains the existence of electron-clouds without spin.Writing the kinematics energy relation in two modes, classical and Coulombian one determines a relation, from which explicitely the mass of the electron is determined.

A new atomic model

Energy Technology Data Exchange (ETDEWEB)

Petrescu, Florian Ion

2012-07-01

The movement of an electron around the atomic nucleus has today a great importance in many engineering fields. Electronics, aeronautics, micro and nanotechnology, electrical engineering, optics, lasers, nuclear power, computing, equipment and automation, telecommunications, genetic engineering, bioengineering, special processing, modern welding, robotics, energy and electromagnetic wave field is today only a few of the many applications of electronic engineering. This book presents, shortly, a new and original relation (20 and 20') who determines the radius with that, the electron is running around the nucleus of an atom. One utilizes, two times the Lorenz relation, the Niels Bohr generalized equation, and a mass relation, which was deduced from the kinematics energy relation written in two modes: classical and Coulombian. Equalizing the mass relation with Lorenz relation one obtains a form which is a relation between the squared electron speed (v{sup 2}) and the radius (r). The second relation between v{sup 2} and r was obtained by equalizing the mass of Bohr equation and the mass of Lorenz relation. For a Bohr energetically level (n=a constant value), one determines now two energetically below levels, which form an electronic layer. The author realizes by this a new atomic model, or a new quantum theory, which explains the existence of electron-clouds without spin.Writing the kinematics energy relation in two modes, classical and Coulombian one determines a relation, from which explicitely the mass of the electron is determined.

Formation and properties of metal-oxygen atomic chains

DEFF Research Database (Denmark)

Thijssen, W.H.A.; Strange, Mikkel; de Brugh, J.M.J.A.

2008-01-01

of longer atomic chains. The mechanical and electrical properties of these diatomic chains have been investigated by determining local vibration modes of the chain and by measuring the dependence of the average chain-conductance on the length of the chain. Additionally, we have performed calculations......Suspended chains consisting of single noble metal and oxygen atoms have been formed. We provide evidence that oxygen can react with and be incorporated into metallic one-dimensional atomic chains. Oxygen incorporation reinforces the linear bonds in the chain, which facilitates the creation...

Significant improvements in stability and reproducibility of atomic-scale atomic force microscopy in liquid

International Nuclear Information System (INIS)

Akrami, S M R; Nakayachi, H; Fukuma, T; Watanabe-Nakayama, T; Asakawa, H

2014-01-01

Recent advancement of dynamic-mode atomic force microscopy (AFM) for liquid-environment applications enabled atomic-scale studies on various interfacial phenomena. However, instabilities and poor reproducibility of the measurements often prevent systematic studies. To solve this problem, we have investigated the effect of various tip treatment methods for atomic-scale imaging and force measurements in liquid. The tested methods include Si coating, Ar plasma, Ar sputtering and UV/O 3 cleaning. We found that all the methods provide significant improvements in both the imaging and force measurements in spite of the tip transfer through the air. Among the methods, we found that the Si coating provides the best stability and reproducibility in the measurements. To understand the origin of the fouling resistance of the cleaned tip surface and the difference between the cleaning methods, we have investigated the tip surface properties by x-ray photoelectron spectroscopy and contact angle measurements. The results show that the contaminations adsorbed on the tip during the tip transfer through the air should desorb from the surface when it is immersed in aqueous solution due to the enhanced hydrophilicity by the tip treatments. The tip surface prepared by the Si coating is oxidized when it is immersed in aqueous solution. This creates local spots where stable hydration structures are formed. For the other methods, there is no active mechanism to create such local hydration sites. Thus, the hydration structure formed under the tip apex is not necessarily stable. These results reveal the desirable tip properties for atomic-scale AFM measurements in liquid, which should serve as a guideline for further improvements of the tip treatment methods. (paper)

Beyond Iron: Iridium-Containing P450 Enzymes for Selective Cyclopropanations of Structurally Diverse Alkenes

International Nuclear Information System (INIS)

Key, Hanna M.; Dydio, Paweł; Liu, Zhennan

2017-01-01

Enzymes catalyze organic transformations with exquisite levels of selectivity, including chemoselectivity, stereoselectivity, and substrate selectivity, but the types of reactions catalyzed by enzymes are more limited than those of chemical catalysts. Thus, the convergence of chemical catalysis and biocatalysis can enable enzymatic systems to catalyze abiological reactions with high selectivity. Recently, we disclosed artificial enzymes constructed from the apo form of heme proteins and iridium porphyrins that catalyze the insertion of carbenes into a C-H bond. Here, we postulated that the same type of Ir(Me)-PIX enzymes could catalyze the cyclopropanation of a broad range of alkenes with control of multiple modes of selectivity. Here, we report the evolution of artificial enzymes that are highly active and highly stereoselective for the addition of carbenes to a wide range of alkenes. These enzymes catalyze the cyclopropanation of terminal and internal, activated and unactivated, electron-rich and electron-deficient, conjugated and nonconjugated alkenes. In particular, Ir(Me)-PIX enzymes derived from CYP119 catalyze highly enantio- and diastereoselective cyclopropanations of styrene with ±98% ee, > 70:1 dr, > 75% yield, and ~10,000 turnovers (TON), as well as 1,2-disubstituted styrenes with up to 99% ee, 35:1 dr, and 54% yield. Moreover, Ir(Me)-PIX enzymes catalyze cyclopropanation of internal, unactivated alkenes with up to 99% stereoselectivity, 76% yield, and 1300 TON. They also catalyze cyclopropanation of natural products with diastereoselectivities that are complementary to those attained with standard transition metal catalysts. Finally, Ir(Me)-PIX P450 variants react with substrate selectivity that is reminiscent of natural enzymes; they react preferentially with less reactive internal alkenes in the presence of more reactive terminal alkenes. Altogether, the studies reveal the suitability of Ir-containing P450s to combine the broad reactivity and

Rotary-Atomizer Electric Power Generator

Science.gov (United States)

Nguyen, Trieu; Tran, Tuan; de Boer, Hans; van den Berg, Albert; Eijkel, Jan C. T.

2015-03-01

We report experimental and theoretical results on a ballistic energy-conversion method based on a rotary atomizer working with a droplet acceleration-deceleration cycle. In a rotary atomizer, liquid is fed onto the center of a rotating flat surface, where it spreads out under the action of the centrifugal force and creates "atomized" droplets at its edge. The advantage of using a rotary atomizer is that the centrifugal force exerted on the fluid on a smooth, large surface is not only a robust form of acceleration, as it avoids clogging, but also easily allows high throughput, and produces high electrical power. We successfully demonstrate an output power of 4.9 mW and a high voltage up to 3120 V. At present, the efficiency of the system is still low (0.14%). However, the conversion mechanism of the system is fully interpreted in this paper, permitting a conceptual understanding of system operation and providing a roadmap for system optimization. This observation will open up a road for building power-generation systems in the near future.

Highly Dense Isolated Metal Atom Catalytic Sites

DEFF Research Database (Denmark)

Chen, Yaxin; Kasama, Takeshi; Huang, Zhiwei

2015-01-01

-ray diffraction. A combination of electron microscopy images with X-ray absorption spectra demonstrated that the silver atoms were anchored on five-fold oxygen-terminated cavities on the surface of the support to form highly dense isolated metal active sites, leading to excellent reactivity in catalytic oxidation......Atomically dispersed noble-metal catalysts with highly dense active sites are promising materials with which to maximise metal efficiency and to enhance catalytic performance; however, their fabrication remains challenging because metal atoms are prone to sintering, especially at a high metal...... loading. A dynamic process of formation of isolated metal atom catalytic sites on the surface of the support, which was achieved starting from silver nanoparticles by using a thermal surface-mediated diffusion method, was observed directly by using in situ electron microscopy and in situ synchrotron X...

Nonequilibrium Quantum Phase Transition in a Hybrid Atom-Optomechanical System

Science.gov (United States)

Mann, Niklas; Bakhtiari, M. Reza; Pelster, Axel; Thorwart, Michael

2018-02-01

We consider a hybrid quantum many-body system formed by a vibrational mode of a nanomembrane, which interacts optomechanically with light in a cavity, and an ultracold atom gas in the optical lattice of the out-coupled light. The adiabatic elimination of the light field yields an effective Hamiltonian which reveals a competition between the force localizing the atoms and the membrane displacement. At a critical atom-membrane interaction, we find a nonequilibrium quantum phase transition from a localized symmetric state of the atom cloud to a shifted symmetry-broken state, the energy of the lowest collective excitation vanishes, and a strong atom-membrane entanglement arises. The effect occurs when the atoms and the membrane are nonresonantly coupled.

Magnetic form factors of rare earth ions

International Nuclear Information System (INIS)

Deckman, H.W.

1976-01-01

The magnetic scattering of neutrons by atoms has been investigated by exploiting its similarity to the radiation problem in spectroscopy. Expressions for the magnetic scattering amplitude were developed for cases in whcih an atom in the l/sup n/ electronic configuration is described either by a relativistic or nonrelativistic Hamiltonian. For each of these cases, it has been shown that the magnetic scattering amplitude can be expressed in terms of relativistic or nonrelativistic matrix elements of magnetic and electric multipole operators. For a nonrelativistic atom, the calculation of these matrix elements has been separated into evaluating radial matrix elements and matrix elements of Racah tensors W/(sup 0,k)k/ and W/(sup 1,k')k/. For a relativistic atom the effective operator approach has been used to define effective multipole operators so that a relativistic result is obtained by taking matrix elements of these effective operators between nonrelativistic states of the atom. The calculation of matrix elements of these effective operators has been reduced to evaluating relativistic radial integrals and matrix elements of the Racah tensors taken between nonrelativistic states of the atom. It is shown tha for the case of elastic scattering by either a relativistic or nonrelativistic atom in single Russel-Saunders state, the magnetic scattering amplitude can be written in the conventional form p(vector q)vector q/sub m/.vector sigma. General expressions for p(vector q) as well as elastic magnetic form factorshave been obtained. The formalism has been illustrated throughout by applying it to the case of scattering by rare earth ions

Momentum diffusion for coupled atom-cavity oscillators

International Nuclear Information System (INIS)

Murr, K.; Maunz, P.; Pinkse, P. W. H.; Puppe, T.; Schuster, I.; Rempe, G.; Vitali, D.

2006-01-01

It is shown that the momentum diffusion of free-space laser cooling has a natural correspondence in optical cavities when the internal state of the atom is treated as a harmonic oscillator. We derive a general expression for the momentum diffusion, which is valid for most configurations of interest: The atom or the cavity or both can be probed by lasers, with or without the presence of traps inducing local atomic frequency shifts. It is shown that, albeit the (possibly strong) coupling between atom and cavity, it is sufficient for deriving the momentum diffusion to consider that the atom couples to a mean cavity field, which gives a first contribution, and that the cavity mode couples to a mean atomic dipole, giving a second contribution. Both contributions have an intuitive form and present a clear symmetry. The total diffusion is the sum of these two contributions plus the diffusion originating from the fluctuations of the forces due to the coupling to the vacuum modes other than the cavity mode (the so-called spontaneous emission term). Examples are given that help to evaluate the heating rates induced by an optical cavity for experiments operating at low atomic saturation. We also point out intriguing situations where the atom is heated although it cannot scatter light

First principles investigation of interaction between impurity atom (Si, Ge, Sn) and carbon atom in diamond-like carbon system

International Nuclear Information System (INIS)

Li, Xiaowei; Wang, Aiying; Lee, Kwang-Ryeol

2012-01-01

The interaction between impurity atom (Si, Ge, and Sn) and carbon atom in diamond-like carbon (DLC) system was investigated by the first principles simulation method based on the density functional theory. The tetrahedral configuration was selected as the calculation model for simplicity. When the bond angle varied in a range of 90°–130° from the equivalent state of 109.471°, the distortion energy and the electronic structures including charge density of the highest occupied molecular orbital (HOMO) and partial density of state (PDOS) in the different systems were calculated. The results showed that the addition of Si, Ge and Sn atom into amorphous carbon matrix significantly decreased the distortion energy of the system as the bond angles deviated from the equilibrium one. Further studies of the HOMO and PDOS indicated that the weak covalent bond between Si(Ge, Sn) and C atoms was formed with the decreased strength and directionality, which were influenced by the electronegative difference. These results implied that the electron transfer behavior at the junction of carbon nano-devices could be tailored by the impurity element, and the compressive stress in DLC films could be reduced by the incorporation of Si, Ge and Sn because of the formation of weaker covalent bonds. - Highlights: ►Distortion energy after bond angle distortion was decreased comparing with C-C unit. ►The weak covalent bond was formed between impurity atoms and corner carbon atoms. ►Observed electron transfer behavior affected the strength and directionality of bond. ►Reduction of strength and directionality of bond contributed to small energy change.

Atoms

International Nuclear Information System (INIS)

Fuchs, Alain; Villani, Cedric; Guthleben, Denis; Leduc, Michele; Brenner, Anastasios; Pouthas, Joel; Perrin, Jean

2014-01-01

Completed by recent contributions on various topics (atoms and the Brownian motion, the career of Jean Perrin, the evolution of atomic physics since Jean Perrin, relationship between scientific atomism and philosophical atomism), this book is a reprint of a book published at the beginning of the twentieth century in which the author addressed the relationship between atomic theory and chemistry (molecules, atoms, the Avogadro hypothesis, molecule structures, solutes, upper limits of molecular quantities), molecular agitation (molecule velocity, molecule rotation or vibration, molecular free range), the Brownian motion and emulsions (history and general features, statistical equilibrium of emulsions), the laws of the Brownian motion (Einstein's theory, experimental control), fluctuations (the theory of Smoluchowski), light and quanta (black body, extension of quantum theory), the electricity atom, the atom genesis and destruction (transmutations, atom counting)

Blue phosphorescent organic light-emitting diodes using an exciplex forming co-host with the external quantum efficiency of theoretical limit.

Science.gov (United States)

Shin, Hyun; Lee, Sunghun; Kim, Kwon-Hyeon; Moon, Chang-Ki; Yoo, Seung-Jun; Lee, Jeong-Hwan; Kim, Jang-Joo

2014-07-16

A high-efficiency blue-emitting organic light-emitting diode (OLED) approaching theoretical efficiency using an exciplex-forming co-host composed of N,N'-dicarbazolyl-3,5-benzene (mCP) and bis-4,6-(3,5-di-3-pyridylphenyl)- 2-methylpyrimidine (B3PYMPM) is fabricated. Iridium(III)bis[(4,6-difluorophenyl)- pyridinato-N,C2']picolinate (FIrpic) is used as the emitter, which turns out to have a preferred horizontal dipole orientation in the emitting layer. The OLED shows a maximum external quantum efficiency of 29.5% (a maximum current efficiency of 62.2 cd A(-1) ), which is in perfect agreement with the theoretical prediction. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On the relativistic and nonrelativistic electron descriptions in high-energy atomic collisions

International Nuclear Information System (INIS)

Voitkiv, A.B

2007-01-01

We consider the relativistic and nonrelativistic descriptions of an atomic electron in collisions with point-like charged projectiles moving at relativistic velocities. We discuss three different forms of the fully relativistic first-order transition amplitude. Using the Schroedinger-Pauli equation to describe the atomic electron we establish the correct form of the nonrelativistic first-order transition amplitude. We also show that the so-called semi-relativistic treatment, in which the Darwin states are used to describe the atomic electron, is in fact fully equivalent to the nonrelativistic consideration. The comparison of results obtained with the relativistic and nonrelativistic electron descriptions shows that the latter is accurate within 20-30% up to Z a ∼ a is the atomic nuclear charge

Atmospheric behavior of urban diesel soot tagged with an iridium tracer

International Nuclear Information System (INIS)

Suarez, A.E.; Caffrey, P.F.; Borgoul, P.V.; Ondov, J.M.

1995-01-01

An important source of polynuclear aromatic hydrocarbons depositing to the Chesapeake Bay is diesel emissions, including, those from the heavily-industrial City of Baltimore which lies 3 of diesel fuel burned by the City of Baltimore's sanitation truck fleet for a 20-day period in August, 1995. Size-segregated aerosol was collected daily using 80-L min -1 dichotomous samplers at four land-bas3ed sites and aboard ship at two locations on the Chesapeake Bay. Shipboard samples were collected on the EPA's Research Vessel Anderson, either east or southeast of Baltimore, off Annapolis. Three of the land sites, i.e., those at Catonsville, MD, the Eastern Avenue Fire Station (14 km from the Bay), and the Coast Guard Station at Still pond (30 km northeast of Baltimore) were chosen to be aligned with prevailing westerly winds. The fourth site was located on Hart Miller Island, about 14 km southeast of the Fire Station to take advantage of drainage flow along the Patapsco River. In addition, 10-stage Micro-Orifice Impactors were operated daily aboard ship and at all but the Catonsville site. Deposition plates were exposed aboard ship and at two of the land sites. Finally, several samples of tagged diesel emissions were collected with an MOI mounted on one of the sanitation trucks. Iridium and ≤ 40 other elements were determined by neutron activation analysis or X-ray fluorescence; graphitic carbon by light transmission, and aerosol mass by gravimetry

Satellite Telemetry and Command using Big LEO Mobile Telecommunications Systems

Science.gov (United States)

Huegel, Fred

1998-01-01

Various issues associated with satellite telemetry and command using Big LEO mobile telecommunications systems are presented in viewgraph form. Specific topics include: 1) Commercial Satellite system overviews: Globalstar, ICO, and Iridium; 2) System capabilities and cost reduction; 3) Satellite constellations and contact limitations; 4) Capabilities of Globalstar, ICO and Iridium with emphasis on Globalstar; and 5) Flight transceiver issues and security.

LiBSi2: a tetrahedral semiconductor framework from boron and silicon atoms bearing lithium atoms in the channels.

Science.gov (United States)

Zeilinger, Michael; van Wüllen, Leo; Benson, Daryn; Kranak, Verina F; Konar, Sumit; Fässler, Thomas F; Häussermann, Ulrich

2013-06-03

Silicon swallows up boron: The novel open tetrahedral framework structure (OTF) of the Zintl phase LiBSi2 was made by applying high pressure to a mixture of LiB and elemental silicon. The compound represents a new topology in the B-Si net (called tum), which hosts Li atoms in the channels (see picture). LiBSi2 is the first example where B and Si atoms form an ordered common framework structure with B engaged exclusively in heteronuclear B-Si contacts.

The energy dependence of selective hydrogen atom abstraction by H(D) atoms in the photolysis of neopentane - ethane mixtures at 77 K

International Nuclear Information System (INIS)

Miyazaki, T.; Fueki, K.

1980-01-01

Selective hydrogen - atom - abstraction reaction by H or D atom has been studied in a neo C 5 H 12 - C 2 H 6 (less than 1 mol %) mixture at 77 K by ESR spectroscopy. The H (or D) atom produced by the photolysis of HI (or DI) reacts with neo - C 2 H 12 and C 2 H 6 to form neo - C 5 H 11 and C 2 H 5 radicals. In order to obtain H atoms with different kinetic energies, the photolysis was performed with different lights of 313, 254 and 229 nm. The selective formation of the C 2 H 5 radical by the reaction of the H (or D) atom with C 2 H 6 becomes more effective with the decrease in the energy of the H (or D) atom. The formation of the neo - C 5 H 11 radical by the reaction of the H (or D) atom with neo - C 2 H 12 becomes more effective with the increase in the energy of the H (or D) atom. (A.R.H.) [pt