WorldWideScience

Sample records for single iodine atom

  1. Atomic iodine laser

    International Nuclear Information System (INIS)

    Fisk, G.A.; Gusinow, M.A.; Hays, A.K.; Padrick, T.D.; Palmer, R.E.; Rice, J.K.; Truby, F.K.; Riley, M.E.

    1978-05-01

    The atomic iodine photodissociation laser has been under intensive study for a number of years. The physics associated with this system is now well understood and it is possible to produce a 0.1 nsec (or longer) near-diffraction-limited laser pulse which can be amplified with negligible temporal distortion and little spatial deformation. The output of either a saturated or unsaturated amplifier consists of a high-fidelity near-diffraction-limited, energetic laser pulse. The report is divided into three chapters. Chapter 1 is a survey of the important areas affecting efficient laser operation and summarizes the findings of Chap. 2. Chapter 2 presents detailed discussions and evaluations pertinent to pumps, chemical regeneration, and other elements in the overall laser system. Chapter 3 briefly discusses those areas that require further work and the nature of the work required to complete the full-scale evaluation of the applicability of the iodine photodissociation laser to the inertial confinement program

  2. Chemical generation of iodine atoms

    Energy Technology Data Exchange (ETDEWEB)

    Hewett, Kevin B. [Directed Energy Directorate, Air Force Research Laboratory, 3550 Aberdeen Avenue SE, Kirtland AFB, NM 87117-5776 (United States)]. E-mail: kevin.hewett@kirtland.af.mil; Hager, Gordon D. [Directed Energy Directorate, Air Force Research Laboratory, 3550 Aberdeen Avenue SE, Kirtland AFB, NM 87117-5776 (United States); Crowell, Peter G. [Northrup Grumman Information Technology, Science and Technology Operating Unit, Advanced Technology Division, P.O. Box 9377, Albuquerque, NM 87119-9377 (United States)

    2005-01-10

    The chemical generation of atomic iodine using a chemical combustor to generate the atomic fluorine intermediate, from the reaction of F{sub 2} + H{sub 2}, followed by the production of atomic iodine, from the reaction of F + HI, was investigated. The maximum conversion efficiency of HI into atomic iodine was observed to be approximately 75%, which is in good agreement with the theoretical model. The conversion efficiency is limited by the formation of iodine monofluoride at the walls of the combustor where the gas phase temperature is insufficient to dissociate the IF.

  3. Atomic iodine production in a gas flow by decomposing methyl iodide in a dc glow discharge

    International Nuclear Information System (INIS)

    Mikheyev, P A; Shepelenko, A A; Voronov, A I; Kupryaev, Nikolai V

    2002-01-01

    The production of atomic iodine for an oxygen - iodine laser is studied by decomposing methyl iodide in a dc glow discharge in a vortex gas flow. The concentration of iodine atoms in discharge products was measured from the atomic iodine absorption of the radiation of a single-frequency tunable diode laser at a wavelength of 1.315 μm. Atomic iodine concentrations sufficient for the operation of an oxygen - iodine laser were obtained. The concentration of atomic iodine amounted to 3.6 x 10 15 cm -3 for a pressure of the carrying argon gas of 15 Torr. The discharge stabilisation by a vortex gas flow allowed the glow discharge to be sustained in a strongly electronegative halogen-containing gas mixture for pressures up to 20 Torr. (active media)

  4. High power atomic iodine photodissociation lasers

    International Nuclear Information System (INIS)

    Palmer, R.E.; Padrick, T.D.; Jones, E.D.

    1976-01-01

    The atomic iodine photodissociation laser has developed into a system capable of producing nanosecond or shorter pulses of near infrared radiation with energies well in excess of a hundred J. Discussed are the operating characteristics, advantages, and potential problem areas associated with this laser

  5. Chemical oxygen-iodine laser with atomic iodine generated via fluorine atoms

    Czech Academy of Sciences Publication Activity Database

    Jirásek, Vít; Čenský, Miroslav; Špalek, Otomar; Kodymová, Jarmila; Picková, Irena; Jakubec, Ivo

    2008-01-01

    Roč. 345, č. 1 (2008), 14-22 ISSN 0301-0104 R&D Projects: GA ČR GA202/05/0359 Institutional research plan: CEZ:AV0Z10100523; CEZ:AV0Z40320502 Keywords : atomic iodine * atomic fluorine * chemical oxygen–iodine laser * COIL Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.961, year: 2008

  6. Solar-simulator-pumped atomic iodine laser kinetics

    Science.gov (United States)

    Wilson, H. W.; Raju, S.; Shiu, Y. J.

    1983-01-01

    The literature contains broad ranges of disagreement in kinetic data for the atomic iodine laser. A kinetic model of a solar-simulator-pumped iodine laser is used to select those kinetic data consistent with recent laser experiments at the Langley Research Center. Analysis of the solar-simulator-pumped laser experiments resulted in the following estimates of rate coefficients: for alkyl radical (n-C3F7) and atomic iodine (I) recombination, 4.3 x 10 to the 11th power (1.9) + or - cu cm/s; for n-C3F7I stabilized atomic iodine recombination (I + I) 3.7 x 10 to the -32nd power (2.3) + or -1 cm to the 6th power/s; and for molecular iodine (I2) quenching, 3.1 x 10 to the -11th power (1.6) + or - 1 cu cm/s. These rates are consistent with the recent measurements.

  7. A Single Atom Antenna

    International Nuclear Information System (INIS)

    Trinter, Florian; Williams, Joshua B; Weller, Miriam; Waitz, Markus; Pitzer, Martin; Voigtsberger, Jörg; Schober, Carl; Kastirke, Gregor; Müller, Christian; Goihl, Christoph; Burzynski, Phillip; Wiegandt, Florian; Wallauer, Robert; Kalinin, Anton; Schmidt, Lothar Ph H; Schöffler, Markus S; Jahnke, Till; Dörner, Reinhard; Chiang, Ying-Chih; Gokhberg, Kirill

    2015-01-01

    Here we demonstrate the smallest possible implementation of an antenna-receiver complex which consists of a single (helium) atom acting as the antenna and a second (neon) atom acting as a receiver. (paper)

  8. Single atom oscillations

    International Nuclear Information System (INIS)

    Wiorkowski, P.; Walther, H.

    1990-01-01

    Modern methods of laser spectroscopy allow the study of single atoms or ions in an unperturbed environment. This has opened up interesting new experiments, among them the detailed study of radiation-atom coupling. In this paper, the following two experiments dealing with this problem are reviewed: the single-atom maser and the study of the resonance fluorescence of a single stored ion. The simplest and most fundamental system for studying radiation-matter coupling is a single two-level atom interacting with a single mode of an electromagnetic field in a cavity. This problem received a great deal of attention shortly after the maser was invented

  9. Generation of atomic iodine via fluorine for chemical oxygen-iodine laser

    Czech Academy of Sciences Publication Activity Database

    Jirásek, Vít; Špalek, Otomar; Čenský, Miroslav; Picková, Irena; Kodymová, Jarmila; Jakubec, Ivo

    2007-01-01

    Roč. 334, - (2007), s. 167-174 ISSN 0301-0104 R&D Projects: GA ČR GA202/05/0359 Grant - others:USAF European Office for Research and Development(XE) FA 8655-05-M-4027 Institutional research plan: CEZ:AV0Z10100523; CEZ:AV0Z40320502 Keywords : atomic iodine * atomic fluorine * chemical oxygen-iodine laser Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.805, year: 2007

  10. Photostop of iodine atoms from electrically oriented ICl molecules

    International Nuclear Information System (INIS)

    Bao Da-Xiao; Lian-Zhong Deng; Xu Liang; Yin Jian-Ping

    2015-01-01

    The dynamics of photostopping iodine atoms from electrically oriented ICl molecules was numerically studied based on their orientational probability distribution functions. Velocity distributions of the iodine atoms and their production rates were investigated for orienting electrical fields of various intensities. For the ICl precursor beams with an initial rotational temperature of ∼ 1 K, the production of the iodine atoms near zero speed will be improved by about ∼ 5 times when an orienting electrical field of ∼ 200 kV/cm is present. A production rate of ∼ 0.5‰ is obtained for photostopped iodine atoms with speeds less than 10 m/s, which are suitable for magnetic trapping. The electrical orientation of ICl precursors and magnetic trapping of photostopped iodine atoms in situ can be conveniently realized with a pair of charged ring magnets. With the maximal value of the trapping field being ∼ 0.28 T, the largest trapping speed is ∼ 7.0 m/s for the iodine atom. (paper)

  11. Sandia high-power atomic iodine photodissociation laser

    International Nuclear Information System (INIS)

    Palmer, R.E.; Padrick, T.D.

    1975-01-01

    One of the more promising candidates for a laser to demonstrate the feasibility of laser fusion is the 1.315 μ atomic iodine laser. In a relatively short time it has been developed into a viable subnanosecond, high energy laser. Although at present the iodine laser cannot equal the output capabilities of a large Nd:glass laser system, there are no foreseeable obstacles in the construction of a 100 psec, 10 KJ or greater atomic iodine laser system. A 100 joule system being constructed at Sandia to investigate many of the scaling parameters essential to the design of a 10 KJ or greater system is described. (U.S.)

  12. Generation of atomic iodine via fluorine for chemical oxygen-iodine laser

    International Nuclear Information System (INIS)

    Jirasek, Vit; Spalek, Otomar; Censky, Miroslav; Pickova, Irena; Kodymova, Jarmila; Jakubec, Ivo

    2007-01-01

    A method of the chemical generation of atomic iodine for a chemical oxygen-iodine laser (COIL) using atomic fluorine as a reaction intermediate was studied experimentally. This method is based on the reaction between F 2 and NO providing F atoms, and the reaction of F with HI resulting in iodine atoms generation. Atomic iodine was produced with efficiency exceeding 40% relative to initial F 2 flow rate. This efficiency was nearly independent on pressure and total gas flow rate. The F atoms were stable in the reactor up to 2 ms. An optimum ratio of the reactants flow rates was F 2 :NO:HI = 1:1:1. A rate constant of the reaction of F 2 with HI was determined. The numerical modelling showed that remaining HI and IF were probably consumed in their mutual reaction. The reaction system was found suitable for employing in a generator of atomic iodine with its subsequent injection into a supersonic nozzle of a COIL

  13. Single atom spintronics

    International Nuclear Information System (INIS)

    Sullivan, M. R.; Armstrong, J. N.; Hua, S. Z.; Chopra, H. D.

    2005-01-01

    Full text: Single atom spintronics (SASS) represents the ultimate physical limit in device miniaturization. SASS is characterized by ballistic electron transport, and is a fertile ground for exploring new phenomena. In addition to the 'stationary' (field independent) scattering centers that have a small and fixed contribution to total transmission probability of electron waves, domain walls constitute an additional and enhanced source of scattering in these magnetic quantum point contacts (QPCs), the latter being both field and spin-dependent. Through the measurement of complete hysteresis loops as a function of quantized conductance, we present definitive evidence of enhanced backscattering of electron waves by atomically sharp domain walls in QPCs formed between microfabricated thin films [1]. Since domain walls move in a magnetic field, the magnitude of spin-dependent scattering changes as the QPC is cycled along its hysteresis loop. For example, as shown in the inset in Fig. 1, from zero towards saturation in a given field direction, the resistance varies as the wall is being swept away, whereas the resistance is constant upon returning from saturation towards zero, since in this segment of the hysteresis loop no domain wall is present across the contact. The observed spin-valve like behavior is realized by control over wall width and shape anisotropy. This behavior also unmistakably sets itself apart from any mechanical artifacts; additionally, measurements made on single atom contacts provide an artifact-free environment [2]. Intuitively, it is simpler to organize the observed BMR data according to all possible transitions between different conductance plateaus, as shown by the dotted line in Fig. 1; the solid circles show experimental data for Co, which follows the predicted scheme. Requisite elements for the observation of the effect will be discussed in detail along with a review of state of research in this field. Practically, the challenge lies in making

  14. A solar simulator-pumped atomic iodine laser

    Science.gov (United States)

    Lee, J. H.; Weaver, W. R.

    1981-01-01

    An atomic iodine laser, a candidate for the direct solar-pumped gas laser, was excited with a 4-kW beam from a xenon arc solar simulator. Continuous lasing at 1.315 micron for over 10 ms was obtained for static filling of n-C3F7I vapor. By momentarily flowing the lasant, a 30-Hz pulsed output was obtained for about 200 ms. The peak laser power observed was 4 W for which the system efficiency reached 0.1%. These results indicate that direct solar pumping of a gas laser for power conversion in space is indeed feasible.

  15. Nuclear-driven flashlamp pumping of the atomic iodine laser

    International Nuclear Information System (INIS)

    Miley, G.H.

    1992-03-01

    This report is a study of the atomic iodine laser pumped with nuclear- excited XeBr fluorescence. Preliminary experiments, conducted in the TRIGA reactor investigated the fluorescence of the excimer XeBr under nuclear pumping with 10 B and 3 He, for use as a flashlamp gas to stimulate the laser. These measurements included a determination of the fluorescence efficiency (light emitted in the wavelength region of interest, divided by energy deposited in the gas) of XeBr under nuclear pumping, with varying excimer mixtures. Maximum fluorescence efficiencies were approximately 1%. In order to better understand XeBr under nuclear excitation, a kinetics model of the system was prepared. The model generated the time-dependant concentrations of 20 reaction species for three pulse sizes, a TRIGA pulse, a fast burst reactor pulse, and an e-beam pulse. The modeling results predicted fluorescence efficiencies significantly higher (peak efficiencies of approximately 10%) than recorded in the fluorescence experiments. The cause of this discrepancy was not fully determined. A ray tracing computer model was also prepared to evaluate the efficiency with which nuclear-induced fluorescence generated in one cavity of a laser could be coupled into another cavity containing an iodine lasant. Finally, an experimental laser cell was constructed to verify that nuclear-induced XeBr fluorescence could be used to stimulate a laser. Lasing was achieved at 1.31 micron in the TRIGA using C 3 F 7 I, a common iodine lasant. Peak laser powers were approximately 20 mW. Measured flashlamp pump powers at threshold agreed well with literature values, as did lasant pressure dependency on laser operation

  16. Iodine

    Science.gov (United States)

    ... Health Information Supplement Fact Sheets Frequently Asked Questions Making Decisions What you Need To Know About Supplements Dietary ... mild iodine deficiency and of iodine supplements on cognitive ... breasts. It mainly affects women of reproductive age but can also occur ...

  17. Mechanism of pulse discharge production of iodine atoms from CF3I molecules for a chemical oxygen-iodine laser

    International Nuclear Information System (INIS)

    Kochetov, I V; Napartovich, A P; Vagin, N P; Yuryshev, N N

    2009-01-01

    The pulsed chemical oxygen-iodine laser (COIL) development is aimed at many new applications. Pulsed electric discharge is most effective in turning COIL operation into the pulse mode by instant production of iodine atoms. A numerical model is developed for simulations of the pulsed COIL initiated by an electric discharge. The model comprises a system of kinetic equations for neutral and charged species, electric circuit equation, gas thermal balance equation and the photon balance equation. Reaction rate coefficients for processes involving electrons are found by solving the electron Boltzmann equation, which is re-calculated in a course of computations when plasma parameters changed. The processes accounted for in the Boltzmann equation include excitation and ionization of atoms and molecules, dissociation of molecules, electron attachment processes, electron-ion recombination, electron-electron collisions, second-kind collisions and stepwise excitation of molecules. The last processes are particularly important because of a high singlet oxygen concentration in gas flow from the singlet oxygen chemical generator. Results of numerical simulations are compared with experimental laser pulse waveforms. It is concluded that there is satisfactory agreement between theory and the experiment. The prevailing mechanism of iodine atom formation from the CF 3 I donor in a very complex kinetic system of the COIL medium under pulse discharge conditions, based on their detailed numerical modelling and by comparing these results both with experimental results of other authors and their own experiments, is established. The dominant iodine atom production mechanism for conditions under study is the electron-impact dissociation of CF 3 I molecules. It was proved that in the conditions of the experiment the secondary chemical reactions with O atoms play an insignificant role.

  18. Numerical analysis of the performance of an atomic iodine laser amplifier chain

    International Nuclear Information System (INIS)

    Uchiyama, T.; Witte, K.J.

    1981-05-01

    The performance of an atomic iodine laser amplifier chain with output pulse powers close to 2 TW is analyzed by a numerical solution of the Maxwell-Bloch equations. Two subjects are discussed in detail. The first one refers to the pulse compression occurring in the chain as a result of saturation and some related aspects such as damage to components, self-focussing, correlation between the input and output pulse shapes, and the means of pulse shape control. The second deals with various schemes suited for achieving extraction efficiencies of about or larger than 55%. These include the single-pass and double-pass schemes, pulses with two carrier frequencies and a variation of the pulse carrier frequency. In addition, the response of the chain to a variation of those parameters which are most easily subject to change in a routine operation is investigated. (orig.)

  19. Iodine

    Science.gov (United States)

    ... leg ulcers and reduce the chance of a future infection. Conjunctivitis (pinkeye). Research suggests that using eye ... National Institute of Medicine has set Adequate Intake (AI) of iodine for infants: 0 to 6 months, ...

  20. Electric field imaging of single atoms

    Science.gov (United States)

    Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D.; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi

    2017-01-01

    In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures. PMID:28555629

  1. Single-atom lasing induced atomic self-trapping

    International Nuclear Information System (INIS)

    Salzburger, T.; Ritsch, H.

    2004-01-01

    We study atomic center of mass motion and field dynamics of a single-atom laser consisting of a single incoherently pumped free atom moving in an optical high-Q resonator. For sufficient pumping, the system starts lasing whenever the atom is close to a field antinode. If the field mode eigenfrequency is larger than the atomic transition frequency, the generated laser light attracts the atom to the field antinode and cools its motion. Using quantum Monte Carlo wave function simulations, we investigate this coupled atom-field dynamics including photon recoil and cavity decay. In the regime of strong coupling, the generated field shows strong nonclassical features like photon antibunching, and the atom is spatially confined and cooled to sub-Doppler temperatures. (author)

  2. Dynamics of production of iodine atoms by dissociation of iodides in a pulsed self-sustained discharge

    International Nuclear Information System (INIS)

    Vagin, Nikolai P; Kochetov, Igor' V; Napartovich, A P; Yuryshev, Nikolai N

    2013-01-01

    Absorption at the laser transition has been used for the first time to assess the evolution of concentration of iodine atoms in a pulsed self-sustained discharge in mixtures of iodides with a buffer gas such as molecular nitrogen and helium. Dynamics of the iodine atom production is studied by the method of absorption spectroscopy. The dissociation of C n F 2n+1 I and CnH 2n+1 I (n = 1, 2) iodides is investigated. The energy required to produce atomic iodine is evaluated. The experimental data obtained for CF 3 I are compared with the results of numerical simulations, their reasonable agreement being demonstrated. (active media)

  3. Evaluation of the potential to upgrade the Sandia Atomic Iodine Laser SAIL-1 to higher output energies

    International Nuclear Information System (INIS)

    Riley, M.E.; Palmer, R.E.

    1977-05-01

    The predicted output energy of the Sandia Atomic Iodine Laser SAIL-1 is given for various numbers of preamplifier stages and for various small signal gains in each stage. Additional possibilities for further increasing the output energy are given

  4. Ab initio atomic simulation of hydrogen and iodine effects in zirconium

    International Nuclear Information System (INIS)

    Domain, Ch.

    2002-03-01

    In this work we present ab initio atomic simulations concerning the effects of hydrogen and iodine in hexagonal zirconium. We first studied the point defects in the dilute Zr-H (and to a less extend Zr-H-O) systems and concluded that it is better described within the generalised gradient approximation for the exchange and correlation functional. We calculated the hydrogen thermal diffusion coefficient in solid solution that agree very well with the experimental values. The calculated formation energy of different self-interstitial configuration are rather small (around 3 eV) and close to each other indicating the high complexity of these defects. We studied the core structure of the screw dislocation that has a preferential prismatic spreading. We also calculated the gamma surface for different gliding planes. The influence of hydrogen, that induces a significant reduction of the gamma surfaces excess energies, allows to qualitatively explain experimental results regarding some hydrogen effects on hexagonal zirconium plastic deformation. We also discussed the effect of zirconium hydride stoichiometry on gamma surfaces. The results concerning the iodine and oxygen adsorption on zirconium surfaces, inducing the evaluation of the effective surface energy reduction as a function of the iodine partial pressure allow for a better description of iodine induced stress corrosion cracking of zirconium. (author)

  5. Single atom counting with accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Woelfli, W [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1984-02-01

    Direct detection of radioisotopes with conventional mass spectrometers is possible when the potential background atoms, in particular stable isotopes of the same mass (isobars) or molecules of similar mass are present in sufficiently low concentrations. Most of the long lived radioisotopes of interest for dating purposes however, occur in such small concentrations that their peak in the mass spectrum is obscured by the stable isobar and molecule distributions. The key idea of the new AMS technique which allows us to measure directly such small concentrations is the acceleration of the sample atoms to MeV energies and to use various filter processes and particle identification techniques developed for nuclear physics research to eliminate the isobaric and molecular interferences. The detection methods used for each radioisotope depend on the dominant background atoms and these in turn depend on the specific accelerator used. The problems encountered in transforming an existing particle accelerator into a high precision dating tool are considerable and have been solved only recently for one type of accelerator, notably the tandem Van de Graaff. For this reason the description of the AMS method and some of its applications is restricted to this type of accelerator only.

  6. Mechanism of single atom switch on silicon

    DEFF Research Database (Denmark)

    Quaade, Ulrich; Stokbro, Kurt; Thirstrup, C.

    1998-01-01

    We demonstrate single atom switch on silicon which operates by displacement of a hydrogen atom on the silicon (100) surface at room temperature. We find two principal effects by which the switch is controlled: a pronounced maximum of the switching probability as function of sample bias...

  7. Feedback Cooling of a Single Neutral Atom

    NARCIS (Netherlands)

    Koch, Markus; Sames, Christian; Kubanek, Alexander; Apel, Matthias; Balbach, Maximilian; Ourjoumtsev, Alexei; Pinkse, Pepijn Willemszoon Harry; Rempe, Gerhard

    2010-01-01

    We demonstrate feedback cooling of the motion of a single rubidium atom trapped in a high-finesse optical resonator to a temperature of about 160  μK. Time-dependent transmission and intensity-correlation measurements prove the reduction of the atomic position uncertainty. The feedback increases the

  8. Laboratory studies on tropospheric iodine chemistry: bridging the atomic, molecular and particle scale

    Science.gov (United States)

    Gomez Martin, J.; Saunders, R. W.; Blitz, M. A.; Mahajan, A. S.; Plane, J. M.

    2008-12-01

    High mixing ratios of the iodine oxides IO and OIO have been observed in the polar, mid-latitude and tropical marine boundary layer (MBL). The impact of the iodine chemistry on the oxidizing capacity of the MBL is well documented. Moreover, there is evidence showing that the bursts of new particles measured in coastal regions are produced by the biogenic emission of iodine containing precursors, followed by the photochemical production and condensation of iodine oxide vapours. Airborne measurements of particle growth rates show that these particles can reach significant sizes where they can contribute to the regional aerosol loading, thus suggesting a potential impact on climate on a regional or global scale. Within the frame of the INSPECT project (INorganic Secondary Particle Evolution, Chemistry and Transport) we wish to understand at a fundamental level the tendency for the iodine oxides formed from IO and OIO recombination to condense into particles. Elemental analysis of iodine oxide particles (IOP) made in the laboratory shows that they have the empirical formula I2O5. The major question is how this happens: through formation of I2O5 in the gas phase, followed by polymerization, or by condensation of various IxOy to form amorphous iodine oxides, which subsequently rearrange to I2O5. We are studying the gas phase photochemistry leading to nucleation of IOP, their growth kinetics, aspects of their heterogeneous chemistry, and their properties as ice condensation nuclei. In order to bridge the molecular and the particle scales, a wide variety of techniques are being used, including CRDS, ARAS, LIF, UV-VIS spectroscopy, PI-TOF-MS and mobility particle size scanning. The results obtained so far provide new and interesting insights to the problem. From the gas phase point of view, a unit iodine atom quantum yield from OIO photolysis has been now established across its strong visible spectral bands. This result implies a short lifetime of OIO and explains why in

  9. Doping efficiency of single and randomly stacked bilayer graphene by iodine adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Kim, HoKwon; Renault, Olivier; Rouchon, Denis; Mariolle, Denis; Chevalier, Nicolas [Univ. Grenoble Alpes, F-38000 Grenoble, France and CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Tyurnina, Anastasia; Simonato, Jean-Pierre; Dijon, Jean [Univ. Grenoble Alpes, F-38000 Grenoble, France and CEA, LITEN, Minatec Campus, F-38054 Grenoble (France)

    2014-07-07

    We report on the efficiency and thermal stability of p-doping by iodine on single and randomly stacked, weakly coupled bilayer polycrystalline graphene, as directly measured by photoelectron emission microscopy. The doping results in work function value increase of 0.4–0.5 eV, with a higher degree of iodine uptake by the bilayer (2%) as compared to the single layer (1%) suggesting iodine intercalation in the bilayer. The chemistry of iodine is identified accordingly as I{sub 3}{sup −} and I{sub 5}{sup −} poly iodide anionic complexes with slightly higher concentration of I{sub 5}{sup −} in bilayer than monolayer graphene, likely attributed to differences in doping mechanisms. Temperature dependent in-situ annealing of the doped films demonstrated that the doping remains efficient up to 200 °C.

  10. Single photon transport by a moving atom

    International Nuclear Information System (INIS)

    Afanasiev, A E; Melentiev, P N; Kuzin, A A; Yu Kalatskiy, A; Balykin, V I

    2017-01-01

    The results of investigation of photon transport through the subwavelength hole in the opaque screen by using single neutral atom are represented. The basis of the proposed and implemented method is the absorption of a photon by a neutral atom immediately before the subwavelength aperture, traveling of the atoms through the hole and emission of a photon on the other side of the screen. Realized method is the alternative approach to existing for photon transport through a subwavelength aperture: 1) self-sustained transmittance of a photon through the aperture according to the Bethe’s model; 2) extra ordinary transmission because of surface-plasmon excitation. (paper)

  11. Vibration spectra of single atomic nanocontacts

    International Nuclear Information System (INIS)

    Bourahla, B; Khater, A; Rafil, O; Tigrine, R

    2006-01-01

    This paper introduces a simple model for an atomic nanocontact, where its mechanical properties are analysed by calculating numerically the local spectral properties at the contact atom and the nearby atoms. The standard methodology for calculating phonon spectral densities is extended to enable the calculation of localized contact modes and local density of states (DOS). The model system considered for the nanocontact consists of two sets of triple parallel semi-infinite atomic chains joined by a single atom in between. The matching method is used, in the harmonic approximation, to calculate the local Green's functions for the irreducible set of sites that constitute the inhomogeneous nanocontact domain. The Green's functions yield the vibration spectra and the DOS for the atomic sites. These are numerically calculated for different cases of elastic hardening and softening of the nanocontact domain. The purpose is to investigate how the local dynamics respond to local changes in the elastic environment. The analysis of the spectra and of the DOS identifies characteristic features and demonstrates the central role of a core subset of these sites for the dynamics of the nanocontact. The system models a situation which may be appropriate for contact atomic force microscopy

  12. Nano-soldering to single atomic layer

    Science.gov (United States)

    Girit, Caglar O [Berkeley, CA; Zettl, Alexander K [Kensington, CA

    2011-10-11

    A simple technique to solder submicron sized, ohmic contacts to nanostructures has been disclosed. The technique has several advantages over standard electron beam lithography methods, which are complex, costly, and can contaminate samples. To demonstrate the soldering technique graphene, a single atomic layer of carbon, has been contacted, and low- and high-field electronic transport properties have been measured.

  13. Vibration dynamics of single atomic nanocontacts

    International Nuclear Information System (INIS)

    Khater, A; Bourahla, B; Tigrine, R

    2007-01-01

    The motivation for this work is to introduce a model for an atomic nanocontact, whereby its mechanical properties can be analysed via the local spectra. The model system consists of two sets of triple parallel semi-infinite atomic chains joined by a single atom in between. We calculate the vibration spectra and the local densities of vibration states, in the harmonic approximation, for the irreducible set of sites that constitute the nanocontact domain. The nanocontact observables are numerically calculated for different cases of elastic hardening and softening, to investigate how the local dynamics can respond to changes in the microscopic environment on the domain. We have also calculated the phonon scattering and coherent conductance at the nanocontact, derived in a Landauer-Buettiker matrix approach. The analysis of the spectra, of the densities of vibration states, and of the phonon conductance, identifies characteristic features and demonstrates the central role of a core subset of sites in the nanocontact domain

  14. Headspace single-drop microextraction coupled to microvolume UV-vis spectrophotometry for iodine determination

    International Nuclear Information System (INIS)

    Pena-Pereira, Francisco; Lavilla, Isela; Bendicho, Carlos

    2009-01-01

    Headspace single-drop microextraction has been combined with microvolume UV-vis spectrophotometry for iodine determination. Matrix separation and preconcentration of iodide following in situ volatile iodine generation and extraction into a microdrop of N,N'-dimethylformamide is performed. An exhaustive characterization of the microextraction system and the experimental variables affecting iodine generation from iodide was carried out. The procedure employed consisted of exposing 2.5 μL of N,N'-dimethylformamide to the headspace of a 10 mL acidic (H 2 SO 4 2 mol L -1 ) aqueous solution containing 1.7 mol L -1 Na 2 SO 4 for 7 min. Addition of 1 mL of H 2 O 2 1 mol L -1 for in situ iodine generation was performed. The limit of detection was determined as 0.69 μg L -1 . The repeatability, expressed as relative standard deviation, was 4.7% (n = 6). The calibration working range was from 5 to 200 μg L -1 (r 2 = 0.9991). The large preconcentration factor obtained, ca. 623 in only 7 min, compensate for the 10-fold loss in sensitivity caused by the decreased optical path, which results in improved detection limits as compared to spectrophotometric measurements carried out with conventional sample cells. The method was successfully applied to the determination of iodine in water, pharmaceutical and food samples

  15. In situ detection of atomic and molecular iodine using Resonance and Off-Resonance Fluorescence by Lamp Excitation: ROFLEX

    Directory of Open Access Journals (Sweden)

    J. C. Gómez Martín

    2011-01-01

    Full Text Available We demonstrate a new instrument for in situ detection of atmospheric iodine atoms and molecules based on atomic and molecular resonance and off-resonance ultraviolet fluorescence excited by lamp emission. The instrument combines the robustness, light weight, low power consumption and efficient excitation of radio-frequency discharge light sources with the high sensitivity of the photon counting technique. Calibration of I2 fluorescence is achieved via quantitative detection of the molecule by Incoherent Broad Band Cavity-enhanced Absorption Spectroscopy. Atomic iodine fluorescence signal is calibrated by controlled broad band photolysis of known I2 concentrations in the visible spectral range at atmospheric pressure. The instrument has been optimised in laboratory experiments to reach detection limits of 1.2 pptv for I atoms and 13 pptv for I2, for S/N = 1 and 10 min of integration time. The ROFLEX system has been deployed in a field campaign in northern Spain, representing the first concurrent observation of ambient mixing ratios of iodine atoms and molecules in the 1–350 pptv range.

  16. Doping monolayer graphene with single atom substitutions

    KAUST Repository

    Wang, Hongtao

    2012-01-11

    Functionalized graphene has been extensively studied with the aim of tailoring properties for gas sensors, superconductors, supercapacitors, nanoelectronics, and spintronics. A bottleneck is the capability to control the carrier type and density by doping. We demonstrate that a two-step process is an efficient way to dope graphene: create vacancies by high-energy atom/ion bombardment and fill these vacancies with desired dopants. Different elements (Pt, Co, and In) have been successfully doped in the single-atom form. The high binding energy of the metal-vacancy complex ensures its stability and is consistent with in situ observation by an aberration-corrected and monochromated transmission electron microscope. © 2011 American Chemical Society.

  17. Periodically Driven Array of Single Rydberg Atoms

    Science.gov (United States)

    Basak, Sagarika; Chougale, Yashwant; Nath, Rejish

    2018-03-01

    An array of single Rydberg atoms driven by a temporally modulated atom-field detuning is studied. The periodic modulation effectively modifies the Rabi coupling, leading to unprecedented dynamics in the presence of Rydberg-Rydberg interactions, in particular, blockade enhancement, antiblockades, and state-dependent population trapping. Interestingly, the Schrieffer-Wolf transformation reveals a fundamental process in Rydberg gases, correlated Rabi coupling, which stems from the extended nature of the Rydberg-Rydberg interactions. Also, the correlated coupling provides an alternative depiction for the Rydberg blockade, exhibiting a nontrivial behavior in the presence of periodic modulation. The dynamical localization of a many-body configuration in a driven Rydberg lattice is discussed.

  18. Single-atom contacts with a scanning tunnelling microscope

    International Nuclear Information System (INIS)

    Kroeger, J; Neel, N; Sperl, A; Wang, Y F; Berndt, R

    2009-01-01

    The tip of a cryogenic scanning tunnelling microscope is used to controllably contact single atoms adsorbed on metal surfaces. The transition between tunnelling and contact is gradual for silver, while contact to adsorbed gold atoms is abrupt. The single-atom junctions are stable and enable spectroscopic measurements of, e.g., the Abrikosov-Suhl resonance of single Kondo impurities.

  19. Use of oxidative and reducing vapor generation for reducing the detection limits of iodine in biological samples by inductively coupled plasma atomic emission spectrometry

    International Nuclear Information System (INIS)

    Vtorushina, Eh.A.; Saprykin, A.I.; Knapp, G.

    2009-01-01

    Procedures of microwave combustion in an oxygen flow and microwave acid decomposition of biological samples were optimized for the subsequent determination of iodine. A new method was proposed for the generation of molecular iodine from periodate iona using hydrogen peroxide as a reductant. Procedures were developed for determining iodine in biological samples by inductively coupled plasma atomic emission spectrometry (ICP-AES) using oxidative and reducing vapor generation; these allowed the detection limit for iodine to be lowered by 3-4 orders of magnitude. The developed procedures were used to analyze certified reference materials of milk (Skim Milk Powder BCR 150) and seaweed (Sea Lettuce BCR 279) and a Supradyn vitamin complex

  20. 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.

  1. Hyperfine structure measurements of neutral iodine atom (127I) using Fourier Transform Spectrometry

    Science.gov (United States)

    Ashok, Chilukoti; Vishwakarma, S. R.; Bhatt, Himal; Ankush, B. K.; Deo, M. N.

    2018-01-01

    We report the hyperfine Structure (hfs) splitting observations of neutral iodine atom (II) in the 6000 - 10,000 cm-1 near infrared spectral region. The measurements were carried out using a high-resolution Fourier Transform Spectrometer (FTS), where an electrodeless discharge lamp (EDL), excited using microwaves, was employed as the light source and InGaAs as the light detector. A specially designed setup was used to lower the plasma temperature of the medium so as to reduce the Doppler width and consequently to increase the spectral resolution of hfs components. A total of 183 lines with hfs splitting have been observed, out of which hfs in 53 spectral lines are reported for the first time. On the basis of hfs analysis, we derived the magnetic dipole and electric quadrupole coupling constants, A and B respectively for 30 even and 30 odd energy levels and are compared with the values available in the literature. New hfs values for 5 even and 4 odd levels are also reported here for the first time.

  2. A single-atom quantum memory.

    Science.gov (United States)

    Specht, Holger P; Nölleke, Christian; Reiserer, Andreas; Uphoff, Manuel; Figueroa, Eden; Ritter, Stephan; Rempe, Gerhard

    2011-05-12

    The faithful storage of a quantum bit (qubit) of light is essential for long-distance quantum communication, quantum networking and distributed quantum computing. The required optical quantum memory must be able to receive and recreate the photonic qubit; additionally, it must store an unknown quantum state of light better than any classical device. So far, these two requirements have been met only by ensembles of material particles that store the information in collective excitations. Recent developments, however, have paved the way for an approach in which the information exchange occurs between single quanta of light and matter. This single-particle approach allows the material qubit to be addressed, which has fundamental advantages for realistic implementations. First, it enables a heralding mechanism that signals the successful storage of a photon by means of state detection; this can be used to combat inevitable losses and finite efficiencies. Second, it allows for individual qubit manipulations, opening up avenues for in situ processing of the stored quantum information. Here we demonstrate the most fundamental implementation of such a quantum memory, by mapping arbitrary polarization states of light into and out of a single atom trapped inside an optical cavity. The memory performance is tested with weak coherent pulses and analysed using full quantum process tomography. The average fidelity is measured to be 93%, and low decoherence rates result in qubit coherence times exceeding 180  microseconds. This makes our system a versatile quantum node with excellent prospects for applications in optical quantum gates and quantum repeaters.

  3. Entangled photons from single atoms and molecules

    Science.gov (United States)

    Nordén, Bengt

    2018-05-01

    The first two-photon entanglement experiment performed 50 years ago by Kocher and Commins (KC) provided isolated pairs of entangled photons from an atomic three-state fluorescence cascade. In view of questioning of Bell's theorem, data from these experiments are re-analyzed and shown sufficiently precise to confirm quantum mechanical and dismiss semi-classical theory without need for Bell's inequalities. Polarization photon correlation anisotropy (A) is useful: A is near unity as predicted quantum mechanically and well above the semi-classic range, 0 ⩽ A ⩽ 1 / 2 . Although yet to be found, one may envisage a three-state molecule emitting entangled photon pairs, in analogy with the KC atomic system. Antibunching in fluorescence from single molecules in matrix and entangled photons from quantum dots promise it be possible. Molecules can have advantages to parametric down-conversion as the latter photon distribution is Poissonian and unsuitable for producing isolated pairs of entangled photons. Analytical molecular applications of entangled light are also envisaged.

  4. Optical spectroscopy of iodine-doped single-wall carbon nanotubes of different diameter

    International Nuclear Information System (INIS)

    Tonkikh, Alexander A.; Obraztsova, Elena D.; Pozharov, Anatolii S.; Obraztsova, Ekaterina A.; Belkin, Alexey V.

    2012-01-01

    Single-wall carbon nanotubes with polyiodide chains inside are interesting from two points of view. According to predictions, first, the iodine structure type inside the nanotube is determined by the nanotube geometry. Second, after iodination all nanotubes become metallic. In this work, we made an attempt to check both predictions. To study the diameter-dependent properties we have taken for a gas-phase iodination the pristine single-wall carbon nanotubes grown by three different techniques providing a different average diameter: a chemical vapor deposition with a Co/Mo catalyst (CoMoCat) with a diameter range (0.6-1.3) nm, a high-pressure CO decomposition (HiPCO) - a diameter range (0.8-1.5) nm, and an aerosol technique with Fe catalyst - a diameter range (1.3-2.0) nm. The Raman spectra have shown a complication of the polyiodide chain structure while the nanotube diameter increased. The optical spectroscopy data (a suppression of E 11 band in the UV-Vis-NIR absorption spectrum) have confirmed the theoretical prediction about transformation of all nanotubes into metallic phase after doping. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Kinetics of an oxygen – iodine active medium with iodine atoms optically pumped on the {sup 2}P{sub 1/2} – {sup 2}P{sub 3/2} transition

    Energy Technology Data Exchange (ETDEWEB)

    Zagidullin, M V; Azyazov, V N [Samara Branch of the P.N. Lebedev Physical Institute, Russian Academy of Sciences, Samara (Russian Federation); Malyshev, M S [S.P. Korolev Samara State Aerospace University, Samara (Russian Federation)

    2015-08-31

    The kinetics of the processes occurring in an O{sub 2} – I{sub 2} – He – H{sub 2}O gas flow in which photodissociation of molecular iodine at a wavelength close to 500 nm and excitation of atomic iodine on the {sup 2}P{sub 1/2} – {sup 2}P{sub 3/2} transition by narrow-band radiation near 1315 nm are implemented successively has been analysed. It is shown that implementation of these processes allows one to form an oxygen – iodine medium with a high degree of dissociation of molecular iodine and a relative content of singlet oxygen O{sub 2}(a{sup 1}Δ) exceeding 10%. Having formed a supersonic gas flow with a temperature ∼100 K from this medium, one can reach a small-signal gain of about 10{sup -2} cm{sup -1} on the {sup 2}P{sub 1/2} – {sup 2}P{sub 3/2} transition in iodine atoms. The specific power per unit flow cross section in the oxygen – iodine laser with this active medium may reach ∼100 W cm{sup -2}. (active media)

  6. Directional emission of single photons from small atomic samples

    DEFF Research Database (Denmark)

    Miroshnychenko, Yevhen; V. Poulsen, Uffe; Mølmer, Klaus

    2013-01-01

    We provide a formalism to describe deterministic emission of single photons with tailored spatial and temporal profiles from a regular array of multi-level atoms. We assume that a single collective excitation is initially shared by all the atoms in a metastable atomic state, and that this state i...... is coupled by a classical laser field to an optically excited state which rapidly decays to the ground atomic state. Our model accounts for the different field polarization components via re-absorption and emission of light by the Zeeman manifold of optically excited states.......We provide a formalism to describe deterministic emission of single photons with tailored spatial and temporal profiles from a regular array of multi-level atoms. We assume that a single collective excitation is initially shared by all the atoms in a metastable atomic state, and that this state...

  7. Electrical properties of zirconium diselenide single crystals grown by iodine transport method

    International Nuclear Information System (INIS)

    Patel, S.G.; Agarwal, M.K.; Batra, N.M.; Lakshminarayana, D.

    1998-01-01

    Single crystals of zirconium diselenide (ZrSe 2 ) were grown by chemical vapour transport method using iodine as the transporting agent. The crystals were found to exhibit metallic behaviour in the temperature range 77-300 K and semiconducting nature in 300-443 K range. The measurements of thermoelectric power and conductivity enabled the determination of both carrier mobility and carrier concentration. The variation of carrier mobility and carrier concentration with temperature indicates the presence of deep trapping centres and their reduction with temperature in these crystals. (author)

  8. Quantum delayed-choice experiment with a single neutral atom.

    Science.gov (United States)

    Li, Gang; Zhang, Pengfei; Zhang, Tiancai

    2017-10-01

    We present a proposal to implement a quantum delayed-choice (QDC) experiment with a single neutral atom, such as a rubidium or cesium atom. In our proposal, a Ramsey interferometer is adopted to observe the wave-like or particle-like behaviors of a single atom depending on the existence or absence of the second π/2-rotation. A quantum-controlled π/2-rotation on target atom is realized through a Rydberg-Rydberg interaction by another ancilla atom. It shows that a heavy neutral atom can also have a morphing behavior between the particle and the wave. The realization of the QDC experiment with such heavy neutral atoms not only is significant to understand the Bohr's complementarity principle in matter-wave and matter-particle domains but also has great potential on the quantum information process with neutral atoms.

  9. Optimizing a single fixed dose of Iodine-131 in Graves' Disease (An Experience)

    International Nuclear Information System (INIS)

    Khan, S.H.

    2007-01-01

    Full text: Kashmir is a Himalayan mountain state of India enclosed by high snow capped ridges of Pir Panjal Mountains at an average height of 4000-5000 meters above the sea level. For most of the 4 million inhabitants in this land locked valley, agriculture horticulture and handcrafts are the main source of income. Due to long and severe winters the terraced farming on the mountain slopes yield just a single crop of rice which is barely sufficient to meet the local needs of this staple diet. People are relatively poor with low annual per capita income. Goiter is endemic in the Valley of Kashmir. In a published report the overall prevalence of goiter among the school going children in Kashmir between the ages of 5 years is 45.2% (+ SEM) with urinary iodine excretion of 49 + 3.55 μg per gram of creatinine. The extremely shy people of Kashmir are casual towards the aesthetic aspects of their goiters but nevertheless seek medical advice when associated with physical symptoms. In a published study of 203 patients of thyrotoxicosis from Kashmir, Graves' disease was the commonest cause, accounting for 63% of patients. One hundred and twentyone patients of Graves' disease were prospectively studied for their response to a single fixed dose of I-131. Patients were randomly treated with two different fixed doses of I- 131. Sixty four patients belonging to Group-I received a fixed dose of 185 MBq (Low Dose) and 57 patients belonging to Group -2 received 370 MBq (High Dose) of I- 131. Following therapy all patients were evaluated at 3 months. Patients with normal or reduced thyroid hormone levels were termed as responders and those with persistently elevated levels of thyroid hormone were termed as non responders. The response rates among the two groups were analyzed for their statistical significance. Patients treated with the high fixed dose of 370 MBq revealed good response to therapy achieving a rate of 91.22%, while the response rate in the group of patients treated with

  10. Iodine-stabilized single-frequency green InGaN diode laser.

    Science.gov (United States)

    Chen, Yi-Hsi; Lin, Wei-Chen; Shy, Jow-Tsong; Chui, Hsiang-Chen

    2018-01-01

    A 520-nm InGaN diode laser can emit a milliwatt-level, single-frequency laser beam when the applied current slightly exceeds the lasing threshold. The laser frequency was less sensitive to diode temperature and could be finely tuned by adjusting the applied current. Laser frequency was stabilized onto a hyperfine component in an iodine transition through the saturated absorption spectroscopy. The uncertainty of frequency stabilization was approximately 8×10 -9 at a 10-s integration time. This compact laser system can replace the conventional green diode-pumped solid-state laser and applied as a frequency reference. A single longitudinal mode operational region with diode temperature, current, and output power was investigated.

  11. Chiral smectogens with four-phenyl-ring molecular core, laterally substituted by iodine atom

    Czech Academy of Sciences Publication Activity Database

    Podoliak, Natalia; Novotná, Vladimíra; Kašpar, Miroslav; Hamplová, Věra; Pacherová, Oliva

    2015-01-01

    Roč. 42, č. 3 (2015), s. 404-411 ISSN 0267-8292 R&D Projects: GA ČR GA13-14133S; GA MŠk(CZ) LD14007 Institutional support: RVO:68378271 Keywords : liquid crystals * iodine lateral substitution * lactic acid unit * ferroelectric phase Subject RIV: JJ - Other Materials Impact factor: 2.244, year: 2015

  12. Role of N2 molecules in pulse discharge production of I atoms for a pulsed chemical oxygen-iodine laser

    International Nuclear Information System (INIS)

    Kochetov, I V; Napartovich, A P; Vagin, N P; Yuryshev, N N

    2011-01-01

    A pulsed electric discharge is the most effective means to turn chemical oxygen-iodine laser (COIL) operation into the pulse mode by fast production of iodine atoms. Experimental studies and numerical simulations are performed on a pulsed COIL initiated by an electric discharge in a mixture CF 3 I : N 2 : O 2 ( 3 X) : O 2 (a 1 Δ g ) flowing out of a chemical singlet oxygen generator. A transverse pulsed discharge is realized at various iodide pressures. The model comprises a system of kinetic equations for neutral and charged species, the electric circuit equation, the gas thermal balance equation and the photon balance equation. Reaction rate coefficients for processes involving electrons are repeatedly re-calculated by the electron Boltzmann equation solver when the plasma parameters are changed. The processes accounted for in the Boltzmann equation include direct and stepwise excitation and ionization of atoms and molecules, dissociation of molecules, electron attachment processes, electron-ion recombination, electron-electron collisions and second-kind collisions. The last processes are particularly important because of a high singlet oxygen concentration in gas flow from the singlet oxygen chemical generator. A conclusion is drawn about satisfactory agreement between the theory and the experiment.

  13. Single-atom-resolved fluorescence imaging of an atomic Mott insulator

    DEFF Research Database (Denmark)

    Sherson, Jacob; Weitenberg, Christof; Andres, Manuel

    2010-01-01

    in situ images of a quantum fluid in which each underlying quantum particle is detected. Here we report fluorescence imaging of strongly interacting bosonic Mott insulators in an optical lattice with single-atom and single-site resolution. From our images, we fully reconstruct the atom distribution...

  14. Single Atoms Preparation Using Light-Assisted Collisions

    Directory of Open Access Journals (Sweden)

    Yin Hsien Fung

    2016-01-01

    Full Text Available The detailed control achieved over single optically trapped neutral atoms makes them candidates for applications in quantum metrology and quantum information processing. The last few decades have seen different methods developed to optimize the preparation efficiency of single atoms in optical traps. Here we review the near-deterministic preparation of single atoms based on light-assisted collisions and describe how this method can be implemented in different trap regimes. The simplicity and versatility of the method makes it feasible to be employed in future quantum technologies such as a quantum logic device.

  15. Single-spin addressing in an atomic Mott insulator

    DEFF Research Database (Denmark)

    Weitenberg, Christof; Endres, Manuel; Sherson, Jacob

    2011-01-01

    directly monitored the tunnelling quantum dynamics of single atoms in the lattice prepared along a single line, and observed that our addressing scheme leaves the atoms in the motional ground state. The results should enable studies of entropy transport and the quantum dynamics of spin impurities...... and quantum spin dynamics. Here we demonstrate how such control can be implemented at the most fundamental level of a single spin at a specific site of an optical lattice. Using a tightly focused laser beam together with a microwave field, we were able to flip the spin of individual atoms in a Mott insulator...... with sub-diffraction-limited resolution, well below the lattice spacing. The Mott insulator provided us with a large two-dimensional array of perfectly arranged atoms, in which we created arbitrary spin patterns by sequentially addressing selected lattice sites after freezing out the atom distribution. We...

  16. From trace chemistry to single atom chemistry

    International Nuclear Information System (INIS)

    Adloff, J.P.

    1993-01-01

    Hot atom chemistry in the vast majority of experimental works deals with the trace amount of radioactive matters. Accordingly, the concept of trace chemistry is at the heart of hot atom chemistry. Some aspects of the chemistry at trace scale and at subtrace scale are presented together with the related problems of speciation and the complication which may arise due to the formation of radio colloids. The examples of 127 I(n,γ) 128 I and 132 Te (β - ) 132 I are shown, and the method based on radioactivity was used. The procedure of separating the elements in pitchblende is shown as the example of the chemistry of traces. 13 27 Al+ 2 4 He→ 0 1 n+ 15 30 P and 15 30 P→ 14 30 Si+e + +V are shown, and how to recognize the presence of radioactive colloids is explained. The formation of radiocolloids is by the sorption of a trace radioelement on pre-existing colloidal impurity or the self-condensation of monomeric species. The temporal parameters of the nature of reactions at trace concentration are listed. The examples of Class A and Class B reactions are shown. The kinetics of reactions at trace level, radon concentration, anthropogenic Pu and natural Pu in environment, the behavior of Pu atoms and so on are described. (K.I.)

  17. Identification of benign and malignant thyroid nodules by in vivo iodine concentration measurement using single-source dual energy CT

    Science.gov (United States)

    Gao, Shun-Yu; Zhang, Xiao-Yan; Wei, Wei; Li, Xiao-Ting; Li, Yan-Ling; Xu, Min; Sun, Ying-Shi; Zhang, Xiao-Peng

    2016-01-01

    Abstract This study proposed to determine whether in vivo iodine concentration measurement by single-source dual energy (SSDE) CT can improve differentiation between benign and malignant thyroid nodules. In total, 53 patients presenting with thyroid nodules underwent SSDE CT scanning. Iodine concentrations were measured for each nodule and normal thyroid tissue using the GSI-viewer image analysis software. A total of 26 thyroid nodules were malignant in 26 patients and confirmed by surgery; 33 nodules from 27 patients were benign, with 10 confirmed by surgery and others after follow-up. Iodine concentrations with plain CT were significantly lower in malignant than benign nodules (0.47 ± 0.20 vs 1.17 ± 0.38 mg/mL, P = 0.00). Receiver operating characteristic (ROC) curve showed an area under the curve (AUC) of 0.93; with a cutoff of 0.67, iodine concentration showed 92.3% sensitivity and 88.5% specificity in diagnosing malignancy. Iodine concentration obtained by enhanced and plain CT were significantly higher in malignant than benign nodules (9.05 ± 3.35 vs 3.46 ± 2.24 mg/mL, P = 0.00). ROC curve analysis showed an AUC of 0.93; with a cutoff value of 3.37, iodine concentration displayed 78% sensitivity, 95% specificity in diagnosing malignancy. Combining unenhanced with enhanced iodine concentrations, the diagnostic equation was: Y = –8.641 × unenhanced iodine concentration + 0.663 × iodine concentration. ROC curve showed an AUC of 0.98 (95% CI, 0.94, 1.00). With Y ≥ –2 considered malignancy, diagnostic sensitivity and specificity were 96%, 96.3%, respectively. This study concluded that SSDE CT can detect the differences in iodine uptake and blood supply between benign and malignant thyroid lesions. PMID:27684811

  18. Electromigration of single metal atoms observed by scanning tunneling microscopy

    NARCIS (Netherlands)

    Braun, K.-F.; Soe, W.H.; Flipse, C.F.J.

    2007-01-01

    The authors show in this letter that single metal atoms on a Ni(111) surface can be pushed by electromigration forces from a scanning tunneling microscope tip. This repulsive interaction is obsd. over a length scale of 6 nm. While for voltages above -300 mV the atoms are pulled by the microscope

  19. Single atom and-molecules chemisorption on solid surfaces

    International Nuclear Information System (INIS)

    Anda, E.V.; Ure, J.E.; Majlis, N.

    1981-01-01

    A simplified model for the microscopic interpretation of single atom and- molecules chemisorption on metallic surfaces is presented. An appropriated hamiltonian for this problem is resolved, through the Green's function formalism. (L.C.) [pt

  20. Kinetics of the processes, plasma parameters, and output characteristics of a UV emitter operating on XeI molecules and iodine molecules and atoms

    Energy Technology Data Exchange (ETDEWEB)

    Shuaibov, A. K.; Grabovaya, I. A.; Minya, A. I.; Homoki, Z. T. [Uzhgorod National University (Ukraine); Kalyuzhnaya, A. G.; Shchedrin, A. I. [National Academy of Sciences of Ukraine, Institute of Physics (Ukraine)

    2011-03-15

    A kinetic model of the processes occurring in the plasma of a high-power low-pressure gas-discharge lamp is presented, and the output characteristics of the lamp are described. The lamp is excited by a longitudinal glow discharge and emits the I{sub 2}(D Prime -A Prime ) 342-nm and XeI(B-X) 253-nm bands and the 206.2-nm spectral line of atomic iodine. When the emitter operates in a sealed-off mode on the p(He): p(Xe): p(I{sub 2}) = 400: 120: (100-200) Pa mixture, the fractions of the UV radiation power of iodine atoms, exciplex molecules of xenon iodide, and iodine molecules comprise 55, 10, and 35%, respectively. At the optimal partial pressure, the maximum total radiation power of the lamp reaches 37 W, the energy efficiency being about 15%.

  1. Investigation on single carbon atom transporting through the single-walled carbon nanotube by MD simulation

    International Nuclear Information System (INIS)

    Ding Yinfeng; Zhang Zhibin; Ke Xuezhi; Zhu Zhiyuan; Zhu Dezhang; Wang Zhenxia; Xu Hongjie

    2005-01-01

    The single carbon atom transporting through the single-walled carbon nanotube has been studied by molecular-dynamics (MD) simulation. We got different trajectories of the carbon atom by changing the input parameters. The simulation results indicate that the single carbon atom with low energy can transport through the carbon nanotube under some input conditions and result in different trajectories being straight line or 'rosette' or circular. (authors)

  2. Single and multiple ionization of sulfur atoms by electron impact

    International Nuclear Information System (INIS)

    Ziegler, D.L.

    1982-01-01

    Laboratory measurements of the cross sections for single, double, triple, and quadruple ionization of sulfur atoms by electron impact are presented for collision energies from threshold to 500 eV. The cross sections for single ionization of sulfur are measured relative to those of several elements whose absolute cross sections for single ionization are known. Cross sections for each multiple ionization process are then measured relative to those for single ionization. The configuration and operation of the apparatus for these measurements are described. The possible effects of excited sulfur reactants are examined, and the reported cross sections are felt to be characteristic of ground state sulfur atoms

  3. Single atoms on demand for cavity QED experiments

    International Nuclear Information System (INIS)

    Dotsenko, I.

    2007-01-01

    Cavity quantum electrodynamics (cavity QED) describes electromagnetic fields in a confined space and the radiative properties of atoms in such fields. The simplest example of such system is a single atom interacting with one mode of a high-finesse resonator. Besides observation and exploration of fundamental quantum mechanical effects, this system bears a high potential for applications quantum information science such as, e.g., quantum logic gates, quantum communication and quantum teleportation. In this thesis I present an experiment on the deterministic coupling of a single neutral atom to the mode of a high-finesse optical resonator. In Chapter 1 I describe our basic techniques for trapping and observing single cesium atoms. As a source of single atoms we use a high-gradient magneto-optical trap, which captures the atoms from background gas in a vacuum chamber and cools them down to millikelvin temperatures. The atoms are then transferred without loss into a standing-wave dipole trap, which provides a conservative potential required for experiments on atomic coherence such as quantum information processing and metrology on trapped atoms. Moreover, shifting the standing-wave pattern allows us to deterministically transport the atoms (Chapter 2). In combination with nondestructive fluorescence imaging of individual trapped atoms, this enables us to control their position with submicrometer precision over several millimeters along the dipole trap. The cavity QED system can distinctly display quantum behaviour in the so-called strong coupling regime, i.e., when the coherent atom-cavity coupling rate dominates dissipation in the system. This sets the main requirements on the resonator's properties: small mode volume and high finesse. Chapter 3 is devoted to the manufacturing, assembling, and testing of an ultra-high finesse optical Fabry-Perot resonator, stabilized to the atomic transition. In Chapter 4 I present the transportation of single atoms into the cavity

  4. Single atoms on demand for cavity QED experiments

    Energy Technology Data Exchange (ETDEWEB)

    Dotsenko, I.

    2007-09-06

    Cavity quantum electrodynamics (cavity QED) describes electromagnetic fields in a confined space and the radiative properties of atoms in such fields. The simplest example of such system is a single atom interacting with one mode of a high-finesse resonator. Besides observation and exploration of fundamental quantum mechanical effects, this system bears a high potential for applications quantum information science such as, e.g., quantum logic gates, quantum communication and quantum teleportation. In this thesis I present an experiment on the deterministic coupling of a single neutral atom to the mode of a high-finesse optical resonator. In Chapter 1 I describe our basic techniques for trapping and observing single cesium atoms. As a source of single atoms we use a high-gradient magneto-optical trap, which captures the atoms from background gas in a vacuum chamber and cools them down to millikelvin temperatures. The atoms are then transferred without loss into a standing-wave dipole trap, which provides a conservative potential required for experiments on atomic coherence such as quantum information processing and metrology on trapped atoms. Moreover, shifting the standing-wave pattern allows us to deterministically transport the atoms (Chapter 2). In combination with nondestructive fluorescence imaging of individual trapped atoms, this enables us to control their position with submicrometer precision over several millimeters along the dipole trap. The cavity QED system can distinctly display quantum behaviour in the so-called strong coupling regime, i.e., when the coherent atom-cavity coupling rate dominates dissipation in the system. This sets the main requirements on the resonator's properties: small mode volume and high finesse. Chapter 3 is devoted to the manufacturing, assembling, and testing of an ultra-high finesse optical Fabry-Perot resonator, stabilized to the atomic transition. In Chapter 4 I present the transportation of single atoms into the

  5. Single-cell atomic quantum memory for light

    International Nuclear Information System (INIS)

    Opatrny, Tomas

    2006-01-01

    Recent experiments demonstrating atomic quantum memory for light [B. Julsgaard et al., Nature 432, 482 (2004)] involve two macroscopic samples of atoms, each with opposite spin polarization. It is shown here that a single atomic cell is enough for the memory function if the atoms are optically pumped with suitable linearly polarized light, and quadratic Zeeman shift and/or ac Stark shift are used to manipulate rotations of the quadratures. This should enhance the performance of our quantum memory devices since less resources are needed and losses of light in crossing different media boundaries are avoided

  6. Manipulating localized molecular orbitals by single-atom contacts.

    Science.gov (United States)

    Wang, Weihua; Shi, Xingqiang; Lin, Chensheng; Zhang, Rui Qin; Minot, Christian; Van Hove, Michel A; Hong, Yuning; Tang, Ben Zhong; Lin, Nian

    2010-09-17

    We have fabricated atom-molecule contacts by attachment of single Cu atoms to terpyridine side groups of bis-terpyridine tetra-phenyl ethylene molecules on a Cu(111) surface. By means of scanning tunneling microscopy, spectroscopy, and density functional calculations, we have found that, due to the localization characteristics of molecular orbitals, the Cu-atom contact modifies the state localized at the terpyridine side group which is in contact with the Cu atom but does not affect the states localized at other parts of the molecule. These results illustrate the contact effects at individual orbitals and offer possibilities to manipulate orbital alignments within molecules.

  7. Analysis of a single-atom dipole trap

    International Nuclear Information System (INIS)

    Weber, Markus; Volz, Juergen; Saucke, Karen; Kurtsiefer, Christian; Weinfurter, Harald

    2006-01-01

    We describe a simple experimental technique which allows us to store a single 87 Rb atom in an optical dipole trap. Due to light-induced two-body collisions during the loading stage of the trap the maximum number of captured atoms is locked to one. This collisional blockade effect is confirmed by the observation of photon antibunching in the detected fluorescence light. The spectral properties of single photons emitted by the atom were studied with a narrow-band scanning cavity. We find that the atomic fluorescence spectrum is dominated by the spectral width of the exciting laser light field. In addition we observe a spectral broadening of the atomic fluorescence light due to the Doppler effect. This allows us to determine the mean kinetic energy of the trapped atom corresponding to a temperature of 105 μK. This simple single-atom trap is the key element for the generation of atom-photon entanglement required for future applications in quantum communication and a first loophole-free test of Bell's inequality

  8. Detection of single atoms by resonance ionization spectroscopy

    International Nuclear Information System (INIS)

    Hurst, G.S.

    1986-01-01

    Rutherford's idea for counting individual atoms can, in principle, be implemented for nearly any type of atom, whether stable or radioactive, by using methods of resonance ionization. With the RIS technique, a laser is tuned to a wavelength which will promote a valence electron in a Z-selected atom to an excited level. Additional resonance or nonresonance photoabsorption steps are used to achieve nearly 100% ionization efficiencies. Hence, the RIS process can be saturated for the Z-selected atoms; and since detectors are available for counting either single electrons or positive ions, one-atom detection is possible. Some examples are given of one-atom detection, including that of the noble gases, in order to show complementarity with AMS methods. For instance, the detection of 81 Kr using RIS has interesting applications for solar neutrino research, ice-cap dating, and groundwater dating. 39 refs., 7 figs., 2 tabs

  9. Single-Atom Catalysts of Precious Metals for Electrochemical Reactions.

    Science.gov (United States)

    Kim, Jiwhan; Kim, Hee-Eun; Lee, Hyunjoo

    2018-01-10

    Single-atom catalysts (SACs), in which metal atoms are dispersed on the support without forming nanoparticles, have been used for various heterogeneous reactions and most recently for electrochemical reactions. In this Minireview, recent examples of single-atom electrocatalysts used for the oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), hydrogen evolution reaction (HER), formic acid oxidation reaction (FAOR), and methanol oxidation reaction (MOR) are introduced. Many density functional theory (DFT) simulations have predicted that SACs may be effective for CO 2 reduction to methane or methanol production while suppressing H 2 evolution, and those cases are introduced here as well. Single atoms, mainly Pt single atoms, have been deposited on TiN or TiC nanoparticles, defective graphene nanosheets, N-doped covalent triazine frameworks, graphitic carbon nitride, S-doped zeolite-templated carbon, and Sb-doped SnO 2 surfaces. Scanning transmission electron microscopy, extended X-ray absorption fine structure measurement, and in situ infrared spectroscopy have been used to detect the single-atom structure and confirm the absence of nanoparticles. SACs have shown high mass activity, minimizing the use of precious metal, and unique selectivity distinct from nanoparticle catalysts owing to the absence of ensemble sites. Additional features that SACs should possess for effective electrochemical applications were also suggested. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Auger transitions in singly and multiply ionized atoms

    International Nuclear Information System (INIS)

    Mehlhorn, W.

    1978-01-01

    Some recent progress in Auger and autoionizing electron spectrometry of free metal atoms and of multiply ionized atoms is reviewed. The differences which arise between the spectra of atoms in the gaseous and the solid state are due to solid state effects. This will be shown for Cd as an example. The super Coster-Kronig transitions 3p-3d 2 (hole notation) and Coster-Kronig transitions 3p-3d 4s have been measured and compared with free-atom calculations for free Zn atoms. The experimental width GAMMA(3p)=(2.1+-0.2)eV found for the free atom agrees with the value obtained for solid Zn but is considerably smaller than the theoretical value for the free atom. Autoionizing spectra of Na following an L-shell excitation or ionization by different particles are compared and discussed. The nonisotropic angular distribution of electrons from the transition 2p 5 3s 2 2 Psub(3/2)→2p 6 +e - is compared with theoretical calculations. Two examples for Auger spectrometry of multiply ionized atoms are given: (1) excitation of neon target atoms by light and heavy ions, and (2) excitation of projectile ions Be + and B + in single gas collisions with CH 4 . A strong alignment of the excited atoms has also been found here

  11. Single Photon Double Ionization of Atomic Oxygen

    Science.gov (United States)

    Wickramarathna, Madhushani; Gorczyca, Thomas; Ballance, Connor; Stolte, Wayne

    2017-04-01

    Single photon double ionization cross sections are calculated using an R-matrix with pseudostates (RMPS) method which was recently applied by Gorczyca et al. for the double photoionization of helium. With the convergence of these theoretical calculations for the simple case of helium, we extend this methodology to consider the more complex case of oxygen double photoionization. We compare our calculated results with recent measurements at the Advanced Light Source, as well as earlier experimental measurements. Our RMPS results agree well, qualitatively, with the experimental measurements, but there exist outstanding discrepancies to be addressed. This project is supported by NASA APRA award NNX17AD41G.

  12. Single-atom gating and magnetic interactions in quantum corrals

    Energy Technology Data Exchange (ETDEWEB)

    Ngo, Anh T.; Kim, Eugene H.; Ulloa, Sergio E.

    2017-04-01

    Single-atom gating, achieved by manipulation of adatoms on a surface, has been shown in experiments to allow precise control over superposition of electronic states in quantum corrals. Using a Green's function approach, we demonstrate theoretically that such atom gating can also be used to control the coupling between magnetic degrees of freedom in these systems. Atomic gating enables control not only on the direct interaction between magnetic adatoms, but also over superpositions of many-body states which can then control long distance interactions. We illustrate this effect by considering the competition between direct exchange between magnetic impurities and the Kondo screening mediated by the host electrons, and how this is affected by gating. These results suggest that both magnetic and nonmagnetic single-atom gating may be used to investigate magnetic impurity systems with tailored interactions, and may allow the control of entanglement of different spin states.

  13. Chemical reaction between single hydrogen atom and graphene

    International Nuclear Information System (INIS)

    Ito, Atsushi; Nakamura, Hiroaki; Takayama, Arimichi

    2007-04-01

    We study chemical reaction between a single hydrogen atom and a graphene, which is the elemental reaction between hydrogen and graphitic carbon materials. In the present work, classical molecular dynamics simulation is used with modified Brenner's empirical bond order potential. The three reactions, that is, absorption reaction, reflection reaction and penetration reaction, are observed in our simulation. Reaction rates depend on the incident energy of the hydrogen atom and the graphene temperature. The dependence can be explained by the following mechanisms: (1) The hydrogen atom receives repulsive force by π-electrons in addition to nuclear repulsion. (2) Absorbing the hydrogen atom, the graphene transforms its structure to the 'overhand' configuration such as sp 3 state. (3) The hexagonal hole of the graphene is expanded during the penetration of the hydrogen atom. (author)

  14. Spin valve effect in single-atom contacts

    International Nuclear Information System (INIS)

    Ziegler, M; Neel, N; Berndt, R; Lazo, C; Ferriani, P; Heinze, S; Kroeger, J

    2011-01-01

    Magnetic single-atom contacts have been controllably fabricated with a scanning tunnelling microscope. A voltage-dependent spin valve effect with conductance variations of ∼40% is reproducibly observed from contacts comprising a Cr-covered tip and Co and Cr atoms on ferromagnetic nanoscale islands on W(110) with opposite magnetization. The spin-dependent conductances are interpreted from first-principles calculations in terms of the orbital character of the relevant electronic states of the junction.

  15. Application of GRID to Foreign Atom Localization in Single Crystals.

    Science.gov (United States)

    Karmann, A; Wesch, W; Weber, B; Börner, H G; Jentschel, M

    2000-01-01

    The application of GRID (Gamma Ray Induced Doppler broadening) spectroscopy to the localization of foreign atoms in single crystals is demonstrated on erbium in YAP. By the investigation of the Doppler broadened secondary γ line for two crystalline directions, the Er was determined to be localized on the Y site. Conditions for the nuclear parameters of the impurity atoms used for the application of GRID spectroscopy are discussed.

  16. Manipulation of single neutral atoms in optical lattices

    International Nuclear Information System (INIS)

    Zhang Chuanwei; Das Sarma, S.; Rolston, S. L.

    2006-01-01

    We analyze a scheme to manipulate quantum states of neutral atoms at individual sites of optical lattices using focused laser beams. Spatial distributions of focused laser intensities induce position-dependent energy shifts of hyperfine states, which, combined with microwave radiation, allow selective manipulation of quantum states of individual target atoms. We show that various errors in the manipulation process are suppressed below 10 -4 with properly chosen microwave pulse sequences and laser parameters. A similar idea is also applied to measure quantum states of single atoms in optical lattices

  17. Ballistic Anisotropic Magnetoresistance of Single-Atom Contacts.

    Science.gov (United States)

    Schöneberg, J; Otte, F; Néel, N; Weismann, A; Mokrousov, Y; Kröger, J; Berndt, R; Heinze, S

    2016-02-10

    Anisotropic magnetoresistance, that is, the sensitivity of the electrical resistance of magnetic materials on the magnetization direction, is expected to be strongly enhanced in ballistic transport through nanoscale junctions. However, unambiguous experimental evidence of this effect is difficult to achieve. We utilize single-atom junctions to measure this ballistic anisotropic magnetoresistance (AMR). Single Co and Ir atoms are deposited on domains and domain walls of ferromagnetic Fe layers on W(110) to control their magnetization directions. They are contacted with nonmagnetic tips in a low-temperature scanning tunneling microscope to measure the junction conductances. Large changes of the magnetoresistance occur from the tunneling to the ballistic regime due to the competition of localized and delocalized d-orbitals, which are differently affected by spin-orbit coupling. This work shows that engineering the AMR at the single atom level is feasible.

  18. Single atom self-diffusion on nickel surfaces

    International Nuclear Information System (INIS)

    Tung, R.T.; Graham, W.R.

    1980-01-01

    Results of a field ion microscope study of single atom self-diffusion on Ni(311), (331), (110), (111) and (100) planes are presented, including detailed information on the self-diffusion parameters on (311), (331), and (110) surfaces, and activation energies for diffusion on the (111), and (100) surfaces. Evidence is presented for the existence of two types of adsorption site and surface site geometry for single nickel atoms on the (111) surface. The presence of adsorbed hydrogen on the (110), (311), and (331) surfaces is shown to lower the onset temperature for self-diffusion on these planes. (orig.)

  19. High performance platinum single atom electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Liu, Jing; Jiao, Menggai; Lu, Lanlu; Barkholtz, Heather M.; Li, Yuping; Wang, Ying; Jiang, Luhua; Wu, Zhijian; Liu, Di-Jia; Zhuang, Lin; Ma, Chao; Zeng, Jie; Zhang, Bingsen; Su, Dangsheng; Song, Ping; Xing, Wei; Xu, Weilin; Wang, Ying; Jiang, Zheng; Sun, Gongquan

    2017-07-01

    For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm-2 at 80 °C with a low platinum loading of 0.09 mgPt cm-2, corresponding to a platinum utilization of 0.13 gPt kW-1 in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.

  20. Single-Atom Gating of Quantum State Superpositions

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Christopher

    2010-04-28

    The ultimate miniaturization of electronic devices will likely require local and coherent control of single electronic wavefunctions. Wavefunctions exist within both physical real space and an abstract state space with a simple geometric interpretation: this state space - or Hilbert space - is spanned by mutually orthogonal state vectors corresponding to the quantized degrees of freedom of the real-space system. Measurement of superpositions is akin to accessing the direction of a vector in Hilbert space, determining an angle of rotation equivalent to quantum phase. Here we show that an individual atom inside a designed quantum corral1 can control this angle, producing arbitrary coherent superpositions of spatial quantum states. Using scanning tunnelling microscopy and nanostructures assembled atom-by-atom we demonstrate how single spins and quantum mirages can be harnessed to image the superposition of two electronic states. We also present a straightforward method to determine the atom path enacting phase rotations between any desired state vectors. A single atom thus becomes a real-space handle for an abstract Hilbert space, providing a simple technique for coherent quantum state manipulation at the spatial limit of condensed matter.

  1. Analytic study of the chain dark decomposition reaction of iodides - atomic iodine donors - in the active medium of a pulsed chemical oxygen-iodine laser: 1. Criteria for the development of the branching chain dark decomposition reaction of iodides

    International Nuclear Information System (INIS)

    Andreeva, Tamara L; Kuznetsova, S V; Maslov, Aleksandr I; Sorokin, Vadim N

    2009-01-01

    The scheme of chemical processes proceeding in the active medium of a pulsed chemical oxygen-iodine laser (COIL) is analysed. Based on the analysis performed, the complete system of differential equations corresponding to this scheme is replaced by a simplified system of equations describing in dimensionless variables the chain dark decomposition of iodides - atomic iodine donors, in the COIL active medium. The procedure solving this system is described, the basic parameters determining the development of the chain reaction are found and its specific time intervals are determined. The initial stage of the reaction is analysed and criteria for the development of the branching chain decomposition reaction of iodide in the COIL active medium are determined. (active media)

  2. Creation and recovery of a W(111) single atom gas field ion source

    International Nuclear Information System (INIS)

    Pitters, Jason L.; Urban, Radovan; Wolkow, Robert A.

    2012-01-01

    Tungsten single atom tips have been prepared from a single crystal W(111) oriented wire using the chemical assisted field evaporation and etching method. Etching to a single atom tip occurs through a symmetric structure and leads to a predictable last atom unlike etching with polycrystalline tips. The single atom tip formation procedure is shown in an atom by atom removal process. Rebuilds of single atom tips occur on the same crystalline axis as the original tip such that ion emission emanates along a fixed direction for all tip rebuilds. This preparation method could be utilized and developed to prepare single atom tips for ion source development.

  3. Unimolecular Logic Gate with Classical Input by Single Gold Atoms.

    Science.gov (United States)

    Skidin, Dmitry; Faizy, Omid; Krüger, Justus; Eisenhut, Frank; Jancarik, Andrej; Nguyen, Khanh-Hung; Cuniberti, Gianaurelio; Gourdon, Andre; Moresco, Francesca; Joachim, Christian

    2018-02-27

    By a combination of solution and on-surface chemistry, we synthesized an asymmetric starphene molecule with two long anthracenyl input branches and a short naphthyl output branch on the Au(111) surface. Starting from this molecule, we could demonstrate the working principle of a single molecule NAND logic gate by selectively contacting single gold atoms by atomic manipulation to the longer branches of the molecule. The logical input "1" ("0") is defined by the interaction (noninteraction) of a gold atom with one of the input branches. The output is measured by scanning tunneling spectroscopy following the shift in energy of the electronic tunneling resonances at the end of the short branch of the molecule.

  4. Atomic-Scale Control of Electron Transport through Single Molecules

    DEFF Research Database (Denmark)

    Wang, Y. F.; Kroger, J.; Berndt, R.

    2010-01-01

    Tin-phthalocyanine molecules adsorbed on Ag(111) were contacted with the tip of a cryogenic scanning tunneling microscope. Orders-of-magnitude variations of the single-molecule junction conductance were achieved by controllably dehydrogenating the molecule and by modifying the atomic structure...

  5. Coherent excitation of a single atom to a Rydberg state

    DEFF Research Database (Denmark)

    Miroshnychenko, Yevhen; Gaëtan, Alpha; Evellin, Charles

    2010-01-01

    We present the coherent excitation of a single Rubidium atom to the Rydberg state 58d3/2 using a two-photon transition. The experimental setup is described in detail, as are experimental techniques and procedures. The coherence of the excitation is revealed by observing Rabi oscillations between...

  6. Single atom identification by energy dispersive x-ray spectroscopy

    International Nuclear Information System (INIS)

    Lovejoy, T. C.; Dellby, N.; Krivanek, O. L.; Ramasse, Q. M.; Falke, M.; Kaeppel, A.; Terborg, R.; Zan, R.

    2012-01-01

    Using aberration-corrected scanning transmission electron microscope and energy dispersive x-ray spectroscopy, single, isolated impurity atoms of silicon and platinum in monolayer and multilayer graphene are identified. Simultaneously acquired electron energy loss spectra confirm the elemental identification. Contamination difficulties are overcome by employing near-UHV sample conditions. Signal intensities agree within a factor of two with standardless estimates.

  7. Iodine-123 phenylpentadecanoic acid: detection of acute myocardial infarction and injury in dogs using an iodinated fatty acid and single-photon emission tomography

    International Nuclear Information System (INIS)

    Rellas, J.S.; Corbett, J.R.; Kulkarni, P.

    1983-01-01

    The ability of an iodinated fatty acid, iodine-123 phenylpentadecanoic acid (1-123 PPA), and single-photon emission computed tomography (SPECT) to detect myocardium injured by temporary or permanent coronary arterial occlusion was evaluated. In 5 control dogs, 11 dogs that underwent 90 to 120 minutes of fixed left anterior descending coronary artery (LAD) occlusion, and 8 dogs that underwent 90 minutes of temporary LAD occlusion and up to 90 minutes of reflow, 2 to 6 mCi of I-123 PPA were injected and the dogs were imaged with SPECT. Control dogs showed relatively uniform uptake and clearance of I-123 PPA in similar left ventricular (LV) regions. Dogs with permanent LAD occlusion were identified by computer algorithm as having regions of decreased I-123 PPA uptake in the infarct-related area and a reduced rate of I-123 PPA clearance (-9.4% in infarct sectors [washin], +3.7% in sectors adjacent to the area of infarction, and +15.4% in control LV sectors [p less than 0.01]). Dogs with temporary LAD occlusion and reperfusion had decreased clearance of I-123 PPA from the regions with infarction; I-123 PPA clearance was -5.2 +/- 16.4% in infarct sectors, 12.7 +/- 7.4% in periinfarct zones, and 30.4 +/- 12% in control LV regions. These data demonstrate that tomographic analysis of I-123 PPA uptake and clearance permits the relatively noninvasive detection of LV myocardium injured by permanent or temporary LAD occlusion and reperfusion

  8. Theoretical study of the gas-phase reactions of iodine atoms ((2)P(3/2)) with H(2), H(2)O, HI, and OH.

    Science.gov (United States)

    Canneaux, Sébastien; Xerri, Bertrand; Louis, Florent; Cantrel, Laurent

    2010-09-02

    The rate constants of the reactions of iodine atoms with H(2), H(2)O, HI, and OH have been estimated using 39, 21, 13, and 39 different levels of theory, respectively, and have been compared to the available literature values over the temperature range of 250-2500 K. The aim of this methodological work is to demonstrate that standard theoretical methods are adequate to obtain quantitative rate constants for the reactions involving iodine-containing species. Geometry optimizations and vibrational frequency calculations are performed using three methods (MP2, MPW1K, and BHandHLYP) combined with three basis sets (cc-pVTZ, cc-pVQZ, and 6-311G(d,p)). Single-point energy calculations are performed with the highly correlated ab initio coupled cluster method in the space of single, double, and triple (pertubatively) electron excitations CCSD(T) using the cc-pVnZ (n = T, Q, and 5), aug-cc-pVnZ (n = T, Q, and 5), 6-311G(d,p), 6-311+G(3df,2p), and 6-311++G(3df,3pd) basis sets. Canonical transition state theory with a simple Wigner tunneling correction is used to predict the rate constants as a function of temperature. CCSD(T)/cc-pVnZ//MP2/cc-pVTZ (n = T and Q), CCSD(T)/6-311+G(3df,2p)//MP2/6-311G(d,p), and CCSD(T)/6-311++G(3df,3pd)//MP2/6-311G(d,p) levels of theory provide accurate kinetic rate constants when compared to available literature data. The use of the CCSD(T)/cc-pVQZ//MP2/cc-pVTZ and CCSD(T)/6-311++G(3df,3pd) levels of theory allows one to obtain a better agreement with the literature data for all reactions with the exception of the I + H(2) reaction R(1) . This computational procedure has been also used to predict rate constants for some reactions where no available experimental data exist. The use of quantum chemistry tools could be therefore extended to other elements and next applied to develop kinetic networks involving various fission products, steam, and hydrogen in the absence of literature data. The final objective is to implement the kinetics of gaseous

  9. Iodine-125 seed brachytherapy for early stage prostate cancer: a single-institution review

    International Nuclear Information System (INIS)

    Zuber, Simon; Weiß, Susan; Baaske, Dieter; Schöpe, Michael; Stevens, Simon; Bodis, Stephan; Zwahlen, Daniel R

    2015-01-01

    We are reporting the five-year biochemical control, toxicity profile and dosimetric parameters using iodine-125 low dose rate brachytherapy (BT) as monotherapy for early stage prostate cancer at a single institution. Between April 2006 and December 2010, 169 men with early stage prostate cancer were treated with BT. Biochemical failure was defined using the Phoenix definition (nadir + 2 ng/mL). Treatment-related morbidities, including urinary, rectal and sexual function, were measured, applying the International Prostate Symptom Score (IPSS), the 7-grade Quality of Life Scale (QoL) and medical status, the International Consultation on Incontinence Modular Questionnaire (ICIQ), the International Index of Erectile Function (IIEF-5) and the Common Terminology Criteria for Adverse Events (CTCAE v4.03). Seed migration and loss, dosimetric parameters and learning effects were also analyzed. Medium follow-up time was 50 months (range, 1–85 months). The five-year biochemical failure rate was 7%. Acute proctitis rates were 19% (grade 1) and 1% (grade 2), respectively. The overall incidence of incontinence was 19% (mild), 16% (moderate) and < 1% (severe). An increase in IPSS ≥ 5 points was detected in 59% of patients, with 38% regaining their baseline. Seed dislocation was found in 24% of patients and correlated with D90 and V100. A learning curve was found for seed migration, D90 and V100. QoL correlated with the general health condition of patient, incontinence symptoms and IPSS. BT for early stage prostate cancer offers excellent five-year biochemical control with low toxicities. QoL aspects are favorable. A learning curve was detected for procedural aspects but its impact on patient relevant endpoints remains inconclusive

  10. Construction of a single atom trap for quantum information protocols

    Science.gov (United States)

    Shea, Margaret E.; Baker, Paul M.; Gauthier, Daniel J.; Duke Physics Department Team

    2016-05-01

    The field of quantum information science addresses outstanding problems such as achieving fundamentally secure communication and solving computationally hard problems. Great progress has been made in the field, particularly using photons coupled to ions and super conducting qubits. Neutral atoms are also interesting for these applications and though the technology for control of neutrals lags behind that of trapped ions, they offer some key advantages: primarily coupling to optical frequencies closer to the telecom band than trapped ions or superconducting qubits. Here we report progress on constructing a single atom trap for 87 Rb. This system is a promising platform for studying the technical problems facing neutral atom quantum computing. For example, most protocols destroy the trap when reading out the neutral atom's state; we will investigate an alternative non-destructive state detection scheme. We detail the experimental systems involved and the challenges addressed in trapping a single atom. All of our hardware components are off the shelf and relatively inexpensive. Unlike many other systems, we place a high numerical aperture lens inside our vacuum system to increase photon collection efficiency. We gratefully acknowledge the financial support of the ARO through Grant # W911NF1520047.

  11. Magnetism of a relaxed single atom vacancy in graphene

    Science.gov (United States)

    Wu, Yunyi; Hu, Yonghong; Xue, Li; Sun, Tieyu; Wang, Yu

    2018-04-01

    It has been suggested in literature that defects in graphene (e.g. absorbed atoms and vacancies) may induce magnetizations due to unpaired electrons. The nature of magnetism, i.e. ferromagnetic or anti-ferromagnetic, is dependent on a number of structural factors including locations of magnetic moments and lattice symmetry. In the present work we investigated the influence of a relaxed single atom vacancy in garphnene on magnetization which were obtained under different pinning boundary conditions, aiming to achieve a better understanding of the magnetic behaviors of graphene. Through first principles calculations, we found that major spin polarizations occur on atoms that deviate slightly from their original lattice positions, and pinning boundaries could also affect the relaxed positions of atoms and determine which atom(s) would become the main source(s) of total spin polarizations and magnetic moments. When the pinning boundary condition is free, a special non-magnetic and semi-conductive structure may be obtained, suggesting that magnetization should more readily occur under pinning boundary conditions.

  12. Engineering Single-Atom Cobalt Catalysts toward Improved Electrocatalysis.

    Science.gov (United States)

    Wan, Gang; Yu, Pengfei; Chen, Hangrong; Wen, Jianguo; Sun, Cheng-Jun; Zhou, Hua; Zhang, Nian; Li, Qianru; Zhao, Wanpeng; Xie, Bing; Li, Tao; Shi, Jianlin

    2018-04-01

    The development of cost-effective catalysts to replace noble metal is attracting increasing interests in many fields of catalysis and energy, and intensive efforts are focused on the integration of transition-metal sites in carbon as noble-metal-free candidates. Recently, the discovery of single-atom dispersed catalyst (SAC) provides a new frontier in heterogeneous catalysis. However, the electrocatalytic application of SAC is still subject to several theoretical and experimental limitations. Further advances depend on a better design of SAC through optimizing its interaction with adsorbates during catalysis. Here, distinctive from previous studies, favorable 3d electronic occupation and enhanced metal-adsorbates interactions in single-atom centers via the construction of nonplanar coordination is achieved, which is confirmed by advanced X-ray spectroscopic and electrochemical studies. The as-designed atomically dispersed cobalt sites within nonplanar coordination show significantly improved catalytic activity and selectivity toward the oxygen reduction reaction, approaching the benchmark Pt-based catalysts. More importantly, the illustration of the active sites in SAC indicates metal-natured catalytic sites and a media-dependent catalytic pathway. Achieving structural and electronic engineering on SAC that promotes its catalytic performances provides a paradigm to bridge the gap between single-atom catalysts design and electrocatalytic applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Feasibility of Single Scan for Simultaneous Evaluation of Regional Krypton and Iodine Concentrations with Dual-Energy CT: An Experimental Study.

    Science.gov (United States)

    Hong, Sae Rom; Chang, Suyon; Im, Dong Jin; Suh, Young Joo; Hong, Yoo Jin; Hur, Jin; Kim, Young Jin; Choi, Byoung Wook; Lee, Hye-Jeong

    2016-11-01

    Purpose To evaluate the feasibility of a simultaneous single scan of regional krypton and iodine concentrations by using dual-energy computed tomography (CT). Materials and Methods The study was approved by the institutional animal experimental committee. An airway obstruction model was first made in 10 beagle dogs, and a pulmonary arterial occlusion was induced in each animal after 1 week. For each model, three sessions of dual-energy CT (80% krypton ventilation [krypton CT], 80% krypton ventilation with iodine enhancement [mixed-contrast agent CT], and iodine enhancement [iodine CT]) were performed. Krypton maps were made from krypton and mixed-contrast agent CT, and iodine maps were made from iodine and mixed-contrast agent CT. Observers measured overlay Hounsfield units of the diseased and contralateral segments on each map. Values were compared by using the Wilcoxon signed-rank test. Results In krypton maps of airway obstruction, overlay Hounsfield units of diseased segments were significantly decreased compared with those of contralateral segments in both krypton and mixed-contrast agent CT (P = .005 for both). However, the values of mixed-contrast agent CT were significantly higher than those of krypton CT for both segments (P = .005 and .007, respectively). In iodine maps of pulmonary arterial occlusion, values were significantly lower in diseased segments than in contralateral segments for both iodine and mixed-contrast agent CT (P = .005 for both), without significant difference between iodine and mixed-contrast agent CT for both segments (P = .126 and .307, respectively). Conclusion Although some limitations may exist, it might be feasible to analyze regional krypton and iodine concentrations simultaneously by using dual-energy CT. © RSNA, 2016.

  14. Single-atom reversible recording at room temperature

    DEFF Research Database (Denmark)

    Quaade, Ulrich; Stokbro, Kurt; Lin, Rong

    2001-01-01

    investigate two important aspects of using this single-atom switch as a memory device. First, the switching is electron stimulated, and through detailed modelling the switching probability per electron is accurately deduced. Second, we have investigated the possibilities for desorbing single hydrogen atoms...... to construct ordered arrays of switches to manufacture a memory device. Two desorption mechanisms have been considered: the well known electron-induced desorption at negative sample bias and a novel mechanism probably involving elastic deformation of the tip. For both mechanisms mechanical stability of the STM...... is of crucial importance. With our equipment it was possible to create a row of four switches in a controlled way.(Some figures in this article are in colour only in the electronic version)....

  15. Quantum Logic with Cavity Photons From Single Atoms.

    Science.gov (United States)

    Holleczek, Annemarie; Barter, Oliver; Rubenok, Allison; Dilley, Jerome; Nisbet-Jones, Peter B R; Langfahl-Klabes, Gunnar; Marshall, Graham D; Sparrow, Chris; O'Brien, Jeremy L; Poulios, Konstantinos; Kuhn, Axel; Matthews, Jonathan C F

    2016-07-08

    We demonstrate quantum logic using narrow linewidth photons that are produced with an a priori nonprobabilistic scheme from a single ^{87}Rb atom strongly coupled to a high-finesse cavity. We use a controlled-not gate integrated into a photonic chip to entangle these photons, and we observe nonclassical correlations between photon detection events separated by periods exceeding the travel time across the chip by 3 orders of magnitude. This enables quantum technology that will use the properties of both narrow-band single photon sources and integrated quantum photonics.

  16. Iodination of phenol

    International Nuclear Information System (INIS)

    Christiansen, J.V.; Feldthus, A.; Carlsen, L.

    1990-01-01

    Phenol is iodinated in aqueous solution at pH 5 (acetate buffer) by elemental iodine or, if the iodine is present as iodide, enzymatically controlled by peroxidases. Generally mono-, di- and triiodophenols are obtained, the overall product composition being virtually identical for the two iodination modes. However, there is a tendency to a higher para to ortho ratio for the enzymatically controlled reaction. The mutual ratios of the single iodophenols depends on the initial concentration ratio between phenol and the iodinating species. The first step in the iodination leads preferentially to substitution in the ortho position rather than in the para position in contract to e.g. the corresponding bromination. The relative rates of the competive reactions in the combined iodination scheme has been derived. (author) 2 tabs., 3 ills., 15 refs

  17. Atomically precise graphene nanoribbon heterojunctions from a single molecular precursor

    Science.gov (United States)

    Nguyen, Giang D.; Tsai, Hsin-Zon; Omrani, Arash A.; Marangoni, Tomas; Wu, Meng; Rizzo, Daniel J.; Rodgers, Griffin F.; Cloke, Ryan R.; Durr, Rebecca A.; Sakai, Yuki; Liou, Franklin; Aikawa, Andrew S.; Chelikowsky, James R.; Louie, Steven G.; Fischer, Felix R.; Crommie, Michael F.

    2017-11-01

    The rational bottom-up synthesis of atomically defined graphene nanoribbon (GNR) heterojunctions represents an enabling technology for the design of nanoscale electronic devices. Synthetic strategies used thus far have relied on the random copolymerization of two electronically distinct molecular precursors to yield GNR heterojunctions. Here we report the fabrication and electronic characterization of atomically precise GNR heterojunctions prepared through late-stage functionalization of chevron GNRs obtained from a single precursor. Post-growth excitation of fully cyclized GNRs induces cleavage of sacrificial carbonyl groups, resulting in atomically well-defined heterojunctions within a single GNR. The GNR heterojunction structure was characterized using bond-resolved scanning tunnelling microscopy, which enables chemical bond imaging at T = 4.5 K. Scanning tunnelling spectroscopy reveals that band alignment across the heterojunction interface yields a type II heterojunction, in agreement with first-principles calculations. GNR heterojunction band realignment proceeds over a distance less than 1 nm, leading to extremely large effective fields.

  18. Probing quantum coherence in single-atom electron spin resonance

    Science.gov (United States)

    Willke, Philip; Paul, William; Natterer, Fabian D.; Yang, Kai; Bae, Yujeong; Choi, Taeyoung; Fernández-Rossier, Joaquin; Heinrich, Andreas J.; Lutz, Christoper P.

    2018-01-01

    Spin resonance of individual spin centers allows applications ranging from quantum information technology to atomic-scale magnetometry. To protect the quantum properties of a spin, control over its local environment, including energy relaxation and decoherence processes, is crucial. However, in most existing architectures, the environment remains fixed by the crystal structure and electrical contacts. Recently, spin-polarized scanning tunneling microscopy (STM), in combination with electron spin resonance (ESR), allowed the study of single adatoms and inter-atomic coupling with an unprecedented combination of spatial and energy resolution. We elucidate and control the interplay of an Fe single spin with its atomic-scale environment by precisely tuning the phase coherence time T2 using the STM tip as a variable electrode. We find that the decoherence rate is the sum of two main contributions. The first scales linearly with tunnel current and shows that, on average, every tunneling electron causes one dephasing event. The second, effective even without current, arises from thermally activated spin-flip processes of tip spins. Understanding these interactions allows us to maximize T2 and improve the energy resolution. It also allows us to maximize the amplitude of the ESR signal, which supports measurements even at elevated temperatures as high as 4 K. Thus, ESR-STM allows control of quantum coherence in individual, electrically accessible spins. PMID:29464211

  19. Localizing gravitational wave sources with single-baseline atom interferometers

    Science.gov (United States)

    Graham, Peter W.; Jung, Sunghoon

    2018-02-01

    Localizing sources on the sky is crucial for realizing the full potential of gravitational waves for astronomy, astrophysics, and cosmology. We show that the midfrequency band, roughly 0.03 to 10 Hz, has significant potential for angular localization. The angular location is measured through the changing Doppler shift as the detector orbits the Sun. This band maximizes the effect since these are the highest frequencies in which sources live for several months. Atom interferometer detectors can observe in the midfrequency band, and even with just a single baseline they can exploit this effect for sensitive angular localization. The single-baseline orbits around the Earth and the Sun, causing it to reorient and change position significantly during the lifetime of the source, and making it similar to having multiple baselines/detectors. For example, atomic detectors could predict the location of upcoming black hole or neutron star merger events with sufficient accuracy to allow optical and other electromagnetic telescopes to observe these events simultaneously. Thus, midband atomic detectors are complementary to other gravitational wave detectors and will help complete the observation of a broad range of the gravitational spectrum.

  20. Iodine Deficiency

    Science.gov (United States)

    ... Fax/Phone Home » Iodine Deficiency Leer en Español Iodine Deficiency Iodine is an element that is needed ... world’s population remains at risk for iodine deficiency. Iodine Deficiency FAQs WHAT IS THE THYROID GLAND? The ...

  1. Preparation of a single atom in an optical microtrap

    International Nuclear Information System (INIS)

    Carpentier, Alicia V; Fung, Yin H; Sompet, Pimonpan; Hilliard, Andrew J; Andersen, Mikkel F; Walker, Thad G

    2013-01-01

    We investigate the use of light assisted collisions for the deterministic preparation of individual atoms in a microtrap. Blue detuned light is used in order to ensure that only one of the collision partners is lost from the trap. We obtain a 91% loading efficiency of single 85 Rb atoms. This can be achieved within a total preparation time of 542 ms. A numerical model of the process quantitatively agrees with the experiment giving an in-depth understanding of the dynamics of the process and allowing us to identify the factors that still limit the loading efficiency. The fast loading time in combination with the high efficiency may be sufficient for loading quantum registers at the size required for competitive quantum computing. (letter)

  2. Site-selective substitutional doping with atomic precision on stepped Al (111) surface by single-atom manipulation.

    Science.gov (United States)

    Chen, Chang; Zhang, Jinhu; Dong, Guofeng; Shao, Hezhu; Ning, Bo-Yuan; Zhao, Li; Ning, Xi-Jing; Zhuang, Jun

    2014-01-01

    In fabrication of nano- and quantum devices, it is sometimes critical to position individual dopants at certain sites precisely to obtain the specific or enhanced functionalities. With first-principles simulations, we propose a method for substitutional doping of individual atom at a certain position on a stepped metal surface by single-atom manipulation. A selected atom at the step of Al (111) surface could be extracted vertically with an Al trimer-apex tip, and then the dopant atom will be positioned to this site. The details of the entire process including potential energy curves are given, which suggests the reliability of the proposed single-atom doping method.

  3. The atomic coilgun and single-photon cooling

    Energy Technology Data Exchange (ETDEWEB)

    Libson, Adam, E-mail: alibson@physics.utexas.edu; Bannerman, Stephen Travis; Clark, Robert J.; Mazur, Thomas R.; Raizen, Mark G. [University of Texas at Austin, Center for Nonlinear Dynamics and Department of Physics (United States)

    2012-12-15

    As the simplest atom, hydrogen has a unique role as a testing ground of fundamental physics. Precision measurements of the hydrogen atomic structure provide stringent tests of current theory, while tritium is an excellent candidate for studies of {beta}-decay and possible measurement of the neutrino rest mass. Furthermore, precision measurement of antihydrogen would allow for tests of fundamental symmetries. Methods demonstrated in our lab provide an avenue by which hydrogen isotopes can be trapped and cooled to near the recoil limit. The atomic coilgun, which we have demonstrated with metastable neon and molecular oxygen, provides a general method of stopping a supersonic beam of any paramagnetic species. This tool provides a method by which hydrogen and its isotopes can be magnetically trapped at around 100 mK using a room temperature apparatus. Another tool developed in our laboratory, single-photon cooling, allows further cooling of a trapped sample to near the recoil limit. This cooling method has already been demonstrated on a trapped sample of rubidium. We report on the progress of implementing these methods to trap and cool hydrogen isotopes, and on the prospects for using cold trapped hydrogen for precision measurements.

  4. Single atom anisotropic magnetoresistance on a topological insulator surface

    KAUST Repository

    Narayan, Awadhesh

    2015-03-12

    © 2015 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. We demonstrate single atom anisotropic magnetoresistance on the surface of a topological insulator, arising from the interplay between the helical spin-momentum-locked surface electronic structure and the hybridization of the magnetic adatom states. Our first-principles quantum transport calculations based on density functional theory for Mn on Bi2Se3 elucidate the underlying mechanism. We complement our findings with a two dimensional model valid for both single adatoms and magnetic clusters, which leads to a proposed device setup for experimental realization. Our results provide an explanation for the conflicting scattering experiments on magnetic adatoms on topological insulator surfaces, and reveal the real space spin texture around the magnetic impurity.

  5. Single molecule DNA detection with an atomic vapor notch filter

    Energy Technology Data Exchange (ETDEWEB)

    Uhland, Denis; Rendler, Torsten; Widmann, Matthias; Lee, Sang-Yun [University of Stuttgart and Stuttgart Research Center of Photonic Engineering (SCoPE) and IQST, 3rd Physics Institute, Stuttgart (Germany); Wrachtrup, Joerg; Gerhardt, Ilja [University of Stuttgart and Stuttgart Research Center of Photonic Engineering (SCoPE) and IQST, 3rd Physics Institute, Stuttgart (Germany); Max Planck Institute for Solid State Research, Stuttgart (Germany)

    2015-12-01

    The detection of single molecules has facilitated many advances in life- and material-science. Commonly the fluorescence of dye molecules is detected, which are attached to a non-fluorescent structure under study. For fluorescence microscopy one desires to maximize the detection efficiency together with an efficient suppression of undesired laser leakage. Here we present the use of the narrow-band filtering properties of hot atomic sodium vapor to selectively filter the excitation light from the red-shifted fluorescence of dye labeled single-stranded DNA molecules. A statistical analysis proves an enhancement in detection efficiency of more than 15% in a confocal and in a wide-field configuration. (orig.)

  6. Investigating single molecule adhesion by atomic force spectroscopy.

    Science.gov (United States)

    Stetter, Frank W S; Kienle, Sandra; Krysiak, Stefanie; Hugel, Thorsten

    2015-02-27

    Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. At the same time the AFM tip is passivated to prevent unspecific interactions between the tip and the substrate, which is a prerequisite to study single molecules attached to the AFM tip. Analyses to determine the adhesion force, the adhesion length, and the free energy of these molecules on solid surfaces and bio-interfaces are shortly presented and external references for further reading are provided. Example molecules are the poly(amino acid) polytyrosine, the graft polymer PI-g-PS and the phospholipid POPE (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine). These molecules are desorbed from different surfaces like CH3-SAMs, hydrogen terminated diamond and supported lipid bilayers under various solvent conditions. Finally, the advantages of force spectroscopic single molecule experiments are discussed including means to decide if truly a single molecule has been studied in the experiment.

  7. Potential of Transition Metal Atoms Embedded in Buckled Monolayer g-C3N4 as Single-Atom Catalysts

    KAUST Repository

    Li, Shu-Long

    2017-10-27

    We use first-principles calculations to systematically explore the potential of transition metal atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) embedded in buckled monolayer g-C3N4 as single-atom catalysts. We show that clustering of Sc and Ti on g-C3N4 is thermodynamically impeded and that V, Cr, Mn, and Cu are much less susceptible to clustering than the other TM atoms under investigation. Strong bonding of the transition metal atoms in the cavities of g-C3N4 and high diffusion barriers together are responsible for single-atom fixation. Analysis of the CO oxidation process indicates that embedding of Cr and Mn in g-C3N4 gives rise to promising single-atom catalysts at low temperature.

  8. Potential of Transition Metal Atoms Embedded in Buckled Monolayer g-C3N4 as Single-Atom Catalysts

    KAUST Repository

    Li, Shu-Long; Kan, Xiang; Yin, Hui; Gan, Li-Yong; Schwingenschlö gl, Udo; Zhao, Yong

    2017-01-01

    We use first-principles calculations to systematically explore the potential of transition metal atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) embedded in buckled monolayer g-C3N4 as single-atom catalysts. We show that clustering of Sc and Ti on g-C3N4 is thermodynamically impeded and that V, Cr, Mn, and Cu are much less susceptible to clustering than the other TM atoms under investigation. Strong bonding of the transition metal atoms in the cavities of g-C3N4 and high diffusion barriers together are responsible for single-atom fixation. Analysis of the CO oxidation process indicates that embedding of Cr and Mn in g-C3N4 gives rise to promising single-atom catalysts at low temperature.

  9. Single-passage read-out of atomic quantum memory

    DEFF Research Database (Denmark)

    Fiurasek, J; Sherson, J; Opatrny, T

    2005-01-01

    Retrieving quantum information, collective atomic spin systems, quantum memory Udgivelsesdato: 17 Feb.......Retrieving quantum information, collective atomic spin systems, quantum memory Udgivelsesdato: 17 Feb....

  10. Optical Microcavity: Sensing down to Single Molecules and Atoms

    Directory of Open Access Journals (Sweden)

    Shu-Yu Su

    2011-02-01

    Full Text Available This review article discusses fundamentals of dielectric, low-loss, optical micro-resonator sensing, including figures of merit and a variety of microcavity designs, and future perspectives in microcavity-based optical sensing. Resonance frequency and quality (Q factor are altered as a means of detecting a small system perturbation, resulting in realization of optical sensing of a small amount of sample materials, down to even single molecules. Sensitivity, Q factor, minimum detectable index change, noises (in sensor system components and microcavity system including environments, microcavity size, and mode volume are essential parameters to be considered for optical sensing applications. Whispering gallery mode, photonic crystal, and slot-type microcavities typically provide compact, high-quality optical resonance modes for optical sensing applications. Surface Bloch modes induced on photonic crystals are shown to be a promising candidate thanks to large field overlap with a sample and ultra-high-Q resonances. Quantum optics effects based on microcavity quantum electrodynamics (QED would provide novel single-photo-level detection of even single atoms and molecules via detection of doublet vacuum Rabi splitting peaks in strong coupling.

  11. Iodine volatility

    International Nuclear Information System (INIS)

    Beahm, E.C.; Shockley, W.E.

    1984-01-01

    The ultimate aim of this program is to couple experimental aqueous iodine volatilities to a fission product release model. Iodine partition coefficients, for inorganic iodine, have been measured during hydrolysis and radiolysis. The hydrolysis experiments have illustrated the importance of reaction time on iodine volatility. However, radiolysis effects can override hydrolysis in determining iodine volatility. In addition, silver metal in radiolysis samples can react to form silver iodide accompanied by a decrease in iodine volatility. Experimental data are now being coupled to an iodine transport and release model that was developed in the Federal Republic of Germany

  12. Simplified atom trap using a single microwave modulated diode laser

    International Nuclear Information System (INIS)

    Newbury, N.R.; Myatt, C.J.; Wieman, C.E.

    1993-01-01

    We have demonstrated microwave modulation of a diode laser which is operated with optical feedback from a diffraction grating. By directly modulating the diode laser current at frequencies up to 6.8 GHz, we observed 2-30% of the laser power in a single sideband for 20mW of microwave power. Using such a diode laser modulated at 6.6GHz, we have trapped 87 Rb in a vapor cell. With 10mW of microwave power, the number of trapped atoms was only 15% smaller than the number obtained using two lasers in the conventional manner. A microwave modulated diode laser should also be useful for driving stimulated Raman transitions between the hyperfine levels of Rb or Cs

  13. Probing Single Pt Atoms in Complex Intermetallic Al13Fe4.

    Science.gov (United States)

    Yamada, Tsunetomo; Kojima, Takayuki; Abe, Eiji; Kameoka, Satoshi; Murakami, Yumi; Gille, Peter; Tsai, An Pang

    2018-03-21

    The atomic structure of a 0.2 atom % Pt-doped complex metallic alloy, monoclinic Al 13 Fe 4 , was investigated using a single crystal prepared by the Czochralski method. High-angle annular dark-field scanning transmission electron microscopy showed that the Pt atoms were dispersed as single atoms and substituted at Fe sites in Al 13 Fe 4 . Single-crystal X-ray structural analysis revealed that the Pt atoms preferentially substitute at Fe(1). Unlike those that have been reported, Pt single atoms in the surface layers showed lower activity and selectivity than those of Al 2 Pt and bulk Pt for propyne hydrogenation, indicating that the active state of a given single-atom Pt site is strongly dominated by the bonding to surrounding Al atoms.

  14. Iodine Prophylaxis and Nuclear Accidents

    International Nuclear Information System (INIS)

    Franic, Z.

    1998-01-01

    Iodine is a highly volatile element therefore being very mobile in the environment. It enters the metabolism of living organisms and is selectively taken up and concentrated in the thyroid gland. The plume (cloud-like formation) of radioactive material that might be released in the environment in the case of a serious nuclear accident, primarily consists of the radioactive isotopes of iodine. Among those, due to its decay properties, is the most important 131 I. The effective means of protecting the thyroid gland against exposure to radioactive iodine is an intake of stable iodine. Therefore, one of the central issues in the emergency planning is to determine whether and at which projected thyroid radiation dose stable iodine should be given to the population. The International Atomic Energy Agency (IAEA) set the generic optimized intervention value for iodine prophylaxis to 100 mGy of avertable committed dose to a thyroid.The prophylaxis is implemented by utilizing the pills of pills of potassium iodine (KI). The efficacy of KI in protecting the thyroid gland depends upon the time of intake relative to the start of exposure to radioactive iodine. The best results are obtained if KI is taken 1-2 hours before or immediately after the start of exposure. The recommended dosage, based upon the study performed by Il'in et.al. is 130 mg/day. KI should be taken at least three days after the acute exposure to radioiodine, to prevent accumulation in a thyroid gland of radioiodine excreted from the other compartments of the body. The largest epidemiological study on the effects of KI prophylaxis ever performed was the one in Poland after the Chernobyl accident. Stable iodine was given as single dose of KI solution to 10.5 million of children and 7 millions of adults. Among children no serious side effects were seen while only two adults (with previously recorded iodine sensitivity) had severe respiratory distresses. Polish experiences showed that rapid response to such

  15. Gravitational Wave Detection with Single-Laser Atom Interferometers

    Science.gov (United States)

    Yu, Nan; Tinto, Massimo

    2011-01-01

    A new design for a broadband detector of gravitational radiation relies on two atom interferometers separated by a distance L. In this scheme, only one arm and one laser are used for operating the two atom interferometers. The innovation here involves the fact that the atoms in the atom interferometers are not only considered as perfect test masses, but also as highly stable clocks. Atomic coherence is intrinsically stable, and can be many orders of magnitude more stable than a laser.

  16. Single atom spectroscopy: Decreased scattering delocalization at high energy losses, effects of atomic movement and X-ray fluorescence yield.

    Science.gov (United States)

    Tizei, Luiz H G; Iizumi, Yoko; Okazaki, Toshiya; Nakanishi, Ryo; Kitaura, Ryo; Shinohara, Hisanori; Suenaga, Kazu

    2016-01-01

    Single atom localization and identification is crucial in understanding effects which depend on the specific local environment of atoms. In advanced nanometer scale materials, the characteristics of individual atoms may play an important role. Here, we describe spectroscopic experiments (electron energy loss spectroscopy, EELS, and Energy Dispersed X-ray spectroscopy, EDX) using a low voltage transmission electron microscope designed towards single atom analysis. For EELS, we discuss the advantages of using lower primary electron energy (30 keV and 60 keV) and higher energy losses (above 800 eV). The effect of atomic movement is considered. Finally, we discuss the possibility of using atomically resolved EELS and EDX data to measure the fluorescence yield for X-ray emission. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Single atom spectroscopy: Decreased scattering delocalization at high energy losses, effects of atomic movement and X-ray fluorescence yield

    International Nuclear Information System (INIS)

    Tizei, Luiz H.G.; Iizumi, Yoko; Okazaki, Toshiya; Nakanishi, Ryo; Kitaura, Ryo; Shinohara, Hisanori; Suenaga, Kazu

    2016-01-01

    Single atom localization and identification is crucial in understanding effects which depend on the specific local environment of atoms. In advanced nanometer scale materials, the characteristics of individual atoms may play an important role. Here, we describe spectroscopic experiments (electron energy loss spectroscopy, EELS, and Energy Dispersed X-ray spectroscopy, EDX) using a low voltage transmission electron microscope designed towards single atom analysis. For EELS, we discuss the advantages of using lower primary electron energy (30 keV and 60 keV) and higher energy losses (above 800 eV). The effect of atomic movement is considered. Finally, we discuss the possibility of using atomically resolved EELS and EDX data to measure the fluorescence yield for X-ray emission.

  18. Single molecule atomic force microscopy and force spectroscopy of chitosan.

    Science.gov (United States)

    Kocun, Marta; Grandbois, Michel; Cuccia, Louis A

    2011-02-01

    Atomic force microscopy (AFM) and AFM-based force spectroscopy was used to study the desorption of individual chitosan polymer chains from substrates with varying chemical composition. AFM images of chitosan adsorbed onto a flat mica substrate show elongated single strands or aggregated bundles. The aggregated state of the polymer is consistent with the high level of flexibility and mobility expected for a highly positively charged polymer strand. Conversely, the visualization of elongated strands indicated the presence of stabilizing interactions with the substrate. Surfaces with varying chemical composition (glass, self-assembled monolayer of mercaptoundecanoic acid/decanethiol and polytetrafluoroethylene (PTFE)) were probed with chitosan modified AFM tips and the corresponding desorption energies, calculated from plateau-like features, were attributed to the desorption of individual polymer strands. Desorption energies of 2.0±0.3×10(-20)J, 1.8±0.3×10(-20)J and 3.5±0.3×10(-20)J were obtained for glass, SAM of mercaptoundecanoic/dodecanethiol and PTFE, respectively. These single molecule level results can be used as a basis for investigating chitosan and chitosan-based materials for biomaterial applications. Copyright © 2010 Elsevier B.V. All rights reserved.

  19. Direct in situ observations of single Fe atom catalytic processes and anomalous diffusion at graphene edges

    Science.gov (United States)

    Zhao, Jiong; Deng, Qingming; Avdoshenko, Stanislav M.; Fu, Lei; Eckert, Jürgen; Rümmeli, Mark H.

    2014-01-01

    Single-atom catalysts are of great interest because of their high efficiency. In the case of chemically deposited sp2 carbon, the implementation of a single transition metal atom for growth can provide crucial insight into the formation mechanisms of graphene and carbon nanotubes. This knowledge is particularly important if we are to overcome fabrication difficulties in these materials and fully take advantage of their distinct band structures and physical properties. In this work, we present atomically resolved transmission EM in situ investigations of single Fe atoms at graphene edges. Our in situ observations show individual iron atoms diffusing along an edge either removing or adding carbon atoms (viz., catalytic action). The experimental observations of the catalytic behavior of a single Fe atom are in excellent agreement with supporting theoretical studies. In addition, the kinetics of Fe atoms at graphene edges are shown to exhibit anomalous diffusion, which again, is in agreement with our theoretical investigations. PMID:25331874

  20. Submicron Positioning of Single Atoms in a Microcavity

    International Nuclear Information System (INIS)

    Nussmann, Stefan; Hijlkema, Markus; Weber, Bernhard; Rohde, Felix; Rempe, Gerhard; Kuhn, Axel

    2005-01-01

    The coupling of individual atoms to a high-finesse optical cavity is precisely controlled and adjusted using a standing-wave dipole-force trap, a challenge for strong atom-cavity coupling. Ultracold Rubidium atoms are first loaded into potential minima of the dipole trap in the center of the cavity. Then we use the trap as a conveyor belt that we set into motion perpendicular to the cavity axis. This allows us to repetitively move atoms out of and back into the cavity mode with a repositioning precision of 135 nm. This makes it possible to either selectively address one atom of a string of atoms by the cavity, or to simultaneously couple two precisely separated atoms to a higher mode of the cavity

  1. Versatile single-chip event sequencer for atomic physics experiments

    Science.gov (United States)

    Eyler, Edward

    2010-03-01

    A very inexpensive dsPIC microcontroller with internal 32-bit counters is used to produce a flexible timing signal generator with up to 16 TTL-compatible digital outputs, with a time resolution and accuracy of 50 ns. This time resolution is easily sufficient for event sequencing in typical experiments involving cold atoms or laser spectroscopy. This single-chip device is capable of triggered operation and can also function as a sweeping delay generator. With one additional chip it can also concurrently produce accurately timed analog ramps, and another one-chip addition allows real-time control from an external computer. Compared to an FPGA-based digital pattern generator, this design is slower but simpler and more flexible, and it can be reprogrammed using ordinary `C' code without special knowledge. I will also describe the use of the same microcontroller with additional hardware to implement a digital lock-in amplifier and PID controller for laser locking, including a simple graphics-based control unit. This work is supported in part by the NSF.

  2. Splitting of 9-iodo-1,7-carborane by potassium hydroxide in butanol with butoxy group substitution for iodine atom when formation of anions of 1-butoxy- and 5-butoxy-nido-7,9-dicarbaundecaborate

    International Nuclear Information System (INIS)

    Zakharkin, L.I.; Ol'shevskaya, V.A.; Guseva, V.V.; Panfilova, S.Yu.

    2000-01-01

    The 9-iodo-1,7-carborane by heating in the potassium hydroxide butanol solution is splitted into the stereoisomeric anions of the nido-7,9-dicarbaundecaborate substituting under the reaction conditions the butoxy-group for iodine atom with formation of anions of the 1-butoxy- and -butoxy-nido-7,9-dicarbaundecaborate [ru

  3. Iodine Deficiency

    NARCIS (Netherlands)

    Zimmermann, M.B.

    2009-01-01

    Iodine deficiency has multiple adverse effects in humans, termed iodine deficiency disorders, due to inadequate thyroid hormone production. Globally, it is estimated that 2 billion individuals have an insufficient iodine intake, and South Asia and sub-Saharan Africa are particularly affected.

  4. Radionuclide Basics: Iodine

    Science.gov (United States)

    ... Centers Radiation Protection Contact Us Share Radionuclide Basics: Iodine Iodine (chemical symbol I) is a chemical element. ... in the environment Iodine sources Iodine and health Iodine in the Environment All 37 isotopes of iodine ...

  5. Force, current and field effects in single atom manipulation

    NARCIS (Netherlands)

    Braun, K.-F.; Hla, S.; Pertaya, N.; Soe, W.H.; Flipse, C.F.J.; Rieder, K.

    2003-01-01

    We present a detailed investigation of the manipulation of Ag and Au atoms with a STM tip on the Ag(111) surface at 5K. The interpretation of the feed-back loop signal gives a precise picture of the movement of the atom during manipulation. The threshold tunnelling resistance and tip-height to move

  6. Single-atom detection on a chip: from realization to application

    Energy Technology Data Exchange (ETDEWEB)

    Stibor, A; Bender, H; Kuehnhold, S; Fortagh, J; Zimmermann, C; Guenther, A, E-mail: aguenth@pit.physik.uni-tuebingen.d [CQ Center for Collective Quantum Phenomena and their Applications, Eberhard-Karls-Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

    2010-06-15

    In this paper, we describe the preparation and detection of ultracold atoms on a microchip with single-atom sensitivity. The detection scheme is based on multi-photon ionization of atoms and the subsequent guiding of the generated ions by ion optics to a channel electron multiplier. We resolve single atoms with a detection efficiency above 60%. The detector is suitable for real-time observations of static and dynamic processes in ultracold quantum gases. Although the ionization is destructive, sampling a small subset of the atomic distribution is sufficient for the determination of the desired information. We take full high-resolution spectra of ultracold atoms by ionizing only 5% of the atoms. Using an additional microwave near 6.8 GHz, the detection scheme becomes energy, position and state selective. This can be used for in situ determination of the energy distribution and temperature of atom clouds inside the trap and applied for future correlation measurements.

  7. Observation of Entanglement of a Single Photon with a Trapped Atom

    International Nuclear Information System (INIS)

    Volz, Juergen; Weber, Markus; Schlenk, Daniel; Rosenfeld, Wenjamin; Vrana, Johannes; Saucke, Karen; Kurtsiefer, Christian; Weinfurter, Harald

    2006-01-01

    We report the observation of entanglement between a single trapped atom and a single photon at a wavelength suitable for low-loss communication over large distances, thereby achieving a crucial step towards long range quantum networks. To verify the entanglement, we introduce a single atom state analysis. This technique is used for full state tomography of the atom-photon qubit pair. The detection efficiency and the entanglement fidelity are high enough to allow in a next step the generation of entangled atoms at large distances, ready for a final loophole-free Bell experiment

  8. In vivo imaging of GABAA receptors using sequential whole-volume iodine-123 iomazenil single-photon emission tomography

    International Nuclear Information System (INIS)

    Busatto, G.F.; Pilowsky, L.S.; Costa, D.C.; Ell, P.J.; Lingford-Hughes, A.; Kerwin, R.W.

    1995-01-01

    Using a brain-dedicated triple-headed single-photon emission tomography (SPET) system, a sequential whole-volume imaging protocol has been devised to evaluate the regional distribution of iodine-123 iomazenil binding to GABA A receptors in the entire brain. The protocol was piloted in eight normal volunteers (seven males and one female; mean age, 24.8±3.9 years). The patterns obtained were largely compatible with the known distribution of GABA A receptors in the brain as reported in autoradiographic studies, with cerebral cortical regions, particularly the occipital and frontal cortices, displaying the highest 123 I-iomazenil uptake. Measures of time to peak uptake and tracer washout rates presented with the same pattern of regional variation, with later times to peak and slower washout rates in cortical regions compared to other brain areas. Semiquantitative analysis of the data using white matter/ventricle regions as reference demonstrated a plateau of specific 123 I-iomazenil binding in neocortical and cerebellar regions from 60-75 min onwards. These data demonstrate the feasibility of sequential, dynamic whole-volume 123 I-iomazenil SPET imaging. The protocol may be particularly useful in the investigation of neuropsychiatric conditions which are likely to involve more than one focus of GABA abnormalities, such as anxiety disorders and schizophrenia. (orig.)

  9. Assessment of endogenous dopamine release by methylphenidate challenge using iodine-123 iodobenzamide single-photon emission tomography

    International Nuclear Information System (INIS)

    Booij, J.; Korn, P.; Linszen, D.H.; Royen, E.A. van

    1997-01-01

    This double-blind, placebo-controlled study assessed pharmacologically induced endogenous dopamine (DA) release in healthy male volunteers (n=12). Changes in endogenous DA release after injection of the psychostimulant drug methylphenidate were evaluated by single-photon emission tomography (SPET) and constant infusion of iodine-123 iodobenzamide ([ 123 I[IBZM), a D 2 receptor radioligand that is sensitive to endogenous DA release. Methylphenidate induced displacement of striatal [ 123 I[IBZM binding, resulting in a significantly decrease in the specific to non-specific [ 123 I[IBZM uptake ratio (average: 8.6%) in comparison with placebo (average: -1.9%). Moreover, injection of methylphenidate induced significant behavioural responses on the following items: excitement, anxiety, tension, and mannerisms and posturing. The results of this study demonstrate the feasibility of using constant infusion of [ 123 I[IBZM and SPET imaging to measure endogenous DA release after methylphenidate challenge and to investigate neurochemical aspects of behaviour. (orig.). With 2 figs., 1 tab

  10. Time profile of harmonics generated by a single atom in a strong electromagnetic field

    International Nuclear Information System (INIS)

    Antoine, P.; Piraux, B.; Maquet, A.

    1995-01-01

    We show that the time profile of the harmonics emitted by a single atom exposed to a strong electromagnetic field may be obtained through a wavelet or a Gabor analysis of the acceleration of the atomic dipole. This analysis is extremely sensitive to the details of the dynamics and sheds some light on the competition between the atomic excitation or ionization processes and photon emission. For illustration we study the interaction of atomic hydrogen with an intense laser pulse

  11. Manipulation and analysis of a single dopant atom in GaAs

    NARCIS (Netherlands)

    Wijnheijmer, A.P.

    2011-01-01

    This thesis focuses on the manipulation and analysis of single dopant atoms in GaAs by scanning tunneling microscopy (STM) and spectroscopy (STS) at low temperatures. The observation of ionization rings is one of the key results, showing that we can control the charge state of a single dopant atom

  12. Lateral and vertical manipulations of single atoms on the Ag(1 1 1) surface with the copper single-atom and trimer-apex tips

    International Nuclear Information System (INIS)

    Xie Yiqun; Yang Tianxing; Ye Xiang; Huang Lei

    2011-01-01

    We study the lateral and vertical manipulations of single Ag and Cu atoms on the Ag(1 1 1) surface with the Cu single-atom and trimer-apex tips using molecular statics simulations. The reliability of the lateral manipulation with the Cu single-atom tip is investigated, and compared with that for the Ag tips. We find that overall the manipulation reliability (MR) increases with the decreasing tip height, and in a wide tip-height range the MR is better than those for both the Ag single-atom and trimer-apex tips. This is due to the stronger attractive force of the Cu tip and its better stability against the interactions with the Ag surface. With the Cu trimer-apex tip, the single Ag and Cu adatoms can be picked up from the flat Ag(1 1 1) surface, and moreover a reversible vertical manipulation of single Ag atoms on the stepped Ag(1 1 1) surface is possible, suggesting a method to modify two-dimensional Ag nanostructures on the Ag(1 1 1) surface with the Cu trimer-apex tip.

  13. Atomic imaging of an InSe single-crystal surface with atomic force microscope

    OpenAIRE

    Uosaki, Kohei; Koinuma, Michio

    1993-01-01

    The atomic force microscope was employed to observed in air the surface atomic structure of InSe, one of III-VI compound semiconductors with layered structures. Atomic arrangements were observed in both n-type and p-type materials. The observed structures are in good agreement with those expected from bulk crystal structures. The atomic images became less clear by repeating the imaging process. Wide area imaging after the imaging of small area clearly showed that a mound was created at the sp...

  14. Single-Atom Catalyst of Platinum Supported on Titanium Nitride for Selective Electrochemical Reactions.

    Science.gov (United States)

    Yang, Sungeun; Kim, Jiwhan; Tak, Young Joo; Soon, Aloysius; Lee, Hyunjoo

    2016-02-05

    As a catalyst, single-atom platinum may provide an ideal structure for platinum minimization. Herein, a single-atom catalyst of platinum supported on titanium nitride nanoparticles were successfully prepared with the aid of chlorine ligands. Unlike platinum nanoparticles, the single-atom active sites predominantly produced hydrogen peroxide in the electrochemical oxygen reduction with the highest mass activity reported so far. The electrocatalytic oxidation of small organic molecules, such as formic acid and methanol, also exhibited unique selectivity on the single-atom platinum catalyst. A lack of platinum ensemble sites changed the reaction pathway for the oxygen-reduction reaction toward a two-electron pathway and formic acid oxidation toward direct dehydrogenation, and also induced no activity for the methanol oxidation. This work demonstrates that single-atom platinum can be an efficient electrocatalyst with high mass activity and unique selectivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. A simple method for the quantification of benzodiazepine receptors using iodine-123 iomazenil and single-photon emission tomography

    International Nuclear Information System (INIS)

    Ito, Hiroshi; Goto, Ryoui; Koyama, Masamichi; Kawashima, Ryuta; Ono, Shuichi; Sato, Kazunori; Fukuda, Hiroshi

    1996-01-01

    Iodine-123 iomazenil (Iomazenil) is a ligand for central type benzodiazepine receptors that is suitable for single-photon emission tomography (SPET). The purpose of this study was to develop a simple method for the quantification of its binding potential (BP). The method is based on a two-compartment model (K 1 , influx rate constant; k 2 ', efflux rate constant; V T '(=K 1 /k 2 '), the total distribution volumes relative to the total arterial tracer concentration), and requires two SPET scans and one blood sampling. For a given input function, the radioactivity ratio of the early to delayed scans can be considered to tabulate as a function of k 2 ', and a table lookup procedure provides the corresponding k 2 ' value, from which K 1 and V t ' values are then calculated. The arterial input function is obtained by calibration of the standard input function by the single blood sampling. SPET studies were performed on 14 patients with cerebrovascular diseases, dementia or brain tumours (mean age ±SD, 56.0±12.2). None of the patients had any heart, renal or liver disease. A dynamic SPET scan was performed following intravenous bolus injection of Iomazenil. A static SPET scan was performed at 180 min after injection. Frequent blood sampling from the brachial artery was performed on all subjects for determination of the arterial input function. Two-compartment model analysis was validated for calculation of the V T ' value of Iomazenil. Good correlations were observed between V T ' values calculated by three-compartment model analysis and those calculated by the present method, in which the scan time combinations (early scan/delayed scan) used were 15/180 min, 30/180 min or 45/180 min (all combinations: r=0.92), supporting the validity of this method. The present method is simple and applicable for clinical use. (orig.)

  16. Iodine stimulates estrogen receptor singling and its systemic level is increased in surgical patients due to topical absorption.

    Science.gov (United States)

    He, Shaohua; Wang, Bingchan; Lu, Xiyi; Miao, Suyu; Yang, Fengming; Zava, Theodore; Ding, Qiang; Zhang, Shijiang; Liu, Jiayin; Zava, David; Shi, Yuenian Eric

    2018-01-02

    Iodine is crucial for thyroid hormone production. However, recent epidemiologic studies have shown that breast cancer patients have an elevated risk of developing thyroid cancer and vice versa. A notable finding in this study is that iodine stimulated the transcriptional activity of estrogen receptor-α (ER-α) in breast cancer cells. Iodine stimulated expression of several ER-α regulated gene including PS2 , Cathepsin D , CyclinD1 , and PR both in vitro and in nude mice, which is consistent with its stimulation of both anchorage-dependent and -independent growth of ER-α positive breast cancer cells and the effect to dampen tumor shrinkage of MCF-7 xenograft in ovariectomized nude mice. Analyses of clinical urine samples from breast cancer patients undergoing surgery demonstrated that urinary iodine levels were significantly higher than that in controls; and this increased level is due to the antiseptic use of iodine during breast surgery. The present study indicates that excess iodine intake may be an unfavorable factor in breast cancer by stimulation of ER-α transcriptional activity.

  17. New Equations for Calculating Principal and Fine-Structure Atomic Spectra for Single and Multi-Electron Atoms

    Energy Technology Data Exchange (ETDEWEB)

    Surdoval, Wayne A. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Berry, David A. [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Shultz, Travis R. [National Energy Technology Lab. (NETL), Morgantown, WV (United States)

    2018-03-09

    A set of equations are presented for calculating atomic principal spectral lines and fine-structure energy splits for single and multi-electron atoms. Calculated results are presented and compared to the National Institute of Science and Technology database demonstrating very good accuracy. The equations do not require fitted parameters. The only experimental parameter required is the Ionization energy for the electron of interest. The equations have comparable accuracy and broader applicability than the single electron Dirac equation. Three Appendices discuss the origin of the new equations and present calculated results. New insights into the special relativistic nature of the Dirac equation and its relationship to the new equations are presented.

  18. The 2P1/2 → 2P3/2 laser transition in atomic iodine and the problem of search for signals from extraterrestrial intelligence

    International Nuclear Information System (INIS)

    Kutaev, Yu F; Mankevich, S K; Nosach, O Yu; Orlov, E P

    2007-01-01

    It is proposed to search for signals from extraterrestrial intelligence (ETI) at a wavelength of 1.315 μm of the laser 2 P 1/2 → 2 P 3/2 transition in the atomic iodine, which can be used for this purpose as the natural frequency reference. The search at this wavelength is promising because active quantum filters (AQFs) with the quantum sensitivity limit have been developed for this wavelength, which are capable of receiving laser signals, consisting of only a few photons, against the background of emission from a star under study. In addition, high-power iodine lasers emitting diffraction-limited radiation at 1.315 μm have been created, which highly developed ETI also can have. If a ETI sends in our direction a diffraction-limited 10-ns, 1-kJ laser pulse with the beam diameter of 10 m, a receiver with an AQF mounted on a ten-meter extra-atmospheric optical telescope can detect this signal at a distance of up to 300 light years, irrespective of the ETI position on the celestial sphere. The realisation of the projects for manufacturing optical telescopes of diameter 30 m will increase the research range up to 2700 light years. A weak absorption of the 1.315-μm radiation in the Earth atmosphere (the signal is attenuated by less than 20%) allows the search for ETI signals by using ground telescopes equipped with adaptive optical systems. (laser applications and other topics in quantum electronics)

  19. In situ single-atom array synthesis using dynamic holographic optical tweezers

    Science.gov (United States)

    Kim, Hyosub; Lee, Woojun; Lee, Han-gyeol; Jo, Hanlae; Song, Yunheung; Ahn, Jaewook

    2016-01-01

    Establishing a reliable method to form scalable neutral-atom platforms is an essential cornerstone for quantum computation, quantum simulation and quantum many-body physics. Here we demonstrate a real-time transport of single atoms using holographic microtraps controlled by a liquid-crystal spatial light modulator. For this, an analytical design approach to flicker-free microtrap movement is devised and cold rubidium atoms are simultaneously rearranged with 2N motional degrees of freedom, representing unprecedented space controllability. We also accomplish an in situ feedback control for single-atom rearrangements with the high success rate of 99% for up to 10 μm translation. We hope this proof-of-principle demonstration of high-fidelity atom-array preparations will be useful for deterministic loading of N single atoms, especially on arbitrary lattice locations, and also for real-time qubit shuttling in high-dimensional quantum computing architectures. PMID:27796372

  20. Perchlorate, iodine supplements, iodized salt and breast milk iodine content

    Energy Technology Data Exchange (ETDEWEB)

    Kirk, Andrea B. [Department of Epidemiology, School of Public Health, University of North Texas Health Sciences Center, 3500 Camp Bowie Blvd., Fort Worth, TX 76107 (United States); Kroll, Martina; Dyke, Jason V.; Ohira, Shin-Ichi; Dias, Rukshan A.; Dasgupta, Purnendu K. [Department of Chemistry and Biochemistry, 700 Planetarium Place, University of Texas at Arlington, Arlington, TX 76019 (United States)

    2012-03-15

    This study was undertaken to determine if increasing maternal iodine intake through single dose tablets will decrease breast milk concentrations of the iodine-uptake inhibitor, perchlorate, through competitive inhibition. We also sought to determine if the timing of supplementation influences the fraction of iodine excreted in milk versus urine and to compare the effectiveness of iodized salt as a means of providing iodine to breastfed infants. Thirteen women who did not use supplements, seven of whom used iodized salt and six of whom used non-iodized salt, submitted four milk samples and a 24-h urine collection daily for three days. Women repeated the sampling protocol for three more days during which {approx} 150 {mu}g of iodine were taken in the evening and again for three days with morning supplementation. Samples were analyzed using isotope-dilution inductively-coupled plasma-mass spectrometry for iodine and isotope-dilution ion chromatography-tandem mass spectrometry for perchlorate. No statistically significant differences were observed in milk iodine or perchlorate concentrations during the two treatment periods. Estimated perchlorate intake was above the U.S. National Academy of Sciences suggested reference dose for most infants. Single daily dose iodine supplementation was not effective in decreasing milk perchlorate concentrations. Users of iodized salt had significantly higher iodine levels in milk than non-users. Iodized salt may be a more effective means of iodine supplementation than tablets. - Highlights: Black-Right-Pointing-Pointer Estimated infant exposures to perchlorate were, on a {mu}g/kg basis, {approx} 5 Multiplication-Sign higher than those of mothers. Black-Right-Pointing-Pointer Daily supplements are less effective than iodized salt in providing iodine to lactating women. Black-Right-Pointing-Pointer Low iodine and high perchlorate in milk may place infants at risk of iodine deficiency.

  1. Parametric feedback cooling of a single atom inside on optical cavity

    International Nuclear Information System (INIS)

    Tatjana Wilk

    2014-01-01

    An optical cavity can be used as a kind of intensifier to study radiation features of an atom, which are hard to detect in free space, like squeezing. Such experiments make use of strong coupling between atom and cavity mode, which experimentally requires the atom to be well localized in the cavity mode. This can be achieved using feedback on the atomic motion: from intensity variations of a probe beam transmitted through the cavity information about the atomic motion is gained, which is used to synchronously modulate the trapping potential holding the atom, leading to cooling and better localization. Here, we report on efficient parametric feedback cooling of a single atom held in an intra-cavity standing wave dipole trap. In contrast to previous feedback strategies, this scheme cools the fast axial oscillation of the atom as well as the slower radial motion. (author)

  2. Joint Remote State Preparation of a Single-Atom Qubit State via a GHZ Entangled State

    Science.gov (United States)

    Xiao, Xiao-Qi; Yao, Fengwei; Lin, Xiaochen; Gong, Lihua

    2018-04-01

    We proposed a physical protocol for the joint remote preparation of a single-atom qubit state via a three-atom entangled GHZ-type state previously shared by the two senders and one receiver. Only rotation operations of single-atom, which can be achieved though the resonant interaction between the two-level atom and the classical field, are required in the scheme. It shows that the splitting way of the classical information of the secret qubit not only determines the success of reconstruction of the secret qubit, but also influences the operations of the senders.

  3. Imaging and manipulation of single viruses by atomic force microscopy

    NARCIS (Netherlands)

    Baclayon, M.; Wuite, G. J. L.; Roos, W. H.

    2010-01-01

    The recent developments in virus research and the application of functional viral particles in nanotechnology and medicine rely on sophisticated imaging and manipulation techniques at nanometre resolution in liquid, air and vacuum. Atomic force microscopy (AFM) is a tool that combines these

  4. Strategies for real-time position control of a single atom in cavity QED

    International Nuclear Information System (INIS)

    Lynn, T W; Birnbaum, K; Kimble, H J

    2005-01-01

    Recent realizations of single-atom trapping and tracking in cavity QED open the door for feedback schemes which actively stabilize the motion of a single atom in real time. We present feedback algorithms for cooling the radial component of motion for a single atom trapped by strong coupling to single-photon fields in an optical cavity. Performance of various algorithms is studied through simulations of single-atom trajectories, with full dynamical and measurement noise included. Closed loop feedback algorithms compare favourably to open loop 'switching' analogues, demonstrating the importance of applying actual position information in real time. The high optical information rate in current experiments enables real-time tracking that approaches the standard quantum limit for broadband position measurements, suggesting that realistic active feedback schemes may reach a regime where measurement backaction appreciably alters the motional dynamics

  5. Analysis of deterministic swapping of photonic and atomic states through single-photon Raman interaction

    Science.gov (United States)

    Rosenblum, Serge; Borne, Adrien; Dayan, Barak

    2017-03-01

    The long-standing goal of deterministic quantum interactions between single photons and single atoms was recently realized in various experiments. Among these, an appealing demonstration relied on single-photon Raman interaction (SPRINT) in a three-level atom coupled to a single-mode waveguide. In essence, the interference-based process of SPRINT deterministically swaps the qubits encoded in a single photon and a single atom, without the need for additional control pulses. It can also be harnessed to construct passive entangling quantum gates, and can therefore form the basis for scalable quantum networks in which communication between the nodes is carried out only by single-photon pulses. Here we present an analytical and numerical study of SPRINT, characterizing its limitations and defining parameters for its optimal operation. Specifically, we study the effect of losses, imperfect polarization, and the presence of multiple excited states. In all cases we discuss strategies for restoring the operation of SPRINT.

  6. Realization of Arbitrary Positive-Operator-Value Measurement of Single Atomic Qubit via Cavity QED

    International Nuclear Information System (INIS)

    Yang, Han; Wei, Wu; Chun-Wang, Wu; Hong-Yi, Dai; Cheng-Zu, Li

    2008-01-01

    Positive-operator-value measurement (POVM) is the most general class of quantum measurement. We propose a scheme to deterministically implement arbitrary POVMs of single atomic qubit via cavity QED catalysed by only one ancilla atomic qubit. By appropriately entangling two atomic qubits and sequentially measuring the ancilla qubit, any POVM can be implemented step by step. As an application of our scheme, the realization of a specific POVM for optimal unambiguous discrimination (OUD) between two nonorthogonal states is given

  7. Realization of arbitrary positive-operator-value measurement of single atomic qubit via cavity QED

    International Nuclear Information System (INIS)

    Han Yang; Wu Wei; Wu Chunwang; Dai Hongyi; Li Chengzu

    2008-01-01

    Positive-operator-value measurement (POVM) is the most general class of quantum measurement. We propose a scheme to deterministically implement arbitrary POVMs of single atomic qubit via cavity QED catalysed by only one ancilla atomic qubit. By appropriately entangling two atomic qubits and sequentially measuring the ancilla qubit, any POVM can be implemented step by step. As an application of our scheme, the realization of a specific POVM for optimal unambiguous discrimination (OUD) between two nonorthogonal states is given. (authors)

  8. Realization of Arbitrary Positive-Operator-Value Measurement of Single Atomic Qubit via Cavity QED

    Science.gov (United States)

    Han, Yang; Wu, Wei; Wu, Chun-Wang; Dai, Hong-Yi; Li, Cheng-Zu

    2008-12-01

    Positive-operator-value measurement (POVM) is the most general class of quantum measurement. We propose a scheme to deterministically implement arbitrary POVMs of single atomic qubit via cavity QED catalysed by only one ancilla atomic qubit. By appropriately entangling two atomic qubits and sequentially measuring the ancilla qubit, any POVM can be implemented step by step. As an application of our scheme, the realization of a specific POVM for optimal unambiguous discrimination (OUD) between two nonorthogonal states is given.

  9. Atomic scale mass delivery driven by bend kink in single walled carbon nanotube

    International Nuclear Information System (INIS)

    Kan Biao; Ding Jianning; Ling Zhiyong; Yuan Ningyi; Cheng Guanggui

    2010-01-01

    The possibility of atomic scale mass delivery by bend kink in single walled carbon nanotube was investigated with the aid of molecular dynamics simulation. By keeping the bending angle while moving the tube end, the encapsulated atomic scale mass such as atom, molecule and atom group were successfully delivered through the nanotube. The van der Waals interaction between the encapsulated mass and the tube wall provided the driving force for the delivery. There were no dramatic changes in the van der Waals interaction, and a smooth and steady delivery was achieved when constant loading rate was applied. The influence of temperature on the atom group delivery was also analyzed. It is found raising temperature is harmful to the smooth movement of the atom group. However, the delivery rate can be promoted under higher temperature when the atom group is situated before the kink during the delivery.

  10. Robustness of tungsten single atom tips to thermal treatment and air exposure

    Energy Technology Data Exchange (ETDEWEB)

    Vesa, Cristian; Urban, Radovan [Department of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2G7 (Canada); National Institute for Nanotechnology, National Research Council of Canada, Edmonton, Alberta, Canada T6G 2M9 (Canada); Pitters, Jason L., E-mail: jason.pitters@nrc-cnrc.gc.ca [National Institute for Nanotechnology, National Research Council of Canada, Edmonton, Alberta, Canada T6G 2M9 (Canada); Wolkow, Robert A. [Department of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2G7 (Canada); National Institute for Nanotechnology, National Research Council of Canada, Edmonton, Alberta, Canada T6G 2M9 (Canada)

    2014-05-01

    Highlights: • W(1 1 1) single atom tips (SATs) were exposed to air. • SATs could be regenerated by field assisted chemical etching after exposure. • Warming procedures to minimize tip contamination were developed. • Degassing temperatures for air exposed tips were established. • Tip faceting occurred when SATs and unetched tips were annealed above 1200 °C. - Abstract: Experiments aimed at assessing the robustness of nitrogen-etched, single-atom tips (SATs) prepared using W(1 1 1) single crystal wire were performed. Our experiments showed that single-atoms tips sustain minimal damage when exposed to atmospheric conditions and can be readily and quickly nitrogen-etched to single-atom tips thereafter. The SATs can be annealed at temperatures up to 1100 °C with minimal shape changes. Moreover, annealing temperatures in excess of 1200 °C resulted in an apex faceting which may prove important in further single-atom tip creation. Procedures for warming of the SATs from operating temperatures of 80 K were also evaluated to determine conditions that limit tip contamination. These results show that SATS could be fabricated in a dedicated vacuum system and subsequently transferred to other instruments where they would undergo a brief conditioning procedure to recover the single-atom apex configuration prior to being subjected to operating conditions.

  11. Trapping a single atom with a fraction of a photon using a photonic crystal nanocavity

    NARCIS (Netherlands)

    van Oosten, D.; Kuipers, L.

    2011-01-01

    We consider the interaction between a single rubidium atom and a photonic crystal nanocavity. Because of the ultrasmall mode volume of the nanocavity, an extremely strong coupling regime can be achieved in which the atom can shift the cavity resonance by many cavity linewidths. We show that this

  12. Iodinated bleomycin

    International Nuclear Information System (INIS)

    Lunghi, F.; Riva, P.; Assone, F.; Villa, M.; Plassic, G.

    1978-01-01

    Bleomycin was labelled with iodine-131 by the iodine monochloride method. Iodination did not alter the chemical and chromatographic features and ''in vitro'' stability studies on freeze-dried 131 I-Bleomycin having a specific activity of 1 mCi/mg, stored at different temperatures, showed no appreciable variation of the free-iodine content. Tissue distribution of 131 I-Bleomycin has been evaluated in tumor bearing rats. Patients have been injected with 0.5-1.0 mCi of 131 I-Bleomycin corresponding to a maximum of 1.5 mg. No adverse reactions have been observed. Total body scans have been performed at 2, 6, 24 and 48 hours after injection. The iodinated Bleomycin was rapidly distributed and cleared from the body and showed an early uptake in the neoplastic tissue. A diagnostic accuracy of 90% has been observed in malignant deseases, while no false positive results have been, at the moment, recorded. (author)

  13. Single Pt Atoms Confined into a Metal-Organic Framework for Efficient Photocatalysis.

    Science.gov (United States)

    Fang, Xinzuo; Shang, Qichao; Wang, Yu; Jiao, Long; Yao, Tao; Li, Yafei; Zhang, Qun; Luo, Yi; Jiang, Hai-Long

    2018-02-01

    It is highly desirable yet remains challenging to improve the dispersion and usage of noble metal cocatalysts, beneficial to charge transfer in photocatalysis. Herein, for the first time, single Pt atoms are successfully confined into a metal-organic framework (MOF), in which electrons transfer from the MOF photosensitizer to the Pt acceptor for hydrogen production by water splitting under visible-light irradiation. Remarkably, the single Pt atoms exhibit a superb activity, giving a turnover frequency of 35 h -1 , ≈30 times that of Pt nanoparticles stabilized by the same MOF. Ultrafast transient absorption spectroscopy further unveils that the single Pt atoms confined into the MOF provide highly efficient electron transfer channels and density functional theory calculations indicate that the introduction of single Pt atoms into the MOF improves the hydrogen binding energy, thus greatly boosting the photocatalytic H 2 production activity. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. 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.

  15. Single atom anisotropic magnetoresistance on a topological insulator surface

    KAUST Repository

    Narayan, Awadhesh; Rungger, Ivan; Sanvito, Stefano

    2015-01-01

    dimensional model valid for both single adatoms and magnetic clusters, which leads to a proposed device setup for experimental realization. Our results provide an explanation for the conflicting scattering experiments on magnetic adatoms on topological

  16. Photoionisation detection of single 87Rb-atoms using channel electron multipliers

    International Nuclear Information System (INIS)

    Henkel, Florian Alexander

    2011-01-01

    Fast and efficient detection of single atoms is a universal requirement concerning modern experiments in atom physics, quantum optics, and precision spectroscopy. In particular for future quantum information and quantum communication technologies, the efficient readout of qubit states encoded in single atoms or ions is an elementary prerequisite. The rapid development in the field of quantum optics and atom optics in the recent years has enabled to prepare individual atoms as quantum memories or arrays of single atoms as qubit registers. With such systems, the implementation of quantum computation or quantum communication protocols seems feasible. This thesis describes a novel detection scheme which enables fast and efficient state analysis of single neutral atoms. The detection scheme is based on photoionisation and consists of two parts: the hyperfine-state selective photoionisation of single atoms and the registration of the generated photoion-electron pairs via two channel electron multipliers (CEMs). In this work, both parts were investigated in two separate experiments. For the first step, a photoionisation probability of p ion =0.991 within an ionisation time of t ion =386 ns is achieved for a single 87 Rb-atom in an optical dipole trap. For the second part, a compact detection system for the ionisation fragments was developed consisting of two opposing CEM detectors. Measurements show that single neutral atoms can be detected via their ionisation fragments with a detection efficiency of η atom =0.991 within a detection time of t det =415.5 ns. In a future combined setup, this will allow the state-selective readout of optically trapped, single neutral 87 Rb-atoms via photoionisation detection with an estimated detection efficiency η=0.982 and a detection time of t tot = 802 ns. Although initially developed for single 87 Rb-atoms, the concept of photoionisation detection is in principle generally applicable to any atomic or molecular species. As efficient

  17. Photoionisation detection of single {sup 87}Rb-atoms using channel electron multipliers

    Energy Technology Data Exchange (ETDEWEB)

    Henkel, Florian Alexander

    2011-09-02

    Fast and efficient detection of single atoms is a universal requirement concerning modern experiments in atom physics, quantum optics, and precision spectroscopy. In particular for future quantum information and quantum communication technologies, the efficient readout of qubit states encoded in single atoms or ions is an elementary prerequisite. The rapid development in the field of quantum optics and atom optics in the recent years has enabled to prepare individual atoms as quantum memories or arrays of single atoms as qubit registers. With such systems, the implementation of quantum computation or quantum communication protocols seems feasible. This thesis describes a novel detection scheme which enables fast and efficient state analysis of single neutral atoms. The detection scheme is based on photoionisation and consists of two parts: the hyperfine-state selective photoionisation of single atoms and the registration of the generated photoion-electron pairs via two channel electron multipliers (CEMs). In this work, both parts were investigated in two separate experiments. For the first step, a photoionisation probability of p{sub ion}=0.991 within an ionisation time of t{sub ion}=386 ns is achieved for a single {sup 87}Rb-atom in an optical dipole trap. For the second part, a compact detection system for the ionisation fragments was developed consisting of two opposing CEM detectors. Measurements show that single neutral atoms can be detected via their ionisation fragments with a detection efficiency of {eta}{sub atom}=0.991 within a detection time of t{sub det}=415.5 ns. In a future combined setup, this will allow the state-selective readout of optically trapped, single neutral {sup 87}Rb-atoms via photoionisation detection with an estimated detection efficiency {eta}=0.982 and a detection time of t{sub tot} = 802 ns. Although initially developed for single {sup 87}Rb-atoms, the concept of photoionisation detection is in principle generally applicable to any

  18. Atomic and nuclear parameters of single electron capture decaying nuclides

    International Nuclear Information System (INIS)

    Grau, A.

    1981-01-01

    Atomic and nuclear parameters of the following nuclides which decay by electron capture have been calculated: 37 A r, 41 C a, 49 V , 53 M n, 55 F e,59 N i, 68Ge,82 S r, 97 T c, 118 T e, 131 C s, 137 L a, 140 N d, 157 T b, 165 E r, 193 p t, 194 H g, and 205 P h The evaluation rules are included in the first part of the paper. The values and the associated uncertainties of the following parameters have been tabulated: decay energy, electron capture probabilities, fluorescence yield, electron emission and X-ray emission. (Author) 27 refs

  19. Fast Excitation and Photon Emission of a Single-Atom-Cavity System

    International Nuclear Information System (INIS)

    Bochmann, J.; Muecke, M.; Langfahl-Klabes, G.; Erbel, C.; Weber, B.; Specht, H. P.; Moehring, D. L.; Rempe, G.

    2008-01-01

    We report on the fast excitation of a single atom coupled to an optical cavity using laser pulses that are much shorter than all other relevant processes. The cavity frequency constitutes a control parameter that allows the creation of single photons in a superposition of two tunable frequencies. Each photon emitted from the cavity thus exhibits a pronounced amplitude modulation determined by the oscillatory energy exchange between the atom and the cavity. Our technique constitutes a versatile tool for future quantum networking experiments

  20. Teleportation of a two-atom entangled state using a single EPR pair in cavity QED

    Institute of Scientific and Technical Information of China (English)

    Ji Xin; Li Ke; Zhang Shou

    2006-01-01

    We propose a scheme for teleporting a two-atom entangled state in cavity quantum electrodynamics(QED).In the scheme,we choose a single Einstein-Podolsky-Rosen (EPR) pair as the quantum channel which is shared by the sender and the receiver.By using the atom-cavity-field interaction and introducing an additional atom,we can teleport the two-atom entangled state successfully with a probability of 1.0.Moreover,we show that the scheme is insensitive to cavity decay and thermal field.

  1. Single-Atom Pt as Co-Catalyst for Enhanced Photocatalytic H2 Evolution.

    Science.gov (United States)

    Li, Xiaogang; Bi, Wentuan; Zhang, Lei; Tao, Shi; Chu, Wangsheng; Zhang, Qun; Luo, Yi; Wu, Changzheng; Xie, Yi

    2016-03-23

    Isolated single-atom platinum (Pt) embedded in the sub-nanoporosity of 2D g-C3 N4 as a new form of co-catalyst is reported. The highly stable single-atom co-catalyst maximizes the atom efficiency and alters the surface trap states of g-C3 N4 , leading to significantly enhanced photocatalytic H2 evolution activity, 8.6 times higher than that of Pt nanoparticles and up to 50 times that for bare g-C3 N4 . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Interactions between C and Cu atoms in single-layer graphene: direct observation and modelling.

    Science.gov (United States)

    Kano, Emi; Hashimoto, Ayako; Kaneko, Tomoaki; Tajima, Nobuo; Ohno, Takahisa; Takeguchi, Masaki

    2016-01-07

    Metal doping into the graphene lattice has been studied recently to develop novel nanoelectronic devices and to gain an understanding of the catalytic activities of metals in nanocarbon structures. Here we report the direct observation of interactions between Cu atoms and single-layer graphene by transmission electron microscopy. We document stable configurations of Cu atoms in the graphene sheet and unique transformations of graphene promoted by Cu atoms. First-principles calculations based on density functional theory reveal a reduction of energy barrier that caused rotation of C-C bonds near Cu atoms. We discuss two driving forces, electron irradiation and in situ heating, and conclude that the observed transformations were mainly promoted by electron irradiation. Our results suggest that individual Cu atoms can promote reconstruction of single-layer graphene.

  3. Three-dimensional rearrangement of single atoms using actively controlled optical microtraps.

    Science.gov (United States)

    Lee, Woojun; Kim, Hyosub; Ahn, Jaewook

    2016-05-02

    We propose and demonstrate three-dimensional rearrangements of single atoms. In experiments performed with single 87Rb atoms in optical microtraps actively controlled by a spatial light modulator, we demonstrate various dynamic rearrangements of up to N = 9 atoms including rotation, 2D vacancy filling, guiding, compactification, and 3D shuffling. With the capability of a phase-only Fourier mask to generate arbitrary shapes of the holographic microtraps, it was possible to place single atoms at arbitrary geometries of a few μm size and even continuously reconfigure them by conveying each atom. For this purpose, we loaded a series of computer-generated phase masks in the full frame rate of 60 Hz of the spatial light modulator, so the animation of phase mask transformed the holographic microtraps in real time, driving each atom along the assigned trajectory. Possible applications of this method of transformation of single atoms include preparation of scalable quantum platforms for quantum computation, quantum simulation, and quantum many-body physics.

  4. Nanosheet Supported Single-Metal Atom Bifunctional Catalyst for Overall Water Splitting.

    Science.gov (United States)

    Ling, Chongyi; Shi, Li; Ouyang, Yixin; Zeng, Xiao Cheng; Wang, Jinlan

    2017-08-09

    Nanosheet supported single-atom catalysts (SACs) can make full use of metal atoms and yet entail high selectivity and activity, and bifunctional catalysts can enable higher performance while lowering the cost than two separate unifunctional catalysts. Supported single-atom bifunctional catalysts are therefore of great economic interest and scientific importance. Here, on the basis of first-principles computations, we report a design of the first single-atom bifunctional eletrocatalyst, namely, isolated nickel atom supported on β 12 boron monolayer (Ni 1 /β 12 -BM), to achieve overall water splitting. This nanosheet supported SAC exhibits remarkable electrocatalytic performance with the computed overpotential for oxygen/hydrogen evolution reaction being just 0.40/0.06 V. The ab initio molecular dynamics simulation shows that the SAC can survive up to 800 K elevated temperature, while enacting a high energy barrier of 1.68 eV to prevent isolated Ni atoms from clustering. A viable experimental route for the synthesis of Ni 1 /β 12 -BM SAC is demonstrated from computer simulation. The desired nanosheet supported single-atom bifunctional catalysts not only show great potential for achieving overall water splitting but also offer cost-effective opportunities for advancing clean energy technology.

  5. Spin magnetic moments from single atoms to small Cr clusters

    Energy Technology Data Exchange (ETDEWEB)

    Boeglin, C.; Decker, R.; Bulou, H.; Scheurer, F.; Chado, I. [IPCMS-GSI - UMR 7504, 67037 Strasbourg Cedex (France); Ohresser, P. [LURE, 91405 Orsay (France); Dhesi, S.S. [ESRF, BP 220, 38043 Grenoble Cedex (France); Present permanent address: Diamond Light Source, Chilton, Didcot OX11 0QX (United Kingdom); Gaudry, E. [LMCP, 4, place Jussieu, 75252 Paris (France); Lazarovits, B. [CCMS, T.U. Vienna, Gumpendorfstr. 1a, 1060 Wien (Austria)

    2005-07-01

    Morphology studies at the first stages of the growth of Cr/Au(111) are reported and compared to the magnetic properties of the nanostructures. We analyze by Scanning Tunneling Microscopy and Low Energy Electron Diffraction the Cr clusters growth between 200 K and 300 K. In the early stages of the growth the morphology of the clusters shows monoatomic high islands located at the kinks of the herringbone reconstructed Au(111) surface. By X-ray Magnetic Circular Dichroism performed on the Cr L{sub 2,3} edges it is shown that the temperature dependent morphology strongly influences the magnetic properties of the Cr clusters. We show that in the sub-monolayer regime Cr clusters are antiferromagnetic and paramagnetic when the size reaches the atomic limit. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Highly Durable Platinum Single-Atom Alloy Catalyst for Electrochemical Reactions

    DEFF Research Database (Denmark)

    Kim, Jiwhan; Roh, Chi-Woo; Sahoo, Suman Kalyan

    2018-01-01

    Single atomic Pt catalyst can offer efficient utilization of the expensive platinum and provide unique selectivity because it lacks ensemble sites. However, designing such a catalyst with high Pt loading and good durability is very challenging. Here, single atomic Pt catalyst supported on antimony...... functional theory calculations show that replacing Sb sites with Pt atoms in the bulk phase or at the surface of SbSn or ATO is energetically favorable. The Pt1/ATO shows superior activity and durability for formic acid oxidation reaction, compared to a commercial Pt/C catalyst. The single atomic Pt...... structure is retained even after a harsh durability test, which is performed by repeating cyclic voltammetry in the range of 0.05–1.4 V for 1800 cycles. A full cell is fabricated for direct formic acid fuel cell using the Pt1/ATO as an anode catalyst, and an order of magnitude higher cell power is obtained...

  7. Atomic structures and mechanical properties of single-crystal GaN nanotubes

    International Nuclear Information System (INIS)

    Xu, B.; Lu, A.J.; Pan, B.C.; Yu, Q.X.

    2005-01-01

    An approach is proposed to theoretically construct a realistic single-crystal GaN nanotube at atomic scale. The generated atomic structures of the single-crystal GaN nanotubes match the structural aspects from experiment very well. Our energetic calculations show that a single-crystal GaN nanotube with [100]-oriented lateral facets is more stable than that with [110]-oriented lateral facets, when they have around the same wall thickness. For a specified orientation of the lateral facets on the single-crystal GaN nanotubes, the energetic stabilities of the tubes obey a P rule, in which P is the ratio of the number of four-coordinated atoms to the number of three-coordinated atoms. Furthermore, the Young's modulus of the considered GaN nanotubes decrease with increasing the ratio of the number of bulk atoms to the number of surface atoms in each type of tube. Our calculations and analysis demonstrate that the surface effect of a single-crystal nanotube enhances its Young's modulus significantly

  8. Atomically flat single-crystalline gold nanostructures for plasmonic nanocircuitry

    Energy Technology Data Exchange (ETDEWEB)

    Huang, J S; Geisler, P; Bruening, C; Kern, J; Prangsma, J C; Wu, X; Feichtner, Thorsten; Ziegler, J; Weinmann, P; Kamp, M; Forchel, A; Hecht, B [Wilhelm-Conrad-Roentgen-Center for Complex Material Systems, University of Wuerzburg (Germany); Biagioni, P [CNISM, Dipartimento di Fisica, Politecnico di Milano (Italy)

    2011-07-01

    Deep subwavelength integration of high-definition plasmonic nano-structures is of key importance for the development of future optical nanocircuitry. So far the experimental realization of proposed extended plasmonic networks remains challenging, mainly due to the multi-crystallinity of commonly used thermally evaporated gold layers. Resulting structural imperfections in individual circuit elements drastically reduce the yield of functional integrated nanocircuits. Here we demonstrate the use of very large but thin chemically grown single-crystalline gold flakes. After immobilization on any arbitrary surface, they serve as an ideal basis for focused-ion beam milling. We present high-definition ultra-smooth gold nanostructures with reproducible nanosized features over micrometer lengthscales. By comparing multi- and single-crystalline optical antennas we prove that the latter have superior optical properties which are in good agreement with numerical simulations.

  9. Iodine poisoning

    Science.gov (United States)

    ... Iodine is also used during the production of methamphetamine. Note: This list may not be all inclusive. ... breathing machine (ventilator) Blood and urine tests Chest x-ray EKG (electrocardiogram, or heart tracing) Fluids through a ...

  10. Multimode electromagnetically induced transparency on a single atomic line

    International Nuclear Information System (INIS)

    Campbell, Geoff; Ordog, Anna; Lvovsky, A I

    2009-01-01

    We experimentally investigate electromagnetically induced transparency (EIT) created on an inhomogeneously broadened 5S 1/2 -5P 1/2 transition in rubidium vapor using a control field of a complex temporal shape. A comb-shaped transparency spectrum enhances the delay-bandwidth product and the light storage capacity for a matched probe pulse by a factor of about 50 compared to a single EIT line (Yavuz 2007 Phys. Rev. A 75 031801). If the temporal mode of the control field is slowly changed while the probe is propagating through the EIT medium, the probe will adiabatically follow, providing a means to perform frequency conversion and optical routing.

  11. Digital atom interferometer with single particle control on a discretized space-time geometry.

    Science.gov (United States)

    Steffen, Andreas; Alberti, Andrea; Alt, Wolfgang; Belmechri, Noomen; Hild, Sebastian; Karski, Michał; Widera, Artur; Meschede, Dieter

    2012-06-19

    Engineering quantum particle systems, such as quantum simulators and quantum cellular automata, relies on full coherent control of quantum paths at the single particle level. Here we present an atom interferometer operating with single trapped atoms, where single particle wave packets are controlled through spin-dependent potentials. The interferometer is constructed from a sequence of discrete operations based on a set of elementary building blocks, which permit composing arbitrary interferometer geometries in a digital manner. We use this modularity to devise a space-time analogue of the well-known spin echo technique, yielding insight into decoherence mechanisms. We also demonstrate mesoscopic delocalization of single atoms with a separation-to-localization ratio exceeding 500; this result suggests their utilization beyond quantum logic applications as nano-resolution quantum probes in precision measurements, being able to measure potential gradients with precision 5 x 10(-4) in units of gravitational acceleration g.

  12. Spin fluctuation effects on the conductance through a single Pd atom contact

    International Nuclear Information System (INIS)

    Romero, M A; Goldberg, E C; Gomez-Carrillo, S C; Bolcatto, P G

    2009-01-01

    A controversy about the conductance through single atoms still exists. There are many experiments where values lower than the quantum unity G 0 = 2e 2 /h have been found associated to Kondo regimes with high Kondo temperatures. Specifically in the Pd single atom contact, conductance values close to G 0 /2 at room temperature have been reported. In this work we propose a theoretical analysis of a break junction of Pd where the charge fluctuation in the single atom contact is limited to the most probable one: d 10 ↔d 9 . The projected density of states and the characteristics of the electron transport are calculated by using a realistic description of the interacting system. A Kondo regime is found where the conductance values and their dependence on temperature are in good agreement with the experimental trends observed in the conduction of single molecule transistors based on transition metal coordination complexes.

  13. Concept for room temperature single-spin tunneling force microscopy with atomic spatial resolution

    Science.gov (United States)

    Payne, Adam

    A study of a force detected single-spin magnetic resonance measurement concept with atomic spatial resolution is presented. The method is based upon electrostatic force detection of spin-selection rule controlled single electron tunneling between two electrically isolated paramagnetic states. Single-spin magnetic resonance detection is possible by measuring the force detected tunneling charge noise on and off spin resonance. Simulation results of this charge noise, based upon physical models of the tunneling and spin physics, are directly compared to measured atomic force microscopy (AFM) system noise. The results show that the approach could provide single-spin measurement of electrically isolated defect states with atomic spatial resolution at room temperature.

  14. Atomic-resolution single-spin magnetic resonance detection concept based on tunneling force microscopy

    Science.gov (United States)

    Payne, A.; Ambal, K.; Boehme, C.; Williams, C. C.

    2015-05-01

    A study of a force detected single-spin magnetic resonance measurement concept with atomic spatial resolution is presented. The method is based upon electrostatic force detection of spin-selection rule controlled single-electron tunneling between two electrically isolated paramagnetic states. Single-spin magnetic resonance detection is possible by measuring the force detected tunneling charge noise on and off spin resonance. Simulation results of this charge noise, based upon physical models of the tunneling and spin physics, are directly compared to measured atomic force microscopy system noise. The results show that the approach could provide single-spin measurement of electrically isolated qubit states with atomic spatial resolution at room temperature.

  15. Single Cobalt Atoms with Precise N-Coordination as Superior Oxygen Reduction Reaction Catalysts.

    Science.gov (United States)

    Yin, Peiqun; Yao, Tao; Wu, Yuen; Zheng, Lirong; Lin, Yue; Liu, Wei; Ju, Huanxin; Zhu, Junfa; Hong, Xun; Deng, Zhaoxiang; Zhou, Gang; Wei, Shiqiang; Li, Yadong

    2016-08-26

    A new strategy for achieving stable Co single atoms (SAs) on nitrogen-doped porous carbon with high metal loading over 4 wt % is reported. The strategy is based on a pyrolysis process of predesigned bimetallic Zn/Co metal-organic frameworks, during which Co can be reduced by carbonization of the organic linker and Zn is selectively evaporated away at high temperatures above 800 °C. The spherical aberration correction electron microscopy and extended X-ray absorption fine structure measurements both confirm the atomic dispersion of Co atoms stabilized by as-generated N-doped porous carbon. Surprisingly, the obtained Co-Nx single sites exhibit superior ORR performance with a half-wave potential (0.881 V) that is more positive than commercial Pt/C (0.811 V) and most reported non-precious metal catalysts. Durability tests revealed that the Co single atoms exhibit outstanding chemical stability during electrocatalysis and thermal stability that resists sintering at 900 °C. Our findings open up a new routine for general and practical synthesis of a variety of materials bearing single atoms, which could facilitate new discoveries at the atomic scale in condensed materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Theoretical study on the photocatalytic properties of graphene oxide with single Au atom adsorption

    Science.gov (United States)

    Ju, Lin; Dai, Ying; Wei, Wei; Li, Mengmeng; Jin, Cui; Huang, Baibiao

    2018-03-01

    The photocatalytic properties of graphene oxide (GO) with single Au atom adsorption are studied via the first-principles calculations based on the density functional theory. The present study addresses the origin of enhancement in photocatalytic efficiency of GO derived from single Au atom depositing. Compared with the clean one, the work function of the single Au atom adsorbed GO is lowered due to the charge transfer from Au to GO, indicating enhanced surface activity. The Au atom plays as an electron trapping center and a mediating role in charge transfer from photon excited GO to target species. The photogenerated electron-hole pairs can be separated effectively. For the GO configuration with atomic Au dispersion, there are some states introduced in the band gap, which are predominantly composed of Au 6s states. Through the in-gap state, the photo-generated electron transfer from the valence band of clean GO to the conductive band more easily. In addition, the reduction of the gap in the system is also presented in the current work, which indicates that the single Au atom adsorption improves light absorption for the GO based photocatalyst. These theoretical results are valuable for the future applications of GO materials as photocatalyst for water splitting.

  17. Probabilistic Cloning of two Single-Atom States via Thermal Cavity

    Science.gov (United States)

    Rui, Pin-Shu; Liu, Dao-Jun

    2016-12-01

    We propose a cavity QED scheme for implementing the 1 → 2 probabilistic quantum cloning (PQC) of two single-atom states. In our scheme, after the to-be-cloned atom and the assistant atom passing through the first cavity, a measurement is carried out on the assistant atom. Based on the measurement outcome we can judge whether the PQC should be continued. If the cloning fails, the other operations are omitted. This makes our scheme economical. If the PQC is continued (with the optimal probability) according to the measurement outcome, two more cavities and some unitary operations are used for achieving the PQC in a deterministic way. Our scheme is insensitive to the decays of the cavities and the atoms.

  18. Precision in single atom localization via Raman-driven coherence: Role of detuning and phase shift

    Energy Technology Data Exchange (ETDEWEB)

    Rahmatullah,; Qamar, Sajid, E-mail: sajid_qamar@comsats.edu.pk

    2013-10-01

    Role of detuning and phase shift associated with the standing-wave driving fields is revisited for precision position measurement of single atom during its motion through two standing-wave fields. A four-level atomic system in diamond configuration is considered where the intermediate levels are coupled to upper and lower level via standing-wave driving fields and atomic decay channels, respectively. The former is responsible for the generation of quantum mechanical coherence via two-photon Raman transition while the latter leads to spontaneous emission of a photon. Due to standing-wave driving fields the atom–field interaction becomes position-dependent and measurement of the frequency of spontaneously emitted photon gives the position information of the atom. The unique position of the atom with much higher spatial resolution, i.e., of the order of λ/100 is observed using detuning and phase shift associated with the standing-wave driving fields.

  19. Iodine in diet

    Science.gov (United States)

    Diet - iodine ... Many months of iodine deficiency in a person's diet may cause goiter or hypothyroidism . Without enough iodine, ... and older children. Getting enough iodine in the diet may prevent a form of physical and intellectual ...

  20. Continuous imaging of a single neutral atom in a variant magneto-optical trap

    International Nuclear Information System (INIS)

    Xia Tian; Zhou Shuyu; Chen Peng; Li Lin; Hong Tao; Wang Yuzhu

    2010-01-01

    We demonstrate continuous imaging of a single 87 Rb atom confined in a steep magneto-optical trap with an electron-multiplying charge-coupled device (EMCCD) camera and realize a one-dimensional micro-optical trap array with a Dammann grating. We adopt several methods to reduce the noise in the fluorescence signal we obtain with the EMCCD. Step jumping characteristics of the fluorescence demonstrate capturing and losing of individual atoms. (authors)

  1. Iodine-123 metaiodobenzylguanidine scintigraphy and iodine-123 ioflupane single photon emission computed tomography in Lewy body diseases: complementary or alternative techniques?

    Science.gov (United States)

    Treglia, Giorgio; Cason, Ernesto; Cortelli, Pietro; Gabellini, Anna; Liguori, Rocco; Bagnato, Antonio; Giordano, Alessandro; Fagioli, Giorgio

    2014-01-01

    To compare myocardial sympathetic imaging using (123)I-Metaiodobenzylguanidine (MIBG) scintigraphy and striatal dopaminergic imaging using (123)I-Ioflupane (FP-CIT) single photon emission computed tomography (SPECT) in patients with suspected Lewy body diseases (LBD). Ninety-nine patients who performed both methods within 2 months for differential diagnosis between Parkinson's disease (PD) and other parkinsonism (n = 68) or between dementia with Lewy bodies (DLB) and other dementia (n = 31) were enrolled. Sensitivity, specificity, accuracy, positive and negative predictive values of both methods were calculated. For (123) I-MIBG scintigraphy, the overall sensitivity, specificity, accuracy, positive and negative predictive values in LBD were 83%, 79%, 82%, 86%, and 76%, respectively. For (123)I-FP-CIT SPECT, the overall sensitivity, specificity, accuracy, positive and negative predictive values in LBD were 93%, 41%, 73%, 71%, and 80%, respectively. There was a statistically significant difference between these two methods in patients without LBD, but not in patients with LBD. LBD usually present both myocardial sympathetic and striatal dopaminergic impairments. (123)I-FP-CIT SPECT presents high sensitivity in the diagnosis of LBD; (123)I-MIBG scintigraphy may have a complementary role in differential diagnosis between PD and other parkinsonism. These scintigraphic methods showed similar diagnostic accuracy in differential diagnosis between DLB and other dementia. Copyright © 2012 by the American Society of Neuroimaging.

  2. Modelling the chemistry of iodine

    International Nuclear Information System (INIS)

    Paquette, J.

    1989-01-01

    We have assembled a kinetic model, based on elementary chemical reactions, that describes the chemical behaviour of iodine in aqueous solution as a function of time and various parameters such as pH, concentration and radiation field. The model is conceptually divided into six section: aqueous iodine chemistry, aqueous organic iodide chemistry, water radiolysis, radiolysis of iodine solutions, radiolysis of organic iodide solutions and mass transfer. The model indicates that, in the absence of a radiation field, the rate of production of volatile iodine species is controlled by the rate of oxidation of the iodide ion. The volatile iodine species are dominated by organic iodides if organic impurities are present. The single most important parameter controlling iodine volatility is the pH of the solution; high pH values tend to minimize iodine volatility. In the presence of a radiation field, the volatility of iodine is controlled by the radiation-induced oxidation of the iodide ion. Again, iodine volatility is dominated by organic iodides if organic impurities are present. High pH values minimize iodine volatility. A sensitivity analysis has been performed on some sections of the model to identify reactions to which the volatility of iodine is most sensitive. In the absence of a radiation field, the volatility is most sensitive, first, to the rate of oxidation of the iodide ion, and, second, to the rate of mass transfer of volatile species between the aqueous and the gaseous phases. This approach should be useful in identifying reactions for which accurate rate constants are required and in decreasing the complexity of the model. 37 refs

  3. Single-atom trapping and transport in DMD-controlled optical tweezers

    Science.gov (United States)

    Stuart, Dustin; Kuhn, Axel

    2018-02-01

    We demonstrate the trapping and manipulation of single neutral atoms in reconfigurable arrays of optical tweezers. Our approach offers unparalleled speed by using a Texas instruments digital micro-mirror device as a holographic amplitude modulator with a frame rate of 20 000 per second. We show the trapping of static arrays of up to 20 atoms, as well as transport of individually selected atoms over a distance of 25 μm with laser cooling and 4 μm without. We discuss the limitations of the technique and the scope for technical improvements.

  4. Conductance of single atoms and molecules studied with a scanning tunnelling microscope

    International Nuclear Information System (INIS)

    Neel, N; Kroeger, J; Limot, L; Berndt, R

    2007-01-01

    The conductance of single atoms and molecules is investigated with a low-temperature scanning tunnelling microscope. In a controlled and reproducible way, clean Ag(111) surfaces, individual silver atoms on Ag(111) as well as individual C 60 molecules adsorbed on Cu(100) are contacted with the tip of the microscope. Upon contact the conductance changes discontinuously in the case of the tip-surface junction while the tip-atom and tip-molecule junctions exhibit a continuous transition from the tunnelling to the contact regime

  5. Single photon transport by a moving atom through sub-wavelength hole

    International Nuclear Information System (INIS)

    Afanasiev, A.E.; Melentiev, P.N.; Kuzin, A.A.; Kalatskiy, A.Yu.; Balykin, V.I.

    2017-01-01

    The results of investigation of photon transport through the subwavelength hole in the opaque screen by using single neutral atom are represented. The basis of the proposed and implemented method is the absorption of a photon by a neutral atom immediately before the subwavelength aperture, traveling of the atoms through the hole and emission of a photon on the other side of the screen. Realized method is the alternative approach to existing for photon transport through a subwavelength aperture: 1) self-sustained transmittance of a photon through the aperture according to the Bethe’s model; 2) extra ordinary transmission because of surface-plasmon excitation.

  6. Cooperative single-photon subradiant states in a three-dimensional atomic array

    Energy Technology Data Exchange (ETDEWEB)

    Jen, H.H., E-mail: sappyjen@gmail.com

    2016-11-15

    We propose a complete superradiant and subradiant states that can be manipulated and prepared in a three-dimensional atomic array. These subradiant states can be realized by absorbing a single photon and imprinting the spatially-dependent phases on the atomic system. We find that the collective decay rates and associated cooperative Lamb shifts are highly dependent on the phases we manage to imprint, and the subradiant state of long lifetime can be found for various lattice spacings and atom numbers. We also investigate both optically thin and thick atomic arrays, which can serve for systematic studies of super- and sub-radiance. Our proposal offers an alternative scheme for quantum memory of light in a three-dimensional array of two-level atoms, which is applicable and potentially advantageous in quantum information processing. - Highlights: • Cooperative single-photon subradiant states in a three-dimensional atomic array. • Subradiant state manipulation via spatially-increasing phase imprinting. • Quantum storage of light in the subradiant state in two-level atoms.

  7. Limits on visibility of single heavy atoms in the scanning transmission electron microscope: an experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Wall, J.S.

    1979-01-01

    Theoretical calculations of the visibility of single heavy atoms on thin carbon substrates have predicted higher signal to noise ratios then experimentally observed. Six experimental measurements were performed to determine where the theory is inadequate, five to determine the absolute value of heavy atom scattering cross sections in practical units, and one to determine substrate noise in some practical units. The practical unit of measure was chosen to be the scattering power of one carbon atom as determined by an internal standard, Tobacco Mosaic Virus. Measurements were performed on the following targets on thin carbon substrates: single isolated uranium atoms; silicotungstate clusters; colloidal platinum particles; fd bacteriophage embedded in negative strain; and fd bacteriophage reacted with a known quantity of heavy atom reagent. These measurements suggest that the scattering power of one heavy atom is approximately 9 +- 4 carbon atom equivalents, instead of 15 to 24 predicted by theory. The same techniques were used to measure intensity fluctuations from area to area of a clean substrate. Substrate noise was found to be less than expected for squares of width less than 10A, but up to 2.5 times greater than expected for larger squares. These signal and noise measurements have been combined to give an empirical formula for calculating signal to noise ratios from specimen and microscope parameters.

  8. Experimental study of single-electron loss by Ar+ ions in rare-gas atoms

    Science.gov (United States)

    Reyes, P. G.; Castillo, F.; Martínez, H.

    2001-04-01

    Absolute differential and total cross sections for single-electron loss were measured for Ar+ ions on rare-gas atoms in the laboratory energy range of 1.5 to 5.0 keV. The electron loss cross sections for all the targets studied are found to be in the order of magnitude between 10-19 and 10-22 cm2, and show a monotonically increasing behaviour as a function of the incident energy. The behaviour of the total single-electron loss cross sections with the atomic target number, Zt, shows different dependences as the collision energy increases. In all cases the present results display experimental evidence of saturation in the single-electron loss cross section as the atomic number of the target increases.

  9. Adsorption modes of molecular iodine on defected boron nitrides: A DFT study

    Science.gov (United States)

    Arabieh, Masoud; Azar, Yavar Taghipour

    2018-03-01

    The interaction of molecular iodine with pristine and monovacant boron-nitride quantum dots (QDs) have been investigated using density functional theory. It was found that removing one B or N single atom significantly decreased the calculated Eg values at various exchange functional. In B-defected BN system, the localized spin densities canceled each other and overall polarization of system was found to be equal to unity. For N-defected system there was smaller spin densities localized on each closest B atoms. Both B- and N-vacancies caused appearance of new states in gap region. Our calculation revealed that spin density and polarization of defected system are localized on vacancy region and other atoms did not take part in this polarization. The results of electron localization function for N-DBN showed there was high density region at the position of removed nitrogen atom. The calculated adsorption energies implied that there was no significant chemical interaction between iodine molecule and pristine BN sheet. We suggested that when a deficiency was imposed to the BN sheet, the reactivity of the modified system toward iodine molecule significantly could increase. We found strong interaction between iodine and nitrogen atoms of B-DBN system. In the case of I2/N-DBN system the neighbor atoms had no contribution in spin polarization of the system and it seemed that all spin density of system transferred to the iodine molecule after adsorption. Strong correlation between molecular iodine orientation and BN-QDs via their interactions type has been clarified in this work. These findings may provide a deeper insight into halogen molecules interactions with low dimensional defected boron nitrides.

  10. 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)

  11. Metal-Insulator-Metal Single Electron Transistors with Tunnel Barriers Prepared by Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Golnaz Karbasian

    2017-03-01

    Full Text Available Single electron transistors are nanoscale electron devices that require thin, high-quality tunnel barriers to operate and have potential applications in sensing, metrology and beyond-CMOS computing schemes. Given that atomic layer deposition is used to form CMOS gate stacks with low trap densities and excellent thickness control, it is well-suited as a technique to form a variety of tunnel barriers. This work is a review of our recent research on atomic layer deposition and post-fabrication treatments to fabricate metallic single electron transistors with a variety of metals and dielectrics.

  12. Quantum optics. All-optical routing of single photons by a one-atom switch controlled by a single photon.

    Science.gov (United States)

    Shomroni, Itay; Rosenblum, Serge; Lovsky, Yulia; Bechler, Orel; Guendelman, Gabriel; Dayan, Barak

    2014-08-22

    The prospect of quantum networks, in which quantum information is carried by single photons in photonic circuits, has long been the driving force behind the effort to achieve all-optical routing of single photons. We realized a single-photon-activated switch capable of routing a photon from any of its two inputs to any of its two outputs. Our device is based on a single atom coupled to a fiber-coupled, chip-based microresonator. A single reflected control photon toggles the switch from high reflection (R ~ 65%) to high transmission (T ~ 90%), with an average of ~1.5 control photons per switching event (~3, including linear losses). No additional control fields are required. The control and target photons are both in-fiber and practically identical, making this scheme compatible with scalable architectures for quantum information processing. Copyright © 2014, American Association for the Advancement of Science.

  13. Dynamics of an atomic wave packet in a standing-wave cavity field: A cavity-assisted single-atom detection

    International Nuclear Information System (INIS)

    Chough, Young-Tak; Nha, Hyunchul; Kim, Sang Wook; An, Kyungwon; Youn, Sun-Hyun

    2002-01-01

    We investigate the single-atom detection system using an optical standing-wave cavity, from the viewpoint of the quantized center-of-mass motion of the atomic wave packet. We show that since the atom-field coupling strength depends upon the overlap integral of the atomic wave packet and the field mode function, the effect of the wave-packet spreading via the momentum exchange process brings about a significant effect in the detection efficiency. We find that, as a result, the detection efficiency is not sensitive to the individual atomic trajectory for reasonably slow atoms. We also address an interesting phenomenon of the atomic wave-packet splitting occurring when an atom passes through a node of the cavity field

  14. Revisiting the inelastic electron tunneling spectroscopy of single hydrogen atom adsorbed on the Cu(100) surface

    International Nuclear Information System (INIS)

    Jiang, Zhuoling; Wang, Hao; Sanvito, Stefano; Hou, Shimin

    2015-01-01

    Inelastic electron tunneling spectroscopy (IETS) of a single hydrogen atom on the Cu(100) surface in a scanning tunneling microscopy (STM) configuration has been investigated by employing the non-equilibrium Green’s function formalism combined with density functional theory. The electron-vibration interaction is treated at the level of lowest order expansion. Our calculations show that the single peak observed in the previous STM-IETS experiments is dominated by the perpendicular mode of the adsorbed H atom, while the parallel one only makes a negligible contribution even when the STM tip is laterally displaced from the top position of the H atom. This propensity of the IETS is deeply rooted in the symmetry of the vibrational modes and the characteristics of the conduction channel of the Cu-H-Cu tunneling junction, which is mainly composed of the 4s and 4p z atomic orbitals of the Cu apex atom and the 1s orbital of the adsorbed H atom. These findings are helpful for deepening our understanding of the propensity rules for IETS and promoting IETS as a more popular spectroscopic tool for molecular devices

  15. Continuous parametric feedback cooling of a single atom in an optical cavity

    Science.gov (United States)

    Sames, C.; Hamsen, C.; Chibani, H.; Altin, P. A.; Wilk, T.; Rempe, G.

    2018-05-01

    We demonstrate a feedback algorithm to cool a single neutral atom trapped inside a standing-wave optical cavity. The algorithm is based on parametric modulation of the confining potential at twice the natural oscillation frequency of the atom, in combination with fast and repetitive atomic position measurements. The latter serve to continuously adjust the modulation phase to a value for which parametric excitation of the atomic motion is avoided. Cooling is limited by the measurement backaction which decoheres the atomic motion after only a few oscillations. Nonetheless, applying this feedback scheme to an ˜5 -kHz oscillation mode increases the average storage time of a single atom in the cavity by a factor of 60 to more than 2 s. In contrast to previous feedback schemes, our algorithm is also capable of cooling a much faster ˜500 -kHz oscillation mode within just microseconds. This demonstrates that parametric cooling is a powerful technique that can be applied in all experiments where optical access is limited.

  16. An assessment of memristor intrinsic fluctuations: a measurement of single atomic motion

    Science.gov (United States)

    Borghetti, Julien; Yang, J. Joshua; Medeiros-Ribeiro, Gilberto; Williams, R. Stanley

    2010-03-01

    Memristors provides electrically tunable resistance for upcoming non-volatile memory and future neuromorphic computing. One of the key benefits of such a device is its scalability, which can be demonstrated from an architectural perspective as well as from a fundamental physics limit. 4D addressing schemes utilizing cross bar structures that can be stacked several layers high above the chip embodies unlimited addressing space. On the other limit, the basic operating principles of memristive devices allow one to reach storage of information in a single atom. In this report of nanoscale (sub 50nm) devices, we detect single atom fluctuations, which would then represent the ultimate limit for noise sources thus delineating the boundary conditions for circuit design. We show that electrically induced individual atom migrations do not affect the overall device atomic configuration until a critical bias where a single local fluctuation triggers a general atomic reconfiguration. This instability illustrates the robustness of the device non-volatility upon small electrical stress.

  17. Collective excitations in circular atomic configurations and single-photon traps

    International Nuclear Information System (INIS)

    Hammer, Hanno

    2004-01-01

    Correlated excitations in a plane circular configuration of identical atoms with parallel dipole moments are investigated. The collective energy eigenstates, which are formally identical to Frenkel excitons, can be computed together with their level shifts and decay rates by decomposing the atomic state space into carrier spaces for the irreducible representations of the symmetry group Z N of the circle. It is shown that the index p of these representations can be used as a quantum number analogously to the orbital angular momentum quantum number l in hydrogenlike systems. Just as the hydrogen s states are the only electronic wave functions which can occupy the central region of the Coulomb potential, the quasiparticle corresponding to a collective excitation of the atoms in the circle can occupy the central atom only for vanishing Z N quantum number p. If a central atom is present, the p=0 state splits into two and shows level crossing at certain radii; in the regions between these radii, damped quantum beats between two 'extreme' p=0 configurations occur. The physical mechanisms behind super- and subradiance at a given radius are discussed. It is shown that, beyond a certain critical number of atoms in the circle, the lifetime of the maximally subradiant state increases exponentially with the number of atoms in the configuration, making the system a natural candidate for a single-photon trap

  18. Understanding strong-field coherent control: Measuring single-atom versus collective dynamics

    International Nuclear Information System (INIS)

    Trallero-Herrero, Carlos; Weinacht, Thomas; Spanner, Michael

    2006-01-01

    We compare the results of two strong field coherent control experiments: one which optimizes multi-photon population transfer in atomic sodium (from the 3s to the 4s state, measured by spontaneous emission from the 3p-3s transition) with one that optimizes stimulated emission on the 3p-3s transition in an ensemble of sodium atoms. Both experiments make use of intense, shaped ultrafast laser pulses discovered by a Genetic Algorithm inside a learning control loop. Optimization leads to improvements in the spontaneous and stimulated emission yields of about 4 and 10 4 , respectively, over an unshaped pulse. We interpret these results by modeling both the single atom dynamics as well as the stimulated emission buildup through numerical integration of Schroedinger's and Maxwell's equations. Our interpretation leads to the conclusion that modest yields for controlling single quantum systems can lead to dramatic effects whenever an ensemble of such systems acts collectively following controlled impulsive excitation

  19. Ramsey spectroscopy by direct use of resonant light on isotope atoms for single-photon detuning

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hoon; Choi, Mi Hyun; Moon, Ye Lin; Kim, Seung Jin; Kim, Jung Bog [Korea National University of Education, Cheongwon (Korea, Republic of)

    2014-03-15

    We demonstrate Ramsey spectroscopy with cold {sup 87}Rb atoms via a two-photon Raman process. One laser beam has a cross-over resonant frequency on the {sup 85}Rb transition and the other beam has a 6.8 GHz shifted frequency. These two laser beams fulfill the two-photon Raman resonance condition, which involves a single-photon detuning of -2.6 GHz. By implementing these two lasers on cold {sup 87}Rb atoms, we demonstrate Ramsey spectroscopy with an interrogation time of the intermediate state by using π/2 Raman pulses. In our laser system, we can change the single-photon detuning to 1.2, 4.2 or -5.6 GHz by changing the {sup 85}Rb transition line used as a locking signal and an injected sideband. The laser system that directly uses resonant light on isotope atoms will be described in this paper.

  20. Semi-classical description of Rydberg atoms in strong, single-cycle electromagnetic pulses

    International Nuclear Information System (INIS)

    Jensen, R.V.; Sanders, M.M.

    1993-01-01

    Recent experimental measurements of the excitation and ionization of Rydberg atoms by single-cycle, electromagnetic pulses have revealed a variety of novel features. Because many quantum states are strongly coupled by the broadband radiation in the short pulse, the traditional methods of quantum mechanics are inadequate to account for the experimental results. We have therefore developed a semi-classical description of the interaction of both hydrogenic and non-hydrogenic atoms with single-cycle pulses of intense, electromagnetic radiation which is based on the strong correspondence theory of Percival and Richards. This theory, which was originally introduced for the description of strong atomic collisions, accounts for some of the surprising features of the experimental measurements and provides new predictions for future experimental studies

  1. Resonance fluorescence and quantum jumps in single atoms: Testing the randomness of quantum mechanics

    International Nuclear Information System (INIS)

    Erber, T.; Hammerling, P.; Hockney, G.; Porrati, M.; Putterman, S.; La Jolla Institute, La Jolla, California 92037; Department of Physics, University of California, Los Angeles, California 90024)

    1989-01-01

    When a single trapped 198 Hg + ion is illuminated by two lasers, each tuned to an approximate transition, the resulting fluorescence switches on and off in a series of pulses resembling a bistable telegraph. This intermittent fluorescence can also be obtained by optical pumping with a single laser. Quantum jumps between successive atomic levels may be traced directly with multiple-resonance fluorescence. Atomic transition rates and photon antibunching distributions can be inferred from the pulse statistics and compared with quantum theory. Stochastic tests also indicate that the quantum telegraphs are good random number generators. During periods when the fluorescence is switched off, the radiationless atomic currents that generate the telegraph signals can be adjusted by varying the laser illumination: if this coherent evolution of the wave functions is sustained over sufficiently long time intervals, novel interactive precision measurements, near the limits of the time-energy uncertainty relations, are possible. Copyright 1989 Academic Press, Inc

  2. Characteristics of single-atom trapping in a magneto-optical trap with a high magnetic-field gradient

    International Nuclear Information System (INIS)

    Yoon, Seokchan; Choi, Youngwoon; Park, Sangbum; Ji, Wangxi; Lee, Jai-Hyung; An, Kyungwon

    2007-01-01

    A quantitative study on characteristics of a magneto-optical trap with a single or a few atoms is presented. A very small number of 85 Rb atoms were trapped in a micron-size magneto-optical trap with a high magnetic-field gradient. In order to find the optimum condition for a single-atom trap, we have investigated how the number of atoms and the size of atomic cloud change as various experimental parameters, such as a magnetic-field gradient and the trapping laser intensity and detuning. The averaged number of atoms was measured very accurately with a calibration procedure based on the single-atom saturation curve of resonance fluorescence. In addition, the number of atoms in a trap could be controlled by suppressing stochastic loading events by means of a real-time active feedback on the magnetic-field gradient

  3. Shot noise as a probe of spin-polarized transport through single atoms

    DEFF Research Database (Denmark)

    Burtzlaff, Andreas; Weismann, Alexander; Brandbyge, Mads

    2015-01-01

    Single atoms on Au(111) surfaces have been contacted with the Au tip of a low temperature scanning tunneling microscope. The shot noise of the current through these contacts has been measured up to frequencies of 120 kHz and Fano factors have been determined to characterize the transport channels...

  4. Single atom doping for quantum device development in diamond and silicon

    NARCIS (Netherlands)

    Weis, C.D.; Schuh, A.; Batra, A.; Persaud, A.; Rangelow, I.W.; Bokor, J.; Lo, C.C.; Cabrini, S.; Sideras-Haddad, E.; Fuchs, G.D.; Hanson, R.; Awschalom, D.D.; Schenkel, T.

    2008-01-01

    The ability to inject dopant atoms with high spatial resolution, flexibility in dopant species, and high single ion detection fidelity opens opportunities for the study of dopant fluctuation effects and the development of devices in which function is based on the manipulation of quantum states in

  5. Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

    Science.gov (United States)

    Liu, Lichen; Corma, Avelino

    2018-05-23

    Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal-support interaction, and metal-reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results obtained from different systems and try to give a picture on how different types of metal species work in different reactions and give perspectives on the future directions toward better understanding of the catalytic behavior of different metal entities (single atoms, nanoclusters, and nanoparticles) in a unifying manner.

  6. Atomic-scale structure of single-layer MoS2 nanoclusters

    DEFF Research Database (Denmark)

    Helveg, S.; Lauritsen, J. V.; Lægsgaard, E.

    2000-01-01

    We have studied using scanning tunneling microscopy (STM) the atomic-scale realm of molybdenum disulfide (MoS2) nanoclusters, which are of interest as a model system in hydrodesulfurization catalysis. The STM gives the first real space images of the shape and edge structure of single-layer MoS2...

  7. Ternary logic implemented on a single dopant atom field effect silicon transistor

    NARCIS (Netherlands)

    Klein, M.; Mol, J.A.; Verduijn, J.; Lansbergen, G.P.; Rogge, S.; Levine, R.D.; Remacle, F.

    2010-01-01

    We provide an experimental proof of principle for a ternary multiplier realized in terms of the charge state of a single dopant atom embedded in a fin field effect transistor (Fin-FET). Robust reading of the logic output is made possible by using two channels to measure the current flowing through

  8. Functionalised metal-organic frameworks : A novel approach to stabilising single metal atoms

    NARCIS (Netherlands)

    Szilagyi, P.A.; Rogers, D. M.; Zaiser, I.; Callini, E; Turner, Stuart; Borgschulte, A; Züttel, A.; Geerlings, J.J.C.; Hirscher, M; Dam, B.

    2017-01-01

    We have investigated the potential of metal-organic frameworks for immobilising single atoms of transition metals using a model system of Pd supported on NH2-MIL-101(Cr). Our transmission electron microscopy and in situ Raman spectroscopy results give evidence for the first time that

  9. Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy

    Science.gov (United States)

    Neuman, Keir C.; Nagy, Attila

    2012-01-01

    Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations. PMID:18511917

  10. Gas to liquid to solid transition in halogen hot atom chemistry. 6. Product formation routes and chemical selectivity of high energy iodine reactions with butyne isomers

    International Nuclear Information System (INIS)

    Garmestani, S.K.; Firouzbakht, M.L.; Rack, E.P.

    1979-01-01

    Reactions of recoil produced iodine-128 with isomers of butyne were studied in gaseous, high pressure, and condensed phase conditions, with rare gas additives and in the presence and absence of radical scavengers (I 2 and O 2 ). It was found that recoil iodine-128 reactions were initiated by thermal electronically excited I + species for both 1-butyne and 2-butyne systems. While the diverse and complex nature of the reactions cannot be explained by simple chemical parameters, comparisons among the alkyne systems demonstrate preferential attack of iodine at the triple bond resulting, mainly, in electronically excited intermediates. A comparison of the various product formation routes results in the characterization of general traits common to the alkynes. 6 figures, 4 tables

  11. Catalytic activity of Pd-doped Cu nanoparticles for hydrogenation as a single-atom-alloy catalyst.

    Science.gov (United States)

    Cao, Xinrui; Fu, Qiang; Luo, Yi

    2014-05-14

    The single atom alloy of extended surfaces is known to provide remarkably enhanced catalytic performance toward heterogeneous hydrogenation. Here we demonstrate from first principles calculations that this approach can be extended to nanostructures, such as bimetallic nanoparticles. The catalytic properties of the single-Pd-doped Cu55 nanoparticles have been systemically examined for H2 dissociation as well as H atom adsorption and diffusion, following the concept of single atom alloy. It is found that doping a single Pd atom at the edge site of the Cu55 shell can considerably reduce the activation energy of H2 dissociation, while the single Pd atom doped at the top site or in the inner layers is much less effective. The H atom adsorption on Cu55 is slightly stronger than that on the Cu(111) surface; however, a larger nanoparticle that contains 147 atoms could effectively recover the weak binding of the H atoms. We have also investigated the H atom diffusion on the 55-atom nanoparticle and found that spillover of the produced H atoms could be a feasible process due to the low diffusion barriers. Our results have demonstrated that facile H2 dissociation and weak H atom adsorption could be combined at the nanoscale. Moreover, the effects of doping one more Pd atom on the H2 dissociation and H atom adsorption have also been investigated. We have found that both the doping Pd atoms in the most stable configuration could independently exhibit their catalytic activity, behaving as two single-atom-alloy catalysts.

  12. Iodine Satellite

    Science.gov (United States)

    Kamhawi, Hani; Dankanich, John; Martinez, Andres; Petro, Andrew

    2015-01-01

    The Iodine Satellite (iSat) spacecraft will be the first CubeSat to demonstrate high change in velocity from a primary propulsion system by using Hall thruster technology and iodine as a propellant. The mission will demonstrate CubeSat maneuverability, including plane change, altitude change and change in its closest approach to Earth to ensure atmospheric reentry in less than 90 days. The mission is planned for launch in fall 2017. Hall thruster technology is a type of electric propulsion. Electric propulsion uses electricity, typically from solar panels, to accelerate the propellant. Electric propulsion can accelerate propellant to 10 times higher velocities than traditional chemical propulsion systems, which significantly increases fuel efficiency. To enable the success of the propulsion subsystem, iSat will also demonstrate power management and thermal control capabilities well beyond the current state-of-the-art for spacecraft of its size. This technology is a viable primary propulsion system that can be used on small satellites ranging from about 22 pounds (10 kilograms) to more than 1,000 pounds (450 kilograms). iSat's fuel efficiency is ten times greater and its propulsion per volume is 100 times greater than current cold-gas systems and three times better than the same system operating on xenon. iSat's iodine propulsion system consists of a 200 watt (W) Hall thruster, a cathode, a tank to store solid iodine, a power processing unit (PPU) and the feed system to supply the iodine. This propulsion system is based on a 200 W Hall thruster developed by Busek Co. Inc., which was previously flown using xenon as the propellant. Several improvements have been made to the original system to include a compact PPU, targeting greater than 80 percent reduction in mass and volume of conventional PPU designs. The cathode technology is planned to enable heaterless cathode conditioning, significantly increasing total system efficiency. The feed system has been designed to

  13. Alternative Dose for Choroidal Melanoma Treated With an Iodine-125 Radioactive Plaque: A Single-Institution Retrospective Study

    International Nuclear Information System (INIS)

    Saconn, Paul A.; Gee, Christopher J.; Greven, Craig M.; McCoy, Thomas P.; Ekstrand, Kenneth E.; Greven, Kathryn M.

    2010-01-01

    Purpose: The Collaborative Ocular Melanoma Study (COMS) established iodine-125 plaque brachytherapy as an accepted standard treatment for medium-size choroidal melanoma. In the COMS, the prescription dose was 85 Gy. This is a retrospective review of our outcomes in patients treated with lower doses than those used in the COMS. Methods and Materials: From 1990 to 2004, 62 patients were treated with iodine-125 plaque brachytherapy for choroidal melanoma. COMS eye plaques were used with dose prescribed to the apex of the tumor. The median and average dose rates at the tumor apex were 63.5 cGy/h and 62.7 cGy/h, respectively. The median and average total doses were 63.0 Gy and 62.5 Gy (range, 56-69 Gy), respectively. The median and mean durations of implant were 100.0 hours and 101.1 hours (range, 71-165 hours). Results: Median follow-up time was 58.2 months. The 5-year outcomes including overall survival, disease-free survival, cause-specific survival, local failure, secondary enucleation rate, and visual acuity (VA) <20/200 were estimated using the Kaplan-Meier method. Overall, there were 7 local failures, 4 distant failures, and 10 secondary enucleations (6 due to local failure and 4 due to treatment complications). Univariate analysis was performed to identify significant prognostic factors associated with disease-free survival (baseline VA in tumor eye, tumor shape), cause-specific survival (diabetic retinopathy), local failure (none found), secondary enucleation rate (diabetic retinopathy, basal tumor dimension) and VA <20/200 (diabetic retinopathy, tumor shape, age, retinal detachment, treatment depth, and history of vision-limiting condition). Conclusions: Our survival and local control outcomes are comparable to those of the COMS. However, VA at 5 years seems to be better. Lower doses of radiation could potentially lead to better visual outcomes.

  14. Single-atom catalysts for CO2 electroreduction with significant activity and selectivity improvements.

    Science.gov (United States)

    Back, Seoin; Lim, Juhyung; Kim, Na-Young; Kim, Yong-Hyun; Jung, Yousung

    2017-02-01

    A single-atom catalyst (SAC) has an electronic structure that is very different from its bulk counterparts, and has shown an unexpectedly high specific activity with a significant reduction in noble metal usage for CO oxidation, fuel cell and hydrogen evolution applications, although physical origins of such performance enhancements are still poorly understood. Herein, by means of density functional theory (DFT) calculations, we for the first time investigate the great potential of single atom catalysts for CO 2 electroreduction applications. In particular, we study a single transition metal atom anchored on defective graphene with single or double vacancies, denoted M@sv-Gr or M@dv-Gr, where M = Ag, Au, Co, Cu, Fe, Ir, Ni, Os, Pd, Pt, Rh or Ru, as a CO 2 reduction catalyst. Many SACs are indeed shown to be highly selective for the CO 2 reduction reaction over a competitive H 2 evolution reaction due to favorable adsorption of carboxyl (*COOH) or formate (*OCHO) over hydrogen (*H) on the catalysts. On the basis of free energy profiles, we identified several promising candidate materials for different products; Ni@dv-Gr (limiting potential U L = -0.41 V) and Pt@dv-Gr (-0.27 V) for CH 3 OH production, and Os@dv-Gr (-0.52 V) and Ru@dv-Gr (-0.52 V) for CH 4 production. In particular, the Pt@dv-Gr catalyst shows remarkable reduction in the limiting potential for CH 3 OH production compared to any existing catalysts, synthesized or predicted. To understand the origin of the activity enhancement of SACs, we find that the lack of an atomic ensemble for adsorbate binding and the unique electronic structure of the single atom catalysts as well as orbital interaction play an important role, contributing to binding energies of SACs that deviate considerably from the conventional scaling relation of bulk transition metals.

  15. Initial experience with single-photon emission tomography using iodine-123-labelled 2β-carbomethoxy-3β(4-iodophnyl)tropane in human brain

    International Nuclear Information System (INIS)

    Kuikka, J.T.; Bergstroem, K.A.; Vanninen, E.; Laulumaa, V.; Hartikainen, P.; Laensimies, E.

    1993-01-01

    The iodinated cocaine analogue 2β-carbomethoxy-3β-(4-iodophenyl)tropane ([ 123 I]β-CIT), a new dopamine transporter, was preliminarily tested in human brain. Two normal volunteers and two patients with Parkinson's disease were imaged with a high-resolution single-photon emission tomography scanner. The specific binding of [ 123 I]β-CIT in the basal ganglia and thalamus was high in normal volunteers. In addition, there was relatively intense uptake in the medial prefrontal area. Patients with Parkinson's disease who were older than controls showed significantly lower specific binding in the basal ganglia and thalamus and no uptake in the medial prefrontal cortex. This decrease in the dopamine transporter may be age related. (orig.)

  16. Initial experience with single-photon emission tomography using iodine-123-labelled 2[beta]-carbomethoxy-3[beta](4-iodophnyl)tropane in human brain

    Energy Technology Data Exchange (ETDEWEB)

    Kuikka, J T [Kuopio Univ. Hospital (Finland). Dept. of Clinical Physiology; Bergstroem, K A [Kuopio Univ. Hospital (Finland). Dept. of Clinical Physiology; Vanninen, E [Kuopio Univ. Hospital (Finland). Dept. of Clinical Physiology; Laulumaa, V [Kuopio Univ. Hospital (Finland). Dept. of Neurology; Hartikainen, P [Kuopio Univ. Hospital (Finland). Dept. of Neurology; Laensimies, E [Kuopio Univ. Hospital (Finland). Dept. of Clinical Physiology

    1993-09-01

    The iodinated cocaine analogue 2[beta]-carbomethoxy-3[beta]-(4-iodophenyl)tropane ([sup 123]I[beta]-CIT), a new dopamine transporter, was preliminarily tested in human brain. Two normal volunteers and two patients with Parkinson's disease were imaged with a high-resolution single-photon emission tomography scanner. The specific binding of [sup 123]I[beta]-CIT in the basal ganglia and thalamus was high in normal volunteers. In addition, there was relatively intense uptake in the medial prefrontal area. Patients with Parkinson's disease who were older than controls showed significantly lower specific binding in the basal ganglia and thalamus and no uptake in the medial prefrontal cortex. This decrease in the dopamine transporter may be age related. (orig.)

  17. Support effects on adsorption and catalytic activation of O2 in single atom iron catalysts with graphene-based substrates.

    Science.gov (United States)

    Gao, Zheng-Yang; Yang, Wei-Jie; Ding, Xun-Lei; Lv, Gang; Yan, Wei-Ping

    2018-03-07

    The adsorption and catalytic activation of O 2 on single atom iron catalysts with graphene-based substrates were investigated systematically by density functional theory calculation. It is found that the support effects of graphene-based substrates have a significant influence on the stability of the single atom catalysts, the adsorption configuration, the electron transfer mechanism, the adsorption energy and the energy barrier. The differences in the stable adsorption configuration of O 2 on single atom iron catalysts with different graphene-based substrates can be well understood by the symmetrical matching principle based on frontier molecular orbital analysis. There are two different mechanisms of electron transfer, in which the Fe atom acts as the electron donor in single vacancy graphene-based substrates while the Fe atom mainly acts as the bridge for electron transfer in double vacancy graphene-based substrates. The Fermi softness and work function are good descriptors of the adsorption energy and they can well reveal the relationship between electronic structure and adsorption energy. This single atom iron catalyst with single vacancy graphene modified by three nitrogen atoms is a promising non-noble metal single atom catalyst in the adsorption and catalytic oxidation of O 2 . Furthermore, the findings can lay the foundation for the further study of graphene-based support effects and provide a guideline for the development and design of new non-noble-metal single atom catalysts.

  18. High Fidelity Preparation of a Single Atom in Its 2D Center of Mass Ground State

    Science.gov (United States)

    Sompet, Pimonpan; Fung, Yin Hsien; Schwartz, Eyal; Hunter, Matthew D. J.; Phrompao, Jindaratsamee; Andersen, Mikkel F.

    2017-04-01

    Complete control over quantum states of individual atoms is important for the study of the microscopic world. Here, we present a push button method for high fidelity preparation of a single 85Rb atom in the vibrational ground state of tightly focused optical tweezers. The method combines near-deterministic preparation of a single atom with magnetically-insensitive Raman sideband cooling. We achieve 2D cooling in the radial plane with a ground state population of 0.85, which provides a fidelity of 0.7 for the entire procedure (loading and cooling). The Raman beams couple two sublevels (| F = 3 , m = 0 〉 and | F = 2 , m = 0 〉) that are indifferent to magnetic noise to first order. This leads to long atomic coherence times, and allows us to implement the cooling in an environment where magnetic field fluctuations prohibit previously demonstrated variations. Additionally, we implement the trapping and manipulation of two atoms confined in separate dynamically reconfigurable optical tweezers, to study few-body dynamics.

  19. Scattering of atomic and molecular ions from single crystal surfaces of Cu, Ag and Fe

    International Nuclear Information System (INIS)

    Zoest, J.M. van.

    1986-01-01

    This thesis deals with analysis of crystal surfaces of Cu, Ag and Fe with Low Energy Ion scattering Spectroscopy (LEIS). Different atomic and molecular ions with fixed energies below 7 keV are scattered by a metal single crystal (with adsorbates). The energy and direction of the scattered particles are analysed for different selected charge states. In that way information can be obtained concerning the composition and atomic and electronic structure of the single crystal surface. Energy spectra contain information on the composition of the surface, while structural atomic information is obtained by direction measurements (photograms). In Ch.1 a description is given of the experimental equipment, in Ch.2 a characterization of the LEIS method. Ch.3 deals with the neutralization of keV-ions in surface scattering. Two different ways of data interpretation are presented. First a model is treated in which the observed directional dependence of neutralization action of the first atom layer of the surface is presented by a laterally varying thickness of the neutralizing layer. Secondly it is shown that the data can be reproduced by a more realistic, physical model based on atomic transition matrix elements. In Ch.4 the low energy hydrogen scattering is described. The study of the dissociation of H 2 + at an Ag surface r0230ted in a model based on electronic dissociation, initialized by electron capture into a repulsive (molecular) state. In Ch.5 finally the method is applied to the investigation of the surface structure of oxidized Fe. (Auth.)

  20. C-C Coupling on Single-Atom-Based Heterogeneous Catalyst.

    Science.gov (United States)

    Zhang, Xiaoyan; Sun, Zaicheng; Wang, Bin; Tang, Yu; Nguyen, Luan; Li, Yuting; Tao, Franklin Feng

    2018-01-24

    Compared to homogeneous catalysis, heterogeneous catalysis allows for ready separation of products from the catalyst and thus reuse of the catalyst. C-C coupling is typically performed on a molecular catalyst which is mixed with reactants in liquid phase during catalysis. This homogeneous mixing at a molecular level in the same phase makes separation of the molecular catalyst extremely challenging and costly. Here we demonstrated that a TiO 2 -based nanoparticle catalyst anchoring singly dispersed Pd atoms (Pd 1 /TiO 2 ) is selective and highly active for more than 10 Sonogashira C-C coupling reactions (R≡CH + R'X → R≡R'; X = Br, I; R' = aryl or vinyl). The coupling between iodobenzene and phenylacetylene on Pd 1 /TiO 2 exhibits a turnover rate of 51.0 diphenylacetylene molecules per anchored Pd atom per minute at 60 °C, with a low apparent activation barrier of 28.9 kJ/mol and no cost of catalyst separation. DFT calculations suggest that the single Pd atom bonded to surface lattice oxygen atoms of TiO 2 acts as a site to dissociatively chemisorb iodobenzene to generate an intermediate phenyl, which then couples with phenylacetylenyl bound to a surface oxygen atom. This coupling of phenyl adsorbed on Pd 1 and phenylacetylenyl bound to O ad of TiO 2 forms the product molecule, diphenylacetylene.

  1. Visualising reacting single atoms under controlled conditions: Advances in atomic resolution in situ Environmental (Scanning) Transmission Electron Microscopy (E(S)TEM)

    Science.gov (United States)

    Boyes, Edward D.; Gai, Pratibha L.

    2014-02-01

    Advances in atomic resolution Environmental (Scanning) Transmission Electron Microscopy (E(S)TEM) for probing gas-solid catalyst reactions in situ at the atomic level under controlled reaction conditions of gas environment and temperature are described. The recent development of the ESTEM extends the capability of the ETEM by providing the direct visualisation of single atoms and the atomic structure of selected solid state heterogeneous catalysts in their working states in real-time. Atomic resolution E(S)TEM provides a deeper understanding of the dynamic atomic processes at the surface of solids and their mechanisms of operation. The benefits of atomic resolution-E(S)TEM to science and technology include new knowledge leading to improved technological processes with substantial economic benefits, improved healthcare, reductions in energy needs and the management of environmental waste generation. xml:lang="fr"

  2. Conduction channels at finite bias in single-atom gold contacts

    DEFF Research Database (Denmark)

    Brandbyge, Mads; Kobayashi, Nobuhiko; Tsukada, Masaru

    1999-01-01

    We consider the effect of a finite voltage bias on the conductance of single-atom gold contacts. We employ a nonorthogonal spn-tight-binding Hamiltonian combined with a local charge neutrality assumption. The conductance and charge distributions for finite bias are calculated using the nonequilib......We consider the effect of a finite voltage bias on the conductance of single-atom gold contacts. We employ a nonorthogonal spn-tight-binding Hamiltonian combined with a local charge neutrality assumption. The conductance and charge distributions for finite bias are calculated using...... of the eigenchannels projected onto tight-binding orbitals. We find a single almost fully transmitting channel with mainly s character for low bias while for high bias this channel becomes less transmitting and additional channels involving only d orbitals start to conduct....

  3. Absolute single electron loss in collisions of Ar+ with various atoms

    Science.gov (United States)

    Reyes, P. G.; Martínez, H.; Castillo, F.

    2001-07-01

    Absolute differential and total cross sections for single electron loss were measured for Ar+ ions on various atoms in the energy range of 1.5 to 5.0 keV. The laboratory angular scan for the distributions ranged from -2.5 to 2.5 degrees. The measured differential cross sections have been integrated over the experimental angular range providing absolute total cross sections. The behavior of the total electron loss cross sections with the target atomic number, Zt, shows different dependences as the collision energy increases. In all cases it displays a saturation as Zt increases.

  4. Atom

    International Nuclear Information System (INIS)

    Auffray, J.P.

    1997-01-01

    The atom through centuries, has been imagined, described, explored, then accelerated, combined...But what happens truly inside the atom? And what are mechanisms who allow its stability? Physicist and historian of sciences, Jean-Paul Auffray explains that these questions are to the heart of the modern physics and it brings them a new lighting. (N.C.)

  5. Atomic force microscopy and spectroscopy to probe single membrane proteins in lipid bilayers.

    Science.gov (United States)

    Sapra, K Tanuj

    2013-01-01

    The atomic force microscope (AFM) has opened vast avenues hitherto inaccessible to the biological scientist. The high temporal (millisecond) and spatial (nanometer) resolutions of the AFM are suited for studying many biological processes in their native conditions. The AFM cantilever stylus is aptly termed as a "lab on a tip" owing to its versatility as an imaging tool as well as a handle to manipulate single bonds and proteins. Recent examples assert that the AFM can be used to study the mechanical properties and monitor processes of single proteins and single cells, thus affording insight into important mechanistic details. This chapter specifically focuses on practical and analytical protocols of single-molecule AFM methodologies related to high-resolution imaging and single-molecule force spectroscopy of membrane proteins. Both these techniques are operator oriented, and require specialized working knowledge of the instrument, theoretical, and practical skills.

  6. Probing living bacterial adhesion by single cell force spectroscopy using atomic force microscopy

    DEFF Research Database (Denmark)

    Zeng, Guanghong; Ogaki, Ryosuke; Regina, Viduthalai R.

    be considered. We have therefore developed a simple and versatile method to make single-cell bacterial probes for measuring single cell adhesion with atomic force microscopy (AFM).[1] A single-cell probe was readily made by picking up a bacterial cell from a glass surface using a tipless AFM cantilever coated...... random immobilization is obtained by submerging the cantilever in a bacterial suspension. The reported method provides a general platform for investigating single cell interactions of bacteria with different surfaces and other cells by AFM force spectroscopy, thus improving our understanding....... The strain-dependent susceptibility to bacterial colonization on conventional PLL-g-PEG illustrates how bacterial diversity challenges development of “universal” antifouling coatings, and AFM single-cell force spectroscopy was proven to be a powerful tool to provide insights into the molecular mechanisms...

  7. Propensity rules for orientation in singly-charged ion-atom collisions

    International Nuclear Information System (INIS)

    Nielsen, S.E.; Dubois, A.; Hansen, J.P.

    1990-01-01

    Orientation effects for electron capture and excitation in singly-charged ion-atom collisions are analysed using the atomic basis impact parameter method with full inclusion of electron translational factors. We find that the orientation preferences previously predicted for excitation in terms of propensity rules may still be observed when capture is present in ion-atom collisions. Furthermore, in spite of intricate behaviour of the direct capture couplings during the collision, we draw some parallel conclusions for the orientation of the capture states. We illustrate these perturbative predictions by close-coupling calculations for H + -Na(3s) collisions where clear propensity for orientation of the H(2p) capture state is demonstrated in impact parameter and velocity dependences. Finally we predict pronounced orientation effects for H(2s) and H(2p) capture in collisions of H + with initially oriented Na(3p) states. (author)

  8. Single-collision studies of hot atom energy transfer and chemical reaction

    International Nuclear Information System (INIS)

    Valentini, J.J.

    1991-01-01

    This report discusses research in the collision dynamics of translationally hot atoms, with funding with DOE for the project ''Single-Collision Studies of Hot Atom Energy Transfer and Chemical Reaction,'' Grant Number DE-FG03-85ER13453. The work reported here was done during the period September 9, 1988 through October 31, 1991. During this period this DOE-funded work has been focused on several different efforts: (1) experimental studies of the state-to-state dynamics of the H + RH → H 2 R reactions where RH is CH 4 , C 2 H 6 , or C 3 H 8 , (2) theoretical (quasiclassical trajectory) studies of hot hydrogen atom collision dynamics, (3) the development of photochemical sources of translationally hot molecular free radicals and characterization of the high resolution CARS spectroscopy of molecular free radicals, (4) the implementation of stimulated Raman excitation (SRE) techniques for the preparation of vibrationally state-selected molecular reactants

  9. Optically pumped semiconductor lasers: Conception and characterization of a single mode source for Cesium atoms manipulation

    International Nuclear Information System (INIS)

    Cocquelin, B.

    2009-02-01

    Lasers currently used in atomic clocks or inertial sensors are suffering from a lack of power, narrow linewidth or compactness for future spatial missions. Optically pumped semiconductor lasers, which combine the approach of classical solid state lasers and the engineering of semiconductor laser, are considered here as a candidate to a metrological laser source dedicated to the manipulation of Cesium atoms in these instruments. These lasers have demonstrated high power laser emission in a circular single transverse mode, as well as single longitudinal mode emission, favoured by the semiconductor structure and the external cavity design. We study the definition and the characterization of a proper semiconductor structure for the cooling and the detection of Cesium atoms at 852 nm. A compact and robust prototype tunable on the Cesium D2 hyperfine structure is built. The laser frequency is locked to an atomic transition thanks to a saturated absorption setup. The emission spectral properties are investigated, with a particular attention to the laser frequency noise and the laser linewidth. Finally, we describe and model the thermal properties of the semiconductor structure, which enables the simulation of the laser power characteristic. The experimental parameters are optimised to obtain the maximum output power with our structure. Thanks to our analysis, we propose several ways to overcome these limitations, by reducing the structure heating. (authors)

  10. Conductance of single-atom platinum contacts: Voltage dependence of the conductance histogram

    DEFF Research Database (Denmark)

    Nielsen, S.K.; Noat, Y.; Brandbyge, Mads

    2003-01-01

    The conductance of a single-atom contact is sensitive to the coupling of this contact atom to the atoms in the leads. Notably for the transition metals this gives rise to a considerable spread in the observed conductance values. The mean conductance value and spread can be obtained from the first...... peak in conductance histograms recorded from a large set of contact-breaking cycles. In contrast to the monovalent metals, this mean value for Pt depends strongly on the applied voltage bias and other experimental conditions and values ranging from about 1 G(0) to 2.5 G(0) (G(0)=2e(2)/h) have been...... reported. We find that at low bias the first peak in the conductance histogram is centered around 1.5 G(0). However, as the bias increases past 300 mV the peak shifts to 1.8 G(0). Here we show that this bias dependence is due to a geometric effect where monatomic chains are replaced by single-atom contacts...

  11. Design of high-activity single-atom catalysts via n-p codoping

    Science.gov (United States)

    Wang, Xiaonan; Zhou, Haiyan; Zhang, Xiaoyang; Jia, Jianfeng; Wu, Haishun

    2018-03-01

    The large-scale synthesis of stable single-atom catalysts (SACs) in experiments remains a significant challenge due to high surface free energy of metal atom. Here, we propose a concise n-p codoping approach, and find it can not only disperse the relatively inexpensive metal, copper (Cu), onto boron (B)-doped graphene, but also result in high-activity SACs. We use CO oxidation on B/Cu codoped graphene as a prototype example, and demonstrate that: (1) a stable SAC can be formed by stronger electrostatic attraction between the metal atom (n-type Cu) and support (p-type B-doped graphene). (2) the energy barrier of the prototype CO oxidation on B/Cu codoped graphene is 0.536 eV by the Eley-Rideal mechanism. Further analysis shows that the spin selection rule can provide well theoretical insight into high activity of our suggested SAC. The concept of n-p codoping may lead to new strategy in large-scale synthesis of stable single-atom catalysts.

  12. Interference of Single Photons Emitted by Entangled Atoms in Free Space

    Science.gov (United States)

    Araneda, G.; Higginbottom, D. B.; Slodička, L.; Colombe, Y.; Blatt, R.

    2018-05-01

    The generation and manipulation of entanglement between isolated particles has precipitated rapid progress in quantum information processing. Entanglement is also known to play an essential role in the optical properties of atomic ensembles, but fundamental effects in the controlled emission and absorption from small, well-defined numbers of entangled emitters in free space have remained unobserved. Here we present the control of the emission rate of a single photon from a pair of distant, entangled atoms into a free-space optical mode. Changing the length of the optical path connecting the atoms modulates the single-photon emission rate in the selected mode with a visibility V =0.27 ±0.03 determined by the degree of entanglement shared between the atoms, corresponding directly to the concurrence Cρ=0.31 ±0.10 of the prepared state. This scheme, together with population measurements, provides a fully optical determination of the amount of entanglement. Furthermore, large sensitivity of the interference phase evolution points to applications of the presented scheme in high-precision gradient sensing.

  13. Measurement of the indium segregation in InGaN based LEDs with single atom sensitivity

    International Nuclear Information System (INIS)

    Jinschek, Joerg; Kisielowski, Christian; Van Dyck, Dirk; Geuens, Philippe

    2003-01-01

    In light emitting diodes (LED) consisting of GaN/InGaN/GaN quantum wells (QWs), the exact indium distribution inside the wells of the active region affects the performance of devices. Indium segregation can take place forming small InGaN clusters of locally varying composition. In the past, we used a local strain analysis from single HRTEM lattice images to determine the In composition inside the InGaN QWs with a resolution of 0.5 nm x 0.3 nm. Truly atomic resolution can be pursued by exploitation of intensity dependencies on the atomic number (Z) of the electron exit-wave (EW). In microscopes with sufficient sensitivity, local variations of amplitude and phase are found to be discrete with sample thickness, which allows for counting the number of atoms in each individual column of ∼0.08 nm diameter. In QW s of ∼17 percent of average indium concentration it is possible to discriminate between pure Ga columns and columns containing 1, 2, 3, or more In atoms because phase changes are discrete and element specific. The preparation of samples with atomically flat surfaces is a limiting factor for the application of the procedure

  14. Formation of molecules in interstellar clouds from singly and multiply ionized atoms

    International Nuclear Information System (INIS)

    Langer, W.D.; and NASA, Institute for Space Studies, Goddard Space Flight Center, New York)

    1978-01-01

    Soft X-ray and cosmic rays produce multiply ionized atoms which may initiate molecule production in interstellar clouds. This molecule production can occur via ion-molecule reactions with H 2 , either directly from the multiply ionized atom (e.g.,C ++ + H 2 →CH + + H + ), or indirectly from the singly ionized atoms (e.g., N + + H 2 →NH + + H) that are formed from the recombination or charge transfer of the highly ionized atom (e.g., N ++ + e→N + + hv). We investigate the contribution of these reactions to the abundances of carbon-, nitrogen-, and oxygen-bearing molecules in isobaric models of diffuse clouds. In the presence of the average flux estimated for the diffuse soft X-ray background, multiply ionized atoms contribute only minimally (a few percent) to carbon-bearing molecules such as CH. In the neighborhood of diffuse structures or discrete sources, however, where the X-ray flux is enhanced, multiple ionization is considerably more important for molecule production

  15. Towards a precise measurement of atomic parity violation in a single Ra+ ion

    International Nuclear Information System (INIS)

    Nuñez Portela, M.; Berg, J. E. van den; Bekker, H.; Böll, O.; Dijck, E. A.; Giri, G. S.; Hoekstra, S.; Jungmann, K.; Mohanty, A.; Onderwater, C. J. G.; Santra, B.; Schlesser, S.; Timmermans, R. G. E.; Versolato, O. O.; Wansbeek, L. W.; Willmann, L.; Wilschut, H. W.

    2013-01-01

    A single trapped Ra  +  (Z = 88) ion provides a very promising route towards a most precise measurement of Atomic Parity Violation (APV), since APV effects grow faster than Z 3 . This experiment promises the best determination of the electroweak coupling constant at the lowest accessible energies. Such a measurement provides a sensitive test of the Standard Model in particle physics. At the present stage of the experiment, we focus on trapping and laser cooling stable Ba  +  ions as a precursor for radioactive Ra  +  . Online laser spectroscopy of the isotopes 209 − 214 Ra  +  in a linear Paul trap has provided information on transition wavelengths, fine and hyperfine structures and excited state lifetimes as test of atomic structure calculations. Additionaly, a single trapped Ra  +  ion could function as a very stable clock.

  16. Supramolecular Rotor and Translator at Work: On-Surface Movement of Single Atoms.

    Science.gov (United States)

    Ohmann, Robin; Meyer, Jörg; Nickel, Anja; Echeverria, Jorge; Grisolia, Maricarmen; Joachim, Christian; Moresco, Francesca; Cuniberti, Gianaurelio

    2015-08-25

    A supramolecular nanostructure composed of four 4-acetylbiphenyl molecules and self-assembled on Au (111) was loaded with single Au adatoms and studied by scanning tunneling microscopy at low temperature. By applying voltage pulses to the supramolecular structure, the loaded Au atoms can be rotated and translated in a controlled manner. The manipulation of the gold adatoms is driven neither by mechanical interaction nor by direct electronic excitation. At the electronic resonance and driven by the tunneling current intensity, the supramolecular nanostructure performs a small amount of work of about 8 × 10(-21) J, while transporting the single Au atom from one adsorption site to the next. Using the measured average excitation time necessary to induce the movement, we determine the mechanical motive power of the device, yielding about 3 × 10(-21) W.

  17. Towards a precise measurement of atomic parity violation in a single Ra{sup +} ion

    Energy Technology Data Exchange (ETDEWEB)

    Nunez Portela, M., E-mail: nunez@kvi.nl; Berg, J. E. van den; Bekker, H.; Boell, O.; Dijck, E. A.; Giri, G. S.; Hoekstra, S.; Jungmann, K.; Mohanty, A.; Onderwater, C. J. G.; Santra, B.; Schlesser, S.; Timmermans, R. G. E.; Versolato, O. O.; Wansbeek, L. W.; Willmann, L.; Wilschut, H. W. [Kernfysisch Versneller Instituut (KVI) (Netherlands)

    2013-03-15

    A single trapped Ra{sup + } (Z = 88) ion provides a very promising route towards a most precise measurement of Atomic Parity Violation (APV), since APV effects grow faster than Z{sup 3}. This experiment promises the best determination of the electroweak coupling constant at the lowest accessible energies. Such a measurement provides a sensitive test of the Standard Model in particle physics. At the present stage of the experiment, we focus on trapping and laser cooling stable Ba{sup + } ions as a precursor for radioactive Ra{sup + }. Online laser spectroscopy of the isotopes {sup 209 - 214}Ra{sup + } in a linear Paul trap has provided information on transition wavelengths, fine and hyperfine structures and excited state lifetimes as test of atomic structure calculations. Additionaly, a single trapped Ra{sup + } ion could function as a very stable clock.

  18. Analysis of imperfections in the coherent optical excitation of single atoms to Rydberg states

    Science.gov (United States)

    de Léséleuc, Sylvain; Barredo, Daniel; Lienhard, Vincent; Browaeys, Antoine; Lahaye, Thierry

    2018-05-01

    We study experimentally various physical limitations and technical imperfections that lead to damping and finite contrast of optically driven Rabi oscillations between ground and Rydberg states of a single atom. Finite contrast is due to preparation and detection errors, and we show how to model and measure them accurately. Part of these errors originates from the finite lifetime of Rydberg states, and we observe its n3 scaling with the principal quantum number n . To explain the damping of Rabi oscillations, we use simple numerical models taking into account independently measured experimental imperfections and show that the observed damping actually results from the accumulation of several small effects, each at the level of a few percent. We discuss prospects for improving the coherence of ground-Rydberg Rabi oscillations in view of applications in quantum simulation and quantum information processing with arrays of single Rydberg atoms.

  19. Reorganization energy upon charging a single molecule on an insulator measured by atomic force microscopy

    Science.gov (United States)

    Fatayer, Shadi; Schuler, Bruno; Steurer, Wolfram; Scivetti, Ivan; Repp, Jascha; Gross, Leo; Persson, Mats; Meyer, Gerhard

    2018-05-01

    Intermolecular single-electron transfer on electrically insulating films is a key process in molecular electronics1-4 and an important example of a redox reaction5,6. Electron-transfer rates in molecular systems depend on a few fundamental parameters, such as interadsorbate distance, temperature and, in particular, the Marcus reorganization energy7. This crucial parameter is the energy gain that results from the distortion of the equilibrium nuclear geometry in the molecule and its environment on charging8,9. The substrate, especially ionic films10, can have an important influence on the reorganization energy11,12. Reorganization energies are measured in electrochemistry13 as well as with optical14,15 and photoemission spectroscopies16,17, but not at the single-molecule limit and nor on insulating surfaces. Atomic force microscopy (AFM), with single-charge sensitivity18-22, atomic-scale spatial resolution20 and operable on insulating films, overcomes these challenges. Here, we investigate redox reactions of single naphthalocyanine (NPc) molecules on multilayered NaCl films. Employing the atomic force microscope as an ultralow current meter allows us to measure the differential conductance related to transitions between two charge states in both directions. Thereby, the reorganization energy of NPc on NaCl is determined as (0.8 ± 0.2) eV, and density functional theory (DFT) calculations provide the atomistic picture of the nuclear relaxations on charging. Our approach presents a route to perform tunnelling spectroscopy of single adsorbates on insulating substrates and provides insight into single-electron intermolecular transport.

  20. Quantum Interference between Autonomous Single-Photon Sources from Doppler-Broadened Atomic Ensemble

    OpenAIRE

    Jeong, Teak; Lee, Yoon-Seok; Park, Jiho; Kim, Heonoh; Moon, Han Seb

    2017-01-01

    To realize a quantum network based on quantum entanglement swapping, bright and completely autonomous sources are essentially required. Here, we experimentally demonstrate Hong-Ou-Mandel (HOM) quantum interference between two independent bright photon pairs generated via the spontaneous four-wave mixing in Doppler-broadened ladder-type 87Rb atoms. Bright autonomous heralded single photons are operated in a continuous-wave (CW) mode with no synchronization or supplemental filters. The four-fol...

  1. Three-dimensional atomic-image reconstruction from a single-energy Si(100) photoelectron hologram

    International Nuclear Information System (INIS)

    Matsushita, T.; Agui, A.; Yoshigoe, A.

    2004-01-01

    Full text: J. J. Barton proposed a basic algorithm for three-dimensional atomic-image reconstruction from photoelectron hologram, which is based on the Fourier transform(FT). In the use of a single-energy hologram, the twin-image appears in principle. The twin image disappears in the use of multi-energy hologram, which requires longer measuring time and variable-energy light source. But the reconstruction in the use of a simple FT is difficult because the scattered electron wave is not s-symmetric wave. Many theoretical and experimental approaches based on the FT have been researched. We propose a new algorithm so-called 'scattering pattern matrix', which is not based on the FT. The algorithm utilizes the 'scattering pattern', and iterative gradient method. Real space image can be reconstructed from a single-energy hologram without initial model. In addition, the twin image disappears. We reconstructed the three-dimensional atomic image of Si bulk structure from an experimental single-energy hologram of Si(100) 2s emission, which is shown The experiment was performed with using a Al-K α light source. The experimental setup is shown in. Then we calculated a vertical slice image of the reconstructed Si bulk structure, which is shown. The atomic images appear around the expected positions

  2. Simple Atomic Quantum Memory Suitable for Semiconductor Quantum Dot Single Photons

    Science.gov (United States)

    Wolters, Janik; Buser, Gianni; Horsley, Andrew; Béguin, Lucas; Jöckel, Andreas; Jahn, Jan-Philipp; Warburton, Richard J.; Treutlein, Philipp

    2017-08-01

    Quantum memories matched to single photon sources will form an important cornerstone of future quantum network technology. We demonstrate such a memory in warm Rb vapor with on-demand storage and retrieval, based on electromagnetically induced transparency. With an acceptance bandwidth of δ f =0.66 GHz , the memory is suitable for single photons emitted by semiconductor quantum dots. In this regime, vapor cell memories offer an excellent compromise between storage efficiency, storage time, noise level, and experimental complexity, and atomic collisions have negligible influence on the optical coherences. Operation of the memory is demonstrated using attenuated laser pulses on the single photon level. For a 50 ns storage time, we measure ηe2 e 50 ns=3.4 (3 )% end-to-end efficiency of the fiber-coupled memory, with a total intrinsic efficiency ηint=17 (3 )%. Straightforward technological improvements can boost the end-to-end-efficiency to ηe 2 e≈35 %; beyond that, increasing the optical depth and exploiting the Zeeman substructure of the atoms will allow such a memory to approach near unity efficiency. In the present memory, the unconditional read-out noise level of 9 ×10-3 photons is dominated by atomic fluorescence, and for input pulses containing on average μ1=0.27 (4 ) photons, the signal to noise level would be unity.

  3. Nanomechanical DNA origami 'single-molecule beacons' directly imaged by atomic force microscopy

    Science.gov (United States)

    Kuzuya, Akinori; Sakai, Yusuke; Yamazaki, Takahiro; Xu, Yan; Komiyama, Makoto

    2011-01-01

    DNA origami involves the folding of long single-stranded DNA into designed structures with the aid of short staple strands; such structures may enable the development of useful nanomechanical DNA devices. Here we develop versatile sensing systems for a variety of chemical and biological targets at molecular resolution. We have designed functional nanomechanical DNA origami devices that can be used as 'single-molecule beacons', and function as pinching devices. Using 'DNA origami pliers' and 'DNA origami forceps', which consist of two levers ~170 nm long connected at a fulcrum, various single-molecule inorganic and organic targets ranging from metal ions to proteins can be visually detected using atomic force microscopy by a shape transition of the origami devices. Any detection mechanism suitable for the target of interest, pinching, zipping or unzipping, can be chosen and used orthogonally with differently shaped origami devices in the same mixture using a single platform. PMID:21863016

  4. Pt Single Atoms Embedded in the Surface of Ni Nanocrystals as Highly Active Catalysts for Selective Hydrogenation of Nitro Compounds.

    Science.gov (United States)

    Peng, Yuhan; Geng, Zhigang; Zhao, Songtao; Wang, Liangbing; Li, Hongliang; Wang, Xu; Zheng, Xusheng; Zhu, Junfa; Li, Zhenyu; Si, Rui; Zeng, Jie

    2018-06-13

    Single-atom catalysts exhibit high selectivity in hydrogenation due to their isolated active sites, which ensure uniform adsorption configurations of substrate molecules. Compared with the achievement in catalytic selectivity, there is still a long way to go in exploiting the catalytic activity of single-atom catalysts. Herein, we developed highly active and selective catalysts in selective hydrogenation by embedding Pt single atoms in the surface of Ni nanocrystals (denoted as Pt 1 /Ni nanocrystals). During the hydrogenation of 3-nitrostyrene, the TOF numbers based on surface Pt atoms of Pt 1 /Ni nanocrystals reached ∼1800 h -1 under 3 atm of H 2 at 40 °C, much higher than that of Pt single atoms supported on active carbon, TiO 2 , SiO 2 , and ZSM-5. Mechanistic studies reveal that the remarkable activity of Pt 1 /Ni nanocrystals derived from sufficient hydrogen supply because of spontaneous dissociation of H 2 on both Pt and Ni atoms as well as facile diffusion of H atoms on Pt 1 /Ni nanocrystals. Moreover, the ensemble composed of the Pt single atom and nearby Ni atoms in Pt 1 /Ni nanocrystals leads to the adsorption configuration of 3-nitrostyrene favorable for the activation of nitro groups, accounting for the high selectivity for 3-vinylaniline.

  5. Modeling an Iodine Hall Thruster Plume in the Iodine Satellite (ISAT)

    Science.gov (United States)

    Choi, Maria

    2016-01-01

    An iodine-operated 200-W Hall thruster plume has been simulated using a hybrid-PIC model to predict the spacecraft surface-plume interaction for spacecraft integration purposes. For validation of the model, the plasma potential, electron temperature, ion current flux, and ion number density of xenon propellant were compared with available measurement data at the nominal operating condition. To simulate iodine plasma, various collision cross sections were found and used in the model. While time-varying atomic iodine species (i.e., I, I+, I2+) information is provided by HPHall simulation at the discharge channel exit, the molecular iodine species (i.e., I2, I2+) are introduced as Maxwellian particles at the channel exit. Simulation results show that xenon and iodine plasma plumes appear to be very similar under the assumptions of the model. Assuming a sticking coefficient of unity, iodine deposition rate is estimated.

  6. 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

  7. Interaction between single gold atom and the graphene edge: A study via aberration-corrected transmission electron microscopy

    KAUST Repository

    Wang, Hongtao

    2012-01-01

    Interaction between single noble metal atoms and graphene edges has been investigated via aberration-corrected and monochromated transmission electron microscopy. A collective motion of the Au atom and the nearby carbon atoms is observed in transition between energy-favorable configurations. Most trapping and detrapping processes are assisted by the dangling carbon atoms, which are more susceptible to knock-on displacements by electron irradiation. Thermal energy is lower than the activation barriers in transition among different energy-favorable configurations, which suggests electron-beam irradiation can be an efficient way of engineering the graphene edge with metal atoms. © 2012 The Royal Society of Chemistry.

  8. Single-molecule studies of DNA transcription using atomic force microscopy

    International Nuclear Information System (INIS)

    Billingsley, Daniel J; Crampton, Neal; Thomson, Neil H; Bonass, William A; Kirkham, Jennifer

    2012-01-01

    Atomic force microscopy (AFM) can detect single biomacromolecules with a high signal-to-noise ratio on atomically flat biocompatible support surfaces, such as mica. Contrast arises from the innate forces and therefore AFM does not require imaging contrast agents, leading to sample preparation that is relatively straightforward. The ability of AFM to operate in hydrated environments, including humid air and aqueous buffers, allows structure and function of biological and biomolecular systems to be retained. These traits of the AFM are ensuring that it is being increasingly used to study deoxyribonucleic acid (DNA) structure and DNA–protein interactions down to the secondary structure level. This report focuses in particular on reviewing the applications of AFM to the study of DNA transcription in reductionist single-molecule bottom-up approaches. The technique has allowed new insights into the interactions between ribonucleic acid (RNA) polymerase to be gained and enabled quantification of some aspects of the transcription process, such as promoter location, DNA wrapping and elongation. More recently, the trend is towards studying the interactions of more than one enzyme operating on a single DNA template. These methods begin to reveal the mechanics of gene expression at the single-molecule level and will enable us to gain greater understanding of how the genome is transcribed and translated into the proteome. (topical review)

  9. Prospects of Optical Single Atom Detection in Noble Gas Solids for Measurements of Rare Nuclear Reactions

    Science.gov (United States)

    Singh, Jaideep; Bailey, Kevin G.; Lu, Zheng-Tian; Mueller, Peter; O'Connor, Thomas P.; Xu, Chen-Yu; Tang, Xiaodong

    2013-04-01

    Optical detection of single atoms captured in solid noble gas matrices provides an alternative technique to study rare nuclear reactions relevant to nuclear astrophysics. I will describe the prospects of applying this approach for cross section measurements of the ^22Ne,,),25Mg reaction, which is the crucial neutron source for the weak s process inside of massive stars. Noble gas solids are a promising medium for the capture, detection, and manipulation of atoms and nuclear spins. They provide stable and chemically inert confinement for a wide variety of guest species. Because noble gas solids are transparent at optical wavelengths, the guest atoms can be probed using lasers. We have observed that ytterbium in solid neon exhibits intersystem crossing (ISC) which results in a strong green fluorescence (546 nm) under excitation with blue light (389 nm). Several groups have observed ISC in many other guest-host pairs, notably magnesium in krypton. Because of the large wavelength separation of the excitation light and fluorescence light, optical detection of individual embedded guest atoms is feasible. This work is supported by DOE, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

  10. Altering iodine metabolism in the calf by feeding iodine-binding agents

    International Nuclear Information System (INIS)

    Miller, J.K.; Swanson, E.W.; Lyke, W.A.; Byrne, W.F.

    1975-01-01

    Effects of feeding cottonseed meal and anion-exchange resin on iodine absorption and excretion by calves were investigated. Each additional amount of resin fed from 0.3 to 3.5 g/kg body weight further increased fecal excretion from single oral iodine-131 and intravenous iodine-125 doses. By feeding 3 to 10 g cottonseed meal/kg body weight, excretion of oral iodine-131 given daily was increased 7 to 94 percent in feces and reduced as much as 35 percent in urine, but plasma iodine-131 was not changed. Introducing 1 g resin/kg body weight daily into the diet increased fecal iodine-131 excretion three to five times that with cottonseed meal alone and reduced both plasma and urinary iodine-131. The same amount of resin fed daily had similar effects on excretion of iodine-131 injected subcutaneously each day. Although iodine depletion by a highly efficient iodine binder (resin) in the gastrointestinal tract is probable, iodine binding by a natural feed constituent (cottonseed meal) was relatively inefficient. (U.S.)

  11. Altering iodine metabolism in the calf by feeding iodine-binding agents

    International Nuclear Information System (INIS)

    Miller, J.K.; Swanson, E.W.; Lyke, W.A.; Byrne, W.F.

    1975-01-01

    Effects of feeding cottonseed meal and anion-exchange resin on iodine absorption and excretion by calves were investigated. Each additional amount of resin fed from 0.3 to 3.5 g/kg body weight further increased fecal excretion from single oral iodine-131 and intravenous iodine-125 doses. By feeding 3 to 10 g cottonseed meal/kg body weight, excretion of oral iodine-131 given daily was increased 7 to 94 percent in feces and reduced as much as 35 percent in urine, but plasma iodine-131 was not changed. Introducing 1 g resin/kg body weight daily into the diet increased fecal iodine-131 excretion three to five times that with cottonseed meal alone and reduced both plasma and urinary iodine-131. The same amount of resin fed daily had similar effects on excretion of iodine-131 injected subcutaneously each day. Although iodine depletion by a highly efficient iodine binder (resin) in the gastrointestinal tract is probable, iodine binding by a natural feed constituent (cottonseed meal) was relatively inefficient. (auth)

  12. Control of single-photon routing in a T-shaped waveguide by another atom

    Science.gov (United States)

    Huang, Jin-Song; Wang, Jing-Wen; Wang, Yan; Li, Yan-Ling; Huang, You-Wen

    2018-04-01

    Quantum routers with a high routing rate of much more than 0.5 are of great importance for quantum networks. We provide a scheme to perform bidirectional high routing-rate transfer in a T-shaped coupled-resonator waveguide (CRW), which extends a recent unidirectional scheme proposed by Lu et al. (Opt Express 23:22955, 2015). By locating an extra two-level atom in the infinite CRW channel of the T-shaped CRW with a three-level system, an effective potential is generated. Our numerical results show that high routing capability from the infinite CRW channel to the semi-infinite channel can be achieved, and routing capability from the semi-infinite CRW channel to the infinite channel can also be significantly enhanced, with the help of the effective potential. Therefore, the proposed double-atom configuration could be utilized as a bidirectional quantum routing controller to implement high transfer rate routing of single photons.

  13. Single OR molecule and OR atomic circuit logic gates interconnected on a Si(100)H surface

    International Nuclear Information System (INIS)

    Ample, F; Joachim, C; Duchemin, I; Hliwa, M

    2011-01-01

    Electron transport calculations were carried out for three terminal OR logic gates constructed either with a single molecule or with a surface dangling bond circuit interconnected on a Si(100)H surface. The corresponding multi-electrode multi-channel scattering matrix (where the central three terminal junction OR gate is the scattering center) was calculated, taking into account the electronic structure of the supporting Si(100)H surface, the metallic interconnection nano-pads, the surface atomic wires and the molecule. Well interconnected, an optimized OR molecule can only run at a maximum of 10 nA output current intensity for a 0.5 V bias voltage. For the same voltage and with no molecule in the circuit, the output current of an OR surface atomic scale circuit can reach 4 μA.

  14. Photon statistics of a single-atom intracavity system involving electromagnetically induced transparency

    International Nuclear Information System (INIS)

    Rebic, S.; Parkins, A.S.; Tan, S.M.

    2002-01-01

    We explore the photon statistics of light emitted from a system comprising a single four-level atom strongly coupled to a high-finesse optical cavity mode that is driven by a coherent laser field. In the weak driving regime this system is found to exhibit a photon blockade effect. For intermediate driving strengths we find a sudden change in the photon statistics of the light emitted from the cavity. Photon antibunching switches to photon bunching over a very narrow range of intracavity photon number. It is proven that this sudden change in photon statistics occurs due to the existence of robust quantum interference of transitions between the dressed states of the atom-cavity system. Furthermore, it is shown that the strong photon bunching is a nonclassical effect for certain values of driving field strength, violating classical inequalities for field correlations

  15. The scattering of low energy helium ions and atoms from a copper single crystal, ch. 2

    International Nuclear Information System (INIS)

    Verheij, L.K.; Poelsema, B.; Boers, A.L.

    1976-01-01

    The scattering of 4-10 keV helium ions from a copper surface cannot be completely described with elastic, single collisions. The general behaviour of the measured energy and width of the surface peak can be explained by differences in inelastic energy losses for scattering from an ideal surface and from surface structures (damage). Multiple scattering effects have a minor influence. Additional information about the inelastic processes is obtained from scattering experiments with a primary atom beam. For large angles of incidence, the energy of the reflected ions is reduced about 20 eV if the primary beam consists of atoms instead of ions. An explanation of this effect and an explanation of the different behaviour of small angles is given. In the investigated energy range, the electronic stopping power might depend on the charge state of the primary particles. The experimental results are rather well explained by the Lindhard, Scharff, Schioett theory

  16. 37Ar based neutron source for calibration of the iodine solar neutrino detector

    International Nuclear Information System (INIS)

    Abdurashitov, D.N.; Gavrin, V.N.; Mirmov, I.N.; Veretenkin, E.P.; Yants, V.Eh.; Cleveland, B.T.; Davis, R. Jr.; Lande, K.; Wildenhain, P.; Khomyakov, Yu.S.

    2001-01-01

    The methodology of the creation of a compact neutrino source based on the 37 Ar isotope as well as the technique of calibration of an iodine detector of solar neutrinos is described. An important overall expected result is the creation of a prototype of the source with the intensity up to 400 kCi, delivery of this source to the Baksan neutrino observatory and the test calibration of the single module of the iodine detector. Simulation shows that at least 45-70 127 Xe atoms will be detected in the irradiation of ∼40 tons of methylene iodide by the source leading to ∼19% of the error on the measured production rate. This result should be considered as a test of the developed technology and will verify overall technical readiness for the creation of a full scale neutrino source and the full scale calibration of the iodine detector

  17. Role of single photon emission computed tomography/computed tomography in diagnostic iodine-131 scintigraphy before initial radioiodine ablation in differentiated thyroid cancer

    International Nuclear Information System (INIS)

    Agrawal, Kanhaiyalal; Bhattacharya, Anish; Mittal, Bhagwant Rai

    2005-01-01

    The study was performed to evaluate the incremental value of single photon emission computed tomography/computed tomography (SPECT/CT) over planar radioiodine imaging before radioiodine ablation in the staging, management and stratification of risk of recurrence (ROR) in differentiated thyroid cancer (DTC) patients. Totally, 83 patients (21 male, 62 female) aged 17–75 (mean 39.9) years with DTC were included consecutively in this prospective study. They underwent postthyroidectomy planar and SPECT/CT scans after oral administration of 37–114 MBq iodine-131 (I-131). The scans were interpreted as positive, negative or suspicious for tracer uptake in the thyroid bed, cervical lymph nodes and sites outside the neck. In each case, the findings on planar images were recorded first, without knowledge of SPECT/CT findings. Operative and pathological findings were used for postsurgical tumor–node–metastasis staging. The tumor staging was reassessed after each of these two scans. Single photon emission computed tomography/computed tomography localized radioiodine uptake in the thyroid bed in 9/83 (10.8%) patients, neck nodes in 24/83 (28.9%) patients and distant metastases in 8/83 (9.6%) patients in addition to the planar study. Staging was changed in 8/83 (9.6%), ROR in 11/83 (13.2%) and management in 26/83 (31.3%) patients by the pretherapy SPECT/CT in comparison to planar imaging. SPECT/CT had incremental value in 32/83 patients (38.5%) over the planar scan. Single photon emission computed tomography/computed tomography is feasible during a diagnostic I-131 scan with a low amount of radiotracer. It improved the interpretation of pretherapy I-131 scintigraphy and changed the staging and subsequent patient management

  18. Iodine and Pregnancy

    OpenAIRE

    Yarrington, Christina; Pearce, Elizabeth N.

    2011-01-01

    Iodine is a necessary element for the production of thyroid hormone. We will review the impact of dietary iodine status on thyroid function in pregnancy. We will discuss iodine metabolism, homeostasis, and nutritional recommendations for pregnancy. We will also discuss the possible effects of environmental contaminants on iodine utilization in pregnant women.

  19. Lattice location of diffused Zn atoms in GaAs and InP single crystals

    International Nuclear Information System (INIS)

    Chan, L.Y.; Yu, K.M.; Ben-Tzur, M.; Haller, E.E.; Jaklevic, J.M.; Walukiewicz, W.; Hanson, C.M.

    1991-01-01

    We have investigated the saturation phenomenon of the free carrier concentration in p-type GaAs and InP single crystals doped by zinc diffusion. The free hole saturation occurs at 10 20 cm -3 for GaAs, but the maximum concentration for InP appears at mid 10 18 cm -3 . The difference in the saturation hole concentrations for these materials is investigated by studying the incorporation and the lattice location of the impurity zinc, an acceptor when located on a group III atom site. Zinc is diffused into the III-V wafers in a sealed quartz ampoule. Particle-induced x-ray emission with ion-channeling techniques are employed to determine the exact lattice location of the zinc atoms. We have found that over 90% of all zinc atoms occupy Ga sites in the diffused GaAs samples, while for the InP case, the zinc substitutionality is dependent on the cooling rate of the sample after high-temperature diffusion. For the slowly cooled sample, a large fraction (∼90%) of the zinc atoms form random precipitates of Zn 3 P 2 and elemental Zn. However, when rapidly cooled only 60% of the zinc forms such precipitates while the rest occupies specific sites in the InP. We analyze our results in terms of the amphoteric native defect model. We show that the difference in the electrical activity of the Zn atoms in GaAs and InP is a consequence of the different location of the Fermi level stabilization energy in these two materials

  20. Clustered atom-replaced structure in single-crystal-like metal oxide

    Science.gov (United States)

    Araki, Takeshi; Hayashi, Mariko; Ishii, Hirotaka; Yokoe, Daisaku; Yoshida, Ryuji; Kato, Takeharu; Nishijima, Gen; Matsumoto, Akiyoshi

    2018-06-01

    By means of metal organic deposition using trifluoroacetates (TFA-MOD), we replaced and localized two or more atoms in a single-crystalline structure having almost perfect orientation. Thus, we created a new functional structure, namely, clustered atom-replaced structure (CARS), having single-crystal-like metal oxide. We replaced metals in the oxide with Sm and Lu and localized them. Energy dispersive x-ray spectroscopy results, where the Sm signal increases with the Lu signal in the single-crystalline structure, confirm evidence of CARS. We also form other CARS with three additional metals, including Pr. The valence number of Pr might change from 3+ to approximately 4+, thereby reducing the Pr–Ba distance. We directly observed the structure by a high-angle annular dark-field image, which provided further evidence of CARS. The key to establishing CARS is an equilibrium chemical reaction and a combination of additional larger and smaller unit cells to matrix cells. We made a new functional metal oxide with CARS and expect to realize CARS in other metal oxide structures in the future by using the above-mentioned process.

  1. Single and multiple ionization of noble gas atoms by H0 impact

    International Nuclear Information System (INIS)

    Sarkadi, L.; Gulyas, L.; Herczku, P.; Kovacs, S.T.S.; Koever, A.

    2012-01-01

    Complete text of publication follows. The understanding of the mechanisms of collisions between energetic charged particles and neutral atoms is of fundamental significance, and it has large importance in many research fields (plasma physics, astrophysics, materials science, etc.), as well as in number of practical applications. In the present work we measured total direct ionization and electron loss cross sections for the collisions of H 0 atoms with noble gas atoms (He, Ne, Ar, Kr) in the energy range 75-300 keV. The experiment was carried out at the 1.5 MV Van de Graaff accelerator of Atomki by coincident detection of the recoil target ions and the charge-state analyzed scattered projectiles. With this study we wished to obtain information about the role played by the electron of the H 0 projectile in the process of the single and multiple vacancy production induced by the collision. For this purpose we repeated the measurements also with proton projectile under the same experimental conditions. For calibration of the measuring system and normalization of our data we used the cross section values of Ref. [1]. The experimental results were analysed with using the classical trajectory Monte Carlo (CTMC) method. CTMC describes well the experimental data for both projectiles for the single vacancy creation, however we observed increasing deviation between the theory and experiment with increasing number of the created vacancies, as well as with decreasing atomic number of the target atoms. Fig. 1 shows our results obtained for the single, double and triple ionization (q = 1, 2, 3) of Kr at H 0 impact for the two cases when the outgoing projectile is H 0 (a) and H + (b), i.e., for pure ionization of the target, and ionization of the target with simultaneous electron loss of the projectile. The curves in the figure were obtained by two versions of the three-body CTMC theory: a conventional model (dashed curves); and a model taking partially account of the many

  2. Active molecular iodine photochemistry in the Arctic.

    Science.gov (United States)

    Raso, Angela R W; Custard, Kyle D; May, Nathaniel W; Tanner, David; Newburn, Matt K; Walker, Lawrence; Moore, Ronald J; Huey, L G; Alexander, Liz; Shepson, Paul B; Pratt, Kerri A

    2017-09-19

    During springtime, the Arctic atmospheric boundary layer undergoes frequent rapid depletions in ozone and gaseous elemental mercury due to reactions with halogen atoms, influencing atmospheric composition and pollutant fate. Although bromine chemistry has been shown to initiate ozone depletion events, and it has long been hypothesized that iodine chemistry may contribute, no previous measurements of molecular iodine (I 2 ) have been reported in the Arctic. Iodine chemistry also contributes to atmospheric new particle formation and therefore cloud properties and radiative forcing. Here we present Arctic atmospheric I 2 and snowpack iodide (I - ) measurements, which were conducted near Utqiaġvik, AK, in February 2014. Using chemical ionization mass spectrometry, I 2 was observed in the atmosphere at mole ratios of 0.3-1.0 ppt, and in the snowpack interstitial air at mole ratios up to 22 ppt under natural sunlit conditions and up to 35 ppt when the snowpack surface was artificially irradiated, suggesting a photochemical production mechanism. Further, snow meltwater I - measurements showed enrichments of up to ∼1,900 times above the seawater ratio of I - /Na + , consistent with iodine activation and recycling. Modeling shows that observed I 2 levels are able to significantly increase ozone depletion rates, while also producing iodine monoxide (IO) at levels recently observed in the Arctic. These results emphasize the significance of iodine chemistry and the role of snowpack photochemistry in Arctic atmospheric composition, and imply that I 2 is likely a dominant source of iodine atoms in the Arctic.

  3. Iodine intake in Denmark

    International Nuclear Information System (INIS)

    Pedersen, K.M.; Noehr, S.B.; Laurberg, P.

    1997-01-01

    Iodine deficiency with a high frequency of goitre and, in severely affected areas, cretinism is common in some areas of the world. In Denmark the iodine intake as evaluated by urinary iodine excretion has been at a stable low level for many years, except for the part of the population now taking iodine supplementation as part of vitamin/mineral preparations. The iodine intake is lowest in the western part to the country where an epidemiological study of elderly subjects has demonstrated a high frequency of goitre and hyperthyroidism in women. This supports the suggestion of a controlled moderate increase in iodine intake via an iodine supplementation program. (au) 40 refs

  4. Single Photon Emission Computed Tomography/Positron Emission Tomography Imaging and Targeted Radionuclide Therapy of Melanoma: New Multimodal Fluorinated and Iodinated Radiotracers

    International Nuclear Information System (INIS)

    Maisonial, A.; Papon, J.; Bayle, M.; Vidal, A.; Auzeloux, Ph.; Rbah, L.; Bonnet-Duquennoy, M.; Miot-Noirault, E.; Galmier, M.J.; Borel, M.; Madelmont, J.C.; Moins, N.; Chezal, J.M.; Kuhnast, B.; Boisgard, R.; Dolle, F.; Tavitian, B.; Boisgard, R.; Tavitian, B.; Askienazy, S.

    2011-01-01

    This study reports a series of 14 new iodinated and fluorinated compounds offering both early imaging ( 123 I, 124 I, 18 F) and systemic treatment ( 131 I) of melanoma potentialities. The biodistribution of each 125 I-labeled tracer was evaluated in a model of melanoma B16F0-bearing mice, using in vivo serial γ scintigraphic imaging. Among this series, [ 125 I]56 emerged as the most promising compound in terms of specific tumoral uptake and in vivo kinetic profile. To validate our multimodality concept, the radiosynthesis of [ 18 F]56 was then optimized and this radiotracer has been successfully investigated for in vivo PET imaging of melanoma in B16F0- and B16F10-bearing mouse model. The therapeutic efficacy of [ 131 I]56 was then evaluated in mice bearing subcutaneous B16F0 melanoma, and a significant slow down in tumoral growth was demonstrated. These data support further development of 56 for PET imaging ( 18 F, 124 I) and targeted radionuclide therapy ( 131 I) of melanoma using a single chemical structure. (authors)

  5. Area at risk can be assessed by iodine-123-meta-iodobenzylguanidine single-photon emission computed tomography after myocardial infarction: a prospective study.

    Science.gov (United States)

    Hedon, Christophe; Huet, Fabien; Ben Bouallegue, Fayçal; Vernhet, Hélène; Macia, Jean-Christophe; Cung, Thien-Tri; Leclercq, Florence; Cade, Stéphane; Cransac, Frédéric; Lattuca, Benoit; Vandenberghe, D'Arcy; Bourdon, Aurélie; Benkiran, Meriem; Vauchot, Fabien; Gervasoni, Richard; D'estanque, Emmanuel; Mariano-Goulart, Denis; Roubille, François

    2018-02-01

    Myocardial salvage is an important surrogate endpoint to estimate the impact of treatments in patients with ST-segment elevation myocardial infarction (STEMI). The aim of this study was to evaluate the correlation between cardiac sympathetic denervation area assessed by single-photon emission computed tomography (SPECT) using iodine-123-meta-iodobenzylguanidine (I-MIBG) and myocardial area at risk (AAR) assessed by cardiac magnetic resonance (CMR) (gold standard). A total of 35 postprimary reperfusion STEMI patients were enrolled prospectively to undergo SPECT using I-MIBG (evaluates cardiac sympathetic denervation) and thallium-201 (evaluates myocardial necrosis), and to undergo CMR imaging using T2-weighted spin-echo turbo inversion recovery for AAR and postgadolinium T1-weighted phase sensitive inversion recovery for scar assessment. I-MIBG imaging showed a wider denervated area (51.1±16.0% of left ventricular area) in comparison with the necrosis area on thallium-201 imaging (16.1±14.4% of left ventricular area, Parea (P=0.23) and was adequately correlated (R=0.56, P=0.0002). Myocardial salvage evaluated by SPECT imaging (mismatch denervated but viable myocardium) was significantly higher than by CMR (P=0.02). In patients with STEMI, I-MIBG SPECT, assessing cardiac sympathetic denervation may precisely evaluate the AAR, providing an alternative to CMR for AAR assessment.

  6. In vivo imaging of GABA{sub A} receptors using sequential whole-volume iodine-123 iomazenil single-photon emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Busatto, G.F. [Dept. of Psychological Medicine, Inst. of Psychiatry, London (United Kingdom); Pilowsky, L.S. [Dept. of Psychological Medicine, Inst. of Psychiatry, London (United Kingdom); Costa, D.C. [Inst. of Nuclear Medicine, University Coll. and Middlesex School of Medicine, London (United Kingdom); Ell, P.J. [Inst. of Nuclear Medicine, University Coll. and Middlesex School of Medicine, London (United Kingdom); Lingford-Hughes, A. [Dept. of Psychological Medicine, Inst. of Psychiatry, London (United Kingdom); Kerwin, R.W. [Dept. of Psychological Medicine, Inst. of Psychiatry, London (United Kingdom)

    1995-01-01

    Using a brain-dedicated triple-headed single-photon emission tomography (SPET) system, a sequential whole-volume imaging protocol has been devised to evaluate the regional distribution of iodine-123 iomazenil binding to GABA{sub A} receptors in the entire brain. The protocol was piloted in eight normal volunteers (seven males and one female; mean age, 24.8{+-}3.9 years). The patterns obtained were largely compatible with the known distribution of GABA{sub A} receptors in the brain as reported in autoradiographic studies, with cerebral cortical regions, particularly the occipital and frontal cortices, displaying the highest {sup 123}I-iomazenil uptake. Measures of time to peak uptake and tracer washout rates presented with the same pattern of regional variation, with later times to peak and slower washout rates in cortical regions compared to other brain areas. Semiquantitative analysis of the data using white matter/ventricle regions as reference demonstrated a plateau of specific {sup 123}I-iomazenil binding in neocortical and cerebellar regions from 60-75 min onwards. These data demonstrate the feasibility of sequential, dynamic whole-volume {sup 123}I-iomazenil SPET imaging. The protocol may be particularly useful in the investigation of neuropsychiatric conditions which are likely to involve more than one focus of GABA abnormalities, such as anxiety disorders and schizophrenia. (orig.)

  7. Iodine intake in Ireland

    International Nuclear Information System (INIS)

    Smith, P.P.A.; Hetherton, A.M.; O'Carroll, D.; Smith, D.F.; O'Halloran, M.J.; O'Donovan, D.K.

    1988-01-01

    A study of urinary iodine excretion and thyroid gland uptake of radioactive iodine 131 I was undertaken in the Dublin area with a view to providing data on the current iodine status in Ireland. A mean urinary iodine excretion of 118±82μg/gram creatinine (Median 96) obtained from 821 subjects attending general hospital outpatient clinics in the Dublin area in 1987, while excluding severe iodine deficiency in this particular cohort, obscured the fact that 250 (30%) had iodine excretion values ≤70 μ/g creatinine, a value approximating to the minimum daily iodine requirement. The results provide sufficient evidence of sporadic iodine deficiency to justify a more widespread study of the iodine status of the Irish population with a view to making recommendations on the possible need for iodine prophylaxis

  8. Prevention of Cardiac Implantable Electronic Device Infections: Single Operator Technique with Use of Povidone-Iodine, Double Gloving, Meticulous Aseptic/Antiseptic Measures and Antibiotic Prophylaxis.

    Science.gov (United States)

    Manolis, Antonis S; Melita, Helen

    2017-01-01

    Cardiac implantable electronic device (CIED) implantation is complicated by infection still at a worrisome rate of 2-5%. Since early on during device implantation procedures, we have adopted an infection-preventive technique which has hitherto resulted in effective prevention of infections. Herein we present our results of applying this technique by a single operator in a prospective series of 762 consecutive patients undergoing device implantation. A meticulous search for and treatment of active, occult, or smoldering infection was undertaken preoperatively. An aseptic/antiseptic technique was used for implantation of each device. Skin preparation is thorough with initial cleansing performed with alcohol followed by povidone-iodine 10% solution, which is also used in the wound and inside the pocket. In addition, we routinely use double gloving, and IV antibiotic prophylaxis 1 hour before and for 48 hours afterwards followed by oral antibiotic for 2-3 days after discharge. The skin is closed with absorbable sutures. The study includes 382 patients having a new pacemaker (n = 333) or battery change, system upgrade or lead revision (n = 49), and 380 patients having a new implantable cardioverter-defibrillator (ICD) (n = 296) or device replacement/upgrade/lead revision (n = 84). The pacemaker group, aged 70.2 ± 16.5 years, includes 18% VVI, 49% DDD, 29% VDD, and 4% cardiac resynchronization therapy (CRT) devices. The ICD group, aged 61.3 ± 13.0 years, with a mean ejection fraction of 36 ± 13%, includes 325 ICD and 55 CRT implants. Over 26.6 ± 33.4 months for the pacemaker group and 36.6 ± 38.3 months for the ICD group, infection occurred in one patient in each group (0.26%) having a device replacement. A consistent and strict approach of aseptic/antiseptic technique with the use of double gloving and povidone-iodine solution within the pocket plus a 4-day regimen of antibiotic prophylaxis minimizes infections in CIED implants. © 2016 Wiley Periodicals, Inc.

  9. Long-term outcomes of {sup 131}Iodine mIBG therapy in metastatic gastrointestinal pancreatic neuroendocrine tumours: single administration predicts non-responders

    Energy Technology Data Exchange (ETDEWEB)

    Mulholland, Nicola; Chakravartty, Riddhika; Devlin, Lindsey; Kalogianni, Eleni; Corcoran, Ben; Vivian, Gillian [King' s College Hospital, Department of Nuclear Medicine, London (United Kingdom)

    2015-12-15

    {sup 131}Iodine (I131)-metaiodobenzylguanidine (mIBG) is a radionuclide-based treatment option for metastatic gastrointestinal-pancreatic neuroendocrine tumours (GEP NET). This study aimed at identifying prognostic indicators of long-term outcome based on initial evaluation following a first mIBG treatment (7400 MBq) in a patient cohort with such tumours, with a secondary aim of evaluating progression-free survival (PFS) and overall survival (OS) following mIBG therapy. Retrospective review of the hospital records was performed to identify a cohort of 38 adult patients who underwent {sup 131}Iodine-mIBG therapy over a 9-year period for metastatic GEP NETs and neuroendocrine tumours with an unknown primary. Treatment response was evaluated based on radiological criteria (RECIST1.1), biochemical markers [serum Chromogranin A (CgA)/urinary 5HIAA] and symptomatic response at clinical follow-up, all evaluated at 3-6 months from first mIBG treatment. Progression-free survival (PFS) and overall survival (OS) from the first mIBG treatment were recorded. At 3-6 months following a single mIBG therapy, 75 %, 67 %, and 63 % of patients showed either a partial response (PR) or stable disease (SD) on radiological, biochemical, and symptomatic criteria, respectively. Complete response (CR) was not seen in any patient. OS from the date of diagnosis and from the first therapy was 8 years +/-1.1 (95 % CI 5.7 to 10.2 years) and 4 years+/-0.69 (95 % CI 2.6-5.3 years), respectively. Twenty-nine percent of patients were alive at 10 years. Significant survival advantage was seen in patients with SD/PR as compared to those who had progressive disease (PD) for each of these three criteria. Biochemical, radiological (RECIST 1.1) and symptomatic assessment of disease status at 3 to 6 months after first I131-mIBG therapy stratifies patients with a poor prognosis. This can be used to identify patients who may benefit from alternative strategies of treatment. (orig.)

  10. The effect of atomic hydrogen adsorption on single-walled carbon nano tubes properties

    International Nuclear Information System (INIS)

    Jalili, S.; Majidi, R.

    2007-01-01

    We investigated the adsorption of hydrogen atoms on metallic single-walled carbon nano tubes using ab initio molecular dynamics method. It was found that the geometric structures and the electronic properties of hydrogenated SWNTs can be strongly changed by varying hydrogen coverage. The circular cross sections of the CNTs were changed with different hydrogen coverage. When hydrogen is chemisorbed on the surface of the carbon nano tube, the energy gap will be appeared. This is due to the degree of the Sp 3 hybridization, and the hydrogen coverage can control the band gap of the carbon nano tube

  11. Highly efficient electron gun with a single-atom electron source

    International Nuclear Information System (INIS)

    Ishikawa, Tsuyoshi; Urata, Tomohiro; Cho, Boklae; Rokuta, Eiji; Oshima, Chuhei; Terui, Yoshinori; Saito, Hidekazu; Yonezawa, Akira; Tsong, Tien T.

    2007-01-01

    The authors have demonstrated highly collimated electron-beam emission from a practical electron gun with a single-atom electron source; ∼80% of the total emission current entered the electron optics. This ratio was two or three orders of magnitude higher than those of the conventional electron sources such as a cold field emission gun and a Zr/O/W Schottky gun. At the pressure of less than 1x10 -9 Pa, the authors observed stable emission of 20 nA, which generates the specimen current of 5 pA required for scanning electron microscopes

  12. Shot noise as a probe of spin-correlated transport through single atoms

    Science.gov (United States)

    Pradhan, S.; Fransson, J.

    2018-03-01

    We address the shot noise in the tunneling current through a local spin, pertaining to recent experiments on magnetic adatoms and single molecular magnets. We show that both uncorrelated and spin-correlated scattering processes contribute vitally to the noise spectrum. The spin-correlated scattering processes provide an additional contribution to the Landauer-Büttiker shot noise expression, accounting for correlations between the tunneling electrons and the localized spin moment. By calculating the Fano factor, we show that both super- and sub-Poissonian shot noise can be described within our approach. Our theory provides transparent insights into noise spectroscopy, consistent with recent experiments using local probing techniques on magnetic atoms.

  13. Electron-ion correlation effects in ion-atom single ionization

    Energy Technology Data Exchange (ETDEWEB)

    Colavecchia, F.D.; Garibotti, C.R. [Centro Atomico Bariloche and Consejo Nacional de Investigaciones Cientificas y Tecnicas, 8400 San Carlos de Bariloche (Argentina); Gasaneo, G. [Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina)

    2000-06-28

    We study the effect of electron-ion correlation in single ionization processes of atoms by ion impact. We present a distorted wave model where the final state is represented by a correlated function solution of a non-separable three-body continuum Hamiltonian, that includes electron-ion correlation as coupling terms of the wave equation. A comparison of the electronic differential cross sections computed with this model with other theories and experimental data reveals that the influence of the electron-ion correlation is more significant for low energy emitted electrons. (author). Letter-to-the-editor.

  14. Communication: atomic force detection of single-molecule nonlinear optical vibrational spectroscopy.

    Science.gov (United States)

    Saurabh, Prasoon; Mukamel, Shaul

    2014-04-28

    Atomic Force Microscopy (AFM) allows for a highly sensitive detection of spectroscopic signals. This has been first demonstrated for NMR of a single molecule and recently extended to stimulated Raman in the optical regime. We theoretically investigate the use of optical forces to detect time and frequency domain nonlinear optical signals. We show that, with proper phase matching, the AFM-detected signals closely resemble coherent heterodyne-detected signals. Applications are made to AFM-detected and heterodyne-detected vibrational resonances in Coherent Anti-Stokes Raman Spectroscopy (χ((3))) and sum or difference frequency generation (χ((2))).

  15. 129I Moessbauer spectroscopic study of several n-σ charge-transfer complexes of iodine with thioethers

    International Nuclear Information System (INIS)

    Sakai, Hiroshi; Matsuyama, Tomochika; Maeda, Yutaka

    1986-01-01

    129 I Moessbauer studies have been made of n-σ charge-transfer complexes of iodine with thioethers, such as thiane, 1,4-oxathiane, and 1,4-dithiane. The spectra of these complexes consist of two sets of quadrupole octets, corresponding to the bridging and terminal iodine atoms. The transferred charges from the thioethers are localized on the terminal iodine atoms, and the bridging iodine atoms have slightly positive charges. This result can be well explained in terms of a covalent bond between the sulfur and bridging iodine atoms or the MO treatment of a delocalized three-center four-electron bonding. The contributions of the dative structure to the ground state are estimated to be 36, 28, and 24 % for thiane-iodine, 1,4-oxathiane-iodine, and 1,4-dithiane-iodine respectively. The nature of the charge-transfer bond is discussed in comparison with amine-iodine complexes. (author)

  16. Manipulating molecular quantum states with classical metal atom inputs: demonstration of a single molecule NOR logic gate.

    Science.gov (United States)

    Soe, We-Hyo; Manzano, Carlos; Renaud, Nicolas; de Mendoza, Paula; De Sarkar, Abir; Ample, Francisco; Hliwa, Mohamed; Echavarren, Antonio M; Chandrasekhar, Natarajan; Joachim, Christian

    2011-02-22

    Quantum states of a trinaphthylene molecule were manipulated by putting its naphthyl branches in contact with single Au atoms. One Au atom carries 1-bit of classical information input that is converted into quantum information throughout the molecule. The Au-trinaphthylene electronic interactions give rise to measurable energy shifts of the molecular electronic states demonstrating a NOR logic gate functionality. The NOR truth table of the single molecule logic gate was characterized by means of scanning tunnelling spectroscopy.

  17. Room-temperature current blockade in atomically defined single-cluster junctions

    Science.gov (United States)

    Lovat, Giacomo; Choi, Bonnie; Paley, Daniel W.; Steigerwald, Michael L.; Venkataraman, Latha; Roy, Xavier

    2017-11-01

    Fabricating nanoscopic devices capable of manipulating and processing single units of charge is an essential step towards creating functional devices where quantum effects dominate transport characteristics. The archetypal single-electron transistor comprises a small conducting or semiconducting island separated from two metallic reservoirs by insulating barriers. By enabling the transfer of a well-defined number of charge carriers between the island and the reservoirs, such a device may enable discrete single-electron operations. Here, we describe a single-molecule junction comprising a redox-active, atomically precise cobalt chalcogenide cluster wired between two nanoscopic electrodes. We observe current blockade at room temperature in thousands of single-cluster junctions. Below a threshold voltage, charge transfer across the junction is suppressed. The device is turned on when the temporary occupation of the core states by a transiting carrier is energetically enabled, resulting in a sequential tunnelling process and an increase in current by a factor of ∼600. We perform in situ and ex situ cyclic voltammetry as well as density functional theory calculations to unveil a two-step process mediated by an orbital localized on the core of the cluster in which charge carriers reside before tunnelling to the collector reservoir. As the bias window of the junction is opened wide enough to include one of the cluster frontier orbitals, the current blockade is lifted and charge carriers can tunnel sequentially across the junction.

  18. Localization and force analysis at the single virus particle level using atomic force microscopy

    International Nuclear Information System (INIS)

    Liu, Chih-Hao; Horng, Jim-Tong; Chang, Jeng-Shian; Hsieh, Chung-Fan; Tseng, You-Chen; Lin, Shiming

    2012-01-01

    Highlights: ► Localization of single virus particle. ► Force measurements. ► Force mapping. -- Abstract: Atomic force microscopy (AFM) is a vital instrument in nanobiotechnology. In this study, we developed a method that enables AFM to simultaneously measure specific unbinding force and map the viral glycoprotein at the single virus particle level. The average diameter of virus particles from AFM images and the specificity between the viral surface antigen and antibody probe were integrated to design a three-stage method that sets the measuring area to a single virus particle before obtaining the force measurements, where the influenza virus was used as the object of measurements. Based on the purposed method and performed analysis, several findings can be derived from the results. The mean unbinding force of a single virus particle can be quantified, and no significant difference exists in this value among virus particles. Furthermore, the repeatability of the proposed method is demonstrated. The force mapping images reveal that the distributions of surface viral antigens recognized by antibody probe were dispersed on the whole surface of individual virus particles under the proposed method and experimental criteria; meanwhile, the binding probabilities are similar among particles. This approach can be easily applied to most AFM systems without specific components or configurations. These results help understand the force-based analysis at the single virus particle level, and therefore, can reinforce the capability of AFM to investigate a specific type of viral surface protein and its distributions.

  19. Image findings of a false positive radioactive iodine-131 uptake mimicking metastasis in pulmonary aspergillosis identified on single photon emission computed tomography-computed tomography

    Directory of Open Access Journals (Sweden)

    Kamaleshwaran Koramadai Karuppusamy

    2015-01-01

    Full Text Available High doses of iodine-131 are commonly used in patients with differentiated thyroid cancer after total or subtotal thyroidectomy, in order to ablate the remaining cancer or normal thyroid tissue. Multiple different false-positive scans can occur in the absence of residual thyroid tissue or metastases. The authors present a case of abnormal uptake of radioactive iodine in the aspergilloma, potentially masquerading as pulmonary metastases.

  20. Iodine Tagging Velocimetry in a Mach 10 Wake

    Science.gov (United States)

    Balla, Robert Jeffrey

    2013-01-01

    A variation on molecular tagging velocimetry (MTV) [1] designated iodine tagging velocimetry (ITV) is demonstrated. Molecular iodine is tagged by two-photon absorption using an Argon Fluoride (ArF) excimer laser. A single camera measures fluid displacement using atomic iodine emission at 206 nm. Two examples ofMTVfor cold-flowmeasurements areN2OMTV [2] and Femtosecond Laser Electronic Excitation Tagging [3]. These, like most MTV methods, are designed for atmospheric pressure applications. Neither can be implemented at the low pressures (0.1- 1 Torr) in typical hypersonic wakes. Of all the single-laser/singlecamera MTV approaches, only Nitric-Oxide Planar Laser Induced Fluorescence-based MTV [4] has been successfully demonstrated in a Mach 10 wake. Oxygen quenching limits transit times to 500 ns and accuracy to typically 30%. The present note describes the photophysics of the ITV method. Off-body velocimetry along a line is demonstrated in the aerothermodynamically important and experimentally challenging region of a hypersonic low-pressure near-wake in a Mach 10 air wind tunnel. Transit times up to 10 µs are demonstrated with conservative errors of 10%.

  1. Simple and efficient absorption filter for single photons from a cold atom quantum memory.

    Science.gov (United States)

    Stack, Daniel T; Lee, Patricia J; Quraishi, Qudsia

    2015-03-09

    The ability to filter unwanted light signals is critical to the operation of quantum memories based on neutral atom ensembles. Here we demonstrate an efficient frequency filter which uses a vapor cell filled with (85)Rb and a buffer gas to attenuate both residual laser light and noise photons by nearly two orders of magnitude with little loss to the single photons associated with our cold (87)Rb quantum memory. This simple, passive filter provides an additional 18 dB attenuation of our pump laser and erroneous spontaneous emissions for every 1 dB loss of the single photon signal. We show that the addition of a frequency filter increases the non-classical correlations and the retrieval efficiency of our quantum memory by ≈ 35%.

  2. Quantum Hall states of atomic Bose gases: Density profiles in single-layer and multilayer geometries

    International Nuclear Information System (INIS)

    Cooper, N. R.; Lankvelt, F. J. M. van; Reijnders, J. W.; Schoutens, K.

    2005-01-01

    We describe the density profiles of confined atomic Bose gases in the high-rotation limit, in single-layer and multilayer geometries. We show that, in a local-density approximation, the density in a single layer shows a landscape of quantized steps due to the formation of incompressible liquids, which are analogous to fractional quantum Hall liquids for a two-dimensional electron gas in a strong magnetic field. In a multilayered setup we find different phases, depending on the strength of the interlayer tunneling t. We discuss the situation where a vortex lattice in the three-dimensional condensate (at large tunneling) undergoes quantum melting at a critical tunneling t c 1 . For tunneling well below t c 1 one expects weakly coupled or isolated layers, each exhibiting a landscape of quantum Hall liquids. After expansion, this gives a radial density distribution with characteristic features (cusps) that provide experimental signatures of the quantum Hall liquids

  3. Single Pd Atoms on θ-Al2O3 (010) Surface do not Catalyze NO Oxidation.

    Science.gov (United States)

    Narula, Chaitanya K; Allard, Lawrence F; Moses-DeBusk, Melanie; Stocks, G Malcom; Wu, Zili

    2017-04-03

    New convenient wet-chemistry synthetic routes have made it possible to explore catalytic activities of a variety of single supported atoms, however, the single supported atoms on inert substrates (e.g. alumina) are limited to adatoms and cations of Pt, Pd, and Ru. Previously, we have found that single supported Pt atoms are remarkable NO oxidation catalysts. In contrast, we report that Pd single atoms are completely inactive for NO oxidation. The diffuse reflectance infra-red spectroscopy (DRIFTS) results show the absence of nitrate formation on catalyst. To explain these results, we explored modified Langmuir-Hinshelwood type pathways that have been proposed for oxidation reactions on single supported atom. In the first pathway, we find that there is energy barrier for the release of NO 2 which prevent NO oxidation. In the second pathway, our results show that there is no driving force for the formation of O=N-O-O intermediate or nitrate on single supported Pd atoms. The decomposition of nitrate, if formed, is an endothermic event.

  4. Calibration of reconstruction parameters in atom probe tomography using a single crystallographic orientation

    International Nuclear Information System (INIS)

    Suram, Santosh K.; Rajan, Krishna

    2013-01-01

    The purpose of this work is to develop a methodology to estimate the APT reconstruction parameters when limited crystallographic information is available. Reliable spatial scaling of APT data currently requires identification of multiple crystallographic poles from the field desorption image for estimating the reconstruction parameters. This requirement limits the capacity of accurately reconstructing APT data for certain complex systems, such as highly alloyed systems and nanostructured materials wherein more than one pole is usually not observed within one grain. To overcome this limitation, we develop a quantitative methodology for calibrating the reconstruction parameters in an APT dataset by ensuring accurate inter-planar spacing and optimizing the curvature correction for the atomic planes corresponding to a single crystallographic orientation. We validate our approach on an aluminum dataset and further illustrate its capabilities by computing geometric reconstruction parameters for W and Al–Mg–Sc datasets. - Highlights: ► Quantitative approach is developed to accurately reconstruct APT data. ► Curvature of atomic planes in APT data is used to calibrate the reconstruction. ► APT reconstruction parameters are determined from a single crystallographic axis. ► Quantitative approach is demonstrated on W, Al and Al–Mg–Sc systems. ► Accurate APT reconstruction of complex materials is now possible

  5. Nonperturbative theory of single/multiphoton processes in atoms and molecules induced by intense laser fields

    International Nuclear Information System (INIS)

    Lau, A.M.F.

    1975-04-01

    A quantum nonperturbative theory is given for the problem of a general n discrete-level atomic/molecular system interacting with a strong single-mode/multimode radiation field. The atomic/molecular energy-level structures are modified due to interaction with the laser field. These energy level shifts are derived in the rigorous solution to the adiabatic eigenvalue problem of the charge--field system, involving a simple iterative procedure. The task of solution is simplified by recurrence relations between matrices connecting probability amplitudes of successive photon numbers. New formulae for calculating probability of single/multiphoton transitions between three resonant shifted levels and between some cases of two near-resonant shifted levels are derived. This general formalism can be applied to calculate transition probabilities of various atomic/molecular photo processes of interest. Numerical values are obtained for the inelastic cross section of the slow-collisional process Li + H and for dissociation cross section of LiH molecule. The transition probabilities of Na (3s → 5s by absorption of two photon of lambda = 0.60233μ -- 0.602396 μ) and of Li (2s → 3s by absorption of eight photons of lambda = 2.9406 μ -- 2.945 μ) irradiated by a strong pulse are calculated. Finally, a parametric study is carried out for the process where a molecular system is interacting with two intense radiation fields of different wavelengths. Owing to potential barrier shift due to the much more intense field, the molecular system penetrates into an otherwise inaccessible region in the potential level where it is allowed to radiate to a lower level by emitting photons at a second wavelength. (12 figures, 6 tables) (U.S.)

  6. Detecting and locating light atoms from high-resolution STEM images: The quest for a single optimal design

    Energy Technology Data Exchange (ETDEWEB)

    Gonnissen, J.; De Backer, A. [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Dekker, A.J. den [iMinds-Vision Lab, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk (Belgium); Delft Center for Systems and Control (DCSC), Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Sijbers, J. [iMinds-Vision Lab, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk (Belgium); Van Aert, S., E-mail: sandra.vanaert@uantwerpen.be [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium)

    2016-11-15

    In the present paper, the optimal detector design is investigated for both detecting and locating light atoms from high resolution scanning transmission electron microscopy (HR STEM) images. The principles of detection theory are used to quantify the probability of error for the detection of light atoms from HR STEM images. To determine the optimal experiment design for locating light atoms, use is made of the so-called Cramér–Rao Lower Bound (CRLB). It is investigated if a single optimal design can be found for both the detection and location problem of light atoms. Furthermore, the incoming electron dose is optimised for both research goals and it is shown that picometre range precision is feasible for the estimation of the atom positions when using an appropriate incoming electron dose under the optimal detector settings to detect light atoms. - Highlights: • The optimal detector design to detect and locate light atoms in HR STEM is derived. • The probability of error is quantified and used to detect light atoms. • The Cramér–Rao lower bound is calculated to determine the atomic column precision. • Both measures are evaluated and result in the single optimal LAADF detector regime. • The incoming electron dose is optimised for both research goals.

  7. Single-cell manipulation and DNA delivery technology using atomic force microscopy and nanoneedle.

    Science.gov (United States)

    Han, Sung-Woong; Nakamura, Chikashi; Miyake, Jun; Chang, Sang-Mok; Adachi, Taiji

    2014-01-01

    The recent single-cell manipulation technology using atomic force microscopy (AFM) not only allows high-resolution visualization and probing of biomolecules and cells but also provides spatial and temporal access to the interior of living cells via the nanoneedle technology. Here we review the development and application of single-cell manipulations and the DNA delivery technology using a nanoneedle. We briefly describe various DNA delivery methods and discuss their advantages and disadvantages. Fabrication of the nanoneedle, visualization of nanoneedle insertion into living cells, DNA modification on the nanoneedle surface, and the invasiveness of nanoneedle insertion into living cells are described. Different methods of DNA delivery into a living cell, such as lipofection, microinjection, and nanoneedles, are then compared. Finally, single-cell diagnostics using the nanoneedle and the perspectives of the nanoneedle technology are outlined. The nanoneedle-based DNA delivery technology provides new opportunities for efficient and specific introduction of DNA and other biomolecules into precious living cells with a high spatial resolution within a desired time frame. This technology has the potential to be applied for many basic cellular studies and for clinical studies such as single-cell diagnostics.

  8. Detecting and locating light atoms from high-resolution STEM images: The quest for a single optimal design.

    Science.gov (United States)

    Gonnissen, J; De Backer, A; den Dekker, A J; Sijbers, J; Van Aert, S

    2016-11-01

    In the present paper, the optimal detector design is investigated for both detecting and locating light atoms from high resolution scanning transmission electron microscopy (HR STEM) images. The principles of detection theory are used to quantify the probability of error for the detection of light atoms from HR STEM images. To determine the optimal experiment design for locating light atoms, use is made of the so-called Cramér-Rao Lower Bound (CRLB). It is investigated if a single optimal design can be found for both the detection and location problem of light atoms. Furthermore, the incoming electron dose is optimised for both research goals and it is shown that picometre range precision is feasible for the estimation of the atom positions when using an appropriate incoming electron dose under the optimal detector settings to detect light atoms. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Content iodine in sauces of type emulsion

    Directory of Open Access Journals (Sweden)

    M. Bakirov

    2015-05-01

    Full Text Available Introduction. The scarcity of natural resources arouse a necessity to find additional sources of protein, fat, carbohydrates, and their complexes with scarce mineral compounds. Therefore, a relevant issue is to enrich the diets deficient iodine compounds through research and development of new food products. Materials and methods. Investigation of iodine content in emulsion-type sauces at all stages was performed using Xray -fluorescence analyzer «Elvax». X-ray -fluorescence method consists of the appearance characteristic X-radiation of atoms of a chemical element at infringement they the primary X-ray irradiation. Results and discussion. Investigated for the determination of organic and inorganic forms of iodine in content of food items, and installed the total loss of iodine in sauces after cooking and storage at +5 ... +10 ° C for 30 days. Using iodine-proteinaceous additive from 0.5 ... 2.5% by mass of iodine 0.01% can be achieved from 15 to 50% of the human daily requirement by iodine. The resulting product does not lose its organoleptic, physico - chemical, consumer characteristics and meets the requirements of normative documents. As a result of our research, it was found that the addition of the supplements enriched protein-mineral (SEPM in composition sauces does not adversely affect the physical -chemical characteristics of sauces, but due to the stabilizing effect of additives iodine-proteinaceous increased emulsion stability up to 98 - 100% without additional foo d additives (emulsifiers. This additive has passed a series of tests that indicate on compliance with requirements normative and technical documentation. Conclusions. Used methodical approach allowed us to estimate the level of organic and inorganic iodine, as well as describe in more detail and correctly interpret the chemical composition of foods fortified with iodine and predict their health properties.

  10. Radiochemistry of iodine

    Energy Technology Data Exchange (ETDEWEB)

    Kahn, M.; Kleinberg, J.

    1977-09-01

    The preparation of isotopes of the element, with selected procedures for its determination in or separation from various media is described along with the separating of iodine species from each other. Each part of the introductory section is referenced separately from the remainder of the monograph. For the preparative and analytical sections there is an extensive, indexed bibliography which was developed from the indexes of Volumes 19 to 30 inclusive (1965-1974) of Nuclear Science Abstracts (NSA). From these indexes the NSA abstracts of possible pertinent references were selected for examination and a choice was made of those references which were to be included in the bibliography. The bibliography has both primary and secondary references. Although the monograph does not cover hot atom chemistry, the kinetics of exchange reactions, decay schemes, or physiological applications, papers in these areas were examined as possible sources of useful preparative and analytical procedures. (JRD)

  11. Radiochemistry of iodine

    International Nuclear Information System (INIS)

    Kahn, M.; Kleinberg, J.

    1977-09-01

    The preparation of isotopes of the element, with selected procedures for its determination in or separation from various media is described along with the separating of iodine species from each other. Each part of the introductory section is referenced separately from the remainder of the monograph. For the preparative and analytical sections there is an extensive, indexed bibliography which was developed from the indexes of Volumes 19 to 30 inclusive (1965-1974) of Nuclear Science Abstracts (NSA). From these indexes the NSA abstracts of possible pertinent references were selected for examination and a choice was made of those references which were to be included in the bibliography. The bibliography has both primary and secondary references. Although the monograph does not cover hot atom chemistry, the kinetics of exchange reactions, decay schemes, or physiological applications, papers in these areas were examined as possible sources of useful preparative and analytical procedures

  12. Radioactive Iodine Treatment for Hyperthyroidism

    Science.gov (United States)

    ... Balance › Radioactive Iodine for Hyperthyroidism Fact Sheet Radioactive Iodine for Hyperthyroidism April, 2012 Download PDFs English Zulu ... prepare for RAI or surgery. How does radioactive iodine treatment work? Iodine is important for making thyroid ...

  13. Self-assembly of iodine in superfluid helium droplets. Halogen bonds and nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    He, Yunteng; Zhang, Jie; Lei, Lei; Kong, Wei [Department of Chemistry, Oregon State University, Corvallis, OR (United States)

    2017-03-20

    We present evidence of halogen bond in iodine clusters formed in superfluid helium droplets based on results from electron diffraction. Iodine crystals are known to form layered structures with intralayer halogen bonds, with interatomic distances shorter than the sum of the van der Waals radii of the two neighboring atoms. The diffraction profile of dimer dominated clusters embedded in helium droplets reveals an interatomic distance of 3.65 Aa, much closer to the value of 3.5 Aa in iodine crystals than to the van der Waals distance of 4.3 Aa. The profile from larger iodine clusters deviates from a single layer structure; instead, a bi-layer structure qualitatively fits the experimental data. This work highlights the possibility of small halogen bonded iodine clusters, albeit in a perhaps limited environment of superfluid helium droplets. The role of superfluid helium in guiding the trapped molecules into local potential minima awaits further investigation. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. The high-power iodine laser

    Science.gov (United States)

    Brederlow, G.; Fill, E.; Witte, K. J.

    The book provides a description of the present state of the art concerning the iodine laser, giving particular attention to the design and operation of pulsed high-power iodine lasers. The basic features of the laser are examined, taking into account aspects of spontaneous emission lifetime, hyperfine structure, line broadening and line shifts, stimulated emission cross sections, the influence of magnetic fields, sublevel relaxation, the photodissociation of alkyl iodides, flashlamp technology, excitation in a direct discharge, chemical excitation, and questions regarding the chemical kinetics of the photodissociation iodine laser. The principles of high-power operation are considered along with aspects of beam quality and losses, the design and layout of an iodine laser system, the scalability and prospects of the iodine laser, and the design of the single-beam Asterix III laser.

  15. Decrease in benzodiazepine receptor binding in a patient with Angelman syndrome detected by iodine-123 iomazenil and single-photon emission tomography

    International Nuclear Information System (INIS)

    Odano, Ikuo; Anezaki, Toshiharu; Ohkubo, Masaki; Yonekura, Yoshiharu; Onishi, Yoshihiro; Inuzuka, Takashi; Takahashi, Makoto; Tsuji, Shoji

    1996-01-01

    A receptor mapping technique using iodine-123 iomazenil and single-photon emission tomography (SPET) was employed to examine benzodiazepine receptor binding in a patient with Angelman syndrome (AS). AS is characterized by developmental delay, seizures, inappropriate laughter and ataxic movement. In this entity there is a cytogenic deletion of the proximal long arm of chromosome 15q11-q13, where the gene encoding the GABA A receptor β3 subunit (GABRB3) is located. Since the benzodiazepine receptor is constructed as a receptor-ionophore complex that contains the GABA A receptor, it is a suitable marker for GABA-ergic synapsis. To determine whether benzodiazepine receptor density, which indirectly indicates changes in GABA A receptor density, is altered in the brain in patients with AS, we investigated a 27-year-old woman with AS using 123 I-iomazenil and SPET. Receptor density was quantitatively assessed by measuring the binding potential using a simplified method. Regional cerebral blood flow was also measured with N-isopropyl-p- 123 iodoamphetamine. We demonstrated that benzodiazepiine receptor density is severely decreased in the cerebellum, and mildly decreased in the frontal and temporal cortices and basal ganglia, a result which is considered to indicate decreased GABA A receptor density in these regions. Although the deletion of GABRB3 was not observed in the present study, we indirectly demonstrated the disturbance of inhibitory neurotransmission mediated by the GABA A receptor in the investigated patient. 123 I-iomazenil with SPET was useful to map benzodiazepine receptors, which indicate GABA A receptor distribution and their density. (orig.)

  16. Iodine and thyroid function

    Directory of Open Access Journals (Sweden)

    Hye Rim Chung

    2014-03-01

    Full Text Available Severe iodine deficiency causes hypothyroidism that results in impaired somatic growth and motor development in children. Mild and moderate iodine deficiencies cause multifocal autonomous growth of thyroid, which results in thyrotoxicosis. On the other hand, iodine excess is associated with the development of hypothyroidism and thyroid autoimmunity. In areas of iodine deficiency, a sudden increase in iodine intake is associated with transient hyperthyroidism. Recent studies demonstrated that long-term thyroid function of subjects who experienced both iodine deficiency and iodine excess during childhood tended to be abnormal despite optimization of their current iodine intake. Iodine status in the Korean Peninsula is very unique because people in the Republic of Korea have been shown to have predominantly excessive iodine levels, whereas the Democratic People's Republic of Korea is known to be an iodine-deficient area. Further research is warranted to verify the optimal ranges of iodine intake and to clarify the effects of iodine intake on thyroid disorders in the Korean Peninsula.

  17. Aspherical-atom modeling of coordination compounds by single-crystal X-ray diffraction allows the correct metal atom to be identified.

    Science.gov (United States)

    Dittrich, Birger; Wandtke, Claudia M; Meents, Alke; Pröpper, Kevin; Mondal, Kartik Chandra; Samuel, Prinson P; Amin Sk, Nurul; Singh, Amit Pratap; Roesky, Herbert W; Sidhu, Navdeep

    2015-02-02

    Single-crystal X-ray diffraction (XRD) is often considered the gold standard in analytical chemistry, as it allows element identification as well as determination of atom connectivity and the solid-state structure of completely unknown samples. Element assignment is based on the number of electrons of an atom, so that a distinction of neighboring heavier elements in the periodic table by XRD is often difficult. A computationally efficient procedure for aspherical-atom least-squares refinement of conventional diffraction data of organometallic compounds is proposed. The iterative procedure is conceptually similar to Hirshfeld-atom refinement (Acta Crystallogr. Sect. A- 2008, 64, 383-393; IUCrJ. 2014, 1,61-79), but it relies on tabulated invariom scattering factors (Acta Crystallogr. Sect. B- 2013, 69, 91-104) and the Hansen/Coppens multipole model; disordered structures can be handled as well. Five linear-coordinate 3d metal complexes, for which the wrong element is found if standard independent-atom model scattering factors are relied upon, are studied, and it is shown that only aspherical-atom scattering factors allow a reliable assignment. The influence of anomalous dispersion in identifying the correct element is investigated and discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Localization and force analysis at the single virus particle level using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chih-Hao [Institute of Applied Mechanics, Nation Taiwan University, Roosevelt Road, Taipei 10617, Taiwan (China); Horng, Jim-Tong [Department of Biochemistry, Chang Gung University, 259 Wen-Hwa First Road, Kweishan, Taoyuan 333, Taiwan (China); Chang, Jeng-Shian [Institute of Applied Mechanics, Nation Taiwan University, Roosevelt Road, Taipei 10617, Taiwan (China); Hsieh, Chung-Fan [Graduate Institute of Biomedical Sciences, Chang Gung University, Kweishan, Taoyuan 333, Taiwan (China); Tseng, You-Chen [Institute of Applied Mechanics, Nation Taiwan University, Roosevelt Road, Taipei 10617, Taiwan (China); Lin, Shiming, E-mail: til@ntu.edu.tw [Institute of Applied Mechanics, Nation Taiwan University, Roosevelt Road, Taipei 10617, Taiwan (China); Center for Optoelectronic Biomedicine, College of Medicine, Nation Taiwan University, 1-1 Jen-Ai Road, Taipei 10051, Taiwan (China)

    2012-01-06

    Highlights: Black-Right-Pointing-Pointer Localization of single virus particle. Black-Right-Pointing-Pointer Force measurements. Black-Right-Pointing-Pointer Force mapping. -- Abstract: Atomic force microscopy (AFM) is a vital instrument in nanobiotechnology. In this study, we developed a method that enables AFM to simultaneously measure specific unbinding force and map the viral glycoprotein at the single virus particle level. The average diameter of virus particles from AFM images and the specificity between the viral surface antigen and antibody probe were integrated to design a three-stage method that sets the measuring area to a single virus particle before obtaining the force measurements, where the influenza virus was used as the object of measurements. Based on the purposed method and performed analysis, several findings can be derived from the results. The mean unbinding force of a single virus particle can be quantified, and no significant difference exists in this value among virus particles. Furthermore, the repeatability of the proposed method is demonstrated. The force mapping images reveal that the distributions of surface viral antigens recognized by antibody probe were dispersed on the whole surface of individual virus particles under the proposed method and experimental criteria; meanwhile, the binding probabilities are similar among particles. This approach can be easily applied to most AFM systems without specific components or configurations. These results help understand the force-based analysis at the single virus particle level, and therefore, can reinforce the capability of AFM to investigate a specific type of viral surface protein and its distributions.

  19. Imaging single atoms using secondary electrons with an aberration-corrected electron microscope.

    Science.gov (United States)

    Zhu, Y; Inada, H; Nakamura, K; Wall, J

    2009-10-01

    Aberration correction has embarked on a new frontier in electron microscopy by overcoming the limitations of conventional round lenses, providing sub-angstrom-sized probes. However, improvement of spatial resolution using aberration correction so far has been limited to the use of transmitted electrons both in scanning and stationary mode, with an improvement of 20-40% (refs 3-8). In contrast, advances in the spatial resolution of scanning electron microscopes (SEMs), which are by far the most widely used instrument for surface imaging at the micrometre-nanometre scale, have been stagnant, despite several recent efforts. Here, we report a new SEM, with aberration correction, able to image single atoms by detecting electrons emerging from its surface as a result of interaction with the small probe. The spatial resolution achieved represents a fourfold improvement over the best-reported resolution in any SEM (refs 10-12). Furthermore, we can simultaneously probe the sample through its entire thickness with transmitted electrons. This ability is significant because it permits the selective visualization of bulk atoms and surface ones, beyond a traditional two-dimensional projection in transmission electron microscopy. It has the potential to revolutionize the field of microscopy and imaging, thereby opening the door to a wide range of applications, especially when combined with simultaneous nanoprobe spectroscopy.

  20. Low-kilovolt coherent electron diffractive imaging instrument based on a single-atom electron source

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chun-Yueh [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Chang, Wei-Tse; Chen, Yi-Sheng; Hwu, En-Te; Chang, Chia-Seng; Hwang, Ing-Shouh, E-mail: ishwang@phys.sinica.edu.tw [Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan (China); Hsu, Wei-Hao [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2016-03-15

    In this work, a transmission-type, low-kilovolt coherent electron diffractive imaging instrument was constructed. It comprised a single-atom field emitter, a triple-element electrostatic lens, a sample holder, and a retractable delay line detector to record the diffraction patterns at different positions behind the sample. It was designed to image materials thinner than 3 nm. The authors analyzed the asymmetric triple-element electrostatic lens for focusing the electron beams and achieved a focused beam spot of 87 nm on the sample plane at the electron energy of 2 kV. High-angle coherent diffraction patterns of a suspended graphene sample corresponding to (0.62 Å){sup −1} were recorded. This work demonstrated the potential of coherent diffractive imaging of thin two-dimensional materials, biological molecules, and nano-objects at a voltage between 1 and 10 kV. The ultimate goal of this instrument is to achieve atomic resolution of these materials with high contrast and little radiation damage.

  1. Positron states and nanoobjects in proton-irradiated quartz single crystals: Positronium atom in quartz

    International Nuclear Information System (INIS)

    Grafutin, V. I.; Zaluzhnyi, A. G.; Timoshenkov, S. P.; Britkov, O. M.; Ilyukhina, O. V.; Myasishcheva, G. G.; Prokop'ev, E. P.; Funtikov, Yu. V.

    2008-01-01

    The influence of proton bombardment and metal atom impurities on the structure of quartz single crystals has been studied. The related defects have been studied using positron annihilation spectroscopy (angular correlation of positron-annihilation photons), acoustic absorption, and optical absorption measurements. It is shown that the presence of a narrow component f in the angular distribution of annihilation photons (ADAP), which is related to the formation of parapositronium, determines a high sensitivity of this method with respect to features of the crystal structure of quartz. It is established that the defectness of the structure of irradiated quartz crystals can be characterized by the ratio f/f 0 of the relative intensities of narrow components in the ADAP curves measured before (f 0 ) and after (f) irradiation. Any process leading to a decrease in the probability of positronium formation (e.g., positron loss as a result of the trapping on defects and the interaction with impurity atoms and lattice distortions) decreases the intensity of the narrow component. Based on the ADAP data, estimates of the radii and concentrations of nanodefects in quartz have been obtained and their variation upon annealing at temperatures up to T = 873 K has been studied

  2. Engineering giant magnetic anisotropy in single-molecule magnets by dimerizing heavy transition-metal atoms

    Science.gov (United States)

    Qu, Jiaxing; Hu, Jun

    2018-05-01

    The search for single-molecule magnets with large magnetic anisotropy energy (MAE) is essential for the development of molecular spintronics devices for use at room temperature. Through systematic first-principles calculations, we found that an Os–Os or Ir–Ir dimer embedded in the (5,5‧-Br2-salophen) molecule gives rise to a large MAE of 41.6 or 51.4 meV, respectively, which is large enough to hold the spin orientation at room temperature. Analysis of the electronic structures reveals that the top Os and Ir atoms play the most important part in the total spin moments and large MAEs of the molecules.

  3. Surface diffusion coefficient of Au atoms on single layer graphene grown on Cu

    Energy Technology Data Exchange (ETDEWEB)

    Ruffino, F., E-mail: francesco.ruffino@ct.infn.it; Cacciato, G.; Grimaldi, M. G. [Dipartimento di Fisica ed Astronomia-Universitá di Catania, via S. Sofia 64, 95123 Catania, Italy and MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy)

    2014-02-28

    A 5 nm thick Au film was deposited on single layer graphene sheets grown on Cu. By thermal processes, the dewetting phenomenon of the Au film on the graphene was induced so to form Au nanoparticles. The mean radius, surface-to-surface distance, and surface density evolution of the nanoparticles on the graphene sheets as a function of the annealing temperature were quantified by scanning electron microscopy analyses. These quantitative data were analyzed within the classical mean-field nucleation theory so to obtain the temperature-dependent Au atoms surface diffusion coefficient on graphene: D{sub S}(T)=[(8.2±0.6)×10{sup −8}]exp[−(0.31±0.02(eV)/(at) )/kT] cm{sup 2}/s.

  4. Phase locking of a semiconductor double-quantum-dot single-atom maser

    Science.gov (United States)

    Liu, Y.-Y.; Hartke, T. R.; Stehlik, J.; Petta, J. R.

    2017-11-01

    We experimentally study the phase stabilization of a semiconductor double-quantum-dot (DQD) single-atom maser by injection locking. A voltage-biased DQD serves as an electrically tunable microwave frequency gain medium. The statistics of the maser output field demonstrate that the maser can be phase locked to an external cavity drive, with a resulting phase noise L =-99 dBc/Hz at a frequency offset of 1.3 MHz. The injection locking range, and the phase of the maser output relative to the injection locking input tone are in good agreement with Adler's theory. Furthermore, the electrically tunable DQD energy level structure allows us to rapidly switch the gain medium on and off, resulting in an emission spectrum that resembles a frequency comb. The free running frequency comb linewidth is ≈8 kHz and can be improved to less than 1 Hz by operating the comb in the injection locked regime.

  5. Atomic force microscope observation of branching in single transcript molecules derived from human cardiac muscle

    International Nuclear Information System (INIS)

    Reed, Jason; Hsueh, Carlin; Gimzewski, James K; Mishra, Bud

    2008-01-01

    We have used an atomic force microscope to examine a clinically derived sample of single-molecule gene transcripts, in the form of double-stranded cDNA, (c: complementary) obtained from human cardiac muscle without the use of polymerase chain reaction (PCR) amplification. We observed a log-normal distribution of transcript sizes, with most molecules being in the range of 0.4-7.0 kilobase pairs (kb) or 130-2300 nm in contour length, in accordance with the expected distribution of mRNA (m: messenger) sizes in mammalian cells. We observed novel branching structures not previously known to exist in cDNA, and which could have profound negative effects on traditional analysis of cDNA samples through cloning, PCR and DNA sequencing

  6. Filling of double vacancy in the K atomic shell with emission of one single photon

    International Nuclear Information System (INIS)

    Jalbert, G.

    1978-12-01

    A method was developed to calculate the transition rate for two-electron one-photon K(sub αα) transition (2s 2p → 1s 2 ). The method was tested for Ni with two K-shell vacancies in the initial state. The (sub αα) rate is calculated within the framework of a single system formed by the atom and the radiation. The transition is originated in the interactiion between the parts of that system. In the dipole approximation, the transition rate is obtained from the second order term of the time dependente perturbation theory. Hartree-Fock-Slater wave functions were used in the calculations for Ni. The results are compared with the available theoretical and experimental information. (Author) [pt

  7. Isotope shifts in odd and even energy levels of the neutral and singly ionised gadolinium atom

    International Nuclear Information System (INIS)

    Ahmad, S.A.; Venugopalan, A.; Saksena, G.D.

    1979-01-01

    Isotope shift studies in the gadolinium spectra have been extended in the region 4140 to 4535 A. Isotope shift Δσ(156 to 160) have been measured in 315 lines of the neutral and singly ionised gadolinium atom using a recording Fabry-Perot Spectrometer and gadolinium samples enriched in 156 Gd and 160 Gd isotopes. Some of the Gd I lines studied involve transitions from newly identified high odd levels of 4f 8 6s6p, 4f 7 5d6s7s and 4f 7 5d 3 configurations to low even levels of 4f 8 6s 2 and 4f 7 6s 2 6p configurations. Electronic configurations of the energy levels have been discussed on the basis of observed isotope shifts. In some cases assigned configurations have been revised and probable configurations have been suggested. (author)

  8. Minimizing pulling geometry errors in atomic force microscope single molecule force spectroscopy.

    Science.gov (United States)

    Rivera, Monica; Lee, Whasil; Ke, Changhong; Marszalek, Piotr E; Cole, Daniel G; Clark, Robert L

    2008-10-01

    In atomic force microscopy-based single molecule force spectroscopy (AFM-SMFS), it is assumed that the pulling angle is negligible and that the force applied to the molecule is equivalent to the force measured by the instrument. Recent studies, however, have indicated that the pulling geometry errors can drastically alter the measured force-extension relationship of molecules. Here we describe a software-based alignment method that repositions the cantilever such that it is located directly above the molecule's substrate attachment site. By aligning the applied force with the measurement axis, the molecule is no longer undergoing combined loading, and the full force can be measured by the cantilever. Simulations and experimental results verify the ability of the alignment program to minimize pulling geometry errors in AFM-SMFS studies.

  9. Piezoelectricity of single-atomic-layer MoS2 for energy conversion and piezotronics.

    Science.gov (United States)

    Wu, Wenzhuo; Wang, Lei; Li, Yilei; Zhang, Fan; Lin, Long; Niu, Simiao; Chenet, Daniel; Zhang, Xian; Hao, Yufeng; Heinz, Tony F; Hone, James; Wang, Zhong Lin

    2014-10-23

    The piezoelectric characteristics of nanowires, thin films and bulk crystals have been closely studied for potential applications in sensors, transducers, energy conversion and electronics. With their high crystallinity and ability to withstand enormous strain, two-dimensional materials are of great interest as high-performance piezoelectric materials. Monolayer MoS2 is predicted to be strongly piezoelectric, an effect that disappears in the bulk owing to the opposite orientations of adjacent atomic layers. Here we report the first experimental study of the piezoelectric properties of two-dimensional MoS2 and show that cyclic stretching and releasing of thin MoS2 flakes with an odd number of atomic layers produces oscillating piezoelectric voltage and current outputs, whereas no output is observed for flakes with an even number of layers. A single monolayer flake strained by 0.53% generates a peak output of 15 mV and 20 pA, corresponding to a power density of 2 mW m(-2) and a 5.08% mechanical-to-electrical energy conversion efficiency. In agreement with theoretical predictions, the output increases with decreasing thickness and reverses sign when the strain direction is rotated by 90°. Transport measurements show a strong piezotronic effect in single-layer MoS2, but not in bilayer and bulk MoS2. The coupling between piezoelectricity and semiconducting properties in two-dimensional nanomaterials may enable the development of applications in powering nanodevices, adaptive bioprobes and tunable/stretchable electronics/optoelectronics.

  10. Pt atoms stabilized on hexagonal boron nitride as efficient single-atom catalysts for CO oxidation: A first-principles investigation

    KAUST Repository

    Liu, Xin

    2015-01-01

    Taking CO oxidation as a probe, we investigated the electronic structure and reactivity of Pt atoms stabilized by vacancy defects on hexagonal boron nitride (h-BN) by first-principles-based calculations. As a joint effect of the high reactivity of both a single Pt atom and a boron vacancy defect (PtBV), the Pt-N interaction is -4.40 eV and is already strong enough to prohibit the diffusion and aggregation of the stabilized Pt atom. Facilitated by the upshifted Pt-d states originated from the Pt-N interaction, the barriers for CO oxidation through the Langmuir-Hinshelwood mechanism for formation and dissociation of peroxide-like intermediate and the regeneration are as low as 0.38, 0.10 and 0.04 eV, respectively, suggesting the superiority of PtBV as a catalyst for low temperature CO oxidation.

  11. Two-layer type filter for removal of radioactive iodine

    Energy Technology Data Exchange (ETDEWEB)

    Taoki, M

    1976-04-16

    The object is to provide a filter for removing radioactive iodine, which is used for disposal of gaseous waste in an atomic power plant, to particularly hold a pressure loss lower. The filter according to the present invention comprises two layers, which are filled at a front stage with active carbon, which is small in pressure loss and has a good collective efficiency relative to iodine, and at a rear stage with silver zeolite, which has a good collective efficiency relative to both iodine and methyl iodine, whereby respective adsorbent are effectively utilized to minimize pressure loss even if a large quantity of air.

  12. Two-layer type filter for removal of radioactive iodine

    International Nuclear Information System (INIS)

    Taoki, Masafumi.

    1976-01-01

    Object: To provide a filter for removing radioactive iodine, which is used for disposal of gaseous waste in an atomic power plant, to particularly hold a pressure loss lower. Structure: The filter according to the present invention comprises two layers, which are filled at a front stage with active carbon, which is small in pressure loss and has a good collective efficiency relative to iodine, and at a rear stage with silver zeolite, which has a good collective efficiency relative to both iodine and methyl iodine, whereby respective adsorbent are effectively utilized to minimize pressure loss even if a large quantity of air. (Kamimura, M.)

  13. Experimental study of single-electron loss by Ar{sup +} ions in rare-gas atoms

    Energy Technology Data Exchange (ETDEWEB)

    Reyes, P.G. [Facultad de Ciencias, UNAM, Coyoacan (Mexico); Castillo, F. [Instituto de Ciencias Nucleares, UNAM, Coyoacan (Mexico); Martinez, H. [Centro de Ciencias Fisicas, UNAM, Cuernavaca, Morelos (Mexico)]. E-mail: hm@fis.unam.mx

    2001-04-28

    Absolute differential and total cross sections for single-electron loss were measured for Ar{sup +} ions on rare-gas atoms in the laboratory energy range of 1.5 to 5.0 keV. The electron loss cross sections for all the targets studied are found to be in the order of magnitude between 10{sup -19} and 10{sup -22} cm{sup 2}, and show a monotonically increasing behaviour as a function of the incident energy. The behaviour of the total single-electron loss cross sections with the atomic target number, Z{sub t}, shows different dependences as the collision energy increases. In all cases the present results display experimental evidence of saturation in the single-electron loss cross section as the atomic number of the target increases. (author)

  14. Electromechanical Characterization of Single GaN Nanobelt Probed with Conductive Atomic Force Microscope

    Science.gov (United States)

    Yan, X. Y.; Peng, J. F.; Yan, S. A.; Zheng, X. J.

    2018-04-01

    The electromechanical characterization of the field effect transistor based on a single GaN nanobelt was performed under different loading forces by using a conductive atomic force microscope (C-AFM), and the effective Schottky barrier height (SBH) and ideality factor are simulated by the thermionic emission model. From 2-D current image, the high value of the current always appears on the nanobelt edge with the increase of the loading force less than 15 nN. The localized (I-V) characteristic reveals a typical rectifying property, and the current significantly increases with the loading force at the range of 10-190 nN. The ideality factor is simulated as 9.8 within the scope of GaN nano-Schottky diode unity (6.5-18), therefore the thermionic emission current is dominant in the electrical transport of the GaN-tip Schottky junction. The SBH is changed through the piezoelectric effect induced by the loading force, and it is attributed to the enhanced current. Furthermore, a single GaN nanobelt has a high mechanical-induced current ratio that could be made use of in a nanoelectromechanical switch.

  15. Interplay of tensor correlations and vibrational coupling for single-particle states in atomic nuclei

    International Nuclear Information System (INIS)

    Colo, G.; SAgawa, H.; Bortignon, P. F.

    2009-01-01

    To study the structure of atomic nuclei, the ab-initio methods can nowadays be applied only for mass number A smaller than ∼ 10-15. For heavier systems, the self-consistent mean-field (SCMF) approach is probably the most microscopic approach which can be systematically applied to stable and exotic nuclei. In practice, the SCMF is mostly based on parametrizations of an effective interaction. However, the are groups who are intensively working on the development of a general density functional (DF) which is not necessarily extracted from an Hamiltonian. The basic question is to what extent this allows improving on the existing functionals. In this contribution we analyze the performance of existing functionals as far as the reproduction of single-particle states is concerned. We start by analyzing the effect of the tensor terms, on which the attention of several groups have recently focused. Then we discuss the impact of the particle-vibration coupling (PVC). Although the basic idea of this approach dates back to long time ago, we present here for the first time calculations which are entirely based on microscopic interactions without dropping any term or introducing ad hoc parameters. We show results both for well-known, benchmark nuclei like 4 0C a and 2 08P b as well as unstable nuclei like 1 32S n. Both single-particle energies and spectroscopic factors are discussed.(author)

  16. Wet chemical deposition of single crystalline epitaxial manganite thin films with atomically flat surface

    International Nuclear Information System (INIS)

    Mishra, Amita; Dutta, Anirban; Samaddar, Sayanti; Gupta, Anjan K.

    2013-01-01

    We report the wet chemical deposition of single crystalline epitaxial thin films of the colossal magneto-resistive manganite La 0.67 Sr 0.33 MnO 3 on the lattice-matched (001)-face of a La 0.3 Sr 0.7 Al 0.65 Ta 0.35 O 3 substrate. Topographic images of these films taken with a scanning tunneling microscope show atomically flat terraces separated by steps of monatomic height. The resistivity of these films shows an insulator-metal transition at 310 K, nearly coincident with the Curie temperature of 340 K, found from magnetization measurements. The films show a magnetoresistance of 7% at 300 K and 1.2 T. Their saturation magnetization value at low temperatures is consistent with that of the bulk. - Highlights: ► Wet chemical deposition of La 0.67 Sr 0.33 MnO 3 (LSMO) on a lattice-matched substrate. ► Single crystalline epitaxial LSMO films obtained. ► Flat terraces separated by monatomic steps observed by scanning tunneling microscope

  17. Single Molecule Science for Personalized Nanomedicine: Atomic Force Microscopy of Biopolymer-Protein Interactions

    Science.gov (United States)

    Hsueh, Carlin

    Nanotechnology has a unique and relatively untapped utility in the fields of medicine and dentistry at the level of single-biopolymer and -molecule diagnostics. In recent years atomic force microscopy (AFM) has garnered much interest due to its ability to obtain atomic-resolution of molecular structures and probe biophysical behaviors of biopolymers and proteins in a variety of biologically significant environments. The work presented in this thesis focuses on the nanoscale manipulation and observation of biopolymers to develop an innovative technology for personalized medicine while understanding complex biological systems. These studies described here primarily use AFM to observe biopolymer interactions with proteins and its surroundings with unprecedented resolution, providing a better understanding of these systems and interactions at the nanoscale. Transcriptional profiling, the measure of messenger RNA (mRNA) abundance in a single cell, is a powerful technique that detects "behavior" or "symptoms" at the tissue and cellular level. We have sought to develop an alternative approach, using our expertise in AFM and single molecule nanotechnology, to achieve a cost-effective high throughput method for sensitive detection and profiling of subtle changes in transcript abundance. The technique does not require amplification of the mRNA sample because the AFM provides three-dimensional views of molecules with unprecedented resolution, requires minimal sample preparation, and utilizes a simple tagging chemistry on cDNA molecules. AFM images showed collagen polymers in teeth and of Drebrin-A remodeling of filamentous actin structure and mechanics. AFM was used to image collagen on exposed dentine tubules and confirmed tubule occlusion with a desensitizing prophylaxis paste by Colgate-Palmolive. The AFM also superseded other microscopy tools in resolving F-actin helix remodeling and possible cooperative binding by a neuronal actin binding protein---Drebrin-A, an

  18. Assembling three-dimensional nanostructures on metal surfaces with a reversible vertical single-atom manipulation: A theoretical modeling

    International Nuclear Information System (INIS)

    Yang Tianxing; Ye Xiang; Huang Lei; Xie Yiqun; Ke Sanhuang

    2012-01-01

    Highlights: ► We simulate the reversible vertical single-atom manipulations on several metal surfaces. ► We propose a method to predict whether a reversible vertical single-atom manipulation can be successful on several metal surfaces. ► A 3-dimensional Ni nanocluster is assembled on the Ni(1 1 1) surface using a Ni trimer-apex tip. - Abstract: We propose a theoretical model to show that pulling up an adatom from an atomic step requires a weaker force than from the flat surfaces of Al(0 0 1), Ni(1 1 1), Pt(1 1 0) and Au(1 1 0). Single adatom in the atomic step can be extracted vertically by a trimer-apex tip while can be released to the flat surface. This reversible vertical manipulation can then be used to fabricate a supported three-dimensional (3D) nanostructure on the Ni(1 1 1) surface. The present modeling can be used to predict whether the reversible vertical single-atom manipulation and thus the assembling of 3D nanostructures can be achieved on a metal surface.

  19. Water Adsorption and Dissociation on Ceria-Supported Single-Atom Catalysts: A First-Principles DFT+U Investigation.

    Science.gov (United States)

    Han, Zhong-Kang; Gao, Yi

    2016-02-01

    Single-atom catalysts have attracted wide attention owing to their extremely high atom efficiency and activities. In this paper, we applied density functional theory with the inclusion of the on-site Coulomb interaction (DFT+U) to investigate water adsorption and dissociation on clean CeO 2 (111) surfaces and single transition metal atoms (STMAs) adsorbed on the CeO 2 (111) surface. It is found that the most stable water configuration is molecular adsorption on the clean CeO 2 (111) surface and dissociative adsorption on STMA/CeO 2 (111) surfaces, respectively. In addition, our results indicate that the more the electrons that transfer from STMA to the ceria substrate, the stronger the binding energies between the STMA and ceria surfaces. A linear relationship is identified between the water dissociation barriers and the d band centers of STMA, known as the generalized Brønsted-Evans-Polanyi principle. By combining the oxygen spillovers, single-atom dispersion stabilities, and water dissociation barriers, Zn, Cr, and V are identified as potential candidates for the future design of ceria-supported single-atom catalysts for reactions in which the dissociation of water plays an important role, such as the water-gas shift reaction. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Thermally stable single atom Pt/m-Al2O3 for selective hydrogenation and CO oxidation

    KAUST Repository

    Zhang, Zailei

    2017-07-27

    Single-atom metal catalysts offer a promising way to utilize precious noble metal elements more effectively, provided that they are catalytically active and sufficiently stable. Herein, we report a synthetic strategy for Pt single-atom catalysts with outstanding stability in several reactions under demanding conditions. The Pt atoms are firmly anchored in the internal surface of mesoporous Al2O3, likely stabilized by coordinatively unsaturated pentahedral Al3+ centres. The catalyst keeps its structural integrity and excellent performance for the selective hydrogenation of 1,3-butadiene after exposure to a reductive atmosphere at 200 °C for 24 h. Compared to commercial Pt nanoparticle catalyst on Al2O3 and control samples, this system exhibits significantly enhanced stability and performance for n-hexane hydro-reforming at 550 °C for 48 h, although agglomeration of Pt single-atoms into clusters is observed after reaction. In CO oxidation, the Pt single-atom identity was fully maintained after 60 cycles between 100 and 400 °C over a one-month period.

  1. 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)

  2. Intensity-gradient induced Sisyphus cooling of a single atom in a localized hollow-beam trap

    International Nuclear Information System (INIS)

    Yin, Yaling; Xia, Yong; Ren, Ruimin; Du, Xiangli; Yin, Jianping

    2015-01-01

    In order to realize a convenient and efficient laser cooling of a single atom, we propose a simple and promising scheme to cool a single neutral atom in a blue-detuned localized hollow-beam trap by intensity-gradient induced Sisyphus cooling, and study the dynamic process of the intensity-gradient cooling of a single 87 Rb atom in the localized hollow-beam trap by using Monte-Carlo simulations. Our study shows that a single 87 Rb atom with a temperature of 120 μK from a magneto-optical trap (MOT) can be directly cooled to a final temperature of 4.64 μK in our proposed scheme. We also investigate the dependences of the cooling results on the laser detuning δ of the localized hollow-beam, the power RP 0 of the re-pumping laser beam, the sizes of both the localized hollow-beam and the re-pumping beam, and find that there is a pair of optimal cooling parameters (δ and RP 0 ) for an expected lowest temperature, and the cooling results strongly depend on the size of the re-pumping beam, but weakly depend on the size of the localized hollow-beam. Finally, we further study the cooling potential of our localized hollow-beam trap for the initial temperature of a single atom, and find that a single 87 Rb atom with an initial temperature of higher than 1 mK can also be cooled directly to about 6.6 μK. (paper)

  3. Molecular Processes Studied at a Single-Molecule Level Using DNA Origami Nanostructures and Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Ilko Bald

    2014-09-01

    Full Text Available DNA origami nanostructures allow for the arrangement of different functionalities such as proteins, specific DNA structures, nanoparticles, and various chemical modifications with unprecedented precision. The arranged functional entities can be visualized by atomic force microscopy (AFM which enables the study of molecular processes at a single-molecular level. Examples comprise the investigation of chemical reactions, electron-induced bond breaking, enzymatic binding and cleavage events, and conformational transitions in DNA. In this paper, we provide an overview of the advances achieved in the field of single-molecule investigations by applying atomic force microscopy to functionalized DNA origami substrates.

  4. Remarkable effects of disorder on superconductivity of single atomic layers of lead on silicon

    Science.gov (United States)

    Brun, Christophe

    2015-03-01

    It is well known that conventional superconductivity is very robust against non-magnetic disorder. Nevertheless for thin and ultrathin films the structural properties play a major role in determining the superconducting properties, through a subtle interplay between disorder and Coulomb interactions. Unexpectedly, in 2010 superconductivity was discovered in single atomic layers of lead and indium grown on silicon substrate using scanning tunneling spectroscopy and confirmed later on by macroscopic transport measurements. Such well-controlled and tunable crystalline monolayers are ideal systems for studying the influence of various kinds of structural defects on the superconducting properties at the atomic and mesoscopic scale. In particular, Pb monolayers offer the opportunity of probing new effects of disorder because not only superconductivity is 2D but also the electronic wave functions are 2D. Our study of two Pb monolayers of different crystal structures by very-low temperature STM (300 mK) under magnetic field reveals unexpected results involving new spatial spectroscopic variations. Our results show that although the sheet resistance of the Pb monolayers is much below the resistance quantum, strong non-BCS corrections appear leading to peak heights fluctuations in the dI/dV tunneling spectra at a spatial scale much smaller than the superconducting coherence length. Furthermore, strong local evidence of the signature of Rashba effect on the superconductivity of the Pb/Si(111) monolayer is revealed through filling of in gap states and local spatial variations of this filling. Finally the nature of vortices in a monolayer is found to be very sensitive to the properties of step edges areas. This work was supported by University Pierre et Marie Curie UPMC `Emergence' project, French ANR Project `ElectroVortex,' ANR-QuDec and Templeton Foundation (40381), ARO (W911NF-13-1-0431) and CNRS PICS funds. Partial funding by US-DOE Grant DE-AC02-07CH1.

  5. Xenon gas field ion source from a single-atom tip

    Science.gov (United States)

    Lai, Wei-Chiao; Lin, Chun-Yueh; Chang, Wei-Tse; Li, Po-Chang; Fu, Tsu-Yi; Chang, Chia-Seng; Tsong, T. T.; Hwang, Ing-Shouh

    2017-06-01

    Focused ion beam (FIB) systems have become powerful diagnostic and modification tools for nanoscience and nanotechnology. Gas field ion sources (GFISs) built from atomic-size emitters offer the highest brightness among all ion sources and thus can improve the spatial resolution of FIB systems. Here we show that the Ir/W(111) single-atom tip (SAT) can emit high-brightness Xe+ ion beams with a high current stability. The ion emission current versus extraction voltage was analyzed from 150 K up to 309 K. The optimal emitter temperature for maximum Xe+ ion emission was ˜150 K and the reduced brightness at the Xe gas pressure of 1 × 10-4 torr is two to three orders of magnitude higher than that of a Ga liquid metal ion source, and four to five orders of magnitude higher than that of a Xe inductively coupled plasma ion source. Most surprisingly, the SAT emitter remained stable even when operated at 309 K. Even though the ion current decreased with increasing temperature, the current at room temperature (RT) could still reach over 1 pA when the gas pressure was higher than 1 × 10-3 torr, indicating the feasibility of RT-Xe-GFIS for application to FIB systems. The operation temperature of Xe-SAT-GFIS is considerably higher than the cryogenic temperature required for the helium ion microscope (HIM), which offers great technical advantages because only simple or no cooling schemes can be adopted. Thus, Xe-GFIS-FIB would be easy to implement and may become a powerful tool for nanoscale milling and secondary ion mass spectroscopy.

  6. Structure sensitivity in CO oxidation by a single Au atom supported on ceria

    NARCIS (Netherlands)

    Song, W.; Hensen, E.J.M.

    2013-01-01

    The mechanism of CO oxidation by a CeO2(110)-supported gold atom has been investigated by DFT calculations. A novel stable surface structure has been identified in which one surface O atom of ceria migrates toward the isolated Au atom, resulting in a surface Au–O species that can react with CO.

  7. WHO's new recommendations about iodine prophylaxis at nuclear catastrophes

    International Nuclear Information System (INIS)

    Paile, Wendla

    1999-01-01

    WHO has prepared new advice about using stable iodine as protection against emission of radioactive iodine from nuclear catastrophes. The experiences from Chernobyl show that the risk for thyroid gland cancer after emission of radio-iodine is significant. The risk of serious side effects of stable iodine as single dose is stated to be minimal. Stable iodine is a safe, effective remedy for protecting the thyroid gland against radioactive iodine. It is recommended to adjust different criteria for iodine prophylaxis for new-born, children, young people and adults older than 40 years. For children of the age up to 18 years iodine prophylaxis should be considered at 10 mGy thyroid gland doses, and for young adults at 100 mGy. For adults of 40 years or more the cancer risk of radioactive iodine is very low and iodine prophylaxis is unnecessary provided that the expected does not exceed 5 Gy. The new information about risk and advantage must be considered in planning for distribution and storage of stable iodine. WHO also commends that everybody has the possibility to buy it in a pharmacy. (EHS)

  8. Influences of H on the Adsorption of a Single Ag Atom on Si(111-7 × 7 Surface

    Directory of Open Access Journals (Sweden)

    Lin Xiu-Zhu

    2009-01-01

    Full Text Available Abstract The adsorption of a single Ag atom on both clear Si(111-7 × 7 and 19 hydrogen terminated Si(111-7 × 7 (hereafter referred as 19H-Si(111-7 × 7 surfaces has been investigated using first-principles calculations. The results indicated that the pre-adsorbed H on Si surface altered the surface electronic properties of Si and influenced the adsorption properties of Ag atom on the H terminated Si surface (e.g., adsorption site and bonding properties. Difference charge density data indicated that covalent bond is formed between adsorbed Ag and H atoms on 19H-Si(111-7 × 7 surface, which increases the adsorption energy of Ag atom on Si surface.

  9. Going Vertical To Improve the Accuracy of Atomic Force Microscopy Based Single-Molecule Force Spectroscopy.

    Science.gov (United States)

    Walder, Robert; Van Patten, William J; Adhikari, Ayush; Perkins, Thomas T

    2018-01-23

    Single-molecule force spectroscopy (SMFS) is a powerful technique to characterize the energy landscape of individual proteins, the mechanical properties of nucleic acids, and the strength of receptor-ligand interactions. Atomic force microscopy (AFM)-based SMFS benefits from ongoing progress in improving the precision and stability of cantilevers and the AFM itself. Underappreciated is that the accuracy of such AFM studies remains hindered by inadvertently stretching molecules at an angle while measuring only the vertical component of the force and extension, degrading both measurements. This inaccuracy is particularly problematic in AFM studies using double-stranded DNA and RNA due to their large persistence length (p ≈ 50 nm), often limiting such studies to other SMFS platforms (e.g., custom-built optical and magnetic tweezers). Here, we developed an automated algorithm that aligns the AFM tip above the DNA's attachment point to a coverslip. Importantly, this algorithm was performed at low force (10-20 pN) and relatively fast (15-25 s), preserving the connection between the tip and the target molecule. Our data revealed large uncorrected lateral offsets for 100 and 650 nm DNA molecules [24 ± 18 nm (mean ± standard deviation) and 180 ± 110 nm, respectively]. Correcting this offset yielded a 3-fold improvement in accuracy and precision when characterizing DNA's overstretching transition. We also demonstrated high throughput by acquiring 88 geometrically corrected force-extension curves of a single individual 100 nm DNA molecule in ∼40 min and versatility by aligning polyprotein- and PEG-based protein-ligand assays. Importantly, our software-based algorithm was implemented on a commercial AFM, so it can be broadly adopted. More generally, this work illustrates how to enhance AFM-based SMFS by developing more sophisticated data-acquisition protocols.

  10. Galvanomagnetic properties of atomic-disordered Sr2RuO4 single crystals

    International Nuclear Information System (INIS)

    Kar'kin, A.E.; Naumov, S.V.; Goshchitskij, V.N.; Balbashov, A.M.

    2005-01-01

    The effect of neutron-bombardment-induced atomic disorder on the galvanomagnetic properties of Sr 2 RuO 4 single crystals has been experimentally studied in a broad range of temperatures (1.7-380 K) and magnetic fields (up to 13.6 T). The disorder leads to the appearance of negative temperature coefficients for both the in-plane electric resistivity (ρ a ) and that along the c axis (ρ c ), as well as the negative magnetoresistance Δρ, which is strongly anisotropic to the magnetic field orientation (H || a and H || c), with the easy magnetization direction along the c axis and a weak dependence on the probing current direction in the low-temperature region. The experimental ρ a (T) and ρ c (T) curves obtained for the initial and radiation-disordered samples can be described in the framework of a theoretical model with two conductivity channels. The first channel corresponds to the charge carriers with increased effective masses and predominantly electron-electron scattering, the second channel corresponds to the charge carriers with lower effective masses exhibiting magnetic scattering at low temperatures [ru

  11. Unveiling the high-activity origin of single-atom iron catalysts for oxygen reduction reaction.

    Science.gov (United States)

    Yang, Liu; Cheng, Daojian; Xu, Haoxiang; Zeng, Xiaofei; Wan, Xin; Shui, Jianglan; Xiang, Zhonghua; Cao, Dapeng

    2018-06-26

    It is still a grand challenge to develop a highly efficient nonprecious-metal electrocatalyst to replace the Pt-based catalysts for oxygen reduction reaction (ORR). Here, we propose a surfactant-assisted method to synthesize single-atom iron catalysts (SA-Fe/NG). The half-wave potential of SA-Fe/NG is only 30 mV less than 20% Pt/C in acidic medium, while it is 30 mV superior to 20% Pt/C in alkaline medium. Moreover, SA-Fe/NG shows extremely high stability with only 12 mV and 15 mV negative shifts after 5,000 cycles in acidic and alkaline media, respectively. Impressively, the SA-Fe/NG-based acidic proton exchange membrane fuel cell (PEMFC) exhibits a high power density of 823 mW cm -2 Combining experimental results and density-functional theory (DFT) calculations, we further reveal that the origin of high-ORR activity of SA-Fe/NG is from the Fe-pyrrolic-N species, because such molecular incorporation is the key, leading to the active site increase in an order of magnitude which successfully clarifies the bottleneck puzzle of why a small amount of iron in the SA-Fe catalysts can exhibit extremely superior ORR activity.

  12. Single-Molecular Imaging of Anticoagulation Factor I from Snake Venom by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    XU,Xiao-Long(徐小龙); ZHOU,Yun-Shen(周云申); LIU,Qing-Liang(刘清亮); HOU,Jian-Guo(侯建国); YANG,Jing-Long(杨金龙); XIE,Yong-Shu(解永树)

    2002-01-01

    Anticoagulation factor I (ACF I) from the venom of Agkistrodon acutus is a binding protein to activated coagulation factor X (FXa) and possesses marked anticoagulant activity. Single ACF I molecule has been successfully imaged in air by tapping mode atomic force microscopy (AFM) with high-resolution using glutaraldehyde as a coupling agent. The physical adsorption and covalent binding of ACF I onto the mica show very different surface topographies. The former exhibits the characteristic strand-like structure with much less reproducibility, the latter displays a elliptic granular structure with better reproducibility, which suggests that the stability of ACF I molecules on the mica is enhanced by covalent bonding in the presence of glutaraldehyde. A small-scale AFM amplitude-mode image clearly shows that the covalently bonded ACF I molecule by glutaraldehyde has olive shape structure with an average size of 7.4 nm× 3.6 nm × 3.1 nm, which is very similar to the size determined from the crystal structure of ACF I.

  13. Novel parallel plate condenser for single particle electrostatic force measurements in atomic force microscope

    KAUST Repository

    Kwek, Jin Wang

    2011-07-01

    A combination of small parallel plate condenser with Indium Tin Oxide (ITO) glass slides as electrodes and an atomic force microscope (AFM) is used to characterize the electrostatic behavior of single glass bead microparticles (105-150 μm) glued to the AFM cantilever. This novel setup allows measurements of the electrostatic forces acting on a particle in an applied electrical field to be performed in ambient air conditions. By varying the position of the microparticle between the electrodes and the strength of the applied electric field, the relative contributions of the particle net charge, induced and image charges were investigated. When the microparticle is positioned in the middle of the electrodes, the force acting on the microparticle was linear with the applied electric field and proportional to the microparticle net charge. At distances close to the bottom electrode, the force follows a parabolic relationship with the applied electric field reflecting the contributions of induced and image charges. The method can be used for the rapid evaluation of the charging and polarizability properties of the microparticle as well as an alternative to the conventional Faraday\\'s pail technique. © 2011 Elsevier B.V.

  14. Open quantum systems and the two-level atom interacting with a single mode of the electromagnetic field

    International Nuclear Information System (INIS)

    Sandulescu, A.; Stefanescu, E.

    1987-07-01

    On the basis of Lindblad theory of open quantum systems we obtain new optical equations for the system of two-level atom interacting with a single mode of the electromagnetic field. The conventional Block equations in a generalized form with field phases are obtained in the hypothesis that all the terms are slowly varying in the rotating frame.(authors)

  15. Photopicking : In Situ Approach for Site-Specific Attachment of Single Multiprotein Nanoparticles to Atomic Force Microscopy Tips

    NARCIS (Netherlands)

    Liashkovich, Ivan; Rosso, Gonzalo; Rangl, Martina; Ebner, Andreas; Hafezi, Wali; Kühn, Joachim; Schön, Peter; Hinterdorfer, Peter; Shahin, Victor

    2017-01-01

    Ligand–receptor interactions are fundamental in life sciences and include hormone–receptor, protein–protein, pathogen–host, and cell–cell interactions, among others. Atomic force microscopy (AFM) proved to be invaluable for scrutinizing ligand–receptor interactions at the single molecular level.

  16. Active molecular iodine photochemistry in the Arctic

    Energy Technology Data Exchange (ETDEWEB)

    Raso, Angela R.; Custard, Kyle D.; May, Nathaniel W.; Tanner, David; Newburn, Matthew K.; Walker, Lawrence R.; Moore, Ronald J.; Huey, L. G.; Alexander, Lizabeth; Shepson, Paul B.; Pratt, Kerri A.

    2017-09-05

    During springtime, the Arctic atmospheric boundary layer undergoes frequent rapid depletions in ozone and gaseous elemental mercury due to reactions with halogen atoms, influencing atmospheric composition and pollutant fate. Although bromine chemistry has been shown to initiate ozone depletion events, and it has long been hypothesized that iodine chemistry may contribute, no previous measurements of molecular iodine (I2) have been reported in the Arctic. Iodine chemistry also contributes to atmospheric new particle formation and therefore cloud properties and radiative forcing. Here we present Arctic atmospheric I2 and snowpack iodide (I-) measurements, which were conducted near Utqiagvik, AK, in February 2014. Using chemical ionization mass spectrometry, I2 was observed in the atmosphere at mole ratios of 0.3–1.0 ppt, and in the snowpack interstitial air at mole ratios up to 22 ppt under natural sunlit conditions and up to 35 ppt when the snowpack surface was artificially irradiated, suggesting a photochemical production mechanism. Further, snow meltwater I-measurements showed enrichments of up to ~1,900 times above the seawater ratio of I-/Na+, consistent with iodine activation and recycling. Modeling shows that observed I2 levels are able to significantly increase ozone depletion rates, while also producing iodine monoxide (IO) at levels recently observed in the Arctic. These results emphasize the significance of iodine chemistry and the role of snowpack photochemistry in Arctic atmospheric composition, and imply that I2 is likely a dominant source of iodine atoms in the Arctic.

  17. Long-term migration of iodine in sedimentary rocks based on iodine speciation and 129I/127I ratio

    Science.gov (United States)

    Togo, Y.; Takahashi, Y.; Amano, Y.; Matsuzaki, H.; Suzuki, Y.; Muramatsu, Y.; Iwatsuki, T.

    2012-12-01

    [Introduction] 129I is one of the available indexes of long-term migration of groundwater solutes, because of its long half-life (15.7 million years) and low sorption characteristics. The Horonobe underground research center (Japan Atomic Energy Agency), at which are conducted research and development of fundamental techniques on geological disposal of high-level radioactive waste, is an appropriate site for natural analogue studies, because iodine concentration in groundwater is high in this area. To predict iodine behavior in natural systems, speciation of iodine is essential because of different mobility among each species. In this study, we determined iodine speciation and129I/127I isotope ratios of rock and groundwater samples to investigate long term migration of iodine. [Methods] All rock and groundwater samples were collected at Horonobe underground research center. The region is underlain mainly by Neogene to Quaternary marine sedimentary rocks, the Wakkanai Formation (Wk Fm, siliceous mudstones), and the overlying Koetoi Formation (Kt Fm, diatomaceous mudstones). Iodine species in rock samples were determined by iodine K-edge X-ray absorption near edge structure (SPring-8 BL01B1). Thin sections of rock samples were prepared, and iodine mapping were obtained by micro-XRF analysis (SPring-8 BL37XU). Iodine species (IO3-, I-, and organic I) in groundwater were separately detected by high performance liquid chromatography connected to ICP-MS. The 129I/127I ratios in groundwater and rock samples were measured by accelerator mass spectrometry (MALT, Univ. of Tokyo). Iodine in rock samples were separated by pyrohydrolysis and water extraction. [Results and discussion] Concentration of iodine in groundwater varied widely and was much higher than that of seawater showing a high correlation with that of chlorine (R2 = 0.90). Species of iodine in groundwater was mainly I-. Iodine in rock samples decreased near the boundary between Wk and Kt Fms. Iodine K-edge XANES

  18. First-principle study of single TM atoms X (X=Fe, Ru or Os) doped monolayer WS2 systems

    Science.gov (United States)

    Zhu, Yuan-Yan; Zhang, Jian-Min

    2018-05-01

    We report the structural, magnetic and electronic properties of the pristine and single TM atoms X (X = Fe, Ru or Os) doped monolayer WS2 systems based on first-principle calculations. The results show that the W-S bond shows a stronger covalent bond, but the covalency is obviously weakened after the substitution of W atom with single X atoms, especially for Ru (4d75s1) with the easily lost electronic configuration. The smaller total energies of the doped systems reveal that the spin-polarized states are energetically favorable than the non-spin-polarized states, and the smallest total energy of -373.918 eV shows the spin-polarized state of the Os doped monolayer WS2 system is most stable among three doped systems. In addition, although the pristine monolayer WS2 system is a nonmagnetic-semiconductor with a direct band gap of 1.813 eV, single TM atoms Fe and Ru doped monolayer WS2 systems transfer to magnetic-HM with the total moments Mtot of 1.993 and 1.962 μB , while single TM atom Os doped monolayer WS2 systems changes to magnetic-metal with the total moments Mtot of 1.569 μB . Moreover, the impurity states with a positive spin splitting energies of 0.543, 0.276 and 0.1999 eV near the Fermi level EF are mainly contributed by X-dxy and X-dx2-y2 states hybridized with its nearest-neighbor atom W-dz2 states for Fe, Ru and Os doped monolayer WS2 system, respectively. Finally, we hope that the present study on monolayer WS2 will provide a useful theoretical guideline for exploring low-dimensional spintronic materials in future experiments.

  19. Magnetic properties of Co and Fe on Pt(111), Rh(111) and Pd(111): From single atoms to ultrathin films

    Energy Technology Data Exchange (ETDEWEB)

    Lehnert, Anne; Rusponi, Stefano; Etzkorn, Markus; Moulas, Geraud; Brune, Harald [IPN, EPF-Lausanne (Switzerland); Gambardella, Pietro [CREA, Catalan Institute of Nanotechnology (Spain); Bencok, Peter [ESRF, Grenoble (France)

    2009-07-01

    Single atoms of Co on Pt(111) are known to have a giant magnetic anisotropy energy (MAE) of 9.3 meV/atom. This is due to the reduced coordination and the strong spin-orbit coupling of the Pt 5d-states. In order to study the contribution of a highly polarizable substrate to the MAE, we investigated single Co atoms on Pd(111) and Rh(111) using X-ray magnetic circular dichroism (XMCD). We find a decreasing MAE moving from a 5d-substrate (Pt) to 4d-substrates (Pd and Rh). Co has a large orbital moment L of about 0.7 independent of the substrate. The easy axis is out-of-plane for Pt(111) and Pd(111) whereas it is in-plane for Co/Rh(111). Fe has on all substrates an out-of-plane easy axis, a very small anisotropy energy, and a L/S ratio of about 0.1. With increasing coverage the coordination number of the adatom increases and generally leads to a reduced MAE and orbital moment compared to the single atom. We measure one monolayer of Co and Fe on Pt(111) and Rh(111) and find MAE values <0.5 meV/atom. For 1 ML Co we find a substantial decrease in the L/S ratio to 0.19. However, the L/S ratio for 1 ML Fe on both substrates does not change much compared with the Fe single atom.

  20. Physical experiments on the utility of non-iodine-containing contrast media

    International Nuclear Information System (INIS)

    Kirschner, H.; Burmester, U.; Stringaris, K.; Jentsch, F.

    1979-01-01

    Because of the excellent ability of the CT scanner in analyzing absorption, the use of non-iodine-containing contrast media will be discussed. Experimental studies of the chemical elements with the atomic number Z = 1-83 with a scan tension of 120 kV were made to determine how many atoms of a given element are necessary to replace one iodine atom in an iodine-containing contrast medium, whereby the same contrast enhancement in the scan picture as with the iodine-containing contrast medium is produced. (orig.) 891 ORU/orig. 892 MB [de

  1. Iodine deficiency and iodine excess in Jiangsu Province, China

    NARCIS (Netherlands)

    Zhao, J.

    2001-01-01

    Keywords:
    iodine deficiency, iodine excess, endemic goiter, drinking water, iodine intake, thyroid function, thyroid size, iodized salt, iodized oil, IQ, physical development, hearing capacity, epidemiology, meta-analysis, IDD, randomized trial, intervention, USA, Bangladesh,

  2. Functionalization of gold and nanocrystalline diamond atomic force microscope tips for single molecule force spectroscopy

    Science.gov (United States)

    Drew, Michael E.

    The atomic force microscope (AFM) has fueled interest in nanotechnology because of its ability to image surfaces at the nanometer level and act as a molecular force sensor. Functionalization of the surface of an AFM tip surface in a stable, controlled manner expands the capabilities of the AFM and enables additional applications in the fields of single molecule force spectroscopy and nanolithography. Two AFM tip functionalizations are described: the assembly of tripodal molecular tips onto gold AFM tips and the photochemical attachment of terminal alkenes to nanocrystalline diamond (NCD) AFM tips. Two separate tripodal molecules with different linker lengths and a monopodal molecule terminated with biotin were synthesized to attach to a gold AFM tip for single molecule force spectroscopy. The immobilization of these molecules was examined by contact angle measurements, spectroscopic ellipsometry, infrared, and near edge x-ray absorption fine structure (NEXAFS) spectroscopy. All three molecules displayed rupture forces that agreed with previously reported values for the biotin--avidin rupture. The tripodal molecular tip displayed narrower distribution in their force histograms than the monopodal molecular tip. The performance of the tripodal molecular tip was compared to the monopodal molecular tip in single molecule force spectroscopy studies. Over repeated measurements, the distribution of forces for the monopodal molecular tip shifted to lower forces, whereas the distribution for the tripodal molecular tip remained constant throughout. Loading rate dependence and control experiments further indicated that the rupture forces of the tripod molecular tips were specific to the biotin--NeutrAvidin interaction. The second functionalization method used the photochemical attachment of undecylenic acid to NCD AFM tips. The photochemical attachment of undecylenic acid to hydrogen-terminated NCD wafer surfaces was investigated by contact angle measurements, x

  3. Immobilization of single argon atoms in nano-cages of two-dimensional zeolite model systems.

    Science.gov (United States)

    Zhong, Jian-Qiang; Wang, Mengen; Akter, Nusnin; Kestell, John D; Boscoboinik, Alejandro M; Kim, Taejin; Stacchiola, Dario J; Lu, Deyu; Boscoboinik, J Anibal

    2017-07-17

    The confinement of noble gases on nanostructured surfaces, in contrast to bulk materials, at non-cryogenic temperatures represents a formidable challenge. In this work, individual Ar atoms are trapped at 300 K in nano-cages consisting of (alumino)silicate hexagonal prisms forming a two-dimensional array on a planar surface. The trapping of Ar atoms is detected in situ using synchrotron-based ambient pressure X-ray photoelectron spectroscopy. The atoms remain in the cages upon heating to 400 K. The trapping and release of Ar is studied combining surface science methods and density functional theory calculations. While the frameworks stay intact with the inclusion of Ar atoms, the permeability of gasses (for example, CO) through them is significantly affected, making these structures also interesting candidates for tunable atomic and molecular sieves. These findings enable the study of individually confined noble gas atoms using surface science methods, opening up new opportunities for fundamental research.

  4. Iodine deficiency disorders

    Energy Technology Data Exchange (ETDEWEB)

    Ali, S M [Pakistan Council for Science and Technology, Islamabad (Pakistan)

    1994-12-31

    Iodine deficiency (IDD) is one of the common problem in the diet. Iodine deficiency as prevalence of goiter in population occurs in the mountainous areas. There is consensus that 800 million people are at risk of IDD from living in iodine deficient area and 190 million from goiter. Very high prevalence of IDD in different parts of the world are striking. It has generally observed that in iodine-deficient areas about 50% are affected with goiter, 1-5% from cretinsim and 20% from impaired mental and/or mortor function. (A.B.).

  5. Analysis of regional cerebral blood flow and distribution volume in Machado-Joseph disease by iodine-{sup 123}I IMP single photon emission computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Tsunemi; Nakajima, Takashi; Fukuhara, Nobuyoshi [National Saigata Hospital, Ohagata, Niigata (Japan)

    2001-09-01

    Machado-Joseph disease (MJD) is an autosomal dominant spinocerebellar ataxia. Its clinical features vary greatly in different generations of the same family. Regional cerebral blood flow (rCBF) and distribution volume (V{sub d}) in the pons, cerebellum, and cerebral cortex were measured in 12 patients with MJD by autoradiography (ARG) and the table look-up (TLU) method of iodine-123 IMP ({sup 123}I-IMP) single photon emission computed tomography (SPECT). Representative cases were as follows: A 46-year-old woman first experienced gait ataxia at age 38. Computed tomography (CT) and magnetic resonance imaging (MRI) showed no atrophy in the pons or cerebellum, but rCBF measured by the {sup 123}I-IMP SPECT ARG method detected hypoperfusion in the pons, and cerebellar vermis and hemisphere. A 76-year-old woman first experienced gait ataxia at age 69. CT and MRI findings showed severe atrophy in the pons, and cerebellar vermis and hemisphere. Moreover, rCBF was decreased in the pons, whereas it was not decreased in the cerebellar vermis and hemisphere. In the pons of patients with MJD, rCBF was markedly decreased regardless of disease severity. Because this SPECT finding for the pons looked like a 'dot', we have called it the 'pontine dot sign'. In the MJD group, rCBF was significantly decreased in the pons (Student's t test, p<0.01) and cerebellar vermis (p<0.05). The V{sub d} was also significantly decreased in the pons (p<0.005) in comparison with that for normal subjects. Pearson's correlation analysis yielded a significant relationship between the rCBF in the pons and age at onset (r=0.578, p<0.05). There was a strong correlation between the V{sub d} for the pons and age at onset (r=0.59, p<0.05). Person's correlation analysis also showed a significant relationship between the V{sub d} in the cerebellar hemispheres and International Cooperative Ataxia Rating Scale (r=0.644, p<0.05). The pontine rCBFs in patients with early onset MJD

  6. Confined-interface-directed synthesis of Palladium single-atom catalysts on graphene/amorphous carbon

    DEFF Research Database (Denmark)

    Xi, Jiangbo; Sun, Hongyu; Zhang, Zheye

    2018-01-01

    The maximized atomic efficiency of supported catalysts is highly desired in heterogeneous catalysis. Therefore, the design and development of active, stable, and atomic metal-based catalysts remains a formidable challenge. To tackle these problems, it is necessary to investigate the interaction b...

  7. A practical theoretical formalism for atomic multielectron processes: direct multiple ionization by a single auger decay or by impact of a single electron or photon

    Science.gov (United States)

    Liu, Pengfei; Zeng, Jiaolong; Yuan, Jianmin

    2018-04-01

    Multiple electron processes occur widely in atoms, molecules, clusters, and condensed matters when they are interacting with energetic particles or intense laser fields. Direct multielectron processes (DMEP) are the most complicated among the general multiple electron processes and are the most difficult to describe theoretically. In this work, a unified and accurate theoretical formalism is proposed on the DMEP of atoms including the multiple auger decay and multiple ionization by an impact of a single electron or a single photon based on the atomic collision theory described by a correlated many-body Green's function. Such a practical treatment is made possible by taking consideration of the different coherence features of the atoms (matter waves) in the initial and final states. We first explain how the coherence characteristics of the ejected continuum electrons is largely destructed, by taking the electron impact direct double ionization process as an example. The direct double ionization process is completely different from the single ionization where the complete interference can be maintained. The detailed expressions are obtained for the energy correlations among the continuum electrons and energy resolved differential and integral cross sections according to the separation of knock-out (KO) and shake-off (SO) mechanisms for the electron impact direct double ionization, direct double and triple auger decay, and double and triple photoionization (TPI) processes. Extension to higher order DMEP than triple ionization is straight forward by adding contributions of the following KO and SO processes. The approach is applied to investigate the electron impact double ionization processes of C+, N+, and O+, the direct double and triple auger decay of the K-shell excited states of C+ 1s2{s}22{p}2{}2D and {}2P, and the double and TPI of lithium. Comparisons with the experimental and other theoretical investigations wherever available in the literature show that our

  8. Correlated motion of two atoms trapped in a single-mode cavity field

    International Nuclear Information System (INIS)

    Asboth, Janos K.; Domokos, Peter; Ritsch, Helmut

    2004-01-01

    We study the motion of two atoms trapped at distant positions in the field of a driven standing-wave high-Q optical resonator. Even without any direct atom-atom interaction the atoms are coupled through their position dependent influence on the intracavity field. For sufficiently good trapping and low cavity losses the atomic motion becomes significantly correlated and the two particles oscillate in their wells preferentially with a 90 deg. relative phase shift. The onset of correlations seriously limits cavity cooling efficiency, raising the achievable temperature to the Doppler limit. The physical origin of the correlation can be traced back to a cavity mediated crossfriction, i.e., a friction force on one particle depending on the velocity of the second particle. Choosing appropriate operating conditions allows for engineering these long range correlations. In addition this cross-friction effect can provide a basis for sympathetic cooling of distant trapped clouds

  9. Stability investigation of a high number density Pt1/Fe2O3 single-atom catalyst under different gas environments by HAADF-STEM

    Science.gov (United States)

    Duan, Sibin; Wang, Rongming; Liu, Jingyue

    2018-05-01

    Catalysis by supported single metal atoms has demonstrated tremendous potential for practical applications due to their unique catalytic properties. Unless they are strongly anchored to the support surfaces, supported single atoms, however, are thermodynamically unstable, which poses a major obstacle for broad applications of single-atom catalysts (SACs). In order to develop strategies to improve the stability of SACs, we need to understand the intrinsic nature of the sintering processes of supported single metal atoms, especially under various gas environments that are relevant to important catalytic reactions. We report on the synthesis of high number density Pt1/Fe2O3 SACs using a facial strong adsorption method and the study of the mobility of these supported Pt single atoms at 250 °C under various gas environments that are relevant to CO oxidation, water–gas shift, and hydrogenation reactions. Under the oxidative gas environment, Fe2O3 supported Pt single atoms are stable even at high temperatures. The presence of either CO or H2 molecules in the gas environment, however, facilitates the movement of the Pt atoms. The strong interaction between CO and Pt weakens the binding between the Pt atoms and the support, facilitating the movement of the Pt single atoms. The dissociation of H2 molecules on the Pt atoms and their subsequent interaction with the oxygen species of the support surfaces dislodge the surface oxygen anchored Pt atoms, resulting in the formation of Pt clusters. The addition of H2O molecules to the CO or H2 significantly accelerates the sintering of the Fe2O3 supported Pt single atoms. An anchoring-site determined sintering mechanism is further proposed, which is related to the metal–support interaction.

  10. Marine geochemistry of iodine

    International Nuclear Information System (INIS)

    Kennedy, H.; Elderfield, H.

    1985-01-01

    Iodine has long been classified as a biophilic element with analyses showing that iodine is strongly enriched, relative to seawater concentrations in both plankton and particulate matter and that the concentration of iodine found in surface sediments is still further enriched relative to that found in the sedimenting particulate matter. The extent of enrichment of iodine relative to carbon in deep sea surface sediments has been shown to depend on the carbon accumulation rate. Iodine decomposition rates have been calculated and are shown to vary with the sedimentation rate in the same manner as has been shown for organic carbon. Vertical profiles of total dissolved iodine, iodate and iodide in interstitial waters of sediments from the north east Atlantic are characterised by three zones of reaction as identified by changes in the concentration of iodate and iodide. These reaction zones represent (i) iodide production (ii) iodide oxidation and (iii) iodate reduction. Pore water and solid phase iodine profiles from cores containing turbidite units have shown that iodine, released to pore waters as iodide during the oxidation of the organic matter, has been scavenged after diffusing upwards into a less reducing region of the sediment. (author)

  11. The iodine reactivity

    International Nuclear Information System (INIS)

    2003-01-01

    The iodine is an important element because it has long life isotopes (such as iodine 129) and a great mobility in natural media. Iodine presents a complex chemistry because of its volatility and its strong redox reactivity. The S.E.C.R. works to better understand the reactivity of this element in different natural, industrial or biological environments. It plays a part in thermochemical sites as a possible way of hydrogen formation. This seminar gives some aspects relative to the chemical reactivity of iodine, since its thermochemistry in the I/S cycles to produce hydrogen to its reactivity in the natural medium and its potential radiological impact. This document includes 4 presentations transparencies) dealing with: the 129 I cycle rejected in the low radioactive gaseous and liquid effluents of the La Hague reprocessing plant (C. Frechou); a bibliographic review of iodine retention in soils (F. Bazer-Bachi); the hydrogen production and the iodine/sulfur thermochemical cycle (role of iodine in the process); and the direct characterization by electro-spray ionization mass spectroscopy of iodine fixation by fulvic acids (P. Reiller, B. Amekraz, C. Moulin, V. Moulin)

  12. Iodine-deficiency disorders

    NARCIS (Netherlands)

    Zimmermann, M.B.; Jooste, P.L.; Pandav, C.S.

    2008-01-01

    billion individuals worldwide have insufficient iodine intake, with those in south Asia and sub-Saharan Africa particularly affected. Iodine deficiency has many adverse effects on growth and development. These effects are due to inadequate production of thyroid hormone and are termed

  13. An Assessment of the Selenium Status of Iodine-Deficient and Non-Iodine Deficient Filipino Children

    Directory of Open Access Journals (Sweden)

    Ma. Sofia Amarra

    2002-06-01

    Full Text Available The aim of this study is to examine and compare blood selenium levels in iodine-deficient and non-iodine deficient children. Two groups of children were examined: one group with iodine deficiency (n=31 and the other group with normal iodine status (n=32. Blood was extracted by venipuncture from children aged 6-10 years attending first grade in Commonwealth Elementary School in Quezon City. Whole blood selenium was examined by electrothermal atomic absorption spectrophotometry (AAS. Iodine status was determined by goiter palpation and urinary iodine excretion. Mean selenium levels of deficient and non-deficient children were compared using T-test. Using a cut-off value of 60 mg Se/L whole blood, the proportion of children with normal and deficient iodine status who fell below this cut-off was compared using chi-square test. Whole blood selenium values ranged from 17.6 to 133.6 mg/L. There were no significant differences in mean selenium levels between children with normal and deficient iodine status. Children with normal iodine status had a mean blood selenium level of 55.87 ± 26.3 mg/L while children with deficient iodine status had a mean level of 58.76 ± 26.4 mg/L. Sixty percent of children had blood selenium levels below the arbitrary cut-off of 60 mg/L with no significant difference between groups (p = 0.165, indicating that selenium deficiency is prevalent in this group of children regardless of iodine status. Since selenium deficiency limits the response to iodine supplementation, further investigation is needed to determine whether the same situation exists in children from other areas.

  14. Mechanical properties and formation mechanisms of a wire of single gold atoms

    DEFF Research Database (Denmark)

    Rubio-Bollinger, G.; Bahn, Sune Rastad; Agrait, N.

    2001-01-01

    initio calculations of the force at chain fracture and compare quantitatively with experimental measurements. The observed mechanical failure and nanoelastic processes involved during atomic wire fabrication are investigated using molecular dynamics simulations, and we find that the total effective...

  15. CO2 electroreduction performance of a single transition metal atom supported on porphyrin-like graphene: a computational study.

    Science.gov (United States)

    Wang, Zhongxu; Zhao, Jingxiang; Cai, Qinghai

    2017-08-30

    Searching for low-cost, efficient, and stable electrocatalysts for CO 2 electroreduction (CO 2 ER) reactions is highly desirable for the reduction of CO 2 emission and its conversion into useful products, but remains a great challenge. In this work, single transition metal atoms supported on porphyrin-like graphene catalysts, i.e., TMN 4 /graphene, acting as electrocatalysts for CO 2 reduction were explored by means of comprehensive density functional theory (DFT) computations. Our results revealed that these anchored TM atoms possess high stability due to their strong hybridization with the unsaturated N atoms of the substrate and function as the active sites. On the basis of the calculated adsorption strength of CO 2 ER intermediates, we have identified that single Co, Rh, and Ir atoms exhibit superior catalytic activity towards CO 2 reduction. In particular, CH 3 OH is the preferred product of CO 2 ER on the CoN 4 /graphene catalyst with an overpotential of 0.59 V, while the RhN 4 /graphene and IrN 4 /graphene catalysts prefer to reduce CO 2 to CH 2 O with an overpotential of 0.35 and 0.29 V, respectively. Our work may open a new avenue for the development of catalytic materials with high efficiency for CO 2 electroreduction.

  16. About vortex-like atomic motion in a loaded single crystal

    Science.gov (United States)

    Dmitriev, A. I.; Nikonov, A. Yu.

    2017-12-01

    The paper presents a molecular dynamics study of internal stress and atomic displacement redistributions in a preliminary loaded solid. The study demonstrates the possibility of self-organized vortices as dynamic defects of typical size 1-5 nm due to atomic motion in the elastic region at the stage of relaxation. The simulation results agree well with experimental data on strain localization in elastic distortion regions which gives rise to nanodipoles of partial disclinations.

  17. Iodine mineral waters

    Directory of Open Access Journals (Sweden)

    Iluta Alexandru

    2011-11-01

    Full Text Available Iodine mineral waters are found especially in sub-Carpathian region, also in regions with Salif deposits. Waters are currently used iodine in drinking cure for chaps and Basedow. Are also indicated in balneology. Iodine water containing at least 1 mg L, there is pure iodine is usually given the nature of other types of mineral waters further: sodium chlorinated water (Bazna (50-70 mg iodine / l, Baile Govora (50 - 70 mg / l, Bălţăteşti (4-5 mg / l, salted Monteoru (30 mg / l, mine water mixed alkaline chlorination, sulphate, which are indicated for crenoterapie (hypo or isotonic to the bathrooms Olăneşti or Călimăneşti-Căciulata.

  18. The Study of Iodine Status among Schoolchildren from Kyiv and Ways to Correct the Revealed Violations

    Directory of Open Access Journals (Sweden)

    O.A. Stroi

    2016-08-01

    Full Text Available Relevance. Lack of iodine in the environment is one of the topical medico-social problems in many countries of the world. Iodine deficiency is an important risk factor for the developmental delay, memory loss, or the ability for analysis and abstract thinking. Traditionally in Ukraine the problem of iodine deficiency was relevant in Western regions, but recent studies indicate the existence of moderate iodine deficiency in all areas. The aim of our study was to assess the iodine status of primary schoolchildren from Kyiv. Materials and methods. The examination of 52 children aged 6–12 years was performed, which involved a survey of families on awareness of the consequences of iodine deficiency and frequency of consumption of foods containing iodine, objective and ultrasound thyroid investigation, determination of urine iodine content in single portions of urine. Results. Iodine deficiency was detected in 87 % of pupils, mostly mild. Diffuse goiter grade 1 was diagnosed in 23 % of patients. To correct iodine deficiency, we have used new generation product — jodis-concentrate as an aqueous solution. Conclusions. Research of iodine status in schoolchildren aged 6–12 years in Kyiv showed the presence of mild iodine deficiency in 87 % of them (in 68 and 19 %, respectively. In 12 (23 % children, we have diagnosed thyroid volume increase under normal echogenicity and homogeneous echostructure. Lack of iodine nutrition is caused by poor nutrition, lack of mass, group and individual iodine prophylaxis, low sanitary hygienic culture of the population. Pupils with iodine deficiency were administered an individual subsidy of iodine in the form of an aqueous solution of jodis-concentrate for 12 months, which has significantly improved the iodine status of children, normalized the level of urine iodine content. Early detection of iodine deficiency and its correction are the promising directions of modern pediatrics in terms of the prevention of thyroid

  19. Tunable reactivity of supported single metal atoms by impurity engineering of the MgO(001) support.

    Science.gov (United States)

    Pašti, Igor A; Johansson, Börje; Skorodumova, Natalia V

    2018-02-28

    Development of novel materials may often require a rational use of high price components, like noble metals, in combination with the possibility to tune their properties in a desirable way. Here we present a theoretical DFT study of Au and Pd single atoms supported by doped MgO(001). By introducing B, C and N impurities into the MgO(001) surface, the interaction between the surface and the supported metal adatoms can be adjusted. Impurity atoms act as strong binding sites for Au and Pd adatoms and can help to produce highly dispersed metal particles. The reactivity of metal atoms supported by doped MgO(001), as probed by CO, is altered compared to their counterparts on pristine MgO(001). We find that Pd atoms on doped MgO(001) are less reactive than on perfect MgO(001). In contrast, Au adatoms bind CO much more strongly when placed on doped MgO(001). In the case of Au on N-doped MgO(001) we find that charge redistribution between the metal atom and impurity takes place even when not in direct contact, which enhances the interaction of Au with CO. The presented results suggest possible ways for optimizing the reactivity of oxide supported metal catalysts through impurity engineering.

  20. Iodine leaflets in chapter D5 'Distribution of iodine pills'

    International Nuclear Information System (INIS)

    1981-01-01

    Jodine leaflet A will be distributed together with iodine pills in a nuclear disaster. Iodine leaflet B is suitable for informing the public in advance. Iodine leaflet C informs physicians in a scientific way on the benefits and risk of iodine pills. (orig./HP) [de

  1. Iodine generator for reclaimed water purification

    Science.gov (United States)

    Wynveen, R. A.; Powell, J. D.; Schubert, F. H. (Inventor)

    1977-01-01

    The system disclosed is for controlling the iodine level in a water supply in a spacecraft. It includes an iodine accumulator which stores crystalline iodine, an electrochemical valve to control the input of iodine to the drinking water and an iodine dispenser. A pump dispenses fluid through the iodine dispenser and an iodine sensor to a potable water tank storage. The iodine sensor electronically detects the iodine level in the water, and through electronic means, produces a correction current control. The correction current control operates the electro-chemical iodine valve to release iodine from the iodine accumulator into the iodine dispenser.

  2. Circuit-quantum electrodynamics with direct magnetic coupling to single-atom spin qubits in isotopically enriched 28Si

    Directory of Open Access Journals (Sweden)

    Guilherme Tosi

    2014-08-01

    Full Text Available Recent advances in silicon nanofabrication have allowed the manipulation of spin qubits that are extremely isolated from noise sources, being therefore the semiconductor equivalent of single atoms in vacuum. We investigate the possibility of directly coupling an electron spin qubit to a superconducting resonator magnetic vacuum field. By using resonators modified to increase the vacuum magnetic field at the qubit location, and isotopically purified 28Si substrates, it is possible to achieve coupling rates faster than the single spin dephasing. This opens up new avenues for circuit-quantum electrodynamics with spins, and provides a pathway for dispersive read-out of spin qubits via superconducting resonators.

  3. CDW-EIS model for single-electron capture in ion-atom collisions involving multielectronic targets

    International Nuclear Information System (INIS)

    Abufager, P N; MartInez, A E; Rivarola, R D; Fainstein, P D

    2004-01-01

    A generalization of the continuum distorted wave eikonal initial state (CDW-EIS) approximation, for the description of single-electron capture in ion-atom collisions involving multielectronic targets is presented. This approximation is developed within the framework of the independent electron model taking particular care of the representation of the bound and continuum target states. Total cross sections for single-electron capture from the K-shell of He, Ne and Ar noble gases by impact of bare ions are calculated. Present results are compared to previous CDW-EIS ones and to experimental data

  4. Screened Coulomb interactions in metallic alloys. II. Screening beyond the single-site and atomic-sphere approximations

    DEFF Research Database (Denmark)

    Ruban, Andrei; Simak, S.I.; Korzhavyi, P.A.

    2002-01-01

    -electron potential and energy. In the case of a random alloy such interactions can be accounted for only by lifting the atomic-sphere and single-site approximations, in order to include the polarization due to local environment effects. Nevertheless, a simple parametrization of the screened Coulomb interactions...... for the ordinary single-site methods, including the generalized perturbation method, is still possible. We obtained such a parametrization for bulk and surface NiPt alloys, which allows one to obtain quantitatively accurate effective interactions in this system....

  5. Atomic hydrogen and oxygen adsorptions in single-walled zigzag silicon nanotubes

    International Nuclear Information System (INIS)

    Chen, Haoliang; Ray, Asok K.

    2013-01-01

    Ab initio calculations have been performed to study the electronic and geometric structure properties of zigzag silicon nanotubes. Full geometry and spin optimizations have been performed without any symmetry constraints with an all electron 3-21G* basis set and the B3LYP hybrid functional. The largest zigzag SiNT studied here, (12, 0), has a binding energy per atom of 3.584 eV. Atomic hydrogen and oxygen adsorptions on (9, 0) and (10, 0) nanotubes have also been studied by optimizing the distances of the adatoms from both inside and outside the tube. The adatom is initially placed in four adsorption sites-parallel bridge (PB), zigzag bridge (ZB), hollow, and on-top site. The on-top site is the most preferred site for hydrogen atom adsorbed on (9, 0), with an adsorption energy of 3.0 eV and an optimized distance of 1.49 Å from the adatom to the nearest silicon atom. For oxygen adsorption on (9, 0), the most preferred site is the ZB site, with an adsorption energy of 5.987 eV and an optimized distance of 1.72 Å. For atomic hydrogen adsorption on (10, 0), the most preferred site is also the on-top site with an adsorption energy of 3.174 eV and an optimized distance of 1.49 Å. For adsorption of atomic oxygen on (10, 0), the most preferred site is PB site, with an adsorption energy of 6.306 eV and an optimized distance of 1.71 Å. The HOMO–LUMO gaps of (9, 0) after adsorptions of hydrogen and oxygen atoms decrease while the HOMO–LUMO gaps of (10, 0) increase after adsorption of hydrogen and oxygen

  6. Is placental iodine content related to dietary iodine intake?

    LENUS (Irish Health Repository)

    Burns, R

    2011-08-01

    Delivery of iodine to the foetus depends not only on maternal dietary iodine intake but also on the presence of a functioning placental transport system. A role for the placenta as an iodine storage organ has been suggested, and this study compares the iodine content of placentas from women giving birth at term in Ireland and Iran, areas with median urinary iodine of 79 and 206 μg\\/l respectively.

  7. Catalyst Architecture for Stable Single Atom Dispersion Enables Site-Specific Spectroscopic and Reactivity Measurements of CO Adsorbed to Pt Atoms, Oxidized Pt Clusters, and Metallic Pt Clusters on TiO2.

    Science.gov (United States)

    DeRita, Leo; Dai, Sheng; Lopez-Zepeda, Kimberly; Pham, Nicholas; Graham, George W; Pan, Xiaoqing; Christopher, Phillip

    2017-10-11

    Oxide-supported precious metal nanoparticles are widely used industrial catalysts. Due to expense and rarity, developing synthetic protocols that reduce precious metal nanoparticle size and stabilize dispersed species is essential. Supported atomically dispersed, single precious metal atoms represent the most efficient metal utilization geometry, although debate regarding the catalytic activity of supported single precious atom species has arisen from difficulty in synthesizing homogeneous and stable single atom dispersions, and a lack of site-specific characterization approaches. We propose a catalyst architecture and characterization approach to overcome these limitations, by depositing ∼1 precious metal atom per support particle and characterizing structures by correlating scanning transmission electron microscopy imaging and CO probe molecule infrared spectroscopy. This is demonstrated for Pt supported on anatase TiO 2 . In these structures, isolated Pt atoms, Pt iso , remain stable through various conditions, and spectroscopic evidence suggests Pt iso species exist in homogeneous local environments. Comparing Pt iso to ∼1 nm preoxidized (Pt ox ) and prereduced (Pt metal ) Pt clusters on TiO 2 , we identify unique spectroscopic signatures of CO bound to each site and find CO adsorption energy is ordered: Pt iso ≪ Pt metal atoms bonded to TiO 2 and that Pt iso exhibits optimal reactivity because every atom is exposed for catalysis and forms an interfacial site with TiO 2 . This approach should be generally useful for studying the behavior of supported precious metal atoms.

  8. Iodine in meat in Macedonia

    International Nuclear Information System (INIS)

    Bogdanov, Bogdan; Gonev, Mihajlo; Tadzher, Isak

    2000-01-01

    Iodine deficiency in Macedonia still persists in a mild form. In 1999 the iodination of salt rose to 20 m gr iodine in Kg salt. The consumption of salt diminished after the last war from 20-30 gr salt per day to 10-20 gr salt daily. This shows that the problem of the elimination of iodine deficiency is being vigorously tackled. Since 1956 the iodine in salt in Macedonia rose to 10 m gr KI/Kg salt. The content of iodine in the Macedonian diet seems to be important. The amount of iodine in milk, eggs and bread is low as found by the investigation of MANU. The content of iodine in meat is low, compared to British meat is 10 times lower. The average iodine content in Macedonian meat is 95.15 micro gr per Kg, whereas in British meat it is 850-1510 micro gr iodine per k gr meat. (Original)

  9. Ionization of highly charged iodine ions near the Bohr velocity

    International Nuclear Information System (INIS)

    Zhou, Xianming; Cheng, Rui; Lei, Yu; Sun, Yuanbo; Ren, Jieru; Liu, Shidong; Deng, Jiachuan; Zhao, Yongtao; Xiao, Guoqing

    2015-01-01

    We have measured the L-shell X-rays of iodine from the collisions of 3 MeV I q+(q=15,20,22,25,26) ions with an iron target. It is found that the X-ray yield decreases with the increasing initial charge state. The energy of the subshell X-ray has a blue shift, which is independent of the projectile charge state. In addition, the relative intensity ratios of Lβ 1,3,4 and Lβ 2,15 to Lα 1,2 X-ray are obtained and compared with the theoretical calculations. That they are larger than for a singly ionized atom can be understood by the multiple ionization effect of the outer-shell electrons

  10. From Single Atoms to Nanoparticles: Autocatalysis and Metal Aggregation in Atomic Layer Deposition of Pt on TiO2 Nanopowder.

    Science.gov (United States)

    Grillo, Fabio; Van Bui, Hao; La Zara, Damiano; Aarnink, Antonius A I; Kovalgin, Alexey Y; Kooyman, Patricia; Kreutzer, Michiel T; van Ommen, Jan Rudolf

    2018-05-10

    A fundamental understanding of the interplay between ligand-removal kinetics and metal aggregation during the formation of platinum nanoparticles (NPs) in atomic layer deposition of Pt on TiO 2 nanopowder using trimethyl(methylcyclo-pentadienyl)platinum(IV) as the precursor and O 2 as the coreactant is presented. The growth follows a pathway from single atoms to NPs as a function of the oxygen exposure (P O2 × time). The growth kinetics is modeled by accounting for the autocatalytic combustion of the precursor ligands via a variant of the Finke-Watzky two-step model. Even at relatively high oxygen exposures ( 120 mbar s. The deposition of more Pt leads to the formation of NPs that can be as large as 6 nm. Crucially, high P O2 (≥5 mbar) hinders metal aggregation, thus leading to narrow particle size distributions. The results show that ALD of Pt NPs is reproducible across small and large surface areas if the precursor ligands are removed at high P O2 . © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Controversies in urinary iodine determinations

    OpenAIRE

    Soldin, Offie Porat

    2002-01-01

    Iodine deficiency (ID) is associated with increased prevalence of goiter, increased risk for neurodevelopmental disorders, and is the world’s leading cause of intellectual deficits. Iodine nutritional status of a population is assessed by measurements of urinary iodine concentrations which are also used to define, indicate, survey and monitor iodine deficiency and consequently its treatment. Several methods are available for urinary iodine determination. Discussed here are some of the limitat...

  12. Tunneling couplings in discrete lattices, single-particle band structure, and eigenstates of interacting atom pairs

    International Nuclear Information System (INIS)

    Piil, Rune; Moelmer, Klaus

    2007-01-01

    By adjusting the tunneling couplings over longer than nearest-neighbor distances, it is possible in discrete lattice models to reproduce the properties of the lowest energy band of a real, continuous periodic potential. We propose to include such terms in problems with interacting particles, and we show that they have significant consequences for scattering and bound states of atom pairs in periodic potentials

  13. Quantum state detection and state preparation based on cavity-enhanced nonlinear interaction of atoms with single photon

    Science.gov (United States)

    Hosseini, Mahdi

    Our ability to engineer quantum states of light and matter has significantly advanced over the past two decades, resulting in the production of both Gaussian and non-Gaussian optical states. The resulting tailored quantum states enable quantum technologies such as quantum optical communication, quantum sensing as well as quantum photonic computation. The strong nonlinear light-atom interaction is the key to deterministic quantum state preparation and quantum photonic processing. One route to enhancing the usually weak nonlinear light-atom interactions is to approach the regime of cavity quantum electrodynamics (cQED) interaction by means of high finesse optical resonators. I present results from the MIT experiment of large conditional cross-phase modulation between a signal photon, stored inside an atomic quantum memory, and a control photon that traverses a high-finesse optical cavity containing the atomic memory. I also present a scheme to probabilistically change the amplitude and phase of a signal photon qubit to, in principle, arbitrary values by postselection on a control photon that has interacted with that state. Notably, small changes of the control photon polarization measurement basis by few degrees can substantially change the amplitude and phase of the signal state. Finally, I present our ongoing effort at Purdue to realize similar peculiar quantum phenomena at the single photon level on chip scale photonic systems.

  14. Single-resonance optical pumping spectroscopy and application in dressed-state measurement with atomic vapor cell at room temperature.

    Science.gov (United States)

    Liang, Qiangbing; Yang, Baodong; Zhang, Tiancai; Wang, Junmin

    2010-06-21

    By monitoring the transmission of probe laser beam (also served as coupling laser beam) which is locked to a cycling hyperfine transition of cesium D(2) line, while pumping laser is scanned across cesium D(1) or D(2) lines, the single-resonance optical pumping (SROP) spectra are obtained with atomic vapor cell. The SROP spectra indicate the variation of the zero-velocity atoms population of one hyperfine fold of ground state, which is optically pumped into another hyperfine fold of ground state by pumping laser. With the virtue of Doppler-free linewidth, high signal-to-noise ratio (SNR), flat background and elimination of crossover resonance lines (CRLs), the SROP spectra with atomic vapor cell around room temperature can be employed to measure dressed-state splitting of ground state, which is normally detected with laser-cooled atomic sample only, even if the dressed-state splitting is much smaller than the Doppler-broaden linewidth at room temperature.

  15. Fe Isolated Single Atoms on S, N Codoped Carbon by Copolymer Pyrolysis Strategy for Highly Efficient Oxygen Reduction Reaction.

    Science.gov (United States)

    Li, Qiheng; Chen, Wenxing; Xiao, Hai; Gong, Yue; Li, Zhi; Zheng, Lirong; Zheng, Xusheng; Yan, Wensheng; Cheong, Weng-Chon; Shen, Rongan; Fu, Ninghua; Gu, Lin; Zhuang, Zhongbin; Chen, Chen; Wang, Dingsheng; Peng, Qing; Li, Jun; Li, Yadong

    2018-06-01

    Heteroatom-doped Fe-NC catalyst has emerged as one of the most promising candidates to replace noble metal-based catalysts for highly efficient oxygen reduction reaction (ORR). However, delicate controls over their structure parameters to optimize the catalytic efficiency and molecular-level understandings of the catalytic mechanism are still challenging. Herein, a novel pyrrole-thiophene copolymer pyrolysis strategy to synthesize Fe-isolated single atoms on sulfur and nitrogen-codoped carbon (Fe-ISA/SNC) with controllable S, N doping is rationally designed. The catalytic efficiency of Fe-ISA/SNC shows a volcano-type curve with the increase of sulfur doping. The optimized Fe-ISA/SNC exhibits a half-wave potential of 0.896 V (vs reversible hydrogen electrode (RHE)), which is more positive than those of Fe-isolated single atoms on nitrogen codoped carbon (Fe-ISA/NC, 0.839 V), commercial Pt/C (0.841 V), and most reported nonprecious metal catalysts. Fe-ISA/SNC is methanol tolerable and shows negligible activity decay in alkaline condition during 15 000 voltage cycles. X-ray absorption fine structure analysis and density functional theory calculations reveal that the incorporated sulfur engineers the charges on N atoms surrounding the Fe reactive center. The enriched charge facilitates the rate-limiting reductive release of OH* and therefore improved the overall ORR efficiency. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. High quality single atomic layer deposition of hexagonal boron nitride on single crystalline Rh(111) four-inch wafers

    Energy Technology Data Exchange (ETDEWEB)

    Hemmi, A.; Bernard, C.; Cun, H.; Roth, S.; Klöckner, M.; Kälin, T.; Osterwalder, J.; Greber, T., E-mail: greber@physik.uzh.ch [Physik-Institut, Universität Zürich, CH-8057 Zürich (Switzerland); Weinl, M.; Gsell, S.; Schreck, M. [Institut für Physik, Universität Augsburg, D-86135 Augsburg (Germany)

    2014-03-15

    The setup of an apparatus for chemical vapor deposition (CVD) of hexagonal boron nitride (h-BN) and its characterization on four-inch wafers in ultra high vacuum (UHV) environment is reported. It provides well-controlled preparation conditions, such as oxygen and argon plasma assisted cleaning and high temperature annealing. In situ characterization of a wafer is accomplished with target current spectroscopy. A piezo motor driven x-y stage allows measurements with a step size of 1 nm on the complete wafer. To benchmark the system performance, we investigated the growth of single layer h-BN on epitaxial Rh(111) thin films. A thorough analysis of the wafer was performed after cutting in atmosphere by low energy electron diffraction, scanning tunneling microscopy, and ultraviolet and X-ray photoelectron spectroscopies. The apparatus is located in a clean room environment and delivers high quality single layers of h-BN and thus grants access to large area UHV processed surfaces, which had been hitherto restricted to expensive, small area single crystal substrates. The facility is versatile enough for customization to other UHV-CVD processes, e.g., graphene on four-inch wafers.

  17. Electrochemistry of iodine

    Energy Technology Data Exchange (ETDEWEB)

    Yaraliev, Ya.A. (AN Azerbajdzhanskoj SSR, Baku. Inst. Neorganicheskoj i Fizicheskoj Khimii)

    1982-06-01

    The review is devoted to investigations into oxidation-reduction processes in different systems including iodine. The data on adsorption of iodine on metals are discussed; the connection between the nature of iodine adsorption and the mechanism of its electrode reactions is considered. The metals studied can be placed in the following series taking into account the degree of I sorption on them: Cd approximately Tl < Sn approximately Pb < Ga < Bi < Hg < Co approximately Ni < Fe < Ag approximately Rh approximately Pd approximately Ir < Pt. The data are given of standard and equilibrium potentials in iodine systems. Electric oxidation and electric reduction of iodide ions is investigated using the methods of Faraday impedance and rectification, methods of voltamperometry and oscillopolarography, rotating disc electrode, chronopotentiometry. Anode and cathode processes of oxidation-reduction reactions in I/sup -//IO/sub 3//sup -/, I/sub 2//IO/sub 3//sup -/ and I/sub 2//I/sup +/ systems are analyzed.

  18. QUALIMETRIC QUALITY ASSESSMENT OF IODINE SUPPLEMENTS

    Directory of Open Access Journals (Sweden)

    F. S. Bazrova

    2015-01-01

    Full Text Available The article discusses the new iodine-containing supplements (ID derived from organic media collagenous animal protein (pork rind, carpatina and collagen and protein concentrates brands SCANGEN and PROMIL C95. It is shown that the use of these proteins as carriers of iodine is due to the high content of the amino acids glycine and alanine, which correlates with the degree of binding of iodine objects. New additives in addition to the special focus improve rheological properties of foods, including texture, appearance and functional properties. To assess the quality'ID and selection of preferred option the proposed qualitative assessment and a systematic approach to consider all'ID as a system to allocate its elements, to justify the principles of its construction and the requirements imposed on it, to build a General decision tree. For the construction of complex criterion for assessing the quality'ID proposed procedure formalization based on selection and evaluation of individual indicators, the definition of the laws of their change, depending on the dose, duration and temperature of exposure, and functional efficiency. For comparative evaluation of single and calculation of group indicators all of them were reduced to a single dimension by introducing the dimensionless coefficients of adequately describing the analyzed indicators. The article presents the calculated values of single and group of indicators characterizing technological properties 'ID: the degree of binding of iodine, the binding rate of iodine, heat losses of iodine and basic functional and technological properties of meat stuffing systems (water-binding, moisture-holding, emulsifying capacity and emulsion stability, obtained by the introduction of stuffing in the system studied'ID. At the final stage is the selection of the best 'ID, on the basis of an assessment of group performance.

  19. The entanglement of two moving atoms interacting with a single-mode field via a three-photon process

    International Nuclear Information System (INIS)

    Chao, Wu; Mao-Fa, Fang

    2010-01-01

    In this paper, the entanglement of two moving atoms induced by a single-mode field via a three-photon process is investigated. It is shown that the entanglement is dependent on the category of the field, the average photon number N, the number p of half-wave lengths of the field mode and the atomic initial state. Also, the sudden death and the sudden birth of the entanglement are detected in this model and the results show that the existence of the sudden death and the sudden birth depends on the parameter and the category of the mode field. In addition, the three-photon process is a higher order nonlinear process. (general)

  20. Iodine Hall Thruster

    Science.gov (United States)

    Szabo, James

    2015-01-01

    Iodine enables dramatic mass and cost savings for lunar and Mars cargo missions, including Earth escape and near-Earth space maneuvers. The demonstrated throttling ability of iodine is important for a singular thruster that might be called upon to propel a spacecraft from Earth to Mars or Venus. The ability to throttle efficiently is even more important for missions beyond Mars. In the Phase I project, Busek Company, Inc., tested an existing Hall thruster, the BHT-8000, on iodine propellant. The thruster was fed by a high-flow iodine feed system and supported by an existing Busek hollow cathode flowing xenon gas. The Phase I propellant feed system was evolved from a previously demonstrated laboratory feed system. Throttling of the thruster between 2 and 11 kW at 200 to 600 V was demonstrated. Testing showed that the efficiency of iodine fueled BHT-8000 is the same as with xenon, with iodine delivering a slightly higher thrust-to-power (T/P) ratio. In Phase II, a complete iodine-fueled system was developed, including the thruster, hollow cathode, and iodine propellant feed system. The nominal power of the Phase II system is 8 kW; however, it can be deeply throttled as well as clustered to much higher power levels. The technology also can be scaled to greater than 100 kW per thruster to support megawatt-class missions. The target thruster efficiency for the full-scale system is 65 percent at high specific impulse (Isp) (approximately 3,000 s) and 60 percent at high thrust (Isp approximately 2,000 s).

  1. Single molecule imaging of RNA polymerase II using atomic force microscopy

    International Nuclear Information System (INIS)

    Rhodin, Thor; Fu Jianhua; Umemura, Kazuo; Gad, Mohammed; Jarvis, Suzi; Ishikawa, Mitsuru

    2003-01-01

    An atomic force microscopy (AFM) study of the shape, orientation and surface topology of RNA polymerase II supported on silanized freshly cleaved mica was made. The overall aim is to define the molecular topology of RNA polymerase II in appropriate fluids to help clarify the relationship of conformational features to biofunctionality. A Nanoscope III atomic force microscope was used in the tapping mode with oxide-sharpened (8-10 nm) Si 3 N 4 probes in aqueous zinc chloride buffer. The main structural features observed by AFM were compared to those derived from electron-density plots based on X-ray crystallographic studies. The conformational features included a bilobal silhouette with an inverted umbrella-shaped crater connected to a reaction site. These studies provide a starting point for constructing a 3D-AFM profiling analysis of proteins such as RNA polymerase complexes

  2. Ultrafast terahertz control of extreme tunnel currents through single atoms on a silicon surface

    DEFF Research Database (Denmark)

    Jelic, Vedran; Iwaszczuk, Krzysztof; Nguyen, Peter H.

    2017-01-01

    scanning tunnelling microscopy (THz-STM) in ultrahigh vacuum as a new platform for exploring ultrafast non-equilibrium tunnelling dynamics with atomic precision. Extreme terahertz-pulse-driven tunnel currents up to 10(7) times larger than steady-state currents in conventional STM are used to image...... terahertz-induced band bending and non-equilibrium charging of surface states opens new conduction pathways to the bulk, enabling extreme transient tunnel currents to flow between the tip and sample.......Ultrafast control of current on the atomic scale is essential for future innovations in nanoelectronics. Extremely localized transient electric fields on the nanoscale can be achieved by coupling picosecond duration terahertz pulses to metallic nanostructures. Here, we demonstrate terahertz...

  3. Direct Atomic Force Microscopy Observation of DNA Tile Crystal Growth at the Single-Molecule Level

    OpenAIRE

    Evans, Constantine G.; Hariadi, Rizal F.; Winfree, Erik

    2012-01-01

    While the theoretical implications of models of DNA tile self-assembly have been extensively researched and such models have been used to design DNA tile systems for use in experiments, there has been little research testing the fundamental assumptions of those models. In this paper, we use direct observation of individual tile attachments and detachments of two DNA tile systems on a mica surface imaged with an atomic force microscope (AFM) to compile statistics of tile attachments and detach...

  4. High Resolution Numerical Simulations of Primary Atomization in Diesel Sprays with Single Component Reference Fuels

    Science.gov (United States)

    2015-09-01

    NC. 14. ABSTRACT A high-resolution numerical simulation of jet breakup and spray formation from a complex diesel fuel injector at diesel engine... diesel fuel injector at diesel engine type conditions has been performed. A full understanding of the primary atomization process in diesel fuel... diesel liquid sprays the complexity is further compounded by the physical attributes present including nozzle turbulence, large density ratios

  5. Adsorption and migration of single metal atoms on the calcite (10.4) surface

    International Nuclear Information System (INIS)

    Pinto, H; Haapasilta, V; Lokhandwala, M; Foster, Adam S; Öberg, S

    2017-01-01

    Transition metal atoms are one of the key ingredients in the formation of functional 2D metal organic coordination networks. Additionally, the co-deposition of metal atoms can play an important role in anchoring the molecular structures to the surface at room temperature. To gain control of such processes requires the understanding of adsorption and diffusion properties of the different transition metals on the target surface. Here, we used density functional theory to investigate the adsorption of 3 d (Ti, Cr, Fe, Ni, Cu), 4 d (Zr, Nb, Mo, Pd, Ag) and 5 d (Hf, W, Ir, Pt, Au) transition metal adatoms on the insulating calcite (10.4) surface. We identified the most stable adsorption sites and calculated binding energies and corresponding ground state structures. We find that the preferential adsorption sites are the Ca–Ca bridge sites. Apart from the Cr, Mo, Cu, Ag and Au all the studied metals bind strongly to the calcite surface. The calculated migration barriers for the representative Ag and Fe atoms indicates that the metal adatoms are mobile on the calcite surface at room temperature. Bader analysis suggests that there is no significant charge transfer between the metal adatoms and the calcite surface. (paper)

  6. Reconstructive surgery for male stress urinary incontinence: Experiences using the ATOMS system at a single center

    Directory of Open Access Journals (Sweden)

    Krause, Jens

    2014-12-01

    Full Text Available Objective: To propose possible success-driven solutions for problem and complication rates encountered with the ATOMS sling system, based on first-hand experience; and to provide possible actual alternative scenarios for the treatment of male . Patients and methods: During the defined period (between 4/2010 and 04/2014, 36 patients received ATOMS system implants at our clinic. We collected pre- and post-operative evaluation data using the International Consultation on Incontinence Questionnaire Short Form (ICIQ SF. As an expansion of the questionnaire, we added questions about post-operative perineal pain, the general satisfaction with the results of the intervention and willingness to recommend the operation to a best friend. Results: Our data shows a relatively high explantation rate, but a surprisingly high patient satisfaction rate. Explantation was required mainly due to late onset infections or other symptomatic factors. Compared to other studies early onset infections were rare. Conclusion: A non-invasive, uncomplicated adjustable system to alleviate male stress urinary incontinence remains a challenge. Although there are various systems available for the treatment of male stress urinary incontinence, it seems that despite the advantages of the ATOMS system, an artificial sphincter system may pose more advantages based on our experience, understanding and knowledge of its well-documented long-term solutions and problems.

  7. Liquid phase hot atom chemistry: At crossroads

    International Nuclear Information System (INIS)

    Rack, E.P.; Veterans Administration Medical Center, Omaha, NE

    1981-01-01

    The state of current research in liquid phase hot atom chemistry is discussed. Four classes of experimental approaches are high-lighted. These include 1) primary physical data for (n,γ)-activated 128 I, (I.T.)-activated 130 I and effects on chemical reactivity; 2) the density-variation technique involving iodine reactions with saturated and unsaturated hydrocarbons; 3) stereochemistry experiments on chlorocarbon molecules with single and multiple chiral centers; and 4) experiments employing dilute aqueous solutions of halogenerated biomolecules in the ice state, exposed to neutron irradiation. (orig.) [de

  8. Evidence for a single hydrogen molecule connected by an atomic chain

    DEFF Research Database (Denmark)

    Kiguchi, M.; Stadler, Robert; Bækgaard, Iben Sig Buur

    2007-01-01

    Stable, single-molecule conducting-bridge configurations are typically identified from peak structures in a conductance histogram. In previous work on Pt with H-2 at cryogenic temperatures it has been shown that a peak near 1G(0) identifies a single-molecule Pt-H-2-Pt bridge. The histogram shows...

  9. Single Atomic Iron Catalysts for Oxygen Reduction in Acidic Media: Particle Size Control and Thermal Activation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hanguang; Hwang, Sooyeon; Wang, Maoyu; Feng, Zhenxing; Karakalos, Stavros; Luo, Langli; Qiao, Zhi; Xie, Xiaohong; Wang, Chongmin; Su, Dong; Shao, Yuyan; Wu, Gang (BNL); (Oregon State U.); (SC); (PNNL); (Buffalo)

    2017-09-26

    It remains a grand challenge to replace platinum group metal (PGM) catalysts with earth-abundant materials for the oxygen reduction reaction (ORR) in acidic media, which is crucial for large-scale deployment of proton exchange membrane fuel cells (PEMFCs). Here, we report a high-performance atomic Fe catalyst derived from chemically Fe-doped zeolitic imidazolate frameworks (ZIFs) by directly bonding Fe ions to imidazolate ligands within 3D frameworks. Although the ZIF was identified as a promising precursor, the new synthetic chemistry enables the creation of well-dispersed atomic Fe sites embedded into porous carbon without the formation of aggregates. The size of catalyst particles is tunable through synthesizing Fe-doped ZIF nanocrystal precursors in a wide range from 20 to 1000 nm followed by one-step thermal activation. Similar to Pt nanoparticles, the unique size control without altering chemical properties afforded by this approach is able to increase the number of PGM-free active sites. The best ORR activity is measured with the catalyst at a size of 50 nm. Further size reduction to 20 nm leads to significant particle agglomeration, thus decreasing the activity. Using the homogeneous atomic Fe model catalysts, we elucidated the active site formation process through correlating measured ORR activity with the change of chemical bonds in precursors during thermal activation up to 1100 °C. The critical temperature to form active sites is 800 °C, which is associated with a new Fe species with a reduced oxidation number (from Fe3+ to Fe2+) likely bonded with pyridinic N (FeN4) embedded into the carbon planes. Further increasing the temperature leads to continuously enhanced activity, linked to the rise of graphitic N and Fe–N species. The new atomic Fe catalyst has achieved respectable ORR activity in challenging acidic media (0.5 M H2SO4), showing a half-wave potential of 0.85 V vs RHE and leaving only a 30 mV gap with Pt/C (60 μgPt/cm2). Enhanced stability

  10. Iodine deficiency and thyroid disorders.

    Science.gov (United States)

    Zimmermann, Michael B; Boelaert, Kristien

    2015-04-01

    Iodine deficiency early in life impairs cognition and growth, but iodine status is also a key determinant of thyroid disorders in adults. Severe iodine deficiency causes goitre and hypothyroidism because, despite an increase in thyroid activity to maximise iodine uptake and recycling in this setting, iodine concentrations are still too low to enable production of thyroid hormone. In mild-to-moderate iodine deficiency, increased thyroid activity can compensate for low iodine intake and maintain euthyroidism in most individuals, but at a price: chronic thyroid stimulation results in an increase in the prevalence of toxic nodular goitre and hyperthyroidism in populations. This high prevalence of nodular autonomy usually results in a further increase in the prevalence of hyperthyroidism if iodine intake is subsequently increased by salt iodisation. However, this increase is transient because iodine sufficiency normalises thyroid activity which, in the long term, reduces nodular autonomy. Increased iodine intake in an iodine-deficient population is associated with a small increase in the prevalence of subclinical hypothyroidism and thyroid autoimmunity; whether these increases are also transient is unclear. Variations in population iodine intake do not affect risk for Graves' disease or thyroid cancer, but correction of iodine deficiency might shift thyroid cancer subtypes toward less malignant forms. Thus, optimisation of population iodine intake is an important component of preventive health care to reduce the prevalence of thyroid disorders. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. A pulsed oxygen - iodine chemical laser excited by a longitudinal electric discharge

    International Nuclear Information System (INIS)

    Vagin, Nikolai P; Yuryshev, Nikolai N

    2002-01-01

    The dependence of the energy parameters of an oxygen - iodine chemical laser with a bulk generation of iodine atoms in a longitudinal electric discharge on the length of the discharge gap is studied for various discharge energies and voltages and various working mixture compositions (at constant oxygen and iodine pressures). Analyses of the results suggests that temperature effects account for a twofold decrease in the specific energy yield for the lasing initiated by a longitudinal electric discharge compared to the photolytic initiation. (lasers)

  12. A comparison of iodine-123 meta-iodobenzylguanidine scintigraphy and single bone marrow aspiration biopsy in the diagnosis and follow-up of 26 children with neuroblastoma

    International Nuclear Information System (INIS)

    Osmanagaoglu, K.; Lippens, M.; Benoit, Y.; Obrie, E.; Schelstraete, K.; Simons, M.

    1993-01-01

    In staging neuroblastomas, the demonstration of tumoural invasion of the bone marrow is an important criterion with regard to the therapeutic prospects and the prognosis. Iliac crest aspiration sampling has been used routinely for the detection of bone marrow metastases in neuroblastoma, but due to the limited character of the sampling it sometimes leads to false-negative results. Another procedure used to determine the extent of neuroblastoma is metaiodobenzylguanidine (mIBG) scintigraphy. To establish the respective merits of both diagnostic techniques, 148 iodine-123 mIBG scans of 26 children with neuroblastoma were re-evaluated and compared with the results of routine bone marrow samples obtained within a 4-week period before or after scanning. The results indicate that for the assessment of bone marrow infiltration by neuroblastoma, 123 I-mIBG scintigraphy is more sensitive than the conventional cytological examination of bone marrow smears routinely obtained from the iliac crest, has a very high sensitivity in excluding bone marrow invasion, has a high specificity for detecting bone marrow invasion, appears to be able to detect early tumoural deposits in the bone marrow before osseous invasion occurs as shown on the MDP scans and is superior to 99m Tc-MDP bone scan in detecting bone/bone marrow metastases of neuroblastoma

  13. Selective alkane activation with single-site atoms on amorphous support

    Science.gov (United States)

    Hock, Adam S.; Schweitzer, Neil M.; Miller, Jeffrey T.; Hu, Bo

    2015-11-24

    The present invention relates generally to catalysts and methods for use in olefin production. More particularly, the present invention relates to novel amorphously supported single-center, Lewis acid metal ions and use of the same as catalysts.

  14. Vertical Alignment of Single-Walled Carbon Nanotubes on Nanostructure Fabricated by Atomic Force Microscope

    National Research Council Canada - National Science Library

    Lee, Haiwon

    2007-01-01

    This project focused on the behavior of single-wall carbon nanotubes (SWCNTs) in the electrophoresis cells and aligned growth of SWCNTs by thermal chemical vapor deposition on selectively deposited metallic nanoparticle...

  15. Accuracy of contrast-enhanced dual-energy MDCT for the assessment of iodine uptake in renal lesions.

    Science.gov (United States)

    Mileto, Achille; Marin, Daniele; Ramirez-Giraldo, Juan Carlos; Scribano, Emanuele; Krauss, Bernhard; Mazziotti, Silvio; Ascenti, Giorgio

    2014-05-01

    The objective of our study was to assess the accuracy of iodine-related attenuation and iodine quantification as imaging biomarkers of iodine uptake in renal lesions on a single-phase nephrographic image with dual-energy MDCT. Fifty-nine patients (41 men, 18 women; age range, 28-84 years) with 80 renal lesions underwent contrast-enhanced dual-energy CT during the nephrographic phase of enhancement. Renal lesions were characterized as enhancing or nonenhancing on color-coded iodine overlay maps using iodine-related attenuation (in Hounsfield units) and iodine quantification (in milligrams per milliliter). For iodine-related attenuation the iodine uptake thresholds of 15 and 20 HU were tested; a threshold of 0.5 mg/mL was used for iodine quantification. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of iodine-related attenuation and iodine quantification were calculated from chi-square tests of contingency with histopathology or imaging follow-up as the reference standard. The 95% CIs were calculated from binomial expression. Differences in sensitivity and specificity were assessed by means of McNemar analysis. A significant difference in sensitivity and specificity was found between iodine-related attenuation with the thresholds of 15 HU (sensitivity, 91.4%; specificity, 93.3%; PPV, 91.4%; NPV, 93.3%) and 20 HU (sensitivity, 77.1%; specificity, 100%; PPV, 100%; NPV, 84.9%) (p = 0.008) and between iodine quantification (sensitivity, 100%; specificity, 97.7%; PPV, 97.2%; NPV, 100%) and iodine-related attenuation with a threshold of 20 HU (p = 0.004). No significant difference in sensitivity and specificity was found between iodine quantification and iodine-related attenuation with a threshold of 15 HU. Contrast-enhanced dual-energy MDCT with iodine-related attenuation and iodine quantification allows accurate evaluation of iodine uptake in renal lesions on a single-phase nephrographic image.

  16. Autoionic microscopy of damage regions of single atom displacement cascades in metals

    International Nuclear Information System (INIS)

    Suvorov, A.L.

    1981-01-01

    The defect region formation characterized by zones of depletion with atoms and interstitial halos arizing during displacement cascade development in an irradiated metal is considered. in experimental autoionmicroscopic analysis technique is used. The analysis procedure is briefly discussed: the experiment, the defect identification on autoionic image microphotos, computer data processing. The technique was applied for pure tungsten irradiated with 12 and 5.8 MeV deuterons and fission neutrons, and for tungsten-1.5% ThO 2 alloy irradiated with fast neutrons from fission fragments

  17. Direct atomic force microscopy observation of DNA tile crystal growth at the single-molecule level.

    Science.gov (United States)

    Evans, Constantine G; Hariadi, Rizal F; Winfree, Erik

    2012-06-27

    While the theoretical implications of models of DNA tile self-assembly have been extensively researched and such models have been used to design DNA tile systems for use in experiments, there has been little research testing the fundamental assumptions of those models. In this paper, we use direct observation of individual tile attachments and detachments of two DNA tile systems on a mica surface imaged with an atomic force microscope (AFM) to compile statistics of tile attachments and detachments. We show that these statistics fit the widely used kinetic Tile Assembly Model and demonstrate AFM movies as a viable technique for directly investigating DNA tile systems during growth rather than after assembly.

  18. Nanoprecipitates in single-crystal molybdenum-alloy nanopillars detected by TEM and atom probe tomography

    International Nuclear Information System (INIS)

    Oveisi, Emad; Bártová, Barbora; Gerstl, Stephan; Zimmermann, Julien; Marichal, Cécile; Van Swygenhoven, Helena; Hébert, Cécile

    2013-01-01

    Transmission electron microscopy (TEM) supported by various chemical analyses techniques as well as atom probe tomography is applied to characterize newly identified nanosized precipitates in Mo-alloy nanopillars that were prepared by directional solidification. It is shown that the α-Mo matrix contains Al-enriched face-centred cubic precipitates which have a 4.12 Å lattice parameter, and exhibit a Kurdjumov–Sachs crystallographic orientation relationship with the matrix. Such precipitates could be responsible for the unusual behaviour of the pillars during compression tests

  19. Direct evidence for coastal iodine particles from Laminaria macroalgae – linkage to emissions of molecular iodine

    Directory of Open Access Journals (Sweden)

    G. McFiggans

    2004-01-01

    Full Text Available Renewal of ultrafine aerosols in the marine boundary layer may lead to repopulation of the marine distribution and ultimately determine the concentration of cloud condensation nuclei (CCN. Thus the formation of nanometre-scale particles can lead to enhanced scattering of incoming radiation and a net cooling of the atmosphere. The recent demonstration of the chamber formation of new particles from the photolytic production of condensable iodine-containing compounds from diiodomethane (CH2I2, (O'Dowd et al., 2002; Kolb, 2002; Jimenez et al., 2003a; Burkholder and Ravishankara, 2003, provides an additional mechanism to the gas-to-particle conversion of sulphuric acid formed in the photo-oxidation of dimethylsulphide for marine aerosol repopulation. CH2I2 is emitted from seaweeds (Carpenter et al., 1999, 2000 and has been suggested as an initiator of particle formation. We demonstrate here for the first time that ultrafine iodine-containing particles are produced by intertidal macroalgae exposed to ambient levels of ozone. The particle composition is very similar both to those formed in the chamber photo-oxidation of diiodomethane and in the oxidation of molecular iodine by ozone. The particles formed in all three systems are similarly aspherical. When small, those formed in the molecular iodine system swell only moderately when exposed to increased humidity environments, and swell progressively less with increasing size; this behaviour occurs whether they are formed in dry or humid environments, in contrast to those in the CH2I2 system. Direct coastal boundary layer observations of molecular iodine, ultrafine particle production and iodocarbons are reported. Using a newly measured molecular iodine photolysis rate, it is shown that, if atomic iodine is involved in the observed particle bursts, it is of the order of at least 1000 times more likely to result from molecular iodine photolysis than diiodomethane photolysis. A hypothesis for molecular

  20. A single-cell scraper based on an atomic force microscope for detaching a living cell from a substrate

    Energy Technology Data Exchange (ETDEWEB)

    Iwata, Futoshi, E-mail: iwata.futoshi@shizuoka.ac.jp [Department of Mechanical Engineering, Faculty of Engineering, Shizuoka University, Johoku, Naka-ku, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Johoku, Naka-ku, Hamamatsu 432-8011 (Japan); Adachi, Makoto; Hashimoto, Shigetaka [Department of Mechanical Engineering, Faculty of Engineering, Shizuoka University, Johoku, Naka-ku, Hamamatsu 432-8561 (Japan)

    2015-10-07

    We describe an atomic force microscope (AFM) manipulator that can detach a single, living adhesion cell from its substrate without compromising the cell's viability. The micrometer-scale cell scraper designed for this purpose was fabricated from an AFM micro cantilever using focused ion beam milling. The homemade AFM equipped with the scraper was compact and standalone and could be mounted on a sample stage of an inverted optical microscope. It was possible to move the scraper using selectable modes of operation, either a manual mode with a haptic device or a computer-controlled mode. The viability of the scraped single cells was evaluated using a fluorescence dye of calcein-acetoxymethl ester. Single cells detached from the substrate were collected by aspiration into a micropipette capillary glass using an electro-osmotic pump. As a demonstration, single HeLa cells were selectively detached from the substrate and collected by the micropipette. It was possible to recultivate HeLa cells from the single cells collected using the system.

  1. Rational Design of Single Molybdenum Atoms Anchored on N-Doped Carbon for Effective Hydrogen Evolution Reaction.

    Science.gov (United States)

    Chen, Wenxing; Pei, Jiajing; He, Chun-Ting; Wan, Jiawei; Ren, Hanlin; Zhu, Youqi; Wang, Yu; Dong, Juncai; Tian, Shubo; Cheong, Weng-Chon; Lu, Siqi; Zheng, Lirong; Zheng, Xusheng; Yan, Wensheng; Zhuang, Zhongbin; Chen, Chen; Peng, Qing; Wang, Dingsheng; Li, Yadong

    2017-12-11

    The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms (Mo-SAs) supported on N-doped carbon having outstanding HER performance. The structure of the catalyst was probed by aberration-corrected scanning transmission electron microscopy (AC-STEM) and X-ray absorption fine structure (XAFS) spectroscopy, indicating the formation of Mo-SAs anchored with one nitrogen atom and two carbon atoms (Mo 1 N 1 C 2 ). Importantly, the Mo 1 N 1 C 2 catalyst displayed much more excellent activity compared with Mo 2 C and MoN, and better stability than commercial Pt/C. Density functional theory (DFT) calculation revealed that the unique structure of Mo 1 N 1 C 2 moiety played a crucial effect to improve the HER performance. This work opens up new opportunities for the preparation and application of highly active and stable Mo-based HER catalysts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Temperature and magnetic field dependence of the Yosida-Kondo resonance for a single magnetic atom adsorbed on a surface

    International Nuclear Information System (INIS)

    Dino, Wilson Agerico; Kasai, Hideaki; Rodulfo, Emmanuel Tapas; Nishi, Mayuko

    2006-01-01

    Manifestations of the Kondo effect on an atomic length scale on and around a magnetic atom adsorbed on a nonmagnetic surface differ depending on the spectroscopic mode of operation of the scanning tunneling microscope. Two prominent signatures of the Kondo effect that can be observed at surfaces are the development of a sharp resonance (Yosida-Kondo resonance) at the Fermi level, which broadens with increasing temperature, and the splitting of this sharp resonance upon application of an external magnetic field. Until recently, observing the temperature and magnetic field dependence has been a challenge, because the experimental conditions strongly depend on the system's critical temperature, the so-called Kondo temperature T K . In order to clearly observe the temperature dependence, one needs to choose a system with a large T K . One can thus perform the experiments at temperatures T K . However, because the applied external magnetic field necessary to observe the magnetic field dependence scales with T K , one needs to choose a system with a very small T K . This in turn means that one should perform the experiments at very low temperatures, e.g., in the mK range. Here we discuss the temperature and magnetic field dependence of the Yosida-Kondo resonance for a single magnetic atom on a metal surface, in relation to recent experimental developments

  3. Alternative types of molecule-decorated atomic chains in Au–CO–Au single-molecule junctions

    Directory of Open Access Journals (Sweden)

    Zoltán Balogh

    2015-06-01

    Full Text Available We investigate the formation and evolution of Au–CO single-molecule break junctions. The conductance histogram exhibits two distinct molecular configurations, which are further investigated by a combined statistical analysis. According to conditional histogram and correlation analysis these molecular configurations show strong anticorrelations with each other and with pure Au monoatomic junctions and atomic chains. We identify molecular precursor configurations with somewhat higher conductance, which are formed prior to single-molecule junctions. According to detailed length analysis two distinct types of molecule-affected chain-formation processes are observed, and we compare these results to former theoretical calculations considering bridge- and atop-type molecular configurations where the latter has reduced conductance due to destructive Fano interference.

  4. Reverse engineering of an affinity-switchable molecular interaction characterized by atomic force microscopy single-molecule force spectroscopy.

    Science.gov (United States)

    Anselmetti, Dario; Bartels, Frank Wilco; Becker, Anke; Decker, Björn; Eckel, Rainer; McIntosh, Matthew; Mattay, Jochen; Plattner, Patrik; Ros, Robert; Schäfer, Christian; Sewald, Norbert

    2008-02-19

    Tunable and switchable interaction between molecules is a key for regulation and control of cellular processes. The translation of the underlying physicochemical principles to synthetic and switchable functional entities and molecules that can mimic the corresponding molecular functions is called reverse molecular engineering. We quantitatively investigated autoinducer-regulated DNA-protein interaction in bacterial gene regulation processes with single atomic force microscopy (AFM) molecule force spectroscopy in vitro, and developed an artificial bistable molecular host-guest system that can be controlled and regulated by external signals (UV light exposure and thermal energy). The intermolecular binding functionality (affinity) and its reproducible and reversible switching has been proven by AFM force spectroscopy at the single-molecule level. This affinity-tunable optomechanical switch will allow novel applications with respect to molecular manipulation, nanoscale rewritable molecular memories, and/or artificial ion channels, which will serve for the controlled transport and release of ions and neutral compounds in the future.

  5. Dielectrophoretic positioning of single nanoparticles on atomic force microscope tips for tip-enhanced Raman spectroscopy.

    Science.gov (United States)

    Leiterer, Christian; Deckert-Gaudig, Tanja; Singh, Prabha; Wirth, Janina; Deckert, Volker; Fritzsche, Wolfgang

    2015-05-01

    Tip-enhanced Raman spectroscopy, a combination of Raman spectroscopy and scanning probe microscopy, is a powerful technique to detect the vibrational fingerprint of molecules at the nanometer scale. A metal nanoparticle at the apex of an atomic force microscope tip leads to a large enhancement of the electromagnetic field when illuminated with an appropriate wavelength, resulting in an increased Raman signal. A controlled positioning of individual nanoparticles at the tip would improve the reproducibility of the probes and is quite demanding due to usually serial and labor-intensive approaches. In contrast to commonly used submicron manipulation techniques, dielectrophoresis allows a parallel and scalable production, and provides a novel approach toward reproducible and at the same time affordable tip-enhanced Raman spectroscopy tips. We demonstrate the successful positioning of an individual plasmonic nanoparticle on a commercial atomic force microscope tip by dielectrophoresis followed by experimental proof of the Raman signal enhancing capabilities of such tips. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Combined thallium-201 and dynamic iodine-123 iodophenylpentadecanoic acid single-photon emission computed tomography in patients after acute myocardial infarction with effective reperfusion.

    Science.gov (United States)

    Richter, W S; Beckmann, S; Cordes, M; Schuppenhauer, T; Schartl, M; Munz, D L

    2000-12-01

    Considerable derangements of energy metabolism are to be expected during ischemia and reperfusion. In ischemic myocardium, the oxidative degradation of carbohydrates is shifted toward the anaerobic production of lactate and the oxidation of fatty acids is suppressed. The aim of this study was to examine the uptake and metabolism of iodine-123 (123I) iodophenylpentadecanoic acid (IPPA) in stunned myocardium. In 15 patients, SPECT with 201Tl and 123I IPPA as well as echocardiography with low-dose dobutamine stimulation were performed 12 +/- 5 days after myocardial infarction with reperfusion. Follow-up echocardiography was carried out 24 +/- 8 days later for documentation of functional improvement. Uptake of 201Tl and 123I IPPA were obtained in five left ventricular segments, and dynamic SPECT imaging was used for calculation of the fast and the slow components of the biexponential myocardial 123I IPPA clearance. Wall motion improved in 14 of 26 dysfunctional segments (54%). Stunned segments were characterized by a reduced 123I IPPA extraction, a shorter half-life of the fast, and a longer half-life of the slow clearance component. All parameters of the combined 201Tl/123I IPPA study predicted functional recovery with similar accuracies (area under the receiver operator characteristic curves between 0.68 and 0.76; p = NS). Analysis of 201Tl uptake alone could not predict functional recovery in this study. Stunned myocardium is characterized by a disturbance of fatty acid metabolism. For prediction of functional improvement, 123I IPPA imaging added significant diagnostic information.

  7. Triple differential cross section for the near threshold single ionization of helium atoms for equal energy sharing

    Energy Technology Data Exchange (ETDEWEB)

    Purohit, G., E-mail: ghanshyam.purohit@spsu.ac.in [Department of Physics, School of Engineering, Sir Padampat Singhania University, Bhatewar, Udaipur 313 601 (India); Singh, P. [Department of Physics, School of Engineering, Sir Padampat Singhania University, Bhatewar, Udaipur 313 601 (India); Dorn, A.; Ren, X. [Max Planck Institute for Nuclear Physics, 69117 Heidelberg (Germany); Patidar, V. [Department of Physics, School of Engineering, Sir Padampat Singhania University, Bhatewar, Udaipur 313 601 (India)

    2016-05-15

    Highlights: • Present paper describes electron impact single ionization of helium atoms near threshold. • This energy range provided challenges to theoretical models due to presence of several physical effects at low energies such as second order processes, PCI, polarization, etc. • Inclusion of second Born term and target polarization is helpful to analyze the measurements. • Present paper also describes usefulness of post collisional interaction in the collision dynamics at low energies. - Abstract: Low energy electron impact single ionization triple differential cross section (TDCS) results are reported for the helium atoms in the threshold regime at 1 eV, 3 eV and 5 eV excess energy. TDCSs are calculated in the doubly symmetric kinematics for the coplanar to perpendicular emission of electrons. Present attempt to calculate TDCS in the second Born approximation and treating target polarization and post collision interaction is helpful to analyze the available measurements. The second order processes, target polarization and post collision interaction (PCI) have been found to be significant in describing the trends of TDCS and helpful to produce reasonably good agreement with measurements.

  8. Triple differential cross section for the near threshold single ionization of helium atoms for equal energy sharing

    International Nuclear Information System (INIS)

    Purohit, G.; Singh, P.; Dorn, A.; Ren, X.; Patidar, V.

    2016-01-01

    Highlights: • Present paper describes electron impact single ionization of helium atoms near threshold. • This energy range provided challenges to theoretical models due to presence of several physical effects at low energies such as second order processes, PCI, polarization, etc. • Inclusion of second Born term and target polarization is helpful to analyze the measurements. • Present paper also describes usefulness of post collisional interaction in the collision dynamics at low energies. - Abstract: Low energy electron impact single ionization triple differential cross section (TDCS) results are reported for the helium atoms in the threshold regime at 1 eV, 3 eV and 5 eV excess energy. TDCSs are calculated in the doubly symmetric kinematics for the coplanar to perpendicular emission of electrons. Present attempt to calculate TDCS in the second Born approximation and treating target polarization and post collision interaction is helpful to analyze the available measurements. The second order processes, target polarization and post collision interaction (PCI) have been found to be significant in describing the trends of TDCS and helpful to produce reasonably good agreement with measurements.

  9. Sub-Poissonian statistics of quantum jumps in single molecule or atomic ion

    International Nuclear Information System (INIS)

    Osad'ko, I.S.; Gus'kov, D.N.

    2007-01-01

    A theory for statistics of quantum jumps in single molecule or ion driven by continues wave laser field is developed. These quantum jumps can relate to nonradiative singlet-triplet transitions in a molecule or to on → off jumps in a single ion with shelving processes. Distribution function w N (T) of quantum jumps in time interval T is found. Computer simulation of quantum jumps is realized. Statistical treatment of simulated jumps reveals sub-Poissonian statistics of quantum jumps. The theoretical distribution function w N (T) fits well the distribution of jumps found from simulated data. Experimental data on quantum jumps found in experiments with single Hg + ion are described by the function w N (T) well

  10. Single Molecule Atomic Force Microscopy Studies of Photosensitized Singlet Oxygen Behavior on a DNA Origami Template

    DEFF Research Database (Denmark)

    Helmig, Sarah Wendelboe; Rotaru, Alexandru; Arian, Dumitru

    2010-01-01

    DNA origami, the folding of a long single-stranded DNA sequence (scaffold strand) by hundreds of short synthetic oligonucleotides (staple strands) into parallel aligned helices, is a highly efficient method to form advanced self-assembled DNA-architectures. Since molecules and various materials can...... be conjugated to each of the short staple strands, the origami method offers a unique possibility of arranging molecules and materials in well-defined positions on a structured surface. Here we combine the action of light with AFM and DNA nanostructures to study the production of singlet oxygen from a single...... photosensitizer molecule conjugated to a selected DNA origami staple strand on an origami structure. We demonstrate a distance-dependent oxidation of organic moieties incorporated in specific positions on DNA origami by singlet oxygen produced from a single photosensitizer located at the center of each origami....

  11. IBIC characterisation of novel detectors for single atom doping of quantum computer devices

    International Nuclear Information System (INIS)

    Yang Changyi; Jamieson, David N.; Pakes, Chris I.; George, Damien P.; Hearne, Sean M.; Dzurak, Andrew S.; Gauja, Eric; Stanley, F.; Clark, R.G.

    2003-01-01

    Single ion implantation and online detection is highly desirable for the emerging application, in which single 31 P ions need to be inserted in prefabricated silicon cells to construct solid-state quantum bits (qubits). In order to fabricate qubit arrays, we have developed novel detectors that employ detector electrodes adjacent to the prefabricated cells that can detect single keV ion strikes appropriate for the fabrication of shallow phosphorus arrays. The method utilises a high purity silicon substrate with very high resistivity, a thin SiO 2 surface layer, nanometer masks for the lateral positioning single phosphorus implantation, biased electrodes applied to the surface of the silicon and sensitive electronics that can detect the charge transient from single keV ion strikes. A TCAD (Technology Computer Aided Design) software package was applied in the optimisation of the device design and simulation of the detector performance. Here we show the characterisation of these detectors using ion beam induced charge (IBIC) with a focused 2 MeV He ions in a nuclear microprobe. The IBIC imaging method in a nuclear microprobe allowed us to measure the dead-layer thickness of the detector structure (required to be very thin for successful detection of keV ions), and the spatial distribution of the charge collection efficiency around the entire region of the detector. We show that our detectors have near 100% charge collection efficiency for MeV ions, extremely thin dead-layer thickness (about 7 nm) and a wide active region extending laterally from the electrodes (10-20 μm) where qubit arrays can be constructed. We demonstrate that the device can be successfully applied in the detection of keV ionisation energy from single events of keV X-rays and keV 31 P ions

  12. IBIC characterisation of novel detectors for single atom doping of quantum computer devices

    Energy Technology Data Exchange (ETDEWEB)

    Yang Changyi E-mail: cjy@physics.unimelb.edu.auc.yang@physics.unimelb.edu.au; Jamieson, David N.; Pakes, Chris I.; George, Damien P.; Hearne, Sean M.; Dzurak, Andrew S.; Gauja, Eric; Stanley, F.; Clark, R.G

    2003-09-01

    Single ion implantation and online detection is highly desirable for the emerging application, in which single {sup 31}P ions need to be inserted in prefabricated silicon cells to construct solid-state quantum bits (qubits). In order to fabricate qubit arrays, we have developed novel detectors that employ detector electrodes adjacent to the prefabricated cells that can detect single keV ion strikes appropriate for the fabrication of shallow phosphorus arrays. The method utilises a high purity silicon substrate with very high resistivity, a thin SiO{sub 2} surface layer, nanometer masks for the lateral positioning single phosphorus implantation, biased electrodes applied to the surface of the silicon and sensitive electronics that can detect the charge transient from single keV ion strikes. A TCAD (Technology Computer Aided Design) software package was applied in the optimisation of the device design and simulation of the detector performance. Here we show the characterisation of these detectors using ion beam induced charge (IBIC) with a focused 2 MeV He ions in a nuclear microprobe. The IBIC imaging method in a nuclear microprobe allowed us to measure the dead-layer thickness of the detector structure (required to be very thin for successful detection of keV ions), and the spatial distribution of the charge collection efficiency around the entire region of the detector. We show that our detectors have near 100% charge collection efficiency for MeV ions, extremely thin dead-layer thickness (about 7 nm) and a wide active region extending laterally from the electrodes (10-20 {mu}m) where qubit arrays can be constructed. We demonstrate that the device can be successfully applied in the detection of keV ionisation energy from single events of keV X-rays and keV {sup 31}P ions.

  13. Influence of gamma radiation and impurity atoms on the photoconductivity of GeS single crystals

    International Nuclear Information System (INIS)

    Madatov, R.S.; Alekperov, A.S.

    2013-01-01

    Wide opportunities for using of layered semiconductors, particularly in optoelectronics have generated considerable interest to them. Recently it was created the unique device from GeS for the storage of solar energy. The investigated GeS 1 -xNd x S single crystals were grown by the Bridgman method. The samples were irradiated by gamma-quanta and was conducted to install 60Co at room temperature. Irradiation of p-GeS 1 -xNd x S single crystals by small doses of gamma rays increases the photoconductivity on 40%

  14. Measurement of Iodine-129 concentration in environmental water samples around Fukushima area - Role of river system in the global iodine cycle

    Science.gov (United States)

    Matsuzaki, Hiroyuki; Tokuyama, Hironori; Miyake, Yasuto; Honda, Maki; Yamagata, Takeyasu; Muramatsu, Yasuyuki

    2013-04-01

    According to Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, vast amount of radioactive nuclides including radioactive iodine were spilled out into the environment. There is no question about that detailed observation of distribution of radioactive nuclides and evaluation of the radiation exposure of residents is extremely important. On the other hand, from the view of an elemental dynamics in the environment, this event can be considered as a spike of the radioactive isotope. It is also the case for the iodine. A rare isotope Iodine-129 was widely distributed in a very short time by the FDNPP accident. Iodine-129 directly landing on the soil surface had been trapped in the upper layer of the soil and the depth profile should indicate the migration in and the interaction with the soil. If Iodine-129 was trapped in the woods, it seems to take rather longer time to landing on the ground. Either way, a certain portion of the Iodine-129 should be moving downward and finally washed out by the groundwater or river with a certain rate and transported into the sea. The concentration of Iodine-129 in environmental water samples taken from rivers and ponds are considered to reflect the iodine transportation process by the fluvial system. For the detailed discussion of the role of the fluvial system in the global iodine cycle, Iodine-129 concentration of various water samples collected from Fukushima area was measured by means of Accelerator Mass Spectrometry. The results ranged from 3E06 atoms/L to 3E09 atoms/L. Samples from Abukuma area (South West of FDNPP) showed lower concentration. On the other hand, samples collected from North West part (Iitate village and Minami Soma region) showed higher concentration (more than 1E8 atoms/L). Delayed enhancement of Iodine-129 concentration over a year in river systems surrounded by woods was also observed which is considered to correspond to the delayed release from the woods.

  15. Atomically Thin Heterostructures Based on Single-Layer Tungsten Diselenide and Graphene

    KAUST Repository

    Lin, Yu-Chuan; Chang, Chih-Yuan S.; Ghosh, Ram Krishna; Li, Jie; Zhu, Hui; Addou, Rafik; Diaconescu, Bogdan; Ohta, Taisuke; Peng, Xin; Lu, Ning; Kim, Moon J.; Robinson, Jeremy T.; Wallace, Robert M; Mayer, Theresa S.; Datta, Suman; Li, Lain-Jong; Robinson, Joshua A.

    2014-01-01

    Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. In order to engineer pristine layers and their interfaces, epitaxial growth of such heterostructures is required. We report the direct growth of crystalline, monolayer tungsten diselenide (WSe2) on epitaxial graphene (EG) grown from silicon carbide. Raman spectroscopy, photoluminescence, and scanning tunneling microscopy confirm high-quality WSe2 monolayers, whereas transmission electron microscopy shows an atomically sharp interface, and low energy electron diffraction confirms near perfect orientation between WSe2 and EG. Vertical transport measurements across the WSe2/EG heterostructure provides evidence that an additional barrier to carrier transport beyond the expected WSe2/EG band offset exists due to the interlayer gap, which is supported by theoretical local density of states (LDOS) calculations using self-consistent density functional theory (DFT) and nonequilibrium Green's function (NEGF).

  16. Atomically Thin Heterostructures Based on Single-Layer Tungsten Diselenide and Graphene

    KAUST Repository

    Lin, Yu-Chuan

    2014-11-10

    Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. In order to engineer pristine layers and their interfaces, epitaxial growth of such heterostructures is required. We report the direct growth of crystalline, monolayer tungsten diselenide (WSe2) on epitaxial graphene (EG) grown from silicon carbide. Raman spectroscopy, photoluminescence, and scanning tunneling microscopy confirm high-quality WSe2 monolayers, whereas transmission electron microscopy shows an atomically sharp interface, and low energy electron diffraction confirms near perfect orientation between WSe2 and EG. Vertical transport measurements across the WSe2/EG heterostructure provides evidence that an additional barrier to carrier transport beyond the expected WSe2/EG band offset exists due to the interlayer gap, which is supported by theoretical local density of states (LDOS) calculations using self-consistent density functional theory (DFT) and nonequilibrium Green\\'s function (NEGF).

  17. Convergence of configuration-interaction single-center calculations of positron-atom interactions

    International Nuclear Information System (INIS)

    Mitroy, J.; Bromley, M. W. J.

    2006-01-01

    The configuration interaction (CI) method using orbitals centered on the nucleus has recently been applied to calculate the interactions of positrons interacting with atoms. Computational investigations of the convergence properties of binding energy, phase shift, and annihilation rate with respect to the maximum angular momentum of the orbital basis for the e + Cu and PsH bound states, and the e + -H scattering system were completed. The annihilation rates converge very slowly with angular momentum, and moreover the convergence with radial basis dimension appears to be slower for high angular momentum. A number of methods of completing the partial wave sum are compared; an approach based on a ΔX J =a(J+(1/2)) -n +b(J+(1/2)) -(n+1) form [with n=4 for phase shift (or energy) and n=2 for the annihilation rate] seems to be preferred on considerations of utility and underlying physical justification

  18. Single Atomic Iron Catalysts for Oxygen Reduction in Acidic Media: Particle Size Control and Thermal Activation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hanguang [Department; Hwang, Sooyeon [Center; Wang, Maoyu [School; Feng, Zhenxing [School; Karakalos, Stavros [Department; Luo, Langli [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Qiao, Zhi [Department; Xie, Xiaohong [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Wang, Chongmin [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Su, Dong [Center; Shao, Yuyan [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Wu, Gang [Department

    2017-09-26

    To significantly reduce the cost of proton exchange membrane (PEM) fuel cells, current Pt must be replaced by platinum-metal-group (PGM)-free catalysts for the oxygen reduction reaction (ORR) in acid. We report here a new class of high-performance atomic iron dispersed carbon catalysts through controlled chemical doping of iron ions into zinc-zeolitic imidazolate framework (ZIF), a type of metal-organic framework (MOF). The novel synthetic chemistry enables accurate size control of Fe-doped ZIF catalyst particles with a wide range from 20 to 1000 nm without changing chemical properties, which provides a great opportunity to increase the density of active sites that is determined by the particle size. We elucidated the active site formation mechanism by correlating the chemical and structural changes with thermal activation process for the conversion from Fe-N4 complex containing hydrocarbon networks in ZIF to highly active FeNx sites embedded into carbon. A temperature of 800oC was identified as the critical point to start forming pyridinic nitrogen doping at the edge of the graphitized carbon planes. Further increasing heating temperature to 1100oC leads to increase of graphitic nitrogen, generating possible synergistic effect with FeNx sites to promote ORR activity. The best performing catalyst, which has well-defined particle size around 50 nm and abundance of atomic FeNx sites embedded into carbon structures, achieve a new performance milestone for the ORR in acid including a half-wave potential of 0.85 V vs RHE and only 20 mV loss after 10,000 cycles in O2 saturated H2SO4 electrolyte. The new class PGM-free catalyst with approaching activity to Pt holds great promise for future PEM fuel cells.

  19. Volatilization of iodine from vegetation

    International Nuclear Information System (INIS)

    Amiro, B.D.; Johnston, F.L.

    1989-01-01

    Gaseous emissions of iodine were measured from bean plant foliage. A gamma-emitting iodine tracer, Na 125 I, was taken up by the plants from a hydroponic growth medium and released to a cuvette atmosphere. The dynamics of the flux were studied using a flow-through gamma detector. The relationship between leaf radioactive tracer activity and growth-medium activity was linear, as was the relationship between the iodine flux and both leaf and growth-medium activity. Iodine flux and leaf conductance to water responded similarly to changes in light levels, suggesting that the stomata may partially control the flux. The flux was inhibited by aeration of the hydroponic growth media, and we postulate that methylation causes the iodine flux. Iodine emissions from living vegetation probably contribute < 0.1% to the stable iodine concentration in the atmosphere above terrestrial areas. However, this pathway may be a direct route for radioactive iodine transport from contaminated soils to the atmosphere. (author)

  20. Radioactive iodine intake through foodstuff

    International Nuclear Information System (INIS)

    Omomo, Yoichiro

    1974-01-01

    The transition of radioactive iodine to human bodies is affected by the amount of coexisting stable iodine. The intake of stable iodine through foodstuffs was studied from the stand point of I) discussion of the literature which states the approximate amounts of stable iodine contained in environmental materials, and II) the authors' research on the consumption of foodstuffs. For example, the amounts of iodine intake of fishermen living in Kuji-cho (Ibaragi Prefecture) was estimated from I and II, and was revealed as 2704p. The national average iodine intake was about 800p indicating that the former estimated value was remarkably high. Eighty Four per cent of the 2.7 mg iodine intake was taken from marine products, indicating that marine products are important sources of iodine supply. (Tsukamoto, Y.)

  1. Atomic force microscopy imaging and 3-D reconstructions of serial thin sections of a single cell and its interior structures

    International Nuclear Information System (INIS)

    Chen Yong; Cai Jiye; Zhao Tao; Wang Chenxi; Dong Shuo; Luo Shuqian; Chen, Zheng W.

    2005-01-01

    The thin sectioning has been widely applied in electron microscopy (EM), and successfully used for an in situ observation of inner ultrastructure of cells. This powerful technique has recently been extended to the research field of atomic force microscopy (AFM). However, there have been no reports describing AFM imaging of serial thin sections and three-dimensional (3-D) reconstruction of cells and their inner structures. In the present study, we used AFM to scan serial thin sections approximately 60 nm thick of a mouse embryonic stem (ES) cell, and to observe the in situ inner ultrastructure including cell membrane, cytoplasm, mitochondria, nucleus membrane, and linear chromatin. The high-magnification AFM imaging of single mitochondria clearly demonstrated the outer membrane, inner boundary membrane and cristal membrane of mitochondria in the cellular compartment. Importantly, AFM imaging on six serial thin sections of a single mouse ES cell showed that mitochondria underwent sequential changes in the number, morphology and distribution. These nanoscale images allowed us to perform 3-D surface reconstruction of interested interior structures in cells. Based on the serial in situ images, 3-D models of morphological characteristics, numbers and distributions of interior structures of the single ES cells were validated and reconstructed. Our results suggest that the combined AFM and serial-thin-section technique is useful for the nanoscale imaging and 3-D reconstruction of single cells and their inner structures. This technique may facilitate studies of proliferating and differentiating stages of stem cells or somatic cells at a nanoscale

  2. Many-body effect in the partial singles N2,3 photoelectron spectroscopy spectrum of atomic Cd

    International Nuclear Information System (INIS)

    Ohno, Masahide

    2008-01-01

    We can extract out the photoelectron kinetic energy (KE) dependent imaginary part of the core-hole self-energy by employing Auger-photoelectron coincidence spectroscopy (APECS). The variation with photoelectron KE in the Auger electron spectroscopy (AES) spectral peak intensity of a selected decay channel measured in coincidence with photoelectrons of a selected KE is the partial singles (non-coincidence) photoelectron spectroscopy (PES) spectrum, i.e., the product of the singles PES one and the branching ratio of the partial Auger decay width of a selected decay channel to the imaginary part of the core-hole self-energy. When a decay channel the partial Auger decay width of which is photoelectron KE independent is selected, we can extract out spectroscopically the imaginary part of the core-hole self-energy because the variation with photoelectron KE in the relative spectral intensity of the partial singles PES spectrum to the singles one is that in the branching ratio of the partial Auger decay width of a selected decay channel. As an example we discussed the N 2,3 -hole self-energy of atomic Cd

  3. Radioactive iodine releases from nuclear power plant, (2)

    International Nuclear Information System (INIS)

    Naritomi, Mitsuo

    1974-01-01

    Internal radiation dose through the respiratory intake of fission products is predominantly due to radioactive iodine not only at the time of reactor accidents but also in normal operation of nuclear facilities. Technological studies in this field have thus been quite active to this day. With the rapid advance of nuclear power generation in recent years, the efforts to reduce environmental release of radioactive iodine and to enhance environmental safety are all the more emphasized. Experiences in the Japan Atomic Energy Research Institute during past about six years are described concerning the radioactive iodine release to the atmosphere in 131 I production and the measures taken to reduce the release. Then, problems are expounded regarding the radioactive iodine release at the time of reactor accidents and in spent fuel reprocessing. (Mori, K.)

  4. Lateral manipulation of small clusters on the Cu and Ag(1 1 1) surfaces with the single-atom and trimer-apex tips: Reliability study

    International Nuclear Information System (INIS)

    Xie Yiqun; Liu Fen; Huang Lei

    2010-01-01

    We study the reliability of the lateral manipulation of small Cu clusters (dimer and trimer) on the flat Cu(1 1 1) surface with both the single-atom and trimer-apex tips and that for the Ag/Ag(1 1 1) system, and compare the results between the two systems as well as with the single-atom manipulation on these surfaces. Manipulations are simulated using molecular statics method with semi-empirical potentials. The dependence of the manipulation reliability on the tip height and tip orientation are investigated. Overall, the manipulation reliability increases with decreasing tip height although it depends obviously on the tip orientation. For the Cu/Cu(1 1 1) system, the manipulation of the dimmer and trimer can be successful with both tips. The manipulation reliability can be improved by the trimer-apex tip, and the tip-height range for the successful manipulation is also broader, as compared to the single-atom apex tip. Differently from the single-atom manipulation, the tip orientation has a noticeable influence on the manipulation reliability even for the single-atom tip due to the stronger tip-cluster and surface-adatom interactions in cluster manipulation. For the Ag/Ag(1 1 1) system, successful manipulations only be achieved with the trimer-apex tip, and the manipulation reliability is worse than that of the Cu/Cu(1 1 1) system, indicating the difference in mechanic properties between the two surfaces at the atomic level.

  5. Fabrication Of Atomic-scale Gold Junctions By Electrochemical Plating Technique Using A Common Medical Disinfectant

    Science.gov (United States)

    Umeno, Akinori; Hirakawa, Kazuhiko

    2005-06-01

    Iodine tincture, a medical liquid familiar as a disinfectant, was introduced as an etching/deposition electrolyte for the fabrication of nanometer-separated gold electrodes. In the gold dissolved iodine tincture, the gold electrodes were grown or eroded slowly in atomic scale, enough to form quantum point contacts. The resistance evolution during the electrochemical deposition showed plateaus at integer multiples of the resistance quantum, (2e2/h)-1, at the room temperature. The iodine tincture is a commercially available common material, which makes the fabrication process to be the simple and cost effective. Moreover, in contrast to the conventional electrochemical approaches, this method is free from highly toxic cyanide compounds or extraordinary strong acid. We expect this method to be a useful interface between single-molecular-scale structures and macroscopic opto-electronic devices.

  6. Mock iodine-125 radiation source

    International Nuclear Information System (INIS)

    Coffey, D.L.

    1976-01-01

    An intimate mixture of americium-241 and iodine-129 provides an energy spectrum that reliably simulates the spectrum of iodine-125 in a well-type detector. As such, it may be used as a long-lived standard to calibrate instruments such as well scintillation spectrometers in which measurements are to be made involving iodine-125

  7. Magnetization distribution of single-particle states and 2/sup +/ rotational states from muonic atoms

    CERN Document Server

    Backe, H; Engfer, R; Kankeleit, E; Link, R; Michaelsen, R; Petitjean, C; Schellenberg, L; Schneuwly, H; Schröder, W U; Vuilleumier, J L; Walter, H K; Zehnder, A

    1973-01-01

    The lowest states in muonic atoms are rather sensitive to the spatial distribution of the nuclear magnetization density, and several results were deduced from the broadening of the muonic 2p/sub 1/2/-1s/sub 1/2/ and 3d/sub 3/2/-2p/sub 1/2/ transitions. By measuring low energetic transitions such as the 2s/sub 1/2/-2p/sub 1/2/ transition or nuclear gamma -transitions, it is possible to resolve the magnetic hyperfine splittings. The magnetic hf splitting of the 2s/sub 1/2/-2p/sub 1/2/ transition in mu /sup 115/In and of the 3/2/sup +/-1/2/sup +/ nuclear gamma -transitions in mu /sup 203/Tl at 279 keV, and in mu /sup 205/Tl at 204 keV, have been resolved. For the 2/sup +/-0/sup +/ nuclear gamma -transition in mu /sup 190,192/Os at 187 keV and 206 keV, respectively, the magnetic hf splitting of the 2/sup +/ rotational levels and the intensities of the hf components were determined from a nearly resolved doublet splitting. (7 refs).

  8. Conditions to minimize soft single biomolecule deformation when imaging with atomic force microscopy.

    Science.gov (United States)

    Godon, Christian; Teulon, Jean-Marie; Odorico, Michael; Basset, Christian; Meillan, Matthieu; Vellutini, Luc; Chen, Shu-Wen W; Pellequer, Jean-Luc

    2017-03-01

    A recurrent interrogation when imaging soft biomolecules using atomic force microscopy (AFM) is the putative deformation of molecules leading to a bias in recording true topographical surfaces. Deformation of biomolecules comes from three sources: sample instability, adsorption to the imaging substrate, and crushing under tip pressure. To disentangle these causes, we measured the maximum height of a well-known biomolecule, the tobacco mosaic virus (TMV), under eight different experimental conditions positing that the maximum height value is a specific indicator of sample deformations. Six basic AFM experimental factors were tested: imaging in air (AIR) versus in liquid (LIQ), imaging with flat minerals (MICA) versus flat organic surfaces (self-assembled monolayers, SAM), and imaging forces with oscillating tapping mode (TAP) versus PeakForce tapping (PFT). The results show that the most critical parameter in accurately measuring the height of TMV in air is the substrate. In a liquid environment, regardless of the substrate, the most critical parameter is the imaging mode. Most importantly, the expected TMV height values were obtained with both imaging with the PeakForce tapping mode either in liquid or in air at the condition of using self-assembled monolayers as substrate. This study unambiguously explains previous poor results of imaging biomolecules on mica in air and suggests alternative methodologies for depositing soft biomolecules on well organized self-assembled monolayers. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Identification of Organic Iodine Compounds and Their Transformation Products in Edible Iodized Salt Using Liquid Chromatography-High Resolution Mass Spectrometry.

    Science.gov (United States)

    Yun, Lifen; Peng, Yue'e; Chang, Qing; Zhu, Qingxin; Guo, Wei; Wang, Yanxin

    2017-07-05

    The consumption of edible iodized salt is a key strategy to control and eliminate iodine deficiency disorders worldwide. We herein report the identification of the organic iodine compounds present in different edible iodized salt products using liquid chromatography combined with high resolution mass spectrometry. A total of 38 organic iodine compounds and their transformation products (TPs) were identified in seaweed iodine salt from China. Our experiments confirmed that the TPs were generated by the replacement of I atoms from organic iodine compounds with Cl atoms. Furthermore, the organic iodine compound contents in 4 seaweed iodine salt samples obtained from different manufacturers were measured, with significant differences in content being observed. We expect that the identification of organic iodine compounds in salt will be important for estimating the validity and safety of edible iodized salt products.

  10. Single electron capture in ion-atom collisions involving multielectronic targets

    International Nuclear Information System (INIS)

    Abufager, P.N.; Martinez, A.E.; Rivarola, R.D.; Fainstein, P.D.

    2005-01-01

    The generalized continuum distorted wave-eikonal initial state (GCDW-EIS) approximation is employed to study single electron capture by impact of protons on Ne and Ar targets. We analyze the contributions to the total cross sections coming from the different target shells. Present results are compared with theoretical calculations obtained using the previous CDW-EIS formulation and to experimental data in order to show the importance of the description of the bound and continuum target states in the entry and exit channels, respectively

  11. Multiple H3+ fragment production in single collision of fast Hn+ clusters with He atoms

    International Nuclear Information System (INIS)

    Farizon, B.; Farizon, M.; Gaillard, M.J.; Gerlic, E.; Ouaskit, S.

    1994-09-01

    The production of H 3 + ions resulting from single collisions of mass-selected ionic hydrogen clusters, H n + (n=9,25,31), with helium at high velocity (1.55 times the Bohr velocity) has been studied. A strong double H 3 + ion production resulting from one incident cluster is observed. Moreover, evidence for a triple H 3 + fragment production is presented for n=25 and 31. Thus, in this energy range, the collision gives rise to multifragmentation processes. The formation of H 3 + ions takes place in the fragmentation of the multicharged cluster resulting from the collision. (authors)

  12. Measurements and Modelling of Reactive Iodine Oxides in the Coastal MBL

    Science.gov (United States)

    Najera, J. J.; Bloss, W. J.

    2012-04-01

    The release of iodine compounds into the marine atmosphere can affect a number of aspects of atmospheric composition: Iodine species can participate in catalytic ozone destruction cycles, which may be augmented by bromine species; reactions of iodine compounds can perturb the OH:HO2 and NO:NO2 ratios, heterogeneous loss of reservoir compounds such as HOI and INO3 can lead to removal of HOx and NOx, and higher iodine oxides can contribute to the formation and/or growth of aerosol particles. In this work, we focus upon understanding the effect of the spatial distribution of iodine emissions upon local HOx and NOx levels in the immediate vicinity of a coastal sites, using new observations to re-evaluate previous field campaign data. We present an analysis of results from a new instruments which measures point inorganic iodine species concentrations. The technique of resonance fluorescence (RF) is employed for the detection of iodine atoms, and the total photolabile iodine content. Measurements made at Mace Head, Ireland during July-August 2007 and May 2011 are presented. A detailed 1-dimensional photochemical box model is employed in a lagrangian sense to simulate the evolving chemical composition of an air column advected across the coastal margin. The model is compared with the observed iodine species, and then used to explore the transient response of the NOx and HOx families at the Mace Head site to heterogeneous iodine emissions: The transit time between the intertidal iodine emission zone and the shoreline site where previous measurements of HOx, NOx etc. have been made is insufficient for steady-state to become established, although this assumption has been used in earlier model studies of such data. Finally, we consider the limitations in our ability to quantify the impacts of iodine chemistry, which arise from uncertainties in the iodine kinetics and photochemistry - for example, what is the atmospheric lifetime of inorganic iodine ? - and explore their

  13. Discriminating Intercalative Effects of Threading Intercalator Nogalamycin, from Classical Intercalator Daunomycin, Using Single Molecule Atomic Force Spectroscopy.

    Directory of Open Access Journals (Sweden)

    T Banerjee

    Full Text Available DNA threading intercalators are a unique class of intercalating agents, albeit little biophysical information is available on their intercalative actions. Herein, the intercalative effects of nogalamycin, which is a naturally-occurring DNA threading intercalator, have been investigated by high-resolution atomic force microscopy (AFM and spectroscopy (AFS. The results have been compared with those of the well-known chemotherapeutic drug daunomycin, which is a non-threading classical intercalator bearing structural similarity to nogalamycin. A comparative AFM assessment revealed a greater increase in DNA contour length over the entire incubation period of 48 h for nogalamycin treatment, whereas the contour length increase manifested faster in case of daunomycin. The elastic response of single DNA molecules to an externally applied force was investigated by the single molecule AFS approach. Characteristic mechanical fingerprints in the overstretching behaviour clearly distinguished the nogalamycin/daunomycin-treated dsDNA from untreated dsDNA-the former appearing less elastic than the latter, and the nogalamycin-treated DNA distinguished from the daunomycin-treated DNA-the classically intercalated dsDNA appearing the least elastic. A single molecule AFS-based discrimination of threading intercalation from the classical type is being reported for the first time.

  14. Imaging and measuring the biophysical properties of Fc gamma receptors on single macrophages using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Mi [State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Liu, Lianqing, E-mail: lqliu@sia.cn [State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016 (China); Xi, Ning [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong (China); Wang, Yuechao [State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016 (China); Xiao, Xiubin [Department of Lymphoma, Affiliated Hospital of Military Medical Academy of Sciences, Beijing 100071 (China); Zhang, Weijing, E-mail: zhangwj3072@163.com [Department of Lymphoma, Affiliated Hospital of Military Medical Academy of Sciences, Beijing 100071 (China)

    2013-09-06

    Highlights: •Nanoscale cellular ultra-structures of macrophages were observed. •The binding affinities of FcγRs were measured directly on macrophages. •The nanoscale distributions of FcγRs were mapped on macrophages. -- Abstract: Fc gamma receptors (FcγR), widely expressed on effector cells (e.g., NK cells, macrophages), play an important role in clinical cancer immunotherapy. The binding of FcγRs to the Fc portions of antibodies that are attached to the target cells can activate the antibody-dependent cell-mediated cytotoxicity (ADCC) killing mechanism which leads to the lysis of target cells. In this work, we used atomic force microscopy (AFM) to observe the cellular ultra-structures and measure the biophysical properties (affinity and distribution) of FcγRs on single macrophages in aqueous environments. AFM imaging was used to obtain the topographies of macrophages, revealing the nanoscale cellular fine structures. For molecular interaction recognition, antibody molecules were attached onto AFM tips via a heterobifunctional polyethylene glycol (PEG) crosslinker. With AFM single-molecule force spectroscopy, the binding affinities of FcγRs were quantitatively measured on single macrophages. Adhesion force mapping method was used to localize the FcγRs, revealing the nanoscale distribution of FcγRs on local areas of macrophages. The experimental results can improve our understanding of FcγRs on macrophages; the established approach will facilitate further research on physiological activities involved in antibody-based immunotherapy.

  15. Discriminating Intercalative Effects of Threading Intercalator Nogalamycin, from Classical Intercalator Daunomycin, Using Single Molecule Atomic Force Spectroscopy.

    Science.gov (United States)

    Banerjee, T; Banerjee, S; Sett, S; Ghosh, S; Rakshit, T; Mukhopadhyay, R

    2016-01-01

    DNA threading intercalators are a unique class of intercalating agents, albeit little biophysical information is available on their intercalative actions. Herein, the intercalative effects of nogalamycin, which is a naturally-occurring DNA threading intercalator, have been investigated by high-resolution atomic force microscopy (AFM) and spectroscopy (AFS). The results have been compared with those of the well-known chemotherapeutic drug daunomycin, which is a non-threading classical intercalator bearing structural similarity to nogalamycin. A comparative AFM assessment revealed a greater increase in DNA contour length over the entire incubation period of 48 h for nogalamycin treatment, whereas the contour length increase manifested faster in case of daunomycin. The elastic response of single DNA molecules to an externally applied force was investigated by the single molecule AFS approach. Characteristic mechanical fingerprints in the overstretching behaviour clearly distinguished the nogalamycin/daunomycin-treated dsDNA from untreated dsDNA-the former appearing less elastic than the latter, and the nogalamycin-treated DNA distinguished from the daunomycin-treated DNA-the classically intercalated dsDNA appearing the least elastic. A single molecule AFS-based discrimination of threading intercalation from the classical type is being reported for the first time.

  16. Pt/Cu single-atom alloys as coke-resistant catalysts for efficient C-H activation

    Science.gov (United States)

    Marcinkowski, Matthew D.; Darby, Matthew T.; Liu, Jilei; Wimble, Joshua M.; Lucci, Felicia R.; Lee, Sungsik; Michaelides, Angelos; Flytzani-Stephanopoulos, Maria; Stamatakis, Michail; Sykes, E. Charles H.

    2018-03-01

    The recent availability of shale gas has led to a renewed interest in C-H bond activation as the first step towards the synthesis of fuels and fine chemicals. Heterogeneous catalysts based on Ni and Pt can perform this chemistry, but deactivate easily due to coke formation. Cu-based catalysts are not practical due to high C-H activation barriers, but their weaker binding to adsorbates offers resilience to coking. Using Pt/Cu single-atom alloys (SAAs), we examine C-H activation in a number of systems including methyl groups, methane and butane using a combination of simulations, surface science and catalysis studies. We find that Pt/Cu SAAs activate C-H bonds more efficiently than Cu, are stable for days under realistic operating conditions, and avoid the problem of coking typically encountered with Pt. Pt/Cu SAAs therefore offer a new approach to coke-resistant C-H activation chemistry, with the added economic benefit that the precious metal is diluted at the atomic limit.

  17. Pt/Cu single-atom alloys as coke-resistant catalysts for efficient C–H activation

    Energy Technology Data Exchange (ETDEWEB)

    Marcinkowski, Matthew D.; Darby, Matthew T.; Liu, Jilei; Wimble, Joshua M.; Lucci, Felicia R.; Lee, Sungsik; Michaelides, Angelos; Flytzani-Stephanopoulos, Maria; Stamatakis, Michail; Sykes, E. Charles H.

    2018-01-08

    The recent availability of shale gas has led to a renewed interest in C-H bond activation as the first step towards synthesis of fuels and fine chemicals. Heterogeneous catalysts based on Ni and Pt can perform this chemistry, but deactivate easily due to coke formation. Cu- based catalysts are not practical for this chemistry due to high C-H activation barriers, but their weaker binding to adsorbates offers resilience to coking. Utilizing Pt/Cu single atom alloys (SAAs) we examine C-H activation in a number of systems including methyl groups, methane, and butane using a combination of simulations, surface science, and catalysis studies. We find that Pt/Cu SAAs activate C-H bonds more efficiently than Cu, are stable for days under realistic operating conditions, and avoid the problem of coking typically encountered with Pt. Pt/Cu SAAs therefore offer a new approach to coke resistant C-H activation chemistry with the added economic benefit that the precious metal is diluted at the atomic limit.

  18. Atomic adsorption on graphene with a single vacancy: systematic DFT study through the periodic table of elements

    Science.gov (United States)

    Pašti, Igor A.; Jovanović, Aleksandar; Dobrota, Ana S.; Mentus, Slavko V.; Johansson, Börje; Skorodumova, Natalia V.

    Vacancies in graphene present sites of altered chemical reactivity and open possibilities to tune graphene properties by defect engineering. The understanding of chemical reactivity of such defects is essential for successful implementation of carbon materials in advanced technologies. We report the results of a systematic DFT study of atomic adsorption on graphene with a single vacancy for the elements of rows 1 to 6 of the Periodic Table of Elements (PTE), excluding lanthanides. The calculations have been performed using PBE, long-range dispersion interaction-corrected PBE (PBE+D2 and PBE+D3) and non-local vdW-DF2 functional. We find that most elements strongly bind to the vacancy, except for the elements of groups 11 and 12, and noble gases, for which the contribution of dispersion interaction to bonding is most significant. The strength of the interaction with the vacancy correlates with the cohesive energy of the elements in their stable phases: the higher the cohesive energy is the stronger bonding to the vacancy can be expected. As most atoms can be trapped at the SV site we have calculated the potentials of dissolution and found that in most cases the metals adsorbed at the vacancy are more "noble" than they are in their corresponding stable phases.

  19. Contribution of a solute atoms in the relaxation phenomenon at high temperature in Cu-Al single crystal alloys

    Science.gov (United States)

    Belamri, C.; Belhas, S.; Rivière, A.

    2009-11-01

    Two Cu-Al single crystals with 7 and 14 at. % Al respectively have been studied using isothermal mechanical spectroscopy (IMS) technique. After a 1% cold work by torsion, the samples have been progressively heated to 1140 K and then cooled until room temperature. IMS experiments allow to compare the isothermal internal friction spectra obtained during the heating (in this case, the annealing temperature is equal to the temperature of measurement) with the measurements performed at various temperature during the cooling after the annealing at 1140 K. Three relaxation peaks were observed. The first one at about 0.4 TM (TM: melting point) is a Zener relaxation peak (PZ) due to the reorientation under constraint of pairs of aluminium atoms. The high temperature annealing does not influence PZ. At about 0.6TM, a peak (P1) related to a dislocation mechanism is evidenced. The relaxation strength of P1 peak decreases with the temperature and a new relaxation peak (P2) is progressively developed. The IMS spectra obtained during the cooling evidenced only P2. The relaxation parameters obtained by the Arrhenius plots and the evolution with the annealing temperature allow to assign P1 and P2 to an interaction between the dislocations and the solute atoms according to the Darinskiy model.

  20. Iodine in soil

    International Nuclear Information System (INIS)

    Johanson, Karl Johan

    2000-12-01

    A literature study of the migration and the appearance of iodine isotopes in the bio-sphere particularly in soil is presented. Some important papers in the field of iodine appearance in soil and the appearance of 129 I in the surroundings of reprocessing plants are discussed. The most important conclusions are: 1. Iodine binds to organic matter in the soil and also to some oxides of aluminium and iron. 2. If the iodine is not bound to the soil a large fraction of added 129 I is volatilized after a rather short period. 3. The binding and also the volatilisation seems to be due to biological activity in the soil. It may take place within living microorganisms or by external enzymes excreted from microorganisms. 4. Due to variations in the composition of soil there may be a large variation in the distribution of 129 I in the vertical profile of soil - usually most of the 129 I in the upper layer - which also results in large variations in the 129 I uptake to plants

  1. Iodine in soil

    Energy Technology Data Exchange (ETDEWEB)

    Johanson, Karl Johan [Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept. of Forest Mycology and Pathology

    2000-12-01

    A literature study of the migration and the appearance of iodine isotopes in the bio-sphere particularly in soil is presented. Some important papers in the field of iodine appearance in soil and the appearance of {sup 129}I in the surroundings of reprocessing plants are discussed. The most important conclusions are: 1. Iodine binds to organic matter in the soil and also to some oxides of aluminium and iron. 2. If the iodine is not bound to the soil a large fraction of added {sup 129}I is volatilized after a rather short period. 3. The binding and also the volatilisation seems to be due to biological activity in the soil. It may take place within living microorganisms or by external enzymes excreted from microorganisms. 4. Due to variations in the composition of soil there may be a large variation in the distribution of {sup 129}I in the vertical profile of soil - usually most of the {sup 129}I in the upper layer - which also results in large variations in the {sup 129}I uptake to plants.

  2. Continuous-wave, single-frequency 229  nm laser source for laser cooling of cadmium atoms.

    Science.gov (United States)

    Kaneda, Yushi; Yarborough, J M; Merzlyak, Yevgeny; Yamaguchi, Atsushi; Hayashida, Keitaro; Ohmae, Noriaki; Katori, Hidetoshi

    2016-02-15

    Continuous-wave output at 229 nm for the application of laser cooling of Cd atoms was generated by the fourth harmonic using two successive second-harmonic generation stages. Employing a single-frequency optically pumped semiconductor laser as a fundamental source, 0.56 W of output at 229 nm was observed with a 10-mm long, Brewster-cut BBO crystal in an external cavity with 1.62 W of 458 nm input. Conversion efficiency from 458 nm to 229 nm was more than 34%. By applying a tapered amplifier (TA) as a fundamental source, we demonstrated magneto-optical trapping of all stable Cd isotopes including isotopes Cd111 and Cd113, which are applicable to optical lattice clocks.

  3. Importance of polarization effects in electron impact single ionization of argon atom

    Energy Technology Data Exchange (ETDEWEB)

    Purohit, G., E-mail: g_vpurohit@yahoo.co [Department of Basic Sciences, School of Engineering, Sir Padampat Singhania University, Bhatewar, Udaipur 313 601 (India); Patidar, Vinod; Sud, K.K. [Department of Basic Sciences, School of Engineering, Sir Padampat Singhania University, Bhatewar, Udaipur 313 601 (India)

    2009-12-15

    We report the results of our calculations of triple differential cross section (TDCS) for electron impact single ionization (i.e. (e, 2e) processes) from the 3s shell of argon using a modified distorted wave Born approximation formalism by including correlation-polarization potential, which accounts for both correlation and polarization effects. We observe that DWBA formalism including polarization potential is able to reproduce most of the trends of experimental data and hence provide a future direction for further investigation of ionization process from the 3s shell of argon. We also compare our results with the available theoretical and experimental results. The present calculations significantly improve the agreement with the experimental results but still there are certain discrepancies, which is a matter of further investigation.

  4. Single-quantum annihilation of positrons with shell-bound atomic electrons

    International Nuclear Information System (INIS)

    Palathingal, J.C.; Asoka-Kumar, P.; Lynn, K.G.; Posada, Y.; Wu, X.Y.

    1991-01-01

    The single-quantum annihilation of positrons has been studied experimentally with a positron beam and a thin lead target, at energies 1 MeV and higher. Spectral peaks corresponding to the K, L, and M shells have been resolved and observed distinctly for the first time. The shell ratios L/K and M/K have been determined. An analysis of the L peak has yielded the (LII+LIII)/L ratio. The first measurements of the directional distributions of the annihilation quanta of the three individual electron shells are also reported. The results are in agreement with theory. They also point out the potential for applying the phenomena to the development of a tunable, highly directional gamma-ray source

  5. Iodine filters in nuclear installations

    International Nuclear Information System (INIS)

    Wilhelm, J.G.

    1982-01-01

    The present report discusses the significance for environmental exposure of the iodine released with the gaseous effluents of nuclear power stations and reprocessing plants in relation to releases of other airborne radionuclides. Iodine filtration processes are described. The release pathways and the composition of airborne fission product iodine mixtures and their bearing on environmental exposure are discussed on the basis of measured fission product iodine emissions. The sorbents which can be used for iodine filtration, their removal efficiencies and range of applications are dealt with in detail. The particular conditions governing iodine removal, which are determined by the various gaseous iodine species, are illustrated on the basis of experimentally determined retention profiles. Particular attention is given to the limitations imposed by temperature, humidity, radiation and filter poisoning. The types of filter normally used are described, their advantages and drawbacks discussed, the principles underlying their design are outlined and the sources of error indicated. The methods normally applied to test the efficiency of various iodine sorbents are described and assessed. Operating experience with iodine filters, gathered from surveillance periods of many years, is supplemented by a large number of test results and the findings of extensive experiments. Possible ways of prolonging the permissible service lives of iodine filters are discussed and information is given on protective measures. The various iodine removal processes applied in reprocessing plants are described and compared with reference to efficiency and cost. The latest developments in filter technology in reprocessing plants are briefly outlined

  6. 4He adsorbed in cylindrical silica nanopores: Effect of size on the single-atom mean kinetic energy

    International Nuclear Information System (INIS)

    Andreani, C.; Senesi, R.; Pantalei, C.

    2007-01-01

    This paper reports a study of the short-time dynamics of helium confined in silica nanopores (xerogel powder), with average pore diameters of 24 and 160 A. The longitudinal momentum distribution of helium adsorbed in xerogels has been determined via deep inelastic neutron scattering (DINS) measurements performed on the VESUVIO spectrometer at the ISIS spallation source. DINS measurements, in the attosecond time scale (i.e., 10 -16 -10 -15 s), were performed at a temperature of T=2.5 K and saturated vapor pressure conditions, with 95% pore volume filling. The average wave-vector transfer q was about 130 A -1 . For confined helium, significant changes in the values of the single-particle mean kinetic energies K > are found in the bulk phase. These are 32.6±8.7 K for the 24 A and 24.4±5.3 K for the 160 A pore diameters, remarkably higher than K >=16.2±0.4 K, the value of normal liquid 4 He at T=2.5 K and saturated vapor pressure conditions. The results are interpreted in terms of a model where 4 He atoms are arranged in concentric annuli along the cylindrical pore axis, with K > mainly dependent on the ratio between the atomic 'effective' diameter and the pore diameter. The number of solid layers close to pore surface is found to be strongly pore-size dependent with one single solid layer for 24 A diameter pore and three solid layers for 160 A diameter pore

  7. Formic acid decomposition on Pt1/Cu (111) single platinum atom catalyst: Insights from DFT calculations and energetic span model analysis

    Science.gov (United States)

    Wang, Ying-Fan; Li, Kun; Wang, Gui-Chang

    2018-04-01

    Inspired by the recent surface experimental results that the monatomic Pt catalysts has more excellent hydrogen production that Cu(111) surface, the mechanism of decomposition of formic acid on Cu(111) and single atom Pt1/Cu(111) surface was studied by periodic density functional theory calculations in the present work. The results show that the formic acid tends to undergo dehydrogenation on both surfaces to obtain the hydrogen product of the target product, and the selectivity and catalytic activity of Pt1/Cu (111) surface for formic acid dehydrogenation are better. The reason is that the single atom Pt1/Cu(111) catalyst reduces the reaction energy barrier (i.e., HCOO → CO2 + H) of the critical step of the dehydrogenation reaction due to the fact that the single atom Pt1/Cu(111) catalyst binds formate weakly compared to that of Cu (111) one. Moreover, it was found that the Pt1/Cu (111) binds CO more strongly than that of Cu (111) one and thus leading to the difficult for the formation of CO. These two factors would make the single Pt atom catalyst had the high selectivity for the H2 production. It is hoped that the present work may help people to design the efficient H2 production from HCOOH decomposition by reduce the surface binding strength of HCOO species, for example, using the low coordination number active site like single atom or other related catalytic system.

  8. Reliable lateral and vertical manipulations of a single Cu adatom on a Cu(111) surface with multi-atom apex tip: semiempirical and first-principles simulations

    International Nuclear Information System (INIS)

    Xie Yiqun; Liu Qingwei; Zhang Peng; Wang Songyou; Li Yufen; Gan Fuxi; Zhuang Jun; Zhang Wenqing; Zhuang Min

    2008-01-01

    We study the reliability of the lateral manipulation of a single Cu adatom on a Cu(111) surface with single-atom, dimer and trimer apex tips using both semiempirical and first-principles simulations. The dependence of the manipulation reliability on tip height is investigated. For the single-atom apex tip the manipulation reliability increases monotonically with decreasing tip height. For the dimer and trimer apex tips the manipulation reliability is greatly improved compared to that for the single-atom apex tip over a certain tip-height range. Two kinds of mechanism are found responsible for this improvement. One is the so-called enhanced interaction mechanism in which the lateral tip-adatom interaction in the manipulation direction is improved. The other is the suspended atom mechanism in which the relative lateral trapping ability of the tip is improved due to the strong vertical attraction of the tip on the adatom. Both mechanisms occur in the manipulations with the trimer apex tip, while in those with the dimer apex tip only the former is effective. Moreover, we present a method to realize reversible vertical manipulation of a single atom on a Cu(111) surface with the trimer apex tip, based on its strong vertical and lateral attraction on the adatom

  9. Variation in the iodine concentrations of foods: considerations for dietary assessment1234

    Science.gov (United States)

    Carriquiry, Alicia L; Spungen, Judith H; Murphy, Suzanne P; Pehrsson, Pamela R; Dwyer, Johanna T; Juan, WenYen; Wirtz, Mark S

    2016-01-01

    Background: Food-composition tables typically give measured nutrient concentrations in foods as a single summary value, often the mean, without providing information as to the shape of the distribution. Objective: Our objective was to explore how the statistical approach chosen to describe the iodine concentrations of foods affects the proportion of the population identified as having either insufficient or excessive iodine intakes. Design: We used food intake data reported by the 2009−2010 NHANES and measured iodine concentrations of Total Diet Study (TDS) foods from 4 US regions sampled in 2004–2011. We created 4 data sets, each by using a different summary statistic (median, mean, and 10th and 90th percentiles), to represent the iodine concentration distribution of each TDS food. We estimated the iodine concentration distribution of each food consumed by NHANES participants as the 4 iodine concentration summary statistics of a similar TDS food and used these, along with NHANES food intake data, to develop 4 estimates of each participant’s iodine intake on each survey day. Using the 4 estimates in turn, we calculated 4 usual iodine intakes for each sex- and age-specific subgroup. We then compared these to guideline values and developed 4 estimates of the proportions of each subgroup with deficient and excessive usual iodine intakes. Results: In general, the distribution of iodine intakes was poorly characterized when food iodine concentrations were expressed as mean values. In addition, mean values predicted lower prevalences of iodine deficiency than did median values. For example, in women aged 19–50 y, the estimated prevalence of iodine deficiency was 25% when based on median food iodine concentrations but only 5.8% when based on mean values. Conclusion: For nutrients such as iodine with highly variable concentrations in important food sources, we recommend that food-composition tables provide useful variability information, including the mean, SD, and

  10. Effect of alkali metal content of carbon on retention of iodine at high temperatures

    International Nuclear Information System (INIS)

    Evans, A.G.

    1975-01-01

    Activated carbon for filters in reactor confinement systems is intentionally impregnated with iodine salts to enhance the removal of radioiodine from air streams containing organic iodides. When a variety of commercial impregnated carbons were evaluated for iodine retention at elevated temperatures (4 hours at 180 0 C), wide variations in iodine penetration were observed. The alkali metal and iodine content of carbon samples was determined by neutron activation analysis, and a strong correlation was shown between the atom ratio of iodine to alkali metals in the carbons and the high-temperature retention performance. Carbons containing excess alkali (especially potassium) have iodine penetration values 10 to 100 times lower than carbons containing excess iodine. Both low I/K ratios and high pH values were shown essential to high efficiency iodine retention; therefore, conversion of elemental iodine to ionic iodine is the basic reaction mechanism. The natural high K + content and high pH coconut carbons make coconut the preferred natural base material for nuclear air cleaning applications. Studies show, however, that treatment of low potassium carbons with a mixture of KOH and I 2 may produce a product equal to or better than I 2 -impregnated coconut carbons at a lower cost. (U.S.)

  11. A new 28Si single crystal: counting the atoms for the new kilogram definition

    Science.gov (United States)

    Bartl, G.; Becker, P.; Beckhoff, B.; Bettin, H.; Beyer, E.; Borys, M.; Busch, I.; Cibik, L.; D'Agostino, G.; Darlatt, E.; Di Luzio, M.; Fujii, K.; Fujimoto, H.; Fujita, K.; Kolbe, M.; Krumrey, M.; Kuramoto, N.; Massa, E.; Mecke, M.; Mizushima, S.; Müller, M.; Narukawa, T.; Nicolaus, A.; Pramann, A.; Rauch, D.; Rienitz, O.; Sasso, C. P.; Stopic, A.; Stosch, R.; Waseda, A.; Wundrack, S.; Zhang, L.; Zhang, X. W.

    2017-10-01

    A new single crystal from isotopically enriched silicon was used to determine the Avogadro constant N A by the x-ray-crystal density method. The new crystal, named Si28-23Pr11, has a higher enrichment than the former ‘AVO28’ crystal allowing a smaller uncertainty of the molar mass determination. Again, two 1 kg spheres were manufactured from this crystal. The crystal and the spheres were measured with improved and new methods. One sphere, Si28kg01a, was measured at NMIJ and PTB with very consistent results. The other sphere, Si28kg01b, was measured only at PTB and yielded nearly the same Avogadro constant value. The mean result for both 1 kg spheres is N A  =  6.022 140 526(70)  ×  1023 mol-1 with a relative standard uncertainty of 1.2  ×  10-8. This value deviates from the Avogadro value published in 2015 for the AVO28 crystal by about 3.9(2.1)  ×  10-8. Possible reasons for this difference are discussed and additional measurements are proposed.

  12. Direct solar-pumped iodine laser amplifier

    Science.gov (United States)

    Han, Kwang S.; Hwang, In Heon

    1990-01-01

    The optimum conditions of a solar pumped iodine laser are found in this research for the case of a continuous wave operation and a pulsed operation. The optimum product of the pressure(p) inside the laser tube and the tube diameter(d) was pd=40 approx. 50 torr-cm on the contrary to the case of a high intensity flashlamp pumped iodine laser where the optimum value of the product is known to be pd=150 torr-cm. The pressure-diameter product is less than 1/3 of that of the high power iodine laser. During the research period, various laser materials were also studied for solar pumping. Among the laser materials, Nd:YAG is found to have the lowest laser threshold pumping intensity of about 200 solar constant. The Rhodamine 6G was also tested as the solar pumped laser material. The threshold pumping power was measured to be about 20,000 solar constant. The amplification experiment for a continuously pumped iodine laser amplifier was performed using Vortek solar simulator and the amplification factors were measured for single pass amplification and triple pass amplification of the 15 cm long amplifier tube. The amplification of 5 was obtained for the triple pass amplification.

  13. Labeling of indocyanine green with carrier-free iodine-123

    International Nuclear Information System (INIS)

    Ansari, A.N.; Lambrecht, R.M.; Redvanly, C.S.; Wolf, A.P.

    1976-01-01

    The method is described for labeling indocyanine green (ICG) with carrier-free iodine-123 by condensing xenon-123 on crystals of ICG followed by permitting decay of the 123 Xe a sufficient length of time to produce 123 I-electronically excited ions and atoms which subsequently label ICG. 4 claims, no drawings

  14. Excitation of the inner 4d shell of neutral iodine

    Energy Technology Data Exchange (ETDEWEB)

    Pettini, M; Tozzi, G P [Osservatorio Astrofisico di Arcetri, Florence (Italy); Mazzoni, M [Florence Univ. (Italy). Ist. di Astronomia

    1981-03-23

    The absorption spectrum of neutral atomic iodine has been photographed in the EUV region and three strong autoionized resonances have been identified. A broad absorption feature has been observed and is ascribed to a collective exitation of the 4d inner shell.

  15. Hyperparathyroidism after radioactive iodine therapy for Graves disease

    International Nuclear Information System (INIS)

    Esselstyn, C.B. Jr.; Schumacher, O.P.; Eversman, J.; Sheeler, L.; Levy, W.J.

    1982-01-01

    The association of external ionizing radiation to the head and neck and the subsequent development of hyperfunctioning parathyroid glands has been documented in recent years. This also has been demonstrated experimentally in animals. Despite the numbers of patients with Graves disease who have been treated with radioactive iodine, there are no reports in the literature of parathyroid surgery for hyperparathyroidism secondary to earlier treatment with radioactive iodine for Graves disease. This report describes the operative and pathologic findings in four patients with hyperparathyroidism. These patients had previously been treated with radioactive iodine for Graves disease. The pathologic findings at surgery included in three cases a single enlarged hyperplastic gland consistent with a parathyroid adenoma. One patient had hyperplasia of all four glands. The two largest glands and halves of the two remaining glands were removed. In a long-term follow-up of children and adolescents treated with radioactive iodine for Graves disease, Levy and Schumacher found calcium elevations in 10 of 159 patients. The increased incidence of hyperparathyroidism following radioactive iodine treatment for Graves disease in children and adolescents would seem several times higher than normal. Whether adults who have radioactive iodine treatment for Graves disease have a similar increase incidence is not known. Meanwhile it would seem reasonable to suggest that patients whose hyperthyroidism is treated with radioactive iodine should have their serum calcium levels determined at 5-year intervals

  16. A theoretical study of the H-abstraction reactions from HOI by moist air radiolytic products (H, OH, and O (3P)) and iodine atoms (2P(3/2)).

    Science.gov (United States)

    Hammaecher, Catherine; Canneaux, Sébastien; Louis, Florent; Cantrel, Laurent

    2011-06-23

    The rate constants of the reactions of HOI molecules with H, OH, O ((3)P), and I ((2)P(3/2)) atoms have been estimated over the temperature range 300-2500 K using four different levels of theory. Geometry optimizations and vibrational frequency calculations are performed using MP2 methods combined with two basis sets (cc-pVTZ and 6-311G(d,p)). Single-point energy calculations are performed with the highly correlated ab initio coupled cluster method in the space of single, double, and triple (pertubatively) electron excitations CCSD(T) using the cc-pVTZ, cc-pVQZ, 6-311+G(3df,2p), and 6-311++G(3df,3pd) basis sets. Reaction enthalpies at 0 K were calculated at the CCSD(T)/cc-pVnZ//MP2/cc-pVTZ (n = T and Q), CCSD(T)/6-311+G(3df,2p)//MP2/6-311G(d,p), and CCSD(T)/6-311++G(3df,3pd)//MP2/6-311G(d,p) levels of theory and compared to the experimental values taken from the literature. Canonical transition-state theory with an Eckart tunneling correction is used to predict the rate constants as a function of temperature. The computational procedure has been used to predict rate constants for H-abstraction elementary reactions because there are actually no literature data to which the calculated rate constants can be directly compared. The final objective is to implement kinetics of gaseous reactions in the ASTEC (accident source term evaluation code) program to improve speciation of fission products, which can be transported along the reactor coolant system (RCS) of a pressurized water reactor (PWR) in the case of a severe accident.

  17. Atom-scale covalent electrochemical modification of single-layer graphene on SiC substrates by diaryliodonium salts

    International Nuclear Information System (INIS)

    Gearba, Raluca I.; Mueller, Kory M.; Veneman, Peter A.; Holliday, Bradley J.; Chan, Calvin K.; Stevenson, Keith J.

    2015-01-01

    Owing to its high conductivity, graphene holds promise as an electrode for energy devices such as batteries and photovoltaics. However, to this end, the work function and doping levels in graphene need to be precisely tuned. One promising route for modifying graphene's electronic properties is via controlled covalent electrochemical grafting of molecules. We show that by employing diaryliodonium salts instead of the commonly used diazonium salts, spontaneous functionalization is avoided. This then allows for precise tuning of the grafting density. Moreover, by employing bis(4-nitrophenyl)iodonium(III) tetrafluoroborate (DNP) salt calibration curves, the surface functionalization density (coverage) of glassy carbon was controlled using cyclic voltammetry in varying salt concentrations. These electro-grafting conditions and calibration curves translated directly over to modifying single layer epitaxial graphene substrates (grown on insulating 6H-SiC (0 0 0 1)). In addition to quantifying the functionalization densities using electrochemical methods, samples with low grafting densities were characterized by low-temperature scanning tunneling microscopy (LT-STM). We show that the use of buffer-layer free graphene substrates is required for clear observation of the nitrophenyl modifications. Furthermore, atomically-resolved STM images of single site modifications were obtained, showing no preferential grafting at defect sites or SiC step edges as supposed previously in the literature. Most of the grafts exhibit threefold symmetry, but occasional extended modifications (larger than 4 nm) were observed as well

  18. Low cost iodine intercalated graphene for fuel cells electrodes

    Science.gov (United States)

    Marinoiu, Adriana; Raceanu, Mircea; Carcadea, Elena; Varlam, Mihai; Stefanescu, Ioan

    2017-12-01

    On the theoretical predictions, we report the synthesis of iodine intercalated graphene for proton exchange membrane fuel cells (PEMFCs) applications. The structure and morphology of the samples were characterized by X-ray photoelectron spectroscopy (XPS) analysis, specific surface area by BET method, Raman investigations. The presence of elemental iodine in the form of triiodide and pentaiodide was validated, suggesting that iodine was trapped between graphene layers, leading to interactions with C atoms. The electrochemical performances of iodinated graphenes were tested and compared with a typical PEMFC configuration, containing different Pt/C loading (0.4 and 0.2 mg cm-2). If iodinated graphene is included as microporous layer, the electrochemical performances of the fuel cell are higher in terms of power density than the typical fuel cell. Iodine-doped graphenes have been successfully obtained by simple and cost effective synthetic strategy and demonstrated new insights for designing of a high performance metal-free ORR catalyst by a scalable technique.

  19. Iodine Status in Pregnant & Breastfeeding Women

    DEFF Research Database (Denmark)

    Andersen, Stine Linding

    Iodine is required for the synthesis of thyroid hormones, which are crucial regulator of early brain development. The source of iodine in the fetus and the breastfed infant is maternal iodine, and adequate iodine intake in pregnant and breastfeeding is of major concern. Severe iodine deficiency can...... cause irreversible brain damage, whereas the consequences of mild to moderate iodine deficiency are less clear. Denmark was previously iodine deficient with regional differences (mild iodine deficiency in East Denmark and moderate iodine deficiency in West Denmark), and also pregnant and breastfeeding...... women suffered from iodine deficiency. A mandatory iodine fortification of household salt and salt used for commercial production of bread was introduced in Denmark in the year 2000. The PhD thesis investigates intake of iodine supplements and urinary iodine status in Danish pregnant and breastfeeding...

  20. Support effects in single atom iron catalysts on adsorption characteristics of toxic gases (NO2, NH3, SO3 and H2S)

    Science.gov (United States)

    Gao, Zhengyang; Yang, Weijie; Ding, Xunlei; Lv, Gang; Yan, Weiping

    2018-04-01

    The effects of support on gas adsorption is crucial for single atom catalysts design and optimization. To gain insight into support effects on gas adsorption characteristics, a comprehensive theoretical study was performed to investigate the adsorption characteristics of toxic gases (NO2, NH3, SO3 and H2S) by utilizing single atom iron catalysts with three graphene-based supports. The adsorption geometry, adsorption energy, electronic and magnetic properties of the adsorption system have been explored. Additionally, the support effects have been analyzed through d-band center and Fermi softness, and thermodynamic analysis has been performed to consider the effect of temperature on gas adsorption. The support effects have a remarkable influence on the adsorption characteristics of four types of toxic gases which is determined by the electronic structure of graphene-based support, and the electronic structure can be characterized by Fermi softness of catalysts. Fermi softness and uplift height of Fe atom could be good descriptors for the adsorption activity of single atom iron catalysts with graphene-based supports. The findings can lay a foundation for the further study of graphene-based support effects in single atom catalysts and provide a guideline for development and design of new graphene-based support materials utilizing the idea of Fermi softness.

  1. The speciation of iodine in the environment

    International Nuclear Information System (INIS)

    Bulman, R.A.

    1986-01-01

    The speciation of iodine in the environment is discussed under the following topics: (i) sea surface to atmosphere, (ii) chemistry in bulk seawater, (iii) iodine in rocks, (iv) iodine in soils, (v) iodine in plants and (vi) iodine in solidified wastes. (author)

  2. Median Urinary Iodine Concentrations Are Indicative of Adequate Iodine Status among Women of Reproductive Age in Prey Veng, Cambodia.

    Science.gov (United States)

    Karakochuk, Crystal D; Michaux, Kristina D; Chai, Tze L; Chan, Benny B; Whitfield, Kyly C; Barr, Susan I; McLean, Judy; Talukder, Aminuzzaman; Hou, Kroeun; Ly, Sokhoing; Green, Tim J

    2016-03-03

    Iodine deficiency disorders are estimated to affect over 1.9 million people worldwide. Iodine deficiency is especially serious for women during pregnancy and lactation because of the negative consequences for both mother and infant. The aim of this cross-sectional study was to determine the median urinary iodine concentration (UIC) as a population-level indicator of iodine status among rural women farmers of reproductive age (18-45 years) in the province of Prey Veng, Cambodia. A total of 450 women provided a spot morning urine sample in 2012. Of those women, 93% (n = 420) were non-pregnant and 7% (n = 30) were pregnant at the time of collection. UIC was quantified using the Sandell-Kolthoff reaction with modifications. The median UIC of non-pregnant (139 μg/L) and pregnant women (157 μg/L) were indicative of adequate iodine status using the WHO/UNICEF/ICCIDD epidemiological criteria for both groups (median UIC between 100-199 and 150-249 μg/L, respectively). We conclude that non-pregnant and pregnant women in rural Prey Veng, Cambodia had adequate iodine status based on single spot morning urine samples collected in 2012. More research is warranted to investigate iodine status among larger and more representative populations of women in Cambodia, especially in light of recent policy changes to the national program for universal salt iodization.

  3. Characterization of iodinated adrenomedullin derivatives suitable for lung nuclear medicine

    Energy Technology Data Exchange (ETDEWEB)

    Fu Yan; Letourneau, Myriam; Chatenet, David [Laboratoire d' etudes moleculaires et pharmacologiques des peptides, INRS-Institut Armand-Frappier, Ville de Laval, Qc, H7V 1B7 (Canada); Dupuis, Jocelyn [Research Center, Montreal Heart Institute, Montreal, Qc (Canada); Department of Medicine, University of Montreal, Montreal, Qc (Canada); Fournier, Alain, E-mail: alain.fournier@iaf.inrs.ca [Laboratoire d' etudes moleculaires et pharmacologiques des peptides, INRS-Institut Armand-Frappier, Ville de Laval, Qc, H7V 1B7 (Canada)

    2011-08-15

    Introduction: We have recently demonstrated the effectiveness of 99m-technetium adrenomedullin (AM) as a new molecular lung imaging agent that could provide significant advantages for the diagnosis and follow-up of disorders affecting the pulmonary circulation such as pulmonary embolism and pulmonary hypertension. Having the possibility to conjugate the targeting molecule with different radionuclides would offer more flexibility and potential advantages depending on clinical situations. Since various iodine isotopes are currently used in nuclear medicine and in pharmacological studies, we have evaluated which iodination method should be privileged in order to produce a good iodinated AM-derived nuclear medicine agent. Methods: Synthetic AM was labeled with iodine through chemical and lactoperoxidase oxidation methods. Position of the iodine atom on the peptide was determined by MALDI-TOF mass spectrometry analysis following cyanogen bromide cleavage and carboxypeptidase Y digestion. Binding affinity of iodinated AM analogues was evaluated by competition and saturation binding experiments on dog lung preparations. Results: In this study, we demonstrated that, upon lactoperoxidase oxidation, iodination occurred at Tyr{sup 1} and that this radioligand retained higher binding affinity and specificity over preparations obtained through chemical oxidation. Conclusions: These results emphasize the fact that even a small chemical modification, i.e. iodination, might deeply modify the pharmacological profile of a compound and support observations that the C-terminal tail of human AM plays an important role in the AM receptor binding process. Consequently, incorporation of a radionuclide to produce an AM-based nuclear medicine agent should privilege the N-terminus of the molecule.

  4. Elemental and Isotopic Tomography at Single-Atom-Scale in 4.0 and 2.4 Ga Zircons

    Science.gov (United States)

    Valley, J. W.; Reinhard, D. A.; Snoeyenbos, D.; Lawrence, D.; Martin, I.; Kelly, T. F.; Ushikubo, T.; Strickland, A.; Cavosie, A. J.

    2012-12-01

    Atom probe tomography can determine identity (mass/charge ratio) and 3-D position of individual atoms in minerals such as zircon. These data provide unique information for understanding the thermal history and mechanisms of mineral reaction and exchange, including radiation damage. Nine needle-shaped specimens ~100 nm in diameter (at the apex) were sampled from 2 zircons by FIB and analyzed with a local-electrode atom probe (LEAP), CAMECA LEAP 4000X HR. The LEAP uses pulsed-laser heating to field evaporate the tip of a zircon needle and accelerates the ions into a position-sensitive TOF-MS. With due care for complex isobaric interferences (molecules, multiple ionizations) and background correction, it is possible to individually identify up to 10E8 atoms/needle (36% detection efficiency) by mass/charge (MRP ~ 1000@ m/n=16Da) and position (X-Y-Z coordinates on 0.2 nm scale) (Kelly & Larson 2012). The 3-D distribution of Pb and Y differ at atom-scale in the 2 zircons. Zircon #1 (4007 Ma, Jack Hills, W. Australia, Cavosie 2005, Ushikubo et al. 2008, Bouvier et al. 2011) is homogeneous in Pb and Y. In contrast, incompatible elements, including Pb and Y, are concentrated in equant 5-10 nm dia. domains, spaced ~50 nm apart in zircon #2 (2438 Ma, Albion-Raft R-Grouse Ck core complex, Utah, Strickland et al. 2011). U is homogeneously distributed in both zircons. The analyzed domains suffered 4-8 x 10E15 α-decay events/mg due to U and Th decay and yet both zircons yield >97% concordant U-Pb ages by SIMS, suggesting annealing of radiation damage during the life of the zircons. The 207-Pb/206-Pb ratios for these nm-scale domains, as measured by LEAP, average 0.17 for the 2.4 Ga Zrc2 (3 needles) and 0.43 for the 4.0 Ga Zrc1 (5 needles). These ratios are less precise (±40% 2σ) due to ultra-small sample size, but are in excellent agreement with values measured by SIMS, 0.1684 and 0.4269, respectively. Thus Pb in both zircons is radiogenic. The Pb-Y-rich domains and lack of

  5. Disposal of Iodine-129

    International Nuclear Information System (INIS)

    Morgan, M.T.; Moore, J.G.; Devaney, H.E.; Rogers, G.C.; Williams, C.; Newman, E.

    1978-01-01

    One of the problems to be solved in the nuclear waste management field is the disposal of radioactive iodine-129, which is one of the more volatile and long-lived fission products. Studies have shown that fission products can be fixed in concrete for permanent disposal. Current studies have demonstrated that practical cementitious grouts may contain up to 18% iodine as barium iodate. The waste disposal criterion is based on the fact that harmful effects to present or future generations can be avoided by isolation and/or dilution. Long-term isolation is effective in deep, dry repositories; however, since penetration by water is possible, although unlikely, release was calculated based on leach rates into water. Further considerations have indicated that sea disposal on or in the ocean floor may be a more acceptable alternative

  6. Hyperthyroidism and radioactive iodine

    International Nuclear Information System (INIS)

    Corstens, F.H.M.

    1980-01-01

    The study details the results of treatment of patients with hyperthyroidism using a combination of fractionated low doses radioactive iodine and anthithyroid drug therapy. The patients studied were treated according to this regimen after August 1968 and all reached euthyroidism before March 1979. None of the patients had been treated with radioactive iodine prior to the start of the protocol. A subgroup of the patients had received an unsuccessfull course with antithyroid drug therapy and, or, surgical therapy before the start of the protocol. Patients who had never been treated for hyperthyroidism were given antithyroid drug therapy for at least 6 months in an attempt to reach euthryroidism without the use of 131 I therapy. Therefore, all patients had experienced a course of unsuccessfull therapy prior to the start of the treatment protocol using combined fractionated low doses of 131 I and antithyroid drug therapy. (Auth.)

  7. Atom-field interaction in the single-quantum limit in a two dimensional travelling-wave cavity

    International Nuclear Information System (INIS)

    Youn, Sun Hyun; Chough, Young Tak; An, Kyung Won

    2003-01-01

    We analyze the interaction of an atom with two dimensional travelling-wave cavity modes in the strong coupling region, with the quantized atomic center of mass motion taken into account. Analytic and numerical calculation shows that the atom in two independent pairs of travelling wave modes can be made to interact only with a particular travelling mode by matching the initial momentum and the detuning of the cavities. We also numerically investigate the atomic momentum deflection in the cavities

  8. Iodine immobilization in apatites

    International Nuclear Information System (INIS)

    Audubert, F.; Lartigue, J.E.

    2000-01-01

    In the context of a scientific program on long-lived radionuclide conditioning, a matrix for iodine 129 immobilization has been studied. A lead vanado-phosphate apatite was prepared from the melt of lead vanado-phosphate Pb 3 (VO 4 ) 1.6 (PO 4 ) 0.4 and lead iodide PbI 2 in stoichiometric proportions by calcination at 700 deg. C during 3 hours. Natural sintering of this apatite is not possible because the product decomposition occurs at 400 deg. C. Reactive sintering is the solution. The principle depends on the coating of lead iodide with lead vanado-phosphate. Lead vanado-phosphate coating is used as iodo-apatite reactant and as dense covering to confine iodine during synthesis. So the best condition to immobilize iodine during iodo-apatite synthesis is a reactive sintering at 700 deg. C under 25 MPa. We obtained an iodo-apatite surrounded with dense lead vanadate. Leaching behaviour of the matrix synthesized by solid-solid reaction is under progress in order to determine chemical durability, basic mechanisms of the iodo-apatite alteration and kinetic rate law. Iodo-apatite dissolution rates were pH and temperature dependent. We obtained a rate of 2.5 10 -3 g.m -2 .d -1 at 90 deg. C in initially de-ionised water. (authors)

  9. Separation and retention of iodine

    International Nuclear Information System (INIS)

    Thomas, T.R.

    1976-01-01

    Caustic and mercuric nitrate scrubbers have been used for iodine recovery from process offgas, but they exhibit low decontamination factors for organic iodide removal and produce liquid wastes that are unsuitable for final storage. The Iodox process gives high decontamination factors for both organic iodides and elemental iodine. The liquid waste can be evaporated to a solid or concentrated and fixed in cement. Efficient separation and retention of gaseous iodine species can be obtained with silver-loaded adsorbents. The waste is a dry solid easily handled and stored. Adsorbents containing cheaper metals appear to have lower iodine-loading capacities and may be unsuitable for bulk iodine removal from process offgas because of the large amounts of solid waste that would be generated. A potential method for regenerationg and recycling silver-loaded adsorbents is being evaluated. In conjunction with the regeneration, lead-exchanged zeolite is used as a secondary adsorbent for the final fixation and storage of the iodine

  10. The effect of defects on the catalytic activity of single Au atom supported carbon nanotubes and reaction mechanism for CO oxidation.

    Science.gov (United States)

    Ali, Sajjad; Fu Liu, Tian; Lian, Zan; Li, Bo; Sheng Su, Dang

    2017-08-23

    The mechanism of CO oxidation by O 2 on a single Au atom supported on pristine, mono atom vacancy (m), di atom vacancy (di) and the Stone Wales defect (SW) on single walled carbon nanotube (SWCNT) surface is systematically investigated theoretically using density functional theory. We determine that single Au atoms can be trapped effectively by the defects on SWCNTs. The defects on SWCNTs can enhance both the binding strength and catalytic activity of the supported single Au atom. Fundamental aspects such as adsorption energy and charge transfer are elucidated to analyze the adsorption properties of CO and O 2 and co-adsorption of CO and O 2 molecules. It is found that CO binds stronger than O 2 on Au supported SWCNT. We clearly demonstrate that the defected SWCNT surface promotes electron transfer from the supported single Au atom to O 2 molecules. On the other hand, this effect is weaker for pristine SWCNTs. It is observed that the high density of spin-polarized states are localized in the region of the Fermi level due to the strong interactions between Au (5d orbital) and the adjacent carbon (2p orbital) atoms, which influence the catalytic performance. In addition, we elucidate both the Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms of CO oxidation by O 2 . For the LH pathway, the barriers of the rate-limiting step are calculated to be 0.02 eV and 0.05 eV for Au/m-SWCNT and Au/di-SWCNT, respectively. To regenerate the active sites, an ER-like reaction occurs to form a second CO 2 molecule. The ER pathway is observed on Au/m-SWCNT, Au/SW-SWCNT and Au/SWCNT in which the Au/m-SWCNT has a smaller barrier. The comparison with a previous study (Lu et al., J. Phys. Chem. C, 2009, 113, 20156-20160.) indicates that the curvature effect of SWCNTs is important for the catalytic property of the supported single Au. Overall, Au/m-SWCNT is identified as the most active catalyst for CO oxidation compared to pristine SWCNT, SW-SWCNT and di-SWCNT. Our findings give a

  11. Detection of de novo single nucleotide variants in offspring of atomic-bomb survivors close to the hypocenter by whole-genome sequencing.

    Science.gov (United States)

    Horai, Makiko; Mishima, Hiroyuki; Hayashida, Chisa; Kinoshita, Akira; Nakane, Yoshibumi; Matsuo, Tatsuki; Tsuruda, Kazuto; Yanagihara, Katsunori; Sato, Shinya; Imanishi, Daisuke; Imaizumi, Yoshitaka; Hata, Tomoko; Miyazaki, Yasushi; Yoshiura, Koh-Ichiro

    2018-03-01

    Ionizing radiation released by the atomic bombs at Hiroshima and Nagasaki, Japan, in 1945 caused many long-term illnesses, including increased risks of malignancies such as leukemia and solid tumours. Radiation has demonstrated genetic effects in animal models, leading to concerns over the potential hereditary effects of atomic bomb-related radiation. However, no direct analyses of whole DNA have yet been reported. We therefore investigated de novo variants in offspring of atomic-bomb survivors by whole-genome sequencing (WGS). We collected peripheral blood from three trios, each comprising a father (atomic-bomb survivor with acute radiation symptoms), a non-exposed mother, and their child, none of whom had any past history of haematological disorders. One trio of non-exposed individuals was included as a control. DNA was extracted and the numbers of de novo single nucleotide variants in the children were counted by WGS with sequencing confirmation. Gross structural variants were also analysed. Written informed consent was obtained from all participants prior to the study. There were 62, 81, and 42 de novo single nucleotide variants in the children of atomic-bomb survivors, compared with 48 in the control trio. There were no gross structural variants in any trio. These findings are in accord with previously published results that also showed no significant genetic effects of atomic-bomb radiation on second-generation survivors.

  12. Immobilization of iodine in concrete

    International Nuclear Information System (INIS)

    Clark, W.E.; Thompson, C.T.

    1977-01-01

    A method for immobilizing fission product radioactive iodine recovered from irradiated nuclear fuel comprises combining material comprising water, Portland cement and about 3 to 20 wt percent iodine as Ba(IO 3 ) 2 to provide a fluid mixture and allowing the fluid mixture to harden, said Ba(IO 3 ) 2 comprising said radioactive iodine. An article for solid waste disposal comprises concrete prepared by this method. 10 claims, 2 figures

  13. Iodine neutron capture therapy

    Science.gov (United States)

    Ahmed, Kazi Fariduddin

    A new technique, Iodine Neutron Capture Therapy (INCT) is proposed to treat hyperthyroidism in people. Present thyroid therapies, surgical removal and 131I treatment, result in hypothyroidism and, for 131I, involve protracted treatment times and excessive whole-body radiation doses. The new technique involves using a low energy neutron beam to convert a fraction of the natural iodine stored in the thyroid to radioactive 128I, which has a 24-minute half-life and decays by emitting 2.12-MeV beta particles. The beta particles are absorbed in and damage some thyroid tissue cells and consequently reduce the production and release of thyroid hormones to the blood stream. Treatment times and whole-body radiation doses are thus reduced substantially. This dissertation addresses the first of the several steps needed to obtain medical profession acceptance and regulatory approval to implement this therapy. As with other such programs, initial feasibility is established by performing experiments on suitable small mammals. Laboratory rats were used and their thyroids were exposed to the beta particles coming from small encapsulated amounts of 128I. Masses of 89.0 mg reagent-grade elemental iodine crystals have been activated in the ISU AGN-201 reactor to provide 0.033 mBq of 128I. This activity delivers 0.2 Gy to the thyroid gland of 300-g male rats having fresh thyroid tissue masses of ˜20 mg. Larger iodine masses are used to provide greater doses. The activated iodine is encapsulated to form a thin (0.16 cm 2/mg) patch that is then applied directly to the surgically exposed thyroid of an anesthetized rat. Direct neutron irradiation of a rat's thyroid was not possible due to its small size. Direct in-vivo exposure of the thyroid of the rat to the emitted radiation from 128I is allowed to continue for 2.5 hours (6 half-lives). Pre- and post-exposure blood samples are taken to quantify thyroid hormone levels. The serum T4 concentration is measured by radioimmunoassay at

  14. Demonstration of a reduction in muscarinic receptor binding in early Alzheimer's disease using iodine-123 dexetimide single-photon emission tomography

    International Nuclear Information System (INIS)

    Claus, J.J.; Dubois, E.A.; Booij, J.; Habraken, J.; Munck, J.C. van; Herk, M. van; Verbeeten, B. Jr.; Royen, E.A. van

    1997-01-01

    Decreased muscarinic receptor binding has been suggested in single-photon emission tomography (SPET) studies of Alzheimer's disease. However, it remains unclear whether these changes are present in mildly demented patients, and the role of cortical atrophy in receptor binding assessment has not been investigated. We studied muscarinic receptor binding normalized to neostriatum with SPET using [ 123 I[4-iododexetimide in five mildly affected patients with probable Alzheimer's disease and in five age-matched control subjects. Region of interest (ROI) analysis was performed in a consensus procedure blind to clinical diagnosis using matched magnetic resonance (MRI) images. Cortical atrophy was assessed by calculating percentages of cerebrospinal fluid in each ROI. An observer study with three observers was conducted to validate this method. Alzheimer patients showed statistically significantly less [ 123 I[4-iododexetimide binding in left temporal and right temporo-parietal cortex compared with controls, independent of age, sex and cortical atrophy. Mean intra-observer variability was 3.6% and inter-observer results showed consistent differences in [ 123 I[4-iododexetimide binding between observers. However, differences between patients and controls were comparable among observers and statistically significant in the same regions as in the consensus procedure. Using an MRI-SPET matching technique, we conclude that [ 123 I[4-iododexetimide binding is reduced in patients with mild probable Alzheimer's disease in areas of temporal and temporo-parietal cortex. (orig.). With 1 fig., 4 tabs

  15. Clinical value of iodine-123 beta-methyliodophenyl pentadecanoic acid (BMIPP) myocardial single photon emission computed tomography for predicting cardiac death among patients with chronic heart failure

    International Nuclear Information System (INIS)

    Sasaki, Ryu; Usui, Takashi; Mitani, Isao

    2003-01-01

    In the present study, the effectiveness of 123 I-β-methyliodophenyl pentadecanoic acid (BMIPP) single photon emission computed tomography (SPECT) for predicting cardiac death of patients with chronic heart failure was evaluated. Abnormalities of fatty acid metabolism are found in patients with chronic heart failure and BMIPP was developed as a tracer for scintigraphic assessment of myocardial fatty acid utilization. The study group comprised 74 patients with chronic heart failure with a left ventricular ejection fraction (LVEF) 201 Tl SPECT and BMIPP SPECT. The uptake of tracer was scored semiquantitatively from 0 (normal) to 4 (defect) in 20 segments and a total defect score (TDS) for all 20 segments was calculated. On planar images the mediastinum to heart count ratio (H/M) was calculated for the BMIPP and Tl studies, and the H/M BMIPP :H/M Tl (H/M BMIPP divided by H/M Tl ) was also calculated. The mean follow-up period was 660 days and there were 17 cases of cardiac death. Multivariate analysis identified H/M BMIPP :H/M Tl (p BMIPP :H/M Tl was situated to the left relative to LVEF. Analysis of the myocardial metabolism by BMIPP SPECT can predict the high-risk patients with chronic heart failure. (author)

  16. Radioactive Iodine (I-131) Therapy for Hyperthyroidism

    Science.gov (United States)

    ... Physician Resources Professions Site Index A-Z Radioactive Iodine (I-131) Therapy Radioiodine therapy is a nuclear ... thyroid cancer. When a small dose of radioactive iodine I-131 (an isotope of iodine that emits ...

  17. Pt atoms stabilized on hexagonal boron nitride as efficient single-atom catalysts for CO oxidation: A first-principles investigation

    KAUST Repository

    Liu, Xin; Duan, Ting; Meng, Changgong; Han, Yu

    2015-01-01

    Taking CO oxidation as a probe, we investigated the electronic structure and reactivity of Pt atoms stabilized by vacancy defects on hexagonal boron nitride (h-BN) by first-principles-based calculations. As a joint effect of the high reactivity

  18. From Single Atoms to Nanoparticles : Autocatalysis and Metal Aggregation in Atomic Layer Deposition of Pt on TiO2 Nanopowder

    NARCIS (Netherlands)

    Grillo, Fabio; Van Bui, Hao; La Zara, Damiano; Aarnink, Antonius A.I.; Kovalgin, Alexey Y.; Kooyman, Patricia; Kreutzer, Michiel T.; van Ommen, Jan Rudolf

    2018-01-01

    A fundamental understanding of the interplay between ligand-removal kinetics and metal aggregation during the formation of platinum nanoparticles (NPs) in atomic layer deposition of Pt on TiO2 nanopowder using trimethyl(methylcyclo-pentadienyl)platinum(IV) as the precursor and O2 as the coreactant

  19. Iodine-123 N-methyl-4-iododexetimide: a new radioligand for single-photon emission tomographic imaging of myocardial muscarinic receptors

    International Nuclear Information System (INIS)

    Hicks, R.J.; Kassiou, M.; Eu, P.; Katsifis, A.G.; Garra, M.; Power, J.; Najdovski, L.; Lambrecht, R.M.

    1995-01-01

    Cardiac muscarinic receptor ligands suitable for positron emission tomography have previously been characterised. Attempts to develop radioligands of these receptors suitable for single-photon emission tomographic (SPET) imaging have not been successful due to high lung retention and high non-specific binding of previously investigated potential tracers. The purpose of this study was to evaluate the biodistribution and in vivo imaging characteristics of a new radiopharmaceutical, [ 123 I]N-methyl-4-iododexetimide. Biodistribution studies performed in rats showed high cardiac uptake (2.4% ID/g) 10 min after injection with a heart to lung activity ratio of 5:1. Specificity and stereoselectivity of cardiac binding were demonstrated using blocking experiments in rats. Dynamic imaging studies in anaesthetised greyhounds demonstrated rapid and high myocardial uptake and low lung binding with stable heart to lung activity ratios of >2.5:1 between 10 and 30 min, making SPET imaging feasible. Administration of an excess of an unlabelled muscarinic antagonist, methyl-quinuclidinyl benzylate rapidly displaced myocardial activity to background levels and the pharmacologically inactive enantiomer, [ 123 I]N-methyl-4-iodolevetimide, had no detectable cardiac uptake, indicating specific and stereoselective muscarinic receptor binding. SPET revealed higher activity in the inferior than in the anterior wall, this being consistent with previously described regional variation of cardiac parasympathetic innervation. [ 123 I]N-methyl-4-iododexetimide shows promise as an imaging agent for muscarinic receptor distribution in the heart and may be helpful in evaluating diverse cardiac diseases associated with altered muscarinic receptor function, including heart failure and diabetic heart disease. (orig.)

  20. Controlling the formation process and atomic structures of single pyrazine molecular junction by tuning the strength of the metal-molecule interaction.

    Science.gov (United States)

    Kaneko, Satoshi; Takahashi, Ryoji; Fujii, Shintaro; Nishino, Tomoaki; Kiguchi, Manabu

    2017-04-12

    The formation process and atomic structures were investigated for single pyrazine molecular junctions sandwiched by three different Au, Ag, and Cu electrodes using a mechanically controllable break junction technique in ultrahigh vacuum conditions at 300 K. We demonstrated that the formation process of the single-molecule junction crucially depended on the choice of the metal electrodes. While single-molecule junction showing two distinct conductance states were found for the Au electrodes, only the single conductance state was evident for the Ag electrodes, and there was no junction formation for the Cu electrodes. These results suggested that metal-molecule interaction dominates the formation process and probability of the single-molecule junction. In addition to the metal-molecule interaction, temperature affected the formation process of the single-molecule junction. The single pyrazine molecular junction formed between Au electrodes exhibited significant temperature dependence where the junction-formation probability was about 8% at 300 K, while there was no junction-formation at 100 K. Instead of the junction formation, an Au atomic wire was formed at the low temperature. This study provides insight into the tuning of the junction-forming process for single-molecule junctions, which is needed to construct device structures on a single molecule scale.

  1. Prediction of left ventricular functional recovery in patients with acute myocardial infarction using single photon emission computed tomography with thallium-201 and iodine-123-beta-methyl-p-iodophenyl-pentadecanoic acid

    International Nuclear Information System (INIS)

    Hashimoto, Akiyoshi; Nakata, Tomoaki; Nagao, Kazuhiko

    1995-01-01

    The relationships between myocardial perfusion, fatty acid metabolism, and cardiac function were investigated using dual single photon emission computed tomography (SPECT) with thallium and iodine-123-β-methyl-p-iodophenyl-pentadecanoic acid ( 123 I-BMIPP) during the acute ( 10±1 days) and recovery (60±14 days) phases in 29 patients with acute myocardial infarction. There were 18 patients who underwent successful primary coronary angioplasty (PTCA group) and 11 patients who received conservative therapy (non PTCA group). Thallium and BMIPP uptakes were scored visually by a 4-point system and left ventricular ejection fraction (LVEF) was calculated by radionuclide ventriculography. Although significant positive correlations between thallium and 123 I-BMIPP scores were observed during both phases, BMIPP scores were significantly lower than thallium scores in both acute and recovery phases in the PTCA group. No significant difference in thallium and 123 I-BMIPP scores was observed at the recovery phase in the non PTCA group. LVEF significantly correlated with thallium and 123 I-BMIPP scores in both phases in the PTCA group. Furthermore, the difference between thallium and 123 I-BMIPP scores during the acute phase significantly correlated with the improvement of LVEF during the follow-up period in the PTCA group (y=0.92x-0.77, r=0.65, p 123 I-BMIPP SPECT is increased by reperfusion therapy and persists at least until the recovery phase of myocardial infarction. The recovery of left ventricular function depends on the extent of the mismatched uptake, indicating a predictor for functional recovery following acute myocardial infarction. (author)

  2. Dimethyl sulfoxide complexing with iodine

    Energy Technology Data Exchange (ETDEWEB)

    Borovikov, Yu Ya; Serguchev, Yu A; Staninets, V I

    1986-01-01

    Dielectrometry, conductometry, IR-spectroscopy are used to study dimethyl sulfoxide complexing with iodine in binary system and in CCl/sub 4/, C/sub 6/H/sub 6/, C/sub 6/H/sub 5/Cl, C/sub 6/H/sub 5/CF/sub 3/, 1, 2-dichloroethane solutions. Complexes of 1:1 composition are formed in solutions, in the binary system of 2:1 and 2:2 composition. I/sub 2/ molecules add to oxygen atoms. In CCl/sub 4/ and in binary system gradual transformation of so called external charge transfer complexes (CTC-1) to internal ones (CTC-2) that are described by the 1st order reaction kinetic equations is observed. On dissolution of CTC of 2:2 composition they disproportionate into two CTC molecules 1:1. Enthalpy of forming CTC-1 1:1 is approximately 4 kcal/mol, CTC-2 1:1 - 8, CTC-1 2:1 - 8 kcal/mol.

  3. Iodine removal from a gas phase

    International Nuclear Information System (INIS)

    Vikis, A. Ch.

    1982-01-01

    Iodine, e.g. radioactive iodine, present as one or more organic iodides, optionally with elemental iodine, in a gas phase (e.g. air) are removed by photochemically decomposing the organic iodides to elemental iodine, reacting the iodine produced, and any initially present with excess ozone, preferably photochemically produced in situ in the gas phase to produce solid iodine oxides, and removing the solid oxides from the gas phase. (author)

  4. Iodine removal from a gas phase

    International Nuclear Information System (INIS)

    Vikis, A.C.

    1984-01-01

    Iodine, e.g. radioactive iodine, present as one or more organic iodides, optionally with elemental iodine, in a gas phase (e.g. air) are removed by photochemically decomposing the organic iodides to elemental iodine, reacting the iodine produced, and any initially present with excess ozone, preferably photochemically produced in situ in the gas phase to produce solid iodine oxides, and removing the solid oxides from the gas phase

  5. Atomization efficiency and photon yield in laser-induced breakdown spectroscopy analysis of single nanoparticles in an optical trap

    Science.gov (United States)

    Purohit, Pablo; Fortes, Francisco J.; Laserna, J. Javier

    2017-04-01

    Laser-induced breakdown spectroscopy (LIBS) was employed for investigating the influence of particle size on the dissociation efficiency and the absolute production of photons per mass unit of airborne solid graphite spheres under single-particle regime. Particles of average diameter of 400 nm were probed and compared with 2 μm particles. Samples were first catapulted into aerosol form and then secluded in an optical trap set by a 532 nm laser. Trap stability was quantified before subjecting particles to LIBS analysis. Fine alignment of the different lines comprising the optical catapulting-optical trapping-laser-induced breakdown spectroscopy instrument and tuning of excitation parameters conditioning the LIBS signal such as fluence and acquisition delay are described in detail with the ultimate goal of acquiring clear spectroscopic data on masses as low as 75 fg. The atomization efficiency and the photon yield increase as the particle size becomes smaller. Time-resolved plasma imaging studies were conducted to elucidate the mechanisms leading to particle disintegration and excitation.

  6. Implementing and Quantifying the Shape-Memory Effect of Single Polymeric Micro/Nanowires with an Atomic Force Microscope.

    Science.gov (United States)

    Fang, Liang; Gould, Oliver E C; Lysyakova, Liudmila; Jiang, Yi; Sauter, Tilman; Frank, Oliver; Becker, Tino; Schossig, Michael; Kratz, Karl; Lendlein, Andreas

    2018-04-23

    The implementation of shape-memory effects (SME) in polymeric micro- or nano-objects currently relies on the application of indirect macroscopic manipulation techniques, for example, stretchable molds or phantoms, to ensembles of small objects. Here, we introduce a method capable of the controlled manipulation and SME quantification of individual micro- and nano-objects in analogy to macroscopic thermomechanical test procedures. An atomic force microscope was utilized to address individual electro-spun poly(ether urethane) (PEU) micro- or nanowires freely suspended between two micropillars on a micro-structured silicon substrate. In this way, programming strains of 10±1% or 21±1% were realized, which could be successfully fixed. An almost complete restoration of the original free-suspended shape during heating confirmed the excellent shape-memory performance of the PEU wires. Apparent recovery stresses of σ max,app =1.2±0.1 and 33.3±0.1 MPa were obtained for a single microwire and nanowire, respectively. The universal AFM test platform described here enables the implementation and quantification of a thermomechanically induced function for individual polymeric micro- and nanosystems. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Determination of methylmercury by electrothermal atomic absorption spectrometry using headspace single-drop microextraction with in situ hydride generation

    Energy Technology Data Exchange (ETDEWEB)

    Gil, Sandra [Departamento de Quimica Analitica y Alimentaria, Area de Quimica Analitica, Universidad de Vigo, Facultad de Ciencias (Quimica), As Lagoas-Marcosende s/n, 36200 Vigo (Spain); Fragueiro, Sandra [Departamento de Quimica Analitica y Alimentaria, Area de Quimica Analitica, Universidad de Vigo, Facultad de Ciencias (Quimica), As Lagoas-Marcosende s/n, 36200 Vigo (Spain); Lavilla, Isela [Departamento de Quimica Analitica y Alimentaria, Area de Quimica Analitica, Universidad de Vigo, Facultad de Ciencias (Quimica), As Lagoas-Marcosende s/n, 36200 Vigo (Spain); Bendicho, Carlos [Departamento de Quimica Analitica y Alimentaria, Area de Quimica Analitica, Universidad de Vigo, Facultad de Ciencias (Quimica), As Lagoas-Marcosende s/n, 36200 Vigo (Spain)]. E-mail: bendicho@uvigo.es

    2005-01-10

    A new method is proposed for preconcentration and matrix separation of methylmercury prior to its determination by electrothermal atomic absorption spectrometry (ETAAS). Generation of methylmercury hydride (MeHgH) from a 5-ml solution is carried out in a closed vial and trapped onto an aqueous single drop (3-{mu}l volume) containing Pd(II) or Pt(IV) (50 and 10 mg/l, respectively). The hydrogen evolved in the headspace (HS) after decomposition of sodium tetrahydroborate (III) injected for hydride generation caused the formation of finely dispersed Pd(0) or Pt(0) in the drop, which in turn, were responsible for the sequestration of MeHgH. A preconcentration factor of ca. 40 is achieved with both noble metals used as trapping agents. The limit of detection of methylmercury was 5 and 4 ng/ml (as Hg) with Pd(II) or Pt(IV) as trapping agents, and the precision expressed as relative standard deviation was about 7%. The preconcentration system was fully characterised through optimisation of the following variables: Pd(II) or Pt(IV) concentration in the drop, extraction time, pH of the medium, temperatures of both sample solution and drop, concentration of salt in the sample solution, sodium tetrahydroborate (III) concentration in the drop and stirring rate. The method has been successfully validated against two fish certified reference materials (CRM 464 tuna fish and CRM DORM-2 dogfish muscle) following selective extraction of methylmercury in 2 mol/l HCl medium.

  8. Ion-atom collisions with laser-prepared target: High resolution study of single charge exchange process

    International Nuclear Information System (INIS)

    Leredde, Arnaud

    2012-01-01

    Single charge transfer in low-energy Na"++"8"7Rb(5s,5p) collisions is investigated using magneto-optically trapped Rb atoms and high-resolution recoil-ion momentum spectroscopy. The three-dimensional reconstruction of the recoil-ion momentum provides accurate relative cross-sections for the active channels and the projectile scattering angle distributions. Thanks to the high experimental resolution, scattering structures such as diffraction-like oscillations in angular distributions are clearly observed. The measurements are compared with molecular close-coupling calculations and an excellent agreement is found. To go further in the test of the theory, the target is prepared in an oriented state. It is the first time that such collision experiments with oriented target is performed with such a high resolution. The right-left asymmetry expected for the scattering angle distribution is evidenced. The agreement between MOCC calculations and experiments is very good. Simple models developed for collisions with oriented target are also discussed. (author) [fr

  9. Determination of methylmercury by electrothermal atomic absorption spectrometry using headspace single-drop microextraction with in situ hydride generation

    International Nuclear Information System (INIS)

    Gil, Sandra; Fragueiro, Sandra; Lavilla, Isela; Bendicho, Carlos

    2005-01-01

    A new method is proposed for preconcentration and matrix separation of methylmercury prior to its determination by electrothermal atomic absorption spectrometry (ETAAS). Generation of methylmercury hydride (MeHgH) from a 5-ml solution is carried out in a closed vial and trapped onto an aqueous single drop (3-μl volume) containing Pd(II) or Pt(IV) (50 and 10 mg/l, respectively). The hydrogen evolved in the headspace (HS) after decomposition of sodium tetrahydroborate (III) injected for hydride generation caused the formation of finely dispersed Pd(0) or Pt(0) in the drop, which in turn, were responsible for the sequestration of MeHgH. A preconcentration factor of ca. 40 is achieved with both noble metals used as trapping agents. The limit of detection of methylmercury was 5 and 4 ng/ml (as Hg) with Pd(II) or Pt(IV) as trapping agents, and the precision expressed as relative standard deviation was about 7%. The preconcentration system was fully characterised through optimisation of the following variables: Pd(II) or Pt(IV) concentration in the drop, extraction time, pH of the medium, temperatures of both sample solution and drop, concentration of salt in the sample solution, sodium tetrahydroborate (III) concentration in the drop and stirring rate. The method has been successfully validated against two fish certified reference materials (CRM 464 tuna fish and CRM DORM-2 dogfish muscle) following selective extraction of methylmercury in 2 mol/l HCl medium

  10. Interaction of Pd single atoms with different CeO2 crystal planes: A first-principles study

    Science.gov (United States)

    He, Bingling; Wang, Jinlong; Ma, Dongwei; Tian, Zhixue; Jiang, Lijuan; Xu, Yan; Cheng, Sujun

    2018-03-01

    The adsorption of single Pd atoms on the various CeO2 surfaces, including (111), (110), and (100), has been studied based on the first-principles calculations. It is found that, according to the calculated adsorption energy, interaction strength between Pd and the three CeO2 surfaces follows the order of (100) > (110) > (111). Interestingly, the effect of the electron localization on the surface Ce ions due to the Pd adsorption on its adsorption stability is more significant for the (110) surface than that for the (111) and (100) surfaces. We also find that the formal oxidation states of Pd0, Pdδ+ (δ < 1) and Pd1+ may appear on the CeO2 (111) surface, and Pdδ+ (δ < 1) and Pd1+ could coexist on the CeO2 (100) surfaces. However, under suitable conditions the CeO2 (110) surface may be covered with Pd2+ ions. Present theoretical results clearly suggest that the interaction between Pd and CeO2 nanocrystals significantly depends on the crystal planes of CeO2. It is expected that our study will give useful insights into the effect of CeO2 crystal plane on the physicochemical and catalytic properties of CeO2 supported Pd catalyst.

  11. Optimizing 1-μs-Resolution Single-Molecule Force Spectroscopy on a Commercial Atomic Force Microscope.

    Science.gov (United States)

    Edwards, Devin T; Faulk, Jaevyn K; Sanders, Aric W; Bull, Matthew S; Walder, Robert; LeBlanc, Marc-Andre; Sousa, Marcelo C; Perkins, Thomas T

    2015-10-14

    Atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) is widely used to mechanically measure the folding and unfolding of proteins. However, the temporal resolution of a standard commercial cantilever is 50-1000 μs, masking rapid transitions and short-lived intermediates. Recently, SMFS with 0.7-μs temporal resolution was achieved using an ultrashort (L = 9 μm) cantilever on a custom-built, high-speed AFM. By micromachining such cantilevers with a focused ion beam, we optimized them for SMFS rather than tapping-mode imaging. To enhance usability and throughput, we detected the modified cantilevers on a commercial AFM retrofitted with a detection laser system featuring a 3-μm circular spot size. Moreover, individual cantilevers were reused over multiple days. The improved capabilities of the modified cantilevers for SMFS were showcased by unfolding a polyprotein, a popular biophysical assay. Specifically, these cantilevers maintained a 1-μs response time while eliminating cantilever ringing (Q ≅ 0.5). We therefore expect such cantilevers, along with the instrumentational improvements to detect them on a commercial AFM, to accelerate high-precision AFM-based SMFS studies.

  12. Atomic force microscopy imaging and single molecule recognition force spectroscopy of coat proteins on the surface of Bacillus subtilis spore.

    Science.gov (United States)

    Tang, Jilin; Krajcikova, Daniela; Zhu, Rong; Ebner, Andreas; Cutting, Simon; Gruber, Hermann J; Barak, Imrich; Hinterdorfer, Peter

    2007-01-01

    Coat assembly in Bacillus subtilis serves as a tractable model for the study of the self-assembly process of biological structures and has a significant potential for use in nano-biotechnological applications. In the present study, the morphology of B. subtilis spores was investigated by magnetically driven dynamic force microscopy (MAC mode atomic force microscopy) under physiological conditions. B. subtilis spores appeared as prolate structures, with a length of 0.6-3 microm and a width of about 0.5-2 microm. The spore surface was mainly covered with bump-like structures with diameters ranging from 8 to 70 nm. Besides topographical explorations, single molecule recognition force spectroscopy (SMRFS) was used to characterize the spore coat protein CotA. This protein was specifically recognized by a polyclonal antibody directed against CotA (anti-CotA), the antibody being covalently tethered to the AFM tip via a polyethylene glycol linker. The unbinding force between CotA and anti-CotA was determined as 55 +/- 2 pN. From the high-binding probability of more than 20% in force-distance cycles it is concluded that CotA locates in the outer surface of B. subtilis spores. Copyright (c) 2007 John Wiley & Sons, Ltd.

  13. Studies of iodine adsorption and desorption on HTGR coolant circuit materials

    International Nuclear Information System (INIS)

    Osborne, M.F.; Compere, E.L.; de Nordwall, H.J.

    1976-04-01

    Safety studies of the HTGR system indicate that radioactive iodine, released from the fuel to the helium coolant, may pose a problem of concern if no attenuation of the amount of iodine released occurs in the coolant circuit. Since information on iodine behavior in this system was incomplete, iodine adsorption on HTGR materials was studied in vacuum as a function of iodine pressure and of adsorber temperature. Iodine coverages on Fe 3 O 4 and Cr 2 O 3 approached maxima of about 2 x 10 14 and 1 x 10 14 atoms/cm 2 , respectively, whereas the iodine coverage on graphite under similar conditions was found to be less by a factor of about 100. Iodine desorption from the same materials into vacuum or flowing helium was investigated, on a limited basis, as a function of iodine coverage, of adsorber temperature, and of dry vs wet helium. The rate of vacuum desorption from Fe 3 O 4 was related to the spectrum of energies of the adsorption sites. A small amount of water vapor in the helium enhanced desorption from iron powder but appeared to have less effect on desorption from the metal oxides

  14. Activation of surface lattice oxygen in single-atom Pt/CeO 2 for low-temperature CO oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Nie, Lei; Mei, Donghai; Xiong, Haifeng; Peng, Bo; Ren, Zhibo; Pereira Hernandez, Xavier I.; DelaRiva, Andrew; Wang, Meng; Engelhard, Mark H.; Kovarik, Libor; Datye, Abhaya K.; Wang, Yong

    2017-12-14

    While single-atom catalysts can provide high catalytic activity and selectivity, application in industrial catalysts demands long term performance and the ability to regenerate the catalysts. We have investigated the factors that lead to improved catalytic activity of a Pt/CeO2 catalyst for low temperature CO oxidation. Single-atom Pt/CeO2 becomes active for CO oxidation under lean condition only at elevated temperatures, because CO is strongly bound to ionic Pt sites. Reducing the catalyst, even under mild conditions, leads to onset of CO oxidation activity even at room temperature. This high activity state involves the transformation of mononuclear Pt species to sub-nanometer sized Pt particles. Under oxidizing conditions, the Pt can be restored to its stable, single-atom state. The key to facile regeneration is the ability to create mobile Pt species and suitable trapping sites on the support, making this a prototypical catalyst system for industrial application of single-atom catalysis.

  15. The Status of Iodine Nutrition and Iodine Deficiency Disorders ...

    African Journals Online (AJOL)

    Background: Iodine deficiency disorders are serious public health problems in Ethiopia. The aim of this study was to measure the prevalence and severity of iodine deficiency disorders among school children in Metekel Zone. Methods: A cross-sectional school based descriptive study was conducted between February 2011 ...

  16. The method of local increments for the calculation of adsorption energies of atoms and small molecules on solid surfaces. Part I. A single Cu atom on the polar surfaces of ZnO.

    Science.gov (United States)

    Schmitt, Ilka; Fink, Karin; Staemmler, Volker

    2009-12-21

    The method of local increments is used in connection with the supermolecule approach and an embedded cluster model to calculate the adsorption energy of single Cu atoms at different adsorption sites at the polar surfaces of ZnO. Hartree-Fock calculations for the full system, adsorbed atom and solid surface, and for the fragments are the first step in this approach. In the present study, restricted open-shell Hartree-Fock (ROHF) calculations are performed since the Cu atom possesses a singly-occupied 4s orbital. The occupied Hartree-Fock orbitals are then localized by means of the Foster-Boys localization procedure. The correlation energies are expanded into a series of many-body increments which are evaluated separately and independently. In this way, the very time-consuming treatment of large systems is replaced with a series of much faster calculations for small subunits. In the present application, these subunits consist of the orbitals localized at the different atoms. Three adsorption situations with rather different bonding characteristics have been studied: a Cu atom atop a threefold-coordinated O atom of an embedded Zn(4)O(4) cluster, a Cu atom in an O vacancy site at the O-terminated ZnO(000-1) surface, and a Cu atom in a Zn vacancy site at the Zn-terminated ZnO(0001) surface. The following properties are analyzed in detail: convergence of the many-body expansion, contributions of the different n-body increments to the adsorption energy, treatment of the singly-occupied orbital as "localized" or "delocalized". Big savings in computer time can be achieved by this approach, particularly if only the localized orbitals in the individual increment under consideration are described by a large correlation adapted basis set, while all other orbitals are treated by a medium-size Hartree-Fock-type basis set. In this way, the method of local increments is a powerful alternative to the widely used methods like DFT or RI-MP2.

  17. Production of 131 Iodine in research reactors from elementary tellurium

    International Nuclear Information System (INIS)

    Silva, Constancia Pagano Goncalves da

    1970-01-01

    Presents the history of the production of iodine-131 in the Institute of Atomic Energy (IEA), SP, Brazil), the preliminary works for the development of the method, which were done in small scale and it was not necessary protection for the operators, the evolution of these operations until the final assembling of the equipment in shielded cells, the efficiency of operations and product purity. The problems linked to the presence of iodate in the preparations and the changes made for elimination of that ion, harmful to many types and use of iodine-131 are examined. The quality of the product delivered today, an average of 140 departures per month, and the number of departures, per year since the beginning of iodine-131 production were indicated

  18. Ductility loss of ion-irradiated zircaloy-2 in iodine

    International Nuclear Information System (INIS)

    Shimada, M.; Terasawa, M.; Yamamoto, S.; Kamei, H.; Koizumi, K.

    1981-01-01

    An ion bombardment simulation technique for neutron irradiation was applied to 'thick' materials to study the effect of radiation damage on the ductility change in Zircaloy-2 in an iodine environment. Specimens were prepared from actual cladding tubes and, prior to the irradiation, they were heat-treated in vacuo at 450, 580, and 700/degree/C for 2 h. Irradiation was performed by 52-MeV alpha particles up to the 0.32 displacements per atom (dpa) at 340/degree/C. Ductility loss begins to appear after 0.03 dpa irradiation, both in iodine and argon gas environments. The iodine presence resulted in ductility reduction, compared with the argon result in all irradiation dose ranges examined. The stress applied during irradiation caused ductility loss to commence at lower dosage than in the case of stress-free irradiation. These results are discussed in relation to the existing stress corrosion cracking models

  19. Electron-collision cross sections for iodine

    International Nuclear Information System (INIS)

    Zatsarinny, O.; Bartschat, K.; Garcia, G.; Blanco, F.; Hargreaves, L.R.; Jones, D.B.; Murrie, R.; Brunton, J.R.; Brunger, M.J.; Hoshino, M.; Buckman, S.J.

    2011-01-01

    We present results from a joint experimental and theoretical study of elastic electron scattering from atomic iodine. The experimental results were obtained by subtracting known cross sections from the measured data obtained with a pyrolyzed mixed beam containing a variety of atomic and molecular species. The calculations were performed using both a fully relativistic Dirac B-spline R-matrix (close-coupling) method and an optical model potential approach. Given the difficulty of the problem, the agreement between the two sets of theoretical predictions and the experimental data for the angle-differential and the angle-integrated elastic cross sections at 40 eV and 50 eV is satisfactory.

  20. Volatilization of iodine from vegetation

    Energy Technology Data Exchange (ETDEWEB)

    Amiro, B D; Johnston, F L [Atomic Energy of Canada Ltd., Pinawa, MB (Canada). Whiteshell Nuclear Research Establishment

    1989-01-01

    Gaseous emissions of iodine were measured from bean plant foliage. A gamma-emitting iodine tracer, Na {sup 125}I, was taken up by the plants from a hydroponic growth medium and released to a cuvette atmosphere. The dynamics of the flux were studied using a flow-through gamma detector. The relationship between leaf radioactive tracer activity and growth-medium activity was linear, as was the relationship between the iodine flux and both leaf and growth-medium activity. Iodine flux and leaf conductance to water responded similarly to changes in light levels, suggesting that the stomata may partially control the flux. The flux was inhibited by aeration of the hydroponic growth media, and we postulate that methylation causes the iodine flux. Iodine emissions from living vegetation probably contribute < 0.1% to the stable iodine concentration in the atmosphere above terrestrial areas. However, this pathway may be a direct route for radioactive iodine transport from contaminated soils to the atmosphere. (author).