WorldWideScience

Sample records for atomic substitution reveals

  1. Substitutionality of Ge atoms in ion implanted AlSb

    International Nuclear Information System (INIS)

    Yu, K.M.; Moll, A.J.; Chan, N.; Walukiewicz, W.; Becla, P.

    1995-01-01

    The substitution of Ge atoms into ion implanted AlSb is investigated by extended x-ray absorption fine structure spectroscopy. Our results reveal that in the as-implanted material, the implanted Ge atoms are equally distributed between two specific sites, one surrounded by Al atoms and the other surrounded by Sb atoms. After annealing at 750 degree C for 5 s, the coordination number of the Ge atoms increases from ∼3 to ∼4 indicating solid phase regrowth of the implantation induced amorphous surface layer. Moreover, in the annealed AlSb, the substitution of Ge atoms into the Al sublattice dominates with an estimated Ge Al :[Ge Sb ]∼0.8:0.2. These results suggest that Ge atoms act preferentially as donor species in AlSb

  2. Stereochemical consequences of recoil halogen atom substitution. Pt. 2

    International Nuclear Information System (INIS)

    Sharma, R.B.; Rack, E.P.; Ferrieri, R.A.; Wolf, A.P.

    1990-01-01

    The stereochemical consequencs of recoil 38 Cl-for-X (X = Br, Cl, F) atom substitutions in (2S, 3R)-dl- and (2S, 3S)-dl-bromofluorobutanes (BFB's) and in (2S, 3R)-dl- and (2S, 3S)-dl-chlorofluorobutanes (CFB's) were investigated in the gas phase as a function of kinetic energy moderator concentration. Results from exothermic 38 Cl-for-Br substitutions in the BFB stereoisomers revealed that the reaction stereochemistry changed from predominant retention configuration to predominant inversion of configuration with increasing kinetic energy moderator concentration. An inspection of individual yields revealed that the channel for inversion product formation was insensitive to moderator concentration, while the channel for retention product formation decreased in importance as the moderator concentration was increased. In contrast, results from thermoneutral 38 Cl-for-Cl and endothermic 38 Cl-for-F substitutions in the CFB stereoisomers revealed that reaction stereochemistry for both cases was insensitive to changes in the moderator concentration. An inspection of the individual product yields from both reactions revealed that the channels for retention and inversion product formation exhibited the same dependence on moderator concentration. Both channels decreased in importance as the moderator concentration was increased. (orig.)

  3. On-surface manipulation of atom substitution between cobalt phthalocyanine and the Cu(111) substrate

    DEFF Research Database (Denmark)

    Shen, Kongchao; Narsu, Bai; Ji, Gengwu

    2017-01-01

    (DFT). Interestingly, the scenario of atom exchange is discovered at the interface at room temperature (RT), namely the substitution of the cobalt atom in CoPc by a surface Cu adatom. Moreover, thermal annealing enhances the substitution process considerably which is demonstrated to be complete...... at about 573 K. As revealed by DFT calculations, the driving force for the observed interface transmetalation is most probably provided by the initial strong molecular-substrate interaction between Co atoms and the Cu(111) surface, the external thermodynamic energy gained from thermal sublimation...

  4. 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.

  5. Computational models of the single substitutional nitrogen atom in diamond

    CERN Document Server

    Lombardi, E B; Osuch, K; Reynhardt, E C

    2003-01-01

    The single substitutional nitrogen atom in diamond is apparently a very simple defect in a very simple elemental solid. It has been modelled by a range of computational models, few of which either agree with each other, or with the experimental data on the defect. If the computational models of less well understood defects in this and more complex materials are to be reliable, we should understand why the discrepancies arise and how they can be avoided in future modelling. This paper presents an all-electron, augmented plane-wave (APW) density functional theory (DFT) calculation using the modern APW with local orbitals full potential periodic approximation. This is compared to DFT, finite cluster pseudopotential calculations and a semi-empirical Hartree-Fock model. Comparisons between the results of these and previous models allow us to discuss the reliability of computational methods of this and similar defects.

  6. 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.

  7. Modeling hydrogen storage in boron-substituted graphene decorated with potassium metal atoms

    CSIR Research Space (South Africa)

    Tokarev, A

    2015-03-01

    Full Text Available Boron-substituted graphene decorated with potassium metal atoms was considered as a novel material for hydrogen storage. Density functional theory calculations were used to model key properties of the material, such as geometry, hydrogen packing...

  8. Enhancing atom densities in solid hydrogen by isotopic substitution

    International Nuclear Information System (INIS)

    Collins, G.W.; Souers, P.C.; Mapoles, E.R.; Magnotta, F.

    1991-01-01

    Atomic hydrogen inside solid H 2 increases the energy density by 200 MegaJoules/m 3 , for each percent mole fraction stored. How many atoms can be stored in solid hydrogen? To answer this, we need to know: (1) how to produce and trap hydrogen atoms in solid hydrogen, (2) how to keep the atoms from recombining into the ground molecular state, and (3) how to measure the atom density in solid hydrogen. Each of these topics will be addressed in this paper. Hydrogen atoms can be trapped in solid hydrogen by co-condensing atoms and molecules, external irradiation of solid H 2 , or introducing a radioactive impurity inside the hydrogen lattice. Tritium, a heavy isotope of hydrogen, is easily condensed as a radioactive isotopic impurity in solid H 2 . Although tritium will probably not be used in future rockets, it provides a way of applying a large, homogenious dose to solid hydrogen. In all of the data presented here, the atoms are produced by the decay of tritium and thus knowing how many atoms are produced from the tritium decay in the solid phase is important. 6 refs., 6 figs

  9. Change of Energy of the Cubic Subnanocluster of Iron Under Influence of Interstitial and Substitutional Atoms.

    Science.gov (United States)

    Nedolya, Anatoliy V; Bondarenko, Natalya V

    2016-12-01

    Energy change of an iron face-centred cubic subnanocluster was evaluated using molecular mechanics method depending on the position of a carbon interstitial atom and substitutional atoms of nickel. Calculations of all possible positions of impurity atoms show that the energy change of the system are discrete and at certain positions of the atoms are close to continuous.In terms of energy, when all impurity atoms are on the same edge of an atomic cluster, their positions are more advantageous. The presence of nickel atoms on the edge of a cubic cluster resulted in decrease of potential barrier for a carbon atom and decrease in energy in the whole cluster. A similar drift of a carbon atom from central octahedral interstitial site to the surface in the direction occurred under the influence of surface factors.Such configuration corresponds to decreasing symmetry and increasing the number of possible energy states of a subnanocluster, and it corresponds to the condition of spontaneous crystallization process in an isolated system.Taking into account accidental positions of the nickel atom in the iron cluster, such behaviour of the carbon atom can explain the mechanism of growth of a new phase and formation of new clusters in the presence of other kind of atoms because of surface influence.

  10. A first-principles study of light non-metallic atom substituted blue phosphorene

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Minglei [School of Mechanical Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Tang, Wencheng, E-mail: 101000185@seu.edu.cn [School of Mechanical Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Ren, Qingqiang [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, Hunan (China); Wang, Sa-ke [Department of Physics, Southeast University, Nanjing 210096, Jiangsu (China); Yu, Jin [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Advanced Metallic Materials, Southeast University, Nanjing 211189, Jiangsu (China); Du, Yanhui [School of Mechanical Engineering, Southeast University, Nanjing 211189, Jiangsu (China)

    2015-11-30

    Graphical abstract: - Highlights: • All the impurities are covalently bonded to blue phosphorene (with a single vacancy). • All the substituted systems are semiconductors. • B-substituted system exhibits direct bandgap semiconductor behavior. • The band gaps with spin polarization are found in C and O-substituted systems. • Our works can paves a new route at nanoscale for novel functionalities of optical and spintronics devices. - Abstract: First-principles calculations are implemented to study the geometric, electronic and magnetic properties of light non-metallic atom (B, C, N, O and F) substituted blue phosphorene. All the substituted systems are highly stable. The B-substituted system is a direct bandgap semiconductor with a bandgap size about 1.5 eV. The C, O-substituted systems are promising systems to explore two-dimensional diluted magnetic semiconductors. Magnetism is observed for C and O substitution, while for the other impurities no magnetic moment is detected. Our works paves a new route at nanoscale for novel functionalities of optical and spintronics devices.

  11. Atom diffraction reveals the impact of atomic core electrons on atom-surface potentials.

    Science.gov (United States)

    Lonij, Vincent P A; Klauss, Catherine E; Holmgren, William F; Cronin, Alexander D

    2010-12-03

    We measured ratios of van der Waals potential coefficients (C3) for different atoms (Li, Na, K, and Rb) interacting with the same surface by studying atom diffraction from a nanograting. These measurements are a sensitive test of atomic structure calculations because C3 ratios are strongly influenced by core electrons and only weakly influenced by the permittivity and geometry of the surface. Our measurement uncertainty of 2% in the ratio C(3)(K)/C(3)(Na) is close to the uncertainty of the best theoretical predictions, and some of these predictions are inconsistent with our measurement.

  12. Influence of substitutional atoms on the solubility limit of carbon in bcc iron

    International Nuclear Information System (INIS)

    Saitoh, Hajime; Ushioda, Kohsaku; Yoshinaga, Naoki; Yamada, Wataru

    2011-01-01

    The influence of substitutional atoms (Mn, Cr, Si, P, and Al) on the solubility limit of C in body-centered cubic iron in equilibrium with cementite was investigated in low-carbon steels at a temperature of 700 o C. The C solubility limit was determined from internal friction measurements combined with infrared analysis of C using a high-frequency combustion technique. Experiments clarified that Mn, Cr and Al hardly change the C solubility limit, whereas P and Si increase it.

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

    Science.gov (United States)

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

    2017-08-01

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

  14. Suppressing Isomerization of Phosphine-Protected Au9Cluster by Bond Stiffening Induced by a Single Pd Atom Substitution.

    Science.gov (United States)

    Yamazoe, Seiji; Matsuo, Shota; Muramatsu, Satoru; Takano, Shinjiro; Nitta, Kiyofumi; Tsukuda, Tatsuya

    2017-07-17

    The fluxional nature of small gold clusters has been exemplified by reversible isomerization between [Au 9 (PPh 3 ) 8 ] 3+ with a crown motif (Au 9 (C)) and that with a butterfly motif (Au 9 (B)) induced by association and dissociation with compact counteranions (NO 3 - , Cl - ). However, structural isomerization was suppressed by substitution of the central Au atom of the Au 9 core in [Au 9 (PPh 3 ) 8 ] 3+ with a Pd atom: [PdAu 8 (PPh 3 ) 8 ] 2+ with a crown motif (PdAu 8 (C)) did not isomerize to that with a butterfly motif (PdAu 8 (B)) upon association with the counteranions. Density functional theory calculation showed that the energy difference between PdAu 8 (C) and PdAu 8 (B) is comparable to that between Au 9 (C) and Au 9 (B), indicating that the relative stabilities of the isomers are not a direct cause for the suppression of isomerization. Temperature dependence of Debye-Waller factors obtained by X-ray absorption fine-structure analysis revealed that the intracluster bonds of PdAu 8 (C) were stiffer than the corresponding bonds in Au 9 (C). Natural bond orbital analysis suggested that the radial Pd-Au and lateral Au-Au bonds in PdAu 8 (C) are stiffened due to the increase in the ionic nature and decrease in electrostatic repulsion between the surface Au atoms, respectively. We conclude that the formation of stiffer metal-metal bonds by Pd atom doping inhibits the isomerization from PdAu 8 (C) to PdAu 8 (B).

  15. Nucleophilic Substitution (SN2): Dependence on Nucleophile, Leaving Group, Central Atom, Substituents, and Solvent.

    Science.gov (United States)

    Hamlin, Trevor A; Swart, Marcel; Bickelhaupt, F Matthias

    2018-03-15

    The reaction potential energy surface (PES) and, thus, the mechanism of bimolecular nucleophilic substitution (SN2) depend profoundly on the nature of the nucleophile and leaving group, but also on the central, electrophilic atom, its substituents, as well as on the medium in which the reaction takes place. Here, we provide an overview of recent studies and demonstrate how changes in any one of the aforementioned factors affect the SN2 mechanism. One of the most striking effects is the transition from a double-well to a single-well PES when the central atom is changed from a second-period (e.g., carbon) to a higher-period element (e.g., silicon, germanium). Variations in nucleophilicity, leaving group ability and bulky substituents around a second-row element central atom can then be exploited to change the single-well PES back into a double-well. Reversely, these variations can also be used to produce a single-well PES for second-period elements, e.g., a stable pentavalent carbon species. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Atom substitution effects of [XF6]- in ionic liquids. 2. Theoretical study.

    Science.gov (United States)

    Ishida, Tateki; Nishikawa, Keiko; Shirota, Hideaki

    2009-07-23

    Following the preceding spectroscopic study, we further investigate atomic mass effects of [XF6]- in 1-butyl-3-methylimidazolium cation ([BMIm]+) based ionic liquids (ILs) on dynamical natures by a computational approach in this study. We carry out the molecular dynamics simulations for 1-butyl-3-methylimidazolium cation based ILs ([BMIm][PF6], [BMIm][AsF6], and [BMIm][SbF6]) with the development of the force fields of [AsF6]- and [SbF6]- by an ab initio calculation. We have calculated density of state (DOS) and velocity autocorrelation function (VACF) profiles, polarizability time correlation function (TCF) and Kerr spectra, intermediate scattering functions, and dynamical structure factors. The decomposition analysis has been also carried out to understand the ion species and types of motion. From these computational studies, we find that the contribution of the reorientation of cations and anions mainly governs the Kerr spectrum profile in all three ILs, while the contribution of the collision-induced and cross terms, which are related to translational motions including coupling with librational motion, is not large at higher frequencies than 50 cm(-1). It is suggested that, with the atom substitution effects of anion units on interionic interactions, many properties in ILs are controllable. In addition, it is emphasized in this study that atomic mass effects in ILs are accessible through a complementary approach of both experimental and theoretical approaches.

  17. A Filtering Method to Reveal Crystalline Patterns from Atom Probe Microscopy Desorption Maps

    Science.gov (United States)

    2016-03-26

    reveal crystalline patterns from atom probe microscopy desorption maps Lan Yao Department of Materials Science and Engineering, University of Michigan, Ann...reveal the crystallographic information present in Atom Probe Microscopy (APM) data is presented. Themethod filters atoms based on the time difference...between their evaporation and the evaporation of the previous atom . Since this time difference correlates with the location and the local structure of

  18. Sample preparation for arsenic speciation analysis in baby food by generation of substituted arsines with atomic absorption spectrometry detection

    Czech Academy of Sciences Publication Activity Database

    Huber, C. S.; Vale, M. G. R.; Dessuy, M. B.; Svoboda, Milan; Musil, Stanislav; Dědina, Jiří

    2017-01-01

    Roč. 175, DEC (2017), s. 406-412 ISSN 0039-9140 R&D Projects: GA MŠk(CZ) LH15174 Institutional support: RVO:68081715 Keywords : slurry sampling * methyl-substituted arsenic species * hydride generation-cryotrapping-atomic absorption spectrometry Subject RIV: CB - Analytical Chemistry, Separation OBOR OECD: Analytical chemistry Impact factor: 4.162, year: 2016

  19. Sample preparation for arsenic speciation analysis in baby food by generation of substituted arsines with atomic absorption spectrometry detection

    Czech Academy of Sciences Publication Activity Database

    Huber, C. S.; Vale, M. G. R.; Dessuy, M. B.; Svoboda, Milan; Musil, Stanislav; Dědina, Jiří

    2017-01-01

    Roč. 175, DEC (2017), s. 406-412 ISSN 0039-9140 R&D Projects: GA MŠk(CZ) LH15174 Institutional support: RVO:68081715 Keywords : slurry sampling * methyl-substituted arsenic species * hydride generation-cryotrapping- atomic absorption spectrometry Subject RIV: CB - Analytical Chemistry, Separation OBOR OECD: Analytical chemistry Impact factor: 4.162, year: 2016

  20. Influence of substitutional pairs of cobalt atoms on the magnetocrystalline anisotropy of cobalt-rich rare-earth compounds

    International Nuclear Information System (INIS)

    Deportes, J.; Givord, D.; Lemaire, R.; Nagai, H.; Yang, Y.T.

    1976-01-01

    The crystallographic structures of cobalt-rich rare-earth (R) compounds are determined by the ordering of substitutional pairs of Co atoms in the same hexagonal RCo 5 basic structure. However, RCo 5 compounds are metastable at room temperature and contain some disordered substitutions. These substitutions induce a large decrease of the anisotropy in Smsub(1-s)2Cosub(s)Co 5 and Ysub(1-s)2Cosub(s)Co 5 alloys. Consequently, with each substitution there is associated a large anisotropy with a negative value of K 1 . A comparison with the strong uniaxial anisotropy of the RCo 5 basic structure allows one to explain the changes of the direction of easy magnetization in Y 2 (Cosub(1-x)Msub(x)) alloys, and the differences in the coercivity of RCo 5 compounds. (Auth.)

  1. Dependencies of photoelectric properties of SiC/Si structures grown by the method of atoms substitution on synthesis time

    Science.gov (United States)

    Grashchenko, A. S.; Kukushkin, S. A.; Osipov, A. V.; Feoktistov, N. A.

    2017-07-01

    This paper is dedicated to an exploration of the photoelectric properties of Si-SiC structures grown by the substitution method on silicon substrates of (001) orientation. For the samples with the synthesis times of 40, 60, 90, 120 and 900 s, magnitudes of the saturation currents are determined and the coefficients of efficiency are calculated. The obtained dependencies of the photoelectric characteristics on the synthesis time are explained using the theory of formation of dilatation dipoles during the synthesis by the method of atoms substitution.

  2. Atom Probe Tomographic Mapping Directly Reveals the Atomic Distribution of Phosphorus in Resin Embedded Ferritin

    Science.gov (United States)

    Perea, Daniel E.; Liu, Jia; Bartrand, Jonah; Dicken, Quinten; Thevuthasan, S. Theva; Browning, Nigel D.; Evans, James E.

    2016-01-01

    Here we report the atomic-scale analysis of biological interfaces within the ferritin protein using atom probe tomography that is facilitated by an advanced specimen preparation approach. Embedding ferritin in an organic polymer resin lacking nitrogen provided chemical contrast to visualise atomic distributions and distinguish the inorganic-organic interface of the ferrihydrite mineral core and protein shell, as well as the organic-organic interface between the ferritin protein shell and embedding resin. In addition, we definitively show the atomic-scale distribution of phosphorus as being at the surface of the ferrihydrite mineral with the distribution of sodium mapped within the protein shell environment with an enhanced distribution at the mineral/protein interface. The sample preparation method is robust and can be directly extended to further enhance the study of biological, organic and inorganic nanomaterials relevant to health, energy or the environment. PMID:26924804

  3. Revealing Quantum Statistics with a Pair of Distant Atoms

    Science.gov (United States)

    Roos, C. F.; Alberti, A.; Meschede, D.; Hauke, P.; Häffner, H.

    2017-10-01

    Quantum statistics have a profound impact on the properties of systems composed of identical particles. At the most elementary level, Bose and Fermi quantum statistics differ in the exchange phase, either 0 or π , which the wave function acquires when two identical particles are exchanged. In this Letter, we demonstrate that the exchange phase can be directly probed with a pair of massive particles by physically exchanging their positions. We present two protocols where the particles always remain spatially well separated, thus ensuring that the exchange contribution to their interaction energy is negligible and that the detected signal can only be attributed to the exchange symmetry of the wave function. We discuss possible implementations with a pair of trapped atoms or ions.

  4. A Rapid Colorimetric Method Reveals Fraudulent Substitutions in Sea Urchin Roe Marketed in Sardinia (Italy).

    Science.gov (United States)

    Meloni, Domenico; Spina, Antonio; Satta, Gianluca; Chessa, Vittorio

    2016-06-25

    In recent years, besides the consumption of fresh sea urchin specimens, the demand of minimally-processed roe has grown considerably. This product has made frequent consumption in restaurants possible and frauds are becoming widespread with the partial replacement of sea urchin roe with surrogates that are similar in colour. One of the main factors that determines the quality of the roe is its colour and small differences in colour scale cannot be easily discerned by the consumers. In this study we have applied a rapid colorimetric method for reveal the fraudulent partial substitution of semi-solid sea urchin roe with liquid egg yolk. Objective assessment of whiteness (L*), redness (a*), yellowness (b*), hue (h*), and chroma (C*) was carried out with a digital spectrophotometer using the CIE L*a*b* colour measurement system. The colorimetric method highlighted statistically significant differences among sea urchin roe and liquid egg yolk that could be easily discerned quantitatively.

  5. 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

  6. Flexibility and Stability in Sensory Processing Revealed Using Visual-to-Auditory Sensory Substitution

    Science.gov (United States)

    Hertz, Uri; Amedi, Amir

    2015-01-01

    The classical view of sensory processing involves independent processing in sensory cortices and multisensory integration in associative areas. This hierarchical structure has been challenged by evidence of multisensory responses in sensory areas, and dynamic weighting of sensory inputs in associative areas, thus far reported independently. Here, we used a visual-to-auditory sensory substitution algorithm (SSA) to manipulate the information conveyed by sensory inputs while keeping the stimuli intact. During scan sessions before and after SSA learning, subjects were presented with visual images and auditory soundscapes. The findings reveal 2 dynamic processes. First, crossmodal attenuation of sensory cortices changed direction after SSA learning from visual attenuations of the auditory cortex to auditory attenuations of the visual cortex. Secondly, associative areas changed their sensory response profile from strongest response for visual to that for auditory. The interaction between these phenomena may play an important role in multisensory processing. Consistent features were also found in the sensory dominance in sensory areas and audiovisual convergence in associative area Middle Temporal Gyrus. These 2 factors allow for both stability and a fast, dynamic tuning of the system when required. PMID:24518756

  7. A filtering method to reveal crystalline patterns from atom probe microscopy desorption maps.

    Science.gov (United States)

    Yao, Lan

    2016-01-01

    A filtering method to reveal the crystallographic information present in Atom Probe Microscopy (APM) data is presented. The method filters atoms based on the time difference between their evaporation and the evaporation of the previous atom. Since this time difference correlates with the location and the local structure of the evaporating atoms on the surface, it can be used to reveal any crystallographic information contained within APM data. The demonstration of this method is illustrated on: •A pure Al specimen for which crystallographic poles are clearly visible on the desorption patterns easily indexed.•Three Fe-15at.% Cr datasets where crystallographic patterns are less obvious and require this filtering method.

  8. Listeria bacteriophage peptidoglycan hydrolases feature high thermoresistance and reveal increased activity after divalent metal cation substitution.

    Science.gov (United States)

    Schmelcher, Mathias; Waldherr, Florian; Loessner, Martin J

    2012-01-01

    The ability of the bacteriophage-encoded peptidoglycan hydrolases (endolysins) to destroy Gram-positive bacteria from without makes these enzymes promising antimicrobials. Recombinant endolysins from Listeria monocytogenes phages have been shown to rapidly lyse and kill the pathogen in all environments. To determine optimum conditions regarding application of recombinant Listeria phage endolysins in food or production equipments, properties of different Listeria endolysins were studied. Optimum NaCl concentration for the amidase HPL511 was 200 nM and 300 mM for the peptidases HPL118, HPL500, and HPLP35. Unlike most other peptidoglycan hydrolases, all four enzymes exhibited highest activity at elevated pH values at around pH 8-9. Lytic activity was abolished by EDTA and could be restored by supplementation with various divalent metal cations, indicating their role in catalytic function. While substitution of the native Zn(2+) by Ca(2+) or Mn(2+) was most effective in case of HPL118, HPL500, and HPLP35, supplementation with Co(2+) and Mn(2+) resulted in an approximately 5-fold increase in HPL511 activity. Interestingly, the glutamate peptidases feature a conserved SxHxxGxAxD zinc-binding motif, which is not present in the amidases, although they also require centrally located divalent metals for activity. The endolysins HPL118, HPL511, and HPLP35 revealed a surprisingly high thermostability, with up to 35% activity remaining after 30 min incubation at 90°C. The available data suggest that denaturation at elevated temperatures is reversible and may be followed by rapid refolding into a functional state.

  9. Comparative proteomics and codon substitution analysis reveal mechanisms of differential resistance to hypoxia in congeneric snails.

    Science.gov (United States)

    Mu, Huawei; Sun, Jin; Cheung, Siu Gin; Fang, Ling; Zhou, Haiyun; Luan, Tiangang; Zhang, Huoming; Wong, Chris K C; Qiu, Jian-Wen

    2018-02-10

    Although high-throughput proteomics has been widely applied to study mechanisms of environmental adaptation, the conclusions from studies that are based on one species can be confounded by phylogeny. We compare the freshwater snail Pomacea canaliculata (a notorious invasive species) and its congener Pomacea diffusa (a non-invasive species) to understand the molecular mechanisms of their differential resistance to hypoxia. A 72-h acute exposure experiment showed that P. canaliculata is more tolerant to hypoxia than P. diffusa. The two species were then exposed to three levels of dissolved oxygen (6.7, 2.0 and 1.0mgL -1 ) for 8h, and their gill proteins were analyzed using iTRAQ-coupled LC-MS/MS. The two species showed striking differences in protein expression profiles, with the more hypoxia tolerant P. canaliculata having more up-regulated proteins in signal transduction and down-regulated proteins in glycolysis and the tricarboxylic acid cycle. Evolutionary analysis revealed five orthologous genes encoding differentially expressed proteins having clear signal of positive selection, indicating selection has acted on some of the hypoxia responsive genes. Our case study has highlighted the potential of integrated proteomics and comparative evolutionary analysis for understanding the genetic basis of adaptation to global environmental change in non-model species. Rapid globalization in recent decades has greatly facilitated species introduction around the world. Successfully established introduced species, so-called invasive species, have threatened the invaded ecosystems. There has been substantial interest in studying how invasive species respond to extreme environmental conditions because the results can help not only predict their range of expansion and manage their impact, but also may reveal the adaptive mechanisms underlying their invasiveness. Our study has adopted a comparative approach to study the differential physiological and proteomic responses of two

  10. Comparative proteomics and codon substitution analysis reveal mechanisms of differential resistance to hypoxia in congeneric snails

    KAUST Repository

    Mu, Huawei

    2017-11-06

    Although high-throughput proteomics has been widely applied to study mechanisms of environmental adaptation, the conclusions from studies that are based on one species can be confounded by phylogeny. We compare the freshwater snail Pomacea canaliculata (a notorious invasive species) and its congener Pomacea diffusa (a non-invasive species) to understand the molecular mechanisms of their differential resistance to hypoxia. A 72-h acute exposure experiment showed that P. canaliculata is more tolerant to hypoxia than P. diffusa. The two species were then exposed to three levels of dissolved oxygen (6.7, 2.0 and 1.0mgL−1) for 8h, and their gill proteins were analyzed using iTRAQ-coupled LC-MS/MS. The two species showed striking differences in protein expression profiles, with the more hypoxia tolerant P. canaliculata having more up-regulated proteins in signal transduction and down-regulated proteins in glycolysis and the tricarboxylic acid cycle. Evolutionary analysis revealed five orthologous genes encoding differentially expressed proteins having clear signal of positive selection, indicating selection has acted on some of the hypoxia responsive genes. Our case study has highlighted the potential of integrated proteomics and comparative evolutionary analysis for understanding the genetic basis of adaptation to global environmental change in non-model species. SignificanceRapid globalization in recent decades has greatly facilitated species introduction around the world. Successfully established introduced species, so-called invasive species, have threatened the invaded ecosystems. There has been substantial interest in studying how invasive species respond to extreme environmental conditions because the results can help not only predict their range of expansion and manage their impact, but also may reveal the adaptive mechanisms underlying their invasiveness. Our study has adopted a comparative approach to study the differential physiological and proteomic

  11. Spectacular enhancement of thermoelectric phenomena in chemically synthesized graphene nanoribbons with substitution atoms.

    Science.gov (United States)

    Zberecki, K; Swirkowicz, R; Wierzbicki, M; Barnaś, J

    2016-07-21

    We analyze theoretically the transport and thermoelectric properties of graphene nanoribbons of a specific geometry, which have been synthesized recently from polymers [Cai, et al., Nature, 2011, 466, 470]. When such nanoribbons are modified at one of the two edges by Al or N substitutions, they acquire a ferromagnetic moment localized at the modified edge. We present numerical results on the electronic structure and thermoelectric properties (including also spin thermoelectricity) of the modified nanoribbons. The results show that such nanoribbons can display large thermoelectric efficiency in certain regions of chemical potential, where the corresponding electric and spin figures of merit achieve unusually large values. The enhancement of thermoelectric efficiency follows from a reduced phonon heat conductance of the nanoribbons and from their peculiar electronic band structure. Thus, such nanoribbons are promising for practical applications in nanoelectronic and spintronic devices.

  12. A General Catalytic Method for Nucleophilic Substitutions in High Cost- and Atom-Efficiency.

    Science.gov (United States)

    Huy, Peter; Filbrich, Isabel

    2018-03-05

    Herein, a general formamide catalyzed protocol for the efficient transformation of alcohols into alkyl chlorides, which is promoted by substoichiometric amounts (down to 34 mol%) of inexpensive trichlorotriazine (TCT), is introduced. Importantly, the present work is the first example of a TCT mediated dehydroxychlorination of an OH-group containing substrate (e. g. alcohols and carboxylic acid), in which all three chlorine atoms of TCT are transferred onto the starting material. The consequently enhanced atom-economy facilitates a significantly improved waste balance (E-factors down to 4), cost-efficiency and scalability (>50 g). Furthermore, the current procedure is distinguished by high levels of functional group compatibility and stereoselectivity, as only weakly acidic cyanuric acid is released as exclusive by-product. Finally, a one-pot protocol for the preparation of amines, azides, ethers and sulfides enabled the synthesis of the drug Rivastigmine under twofold SN2-inversion, which demonstrates the high practical value of the presented method. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Resolving mass spectral overlaps in atom probe tomography by isotopic substitutions - case of TiSi15N.

    Science.gov (United States)

    Engberg, David L J; Johnson, Lars J S; Jensen, Jens; Thuvander, Mattias; Hultman, Lars

    2018-01-01

    Mass spectral overlaps in atom probe tomography (APT) analyses of complex compounds typically limit the identification of elements and microstructural analysis of a material. This study concerns the TiSiN system, chosen because of severe mass-to-charge-state ratio overlaps of the 14 N + and 28 Si 2+ peaks as well as the 14 N 2 + and 28 Si + peaks. By substituting 14 N with 15 N, mass spectrum peaks generated by ions composed of one or more N atoms will be shifted toward higher mass-to-charge-state ratios, thereby enabling the separation of N from the predominant Si isotope. We thus resolve thermodynamically driven Si segregation on the nanometer scale in cubic phase Ti 1- x Si x 15 N thin films for Si contents 0.08 ≤ x ≤ 0.19 by APT, as corroborated by transmission electron microscopy. The APT analysis yields a composition determination that is in good agreement with energy dispersive X-ray spectroscopy and elastic recoil detection analyses. Additionally, a method for determining good voxel sizes for visualizing small-scale fluctuations is presented and demonstrated for the TiSiN system. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Experimental observations of rapid Maize streak virus evolution reveal a strand-specific nucleotide substitution bias

    Directory of Open Access Journals (Sweden)

    Varsani Arvind

    2008-09-01

    Full Text Available Abstract Background Recent reports have indicated that single-stranded DNA (ssDNA viruses in the taxonomic families Geminiviridae, Parvoviridae and Anellovirus may be evolving at rates of ~10-4 substitutions per site per year (subs/site/year. These evolution rates are similar to those of RNA viruses and are surprisingly high given that ssDNA virus replication involves host DNA polymerases with fidelities approximately 10 000 times greater than those of error-prone viral RNA polymerases. Although high ssDNA virus evolution rates were first suggested in evolution experiments involving the geminivirus maize streak virus (MSV, the evolution rate of this virus has never been accurately measured. Also, questions regarding both the mechanistic basis and adaptive value of high geminivirus mutation rates remain unanswered. Results We determined the short-term evolution rate of MSV using full genome analysis of virus populations initiated from cloned genomes. Three wild type viruses and three defective artificial chimaeric viruses were maintained in planta for up to five years and displayed evolution rates of between 7.4 × 10-4 and 7.9 × 10-4 subs/site/year. Conclusion These MSV evolution rates are within the ranges observed for other ssDNA viruses and RNA viruses. Although no obvious evidence of positive selection was detected, the uneven distribution of mutations within the defective virus genomes suggests that some of the changes may have been adaptive. We also observed inter-strand nucleotide substitution imbalances that are consistent with a recent proposal that high mutation rates in geminiviruses (and possibly ssDNA viruses in general may be due to mutagenic processes acting specifically on ssDNA molecules.

  15. 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)

  16. Electron self-exchange in hemoglobins revealed by deutero-hemin substitution.

    Science.gov (United States)

    Athwal, Navjot Singh; Alagurajan, Jagannathan; Sturms, Ryan; Fulton, D Bruce; Andreotti, Amy H; Hargrove, Mark S

    2015-09-01

    Hemoglobins (phytoglobins) from rice plants (nsHb1) and from the cyanobacterium Synechocystis (PCC 6803) (SynHb) can reduce hydroxylamine with two electrons to form ammonium. The reaction requires intermolecular electron transfer between protein molecules, and rapid electron self-exchange might play a role in distinguishing these hemoglobins from others with slower reaction rates, such as myoglobin. A relatively rapid electron self-exchange rate constant has been measured for SynHb by NMR, but the rate constant for myoglobin is equivocal and a value for nsHb1 has not yet been measured. Here we report electron self-exchange rate constants for nsHb1 and Mb as a test of their role in hydroxylamine reduction. These proteins are not suitable for analysis by NMR ZZ exchange, so a method was developed that uses cross-reactions between each hemoglobin and its deutero-hemin substituted counterpart. The resulting electron transfer is between identical proteins with low driving forces and thus closely approximates true electron self-exchange. The reactions can be monitored spectrally due to the distinct spectra of the prosthetic groups, and from this electron self-exchange rate constants of 880 (SynHb), 2900 (nsHb1), and 0.05M(-1) s(-1) (Mb) have been measured for each hemoglobin. Calculations of cross-reactions using these values accurately predict hydroxylamine reduction rates for each protein, suggesting that electron self-exchange plays an important role in the reaction. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Revealing the correlation between real-space structure and chiral magnetic order at the atomic scale

    Science.gov (United States)

    Hauptmann, Nadine; Dupé, Melanie; Hung, Tzu-Chao; Lemmens, Alexander K.; Wegner, Daniel; Dupé, Bertrand; Khajetoorians, Alexander A.

    2018-03-01

    We image simultaneously the geometric, the electronic, and the magnetic structures of a buckled iron bilayer film that exhibits chiral magnetic order. We achieve this by combining spin-polarized scanning tunneling microscopy and magnetic exchange force microscopy (SPEX) to independently characterize the geometric as well as the electronic and magnetic structures of nonflat surfaces. This new SPEX imaging technique reveals the geometric height corrugation of the reconstruction lines resulting from strong strain relaxation in the bilayer, enabling the decomposition of the real-space from the electronic structure at the atomic level and the correlation with the resultant spin-spiral ground state. By additionally utilizing adatom manipulation, we reveal the chiral magnetic ground state of portions of the unit cell that were not previously imaged with spin-polarized scanning tunneling microscopy alone. Using density functional theory, we investigate the structural and electronic properties of the reconstructed bilayer and identify the favorable stoichiometry regime in agreement with our experimental result.

  18. The Slow:Fast substitution ratio reveals changing patterns of natural selection in gamma-proteobacterial genomes

    Energy Technology Data Exchange (ETDEWEB)

    Alm, Eric; Shapiro, B. Jesse

    2009-04-15

    Different microbial species are thought to occupy distinct ecological niches, subjecting each species to unique selective constraints, which may leave a recognizable signal in their genomes. Thus, it may be possible to extract insight into the genetic basis of ecological differences among lineages by identifying unusual patterns of substitutions in orthologous gene or protein sequences. We use the ratio of substitutions in slow versus fast-evolving sites (nucleotides in DNA, or amino acids in protein sequence) to quantify deviations from the typical pattern of selective constraint observed across bacterial lineages. We propose that elevated S:F in one branch (an excess of slow-site substitutions) can indicate a functionally-relevant change, due to either positive selection or relaxed evolutionary constraint. In a genome-wide comparative study of gamma-proteobacterial proteins, we find that cell-surface proteins involved with motility and secretion functions often have high S:F ratios, while information-processing genes do not. Change in evolutionary constraints in some species is evidenced by increased S:F ratios within functionally-related sets of genes (e.g., energy production in Pseudomonas fluorescens), while other species apparently evolve mostly by drift (e.g., uniformly elevated S:F across most genes in Buchnera spp.). Overall, S:F reveals several species-specific, protein-level changes with potential functional/ecological importance. As microbial genome projects yield more species-rich gene-trees, the S:F ratio will become an increasingly powerful tool for uncovering functional genetic differences among species.

  19. Effect of a bulky lateral substitution by chlorine atom and methoxy group on self-assembling properties of lactic acid derivatives

    International Nuclear Information System (INIS)

    Stojanović, Maja; Bubnov, Alexej; Obadović, Dušanka Ž.; Hamplová, Věra; Cvetinov, Miroslav; Kašpar, Miroslav

    2014-01-01

    Several chiral liquid crystalline materials derived from the lactic acid have been studied with the aim to establish the effect of bulky lateral substituents on their self-assembling properties. A chlorine atom and methoxy group have been used as lateral substituents in ortho position to ether group position on phenyl ring far from the chiral centre. All the studied materials possess tilted ferroelectric smectic C* phase in a broad temperature range. In dependence on the molecular structure namely type of lateral substituent and length of the chiral chain, the cholesteric mesophase, orthogonal paraelectric smectic A* and crystal mesophases have been detected. Lateral chlorine substitution results in decrease of both the clearing point and crystallisation temperature as well as in a distinct increase of spontaneous polarization. Bulky methoxy substitution slightly suppresses the spontaneous polarisation but strongly increases the melting point that results in monotropic peculiarity of the SmC* phase. Mesomorphic, spontaneous, structural and dielectric properties of the substituted compounds were established and compared to those of the non-substituted ones in order to contribute to better understanding of the structure–property relationship for such chiral self-assembling materials. - Highlights: • Chiral liquid crystalline materials derived from the lactic acid have been studied. • Effect of bulky lateral substituents on self-assembling properties has been established. • Bulky methoxy substitution suppresses spontaneous polarisation but increases the melting point. • The compounds might have a strong potential for many advanced electro-optic applications

  20. Isotope Substitution of Promiscuous Alcohol Dehydrogenase Reveals the Origin of Substrate Preference in the Transition State.

    Science.gov (United States)

    Behiry, Enas M; Ruiz-Pernia, J Javier; Luk, Louis; Tuñón, Iñaki; Moliner, Vicent; Allemann, Rudolf K

    2018-03-12

    The origin of substrate preference in promiscuous enzymes was investigated by enzyme isotope labelling of the alcohol dehydrogenase from Geobacillus stearothermophilus (BsADH). At physiological temperature, protein dynamic coupling to the reaction coordinate was insignificant. However, the extent of dynamic coupling was highly substrate-dependent at lower temperatures. For benzyl alcohol, an enzyme isotope effect larger than unity was observed, whereas the enzyme isotope effect was close to unity for isopropanol. Frequency motion analysis on the transition states revealed that residues surrounding the active site undergo substantial displacement during catalysis for sterically bulky alcohols. BsADH prefers smaller substrates, which cause less protein friction along the reaction coordinate and reduced frequencies of dynamic recrossing. This hypothesis allows a prediction of the trend of enzyme isotope effects for a wide variety of substrates. © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  1. Deformation-induced trace element redistribution in zircon revealed using atom probe tomography.

    Science.gov (United States)

    Piazolo, Sandra; La Fontaine, Alexandre; Trimby, Patrick; Harley, Simon; Yang, Limei; Armstrong, Richard; Cairney, Julie M

    2016-02-12

    Trace elements diffuse negligible distances through the pristine crystal lattice in minerals: this is a fundamental assumption when using them to decipher geological processes. For example, the reliable use of the mineral zircon (ZrSiO4) as a U-Th-Pb geochronometer and trace element monitor requires minimal radiogenic isotope and trace element mobility. Here, using atom probe tomography, we document the effects of crystal-plastic deformation on atomic-scale elemental distributions in zircon revealing sub-micrometre-scale mechanisms of trace element mobility. Dislocations that move through the lattice accumulate U and other trace elements. Pipe diffusion along dislocation arrays connected to a chemical or structural sink results in continuous removal of selected elements (for example, Pb), even after deformation has ceased. However, in disconnected dislocations, trace elements remain locked. Our findings have important implications for the use of zircon as a geochronometer, and highlight the importance of deformation on trace element redistribution in minerals and engineering materials.

  2. Deformation-induced trace element redistribution in zircon revealed using atom probe tomography

    Science.gov (United States)

    Piazolo, Sandra; La Fontaine, Alexandre; Trimby, Patrick; Harley, Simon; Yang, Limei; Armstrong, Richard; Cairney, Julie M.

    2016-01-01

    Trace elements diffuse negligible distances through the pristine crystal lattice in minerals: this is a fundamental assumption when using them to decipher geological processes. For example, the reliable use of the mineral zircon (ZrSiO4) as a U-Th-Pb geochronometer and trace element monitor requires minimal radiogenic isotope and trace element mobility. Here, using atom probe tomography, we document the effects of crystal–plastic deformation on atomic-scale elemental distributions in zircon revealing sub-micrometre-scale mechanisms of trace element mobility. Dislocations that move through the lattice accumulate U and other trace elements. Pipe diffusion along dislocation arrays connected to a chemical or structural sink results in continuous removal of selected elements (for example, Pb), even after deformation has ceased. However, in disconnected dislocations, trace elements remain locked. Our findings have important implications for the use of zircon as a geochronometer, and highlight the importance of deformation on trace element redistribution in minerals and engineering materials. PMID:26868040

  3. Near-atomic structure of Japanese encephalitis virus reveals critical determinants of virulence and stability.

    Science.gov (United States)

    Wang, Xiangxi; Li, Shi-Hua; Zhu, Ling; Nian, Qing-Gong; Yuan, Shuai; Gao, Qiang; Hu, Zhongyu; Ye, Qing; Li, Xiao-Feng; Xie, Dong-Yang; Shaw, Neil; Wang, Junzhi; Walter, Thomas S; Huiskonen, Juha T; Fry, Elizabeth E; Qin, Cheng-Feng; Stuart, David I; Rao, Zihe

    2017-04-26

    Although several different flaviviruses may cause encephalitis, Japanese encephalitis virus is the most significant, being responsible for thousands of deaths each year in Asia. The structural and molecular basis of this encephalitis is not fully understood. Here, we report the cryo-electron microscopy structure of mature Japanese encephalitis virus at near-atomic resolution, which reveals an unusual "hole" on the surface, surrounded by five encephalitic-specific motifs implicated in receptor binding. Glu138 of E, which is highly conserved in encephalitic flaviviruses, maps onto one of these motifs and is essential for binding to neuroblastoma cells, with the E138K mutation abrogating the neurovirulence and neuroinvasiveness of Japanese encephalitis virus in mice. We also identify structural elements modulating viral stability, notably Gln264 of E, which, when replaced by His264 strengthens a hydrogen-bonding network, leading to a more stable virus. These studies unveil determinants of neurovirulence and stability in Japanese encephalitis virus, opening up new avenues for therapeutic interventions against neurotropic flaviviruses.Japanese encephalitis virus (JEV) is a Flavivirus responsible for thousands of deaths every year for which there are no specific anti-virals. Here, Wang et al. report the cryo-EM structure of mature JEV at near-atomic resolution and identify structural elements that modulate stability and virulence.

  4. An atomic model of HIV-1 capsid-SP1 reveals structures regulating assembly and maturation.

    Science.gov (United States)

    Schur, Florian K M; Obr, Martin; Hagen, Wim J H; Wan, William; Jakobi, Arjen J; Kirkpatrick, Joanna M; Sachse, Carsten; Kräusslich, Hans-Georg; Briggs, John A G

    2016-07-29

    Immature HIV-1 assembles at and buds from the plasma membrane before proteolytic cleavage of the viral Gag polyprotein induces structural maturation. Maturation can be blocked by maturation inhibitors (MIs), thereby abolishing infectivity. The CA (capsid) and SP1 (spacer peptide 1) region of Gag is the key regulator of assembly and maturation and is the target of MIs. We applied optimized cryo-electron tomography and subtomogram averaging to resolve this region within assembled immature HIV-1 particles at 3.9 angstrom resolution and built an atomic model. The structure reveals a network of intra- and intermolecular interactions mediating immature HIV-1 assembly. The proteolytic cleavage site between CA and SP1 is inaccessible to protease. We suggest that MIs prevent CA-SP1 cleavage by stabilizing the structure, and MI resistance develops by destabilizing CA-SP1. Copyright © 2016, American Association for the Advancement of Science.

  5. Giant Gas Cloud Made of Atoms Formed in First Stars Revealed in Universe's Most Distant Quasar

    Science.gov (United States)

    2003-07-01

    Astronomers studying the most distant quasar yet found in the Universe have discovered a massive reservoir of gas containing atoms made in the cores of some of the first stars ever formed. The carbon-monoxide gas was revealed by the National Science Foundation's Very Large Array (VLA) and the Plateau de Bure radio interferometer in Europe. The gas, along with the young galaxy containing it, is seen as it was when the Universe was only one-sixteenth its current age, just emerging from the primeval "Dark Ages" before light could travel freely through the cosmos. VLA Image of Quasar VLA Image of J1148+5251 CREDIT: NRAO/AUI/NSF (Click on Image for Larger Version) "Our discovery of this much carbon monoxide gas in such an extremely distant and young galaxy is surprising. It means that, even at a very early time in the history of the Universe, galaxies already had huge amounts of molecular gas that would eventually form new generations of stars," said Chris Carilli, of the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. The distant galaxy, dubbed J1148+5251, contains a bright quasar powered by a black hole at least a billion times more massive than the Sun. The galaxy is seen as it was only 870 million years after the Big Bang. The Universe now is 13.7 billion years old. J1148+5251 would have been among the first luminous objects in the Universe. The original atoms formed in the Universe within the first three minutes of the Big Bang were only hydrogen and helium. Carbon and oxygen -- the atoms making up carbon monoxide -- had to be made in the thermonuclear furnaces at the cores of the earliest stars. "The carbon and oxygen atoms in the gas we detected were made by some of the first stars ever formed, only about 650 million years after the Big Bang. In the next 200 million years or so, those stars -- probably very different stars from those we see today -- exploded as supernovae, spreading the carbon and oxygen out into space. Those atoms then cooled

  6. [Synthesis and biological activity of 1,4-benzoquinone-guanylhydrazone-thiosemicarbazone analogs. 1. Substitution at the S atom].

    Science.gov (United States)

    Schulze, W; Gutsche, W; Wohlrabe, K; Fleck, W; Tresselt, D

    1985-08-01

    The synthesis of S-substituted derivatives of 1,4-benzoquinone-guanylhydrazone-thiosemicarbazone is described. The obtained 1,4-benzoquinone-guanylhydrazone-S-alkyl (resp. aralkyl)-isothiosemicarbazones, in comparison with the unsubstituted standard compound, showed a significantly decreased biological activity against the murine leukemias L 1210 and P 388 as well as against the growth of several kinds of bacteria. Therefore the S-substitution seems not to be useful for reaching a maximum activity.

  7. The asymmetrical structure of Golgi apparatus membranes revealed by in situ atomic force microscope.

    Directory of Open Access Journals (Sweden)

    Haijiao Xu

    Full Text Available The Golgi apparatus has attracted intense attentions due to its fascinating morphology and vital role as the pivot of cellular secretory pathway since its discovery. However, its complex structure at the molecular level remains elusive due to limited approaches. In this study, the structure of Golgi apparatus, including the Golgi stack, cisternal structure, relevant tubules and vesicles, were directly visualized by high-resolution atomic force microscope. We imaged both sides of Golgi apparatus membranes and revealed that the outer leaflet of Golgi membranes is relatively smooth while the inner membrane leaflet is rough and covered by dense proteins. With the treatment of methyl-β-cyclodextrin and Triton X-100, we confirmed the existence of lipid rafts in Golgi apparatus membrane, which are mostly in the size of 20 nm -200 nm and appear irregular in shape. Our results may be of significance to reveal the structure-function relationship of the Golgi complex and pave the way for visualizing the endomembrane system in mammalian cells at the molecular level.

  8. Effect of Ru substitution on atomic displacements in the layered SmFe1-xRuxAsO0.85F0.15 superconductor

    Science.gov (United States)

    Iadecola, A.; Joseph, B.; Simonelli, L.; Maugeri, L.; Fratini, M.; Martinelli, A.; Palenzona, A.; Putti, M.; Saini, N. L.

    2012-06-01

    The effect of Ru substitution on the local structure of layered SmFe1-xRuxAsO0.85F0.15 superconductor has been studied by As K- and Sm L3-edge x-ray-absorption spectroscopy. The extended x-ray-absorption fine-structure measurements reveal distinct Fe-As and Ru-As bond lengths in the Ru substituted samples with the latter being ˜0.03 Å longer. Local disorder induced by the Ru substitution is mainly confined to the FeAs layer while the SmO spacer layer sustains a relative order, consistent with the x-ray-absorption near-edge structure spectra. The results suggest that, in addition to the order/disorder in the active FeAs layer, its coupling to the rare-earth-oxygen spacer layer needs to be considered for describing the electronic properties of these layered superconductors.

  9. Substitution patterns in methylated potato starch as revealed from the structure and composition of fragments in enzymatic digests

    NARCIS (Netherlands)

    Steeneken, P.A.M.; Tas, A.C.; Woortman, A.J.J.; Sanders, P.; Mijland, P.J.H.C.; Weijs, L.G.R.de

    2008-01-01

    The effect of the granule structure on the methylation of starch was investigated by comparing the substitution patterns of potato starch methylated in granular suspension and in solution to DS 0.3. Substitution patterns were analyzed by successive digestion with α-amylase and amyloglucosidase,

  10. Reactions of substituted benzene anions with N and O atoms: Chemistry in Titan's upper atmosphere and the interstellar medium.

    Science.gov (United States)

    Wang, Zhe-Chen; Bierbaum, Veronica M

    2016-06-07

    The likely existence of aromatic anions in many important extraterrestrial environments, from the atmosphere of Titan to the interstellar medium (ISM), is attracting increasing attention. Nitrogen and oxygen atoms are also widely observed in the ISM and in the ionospheres of planets and moons. In the current work, we extend previous studies to explore the reactivity of prototypical aromatic anions (deprotonated toluene, aniline, and phenol) with N and O atoms both experimentally and computationally. The benzyl and anilinide anions both exhibit slow associative electron detachment (AED) processes with N atom, and moderate reactivity with O atom in which AED dominates but ionic products are also formed. The reactivity of phenoxide is dramatically different; there is no measurable reaction with N atom, and the moderate reactivity with O atom produces almost exclusively ionic products. The reaction mechanisms are studied theoretically by employing density functional theory calculations, and spin conversion is found to be critical for understanding some product distributions. This work provides insight into the rich gas-phase chemistry of aromatic ion-atom reactions and their relevance to ionospheric and interstellar chemistry.

  11. Peculiarities of living cell response to the external stimuli revealed via quasistatic mode of atomic force microscopy

    Science.gov (United States)

    Khalisov, M. M.; Ankudinov, A. V.; Penniyaynen, V. A.; Timoshenko, T. E.; Timoshchuk, K. I.; Samsonov, M. V.; Shirinsky, V. P.

    2017-10-01

    The technique of atomic force microscopy allows revealing living cell morphology and mechanical properties characterization under physiologically relevant conditions. Here, we review our recent results on living cell reaction to different external influences obtained by this technique. The Bruker PeakForce QNM quasistatic mode was used to study living fibroblasts, erythrocytes, sensory neurons, and endothelial cells.

  12. Modes of Escherichia coli Dps Interaction with DNA as Revealed by Atomic Force Microscopy.

    Directory of Open Access Journals (Sweden)

    Vladislav V Melekhov

    Full Text Available Multifunctional protein Dps plays an important role in iron assimilation and a crucial role in bacterial genome packaging. Its monomers form dodecameric spherical particles accumulating ~400 molecules of oxidized iron ions within the protein cavity and applying a flexible N-terminal ends of each subunit for interaction with DNA. Deposition of iron is a well-studied process by which cells remove toxic Fe2+ ions from the genetic material and store them in an easily accessible form. However, the mode of interaction with linear DNA remained mysterious and binary complexes with Dps have not been characterized so far. It is widely believed that Dps binds DNA without any sequence or structural preferences but several lines of evidence have demonstrated its ability to differentiate gene expression, which assumes certain specificity. Here we show that Dps has a different affinity for the two DNA fragments taken from the dps gene regulatory region. We found by atomic force microscopy that Dps predominantly occupies thermodynamically unstable ends of linear double-stranded DNA fragments and has high affinity to the central part of the branched DNA molecule self-assembled from three single-stranded oligonucleotides. It was proposed that Dps prefers binding to those regions in DNA that provide more contact pads for the triad of its DNA-binding bundle associated with one vertex of the protein globule. To our knowledge, this is the first study revealed the nucleoid protein with an affinity to branched DNA typical for genomic regions with direct and inverted repeats. As a ubiquitous feature of bacterial and eukaryotic genomes, such structural elements should be of particular care, but the protein system evolutionarily adapted for this function is not yet known, and we suggest Dps as a putative component of this system.

  13. A novel type of colony formation in marine planktonic diatoms revealed by atomic force microscopy.

    Directory of Open Access Journals (Sweden)

    Sunčica Bosak

    Full Text Available Diatoms have evolved a variety of colonial life forms in which cells are connected by organic threads, mucilage pads or silicate structures. In this study, we provide the first description of a novel strategy of colony formation among marine planktonic diatoms. Bacteriastrum jadranum forms loose but regular chains with distinct heterovalvate terminal cells. The colonial cells and their siliceous projections, the setae, are not in direct contact; instead, they are enclosed within the optically transparent organic matrix. This cell jacket structure was detected by staining procedure with Alcian Blue, which showed that the polysaccharides are predominant matrix constituents and revealed that the jacket reaches the span of the setae. The scanning electron microscopy (SEM observations showed distinguishable fibrillar network firmly associated with cells. Using atomic force microscopy (AFM, we were able to visualise and characterise the cell jacket structure at molecular resolution. At nanoscale resolution, the cell jacket appears as a cross-linked fibrillar network organised into a recognisable structure. The circular patches of self-repeating pattern (hexagonal pores with openings of 8-100 nm are connected through thicker surrounding fibrils and reinforced by branching fibrils. The pore-forming fibrils within the patches are only 0.6-1.6 nm high, the surrounding fibrils connecting patches are 2.0-2.8 nm high, and the branching fibrils are considerably wider but not higher than 4.0 nm. The discovered polysaccharide fibrillar network is highly organised and delicately structured with a monomolecular fibril height of 0.6 nm. We conclude that the Bacteriastrum polysaccharide jacket represents an essential part of the cell, as the conjunction of the polymer network with the frustule appears to be extremely tight and such specific and unique patterns have never been found in self-assembled polysaccharide gel networks, which are usually encountered in the

  14. Hydrogen storage and stability properties of Pd-Pt solid-solution nanoparticles revealed via atomic and electronic structure.

    Science.gov (United States)

    Kumara, Loku Singgappulige Rosantha; Sakata, Osami; Kobayashi, Hirokazu; Song, Chulho; Kohara, Shinji; Ina, Toshiaki; Yoshimoto, Toshiki; Yoshioka, Satoru; Matsumura, Syo; Kitagawa, Hiroshi

    2017-11-06

    Bimetallic Pd 1-x Pt x solid-solution nanoparticles (NPs) display charging/discharging of hydrogen gas, which has relevance for fuel cell technologies; however, the constituent elements are immiscible in the bulk phase. We examined these material systems using high-energy synchrotron X-ray diffraction, X-ray absorption fine structure and hard X-ray photoelectron spectroscopy techniques. Recent studies have demonstrated the hydrogen storage properties and catalytic activities of Pd-Pt alloys; however, comprehensive details of their structural and electronic functionality at the atomic scale have yet to be reported. Three-dimensional atomic-scale structure results obtained from the pair distribution function (PDF) and reverse Monte Carlo (RMC) methods suggest the formation of a highly disordered structure with a high cavity-volume-fraction for low-Pt content NPs. The NP conduction band features, as extracted from X-ray absorption near-edge spectra at the Pd and Pt L III -edge, suggest that the Pd conduction band is filled by Pt valence electrons. This behaviour is consistent with observations of the hydrogen storage capacity of these NPs. The broadening of the valence band width and the down-shift of the d-band centre away from the Fermi level upon Pt substitution also provided evidence for enhanced stability of the hydride (ΔH) features of the Pd 1-x Pt x solid-solution NPs with a Pt content of 8-21 atomic percent.

  15. Composition measurement in substitutionally disordered materials by atomic resolution energy dispersive X-ray spectroscopy in scanning transmission electron microscopy.

    Science.gov (United States)

    Chen, Z; Taplin, D J; Weyland, M; Allen, L J; Findlay, S D

    2017-05-01

    The increasing use of energy dispersive X-ray spectroscopy in atomic resolution scanning transmission electron microscopy invites the question of whether its success in precision composition determination at lower magnifications can be replicated in the atomic resolution regime. In this paper, we explore, through simulation, the prospects for composition measurement via the model system of Al x Ga 1-x As, discussing the approximations used in the modelling, the variability in the signal due to changes in configuration at constant composition, and the ability to distinguish between different compositions. Results are presented in such a way that the number of X-ray counts, and thus the expected variation due to counting statistics, can be gauged for a range of operating conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Electronic structure engineering in silicene via atom substitution and a new two-dimensional Dirac structure Si3C

    Science.gov (United States)

    Yin, Na; Dai, Ying; Wei, Wei; Huang, Baibiao

    2018-04-01

    A lot of efforts have been made towards the band gap opening in two-dimensional silicene, the silicon version of graphene. In the present work, the electronic structures of single atom doped (B, N, Al and P) and codoped (B/N and Al/P) silicene monolayers are systematically examined on the base of density functional electronic calculations. Our results demonstrate that single atom doping can realize electron or hole doping in the silicene; while codoping, due to the syergistic effects, results in finite band gap in silicene at the Dirac point without significantly degrading the electronic properties. In addition, the characteristic of band gap shows dependence on the doping concentration. Importantly, we predict a new two-dimensional Dirac structure, the graphene-like Si3C, which also shows linear band dispersion relation around the Fermi level. Our results demonstrates an important perspective to engineer the electronic and optical properties of silicene.

  17. Atomic-scale processes revealing dynamic twin boundary strengthening mechanisms in face-centered cubic materials

    International Nuclear Information System (INIS)

    Yang, Z.Q.; Chisholm, M.F.; He, L.L.; Pennycook, S.J.; Ye, H.Q.

    2012-01-01

    We report experimental investigations on interactions/reactions between dislocations and twin boundaries in Al. The absorption of screw dislocations via cross-slip and the production of stair-rods via reactions with non-screw dislocations were verified by atomic resolution imaging. Importantly, the resulting partial dislocations moving along twin boundaries can produce secondary sessile defects. These immobile defects act as obstacles to other dislocations and also serve to pin the twin boundaries. These findings show the atomic-level dynamics of the dislocation–twin boundary processes and the unique strengthening mechanism of twin boundaries in face-centered cubic metals.

  18. Acid bi-sulphite pulping effects on hardwoods and a softwood revealed by atomic force microscopy

    CSIR Research Space (South Africa)

    Chunilall, Viren

    2009-12-01

    Full Text Available aggregation of cellulose fibril aggregates (CFA) during processing in order to preserve the reactivity of dissolving pulp. Previous atomic force microscopy (AFM) studies on a species of Eucalyptus showed that there is an increase in the CFA dimensions during...

  19. Experimental and theoretical study of magnetic ordering and local atomic polarization in Ru-substituted Lu2Fe17

    Science.gov (United States)

    Tereshina, E. A.; Isnard, O.; Smekhova, A.; Andreev, A. V.; Rogalev, A.; Khmelevskyi, S.

    2014-03-01

    The distribution of magnetic moments in the iron-rich intermetallic compound Lu2Fe17 with Fe partly substituted by Ru has been investigated on Lu2Fe16.5Ru0.5 by using several techniques. The crystal structure and temperature evolution of the magnetic structure was studied using high resolution and high flux neutron powder diffractometers. In contrast to the parent Lu2Fe17, which transforms on cooling from an antiferromagnetic to a ferromagnetic state, Lu2Fe16.5Ru0.5 is an antiferromagnet (Néel temperature TN = 208 K) down to the lowest temperatures. The magnetic polarization at the lutetium L2,3 absorption edges, iron K and ruthenium L2 edges was studied by x-ray magnetic circular dichroism (XMCD) on a single crystal of Lu2Fe16.5Ru0.5 in a magnetic field of 3 T, i.e., above the field-induced metamagnetic transition. The Ru XMCD signal proves the existence of induced magnetic polarization parallel to the dominant Fe sublattice magnetization. A corresponding theoretical analysis in the framework of the local spin density formalism is provided in order to discern the structural disorder effects and magnetism in the system.

  20. Mass Spectrometry Analysis Coupled with de novo Sequencing Reveals Amino Acid Substitutions in Nucleocapsid Protein from Influenza A Virus

    Directory of Open Access Journals (Sweden)

    Zijian Li

    2014-02-01

    Full Text Available Amino acid substitutions in influenza A virus are the main reasons for both antigenic shift and virulence change, which result from non-synonymous mutations in the viral genome. Nucleocapsid protein (NP, one of the major structural proteins of influenza virus, is responsible for regulation of viral RNA synthesis and replication. In this report we used LC-MS/MS to analyze tryptic digestion of nucleocapsid protein of influenza virus (A/Puerto Rico/8/1934 H1N1, which was isolated and purified by SDS poly-acrylamide gel electrophoresis. Thus, LC-MS/MS analyses, coupled with manual de novo sequencing, allowed the determination of three substituted amino acid residues R452K, T423A and N430T in two tryptic peptides. The obtained results provided experimental evidence that amino acid substitutions resulted from non-synonymous gene mutations could be directly characterized by mass spectrometry in proteins of RNA viruses such as influenza A virus.

  1. Quantum degeneracy in atomic point contacts revealed by chemical force and conductance

    Czech Academy of Sciences Publication Activity Database

    Sugimoto, Y.; Ondráček, Martin; Abe, M.; Pou, P.; Morita, S.; Perez, R.; Flores, F.; Jelínek, Pavel

    2013-01-01

    Roč. 111, č. 10 (2013), "106803-1"-"106803-5" ISSN 0031-9007 R&D Projects: GA ČR(CZ) GPP204/11/P578 Grant - others:GA AV ČR(CZ) M100101207 Institutional support: RVO:68378271 Keywords : scanning tunneling microscopy * atomic force microscopy * degenerate states * silicon surface * dangling bonds Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.728, year: 2013

  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. Isotope-specific and amino acid-specific heavy atom substitutions alter barrier crossing in human purine nucleoside phosphorylase.

    Science.gov (United States)

    Suarez, Javier; Schramm, Vern L

    2015-09-08

    Computational chemistry predicts that atomic motions on the femtosecond timescale are coupled to transition-state formation (barrier-crossing) in human purine nucleoside phosphorylase (PNP). The prediction is experimentally supported by slowed catalytic site chemistry in isotopically labeled PNP (13C, 15N, and 2H). However, other explanations are possible, including altered volume or bond polarization from carbon-deuterium bonds or propagation of the femtosecond bond motions into slower (nanoseconds to milliseconds) motions of the larger protein architecture to alter catalytic site chemistry. We address these possibilities by analysis of chemistry rates in isotope-specific labeled PNPs. Catalytic site chemistry was slowed for both [2H]PNP and [13C, 15N]PNP in proportion to their altered protein masses. Secondary effects emanating from carbon-deuterium bond properties can therefore be eliminated. Heavy-enzyme mass effects were probed for local or global contributions to catalytic site chemistry by generating [15N, 2H]His8-PNP. Of the eight His per subunit, three participate in contacts to the bound reactants and five are remote from the catalytic sites. [15N, 2H]His8-PNP had reduced catalytic site chemistry larger than proportional to the enzymatic mass difference. Altered barrier crossing when only His are heavy supports local catalytic site femtosecond perturbations coupled to transition-state formation. Isotope-specific and amino acid specific labels extend the use of heavy enzyme methods to distinguish global from local isotope effects.

  4. Attoclock reveals natural coordinates of the laser-induced tunnelling current flow in atoms

    DEFF Research Database (Denmark)

    Pfeiffer, Adrian N.; Cirelli, Claudio; Smolarski, Mathias

    2012-01-01

    In the research area of strong-laser-field interactions and attosecond science1, tunnelling of an electron through the barrier formed by the electric field of the laser and the atomic potential is typically assumed to be the initial key process that triggers subsequent dynamics1, 2, 3. Here we use...... the attoclock technique4 to obtain experimental information about the electron tunnelling geometry (the natural coordinates of the tunnelling current flow) and exit point. We confirm vanishing tunnelling delay time, show the importance of the inclusion of Stark shifts5, 6 and report on multi-electron effects...

  5. Revealing thermal effects in the electronic transport through irradiated atomic metal point contacts

    Directory of Open Access Journals (Sweden)

    Bastian Kopp

    2012-10-01

    Full Text Available We report on the electronic transport through nanoscopic metallic contacts under the influence of external light fields. Various processes can be of relevance here, whose underlying mechanisms can be studied by comparing different kinds of atomic contacts. For this purpose two kinds of contacts, which were established by electrochemical deposition, forming a gate-controlled quantum switch (GCQS, have been studied. We demonstrate that in these kinds of contacts thermal effects resulting from local heating due to the incident light, namely thermovoltage and the temperature dependences of the electrical resistivity and the electrochemical (Helmholtz double layer are the most prominent effects.

  6. Sample preparation for arsenic speciation analysis in baby food by generation of substituted arsines with atomic absorption spectrometry detection.

    Science.gov (United States)

    Huber, Charles S; Vale, Maria Goreti R; Dessuy, Morgana B; Svoboda, Milan; Musil, Stanislav; Dědina, Jiři

    2017-12-01

    A slurry sampling procedure for arsenic speciation analysis in baby food by arsane generation, cryogenic trapping and detection with atomic absorption spectrometry is presented. Several procedures were tested for slurry preparation, including different reagents (HNO 3 , HCl and tetramethylammonium hydroxide - TMAH) and their concentrations, water bath heating and ultrasound-assisted agitation. The best results for inorganic arsenic (iAs) and dimethylarsinate (DMA) were reached when using 3molL -1 HCl under heating and ultrasound-assisted agitation. The developed method was applied for the analysis of five porridge powder and six baby meal samples. The trueness of the method was checked with a certified reference material (CRM) of total arsenic (tAs), iAs and DMA in rice (ERM-BC211). Arsenic recoveries (mass balance) for all samples and CRM were performed by the determination of the tAs by inductively coupled plasma mass spectrometry (ICP-MS) after microwave-assisted digestion and its comparison against the sum of the results from the speciation analysis. The relative limits of detection were 0.44, 0.24 and 0.16µgkg -1 for iAs, methylarsonate and DMA, respectively. The concentrations of the most toxic arsenic species (iAs) in the analyzed baby food samples ranged between 4.2 and 99µgkg -1 which were below the limits of 300, 200 and 100µgkg -1 set by the Brazilian, Chinese and European legislation, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. High Deformability and Particle Size Distribution of Monodisperse Phytoglycogen Nanoparticles Revealed By Atomic Force Microscopy Imaging

    Science.gov (United States)

    Baylis, Benjamin; Dutcher, John

    We have used atomic force microscopy (AFM) imaging in water to determine the volume of hydrated monodisperse phytoglycogen nanoparticles adsorbed onto mica surfaces. By significantly reducing the interaction between the AFM tip and the ``sticky'' nanoparticles, we were able to obtain high quality images. We found that the adsorbed particles are highly deformed, forming pancake-like objects on the hydrophilic mica surface. By measuring the distribution of particle volumes, we calculated the average effective spherical radius of the hydrated particles, and compared this value with that measured in solution using small angle neutron scattering. These measurements illustrate the distinct advantages of AFM imaging over other imaging techniques, namely the ability to measure the height of objects in a liquid environment.

  8. Using Lasers and X-rays to Reveal the Motion of Atoms and Electrons (LBNL Summer Lecture Series)

    Energy Technology Data Exchange (ETDEWEB)

    Schoenlein, Robert [Deputy Director, Advanced Light Source

    2009-07-07

    Summer Lecture Series 2009: The ultrafast motion of atoms and electrons lies at the heart of chemical reactions, advanced materials with exotic properties, and biological processes such as the first event in vision. Bob Schoenlein, Deputy Director for Science at the Advanced Light Source, will discuss how such processes are revealed by using laser pulses spanning a millionth of a billionth of a second, and how a new generation of light sources will bring the penetrating power of x-rays to the world of ultrafast science.

  9. Reaction of α-bromocyclopropyl phenyl ketones with lithium thiophenolate by a mechanism or latent nucleophilic substitution at the halogen atom

    International Nuclear Information System (INIS)

    Kulinkovich, O.G.; Tishchenko, I.G.; Sviridov, S.V.; Divak, V.A.

    1987-01-01

    The reaction of E-1-benzoyl-1-bromo-2-phenylcyclopropane with lithium thiophenolate in THF leads to the formation of E-1-benzoyl-2-phenyl-1-phenylthiocyclopropane. Phenyl α-phenylthiocyclopropyl ketones are also produced with good yields by the action of sodium thiophenolate on 7-endo-benzoyl-7-exo-bromobicyclo[4.1.0]-heptane, E-1-benzoyl-1-bromo-2-butylcyclopropane, and 1-benzoyl-1-bromocyclopropane, whereas Z-1-benzoyl-1-bromo-2-phenylcyclopropane undergoes reductive dehalogenation under analogous conditions. The stereochemical data and also the data on the composition of the products from the reaction in the presence of methanol indicate that the phenyl α-phenylthiocyclopropyl ketones are formed by a mechanism of latent nucleophilic substitution at the halogen atom in the initial α-bromocyclopropyl phenyl ketones. The PMR spectra of solutions of the substances in carbon tetrachloride or benzene were obtained on a Tesla BS-467A spectrometer at 60 MHz with HMDS as internal standard. The IR spectra of solutions of the substances in carbon tetrachloride were recorded on a Specord IR-75 spectrometer. The reactions were carried out in an atmosphere of dry argon

  10. Phase evolution, microstructure and mechanical properties of equi-atomic substituted TiZrHfNiCu and TiZrHfNiCuM (M = Co, Nb) high-entropy alloys

    Science.gov (United States)

    Park, Hae Jin; Na, Young Sang; Hong, Sung Hwan; Kim, Jeong Tae; Kim, Young Seok; Lim, Ka Ram; Park, Jin Man; Kim, Ki Buem

    2016-07-01

    In this study, alloys with composition of equi-atomic substituted TiZrHfNiCu, TiZrHfNiCuCo, and TiZrHfNiCuNb high-entropy alloys (HEAs) were produced by suction casting method. The effects of addition elements on phase composition, microstructure and mechanical behaviors of the HEA were studied. The suction casted Ti20Zr20Hf20Ni20Cu20 HEA exhibits single C14 Laves phase (MgZn2-type) with fine homogeneous microstructure. When Co or Nb elements are added, morphologies are slightly modulated toward well-developed dendritic microstructure, phase constitutions are significantly changed from single Laves phase to mixed multi-phases as well as mechanical properties are also altered with increased plasticity and high strength. It is believed that modulated mechanical properties are mainly ascribed to the change of phase constitution and crystalline structure, together with the microstructural characteristics. This clearly reveals that the selection and addition of supplementary elements based on the formation rule for HEAs play an important role on the evolution of phase, microstructural morphology and mechanical properties of Ti20Zr20Hf20Ni20Cu20 HEA.

  11. Modeling competitive substitution in a polyelectrolyte complex

    International Nuclear Information System (INIS)

    Peng, B.; Muthukumar, M.

    2015-01-01

    We have simulated the invasion of a polyelectrolyte complex made of a polycation chain and a polyanion chain, by another longer polyanion chain, using the coarse-grained united atom model for the chains and the Langevin dynamics methodology. Our simulations reveal many intricate details of the substitution reaction in terms of conformational changes of the chains and competition between the invading chain and the chain being displaced for the common complementary chain. We show that the invading chain is required to be sufficiently longer than the chain being displaced for effecting the substitution. Yet, having the invading chain to be longer than a certain threshold value does not reduce the substitution time much further. While most of the simulations were carried out in salt-free conditions, we show that presence of salt facilitates the substitution reaction and reduces the substitution time. Analysis of our data shows that the dominant driving force for the substitution process involving polyelectrolytes lies in the release of counterions during the substitution

  12. Media audit reveals inappropriate promotion of products under the scope of the International Code of Marketing of Breast-milk Substitutes in South-East Asia.

    Science.gov (United States)

    Vinje, Kristine Hansen; Phan, Linh Thi Hong; Nguyen, Tuan Thanh; Henjum, Sigrun; Ribe, Lovise Omoijuanfo; Mathisen, Roger

    2017-06-01

    To review regulations and to perform a media audit of promotion of products under the scope of the International Code of Marketing of Breast-milk Substitutes ('the Code') in South-East Asia. We reviewed national regulations relating to the Code and 800 clips of editorial content, 387 advertisements and 217 Facebook posts from January 2015 to January 2016. We explored the ecological association between regulations and market size, and between the number of advertisements and market size and growth of milk formula. Cambodia, Indonesia, Myanmar, Thailand and Vietnam. Regulations on the child's age for inappropriate marketing of products are all below the Code's updated recommendation of 36 months (i.e. 12 months in Thailand and Indonesia; 24 months in the other three countries) and are voluntary in Thailand. Although the advertisements complied with the national regulations on the age limit, they had content (e.g. stages of milk formula; messages about the benefit; pictures of a child) that confused audiences. Market size and growth of milk formula were positively associated with the number of newborns and the number of advertisements, and were not affected by the current level of implementation of breast-milk substitute laws and regulations. The present media audit reveals inappropriate promotion and insufficient national regulation of products under the scope of the Code in South-East Asia. Strengthened implementation of regulations aligned with the Code's updated recommendation should be part of comprehensive strategies to minimize the harmful effects of advertisements of breast-milk substitutes on maternal and child nutrition and health.

  13. Atomic force microscopy of bacteria reveals the mechanobiology of pore forming peptide action.

    Science.gov (United States)

    Mularski, Anna; Wilksch, Jonathan J; Hanssen, Eric; Strugnell, Richard A; Separovic, Frances

    2016-06-01

    Time-resolved AFM images revealed that the antimicrobial peptide (AMP) caerin 1.1 caused localised defects in the cell walls of lysed Klebsiella pneumoniae cells, corroborating a pore-forming mechanism of action. The defects continued to grow during the AFM experiment, in corroboration with large holes that were visualised by scanning electron microscopy. Defects in cytoplasmic membranes were visualised by cryo-EM using the same peptide concentration as in the AFM experiments. At three times the minimum inhibitory concentration of caerin, 'pores' were apparent in the outer membrane. The capsule of K. pneumoniae AJ218 was unchanged by exposure to caerin, indicating that the ionic interaction of the positively charged peptide with the negatively charged capsular polysaccharide is not a critical component of AMP interaction with K. pneumoniae AJ218 cells. Further, the presence of a capsule confers no advantage to wild-type over capsule-deficient cells when exposed to the AMP caerin. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. High-speed atomic force microscopy reveals structural dynamics of α -synuclein monomers and dimers

    Science.gov (United States)

    Zhang, Yuliang; Hashemi, Mohtadin; Lv, Zhengjian; Williams, Benfeard; Popov, Konstantin I.; Dokholyan, Nikolay V.; Lyubchenko, Yuri L.

    2018-03-01

    α-Synuclein (α-syn) is the major component of the intraneuronal inclusions called Lewy bodies, which are the pathological hallmark of Parkinson's disease. α-Syn is capable of self-assembly into many different species, such as soluble oligomers and fibrils. Even though attempts to resolve the structures of the protein have been made, detailed understanding about the structures and their relationship with the different aggregation steps is lacking, which is of interest to provide insights into the pathogenic mechanism of Parkinson's disease. Here we report the structural flexibility of α-syn monomers and dimers in an aqueous solution environment as probed by single-molecule time-lapse high-speed AFM. In addition, we present the molecular basis for the structural transitions using discrete molecular dynamics (DMD) simulations. α-Syn monomers assume a globular conformation, which is capable of forming tail-like protrusions over dozens of seconds. Importantly, a globular monomer can adopt fully extended conformations. Dimers, on the other hand, are less dynamic and show a dumbbell conformation that experiences morphological changes over time. DMD simulations revealed that the α-syn monomer consists of several tightly packed small helices. The tail-like protrusions are also helical with a small β-sheet, acting as a "hinge". Monomers within dimers have a large interfacial interaction area and are stabilized by interactions in the non-amyloid central (NAC) regions. Furthermore, the dimer NAC-region of each α-syn monomer forms a β-rich segment. Moreover, NAC-regions are located in the hydrophobic core of the dimer.

  15. Atomic force microscopy imaging reveals the formation of ASIC/ENaC cross-clade ion channels.

    Science.gov (United States)

    Jeggle, Pia; Smith, Ewan St J; Stewart, Andrew P; Haerteis, Silke; Korbmacher, Christoph; Edwardson, J Michael

    2015-08-14

    ASIC and ENaC are co-expressed in various cell types, and there is evidence for a close association between them. Here, we used atomic force microscopy (AFM) to determine whether ASIC1a and ENaC subunits are able to form cross-clade hybrid ion channels. ASIC1a and ENaC could be co-isolated from detergent extracts of tsA 201 cells co-expressing the two subunits. Isolated proteins were incubated with antibodies against ENaC and Fab fragments against ASIC1a. AFM imaging revealed proteins that were decorated by both an antibody and a Fab fragment with an angle of ∼120° between them, indicating the formation of ASIC1a/ENaC heterotrimers. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Muon substituted free radicals

    International Nuclear Information System (INIS)

    Burkhard, P.; Fischer, H.; Roduner, E.; Strub, W.; Gygax, F.N.; Brinkman, G.A.; Louwrier, P.W.F.; McKenna, D.; Ramos, M.; Webster, B.C.

    1984-01-01

    Spin polarized energetic positive muons are injected as magnetic probes into unsaturated organic liquids. They are implemented via fast chemical processes ( -10 s) in various molecules. Of particular interest among these are muonium substituted free radicals. The technique allows determination of accurate rate coefficients for fast chemical reactions of radicals. Furthermore, radiochemical processes occuring in picoseconds after injection of the muon are studied. Of fundamental interest are also the structural and dynamical implications of substituting a proton by a muon, or in other terms, a hydrogen atom by a muonium atom. Selected examples for each of these three types of experiments are given. (Auth.)

  17. Effect of a bulky lateral substitution by chlorine atom and methoxy group on self-assembling properties of lactic acid derivatives

    Czech Academy of Sciences Publication Activity Database

    Stojanović, M.; Bubnov, Alexej; Obadović, D.Ž.; Hamplová, Věra; Cvetinov, M.; Kašpar, Miroslav

    2014-01-01

    Roč. 146, 1-2 (2014), s. 18-25 ISSN 0254-0584 R&D Projects: GA ČR GA13-14133S Grant - others:AVČR(CZ) M100101204 Institutional support: RVO:68378271 Keywords : ferroelectric liquid crystal * lactic acid derivative * lateral substitution * methoxy group * chlorine substitution * dielectric spectroscopy Subject RIV: JJ - Other Materials Impact factor: 2.259, year: 2014

  18. Crystal growth mechanisms and morphological control of the prototypical metal-organic framework MOF-5 revealed by atomic force microscopy.

    Science.gov (United States)

    Cubillas, Pablo; Anderson, Michael W; Attfield, Martin P

    2012-11-26

    Crystal growth of the metal-organic framework MOF-5 was studied by atomic force microscopy (AFM) for the first time. Growth under low supersaturation conditions was found to occur by a two-dimensional or spiral crystal growth mechanism. Observation of developing nuclei during the former reveals growth occurs through a process of nucleation and spreading of metastable and stable sub-layers revealing that MOFs may be considered as dense phase structures in terms of crystal growth, even though they contain sub-layers consisting of ordered framework and disordered non-framework components. These results also support the notion this may be a general mechanism of surface crystal growth at low supersaturation applicable to crystalline nanoporous materials. The crystal growth mechanism at the atomistic level was also seen to vary as a function of the growth solution Zn/H(2)bdc ratio producing square terraces with steps parallel to the direction or rhombus-shaped terraces with steps parallel to the direction when the Zn/H(2)bdc ratio was >1 or about 1, respectively. The change in relative growth rates can be explained in terms of changes in the solution species concentrations and their influence on growth at different terrace growth sites. These results were successfully applied to the growth of as-synthesized cube-shaped crystals to increase expression of the {111} faces and to grow octahedral crystals of suitable quality to image using AFM. This modulator-free route to control the crystal morphology of MOF-5 crystals should be applicable to a wide variety of MOFs to achieve the desired morphological control for performance enhancement in applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Surface topological differences of phage infected uropathogenicEscherichia coli(UPEC) strains, revealed by atomic force microscopy.

    Science.gov (United States)

    Hanif, Bassamah; Jamil, Nusrat; Shah, Muhammad Raza

    2016-01-01

    Atomic force microscopy (AFM) is an advance microscopic technique that provides three dimensional structures of cell surfaces with high resolution. In the present study AFM was used for comparative analysis of surface topology of phage infected and uninfected Uropathogenic Escherichia coli (UPEC) cells. Two UPEC strains NE and HN were isolated from urine samples of Urinary tract infection patients and their specific narrow host range lytic phages 3S and HNΦ were isolated from the sewage of different areas. On the basis of one step growth curve both phages characterized as short latent period phages with latency period of about 30 min. On AFM analysis significant difference in topology of healthy and infected cells were observed. It was hypothesized that progeny of both lytic phages released out from their respective host cells in different manner. The image of 3S infected UPEC host cells (NE) revealed multiple internal projections which showed progeny phages released out from host cells through these multiple sites. Whereas images of HNΦ infected HN host cells showed central depression which illustrated that new phages released out through single exit point from the middle of cell. These results are significant to extend future studies on isolated phages as an effective tool for phage therapy.

  20. Atomic force microscopy imaging reveals the formation of ASIC/ENaC cross-clade ion channels

    Energy Technology Data Exchange (ETDEWEB)

    Jeggle, Pia; Smith, Ewan St. J.; Stewart, Andrew P. [Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD (United Kingdom); Haerteis, Silke; Korbmacher, Christoph [Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstrasse 6, 91054 Erlangen (Germany); Edwardson, J. Michael, E-mail: jme1000@cam.ac.uk [Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD (United Kingdom)

    2015-08-14

    ASIC and ENaC are co-expressed in various cell types, and there is evidence for a close association between them. Here, we used atomic force microscopy (AFM) to determine whether ASIC1a and ENaC subunits are able to form cross-clade hybrid ion channels. ASIC1a and ENaC could be co-isolated from detergent extracts of tsA 201 cells co-expressing the two subunits. Isolated proteins were incubated with antibodies against ENaC and Fab fragments against ASIC1a. AFM imaging revealed proteins that were decorated by both an antibody and a Fab fragment with an angle of ∼120° between them, indicating the formation of ASIC1a/ENaC heterotrimers. - Highlights: • There is evidence for a close association between ASIC and ENaC. • We used AFM to test whether ASIC1a and ENaC subunits form cross-clade ion channels. • Isolated proteins were incubated with subunit-specific antibodies and Fab fragments. • Some proteins were doubly decorated at ∼120° by an antibody and a Fab fragment. • Our results indicate the formation of ASIC1a/ENaC heterotrimers.

  1. Atomic-Scale Mechanism on Nucleation and Growth of Mo2C Nanoparticles Revealed by in Situ Transmission Electron Microscopy.

    Science.gov (United States)

    Fei, Linfeng; Ng, Sheung Mei; Lu, Wei; Xu, Ming; Shu, Longlong; Zhang, Wei-Bing; Yong, Zehui; Sun, Tieyu; Lam, Chi Hang; Leung, Chi Wah; Mak, Chee Leung; Wang, Yu

    2016-12-14

    With a similar electronic structure as that of platinum, molybdenum carbide (Mo 2 C) holds significant potential as a high performance catalyst across many chemical reactions. Empirically, the precise control of particle size, shape, and surface nature during synthesis largely determines the catalytic performance of nanoparticles, giving rise to the need of clarifying the underlying growth characteristics in the nucleation and growth of Mo 2 C. However, the high-temperature annealing involved during the growth of carbides makes it difficult to directly observe and understand the nucleation and growth processes. Here, we report on the use of advanced in situ transmission electron microscopy with atomic resolution to reveal a three-stage mechanism during the growth of Mo 2 C nanoparticles over a wide temperature range: initial nucleation via a mechanism consistent with spinodal decomposition, subsequent particle coalescence and monomer attachment, and final surface faceting to well-defined particles with minimum surface energy. These microscopic observations made under a heating atmosphere offer new perspectives toward the design of carbide-based catalysts, as well as the tuning of their catalytic performances.

  2. Substitutions in PBP3 confer resistance to both ampicillin and extended-spectrum cephalosporins in Haemophilus parainfluenzae as revealed by site-directed mutagenesis and gene recombinants

    DEFF Research Database (Denmark)

    Wienholtz, Nanna H; Ciechanowski, Aynur Barut; Nørskov-Lauritsen, Niels

    2017-01-01

    I from clinical strains encoding four substitutions in the transpeptidase region of PBP3 conferred resistance to ampicillin, but not to cephalosporins. Introduction of ftsI from a clinical strain encoding eight substitutions conferred resistance to ampicillin, cefotaxime and ceftriaxone. MICs....../H/S in combination with V511A were resistant to ampicillin. Substitution S385T increased the MICs of third-generation cephalosporins if V511A was also present. Conclusions: Substitutions in PBP3 are sufficient to confer resistance to both ampicillin and third-generation cephalosporins in H. parainfluenzae...... . A combination of substitutions at positions Val-511 and Asn-526 confers resistance to ampicillin. Resistance to third-generation cephalosporins probably requires more than four substitutions in PBP3....

  3. Reactions of substituted benzene anions with N and O atoms: Chemistry in Titan’s upper atmosphere and the interstellar medium

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhe-Chen; Bierbaum, Veronica M. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309 (United States)

    2016-06-07

    The likely existence of aromatic anions in many important extraterrestrial environments, from the atmosphere of Titan to the interstellar medium (ISM), is attracting increasing attention. Nitrogen and oxygen atoms are also widely observed in the ISM and in the ionospheres of planets and moons. In the current work, we extend previous studies to explore the reactivity of prototypical aromatic anions (deprotonated toluene, aniline, and phenol) with N and O atoms both experimentally and computationally. The benzyl and anilinide anions both exhibit slow associative electron detachment (AED) processes with N atom, and moderate reactivity with O atom in which AED dominates but ionic products are also formed. The reactivity of phenoxide is dramatically different; there is no measurable reaction with N atom, and the moderate reactivity with O atom produces almost exclusively ionic products. The reaction mechanisms are studied theoretically by employing density functional theory calculations, and spin conversion is found to be critical for understanding some product distributions. This work provides insight into the rich gas-phase chemistry of aromatic ion-atom reactions and their relevance to ionospheric and interstellar chemistry.

  4. Revealing the atomic and electronic structure of a SrTiO3/LaNiO3/SrTiO3 heterostructure interface

    International Nuclear Information System (INIS)

    Zhang, Zaoli; Soltan, S.; Schmid, H.; Habermeier, H.-U.; Keimer, B.; Kaiser, U.

    2014-01-01

    The atomic structures of SrTiO 3 (STO)/LaNiO 3 (LNO)/STO heterostructure interfaces were investigated by spherical aberration-corrected (C S ) (scanning) transmission electron microscopy. Atomic displacement and lattice distortion measurements and electron energy loss spectroscopy (EELS) were used to quantitatively analyze the distortion of the interfacial octahedra and the bond length at the interfaces. Combined with high-resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy analyses, two distinct interfacial atomic terminating layers are unambiguously determined. Ensuing quantitative HRTEM measurements revealed that the Ni-O bond length in the interfacial octahedral is elongated at the bottom interface (–NiO 2 -SrO–). Atomic displacement shows structural relaxation effects when crossing the interfaces and lattice distortions across the interface is more pronounced in LNO than in STO. The Ti/O atomic ratio, La and Ti relative atomic ratio as derived by EELS quantification indicate non-stoichiometric composition at the interfaces. Distinct fine structures of Ti-L 2,3 edge and O-K edge at the bottom and top interfaces are observed. By comparison, we are able to estimate Ti valency at both interfaces. Combining the structural distortions and Ti valency, the polar discontinuity and charge transfer at the interfaces are discussed

  5. 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.

  6. Temperature dependent local atomic displacements in Ru substituted SmFe1-xRuxAsO0.85F0.15 superconductors

    Science.gov (United States)

    Joseph, Boby; Iadecola, Antonella; Simonelli, Laura; Maugeri, Laura; Martinelli, Alberto; Palenzona, Andrea; Putti, Marina; Saini, Naurang L.

    2013-06-01

    The local structure of SmFe1-xRuxAsO0.85F0.15 (x = 0.0, 0.05, 0.25 and 0.5) superconductors has been investigated by temperature dependent As K-edge extended x-ray absorption fine structure analysis. The effect of Ru substitution remains confined to the iron-arsenide layer but neither the static disorder nor the Fe-As bond strength suffers any change for x ≤ 0.25. With further Ru substitution the static disorder increases while the Fe-As bond strength remains unchanged. Also, the Ru-As distance (˜2.42 Å), different from the Fe-As distance (˜2.39 Å), does not show any change in its force constant with Ru substitution. These observations suggest that the SmFe1-xRuxAsO0.85F0.15 system breaks down into coexisting local electronic phases on isoelectric substitution in the active FeAs layer.

  7. Atomic structure of recombinant thaumatin II reveals flexible conformations in two residues critical for sweetness and three consecutive glycine residues.

    Science.gov (United States)

    Masuda, Tetsuya; Mikami, Bunzo; Tani, Fumito

    2014-11-01

    Thaumatin, an intensely sweet-tasting protein used as a sweetener, elicits a sweet taste at 50 nM. Although two major variants designated thaumatin I and thaumatin II exist in plants, there have been few dedicated thaumatin II structural studies and, to date, data beyond atomic resolution had not been obtained. To identify the detailed structural properties explaining why thaumatin elicits a sweet taste, the structure of recombinant thaumatin II was determined at the resolution of 0.99 Å. Atomic resolution structural analysis with riding hydrogen atoms illustrated the differences in the direction of the side-chains more precisely and the electron density maps of the C-terminal regions were markedly improved. Though it had been suggested that the three consecutive glycine residues (G142-G143-G144) have highly flexible conformations, G143, the central glycine residue was successfully modelled in two conformations for the first time. Furthermore, the side chain r.m.s.d. values for two residues (R67 and R82) critical for sweetness exhibited substantially higher values, suggesting that these residues are highly disordered. These results demonstrated that the flexible conformations in two critical residues favoring their interaction with sweet taste receptors are prominent features of the intensely sweet taste of thaumatin. Copyright © 2014 Elsevier B.V. and Société française de biochimie et biologie Moléculaire (SFBBM). All rights reserved.

  8. Local crystal structures of Ge2Sb2Te5 revealed by the atomic pair distribution function analysis

    International Nuclear Information System (INIS)

    Shamoto, Shin-ichi; Kodama, Katsuaki; Iikubo, Satoshi; Taguchi, Tomitsugu; Yamada, Noboru; Proffen, Thomas

    2006-01-01

    Two types of optical recording crystalline material Ge 2 Sb 2 Te 5 have been studied by neutron and X-ray powder diffraction measurements. One is the crystalline cubic-phase Ge 2 Sb 2 Te 5 . The other is nanocrystalline-phase Ge 2 Sb 2 Te 5 . In the former, a large atomic displacement of germanium atoms was found by the atomic pair distribution function (PDF) analysis of neutron powder diffraction data. According to the electronic band structure calculation of isoelectronic GeTe, the electrical conductivity at the valence band with holes is not severely affected by the randomness at the cation site, whereas the thermal conductivity is significantly reduced by the randomness. For the nanocrystalline phase, the local crystal structure and the particle size distribution were obtained simultaneously by PDF analysis using a spherical-particle form factor. The lattice parameter is longer than that of the crystalline phase, suggesting an antimony-richer composition than the matrix. This compositional deviation would form the nanoparticle, resulting in nucleation-dominated crystal growth. (author)

  9. First-principles study on silicon atom doped monolayer graphene

    Science.gov (United States)

    Rafique, Muhammad; Shuai, Yong; Hussain, Nayyar

    2018-01-01

    This paper illustrates the structural, electronic and optical properties of individual silicon (Si) atom-doped single layer graphene using density functional theory method. Si atom forms tight bonding with graphene layer. The effect of doping has been investigated by varying the concentration of Si atoms from 3.125% to 9.37% (i.e. From one to three Si atoms in 4 × 4 pure graphene supercell containing 32 carbon atoms), respectively. Electronic structure, partial density of states (PDOS) and optical properties of pure and Si atom-doped graphene sheet were calculated using VASP (Vienna ab-initio Simulation Package). The calculated results for pure graphene sheet were then compared with Si atom doped graphene. It is revealed that upon Si doping in graphene, a finite band gap appears at the high symmetric K-point, thereby making graphene a direct band gap semiconductor. Moreover, the band gap value is directly proportional to the concentration of impurity Si atoms present in graphene lattice. Upon analyzing the optical properties of Si atom-doped graphene structures, it is found that, there is significant change in the refractive index of the graphene after Si atom substitution in graphene. In addition, the overall absorption spectrum of graphene is decreased after Si atom doping. Although a significant red shift in absorption is found to occur towards visible range of radiation when Si atom is substituted in its lattice. The reflectivity of graphene improves in low energy region after Si atom substitution in graphene. These results can be useful for tuning the electronic structure and to manipulate the optical properties of graphene layer in the visible region.

  10. All-atom normal-mode analysis reveals an RNA-induced allostery in a bacteriophage coat protein.

    Science.gov (United States)

    Dykeman, Eric C; Twarock, Reidun

    2010-03-01

    Assembly of the T=3 bacteriophage MS2 is initiated by the binding of a 19 nucleotide RNA stem loop from within the phage genome to a symmetric coat protein dimer. This binding event effects a folding of the FG loop in one of the protein subunits of the dimer and results in the formation of an asymmetric dimer. Since both the symmetric and asymmetric forms of the dimer are needed for the assembly of the protein container, this allosteric switch plays an important role in the life cycle of the phage. We provide here details of an all-atom normal-mode analysis of this allosteric effect. The results suggest that asymmetric contacts between the A -duplex RNA phosphodiester backbone of the stem loop with the EF loop in one coat protein subunit results in an increased dynamic behavior of its FG loop. The four lowest-frequency modes, which encompass motions predominantly on the FG loops, account for over 90% of the increased dynamic behavior due to a localization of the vibrational pattern on a single FG loop. Finally, we show that an analysis of the allosteric effect using an elastic network model fails to predict this localization effect, highlighting the importance of using an all-atom full force field method for this problem.

  11. Substitutional analysis

    CERN Document Server

    Rutherford, Daniel Edwin

    2013-01-01

    Classic monograph, suitable for advanced undergraduates and graduate students. Topics include calculus of permutations and tableaux, semi-normal representation, orthogonal and natural representations, group characters, and substitutional equations. 1968 edition.

  12. Ultrafast Crystallization Dynamics at an Organic-Inorganic Interface Revealed in Real Time by Grazing Incidence Fast Atom Diffraction.

    Science.gov (United States)

    Momeni, Anouchah; Staicu Casagrande, Elena M; Dechaux, Alexia; Khemliche, Hocine

    2018-02-15

    The poor structural properties of organic-inorganic interfaces and their variability represent the main cause of device under-performance. Understanding and controlling the development of these properties in real time has been a difficult experimental challenge. Using a recent technique based on grazing incidence fast atom diffraction (GIFAD), we were able to directly observe during deposition structural transitions in a perylene monolayer on Ag(110). Crystallization from the liquid phase occurs into two distinct structures with drastically different dynamics. Transition to the most compact packing occurs by self-organization only after a second layer has started to build up; subsequent incorporation of molecules from second to first layer triggers an ultrafast crystallization on a macroscopic sale. The final compact crystalline structure shows a long-range order and superior stability, which opens good perspectives for producing in a controlled manner highly ordered hybrid interfaces for photovoltaics and molecular electronics.

  13. Insulating nanoparticles on YBa2Cu3O7-δ thin films revealed by comparison of atomic force and scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Thomson, R.E.; Moreland, J.; Missert, N.; Rudman, D.A.; Sanders, S.C.; Cole, B.F.

    1993-01-01

    The surface topography of YBa 2 Cu 3 O 7-δ thin films has been studied with both atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The AFM images reveal a high density of small distinct nanoparticles, 10--50 nm across and 5--20 nm high, which do not appear in STM images of the same samples. In addition, we have shown that scanning the STM tip across the surface breaks off these particles and moves them to the edge of the scanned area, where they can later be imaged with the AFM

  14. Regiospecifically Fluorinated Polycyclic Aromatic Hydrocarbons via Julia-Kocienski Olefination and Oxidative Photocyclization. Effect of Fluorine Atom Substitution on Molecular Shape.

    Science.gov (United States)

    Banerjee, Shaibal; Sinha, Saikat; Pradhan, Padmanava; Caruso, Alessio; Liebowitz, Daniel; Parrish, Damon; Rossi, Miriam; Zajc, Barbara

    2016-05-20

    A modular synthesis of regiospecifically fluorinated polycyclic aromatic hydrocarbons (PAHs) is described. 1,2-Diarylfluoroalkenes, synthesized via Julia-Kocienski olefination (70-99% yields), were converted to isomeric 5- and 6-fluorobenzo[c]phenanthrene, 5-and 6-fluorochrysene, and 9- and 10-benzo[g]chrysene (66-83% yields) by oxidative photocyclization. Photocyclization to 6-fluorochrysene proceeded more slowly than conversion of 1-styrylnaphthalene to chrysene. Higher fluoroalkene dilution led to a more rapid cyclization. Therefore, photocyclizations were performed at higher dilutions. To evaluate the effect of fluorine atom on molecular shapes, X-ray data for 5- and 6-fluorobenzo[c]phenanthrene, 6-fluorochrysene, 9- and 10-fluorobenzo[g]chrysene, and unfluorinated chrysene as well as benzo[g]chrysene were obtained and compared. The fluorine atom caused a small deviation from planarity in the chrysene series and decreased nonplanarity in the benzo[c]phenanthrene derivatives, but its influence was most pronounced in the benzo[g]chrysene series. A remarkable flattening of the molecule was observed in 9-fluorobenzo[g]chrysene, where the short 2.055 Å interatomic distance between bay-region F-9 and H-8, downfield shift of H-8, and a 26.1 Hz coupling between F-9 and C-8 indicate a possible F-9···H-8 hydrogen bond. In addition, in 9-fluorobenzo[g]chrysene, the stacking distance is short at 3.365 Å and there is an additional interaction between the C-11-H and C-10a of a nearby molecule that is almost perpendicular.

  15. Aspartic acid substitutions in monoamine oxidase-A reveal both catalytic-dependent and -independent influences on cell viability and proliferation.

    Science.gov (United States)

    Wei, Zelan; Satram-Maharaj, Tamara; Chaharyn, Bradley; Kuski, Kelly; Pennington, Paul R; Cao, Xia; Chlan, Jennifer; Mousseau, Darrell D

    2012-11-01

    Post-translational influences could underlie the ambiguous roles of monoamine oxidase-A (MAO-A) in pathologies such as depression, cancer and Alzheimer disease. In support of this, we recently demonstrated that the Ca²⁺-sensitive component of MAO-A catalytic activity is inhibited by a pro-survival p38 (MAPK)-dependent mechanism. We substituted three aspartic acid (D) residues in human MAO-A that reside in putative Ca²⁺-binding motifs and overexpressed the individual proteins in the human HEK293 cell line. We assayed the overexpressed proteins for catalytic activity and for their influence on cell viability (using MTT conversion and trypan blue exclusion) and proliferation/DNA synthesis [using bromodeoxyuridine (BrdU) incorporation]. Innate MAO-A catalytic activity (and the capacity for generating hydrogen peroxide) was unaffected by the D61A substitution, but inhibited moderately or completely by the D248A and D328G substitutions, respectively. The Ca²⁺-sensitive activities of wild-type and D248A MAO-A proteins were enhanced by treatment with the selective p38(MAPK) inhibitor, SB203580, but was completely abrogated by the D61A substitution. Monoamine oxidase-A(D61A) was toxic to cells and exerted no effect on cell proliferation, while MAO-A(D248A) was generally comparable to wild-type MAO-A. As expected, the catalytic-dead MAO-A(D328G) was not cytotoxic, but unexpectedly enhanced both MTT conversion and BrdU staining. Variant-dependent changes in Bax and Bcl-2/Bcl-XL protein expression were observed. A different pattern of effects in N2-a cells suggests cell line-dependent roles for MAO-A. A catalytic-dependent mechanism influences MAO-A-mediated cytotoxicity, whereas a catalytic-independent mechanism contributes to proliferation. Context-dependent inputs by either mechanism could underlie the ambiguous pathological contributions of MAO-A.

  16. Correlating confocal microscopy and atomic force indentation reveals metastatic cancer cells stiffen during invasion into collagen I matrices

    Science.gov (United States)

    Staunton, Jack R.; Doss, Bryant L.; Lindsay, Stuart; Ros, Robert

    2016-01-01

    Mechanical interactions between cells and their microenvironment dictate cell phenotype and behavior, calling for cell mechanics measurements in three-dimensional (3D) extracellular matrices (ECM). Here we describe a novel technique for quantitative mechanical characterization of soft, heterogeneous samples in 3D. The technique is based on the integration of atomic force microscopy (AFM) based deep indentation, confocal fluorescence microscopy, finite element (FE) simulations and analytical modeling. With this method, the force response of a cell embedded in 3D ECM can be decoupled from that of its surroundings, enabling quantitative determination of the elastic properties of both the cell and the matrix. We applied the technique to the quantification of the elastic properties of metastatic breast adenocarcinoma cells invading into collagen hydrogels. We found that actively invading and fully embedded cells are significantly stiffer than cells remaining on top of the collagen, a clear example of phenotypical change in response to the 3D environment. Treatment with Rho-associated protein kinase (ROCK) inhibitor significantly reduces this stiffening, indicating that actomyosin contractility plays a major role in the initial steps of metastatic invasion.

  17. Correlating confocal microscopy and atomic force indentation reveals metastatic cancer cells stiffen during invasion into collagen I matrices.

    Science.gov (United States)

    Staunton, Jack R; Doss, Bryant L; Lindsay, Stuart; Ros, Robert

    2016-01-27

    Mechanical interactions between cells and their microenvironment dictate cell phenotype and behavior, calling for cell mechanics measurements in three-dimensional (3D) extracellular matrices (ECM). Here we describe a novel technique for quantitative mechanical characterization of soft, heterogeneous samples in 3D. The technique is based on the integration of atomic force microscopy (AFM) based deep indentation, confocal fluorescence microscopy, finite element (FE) simulations and analytical modeling. With this method, the force response of a cell embedded in 3D ECM can be decoupled from that of its surroundings, enabling quantitative determination of the elastic properties of both the cell and the matrix. We applied the technique to the quantification of the elastic properties of metastatic breast adenocarcinoma cells invading into collagen hydrogels. We found that actively invading and fully embedded cells are significantly stiffer than cells remaining on top of the collagen, a clear example of phenotypical change in response to the 3D environment. Treatment with Rho-associated protein kinase (ROCK) inhibitor significantly reduces this stiffening, indicating that actomyosin contractility plays a major role in the initial steps of metastatic invasion.

  18. Capsid expansion mechanism of bacteriophage T7 revealed by multistate atomic models derived from cryo-EM reconstructions.

    Science.gov (United States)

    Guo, Fei; Liu, Zheng; Fang, Ping-An; Zhang, Qinfen; Wright, Elena T; Wu, Weimin; Zhang, Ci; Vago, Frank; Ren, Yue; Jakana, Joanita; Chiu, Wah; Serwer, Philip; Jiang, Wen

    2014-10-28

    Many dsDNA viruses first assemble a DNA-free procapsid, using a scaffolding protein-dependent process. The procapsid, then, undergoes dramatic conformational maturation while packaging DNA. For bacteriophage T7 we report the following four single-particle cryo-EM 3D reconstructions and the derived atomic models: procapsid (4.6-Å resolution), an early-stage DNA packaging intermediate (3.5 Å), a later-stage packaging intermediate (6.6 Å), and the final infectious phage (3.6 Å). In the procapsid, the N terminus of the major capsid protein, gp10, has a six-turn helix at the inner surface of the shell, where each skewed hexamer of gp10 interacts with two scaffolding proteins. With the exit of scaffolding proteins during maturation the gp10 N-terminal helix unfolds and swings through the capsid shell to the outer surface. The refolded N-terminal region has a hairpin that forms a novel noncovalent, joint-like, intercapsomeric interaction with a pocket formed during shell expansion. These large conformational changes also result in a new noncovalent, intracapsomeric topological linking. Both interactions further stabilize the capsids by interlocking all pentameric and hexameric capsomeres in both DNA packaging intermediate and phage. Although the final phage shell has nearly identical structure to the shell of the DNA-free intermediate, surprisingly we found that the icosahedral faces of the phage are slightly (∼4 Å) contracted relative to the faces of the intermediate, despite the internal pressure from the densely packaged DNA genome. These structures provide a basis for understanding the capsid maturation process during DNA packaging that is essential for large numbers of dsDNA viruses.

  19. Solvent substitution

    International Nuclear Information System (INIS)

    1990-01-01

    The DOE Environmental Restoration and Waste Management Office of Technology Development and the Air Force Engineering and Services Center convened the First Annual International Workshop on Solvent Substitution on December 4--7, 1990. The primary objectives of this joint effort were to share information and ideas among attendees in order to enhance the development and implementation of required new technologies for the elimination of pollutants associated with industrial use of hazardous and toxic solvents; and to aid in accelerating collaborative efforts and technology transfer between government and industry for solvent substitution. There were workshop sessions focusing on Alternative Technologies, Alternative Solvents, Recovery/Recycling, Low VOC Materials and Treatment for Environmentally Safe Disposal. The 35 invited papers presented covered a wide range of solvent substitution activities including: hardware and weapons production and maintenance, paint stripping, coating applications, printed circuit boards, metal cleaning, metal finishing, manufacturing, compliance monitoring and process control monitoring. This publication includes the majority of these presentations. In addition, in order to further facilitate information exchange and technology transfer, the US Air Force and DOE solicited additional papers under a general ''Call for Papers.'' These papers, which underwent review and final selection by a peer review committee, are also included in this combined Proceedings/Compendium. For those involved in handling, using or managing hazardous and toxic solvents, this document should prove to be a valuable resource, providing the most up-to-date information on current technologies and practices in solvent substitution. Individual papers are abstracted separated

  20. Solvent substitution

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    The DOE Environmental Restoration and Waste Management Office of Technology Development and the Air Force Engineering and Services Center convened the First Annual International Workshop on Solvent Substitution on December 4--7, 1990. The primary objectives of this joint effort were to share information and ideas among attendees in order to enhance the development and implementation of required new technologies for the elimination of pollutants associated with industrial use of hazardous and toxic solvents; and to aid in accelerating collaborative efforts and technology transfer between government and industry for solvent substitution. There were workshop sessions focusing on Alternative Technologies, Alternative Solvents, Recovery/Recycling, Low VOC Materials and Treatment for Environmentally Safe Disposal. The 35 invited papers presented covered a wide range of solvent substitution activities including: hardware and weapons production and maintenance, paint stripping, coating applications, printed circuit boards, metal cleaning, metal finishing, manufacturing, compliance monitoring and process control monitoring. This publication includes the majority of these presentations. In addition, in order to further facilitate information exchange and technology transfer, the US Air Force and DOE solicited additional papers under a general Call for Papers.'' These papers, which underwent review and final selection by a peer review committee, are also included in this combined Proceedings/Compendium. For those involved in handling, using or managing hazardous and toxic solvents, this document should prove to be a valuable resource, providing the most up-to-date information on current technologies and practices in solvent substitution. Individual papers are abstracted separated.

  1. Sugar Substitutes

    Science.gov (United States)

    ... and drinks. You may have heard them called “artificial sweeteners” or “non-caloric sweeteners.” They can be used ... a food or drink contains. What sugar substitutes/artificial sweeteners are approved by the FDA? The following sugar ...

  2. Story of skeletally substituted benzenes

    Indian Academy of Sciences (India)

    Unknown

    corresponds to the out-of-plane distortion of the hydrogen atom connected to the heteroatoms, which is then ..... etc. exhibits significant localization.24 The skeletally substituted benzenes considered in the study with a wide ... involving cationic and anionic systems are expected to show considerable localization. In. Table 3.

  3. Atomic details of near-transition state conformers for enzyme phosphoryl transfer revealed by MgF-3 rather than by phosphoranes.

    Science.gov (United States)

    Baxter, Nicola J; Bowler, Matthew W; Alizadeh, Tooba; Cliff, Matthew J; Hounslow, Andrea M; Wu, Bin; Berkowitz, David B; Williams, Nicholas H; Blackburn, G Michael; Waltho, Jonathan P

    2010-03-09

    Prior evidence supporting the direct observation of phosphorane intermediates in enzymatic phosphoryl transfer reactions was based on the interpretation of electron density corresponding to trigonal species bridging the donor and acceptor atoms. Close examination of the crystalline state of beta-phosphoglucomutase, the archetypal phosphorane intermediate-containing enzyme, reveals that the trigonal species is not PO-3 , but is MgF-3 (trifluoromagnesate). Although MgF-3 complexes are transition state analogues rather than phosphoryl group transfer reaction intermediates, the presence of fluorine nuclei in near-transition state conformations offers new opportunities to explore the nature of the interactions, in particular the independent measures of local electrostatic and hydrogen-bonding distributions using 19F NMR. Measurements on three beta-PGM-MgF-3 -sugar phosphate complexes show a remarkable relationship between NMR chemical shifts, primary isotope shifts, NOEs, cross hydrogen bond F...H-N scalar couplings, and the atomic positions determined from the high-resolution crystal structure of the beta-PGM-MgF--3 -G6P complex. The measurements provide independent validation of the structural and isoelectronic MgF--3 model of near-transition state conformations.

  4. Experimental and DFT Investigations Reveal the Influence of the Outer Coordination Sphere on the Vibrational Spectra of Nickel-Substituted Rubredoxin, a Model Hydrogenase Enzyme.

    Science.gov (United States)

    Slater, Jeffrey W; Marguet, Sean C; Cirino, Sabrina L; Maugeri, Pearson T; Shafaat, Hannah S

    2017-04-03

    Nickel-substituted rubredoxin (NiRd) is a functional enzyme mimic of hydrogenase, highly active for electrocatalytic and solution-phase hydrogen generation. Spectroscopic methods can provide valuable insight into the catalytic mechanism, provided the appropriate technique is used. In this study, we have employed multiwavelength resonance Raman spectroscopy coupled with DFT calculations on an extended active-site model of NiRd to probe the electronic and geometric structures of the resting state of this system. Excellent agreement between experiment and theory is observed, allowing normal mode assignments to be made on the basis of frequency and intensity analyses. Both metal-ligand and ligand-centered vibrational modes are enhanced in the resonance Raman spectra. The latter provide information about the hydrogen bonding network and structural distortions due to perturbations in the secondary coordination sphere. To reproduce the resonance enhancement patterns seen for high-frequency vibrational modes, the secondary coordination sphere must be included in the computational model. The structure and reduction potential of the Ni III Rd state have also been investigated both experimentally and computationally. This work begins to establish a foundation for computational resonance Raman spectroscopy to serve in a predictive fashion for investigating catalytic intermediates of NiRd.

  5. Meta-Alkoxy-Substituted Difluoroboron Dibenzoylmethane Complexes as Environment-Sensitive Materials.

    Science.gov (United States)

    Daly, Margaret L; Kerr, Caroline; DeRosa, Christopher A; Fraser, Cassandra L

    2017-09-20

    The optical properties of meta-alkoxy-substituted difluoroboron dibenzoylmethane dyes were investigated in solution and in the solid state. Meta-alkoxy substitution induced strong intramolecular charge transfer (ICT) from the oxygen-donating substituent to the halide and boron acceptors in the excited state, as compared to the π-π* transition that is observed with para-alkoxy substitution. The optical properties of para- and meta-substituted alkoxy boron dyes were evaluated by calculations, in dilute solution, and in solid-state films. When embedded in amorphous matrixes (e.g., PLA, PMMA, PS, cholesterol), all dyes showed fluorescence (F) and phosphorescence (P) emission. In this report, we show that meta-substitution resulted in enhanced solvatochromism and an increased phosphorescence-to-fluorescence ratio in solid-state films compared to analogous para-substituted samples. With enhanced phosphorescence intensity via the heavy-atom effect, iodo-substituted dyes were further studied in PLA-PEG nanoparticles. Oxygen calibrations revealed stronger phosphorescence and a greater oxygen-sensing range for the meta- versus para-alkoxy-substituted dyes, features that are important for oxygen-sensing materials design.

  6. Highly excited atoms

    International Nuclear Information System (INIS)

    Kleppner, D.; Littman, M.G.; Zimmerman, M.L.

    1981-01-01

    Highly excited atoms are often called Rydberg atoms. These atoms have a wealth of exotic properties which are discussed. Of special interest, are the effects of electric and magnetic fields on Rydberg atoms. Ordinary atoms are scarcely affected by an applied electric or magnetic field; Rydberg atoms can be strongly distorted and even pulled apart by a relatively weak electric field, and they can be squeezed into unexpected shapes by a magnetic field. Studies of the structure of Rydberg atoms in electric and magnetic fields have revealed dramatic atomic phenomena that had not been observed before

  7. C-Terminal Substitution of HBV Core Proteins with Those from DHBV Reveals That Arginine-Rich 167RRRSQSPRR175 Domain Is Critical for HBV Replication

    Science.gov (United States)

    Kim, Taeyeung; Shin, Bo-Hye; Park, Gil-Soon; Park, Sun; Chwae, Yong-Joon; Shin, Ho-Joon; Kim, Kyongmin

    2012-01-01

    To investigate the contributions of carboxyl-terminal nucleic acid binding domain of HBV core (C) protein for hepatitis B virus (HBV) replication, chimeric HBV C proteins were generated by substituting varying lengths of the carboxyl-terminus of duck hepatitis B virus (DHBV) C protein for the corresponding regions of HBV C protein. All chimeric C proteins formed core particles. A chimeric C protein with 221–262 amino acids of DHBV C protein, in place of 146–185 amino acids of the HBV C protein, supported HBV pregenomic RNA (pgRNA) encapsidation and DNA synthesis: 40% amino acid sequence identity or 45% homology in the nucleic-acid binding domain of HBV C protein was sufficient for pgRNA encapsidation and DNA synthesis, although we predominantly detected spliced DNA. A chimeric C protein with 221–241 and 251–262 amino acids of DHBV C, in place of HBV C 146–166 and 176–185 amino acids, respectively, could rescue full-length DNA synthesis. However, a reciprocal C chimera with 242–250 of DHBV C (242RAGSPLPRS 250) introduced in place of 167–175 of HBV C (167RRRSQSPRR 175) significantly decreased pgRNA encapsidation and DNA synthesis, and full-length DNA was not detected, demonstrating that the arginine-rich 167RRRSQSPRR175 domain may be critical for efficient viral replication. Five amino acids differing between viral species (underlined above) were tested for replication rescue; R169 and R175 were found to be important. PMID:22911745

  8. Sequencing of the needle transcriptome from Norway spruce (Picea abies Karst L. reveals lower substitution rates, but similar selective constraints in gymnosperms and angiosperms

    Directory of Open Access Journals (Sweden)

    Chen Jun

    2012-11-01

    Full Text Available Abstract Background A detailed knowledge about spatial and temporal gene expression is important for understanding both the function of genes and their evolution. For the vast majority of species, transcriptomes are still largely uncharacterized and even in those where substantial information is available it is often in the form of partially sequenced transcriptomes. With the development of next generation sequencing, a single experiment can now simultaneously identify the transcribed part of a species genome and estimate levels of gene expression. Results mRNA from actively growing needles of Norway spruce (Picea abies was sequenced using next generation sequencing technology. In total, close to 70 million fragments with a length of 76 bp were sequenced resulting in 5 Gbp of raw data. A de novo assembly of these reads, together with publicly available expressed sequence tag (EST data from Norway spruce, was used to create a reference transcriptome. Of the 38,419 PUTs (putative unique transcripts longer than 150 bp in this reference assembly, 83.5% show similarity to ESTs from other spruce species and of the remaining PUTs, 3,704 show similarity to protein sequences from other plant species, leaving 4,167 PUTs with limited similarity to currently available plant proteins. By predicting coding frames and comparing not only the Norway spruce PUTs, but also PUTs from the close relatives Picea glauca and Picea sitchensis to both Pinus taeda and Taxus mairei, we obtained estimates of synonymous and non-synonymous divergence among conifer species. In addition, we detected close to 15,000 SNPs of high quality and estimated gene expression differences between samples collected under dark and light conditions. Conclusions Our study yielded a large number of single nucleotide polymorphisms as well as estimates of gene expression on transcriptome scale. In agreement with a recent study we find that the synonymous substitution rate per year (0.6 × 10

  9. Chemical reactions of recoil atoms and thermal atoms of tritium with haloid benzenes

    International Nuclear Information System (INIS)

    Simirskij, Yu.N.; Firsova, L.P.

    1978-01-01

    Radiochemical yields have been determined for the products of substitution of hydrogen atoms and halides in Cl-, Br-, and I-benzenes with tritium atoms obtained during thermal dissociation of T 2 and with recoil atoms T arising in nuclear reaction 6 Li(n, P)T. It is shown that in the series of Cl-, Br-, and I-benzenes yields of the products of substitution of halides atoms with tritium grow, whereas those of hydrogen atom substitution change only little. The correlation nature of the yields of substitution products of halide atoms with tritium remains constant in a wide range of the initial kinetic energies of T atoms for the recoil atoms with E 0 =2.7 MeV and for the completely thermolized atoms during thermal dissociation of T 2

  10. Atomic force microscopy reveals a morphological differentiation of chromobacterium violaceum cells associated with biofilm development and directed by N-hexanoyl-L-homoserine lactone.

    Directory of Open Access Journals (Sweden)

    Anara A Kamaeva

    Full Text Available Chromobacterium violaceum abounds in soil and water ecosystems in tropical and subtropical regions and occasionally causes severe and often fatal human and animal infections. The quorum sensing (QS system and biofilm formation are essential for C. violaceum's adaptability and pathogenicity, however, their interrelation is still unknown. C. violaceum's cell and biofilm morphology were examined by atomic force microscopy (AFM in comparison with growth rates, QS-dependent violacein biosynthesis and biofilm biomass quantification. To evaluate QS regulation of these processes, the wild-type strain C. violaceum ATCC 31532 and its mini-Tn5 mutant C. violaceum NCTC 13274, cultivated with and without the QS autoinducer N-hexanoyl-L-homoserine lactone (C6-HSL, were used. We report for the first time the unusual morphological differentiation of C. violaceum cells, associated with biofilm development and directed by the QS autoinducer. AFM revealed numerous invaginations of the external cytoplasmic membrane of wild-type cells, which were repressed in the mutant strain and restored by exogenous C6-HSL. With increasing bacterial growth, polymer matrix extrusions formed in place of invaginations, whereas mutant cells were covered with a diffusely distributed extracellular substance. Thus, quorum sensing in C. violaceum involves a morphological differentiation that organises biofilm formation and leads to a highly differentiated matrix structure.

  11. Correlative STED and Atomic Force Microscopy on Live Astrocytes Reveals Plasticity of Cytoskeletal Structure and Membrane Physical Properties during Polarized Migration

    Directory of Open Access Journals (Sweden)

    Nathalie Rouach

    2017-04-01

    Full Text Available The plasticity of the cytoskeleton architecture and membrane properties is important for the establishment of cell polarity, adhesion and migration. Here, we present a method which combines stimulated emission depletion (STED super-resolution imaging and atomic force microscopy (AFM to correlate cytoskeletal structural information with membrane physical properties in live astrocytes. Using STED compatible dyes for live cell imaging of the cytoskeleton, and simultaneously mapping the cell surface topology with AFM, we obtain unprecedented detail of highly organized networks of actin and microtubules in astrocytes. Combining mechanical data from AFM with optical imaging of actin and tubulin further reveals links between cytoskeleton organization and membrane properties. Using this methodology we illustrate that scratch-induced migration induces cytoskeleton remodeling. The latter is caused by a polarization of actin and microtubule elements within astroglial cell processes, which correlates strongly with changes in cell stiffness. The method opens new avenues for the dynamic probing of the membrane structural and functional plasticity of living brain cells. It is a powerful tool for providing new insights into mechanisms of cell structural remodeling during physiological or pathological processes, such as brain development or tumorigenesis.

  12. Assessment of chlorine atoms substitution step with alkoxy groups in poly(dichloro)phosphazene. {sup 31}P NMR; Ocena stopnia podstawienia atomow chloru w poli(dichloro)fosfazenie grupami alkoksylowymi. {sup 31}P NMR

    Energy Technology Data Exchange (ETDEWEB)

    Sulkowska, A. [Wydzial Farmaceutyczny, Slaska Akademia Medyczna, Sosnowiec (Poland); Sulkowski, W. [Wydzial Budownictwa i Inzynierii Srodowiska, Politechnika Czestochowska, Czestochowa (Poland)

    1995-12-31

    The {sup 31}P NMR method has been used for fast assessment of chlorine substitution by alkoxy groups in polyphosphazenes. For this reason the changes in NMR spectra between dialkoxy and alkoxychloro polyphosphazenes have been analysed. The influence of physical conditions (temperature, solvent, reaction time) on the step of chlorine substitution reaction for different poly phosphazenes has been also investigated. 3 refs, 1 fig., 3 tab.

  13. Diphosphorus-substituted derivatives of ketones

    International Nuclear Information System (INIS)

    Novikova, Z.S.; Kurkin, A.N.; Lutsenko, I.F.

    1986-01-01

    The structure of C,0-diphosphorus-substituted derivatives of ketones formed in the phosphorylation of sodium enolates of C-phosphorus-substituted ketones depends on the structure of the phosphorus-containing group in the molecule of the original ketone; increase in the electron-acceptor power of the substituents on the phosphorus atom and rise in its valence favor the formation of β-phosphorus-containing vinyl esters of phosphorus acids

  14. Analysis of 6912 unselected somatic hypermutations in human VDJ rearrangements reveals lack of strand specificity and correlation between phase II substitution rates and distance to the nearest 3' activation-induced cytidine deaminase target

    DEFF Research Database (Denmark)

    Ohm-Laursen, Line; Barington, Torben

    2007-01-01

    -nucleotide motifs present on both strands of the V(H) gene showed significant correlations between the substitution frequencies in reverse complementary motifs, suggesting that the SHM machinery targets both strands equally well. An analysis of individual J(H) and D gene segments showed that the substitution...

  15. Application of high-resolution continuum source flame atomic absorption spectrometry to reveal, evaluate and overcome certain spectral effects in Pb determination of unleaded gasoline

    Science.gov (United States)

    Kowalewska, Zofia; Laskowska, Hanna; Gzylewski, Michał

    2017-06-01

    High-resolution continuum source and line source flame atomic absorption spectrometry (HR-CS FAAS and LS FAAS, respectively) were applied for Pb determination in unleaded aviation or automotive gasoline that was dissolved in methyl-isobutyl ketone. When using HR-CS FAAS, a structured background (BG) was registered in the vicinity of both the 217.001 nm and 283.306 nm Pb lines. In the first case, the BG, which could be attributed to absorption by the OH molecule, directly overlaps with the 217 nm line, but it is of relatively low intensity. For the 283 nm line, the structured BG occurs due to uncompensated absorption by OH molecules present in the flame. BG lines of relatively high intensity are situated at a large distance from the 283 nm line, which enables accurate analysis, not only when using simple variants of HR-CS FAAS but also for LS FAAS with a bandpass of 0.1 nm. The lines of the structured spectrum at 283 nm can have ;absorption; (maxima) or ;emission; (minima) character. The intensity of the OH spectra can significantly depend on the flame character and composition of the investigated organic solution. The best detection limit for the analytical procedure, which was 0.01 mg L- 1 for Pb in the investigated solution, could be achieved using HR-CS FAAS with the 283 nm Pb line, 5 pixels for the analyte line measurement and iterative background correction (IBC). In this case, least squares background correction (LSBC) is not recommended. However, LSBC (available as the ;permanent structures; option) would be recommended when using the 217 nm Pb line. In LS FAAS, an additional phenomenon related to the nature of the organic matrix (for example, isooctane or toluene) can play an important role. The effect is of continuous character and probably due to the simultaneous efficient correction of the continuous background (IBC) it is not observed in HR-CS FAAS. The fact that the effect does not depend on the flame character indicates that it is not radiation

  16. Global alteration of the drug-binding pocket of human P-glycoprotein (ABCB1) by substitution of fifteen conserved residues reveals a negative correlation between substrate size and transport efficiency.

    Science.gov (United States)

    Vahedi, Shahrooz; Chufan, Eduardo E; Ambudkar, Suresh V

    2017-11-01

    P-glycoprotein (P-gp), an ATP-dependent efflux pump, is linked to the development of multidrug resistance in cancer cells. However, the drug-binding sites and translocation pathways of this transporter are not yet well-characterized. We recently demonstrated the important role of tyrosine residues in regulating P-gp ATP hydrolysis via hydrogen bond formations with high affinity modulators. Since tyrosine is both a hydrogen bond donor and acceptor, and non-covalent interactions are key in drug transport, in this study we investigated the global effect of enrichment of tyrosine residues in the drug-binding pocket on the drug binding and transport function of P-gp. By employing computational analysis, 15 conserved residues in the drug-binding pocket of human P-gp that interact with substrates were identified and then substituted with tyrosine, including 11 phenylalanine (F72, F303, F314, F336, F732, F759, F770, F938, F942, F983, F994), two leucine (L339, L975), one isoleucine (I306), and one methionine (M949). Characterization of the tyrosine-rich P-gp mutant in HeLa cells demonstrated that this major alteration in the drug-binding pocket by introducing fifteen additional tyrosine residues is well tolerated and has no measurable effect on total or cell surface expression of this mutant. Although the tyrosine-enriched mutant P-gp could transport small to moderate size (transport large (>1000 Daltons) substrates such as NBD-cyclosporine A, Bodipy-paclitaxel and Bodipy-vinblastine was significantly decreased. This was further supported by the physico-chemical characterization of seventeen tested substrates, which revealed a negative correlation between drug transport and molecular size for the tyrosine-enriched P-gp mutant. Published by Elsevier Inc.

  17. Structural properties and hyperfine characterization of Sn-substituted goethites

    Energy Technology Data Exchange (ETDEWEB)

    Larralde, A.L. [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Ramos, C.P. [Departamento de Fisica de la Materia Condensada, GIyA - CAC - CNEA, Av. Gral. Paz 1499 (1650), San Martin, Bs. As. (Argentina); Arcondo, B. [Departamento de Fisica, Facultad de Ingenieria, Universidad de Buenos Aires, Av. Paseo Colon 850 (C1063ACV), Bs. As. (Argentina); Tufo, A.E. [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Saragovi, C. [Departamento de Fisica de la Materia Condensada, GIyA - CAC - CNEA, Av. Gral. Paz 1499 (1650), San Martin, Bs. As. (Argentina); Sileo, E.E., E-mail: sileo@qi.fcen.uba.ar [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Pure and tin-doped goethites were synthesized from Sn(II) solutions at ambient pressure and 70 Degree-Sign C. Black-Right-Pointing-Pointer The Rietveld refinement of PXRD data indicated that Sn partially substituted the Fe(III) ions. Black-Right-Pointing-Pointer The substitution provoked unit cell expansion, and a distortion of the coordination polyhedron. Black-Right-Pointing-Pointer {sup 119}Sn Moessbauer spectroscopy revealed that Sn(II) is incorporated as Sn(IV). Black-Right-Pointing-Pointer {sup 57}Fe Moessbauer spectroscopy showed a lower magnetic coupling as tin concentration increased. - Abstract: Tin-doped goethites obtained by a simple method at ambient pressure and 70 Degree-Sign C were characterized by inductively coupled plasma atomic emission spectrometry, scanning electron microscopy, Rietveld refinement of powder X-ray diffraction data, and {sup 57}Fe and {sup 119}Sn Moessbauer spectroscopy. The particles size and the length to width ratios decreased with tin-doping. Sn partially substituted the Fe(III) ions provoking unit cell expansion and increasing the crystallinity of the particles with enlarged domains that grow in the perpendicular and parallel directions to the anisotropic broadening (1 1 1) axis. Intermetallic E, E Prime and DC distances also change although the variations are not monotonous, indicating different variations in the coordination polyhedron. In general, the Sn-substituted samples present larger intermetallic distances than pure goethite, and the greatest change is shown in the E Prime distance which coincides with the c-parameter. {sup 119}Sn Moessbauer spectroscopy revealed that Sn(II) is incorporated as Sn(IV) in the samples. On the other hand, Fe(II) presence was not detected by {sup 57}Fe Moessbauer spectroscopy, suggesting the existence of vacancies in the Sn-doped samples. A lower magnetic coupling is also evidenced from the average magnetic hyperfine field values obtained as tin

  18. Electronic dipole moment and tunneling state of hydrogen atom in hydrogen-bond materials revealed by neutron and X-ray structure analyses

    International Nuclear Information System (INIS)

    Kiyanagi, Ryoji; Noda, Yukio; Mochida, Tomoyuki; Sugawara, Tadashi

    2007-01-01

    The isolated hydrogen-bonded materials, 5-methyl-9-hydroxyphenalenone (MeHPLN) and 5-bromo-9-hydroxyphenalenone (Br-HPLN), were studied by means of X-ray and neutron diffraction methods. It was found that the position of the nucleus of the hydrogen atom in the hydrogen-bond region does not agree with the center of mass of the electron cloud of the hydrogen atom. This leads to a local electronic dipole moment in the hydrogen-bond region. Using the experimentally obtained dipole moment, phase transition temperatures for MeHPLN and BrHPLN were calculated based on a tunneling model. Result shows good agreement with the ones obtained by a dielectric measurement. (author)

  19. Stabilisation of the [6]-prismane structure by silicon substitution

    Indian Academy of Sciences (India)

    Asif Equbal

    effect of substitution on its mechanical properties.15–21. While the synthesis of lower prismanes (n < 6) was. *For correspondence. †Dedicated to the memory of the late Professor Charusita. Chakravarty. readily achieved,22–25 ..... The light green color in the ring indicates silicon atoms. of all Ge-substituted-benzene dimers ...

  20. Mapping the Trajectory of Nucleophilic Substitution at Silicon Using a peri-Substituted Acenaphthyl Scaffold.

    Science.gov (United States)

    Hupf, Emanuel; Olaru, Marian; Raţ, Ciprian I; Fugel, Malte; Hübschle, Christian B; Lork, Enno; Grabowsky, Simon; Mebs, Stefan; Beckmann, Jens

    2017-08-04

    The second-order nucleophilic substitution (S N 2) reaction at a silicon atom is scrutinized by means of snapshots along a pseudoreaction coordinate. Phosphine and fluoride represent both attacking and leaving groups in the modeled S N 2 reaction. In the experimentally obtained 5-diphenylphosphinoacenaphth-6-yl-dimethylfluorosilane, 1, the phosphine and fluorosilane moieties are forced into immediate proximity through an acenaphthyl scaffold, that is, they exhibit peri interactions that serve as the model of the reactant ion-molecule complex and starting point for a theoretical potential-energy surface (PES) scan. Upon dissociation of fluoride, the experimentally obtained silylphosphonium cation 2 serves as a model of the product and end point of the PES scan. The pseudoreaction pathway is studied using geometric, energetic, spectroscopic, molecular-orbital, and topological real-space bonding indicators. It becomes evident that it is crucial to combine such methods to understand the pseudoreaction because they reveal different aspects based on different sensitivity to dispersive, electrostatic, and polar-covalent contributions to bonding, as shown by the reduced density gradient analysis. For example, atoms-in-molecules theory describes a late topological catastrophe, whereas the electron localizability indicator describes an early concerted reaction and natural resonance theory describes a more gradual change of properties. This case study encourages the use of a well-balanced toolbox equipped with complementary methods to emphasize different aspects of bonding. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Analysis of 6912 unselected somatic hypermutations in human VDJ rearrangements reveals lack of strand specificity and correlation between phase II substitution rates and distance to the nearest 3' activation-induced cytidine deaminase target

    DEFF Research Database (Denmark)

    Ohm-Laursen, Line; Barington, Torben

    2007-01-01

    -23*01) from blood B lymphocytes enriched for CD27-positive memory cells. Analyses of 6,912 unique, unselected substitutions showed that in vivo hot and cold spots for the SHM of C and G residues corresponded closely to the target preferences reported for AID in vitro. A detailed analysis of all possible four......-nucleotide motifs present on both strands of the V(H) gene showed significant correlations between the substitution frequencies in reverse complementary motifs, suggesting that the SHM machinery targets both strands equally well. An analysis of individual J(H) and D gene segments showed that the substitution...... rates in G and T residues correlated inversely with the distance to the nearest 3' WRC AID hot spot motif on both the nontranscribed and transcribed strands. This suggests that phase II SHM takes place 5' of the initial AID deamination target and primarily targets T and G residues or, alternatively...

  2. An all-atom model of the chromatin fiber containing linker histones reveals a versatile structure tuned by the nucleosomal repeat length.

    Directory of Open Access Journals (Sweden)

    Hua Wong

    Full Text Available In the nucleus of eukaryotic cells, histone proteins organize the linear genome into a functional and hierarchical architecture. In this paper, we use the crystal structures of the nucleosome core particle, B-DNA and the globular domain of H5 linker histone to build the first all-atom model of compact chromatin fibers. In this 3D jigsaw puzzle, DNA bending is achieved by solving an inverse kinematics problem. Our model is based on recent electron microscopy measurements of reconstituted fiber dimensions. Strikingly, we find that the chromatin fiber containing linker histones is a polymorphic structure. We show that different fiber conformations are obtained by tuning the linker histone orientation at the nucleosomes entry/exit according to the nucleosomal repeat length. We propose that the observed in vivo quantization of nucleosomal repeat length could reflect nature's ability to use the DNA molecule's helical geometry in order to give chromatin versatile topological and mechanical properties.

  3. Atom optics

    International Nuclear Information System (INIS)

    Balykin, V. I.; Jhe, W.

    1999-01-01

    Atom optics, in analogy to neutron and electron optics, deals with the realization of as a traditional elements, such as lenes, mirrors, beam splitters and atom interferometers, as well as a new 'dissipative' elements such as a slower and a cooler, which have no analogy in an another types of optics. Atom optics made the development of atom interferometer with high sensitivity for measurement of acceleration and rotational possible. The practical interest in atom optics lies in the opportunities to create atom microprobe with atom-size resolution and minimum damage of investigated objects. (Cho, G. S.)

  4. Iron(III) and manganese(II) substituted hydroxyapatite nanoparticles: Characterization and cytotoxicity analysis

    Energy Technology Data Exchange (ETDEWEB)

    Li Yan; Nam, C T; Ooi, C P [Division of Bioengineering, School of Chemical and Biomedical Engineering, Nanyang Technological University, 639798 (Singapore)], E-mail: ascpooi@ntu.edu.sg

    2009-09-01

    Calcium hydroxyapatite (HA) is the main inorganic component of natural bones and can bond to bone directly in vivo. Thus HA is widely used as coating material on bone implants due to its good osteoconductivity and osteoinductivity. Metal ions doped HA have been used as catalyst or absorbents since the ion exchange method has introduced new properties in HA which are inherent to the metal ions. For example, Mn{sup 2+} ions have the potential to increase cell adhesion while Fe{sup 3+} ions have magnetic properties. Here, Fe(III) substituted hydroxyapatite (Fe-HA) and Mn(II) substituted hydroxyapatite (Mn-HA) were produced by wet chemical method coupled with ion exchange mechanism. Compared with pure HA, the colour of both Fe-HA and Mn-HA nanoparticles changed from white to brown and pink respectively. The intensity of the colours increased with increasing substitution concentrations. XRD patterns showed that all samples were single phased HA while the FTIR spectra revealed all samples possessed the characteristic phosphate and hydroxyl adsorption bands of HA. However, undesired adsorption bands of carbonate substitution (B-type carbonated HA) and H{sub 2}O were also detected, which was reasonable since the wet chemical method was used in the synthesis of these nanoparticles. FESEM images showed all samples were elongated spheroids with small size distribution and of around 70 nm, regardless of metal ion substitution concentrations. EDX spectra showed the presence of Fe and Mn and ICP-AES results revealed all metal ion substituted HA were non-stoichiometric (Ca/P atomic ratio deviates from 1.67). Fe-HA nanoparticles were paramagnetic and the magnetic susceptibility increased with the increase of Fe content. Based on the extraction assay for cytotoxicity test, both Fe-HA and Mn-HA displayed non-cytotoxicity to osteoblast.

  5. Iron(III) and manganese(II) substituted hydroxyapatite nanoparticles: Characterization and cytotoxicity analysis

    Science.gov (United States)

    Li, Yan; Teck Nam, Chai; Ooi, Chui Ping

    2009-09-01

    Calcium hydroxyapatite (HA) is the main inorganic component of natural bones and can bond to bone directly in vivo. Thus HA is widely used as coating material on bone implants due to its good osteoconductivity and osteoinductivity. Metal ions doped HA have been used as catalyst or absorbents since the ion exchange method has introduced new properties in HA which are inherent to the metal ions. For example, Mn2+ ions have the potential to increase cell adhesion while Fe3+ ions have magnetic properties. Here, Fe(III) substituted hydroxyapatite (Fe-HA) and Mn(II) substituted hydroxyapatite (Mn-HA) were produced by wet chemical method coupled with ion exchange mechanism. Compared with pure HA, the colour of both Fe-HA and Mn-HA nanoparticles changed from white to brown and pink respectively. The intensity of the colours increased with increasing substitution concentrations. XRD patterns showed that all samples were single phased HA while the FTIR spectra revealed all samples possessed the characteristic phosphate and hydroxyl adsorption bands of HA. However, undesired adsorption bands of carbonate substitution (B-type carbonated HA) and H2O were also detected, which was reasonable since the wet chemical method was used in the synthesis of these nanoparticles. FESEM images showed all samples were elongated spheroids with small size distribution and of around 70 nm, regardless of metal ion substitution concentrations. EDX spectra showed the presence of Fe and Mn and ICP-AES results revealed all metal ion substituted HA were non-stoichiometric (Ca/P atomic ratio deviates from 1.67). Fe-HA nanoparticles were paramagnetic and the magnetic susceptibility increased with the increase of Fe content. Based on the extraction assay for cytotoxicity test, both Fe-HA and Mn-HA displayed non-cytotoxicity to osteoblast.

  6. On the bosonic atoms

    Science.gov (United States)

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

    2018-01-01

    We investigate ground state properties of atoms, in which substitute fermions - electrons by bosons, namely π --mesons. We perform some calculations in the frame of modified Hartree-Fock (HF) equation. The modification takes into account symmetry, instead of anti-symmetry of the pair identical bosons wave function. The modified HF approach thus enhances (doubles) the effect of self-action for the boson case. Therefore, we accordingly modify the HF equations by eliminating the self-action terms "by hand". The contribution of meson-meson and meson-nucleon non-Coulomb interaction is inessential at least for atoms with low and intermediate nuclear charge, which is our main subject. We found that the binding energy of pion negative ions A π - , pion atoms A π , and the number of extra bound pions ΔN π increases with the growth of nuclear charge Z. For e.g. Xe ΔN π = 4. As an example of a simple process with a pion atom, we consider photoionization that differs essentially from that for electron atoms. Namely, it is not monotonic decreasing from the threshold but has instead a prominent maximum above threshold. We study also elastic scattering of pions by pion atoms.

  7. Atom-by-atom assembly

    International Nuclear Information System (INIS)

    Hla, Saw Wai

    2014-01-01

    Atomic manipulation using a scanning tunneling microscope (STM) tip enables the construction of quantum structures on an atom-by-atom basis, as well as the investigation of the electronic and dynamical properties of individual atoms on a one-atom-at-a-time basis. An STM is not only an instrument that is used to ‘see’ individual atoms by means of imaging, but is also a tool that is used to ‘touch’ and ‘take’ the atoms, or to ‘hear’ their movements. Therefore, the STM can be considered as the ‘eyes’, ‘hands’ and ‘ears’ of the scientists, connecting our macroscopic world to the exciting atomic world. In this article, various STM atom manipulation schemes and their example applications are described. The future directions of atomic level assembly on surfaces using scanning probe tips are also discussed. (review article)

  8. Revealing the atomic structure and strontium distribution in nanometer-thick La0.8Sr0.2CoO3−δ grown on (001)-oriented SrTiO3

    KAUST Repository

    Feng, Zhenxing

    2014-01-01

    Surface segregation in metal oxides can greatly influence the oxygen transport and surface oxygen exchange kinetics critical to the performance of solid-state devices such as oxygen permeation membranes and solid oxide fuel/electrolytic cell electrodes. Unfortunately detecting elemental distributions at the atomic scale near the surface remains challenging, which hampers the understanding of underpinning mechanisms and control of surface segregation for the design of high-performance materials. Using the coherent Bragg rod analysis (COBRA) method, we report the first direct 3D atomic imaging of a 4 nm-thick "La0.8Sr0.2CoO 3-δ"/SrTiO3 epitaxial film. Of significance, energy differential COBRA revealed pronounced Sr segregation (La 1-xSrxCoO3-δ, x ∼ 0.4) in the four unit cells from the top surface while complete Sr depletion was detected in the five unit cells from the "La0.8Sr0.2CoO 3-δ"/SrTiO3 interface. The drastic strontium compositional changes in the film were associated with large changes in the atomic positions of apical oxygen sites in the perovskite structure. Such Sr segregation tendencies toward the surface were also found in nominal "La0.6Sr0.4CoO3-δ" thin films, which can greatly enhance the surface oxygen exchange properties of oxides. The results presented here show that COBRA and the differential COBRA methods can be used to investigate a variety of electrochemically active systems providing atomic scale structural and chemical information that can help understand the physical and chemical properties of these systems and serve as a basis for comparison with DFT calculations. © 2014 The Royal Society of Chemistry.

  9. Medicineringsfejl ved generisk substitution

    DEFF Research Database (Denmark)

    Rölfing, Jan

    2012-01-01

    Generic substitution is a major cause of medical mistakes in the general population. Danish legislation obligates pharmacies to substitute prescribed medicine with the cheapest equivalent formulation, despite variations in product name, packaging, shape and colour. Consequently, medical mistakes ...... occur. Scientific evidence on the consequences of generic substitution is sparse. Call upon fellow health workers to report medical mistakes to the national entities and scientific peers, in order to increase awareness and scientific evidence about the problem....

  10. An Atomic Force Microscope Study Revealed Two Mechanisms in the Effect of Anticancer Drugs on Rate-Dependent Young's Modulus of Human Prostate Cancer Cells.

    Directory of Open Access Journals (Sweden)

    Juan Ren

    Full Text Available Mechanical properties of cells have been recognized as a biomarker for cellular cytoskeletal organization. As chemical treatments lead to cell cytoskeletal rearrangements, thereby, modifications of cellular mechanical properties, investigating cellular mechanical property variations provides insightful knowledge to effects of chemical treatments on cancer cells. In this study, the effects of eight different anticancer drugs on the mechanical properties of human prostate cancer cell (PC-3 are investigated using a recently developed control-based nanoindentation measurement (CNM protocol on atomic force microscope (AFM. The CNM protocol overcomes the limits of other existing methods to in-liquid nanoindentation measurement of live cells on AFM, particularly for measuring mechanical properties of live cells. The Young's modulus of PC-3 cells treated by the eight drugs was measured by varying force loading rates over three orders of magnitude, and compared to the values of the control. The results showed that the Young's modulus of the PC-3 cells increased substantially by the eight drugs tested, and became much more pronounced as the force load rate increased. Moreover, two distinct trends were clearly expressed, where under the treatment of Disulfiram, paclitaxel, and MK-2206, the exponent coefficient of the frequency- modulus function remained almost unchanged, while with Celebrex, BAY, Totamine, TPA, and Vaproic acid, the exponential rate was significantly increased.

  11. Thermal stability of atom configurations around Er atoms doped in InP by OMVPE

    International Nuclear Information System (INIS)

    Ofuchi, Hironori; Ito, Takashi; Kawamoto, Takeshi; Tabuchi, Masao; Fujiwara, Yasufumi; Takeda, Yoshikazu

    1999-01-01

    It has been found that there is a threshold growth temperature between 550 deg C and 580 deg C for the change of local structure around Er atoms in InP doped Er atoms grown by organometallic vapor phase epitaxy (OMVPE). To understand whether the structure change is induced at the growing surface or during the growth as an in situ annealing, the thermal stability of the local structures around the Er atoms doped in InP by the OMVPE at 530 deg C has been investigated by the extended X-ray absorption fine structure (EXAFS). The EXAFS analysis revealed that the local structure around the Er atoms, which existed substitutionally on In sites in the InP lattice, was stable against the post-growth annealing even for 1 h at 650 deg C. Therefore, it is concluded that the local structures are formed on the growth front, and not in the volume of InP by thermal annealing during or after the growth. (author)

  12. Hyperfine structure of the metastable p-barHe+ atom revealed by a laser-induced (n,l) = (37,35) → (38,34) transition

    International Nuclear Information System (INIS)

    Widmann, E.; Eades, J.; Yamazaki, T.

    1996-11-01

    A precise scan of the previously discovered laser-induced transition (n,l) = (37,35) → (38,34) in p-barHe + revealed a doublet structure with a separation of Δν HF = 1.70 ± 0.05 GHz. This new type of 'hyperfine' splitting is ascribed to the interaction of the antiproton orbital angular momentum and the electron spin. (author)

  13. Atomic displacements in bcc dilute alloys

    Indian Academy of Sciences (India)

    We present here a systematic investigation of the atomic displacements in bcc transition metal (TM) dilute alloys. We have calculated the atomic displacements in bcc (V, Cr, Fe, Nb, Mo, Ta and W) transition metals (TMs) due to 3d, 4d and 5d TMs at the substitutional site using the Kanzaki lattice static method. Wills and ...

  14. Atomic displacements in bcc dilute alloys

    Indian Academy of Sciences (India)

    Abstract. We present here a systematic investigation of the atomic displacements in bcc transition metal (TM) dilute alloys. We have calculated the atomic displacements in bcc. (V, Cr, Fe, Nb, Mo, Ta and W) transition metals (TMs) due to 3d, 4d and 5d TMs at the substitutional site using the Kanzaki lattice static method.

  15. Interactions of Histone Acetyltransferase p300 with the Nuclear Proteins Histone and HMGB1, As Revealed by Single Molecule Atomic Force Spectroscopy.

    Science.gov (United States)

    Banerjee, S; Rakshit, T; Sett, S; Mukhopadhyay, R

    2015-10-22

    One of the important properties of the transcriptional coactivator p300 is histone acetyltransferase (HAT) activity that enables p300 to influence chromatin action via histone modulation. p300 can exert its HAT action upon the other nuclear proteins too--one notable example being the transcription-factor-like protein HMGB1, which functions also as a cytokine, and whose accumulation in the cytoplasm, as a response to tissue damage, is triggered by its acetylation. Hitherto, no information on the structure and stability of the complexes between full-length p300 (p300FL) (300 kDa) and the histone/HMGB1 proteins are available, probably due to the presence of unstructured regions within p300FL that makes it difficult to be crystallized. Herein, we have adopted the high-resolution atomic force microscopy (AFM) approach, which allows molecularly resolved three-dimensional contour mapping of a protein molecule of any size and structure. From the off-rate and activation barrier values, obtained using single molecule dynamic force spectroscopy, the biochemical proposition of preferential binding of p300FL to histone H3, compared to the octameric histone, can be validated. Importantly, from the energy landscape of the dissociation events, a model for the p300-histone and the p300-HMGB1 dynamic complexes that HAT forms, can be proposed. The lower unbinding forces of the complexes observed in acetylating conditions, compared to those observed in non-acetylating conditions, indicate that upon acetylation, p300 tends to weakly associate, probably as an outcome of charge alterations on the histone/HMGB1 surface and/or acetylation-induced conformational changes. To our knowledge, for the first time, a single molecule level treatment of the interactions of HAT, where the full-length protein is considered, is being reported.

  16. Phage display-mediated discovery of novel tyrosinase-targeting tetrapeptide inhibitors reveals the significance of N-terminal preference of cysteine residues and their functional sulfur atom.

    Science.gov (United States)

    Lee, Yu-Ching; Hsiao, Nai-Wan; Tseng, Tien-Sheng; Chen, Wang-Chuan; Lin, Hui-Hsiung; Leu, Sy-Jye; Yang, Ei-Wen; Tsai, Keng-Chang

    2015-02-01

    Tyrosinase, a key copper-containing enzyme involved in melanin biosynthesis, is closely associated with hyperpigmentation disorders, cancer, and neurodegenerative diseases, and as such, it is an essential target in medicine and cosmetics. Known tyrosinase inhibitors possess adverse side effects, and there are no safety regulations; therefore, it is necessary to develop new inhibitors with fewer side effects and less toxicity. Peptides are exquisitely specific to their in vivo targets, with high potencies and relatively few off-target side effects. Thus, we systematically and comprehensively investigated the tyrosinase-inhibitory abilities of N- and C-terminal cysteine/tyrosine-containing tetrapeptides by constructing a phage-display random tetrapeptide library and conducting computational molecular docking studies on novel tyrosinase tetrapeptide inhibitors. We found that N-terminal cysteine-containing tetrapeptides exhibited the most potent tyrosinase-inhibitory abilities. The positional preference of cysteine residues at the N terminus in the tetrapeptides significantly contributed to their tyrosinase-inhibitory function. The sulfur atom in cysteine moieties of N- and C-terminal cysteine-containing tetrapeptides coordinated with copper ions, which then tightly blocked substrate-binding sites. N- and C-terminal tyrosine-containing tetrapeptides functioned as competitive inhibitors against mushroom tyrosinase by using the phenol ring of tyrosine to stack with the imidazole ring of His263, thus competing for the substrate-binding site. The N-terminal cysteine-containing tetrapeptide CRVI exhibited the strongest tyrosinase-inhibitory potency (with an IC50 of 2.7 ± 0.5 μM), which was superior to those of the known tyrosinase inhibitors (arbutin and kojic acid) and outperformed kojic acid-tripeptides, mimosine-FFY, and short-sequence oligopeptides at inhibiting mushroom tyrosinase. Copyright © 2014 by The American Society for Pharmacology and Experimental

  17. The influence of silicon atom doping phagraphene nanoribbons on the electronic and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yunjin, E-mail: 18165382763@163.com; Chen, Zheng; Hu, Shi; Yu, Genggeng; Peng, Yingying

    2017-06-15

    Highlights: • When carbon atom on 5-6-7 rings is substituted by a silicon atom, the substitution prefers to take place at the edges and heptagon carbon ring. • Si doping can significantly adjust electronic and magnetic properties of PHAGNRs. • Doping can change the bandgaps from 0.14 eV to 0.935 eV, and transfer a semiconductor from a direct bandgap into indirect bandgap for 6-MPHAGNRs. - Abstract: Based on a first-principles approach, the structural, electronic and magnetic properties are investigated systematically of pristine and Si-doped phagraphene nanoribbons (PHAGNRs) with different edges, including zigzag edge (ZPHAGNR) and mixed edge (MPHAGNR). The geometric structure is drastically changed when silicon atom replaces the different carbon atom on 5-6-7 rings of PHAGNRs. The calculations of formation energy show that silicon atom always prefers to substitute carbon atom at the edge position or on heptagon carbon ring both in 6-MPHAGNR and 4-ZPHAGNR. Further studies reveal that Si doping can significantly adjust electronic and magnetic properties of PHAGNRs, and the sizes of bandgaps and magnetic moments depend heavily on the doping position. Besides, doping can transfer a direct bandgap semiconductor into an indirect bandgap semiconductor for MPHAGNR, and separate the band structure near the fermi level for the ZPHAGNR. In addition, the biggest advantage for doping silicon atom in PHAGNRs is that no impurity energy levels are introduced. All these open an approach to design electronic and magnetic nanometer devices based on PHAGNRs in the future.

  18. Atomic Force Microscopy for DNA SNP Identification

    Science.gov (United States)

    Valbusa, Ugo; Ierardi, Vincenzo

    The knowledge of the effects of single-nucleotide polymorphisms (SNPs) in the human genome greatly contributes to better comprehension of the relation between genetic factors and diseases. Sequence analysis of genomic DNA in different individuals reveals positions where variations that involve individual base substitutions can occur. Single-nucleotide polymorphisms are highly abundant and can have different consequences at phenotypic level. Several attempts were made to apply atomic force microscopy (AFM) to detect and map SNP sites in DNA strands. The most promising approach is the study of DNA mutations producing heteroduplex DNA strands and identifying the mismatches by means of a protein that labels the mismatches. MutS is a protein that is part of a well-known complex of mismatch repair, which initiates the process of repairing when the MutS binds to the mismatched DNA filament. The position of MutS on the DNA filament can be easily recorded by means of AFM imaging.

  19. What governs nitrogen configuration in substituted aminophosphines?

    OpenAIRE

    Wodrich, Matthew D.; Vargas, Alfredo; Morgantini, Pierre-Yves; Merino, Gabriel; Corminboeuf, Anne-Clémence

    2009-01-01

    The trigonal planar geometry of the nitrogen atom in commonly used phosphoramidite ligands is not in line with the traditional valence shell electron pair repulsion (VSEPR) model. In this work, the effects governing nitrogen configuration in several substituted aminophosphines, A2PNB2 (A or B¼H, F, Cl, Br, Me, OMe, BINOP), are examined using modern computational analytic tools. The electron delocalization descriptions provided by both electron localization function (ELF) and block localized w...

  20. Atomic polarizabilities

    International Nuclear Information System (INIS)

    Safronova, M. S.; Mitroy, J.; Clark, Charles W.; Kozlov, M. G.

    2015-01-01

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed

  1. Atomic polarizabilities

    Energy Technology Data Exchange (ETDEWEB)

    Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)

    2015-01-22

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.

  2. Atomic physics

    International Nuclear Information System (INIS)

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

    1984-01-01

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

  3. Atom probe crystallography

    OpenAIRE

    Gault, Baptiste; Moody, Michael P.; Cairney, Julie M.; Ringer, Simon P.

    2012-01-01

    This review addresses new developments in the emerging area of “atom probe crystallography”, a materials characterization tool with the unique capacity to reveal both composition and crystallographic structure at the atomic scale. This information is crucial for the manipulation of microstructure for the design of both structural and functional materials with optimized mechanical, electric, optoelectronic, magnetic, or superconducting properties that will find application in, for example, nan...

  4. Ultracold atoms on atom chips

    DEFF Research Database (Denmark)

    Krüger, Peter; Hofferberth, S.; Haller, E.

    2005-01-01

    Miniaturized potentials near the surface of atom chips can be used as flexible and versatile tools for the manipulation of ultracold atoms on a microscale. The full scope of possibilities is only accessible if atom-surface distances can be reduced to microns. We discuss experiments in this regime...

  5. Effects of Al addition on atomic structure of Cu-Zr metallic glass

    Science.gov (United States)

    Li, Feng; Zhang, Huajian; Liu, Xiongjun; Dong, Yuecheng; Yu, Chunyan; Lu, Zhaoping

    2018-02-01

    The atomic structures of Cu52Zr48 and Cu45Zr48Al7 metallic glasses (MGs) have been studied by molecular dynamic simulations. The results reveal that the molar volume of the Cu45Zr48Al7 MG is smaller than that of the Cu52Zr48 MG, although the size of the Al atom is larger than that of the Cu atom, implying an enhanced atomic packing density achieved by introducing Al into the ternary MG. Bond shortening in unlike atomic pairs Zr-Al and Cu-Al is observed in the Cu45Zr48Al7 MG, which is attributed to strong interactions between Al and (Zr, Cu) atoms. Meanwhile, the atomic packing efficiency is enhanced by the minor addition of Al. Compared with the Cu52Zr48 binary MG, the potential energy of the ternary MG decreases and the glass transition temperature increases. Structural analyses indicate that more Cu- and Al-centered full icosahedral clusters emerge in the Cu45Zr48Al7 MG as some Cu atoms are substituted by Al. Furthermore, the addition of Al leads to more icosahedral medium-range orders in the ternary MG. The increase of full icosahedral clusters and the enhancement of the packing density are responsible for the improved glass-forming ability of Cu45Zr48Al7.

  6. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Science.gov (United States)

    2010-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject to...

  7. Substitutionally doped phosphorene: electronic properties and gas sensing.

    Science.gov (United States)

    Suvansinpan, Nawat; Hussain, Fayyaz; Zhang, Gang; Chiu, Cheng Hsin; Cai, Yongqing; Zhang, Yong-Wei

    2016-02-12

    Phosphorene, a new elemental two-dimensional material, has attracted increasing attention owing to its intriguing electronic properties. In particular, pristine phospohorene, due to its ultrahigh surface-volume ratio and high chemical activity, has been shown to be promising for gas sensing (Abbas et al 2015 ACS Nano 9 5618). To further enhance its sensing ability, we perform first-principles calculations based on density functional theory to study substitutionally doped phosphorene with 17 different atoms, focusing on structures, energetics, electronic properties and gas sensing. Our calculations reveal that anionic X (X = O, C and S) dopants have a large binding energy and highly dispersive electronic states, signifying the formation of covalent X-P bonds and thus strong structural stability. Alkali atom (Li and Na) doping is found to donate most of the electrons in the outer s-orbital by forming ionic bonds with P, and the band gap decreases by pushing down the conduction band, suggesting that the optical and electronic properties of the doped phosphorene can be tailored. For doping with VIIIB-group (Fe, Co and Ni) elements, a strong affinity is predicted and the binding energy and charge transfer are correlated strongly with their electronegativity. By examining NO molecule adsorption, we find that these metal doped phosphorenes (MDPs) in general exhibit a significantly enhanced chemical activity compared with pristine phosphorene. Our study suggests that substitutionally doped phosphorene shows many intriguing electronic and optic properties different from pristine phosphorene and MDPs are promising in chemical applications involving molecular adsorption and desorption processes, such as materials growth, catalysis, gas sensing and storage.

  8. Ab initio supercell calculations of the (0001) α-Cr2O3 surface with a partially or totally Al-substituted external layer

    International Nuclear Information System (INIS)

    Sun Jizhong; Stirner, Thomas

    2009-01-01

    Ab initio supercell calculations employing the periodic Hartree-Fock formalism are presented of the (0001) α-Cr 2 O 3 surface with a partially or totally Al-substituted external layer. In the simulations a fraction of the Cr atoms at the surface of the chromia slab are replaced by Al atoms, and the Al surface coverage is varied between zero (pure chromia) and 100% (Al-terminated chromia). The surface Al atoms are found to relax inwards considerably, with the magnitude of the relaxation decreasing with increasing Al surface coverage. The calculations also reveal that the surface energy of the slab decreases with increasing Al coverage. Finally, the electronic properties at the surface of the Al-substituted (0001) α-Cr 2 O 3 slabs are investigated. Here the calculations show that the substitution of Cr by Al gives rise to an increase in the covalency of the Al-O bonds compared to slabs of pure alumina. In contrast, the influence of the surface Al atoms on the electrostatic potential in the (0001) plane of metal ions is relatively small. These findings support the utilisation of α-chromia substrates for the templated growth of α-alumina, which is consistent with recent experiments.

  9. Electricity/oil substitution

    International Nuclear Information System (INIS)

    Melvin, J.G.

    1980-09-01

    The extent to which electricity could substitute for imported oil in Canada is assessed and it is concluded that the bulk of projected oil imports could be displaced. This substitution of electricity for oil could be largely completed within two decades, with existing technology, using Canadian resources. The substitution of electricity for imported oil would result in relatively low energy costs and would stimulate economic growth. Energy self-sufficiency through the substitution of electricity for oil is uniquely a Canadian option; it is not open to other industrial countries. The option exists because of Canada's resources of oil sands for essential liquid fuels, hydraulic and nuclear electrical potential, and natural gas as an interim source of energy. While other countries face an energy crisis due to declining supplies of oil, Canada faces opportunities. The policies of Federal and Provincial governments, as perceived by individual decision makers, will have a major influence on Canada's ability to realize opportunities. (auth)

  10. The substitutability of reinforcers

    OpenAIRE

    Green, Leonard; Freed, Debra E.

    1993-01-01

    Substitutability is a construct borrowed from microeconomics that describes a continuum of possible interactions among the reinforcers in a given situation. Highly substitutable reinforcers, which occupy one end of the continuum, are readily traded for each other due to their functional similarity. Complementary reinforcers, at the other end of the continuum, tend to be consumed jointly in fairly rigid proportion, and therefore cannot be traded for one another except to achieve that proportio...

  11. Synthesis of substituted pyrazines

    Science.gov (United States)

    Pagoria, Philip F.; Zhang, Mao Xi

    2016-10-04

    A method for synthesizing a pyrazine-containing material according to one embodiment includes contacting an iminodiacetonitrile derivative with a base and a reagent selected from a group consisting of hydroxylamine, a hydroxylamine salt, an aliphatic primary amine, a secondary amine, an aryl-substituted alkylamine a heteroaryl-substituted alkyl amine, an alcohol, an alkanolamine and an aryl alcoholamine. Additional methods and several reaction products are presented. ##STR00001##

  12. Effect of ionic substitutions on the magnetic properties of strontium hexaferrite: A first principles study

    Directory of Open Access Journals (Sweden)

    Vivek Dixit

    2017-11-01

    Full Text Available We investigated the effect of substitution of various ions at the Fe sites on magnetic properties of strontium hexaferrite (SrFe12O19 using first principles method based on density functional theory. The site occupancies of substituted atoms were estimated by calculating the substitution energies of different configurations. The formation probabilities of configurations were used to calculate magnetic properties of substituted strontium hexaferrite. A total of 21 elements (M were screened for their possible substitution in strontium hexaferrite, SrFe12−xMxO19 with x = 0.5. In each case the site preference of the substituted atom and the magnetic properties were calculated. We found that Bi, Sb, Sn, and Sc can effectively increase the magnetization and P, Co, Al, Ga, and Ti can enhance the anisotropy field when substituted into strontium hexaferrite.

  13. Atomic physics

    International Nuclear Information System (INIS)

    Anon.

    1976-01-01

    Research activities in atomic physics at Lawrence Berkeley Laboratory during 1976 are described. Topics covered include: experiments on stored ions; test for parity violation in neutral weak currents; energy conservation and astrophysics; atomic absorption spectroscopy, atomic and molecular detectors; theoretical studies of quantum electrodynamics and high-z ions; atomic beam magnetic resonance; radiative decay from the 2 3 Po, 2 levels of helium-like argon; quenching of the metastable 2S/sub 1/2/ state of hydrogen-like argon in an external electric field; and lifetime of the 2 3 Po level of helium-like krypton

  14. Antimony substitution in SmFeAsO

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Daniel; Braun, Hans F. [Universitaet Bayreuth (Germany)

    2015-07-01

    In the iron based compounds structural and magnetic phase transitions can be suppressed by applying external hydrostatic pressure and superconductivity emerges. Beside hydrostatic pressure, it is possible to apply chemical pressure by the substitution of atoms in the compounds with smaller ones. Such a substitution was successful for example in LaFeAs{sub 1-x}P{sub x}O, where the parent compound shows a structural and a spin-density-wave transition and the P doped samples become superconducting. We are interested in the opposite way and substitute the As by the bigger Sb. In literature, the substitution in the La-1111 compounds was possible up to a substitution level of 40 %. With Sm, instead of La, we used a smaller rare-earth metal. We present the results obtained on polycrystalline samples characterized by Xray powder diffraction and resistivity measurements.

  15. Physico-chemical properties and solubility behaviour of multi-substituted hydroxyapatite powders containing silicon

    International Nuclear Information System (INIS)

    Sprio, S.; Tampieri, A.; Landi, E.; Sandri, M.; Martorana, S.; Celotti, G.; Logroscino, G.

    2008-01-01

    Hydroxyapatite powders characterized by ionic substitutions both in anionic and cationic sites were successfully prepared by synthesis in aqueous medium. The process parameters were set up to allow the simultaneous substitution of the foreign ions, namely carbonate, magnesium and silicon in the crystallographic site of calcium and phosphorus, keeping in count the competition which arises between atoms destined to occupy the same crystallographic site. The chemico-physical properties of the powders were investigated through several analytical techniques, i.e. X-ray diffraction, infrared spectroscopy, atomic emission spectroscopy and thermo-gravimetric analysis. The results show that the utilization of sodium hydrogen-carbonate as a reactant allows the entering of carbonate into the HA structure, mainly in phosphate position, while sodium is eliminated during the process of the powder washing. The entering of silicon in the HA structure progressively reduces its crystallinity, as also carbonate ions do. Silicate and carbonate ions can enter simultaneously into the HA structure, in biological-like amounts, although they compete for the occupation of the phosphate site; the powder crystallinity is strongly reduced as the content of the two substituting ions increases, so that a limit molar concentration exists where the apatite structure collapses and an amorphous phase forms with the simultaneous formation of crystalline calcium carbonate. Solubility tests, carried out at physiological conditions, reveal an increased calcium release in the HA powders containing silicon compared to the silicon-free HA; the solubility behaviour of the multi-substituted HA powders at physiological conditions makes these materials promising as bioactive bone scaffold, as they are able to continuously supply ions which are essential for the process of bone reconstruction

  16. Early Atomism

    Indian Academy of Sciences (India)

    https://www.ias.ac.in/article/fulltext/reso/015/10/0905-0925. Keywords. Atomic theory; Avogadro's hypothesis; atomic weights; periodic table; valence; molecular weights; molecular formula; isomerism. Author Affiliations. S Ramasesha1. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, ...

  17. Atomic physics

    CERN Document Server

    Born, Max

    1969-01-01

    The Nobel Laureate's brilliant exposition of the kinetic theory of gases, elementary particles, the nuclear atom, wave-corpuscles, atomic structure and spectral lines, electron spin and Pauli's principle, quantum statistics, molecular structure and nuclear physics. Over 40 appendices, a bibliography, numerous figures and graphs.

  18. Exotic atoms

    International Nuclear Information System (INIS)

    Backenstoss, G.

    1986-01-01

    Recent developments in the field of exotic atoms are presented. The improved quality of accelerator facilities and experimental techniques leads to a more precise determination of data. This opens new fields in nuclear and particle physics to which exotic atoms may contribute valuable knowledge. (author)

  19. substituted ethylenediamine derivatives

    Indian Academy of Sciences (India)

    Administrator

    chemistry of platinum metal complexes containing bis-(diphenylphosphino)- methane(dppm) has been extensively studied in this regard whereas similar types of reports concerning bisphosphines wherein the phosphorus atoms are separated by more than two atoms/heteroatoms are limited. We report here the synthesis of ...

  20. Crystal structures of unsymmetrically mixed β-pyrrole substituted ...

    Indian Academy of Sciences (India)

    The normal-coordinate structural decomposition analysis of these structures revealed mainly saddle distortion of the macrocycle ... Unsymmetrical mixed substituted porphyrins; β-pyrrole substituted porphyrins; NSD analysis;. Hirshfeld surface ..... out-of-plane (Doop) displacement values of the macro- cycle based on the ...

  1. Bone substitute biomaterials

    CERN Document Server

    Mallick, K

    2014-01-01

    Bone substitute biomaterials are fundamental to the biomedical sector, and have recently benefitted from extensive research and technological advances aimed at minimizing failure rates and reducing the need for further surgery. This book reviews these developments, with a particular focus on the desirable properties for bone substitute materials and their potential to encourage bone repair and regeneration. Part I covers the principles of bone substitute biomaterials for medical applications. One chapter reviews the quantification of bone mechanics at the whole-bone, micro-scale, and non-scale levels, while others discuss biomineralization, osteoductivization, materials to fill bone defects, and bioresorbable materials. Part II focuses on biomaterials as scaffolds and implants, including multi-functional scaffolds, bioceramics, and titanium-based foams. Finally, Part III reviews further materials with the potential to encourage bone repair and regeneration, including cartilage grafts, chitosan, inorganic poly...

  2. Muon-Substituted Malonaldehyde: Transforming a Transition State into a Stable Structure by Isotope Substitution.

    Science.gov (United States)

    Goli, Mohammad; Shahbazian, Shant

    2016-02-12

    Isotope substitutions are usually conceived to play a marginal role on the structure and bonding pattern of molecules. However, a recent study [Angew. Chem. Int. Ed. 2014, 53, 13706-13709; Angew. Chem. 2014, 126, 13925-13929] further demonstrates that upon replacing a proton with a positively charged muon, as the lightest radioisotope of hydrogen, radical changes in the nature of the structure and bonding of certain species may take place. The present report is a primary attempt to introduce another example of structural transformation on the basis of the malonaldehyde system. Accordingly, upon replacing the proton between the two oxygen atoms of malonaldehyde with the positively charged muon a serious structural transformation is observed. By using the ab initio nuclear-electronic orbital non-Born-Oppenheimer procedure, the nuclear configuration of the muon-substituted species is derived. The resulting nuclear configuration is much more similar to the transition state of the proton transfer in malonaldehyde rather than to the stable configuration of malonaldehyde. The comparison of the "atoms in molecules" (AIM) structure of the muon-substituted malonaldehyde and the AIM structure of the stable and the transition-state configurations of malonaldehyde also unequivocally demonstrates substantial similarities of the muon-substituted malonaldehyde to the transition state. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Heat transport through atomic contacts.

    Science.gov (United States)

    Mosso, Nico; Drechsler, Ute; Menges, Fabian; Nirmalraj, Peter; Karg, Siegfried; Riel, Heike; Gotsmann, Bernd

    2017-05-01

    Heat transport and dissipation at the nanoscale severely limit the scaling of high-performance electronic devices and circuits. Metallic atomic junctions serve as model systems to probe electrical and thermal transport down to the atomic level as well as quantum effects that occur in one-dimensional (1D) systems. Whereas charge transport in atomic junctions has been studied intensively in the past two decades, heat transport remains poorly characterized because it requires the combination of a high sensitivity to small heat fluxes and the formation of stable atomic contacts. Here we report heat-transfer measurements through atomic junctions and analyse the thermal conductance of single-atom gold contacts at room temperature. Simultaneous measurements of charge and heat transport reveal the proportionality of electrical and thermal conductance, quantized with the respective conductance quanta. This constitutes a verification of the Wiedemann-Franz law at the atomic scale.

  4. Superradiators created atom by atom

    Science.gov (United States)

    Meschede, Dieter

    2018-02-01

    High radiation rates are usually associated with macroscopic lasers. Laser radiation is “coherent”—its amplitude and phase are well-defined—but its generation requires energy inputs to overcome loss. Excited atoms spontaneously emit in a random and incoherent fashion, and for N such atoms, the emission rate simply increases as N. However, if these atoms are in close proximity and coherently coupled by a radiation field, this microscopic ensemble acts as a single emitter whose emission rate increases as N2 and becomes “superradiant,” to use Dicke's terminology (1). On page 662 of this issue, Kim et al. (2) show the buildup of coherent light fields through collective emission from atomic radiators injected one by one into a resonator field. There is only one atom ever in the cavity, but the emission is still collective and superradiant. These results suggest another route toward thresholdless lasing.

  5. [Artificial bone substitutes].

    Science.gov (United States)

    Koníček, Petr

    Bone tissue substitutes are divided into basic classification with its pros and cons described. Arteficial bone grafts are especially pointed out in article, publishing our own experience with two specific synthetic preps. Finally there is a blink in the near future of bone tissue augmentation.

  6. A first-principles study on the magnetic properties of nonmetal atom doped phosphorene monolayers.

    Science.gov (United States)

    Zheng, Huiling; Zhang, Jianmin; Yang, Baishun; Du, Xiaobo; Yan, Yu

    2015-07-07

    In order to induce magnetism in two-dimensional semiconductors for their applications in spintronic devices and novel chemical and electronic properties of semiconducting phosphorene, the geometrical structure, electronic and magnetic properties of doped phosphorene monolayers with a series of nonmetal atoms, including H, F, Cl, Br, I, B, C, Si, N, As, O, S and Se, were systematically investigated using first-principles calculations. The results show that although the substitutional doping of H, F, Cl, Br, I, B, N, O, S or Se results in large structural deformation at the doping sites of phosphorene monolayers, all neutral nonmetal atom doped systems are stable. The calculated formation energies reveal that the substitutional doping of numerous nonmetal atoms in phosphorene monolayer are possible under appropriate experimental conditions, and the charged dopants C(-), Si(-), S(+) and Se(+) are stable. Moreover, the substitutional doping of H, F, Cl, Br, I, B, N, As, C(-), Si(-), S(+) or Se(+) cannot induce magnetism in phosphorene monolayer due to the saturation or pairing of valence electrons of dopant and its neighboring P atoms, whereas ground states of neutral C, Si, O, S or Se doped systems are magnetic due to the appearance of an unpaired valence electron of C and Si or the formation of a nonbonding 3p electron of a neighboring P atom around O, S and Se. Furthermore, the magnetic coupling between the moments induced by two Si, O, S or Se are long-range anti-ferromagnetic and the coupling can be attributed to the hybridization interaction involving polarized electrons, whereas the coupling between the moments induced by two C is weak.

  7. Quantum Dots Embedded in Graphene Nanoribbons by Chemical Substitution

    DEFF Research Database (Denmark)

    Carbonell-Sanroma, Eduard; Brandimarte, Pedro; Balog, Richard

    2017-01-01

    Bottom-up chemical reactions of selected molecular precursors on a gold surface can produce high quality graphene nanoribbons (GNRs). Here, we report on the formation of quantum dots embedded in an armchair GNR by substitutional inclusion of pairs of boron atoms into the GNR backbone. The boron...

  8. A study of photon interaction parameters in lung tissue substitutes

    Directory of Open Access Journals (Sweden)

    H C Manjunatha

    2014-01-01

    Full Text Available The study of photon interaction with different composite materials has become a topic of prime importance for radiation physicists. Some parameters of dosimetric interest are the mass attenuation coefficient, effective atomic number, and electron density; these help in the basic understanding of photon interactions with composite materials. The photon interaction parameters such as mass attenuation coefficient (μ/ρ, effective atomic number (Z eff , and effective electron density (N el must be identical for the phantom material and their tissue. In the present study, we have evaluated the photon interaction parameters such as (μ/ρ, Z eff and N el of 13 lung tissue substitutes. The variations of these parameters of lung tissue substitutes with photon energy are graphically represented. The photon interaction parameters of lung tissue substitutes are compared with that of lung tissue. The variation of photon interaction parameters of the studied lung tissue substitutes is similar that of the lung. Logically, it can be shown that Alderson lung is good substitute for lung than the other substitutes.

  9. A study of photon interaction parameters in lung tissue substitutes.

    Science.gov (United States)

    Manjunatha, H C

    2014-04-01

    The study of photon interaction with different composite materials has become a topic of prime importance for radiation physicists. Some parameters of dosimetric interest are the mass attenuation coefficient, effective atomic number, and electron density; these help in the basic understanding of photon interactions with composite materials. The photon interaction parameters such as mass attenuation coefficient (μ/ρ), effective atomic number (Zeff), and effective electron density (N el) must be identical for the phantom material and their tissue. In the present study, we have evaluated the photon interaction parameters such as (μ/ρ), Z eff and N el of 13 lung tissue substitutes. The variations of these parameters of lung tissue substitutes with photon energy are graphically represented. The photon interaction parameters of lung tissue substitutes are compared with that of lung tissue. The variation of photon interaction parameters of the studied lung tissue substitutes is similar that of the lung. Logically, it can be shown that Alderson lung is good substitute for lung than the other substitutes.

  10. Atomic politics

    International Nuclear Information System (INIS)

    Skogmar, G.

    1979-01-01

    The authors basic point is that the military and civil sides of atomic energy cannot be separated. The general aim of the book is to analyze both the military and civil branches, and the interdependence between them, of American foreign policy in the atomic field. Atomic policy is seen as one of the most important imstruments of foreign policy which, in turn, is seen against the background of American imperialism in general. Firstly, the book investigates the most important means by which the United States has controlled the development in the nuclear field in other countries. These means include influencing the conditions of access to nuclear resources of various kinds, influencing the flow of technical-economic information and influencing international organizations and treaties bearing on atomic energy. The time period treated is 1945-1973. 1973 is chosen as the end-year of the study mainly because of the new conditions in the whole energy field initiated by the oil crisis in that year. The sources of the empirical work are mainly hearings before the Joint Committee on Atomic Energy of the U.S. Congress and legal material of various kinds. Secondly, the goals of the American policy are analyzed. The goals identified are armament effect, non-proliferation (horizontal), sales, and energy dependence. The relation between the main goals is discussed.The discussion is centered on the interdependence between the military and the civil aspects, conflict and coincidence of various goals, the relation between short-term and long-term goals, and the possibilities of using one goal as pretext for another. Thirdly, some causes of the changes in the atomic policy around 1953 and 1963 are identified. These are the strategic balance, the competitive situation, the capacity (of the American atomic productive apparatus), and the nuclear technological stage. The specific composition of these four factors at the two time-points can explain the changes of policy. (author)

  11. Steam Reforming of CH4 Using Ni- Substituted Pyrochlore Catalysts

    Science.gov (United States)

    Haynes, Daniel J.

    The steam reforming of methane (SMR) continues to remain an important industrial reaction for large-scale production of H2 as well as synthesis gas mixtures which can be used for the production of useful chemicals (e.g. methanol). Although SMR is a rather mature technology, traditional nickel based catalysts used industrially are subjected to severe temperatures and reaction conditions, which lead to irreversible activity loss through sintering, support collapse, and carbon formation. Pyrochlore-based mixed oxide have been identified as refractory materials that can be modified through the substitution of catalytic metals and other promoting species into the structure to mitigate these issues causing deactivation. For this study, a lanthanum zirconate pyrochlore catalyst was substituted with Ni to determine whether the oxide structure could effectively stabilize the activity of the catalytic metal during the SMR. The effect of different variables including calcination temperature, a comparison of a substituted versus supported Ni pyrochlore catalyst, Ni weight loading, and Sr promotion have been evaluated to determine the location of the Ni in the structure, and their effect on catalytic behavior. It was revealed that the effect of calcination temperature on a 6wt% Ni substituted pyrochlore produced by the Pechini method demonstrated very little Ni was soluble in the pyrochlore lattice. It was further revealed that by XRD, TEM, and atom probe tomography that, despite the metal loading, Ni exsolves from the structure upon crystallization of the pyrochlore at 700°C, and forms NiO at the surface and grain boundaries. An additional separate La2ZrNiO6 perovskite phase also began to form at higher temperatures (>800°C). Increasing calcination temperature was found to lead to slight sintering of the NiO at the surface, which made the NiO more reducible. Meanwhile decreasing the Ni weight loading was found to produce a lower reduction temperature due to the presence of

  12. Solvation properties of N-substituted cis and trans amides are not identical: significant enthalpy and entropy changes are revealed by the use of variable temperature 1H NMR in aqueous and chloroform solutions and ab initio calculations.

    Science.gov (United States)

    Troganis, Anastassios N; Sicilia, Emilia; Barbarossou, Klimentini; Gerothanassis, Ioannis P; Russo, Nino

    2005-12-29

    The cis/trans conformational equilibrium of N-methyl formamide (NMF) and the sterically hindered tert-butylformamide (TBF) was investigated by the use of variable temperature gradient 1H NMR in aqueous solution and in the low dielectric constant and solvation ability solvent CDCl3 and various levels of first principles calculations. The trans isomer of NMF in aqueous solution is enthalpically favored relative to the cis (deltaH(o) = -5.79 +/- 0.18 kJ mol(-1)) with entropy differences at 298 K (298 x deltaS(o) = -0.23 +/- 0.17 kJ mol(-1)) playing a minor role. The experimental value of the enthalpy difference strongly decreases (deltaH(o) = -1.72 +/- 0.06 kJ mol(-1)), and the contribution of entropy at 298 K (298 x deltaS(o) = -1.87 +/- 0.06 kJ mol(-1)) increases in the case of the sterically hindered tert-butylformamide. The trans isomer of NMF in CDCl3 solution is enthalpically favored relative to the cis (deltaH(o) = -3.71 +/- 0.17 kJ mol(-1)) with entropy differences at 298 K (298 x deltaS(o) = 1.02 +/- 0.19 kJ mol(-1)) playing a minor role. In the sterically hindered tert-butylformamide, the trans isomer is enthalpically disfavored (deltaH(o) = 1.60 +/- 0.09 kJ mol(-1)) but is entropically favored (298 x deltaS(o) = 1.71 +/- 0.10 kJ mol(-1)). The results are compared with literature data of model peptides. It is concluded that, in amide bonds at 298 K and in the absence of strongly stabilizing sequence-specific inter-residue interactions involving side chains, the free energy difference of the cis/trans isomers and both the enthalpy and entropy contributions are strongly dependent on the N-alkyl substitution and the solvent. The significant decreasing enthalpic benefit of the trans isomer in CDCl3 compared to that in H2O, in the case of NMF and TBF, is partially offset by an adverse entropy contribution. This is in agreement with the general phenomenon of enthalpy versus entropy compensation. B3LY/6-311++G** and MP2/6-311++G** quantum chemical calculations

  13. Atomic structure of the sweet-tasting protein thaumatin I at pH 8.0 reveals the large disulfide-rich region in domain II to be sensitive to a pH change

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, Tetsuya, E-mail: t2masuda@kais.kyoto-u.ac.jp [Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Department of Natural Resources, Graduate School of Global Environmental Studies, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Ohta, Keisuke [Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Department of Natural Resources, Graduate School of Global Environmental Studies, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Mikami, Bunzo [Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kitabatake, Naofumi [Department of Foods and Human Nutrition, Notre Dame Seishin University, Okayama 700-8516 (Japan); Tani, Fumito [Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Department of Natural Resources, Graduate School of Global Environmental Studies, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

    2012-03-02

    Highlights: Black-Right-Pointing-Pointer Structure of a recombinant thaumatin at pH 8.0 determined at a resolution of 1.0 A. Black-Right-Pointing-Pointer Substantial fluctuations of a loop in domain II was found in the structure at pH 8.0. Black-Right-Pointing-Pointer B-factors for Lys137, Lys163, and Lys187 were significantly affected by pH change. Black-Right-Pointing-Pointer An increase in mobility might play an important role in the heat-induced aggregation. -- Abstract: Thaumatin, an intensely sweet-tasting plant protein, elicits a sweet taste at 50 nM. Although the sweetness remains when thaumatin is heated at 80 Degree-Sign C for 4 h under acid conditions, it rapidly declines when heating at a pH above 6.5. To clarify the structural difference at high pH, the atomic structure of a recombinant thaumatin I at pH 8.0 was determined at a resolution of 1.0 A. Comparison to the crystal structure of thaumatin at pH 7.3 and 7.0 revealed the root-mean square deviation value of a C{alpha} atom to be substantially greater in the large disulfide-rich region of domain II, especially residues 154-164, suggesting that a loop region in domain II to be affected by solvent conditions. Furthermore, B-factors of Lys137, Lys163, and Lys187 were significantly affected by pH change, suggesting that a striking increase in the mobility of these lysine residues, which could facilitate a reaction with a free sulfhydryl residue produced via the {beta}-elimination of disulfide bonds by heating at a pH above 7.0. The increase in mobility of lysine residues as well as a loop region in domain II might play an important role in the heat-induced aggregation of thaumatin above pH 7.0.

  14. Influence of Donor Atom Exchange and Intercalator Substitution

    OpenAIRE

    Hormann, Jan

    2016-01-01

    Cancer is among the two leading causes of death worldwide. While mutations of DNA are causing cancer, wilful modification of the DNA structure and its damage can cause death of cancer cells. In this fashion the DNA alkylating agent cisplatin has been used for the treatment of cancer since 1978. Dose-limiting side effects and the increasing resistance of some cancer types against certain drugs call for the development of novel treatments. Among the candidates of such new drugs are metallonucle...

  15. Structural and electronic properties of Sn substituted Cun (n=10, 13) clusters: A first principles study

    Science.gov (United States)

    Choudhury, Koushik; Majumder, Chiranjib

    2017-05-01

    Here we present the structural and electronic properties of free and tin substituted copper Cun-mSnm (n=10, 13; m=0, 1, 2) clusters. The ground state properties have been calculated using plane wave based pseudopotential approach under the spin-polarized density functional theory. The results show that Cu13 cluster favors a stacked layer structure over the spherically symmetric icosahedron structure. The substitution of Cu atoms by Sn changes the relative stability pattern of the Cu13 isomers. Moreover, Sn atoms favor to substitute the surface Cu atoms than Cu atom at the center. Thus it is predicted that for bimetallic Cu-Sn nanoclusters, segregation of Sn atoms to the outer surface will lead to significant change in the chemical reactivity.

  16. [Currently available skin substitutes].

    Science.gov (United States)

    Oravcová, Darina; Koller, Ján

    2014-01-01

    The current trend of burn wound care has shifted to more holistic approach of improvement in the long-term form and function of the healed burn wounds and quality of life. Autologous split or full-thickness skin graft are the best definitive burn wound coverage, but it is constrained by the limited available sources, especially in major burns. Donor site morbidities in term of additional wounds and scarring are also of concern of the autograft application. This has demanded the emergence of various skin substitutes in the management of acute burn injury as well as post burn reconstructions. This paper reviews currently available skin substitutes, produced in not for-profit skin banks as well as commercially available. They are divided according to type of material included, as biological, biosynthetic and synthetic and named respectively.

  17. Atomic theories

    CERN Document Server

    Loring, FH

    2014-01-01

    Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec

  18. Substituent effects in surface-initiated ATRP of substituted styrenes

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Sampa, E-mail: ssaha@polymers.iitd.ac.in; Baker, Gregory L.

    2015-12-30

    Graphical abstract: - Highlights: • Suitably substituted styrenes can lead to rapid synthesis of uniform and thick polystyrene brushes (>100 nm in 1 h) from gold surface via surface initiated ATRP. • High growth rates were observed for styrenes substituted with electron withdrawing groups in meta/para positions. • Electron donors at meta sites show surprisingly fast growth rates, which may be due to steric inhibition of termination. • Surface polymerization rates for substituted styrenes followed the Hammett relation with ρ = 0.51, similar to conventional radical polymerization in solution. - Abstract: Surface initiated atom transfer radical polymerization (ATRP) of substituted styrenes leads to rapid synthesis of uniform and thick substituted polystyrene brushes (>100 nm in 1 h) from gold surface. High growth rates were observed for styrenes substituted with electron withdrawing groups in meta/para positions. The effects seen in surface and solution polymerizations are similar for styrenes with electron withdrawing groups, and for electron donors in ortho and para positions. However, electron donors at meta sites have surprisingly fast growth rates, which may be due to steric inhibition of termination. The overall surface polymerization rates for substituted styrenes was analyzed and found to follow the Hammett relation with ρ = 0.51. The ratio of k{sub p} to k{sub t}, is as an indicator of the likelihood that a reaction will reach high degrees of polymerization before termination.

  19. Atomic physics

    International Nuclear Information System (INIS)

    Held, B.

    1991-01-01

    This general book describes the change from classical physics to quantum physics. The first part presents atom evolution since antiquity and introduces fundamental quantities and elements of relativity. Experiments which have contributed to the evolution of knowledge on matter are analyzed in the second part. Applications of wave mechanics to the study of matter properties are presented in the third part [fr

  20. Atomic Power

    African Journals Online (AJOL)

    Atomic Power. By Denis Taylor: Dr. Taylor was formerly Chief UNESCO Advisor at the University. College, Nairobi, Kenya and is now Professor of Electrical Engineering in the Uni- versity of Strachlyde, Scotland. He is a leading scientist in the electronics field. He was among the British scientists who developed radar during ...

  1. Atomic Power

    African Journals Online (AJOL)

    that atom-produced electricity began to be more economic than electricity produced by conventional means. In the A.G.R., the uranium metal fuel elements are replaced by uranium dioxide, the higher gas temperatures permitting a more efficient steam cycle and allowing several economies. Initially a reactor of this type was ...

  2. Atomic Warrior

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 6; Issue 9. Atomic Warrior. Shabhana Narasimhan. Book Review Volume 6 Issue 9 September 2001 pp 106-109. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/006/09/0106-0109. Author Affiliations.

  3. Interactive Web-based Visualization of Atomic Position-time Series Data

    Science.gov (United States)

    Thapa, S.; Karki, B. B.

    2017-12-01

    Extracting and interpreting the information contained in large sets of time-varying three dimensional positional data for the constituent atoms of simulated material is a challenging task. We have recently implemented a web-based visualization system to analyze the position-time series data extracted from the local or remote hosts. It involves a pre-processing step for data reduction, which involves skipping uninteresting parts of the data uniformly (at full atomic configuration level) or non-uniformly (at atomic species level or individual atom level). Atomic configuration snapshot is rendered using the ball-stick representation and can be animated by rendering successive configurations. The entire atomic dynamics can be captured as the trajectories by rendering the atomic positions at all time steps together as points. The trajectories can be manipulated at both species and atomic levels so that we can focus on one or more trajectories of interest, and can be also superimposed with the instantaneous atomic structure. The implementation was done using WebGL and Three.js for graphical rendering, HTML5 and Javascript for GUI, and Elasticsearch and JSON for data storage and retrieval within the Grails Framework. We have applied our visualization system to the simulation datatsets for proton-bearing forsterite (Mg2SiO4) - an abundant mineral of Earths upper mantle. Visualization reveals that protons (hydrogen ions) incorporated as interstitials are much more mobile than protons substituting the host Mg and Si cation sites. The proton diffusion appears to be anisotropic with high mobility along the x-direction, showing limited discrete jumps in other two directions.

  4. Atomic emission spectroscopy

    Science.gov (United States)

    Andrew, K. H.

    1975-01-01

    The relationship between the Slater-Condon theory and the conditions within the atom as revealed by experimental data was investigated. The first spectrum of Si, Rb, Cl, Br, I, Ne, Ar, and Xe-136 and the second spectrum of As, Cu, and P were determined. Methods for assessing the phase stability of fringe counting interferometers and the design of an autoranging scanning system for digitizing the output of an infrared spectrometer and recording it on magnetic tape are described.

  5. Energy Dependence of Measured CT Numbers on Substituted Materials Used for CT Number Calibration of Radiotherapy Treatment Planning Systems.

    Directory of Open Access Journals (Sweden)

    Reza Mahmoudi

    Full Text Available For accurate dose calculations, it is necessary to provide a correct relationship between the CT numbers and electron density in radiotherapy treatment planning systems (TPSs. The purpose of this study was to investigate the energy dependence of measured CT numbers on substituted materials used for CT number calibration of radiotherapy TPSs and the resulting errors in the treatment planning calculation doses.In this study, we designed a cylindrical water phantom with different materials used as tissue equivalent materials for the simulation of tissues and obtaining the related CT numbers. For evaluating the effect of CT number variations of substituted materials due to energy changing of scanner (kVp on the dose calculation of TPS, the slices of the scanned phantom at three kVp's were imported into the desired TPSs (MIRS and CorePLAN. Dose calculations were performed on two TPSs.The mean absolute percentage differences between the CT numbers of CT scanner and two treatment planning systems for all the samples were 3.22%±2.57% for CorePLAN and 2.88%±2.11% for MIRS. It was also found that the maximum absolute percentage difference between all of the calculated doses from each photon beam of linac (6 and 15 MV at three kVp's was less than 1.2%.The present study revealed that, for the materials with effective low atomic number, the mean CT number increased with increasing energy, which was opposite for the materials with an effective high atomic number. We concluded that the tissue substitute materials had a different behavior in the energy ranges from 80 to 130 kVp. So, it is necessary to consider the energy dependence of the substitute materials used for the measurement or calibration of CT number for radiotherapy treatment planning systems.

  6. Watching Atoms Work: Nanocluster Structure and Dynamics.

    Science.gov (United States)

    Pennycook, Stephen J; Zhou, Wu; Pantelides, Sokrates T

    2015-10-27

    In the space of little more than a decade, the resolution of the electron microscope has improved to provide clear views of the atomic world. Not only can atomic arrangements be imaged, but with a little gentle provocation from the electron beam, atoms can be energized and their dynamics can also be revealed. In this issue of ACS Nano, Chen et al. image Si atoms growing under the beam into cubic crystalline arrangements.

  7. Effects of Al substitution in Nd2Fe17 studied by first-principles calculations

    International Nuclear Information System (INIS)

    Huang, M.; Ching, W.Y.

    1994-01-01

    We have studied the effect of Al substitution in Nd 2 Fe 17 compound by means of first-principles calculations. We first obtain the site-decomposed potentials for Fe from self-consistent calculation on Y 2 Fe 17 and the atomiclike potentials in the crystalline environment for Al and Nd. Calculations are carried out for a single Al substituting one Fe at four different Fe sites (6c), (9d), (18f ), and (18h), two Al substituting two Fe (18h), and four Al substituting three Fe (18h) and one Fe (18f ). Our results show that the Al moment is oppositely polarized to Fe. The average moment per Fe atom actually increases for Al substituting Fe (18h) and Fe (18f ) is about the same for Al substituting Fe (6c), and is drastically reduced when replacing Fe (9d). Experimentally, Al is shown to be excluded from the (9d) sites because of the small Wigner--Seitz volume. When two Fe atoms are replaced by two Al atoms, the total moment is only slightly less than when only one Fe atom is replaced, and the M s per Fe site actually increases, in agreement with the Moessbauer data. These results are analyzed in terms of the local atomic geometry and the charge transfer effect from the neighboring Fe to Al

  8. Arsenic in ZnO and GaN: substitutional cation or anion sites?

    CERN Document Server

    Wahl, Ulrich; Rita, Elisabete; Marques, Ana Claudia; Alves, Eduardo; Carvalho Soares, José

    2007-01-01

    We have determined the lattice location of ion implanted As in ZnO and GaN by means of conversion electron emission channeling from radioactive $^{73}$As. In contrast to what one might expect from its nature as a group V element, we find that As does not occupy substitutional O sites in ZnO but in its large majority substitutional Zn sites. Arsenic in ZnO is thus an interesting example for an impurity in a semiconductor where the major impurity lattice site is determined by atomic size and electronegativity rather than its position in the periodic system. In contrast, in GaN the preference of As for substitutional cation sites is less pronounced and about half of the implanted As atoms occupy Ga and the other half N sites. Apparently, the smaller size-mismatch between As and N and the chemical similarity of both elements make it feasible that As partly substitutes for N atoms.

  9. Characterisation of β-tricalcium phosphate-based bone substitute materials by electron paramagnetic resonance spectroscopy

    Science.gov (United States)

    Matković, Ivo; Maltar-Strmečki, Nadica; Babić-Ivančić, Vesna; Dutour Sikirić, Maja; Noethig-Laslo, Vesna

    2012-10-01

    β-TCP based materials are frequently used as dental implants. Due to their resorption in the body and direct contact with tissues, in order to inactivate bacteria, fungal spores and viruses, they are usually sterilized by γ-irradiation. However, the current literature provides little information about effects of the γ-irradiation on the formation and stability of the free radicals in the bone graft materials during and after sterilization procedure. In this work five different bone graft substitution materials, composed of synthetic beta tricalcium phosphate (β-TCP) and hydroxyapatite (HAP) present in the market were characterized by electron paramagnetic resonance (EPR) spectroscopy, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Paramagnetic species Mn2+, Fe3+, trapped H-atoms and CO2- radicals were detected in the biphasic material (60% HAP, 40% β-TCP), while in β-TCP materials only Mn2+ andor trapped hydrogen atoms were detected. EPR analysis revealed the details of the structure of these materials at the atomic level. The results have shown that EPR spectroscopy is a method which can be used to improve the quality control of bone graft materials after syntering, processing and sterilization procedure.

  10. Resources, recycle, and substitution

    International Nuclear Information System (INIS)

    Wymer, R.G.

    A two-fold strategy appears necessary to ensure that the resource needs of the developed and developing nations are met. First, recycle and substitution must be encouraged in those instances where they do find application. Although these measures have limited applicability, they may be of vital importance in those instances where they do apply; in any event, they buy time. Second, practical and economical technologies must be developed to exploit the lower-grade and marginal ores and the oftentimes abundant but highly refractory ores, as well as to greatly increase the recovery of secondary elements present in the ores - elements whose form and amounts in the ores make them economically unrecoverable by themselves, but which are economically recoverable as by-products. It is often the case that if these elements are not recovered during the initial mining and milling operations, they are rendered unrecoverable, in a practical sense, forever. Furthermore, they may even become environmental pollutants. Specific examples of recovery from refractory ores, by-product recovery, and recycle are given. Also, some suggestions of substitutes for important resources are tabulated

  11. Atom-surface potentials and atom interferometry

    International Nuclear Information System (INIS)

    Babb, J.F.

    1998-01-01

    Long-range atom-surface potentials characterize the physics of many actual systems and are now measurable spectroscopically in deflection of atomic beams in cavities or in reflection of atoms in atomic fountains. For a ground state, spherically symmetric atom the potential varies as -1/R 3 near the wall, where R is the atom-surface distance. For asymptotically large distances the potential is weaker and goes as -1/R 4 due to retardation arising from the finite speed of light. This diminished interaction can also be interpreted as a Casimir effect. The possibility of measuring atom-surface potentials using atomic interferometry is explored. The particular cases studied are the interactions of a ground-state alkali-metal atom and a dielectric or a conducting wall. Accurate descriptions of atom-surface potentials in theories of evanescent-wave atomic mirrors and evanescent wave-guided atoms are also discussed. (author)

  12. QSAR modeling for anti-human African trypanosomiasis activity of substituted 2-Phenylimidazopyridines

    Science.gov (United States)

    Masand, Vijay H.; El-Sayed, Nahed N. E.; Mahajan, Devidas T.; Mercader, Andrew G.; Alafeefy, Ahmed M.; Shibi, I. G.

    2017-02-01

    In the present work, sixty substituted 2-Phenylimidazopyridines previously reported with potent anti-human African trypanosomiasis (HAT) activity were selected to build genetic algorithm (GA) based QSAR models to determine the structural features that have significant correlation with the activity. Multiple QSAR models were built using easily interpretable descriptors that are directly associated with the presence or the absence of a structural scaffold, or a specific atom. All the QSAR models have been thoroughly validated according to the OECD principles. All the QSAR models are statistically very robust (R2 = 0.80-0.87) with high external predictive ability (CCCex = 0.81-0.92). The QSAR analysis reveals that the HAT activity has good correlation with the presence of five membered rings in the molecule.

  13. Dynamical barrier and isotope effects in the simplest substitution reaction via Walden inversion mechanism

    Science.gov (United States)

    Zhao, Zhiqiang; Zhang, Zhaojun; Liu, Shu; Zhang, Dong H.

    2017-02-01

    Reactions occurring at a carbon atom through the Walden inversion mechanism are one of the most important and useful classes of reactions in chemistry. Here we report an accurate theoretical study of the simplest reaction of that type: the H+CH4 substitution reaction and its isotope analogues. It is found that the reaction threshold versus collision energy is considerably higher than the barrier height. The reaction exhibits a strong normal secondary isotope effect on the cross-sections measured above the reaction threshold, and a small but reverse secondary kinetic isotope effect at room temperature. Detailed analysis reveals that the reaction proceeds along a path with a higher barrier height instead of the minimum-energy path because the umbrella angle of the non-reacting methyl group cannot change synchronously with the other reaction coordinates during the reaction due to insufficient energy transfer from the translational motion to the umbrella mode.

  14. complexes with thiophene based N -substituted thiosemicarbazones

    Indian Academy of Sciences (India)

    )2]·2MeOH 1, [Ag2Cl2(κ1-S-. Httsc-NPh)2(μ-S ... Further, the sulfur donor atoms have shown variable coordination modes in complexes, namely, κ1-S in 1 and 3; ..... which reveal that Ag2Br2 core forms a parallelogram. Other important bond ...

  15. Preferred site occupation of 3 d atoms in NixF e4 -xN (x =1 and 3) films revealed by x-ray absorption spectroscopy and magnetic circular dichroism

    Science.gov (United States)

    Takata, Fumiya; Ito, Keita; Takeda, Yukiharu; Saitoh, Yuji; Takanashi, Koki; Kimura, Akio; Suemasu, Takashi

    2018-02-01

    X-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism measurements were performed at the Ni and Fe L2 ,3 absorption edges for N ixF e4 -xN (x =1 and 3) epitaxial films. Spectral line-shape analysis and element-specific magnetic moment evaluations are presented. Shoulders at approximately 2 eV above the Ni L2 ,3 main peaks in the XAS spectrum of N i3FeN were interpreted to originate from hybridization of orbitals between Ni 3 d at face-centered (II) sites and N 2 p at body-centered sites, while such features were missing in NiF e3N film. Similar shoulders were observed at Fe L2 ,3 edges in both films. These results indicate that the orbitals of Ni atoms did not hybridize with those of N atoms in the NiF e3N film. Hence, Ni atoms preferentially occupied corner (I) sites, where the hybridization was weak because of the relatively long distance between Ni at I sites and N atoms. The relatively large magnetic moment deduced from sum-rule analysis of NiF e3N also showed a good agreement with the presence of Ni atoms at I sites.

  16. Oxygen-storage behavior and local structure in Ti-substituted YMnO3

    International Nuclear Information System (INIS)

    Levin, I.; Krayzman, V.; Vanderah, T.A.; Tomczyk, M.; Wu, H.; Tucker, M.G.; Playford, H.Y.; Woicik, J.C.; Dennis, C.L.; Vilarinho, P.M.

    2017-01-01

    Hexagonal manganates RMnO 3 (R=Y, Ho, Dy) have been recently shown to exhibit oxygen-storage capacities promising for three-way catalysts, air-separation, and related technologies. Here, we demonstrate that Ti substitution for Mn can be used to chemically tune the oxygen-breathing properties of these materials towards practical applications. Specifically, Y(Mn 1−x Ti x )O 3 solid solutions exhibit facile oxygen absorption/desorption via reversible Ti 3+ ↔Ti 4+ and Mn 3+ ↔Mn 4+ reactions already in ambient air at ≈400 °C and ≈250 °C, respectively. On cooling, the oxidation of both cations is accompanied by oxygen uptake yielding a formula YMn 3+ 1−x-y Mn 4+ y Ti 4+ x O 3+δ . The presence of Ti promotes the oxidation of Mn 3+ to Mn 4+ , which is almost negligible for YMnO 3 in air, thereby increasing the uptake of oxygen beyond that required for a given Ti 4+ concentration. The reversibility of the redox reactions is limited by sluggish kinetics; however, the oxidation process continues, if slowly, even at room temperature. The extra oxygen atoms are accommodated by the large interstices within a triangular lattice formed by the [MnO 5 ] trigonal bipyramids. According to bond distances from Rietveld refinements using the neutron diffraction data, the YMnO 3 structure features under-bonded Mn and even more severely under-bonded oxygen atoms that form the trigonal bases of the [MnO 5 ] bipyramids. The tensile bond strain around the 5-fold coordinated Mn site and the strong preference of Ti 4+ (and Mn 4+ ) for higher coordination numbers likely provide driving forces for the oxidation reaction. Reverse Monte Carlo refinements of the local atomic displacements using neutron total scattering revealed how the excess oxygen atoms are accommodated in the structure by correlated local displacements of the host atoms. Large displacements of the under-bonded host oxygen atoms play a key part in this lattice-relaxation process, facilitating reversible exchange of

  17. Location and coordination of promoter atoms in Co- and Ni-promoted MoS2-based hydrotreating catalysts

    DEFF Research Database (Denmark)

    Lauritsen, Jeppe V.; Kibsgaard, Jakob; Olesen, Georg H.

    2007-01-01

    In this study, we used scanning tunneling microscopy (STM) and density functional theory (DFT) to investigate the atomic-scale structure of the active Co- or Ni-promoted MoS2 nanoclusters in hydrotreating catalysts. Co-promoted MoS2 nanoclusters (Co–Mo–S) are found to adopt a hexagonal shape...... on the nanocluster size. Larger clusters (type A) are structurally similar to Co–Mo–S exposing fully Ni-substituted (1010) edges with a 50% S coverage. Smaller clusters (type B) show dodecagonal shapes terminated by three different edges, all of which contain Ni-promoter atoms fully or partially substituting the Mo......, with Co atoms preferentially located at (1010) edges with a 50% sulfur coverage. The first atom-resolved STM images of the Ni-promoted MoS2 nanoclusters (Ni–Mo–S) reveal that the addition of Ni also leads to truncated morphologies, but the degree of truncation and the Ni sites are observed to depend...

  18. Substitution site and effects on magnetism in Sr-for-Ca substituted CaBaCo4O7

    Science.gov (United States)

    Aurelio, G.; Curiale, J.; Bardelli, F.; Junqueira Prado, R.; Hennet, L.; Cuello, G.; Campo, J.; Thiaudière, D.

    2015-10-01

    Cationic substitutions in the novel magnetoelectric compound CaBaCo4O7 lead to profound changes in its magnetic and electric behaviors. In this work, we present a structural study of the isovalent substitution Sr-for-Ca in CaBaCo4O7. X-ray diffraction, as well as neutron powder diffraction experiments, are reported for a series of samples Ca1-xSrxBaCo4O7 with 0 ≤ x ≤ 0.10 . Special emphasis is given to the identification of the substitution site, as Sr has also been reported to substitute for Ba in this crystal structure. The solubility limit for Sr at the Ca site is shown to be at x ≃ 0.08 . The variation of lattice constants with Sr-doping firmly supports the Sr-for-Ca substitution. Rietveld refinements of the Sr-substituted samples are presented, and used as starting point to analyse the local structure around Sr by means of X-ray absorption spectroscopy at the Sr K-edge. Both the near-edge absorption and the extended absorption fine-structure confirm the substitution of Sr for Ca, giving definite support to the proposed nominal formula. In addition, macroscopic magnetization measurements are presented which reveal the striking effects of Sr-substitution over the magnetic landscape of this puzzling compound.

  19. Atom Skimmers and Atom Lasers Utilizing Them

    Science.gov (United States)

    Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.

    2005-01-01

    Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

  20. Sites of Au atoms in Sn crystals as determined by channeling

    International Nuclear Information System (INIS)

    Miller, J.W.; Gemmell, D.S.; Holland, R.E.; Poizat, J.C.; Worthington, J.N.; Loess, R.E.

    1974-01-01

    The position of Au atoms diffused into Sn monocrystals has been studied by channeling and backscattering of 2.5-MeV Ne ions. For equilibrium conditions at 217 0 C, Au atoms are found almost entirely in substitutional positions, so that the unusually fast diffusion of Au in Sn most likely arises from a small fraction of Au atoms migrating interstitially

  1. Nucleophilic substitution and oxidative coupling in reaction of metallated lithium salt of acetic acid with 1,2-dibromoethane

    OpenAIRE

    Chanysheva, A.; Zorin, A.; Klimakov, V.; Spirikhin, L.; Zorin, V.

    2009-01-01

    When lithium salt of acetic acid metallated by lithium diisopropylamide in tetrahydrofuran interacts with 1,2-dibromoethane products of nucleophilic substitution of bromine atoms for oxycarbomethyl group and oxidative coupling of acetoxydianions are obtained.

  2. Molecular Beam Studies of Hot Atom Chemical Reactions: Reactive Scattering of Energetic Deuterium Atoms

    Science.gov (United States)

    Continetti, R. E.; Balko, B. A.; Lee, Y. T.

    1989-02-01

    A brief review of the application of the crossed molecular beams technique to the study of hot atom chemical reactions in the last twenty years is given. Specific emphasis is placed on recent advances in the use of photolytically produced energetic deuterium atoms in the study of the fundamental elementary reactions D + H{sub 2} -> DH + H and the substitution reaction D + C{sub 2}H{sub 2} -> C{sub 2}HD + H. Recent advances in uv laser and pulsed molecular beam techniques have made the detailed study of hydrogen atom reactions under single collision conditions possible.

  3. Substitution in recreation choice behavior

    Science.gov (United States)

    George L. Peterson; Daniel J. Stynes; Donald H. Rosenthal; John F. Dwyer

    1985-01-01

    This review discusses concepts and theories of substitution in recreation choice. It brings together the literature of recreation research, psychology, geography, economics, and transportation. Parallel and complementary developments need integration into an improved theory of substitution. Recreation decision behavior is characterized as a nested or sequential choice...

  4. Biological background of dermal substitutes

    NARCIS (Netherlands)

    van der Veen, V. C.; van der Wal, M.B.; van Leeuwen, M.C.; Ulrich, M.; Middelkoop, E.

    2010-01-01

    Dermal substitutes are of major importance in treating full thickness skin defects, both in acute and chronic wounds. In this review we will outline specific requirements of three classes of dermal substitutes:-natural biological materials, with a more or less intact extracellular matrix

  5. Atomic magnetometer

    Science.gov (United States)

    Schwindt, Peter [Albuquerque, NM; Johnson, Cort N [Albuquerque, NM

    2012-07-03

    An atomic magnetometer is disclosed which uses a pump light beam at a D1 or D2 transition of an alkali metal vapor to magnetically polarize the vapor in a heated cell, and a probe light beam at a different D2 or D1 transition to sense the magnetic field via a polarization rotation of the probe light beam. The pump and probe light beams are both directed along substantially the same optical path through an optical waveplate and through the heated cell to an optical filter which blocks the pump light beam while transmitting the probe light beam to one or more photodetectors which generate electrical signals to sense the magnetic field. The optical waveplate functions as a quarter waveplate to circularly polarize the pump light beam, and as a half waveplate to maintain the probe light beam linearly polarized.

  6. Exotic aspects of hadronic atoms-anomalous quasi-stabilities

    International Nuclear Information System (INIS)

    Yamazaki, Toshimitsu.

    1993-07-01

    Recently revealed, but hitherto unknown, new aspects of hadronic atoms, namely, anomalous quasi-stabilities of negative hadrons, are discussed. One is on long-lived antiprotonic helium atoms, characterized as 'atomic exotic halo' and the other is on deeply bound pionic atoms, characterized as 'nuclear exotic halo'. (author)

  7. Manipulation of inherent characteristics of graphene through N and Mg atom co-doping; a DFT study

    Science.gov (United States)

    Rafique, Muhammad; Mirjat, Nayyar H.; Soomro, Aamir M.; Khokhar, Suhail; Shuai, Yong

    2018-04-01

    First-principles calculations were performed to investigate the structural, electronic, magnetic and optical properties of nitrogen (N) and magnesium (Mg) atom co-doped graphene systems. We observed that, N and Mg atom co-doping in graphene, introduces half-metallic properties in the electronic structure of graphene, introduces ferromagnetism behavior along with new trends in optical properties of graphene. Doping site and concentration of N and Mg atoms in graphene was changed and resulting effects of these changes on aforementioned properties were investigated. Through density of states plots we observed that, Mg atom sp orbitals mainly induced magnetic moments in graphene. It was revealed that, N/Mg atoms substitution in graphene introduces a red shift in absorption spectrum towards visible range and a finite absorption coefficient quantity value in 0 to 3 eV and 7 to 11 eV energy intervals is also produced, that is unavailable for absorption spectrum of intrinsic graphene. Moreover, N/Mg atoms co-doping produces increment in the reflectivity parameter of graphene in low lying energy region, while producing diminishing behavior in the higher energy range. These results offer a possibility to tune electronic, magnetic and optical characteristics of graphene sufficiently for utilization in graphene based spintronic and optoelectronic devices.

  8. High Atom Number in Microsized Atom Traps

    Science.gov (United States)

    2015-12-14

    Final Performance Report on ONR Grant N00014-12-1-0608 High atom number in microsized atom traps for the period 15 May 2012 through 14 September...TYPE Final Technical Report 3. DATES COVERED (From - To) 05/15/2012-09/14/2012 4. TITLE AND SUBTITLE High atom number in microsized atom traps...forces for implementing a small-footprint, large-number atom -chip instrument. Bichromatic forces rely on absorption and stimulated emission to produce

  9. Synthesis and first-principle calculations of the structural and electronic properties of Ge-substituted type-VIII Ba{sub 8}Ga{sub 16}Sn{sub 30} clathrate

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Lanxian [Education Ministry Key Laboratory of Renewable Energy Advanced Materials and Manufacturing Technology, Yunnan Provincial Renewable Energy Engineering Key Lab, Solar Energy Research Institution, Yunnan Normal University, Kunming 650500 (China); Li, Decong [College of Optoelectronic Engineering, Yunnan Open University, Kunming 650500 (China); Liu, Hongxia; Liu, Zuming [Education Ministry Key Laboratory of Renewable Energy Advanced Materials and Manufacturing Technology, Yunnan Provincial Renewable Energy Engineering Key Lab, Solar Energy Research Institution, Yunnan Normal University, Kunming 650500 (China); Deng, Shukang, E-mail: skdeng@126.com [Education Ministry Key Laboratory of Renewable Energy Advanced Materials and Manufacturing Technology, Yunnan Provincial Renewable Energy Engineering Key Lab, Solar Energy Research Institution, Yunnan Normal University, Kunming 650500 (China)

    2016-12-01

    In this study, the structural and electronic structural properties of Ba{sub 8}Ga{sub 16}Sn{sub 30−x}Ge{sub x} (0≤x≤30) are determined by the first-principle method on the basis of density functional theory. Consistent with experimental findings, calculated results reveal that Ge atoms preferentially occupy the 2a and 24g sites in these compounds. As the content of Ge in Ge-substituted clathrate is increased, the lattice parameter is decreased, and the structural stability is enhanced. The bandgaps of the compound at 1≤x≤10 are smaller than those of Ba{sub 8}Ga{sub 16}Sn{sub 30}. By contrast, the bandgaps of the compound at x>10 are larger than those of Ba{sub 8}Ga{sub 16}Sn{sub 30}. The substitution of Ge for Sn affects p-type conductivity but not n-type conductivity. As Ge content increases, the whole conduction band moves to the direction of high energy, and the density of states of valence-band top decreases. The calculated potential energy versus displacement of Ba indicates that the vibration energy of this atom increases as cage size decreases. Because Ge substitution also affects clathrate structural symmetry, the distance of Ba atom deviation from the center of the cage initially increases and subsequently decreases as the Ge content increases.

  10. Semiconducting behavior of substitutionally doped bilayer graphene

    Science.gov (United States)

    Mousavi, Hamze; Khodadadi, Jabbar; Grabowski, Marek

    2018-02-01

    In the framework of the Green's functions approach, random tight-binding model and using the coherent potential approximation, electronic characteristics of the bilayer graphene are investigated by exploring various forms of substitutional doping of a single or both layers of the system by either boron and (or) nitrogen atoms. The results for displacement of the Fermi level resemble the behavior of acceptor or donor doping in a conventional semiconductor, dependent on the impurity type and concentration. The particular pattern of doping of just one layer with one impurity type is most efficient for opening a gap within the energy bands which could be tuned directly by impurity concentration. Doping both layers at the same time, each with one impurity type, leads to an anomaly whereby the gap decreases with increasing impurity concentration.

  11. The role of biomass in US industrial interfuel substitution

    International Nuclear Information System (INIS)

    Jones, Clifton T.

    2014-01-01

    The role of biomass in US industrial interfuel substitution in the industrial sector has typically been analyzed using data for the four traditional fuels of coal, oil, electricity and natural gas. However, the use of biomass as an industrial fuel in the US has grown, and now exceeds that of coal. Using data from 1960 to 2011, interfuel substitution in the US industrial sector is modeled with a dynamic linear logit model which includes biomass alongside the other four traditional fuels. Adding biomass to the model reduces somewhat the estimated own-price and cross-price elasticities for the other four fuels, while revealing that biomass and natural gas are substitute fuels. This implies that previous studies excluding biomass may have overestimated the potential for interfuel substitution, giving policy makers an inaccurate impression of the ability of carbon taxes or other environmental regulation to reduce greenhouse gas (GHG) emissions. - Highlights: • Biomass usage by the US industrial sector now exceeds coal usage. • Previous interfuel substitution studies have not included biomass as a fuel. • Linear logit model is used to examine role of biomass in interfuel substitution. • Including biomass in the model lowers estimated price elasticities for traditional fuels. • Biomass is found to be a substitute for natural gas for industrial users

  12. Structural and electronic properties of isovalent boron atoms in GaAs

    Science.gov (United States)

    Krammel, C. M.; Nattermann, L.; Sterzer, E.; Volz, K.; Koenraad, P. M.

    2018-04-01

    Boron containing GaAs, which is grown by metal organic vapour phase epitaxy, is studied at the atomic level by cross-sectional scanning tunneling microscopy (X-STM) and spectroscopy (STS). In topographic X-STM images, three classes of B related features are identified, which are attributed to individual B atoms on substitutional Ga sites down to the second layer below the natural {110} cleavage planes. The X-STM contrast of B atoms below the surface reflects primarily the structural modification of the GaAs matrix by the small B atoms. However, B atoms in the cleavage plane have in contrast to conventional isovalent impurities, such as Al and In, a strong influence on the local electronic structure similar to donors or acceptors. STS measurements show that B in the GaAs {110} surfaces gives rise to a localized state short below the conduction band (CB) edge while in bulk GaAs, the B impurity state is resonant with the CB. The analysis of BxGa1-xAs/GaAs quantum wells reveals a good crystal quality and shows that the incorporation of B atoms in GaAs can be controlled along the [001] growth direction at the atomic level. Surprisingly, the formation of the first and fourth nearest neighbor B pairs, which are oriented along the directions, is strongly suppressed at a B concentration of 1% while the third nearest neighbor B pairs are found more than twice as often than expected for a completely spatially random pattern.

  13. Chitosan Dermal Substitute and Chitosan Skin Substitute Contribute to Accelerated Full-Thickness Wound Healing in Irradiated Rats

    Directory of Open Access Journals (Sweden)

    Abu Bakar Mohd Hilmi

    2013-01-01

    Full Text Available Wounds with full-thickness skin loss are commonly managed by skin grafting. In the absence of a graft, reepithelialization is imperfect and leads to increased scar formation. Biomaterials can alter wound healing so that it produces more regenerative tissue and fewer scars. This current study use the new chitosan based biomaterial in full-thickness wound with impaired healing on rat model. Wounds were evaluated after being treated with a chitosan dermal substitute, a chitosan skin substitute, or duoderm CGF. Wounds treated with the chitosan skin substitute showed the most re-epithelialization (33.2 ± 2.8%, longest epithelial tongue (1.62 ± 0.13 mm, and shortest migratory tongue distance (7.11 ± 0.25 mm. The scar size of wounds treated with the chitosan dermal substitute (0.13 ± 0.02 cm and chitosan skin substitute (0.16 ± 0.05 cm were significantly decreased (P<0.05 compared with duoderm (0.45 ± 0.11 cm. Human leukocyte antigen (HLA expression on days 7, 14, and 21 revealed the presence of human hair follicle stem cells and fibroblasts that were incorporated into and surviving in the irradiated wound. We have proven that a chitosan dermal substitute and chitosan skin substitute are suitable for wound healing in full-thickness wounds that are impaired due to radiation.

  14. Bremsstrahlung in atom-atom collisions

    International Nuclear Information System (INIS)

    Amus'ya, M.Y.; Kuchiev, M.Y.; Solov'ev, A.V.

    1985-01-01

    It is shown that in the collision of a fast atom with a target atom when the frequencies are on the order of the potentials or higher, there arises bremsstrahlung comparable in intensity with the bremsstrahlung emitted by an electron with the same velocity in the field of the target atom. The mechanism by which bremsstrahlung is produced in atom-atom collisions is elucidated. Results of specific calculations of the bremsstrahlung spectra are given for α particles and helium atoms colliding with xenon

  15. Fine structure study on low concentration zinc substituted hydroxyapatite nanoparticles

    International Nuclear Information System (INIS)

    Hu, Wei; Ma, Jun; Wang, Jianglin; Zhang, Shengmin

    2012-01-01

    The fine structure of zinc substituted hydroxyapatite was studied using experimental analysis and first-principles calculations. The synthetic hydroxyapatite nanoparticles containing low Zn concentration show rod-like morphology. The crystallite sizes and unit-cell volumes tended to decrease with the increased Zn concentration according to X-ray diffraction patterns. The Zn K-edge X-ray absorption spectra and fitting results suggest that the hydroxyapatite doped with 0.1 mole% zinc is different in the zinc coordination environments compared with that containing more zinc. The density function theory calculations were performed on zinc substituted hydroxyapatite. Two mechanisms included replacing calcium by zinc and inserting zinc along the hydroxyl column and were investigated, and the related substitution energies were calculated separately. It is found that the substitution energies are negative and lowest for inserting zinc between the two oxygen atoms along the hydroxyl column (c-axis). Combined with the spectral analysis, it is suggested that the inserting mechanism is favored for low concentration zinc substituted hydroxyapatite. Highlights: ► We investigate the fine structure of hydroxyapatite with low content of Zn. ► XANES spectra are similar but a little different at low zinc content. ► Zinc ions influence hydroxyapatite crystal formation and lattice parameters. ► Formation energies are calculated according to plane-wave density function theory. ► Low content of zinc prefers to locate at hydroxyl column in hydroxyapatite lattice.

  16. From hot atom chemistry to epithermal chemistry

    International Nuclear Information System (INIS)

    Roessler, K.

    2004-01-01

    The rise and fall of hot atom chemistry (HAC) over the years from 1934 to 2004 is reviewed. Several applications are discussed, in particular to astrophysics and the interaction of energetic ions and atoms in space. Epithermal chemistry (ETC) is proposed to substitute the old name, since it better fits the energy range as well as the non-thermal and non-equilibrium character of the reactions. ETC also avoids the strong connexion of HAC to nuclear chemistry and stands for the opening of the field to physical chemistry and astrophysics. (orig.)

  17. Magnetic and dielectric studies of Fe substituted sillenite phase bismuth cobaltite nanoparticles

    International Nuclear Information System (INIS)

    Ray, J.; Biswal, A.K.; Kuila, S.; Vishwakarma, P.N.

    2015-01-01

    Highlights: • The samples prepared under ambient conditions, crystalizes in sillenite phase. • Ferrimagnetic ordering in BCO occurs at 30 K, with no bifurcation in ZFC and FC. • BCFO shows large bifurcation in ZFC and FC data as the sample is cooled down. • Dielectric loss improves by one order when 50% of cobalt is replaced with Fe. • Well distinguished extrinsic and intrinsic contributions in BCO and BCFO are seen. - Abstract: (Bi 13 Co 12 )CoO 40 (BCO) and (Bi 13 Co 5.5 Fe 6.5 )CoO 40 (BCFO) nanoparticles are prepared by sol–gel auto combustion method. The X-ray diffraction study (XRD) reveals cubic crystal structure with space group I23. Surface scanning via atomic force microscopy shows the particle size decreases from 100 nm to 75 nm on partially substituting Fe at Co site. At room temperature, BCO is paramagnetic and shows signature of magnetic ordering at 30 K, which seems to be competing paramagnetic and antiferromagnetic behavior. No sign of magnetic disorder is seen, though indication of magnetic frustration is seen. Interestingly, the Fe substituted BCFO shows large magnetic disorder (even at room temperature) with strengthening ferromagnetic ordering as the temperature is lowered. The low temperature dielectric and magnetodielectric measurement shows dominance of extrinsic contributions, through-out the temperature range for BCO. For BCFO, the behavior may be divided under two regions viz., intrinsic (<260 K) and extrinsic (>260 K). Relaxation in both the regions is described by Arrhenius behavior with activation energies 0.25 eV and 0.04 eV in the extrinsic and intrinsic regions respectively. Most interestingly, the dielectric loss decreases by one order for Fe substituted sample. The Haverliak–Negami equation is found to better describe the observed relaxation data

  18. "Bohr's Atomic Model."

    Science.gov (United States)

    Willden, Jeff

    2001-01-01

    "Bohr's Atomic Model" is a small interactive multimedia program that introduces the viewer to a simplified model of the atom. This interactive simulation lets students build an atom using an atomic construction set. The underlying design methodology for "Bohr's Atomic Model" is model-centered instruction, which means the central model of the…

  19. Relativistic elementary atoms

    International Nuclear Information System (INIS)

    Mrowczynski, S.

    1989-01-01

    The physics of relativistic elementary atoms,i.e. of Coulomb bound states of elementary particles, like positronium, pionium or an atom of μ + π - , is presented. The atom lifetimes and processes, in which the atoms are produced, are discussed. The interaction of the atoms with matter is also described. A simple derivation of most results is given. 33 refs. (author)

  20. Simple, heart-smart substitutions

    Science.gov (United States)

    ... food choices does not mean you have to sacrifice flavor. The key is to substitute less healthy ... trout, and mackerel. Shrimp has less cholesterol than chicken, pork, or beef. Choose lean meats. They have ...

  1. bis(n'-substituted a

    African Journals Online (AJOL)

    Preferred Customer

    substituted acetohydrazide) ... biological activity associated with their corresponding hydrazones attributed to the presence of the active ... Hence, in this paper, we are reporting eco-friendly synthesis of some new Schiff bases by condensing 2 ...

  2. N-substituted iminodiacetic acids

    International Nuclear Information System (INIS)

    Nunn, A.; Loberg, M.

    1982-01-01

    The chemical preparation of several new N-substituted iminodiacetic acid derivatives are described. These compounds when complexed with sup(99m)Tc provide useful radiopharmaceuticals for the external imaging of the hepatobiliary system. (U.K.)

  3. Atom lasers and nonlinear atom optics

    International Nuclear Information System (INIS)

    Deng Lu

    2000-01-01

    Two recent experimental breakthroughs in the field of atomic physics are reported: the realization of a well-collimated, widely tunable, quasi-continuous wave atom laser, and the generation of matter waves via coherent multi-wave mixing. The former is a critical step towards a continuous wave, high brightness atom laser while the latter has opened a new field of research: nonlinear atom optics

  4. Atomic weight versus atomic mass controversy

    International Nuclear Information System (INIS)

    Holden, N.E.

    1985-01-01

    A problem for the Atomic Weights Commission for the past decade has been the controversial battle over the names ''atomic weight'' and ''atomic mass''. The Commission has considered the arguments on both sides over the years and it appears that this meeting will see more of the same discussion taking place. In this paper, I review the situation and offer some alternatives

  5. Teach us atom structure

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Suh Yeon

    2006-08-15

    This book is written to teach atom structure in very easy way. It is divided into nine chapters, which indicates what is the components of matter? when we divide matter continuously, it becomes atom, what did atom look like? particles comprised of matter is not only atom, discover of particles comprised of atom, symbol of element, various radiation, form alchemy to nuclear transmutation, shape of atom is evolving. It also has various pictures in each chapters to explain easily.

  6. Nucleophilic Aromatic tele-Substitution of Hydrogen of 9-Nitroanthracene with 2-Naphthols and Phloroglucinol

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Su Yeon; Lim, Jin Woo; Nam, Kye Chun; Kim, Jae Nyoung [Chonnam National Univ., Gwangju (Korea, Republic of)

    2016-09-15

    Nucleophilic substitution reaction of hydrogen atom in electron-deficient arenes has been extensively studied. An addition of nucleophile to electron-deficient arenes such as nitroarene proceeds readily at the positions occupied by hydrogen atom to form σ{sup H}-adducts. A selective nucleophilic aromatic tele-substitution reaction has been observed in the reaction of 9-nitroanthracene with 2-naphthols, 1,3-cyclohexanediones, and phloroglucinol. The corresponding nitroanthracene derivatives, obtained by an ONSH process, were formed in variable yields as minor products depending on the substrates.

  7. Impact of Lanthanoid Substitution on the Structural and Physical Properties of an Infinite-Layer Iron Oxide.

    Science.gov (United States)

    Yamamoto, Takafumi; Ohkubo, Hiroshi; Tassel, Cédric; Hayashi, Naoaki; Kawasaki, Shota; Okada, Taku; Yagi, Takehiko; Hester, James; Avdeev, Maxim; Kobayashi, Yoji; Kageyama, Hiroshi

    2016-11-21

    The effect of lanthanoid (Ln = Nd, Sm, Ho) substitution on the structural and physical properties of the infinite-layer iron oxide SrFeO 2 was investigated by X-ray diffraction (XRD) at ambient and high pressure, neutron diffraction, and 57 Fe Mössbauer spectroscopy. Ln for Sr substituted samples up to ∼30% were synthesized by topochemical reduction using CaH 2 . While the introduction of the smaller Ln 3+ ion reduces the a axis as expected, we found an unusual expansion of the c axis as well as the volume. Rietveld refinements along with pair distribution function analysis revealed the incorporation of oxygen atoms between FeO 2 layers with a charge-compensated composition of (Sr 1-x Ln x )FeO 2+x/2 , which accounts for the failed electron doping to the FeO 2 layer. The incorporated partial apical oxygen or the pyramidal coordination induces incoherent buckling of the FeO 2 sheet, leading to a significant reduction of the Néel temperature. High-pressure XRD experiments for (Sr 0.75 Ho 0.25 )FeO 2.125 suggest a possible stabilization of an intermediate spin state in comparison with SrFeO 2 , revealing a certain contribution of the in-plane Fe-O distance to the pressure-induced transition.

  8. Laser-assisted atom-atom collisions

    International Nuclear Information System (INIS)

    Roussel, F.

    1984-01-01

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

  9. Oxygen-storage behavior and local structure in Ti-substituted YMnO3

    Science.gov (United States)

    Levin, I.; Krayzman, V.; Vanderah, T. A.; Tomczyk, M.; Wu, H.; Tucker, M. G.; Playford, H. Y.; Woicik, J. C.; Dennis, C. L.; Vilarinho, P. M.

    2017-02-01

    Hexagonal manganates RMnO3 (R=Y, Ho, Dy) have been recently shown to exhibit oxygen-storage capacities promising for three-way catalysts, air-separation, and related technologies. Here, we demonstrate that Ti substitution for Mn can be used to chemically tune the oxygen-breathing properties of these materials towards practical applications. Specifically, Y(Mn1-xTix)O3 solid solutions exhibit facile oxygen absorption/desorption via reversible Ti3+↔Ti4+ and Mn3+↔Mn4+ reactions already in ambient air at ≈400 °C and ≈250 °C, respectively. On cooling, the oxidation of both cations is accompanied by oxygen uptake yielding a formula YMn3+1-x-yMn4+yTi4+xO3+δ. The presence of Ti promotes the oxidation of Mn3+ to Mn4+, which is almost negligible for YMnO3 in air, thereby increasing the uptake of oxygen beyond that required for a given Ti4+ concentration. The reversibility of the redox reactions is limited by sluggish kinetics; however, the oxidation process continues, if slowly, even at room temperature. The extra oxygen atoms are accommodated by the large interstices within a triangular lattice formed by the [MnO5] trigonal bipyramids. According to bond distances from Rietveld refinements using the neutron diffraction data, the YMnO3 structure features under-bonded Mn and even more severely under-bonded oxygen atoms that form the trigonal bases of the [MnO5] bipyramids. The tensile bond strain around the 5-fold coordinated Mn site and the strong preference of Ti4+(and Mn4+) for higher coordination numbers likely provide driving forces for the oxidation reaction. Reverse Monte Carlo refinements of the local atomic displacements using neutron total scattering revealed how the excess oxygen atoms are accommodated in the structure by correlated local displacements of the host atoms. Large displacements of the under-bonded host oxygen atoms play a key part in this lattice-relaxation process, facilitating reversible exchange of significant amounts of oxygen with

  10. Code ATOM for calculation of atomic characteristics

    International Nuclear Information System (INIS)

    Vainshtein, L.A.

    1990-01-01

    In applying atomic physics to problems of plasma diagnostics, it is necessary to determine some atomic characteristics, including energies and transition probabilities, for very many atoms and ions. Development of general codes for calculation of many types of atomic characteristics has been based on general but comparatively simple approximate methods. The program ATOM represents an attempt at effective use of such a general code. This report gives a brief description of the methods used, and the possibilities of and limitations to the code are discussed. Characteristics of the following processes can be calculated by ATOM: radiative transitions between discrete levels, radiative ionization and recombination, collisional excitation and ionization by electron impact, collisional excitation and ionization by point heavy particle (Born approximation only), dielectronic recombination, and autoionization. ATOM explores Born (for z=1) or Coulomb-Born (for z>1) approximations. In both cases exchange and normalization can be included. (N.K.)

  11. Atomic physics: Cold gases venture into Flatland

    Science.gov (United States)

    Burnett, Keith

    2007-09-01

    Vortex structures have revealed a lot about the nature of three-dimensional Bose-Einstein condensates. They play an even bigger part in two-dimensional cold atomic gases and drive a fundamentally different phase transition.

  12. Approaches in Substitution of Organic Solvents

    DEFF Research Database (Denmark)

    Jacobsen, Thomas

    2000-01-01

    In substitution of harmful chemicals or products with less harmful or harmless ones, there are different approaches according to the different situations, the technical requirements to the substitutes, and the goals for the substitution. Three different cases are presented. The substitution process...

  13. Effect of nickel oxide substitution on bioactivity and mechanical ...

    Indian Academy of Sciences (India)

    glass revealed that isomorphic substitution of nickel in the silicate network in tetrahedral coordination or as modifier in higher coordination do not adversely affect the existing glass structure. The present work aims to measure the bioactivity and mechanical properties of base glass and nickel oxide substi- tute bioactive glass ...

  14. Synthesis of meta-substituted monodentate phosphinite ligands and ...

    Indian Academy of Sciences (India)

    To demonstrate the synthetic usefulness of 4a and 4b, these ligands were tested in the rhodium catalyzed hydroformylation of 1-octene. The diethylamine substituted ligand 4a was found to be highly active, whereas4bwas less reactive but revealed slightly better regioselectivity of 62% under optimized conditions.

  15. Synthesis and microwave dielectric properties of Ca substituted ...

    Indian Academy of Sciences (India)

    Keywords. Patch antenna; theoretical density; phase; ceramics. Abstract. Microwave dielectric ceramics in Sr1-CaLa4Ti4.93Zr0.07O17 (0 ≤ ≤ 0.5) composition series were processed via a solid-state sintering rout. X-ray diffraction revealed single phase ceramics. Ca substitutions for Sr tuned f towards zero with ...

  16. A DFT Study of R-X Bond Dissociation Enthalpies of Relevance to the Initiation Process of Atom Transfer Radical Polymerization

    DEFF Research Database (Denmark)

    Gillies, Malcolm Bjørn; Matyjaszewski, Krzysztof; Norrby, Per-Ola

    2003-01-01

    DFT calculations at the B3P86/6-31G** level have been carried out to derive the bond dissociation energies (BDE) and free energies for a number of R-X systems (X ) Cl, Br, I, N3, and S2-CNMe2) that have been or can potentially be used as initiators for atom transfer radical polymerization (ATRP...... energies are in good agreement with the experimentally available BDEs and reveal a small weakening effect caused by the substitution of an R-H atom with a CH3 group. The free energies are used to derive the relative equilibrium constant for the ATRP activation/deactivation process. These are compared...... with the equilibrium constants that have been determined from ATRP polymerization rates and from model studies of activation-deactivation-termination processes in the absence of monomer. These comparisons reveal the effectiveness of the DFT-computed BDEs for predicting polymerization rates for new monomers in ATRP...

  17. First principles calculations of hyperfine parameters on the Ca manganite with substitutional Cd-modeling of a PAC experiment

    CERN Document Server

    Goncalves, JN; Lopes, A M L; Haas, H; Amaral, V S; Goncalves, J N

    2010-01-01

    The APW + lo (augmented plane waves + local orbitals) method of density functional theory, as implemented in the Wien2k code, is applied to calculate the electric field gradient of manganites. We report the first principles calculations on CaMnO3, and modeling of a perturbed angular correlation experiment with implanted Cd-111m isotope. To model the experiment we additionally calculate in Ca1-xCdxMnO3, where we substitute Cd at the Ca site. Increasing Cd dilution is done with the use of supercells. We find that the experimental CaMnO3 low-temperature value V-zz approximate to 6 x 10(-21) V/m(2) is reproduced, whenoptimizinginternalparameters. The analysis of the EFG tensor at the Ca atoms, with different electric field gradients at inequivalent positions, reveals that the convergence of the calculations is obtained. (C) 2009 Elsevier B.V. All rights reserved.

  18. Commercial formalin substitutes for histopathology

    DEFF Research Database (Denmark)

    Prentø, P; Lyon, H

    1997-01-01

    We compared the performance of six commercial fixatives proposed to be formalin substitutes with the performance of buffered formalin, Clarke's ethanol-acetic acid, and ethanol, using rat liver, small intestine, and kidney. We investigated the rate of penetration, mode of fixation, extent...... performed equally well on all tissues tested. While several of the commercial fixatives appeared to preserve liver tissue at 200x, the preservation of kidney, intestinal villi, and smooth muscle was unacceptable. Histological distortion, cell shrinkage and vacuolization were prominent when the substitutes...... was obtained by combining formalin fixation with antigen retrieval. We conclude that none of the proposed commercial substitutes for buffered formalin are adequate for critical histology or histopathology....

  19. Neutral atom traps.

    Energy Technology Data Exchange (ETDEWEB)

    Pack, Michael Vern

    2008-12-01

    This report describes progress in designing a neutral atom trap capable of trapping sub millikelvin atom in a magnetic trap and shuttling the atoms across the atom chip from a collection area to an optical cavity. The numerical simulation and atom chip design are discussed. Also, discussed are preliminary calculations of quantum noise sources in Kerr nonlinear optics measurements based on electromagnetically induced transparency. These types of measurements may be important for quantum nondemolition measurements at the few photon limit.

  20. Three-atom clusters

    International Nuclear Information System (INIS)

    Pen'kov, F.M.

    1998-01-01

    The Born-Oppenheimer approximation is used to obtain an equation for the effective interaction in three atoms bound by a single electron. For low binding energies in an 'electron + atom' pair, long-range forces arise between the atoms, leading to bound states when the size of the three-atom cluster is a few tens of angstrom. A system made of alkali-metal atoms is considered as an example

  1. Stable atomic hydrogen: Polarized atomic beam source

    International Nuclear Information System (INIS)

    Niinikoski, T.O.; Penttilae, S.; Rieubland, J.M.; Rijllart, A.

    1984-01-01

    We have carried out experiments with stable atomic hydrogen with a view to possible applications in polarized targets or polarized atomic beam sources. Recent results from the stabilization apparatus are described. The first stable atomic hydrogen beam source based on the microwave extraction method (which is being tested ) is presented. The effect of the stabilized hydrogen gas density on the properties of the source is discussed. (orig.)

  2. Exfoliation and thermal transformations of Nb-substituted layered titanates

    DEFF Research Database (Denmark)

    Song, H.; Sjåstad, Anja O.; Fjellvåg, Helmer

    2011-01-01

    Single-layer Nb-substituted titanate nanosheets of ca. 1 nm thickness were obtained by exfoliating tetrabutylammonium (TBA)-intercalated Nb-substituted titanates in water. AFM images and turbidity measurements reveal that the exfoliated nanosheets crack and corrugate when sonicated. Upon heating...... factors for increasing the transformation temperatures for conversion of the nanosheets to anatase and finally into rutile. It is further tempting to link the delay in crystallization to morphology limitations originating from the nanosheets. The present work shows that layered Nb-titanates...

  3. Researcher’s Perspective of Substitution Method on Text Steganography

    Science.gov (United States)

    Zamir Mansor, Fawwaz; Mustapha, Aida; Azah Samsudin, Noor

    2017-08-01

    The linguistic steganography studies are still in the stage of development and empowerment practices. This paper will present several text steganography on substitution methods based on the researcher’s perspective, all scholar paper will analyse and compared. The objective of this paper is to give basic information in the substitution method of text domain steganography that has been applied by previous researchers. The typical ways of this method also will be identified in this paper to reveal the most effective method in text domain steganography. Finally, the advantage of the characteristic and drawback on these techniques in generally also presented in this paper.

  4. Substituted 4-hydroxy-1,2,3-triazoles

    DEFF Research Database (Denmark)

    Pippione, Agnese C.; Dosio, Franco; Ducime, Alex

    2015-01-01

    Bioisosterism and scaffold hopping are two widely used approaches in medicinal chemistry for the purpose of lead optimization. The study highlights the physicochemical properties of the 4-hydroxy-1,2,3-triazole scaffold, a less investigated heterocyclic system. Synthetic strategies to obtain...... different N-substituted 4-hydroxy-1,2,3-triazole isomers are presented, and their role as possible isosteres of the carboxylic acid is discussed. The aim is to use this system to modulate the acidic moieties present in lead compounds and, at the same time, to regiodirect substituents in set directions......, through targeted substitution on the three nitrogen atoms of the triazole ring. Through this approach, compounds having enhanced binding affinity, will be sought. Two examples of bioisosteric applications of this moiety are presented. In the first example, a classical bioisosteric approach mimicking...

  5. Ab initio studies on proton affinities of substituted furans

    International Nuclear Information System (INIS)

    Lee, Gab Yong; Lee, Hyun Mee

    1998-01-01

    The geometry of furan, relevant to the binding of bis-furan lexitropsin that contains this ring to the base pair of minor groove of DNA, is optimized by semiempirical (MNDO) and ab initio (Hartree-Fock) methods. The proton affinity and electronic structure are evaluated at the 6-31G and 6-31G level of theory for the optimized geometry. The proton affinities are also studied for various substituted furans with the electron donating and -withdrawing groups to estimate the substituent effect on the proton affinity of furans. It has been found that the electron-donating substituents increase the proton affinity of of furan, whereas the electron-withdrawing substituents decrease it. This result can be explained with atomic charge and electron density at oxygen of substituted furans

  6. Accelerated hydrolysis of substituted cellulose for potential biofuel production: kinetic study and modeling.

    Science.gov (United States)

    Mu, Bingnan; Xu, Helan; Yang, Yiqi

    2015-11-01

    In this work, kinetics of substitution accelerated cellulose hydrolysis with multiple reaction stages was investigated to lay foundation for mechanism study and molecular design of substituting compounds. High-efficiency hydrolysis of cellulose is critical for cellulose-based bioethanol production. It is known that, substitution could substantially decrease activation energy and increase reaction rate of acidic hydrolysis of glycosidic bonds in cellulose. However, reaction kinetics and mechanism of the accelerated hydrolysis were not fully revealed. In this research, it was proved that substitution therefore accelerated hydrolysis only occurred in amorphous regions of cellulose fibers, and was a process with multiple reaction stages. With molar ratio of substitution less than 1%, the overall hydrolysis rate could be increased for around 10 times. We also quantified the relationship between the hydrolysis rate of individual reaction stage and its major influences, including molar ratio of substitution, activation energy of acidic hydrolysis, pH and temperature. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Efficient synthesis of substituted dihydrotetraazapentacenes.

    Science.gov (United States)

    Seillan, Claire; Brisset, Hugues; Siri, Olivier

    2008-09-18

    We describe a versatile and very efficient synthesis of previously unknown substituted 5,14-dihydro-5,7,12,14-tetraazapentacenes (DHTAPs). A structural study by NMR spectroscopy showed that the conjugated pi-system of the pentacyclic skeleton rearranges depending on the electronic effect of the substituent(s).

  8. Tax rates as strategic substitutes

    NARCIS (Netherlands)

    H. Vrijburg (Hendrik); R.A. de Mooij (Ruud)

    2016-01-01

    textabstractThis paper analytically derives conditions under which the slope of the tax-reaction function is negative in a classical tax competition model. If countries maximize welfare, a negative slope (reflecting strategic substitutability) occurs under relatively mild conditions. The strategic

  9. High-Temperature Decomposition of Brønsted Acid Sites in Gallium-Substituted Zeolites

    Energy Technology Data Exchange (ETDEWEB)

    K Al-majnouni; N Hould; W Lonergan; D Vlachos; R Lobo

    2011-12-31

    The dehydroxylation of Broensted acid sites (BAS) in Ga-substituted zeolites was investigated at temperatures up to 850 C using X-ray absorption spectroscopy (XAS), Fourier transform infrared spectroscopy (FTIR), and mass spectrometry-temperature programmed desorption (MS-TPD). X-ray absorption near-edge spectroscopy (XANES) revealed that the majority of gallium has tetrahedral coordination even after complete dehydroxylation. The interatomic gallium-oxygen distance and gallium coordination number determined by extended X-ray absorption fine structure (EXAFS) are consistent with gallium in tetrahedral coordination at low T (< 550 C). Upon heating Ga-Beta and Ga-ZSM5 to 850 C, analysis of the EXAFS showed that 70 and 80% of the gallium was still in tetrahedral coordination. The remainder of the gallium was found to be in octahedral coordination. No trigonal Ga atoms were observed. FTIR measurements carried out at similar temperatures show that the intensity of the OH vibration due to BAS has been eliminated. MS-TPD revealed that hydrogen in addition to water evolved from the samples during dehydroxylation. This shows that dehydrogenation in addition to dehydration is a mechanism that contributes to BAS decomposition. Dehydrogenation was further confirmed by exposing the sample to hydrogen to regenerate some of the BAS as monitored by FTIR and MS-TPD.

  10. Atomic and molecular manipulation

    CERN Document Server

    Mayne, Andrew J

    2011-01-01

    Work with individual atoms and molecules aims to demonstrate that miniaturized electronic, optical, magnetic, and mechanical devices can operate ultimately even at the level of a single atom or molecule. As such, atomic and molecular manipulation has played an emblematic role in the development of the field of nanoscience. New methods based on the use of the scanning tunnelling microscope (STM) have been developed to characterize and manipulate all the degrees of freedom of individual atoms and molecules with an unprecedented precision. In the meantime, new concepts have emerged to design molecules and substrates having specific optical, mechanical and electronic functions, thus opening the way to the fabrication of real nano-machines. Manipulation of individual atoms and molecules has also opened up completely new areas of research and knowledge, raising fundamental questions of "Optics at the atomic scale", "Mechanics at the atomic scale", Electronics at the atomic scale", "Quantum physics at the atomic sca...

  11. Microfabricated Waveguide Atom Traps.

    Energy Technology Data Exchange (ETDEWEB)

    Jau, Yuan-Yu [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-09-01

    A nanoscale , microfabricated waveguide structure can in - principle be used to trap atoms in well - defined locations and enable strong photon-atom interactions . A neutral - atom platform based on this microfabrication technology will be prealigned , which is especially important for quantum - control applications. At present, there is still no reported demonstration of evanescent - field atom trapping using a microfabricated waveguide structure. We described the capabilities established by our team for future development of the waveguide atom - trapping technology at SNL and report our studies to overcome the technical challenges of loading cold atoms into the waveguide atom traps, efficient and broadband optical coupling to a waveguide, and the waveguide material for high - power optical transmission. From the atomic - physics and the waveguide modeling, w e have shown that a square nano-waveguide can be utilized t o achieve better atomic spin squeezing than using a nanofiber for first time.

  12. Advances in atomic spectroscopy

    CERN Document Server

    Sneddon, J

    2000-01-01

    This fifth volume of the successful series Advances in Atomic Spectroscopy continues to discuss and investigate the area of atomic spectroscopy.It begins with a description of the use of various atomic spectroscopic methods and applications of speciation studies in atomic spectroscopy. The emphasis is on combining atomic spectroscopy with gas and liquid chromatography. In chapter two the authors describe new developments in tunable lasers and the impact they will have on atomic spectroscopy. The traditional methods of detection, such as photography and the photomultiplier, and how they are being replaced by new detectors is discussed in chapter three. The very active area of glow discharge atomic spectrometry is presented in chapter four where, after a brief introduction and historical review, the use of glow discharge lamps for atomic spectroscopy and mass spectrometry are discussed. Included in this discussion is geometry and radiofrequency power. The future of this source in atomic spectroscopy is also dis...

  13. The prevalence of natural 3-alk(en)yl-substituted phenols and their ...

    African Journals Online (AJOL)

    substituted phenolic sub-structure embedded in a particular natural product and reveal the CNSL phenolic component that has the corresponding structural motif. In addition, the author prompts the reader into a thinking process that should eventually ...

  14. Site preference and magnetic properties of Ga/In-substituted strontium hexaferrite: An ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Dixit, Vivek; Nandadasa, Chandani N.; Kim, Seong-Gon, E-mail: kimsg@ccs.msstate.edu [Department of Physics and Astronomy, Mississippi State University, Mississippi State, Mississippi 39762, USA and Center for Computational Sciences, Mississippi State University, Mississippi State, Mississippi 39762 (United States); Kim, Sungho [Center for Computational Sciences, Mississippi State University, Mississippi State, Mississippi 39762 (United States); Park, Jihoon; Hong, Yang-Ki [Department of Electrical and Computer Engineering and MINT Center, The University of Alabama, Tuscaloosa, Alabama 35487 (United States)

    2015-11-28

    The first-principles density functional theory has been used to study Ga/In-substituted strontium hexaferrite (SrFe{sub 12}O{sub 19}). Based on the calculation of the substitution energy of Ga and In in SrFe{sub 12}O{sub 19} and the formation probability analysis, we conclude that in SrFe{sub 12−x}Ga{sub x}O{sub 19} the substituted Ga atoms prefer to occupy the 12k, 2a, and 4f{sub 1} sites, while In atoms in SrFe{sub 12−x}In{sub x}O{sub 19} occupy the 12k, 4f{sub 2}, and 4f{sub 1} sites. We used the site occupation probabilities to calculate the magnetic properties of the substituted SrFe{sub 12}O{sub 19}. It was found that as the fraction of Ga atoms in SrFe{sub 12−x}Ga{sub x}O{sub 19} increases, the saturation magnetization (M{sub s}) as well as magnetic anisotropy energy (MAE) decrease, while the anisotropy field (H{sub a}) increases. In the case of SrFe{sub 12−x}In{sub x}O{sub 19}, M{sub s}, MAE, and H{sub a} decrease with an increase of the concentration of In atoms.

  15. Atomic Fuel, Understanding the Atom Series. Revised.

    Science.gov (United States)

    Hogerton, John F.

    This publication is part of the "Understanding the Atom" series. Complete sets of the series are available free to teachers, schools, and public librarians who can make them available for reference or use by groups. Among the topics discussed are: What Atomic Fuel Is; The Odyssey of Uranium; Production of Uranium; Fabrication of Reactor…

  16. Atomic Fisher information versus atomic number

    International Nuclear Information System (INIS)

    Nagy, A.; Sen, K.D.

    2006-01-01

    It is shown that the Thomas-Fermi Fisher information is negative. A slightly more sophisticated model proposed by Gaspar provides a qualitatively correct expression for the Fisher information: Gaspar's Fisher information is proportional to the two-third power of the atomic number. Accurate numerical calculations show an almost linear dependence on the atomic number

  17. Atomic-fluorescence spectrophotometry

    International Nuclear Information System (INIS)

    Bakhturova, N.F.; Yudelevich, I.G.

    1975-01-01

    Atomic-fluorescence spectrophotometry, a comparatively new method for the analysis of trace quantities, has developed rapidly in the past ten years. Theoretical and experimental studies by many workers have shown that atomic-fluorescence spectrophotometry (AFS) is capable of achieving a better limit than atomic absorption for a large number of elements. The present review examines briefly the principles of atomic-fluorescence spectrophotometry and the types of fluorescent transition. The excitation sources, flame and nonflame atomizers, used in AFS are described. The limits of detection achieved up to the present, using flame and nonflame methods of atomization are given

  18. PHYSICS: Toward Atom Chips.

    Science.gov (United States)

    Fortágh, József; Zimmermann, Claus

    2005-02-11

    As a novel approach for turning the peculiar features of quantum mechanics into practical devices, researchers are investigating the use of ultracold atomic clouds above microchips. Such "atom chips" may find use as sensitive probes for gravity, acceleration, rotation, and tiny magnetic forces. In their Perspective, Fortagh and Zimmermann discuss recent advances toward creating atom chips, in which current-carrying conductors in the chips create magnetic microtraps that confine the atomic clouds. Despite some intrinsic limits to the performance of atom chips, existing technologies are capable of producing atom chips, and many possibilities for their construction remain to be explored.

  19. THE ORNL ATOM PROBE

    OpenAIRE

    Miller, M.

    1986-01-01

    The ORNL Atom Probe is a microanalytical tool for studies in materials science. The instrument is a combination of a customized version of the vacuum system of the VG FIM-100 atom probe, an ORNL-designed microcomputer-controlled digital timing system, and a double curved CEMA Imaging Atom Probe detector. The atom probe combines four instruments into one - namely a field ion microscope, an energy compensated time-of-flight mass spectrometer, an imaging atom probe, and a pulsed laser atom probe.

  20. Lattice site occupation of insoluble impurity atoms in aluminium after implantation and irradiation

    International Nuclear Information System (INIS)

    Kloska, M.K.

    1987-03-01

    Several elements, whose atoms are oversized and insoluble in aluminium, were implanted in aluminium single crystals at different temperatures. The substitutional fraction and the lattice site location were determined using the ion-channeling technique. The substitutional fractions obtained by in situ analyses are strongly dependent on the implantation temperature. At implantation and analysis temperatures below the temperature of stage III the substitutional fraction is significant larger than at temperatures above. With increasing heat of solution the substitutional fraction decreases for all implantation temperatures. The nonsubstitutional component consists of impurity atom-vacancy complexes. These complexes are formed in the cooling phase of the cascade. At temperatures above the temperature of stage III additional free mobile vacancies were captured by the impurity atoms. The capture radius is correlated with the heat of solution and the size mismatch energy. The results constitute for the first time an experimental confirmation of molecular dynamics calculations of cascade evolution. (orig./BHO)

  1. Chemical environment of iron atoms in iron oxynitride films synthesized by reactive magnetron sputtering

    International Nuclear Information System (INIS)

    Grafoute, M.; Petitjean, C.; Rousselot, C.; Pierson, J.F.; Greneche, J.M.

    2007-01-01

    An iron oxynitride film was deposited on silicon and glass substrates by magnetron sputtering in an Ar-N 2 -O 2 reactive mixture. Rutherford back-scattering spectrometry was used to determine the film composition (Fe 1.06 O 0.35 N 0.65 ). X-ray diffraction revealed the formation of a face-centred cubic (fcc) structure with a lattice parameter close to that of γ'''-FeN. X-ray photoelectron spectroscopy showed the occurrence of Fe-N and Fe-O bonds in the film. The local environment of iron atoms studied by 57 Fe Moessbauer spectrometry at both 300 and 77 K gives clear evidence that the Fe 1.06 O 0.35 N 0.65 is not a mixture of iron oxide and iron nitride phases. Despite a small amount of an iron nitride phase, the main sample consists of an iron oxynitride phase with an NaCl-type structure where oxygen atoms partially substitute for nitrogen atoms, thus indicating the formation of a iron oxynitride with an fcc structure

  2. Theoretical Calculation of Absolute Radii of Atoms and Ions. Part 1. The Atomic Radii

    Directory of Open Access Journals (Sweden)

    Raka Biswas

    2002-02-01

    Full Text Available Abstract. A set of theoretical atomic radii corresponding to the principal maximum in the radial distribution function, 4πr2R2 for the outermost orbital has been calculated for the ground state of 103 elements of the periodic table using Slater orbitals. The set of theoretical radii are found to reproduce the periodic law and the Lother Meyer’s atomic volume curve and reproduce the expected vertical and horizontal trend of variation in atomic size in the periodic table. The d-block and f-block contractions are distinct in the calculated sizes. The computed sizes qualitatively correlate with the absolute size dependent properties like ionization potentials and electronegativity of elements. The radii are used to calculate a number of size dependent periodic physical properties of isolated atoms viz., the diamagnetic part of the atomic susceptibility, atomic polarizability and the chemical hardness. The calculated global hardness and atomic polarizability of a number of atoms are found to be close to the available experimental values and the profiles of the physical properties computed in terms of the theoretical atomic radii exhibit their inherent periodicity. A simple method of computing the absolute size of atoms has been explored and a large body of known material has been brought together to reveal how many different properties correlate with atomic size.

  3. Atom localization via controlled spontaneous emission in a five-level atomic system

    International Nuclear Information System (INIS)

    Wang Zhiping; Yu Benli; Zhu Jun; Cao Zhigang; Zhen Shenglai; Wu Xuqiang; Xu Feng

    2012-01-01

    We investigate the one- and two-dimensional atom localization behaviors via spontaneous emission in a coherently driven five-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found that the detecting probability and precision of atom localization behaviors can be significantly improved via adjusting the system parameters. More importantly, the two-dimensional atom localization patterns reveal that the maximal probability of finding an atom within the sub-wavelength domain of the standing waves can reach unity when the corresponding conditions are satisfied. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization. - Highlights: ► One- and two-dimensional atom localization behaviors via spontaneous emission in five-level atoms are investigated. ► An assisting radio-frequency field is used to control the atom localization behaviors. ► High-precision and high-resolution two-dimensional atom localization can be realized in this scheme.

  4. 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)

  5. Deep Space Atomic Clock

    Data.gov (United States)

    National Aeronautics and Space Administration — The Deep Space Atomic Clock (DSAC) project will develop a small, low mass atomic clock based on mercury-ion trap technology and demonstrate it in space providing the...

  6. Molecular beam studies and hot atom chemistry

    International Nuclear Information System (INIS)

    Continetti, R.E.; Lee, Y.T.

    1993-01-01

    The application of the crossed molecular beam technique to the study of hot atom chemistry has provided significant insights into the dynamics of hot atom reaction. To illustrate this, two recent studies are discussed. Those are the study on the influence of translational energy in 0.6 to 1.5 eV range on endoergic reaction, and the experimental study on the detailed dynamics of elementary reaction at translational energy of 0.53 and 1.01 eV. The first example illustrates the contribution that molecular beam experiment can make in the understanding of the dynamics of endoergic substitution reaction. The second example illustrates the role that such studies can play in evaluating exact three-dimensional quantum scattering calculation and ab initio potential energy surfaces for chemical reaction. In the case of endoergic reaction of halogen substitution, it was observed that the reactive collision involved short lived collision complexes. It is suggested that energetic effect alone cannot account for the difference in cross sections, and dynamic effect most play a large role. In atom-diatom reaction, the differential cross section measurement of D+H 2 →DH+H reaction was carried out, and the results are discussed. (K.I.)

  7. Navigation with Atom Interferometers

    Science.gov (United States)

    2017-03-20

    Navigation with Atom Interferometers Mary F. Locke and Frank A. Narducci Avionics Department Naval Air Systems Command Patuxent River, Md...20670 Abstract: In this article, we review the basic physics of an atom interferometer. We highlight the usefulness of atom interferometers for...inertial navigation due to their high phase sensitivity to both linear acceleration and angular rotation, but also the drawback that a single atom

  8. First-Principles Study of Substitution of Au for Ni in Ni3Sn4

    Science.gov (United States)

    Tian, Yali; Wu, Ping

    2018-02-01

    First-principles calculations were performed to investigate the effects of substitution of Au for Ni on the structural, elastic, thermodynamic and electronic properties of Ni3Sn4. The calculated lattice constants for the pure phase are consistent with the reported values. Substitution of Au for Ni results in a stable thermodynamic structure. The bulk modulus, shear modulus, Young's modulus, hardness and thermal conductivity are decreased and the relative brittleness is improved after substitution. A three-dimensional graphic representation of the anisotropy of Young's modulus indicates that substitution of Au for Ni increases the anisotropy. All of the compound compositions examined are metallic and nonmagnetic. The electronic density of states manifests a conjoined peak between - 6 eV and - 4 eV hybridized by Au-d electrons and Sn-p electrons when the fraction of Au atom is above 14.29 at.% in Ni3Sn4.

  9. Smart Phones and their Substitutes

    DEFF Research Database (Denmark)

    Bødker, Mads; Gimpel, Gregory; Hedman, Jonas

    2009-01-01

    Drawing on data from a longitudinal field study, this paper investigates the influence of existing, better and stand-alone technology substitutes on the use of smart phones. By applying prospect theory, media richness theory, and business model literature, the purpose of this paper is to improve...... our understanding of the role of substitutes, device content fit issues, and implications for business models by asking the question: What is an effective business model to address the relationship between user preference and the fit of the smart phone and everyday task? The field study data suggest...... the need for business models to recognize that adoption decisions are reference-dependent and strongly influenced by the fit between task and smart phone....

  10. Substituting oil by electric power

    International Nuclear Information System (INIS)

    Lichtenberg, H.

    1981-01-01

    Parting from the development of primary energy use the author refers to the latest investigations and results presented on the 1980 World Energy Conference and with special regard to oil points out the threatening exhaustion of fossil energy resources. Maintaining the economic structure of the Federal Republic of Germany implies an orientation away from oil. Due to its flexible application technology and quasi-inexhaustible energy resources electric power may substantially contribute to oil substitution which as a matter of fact is of particular interest in connection with the heat market. Coal alone cannot substitute both oil and nuclear energy. Thus, the above postulates the use of the latter. Leaving nuclear energy inactive today will effect an increase in the demand for oil the negative consequences of which would weight heavily upon the anyhow unbalanced import/export ratio of the Federal Republic of Germany. (orig.) [de

  11. Use of atomic force microscopy and transmission electron microscopy for correlative studies of bacterial capsules.

    Science.gov (United States)

    Stukalov, Oleg; Korenevsky, Anton; Beveridge, Terry J; Dutcher, John R

    2008-09-01

    Bacteria can possess an outermost assembly of polysaccharide molecules, a capsule, which is attached to their cell wall. We have used two complementary, high-resolution microscopy techniques, atomic force microscopy (AFM) and transmission electron microscopy (TEM), to study bacterial capsules of four different gram-negative bacterial strains: Escherichia coli K30, Pseudomonas aeruginosa FRD1, Shewanella oneidensis MR-4, and Geobacter sulfurreducens PCA. TEM analysis of bacterial cells using different preparative techniques (whole-cell mounts, conventional embeddings, and freeze-substitution) revealed capsules for some but not all of the strains. In contrast, the use of AFM allowed the unambiguous identification of the presence of capsules on all strains used in the present study, including those that were shown by TEM to be not encapsulated. In addition, the use of AFM phase imaging allowed the visualization of the bacterial cell within the capsule, with a depth sensitivity that decreased with increasing tapping frequency.

  12. Atomic Ferris wheel beams

    OpenAIRE

    Lembessis, Vasileios E.

    2017-01-01

    We study the generation of atom vortex beams in the case where an atomic wave-packet, moving in free space, is diffracted from a properly tailored light mask with a spiral transverse profile. We show how such a diffraction scheme could lead to the production of an atomic Ferris wheel beam.

  13. Atomic Energy Control Act

    International Nuclear Information System (INIS)

    1970-01-01

    This act provides for the establishment of the Atomic Energy Control Board. The board is responsible for the control and supervision of the development, application and use of atomic energy. The board is also considered necessary to enable Canada to participate effectively in measures of international control of atomic energy

  14. Atomic Spectra Database (ASD)

    Science.gov (United States)

    SRD 78 NIST Atomic Spectra Database (ASD) (Web, free access)   This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The NIST Atomic Spectroscopy Data Center has carried out these critical compilations.

  15. 40 CFR 721.9100 - Substituted quinoline.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted quinoline. 721.9100... Substances § 721.9100 Substituted quinoline. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted quinoline (PMN P-93-1183) is...

  16. Substituted Indoleacetic Acids Tested in Tissue Cultures

    DEFF Research Database (Denmark)

    Engvild, Kjeld Christensen

    1978-01-01

    Monochloro substituted IAA inhibited shoot induction in tobacco tissue cultures about as much as IAA. Dichloro substituted IAA inhibited shoot formation less. Other substituted IAA except 5-fluoro- and 5-bromoindole-3-acetic acid were less active than IAA. Callus growth was quite variable...

  17. Substituted Indoleacetic Acids Tested in Tissue Cultures

    DEFF Research Database (Denmark)

    Engvild, Kjeld Christensen

    1978-01-01

    Monochloro substituted IAA inhibited shoot induction in tobacco tissue cultures about as much as IAA. Dichloro substituted IAA inhibited shoot formation less. Other substituted IAA except 5-fluoro- and 5-bromoindole-3-acetic acid were less active than IAA. Callus growth was quite variable and not...... and not correlated with auxin strength measured in the Avena coleoptile test....

  18. 40 CFR 721.9488 - Substituted resorcinols.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted resorcinols. 721.9488... Substances § 721.9488 Substituted resorcinols. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as substituted resorcinols (PMNs P-95-1103, P...

  19. Quantitative characterization of new supramolecular synthons involving fluorine atoms in the crystal structures of di- and tetrafluorinated benzamides.

    Science.gov (United States)

    Mondal, Pradip Kumar; Yadav, Hare Ram; Choudhury, Angshuman Roy; Chopra, Deepak

    2017-10-01

    Strong hydrogen bonds play a significant role in crystal packing. In particular, the involvement of interactions involving fluorine in controlling the crystal packing requires appropriate attention, especially in the presence of other strong hydrogen bonds. In the present study, a detailed quantitative assessment has been performed of the nature, energetics and topological properties derived from the electron density in model compounds based on fluorinated benzamides (a total of 46 fluorine-substituted benzamides containing multiple fluorine atoms) in the solid state. The primary motivation in the design of such molecules is to enhance the acidity of the interacting H atoms in the presence of an increasing number of F atoms on the molecular scaffold, resulting in increased propensity towards the formation of intermolecular interactions involving organic fluorine. This exercise has resulted in the identification of new and frequently occurring supramolecular synthons involving F atoms in the packing of molecules in the solid state. The energetics associated with short and directional intermolecular Csp 2 -H...F-Csp 2 interactions with significantly high electrostatic contributions is noteworthy, and the topological analysis reveals the bonding character of these ubiquitous interactions in crystal packing in addition to the presence of Csp 2 -F...F-Csp 2 contacts.

  20. Size effects on cation heats of formation. I. Methyl substitutions in nitrogenous compounds

    International Nuclear Information System (INIS)

    Leach, Sydney

    2012-01-01

    Graphical abstract: Heat of formation of cations as a function of ln(n) where n is the number of atoms in the ion: methyl substituted immonium cations. N = substitution at nitrogen sites, C = substitution at carbon sites. Highlights: ► Heats of formation of nitrogenous cations by graphical method relating to ion size. ► Methyl substitution in formamides, acetamides, immonium, amine, and imine cations. ► Methyl substitution in ammonium and amino cations. ► New studies ionization energies and heats of formation required in several cases. - Abstract: The heats of formation of molecular ions are often not known to better than 10 or 20 kJ/mol. The present study on nitrogenous compounds adopts the graphical approach of Holmes and Lossing which relates cation heats of formation to cation size. A study of methyl substitution in formamides and acetamides is followed by an examination of heat of formation data on carbon-site and nitrogen-site methyl substitution in immonium, amine, imine, ammonium and amino cations. The results provide tests of the validity of this graphical method and also suggest investigating or re-investigating the ionization energies and the heats of formation of several of the molecules studied.

  1. Atom-atom collision cascades localization

    International Nuclear Information System (INIS)

    Kirsanov, V.V.

    1980-01-01

    The presence of an impurity and thermal vibration influence on the atom-atom collision cascade development is analysed by the computer simulation method (the modificated dynamic model). It is discovered that the relatively low energetic cascades are localized with the temperature increase of an irradiated crystal. On the basis of the given effect the mechanism of splitting of the high energetic cascades into subcascades is proposed. It accounts for two factors: the primary knocked atom energy and the irradiated crystal temperature. Introduction of an impurity also localizes the cascades independently from the impurity atom mass. The cascades localization leads to intensification of the process of annealing in the cascades and reduction of the post-cascade vacancy cluster sizes. (author)

  2. Cold Atom Interferometry

    International Nuclear Information System (INIS)

    Zhan Mingsheng; Li Ke; Wang Ping; Kong Lingbo; Wang Xiaorui; Li Runbing; Tu Xianhua; He Lingxiang; Wang Jin; Lu Baolong

    2007-01-01

    In this article the recent experimental works on cold atoms carried out at Wuhan Institute of Physics and Mathematics (WIPM) are reported. These include the experimental realization of Bose-Einstein condensation (BEC), different type of cold atom interferometers, and bichromatic electromagnetically-induced transparency (EIT). We have realized Bose-Einstein condensates of 87 Rb dilute atomic gases. The apparatus consists of two horizontally mounted magneto-optic-traps (MOTs) and a QUIC magnetic trap. Nearly 3x10 8 atoms were trapped in the second MOT, and up to 1.2x10 8 atoms were adiabatically transferred to the QUIC trap. A pure condensate with about 1.1x10 5 atoms at about 30 nK was achieved. We also demonstrated two type of cold atom interferometers, the Sagnac and Ramsey interference fringes were recorded with contrast of up to 37%

  3. Oxygen-storage behavior and local structure in Ti-substituted YMnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Levin, I., E-mail: igor.levin@nist.gov [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Krayzman, V.; Vanderah, T.A. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Tomczyk, M. [Department of Ceramics and Glass Engineering, University of Aveiro, Aveiro 3810-193 (Portugal); Wu, H. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Tucker, M.G. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Playford, H.Y. [ISIS Facility, Rutherford Appleton Laboratory, Didcot, Oxford (United Kingdom); Woicik, J.C.; Dennis, C.L. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Vilarinho, P.M. [Department of Ceramics and Glass Engineering, University of Aveiro, Aveiro 3810-193 (Portugal)

    2017-02-15

    Hexagonal manganates RMnO{sub 3} (R=Y, Ho, Dy) have been recently shown to exhibit oxygen-storage capacities promising for three-way catalysts, air-separation, and related technologies. Here, we demonstrate that Ti substitution for Mn can be used to chemically tune the oxygen-breathing properties of these materials towards practical applications. Specifically, Y(Mn{sub 1−x}Ti{sub x})O{sub 3} solid solutions exhibit facile oxygen absorption/desorption via reversible Ti{sup 3+}↔Ti{sup 4+} and Mn{sup 3+}↔Mn{sup 4+} reactions already in ambient air at ≈400 °C and ≈250 °C, respectively. On cooling, the oxidation of both cations is accompanied by oxygen uptake yielding a formula YMn{sup 3+}{sub 1−x-y}Mn{sup 4+}{sub y}Ti{sup 4+}{sub x}O{sub 3+δ}. The presence of Ti promotes the oxidation of Mn{sup 3+} to Mn{sup 4+}, which is almost negligible for YMnO{sub 3} in air, thereby increasing the uptake of oxygen beyond that required for a given Ti{sup 4+} concentration. The reversibility of the redox reactions is limited by sluggish kinetics; however, the oxidation process continues, if slowly, even at room temperature. The extra oxygen atoms are accommodated by the large interstices within a triangular lattice formed by the [MnO{sub 5}] trigonal bipyramids. According to bond distances from Rietveld refinements using the neutron diffraction data, the YMnO{sub 3} structure features under-bonded Mn and even more severely under-bonded oxygen atoms that form the trigonal bases of the [MnO{sub 5}] bipyramids. The tensile bond strain around the 5-fold coordinated Mn site and the strong preference of Ti{sup 4+}(and Mn{sup 4+}) for higher coordination numbers likely provide driving forces for the oxidation reaction. Reverse Monte Carlo refinements of the local atomic displacements using neutron total scattering revealed how the excess oxygen atoms are accommodated in the structure by correlated local displacements of the host atoms. Large displacements of the under

  4. Thermal 18F atom addition to olefins

    International Nuclear Information System (INIS)

    Rogers, P.J.M.

    1986-01-01

    The addition of thermal 18 F atoms to olefins was investigated using various substrate molecules. The 18 F atoms were produced by the 19 F(n,2n) 18 F nuclear reaction with >10 5 eV of energy which is removed by multiple collisions with SF 6 molecules before reaction occurs with an olefin. By varying the SF 6 /substrate mole ratio it was demonstrated that the fraction of non-thermal reactions is dependent upon the frequency of non-reactive energy reducing collisions with SF 6 . The rate constants for addition and abstraction reactions with propene, cis-1-chloropropene and trans-1-chloropropene were determined. The substitution of a C1 atom for the olefinic H atom in the C 1 position does not affect the rate of 18 F bond formation but it changes the orientation of attack. The 18 F atom prefers the terminal carbon-in propene and propene-d 6 by a factor of 1.35 while the preference is less than 0.5 for the terminal carbon in cis-1-chloropropene and trans-1-chloropropene. The addition of 18 F atoms to olefins creates vibrationally excited fluoroalkyl radicals which can either decompose or stabilize by collision with another molecule. The rate constants for decomposition of excited CH 3 CHCHC1F radicals formed by 18 F addition to cis-1-chloropropene and trans-1-chloropropene are competitive with C 1 -C 2 bond rotation. The 18 F atoms add to the parent molecule with retention of geometry and a memory of the geometry persists as demonstrated by the cis-1-fluoropropene/trans-1-fluoropropene decomposition product ratio

  5. The Britannica guide to the atom

    CERN Document Server

    Gregersen, Erik

    2011-01-01

    Common to all matter and its smallest and most fundamental unit, the atom determines the properties of a substance and how it responds to other materials and stimuli. Dividing the atom further reveals several smaller particles whose activity forms the heart of nuclear physics. Readers will discover the structure of the atom as well as the ways in which its electrons, protons, and neutrons facilitate both radioactivity and nuclear reactions, both of which have been crucial to technological advancements since the 20th century.

  6. CO 2 sorption on substituted carbon materials . Computational chemistry studies

    Science.gov (United States)

    Gauden, P. A.; Wiśniewski, M.

    2007-04-01

    Theoretical study of sorption of CO 2 on the 4-ring graphene ("unmodified" or N-, O-, and OH-substituted) structures possessing one completely unsaturated edge zigzag site is reported using the DFT (B3LYP/6-31G(d,p)) method. Lactone and heterocyclic complexes (due to thermodynamic favourability) are taken into account. The analysis of theoretical results shows that the enthalpy of reaction strongly depends on the chemical nature, i.e. the position of the doping of atom(s) is crucial. All substitutions do not change or decrease the enthalpy in comparison with the "unmodified" graphene sheet. The well-known theoretical reactivity indices (ionization potential, electron affinity, global softness, and HOMO-LUMO gaps) are calculated for the studied adsorbents in order to explain the above-mentioned tendencies. Finally, the effect of the presence of heteroatoms on the enthalpy of reaction (Δ H298) for all CO 2-heteroatom-doping adsorbent complexes is shown. Thus, carbon dioxide molecules adsorb on the edge plane surface of N-, O-, OH-containing carbon surfaces similarly or much less favourably in comparison with the "unmodified" adsorbents. This confirms some experimental observations.

  7. Algorithms for solving atomic structures of nanodimensional clusters in single crystals based on X-ray and neutron diffuse scattering data

    International Nuclear Information System (INIS)

    Andrushevskii, N.M.; Shchedrin, B.M.; Simonov, V.I.

    2004-01-01

    New algorithms for solving the atomic structure of equivalent nanodimensional clusters of the same orientations randomly distributed over the initial single crystal (crystal matrix) have been suggested. A cluster is a compact group of substitutional, interstitial or other atoms displaced from their positions in the crystal matrix. The structure is solved based on X-ray or neutron diffuse scattering data obtained from such objects. The use of the mathematical apparatus of Fourier transformations of finite functions showed that the appropriate sampling of the intensities of continuous diffuse scattering allows one to synthesize multiperiodic difference Patterson functions that reveal the systems of the interatomic vectors of an individual cluster. The suggested algorithms are tested on a model one-dimensional structure

  8. 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.

  9. Hydrogen-assisted post-growth substitution of tellurium into molybdenum disulfide monolayers with tunable compositions

    Science.gov (United States)

    Yin, Guoli; Zhu, Dancheng; Lv, Danhui; Hashemi, Arsalan; Fei, Zhen; Lin, Fang; Krasheninnikov, Arkady V.; Zhang, Ze; Komsa, Hannu-Pekka; Jin, Chuanhong

    2018-04-01

    Herein we report the successful doping of tellurium (Te) into molybdenum disulfide (MoS2) monolayers to form MoS2x Te2(1-x) alloy with variable compositions via a hydrogen-assisted post-growth chemical vapor deposition process. It is confirmed that H2 plays an indispensable role in the Te substitution into as-grown MoS2 monolayers. Atomic-resolution transmission electron microscopy allows us to determine the lattice sites and the concentration of introduced Te atoms. At a relatively low concentration, tellurium is only substituted in the sulfur sublattice to form monolayer MoS2(1-x)Te2x alloy, while with increasing Te concentration (up to ˜27.6% achieved in this study), local regions with enriched tellurium, large structural distortions, and obvious sulfur deficiency are observed. Statistical analysis of the Te distribution indicates the random substitution. Density functional theory calculations are used to investigate the stability of the alloy structures and their electronic properties. Comparison with experimental results indicate that the samples are unstrained and the Te atoms are predominantly substituted in the top S sublattice. Importantly, such ultimately thin Janus structure of MoS2(1-x)Te2x exhibits properties that are distinct from their constituents. We believe our results will inspire further exploration of the versatile properties of asymmetric 2D TMD alloys.

  10. Mathematics revealed

    CERN Document Server

    Berman, Elizabeth

    1979-01-01

    Mathematics Revealed focuses on the principles, processes, operations, and exercises in mathematics.The book first offers information on whole numbers, fractions, and decimals and percents. Discussions focus on measuring length, percent, decimals, numbers as products, addition and subtraction of fractions, mixed numbers and ratios, division of fractions, addition, subtraction, multiplication, and division. The text then examines positive and negative numbers and powers and computation. Topics include division and averages, multiplication, ratios, and measurements, scientific notation and estim

  11. What happened to blood substitutes?

    Science.gov (United States)

    Stowell, C P

    2005-11-01

    Concerns about the safety and adequacy of the blood supply have fostered twenty years of research into the so-called "blood substitutes" among them the oxygen carriers based on modified hemoglobin. Although none of these materials has yet been licensed for use in North America or Europe, the results of research and clinical trials have increased our understanding of oxygen delivery and its regulation. In particular, the examination of the basis for the vasoactivity observed with some of the hemoglobin based oxygen carriers has led to the insight that several colligative properties of hemoglobin solutions, such as their diffusion coefficient for oxygen, viscosity and colloid oncotic pressure, are important determinants of efficacy.

  12. Atoms - molecules - nuclei. Vol. 1

    International Nuclear Information System (INIS)

    Otter, G.; Honecker, R.

    1993-01-01

    This first volume covers the following topics: Wave-particle dualism, classical atomic physics; the Schroedinger equation, angular momentum in quantum physics, one-electron atoms and many-electron atoms with atomic structure, atomic spectra, exotic atoms, influence of electric and magnetic fields

  13. Atomic collisions research with excited atomic species

    International Nuclear Information System (INIS)

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

    1999-01-01

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

  14. Biologic and synthetic skin substitutes: An overview.

    Science.gov (United States)

    Halim, Ahmad Sukari; Khoo, Teng Lye; Mohd Yussof, Shah Jumaat

    2010-09-01

    The current trend of burn wound care has shifted to more holistic approach of improvement in the long-term form and function of the healed burn wounds and quality of life. This has demanded the emergence of various skin substitutes in the management of acute burn injury as well as post burn reconstructions. Skin substitutes have important roles in the treatment of deep dermal and full thickness wounds of various aetiologies. At present, there is no ideal substitute in the market. Skin substitutes can be divided into two main classes, namely, biological and synthetic substitutes. The biological skin substitutes have a more intact extracellular matrix structure, while the synthetic skin substitutes can be synthesised on demand and can be modulated for specific purposes. Each class has its advantages and disadvantages. The biological skin substitutes may allow the construction of a more natural new dermis and allow excellent re-epithelialisation characteristics due to the presence of a basement membrane. Synthetic skin substitutes demonstrate the advantages of increase control over scaffold composition. The ultimate goal is to achieve an ideal skin substitute that provides an effective and scar-free wound healing.

  15. Biologic and synthetic skin substitutes: An overview

    Directory of Open Access Journals (Sweden)

    Halim Ahmad

    2010-10-01

    Full Text Available The current trend of burn wound care has shifted to more holistic approach of improvement in the long-term form and function of the healed burn wounds and quality of life. This has demanded the emergence of various skin substitutes in the management of acute burn injury as well as post burn reconstructions. Skin substitutes have important roles in the treatment of deep dermal and full thickness wounds of various aetiologies. At present, there is no ideal substitute in the market. Skin substitutes can be divided into two main classes, namely, biological and synthetic substitutes. The biological skin substitutes have a more intact extracellular matrix structure, while the synthetic skin substitutes can be synthesised on demand and can be modulated for specific purposes. Each class has its advantages and disadvantages. The biological skin substitutes may allow the construction of a more natural new dermis and allow excellent re-epithelialisation characteristics due to the presence of a basement membrane. Synthetic skin substitutes demonstrate the advantages of increase control over scaffold composition. The ultimate goal is to achieve an ideal skin substitute that provides an effective and scar-free wound healing.

  16. Preparation of fluoride substituted apatite cements as the building blocks for tooth enamel restoration

    Science.gov (United States)

    Wei, Jie; Wang, Jiecheng; Liu, Xiaochen; Ma, Jian; Liu, Changsheng; Fang, Jing; Wei, Shicheng

    2011-06-01

    Fluoride substituted apatite cement (fs-AC) was synthesized by using the cement powders of tetracalcium phosphate (TTCP) and sodium fluoride (NaF), and the cement powders were mixed with diluted phosphoric acid (H 3PO 4) as cement liquid to form fs-AC paste. The fs-AC paste could be directly filled into the carious cavities to repair damaged dental enamel. The results indicated that the fs-AC paste was changed into fluorapatite crystals with the atom molar ratio for calcium to phosphorus of 1.66 and the F ion amount of 3 wt% after self-hardening for 2 days. The solubility of fs-AC in Tris-HCl solution (pH 6) was slightly lower than hydroxyapatite cement (HAC) that was similar to the apatite in enamel, indicating the fs-AC was much insensitive to the weakly acidic solution than the apatite in enamel. The fs-AC was tightly combined with the enamel surface because of the chemical reaction between the fs-AC and the apatite in enamel after the caries cavities was filled with fs-AC. The extracts of fs-AC caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. The fs-AC had potential prospect for the reconstitution of carious lesion of dental enamel.

  17. Preparation of fluoride substituted apatite cements as the building blocks for tooth enamel restoration

    International Nuclear Information System (INIS)

    Wei Jie; Wang Jiecheng; Liu Xiaochen; Ma Jian; Liu Changsheng; Fang Jing; Wei Shicheng

    2011-01-01

    Fluoride substituted apatite cement (fs-AC) was synthesized by using the cement powders of tetracalcium phosphate (TTCP) and sodium fluoride (NaF), and the cement powders were mixed with diluted phosphoric acid (H 3 PO 4 ) as cement liquid to form fs-AC paste. The fs-AC paste could be directly filled into the carious cavities to repair damaged dental enamel. The results indicated that the fs-AC paste was changed into fluorapatite crystals with the atom molar ratio for calcium to phosphorus of 1.66 and the F ion amount of 3 wt% after self-hardening for 2 days. The solubility of fs-AC in Tris-HCl solution (pH 6) was slightly lower than hydroxyapatite cement (HAC) that was similar to the apatite in enamel, indicating the fs-AC was much insensitive to the weakly acidic solution than the apatite in enamel. The fs-AC was tightly combined with the enamel surface because of the chemical reaction between the fs-AC and the apatite in enamel after the caries cavities was filled with fs-AC. The extracts of fs-AC caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. The fs-AC had potential prospect for the reconstitution of carious lesion of dental enamel.

  18. Electron transport and nonlinear optical properties of substituted aryldimesityl boranes: a DFT study.

    Directory of Open Access Journals (Sweden)

    Altaf Hussain Pandith

    Full Text Available A comprehensive theoretical study was carried out on a series of aryldimesityl borane (DMB derivatives using Density Functional theory. Optimized geometries and electronic parameters like electron affinity, reorganization energy, frontiers molecular contours, polarizability and hyperpolarizability have been calculated by employing B3PW91/6-311++G (d, p level of theory. Our results show that the Hammett function and geometrical parameters correlates well with the reorganization energies and hyperpolarizability for the series of DMB derivatives studied in this work. The orbital energy study reveals that the electron releasing substituents increase the LUMO energies and electron withdrawing substituents decrease the LUMO energies, reflecting the electron transport character of aryldimesityl borane derivatives. From frontier molecular orbitals diagram it is evident that mesityl rings act as the donor, while the phenylene and Boron atom appear as acceptors in these systems. The calculated hyperpolarizability of secondary amine derivative of DMB is 40 times higher than DMB (1. The electronic excitation contributions to the hyperpolarizability studied by using TDDFT calculation shows that hyperpolarizability correlates well with dipole moment in ground and excited state and excitation energy in terms of the two-level model. Thus the results of these calculations can be helpful in designing the DMB derivatives for efficient electron transport and nonlinear optical material by appropriate substitution with electron releasing or withdrawing substituents on phenyl ring of DMB system.

  19. Beta radiation effects in sup 1 sup 3 sup 7 Cs-substituted pollucite

    CERN Document Server

    Hess, N J; Conradson, S D; Weber, W J

    2000-01-01

    The effect of high-energy beta radiation on the long-range and local structure of sup 1 sup 3 sup 7 Cs-substituted CsAlSi sub 2 O sub 6 (pollucite) was studied by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques at the Cs K-edge. Analysis of the XRD pattern of pollucite with an absorbed dose of 10 sup 1 sup 8 beta decays/g using Rietveld analysis indicates a 0.5-1% volume expansion of the tetrahedral structure as measured at 50 K and a minor displacement of the Cs cation toward the face of one of the six-membered rings. Analysis of the real-space pair-distribution function obtained from Fourier transformation of the diffraction pattern indicates significant correlated movement of the (Si,Al)-O pairs and large static disorder between Cs-O pairs. Analysis of the Cs K-edge XAS revealed substantial contributions from the Cs atomic X-ray absorption. This likely results from the exceedingly long Cs-O bond distances in the pollucite structure, which diminish the fine structure of the XAS os...

  20. Preparation of fluoride substituted apatite cements as the building blocks for tooth enamel restoration

    Energy Technology Data Exchange (ETDEWEB)

    Wei Jie [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Inter-disciplinary Studies, Peking University, Beijing 100871 (China); Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China); Wang Jiecheng; Liu Xiaochen [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Inter-disciplinary Studies, Peking University, Beijing 100871 (China); Ma Jian [Hospital of Stomatology, Tongji University, Shanghai 200072 (China); Liu Changsheng [Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China); Fang Jing, E-mail: biomater2006@yahoo.com.cn [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Inter-disciplinary Studies, Peking University, Beijing 100871 (China); Wei Shicheng, E-mail: nic7505@263.net [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Inter-disciplinary Studies, Peking University, Beijing 100871 (China) and School and Hospital of Stomatology, Peking University, Beijing 100081 (China)

    2011-06-15

    Fluoride substituted apatite cement (fs-AC) was synthesized by using the cement powders of tetracalcium phosphate (TTCP) and sodium fluoride (NaF), and the cement powders were mixed with diluted phosphoric acid (H{sub 3}PO{sub 4}) as cement liquid to form fs-AC paste. The fs-AC paste could be directly filled into the carious cavities to repair damaged dental enamel. The results indicated that the fs-AC paste was changed into fluorapatite crystals with the atom molar ratio for calcium to phosphorus of 1.66 and the F ion amount of 3 wt% after self-hardening for 2 days. The solubility of fs-AC in Tris-HCl solution (pH 6) was slightly lower than hydroxyapatite cement (HAC) that was similar to the apatite in enamel, indicating the fs-AC was much insensitive to the weakly acidic solution than the apatite in enamel. The fs-AC was tightly combined with the enamel surface because of the chemical reaction between the fs-AC and the apatite in enamel after the caries cavities was filled with fs-AC. The extracts of fs-AC caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. The fs-AC had potential prospect for the reconstitution of carious lesion of dental enamel.

  1. Polylutidines: Multifunctional Surfaces through Vapor-Based Polymerization of Substituted Pyridinophanes.

    Science.gov (United States)

    Bally-Le Gall, Florence; Hussal, Christoph; Kramer, Joshua; Cheng, Kenneth; Kumar, Ramya; Eyster, Thomas; Baek, Amy; Trouillet, Vanessa; Nieger, Martin; Bräse, Stefan; Lahann, Joerg

    2017-09-27

    We report a new class of functionalized polylutidine polymers that are prepared by chemical vapor deposition polymerization of substituted [2](1,4)benzeno[2](2,5)pyridinophanes. To prepare sufficient amounts of monomer for CVD polymerization, a new synthesis route for ethynylpyridinophane has been developed in three steps with an overall yield of 59 %. Subsequent CVD polymerization yielded well-defined films of poly(2,5-lutidinylene-co-p-xylylene) and poly(4-ethynyl-2,5-lutidinylene-co-p-xylylene). All polymers were characterized by infrared reflection-absorption spectroscopy, ellipsometry, contact angle studies, and X-ray photoelectron spectroscopy. Moreover, ζ-potential measurements revealed that polylutidine films have higher isoelectric points than the corresponding poly-xylylene surfaces owing to the nitrogen atoms in the polymer backbone. The availability of reactive alkyne groups on the surface of poly(4-ethynyl-2,5-lutidinylene-co-p-xylylene) coatings was confirmed by spatially controlled surface modification by means of Huisgen 1,3-dipolar cycloaddition. Compared to the more hydrophobic poly-p-xylylyenes, the presence of the heteroatom in the polymer backbone of polylutidine polymers resulted in surfaces that supported an increased adhesion of primary human umbilical vein endothelial cells (HUVECs). Vapor-based polylutidine coatings are a new class of polymers that feature increased hydrophilicity and increased cell adhesion without limiting the flexibility in selecting appropriate functional side groups. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Fe atom exchange between aqueous Fe2+ and magnetite.

    Science.gov (United States)

    Gorski, Christopher A; Handler, Robert M; Beard, Brian L; Pasakarnis, Timothy; Johnson, Clark M; Scherer, Michelle M

    2012-11-20

    The reaction between magnetite and aqueous Fe(2+) has been extensively studied due to its role in contaminant reduction, trace-metal sequestration, and microbial respiration. Previous work has demonstrated that the reaction of Fe(2+) with magnetite (Fe(3)O(4)) results in the structural incorporation of Fe(2+) and an increase in the bulk Fe(2+) content of magnetite. It is unclear, however, whether significant Fe atom exchange occurs between magnetite and aqueous Fe(2+), as has been observed for other Fe oxides. Here, we measured the extent of Fe atom exchange between aqueous Fe(2+) and magnetite by reacting isotopically "normal" magnetite with (57)Fe-enriched aqueous Fe(2+). The extent of Fe atom exchange between magnetite and aqueous Fe(2+) was significant (54-71%), and went well beyond the amount of Fe atoms found at the near surface. Mössbauer spectroscopy of magnetite reacted with (56)Fe(2+) indicate that no preferential exchange of octahedral or tetrahedral sites occurred. Exchange experiments conducted with Co-ferrite (Co(2+)Fe(2)(3+)O(4)) showed little impact of Co substitution on the rate or extent of atom exchange. Bulk electron conduction, as previously invoked to explain Fe atom exchange in goethite, is a possible mechanism, but if it is occurring, conduction does not appear to be the rate-limiting step. The lack of significant impact of Co substitution on the kinetics of Fe atom exchange, and the relatively high diffusion coefficients reported for magnetite suggest that for magnetite, unlike goethite, Fe atom diffusion is a plausible mechanism to explain the rapid rates of Fe atom exchange in magnetite.

  3. Distribution and Substitution Mechanism of Ge in a Ge-(Fe-Bearing Sphalerite

    Directory of Open Access Journals (Sweden)

    Nigel J. Cook

    2015-03-01

    Full Text Available The distribution and substitution mechanism of Ge in the Ge-rich sphalerite from the Tres Marias Zn deposit, Mexico, was studied using a combination of techniques at μm- to atomic scales. Trace element mapping by Laser Ablation Inductively Coupled Mass Spectrometry shows that Ge is enriched in the same bands as Fe, and that Ge-rich sphalerite also contains measurable levels of several other minor elements, including As, Pb and Tl. Micron- to nanoscale heterogeneity in the sample, both textural and compositional, is revealed by investigation using Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM combined with Synchrotron X-ray Fluorescence mapping and High-Resolution Transmission Electron Microscopy imaging of FIB-prepared samples. Results show that Ge is preferentially incorporated within Fe-rich sphalerite with textural complexity finer than that of the microbeam used for the X-ray Absorption Near Edge Structure (XANES measurements. Such heterogeneity, expressed as intergrowths between 3C sphalerite and 2H wurtzite on  zones, could be the result of either a primary growth process, or alternatively, polystage crystallization, in which early Fe-Ge-rich sphalerite is partially replaced by Fe-Ge-poor wurtzite. FIB-SEM imaging shows evidence for replacement supporting the latter. Transformation of sphalerite into wurtzite is promoted by (111* twinning or lattice-scale defects, leading to a heterogeneous ZnS sample, in which the dominant component, sphalerite, can host up to ~20% wurtzite. Ge K-edge XANES spectra for this sphalerite are identical to those of the germanite and argyrodite standards and the synthetic chalcogenide glasses GeS2 and GeSe2, indicating the Ge formally exists in the tetravalent form in this sphalerite. Fe K-edge XANES spectra for the same sample indicate that Fe is present mainly as Fe2+, and Cu K-edge XANES spectra are characteristic for Cu+. Since there is no evidence for coupled substitution involving a monovalent

  4. Atomic and molecular sciences

    International Nuclear Information System (INIS)

    Lane, N.F.

    1989-01-01

    The theoretical atomic and molecular physics program at Rice University addresses basic questions about the collision dynamics of electrons, atoms, ions and molecules, emphasizing processes related to possible new energy technologies and other applications. The program focuses on inelastic collision processes that are important in understanding energy and ionization balance in disturbed gases and plasmas. Emphasis is placed on systems and processes where some experimental information is available or where theoretical results may be expected to stimulate new measurements. Examples of current projects include: excitation and charge-transfer processes; orientation and alignment of excited states following collisions; Rydberg atom collisions with atoms and molecules; Penning ionization and ion-pair formation in atom-atom collisions; electron-impact ionization in dense, high-temperature plasmas; electron-molecule collisions; and related topics

  5. Modern atomic physics

    CERN Document Server

    Natarajan, Vasant

    2015-01-01

    Much of our understanding of physics in the last 30-plus years has come from research on atoms, photons, and their interactions. Collecting information previously scattered throughout the literature, Modern Atomic Physics provides students with one unified guide to contemporary developments in the field. After reviewing metrology and preliminary material, the text explains core areas of atomic physics. Important topics discussed include the spontaneous emission of radiation, stimulated transitions and the properties of gas, the physics and applications of resonance fluorescence, coherence, cooling and trapping of charged and neutral particles, and atomic beam magnetic resonance experiments. Covering standards, a different way of looking at a photon, stimulated radiation, and frequency combs, the appendices avoid jargon and use historical notes and personal anecdotes to make the topics accessible to non-atomic physics students. Written by a leader in atomic and optical physics, this text gives a state-of-the...

  6. Atomic Power Safety

    Energy Technology Data Exchange (ETDEWEB)

    Hogerton, John F

    1964-01-01

    This booklet is condensed from a larger publication, -Background Information on Atomic Power Safety-, published in January 1964, by the .Atomic Industrial Forum. That publication and this abridgment were produced in recognition of the emergence of commercial atomic power as an important factor in our national economy, and of the resulting need for readily available information in nontechnical form on the characteristics of nuclear power plants and on the various measures taken during their design, construction, and operation for public safety.

  7. Atomic physics made clear

    International Nuclear Information System (INIS)

    Meinhold, H.

    1980-01-01

    This book is a popular introduction into the foundations of atomic physics und quantum mechanics. Starting from some phenomenological concepts Bohr's model and the construction of the periodic system regarding the shell structure of atoms are introduced. In this framework the selection rules and magnetic moments of atomic electrons are considered. Finally the wave-particle dualism is considered. In the appendix some mathematical methods are described which are useful for a deeper penetration into the considered ideas. (HSI)

  8. Advances in atomic spectroscopy

    CERN Document Server

    Sneddon, J

    1997-01-01

    This series describes selected advances in the area of atomic spectroscopy. It is primarily intended for the reader who has a background in atmoic spectroscopy; suitable to the novice and expert. Although a widely used and accepted method for metal and non-metal analysis in a variety of complex samples, Advances in Atomic Spectroscopy covers a wide range of materials. Each Chapter will completely cover an area of atomic spectroscopy where rapid development has occurred.

  9. Atomic hydrogen reactor

    International Nuclear Information System (INIS)

    Massip de Turville, C.M.D.

    1982-01-01

    Methods are discussed of generating heat in an atomic hydrogen reactor which involve; the production of atomic hydrogen by an electrical discharge, the capture of nascent neutrons from atomic hydrogen in a number of surrounding steel alloy tubes having a high manganese content to produce 56 Mn, the irradiation of atomic hydrogen by the high energy antineutrinos from the beta decay of 56 Mn to yield nascent neutrons, and the removal of the heat generated by the capture of nascent neutrons by 55 Mn and the beta decay of 56 Mn. (U.K.)

  10. Emission Channeling Studies of the Lattice Site of Oversized Alkali Atoms Implanted in Metals

    CERN Multimedia

    2002-01-01

    % IS340 \\\\ \\\\ As alkali atoms have the largest atomic radius of all elements, the determination of their lattice configuration following implantation into metals forms a critical test for the various models predicting the lattice site of implanted impurity atoms. The site determination of these large atoms will especially be a crucial check for the most recent model that relates the substitutional fraction of oversized elements to their solution enthalpy. Recent exploratory $^{213}$Fr and $^{221}$Fr $\\alpha$-emission channeling experiments at ISOLDE-CERN and hyperfine interaction measurements on Fr implanted in Fe gave an indication for anomalously large substitutional fractions. To investigate further the behaviour of Fr and other alkali atoms like Cs and Rb thoroughly, more on-line emission channeling experiments are needed. We propose a number of shifts for each element, where the temperature of the implanted metals will be varied between 50$^\\circ$ and 700$^\\circ$~K. Temperature dependent measurements wi...

  11. Stereochemistry of the epoxidation of bicyclo[2.2.1]hept-2-ene and its 7-syn-substituted derivatives. A DFT study

    Directory of Open Access Journals (Sweden)

    Sergiy I. Okovytyy

    2014-12-01

    Full Text Available The stereochemical aspects of epoxidation of norbornene and its 7-syn-substituted derivatives by performic acid were investigated. Geometry and thermodynamic parameters of transition states and prereactive complexes were computed at the UBHandHLYP/6-31G(d level of theory. It is shown that the transition states have a pronounced biradical character and a nearly coplanar orientation of the C=C bond and the molecule of performic acid. Transition state analysis revealed that, in the case of the syn-7-hydroxy derivative, the preference for the exo-approach of the oxidant can be explained by the stabilization of transition state with hydrogen bonding. In contrast, a chlorine atom or a methyl group at the 7-syn position facilitated the formation of endo-epoxides due to steric repulsion between the substituent and the oxidant.

  12. Atom dynamics in laser fields

    International Nuclear Information System (INIS)

    Jang, Su; Mi, No Gin

    2004-12-01

    This book introduces coherent dynamics of internal state, spread of atoms wave speed, semiclassical atoms density matrix such as dynamics equation in both still and moving atoms, excitation of atoms in movement by light, dipole radiating power, quantum statistical mechanics by atoms in movement, semiclassical atoms in movement, atoms in movement in the uniform magnetic field including effects of uniform magnetic field, atom cooling using laser such as Doppler cooling, atom traps using laser and mirrors, radiant heat which particles receive, and near field interactions among atoms in laser light.

  13. A theoretical study of dopant atom detection and probe behavior in STEM

    Science.gov (United States)

    Mittal, Anudha

    Very detailed information about the atomic and electronic structure of materials can be obtained via atomic-scale resolution scanning transmission electron microscopy (STEM). These experiments reach the limits of current microscopes, which means that optimal experimental design is a key ingredient in success. The step following experiment, extraction of information from experimental data is also complex. Comprehension of experimental data depends on comparison with simulated data and on fundamental understanding of aspects of scattering behavior. The research projects discussed in this thesis are formulated within three large concepts. 1. Usage of simulation to suggest experimental technique for observation of a particular structural feature.. Two specific structural features are explored. One is the characterization of a substitutional dopant atom in a crystal. Annular dark field scanning transmission electron microscope (ADF-STEM) images allow detection of individual dopant atoms in a crystal based on contrast between intensities of doped and non-doped column in the image. The magnitude of the said contrast is heavily influenced by specimen and microscope parameters. Analysis of multislice-based simulations of ADF-STEM images of crystals doped with one substitutional dopant atom for a wide range of crystal thicknesses, types and locations of dopant atom inside the crystal, and crystals with different atoms revealed trends and non-intuitive behaviors in visibility of the dopant atom. The results provide practical guidelines for the optimal experimental setup regarding both the microscope and specimen conditions in order to characterize the presence and location of a dopant atom. Furthermore, the simulations help in recognizing the cases where detecting a single dopant atom via ADF-STEM imaging is not possible. The second is a more specific case of detecting intrinsic twist in MoS2 nanotubes. Objective molecular dynamics simulations coupled with a density

  14. Statistical Physics of Complex Substitutive Systems

    Science.gov (United States)

    Jin, Qing

    Diffusion processes are central to human interactions. Despite extensive studies that span multiple disciplines, our knowledge is limited to spreading processes in non-substitutive systems. Yet, a considerable number of ideas, products, and behaviors spread by substitution; to adopt a new one, agents must give up an existing one. This captures the spread of scientific constructs--forcing scientists to choose, for example, a deterministic or probabilistic worldview, as well as the adoption of durable items, such as mobile phones, cars, or homes. In this dissertation, I develop a statistical physics framework to describe, quantify, and understand substitutive systems. By empirically exploring three collected high-resolution datasets pertaining to such systems, I build a mechanistic model describing substitutions, which not only analytically predicts the universal macroscopic phenomenon discovered in the collected datasets, but also accurately captures the trajectories of individual items in a complex substitutive system, demonstrating a high degree of regularity and universality in substitutive systems. I also discuss the origins and insights of the parameters in the substitution model and possible generalization form of the mathematical framework. The systematical study of substitutive systems presented in this dissertation could potentially guide the understanding and prediction of all spreading phenomena driven by substitutions, from electric cars to scientific paradigms, and from renewable energy to new healthy habits.

  15. Intangible Capital: Complement or Substitute in the Creation of Public Goods?

    OpenAIRE

    Gornig, Martin; Schiersch, Alexander

    2017-01-01

    This paper tests whether intangible capital is a substitute or, to some degree, a complement to standard inputs in the production process. The analysis is conducted for public sectors in which governmental institutions are directly responsible both for efficiently producing public goods and for investing in new production factors. The results reveal that intangible capital is a relevant input factor in the production of public goods and only weakly substitutable with other inputs.

  16. Substitution dynamical systems spectral analysis

    CERN Document Server

    Queffélec, Martine

    2010-01-01

    This volume mainly deals with the dynamics of finitely valued sequences, and more specifically, of sequences generated by substitutions and automata. Those sequences demonstrate fairly simple combinatorical and arithmetical properties and naturally appear in various domains. As the title suggests, the aim of the initial version of this book was the spectral study of the associated dynamical systems: the first chapters consisted in a detailed introduction to the mathematical notions involved, and the description of the spectral invariants followed in the closing chapters. This approach, combined with new material added to the new edition, results in a nearly self-contained book on the subject. New tools - which have also proven helpful in other contexts - had to be developed for this study. Moreover, its findings can be concretely applied, the method providing an algorithm to exhibit the spectral measures and the spectral multiplicity, as is demonstrated in several examples. Beyond this advanced analysis, many...

  17. Controversial issues of maternity substitution

    Directory of Open Access Journals (Sweden)

    Andy Pușcă

    2009-06-01

    Full Text Available Substitute maternity consists in a woman carrying a pregnancy (the implant of an embryo, at therequest of a sterile couple, most of the times in exchange of a sum of money, with her commitment tounconditionally give away the newborn after birth to the couple she concluded the agreement with. Manycontroversies emerged in what concerns the contract between the sterile couple and the carrying mother,especially when this contract is by onerous title, which happens in most of the cases. In that a civil contract? Is ita sales contract for the child? Is it a contract to provide services? Is it body marketing? Between total prohibitionand excessive liberalism, the middle way, which is the regulation according to ethical religious, cultural andsocial norms of each community, represents a realistic solution.

  18. Atomic Ferris wheel beams

    Science.gov (United States)

    Lembessis, Vasileios E.

    2017-07-01

    We study the generation of atom vortex beams in the case where a Bose-Einstein condensate, released from a trap and moving in free space, is diffracted from a properly tailored light mask with a spiral transverse profile. We show how such a diffraction scheme could lead to the production of an atomic Ferris wheel beam.

  19. Atomic Energy Control Board

    International Nuclear Information System (INIS)

    Blackman, N.S.; Gummer, W.K.

    1982-02-01

    This paper has been prepared to provide an overview of the responsibilities and activities of the Atomic Energy Control Board. It is designed to address questions that are often asked concerning the establishment of the Atomic Energy Control Board, its enabling legislation, licensing and compliance activities, federal-provincial relationships, international obligations, and communications with the public

  20. Beyond the Atom

    Science.gov (United States)

    Cox, John

    2011-08-01

    1. Introduction - the atom in the seventies; 2. The vacuum tube; 3. The new rays; 4. The new substances; 5. Disintegration; 6. A family tree; 7. Verifications and results; 8. The objective reality of molecules; 9. The new atom; Bibliography; Index.

  1. Atoms, Molecules, and Compounds

    CERN Document Server

    Manning, Phillip

    2007-01-01

    Explores the atoms that govern chemical processes. This book shows how the interactions between simple substances such as salt and water are crucial to life on Earth and how those interactions are predestined by the atoms that make up the molecules.

  2. Atoms, Molecules and Radiation

    Indian Academy of Sciences (India)

    IAS Admin

    A Refresher Course in Applications of Quantum Mechanics to 'Atoms, Molecules and Radiation' will be held at the Indian Academy of Sciences, Bangalore from December 8 to 20. 2014. The Course is primarily aimed at teachers teaching quantum mechanics and/ or atomic and molecular physics at the UG / PG level.

  3. When Atoms Want

    Science.gov (United States)

    Talanquer, Vicente

    2013-01-01

    Chemistry students and teachers often explain the chemical reactivity of atoms, molecules, and chemical substances in terms of purposes or needs (e.g., atoms want or need to gain, lose, or share electrons in order to become more stable). These teleological explanations seem to have pedagogical value as they help students understand and use…

  4. Zeeman atomic absorption spectroscopy

    International Nuclear Information System (INIS)

    Loos-Vollebregt, M.T.C. de.

    1980-01-01

    A new method of background correction in atomic absorption spectroscopy has recently been introduced, based on the Zeeman splitting of spectral lines in a magnetic field. A theoretical analysis of the background correction capability observed in such instruments is presented. A Zeeman atomic absorption spectrometer utilizing a 50 Hz sine wave modulated magnetic field is described. (Auth.)

  5. Theoretical atomic physics

    CERN Document Server

    Friedrich, Harald

    2017-01-01

    This expanded and updated well-established textbook contains an advanced presentation of quantum mechanics adapted to the requirements of modern atomic physics. It includes topics of current interest such as semiclassical theory, chaos, atom optics and Bose-Einstein condensation in atomic gases. In order to facilitate the consolidation of the material covered, various problems are included, together with complete solutions. The emphasis on theory enables the reader to appreciate the fundamental assumptions underlying standard theoretical constructs and to embark on independent research projects. The fourth edition of Theoretical Atomic Physics contains an updated treatment of the sections involving scattering theory and near-threshold phenomena manifest in the behaviour of cold atoms (and molecules). Special attention is given to the quantization of weakly bound states just below the continuum threshold and to low-energy scattering and quantum reflection just above. Particular emphasis is laid on the fundamen...

  6. Atomic diffusion in stars

    CERN Document Server

    Michaud, Georges; Richer, Jacques

    2015-01-01

    This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling.  In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...

  7. Antiprotonic-hydrogen atoms

    International Nuclear Information System (INIS)

    Batty, C.J.

    1989-07-01

    Experimental studies of antiprotonic-hydrogen atoms have recently made great progress following the commissioning of the low energy antiproton facility (LEAR) at CERN in 1983. At the same time our understanding of the atomic cascade has increased considerably through measurements of the X-ray spectra. The life history of the p-bar-p atom is considered in some detail, from the initial capture of the antiproton when stopping in hydrogen, through the atomic cascade with the emission of X-rays, to the final antiproton annihilation and production of mesons. The experiments carried out at LEAR are described and the results compared with atomic cascade calculations and predictions of strong interaction effects. (author)

  8. Atomic collisions under extreme conditions in space

    International Nuclear Information System (INIS)

    Itikawa, Yukikazu

    1987-01-01

    In space, atoms and molecules are often placed under the extreme conditions which are very difficult to be realized on Earth. For instance, extremely hot and dense plasmas are found in and around various stellar objects (e.g., neutron stars) on one hand and extremely cold and diffuse gases prevail in interstellar space on the other. There is so strong a magnetic field that electron clouds in atoms and molecules are distorted. The study of atomic collisions under the extreme conditions is not only helpful in understanding the astrophysical environment but also reveals new aspects of the physics of atoms and molecules. This paper is an invitation to the study. (References are not exhaustive but only provide a clue with which more details can be found.) (author)

  9. Synthesis, characterization, fluorescence and biological studies of Mn(II, Fe(III and Zn(II complexes of Schiff bases derived from Isatin and 3-substituted-4-amino-5-mercapto-1,2,4-triazoles

    Directory of Open Access Journals (Sweden)

    Sangamesh A. Patil

    2014-12-01

    Full Text Available A series of Mn(II, Fe(III and Zn(II complexes have been synthesized with Schiff bases derived from isatin and 3-substituted-4-amino-5-mercapto-1,2,4-triazole. The elemental, spectroscopic (Infrared, nuclear magnetic resonance, ultraviolet-visible, fast atom bombardment-mass, fluorescence and electrochemistry and magnetic studies suggested that the metal complexes possess octahedral geometry. The Schiff bases and their metal complexes exhibit fluorescent properties. The antimicrobial studies of Schiff bases and their metal complexes against various bacterial (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus subtilis and fungal (Aspergillus niger, and Penicillium chrysogenum species by the minimum inhibitory concentration method revealed that the metal complexes possess more healing antibacterial activities than the Schiff bases. DNA cleavage property of Mn(II, Fe(III and Zn(II complexes revealed the important role of metal ion in the biological system.

  10. Atomic Covalent Functionalization of Graphene

    Science.gov (United States)

    Johns, James E.; Hersam, Mark C.

    2012-01-01

    -dimensional materials with fundamentally different electronic and physical properties. Specifically, we focus on recent studies of the addition of atomic hydrogen, fluorine, and oxygen to the basal plane of graphene. In each of these reactions a high energy, activating step initiates the process, breaking the local π structure and distorting the surrounding lattice. Scanning tunneling microscopy experiments reveal that substrate mediated interactions often dominate when the initial binding event occurs. We then compare these substrate effects with the results of theoretical studies that typically assume a vacuum environment. As the surface coverage increases, clusters often form around the initial distortion, and the stoichiometric composition of the saturated end product depends strongly on both the substrate and reactant species. In addition to these chemical and structural observations, we review how covalent modification can extend the range of physical properties that are achievable in two-dimensional materials. PMID:23030800

  11. Steric Effects of Solvent Molecules on SN2 Substitution Dynamics.

    Science.gov (United States)

    Liu, Xu; Xie, Jing; Zhang, Jiaxu; Yang, Li; Hase, William L

    2017-04-20

    Influences of solvent molecules on S N 2 reaction dynamics of microsolvated F - (H 2 O) n with CH 3 I, for n = 0-3, are uncovered by direct chemical dynamics simulations. The direct substitution mechanism, which is important without microsolvation, is quenched dramatically upon increasing hydration. The water molecules tend to force reactive encounters to proceed through the prereaction collision complex leading to indirect reaction. In contrast to F - (H 2 O), reaction with higher hydrated ions shows a strong propensity for ion desolvation in the entrance channel, diminishing steric hindrance for nucleophilic attack. Thus, nucleophilic substitution avoids the potential energy barrier with all of the solvent molecules intact and instead occurs through the less solvated barrier, which is energetically unexpected because the former barrier has a lower energy. The work presented here reveals a trade-off between reaction energetics and steric effects, with the latter found to be crucial in understanding how hydration influences microsolvated S N 2 dynamics.

  12. Experimental atomic physics

    International Nuclear Information System (INIS)

    Anon.

    1985-01-01

    The experimental atomic physics program within the physics division is carried out by two groups, whose reports are given in this section. Work of the accelerator atomic physics group is centered around the 6.5-MV EN tandem accelerator; consequently, most of its research is concerned with atomic processes occurring to, or initiated by, few MeV/amu heavy ions. Other activities of this group include higher energy experiments at the Holifield Heavy Ion Research Facility (HHIRF), studies of electron and positron channeling radiation, and collaborative experiments at other institutions. The second experimental group concerns itself with lower energy atomic collision physics in support of the Fusion Energy Program. During the past year, the new Electron Cyclotron Resonance Source has been completed and some of the first data from this facility is presented. In addition to these two activities in experimental atomic physics, other chapters of this report describe progress in theoretical atomic physics, experimental plasma diagnostic development, and atomic data center compilation activities

  13. Electron-transporting oligothiophenes containing dicyanomethylene-substituted cyclopenta[b]thiophene: chemical tuning for air stability in OFETs.

    Science.gov (United States)

    Ie, Yutaka; Nishida, Kazufumi; Karakawa, Makoto; Tada, Hirokazu; Aso, Yoshio

    2011-08-19

    We have synthesized new electron-transporting oligothiophenes containing dicyanomethylene-substituted cyclopenta[b]thiophene as an active material for the fabrication of solution-processable n-type organic field-effect transistors (OFETs). The influence of the number of dicyanomethylene groups as well as the position of hexyl groups was investigated in detail by performing photophysical and electrochemical measurements. Results revealed that the optical energy gaps and the lowest unoccupied molecular orbital (LUMO) energy levels can be controlled by changing the number of dicyanomethylene groups. In contrast, the position of hexyl groups has little influence on molecular electronic properties. X-ray diffraction and atomic force microscopy measurements revealed that spin-coated thin films of the new compounds had a crystalline structure. OFETs based on these compounds were evaluated in vacuum and air-exposed conditions, and the electron mobility of up to 0.016 cm(2) V(-1) s(-1) was achieved. Furthermore, we demonstrated that the air stability of the OFETs depends on the LUMO energy level of the compounds.

  14. Type Substitution for Object-Oriented Programming

    DEFF Research Database (Denmark)

    Schwartzbach, Michael Ignatieff; Palsberg, Jens

    1990-01-01

    Genericity allows the substitution of types in a class. This is usually obtained through parameterized classes, although they are inflexible since any class can be inherited but is not in itself parameterized. We suggest a new genericity mechanism, type substitution, which is a subclassing concep...

  15. Educators Take Another Look at Substitutes

    Science.gov (United States)

    Zubrzycki, Jaclyn

    2012-01-01

    The mythology surrounding the substitute teacher is not a pretty one: Paper airplanes, lost learning, bullying. But as schools collect more information about teacher absenteeism and its consequences, districts and schools are exploring ways to professionalize substitute teaching--or experiment with alternative ways of coping with teacher absences.…

  16. Strategic Resource Extraction And Substitute Development

    NARCIS (Netherlands)

    Michielsen, T.O.

    2013-01-01

    Abstract We analyze a dynamic game between a buyer and a seller of an exhaustible resource. The seller chooses resource supply; the buyer can pay a fixed cost to invent a perfect substitute for the resource at any time. In closed-loop equilibrium, the buyer adopts the substitute when the resource is

  17. Multisensory integration, sensory substitution and visual rehabilitation

    DEFF Research Database (Denmark)

    Proulx, Michael J; Ptito, Maurice; Amedi, Amir

    2014-01-01

    Sensory substitution has advanced remarkably over the past 35 years since first introduced to the scientific literature by Paul Bach-y-Rita. In this issue dedicated to his memory, we describe a collection of reviews that assess the current state of neuroscience research on sensory substitution, v......, visual rehabilitation, and multisensory processes....

  18. Current bone substitutes for implant dentistry.

    Science.gov (United States)

    Yamada, Masahiro; Egusa, Hiroshi

    2017-09-15

    Alveolar ridge augmentation is essential for success in implant therapy and depends on the biological performance of bone graft materials. This literature review aims to comprehensively explain the clinically relevant capabilities and limitations of currently available bone substitutes for bone augmentation in light of biomaterial science. The biological performance of calcium phosphate-based bone substitutes was categorized according to space-making capability, biocompatibility, bioabsorption, and volume maintenance over time. Each category was reviewed based on clinical studies, preclinical animal studies, and in vitro studies. Currently available bone substitutes provide only osteoconduction as a scaffold but not osteoinduction. Particle size, sensitivity to enzymatic or chemical dissolution, and mechanical properties affect the space-making capability of bone substitutes. The nature of collagen fibers, particulate size, and release of calcium ions influence the biocompatibility of bone substitutes. Bioabsorption of bone substitutes is determined by water solubility (chemical composition) and acid resistance (integrity of apatite structure). Bioabsorption of remnant bone substitute material and volume maintenance of the augmented bone are inversely related. It is necessary to improve the biocompatibility of currently available bone substitutes and to strike an appropriate balance between bioabsorption and volume maintenance to achieve ideal bone remodeling. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  19. Substitute Teachers: Making Lost Days Count

    Science.gov (United States)

    True, Charlene; Butler, Kyle; Sefton, Rachel

    2011-01-01

    As K-12 teachers and administrators grow increasingly concerned with issues of accountability, research-based methods, and intervention strategies, little discussion exists on the impact of substitute teachers in the classroom. In the rush to analyze test scores, are the days covered by substitute teachers even considered? Though districts are…

  20. Atomic Structure Theory Lectures on Atomic Physics

    CERN Document Server

    Johnson, Walter R

    2007-01-01

    Atomic Structure Theory is a textbook for students with a background in quantum mechanics. The text is designed to give hands-on experience with atomic structure calculations. Material covered includes angular momentum methods, the central field Schrödinger and Dirac equations, Hartree-Fock and Dirac-Hartree-Fock equations, multiplet structure, hyperfine structure, the isotope shift, dipole and multipole transitions, basic many-body perturbation theory, configuration interaction, and correlation corrections to matrix elements. Numerical methods for solving the Schrödinger and Dirac eigenvalue problems and the (Dirac)-Hartree-Fock equations are given as well. B-spline basis sets are used to carry out sums arising in higher-order many-body calculations. Illustrative problems are provided, together with solutions. FORTRAN programs implementing the numerical methods in the text are included.

  1. X- and γ-ray interaction characteristics of Griffith, Alderson, Frigerio, Goodman and Rossi tissue substitutes

    Energy Technology Data Exchange (ETDEWEB)

    Singh, V. P.; Badiger, N. M. [Karnatak University, Department of Physics, Dharwad-580003, Karnataka (India); Vega C, H. R., E-mail: kudphyvps@rediffmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico)

    2015-10-15

    Detailed information of radiation interaction, exposure and dose delivery to tissue substitutes is necessary for various branches of radiation physics. In the present investigation X- and γ-ray interaction characteristics of some tissue substitutes such as Griffith, Alderson, Frigerio, Goodman and Rossi have been studied and compared with standard tissues. Effective atomic numbers and air-kerma have been computed using mass attenuation coefficients and mass energy-absorption coefficients, respectively. Energy-absorption buildup factors for photon energy 0.015 to 15 MeV up to 40 mean free path were calculated using G-P fitting method. These investigations provide further information on the X- and γ-ray interaction of tissue substitutes for various applications in radiation physics and medical physics. (Author)

  2. X- and γ-ray interaction characteristics of Griffith, Alderson, Frigerio, Goodman and Rossi tissue substitutes

    International Nuclear Information System (INIS)

    Singh, V. P.; Badiger, N. M.; Vega C, H. R.

    2015-10-01

    Detailed information of radiation interaction, exposure and dose delivery to tissue substitutes is necessary for various branches of radiation physics. In the present investigation X- and γ-ray interaction characteristics of some tissue substitutes such as Griffith, Alderson, Frigerio, Goodman and Rossi have been studied and compared with standard tissues. Effective atomic numbers and air-kerma have been computed using mass attenuation coefficients and mass energy-absorption coefficients, respectively. Energy-absorption buildup factors for photon energy 0.015 to 15 MeV up to 40 mean free path were calculated using G-P fitting method. These investigations provide further information on the X- and γ-ray interaction of tissue substitutes for various applications in radiation physics and medical physics. (Author)

  3. Storage ring to investigate cold unidimensional atomic collisions

    International Nuclear Information System (INIS)

    Marcassa, L. G.; Caires, A. R. L.; Nascimento, V. A.; Dulieu, O.; Weiner, J.; Bagnato, V. S.

    2005-01-01

    In this paper we employ a circulating ring of trapped atoms, that we have named the atomotron, to study cold collisions. The atomotron is obtained from a conventional magneto-optical trap when the two pairs of normally retroreflecting Gaussian laser beams in the x-y plane are slightly offset. Circulating stable atomic orbits then form a racetrack geometry in this plane. The circulating atom flux behaves similarly to an atomic beam with an average tangential velocity much greater than the transverse components, and is therefore suitable for one-dimensional atomic collision studies. Using the atomotron, we have investigated the polarization dependence of ultracold photoassociation collisions between Rb atoms circulating in the racetrack. The ability to investigate collisions in ultracold circulating atomic rings reveals alignment and orientation properties that are averaged away in ordinary three-dimensional magneto-optical trap collision processes

  4. Substitution between cars within the household

    DEFF Research Database (Denmark)

    De Borger, Bruno; Mulalic, Ismir; Rouwendal, Jan

    2016-01-01

    In this paper we study the demand for car kilometres in two-car households, focusing on the substitution between cars of different fuel efficiency in response to fuel price changes. We use a large sample of detailed Danish data on two-car households to estimate – for each car owned by the household...... – own and cross-price effects of increases in fuel costs per kilometre. The empirical results show that failure to capture substitution between cars within the household can result in substantial misspecification biases. Ignoring substitution, the basic model yielded fuel price elasticities of 0.......98 and 1.41 for the primary and secondary cars, respectively. Accounting for substitution effects, these figures reduce to, respectively, 0.32 and 0.45. Consistent with substitution behaviour, we find that the fuel price elasticity of fuel demand exceeds the elasticity of kilometre demands with respect...

  5. Aluminum substitution in goethite in lake ore

    Directory of Open Access Journals (Sweden)

    Carlson, L.

    1995-06-01

    Full Text Available The extent of substitution of Fe by Al in goethite in 32 lake ore samples collected from 11 lakes in Finland varied between 0 and 23 mol-%. The data indicated a negative relationship between Al-substitution and the particle size of lake ore. Differences in the Al-substitution were apparent between sampling sites, suggesting that kinetic and environmental variation in lake ore formation influences the substitution. Non-substituted goethite is formed in coarse-grained sediments with locally high concentrations of Fe due to iron-rich springs. Unit cell edge lengths and volumes of goethite varied as function of Al-subsitution but deviated from the Vegard relationship towards higher values.

  6. Division of atomic physics

    International Nuclear Information System (INIS)

    Kroell, S.

    1994-01-01

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

  7. Atomic mass spectrometry

    International Nuclear Information System (INIS)

    Sanz-Medel, A.

    1997-01-01

    The elemental inorganic analysis seems to be dominated today by techniques based on atomic spectrometry. After an evaluation of advantages and limitations of using mass analysers (ion detectors) versus conventional photomultipliers (photon detector) a brief review of the more popular techniques of the emerging Atomic Mass spectrometry is carried out. Their huge potential for inorganic trace analysis is such that in the future we could well witness how this end of the century and millennium marked the fall of the photons empire in Analytical Atomic Spectrometry. (Author)

  8. Atom trap trace analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Z.-T.; Bailey, K.; Chen, C.-Y.; Du, X.; Li, Y.-M.; O' Connor, T. P.; Young, L.

    2000-05-25

    A new method of ultrasensitive trace-isotope analysis has been developed based upon the technique of laser manipulation of neutral atoms. It has been used to count individual {sup 85}Kr and {sup 81}Kr atoms present in a natural krypton sample with isotopic abundances in the range of 10{sup {minus}11} and 10{sup {minus}13}, respectively. The atom counts are free of contamination from other isotopes, elements,or molecules. The method is applicable to other trace-isotopes that can be efficiently captured with a magneto-optical trap, and has a broad range of potential applications.

  9. Physics of the atom

    CERN Document Server

    Wehr, Russell M; Adair, Thomas W

    1984-01-01

    The fourth edition of Physics of the Atom is designed to meet the modern need for a better understanding of the atomic age. It is an introduction suitable for students with a background in university physics and mathematical competence at the level of calculus. This book is designed to be an extension of the introductory university physics course into the realm of atomic physics. It should give students a proficiency in this field comparable to their proficiency in mechanics, heat, sound, light, and electricity.

  10. Protein Adhesion and Ion Substitution (on/in)to Minerals

    Science.gov (United States)

    Charlet, L.; Fernandez Martinez, A.; Chapron, Y.; Sahai, N.; Cuello, G.; Brendle, J.; Marichal, C.

    2008-12-01

    Arsenic and pathogenic prion protein-scrapie (PrPsc) are important contaminants which may soil and water for decades, unless they are removed by sorption. Two sorption mechanisms will be discussed, namely the organics (Prp and single aminoacid) adsorption on clay and the arsenic substitution in gypsum. The elucidation of these contrasted mechanisms will be shown to request complementary molecular-mechanical simulations with experimental spectroscopic investigations. As first example, structural studies performed at ILL/ESRF on As-doped gypsum (CaSO4 2H2O) using neutron and X-ray diffraction data and EXAFS were performed to determine how As fits into the bulk of gypsum structure. The combined Rietveld analysis of neutron and X-ray diffraction data shows an expansion of the unit cell volume proportional to the As concentration within the samples. to-sulfate substitution mechanisms were used as simulation starting hypotheses. DFT-based simulations (Mulliken analysis) were used to interpret charge distribution and to show that among the possible mechanisms, a sulphate substitution by either protonated, or fully deprotonated, arsenate ion, only the protonated arsenate substitution could best fit the EXAFS data. In the second example, we used Molecular Dynamics to understand the mechanism of strong binding of the pathogenic PrP peptide with clay mineral surfaces. We modeled only the infectious moiety, PrP92-138, of the whole PrPsc structure, with explicitly solvating water molecules in contact with the cleavage plane of pyrophillite, as a model for montmorillonite without any cationic substitution. Partial residual negative charges on the cleavage plane were balanced with K+ ions. The peptide anchored to the clay surface via up to 10 hydrogen bonds from lysine and histidine residues to oxygen atoms of the siloxane cavities, and a total adsorption energy of 3465 KJ.mol-1 was obtained. Our results were compared to the one obtained by chemical and thermal analysis, 23Na, 1H

  11. Section of Atomic Collisions

    International Nuclear Information System (INIS)

    Berenyi, D.; Biri, S.; Gulyas, L.; Juhasz, Z.; Kover, A.; Orban, A.; Palinkas, J.; Papp, T.; Racz, R.; Ricz, S.

    2009-01-01

    The Section of Atomic Collisions is a research unit with extended activity in the field of atomic and molecular physics. Starting from the study of atomic processes at the beamlines of nuclear physics accelerators in the seventies, our research community became one of the centers of fundamental research in Atomki. We also have a strong connection to materials sciences especially along the line of electron and ion spectroscopy methods. Our present activity covers a wide range of topics from atomic collision mechanisms of fundamental interest, to the complex interactions of electrons, ions, photons and antiparticles with atoms, molecules, surfaces, and specific nanostructures. In the last few years, an increasing fraction of our present topics has become relevant for applications, e.g., molecular collision studies for the radiation therapy methods of tumors, or ion-nanostructure interactions for the future construction of small ion-focusing elements. Our section belongs to the Division of Atomic Physics. The other unit of the Division is the Section of Electron Spectroscopy and Materials Sciences. There are traditionally good connections and a strong collaboration between the groups of the two sections in many fields. From the very beginning of our research work in atomic collisions, external collaborations were of vital importance for us. We regularly organize international workshops in the field of fast ion-atom collisions and related small conferences in Debrecen from 1981. Recently, we organized the Conference on Radiation Damage in Biomolecular Systems (RADAM 2008, Debrecen), and coorganized the Conference on Elementary Processes in Atomic Systems (CEPAS 2008, Cluj). We have access to several large scale facilities in Europe within the framework of formal and informal collaborations. The next themes are in this article: Forward electron emission from energetic atomic collisions; Positron-atom collisions; Photon-atom interactions; Interference effects in electron

  12. Synthesis, Reactivity and Stability of Aryl Halide Protecting Groups towards Di-Substituted Pyridines

    Directory of Open Access Journals (Sweden)

    Ptoton Mnangat Brian

    2016-03-01

    Full Text Available This paper reports the synthesis and reactivity of different Benzyl derivative protecting groups. The synthesis and stability of Benzyl halides, 4-methoxybenzyl halides, 3,5-dimethoxybenzyl halides, 3,4-dimethoxybenzyl halides, 3,4,5-trimethoxybenzyl halide protecting groups and their reactivity towards nitrogen atom of a di-substituted pyridine ring in formation of pyridinium salts is also reported.

  13. Observation of dynamic atom-atom correlation in liquid helium in real space.

    Science.gov (United States)

    Dmowski, W; Diallo, S O; Lokshin, K; Ehlers, G; Ferré, G; Boronat, J; Egami, T

    2017-05-04

    Liquid 4 He becomes superfluid and flows without resistance below temperature 2.17 K. Superfluidity has been a subject of intense studies and notable advances were made in elucidating the phenomenon by experiment and theory. Nevertheless, details of the microscopic state, including dynamic atom-atom correlations in the superfluid state, are not fully understood. Here using a technique of neutron dynamic pair-density function (DPDF) analysis we show that 4 He atoms in the Bose-Einstein condensate have environment significantly different from uncondensed atoms, with the interatomic distance larger than the average by about 10%, whereas the average structure changes little through the superfluid transition. DPDF peak not seen in the snap-shot pair-density function is found at 2.3 Å, and is interpreted in terms of atomic tunnelling. The real space picture of dynamic atom-atom correlations presented here reveal characteristics of atomic dynamics not recognized so far, compelling yet another look at the phenomenon.

  14. Modeling molecular acidity with electronic properties and Hammett constants for substituted benzoic acids.

    Science.gov (United States)

    Huang, Ying; Liu, Lianghong; Liu, Wanhui; Liu, Shaogang; Liu, Shubin

    2011-12-29

    Molecular acidity is an important physiochemical property essential in many fields of molecular studies, but an efficient and reliable computational approach to make accurate predictions is still missing. In this work, based on our previous studies to use gas phase electronic properties such as molecular electrostatic potential and valence natural atomic orbitals of the acidic atom and leaving proton, we demonstrate here that different approaches can be employed to tackle this problem. To that end, we employ 196 singly, doubly, and triply substituted benzoic acids for the study. We show that two different approaches are possible, one focusing on the carboxyl group through its localized electronic properties and the other on the substituting groups via Hammett constants and their additivity rule. Our present results clearly exhibit that with the linear models built from the singly substituted species, one can accurately predict the pK(a) values for the doubly and triply substituted species with both of these two approaches. The predictions from these approaches are consistent with each other and agree well with the experimental data. These intrinsically different approaches are the two manifestations of the same molecular acidity property, both valid and complementary to each other. © 2011 American Chemical Society

  15. Uproar over Milk Substitutes Act.

    Science.gov (United States)

    1993-11-15

    Health policy activists lobbied 7 years for the Infant Milk Substitutes, Feeding Bottles and Infant Food Bill. Proponents of the bill say that it basically curtails unethical marketing practices, not the sales of baby foods, and argue that it was conceived to reduce the trend of mothers over-diluting commercial milk in order to reduce household expenses as well as stem the potential erosion of knowledge on locally available weaning foods. Even though the bill will become an Act only after its rules and regulations have been finalized, the government has already banned baby food advertisements on television and in other electronic media under its control. Women's groups now argue that the bill tends to focus almost exclusively upon the welfare of children and compromises the position of women who can not lactate adequately. Moreover, they hold that the bill may be used to compel wives to stay out of the formal workforce so that they may feed their babies. The intention of the bill may be meaningless without complementary legislation addressing the problems of working mothers. Specifically, amendments to the Maternity Benefits Act of 1961 would extend maternity leave to 4 months after delivery and lengthen the duration of nursing breaks. It is, however, feared that these changes may reduce employment prospects for women.

  16. Substituted Hydroxyapatites with Antibacterial Properties

    Directory of Open Access Journals (Sweden)

    Joanna Kolmas

    2014-01-01

    Full Text Available Reconstructive surgery is presently struggling with the problem of infections located within implantation biomaterials. Of course, the best antibacterial protection is antibiotic therapy. However, oral antibiotic therapy is sometimes ineffective, while administering an antibiotic at the location of infection is often associated with an unfavourable ratio of dosage efficiency and toxic effect. Thus, the present study aims to find a new factor which may improve antibacterial activity while also presenting low toxicity to the human cells. Such factors are usually implemented along with the implant itself and may be an integral part of it. Many recent studies have focused on inorganic factors, such as metal nanoparticles, salts, and metal oxides. The advantages of inorganic factors include the ease with which they can be combined with ceramic and polymeric biomaterials. The following review focuses on hydroxyapatites substituted with ions with antibacterial properties. It considers materials that have already been applied in regenerative medicine (e.g., hydroxyapatites with silver ions and those that are only at the preliminary stage of research and which could potentially be used in implantology or dentistry. We present methods for the synthesis of modified apatites and the antibacterial mechanisms of various ions as well as their antibacterial efficiency.

  17. Substituted Hydroxyapatites with Antibacterial Properties

    Science.gov (United States)

    Kolmas, Joanna; Groszyk, Ewa; Kwiatkowska-Różycka, Dagmara

    2014-01-01

    Reconstructive surgery is presently struggling with the problem of infections located within implantation biomaterials. Of course, the best antibacterial protection is antibiotic therapy. However, oral antibiotic therapy is sometimes ineffective, while administering an antibiotic at the location of infection is often associated with an unfavourable ratio of dosage efficiency and toxic effect. Thus, the present study aims to find a new factor which may improve antibacterial activity while also presenting low toxicity to the human cells. Such factors are usually implemented along with the implant itself and may be an integral part of it. Many recent studies have focused on inorganic factors, such as metal nanoparticles, salts, and metal oxides. The advantages of inorganic factors include the ease with which they can be combined with ceramic and polymeric biomaterials. The following review focuses on hydroxyapatites substituted with ions with antibacterial properties. It considers materials that have already been applied in regenerative medicine (e.g., hydroxyapatites with silver ions) and those that are only at the preliminary stage of research and which could potentially be used in implantology or dentistry. We present methods for the synthesis of modified apatites and the antibacterial mechanisms of various ions as well as their antibacterial efficiency. PMID:24949423

  18. Substituted androstanes as aromatase inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Levina, Inna S [N.D.Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow (Russian Federation)

    1998-11-30

    The synthesis and structure-activity relationships of inhibitors of steroid aromatase which catalyses the last stage of a multistep biotransformation of cholesterol into estrogens, viz., aromatisation of C{sub 19}-steroids into C{sub 18}-phenolic steroids, are discussed. Compounds of the androstane series which are structurally related to the natural substrate, viz., androst-4-ene-3,17-dione, are the subjects of consideration. The review encompasses problems of synthesis of various substituted androstanes and their aromatase-inhibiting activities and structural requirements for selective specific aromatase inhibitors based on in vitro and in vivo structure-activity studies of compounds synthesised, their biological properties and the results of clinical trials. Special attention is paid to practical applications of aromatase inhibitors in the treatment of hormone-dependent mammary and ovarian tumours as well as benign prostatic tumours. In writing this report, the author has used all the information currently available in the chemical, biochemical, endocrinological and medicinal literature as well as in patents. The bibliography includes 173 references.

  19. Substituted androstanes as aromatase inhibitors

    Science.gov (United States)

    Levina, Inna S.

    1998-11-01

    The synthesis and structure-activity relationships of inhibitors of steroid aromatase which catalyses the last stage of a multistep biotransformation of cholesterol into estrogens, viz., aromatisation of C19-steroids into C18-phenolic steroids, are discussed. Compounds of the androstane series which are structurally related to the natural substrate, viz., androst-4-ene-3,17-dione, are the subjects of consideration. The review encompasses problems of synthesis of various substituted androstanes and their aromatase-inhibiting activities and structural requirements for selective specific aromatase inhibitors based on in vitro and in vivo structure-activity studies of compounds synthesised, their biological properties and the results of clinical trials. Special attention is paid to practical applications of aromatase inhibitors in the treatment of hormone-dependent mammary and ovarian tumours as well as benign prostatic tumours. In writing this report, the author has used all the information currently available in the chemical, biochemical, endocrinological and medicinal literature as well as in patents. The bibliography includes 173 references.

  20. Atomic Energy Authority Bill

    International Nuclear Information System (INIS)

    Gray, J.H.N.; Stoddart, D.L.; Sinclair, R.M.; Ezra, D.

    1985-01-01

    The House, in Committee, discussed the following matters in relation to the Atomic Energy Authority Bill; financing; trading; personnel conditions of employment; public relations; organization; research programmes; fuels; energy sources; information dissemination. (U.K.)

  1. Atomic Interferometry, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Vertical cavity surface emitting lasers (VCSELs) is a new technology which can be used for developing high performance laser components for atom-based sensors...

  2. Atomic bomb cataracts

    International Nuclear Information System (INIS)

    Shiraeda, Kanji

    1992-01-01

    Eye disturbance caused by atomic bomb radiation can be divided into three groups: direct injury immediately after exposure, eye lesions associated with radiation syndrome, and delayed disturbance. The crystalline lens of the eye is the most radiosensitive. Atomic bomb cataract has been investigated in a number of studies. The first section of this chapter discusses radiation cataract in terms of the incidence and characteristics. The second section deals with atomic bomb cataract, which can be diagnosed based on the four criteria: (1) opacity of the crystalline lens, (2) a history of proximal exposure, (3) lack of eye disease complicating cataract, and (4) non-exposure to radiation other than atomic bombing. The prevalence of cataract and severity of opacity are found to correlate with exposure doses and age at the time of exposure. Furthermore, it is found to correlate with distance from the hypocenter, the condition of shielding, epilation, and the presence or absence or degree of radiation syndrome. (N.K.)

  3. Topics in atomic physics

    CERN Document Server

    Burkhardt, Charles E

    2006-01-01

    The study of atomic physics propelled us into the quantum age in the early twentieth century and carried us into the twenty-first century with a wealth of new and, in some cases, unexplained phenomena. Topics in Atomic Physics provides a foundation for students to begin research in modern atomic physics. It can also serve as a reference because it contains material that is not easily located in other sources. A distinguishing feature is the thorough exposition of the quantum mechanical hydrogen atom using both the traditional formulation and an alternative treatment not usually found in textbooks. The alternative treatment exploits the preeminent nature of the pure Coulomb potential and places the Lenz vector operator on an equal footing with other operators corresponding to classically conserved quantities. A number of difficult to find proofs and derivations are included as is development of operator formalism that permits facile solution of the Stark effect in hydrogen. Discussion of the classical hydrogen...

  4. Atoms at work

    International Nuclear Information System (INIS)

    1982-07-01

    This illustrated booklet discusses the following: atoms; fission of uranium; nuclear power plants; reactor types; plutonium (formation, properties, uses); radioactive waste (fuel cycle, reprocessing, waste management); nuclear fusion; fusion reactors; radiation; radioisotopes and their uses. (U.K.)

  5. Advances in atomic spectroscopy

    CERN Document Server

    Sneddon, J

    1998-01-01

    This volume continues the series'' cutting-edge reviews on developments in this field. Since its invention in the 1920s, electrostatic precipitation has been extensively used in industrial hygiene to remove dust and particulate matter from gases before entering the atmosphere. This combination of electrostatic precipitation is reported upon in the first chapter. Following this, chapter two reviews recent advances in the area of chemical modification in electrothermal atomization. Chapter three consists of a review which deal with advances and uses of electrothermal atomization atomic absorption spectrometry. Flow injection atomic spectroscopy has developed rapidly in recent years and after a general introduction, various aspects of this technique are looked at in chapter four. Finally, in chapter five the use of various spectrometric techniques for the determination of mercury are described.

  6. Atomic and Molecular Interactions

    International Nuclear Information System (INIS)

    2002-01-01

    The Gordon Research Conference (GRC) on Atomic and Molecular Interactions was held at Roger Williams University, Bristol, RI. Emphasis was placed on current unpublished research and discussion of the future target areas in this field

  7. Hydrogen isotopic substitution experiments in nanostructured porous silicon

    International Nuclear Information System (INIS)

    Palacios, W.D.; Koropecki, R.R.; Arce, R.D.; Busso, A.

    2008-01-01

    Nanostructured porous silicon is usually prepared by electrochemical anodization of monocrystalline silicon using a fluorine-rich electrolyte. As a result of this process, the silicon atoms conserve their original crystalline location, and many of the dangling bonds appearing on the surface of the nanostructure are saturated by hydrogen coming from the electrolyte. This work presents an IR study of the effects produced by partial substitution of water in the electrolytic solution by deuterium oxide. The isotopic effects on the IR spectra are analyzed for the as-prepared samples and for the samples subjected to partial thermal effusion of hydrogen and deuterium. We demonstrate that, although deuterium is chemically indistinguishable from hydrogen, it presents a singular behaviour when used in porous silicon preparation. We found that deuterium preferentially bonds forming Si-DH groups. A possible explanation of the phenomenon is presented, based on the different diffusivities of hydrogen and deuterium

  8. Hydrogen isotopic substitution experiments in nanostructured porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, W.D. [Facultad de Ciencias Exactas y Naturales y Agrimensura - (UNNE), Avenida Libertad 5500, 3400 Corrientes (Argentina); Koropecki, R.R. [INTEC (CONICET-UNL), Gueemes 3450, 3000 Santa Fe (Argentina)], E-mail: rkoro@intec.ceride.gov.ar; Arce, R.D. [INTEC (CONICET-UNL), Gueemes 3450, 3000 Santa Fe (Argentina); Busso, A. [Facultad de Ciencias Exactas y Naturales y Agrimensura - (UNNE), Avenida Libertad 5500, 3400 Corrientes (Argentina)

    2008-04-30

    Nanostructured porous silicon is usually prepared by electrochemical anodization of monocrystalline silicon using a fluorine-rich electrolyte. As a result of this process, the silicon atoms conserve their original crystalline location, and many of the dangling bonds appearing on the surface of the nanostructure are saturated by hydrogen coming from the electrolyte. This work presents an IR study of the effects produced by partial substitution of water in the electrolytic solution by deuterium oxide. The isotopic effects on the IR spectra are analyzed for the as-prepared samples and for the samples subjected to partial thermal effusion of hydrogen and deuterium. We demonstrate that, although deuterium is chemically indistinguishable from hydrogen, it presents a singular behaviour when used in porous silicon preparation. We found that deuterium preferentially bonds forming Si-DH groups. A possible explanation of the phenomenon is presented, based on the different diffusivities of hydrogen and deuterium.

  9. The Atomic Energy Control Board

    International Nuclear Information System (INIS)

    Doern, G.B.

    1976-01-01

    This study describes and assesses the regulatory and administrative processes and procedures of the Atomic Energy Control Board, the AECB. The Atomic Energy Control Act authorized the AECB to control atomic energy materials and equipment in the national interest and to participate in measures for the international control of atomic energy. The AECB is authorized to make regulations to control atomic energy materials and equipment and to make grants in support of atomic energy research. (author)

  10. Atoms, molecules & elements

    CERN Document Server

    Graybill, George

    2007-01-01

    Young scientists will be thrilled to explore the invisible world of atoms, molecules and elements. Our resource provides ready-to-use information and activities for remedial students using simplified language and vocabulary. Students will label each part of the atom, learn what compounds are, and explore the patterns in the periodic table of elements to find calcium (Ca), chlorine (Cl), and helium (He) through hands-on activities.

  11. Harnessing the atom

    International Nuclear Information System (INIS)

    1999-01-01

    Splitting the atom has had a major impact on the history of the latter part of the 20th century. This film depicts the many benefits - and also drawbacks - of nuclear technology, and describes how the International Atomic Energy Agency performs its various tasks. It touches on challenges such as the choice between major energy sources, growing concerns about the global climate, and prospects for nuclear arms control and disarmament

  12. Optical atomic magnetometer

    Science.gov (United States)

    Budker, Dmitry; Higbie, James; Corsini, Eric P

    2013-11-19

    An optical atomic magnetometers is provided operating on the principles of nonlinear magneto-optical rotation. An atomic vapor is optically pumped using linearly polarized modulated light. The vapor is then probed using a non-modulated linearly polarized light beam. The resulting modulation in polarization angle of the probe light is detected and used in a feedback loop to induce self-oscillation at the resonant frequency.

  13. Atomic Energy Act 1946

    International Nuclear Information System (INIS)

    1946-01-01

    This Act provides for the development of atomic energy in the United Kingdom and for its control. It details the duties and powers of the competent Minister, in particular his powers to obtain information on and to inspect materials, plant and processes, to control production and use of atomic energy and publication of information thereon. Also specified is the power to search for and work minerals and to acquire property. (NEA) [fr

  14. Hirshfeld atom refinement.

    Science.gov (United States)

    Capelli, Silvia C; Bürgi, Hans-Beat; Dittrich, Birger; Grabowsky, Simon; Jayatilaka, Dylan

    2014-09-01

    Hirshfeld atom refinement (HAR) is a method which determines structural parameters from single-crystal X-ray diffraction data by using an aspherical atom partitioning of tailor-made ab initio quantum mechanical molecular electron densities without any further approximation. Here the original HAR method is extended by implementing an iterative procedure of successive cycles of electron density calculations, Hirshfeld atom scattering factor calculations and structural least-squares refinements, repeated until convergence. The importance of this iterative procedure is illustrated via the example of crystalline ammonia. The new HAR method is then applied to X-ray diffraction data of the dipeptide Gly-l-Ala measured at 12, 50, 100, 150, 220 and 295 K, using Hartree-Fock and BLYP density functional theory electron densities and three different basis sets. All positions and anisotropic displacement parameters (ADPs) are freely refined without constraints or restraints - even those for hydrogen atoms. The results are systematically compared with those from neutron diffraction experiments at the temperatures 12, 50, 150 and 295 K. Although non-hydrogen-atom ADPs differ by up to three combined standard uncertainties (csu's), all other structural parameters agree within less than 2 csu's. Using our best calculations (BLYP/cc-pVTZ, recommended for organic molecules), the accuracy of determining bond lengths involving hydrogen atoms from HAR is better than 0.009 Å for temperatures of 150 K or below; for hydrogen-atom ADPs it is better than 0.006 Å(2) as judged from the mean absolute X-ray minus neutron differences. These results are among the best ever obtained. Remarkably, the precision of determining bond lengths and ADPs for the hydrogen atoms from the HAR procedure is comparable with that from the neutron measurements - an outcome which is obtained with a routinely achievable resolution of the X-ray data of 0.65 Å.

  15. Atomic phenomena in dense plasmas

    International Nuclear Information System (INIS)

    Weisheit, J.C.

    1981-03-01

    The following chapters are included: (1) the plasma environment, (2) perturbations of atomic structure, (3) perturbations of atomic collisions, (4) formation of spectral lines, and (5) dielectronic recombination

  16. Atomic bomb and leukemia

    International Nuclear Information System (INIS)

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

    1991-01-01

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

  17. FAO and atomic energy

    International Nuclear Information System (INIS)

    1960-01-01

    During the past six years FAO has become more engaged in work concerned with atomic energy. In 1957 it established an Atomic Energy Branch. The new forces and new tools which have become available for use in the fight against poverty, disease and malnutrition can be of the greatest assistance in FAO's work in nearly all phases of the production, storage and distribution of food and other agricultural products. The Organization promotes their use to improve the standards of feeding, clothing and housing throughout the world. Another side of work related to atomic energy is concerned with combating contamination from the use of atomic energy for power production and other purposes. This raises considerable problems for food and agriculture, so that FAO also has a responsibility for assisting Governments in safeguarding their food and food-producing resources from contamination. FAO is essentially concerned with fostering wider knowledge of the many contributions that atomic science can make to agriculture, forestry, fisheries and nutrition. It is also concerned in assisting governments to establish sound programmes for applying atomic science in food and agriculture. One way of spreading such knowledge is through the publication of documents and reports

  18. Atomic bomb and leukemia

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-12-01

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

  19. Activation of Graphenic Carbon Due to Substitutional Doping by Nitrogen: Mechanistic Understanding from First Principles.

    Science.gov (United States)

    Bhattacharjee, Joydeep

    2015-05-07

    Nitrogen-doped graphene and carbon nanotubes are popularly in focus as metal-free electrocatalysts for oxygen reduction reactions (ORR) central to fuel cells. N-doped CNTs have been also reported to chemisorb mutually, promising a route to their robust predetermined assembly into devices and mechanical reinforcements. We propose from first principles a common mechanistic understanding of these two aspects pointing further to a generic chemical activation of carbon atoms due to substitution by nitrogen in experimentally observed configurations. Wannier-function based orbital resolved study of mechanisms suggests increase in C-N bond-orders in attempt to retain π-conjugation among carbon atoms, causing mechanical stress and loss of charge neutrality of nitrogen and carbon atoms, which remedially facilitate chemical activation of N-coordinated C atoms, enhancing sharply with increasing coordination to N and proximity to zigzag edges. Activated C atoms facilitate covalent adsorption of radicals in general, diradicals like O2 relevant to ORR, and also other similarly activated C atoms, leading to self-assembly of graphenic nanostructures while remaining inert to ordinary graphenic C atoms.

  20. Interaction-Free Effects Between Distant Atoms

    Science.gov (United States)

    Aharonov, Yakir; Cohen, Eliahu; Elitzur, Avshalom C.; Smolin, Lee

    2018-01-01

    A Gedanken experiment is presented where an excited and a ground-state atom are positioned such that, within the former's half-life time, they exchange a photon with 50% probability. A measurement of their energy state will therefore indicate in 50% of the cases that no photon was exchanged. Yet other measurements would reveal that, by the mere possibility of exchange, the two atoms have become entangled. Consequently, the "no exchange" result, apparently precluding entanglement, is non-locally established between the atoms by this very entanglement. This quantum-mechanical version of the ancient Liar Paradox can be realized with already existing transmission schemes, with the addition of Bell's theorem applied to the no-exchange cases. Under appropriate probabilities, the initially-excited atom, still excited, can be entangled with additional atoms time and again, or alternatively, exert multipartite nonlocal correlations in an interaction free manner. When densely repeated several times, this result also gives rise to the Quantum Zeno effect, again exerted between distant atoms without photon exchange. We discuss these experiments as variants of interaction-free-measurement, now generalized for both spatial and temporal uncertainties. We next employ weak measurements for elucidating the paradox. Interpretational issues are discussed in the conclusion, and a resolution is offered within the Two-State Vector Formalism and its new Heisenberg framework.

  1. Cavity electromagnetically induced transparency with Rydberg atoms

    Science.gov (United States)

    Bakar Ali, Abu; Ziauddin

    2018-02-01

    Cavity electromagnetically induced transparency (EIT) is revisited via the input probe field intensity. A strongly interacting Rydberg atomic medium ensemble is considered in a cavity, where atoms behave as superatoms (SAs) under the dipole blockade mechanism. Each atom in the strongly interacting Rydberg atomic medium (87 Rb) follows a three-level cascade atomic configuration. A strong control and weak probe field are employed in the cavity with the ensemble of Rydberg atoms. The features of the reflected and transmitted probe light are studied under the influence of the input probe field intensity. A transparency peak (cavity EIT) is revealed at a resonance condition for small values of input probe field intensity. The manipulation of the cavity EIT is reported by tuning the strength of the input probe field intensity. Further, the phase and group delay of the transmitted and reflected probe light are studied. It is found that group delay and phase in the reflected light are negative, while for the transmitted light they are positive. The magnitude control of group delay in the transmitted and reflected light is investigated via the input probe field intensity.

  2. Temperature dependent nanoscale atomic correlations in Ir1-xPtxTe2 (x = 0.0, 0.03 and 0.04) system

    Science.gov (United States)

    Joseph, B.; Paris, E.; Mulato-Gómez, D. F.; Simonelli, L.; Bendele, M.; Maugeri, L.; Iadecola, A.; Pyon, S.; Kudo, K.; Nohara, M.; Mustre de Leon, J.; Mizokawa, T.; Saini, N. L.

    2014-09-01

    X-ray absorption near-edge structure (XANES) spectroscopy has been used to investigate the unoccupied electronic states and local geometry of Ir1-xPtxTe2(x = 0.0, 0.03 and 0.04) as a function of temperature. The Ir L3-edge absorption white line, as well as high energy XANES features due to the photoelectron multiple scatterings with near neighbours, reveal clear changes in the unoccupied 5d-electronic states and the local geometry with Pt substitution. We find an anomalous spectral weight transfer across the known first-order structural phase transition from the trigonal to monoclinic phase in IrTe2, which characterizes the reduced atomic structure symmetry below the transition temperature. No such changes with temperature are seen in the Pt substituted superconducting samples. In addition, a gradual increase of the spectral weight transfer is observed in IrTe2 with a further decrease in temperature below the transition, indicating that the low temperature phase is likely to have a symmetry lower than the monoclinic one. The results suggest that the interplay between inter-layer and intra-layer atomic correlations should have a significant role in the properties of an Ir1-xPtxTe2 system.

  3. Insights into the Hydrogen-Atom Transfer of the Blue Aroxyl.

    Science.gov (United States)

    Bächle, Josua; Marković, Marijana; Kelterer, Anne-Marie; Grampp, Günter

    2017-10-19

    An experimental and theoretical study on hydrogen-atom transfer dynamics in the hydrogen-bonded substituted phenol/phenoxyl complex of the blue aroxyl (2,4,6-tri-tert-butylphenoxyl) is presented. The experimental exchange dynamics is determined in different organic solvents from the temperature-dependent alternating line-width effect in the continuous-wave ESR spectrum. From bent Arrhenius plots, effective tunnelling contributions with parallel heavy-atom motion are concluded. To clarify the transfer mechanism, reaction paths for different conformers of the substituted phenol/phenoxyl complex are modelled theoretically. Various DFT and post-Hartree-Fock methods including multireference methods are applied. From the comparison of experimental and theoretical data it is concluded that the system favours concerted hydrogen-atom transfer along a parabolic reaction path caused by heavy-atom motion. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Kinetic study on alkaline hydrolysis of Y-substituted phenyl X-substituted benzenesulfonates: Effects of changing nucleophile from azide to hydroxide ion on reactivity and transition-state structure

    International Nuclear Information System (INIS)

    Moon, Ji Hyun; Kim, Min Young; Han, So Yeop; Um, Ik Hwan

    2015-01-01

    Second-order rate constants (math formula) for alkaline hydrolysis of 2,4-dinitrophenyl X-substituted benzenesulfonates (1a–1f) and Y-substituted phenyl 4-nitrobezenesulfonates (2a–2g) have been measured spectrophotometrically. Comparison of math formula with the math formula values reported previously for the corresponding reactions with math formula has revealed that OH [BOND] is only 10 3 -fold more reactive than math formula, although the former is 11 pK a units more basic than the latter. The Yukawa–Tsuno plot for the reactions of 1a–1f results in an excellent linear correlation with ρ X  = 2.09 and r = 0.41. The Brønsted-type plot for the reactions of 2a–2g is linear with β lg  = −0.51, which is typical for reactions reported to proceed through a concerted mechanism. The Yukawa–Tsuno plot for the reactions of 2a–2g exhibits excellent linearity with ρ Y  = 1.85 and r = 0.25, indicating that a partial negative charge develops on the O atom of the leaving group in the transition state. Thus, the alkaline hydrolysis of 1a–1f and 2a–2g has been concluded to proceed through a concerted mechanism. Comparison of the ρ X and β lg values for the reactions with math formula ions suggests that the reactions with hydroxide ion proceed through a tighter transition-state structure than those with azide ion

  5. Structures and spectroscopic properties of nonperipherally and peripherally substituted metal-free phthalocyanines: a substitution effect study based on density functional theory calculations.

    Science.gov (United States)

    Zhong, Aimin; Zhang, Yuexing; Bian, Yongzhong

    2010-11-01

    The molecular structures, molecular orbitals, atomic charges, electronic absorption spectra, and infrared (IR) and Raman spectra of a series of substituted metal-free phthalocyanine compounds with four (1, 3, 5, 7) or eight (2, 4, 6, 8) methoxyl (1, 2, 5, 6) or methylthio groups (3, 4, 7, 8) on the nonperipheral (1-4) or peripheral positions (5-8) of the phthalocyanine ring are studied by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The calculated structural parameters and simulated electronic absorption and IR spectra are compared with the X-ray crystallography structures and the experimentally observed electronic absorption and IR spectra of the similar molecules, and good agreement between the calculated and experimental results is found. The substitution of the methoxyl or methylthio groups at the nonperipheral positions of the phthalocyanine ring has obvious effects on the molecular structure and spectroscopic properties of the metal-free phthalocyanine. Nonperipheral substitution has a more significant influence than peripheral substitution. The substitution effect increases with an increase in the number of substituents. The methylthio group shows more significant influence than the methoxyl group, despite the stronger electron-donating property of the methoxyl group than the methylthio group. The octa-methylthio-substituted metal-free phthalocyanine compounds have nonplanar structures whose low-lying occupied molecular orbitals and electronic absorption spectra are significantly changed by the substituents. The present systematical study will be helpful for understanding the relationship between structures and properties in phthalocyanine compounds and designing phthalocyanines with typical properties. Copyright © 2010 Elsevier Inc. All rights reserved.

  6. Elasticity of Substitution and Antidumping Measures

    DEFF Research Database (Denmark)

    Drud Hansen, Jørgen; Meinen, Philipp; Nielsen, Jørgen Ulff-Møller

    therefore also vary inversely with the elasticity of substitution at least for countries which have a strong focus on prices in the determination of their anti-dumping measures. We test this for ten countries from 1990 to 2009 using data on anti-dumping from Chad Bown (2010) and US-data at 8-digit level......Abstract This paper analyzes the role of the elasticity of substitution for anti-dumping decisions across countries. In monopolistic competition models with cost heterogeneous firms across countries, price differences vary inversely with the elasticity of substitution. Anti-dumping duties should...

  7. Biologic and synthetic skin substitutes: An overview

    OpenAIRE

    Halim, Ahmad Sukari; Khoo, Teng Lye; Mohd. Yussof, Shah Jumaat

    2010-01-01

    The current trend of burn wound care has shifted to more holistic approach of improvement in the long-term form and function of the healed burn wounds and quality of life. This has demanded the emergence of various skin substitutes in the management of acute burn injury as well as post burn reconstructions. Skin substitutes have important roles in the treatment of deep dermal and full thickness wounds of various aetiologies. At present, there is no ideal substitute in the market. Skin substit...

  8. Vitreous substitutes:challenges and directions

    Directory of Open Access Journals (Sweden)

    Qian-Ying Gao

    2015-06-01

    Full Text Available Thenatural vitreous body has a fine structure and complex functions. The imitation of the natural vitreous body by vitreous substitutes is a challenging work for both researchers and ophthalmologists. Gases, silicone oil, heavy silicone oil and hydrogels, particularly the former two vitreous substitutes are clinically widely used with certain complications. Those, however, are not real artificial vitreous due to lack of structure and function like the natural vitreous body. This article reviews the situations, challenges, and future directions in the development of vitreous substitutes, particularly the experimental and clinical use of a new artificial foldable capsular vitreous body .

  9. Chromium Substituted Cobalt Ferrites by Glycine-Nitrates Process

    Directory of Open Access Journals (Sweden)

    Dana Gingasu

    2015-12-01

    Full Text Available Chromium substituted cobalt ferrites (CoFe2–xCrxO4, 0 ≤ x ≤ 2 were synthesized through solution combustion method using glycine as fuel, named glycine-nitrates process (GNP. As evidenced by X-ray diffraction data (XRD, single cubic spinel phase was formed for all CoFe2–xCrxO4 (0 ≤ x ≤ 2 series. The cubic lattice parameter (a decreases with increasing chromium content. Room temperature 57Fe Mössbauer spectra revealed the Fe3+ and Cr3+ site occupancy, the local hyperfine magnetic fields and the substitution of Fe3+ by Cr3+ in the lattice. Scanning electron microscopy (SEM showed a refinement of particle size with the increase of Cr3+ content. Magnetic measurements from 5 K to 120 K have shown a dropping in the saturation magnetization as the chromium content increases. This behaviour has been explained in terms of substitution of Fe3+ by Cr3+ in the cubic lattice of cobalt ferrite.

  10. Recognizing nitrogen dopant atoms in graphene using atomic force microscopy

    DEFF Research Database (Denmark)

    van der Heijden, Nadine J.; Smith, Daniel; Calogero, Gaetano

    2016-01-01

    as a benchmark, we show that the position of the dopant atoms can be determined using atomic force microscopy. Specifically, the frequency shift-distance curves Delta f(z) acquired above a N atom are significantly different from the curves measured over a C atom. Similar behavior was found for N-doped graphene...

  11. Spectral properties of substituted coumarins in solution and polymer matrices.

    Science.gov (United States)

    Donovalová, Jana; Cigáň, Marek; Stankovičová, Henrieta; Gašpar, Jan; Danko, Martin; Gáplovský, Anton; Hrdlovič, Pavol

    2012-03-14

    The absorption and fluorescence spectra of substituted coumarins (2-oxo-2H-chromenes) were investigated in solvents and in polymer matrices. The substitutions involved were: (1) by groups with varying electron donating ability such as CH₃, OCH₃ and N(CH₃)₂, mainly, but not exclusively, in positions 7 and (2), by either CHO or 4-PhNHCONHN=CH- in position 3. While the spectra of non-substituted coumarin-3-carbaldehyde has absorptions at approximately 305 and 350 nm, substitution at position 7 leads to remarkable changes in the shape of the absorption spectrum and shifts the absorption to a longer wavelength. Similarly, the replacement of the formyl group with a semicarbazide group substantially influences the shape of the absorption spectrum, and coumarins which have only N(CH₃)₂ in position 7 experience small changes. These changes are associated with the increasing intramolecular charge transfer (ICT) character and increasing conjugation length of the chromophoric system, respectively, in the studied molecules. The fluorescence is almost negligible for derivatives which have H in this position. With increasing electron donating ability, and the possibility of a positive mesomeric (+M) effect of the substituent in position 7 of the coumarin moiety, the fluorescence increases, and this increase is most intense when N(CH₃)₂ substitutes in this position, for both 3-substituted derivatives. Spectral measurements of the studied coumarins in polymer matrices revealed that the absorption and fluorescence maxima lay within the maxima for solvents, and that coumarins yield more intense fluorescence in polymer matrices than when they are in solution. The quantum yield of derivatives which have a dimethylamino group in position 7 in polymer matrices approaches 1, and the fluorescence lifetime is within the range of 0.5-4 ns. The high quantum yield of 7-dimethylamino derivatives qualifies them as laser dyes which have k(F) higher than k(nr) in the given medium

  12. Spectral Properties of Substituted Coumarins in Solution and Polymer Matrices

    Directory of Open Access Journals (Sweden)

    Jana Donovalová

    2012-03-01

    Full Text Available The absorption and fluorescence spectra of substituted coumarins (2-oxo-2H-chromenes were investigated in solvents and in polymer matrices. The substitutions involved were: (1 by groups with varying electron donating ability such as CH3, OCH3 and N(CH32, mainly, but not exclusively, in positions 7 and (2, by either CHO or 4-PhNHCONHN=CH- in position 3. While the spectra of non-substituted coumarin-3-carbaldehyde has absorptions at approximately 305 and 350 nm, substitution at position 7 leads to remarkable changes in the shape of the absorption spectrum and shifts the absorption to a longer wavelength. Similarly, the replacement of the formyl group with a semicarbazide group substantially influences the shape of the absorption spectrum, and coumarins which have only N(CH32 in position 7 experience small changes. These changes are associated with the increasing intramolecular charge transfer (ICT character and increasing conjugation length of the chromophoric system, respectively, in the studied molecules. The fluorescence is almost negligible for derivatives which have H in this position. With increasing electron donating ability, and the possibility of a positive mesomeric (+M effect of the substituent in position 7 of the coumarin moiety, the fluorescence increases, and this increase is most intense when N(CH32 substitutes in this position, for both 3-substituted derivatives. Spectral measurements of the studied coumarins in polymer matrices revealed that the absorption and fluorescence maxima lay within the maxima for solvents, and that coumarins yield more intense fluorescence in polymer matrices than when they are in solution. The quantum yield of derivatives which have a dimethylamino group in position 7 in polymer matrices approaches 1, and the fluorescence lifetime is within the range of 0.5–4 ns. The high quantum yield of 7-dimethylamino derivatives qualifies them as laser dyes which have kF higher than knr in the given medium. This

  13. Optical method of atomic ordering estimation

    Energy Technology Data Exchange (ETDEWEB)

    Prutskij, T. [Instituto de Ciencias, BUAP, Privada 17 Norte, No 3417, col. San Miguel Huyeotlipan, Puebla, Pue. (Mexico); Attolini, G. [IMEM/CNR, Parco Area delle Scienze 37/A - 43010, Parma (Italy); Lantratov, V.; Kalyuzhnyy, N. [Ioffe Physico-Technical Institute, 26 Polytekhnicheskaya, St Petersburg 194021, Russian Federation (Russian Federation)

    2013-12-04

    It is well known that within metal-organic vapor-phase epitaxy (MOVPE) grown semiconductor III-V ternary alloys atomically ordered regions are spontaneously formed during the epitaxial growth. This ordering leads to bandgap reduction and to valence bands splitting, and therefore to anisotropy of the photoluminescence (PL) emission polarization. The same phenomenon occurs within quaternary semiconductor alloys. While the ordering in ternary alloys is widely studied, for quaternaries there have been only a few detailed experimental studies of it, probably because of the absence of appropriate methods of its detection. Here we propose an optical method to reveal atomic ordering within quaternary alloys by measuring the PL emission polarization.

  14. In vitro Antibacterial Activity of 7-Substituted-6-Fluoroquinolone and 7-Substituted-6,8-Difluoroquinolone Derivatives.

    Science.gov (United States)

    Leyva-Ramos, Socorro; de Loera, Denisse; Cardoso-Ortiz, Jaime

    2017-01-01

    Fluoroquinolones are widely prescribed synthetic antimicrobial agents. Quinolones act by converting their targets, gyrase and topoisomerase IV, into toxic enzymes that fragment the bacterial chromosome; the irreversible DNA damage eventually causes the killing of bacteria. Thorough knowledge of the structure-activity relationship of quinolones is essential for the development of new drugs with improved activity against resistant strains. The compounds were screened for their antibacterial activity against 4 representing strains using the Kirby-Bauer disk diffusion method. Minimal inhibitory concentration (MIC) was determined by measuring the diameter of the inhibition zone using concentrations between 250 and 0.004 μg/mL. MIC of derivatives 2, 3, and 4 showed potent antimicrobial activity against gram-positive and gram-negative bacteria. The effective concentrations were 0.860 μg/mL or lower. MIC for compounds 5-11 were between 120 and 515 μg/mL against Escherichia coli and Staphylococcus aureus, and substituted hydrazinoquinolones 7-10 showed poor antibacterial activity against gram-positive and gram-negative bacteria compared with other quinolones. Compounds obtained by modifications on C-7 of norfloxacin with the acetylated piperazinyl, halogen atoms, and substituted hydrazinyl showed good in vitro activity - some even better than the original compound. © 2017 S. Karger AG, Basel.

  15. The effect of cobalt substitution on magnetic hardening of magnetite

    Energy Technology Data Exchange (ETDEWEB)

    Mozaffari, M., E-mail: mozafari@sci.ui.ac.ir [Department of Physics, Faculty of Science, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Hadadian, Y. [Physics Department, Razi University, Taghebostan, Kermanshah (Iran, Islamic Republic of); Aftabi, A. [Department of Physics, University of Kurdistan, Sanandaj 66177-15175 (Iran, Islamic Republic of); Oveisy Moakhar, M. [Physics Department, Razi University, Taghebostan, Kermanshah (Iran, Islamic Republic of)

    2014-03-15

    In this work cobalt-substituted magnetite (Co{sub x}Fe{sub 1−x}Fe{sub 2}O{sub 4}, x=0, 0.25, 0.50 and 0.75) nanoparticles were synthesized by coprecipitation method and their structural and magnetic properties were investigated. X-ray diffraction was carried out and the results show that all of the samples have single phase spinel structure. Microstructure of the samples was studied using a field emission scanning electron microscope and the results show that particle sizes of the prepared nanoparticles were uniform and in the 50–55 nm range. Room temperature magnetic properties of the nanoparticles were measured by an alternating gradient force magnetometer and the results revealed that substituting cobalt for iron in magnetite structure, changes the magnetite from a soft magnetic material to a hard one. So that coercivity changes from 0 (a superparamagnetic state) to 337 Oe (a hard magnetic material), which is a remarkable change. Curie temperatures of the samples were determined by recording their susceptibility-temperature (χ–T) curves and the results show that by increasing cobalt content, Curie temperature of the samples also increases. Also χ–T curves of the samples were recorded from above Curie temperature to room temperature (first cooling), while the curves in the second heating and second cooling have the same behaviour as the first cooling curve. The results depict that all samples have different behaviour in the first cooling and in the first heating processes. This shows remarkable changes of the cation distribution in the course of first heating. - Highlights: • It is possible to get Co substituted magnetite nanoparticles by coprecipitation method. • Prepared nanoparticles have different cation distribution in comparison with that of bulk counterparts. • Co substitution increases coercivity of the magnetite.

  16. Magnetic Behaviour Of Bismuth Substituted Perovskites La1-xBixMn0.8Co0.2O3

    International Nuclear Information System (INIS)

    Choudhary, B. L.; Krishnamurthy, Anjali; Srivastava, Bipin K.

    2010-01-01

    DC magnetization measurements have been made on two systems with 30 atomic% and 50 atomic% substitutions of Bi for La in the perovskite LaMn 0.8 Co 0.2 O 3 . At 50 atomic% substitution the system switches over from hexagonal to orthorhombic structure. The two systems are ferromagnetic and the Curie temperature decreasing with increasing substitution of Bi; showing weakening of ferromagnetism. Departures between magnetization (M)--temperature (T) curves and observed dynamic relaxation are indicative of magnetic disorder. However, for both the samples the magnetic field (upto 1 kOe) does not show a marked effect on the peak temperature, T m in M--T curves recorded in zero field cooling mode.

  17. Magnetic hysterysis evolution of Ni-Al alloy with Fe and Mn substitution by vacuum arc melting to produce the room temperature magnetocaloric effect material

    Energy Technology Data Exchange (ETDEWEB)

    Notonegoro, Hamdan Akbar [PPS Materials Science, FMIPA-Universitas Indonesia, Depok 16424 (Indonesia); Mechanical Engineering Dept., FT-Universitas Sultan Ageng Tirtayasa, Cilegon 42435 (Indonesia); Kurniawan, Budhy; Manaf, Azwar, E-mail: azwar@sci.ui.ac.id [PPS Materials Science, FMIPA-Universitas Indonesia, Depok 16424 (Indonesia); Setiawan, Jan [Center for Nuclear Fuel Tecnology-Badan Tenaga Atom Nasional, Tangerang Selatan 15310 (Indonesia)

    2016-06-17

    The development of magnetocaloric effect (MCE) material is done in order to reduce the damage of the ozone layer caused by the chlorofluorocarbons (CFCs) emitted into the air. The research dealing with synthesis of magnetocaloric materials based of Ni-Al Heusler Alloy structure and by varying substitution some atoms of Ni with Fe and Al with Mn on Ni-Al Heusler Alloy structure to become Ni{sub 44}Fe{sub 6}Mn{sub 32}Al{sub 18}. Vacuum Arc Melting (VAM) equipment is used to form the alloys on vacuum condition and by flowing argon gas atmosphere and then followed by annealing process for 72 hours. X-Ray Diffraction (XRD) reveals that crystallite structure of material is observed. We define that Ni{sub 44}Fe{sub 6} as X{sub 2}, Mn{sub 25} as Y, and Al{sub 18}Mn{sub 7} as Z. Based on the XRD result, we observed that the general formula X{sub 2}YZ is not changed. The PERMAGRAF measurement revealed that there exists of magnetic hysterysis. The hysterysis show that the magnetic structures of the system undego evolution from diamagnetic to soft ferromagnetic material which all of the compound have the same crystallite structure. This evolution indicated that the change in the composition has led to changes the magnetic composition. Mn is the major element that gives strong magnetic properties to the sample. When Mn partially replaced position of Al, the sample became dominant to be influenced to improve their magnetic properties. In addition, substitution a part of Ni by Fe in the composition reveals a pinning of the domain walls in the sample.

  18. Atomic oxygen stimulated outgassing

    Science.gov (United States)

    Linton, Roger C.; Reynolds, John M.

    1991-01-01

    The passive Long Duration Exposure Facility (LDEF) Experiment A0034, Atomic Oxygen Simulated Outgassing, consisted of two identical one-sixth tray modules, exposing selected thermal control coatings to atomic oxygen and the combined space environment on the leading edge and, for reference, to the relative wake environment on the trailing edge. Optical mirrors were included adjacent to the thermal coatings for deposition of outgassing products. Ultraviolet grade windows and metal covers were provided for additional assessment of the effects of the various environmental factors. Preliminary results indicate that orbital atomic oxygen is both a degrading and a optically restorative factor in the thermo-optical properties of selected thermal coatings. There is evidence of more severe optical degradation on collector mirrors adjacent to coatings that were exposed to the RAM-impinging atomic oxygen. This evidence of atomic oxygen stimulated outgassing is discussed in relation to alternative factors that could affect degradation. The general effects of the space environment on the experiment hardware as well as the specimens are discussed.

  19. Hydroxylation of p-substituted phenols by tyrosinase: Further insight into the mechanism of tyrosinase activity

    Energy Technology Data Exchange (ETDEWEB)

    Munoz-Munoz, Jose Luis [GENZ - Grupo de Investigacion Enzimologia, Departamento de Bioquimica y Biologia Molecular-A, Facultad de Biologia, Campus Internacional de Excelencia Campus Mare Nostrum, Universidad de Murcia, E-30100 Espinardo, Murcia (Spain); Berna, Jose [Grupo de Quimica Organica Sintetica, Departamento de Quimica Organica, Facultad de Quimica Campus Internacional de Excelencia Campus Mare Nostrum, Universidad de Murcia (Spain); Garcia-Molina, Maria del Mar; Garcia-Molina, Francisco [GENZ - Grupo de Investigacion Enzimologia, Departamento de Bioquimica y Biologia Molecular-A, Facultad de Biologia, Campus Internacional de Excelencia Campus Mare Nostrum, Universidad de Murcia, E-30100 Espinardo, Murcia (Spain); Garcia-Ruiz, Pedro Antonio [QCPAI - Grupo de Quimica de Carbohidratos, Polimeros y Aditivos Industriales, Departamento de Quimica Organica, Facultad de Quimica Campus Internacional de Excelencia Campus Mare Nostrum, Universidad de Murcia (Spain); Varon, Ramon [Departamento de Quimica-Fisica, Escuela de Ingenieros Industriales de Albacete, Universidad de Castilla la Mancha, Avda. Espana s/n. Campus Universitario, E-02071 Albacete (Spain); and others

    2012-07-27

    Highlights: Black-Right-Pointing-Pointer The action the copper complexes and tyrosinase on phenols is equivalent. Black-Right-Pointing-Pointer Isotope effect showed that nucleophilic attack to copper atom may be the slower step. Black-Right-Pointing-Pointer The value of {rho} (Hammett constant) supports an electrophilic aromatic substitution. Black-Right-Pointing-Pointer Data obtained in steady state pH 7 conditions support the mechanism of Scheme 1SM. -- Abstract: A study of the monophenolase activity of tyrosinase by measuring the steady state rate with a group of p-substituted monophenols provides the following kinetic information: k{sub cat}{sup m} and the Michaelis constant, K{sub M}{sup m}. Analysis of these data taking into account chemical shifts of the carbon atom supporting the hydroxyl group ({delta}) and {sigma}{sub p}{sup +}, enables a mechanism to be proposed for the transformation of monophenols into o-diphenols, in which the first step is a nucleophilic attack on the copper atom on the form E{sub ox} (attack of the oxygen of the hydroxyl group of C-1 on the copper atom) followed by an electrophilic attack (attack of the hydroperoxide group on the ortho position with respect to the hydroxyl group of the benzene ring, electrophilic aromatic substitution with a reaction constant {rho} of -1.75). These steps show the same dependency on the electronic effect of the substituent groups in C-4. Furthermore, a study of a solvent deuterium isotope effect on the oxidation of monophenols by tyrosinase points to an appreciable isotopic effect. In a proton inventory study with a series of p-substituted phenols, the representation of k{sub cat}{sup f{sub n}}/k{sub cat}{sup f{sub 0}} against n (atom fractions of deuterium), where k{sub cat}{sup f{sub n}} is the catalytic constant for a molar fraction of deuterium (n) and k{sub cat}{sup f{sub 0}} is the corresponding kinetic parameter in a water solution, was linear for all substrates. These results indicate that

  20. Hydroxylation of p-substituted phenols by tyrosinase: Further insight into the mechanism of tyrosinase activity

    International Nuclear Information System (INIS)

    Muñoz-Muñoz, Jose Luis; Berna, Jose; García-Molina, María del Mar; Garcia-Molina, Francisco; Garcia-Ruiz, Pedro Antonio; Varon, Ramon

    2012-01-01

    Highlights: ► The action the copper complexes and tyrosinase on phenols is equivalent. ► Isotope effect showed that nucleophilic attack to copper atom may be the slower step. ► The value of ρ (Hammett constant) supports an electrophilic aromatic substitution. ► Data obtained in steady state pH 7 conditions support the mechanism of Scheme 1SM. -- Abstract: A study of the monophenolase activity of tyrosinase by measuring the steady state rate with a group of p-substituted monophenols provides the following kinetic information: k cat m and the Michaelis constant, K M m . Analysis of these data taking into account chemical shifts of the carbon atom supporting the hydroxyl group (δ) and σ p + , enables a mechanism to be proposed for the transformation of monophenols into o-diphenols, in which the first step is a nucleophilic attack on the copper atom on the form E ox (attack of the oxygen of the hydroxyl group of C-1 on the copper atom) followed by an electrophilic attack (attack of the hydroperoxide group on the ortho position with respect to the hydroxyl group of the benzene ring, electrophilic aromatic substitution with a reaction constant ρ of −1.75). These steps show the same dependency on the electronic effect of the substituent groups in C-4. Furthermore, a study of a solvent deuterium isotope effect on the oxidation of monophenols by tyrosinase points to an appreciable isotopic effect. In a proton inventory study with a series of p-substituted phenols, the representation of k cat f n /k cat f 0 against n (atom fractions of deuterium), where k cat f n is the catalytic constant for a molar fraction of deuterium (n) and k cat f 0 is the corresponding kinetic parameter in a water solution, was linear for all substrates. These results indicate that only one of the proton transfer processes from the hydroxyl groups involved the catalytic cycle is responsible for the isotope effects. We suggest that this step is the proton transfer from the hydroxyl group

  1. Peripheral dysgraphia characterized by the co-occurrence of case substitutions in uppercase and letter substitutions in lowercase writing.

    Science.gov (United States)

    Di Pietro, M; Schnider, A; Ptak, R

    2011-10-01

    Patients with peripheral dysgraphia due to impairment at the allographic level produce writing errors that affect the letter-form and are characterized by case confusions or the failure to write in a specific case or style (e.g., cursive). We studied the writing errors of a patient with pure peripheral dysgraphia who had entirely intact oral spelling, but produced many well-formed letter errors in written spelling. The comparison of uppercase print and lowercase cursive spelling revealed an uncommon pattern: while most uppercase errors were case substitutions (e.g., A - a), almost all lowercase errors were letter substitutions (e.g., n - r). Analyses of the relationship between target letters and substitution errors showed that errors were neither influenced by consonant-vowel status nor by letter frequency, though word length affected error frequency in lowercase writing. Moreover, while graphomotor similarity did not predict either the occurrence of uppercase or lowercase errors, visuospatial similarity was a significant predictor of lowercase errors. These results suggest that lowercase representations of cursive letter-forms are based on a description of entire letters (visuospatial features) and are not - as previously found for uppercase letters - specified in terms of strokes (graphomotor features). Copyright © 2010 Elsevier Srl. All rights reserved.

  2. Compilation of data from hadronic atoms

    International Nuclear Information System (INIS)

    Poth, H.

    1979-01-01

    This compilation is a survey of the existing data of hadronic atoms (pionic-atoms, kaonic-atoms, antiprotonic-atoms, sigmonic-atoms). It collects measurements of the energies, intensities and line width of X-rays from hadronic atoms. Averaged values for each hadronic atom are given and the data are summarized. The listing contains data on 58 pionic-atoms, on 54 kaonic-atoms, on 23 antiprotonic-atoms and on 20 sigmonic-atoms. (orig./HB) [de

  3. Questioning nuclear waste substitution: a case study.

    Science.gov (United States)

    Marshall, Alan

    2007-03-01

    This article looks at the ethical quandaries, and their social and political context, which emerge as a result of international nuclear waste substitution. In particular it addresses the dilemmas inherent within the proposed return of nuclear waste owned by Japanese nuclear companies and currently stored in the United Kingdom. The UK company responsible for this waste, British Nuclear Fuels Limited (BNFL), wish to substitute this high volume intermediate-level Japanese-owned radioactive waste for a much lower volume of much more highly radioactive waste. Special focus is given to ethical problems that they, and the UK government, have not wished to address as they move forward with waste substitution. The conclusion is that waste substitution can only be considered an ethical practice if a set of moderating conditions are observed by all parties. These conditions are listed and, as of yet, they are not being observed.

  4. Towards hemerythrin-based blood substitutes: Comparative ...

    Indian Academy of Sciences (India)

    related reactivity is lower than that of hemoglobin, which may warrant investigation of hemerythrin as raw material for artificial oxygen carriers ('blood substitutes'). We report here the first biological tests for hemerythrin and its chemical derivatives, ...

  5. Symbolic Substitution Methods For Optical Computing

    Science.gov (United States)

    Murdocca, M. J.; Huang, A.

    1989-02-01

    Symbolic substitution is a method of computing based on parallel binary pattern replacement, that can be implemented with simple optical components and regular free-space interconnection schemes. A two-dimensional pattern is searched for in parallel in an array and is replaced with another pattern. Pattern transformation rules can be applied sequentially or in parallel to realize complex functions. When the substitution space is modified to be loge SIT connected for N binary spots, and masks are allowed to customize the system, then optical digital circuits using symbolic substitution for network interconnects can be made nearly as efficient in terms of gate count and circuit depth as conventional arbitrary interconnection schemes allow. We describe an optical setup that requires no more than a fanin and fanout of two using optically nonlinear logic devices and a free space interconnection scheme based on symbolic substitution.

  6. Synthesis and biological activities of substituted N ...

    African Journals Online (AJOL)

    use

    2011-12-07

    Dec 7, 2011 ... The present study describes the synthesis, antioxidant and antibacterial activities of substituted N'- benzoylhydrazone derivatives, to ... addition, the dramatically rising prevalence of multidrug- resistant microbial infections has ...... extract of Chinese green tea (Camellia sinensis) on Listeria monocytogenes.

  7. SYNTHESIS OF SUBSTITUTED FLAVONE DERIVATIVES AS ...

    African Journals Online (AJOL)

    Preferred Customer

    results showed that this skeletal framework exhibited marked potency as antimicrobial agents. KEY WORDS. KEY WORDS: Chalcone ... It showed significant role in pharmaceutical effects [1] including leishmanicidal activity, oviposter ... new substituted flavone derivative as potent antimicrobial agent. EXPERIMENTAL.

  8. Transnationalism and integration : complements or Substitutes?

    NARCIS (Netherlands)

    Dekker, B.; Siegel, M.

    2013-01-01

    This paper investigates the relationship between transnational practices and integration by testing whether they are substitutes or complements. For this purpose, we use a multidimensional transnationalism index. The index includes three dimensions of transnational practices, including migrants'

  9. Development of a diesel substitute fuel

    Energy Technology Data Exchange (ETDEWEB)

    Reiter, Anton; Mair-Zelenka, Philipp [Graz Univ. of Technology (Austria). Inst. of Chemical Engineering and Environmental Technology; Zeymer, Marc [OMV Refining and Marketing GmbH, Vienna (Austria). MRDI-D Product Development and Innovation

    2013-06-01

    Substitute fuels composed of few real chemical compounds are an alternative characterisation approach for conventional fuels as opposed to the traditional pseudo-component method. With the algorithm proposed in this paper the generation of such substitutes will be facilitated and well-established thermodynamic methods can be applied for physical property-data prediction. Based on some quality criteria like true boiling-point curve, liquid density, C/H ratio, or cloud point of a target fuel a surrogate which meets these properties is determined by fitting its composition. The application and capabilities of the algorithm developed are demonstrated by means of an exemplary diesel substitute fuel. The substitute mixture obtained can be generated and used for evaluation of property-prediction methods. Furthermore this approach can help to understand the effects of mixing fossil fuels with biogenic compounds. (orig.)

  10. 47 CFR 76.110 - Substitutions.

    Science.gov (United States)

    2010-10-01

    ... blackout rules at § 76.111, substitute a program from any other television broadcast station. Programs... CABLE TELEVISION SERVICE Network Non-duplication Protection, Syndicated Exclusivity and Sports Blackout...

  11. Substituted hydroxyapatites for biomedical applications: A review

    Czech Academy of Sciences Publication Activity Database

    Šupová, Monika

    2015-01-01

    Roč. 41, č. 8 (2015), s. 9203-9231 ISSN 0272-8842 Institutional support: RVO:67985891 Keywords : bioapatite * calcium phosphate * hydroxyapatite * substitution Subject RIV: JJ - Other Materials Impact factor: 2.758, year: 2015

  12. Synthesis of substituted 2-cyanoarylboronic esters

    DEFF Research Database (Denmark)

    Lysén, Morten; Hansen, Henriette M; Begtrup, Mikael

    2006-01-01

    The synthesis of substituted 2-cyanoarylboronic esters is described via lithiation/in situ trapping of the corresponding methoxy-, trifluoromethyl-, fluoro-, chloro-, and bromobenzonitriles. The crude arylboronic esters were obtained in high yields and purities and with good regioselectivities....

  13. Substitution within the Danish printing industry

    DEFF Research Database (Denmark)

    Larsen, Henrik Fred; Bøg, Carsten

    2009-01-01

    The implementation of the EU REACH regulation will most probably promote substitution within sectors handling a lot of different chemicals like the printing industry. With the aim of being at the cutting edge of this development the Danish EPA together with the Danish printing industry and IPU...... are running a substitution project. A major part of the work has been mapping the presence of chemicals which are potential candidates for substitution (e.g. PBT, CMR, vPvB, EDS) within the Danish printing industry and this work was recently finished. The mapping comprises a combination of a literature study...... total 15 substances) were found in the Danish printing industry. This paper presents the results of the mapping of chemical candidates and the first results on preparing for actual substitutions....

  14. Towards hemerythrin-based blood substitutes

    Indian Academy of Sciences (India)

    related reactivity is lower than that of hemoglobin, which may warrant investigation of hemerythrin as raw material for artificial oxygen carriers ('blood substitutes'). We report here the first biological tests for hemerythrin and its chemical derivatives, ...

  15. Accelerators for atomic energy research

    International Nuclear Information System (INIS)

    Shibata, Tokushi

    1999-01-01

    The research and educational activities accomplished using accelerators for atomic energy research were studied. The studied items are research subjects, facility operation, the number of master theses and doctor theses on atomic energy research using accelerators and the future role of accelerators in atomic energy research. The strategy for promotion of the accelerator facility for atomic energy research is discussed. (author)

  16. Atomic nucleus and elementary particles

    International Nuclear Information System (INIS)

    Zakrzewski, J.

    1976-01-01

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

  17. Product portfolio optimization based on substitution

    DEFF Research Database (Denmark)

    Myrodia, Anna; Moseley, A.; Hvam, Lars

    2017-01-01

    The development of production capabilities has led to proliferation of the product variety offered to the customer. Yet this fact does not directly imply increase of manufacturers' profitability, nor customers' satisfaction. Consequently, recent research focuses on portfolio optimization through...... substitution and standardization techniques. However when re-defining the strategic market decisions are characterized by uncertainty due to several parameters. In this study, by using a GAMS optimization model we present a method for supporting strategic decisions on substitution, by quantifying the impact...

  18. Substitutability between Equity REITs and Mortgage REITs

    OpenAIRE

    Ming-Long Lee; Kevin C.H. Chiang

    2004-01-01

    This study extends Seck’s (1996) approach to investigate the degree of substitutability between equity real estate investment trusts (EREITs) and mortgage real estate investment trusts (MREITs). The variance ratio test and the variance decomposition of forecast errors yield results indicating the existence of informational commonality between EREITs and MREITs. The findings indicate that the two types of REITs are substitutable. A direct implication is that investors who believe they have s...

  19. Competition Among Near-Substitutable Systems

    Science.gov (United States)

    2012-09-01

    the context of the dominant “Weapon System Franchise ” model of competition for major defense acquisition programs (MDAPs). Competition between near...leading to the award of a franchise . AoAs or other cost-effectiveness analyses can be pivotal in bringing attention to near-substitute systems. However...Symposium, 18-19 Sep 2012, Fort Belvoir, VA. U.S. Government or Federal Rights License 14. ABSTRACT We define near-substitutable systems as systems that

  20. Trace maps of general substitutional sequences

    International Nuclear Information System (INIS)

    Kolar, M.; Nori, F.

    1990-01-01

    It is shown that for arbitrary n, there exists a trace map for any n-letter substitutional sequence. Trace maps are explicitly obtained for the well-known circle and Rudin-Shapiro sequences which can be defined by means of substitution rules on three and four letters, respectively. The properties of the two trace maps and their consequences for various spectral properties are briefly discussed

  1. Graphene as a flexible template for controlling magnetic interactions between metal atoms.

    Science.gov (United States)

    Lee, Sungwoo; Kim, Dongwook; Robertson, Alex W; Yoon, Euijoon; Hong, Suklyun; Ihm, Jisoon; Yu, Jaejun; Warner, Jamie H; Lee, Gun-Do

    2017-03-01

    Metal-doped graphene produces magnetic moments that have potential application in spintronics. Here we use density function theory computational methods to show how the magnetic interaction between metal atoms doped in graphene can be controlled by the degree of flexure in a graphene membrane. Bending graphene by flexing causes the distance between two substitutional Fe atoms covalently bonded in graphene to gradually increase and these results in the magnetic moment disappearing at a critical strain value. At the critical strain, a carbon atom can enter between the two Fe atoms and blocks the interaction between relevant orbitals of Fe atoms to quench the magnetic moment. The control of interactions between doped atoms by exploiting the mechanical flexibility of graphene is a unique approach to manipulating the magnetic properties and opens up new opportunities for mechanical-magnetic 2D device systems.

  2. Rydberg atoms in strong fields

    International Nuclear Information System (INIS)

    Kleppner, D.; Tsimmerman, M.

    1985-01-01

    Experimental and theoretical achievements in studying Rydberg atoms in external fields are considered. Only static (or quasistatic) fields and ''one-electron'' atoms, i.e. atoms that are well described by one-electron states, are discussed. Mainly behaviour of alkali metal atoms in electric field is considered. The state of theoretical investigations for hydrogen atom in magnetic field is described, but experimental data for atoms of alkali metals are presented as an illustration. Results of the latest experimental and theoretical investigations into the structure of Rydberg atoms in strong fields are presented

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

    Science.gov (United States)

    Nishikawa, Osamu; Taniguchi, Masahiro

    2017-04-01

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

  4. Sampling the Hydrogen Atom

    Directory of Open Access Journals (Sweden)

    Graves N.

    2013-01-01

    Full Text Available A model is proposed for the hydrogen atom in which the electron is an objectively real particle orbiting at very near to light speed. The model is based on the postulate that certain velocity terms associated with orbiting bodies can be considered as being af- fected by relativity. This leads to a model for the atom in which the stable electron orbits are associated with orbital velocities where Gamma is n /α , leading to the idea that it is Gamma that is quantized and not angular momentum as in the Bohr and other models. The model provides a mechanism which leads to quantization of energy levels within the atom and also provides a simple mechanical explanation for the Fine Struc- ture Constant. The mechanism is closely associated with the Sampling theorem and the related phenomenon of aliasing developed in the mid-20th century by engineers at Bell labs.

  5. US Atomic Energy Law

    International Nuclear Information System (INIS)

    1981-01-01

    This is a new volume follows in the series supplementing the volumes 11 and 12 published in 1965 and 1966, updating the collection of Federal Acts and Executive Orders of the President of the United States of America relating to atomic energy legislation. Since the publication of volumes 11 and 12, the US Atomic Energy Act of 1954 alone has been amended 25 times, mainly as a consequence of by the Nuclear Non-Proliferation Act and the Uranium Mill Tailings Radiation Control Act, both of 1978. The Atomic Energy Act of 1954 is supplemented by a selection of the most important Federal Acts, Executive Orders of the President and Resolutions of the Congress. (orig./HSCH) [de

  6. CP violation in atoms

    International Nuclear Information System (INIS)

    Barr, S.M.

    1992-01-01

    Electric dipole moments of large atoms are an excellent tool to search for CP violation beyond the Standard Model. These tell us about the electron EDM but also about CP-violating electron-nucleon dimension-6 operators that arise from Higgs-exchange. Rapid strides are being made in searches for atomic EDMs. Limits on the electron EDM approaching the values which would be expected from Higgs-exchange mediated CP violation have been achieved. It is pointed out that in this same kind of model if tan β is large the effects in atoms of the dimension-6 e - n operators may outweigh the effect of the electron EDM. (author) 21 refs

  7. Substituting missing data in compositional analysis

    Energy Technology Data Exchange (ETDEWEB)

    Real, Carlos, E-mail: carlos.real@usc.es [Area de Ecologia, Departamento de Biologia Celular y Ecologia, Escuela Politecnica Superior, Universidad de Santiago de Compostela, 27002 Lugo (Spain); Angel Fernandez, J.; Aboal, Jesus R.; Carballeira, Alejo [Area de Ecologia, Departamento de Biologia Celular y Ecologia, Facultad de Biologia, Universidad de Santiago de Compostela, 15782 Santiago de Compostela (Spain)

    2011-10-15

    Multivariate analysis of environmental data sets requires the absence of missing values or their substitution by small values. However, if the data is transformed logarithmically prior to the analysis, this solution cannot be applied because the logarithm of a small value might become an outlier. Several methods for substituting the missing values can be found in the literature although none of them guarantees that no distortion of the structure of the data set is produced. We propose a method for the assessment of these distortions which can be used for deciding whether to retain or not the samples or variables containing missing values and for the investigation of the performance of different substitution techniques. The method analyzes the structure of the distances among samples using Mantel tests. We present an application of the method to PCDD/F data measured in samples of terrestrial moss as part of a biomonitoring study. - Highlights: > Missing values in multivariate data sets must be substituted prior to analysis. > The substituted values can modify the structure of the data set. > We developed a method to estimate the magnitude of the alterations. > The method is simple and based on the Mantel test. > The method allowed the identification of problematic variables in a sample data set. - A method is presented for the assessment of the possible distortions in multivariate analysis caused by the substitution of missing values.

  8. Atoms in Slovakia

    International Nuclear Information System (INIS)

    Danis, D.; Feik, K.; Florek, M.; Kmosena, J.; Chrapan, J.; Morovic, M.; Slugen, V.; Seliga, M.; Valovic, J.

    2006-01-01

    In this book the history of development of using of nuclear energy in the Slovak Republic as well as in the Czechoslovakia (before 1993 year) is presented. The aim of the book is to preserve the memory of the period when the creation and development of nuclear physics, technology, nuclear medicine, radioecology and energetics in Slovakia occurred - as witnessed by people who experienced this period and to adapt it to future generations. The Editorial board of the SNUS collected the views of 60 contributors and distinguished workers - Slovakian experts in nuclear science, education and technology. Calling upon a wide spectrum of experts ensured an objective historical description of the period. A huge amount of subjective views on recent decades were collected and supported by a wealth of photographic documentation. This created a synthesised reflection on the history of the 'atoms' in Slovakia. The book contains 15 tables, 192 black and white and 119 colour pictures from around the world and from places involved in the compilation of the study and with the study of atomic science in Slovakia. The main chapters are as follows: Atoms in the world, Atoms in Slovakia, Atoms in the educational system, Atoms in health services (Radiology, Nuclear medicine, Radiation protection, the Cyclotron centre of the Slovak Republic), Radioecology, Other applications of irradiation, Nuclear energetics (Electric energy in the second half of the 20 th century, NPP Bohunice, NPP Mochovce, the back-end of Nuclear energetics, Big names in Nuclear energetics in Slovakia), Chronology and an Appendix entitled 'Slovak companies in nuclear energetics'

  9. Cavity quantum electrodynamics with a Rydberg-blocked atomic ensemble

    DEFF Research Database (Denmark)

    Guerlin, Christine; Brion, Etienne; Esslinger, Tilman

    2010-01-01

    The realization of a Jaynes-Cummings model in the optical domain is proposed for an atomic ensemble. The scheme exploits the collective coupling of the atoms to a quantized cavity mode and the nonlinearity introduced by coupling to high-lying Rydberg states. A two-photon transition resonantly...... effective Jaynes-Cummings model. We use numerical simulations to show that the cavity transmission can be used to reveal detailed properties of the Jaynes-Cummings ladder of excited states and that the atomic nonlinearity gives rise to highly nontrivial photon emission from the cavity. Finally, we suggest...... couples the single-atom ground state |g> to a Rydberg state |e>via a nonresonant intermediate state |i>, but due to the interaction between Rydberg atoms only a single atom can be resonantly excited in the ensemble. This restricts the state space of the ensemble to the collective ground state |G...

  10. Radiative processes of two entangled atoms in cosmic string spacetime

    Science.gov (United States)

    Cai, Huabing; Ren, Zhongzhou

    2018-01-01

    We investigate the radiative processes of two static two-level atoms in a maximally entangled state coupled to vacuum electromagnetic field in the cosmic string spacetime. We find that the decay rate from the entangled state to the ground state crucially depends on the atomic separation, the polarization directions of the individual atoms, the atom-string distance and the deficit angle induced by the string. As the atom-string distance increases, the decay rate oscillates around the result in Minkowski spacetime and the amplitude gradually decreases. The oscillation is more severe for larger planar angle deficit. We analyze the decay rate in different circumstances such as near zone and specific polarization cases. Some comparisons between symmetric and antisymmetric states are performed. By contrast with the case in Minkowski spacetime, we can reveal the effects of the cosmic string on the radiative properties of the entangled atoms.

  11. Polarized atomic beams for targets

    International Nuclear Information System (INIS)

    Grueebler, W.

    1984-01-01

    The basic principle of the production of polarized atomic hydrogen and deuterium beams are reviewed. The status of the present available polarization, density and intensity are presented. The improvement of atomic beam density by cooling the hydrogen atoms to low velocity is discussed. The possible use of polarized atomic beams as targets in storage rings is shown. It is proposed that polarized atomic beams can be used to produce polarized gas targets with high polarization and greatly improved density

  12. Stationary Electron Atomic Model

    Science.gov (United States)

    Pressler, David E.

    1998-04-01

    I will present a novel theory concerning the position and nature of the electron inside the atom. This new concept is consistant with present experimental evidence and adheres strictly to the valence-shell electron-pair repulsion (VSEPR) model presently used in chemistry for predicting the shapes of molecules and ions. In addition, I will discuss the atomic model concept as being a true harmonic oscillator, periodic motion at resonant frequency which produces radiation at discrete frequencies or line spectra is possible because the electron is under the action of two restoring forces, electrostatic attraction and superconducting respulsion of the electron's magnetic field by the nucleus.

  13. Warm Vapor Atom Interferometer

    Science.gov (United States)

    Biedermann, Grant; Wheeler, David; Jau, Yuan-Yu; McGuinness, Hayden

    2014-05-01

    We present a light pulse atom interferometer using room temperature rubidium vapor. Doppler sensitive stimulated Raman transitions forming the atom optical elements inherently select a cold velocity group for the interferometer. The interferometer is configured to be sensitive to accelerations. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  14. Atomic Force Microscope

    Energy Technology Data Exchange (ETDEWEB)

    Day, R.D.; Russell, P.E.

    1988-12-01

    The Atomic Force Microscope (AFM) is a recently developed instrument that has achieved atomic resolution imaging of both conducting and non- conducting surfaces. Because the AFM is in the early stages of development, and because of the difficulty of building the instrument, it is currently in use in fewer than ten laboratories worldwide. It promises to be a valuable tool for obtaining information about engineering surfaces and aiding the .study of precision fabrication processes. This paper gives an overview of AFM technology and presents plans to build an instrument designed to look at engineering surfaces.

  15. Korean atomic bomb victims.

    Science.gov (United States)

    Sasamoto, Yukuo

    2009-01-01

    After colonizing Korea, Japan invaded China, and subsequently initiated the Pacific War against the United States, Britain, and their allies. Towards the end of the war, U.S. warplanes dropped atomic bombs on Hiroshima and Nagasaki, which resulted in a large number of Koreans who lived in Hiroshima and Nagasaki suffering from the effects of the bombs. The objective of this paper is to examine the history of Korea atomic bomb victims who were caught in between the U.S., Japan, the Republic of Korea (South Korea) and the Democratic People's Republic of Korea (North Korea).

  16. Atomic bomb and leukemia

    Energy Technology Data Exchange (ETDEWEB)

    Ichimaru, Michito; Tomonaga, Masao; Amenomori, Tatsuhiko; Matsuo, Tatsuki (Nagasaki Univ. (Japan). School of Medicine)

    1991-03-01

    Characteristic features of leukemia among atomic bomb survivors were studied. The ratio of a single leukemia type to all leukemias was highest for CML in Hiroshima, and the occurrence of CML was thought to be most characteristic for atomic bomb radiation induced leukemia. In the distribution of AML subtypes of FAB classification, there was no M3 cases in 1 Gy or more group, although several atypical AML cases of survivors were observed. Chromosome study was conducted using colony forming cells induced by hemopoietic stem cells of peripheral blood of proximal survivors. Same chromosome aberrations were observed in colony forming cells and peripheral blood of proximal survivors. (author).

  17. Atoms in Agriculture

    Energy Technology Data Exchange (ETDEWEB)

    Osborne, Thomas S. [University of Tennessee

    1965-01-01

    Agriculture benefits from the applications of research. Radioactive techniques have been used to study soils, plants, microbes, insects, farm animals, and new ways to use and preserve foodstuffs. Radioactive atoms are not used directly by farmers but are used in research directed by the U. S. Department of Agriculture and Atomic Energy Commission, by the agricultural experiment stations of the various states, and by numerous public and private research institutions. From such research come improved materials and methods which are used on the farm.

  18. Optically pumped atoms

    CERN Document Server

    Happer, William; Walker, Thad

    2010-01-01

    Covering the most important knowledge on optical pumping of atoms, this ready reference is backed by numerous examples of modelling computation for optical pumped systems. The authors show for the first time that modern scientific computing software makes it practical to analyze the full, multilevel system of optically pumped atoms. To make the discussion less abstract, the authors have illustrated key points with sections of MATLAB codes. To make most effective use of contemporary mathematical software, it is especially useful to analyze optical pumping situations in the Liouville spa

  19. Machine Learning methods in fitting first-principles total energies for substitutionally disordered solid

    Science.gov (United States)

    Gao, Qin; Yao, Sanxi; Widom, Michael

    2015-03-01

    Density functional theory (DFT) provides an accurate and first-principles description of solid structures and total energies. However, it is highly time-consuming to calculate structures with hundreds of atoms in the unit cell and almost not possible to calculate thousands of atoms. We apply and adapt machine learning algorithms, including compressive sensing, support vector regression and artificial neural networks to fit the DFT total energies of substitutionally disordered boron carbide. The nonparametric kernel method is also included in our models. Our fitted total energy model reproduces the DFT energies with prediction error of around 1 meV/atom. The assumptions of these machine learning models and applications of the fitted total energies will also be discussed. Financial support from McWilliams Fellowship and the ONR-MURI under the Grant No. N00014-11-1-0678 is gratefully acknowledged.

  20. Atomic compressibility and reversible insertion of atoms into solids

    International Nuclear Information System (INIS)

    Connerade, J.P.; Semaoune, R.

    2000-01-01

    We developed a theoretical model to investigate the compressibility of atoms. Atoms are confined inside a spherical cavity, simulated numerically by a finite repulsive potential barrier. The energy levels and wavefunctions of confined atoms are determined by solving, for different cavity radii, the relativistic Dirac-Fock equations, including formally the repulsive barrier. The changes in the atomic size and in the ground-state energy level allow one to define a positive isotropic pressure exerted on the confined atom. The model is applied to atomic caesium and it is demonstrated quantitatively that the remarkable compressibility of caesium originates from a purely atomic mechanism, namely the pressure-induced collapse of the 5d orbital. We propose that this mechanism can also drive, at an atomic level, a reversible insertion of atoms into solids. Applications to lithium-ion batteries are briefly discussed at the end of this paper. (author)

  1. Spatially resolved photoionization of ultracold atoms on an atom chip

    International Nuclear Information System (INIS)

    Kraft, S.; Guenther, A.; Fortagh, J.; Zimmermann, C.

    2007-01-01

    We report on photoionization of ultracold magnetically trapped Rb atoms on an atom chip. The atoms are trapped at 5 μK in a strongly anisotropic trap. Through a hole in the chip with a diameter of 150 μm, two laser beams are focused onto a fraction of the atomic cloud. A first laser beam with a wavelength of 778 nm excites the atoms via a two-photon transition to the 5D level. With a fiber laser at 1080 nm the excited atoms are photoionized. Ionization leads to depletion of the atomic density distribution observed by absorption imaging. The resonant ionization spectrum is reported. The setup used in this experiment is suitable not only to investigate mixtures of Bose-Einstein condensates and ions but also for single-atom detection on an atom chip

  2. Atomic collisions related to atomic laser isotope separation

    International Nuclear Information System (INIS)

    Shibata, Takemasa

    1995-01-01

    Atomic collisions are important in various places in atomic vapor laser isotope separation (AVLIS). At a vaporization zone, many atomic collisions due to high density have influence on the atomic beam characteristics such as velocity distribution and metastable states' populations at a separation zone. In the separation zone, a symmetric charge transfer between the produced ions and the neutral atoms may degrade selectivity. We have measured atomic excitation temperatures of atomic beams and symmetric charge transfer cross sections for gadolinium and neodymium. Gadolinium and neodymium are both lanthanides. Nevertheless, results for gadolinium and neodymium are very different. The gadolinium atom has one 5d electron and neodymium atom has no 5d electron. It is considered that the differences are due to existence of 5d electron. (author)

  3. Atom Pairing in Optical Superlattices.

    Science.gov (United States)

    Kangara, J; Cheng, Chingyun; Pegahan, S; Arakelyan, I; Thomas, J E

    2018-02-23

    We study the pairing of fermions in a one-dimensional lattice of tunable double-well potentials using radio-frequency spectroscopy. The spectra reveal the coexistence of two types of atom pairs with different symmetries. Our measurements are in excellent quantitative agreement with a theoretical model, obtained by extending the Green's function method of Orso et al. [Phys. Rev. Lett. 95, 060402 (2005)PRLTAO0031-900710.1103/PhysRevLett.95.060402] to a bichromatic 1D lattice with nonzero harmonic radial confinement. The predicted spectra comprise hundreds of discrete transitions, with symmetry-dependent initial state populations and transition strengths. Our work provides an understanding of the elementary pairing states in a superlattice, paving the way for new studies of strongly interacting many-body systems.

  4. Control of triplet state generation in heavy atom-free BODIPY-anthracene dyads by media polarity and structural factors.

    Science.gov (United States)

    Filatov, Mikhail A; Karuthedath, Safakath; Polestshuk, Pavel M; Callaghan, Susan; Flanagan, Keith J; Telitchko, Maxime; Wiesner, Thomas; Laquai, Frédéric; Senge, Mathias O

    2018-03-28

    A family of heavy atom-free BODIPY-anthracene dyads (BADs) exhibiting triplet excited state formation from charge-transfer states is reported. Four types of BODIPY scaffolds, different in the alkyl substitution pattern, and four anthracene derivatives have been used to access BADs. Fluorescence and intersystem crossing (ISC) in these dyads depend on donor-acceptor couplings and can be accurately controlled by substitution or media polarity. Under conditions that do not allow charge transfer (CT), the dyads exhibit fluorescence with high quantum yields. Formation of charge-transfer states triggers ISC and the formation of long-lived triplet excited states in the dyads. The excited state properties were studied by steady-state techniques and ultrafast pump-probe spectroscopy to determine the parameters of the observed processes. Structural information for various BADs was derived from single crystal X-ray structure determinations alongside DFT molecular geometry optimization, revealing the effects of mutual orientation of subunits on the photophysical properties. The calculations showed that alkyl substituents on the BODIPY destabilize CT states in the dyads, thus controlling the charge transfer between the subunits. The effect of the dyad structure on the ISC efficiency was considered at the M06-2X level of theory, and a correlation between mutual orientation of the subunits and the energy gap between singlet and triplet CT states was studied using a multireference CASSCF method.

  5. Control of triplet state generation in heavy atom-free BODIPY-anthracene dyads by media polarity and structural factors

    KAUST Repository

    Filatov, Mikhail A.

    2018-02-12

    A family of heavy atom-free BODIPY-anthracene dyads (BADs) exhibiting triplet excited state formation from charge-transfer states is reported. Four types of BODIPY scaffolds, different in the alkyl substitution pattern, and four anthracene derivatives have been used to access BADs. The fluorescence and intersystem crossing (ISC) in these dyads depend on donor-acceptor couplings and can be accurately controlled by the substitution or media polarity. Under conditions that do not allow charge transfer (CT), the dyads exhibit fluorescence with high quantum yields. Formation of charge-transfer states triggers ISC and the formation of long-lived triplet excited states in the dyads. The excited state properties were studied by steady-state techniques and ultrafast pump-probe spectroscopy to determine the parameters of the observed processes. Structural information for various BADs was derived from single crystal X-ray structure determinations alongside DFT molecular geometry optimization, revealing the effects of mutual orientation of subunits on the photophysical properties. The calculations showed that alkyl substituents on the BODIPY destabilize CT states in the dyads, thus controlling the charge transfer between the subunits. The effect of the dyad structure on the ISC efficiency was considered at M06-2X level of theory and a correlation between mutual orientation of the subunits and the energy gap between singlet and triplet CT states was studied using multireference CASSCF method.

  6. Isotope substitution extends the lifetime of organic molecules in transmission electron microscopy.

    Science.gov (United States)

    Chamberlain, Thomas W; Biskupek, Johannes; Skowron, Stephen T; Bayliss, Peter A; Bichoutskaia, Elena; Kaiser, Ute; Khlobystov, Andrei N

    2015-02-04

    Structural characterisation of individual molecules by high-resolution transmission electron microscopy (HRTEM) is fundamentally limited by the element and electron energy-specific interactions of the material with the high energy electron beam. Here, the key mechanisms controlling the interactions between the e-beam and C-H bonds, present in all organic molecules, are examined, and the low atomic weight of hydrogen-resulting in its facile atomic displacement by the e-beam-is identified as the principal cause of the instability of individual organic molecules. It is demonstrated theoretically and proven experimentally that exchanging all hydrogen atoms within molecules with the deuterium isotope, and therefore doubling the atomic weight of the lightest atoms in the structure, leads to a more than two-fold increase in the stability of organic molecules in the e-beam. Substitution of H for D significantly reduces the amount of kinetic energy transferred from the e-beam to the atom (main factor contributing to stability) and also increases the barrier for bond dissociation, primarily due to the changes in the zero-point energy of the C-D vibration (minor factor). The extended lifetime of coronene-d12 , used as a model molecule, enables more precise analysis of the inter-molecular spacing and more accurate measurement of the molecular orientations. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Atomic Physics 16: Sixteenth International Conference on Atomic Physics. Proceedings

    International Nuclear Information System (INIS)

    Baylis, W.E.; Drake, G.W.

    1999-01-01

    These proceedings represent papers presented at the 16th International Conference on Atomic Physics held in Windsor, Ontario, Canada, in August, 1998. The topics discussed included a wide array of subjects in atomic physics such as atom holography, alignment in atomic collisions, coulomb-interacting particles, muon experiments, x-rays from comets, atomic electron collisions in intense laser fields, spectroscopy of trapped ions, and Bose-Einstein condensates. This conference represents the single most important meeting world wide on fundamental advances in atomic physics. There were 30 papers presented at the conference,out of which 4 have been abstracted for the Energy, Science and Technology database

  8. Atomic spectrum of neptunium

    International Nuclear Information System (INIS)

    Fred, M.; Tomkins, F.S.; Blaise, J.E.; Camus, P.; Verges, J.

    1976-05-01

    A description and interpretation of the atomic spectrum of neptunium are given. Wavelengths were measured for 6096 spectrum lines in the range 3793 to 38,812 cm -1 (26,353 to 2575 A), of which 2526 were classified as transitions between 329 odd levels and 130 even levels of neutral neptunium (Np I). The data are presented in five tables

  9. Atoms in Astronomy.

    Science.gov (United States)

    Blanchard, Paul A.

    This booklet is part of an American Astronomical Society curriculum project designed to provide teaching materials to teachers of secondary school chemistry, physics, and earth science. A Basic Topics section discusses atomic structure, emphasizing states of matter at high temperature and spectroscopic analysis of light from the stars. A section…

  10. FAC: Flexible Atomic Code

    Science.gov (United States)

    Gu, Ming Feng

    2018-02-01

    FAC calculates various atomic radiative and collisional processes, including radiative transition rates, collisional excitation and ionization by electron impact, energy levels, photoionization, and autoionization, and their inverse processes radiative recombination and dielectronic capture. The package also includes a collisional radiative model to construct synthetic spectra for plasmas under different physical conditions.

  11. Deep diode atomic battery

    International Nuclear Information System (INIS)

    Anthony, T.R.; Cline, H.E.

    1977-01-01

    A deep diode atomic battery is made from a bulk semiconductor crystal containing three-dimensional arrays of columnar and lamellar P-N junctions. The battery is powered by gamma rays and x-ray emission from a radioactive source embedded in the interior of the semiconductor crystal

  12. Atomic transport properties

    International Nuclear Information System (INIS)

    Freyss, M.

    2015-01-01

    As presented in the first chapter of this book, atomic transport properties govern a large panel of nuclear fuel properties, from its microstructure after fabrication to its behaviour under irradiation: grain growth, oxidation, fission product release, gas bubble nucleation. The modelling of the atomic transport properties is therefore the key to understanding and predicting the material behaviour under irradiation or in storage conditions. In particular, it is noteworthy that many modelling techniques within the so-called multi-scale modelling scheme of materials make use of atomic transport data as input parameters: activation energies of diffusion, diffusion coefficients, diffusion mechanisms, all of which are then required to be known accurately. Modelling approaches that are readily used or which could be used to determine atomic transport properties of nuclear materials are reviewed here. They comprise, on the one hand, static atomistic calculations, in which the migration mechanism is fixed and the corresponding migration energy barrier is calculated, and, on the other hand, molecular dynamics calculations and kinetic Monte-Carlo simulations, for which the time evolution of the system is explicitly calculated. (author)

  13. The atomic society

    International Nuclear Information System (INIS)

    Hallerbach, J.; Hinz, M.O.; Huebner, H.; Huelsmann, H.; Krusewitz, K.; Mechels, E.; Moneta, J.; Mossmann, W.; Reuleaux, F.

    1978-01-01

    Nuclear power and social progress. Analyses and alternative. Organisation and development of the electric power industry. Conflicts in trade unions and churches. Processes of learning in court and in the science business. Materials, data, and figures on the development of power machinery and international atomic policy. Songs of the anti-nuclear movement. (orig.) [de

  14. Observational Evidence for Atoms.

    Science.gov (United States)

    Jones, Edwin R., Jr.; Childers, Richard L.

    1984-01-01

    Discusses the development of the concept of atomicity and some of the many which can be used to establish its validity. Chemical evidence, evidence from crystals, Faraday's law of electrolysis, and Avogadro's number are among the areas which show how the concept originally developed from a purely philosophical idea. (JN)

  15. Spectra of alkali atoms

    International Nuclear Information System (INIS)

    Santoso, Budi; Arumbinang, Haryono.

    1981-01-01

    Emission spectra of alkali atoms has been determined by using spectrometer at the ultraviolet to infra red waves range. The spectra emission can be obtained by absorption spectrophotometric analysis. Comparative evaluations between experimental data and data handbook obtained by spark method were also presented. (author tr.)

  16. Experimental atomic physics

    International Nuclear Information System (INIS)

    Sellin, I.A.; Elston, S.B.; Forester, J.P.; Liao, K.H.; Pegg, D.J.; Peterson, R.S.; Thoe, R.S.; Hayden, H.C.; Griffin, P.M.

    1976-01-01

    The atomic structure and collision phenomena of highly stripped ions in the range Z = 6 to 35 were studied. Charge-transfer and multiple-electron-loss cross sections were determined. Absolute x-ray-production cross sections for incident heavy ions were measured. 10 figures, 1 table

  17. Atomic Particle Detection

    Energy Technology Data Exchange (ETDEWEB)

    Hellman, Hal

    1970-01-01

    This booklet tells how scientists observe the particles and electromagnetic radiation that emerges from an atomic nucleus. The equipment used falls into two general categories: counters which count each particle as it passes by, and track detectors, which make a photographic record of the particle's track.

  18. Dynamics of cascade processes of muonic atoms

    International Nuclear Information System (INIS)

    Kalantari, Z.; Pirahmadian, M. H.; Ebrahimi, A.

    2006-01-01

    Studies on exotic atoms are important in different ways. They are important for strong interaction with nucleus and the theory of QCD in low energies. They are also important in muon catalyzed fusion. Their properties can be revealed by studies on cascade of muonic atoms. In this paper, unlike the others, we do not consider the kinetic energy of muonic atoms, constant (the kinetic energy of muonic atoms can vary due to cascade processes). We have used multi group method. The energy dependence of the rates of collisional cascade processes can take into account by this method. In addition, the energy spectra of muonic atoms in the ground state are calculated. For this purpose we divided the energy spectrum to 10 groups, and then use the rate of external Auger effect, Coulomb de-excitation, muon transfer and elastic scattering to solve the dynamics of cascade processes in each group. These equations are coupled linear differential equations. To solve them we use the Runge-Kutta method in the fourth order. One of the conclusions of this paper is that, this energy spectrum is not Maxwellian distribution. Finally our results are compared with the results of the Monte-Carlo simulation.

  19. Effective atomic numbers of some H-, C-, N-and O-based composite ...

    Indian Academy of Sciences (India)

    The differential incoherent scattering cross-sections of the composite materials of interest measured at these three angles in the same set-up and substituted in this expression would yield their effective atomic number at the three energies. Results obtained in this manner for bakelite, nylon, epoxy, teflon, perspex and some ...

  20. Lattice location of dopant atoms: An N-body model calculation

    Indian Academy of Sciences (India)

    from the concerned channelling direction. Here we applied the superior N-body model to study the yield from bismuth in silicon. The finding that bismuth atom occupies a position close to the silicon substitutional site is new. The transverse displacement of the suggested lattice site from the channelling direction is consistent ...

  1. Lattice location of dopant atoms: An N-body model calculation

    Indian Academy of Sciences (India)

    2015-11-27

    Nov 27, 2015 ... The finding that bismuth atom occupies a position close to the silicon substitutional site is new. The transverse displacement of the suggested lattice site from the channelling direction is consistent with the experimental results. The above model is also applied to determine the location of ytterbium in silicon.

  2. Inconsistent Distances in Substitution Matrices can be Avoided by Properly Handling Hydrophobic Residues

    Directory of Open Access Journals (Sweden)

    J. Baussand

    2008-01-01

    Full Text Available The adequacy of substitution matrices to model evolutionary relationships between amino acid sequences can be numerically evaluated by checking the mathematical property of triangle inequality for all triplets of residues. By converting substitution scores into distances, one can verify that a direct path between two amino acids is shorter than a path passing through a third amino acid in the amino acid space modeled by the matrix. If the triangle inequality is not verified, the intuition is that the evolutionary signal is not well modeled by the matrix, that the space is locally inconsistent and that the matrix construction was probably based on insufficient biological data. Previous analysis on several substitution matrices revealed that the number of triplets violating the triangle inequality increases with sequence divergence. Here, we compare matrices which are dedicated to the alignment of highly divergent proteins. The triangle inequality is tested on several classical substitution matrices as well as in a pair of “complementary” substitution matrices recording the evolutionary pressures inside and outside hydrophobic blocks in protein sequences. The analysis proves the crucial role of hydrophobic residues in substitution matrices dedicated to the alignment of distantly related proteins.

  3. The Pre-Service Science Teachers' Mental Models for Concept of Atoms and Learning Difficulties

    Science.gov (United States)

    Kiray, Seyit Ahmet

    2016-01-01

    The purpose of this study is to reveal the pre-service science teachers' difficulties about the concept of atoms. The data was collected from two different sources: The Draw an Atom Test (DAAT) and face-to-face interviews. Draw an atom test (DAAT) were administered to the 142 science teacher candidates. To elaborate the results, the researcher…

  4. Mechanism and Regioselectivity of Rh(III)-Catalyzed Intermolecular Annulation of Aryl-Substituted Diazenecarboxylates and Alkenes: DFT Insights

    KAUST Repository

    Ajitha, Manjaly John

    2016-02-05

    The mechanism of Rh-catalyzed intermolecular annulation of aryl-substituted diazenecarboxylates and alkenes was investigated using density functional theory (DFT) (PCM-M062X/6-311+G(d,p)//M062X/6-31G(d)). The acetate ligand (OAc)-assisted C-H activation via the formation of a five-membered rhodacycle (I-TS1; ΔG‡ = 19.4 kcal/mol) is more favorable compared to that via a four-membered intermediate (II-TS1; ΔG‡ = 27.8 kcal/mol). Our results also revealed that the seven-membered intermediate (I-3, ΔGrel = -6.8 kcal/mol) formed after the alkene insertion could undergo a coordination switch with the adjacent nitrogen atom (via TScs; ΔG‡ = 16.5 kcal/mol) to produce a thermodynamically stable six-membered intermediate (II-3, ΔGrel = -10.4 kcal/mol), eventually leading to a cyclization process followed by a barrierless ligand-assisted protonation to yield the final product. The β-hydride elimination product was found to be kinetically and thermodynamically undesirable. The rate-determining step is identified as the initial C-H activation, consistent with the previous kinetic studies. Notably, DFT studies offered important insights on the ability of the substrate (diazene carboxylate) to promote the switchable coordination site selectivity during the reaction to achieve a lower energy pathway. © 2016 American Chemical Society.

  5. Fluorescent J-aggregates of core-substituted perylene bisimides: studies on structure-property relationship, nucleation-elongation mechanism, and sergeants-and-soldiers principle.

    Science.gov (United States)

    Kaiser, Theo E; Stepanenko, Vladimir; Würthner, Frank

    2009-05-20

    A series of highly soluble and fluorescent, at core tetraaryloxy-substituted and in imide positions hydrogen atom containing perylene bisimide (PBI) dyes 1a-e with varying peripheral side chains have been synthesized and thoroughly characterized. The self-assembly of these PBIs has been studied in detail by UV/vis, linear dichroism (LD) and circular dichroism (CD) spectroscopy, and scanning probe microscopy (AFM, STM). These studies revealed that the present PBIs self-assemble into extended double string cables, which consist of two hydrogen-bonded supramolecular polymeric chains of densely packed and strongly excitonically coupled PBI chromophores, providing highly fluorescent J-aggregates. The aggregation strength ("melting" temperature) and the fluorescence properties of these J-aggregates are dependent on the number and chain length of the peripheral alkoxy substituents, thus revealing a structure-property relationship. In contrast to previously reported assemblies of PBIs, for which the aggregation process is described by the isodesmic (or equal K) model, a cooperative nucleation-elongation mechanism applies for the aggregation of the present assemblies as revealed by concentration-dependent UV/vis absorption studies with the chiral PBI 1e, providing equilibrium constants for dimerization (= nucleation) of K(2) = 13 +/- 11 L mol(-1) and for elongation of K = 2.3 +/- 0.1 x 10(6) L mol(-1) in methylcyclohexane (MCH). LD spectroscopic measurements have been performed to analyze the orientation of the monomers within the aggregates. The nonlinearity of chiral amplification in PBI aggregates directed by sergeants-and-soldiers principle has been elucidated by coaggregation experiments of different PBI dyes using CD spectroscopy. The dimensions as well as the molecular arrangement of the monomeric units in assemblies have been explored by atomic force microscopy (AFM) and scanning tunneling microscopy (STM).

  6. A note on a proof of F. Hahn concerning the gross substitutability

    Directory of Open Access Journals (Sweden)

    Giorgi, G

    2007-02-01

    Full Text Available The aim of this note is to investigate the assumptions and the proofs of some results by F. Hahn, which have been stated in several other classics of Economic Theory. The results deal with the relations between the gross substitutability and the weak axiom of revealed preference, in a pure exchange economy, ruled by the Walras law.

  7. STM studies of individual Ti impurity atoms in Sr2RuO4

    International Nuclear Information System (INIS)

    Barker, B.I.; Dutta, S.K.; Lupien, C.; McEuen, P.L.; Kikugawa, N.; Maeno, Y.; Davis, J.C.

    2003-01-01

    The unconventional superconductor, Sr 2 RuO 4 , was studied with an ultra-low temperature scanning tunneling microscope. Atomic resolution images of the SrO plane were obtained with perturbations caused by Ti impurities substituted for 0.125% of the Ru atoms clearly visible. A complicated gap-like structure in local density of states was measured at all locations on the surface, with some modifications caused by the Ti atoms. The superconducting gap was not clearly visible, possibly due to surface termination effects, but other gap-like structures were found at ∼5 and ∼50 meV

  8. Reaction mechanism of oxygen atoms with unsaturated hydrocarbons by the crossed molecular beams method

    Energy Technology Data Exchange (ETDEWEB)

    Buss, R.J.; Baseman, R.J.; Guozhong, H.; Lee, Y.T.

    1982-04-01

    From a series of studies of the reaction of oxygen atoms with unsaturated hydrocarbons using the crossed molecular beam method, the dominant reaction mechanisms were found to be the simple substitution reactions with oxygen atoms replacing H, Cl, Br atom or alkyl groups. Complication due to secondary reaction was avoided by carrying out experiments under single collisions and observing primary products directly. Primary products were identified by measuring the angular and velocity distributions of products at all the mass numbers which could be detected by the mass spectrometer, and from comparison of these distributions, applying the requirement of energy and momentum conservation.

  9. Reaction Mechanism of Oxygen Atoms with Unsaturated Hydrocarbons by the Crossed-Molecular-Beams Method

    Science.gov (United States)

    Buss, R. J.; Baseman, R. J.; Guozhong, H.; Lee, Y. T.

    1982-04-01

    From a series of studies of the reaction of oxygen atoms with unsaturated hydrocarbons using the crossed molecular beam method, the dominant reaction mechanisms were found to be the simple substitution reactions with oxygen atoms replacing H, Cl, Br atom or alkyl groups. Complication due to secondary reaction was avoided by carrying out experiments under single collisions and observing primary products directly. Primary products were identified by measuring the angular and velocity distributions of products at all the mass numbers which could be detected by the mass spectrometer, and from comparison of these distributions, applying the requirement of energy and momentum conservation.

  10. 40 CFR Appendix B to Subpart G of... - Substitutes Subject to Use Restrictions and Unacceptable Substitutes

    Science.gov (United States)

    2010-07-01

    ... Conditions Application Substitute Decision Conditions Comments CFC-12 Automobile Motor Vehicle Air... refrigerant. CFC-12 Automobile Motor Vehicle Air Conditioning (New equipment only) R-152a as a substitute for... excluding the space enclosed by the ducting in the HVAC module. Refrigerants—Acceptable Subject to Narrowed...

  11. Role of atoms in atomic gravitational-wave detectors

    Science.gov (United States)

    Norcia, Matthew A.; Cline, Julia R. K.; Thompson, James K.

    2017-10-01

    Recently, it has been proposed that space-based atomic sensors may be used to detect gravitational waves. These proposals describe the sensors either as clocks or as atom interferometers. Here, we seek to explore the fundamental similarities and differences between the two types of proposals. We present a framework in which the fundamental mechanism for sensitivity is identical for clock and atom interferometer proposals, with the key difference being whether or not the atoms are tightly confined by an external potential. With this interpretation in mind, we propose two major enhancements to detectors using confined atoms, which allow for an enhanced sensitivity analogous to large momentum transfer used in atom interferometry (though with no transfer of momentum to the atoms), and a way to extend the useful coherence time of the sensor beyond the atom's excited-state lifetime.

  12. Ionization of highly excited atoms by atomic particle impact

    International Nuclear Information System (INIS)

    Smirnov, B.M.

    1976-01-01

    The ionization of a highly excited atom by a collision with an atom or molecule is considered. The theory of these processes is presented and compared with experimental data. Cross sections and ionization potential are discussed. 23 refs

  13. Improved persistent luminescence of CaTiO3:Pr by fluorine substitution and thermochemical treatment

    International Nuclear Information System (INIS)

    Yoon, Songhak; Otal, Eugenio H.; Maegli, Alexandra E.; Karvonen, Lassi; Matam, Santhosh K.; Ebbinghaus, Stefan G.; Walfort, Bernhard; Hagemann, Hans; Pokrant, Simone; Weidenkaff, Anke

    2014-01-01

    Highlights: • Synthesis of fluorine-substituted CaTiO 3 :Pr phosphors. • Rietveld refinement of CaTi(O,F) 3 :Pr phosphors. • Afterglow intensity improvement of ca. 450% compared to CaTiO 3 :Pr. - Abstract: Fluorine-substituted CaTiO 3 :Pr phosphors were prepared by a solid-state reaction. Rietveld refinements of powder X-ray diffraction patterns revealed that increasing fluorine-substitution leads to the gradual shrinkage of the unit-cell. Enhanced afterglow intensities were observed with fluorine-substitution. Furthermore, the effect of annealing atmosphere was investigated by thermochemical treatment in different atmospheres (Ar, air and NH 3 ). UV–Vis diffuse reflectance spectra and photoluminescence excitation spectra revealed that Pr 4+ in the pristine CaTi(O,F) 3 :Pr phosphor was partially reduced to Pr 3+ under NH 3 flow leading to an intensity improvement of ca. 450% compared to CaTiO 3 :Pr. The substantial improvement of afterglow intensity by fluorine substitution and annealing in NH 3 is considered to be connected with the generation of oxygen vacancies and the partial reduction of Pr 4+ to Pr 3+

  14. Atomic Force Microscope for Imaging and Spectroscopy

    Science.gov (United States)

    Pike, W. T.; Hecht, M. H.; Anderson, M. S.; Akiyama, T.; Gautsch, S.; deRooij, N. F.; Staufer, U.; Niedermann, Ph.; Howald, L.; Mueller, D.

    2000-01-01

    We have developed, built, and tested an atomic force microscope (AFM) for extraterrestrial applications incorporating a micromachined tip array to allow for probe replacement. It is part of a microscopy station originally intended for NASA's 2001 Mars lander to identify the size, distribution, and shape of Martian dust and soil particles. As well as imaging topographically down to nanometer resolution, this instrument can be used to reveal chemical information and perform infrared and Raman spectroscopy at unprecedented resolution.

  15. Refining molecular potentials using atom interferometry

    International Nuclear Information System (INIS)

    Forrey, R.C.; Kharchenko, V.; Dalgarno, A.; You, L.

    1997-01-01

    We present a theoretical study of the index of refraction of argon for the propagation of sodium matter waves. The sensitivity of the index of refraction to the details of the molecular potential curve is analyzed. Our calculations reveal velocity-dependent oscillations in the index of refraction that may be detectable, particularly at low temperatures, in atom interferometry measurements. A procedure for refining molecular potential curves is outlined. copyright 1997 The American Physical Society

  16. Atomic Layer Thermopile Materials: Physics and Application

    OpenAIRE

    P. X. Zhang; H.-U. Habermeier

    2008-01-01

    New types of thermoelectric materials characterized by highly anisotropic Fermi surfaces and thus anisotropic Seebeck coefficients are reviewed. Early studies revealed that there is an induced voltage in high TC oxide superconductors when the surface of the films is exposed to short light pulses. Subsequent investigations proved that the effect is due to anisotropic components of the Seebeck tensor, and the type of materials is referred to atomic layer thermopile (ALT). Our recent studies ind...

  17. Absorption imaging of ultracold atoms on atom chips

    DEFF Research Database (Denmark)

    Smith, David A.; Aigner, Simon; Hofferberth, Sebastian

    2011-01-01

    Imaging ultracold atomic gases close to surfaces is an important tool for the detailed analysis of experiments carried out using atom chips. We describe the critical factors that need be considered, especially when the imaging beam is purposely reflected from the surface. In particular we present...... methods to measure the atom-surface distance, which is a prerequisite for magnetic field imaging and studies of atom surface-interactions....

  18. Angular momentum coupling in atom-atom collisions

    International Nuclear Information System (INIS)

    Grosser, J.

    1986-01-01

    The coupling between the electronic angular momentum and the rotating atom-atom axis in the initial or the final phase of an atom-atom collision is discussed, making use of the concepts of radial and rotational (Coriolis) coupling between different molecular states. The description is based on a limited number of well-understood approximations, and it allows an illustrative geometric representation of the transition from the body fixed to the space fixed motion of the electrons. (orig.)

  19. Atomic-Layer-Confined Doping for Atomic-Level Insights into Visible-Light Water Splitting.

    Science.gov (United States)

    Lei, Fengcai; Zhang, Lei; Sun, Yongfu; Liang, Liang; Liu, Katong; Xu, Jiaqi; Zhang, Qun; Pan, Bicai; Luo, Yi; Xie, Yi

    2015-08-03

    A model of doping confined in atomic layers is proposed for atomic-level insights into the effect of doping on photocatalysis. Co doping confined in three atomic layers of In2S3 was implemented with a lamellar hybrid intermediate strategy. Density functional calculations reveal that the introduction of Co ions brings about several new energy levels and increased density of states at the conduction band minimum, leading to sharply increased visible-light absorption and three times higher carrier concentration. Ultrafast transient absorption spectroscopy reveals that the electron transfer time of about 1.6 ps from the valence band to newly formed localized states is due to Co doping. The 25-fold increase in average recovery lifetime is believed to be responsible for the increased of electron-hole separation. The synthesized Co-doped In2S3 (three atomic layers) yield a photocurrent of 1.17 mA cm(-2) at 1.5 V vs. RHE, nearly 10 and 17 times higher than that of the perfect In2S3 (three atomic layers) and the bulk counterpart, respectively. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Modulating short tryptophan- and arginine-rich peptides activity by substitution with histidine.

    Science.gov (United States)

    Bacalum, Mihaela; Janosi, Lorant; Zorila, Florina; Tepes, Ana-Maria; Ionescu, Cristina; Bogdan, Elena; Hadade, Niculina; Craciun, Liviu; Grosu, Ion; Turcu, Ioan; Radu, Mihai

    2017-07-01

    High antimicrobial efficacy of short tryptophan-and arginine-rich peptides makes them good candidates in the fight against pathogens. Substitution of tryptophan and arginine by histidine could be used to modulate the peptides efficacy by optimizing their structures. The peptide (RRWWRWWRR), reported to showed good antimicrobial efficacy, was used as template, seven new analogs being designed substituting tryptophan or arginine with histidine. The peptides' efficacy was tested against E. coli, B. subtilis and S. aureus. The cytotoxicity and hemolytic effect were evaluated and the therapeutic index was inferred for each peptide. Atomic force microscopy and molecular simulation were used to analyze the effects of peptides on bacterial membrane. The substitution of tryptophan by histidine proved to strongly modulate the antimicrobial activity, mainly by changing the peptide-to-membrane binding energy. The substitution of arginine has low effect on the antimicrobial efficacy. The presence of histidine residue reduced the cytotoxic and hemolytic activity of the peptides in some cases maintaining the same efficacy against bacteria. The peptides' antimicrobial activity was correlated to the 3D-hydrophobic moment and to a simple structure-based packing parameter. The results show that some of these peptides have the potential to become good candidates to fight against bacteria. The substitution by histidine proved to fine tune the therapeutic index allowing the optimization of the peptide structure mainly by changing its binding energy and 3D-hydrophobic moment. The short tryptophan reach peptides therapeutic index can be maximized using the histidine substitution to optimize their structure. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Atomic Absorption, Atomic Fluorescence, and Flame Emission Spectrometry.

    Science.gov (United States)

    Horlick, Gary

    1984-01-01

    This review is presented in six sections. Sections focus on literature related to: (1) developments in instrumentation, measurement techniques, and procedures; (2) performance studies of flames and electrothermal atomizers; (3) applications of atomic absorption spectrometry; (4) analytical comparisons; (5) atomic fluorescence spectrometry; and (6)…

  2. Substitution between Cars within the Household

    DEFF Research Database (Denmark)

    de Borger, Bruno; Mulalic, Ismir; Rouwendal, Jan

    In this paper we study the demand for car kilometres in two-car households, focusing on the substitution between cars in response to fuel price changes. We use a large sample of detailed Danish data on two-car households to estimate—for each car owned by the household—own and cross-price effects...... of increases in fuel costs per kilometre. The empirical results show that failure to capture substitution between cars within the household can result in substantial misspecification biases. Ignoring substitution, we estimate fuel price elasticities of –0.81 and -0.65 for the primary and secondary cars...... efficient car, finding partial support for the underlying hypothesis. More importantly, the results of this extended model emphasize the importance of behavioural differences related to the position of the most fuel efficient car in the household, suggesting that households’ fuel efficiency choices...

  3. Substitute energy resource policy in Japan

    International Nuclear Information System (INIS)

    Umehara, Katsuhiko

    1980-01-01

    Japan depends 88% of energy resources and 99.8% of petroleum on imports. The solution of energy problems is now made internationally. As the means for Japan, there are the substitution of other resources for petroleum and its promotion. However, this involves the considerable funds for the development and utilization, which must be borne by the people in the form of tax. For governmental financing, a special account must be set up for the particular purpose. In the research and development of new energy resources, new institution is required. The following matters are described: petroleum shortage coming even in 1980s, the international need of substitute energy development, the need for establishing measures for substitute energy resources, acquisition of the funds, special-account governmental financing, and an institute of new energy development. (author)

  4. [Contingency management in opioid substitution treatment].

    Science.gov (United States)

    Specka, M; Böning, A; Scherbaum, N

    2011-07-01

    The majority of opiate-dependent patients in substitution treatment show additional substance-related disorders. Concomitant use of heroin, alcohol, benzodiazepines or cocaine compromises treatment success. Concomitant drug use may be treated by using contingency management (CM) which is based on learning theory. In CM, abstinence from drugs, as verified by drug screenings, is reinforced directly and contingently. Reinforcers used in CM studies with substituted patients were, amongst others, vouchers and take-home privileges. Studies in the USA show a medium average effect of CM on drug consumption rates and abstinence. The effects decrease markedly after the end of the intervention. We discuss whether CM is applicable within the German substitution treatment system and how it can be combined with other interventions such as selective detoxification treatments or cognitive-behavioural programmes. © Georg Thieme Verlag KG Stuttgart · New York.

  5. Biomaterials in search of a meniscus substitute.

    Science.gov (United States)

    Rongen, Jan J; van Tienen, Tony G; van Bochove, Bas; Grijpma, Dirk W; Buma, Pieter

    2014-04-01

    The menisci fulfill key biomechanical functions in the tibiofemoral (knee) joint. Unfortunately meniscal injuries are quite common and most often treated by (partial) meniscectomy. However, some patients experience enduring symptoms, and, more importantly, it leads to an increased risk for symptomatic osteoarthritis. Over the past decades, researchers have put effort in developing a meniscal substitute able to prevent osteoarthritis and treat enduring clinical symptoms. Grossly, two categories of substitutes are observed: First, a resorbable scaffold mimicking biomechanical function which slowly degrades while tissue regeneration and organization is promoted. Second, a non resorbable, permanent implant which mimics the biomechanical function of the native meniscus. Numerous biomaterials with different (material) properties have been used in order to provide such a substitute. Nevertheless, a clinically applicable cartilage protecting material is not yet emerged. In the current review we provide an overview, and discuss, these different materials and extract recommendations regarding material properties for future developmental research. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Reaction mechanisms for the CO oxidation on Au/CeO(2) catalysts: activity of substitutional Au(3+)/Au(+) cations and deactivation of supported Au(+) adatoms.

    Science.gov (United States)

    Camellone, Matteo Farnesi; Fabris, Stefano

    2009-08-05

    Density functional theory calculations that account for the on-site Coulomb interaction via a Hubbard term (DFT+U) reveal the mechanisms for the oxidation of CO catalyzed by isolated Au atoms as well as small clusters in Au/CeO(2) catalysts. Ceria (111) surfaces containing positively charged Au ions, either as supported Au(+) adatoms or as substitutional Au(3+) ions, are shown to activate molecular CO and to catalyze its oxidation to CO(2). In the case of supported single Au(+) adatoms, the limiting rate for the CO oxidation is determined by the adsorbate spillover from the adatom to the oxide support. The reaction then proceeds with the CO oxidation via lattice oxygen and O vacancy formation. These vacancies are shown to readily attract the supported Au(+) adatoms and to turn them into negatively charged Au(delta-) adspecies that deactivate the catalyst, preventing further CO adsorption. Au(3+) ions dispersed into the ceria lattice as substitutional point defects can instead sustain a full catalytic cycle consisting of three individual steps maintaining their activity along the reaction process: Au cations in Au(x)Ce(1-x)O(2) systems promote multiple oxidations of CO without any activation energy via formation of surface O vacancies. Molecular oxygen adsorbs at these vacancies and forms O adspecies that then catalyze the oxidation of molecular CO, closing the catalytic cycle and recovering the stoichiometric Au(x)Ce(1-x)O(2) system. The interplay between the reversible Ce(4+)/Ce(3+) and Au(3+)/Au(+) reductions underpins the high catalytic activity of dispersed Au atoms into the ceria substrate. It is shown that the positive oxidation state of the substitutional Au ions is retained along the catalytic cycle, thus preventing the deactivation of Au(x)Ce(1-x)O(2) catalysts in operation conditions. Finally, although a single Au(+) adatom bound to an O vacancy is shown to deactivate during CO oxidation, the calculations predict that the reactivity of gold nanoparticles

  7. Density functional theory calculations of stability and diffusion mechanisms of impurity atoms in Ge crystals

    Energy Technology Data Exchange (ETDEWEB)

    Maeta, Takahiro [Graduate School of System Engineering, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197 (Japan); GlobalWafers Japan Co., Ltd., Higashikou, Seirou-machi, Kitakanbara-gun, Niigata 957-0197 (Japan); Sueoka, Koji [Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197 (Japan)

    2014-08-21

    Ge-based substrates are being developed for applications in advanced nano-electronic devices because of their higher intrinsic carrier mobility than Si. The stability and diffusion mechanism of impurity atoms in Ge are not well known in contrast to those of Si. Systematic studies of the stable sites of 2nd to 6th row element impurity atoms in Ge crystal were undertaken with density functional theory (DFT) and compared with those in Si crystal. It was found that most of the impurity atoms in Ge were stable at substitutional sites, while transition metals in Si were stable at interstitial sites and the other impurity atoms in Si were stable at substitutional sites. Furthermore, DFT calculations were carried out to clarify the mechanism responsible for the diffusion of impurity atoms in Ge crystals. The diffusion mechanism for 3d transition metals in Ge was found to be an interstitial-substitutional diffusion mechanism, while in Si this was an interstitial diffusion mechanism. The diffusion barriers in the proposed diffusion mechanisms in Ge and Si were quantitatively verified by comparing them to the experimental values in the literature.

  8. Atomic Act amended

    International Nuclear Information System (INIS)

    Drabova, D.

    2002-01-01

    In the paper by the chairwoman of the Czech nuclear regulatory authority, the history of Czech nuclear legislation is outlined, the reasons for the amendment of the Atomic Act (Act No. 18/1997) are explained, and the amendments themselves are highlighted. The Act No. 13/2002 of 18 December 2001 is reproduced from the official Collection of Acts of the Czech Republic in the facsimile form. The following acts were thereby amended: Atomic Act No. 18/1997, Metrology Act No. 505/1990, Public Health Protection Act No. 258/2000, and Act No. 2/1969 on the Establishment of Ministries and Other Governmental Agencies of the Czech Republic. (P.A.)

  9. Atomic assistance in 1961

    International Nuclear Information System (INIS)

    1961-01-01

    More than 100 experts provided by the International Atomic Energy Agency will be working in different parts of the world this year, assisting the Agency's Member States in building up their national programs of peaceful atomic development. The total allocation of EPTA funds to the Agency for the two-year period 1961-62 is $1 393 600 (of which approximately half is available in 1961), and is meant not only for the provision of experts and equipment but also for training fellowships and regional projects. The countries which will receive Agency assistance in the form of experts and equipment this year are: Afghanistan, Argentina, Austria, Brazil, Burma, Ceylon, Chile, the Republic of China, Denmark, Greece, Guatemala, Iceland, Indonesia, Iran, Iraq, Israel, Japan, the Republic of Korea, the Republic of Mali, Mexico, Morocco, Pakistan, the Philippines, Senegal, the Sudan, Thailand, Tunisia, Turkey, the United Arab Republic, Vietnam and Yugoslavia

  10. Atomicity for XML Databases

    Science.gov (United States)

    Biswas, Debmalya; Jiwane, Ashwin; Genest, Blaise

    With more and more data stored into XML databases, there is a need to provide the same level of failure resilience and robustness that users have come to expect from relational database systems. In this work, we discuss strategies to provide the transactional aspect of atomicity to XML databases. The main contribution of this paper is to propose a novel approach for performing updates-in-place on XML databases, with the undo statements stored in the same high level language as the update statements. Finally, we give experimental results to study the performance/storage trade-off of the updates-in-place strategy (based on our undo proposal) against the deferred updates strategy to providing atomicity.

  11. Elementary relativistic atoms

    International Nuclear Information System (INIS)

    Nemenov, L.

    2001-01-01

    The Coulomb interaction which occurs in the final state between two particles with opposite charges allows for creation of the bound state of these particles. In the case when particles are generated with large momentum in lab frame, the Lorentz factors of the bound state will also be much larger than one. The relativistic velocity of the atoms provides the opportunity to observe bound states of (π + μ - ), (π + π - ) and (π + K - ) with a lifetime as short as 10 -16 s, and to measure their parameters. The ultrarelativistic positronium atoms (A 2e ) allow us to observe the e.ect of superpenetration in matter, to study the effects caused by the formation time of A 2e from virtual e + e - pairs and to investigate the process of transformation of two virtual particles into the bound state

  12. Atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Haswell, S.J.

    1991-01-01

    Atomic absorption spectroscopy is now well established and widely used technique for the determination of trace and major elements in a wide range analyte types. There have been many advances in the atomic spectroscopy over the last decade and for this reason and to meet the demand, it was felt that there was a need for an updated book. Whilst interest in instrumental design has tended to dominate the minds of the spectrocopist, the analyst concerned with obtaining reliable and representative data, in diverse areas of application, has been diligently modifying and developing sample treatment and instrumental introduction techniques. Such methodology is de fundamental part of analysis and form the basis of the fourteen application chapters of this book. The text focuses in the main on AAS; however, the sample handling techniques described are in many cases equally applicable to ICP-OES and ICP-MS analysis. (author). refs.; figs.; tabs

  13. Glossary of atomic terms

    International Nuclear Information System (INIS)

    1980-01-01

    This glossary (of about 400 terms) has been compiled to help people outside the atomic energy industry to understand what those inside it are saying. It is not intended to be a definitive dictionary of scientific or technical terms, nor does it aim to cover terms that are in general use in science and technology. A list of some initials and acronyms is appended. (author)

  14. Glossary of atomic terms

    International Nuclear Information System (INIS)

    1982-04-01

    This glossary, containing almost 400 terms, has been compiled to help people outside the atomic energy industry to understand what those inside it are saying. It is not intended to be a definitive dictionary of scientific or technical terms, nor does it aim to cover terms that are in general use in science and technology. A list of about 100 initials and acronyms will be found at the end. (author)

  15. Atomic and molecular theory

    International Nuclear Information System (INIS)

    Inokuti, Mitio.

    1990-01-01

    The multifaceted role of theoretical physics in understanding the earliest stages of radiation action is discussed. Scientific topics chosen for the present discourse include photoabsorption, electron collisions, and ionic collisions, and electron transport theory, Connections of atomic and molecular physics with condensed-matter physics are also discussed. The present article includes some historical perspective and an outlook for the future. 114 refs., 3 figs

  16. Atomic physics issues in fusion

    International Nuclear Information System (INIS)

    Post, D.E.

    1982-01-01

    Atomic physics issues have played a large role in controlled fusion research. A general introduction to the present role of atomic processes in both inertial and magnetic controlled fusion work is presented. (Auth.)

  17. Real and Hybrid Atomic Orbitals.

    Science.gov (United States)

    Cook, D. B.; Fowler, P. W.

    1981-01-01

    Demonstrates that the Schrodinger equation for the hydrogenlike atom separates in both spheroconal and prolate spheroidal coordinates and that these separations provide a sound theoretical basis for the real and hybrid atomic orbitals. (Author/SK)

  18. Electromagnetic trapping of cold atoms

    International Nuclear Information System (INIS)

    Balykin, V.I.; Minogin, V.G.; Letokhov, V.S.

    2000-01-01

    This review describes the methods of trapping cold atoms in electromagnetic fields and in the combined electromagnetic and gravity fields. We discuss first the basic types of the dipole radiation forces used for cooling and trapping atoms in the laser fields. We outline next the fundamentals of the laser cooling of atoms and classify the temperature limits for basic laser cooling processes. The main body of the review is devoted to discussion of atom traps based on the dipole radiation forces, dipole magnetic forces, combined dipole radiation-magnetic forces, and the forces combined of the dipole radiation-magnetic and gravity forces. Physical fundamentals of atom traps operating as waveguides and cavities for cold atoms are also considered. The review ends with the applications of cold and trapped atoms in atomic, molecular and optical physics. (author)

  19. Physics of atoms and molecules

    International Nuclear Information System (INIS)

    Bransden, B.H.; Joachain, C.J.

    1983-01-01

    This book presents a unified account of the physics of atoms and molecules at a level suitable for second- and third-year undergraduate students of physics and physical chemistry. Following a brief historical introduction to the subject the authors outline the ideas and approximation methods of quantum mechanics to be used later in the book. Six chapters look at the structure of atoms and the interactions between atoms and electromagnetic radiation. The authors then move on to describe the structure of molecules and molecular spectra. Three chapters deal with atomic collisions, the scattering of electrons by atoms and the scattering of atoms by atoms. The concluding chapter considers a few of the many important applications of atomic physics within astrophysics, laser technology, and nuclear fusion. Problems are given at the end of each chapter, with hints at the solutions in an appendix. Other appendices include various special topics and derivations together with useful tables of units. (author)

  20. Atomic inner-shell physics

    International Nuclear Information System (INIS)

    Crasemann, B.

    1985-01-01

    This book discusses: relativistic and quantum electrodynamic effects on atomic inner shells; relativistic calculation of atomic transition probabilities; many-body effects in energetic atomic transitions; Auger Electron spectrometry of core levels of atoms; experimental evaluation of inner-vacancy level energies for comparison with theory; mechanisms for energy shifts of atomic K-X rays; atomic physics research with synchrotron radiation; investigations of inner-shell states by the electron energy-loss technique at high resolution; coherence effects in electron emission by atoms; inelastic X-ray scattering including resonance phenomena; Rayleigh scattering: elastic photon scattering by bound electrons; electron-atom bremsstrahlung; X-ray and bremsstrahlung production in nuclear reactions; positron production in heavy-ion collisions, and X-ray processes in heavy-ion collisions