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Sample records for inner-shell vacancy cascades

  1. Study of inner-shell vacancy cascades by coincidence techniques

    SciTech Connect

    LeBrun, T.; Arp, U.; MacDonald, M.; Southworth, S.H.

    1995-08-01

    An inner-shell vacancy in an atom decays by an intricate combination of Auger and fluorescence processes. The interrelation between these processes is not well understood because traditional studies of core-excited atoms focus on only one of the many particles that participate in the relaxation - largely ignoring the other components and the correlations between them. To understand these correlations we developed a coincidence technique that uses coincident detection of X-rays and electrons to select decay pathways that involve emission of both an X-ray photon and electrons. In the first application of this technique, the Ar 1s photoelectron spectrum was recorded selectively in coincidence with X-ray fluorescence to eliminate the asymmetric broadening and shifting of the energy distribution which results due to post-collision interaction with K-Auger electrons. This allowed the direct observation of the interaction between the photoelectron and the decay of core holes created after the initial photoionization event. We have also applied this technique to the much more complex problem of understanding Auger-electron spectra produced by vacancy cascades following inner-shell excitation. For example, we previously recorded non-coincident electron spectra of L{sub 2,3}MM Auger transitions following K-shell excitation of argon. Interpretation of these spectra is difficult because they are complicated and consist of many overlapping or unresolved Auger transitions between different ionic states.

  2. Vacancy cascades in small molecules following x-ray inner shell photoionization

    NASA Astrophysics Data System (ADS)

    Ray, D.; Dunford, R. W.; Southworth, S. H.; Kanter, E. P.; Doumy, G.; Gao, Y.; Ho, P. J.; Picon, A.

    2014-05-01

    We are investigating molecular effects in vacancy cascades of small molecules containing heavy atoms - IBr, Br2 and CH2BrI - following K-shell ionization. In addition to fundamental interest in the physics of such decay processes, there are practical applications such as medical treatments that use energetic fragmentation of iodinated compounds with high energy x-rays to selectively treat tumorous cells. Other biological applications are also promising. We utilize the tunable monochromatic x-ray beam at the Advanced Photon Source to trigger K-shell photoionization of Br and I, and measure charge distributions and the kinetic energies released to the fragment ions. A newly designed detection device allows us to do multi-fold coincidence measurements involving momentum imaging of all the ion fragments with very high detection efficiency in coincidence with x-ray fluorescence detection. By comparing the molecular fragmentation probabilities and the kinetic energies released in Br2, IBr and CH2BrI we aim to gain understanding of the fragmentation mechanism as a function of the bond distance between I and Br. Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, US Dept of Energy, Contract DE-AC02-06CH11357.

  3. Evidence for autoexcitation producing inner-shell vacancies in slow ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Stolterfoht, N.

    1993-02-01

    A previous experimental study of Ar L-vacancy production in slow Ar++SiH4 collisions is reanalyzed to provide evidence for the dielectronic process of (inverse) autoexcitation, which removes an electron from a deep inner shell by interaction with another electron decaying from an upper level. Analytic models are evaluated to treat alternative cases where two electrons are transferred at a curve crossing and between parallel potential curves. The theoretical results confirm the experimental observation that the Ar L-vacancy production increases with decreasing energy.

  4. Inner shell vacancy filling and production in highly-charged-ion surface collisions

    SciTech Connect

    Grether, M.

    1994-12-31

    Secondary electron spectra of H-like Ne{sup 9+} ions incident with impact energies from 135 eV to 22.5 keV on a solid Al(111) surface were measured. The dependence of the K Auger electron yield on the observation angle and on the projectile energy is studied in detail. The data show clear evidence for Auger emission from below the surface even for the lowest projectile velocity. In addition, it is found that the Ne L shell filling via charge exchange decrease with decreasing impact energy and reaches zero near an incident energy of 200 eV. Also, the authors measured the intensity of the Au N{sub 5}N{sub 6,7}N{sub 6,7} Auger electrons for Ar{sup 9+} ions with kinetic energies from 125 eV up to 5.3 keV. A threshold behavior is observed in the production of target Au N{sub 5} vacancies by Ar{sup 9+} ions. To analyse the data, they calculated correlation diagrams involving model energies to obtain the internuclear distance of orbital and potential curve crossings. The comparison of experiment and theory shows that the excitation process is not expected to be due to a resonant vacancy transfer from the projectile to the target but due to a dielectronic process which is governed by the electron-electron interaction.

  5. Yields of multiply charged ions in cascading decays of hollow argon and krypton with two initial vacancies in their K and/or L shells.

    PubMed

    Kochur, A

    2001-03-01

    The yields of multiply charged ions produced by the cascading decay of doubly-inner-shell-ionized argon and krypton atoms are calculated via straightforward construction of de-excitation trees. The final-ion-charge spectra are found to be sensitive to the distribution of initial vacancies within K and L shells.

  6. Atomic inner-shell transitions

    NASA Technical Reports Server (NTRS)

    Crasemann, B.; Chen, M. H.; Mark, H.

    1984-01-01

    Atomic inner-shell processes have quite different characteristics, in several important aspects, from processes in the optical regime. Energies are large, e.g., the 1s binding energy reaches 100 keV at Z = 87; relativistic and quantum-electrodynamic effects therefore are strong. Radiationless transitions vastly dominate over photon emission in most cases. Isolated inner-shell vacancies have pronounced single-particle character, with correlations generally contributing only approximately 1 eV to the 1s and 2p binding energies; the structure of such systems is thus well tractable by independent-particle self-consistent-field atomic models. For systems containing multiple deep inner-shell vacancies, or for highly stripped ions, the importance of relativistic intermediate coupling and configuration interaction becomes pronounced. Cancellation of the Coulomb interaction can lead to strong manifestations of the Breit interaction in such phenomena as multiplet splitting and hypersatellite X-ray shifts. Unique opportunities arise for the test of theory.

  7. Atomic inner-shell transitions

    NASA Technical Reports Server (NTRS)

    Crasemann, B.; Chen, M. H.; Mark, H.

    1984-01-01

    Atomic inner-shell processes have quite different characteristics, in several important aspects, from processes in the optical regime. Energies are large, e.g., the 1s binding energy reaches 100 keV at Z = 87; relativistic and quantum-electrodynamic effects therefore are strong. Radiationless transitions vastly dominate over photon emission in most cases. Isolated inner-shell vacancies have pronounced single-particle character, with correlations generally contributing only approximately 1 eV to the 1s and 2p binding energies; the structure of such systems is thus well tractable by independent-particle self-consistent-field atomic models. For systems containing multiple deep inner-shell vacancies, or for highly stripped ions, the importance of relativistic intermediate coupling and configuration interaction becomes pronounced. Cancellation of the Coulomb interaction can lead to strong manifestations of the Breit interaction in such phenomena as multiplet splitting and hypersatellite X-ray shifts. Unique opportunities arise for the test of theory.

  8. CASCADES AFTER K-VACANCY PRODUCTION IN ATOMS AND IONS OF LIGHT ELEMENTS

    SciTech Connect

    Kucas, S.; Karazija, R.; Momkauskaite, A.

    2012-05-10

    The results of detailed level-by-level calculations of Auger and radiative cascades after K-vacancy production are presented for the astrophysically important elements, namely Ne, Mg, Si, S, and Ar. Calculations are performed using the single-configuration, quasi-relativistic approximation. The whole isonuclear sequence of ions for a given element is considered. For the first time, the dependence of the cascade on the initial vacancy state is investigated. The populations are presented not only for the levels of the final configurations, but also for the levels of the excited configurations after the Auger transitions. An intense characteristic emission can be observed from such levels.

  9. CASCADES AFTER K-VACANCY PRODUCTION AND ADDITIONAL IONIZATION OR EXCITATION IN ATOMS OF LIGHT ELEMENTS

    SciTech Connect

    Kucas, S.; Momkauskaitė, A.; Karazija, R.

    2015-09-01

    The results of Auger and radiative cascades after the production of a vacancy in the K-shell and the additional ionization or excitation of the other shell are presented for the various ions of astrophysically important elements, namely, Ne, Mg, Si, S, and Ar. The detailed level-by-level calculations are performed using a single-configuration quasi-relativistic approximation. The populations of the levels of the excited configurations produced during a cascade as well as for the final ions are presented. These data enable us to take into account two-electron processes at the K-shell ionization, and thus to supplement the results of our earlier investigation of K-vacancy cascades.

  10. Inner-shell excitation spectroscopy of peroxides

    NASA Astrophysics Data System (ADS)

    Harding, K. L.; Kalirai, S.; Hayes, R.; Ju, V.; Cooper, G.; Hitchcock, A. P.; Thompson, M. R.

    2015-11-01

    O 1s inner-shell excitation spectra of a number of vapor phase molecules containing peroxide bonds - hydrogen peroxide (H2O2), di-t-butylperoxide (tBuOtBu), benzoyl peroxide, ((C6H5(CO)O)2), luperox-F [1,3(4)-bis(tertbutylperoxyisopropyl) benzene], and analogous, non-peroxide compounds - water, t-butanol and benzoic acid have been measured. C 1s spectra are also reported. O 1s spectra of solid benzoic acid, di-t-butylperoxide and luperox-F recorded using a scanning transmission X-ray microscope, are also reported, and compared to the corresponding gaseous spectra. Spectral interpretation was aided by comparing the spectra of the peroxide and non-peroxide counterparts and with ab initio calculations. A characteristic O 1s → σ∗O-O transition at 533.0(3) eV is identified in each peroxide species, which is absent in the corresponding non-peroxide counterpart species. The energy and intensity of the 533 eV peroxide feature is stable and thus useful for analysis of peroxides in mixtures, such as tracking residual peroxide initiators, or peroxides produced in fuel cells.

  11. Auger decay of 4 d inner-shell holes in atomic Hg leading to triple ionization

    NASA Astrophysics Data System (ADS)

    Andersson, J.; Beerwerth, R.; Roos, A. Hult; Squibb, R. J.; Singh, R.; Zagorodskikh, S.; Talaee, O.; Koulentianos, D.; Eland, J. H. D.; Fritzsche, S.; Feifel, R.

    2017-07-01

    Formation of triply ionized states upon the creation of 4 d inner-shell holes in atomic Hg is investigated by using synchrotron radiation of 730 eV photon energy and a versatile multielectron coincidence detection technique in combination with multiconfiguration Dirac-Fock calculations. By carefully selecting Coster-Kronig electrons detected only in coincidence with a 4 d photoelectron, the Coster-Kronig spectrum has been extracted and the corresponding branching ratios of the 4 d hole have been determined. The results are found to differ from previously established experimental ratios based on electron impact ionization but to agree now better with theory. We also present an Auger cascade analysis of pathways leading to triply ionized states of atomic Hg upon removal of a 4 d inner-shell electron.

  12. Inner-shell ionization of lithium-like chromium ions

    SciTech Connect

    Vogel, D.A.; Beiersdorfer, P.; Marrs, R.E.; Wong, K.L.; Zasadzinski, R.

    1990-09-07

    We have used high-resolution x-ray spectroscopy to investigate inner-shell ionization of Cr{sup 21+} ions by electron impact using the Electron Beam Ion Trap at Lawrence Livermore Laboratory. Our measurements indicate that inner-shell ionization enhances the intensity of the radiative transition 1s2s {sup 3}S{sub 1}{yields}1s{sup 2}{sup 1}S{sub 0}. 7 refs., 4 figs., 1 tab.

  13. X-ray fluorescence/Auger-electron coincidence spectroscopy of vacancy cascades in atomic argon

    SciTech Connect

    Arp, U.; LeBrun, T.; Southworth, S.H.; Jung, M.; MacDonald, M.A.

    1996-12-01

    Argon L{sub 2.3}-M{sub 2.3}M{sub 2.3} Auger-electron spectra were measured in coincidence with K{alpha} fluorescent x-rays in studies of Ar K-shell vacancy decays at several photon energies above the K-threshold and on the 1s-4p resonance in atomic argon. The complex spectra recorded by conventional electron spectroscopy are greatly simplified when recorded in coincidence with fluorescent x-rays, allowing a more detailed analysis of the vacancy cascade process. The resulting coincidence spectra are compared with Hartree-Fock calculations which include shake-up transitions in the resonant case. Small energy shifts of the coincidence electron spectra are attributed to post-collision interaction with 1s photoelectrons.

  14. Inner-shell Photoionization Studies of Neutral Atomic Nitrogen

    NASA Astrophysics Data System (ADS)

    Stolte, W. C.; Jonauskas, V.; Lindle, D. W.; Sant'Anna, M. M.; Savin, D. W.

    2016-02-01

    Inner-shell ionization of a 1s electron by either photons or electrons is important for X-ray photoionized objects such as active galactic nuclei and electron-ionized sources such as supernova remnants. Modeling and interpreting observations of such objects requires accurate predictions for the charge state distribution (CSD), which results as the 1s-hole system stabilizes. Due to the complexity of the complete stabilization process, few modern calculations exist and the community currently relies on 40-year-old atomic data. Here, we present a combined experimental and theoretical study for inner-shell photoionization of neutral atomic nitrogen for photon energies of 403-475 eV. Results are reported for the total ion yield cross section, for the branching ratios for formation of N+, {{{N}}}2+, and {{{N}}}3+, and for the average charge state. We find significant differences when comparing to the data currently available to the astrophysics community. For example, while the branching ratio to {{{N}}}2+ is somewhat reduced, that for N+ is greatly increased, and that to {{{N}}}3+, which was predicted to be zero, grows to ≈ 10% at the higher photon energies studied. This work demonstrates some of the shortcomings in the theoretical CSD data base for inner-shell ionization and points the way for the improvements needed to more reliably model the role of inner-shell ionization of cosmic plasmas.

  15. Polarization transfer in the inner-shell photoionization of sodiumlike ions

    SciTech Connect

    Sharma, L.; Surzhykov, A.; Inal, M. K.; Fritzsche, S.

    2010-02-15

    The inner-shell photoionization of highly charged ions is studied, together with their subsequent radiative decay, within the framework of the density matrix theory and the multiconfiguration Dirac-Fock (MCDF) approach. For the subsequent radiative decay of the ions, we investigate in particular how the linear polarization of characteristic radiation is affected if the incident light is itself polarized. Detailed calculations are performed for the 2p{sup 5}3s{yields}2p{sup 6} radiative transitions following the production of a 2p vacancy in the sodiumlike Fe{sup 15+}, W{sup 63+}, and U{sup 81+} ions. From these calculations, it is shown that the (degree of) linear polarization of the characteristic radiation may be enhanced by a factor of 2 due to the polarization transfer from the incident light.

  16. On the difference in oscillator strengths of inner shell excitations in noble gases and their alkali neighbors

    SciTech Connect

    Amusia, M.Y.; Baltenkov, A.S.; Zhuravleva, G.I.

    1995-08-01

    It is demonstrated that the oscillator strength of resonant inner-shell excitation in a noble gas atom is considerably smaller than that in its alkali neighbor because in the latter case the effective charge acting upon excited electron is much bigger. With increase of the excitation`s principal quantum number the difference between line intensities in noble gases and their alkali neighbors rapidly disappears. The calculations are performed in the Hartree-Fock approximation and with inclusion of rearrangement effects due to inner vacancy creation and its Auger decay. A paper has been submitted for publication.

  17. Inner-shell excitation and ionic fragmentation of molecules

    SciTech Connect

    Hitchcock, A.P.; Tyliszczak, T.; Cavell, R.G.

    1997-04-01

    Inner-shell excitation and associated decay spectroscopies are site specific probes of electronic and geometrical structure and photoionization dynamics. X-ray absorption probes the geometric and electronic structure, while time-of-flight mass spectrometry with multi-coincidence detection provides information on the photofragmentation dynamics of the initially produced inner-shell state. Auger decay of inner-shell excited and ionised states is an efficient source of multiply charged ions. The charge separation and fragmentation of these species, studied by photoelectron-photoion-photoion coincidence (also called charge separation mass spectrometry) gives insights into bonding and electronic structure. In molecules, the dependence of the fragmentation process on the X-ray energy can reveal cases of site and/or state selective fragmentation. At the ALS the authors have examined the soft X-ray spectroscopy and ionic fragmentation of a number of molecules, including carboranes, silylenes, phosphorus halides, SF{sub 6} and CO{sub 2}. Their work is illustrated using results from the carborane and PF{sub 3} studies.

  18. Two-photon inner-shell transitions in molybdenum

    NASA Astrophysics Data System (ADS)

    Bannett, Yigal B.; Freund, Isaac

    1984-07-01

    The two-photon x-ray emission spectra of inner-shell transitions in metallic Mo have been studied using large-area energy-dispersive Si(Li) detectors and fast, computer-controlled, time-coincidence electronics. The discrete energy-summation spectrum displays a peak at 17.1 keV corresponding to the expected 2s-->1s transition, as well as a second, more intense peak at 19.7 keV. Based upon very recent analytical H-atom calculations by Florescu, this latter peak is tentatively identified as due primarily to 3d-->1s transitions. The continuous two-photon spectrum has also been measured on an absolute intensity scale and compared with a frozen-orbital calculation based upon direct summation of the second-order perturbation expansion for the relevant matrix elements. For the 2s-->1s transition, excellent quantitative agreement is found using the self-consistent-field Hartree-Fock wave functions of Clementi and Roetti. The same calculation predicts that the 3s-->1s transition is of negligible relative amplitude. Because the calculational method is inapplicable to d states, a simple closure approximation is developed which is found to be reasonably good for both the 2s and 3s two-photon transitions, but apparently fails for the 3d transition since it predicts a result which is relatively much too small. Our data are the first for inner-shell transitions and it is anticipated that further developments in both instrumentation and in theory will yield a new, rich, multiphoton inner-shell spectroscopy.

  19. Inner-shell photoionized x-ray lasers

    SciTech Connect

    Moon, Stephen J.

    1998-09-01

    The inner-shell photoionized x-ray lasing scheme is an attractive method for achieving x-ray lasing at short wavelengths, via population inversion following inner-shell photoionization (ISPI). This scheme promises both a short wavelength and a short pulse source of coherent x rays with high average power. In this dissertation a very complete study of the ISPI x-ray laser scheme is done concerning target structure, filter design and lasant medium. An investigation of the rapid rise time of x-ray emission from targets heated by an ultra-short pulse high-intensity optical laser was conducted for use as the x-ray source for ISPI x-ray lasing. Lasing by this approach in C at a wavelength of 45 Å requires a short pulse (about 50 fsec) driving optical laser with an energy of 1-5 J and traveling wave optics with an accuracy of ~ 15 μm. The optical laser is incident on a high-Z target creating a high-density plasma which emits a broadband spectrum of x rays. This x-ray source is passed through a filter to eliminate the low-energy x rays. The remaining high-energy x rays preferentially photoionize inner-shell electrons resulting in a population inversion. Inner-shell photoionized x-ray lasing relies on the large energy of a K-α transition in the initially neutral lasant. The photo energy required to pump this scheme is only slightly greater than the photon energy of the lasing transition yielding a lasing scheme with high quantum efficiency. However, the overall efficiency is reduced due to low x-ray conversion efficiency and the large probability of Auger decay yielding an overall efficiency of ~ 10-7 resulting in an output energy of μJ's. They calculate that a driving laser with a pulse duration of 40 fs, a 10μm x 1 cm line focus, and an energy of 1 J gives an effective gain length product (gl) of 10 in C at 45 Å. At saturation (gl ~ 18) they expect an output of ~ 0.1 μJ per pulse. The short duration of x-ray lasing (< 100 fs) combined with a 10-Hz

  20. Inner shell radial pin geometry and mounting arrangement

    DOEpatents

    Leach, David; Bergendahl, Peter Allen

    2002-01-01

    Circumferentially spaced arrays of support pins are disposed through access openings in an outer turbine shell and have projections received in recesses in forward and aft sections of an inner turbine shell supported from the outer shell. The projections have arcuate sides in a circumferential direction affording line contacts with the side walls of the recesses and are spaced from end faces of the recesses, enabling radial and axial expansion and contraction of the inner shell relative to the outer shell. All loads are taken up in a tangential direction by the outer shell with the support pins taking no radial loadings.

  1. Multiphoton inner-shell ionization of the carbon atom

    NASA Astrophysics Data System (ADS)

    Rey, H. F.; van der Hart, H. W.

    2015-07-01

    We apply time-dependent R -matrix theory to study inner-shell ionization of C atoms in ultrashort high-frequency light fields with a photon energy between 170 and 245 eV. At an intensity of 1017 W /cm2, ionization is dominated by single-photon emission of a 2 ℓ electron, with two-photon emission of a 1 s electron accounting for about 2-3% of all emission processes, and two-photon emission of 2 ℓ contributing about 0.5-1%. Three-photon emission of a 1 s electron is estimated to contribute about 0.01-0.03%. Around a photon energy of 225 eV, two-photon emission of a 1 s electron, leaving C+ in either 1 s 2 s 2 p3 or 1 s 2 p4 , is resonantly enhanced by intermediate 1 s 2 s22 p3 states. The results demonstrate the capability of time-dependent R -matrix theory to describe inner-shell ionization processes including rearrangement of the outer electrons.

  2. Inner-Shell Photodetachment of Nickel Negative Ions

    NASA Astrophysics Data System (ADS)

    Dumitriu, Ileana; Bilodeau, Rene; Gibson, Daniel; Walter, Wes; Gorczyca, Thomas; Aguilar, Alex; Rolles, Daniel; Pesic, Zoran; Berrah, Nora

    2015-05-01

    Transition metals are of interest for their catalytic properties and participation of d-orbital electrons in the bonding properties. Theoretical studies of transition metal negative ions are challenging due to strong electron correlation effects and existence of low-lying electronic states as a result of open d-shell configurations. Experimental studies of transition metal negative ions are limited compared with the ions belonging to the main groups of periodic table and these studies have mostly investigated the valence-shell electrons using laser spectroscopy. Our experiment focuses on inner-shell photodetachment studies of Ni- transition metal ions using the Ion-Photon Beamline on the ALS beamline 10.0.1. Inner-shell photodetachment spectrum was recorded over a range of 30 to 90 eV which includes the 3 p threshold for Ni-. The higher-charge state formation was also observed, indicating multi-electron ejection processes. The absolute cross-section for the production of Ni+ will also be presented.

  3. Inner-shell ionization of atomic targets by Electron Impact

    NASA Astrophysics Data System (ADS)

    Haque, A. K. F.; Talukder, M. R.; Shahjahan, M.; Uddin, M. A.; Basak, A. K.; Saha, B. C.

    2010-03-01

    The knowledge of inner-shell ionization cross sections has not only fundamental importance for understanding collision dynamics of electron-atom interactions, etc, but also is used extensively in many applied fields such as radiation science, astrophysics, plasma physics, etc. The enormous demands of ionization cross sections can only be met by suitable analytical formula that are easy to use and can produce reliable result. We report here an extension of the CVTS [1] model incorporating both the relativistic and ionic factors and tested on 23 atomic targets ranging from He to U [2] with excellent account of the experimental cross sections. [4pt] [1] C. S. Campos, M. A. Z. Vasconcellos, J. C. Trincavelli, and S. Segui, J. Phys. B. 40, 3835 (2007).[0pt] [2] A K F Haque, M R Talukder, M. Shahjahan, M A Uddin, A K Basak and B C Saha, J. Phys. B.; At. Mol. Opt. Phys (under consideration), (2010).

  4. Dislocation-enhanced experimental-scale vacancy loop formation in hcp Zirconium in one single collision cascade.

    PubMed

    Zhou, Wei; Tian, Jiting; Zheng, Jian; Xue, Jianming; Peng, Shuming

    2016-02-12

    Large defects are the main factor leading to the degradation of material properties under irradiation environments. It is commonly assumed that the large defects are mainly formed through cluster growth under continuous irradiations. Besides this mechanism, recent experiments and simulations show that sometimes an individual ion can also directly create a large defect. Here we report a novel mechanism for the formation of the large defects, as discovered by our Molecular Dynamics (MD) simulations of the collision cascades in hcp Zirconium (Zr): a pre-existing edge dislocation (ED) can significantly promote the nucleation of the vacancy clusters, and even facilitate the direct formation of an experimental-scale large vacancy loop (about 3 nm) in only one single displacement cascade. This dislocation-related mechanism may be the key for understanding the experimental results in the low-dose irradiated Zr where the high-density large dislocation loops are observed but difficult to be explained by the two mechanisms mentioned above. Considering that intrinsic dislocations exist in nearly all crystalline materials, our results provide a significant concept: pre-existing dislocations have a strong influence on the primary damage production, and taking them into account is indispensable for assessing and improving the material's irradiation-resistance.

  5. Dislocation-enhanced experimental-scale vacancy loop formation in hcp Zirconium in one single collision cascade

    NASA Astrophysics Data System (ADS)

    Zhou, Wei; Tian, Jiting; Zheng, Jian; Xue, Jianming; Peng, Shuming

    2016-02-01

    Large defects are the main factor leading to the degradation of material properties under irradiation environments. It is commonly assumed that the large defects are mainly formed through cluster growth under continuous irradiations. Besides this mechanism, recent experiments and simulations show that sometimes an individual ion can also directly create a large defect. Here we report a novel mechanism for the formation of the large defects, as discovered by our Molecular Dynamics (MD) simulations of the collision cascades in hcp Zirconium (Zr): a pre-existing edge dislocation (ED) can significantly promote the nucleation of the vacancy clusters, and even facilitate the direct formation of an experimental-scale large vacancy loop (about 3 nm) in only one single displacement cascade. This dislocation-related mechanism may be the key for understanding the experimental results in the low-dose irradiated Zr where the high-density large dislocation loops are observed but difficult to be explained by the two mechanisms mentioned above. Considering that intrinsic dislocations exist in nearly all crystalline materials, our results provide a significant concept: pre-existing dislocations have a strong influence on the primary damage production, and taking them into account is indispensable for assessing and improving the material’s irradiation-resistance.

  6. Dislocation-enhanced experimental-scale vacancy loop formation in hcp Zirconium in one single collision cascade

    PubMed Central

    Zhou, Wei; Tian, Jiting; Zheng, Jian; Xue, Jianming; Peng, Shuming

    2016-01-01

    Large defects are the main factor leading to the degradation of material properties under irradiation environments. It is commonly assumed that the large defects are mainly formed through cluster growth under continuous irradiations. Besides this mechanism, recent experiments and simulations show that sometimes an individual ion can also directly create a large defect. Here we report a novel mechanism for the formation of the large defects, as discovered by our Molecular Dynamics (MD) simulations of the collision cascades in hcp Zirconium (Zr): a pre-existing edge dislocation (ED) can significantly promote the nucleation of the vacancy clusters, and even facilitate the direct formation of an experimental-scale large vacancy loop (about 3 nm) in only one single displacement cascade. This dislocation-related mechanism may be the key for understanding the experimental results in the low-dose irradiated Zr where the high-density large dislocation loops are observed but difficult to be explained by the two mechanisms mentioned above. Considering that intrinsic dislocations exist in nearly all crystalline materials, our results provide a significant concept: pre-existing dislocations have a strong influence on the primary damage production, and taking them into account is indispensable for assessing and improving the material’s irradiation-resistance. PMID:26868496

  7. Electron spectroscopy studies of argon K-shell excitation and vacancy cascades

    SciTech Connect

    Southworth, S.H.; MacDonald, M.A.; LeBrun, T.; Azuma, Y.; Cooper, J.W.

    1995-02-01

    Electron spectroscopy combined with tunable synchrotron radiation has been used for studies of Ar K-shell excitation and vacancy decay processes. In addition, electrons and fluorescent X-rays have been recorded in coincidence to select subsets of the ejected electron spectra. Examples are presented for Ar 1s photoelectrons and KLL and LMM Auger spectra.

  8. Inner shell excitation of Cu, Ag and Au

    NASA Astrophysics Data System (ADS)

    Stauffer, Allan; McEachran, Robert

    2016-09-01

    The ground states of Cu, Ag and Au have the configuration nd10(n +1)s with n = 3, 4 and 5. The lowest excited manifold for Cu and Au has the configuration nd9(n +1)s2 which is well separated from the next excited manifold nd10(n +1)p. However, for Ag, the lowest 4d95s2 level with J = 5/2 lies between the two levels of the 4d105p manifold. In we compared our Relativistic Distorted Wave calculations for the excitation of the 4d105p manifold with experimental measurements which would have included a contribution from the 4d95s2 J = 5/2 level. While we do not expect the cross section for this forbidden transition to be large compared to the optical allowed transitions of the P levels, we decided to investigate excitation of these inner shell levels, in part because they are the lowest excited levels in Cu and Au, We will discuss the theoretical expressions for these excitations as well as give numerical results of our cross section calculations.

  9. Density functional computations for inner-shell excitation spectroscopy

    NASA Astrophysics Data System (ADS)

    Hu, Ching-Han; Chong, Delano P.

    1996-11-01

    The 1 s → π ∗ inner-shell excitation spectra of seven molecules have been studied using density functional theory along with the unrestricted generalized transition state (uGTS) approach. The exchange-correlation potential is based on a combined functional of Becke's exchange (B88) and Perdew's correlation (P86). A scaling procedure based on Clementi and Raimondi's rules for atomic screening is applied to the cc-pVTZ basis set of atoms where a partial core-hole is created in the uGTS calculations. The average absolute deviation between our predicted 1 s → π ∗ excitations eneergies and experimental values is only 0.16 eV. Singlet-triplet splittings of C 1 s → π ∗ transitions of CO, C 2H 2, C 2H 4, and C 6H 6 also agree with experimental observations. The average absolute deviation of our predicted core-electron binding energies and term values is 0.23 and 0.29 eV, respectively.

  10. Cross Sections for Inner-Shell Ionization by Electron Impact

    SciTech Connect

    Llovet, Xavier; Powell, Cedric J.; Salvat, Francesc; Jablonski, Aleksander

    2014-03-15

    An analysis is presented of measured and calculated cross sections for inner-shell ionization by electron impact. We describe the essentials of classical and semiclassical models and of quantum approximations for computing ionization cross sections. The emphasis is on the recent formulation of the distorted-wave Born approximation by Bote and Salvat [Phys. Rev. A 77, 042701 (2008)] that has been used to generate an extensive database of cross sections for the ionization of the K shell and the L and M subshells of all elements from hydrogen to einsteinium (Z = 1 to Z = 99) by electrons and positrons with kinetic energies up to 1 GeV. We describe a systematic method for evaluating cross sections for emission of x rays and Auger electrons based on atomic transition probabilities from the Evaluated Atomic Data Library of Perkins et al. [Lawrence Livermore National Laboratory, UCRL-ID-50400, 1991]. We made an extensive comparison of measured K-shell, L-subshell, and M-subshell ionization cross sections and of Lα x-ray production cross sections with the corresponding calculated cross sections. We identified elements for which there were at least three (for K shells) or two (for L and M subshells) mutually consistent sets of cross-section measurements and for which the cross sections varied with energy as expected by theory. The overall average root-mean-square deviation between the measured and calculated cross sections was 10.9% and the overall average deviation was −2.5%. This degree of agreement between measured and calculated ionization and x-ray production cross sections was considered to be very satisfactory given the difficulties of these measurements.

  11. Contribution of inner shell Compton ionization to the X-ray fluorescence line intensity

    NASA Astrophysics Data System (ADS)

    Fernández, Jorge E.; Scot, Viviana; Di Giulio, Eugenio

    2016-10-01

    The Compton effect is a potential ionization mechanism of atoms. It produces vacancies in inner shells that are filled with the same mechanism of atomic relaxation as the one following photo-absorption. This contribution to X-ray fluorescence emission is frequently neglected because the total Compton cross-section is apparently much lower than the photoelectric one at useful X-ray energies. However, a more careful analysis suggests that is necessary to consider single shell cross sections (instead of total cross sections) as a function of energy. In this article these Compton cross sections are computed for the shells K, L1-L3 and M1-M5 in the framework of the impulse approximation. By comparing the Compton and the photoelectric cross-section for each shell it is then possible to determine the extent of the Compton correction to the intensity of the corresponding characteristic lines. It is shown that for the K shell the correction becomes relevant for excitation energies which are too high to be influent in X-ray spectrometry. In contrast, for L and M shells the Compton contribution is relevant for medium-Z elements and medium energies. To illustrate the different grades of relevance of the correction, for each ionized shell, the energies for which the Compton contribution reaches the extent levels of 1, 5, 10, 20, 50 and 100% of the photoelectric one are determined for all the elements with Z = 11-92. For practical applications it is provided a simple formula and fitting coefficients to compute average correction levels for the shells considered.

  12. Localized hole effects in inner-shell excitation

    SciTech Connect

    Rescigno, T.N.; Orel, A.E.

    1983-10-14

    Ab initio calculations of valence shell ionization potentials have shown that orbital relaxation and correlation differences usually make contributions of comparable magnitude. In marked contrast to this observation is the situation for deep core ionization, where correlation differences (approx. 1 eV) play a relatively minor role compared to orbital relaxation (approx. 20 eV). Theoretical calculations have shown that this relaxation is most easily described if the 1s-vacancy created by a K-shell excitation is allowed to localize on one of the atomic centers. For molecules possessing a center of inversion, this means that the molecular orbitals that best describe the final state do not transform as any irreducible representation of the molecular point group. Recent experimental work by Shaw, King, Read and Cvejanovic and by Stefani and coworkers has prompted us to carry out further calculations on N/sub 2/, as well as analogous investigations of 1s/sub N/ ..-->.. ..pi..* excitation in NO and N/sub 2/O. The generalized oscillator strengths display a striking similarity and point to the essential correctness of the localized hole picture for N/sub 2/. The theoretical calculations are briefly described, followed by a summary of the results and comparison to experiment, followed by a short discussion.

  13. The Attachment of Amino Fragment to Purine: Inner-Shell Structures And Spectra

    SciTech Connect

    Saha, Saumitra; Wang, Feng; MacNaughton, Janay B.; Moewes, Alex; Chong, Denalo P.; /British Columbia U.

    2009-05-11

    The impact of the amino fragment (-NH{sub 2}) attachment on the inner-shell structures and spectra of unsubstituted purine and the purine ring of adenine are studied. Density functional theory calculations, using the LB94/TZ2P//B3LYP/TZVP model, reveal significant site-dependent electronic structural changes in the inner shell of the species. A condensed Fukui function indicates that all of the N and C sites, except for N{sub (1)} and C{sub (5)}, demonstrate significant electrophilic reactivity (f > 0.5 in |e|) in the unsubstituted purine. Once the amino fragment binds to the C{sub (6)} position of purine to form adenine, the electrophilic reactivity of these N and C sites is greatly reduced. As expected, the C{sub (6)} position experiences substantial changes in energy and charge transfer, owing to the formation of the C-NH{sub 2} bond in adenine. The present study reveals that the N1s spectra of adenine inherit the N1s spectra of the unsubstituted purine, whereas the C1s spectra experience significant changes although purine and adenine have geometrically similar carbon frames. The findings also indicate that the attachment of the NH{sub 2} fragment to purine exhibits deeply rooted influences to the inner-shell structures of DNA/RNA bases. The present study suggests that some fragment-based methods may not be applicable to spectral analyses in the inner shell.

  14. Characterizing inner-shell with spectral phase interferometry for direct electric-field reconstruction

    NASA Astrophysics Data System (ADS)

    Mashiko, Hiroki; Yamaguchi, Tomohiko; Oguri, Katsuya; Suda, Akira; Gotoh, Hideki

    2014-12-01

    In many atomic, molecular and solid systems, Lorentzian and Fano profiles are commonly observed in a broad research fields throughout a variety of spectroscopies. As the profile structure is related to the phase of the time-dependent dipole moment, it plays an important role in the study of quantum properties. Here we determine the dipole phase in the inner-shell transition using spectral phase interferometry for direct electric-field reconstruction (SPIDER) with isolated attosecond pulses (IAPs). In addition, we propose a scheme for pulse generation and compression by manipulating the inner-shell transition. The electromagnetic radiation generated by the transition is temporally compressed to a few femtoseconds in the extreme ultraviolet (XUV) region. The proposed pulse-compression scheme may provide an alternative route to producing attosecond pulses of light.

  15. Multislice theory of fast electron scattering incorporating atomic inner-shell ionization.

    PubMed

    Dwyer, C

    2005-09-01

    It is demonstrated how atomic inner-shell ionization can be incorporated into a multislice theory of fast electron scattering. The resulting theory therefore accounts for both inelastic scattering due to inner-shell ionization and dynamical elastic scattering. The theory uses a description of the ionization process based on the angular momentum representation for both the initial and final states of the atomic electron. For energy losses near threshold, only a small number of independent states of the ejected atomic electron need to be considered, reducing demands on computing time, and eliminating the need for tabulated inelastic scattering factors. The theory is used to investigate the influence of the collection aperture size on the spatial origin of the silicon K-shell EELS signal generated by a STEM probe. The validity of a so-called local approximation is also considered.

  16. Inner-shell photoemission from atoms and molecules using synchrotron radiation

    SciTech Connect

    Lindle, D.W.

    1983-12-01

    Photoelectron spectroscopy, in conjunction with synchrotron radiation, has been used to study inner-shell photoemission from atoms and molecules. The time structure of the synchrotron radiation permits the measurements of time-of-flight (TOF) spectra of Auger and photoelectrons, thereby increasing the electron collection efficiency. The double-angle TOF method yielded angle-resolved photoelectron intensities, which were used to determine photoionization cross sections and photoelectron angular distributions in several cases. Comparison to theoretical calculations has been made where possible to help explain observed phenomena in terms of the electronic structure and photoionization dynamics of the systems studied. 154 references, 23 figures, 7 tables.

  17. Ultrafast Charge Rearrangement and Nuclear Dynamics upon Inner-Shell Multiple Ionization of Small Polyatomic Molecules

    NASA Astrophysics Data System (ADS)

    Erk, B.; Rolles, D.; Foucar, L.; Rudek, B.; Epp, S. W.; Cryle, M.; Bostedt, C.; Schorb, S.; Bozek, J.; Rouzee, A.; Hundertmark, A.; Marchenko, T.; Simon, M.; Filsinger, F.; Christensen, L.; De, S.; Trippel, S.; Küpper, J.; Stapelfeldt, H.; Wada, S.; Ueda, K.; Swiggers, M.; Messerschmidt, M.; Schröter, C. D.; Moshammer, R.; Schlichting, I.; Ullrich, J.; Rudenko, A.

    2013-02-01

    Ionization and fragmentation of methylselenol (CH3SeH) molecules by intense (>1017W/cm2) 5 fs x-ray pulses (ℏω=2keV) are studied by coincident ion momentum spectroscopy. We contrast the measured charge state distribution with data on atomic Kr, determine kinetic energies of resulting ionic fragments, and compare them to the outcome of a Coulomb explosion model. We find signatures of ultrafast charge redistribution from the inner-shell ionized Se atom to its molecular partners, and observe significant displacement of the atomic constituents in the course of multiple ionization.

  18. Ultrafast charge rearrangement and nuclear dynamics upon inner-shell multiple ionization of small polyatomic molecules.

    PubMed

    Erk, B; Rolles, D; Foucar, L; Rudek, B; Epp, S W; Cryle, M; Bostedt, C; Schorb, S; Bozek, J; Rouzee, A; Hundertmark, A; Marchenko, T; Simon, M; Filsinger, F; Christensen, L; De, S; Trippel, S; Küpper, J; Stapelfeldt, H; Wada, S; Ueda, K; Swiggers, M; Messerschmidt, M; Schröter, C D; Moshammer, R; Schlichting, I; Ullrich, J; Rudenko, A

    2013-02-01

    Ionization and fragmentation of methylselenol (CH(3)SeH) molecules by intense (>10(17) W/cm(2)) 5 fs x-ray pulses (ħω=2 keV) are studied by coincident ion momentum spectroscopy. We contrast the measured charge state distribution with data on atomic Kr, determine kinetic energies of resulting ionic fragments, and compare them to the outcome of a Coulomb explosion model. We find signatures of ultrafast charge redistribution from the inner-shell ionized Se atom to its molecular partners, and observe significant displacement of the atomic constituents in the course of multiple ionization.

  19. HST/ACS observations of shell galaxies: inner shells, shell colours and dust

    NASA Astrophysics Data System (ADS)

    Sikkema, G.; Carter, D.; Peletier, R. F.; Balcells, M.; Del Burgo, C.; Valentijn, E. A.

    2007-06-01

    Context: Shells in Elliptical Galaxies are faint, sharp-edged features, believed to provide evidence for a merger event. Accurate photometry at high spatial resolution is needed to learn on presence of inner shells, population properties of shells, and dust in shell galaxies. Aims: Learn more about the origin of shells and dust in early type galaxies. Methods: V-I colours of shells and underlying galaxies are derived, using HST Advanced Camera for Surveys (ACS) data. A galaxy model is made locally in wedges and subtracted to determine shell profiles and colours. We applied Voronoi binning to our data to get smoothed colour maps of the galaxies. Comparison with N-body simulations from the literature gives more insight to the origin of the shell features. Shell positions and dust characteristics are inferred from model galaxy subtracted images. Results: The ACS images reveal shells well within the effective radius in some galaxies (at 0.24 re = 1.7 kpc in the case of NGC 5982). In some cases, strong nuclear dust patches prevent detection of inner shells. Most shells have colours which are similar to the underlying galaxy. Some inner shells are redder than the galaxy. All six shell galaxies show out of dynamical equilibrium dust features, like lanes or patches, in their central regions. Our detection rate for dust in the shell ellipticals is greater than that found from HST archive data for a sample of normal early-type galaxies, at the 95% confidence level. Conclusions: The merger model describes better the shell distributions and morphologies than the interaction model. Red shell colours are most likely due to the presence of dust and/or older stellar populations. The high prevalence and out of dynamical equilibrium morphologies of the central dust features point towards external influences being responsible for visible dust features in early type shell galaxies. Inner shells are able to manifest themselves in relatively old shell systems. Based on observations made

  20. Separation of two-electron photoexcited atomic processes near the inner-shell threshold.

    PubMed

    Kavcic, M; Zitnik, M; Bucar, K; Mihelic, A; Stuhec, M; Szlachetko, J; Cao, W; Alonso Mori, R; Glatzel, P

    2009-04-10

    By means of a high resolution resonant inelastic x-ray scattering spectroscopy, we have for the first time separated spectral features pertaining to different two-electron atomic processes in the vicinity of an inner-shell threshold. Contributions of shakeoff, shakeup, and resonant 1s3p double excitations were extracted from the Ar KM-M{2,3}M x-ray satellite line intensity measured as a function of photon energy from [1s3p] double excitation threshold to saturation. The isolated [1s3p]nln'l' excitation spectrum is critically compared to the outcome of the multiconfiguration Dirac-Fock model with relaxation.

  1. 4 d -inner-shell ionization of X e+ ions and subsequent Auger decay

    NASA Astrophysics Data System (ADS)

    Khalal, M. A.; Lablanquie, P.; Andric, L.; Palaudoux, J.; Penent, F.; Bučar, K.; Žitnik, M.; Püttner, R.; Jänkälä, K.; Cubaynes, D.; Guilbaud, S.; Bizau, J.-M.

    2017-07-01

    We have studied X e+4 d inner-shell photoionization in a direct experiment on X e+ ions, merging an ion and a photon beam and detecting the ejected electrons with a cylindrical mirror analyzer. The measured 4 d photoelectron spectrum is compared to the 4 d core valence double ionization spectrum of the neutral Xe atom, obtained with a magnetic bottle spectrometer. This multicoincidence experiment gives access to the spectroscopy of the individual X e2 +4 d-15 p-1 states and to their respective Auger decays, which are found to present a strong selectivity. The experimental results are interpreted with the help of ab initio calculations.

  2. Inner-Shell Photoionization: Teijo A˚berg's Concept of RRRS

    NASA Astrophysics Data System (ADS)

    Armen, G. Bradley

    2003-01-01

    Teijo Åberg died on December 29, 2000 — and with his passing we have lost a gifted and important member of our community. Over the years Teijo has made many major contributions to the science of x-ray and inner-shell physics. Perhaps the most visionary of these was his idea of radiative and radiationless resonant Raman scattering (RRRRS) [1]. This arose as an outgrowth of his earlier thoughts on Auger [2] and x-ray [3] processes. It is visionary in that it attempts to unify the various aspects of inner-shell photoexcitation and decay as different aspects of the same basic process, i.e. resonant inelastic x-ray scattering. In honor and memory of Teijo, and as a last attempt to promote his ideas, I describe here the theory and some of its consequences. First, RRRRS is outlined in a semi-rigorous form, with emphasis placed on the physical nature of the concepts. Then, using the example of atomic K-shell photoionization, we see how features such as fluorescence and photoelectron lines arise in a natural way as manifestations of resonance scattering.

  3. Inner-shell radiation from wire array implosions on the Zebra generator

    SciTech Connect

    Ouart, N. D.; Giuliani, J. L.; Dasgupta, A.; Safronova, A. S.; Kantsyrev, V. L.; Esaulov, A. A.; Shrestha, I.; Weller, M. E.; Shlyaptseva, V.; Osborne, G. C.; Stafford, A.; Keim, S.; Apruzese, J. P.; Clark, R. W.

    2014-03-15

    Implosions of brass wire arrays on Zebra have produced L-shell radiation as well as inner-shell Kα and Kβ transitions. The L-shell radiation comes from ionization stages around the Ne-like charge state that is largely populated by a thermal electron energy distribution function, while the K-shell photons are a result of high-energy electrons ionizing or exciting an inner-shell (1s) electron from ionization stages around Ne-like. The K- and L-shell radiations were captured using two time-gated and two axially resolved time-integrated spectrometers. The electron beam was measured using a Faraday cup. A multi-zone non-local thermodynamic equilibrium pinch model with radiation transport is used to model the x-ray emission from experiments for the purpose of obtaining plasma conditions. These plasma conditions are used to discuss some properties of the electron beam generated by runaway electrons. A simple model for runaway electrons is examined to produce the Kα radiation, but it is found to be insufficient.

  4. Inner-Shell Photon-Ionized X-Ray Laser at 45(Angstrom)

    SciTech Connect

    Weber, F; Celliers, P; Moon, S; Snavely, R; Da Silva, L

    2002-02-01

    This report summarizes the major accomplishments of this three-year Laboratory Directed Research and Development (LDRD) Lab Wide (LW) project entitled, ''An Inner-Shell Photo-Ionized X-Ray Laser at 45 {angstrom}'', tracking code 99-LW-042. The most significant accomplishments of this project include the design of a suitable x-ray laser target, the invention of a measurement technique for the determination of rise times of x-ray pulses on the order of 50 femtoseconds, and a novel setup for generating a traveling wave with an ultrashort optical laser pulse. The pump probe technique for rise time measurement will allow us to detect ultrashort x-ray pulses, whose generation by means of a variety of 4th generation light sources is currently under planning elsewhere.

  5. Retrieving transient conformational molecular structure information from inner-shell photoionization of laser-aligned molecules

    SciTech Connect

    Wang, Xu; Le, Anh -Thu; Yu, Chao; Lucchese, R. R.; Lin, C. D.

    2016-03-30

    We discuss a scheme to retrieve transient conformational molecular structure information using photoelectron angular distributions (PADs) that have averaged over partial alignments of isolated molecules. The photoelectron is pulled out from a localized inner-shell molecular orbital by an X-ray photon. We show that a transient change in the atomic positions from their equilibrium will lead to a sensitive change in the alignment-averaged PADs, which can be measured and used to retrieve the former. Exploiting the experimental convenience of changing the photon polarization direction, we show that it is advantageous to use PADs obtained from multiple photon polarization directions. Lastly, a simple single-scattering model is proposed and benchmarked to describe the photoionization process and to do the retrieval using a multiple-parameter fitting method.

  6. Separation of Two-Electron Photoexcited Atomic Processes near the Inner-Shell Threshold

    SciTech Connect

    Kavcic, M.; Zitnik, M.; Bucar, K.; Mihelic, A.; Stuhec, M.; Szlachetko, J.; Cao, W.; Alonso Mori, R.; Glatzel, P.

    2009-04-10

    By means of a high resolution resonant inelastic x-ray scattering spectroscopy, we have for the first time separated spectral features pertaining to different two-electron atomic processes in the vicinity of an inner-shell threshold. Contributions of shakeoff, shakeup, and resonant 1s3p double excitations were extracted from the Ar KM-M{sub 2,3}M x-ray satellite line intensity measured as a function of photon energy from [1s3p] double excitation threshold to saturation. The isolated [1s3p]nln{sup '}l{sup '} excitation spectrum is critically compared to the outcome of the multiconfiguration Dirac-Fock model with relaxation.

  7. Retrieving transient conformational molecular structure information from inner-shell photoionization of laser-aligned molecules

    DOE PAGES

    Wang, Xu; Le, Anh -Thu; Yu, Chao; ...

    2016-03-30

    We discuss a scheme to retrieve transient conformational molecular structure information using photoelectron angular distributions (PADs) that have averaged over partial alignments of isolated molecules. The photoelectron is pulled out from a localized inner-shell molecular orbital by an X-ray photon. We show that a transient change in the atomic positions from their equilibrium will lead to a sensitive change in the alignment-averaged PADs, which can be measured and used to retrieve the former. Exploiting the experimental convenience of changing the photon polarization direction, we show that it is advantageous to use PADs obtained from multiple photon polarization directions. Lastly, amore » simple single-scattering model is proposed and benchmarked to describe the photoionization process and to do the retrieval using a multiple-parameter fitting method.« less

  8. Inner-shell photodetachment from N i- : A giant Feshbach resonance

    NASA Astrophysics Data System (ADS)

    Dumitriu, I.; Bilodeau, R. C.; Gorczyca, T. W.; Walter, C. W.; Gibson, N. D.; Rolles, D.; Pešić, Z. D.; Aguilar, A.; Berrah, N.

    2017-08-01

    Inner-shell photodetachment from N i-([Ar ] 3 d94 s2) leading to N i+,N i2 + , and N i3 + ion production was studied near and above the 3 p excitation region, in the 60-90 eV photon energy range, using a merged ion-photon beam technique. The absolute photodetachment cross section of N i- leading to N i+ ion production was measured. The 3 p →3 d photoexcitation in N i- gives rise to a giant Feshbach resonance. In the near-threshold region, a Fano profile, modified by a Wigner s -wave (l =0 ) threshold law, accurately fits the N i- single-photodetachment cross section. A lower-order R -matrix calculation shows overall agreement with essential features of the experimental data, confirming the nature of the strong, asymmetric Fano profile of the giant 3 p →3 d photoexcitation-autodetachment resonance in N i- .

  9. Isomer-dependent fragmentation dynamics of inner-shell photoionized difluoroiodobenzene

    DOE PAGES

    Ablikim, Utuq; Bomme, Cédric; Savelyev, Evgeny; ...

    2017-05-11

    The fragmentation dynamics of 2,6- and 3,5-difluoroiodobenzene after iodine 4d inner-shell photoionization with soft X-rays are studied using coincident electron and ion momentum imaging. By analyzing the momentum correlation between iodine and fluorine cations in three-fold ion coincidence events, we can distinguish the two isomers experimentally. Classical Coulomb explosion simulations are in overall agreement with the experimentally determined fragment ion kinetic energies and momentum correlations and point toward different fragmentation mechanisms and time scales. Finally, while most three-body fragmentation channels show clear evidence for sequential fragmentation on a time scale larger than the rotational period of the fragments, the breakupmore » into iodine and fluorine cations and a third charged co-fragment appears to occur within several hundred femtoseconds.« less

  10. Retrieving transient conformational molecular structure information from inner-shell photoionization of laser-aligned molecules

    PubMed Central

    Wang, Xu; Le, Anh-Thu; Yu, Chao; Lucchese, R. R.; Lin, C. D.

    2016-01-01

    We discuss a scheme to retrieve transient conformational molecular structure information using photoelectron angular distributions (PADs) that have averaged over partial alignments of isolated molecules. The photoelectron is pulled out from a localized inner-shell molecular orbital by an X-ray photon. We show that a transient change in the atomic positions from their equilibrium will lead to a sensitive change in the alignment-averaged PADs, which can be measured and used to retrieve the former. Exploiting the experimental convenience of changing the photon polarization direction, we show that it is advantageous to use PADs obtained from multiple photon polarization directions. A simple single-scattering model is proposed and benchmarked to describe the photoionization process and to do the retrieval using a multiple-parameter fitting method. PMID:27025410

  11. Any Density Changes Near the Inner Shell of the Planetary Nebula NGC 6803?

    NASA Astrophysics Data System (ADS)

    Lee, Seong-Jae; Hyung, S.

    2013-06-01

    Most recent high dispersion spectral data, secured at Lick Observatory in 1995 and 2001, suggested a large density increase near the inner shell boundary of the elliptical ring planetary nebula NGC 6803, e.g., Ne = 8900 (10^3.95) --> 14,400 (10^4.16)/cm^3 in [Ar IV] (Lee and Hyung 2013). We further analyzed high dispersion spectroscopic data observed in 2012 February with the Bohyunsan fiber-fed echelle spectrograph (BOES) attached to the Bohyunsan Observatory 1.8m telescope. The BOES diagnostic line ratios indicate a large change between 2001 & 2012 observations; -0.23, +0.39, +0.13, -0.28 dex for [S II], [O II], [N II], and [Cl III], respectively. For example, the 2012 BOES [Ar IV] line ratio implies a decreasing density of N=11,700 (10^4.07)/cm^3. We discuss the changes of physical conditions and kinematics of NGC 6803.

  12. Advances Toward Inner-Shell Photo-Ionization X-Ray Lasing at 45 (Angstrom)

    SciTech Connect

    Moon, S J; Weber, F A; Celliers, P M; Eder, D C

    2002-07-18

    The inner-shell photo-ionization (ISPI) scheme requires photon energies at least high enough to photo-ionize the K-shell. {approx}286 eV, in the case of carbon. As a consequence of the higher cross-section, the inner-shell are selectively knocked out, leaving a hole state 1s2s{sup 2}2p{sup 2} in the singly charged carbon ion. This generates a population inversion to the radiatively connected state 1s{sup 2}2s{sup 2}2p in C+, leading to gain on the 1s-2p transition at 45 {angstrom}. The resonant character of the lasing transition in the single ionization state intrinsically allows much higher quantum efficiency compared to other schemes. Competing processes that deplete the population inversion include auto-ionization, Auger decay, and in particular collisional ionization of the outer-shell electrons by electrons generated during photo-ionization. These competing processes rapidly quench the gain. Consequently, the pump method must be capable of populating the inversion at a rate faster than the competing processes. This can be achieved by an ultra-fast, high intensity laser that is able to generate an ultra-fast, bright x-ray source. With current advances in the development of high-power, ultra-short pulse lasers it is possible to realize fast x-ray sources based that can deliver powerful pulses of light in the multiple hundred terawatt regime and beyond. They will discuss in greater detail concept, target design and a series of x-ray spectroscopy investigations they have conducted in order to optimize the absorber/x-ray converter--filter package.

  13. The importance of inner-shell electronic structure for enhancing the EUV absorption of photoresist materials

    NASA Astrophysics Data System (ADS)

    Closser, Kristina D.; Ogletree, D. Frank; Naulleau, Patrick; Prendergast, David

    2017-04-01

    In order to increase computation power and efficiency, the semiconductor industry continually strives to reduce the size of features written using lithographic techniques. The planned switch to a shorter wavelength extreme ultraviolet (EUV) source presents a challenge for the associated photoresists, which in their current manifestation show much poorer photoabsorption cross sections for the same dose. Here we consider the critical role that an inner-shell electronic structure might play in enhancing photoabsorption cross sections, which one can control by the choice of substituent elements in the photoresist. In order to increase the EUV sensitivity of current photoresists, it is critical to consider the inner-shell atomic structure of the elements that compose the materials. We validate this hypothesis using a series of halogenated organic molecules, which all have similar valence structures, but differ in the character of their semi-core and deep valence levels. Using various implementations of time-dependent density functional theory, the absorption cross sections are computed for the model systems of CH3X , X = H, OH, F, Cl, Br, I, as well as a representative polymer fragment: 2-methyl-phenol and its halogenated analogues. Iodine has a particularly high cross section in the EUV range, which is due to delayed absorption by its 4d electrons. The computational results are compared to standard database values and experimental data when available. Generally we find that the states that dominate the EUV oscillator strength are generated by excitations of deep valence or semi-core electrons, which are primarily atomic-like and relatively insensitive to the specific molecular structure.

  14. Analysis of uv-visible fluorescence following inner-shell excitation of N2 molecules

    NASA Astrophysics Data System (ADS)

    Marquette, A.; Gisselbrecht, M.; Benten, W.; Meyer, M.

    2000-08-01

    Light emission induced by inner-shell excitation of N2 molecules has been investigated in the wavelength region 250<=λfluo<=1000 nm. Synchrotron radiation from the SuperACO storage ring in Orsay (France) has been used for the photoexcitation and a high-resolution secondary monochromator (Δλfluo=0.2 nm) for the spectral analysis of the fluorescence light. Vibrationally resolved molecular N+2 (B 2Σ+u-->X 2Σ+g) transitions show clearly the coupling between the (1s-->π*) core excitation and the ionization of the (2σu) valence electron. The main contribution to the fluorescence spectra stems from excited neutral and excited singly charged atoms produced by the dissociation of highly excited molecular states. The singly ionized N+ atoms are produced upon resonant (1s-->π*) excitation as well as upon excitation to the (1s-1-σ*) continuum resonance. Fluorescence transitions of the type N+ 1s22s22p4f-->1s22s22p3d as well as 2p3d-->2p3p and 2p3p-->2p3s have been analyzed. The neutral N fragment is found nearly exclusively after excitation of the (1s-1-π*) resonance, and mainly radiative decay of the N 1s22s22p23p excited states has been observed. The obtained experimental results represent additional and very detailed information on the final states of the molecular dissociation and provide a necessary basis for a theoretical treatment of the relaxation processes of inner-shell excited molecules.

  15. Use of the Bethe equation for inner-shell ionization by electron impact

    NASA Astrophysics Data System (ADS)

    Powell, Cedric J.; Llovet, Xavier; Salvat, Francesc

    2016-05-01

    We analyzed calculated cross sections for K-, L-, and M-shell ionization by electron impact to determine the energy ranges over which these cross sections are consistent with the Bethe equation for inner-shell ionization. Our analysis was performed with K-shell ionization cross sections for 26 elements, with L-shell ionization cross sections for seven elements, L3-subshell ionization cross sections for Xe, and M-shell ionization cross sections for three elements. The validity (or otherwise) of the Bethe equation could be checked with Fano plots based on a linearized form of the Bethe equation. Our Fano plots, which display theoretical cross sections and available measured cross sections, reveal two linear regions as predicted by de Heer and Inokuti [in Electron Impact Ionization, edited by T. D. Märk and G. H. Dunn, (Springer-Verlag, Vienna, 1985), Chap. 7, pp. 232-276]. For each region, we made linear fits and determined values of the two element-specific Bethe parameters. We found systematic variations of these parameters with atomic number for both the low- and the high-energy linear regions of the Fano plots. We also determined the energy ranges over which the Bethe equation can be used.

  16. Use of the Bethe equation for inner-shell ionization by electron impact

    SciTech Connect

    Powell, Cedric J.; Llovet, Xavier; Salvat, Francesc

    2016-05-14

    We analyzed calculated cross sections for K-, L-, and M-shell ionization by electron impact to determine the energy ranges over which these cross sections are consistent with the Bethe equation for inner-shell ionization. Our analysis was performed with K-shell ionization cross sections for 26 elements, with L-shell ionization cross sections for seven elements, L{sub 3}-subshell ionization cross sections for Xe, and M-shell ionization cross sections for three elements. The validity (or otherwise) of the Bethe equation could be checked with Fano plots based on a linearized form of the Bethe equation. Our Fano plots, which display theoretical cross sections and available measured cross sections, reveal two linear regions as predicted by de Heer and Inokuti [in Electron Impact Ionization, edited by T. D. Märk and G. H. Dunn, (Springer-Verlag, Vienna, 1985), Chap. 7, pp. 232–276]. For each region, we made linear fits and determined values of the two element-specific Bethe parameters. We found systematic variations of these parameters with atomic number for both the low- and the high-energy linear regions of the Fano plots. We also determined the energy ranges over which the Bethe equation can be used.

  17. Inner-shell electron spectroscopy and chemical properties of atoms and small molecules

    SciTech Connect

    T. Darrah Thomas

    2009-01-21

    The program has been concerned with gas-phase carbon 1s photoelectron spectroscopy of a number of molecules of potential chemical interest. The primary goals have been to determine carbon 1s ionization energies with a view of relating these to other chemical properties such as electronegativity, acidity, basicity, and reactivity, in order to provide a better understanding of these fundamental properties. The role of electron-donating (methyl) and electron-withdrawing (fluoro) substituents on the carbon 1s ionization energies of substituted benzenes has been studied., and these results have been related to measurements of the reactivities of the same molecule as well as to their affinities for protons (basicity). Opportunities for investigation in unplanned areas have arisen, and the program has been modified to take advantage of these. One has been the realization that, under certain circumstances, inner-shell ionization energies may depend on the molecular conformation. Several examples of this phenomenon have been investigated and it has been shown that this technique provides a tool for the measurement of the energy differences between different conformers of the same substance. The other has been the demonstration that photoelectron recoil can lead to the excitation of vibrational modes that are forbidden in the normal view of photoemission and to rotational heating of the molecule that increases with the energy of the exciting radiation.

  18. Progress on precision measurements of inner shell transitions in highly charged ions at an ECR ion source

    SciTech Connect

    Szabo, Csilla I.; Indelicato, Paul; LeBigot, Eric-Olivier; Vallette, Alexandre; Amaro, Pedro; Guerra, Mauro; Gumberidze, Alex

    2012-05-25

    Inner shell transitions of highly charged ions produced in the plasma of an Electron Cyclotron Resonance Ion Source (ECRIS) were observed the first time by a Double Crystal Spectrometer (DCS). The DCS is a well-used tool in precision x-ray spectroscopy due to its ability of precision wavelength measurement traced back to a relative angle measurement. Because of its requirement for a bright x-ray source the DCS has not been used before in direct measurements of highly charged ions (HCI). Our new precision measurement of inner shell transitions in HCI is not just going to provide new x-ray standards for quantum metrology but can also give information about the plasma in which the ions reside. Ionic temperatures and with that the electron density can be determined by thorough examination of line widths measured with great accuracy.

  19. Optical oscillator strengths for valence-shell and Br-3d inner-shell excitations of HCl and HBr.

    PubMed

    Li, Wen-Bin; Zhu, Lin-Fan; Yuan, Zhen-Sheng; Liu, Xiao-Jing; Xu, Ke-Zun

    2006-10-21

    Absolute optical oscillator strength density spectra for valence-shell excitations of HCl and HBr, as well as for Br-3d inner-shell excitations of HBr, have been determined by high-resolution electron-energy-loss-spectroscopy method in the dipole limit. Absolute optical oscillator strengths for the discrete transitions of HCl and HBr are reported and compared with the previous results determined by the photoabsorption method.

  20. Multilayer nanoparticles with a magnetite core and a polycation inner shell as pH-responsive carriers for drug delivery

    NASA Astrophysics Data System (ADS)

    Guo, Miao; Yan, Yu; Liu, Xiaozhou; Yan, Husheng; Liu, Keliang; Zhang, Hongkai; Cao, Youjia

    2010-03-01

    Nanocarriers with multilayer core-shell architecture were prepared by coating a superparamagnetic Fe3O4 core with a triblock copolymer. The first block of the copolymer formed the biocompatible outermost shell of the nanocarrier. The second block that contains amino groups and hydrophobic moiety formed the inner shell. The third block bound tightly onto the Fe3O4 core. Chlorambucil (an anticancer agent) and indomethacin (an anti-inflammation agent), each containing a carboxyl group and a hydrophobic moiety, were loaded into the amino-group-containing inner shell by a combination of ionic and hydrophobic interactions. The release rate of the loaded drugs was slow at pH 7.4, mimicking the blood environment, whereas the release rate increased significantly at acidic pH, mimicking the intracellular conditions in the endosome/lysosome. This can be attributed to the disruption of the ionic bond caused by protonation of the carboxylate anion of the drugs and the swelling of the inner shell caused by protonation of the amino groups.

  1. Multilayer nanoparticles with a magnetite core and a polycation inner shell as pH-responsive carriers for drug delivery.

    PubMed

    Guo, Miao; Yan, Yu; Liu, Xiaozhou; Yan, Husheng; Liu, Keliang; Zhang, Hongkai; Cao, Youjia

    2010-03-01

    Nanocarriers with multilayer core-shell architecture were prepared by coating a superparamagnetic Fe(3)O(4) core with a triblock copolymer. The first block of the copolymer formed the biocompatible outermost shell of the nanocarrier. The second block that contains amino groups and hydrophobic moiety formed the inner shell. The third block bound tightly onto the Fe(3)O(4) core. Chlorambucil (an anticancer agent) and indomethacin (an anti-inflammation agent), each containing a carboxyl group and a hydrophobic moiety, were loaded into the amino-group-containing inner shell by a combination of ionic and hydrophobic interactions. The release rate of the loaded drugs was slow at pH 7.4, mimicking the blood environment, whereas the release rate increased significantly at acidic pH, mimicking the intracellular conditions in the endosome/lysosome. This can be attributed to the disruption of the ionic bond caused by protonation of the carboxylate anion of the drugs and the swelling of the inner shell caused by protonation of the amino groups.

  2. Selective Fragmentation of Radiation-Sensitive Novel Polymeric Resist Materials by Inner-Shell Irradiation.

    PubMed

    Chagas, Gabriela Ramos; Satyanarayana, Vardhineedi Sri Venkata; Kessler, Felipe; Belmonte, Guilherme Kretzmann; Gonsalves, Kenneth E; Weibel, Daniel Eduardo

    2015-08-05

    Two key concepts in extreme ultraviolet lithography (EUVL) are important for it to be a candidate for the mass production of future integrated circuits: the polymer formulation and the photofragmentation process. In this work, both concepts were carefully studied. The design and synthesis of radiation-sensitive organic polymeric materials based on the inclusion of a radiation-sensitive tetrahydrothiophenium functional group are outlined. A 1-(4-methacryloyoxy)naphthalene-1-yl)tetrahydro-1H-thiophenium trifluoromethanesulfonate (MANTMS) monomer containing the tetrahydrothiophenium group undergoes homo- and copolymerizations using free-radical polymerization with a 2,2'-azobis(isobutyronitrile) initiator. The surface photodegradation and oxidation of these novel polymeric materials were investigated using highly monochromatized soft X-rays from synchrotron radiation at the carbon K-edge excitation region. An efficient functionalization was observed when the excitation energy was tuned to C 1s → π*C═C. A high rate of defluorination and a loss of sulfonated groups as a result of an increase in the irradiation time for the MANTMS homopolymer thin films were mainly observed under the π*C═C excitation of the naphthyl functional groups. On the contrary, excitation similar to C 1s → π*C═O or C 1s → σ*C-F did not produce important degradation, showing a highly selective process of bond breaking. Additionally, the presence of methyl methacrylate copolymer in the original MANTMS yielded a much higher degree of stability against inner-shell radiation damage. Our results highlight the importance of choosing the right polymer formulation and excitation energy to produce a sensitive material for EUVL without using the concept of chemical amplification.

  3. Influence of the Inner-Shell Architecture on Quantum Yield and Blinking Dynamics in Core/Multishell Quantum Dots.

    PubMed

    Bajwa, Pooja; Gao, Feng; Nguyen, Anh; Omogo, Benard; Heyes, Colin D

    2016-03-03

    Choosing the composition of a shell for QDs is not trivial, as both the band-edge energy offset and interfacial lattice mismatch influence the final optical properties. One way to balance these competing effects is by forming multishells and/or gradient-alloy shells. However, this introduces multiple interfaces, and their relative effects on quantum yield and blinking are not yet fully understood. Here, we undertake a systematic, comparative study of the addition of inner shells of a single component versus gradient-alloy shells of cadmium/zinc chalogenides onto CdSe cores, and then capping with a thin ZnS outer shell to form various core/multishell configurations. We show that architecture of the inner shell between the CdSe core and the outer ZnS shell significantly influences both the quantum yield and blinking dynamics, but that these effects are not correlated-a high ensemble quantum yield doesn't necessarily equate to reduced blinking. Two mathematical models have been proposed to describe the blinking dynamics-the more common power-law model and a more recent multiexponential model. By binning the same data with 1 and 20 ms resolution, we show that the on times can be better described by the multiexponential model, whereas the off times can be better described by the power-law model. We discuss physical mechanisms that might explain this behavior and how it can be affected by the inner-shell architecture. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Hot surface ionic line emission and cold K-inner shell emission from petawatt-laser irradiated Cu foil targets

    SciTech Connect

    Theobald, W; Akli, K; Clarke, R; Delettrez, J A; Freeman, R R; Glenzer, S; Green, J; Gregori, G; Heathcote, R; Izumi, N; King, J A; Koch, J A; Kuba, J; Lancaster, K; MacKinnon, A J; Key, M; Mileham, C; Myatt, J; Neely, D; Norreys, P A; Park, H; Pasely, J; Patel, P; Regan, S P; Sawada, H; Shepherd, R; Snavely, R; Stephens, R B; Stoeckl, C; Storm, M; Zhang, B; Sangster, T C

    2005-12-13

    A hot, T{sub e} {approx} 2- to 3-keV surface plasma was observed in the interaction of a 0.7-ps petawatt laser beam with solid copper-foil targets at intensities >10{sup 20} W/cm{sup 2}. Copper K-shell spectra were measured in the range of 8 to 9 keV using a single-photon-counting x-ray CCD camera. In addition to K{sub {alpha}} and K{sub {beta}} inner-shell lines, the emission contained the Cu He{sub {alpha}} and Ly{sub {alpha}} lines, allowing the temperature to be inferred. These lines have not been observed previously with ultrafast laser pulses. For intensities less than 3 x 10{sup 18} W/cm{sup 2}, only the K{sub {alpha}} and K{sub {beta}} inner-shell emissions are detected. Measurements of the absolute K{sub {alpha}} yield as a function of the laser intensity are in agreement with a model that includes refluxing and confinement of the suprathermal electrons in the target volume.

  5. Electron impact action spectroscopy of mass/charge selected macromolecular ions: Inner-shell excitation of ubiquitin protein

    SciTech Connect

    Rankovic, Milos Lj.; Giuliani, Alexandre; Milosavljevic, Aleksandar R.

    2016-02-11

    In this study, we have performed inner-shell electron impact action spectroscopy of mass and charge selected macromolecular ions. For this purpose, we have coupled a focusing electron gun with a linear quadrupole ion trap mass spectrometer. This experiment represents a proof of principle that an energy-tunable electron beam can be used in combination with radio frequency traps as an activation method in tandem mass spectrometry (MS2) and allows performing action spectroscopy. Electron impact MS2 spectra of multiply protonated ubiquitin protein ion have been recorded at incident electron energies around the carbon 1s excitation. Both MS2 and single ionization energy dependence spectra are compared with literature data obtained using the soft X-ray activation conditions.

  6. Electron impact action spectroscopy of mass/charge selected macromolecular ions: Inner-shell excitation of ubiquitin protein

    DOE PAGES

    Rankovic, Milos Lj.; Giuliani, Alexandre; Milosavljevic, Aleksandar R.

    2016-02-11

    In this study, we have performed inner-shell electron impact action spectroscopy of mass and charge selected macromolecular ions. For this purpose, we have coupled a focusing electron gun with a linear quadrupole ion trap mass spectrometer. This experiment represents a proof of principle that an energy-tunable electron beam can be used in combination with radio frequency traps as an activation method in tandem mass spectrometry (MS2) and allows performing action spectroscopy. Electron impact MS2 spectra of multiply protonated ubiquitin protein ion have been recorded at incident electron energies around the carbon 1s excitation. Both MS2 and single ionization energy dependencemore » spectra are compared with literature data obtained using the soft X-ray activation conditions.« less

  7. Exciton Lines in Luminescence Spectra of NixZn1-xO under Inner Shell Excitation

    NASA Astrophysics Data System (ADS)

    Churmanov, V. N.; Sokolov, V. I.; Gruzdev, N. B.; Ivanov, V. Yu.; Pustovarov, V. A.

    The paper presents the results of the study of two narrow luminescence lines I1 and I2 at the energies of 3.339 and 3.393 eV respectively in NiO and solid state solution Ni0.6Zn0.4O. The luminescence spectroscopy with a sub-nanosecond time resolution upon selective photoexcitation in the energy range of absorption of the inner shells Zn M- and Ni L2,3- edges of Zn- and Ni- ions was used to promote proposed earlier mechanism of origin of luminescence lines I1 and I2. Photoluminescence decay kinetics of NiO and solid state solution Ni0.6Zn0.4O under soft x-ray excitation are discussed. The doublet of I1 and I2 lines is believed to arise due to the radiative annihilation of p-d excitons.

  8. Direct observation of ring-opening dynamics in strong-field ionized selenophene using femtosecond inner-shell absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Lackner, Florian; Chatterley, Adam S.; Pemmaraju, C. D.; Closser, Kristina D.; Prendergast, David; Neumark, Daniel M.; Leone, Stephen R.; Gessner, Oliver

    2016-12-01

    Femtosecond extreme ultraviolet transient absorption spectroscopy is used to explore strong-field ionization induced dynamics in selenophene (C4H4Se). The dynamics are monitored in real-time from the viewpoint of the Se atom by recording the temporal evolution of element-specific spectral features near the Se 3d inner-shell absorption edge (˜58 eV). The interpretation of the experimental results is supported by first-principles time-dependent density functional theory calculations. The experiments simultaneously capture the instantaneous population of stable molecular ions, the emergence and decay of excited cation states, and the appearance of atomic fragments. The experiments reveal, in particular, insight into the strong-field induced ring-opening dynamics in the selenophene cation, which are traced by the emergence of non-cyclic molecules as well as the liberation of Se+ ions within an overall time scale of approximately 170 fs. We propose that both products may be associated with dynamics on the same electronic surfaces but with different degrees of vibrational excitation. The time-dependent inner-shell absorption features provide direct evidence for a complex relaxation mechanism that may be approximated by a two-step model, whereby the initially prepared, excited cyclic cation decays within τ1 = 80 ± 30 fs into a transient molecular species, which then gives rise to the emergence of bare Se+ and ring-open cations within an additional τ2 = 80 ± 30 fs. The combined experimental and theoretical results suggest a close relationship between σ* excited cation states and the observed ring-opening reactions. The findings demonstrate that the combination of femtosecond time-resolved core-level spectroscopy with ab initio estimates of spectroscopic signatures provide new insights into complex, ultrafast photochemical reactions such as ring-opening dynamics in organic molecules in real-time and with simultaneous sensitivity for electronic and structural

  9. Compton scattering cross section for inner-shell electrons in the relativistic impulse approximation

    NASA Astrophysics Data System (ADS)

    Stutz, G. E.

    2014-01-01

    Total Compton scattering cross sections and inelastic scattering factors for bound electron states of several elements have been evaluated in the framework of the relativistic impulse approximation (RIA). The accuracy of different approximate expressions for the singly differential cross section within the RIA is discussed. Accurate evaluations of bound state scattering factors require the use of the full RIA expression. Compton scattering from K-shell electrons dominates over the photoelectric absorption at higher energies. Energy values at which the Compton interaction become the main process of creation of K-shell vacancies are assessed. The role of binding effects in Compton processes at lower energies are clearly evidenced by the computed total cross sections. Calculated K-shell ionization total cross sections, defined as the sum of the photoelectric absorption and the Compton scattering cross sections, are in good agreement with available experimental data. The total Compton cross section for the 2s atomic orbital exhibits a shoulder-like structure, which can be traced back to the node structure of the 2s wave function.

  10. High-gain inner-shell photoionization laser in Cd vapor pumped by soft-x-ray radiation from a laser-produced plasma source.

    PubMed

    Silfvast, W T; Macklin, J J; Ii, O R

    1983-11-01

    A soft-x-ray-pumped inner-shell photoionization laser has been produced in Cd vapor at 4416 and 3250 A. A gain of 5.6 cm(-1) has been measured at 4416 A, and a reasonably high-energy storage of 0.2 mJ/cm(3) in the upper laser states has been obtained.

  11. Lifetime of inner-shell hole states of Ar (2p) and Kr (3d) using equation-of-motion coupled cluster method

    SciTech Connect

    Ghosh, Aryya; Vaval, Nayana; Pal, Sourav

    2015-07-14

    Auger decay is an efficient ultrafast relaxation process of core-shell or inner-shell excited atom or molecule. Generally, it occurs in femto-second or even atto-second time domain. Direct measurement of lifetimes of Auger process of single ionized and double ionized inner-shell state of an atom or molecule is an extremely difficult task. In this paper, we have applied the highly correlated complex absorbing potential-equation-of-motion coupled cluster (CAP-EOMCC) approach which is a combination of CAP and EOMCC approach to calculate the lifetime of the states arising from 2p inner-shell ionization of an Ar atom and 3d inner-shell ionization of Kr atom. We have also calculated the lifetime of Ar{sup 2+}(2p{sup −1}3p{sup −1}) {sup 1}D, Ar{sup 2+}(2p{sup −1}3p{sup −1}) {sup 1}S, and Ar{sup 2+}(2p{sup −1}3s{sup −1}) {sup 1}P double ionized states. The predicted results are compared with the other theoretical results as well as experimental results available in the literature.

  12. Investigation of a vortex in Coulomb-Born calculations of inner-shell ionization of carbon by electron impact

    NASA Astrophysics Data System (ADS)

    Ward, S. J.; Macek, J. H.

    2013-05-01

    Previously, we reported vortices in Coulomb-Born calculations of inner-shell ionization of carbon by electron impact. A vortex was obtained for the kinematics of an incident energy Ei = 1801 . 2 eV , scattering angle θf =4° , energy of the ejected electron Ek = 5 . 524 eV and angle of the ejected electron θk =239° . We showed that for this set of kinematics, the real and imaginary parts of the T-matrix are zero at the same angle (to a good approximation). Furthermore, we showed the velocity field rotates about the position of the vortex. Recently, following the treatment of Botero and Macek, we decomposed the Coulomb-Born T-matrix into its multipole components. We show that the T-matrix and the quintuple differential cross section obtained by simply adding the l = 1 , m = +/- 1 multipole components to the l = 0 --> 4 , m = 0 components is very close to the Coulomb-Born T-matrix and the quintuple differential cross section, respectively. Our analysis shows the importance of the l = 1 , m = +/- 1 multipole components in obtaining a vortex in the Coulomb-Born calculation. S.J.W. acknowledges support from NSF under grant no. PHYS-0968638. J.H.M. acknowledges support by the D.O.E. under grant number DE-FG02-02ER15283.

  13. Distorted-wave calculation of cross sections for inner-shell ionization by electron and positron impact

    SciTech Connect

    Segui, Silvina; Dingfelder, Michael; Salvat, Francesc

    2003-06-01

    The relativistic distorted-wave Born approximation is used to calculate differential and total cross sections for inner shell ionization of neutral atoms by electron and positron impact. The target atom is described within the independent-electron approximation using the self-consistent Dirac-Fock-Slater potential. The distorting potential for the projectile is also set equal to the Dirac-Fock-Slater potential. For electrons, this guarantees orthogonality of all the orbitals involved and simplifies the calculation of exchange T-matrix elements. The interaction between the projectile and the target electrons is assumed to reduce to the instantaneous Coulomb interaction. The adopted numerical algorithm allows the calculation of differential and total cross sections for projectiles with kinetic energies ranging from the ionization threshold up to about ten times this value. Algorithm accuracy and stability are demonstrated by comparing differential cross sections calculated by our code with the distorting potential set to zero with equivalent results generated by a more robust code that uses the conventional plane-wave Born approximation. Sample calculation results are presented for ionization of K- and L-shells of various elements and compared with the available experimental data.

  14. Charge and Nuclear Dynamics Induced by Deep Inner-Shell Multiphoton Ionization of CH3I Molecules by Intense X-ray Free-Electron Laser Pulses.

    PubMed

    Motomura, Koji; Kukk, Edwin; Fukuzawa, Hironobu; Wada, Shin-ichi; Nagaya, Kiyonobu; Ohmura, Satoshi; Mondal, Subhendu; Tachibana, Tetsuya; Ito, Yuta; Koga, Ryosuke; Sakai, Tsukasa; Matsunami, Kenji; Rudenko, Artem; Nicolas, Christophe; Liu, Xiao-Jing; Miron, Catalin; Zhang, Yizhu; Jiang, Yuhai; Chen, Jianhui; Anand, Mailam; Kim, Dong Eon; Tono, Kensuke; Yabashi, Makina; Yao, Makoto; Ueda, Kiyoshi

    2015-08-06

    In recent years, free-electron lasers operating in the true X-ray regime have opened up access to the femtosecond-scale dynamics induced by deep inner-shell ionization. We have investigated charge creation and transfer dynamics in the context of molecular Coulomb explosion of a single molecule, exposed to sequential deep inner-shell ionization within an ultrashort (10 fs) X-ray pulse. The target molecule was CH3I, methane sensitized to X-rays by halogenization with a heavy element, iodine. Time-of-flight ion spectroscopy and coincident ion analysis was employed to investigate, via the properties of the atomic fragments, single-molecule charge states of up to +22. Experimental findings have been compared with a parametric model of simultaneous Coulomb explosion and charge transfer in the molecule. The study demonstrates that including realistic charge dynamics is imperative when molecular Coulomb explosion experiments using short-pulse facilities are performed.

  15. High resolution X-ray spectra of solar flares. V - Interpretation of inner-shell transitions in Fe XX-Fe XXIII

    NASA Technical Reports Server (NTRS)

    Doschek, G. A.; Feldman, U.; Cowan, R. D.

    1981-01-01

    The paper examines high-resolution solar flare iron line spectra recorded between 1.82 and 1.97 A by a spectrometer flown by the Naval Research Laboratory on an Air Force spacecraft launched on 1979 February 24. The emission line spectrum is due to inner-shell transitions in the ions Fe XX-Fe XXV. Using theoretical spectra and calculations of line intensities obtained by methods discussed by Merts, Cowan, and Magee (1976), electron temperatures as a function of time for two large class X flares are derived. These temperatures are deduced from intensities of lines of Fe XXII, Fe XXIII, and Fe XXIV. The determination of the differential emission measure between about 12-million and 20-million K using these temperatures is considered. The possibility of determining electron densities in flare and tokamak plasmas using the inner-shell spectra of Fe XXI and Fe XX is discussed.

  16. Measurement of wavelengths and lamb shifts for inner-shell transitions in Fe XVIII-XXIV. [from solar flare X-ray spectra

    NASA Technical Reports Server (NTRS)

    Seely, J. F.; Feldman, U.; Safronova, U. I.

    1986-01-01

    The wavelengths of inner-shell 1s-2p transitions in the ions Fe XVIII-XXIV have been measured in solar flare spectra recorded by the Naval Research Laboratory crystal spectrometer (SOLFLEX) on the Air Force P78-1 spacecraft. The measurements are compared with previous measurements and with recently calculated wavelengths. It is found that the measured wavelengths are systematically larger than the wavelengths calculated using the Z-expansion method by up to 0.65 mA. For the more highly charged ions, these differences can be attributed to the QED contributions to the transition energies that are not included in the Z-expansion calculations.

  17. Inner-shell capture and ionization in collisions of H+, He2+, and Li3+ projectiles with neon and carbon

    NASA Astrophysics Data System (ADS)

    Ford, A. L.; Reading, J. F.; Becker, R. L.

    1981-02-01

    Theoretical methods used previously for H+, He2+, and C6+ collisions with neutral argon atoms have been applied to collisions of H+, He2+, and Li3+ projectiles with neon, and to collisions of H+ with carbon targets. The energy range covered by the calculations is 0.4 to 4.0 MeV/amu for the neon target, and 0.2 to 2.0 MeV/amu for carbon. We calculate single-electron amplitudes for target K-shell ionization and target K- and L-shell, to projectile K-shell, charge transfer. These single-electron amplitudes are used, in an independent-particle model that allows for multielectron processes, to compute K-shell vacancy production cross sections σIPMVK, and cross sections σIPMC,VK for producing a charge-transfer state of the projectile in the coincidence with a K-shell vacancy in the target. These cross sections are in reasonable agreement with the recent experiments of Rødbro et al. at Aarhus. In particular, the calculated, as well as the experimental, σC,VK scale with projectile nuclear charge Zp less strongly than the Z5p of the Oppenheimer-Brinkman-Kramers (OBK) approximation. For He2+ and Li3+ projectiles at collision energies below where experimental data are available, our calculated multielectron corrections to the single-electron approximation for σC,VK are large.

  18. Mango core inner shell membrane template-directed synthesis of porous ZnO films and their application for enzymatic glucose biosensor

    NASA Astrophysics Data System (ADS)

    Zhou, Yu; Wang, Lei; Ye, Zhizhen; Zhao, Minggang; Cai, Hui; Huang, Jingyun

    2013-11-01

    Micro/nano-porous ZnO films were synthesized through a simple biotemplate-directed method using mango core inner shell membranes as templates. The achieved ZnO films with wrinkles on the surface are combined of large holes and small pores in the bulk. High specific surface area, numerous microspaces, and small channels for fluid circulation provided by this unique structure along with the good biocompatibility and electron communication features of ZnO material make the product an ideal platform for the immobilization of enzymes The fabricated glucose biosensor based on the porous ZnO films exhibits good selective detection ability of analyte with good stability, high sensitivity of 50.58 μA cm-2 mM-1 and a wide linear range of 0.2-5.6 mM along with a low detection limit of 10 μM.

  19. Modeling energy dependence of the inner-shell x-ray emission produced by femtosecond-pulse laser irradiation of xenon clusters

    SciTech Connect

    Colgan, James P

    2008-01-01

    We employ the Los Alamos suite of atomic physics codes to model the inner-shell x-ray emission spectrum of xenon and compare results with those obtained via high-resolution x-ray spectroscopy of xenon clusters irradiated by 30 fs Ti:Sa laser pulses. We find that the commonly employed configuration average approximation breaks down and significant spin-orbit splitting necessitates a detailed level accounting. Additionally, we reproduce an interesting spectral trend for a series of experimental spectra taken with varying pulse energy for fixed pulse duration. To simulate the experimental measurements at increasing beam energies, we find that spectral modeling requires an increased hot electron fraction, but decreased atomic density and bulk electron temperature. We believe these latter conditions to be a result of partial cluster destruction due to the increased energy in the laser prepulse.

  20. Inner-shell resonant absorption effects on evolution dynamics of the charge state distribution in a neon atom interacting with ultraintense x-ray pulses

    NASA Astrophysics Data System (ADS)

    Xiang, Wenjun; Gao, Cheng; Fu, Yongsheng; Zeng, Jiaolong; Yuan, Jianmin

    2012-12-01

    Inner-shell resonant absorption (IRA) effects were investigated on evolution dynamics of charge state distribution (CSD) in the interaction of ultraintense x-ray pulses with a neon atom. IRA is the physical origin of the large discrepancies found between theory and experiment at a photon energy of 1050 eV [L. Young , Nature (London)NATUAS0028-083610.1038/nature09177 466, 56 (2010)], where the rates of K-shell resonant absorption 1s→4p of Ne6+ and 1s→3p of Ne7+ are larger than the direct single-photon ionization rates by more than one order of magnitude, and hence IRA becomes the dominant absorption mechanism. Only when the IRA effects are properly taken into account can we correctly explain the observed CSD.

  1. Laboratory Measurement and Theoretical Modeling of K-shell X-ray Lines from Inner-shell Excited and Ionized Ions of Oxygen

    SciTech Connect

    Gu, M; Schmidt, M; Beiersdorfer, P; Chen, H; Thorn, D B; Tr?bert, E; Behar, E; Kahn, S M

    2005-02-05

    We present high resolution laboratory spectra of K-shell X-ray lines from inner-shell excited and ionized ions of oxygen, obtained with a reflection grating spectrometer on the electron beam ion trap (EBIT-I) at the Lawrence Livermore National Laboratory. Only with a multi-ion model including all major atomic collisional and radiative processes, are we able to identify the observed K-shell transitions of oxygen ions from O III to O VI. The wavelengths and associated errors for some of the strongest transitions are given, taking into account both the experimental and modeling uncertainties. The present data should be useful in identifying the absorption features present in astrophysical sources, such as active galactic nuclei and X-ray binaries. They are also useful in providing benchmarks for the testing of theoretical atomic structure calculations.

  2. Stochastic annealing simulation of cascades in metals

    SciTech Connect

    Heinisch, H.L.

    1996-04-01

    The stochastic annealing simulation code ALSOME is used to investigate quantitatively the differential production of mobile vacancy and SIA defects as a function of temperature for isolated 25 KeV cascades in copper generated by MD simulations. The ALSOME code and cascade annealing simulations are described. The annealing simulations indicate that the above Stage V, where the cascade vacancy clusters are unstable,m nearly 80% of the post-quench vacancies escape the cascade volume, while about half of the post-quench SIAs remain in clusters. The results are sensitive to the relative fractions of SIAs that occur in small, highly mobile clusters and large stable clusters, respectively, which may be dependent on the cascade energy.

  3. Atomic Data for the K-vacancy States of Fe XXIV

    NASA Technical Reports Server (NTRS)

    Bautista, M. A.; Mendoza, C.; Kallman, T. R.; Palmeri, P.

    2003-01-01

    As part of a project to compute improved atomic data for the spectral modeling of iron K lines, we report extensive calculations and comparisons of atomic data for K-vacancy states in Fe XXIV. The data sets include: (i) energy levels, line wavelengths, radiative and Auger rates; (ii) inner-shell electron impact excitation rates and (iii) fine structure inner-shell photoionization cross sections. The calculations of energy levels and radiative and Auger rates have involved a detailed study of orbital representations, core relaxation, configuration interaction, relativistic corrections, cancellation effects and semi-empirical corrections. It is shown that a formal treatment of the Breit interaction is essential to render the important magnetic correlations that take part in the decay pathways of this ion. As a result, the accuracy of the present A-values is firmly ranked at better than 10% while that of the Auger rates at only 15%. The calculations of collisional excitation and photoionization cross sections take into account the effects of radiation and spectator Auger dampings. In the former, these effects cause significant attenuation of resonances leading to a good agreement with a simpler method where resonances are excluded. In the latter, resonances converging to the K threshold display symmetric profiles of constant width that causes edge smearing.

  4. Atomic Data for the K-Vacancy States of Fe XXIV

    NASA Technical Reports Server (NTRS)

    Bautista, M. A.; Mendoza, C.; Kallman, T. R.; Palmeri, P.

    2002-01-01

    As part of a project to compute improved atomic data for the spectral modeling of iron K lines, we report extensive calculations and comparisons of atomic data for K-vacancy states in Fe XXIV. The data sets include: (i) energy levels, line wavelengths, radiative and Auger rates; (ii) inner-shell electron impact excitation rates and (iii) fine structure inner-shell photoionization cross sections. The calculations of energy levels and radiative and Auger rates have involved a detailed study of orbital representations, core relaxation, configuration interaction, relativistic corrections, cancellation effects and semi-empirical corrections. It is shown that a formal treatment of the Breit interaction is essential to render the important magnetic correlations that take part in the decay pathways of this ion. As a result, the accuracy of the present A-values is firmly ranked at better than 10% while that of the Auger rates at only 15%. The calculations of collisional excitation and photoionization cross sections take into account the effects of radiation and spectator Auger dampings. In the former, these effects cause significant attenuation of resonances leading to a good agreement with a simpler method where resonances are excluded. In the latter, resonances converging to the K threshold display symmetric profiles of constant width that causes edge smearing.

  5. Inner-shell promotions in low-energy Li+-Al collisions at clean and alkali-covered Al(100) surfaces

    NASA Astrophysics Data System (ADS)

    German, K. A. H.; Weare, C. B.; Yarmoff, J. A.

    1994-11-01

    Spectra of scattered ions and ion-induced electron emissions are used to investigate the electronic processes that occur during 0.4-5.0-keV Li+ bombardment of clean and alkali-atom-covered Al(100). The results show that Li 1s electrons are promoted during hard Li-Al collisions, but not during Li-K or Li-Na collisions. Consequences of the inner-shell electron promotions are evident in the inelastic loss, neutralization behavior, and electron emissions of the scattered Li particles. Spectra of scattered Li+ ions exhibit discrete-loss features, which are resistant to the usual increase in resonant neutralization that accompanies the deposition of alkali atoms on the surface. The loss features are due to Li 1s excitation via electron promotion, while the production of ions away from the surface via autoionization is responsible for their lack of response to alkali-atom adsorption. Spectra of ion-induced electron emissions confirm that Li*(1s2s2) is produced and that it undergoes autoionization.

  6. Improved atomic data for electron-transport predictions by the codes TIGER and TIGERP. I. Inner-shell ionization by electron collision

    SciTech Connect

    Peek, J.M.; Halbleib, J.A.

    1983-01-01

    The inner-shell ionization data for electron-target collisions now in use in the TIGER and TIGERP electron-transport codes are extracted and compared with other data for these processes. The TIGER cross sections for K-shell ionization by electron collisions are found to be seriously in error for large-Z targets and incident electron energies greater than 1 MeV. A series of TIGER and TIGERP runs were carried out with and without improved K-shell electron ionization cross section data replacing that now in use. The relative importance of electron-impact and photon ionization of the various subshells was also extracted from these runs. In general, photon ionization dominated in the examples studied so the sensitivity of many predicted properties to errors in the electron-impact subshell ionization data was not large. However, some differences were found and, as all possible applications were not covered in this study, it is recommended that these electron-impact data now in TIGER and TIGERP be replaced. Cross section data for the processes under study are reviewed and those that are most suitable for this application are identified. 19 references, 9 figures, 2 tables.

  7. Polarization and Angular Distribution of Ll X-Ray Following Inner-Shell 2p3/2 Photoionization of Magnesium-Like Ions

    NASA Astrophysics Data System (ADS)

    Ma, Kun; Dong, Chen-Zhong; Xie, Lu-You; Ding, Xiao-Bin; Qu, Yi-Zhi

    2014-05-01

    The inner-shell 2p3/2 photoionization and the subsequent decay of Mg-like Fe14+, Cd36+, W62+ and U80+ ions are studied theoretically within the multiconfiguration Dirac—Fock method and the density matrix theory. Special attention is paid to exploring the influence of the non-dipole terms which arise from the multipole expansion of the electron-photon interaction in the photoionization process. The results show that the non-dipole contribution to the total cross section, the magnetic sublevels cross section of the photoionization process, the degree of linear polarization and angular distribution of the subsequent characteristic x-ray radiation become more important with the increase of photons energy and atomic nuclear Z. Especially for the cross section and the degree of linear polarization, the non-dipole contribution arrives at 50% for U80+ at four time energy threshold units. However, for the angular distribution, the maximum contribution does not exceed 4%, even for U80+ ions.

  8. Linear polarization of the 2p{sup 5}3s{yields}2p{sup 6} lines following the inner-shell photoionization of sodiumlike ions

    SciTech Connect

    Inal, M.K.; Surzhykov, A.; Fritzsche, S.

    2005-10-15

    The inner-shell photoionization of highly charged, many-electron ions and their subsequent radiative decay are studied theoretically within the multiconfiguration Dirac-Fock approach. Special attention is paid to the linear polarization of the characteristic x-ray radiation. Detailed calculations have been carried out, in particular for the 2p{sup 5}3s{yields}2p{sup 6} radiative transitions following ionization of the 2p electron of the sodiumlike iron Fe{sup 15+} and uranium U{sup 81+} ions. For these elements, the inner-shell photoionization was found to induce the (relatively) low linear polarization of the subsequently emitted photons which is strongly affected, moreover, by the higher-order (nondipole) effects in the electron-photon interaction.

  9. Atomic inner-shell laser at 1.5-ångström wavelength pumped by an X-ray free-electron laser.

    PubMed

    Yoneda, Hitoki; Inubushi, Yuichi; Nagamine, Kazunori; Michine, Yurina; Ohashi, Haruhiko; Yumoto, Hirokatsu; Yamauchi, Kazuto; Mimura, Hidekazu; Kitamura, Hikaru; Katayama, Tetsuo; Ishikawa, Tetsuya; Yabashi, Makina

    2015-08-27

    Since the invention of the first lasers in the visible-light region, research has aimed to produce short-wavelength lasers that generate coherent X-rays; the shorter the wavelength, the better the imaging resolution of the laser and the shorter the pulse duration, leading to better temporal resolution in probe measurements. Recently, free-electron lasers based on self-amplified spontaneous emission have made it possible to generate a hard-X-ray laser (that is, the photon energy is of the order of ten kiloelectronvolts) in an ångström-wavelength regime, enabling advances in fields from ultrafast X-ray spectrosopy to X-ray quantum optics. An atomic laser based on neon atoms and pumped by a soft-X-ray (that is, a photon energy of less than one kiloelectronvolt) free-electron laser has been achieved at a wavelength of 14 nanometres. Here, we use a copper target and report a hard-X-ray inner-shell atomic laser operating at a wavelength of 1.5 ångströms. X-ray free-electron laser pulses with an intensity of about 10(19) watts per square centimetre tuned to the copper K-absorption edge produced sufficient population inversion to generate strong amplified spontaneous emission on the copper Kα lines. Furthermore, we operated the X-ray free-electron laser source in a two-colour mode, with one colour tuned for pumping and the other for the seed (starting) light for the laser.

  10. Atomic inner-shell laser at 1.5-ångström wavelength pumped by an X-ray free-electron laser

    NASA Astrophysics Data System (ADS)

    Yoneda, Hitoki; Inubushi, Yuichi; Nagamine, Kazunori; Michine, Yurina; Ohashi, Haruhiko; Yumoto, Hirokatsu; Yamauchi, Kazuto; Mimura, Hidekazu; Kitamura, Hikaru; Katayama, Tetsuo; Ishikawa, Tetsuya; Yabashi, Makina

    2015-08-01

    Since the invention of the first lasers in the visible-light region, research has aimed to produce short-wavelength lasers that generate coherent X-rays; the shorter the wavelength, the better the imaging resolution of the laser and the shorter the pulse duration, leading to better temporal resolution in probe measurements. Recently, free-electron lasers based on self-amplified spontaneous emission have made it possible to generate a hard-X-ray laser (that is, the photon energy is of the order of ten kiloelectronvolts) in an ångström-wavelength regime, enabling advances in fields from ultrafast X-ray spectrosopy to X-ray quantum optics. An atomic laser based on neon atoms and pumped by a soft-X-ray (that is, a photon energy of less than one kiloelectronvolt) free-electron laser has been achieved at a wavelength of 14 nanometres. Here, we use a copper target and report a hard-X-ray inner-shell atomic laser operating at a wavelength of 1.5 ångströms. X-ray free-electron laser pulses with an intensity of about 1019 watts per square centimetre tuned to the copper K-absorption edge produced sufficient population inversion to generate strong amplified spontaneous emission on the copper Kα lines. Furthermore, we operated the X-ray free-electron laser source in a two-colour mode, with one colour tuned for pumping and the other for the seed (starting) light for the laser.

  11. Atomic inner-shell ionization

    NASA Astrophysics Data System (ADS)

    Das, J. N.; Chakraborty, S.

    1985-07-01

    Cross sections for the K-shell ionization of medium-heavy atoms by relativistic electrons have been calculated in a relativistic framework in the Coulomb gauge to order α0 (=e2/ħc) in the interaction Hamiltonian. Here exchange is neglected. The incident- and scattered-electron wave functions are described by Dirac plane waves. Only the bound- and ejected-electron wave functions are described nonrelativistically for a screened Coulomb potential, used earlier by the present authors. Thus the screening effect is taken into account in this calculation in a satisfactory manner. The calculation is a repetition of what has been published recently by the present authors with one important exception: Here, the ejected-electron continuum state wave function that is used is determined variationally for the above screened Coulomb potential. Thereby some perturbation approximation of ad hoc nature could be avoided. As a consequence, considerable improvement is noticed in the total cross-section results. Comparison with experimental results for 29Cu, 47Ag, and 79Au shows a good agreement. The calculation may easily be extended to ionization from other shells.

  12. Point Defect Cluster Formation in Iron Displacement Cascades Up to 50 keV

    SciTech Connect

    Stoller, R.E.

    1998-11-30

    The results of molecular dynamics displacement cascade simulations in iron at energies up to 50 keV and temperatures of 100, 600, and 900K are summarized, with a focus on the characterization of interstitial and vacancy clusters that are formed directly within the cascade. The fraction of the surviving point defects contained in clusters, and the size distributions of these in-cascade clusters have been determined. Although the formation of true vacancy clusters appears to be inhibited in iron, a significant degree of vacancy site correlation was observed. These well correlated arrangements of vacancies can be considered nascent clusters, and they have been observed to coalesce during longer term Monte Carlo simulations which permit short range vacancy diffusion. Extensive interstitial clustering was observed. The temperature and cascade energy dependence of the cluster size distributions are discussed in terms of their relevance to microstructural evolution and mechanical property changes in irradiated iron-based alloys.

  13. Effects of internal hydrogen on the vacancy loop formation probability in Al

    SciTech Connect

    Bui, T.X.; Sirois, E.; Robertson, I.M. . Dept. of Materials Science and Engineering); Kirk, M.A. )

    1990-04-01

    The effect of internal hydrogen on the formation of vacancy dislocation loops from heavy-ion generated displacement cascades in Al has been investigated. Samples of high-purity aluminum and aluminum containing 900 and 1300 appM of hydrogen were irradiated at room temperature with 50 keV Kr+ ions. The ion dose rate was typically 2 {times} 10{sup 10}ions cm{sup {minus}2} sec{sup {minus}1} and the ion dose was between 10{sup 11} and 10{sup 13} ion cm{sup {minus}2}. Under these irradiation conditions, dislocation loops were observed in all compositions, although the formation probability was relatively low (less than 10 percent of the displacement cascades produced a vacancy loop). The loop formation probability was further reduced by the presence of hydrogen. No difference in the geometry or the size of the loops created in the hydrogen free and hydrogen charged samples was found. These results are difficult to interpret, and the explanation may lie in the distribution and form of the hydrogen. To account for the large hydrogen concentrations and from calculations of the energy associated with hydrogen entry into aluminum, it has been suggested that the hydrogen enters the aluminum lattice with an accompanying vacancy. This will create hydrogen-vacancy complexes in the material; two dimensional complexes have been detected in the hydrogen-charged, but unirradiated, samples by the small-angle x-ray scattering technique. The possibility of these complexes trapping the vacancies produced by the cascade process exists thus lowering the formation probability. However, such a mechanism must occur within the lifetime of the cascade. Alternatively, if a displacement cascade overlaps with the hydrogen-vacancy complexes, the lower atomic density of the region will result in an increase in the cascade volume (decrease in the local vacancy concentration) which will also reduce the loop formation probability.

  14. Vacancies in epitaxial graphene

    SciTech Connect

    Davydov, S. Yu.

    2015-08-15

    The coherent-potential method is used to consider the problem of the influence of a finite concentration of randomly arranged vacancies on the density of states of epitaxial graphene. To describe the density of states of the substrate, simple models (the Anderson model, Haldane-Anderson model, and parabolic model) are used. The electronic spectrum of free single-sheet graphene is considered in the low-energy approximation. Charge transfer in the graphene-substrate system is discussed. It is shown that, in all cases, the density of states of epitaxial graphene decreases proportionally to the vacancy concentration. At the same time, the average charge transferred from graphene to the substrate increases.

  15. Counting vacancies and nitrogen-vacancy centers in detonation nanodiamond.

    PubMed

    Chang, Shery L Y; Barnard, Amanda S; Dwyer, Christian; Boothroyd, Chris B; Hocking, Rosalie K; Ōsawa, Eiji; Nicholls, Rebecca J

    2016-05-19

    Detonation nanodiamond particles (DND) contain highly-stable nitrogen-vacancy (N-V) centers, making it important for quantum-optical and biotechnology applications. However, due to the small particle size, the N-V concentrations are believed to be intrinsically very low, spawning efforts to understand the formation of N-V centers and vacancies, and increase their concentration. Here we show that vacancies in DND can be detected and quantified using simulation-aided electron energy loss spectroscopy. Despite the small particle size, we find that vacancies exist at concentrations of about 1 at%. Based on this experimental finding, we use ab initio calculations to predict that about one fifth of vacancies in DND form N-V centers. The ability to directly detect and quantify vacancies in DND, and predict the corresponding N-V formation probability, has a significant impact to those emerging technologies where higher concentrations and better dispersion of N-V centres are critically required.

  16. Formation and Growth of Stacking Fault Tetrahedra in Ni via Vacancy Aggregation Mechanism

    DOE PAGES

    Aidhy, Dilpuneet S.; Lu, Chenyang; Jin, Ke; ...

    2015-12-29

    Using molecular dynamics simulations, the formation and growth of stacking fault tetrahedra (SFT) are captured by vacancy cluster diffusion and aggregation mechanisms in Ni. The vacancytetrahedron acts as a nucleation point for SFT formation. Simulations show that perfect SFT can grow to the next size perfect SFT via a vacancy aggregation mechanism. The stopping and range of ions in matter (SRIM) calculations and transmission electron microscopy (TEM) observations reveal that SFT can form farther away from the initial cascade-event locations, indicating the operation of diffusion-based vacancy-aggregation mechanism.

  17. Formation and Growth of Stacking Fault Tetrahedra in Ni via Vacancy Aggregation Mechanism

    SciTech Connect

    Aidhy, Dilpuneet S.; Lu, Chenyang; Jin, Ke; Bei, Hongbin; Zhang, Yanwen; Wang, Lumin; Weber, William J.

    2015-12-29

    Using molecular dynamics simulations, the formation and growth of stacking fault tetrahedra (SFT) are captured by vacancy cluster diffusion and aggregation mechanisms in Ni. The vacancytetrahedron acts as a nucleation point for SFT formation. Simulations show that perfect SFT can grow to the next size perfect SFT via a vacancy aggregation mechanism. The stopping and range of ions in matter (SRIM) calculations and transmission electron microscopy (TEM) observations reveal that SFT can form farther away from the initial cascade-event locations, indicating the operation of diffusion-based vacancy-aggregation mechanism.

  18. Contributions to the generalized oscillator strength for the inner-shell C 1s{yields}3s{sigma}{sub g} transition in CO{sub 2} from the vibronic coupling mechanism

    SciTech Connect

    Rocha, Alexandre B.; Bielschowsky, Carlos E.

    2002-11-01

    An approach is proposed to account for the general effect of the nuclei motion in the intensity of electronic transitions caused by fast electron collision with molecular targets, following a similar procedure that has recently been used by our group to determine the optical oscillator strength of symmetry-forbidden transition, and which consists of expanding the (squared) transition moment along the normal coordinates of vibration. It is shown that the profile of total generalized oscillator strength as a function of the squared transferred moment can be significantly changed by the inclusion of terms that depend explicitly on the normal coordinates of vibration. The generalized oscillator strength for the inner-shell C 1s{yields}3s{sigma}{sub g} transition in CO{sub 2} is calculated within this approach and compared with experimental results.

  19. Feasibility study of thin films deposited on a self-supporting carbon grid substrate target on the measurement of atomic inner-shell ionization cross-sections impacted by 3-30 keV electrons

    NASA Astrophysics Data System (ADS)

    Qian, Z. C.; Wu, Y.; Chang, C. H.; Yuan, Y.; Mei, C. S.; Zhu, J. J.; Moharram, K.

    2017-04-01

    In this paper, we have measured the Lα , Lβ and Mα β X-ray production cross-sections of the W element and the K-shell ionization cross-sections of the Al element impacted by 3-30 keV electrons. A new kind of target consisting of a thin film deposited on a self-supporting carbon grid substrate has been used in this work. The self-supporting carbon grid substrate is made of several layers of super-aligned carbon nanotube arrays (the mass thickness of each layer of super-aligned carbon nanotube arrays is 20 μg/cm2). As a comparison, three kinds of targets consisting of a) the studied element deposited onto four layers of super-aligned carbon nanotube arrays and separated from each other by one layer of single carbon atoms, b) the studied element deposited directly onto four layers of super-aligned carbon nanotube arrays, and c) the studied element deposited directly onto two layers of super-aligned carbon nanotube arrays, were respectively prepared to figure out which type is fit for the measurement of inner-shell ionization cross-sections induced by 3-30 keV electrons. The experimental data are compared with the distorted-wave Born approximation (DWBA) theoretical predictions and with the available experimental data from other references. The results show that the first and the second targets are both suitable for the inner-shell ionization cross-section measurements by 3-30 keV electrons, but the third target is not. Besides, we present the M-shell X-ray production cross-sections of the W element by 5-30 keV electrons in this paper for the first time.

  20. Modeling the gain of inner-shell X-ray laser transitions in neon, argon, and copper driven by X-ray free electron laser radiation using photo-ionization and photo-excitation processes

    DOE PAGES

    Nilsen, Joseph

    2015-12-16

    Using an X-ray free electron laser (XFEL) at 960 eV to photo-ionize the 1s electron in neutral neon followed by lasing on the 2p-1s transition in singly-ionized neon, an inner-shell X-ray laser was demonstrated at 849 eV in singly-ionized neon gas several years ago. It took decades to demonstrate this scheme, because it required a very strong X-ray source that could photo-ionize the 1s (K shell) electron in neon on a timescale comparable to the intrinsic Auger lifetime in neon of 2 fs. In this paper, we model the neon inner shell X-ray laser under similar conditions to those usedmore » in the XFEL experiments at the SLAC Linac Coherent Light Source (LCLS), and show how we can improve the efficiency of the neon laser and reduce the drive requirements by tuning the XFEL to the 1s-3p transition in neutral neon in order to create gain on the 2p-1s line in neutral neon. We also show how the XFEL could be used to photo-ionize L-shell electrons to drive gain on n = 3–2 transitions in singly-ionized Ar and Cu plasmas. Furthermore, these bright, coherent, and monochromatic X-ray lasers may prove very useful for doing high-resolution spectroscopy and for studying non-linear process in the X-ray regime.« less

  1. 24 CFR 983.352 - Vacancy payment.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... keep the payment if the PHA determines that the vacancy is the owner's fault. (b) Vacancy payment at...); (ii) The owner certifies that the vacancy is not the fault of the owner and that the unit was...

  2. 24 CFR 983.352 - Vacancy payment.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... keep the payment if the PHA determines that the vacancy is the owner's fault. (b) Vacancy payment at...); (ii) The owner certifies that the vacancy is not the fault of the owner and that the unit was...

  3. Counting vacancies and nitrogen-vacancy centers in detonation nanodiamond

    NASA Astrophysics Data System (ADS)

    Chang, Shery L. Y.; Barnard, Amanda S.; Dwyer, Christian; Boothroyd, Chris B.; Hocking, Rosalie K.; Ōsawa, Eiji; Nicholls, Rebecca J.

    2016-05-01

    Detonation nanodiamond particles (DND) contain highly-stable nitrogen-vacancy (N-V) centers, making it important for quantum-optical and biotechnology applications. However, due to the small particle size, the N-V concentrations are believed to be intrinsically very low, spawning efforts to understand the formation of N-V centers and vacancies, and increase their concentration. Here we show that vacancies in DND can be detected and quantified using simulation-aided electron energy loss spectroscopy. Despite the small particle size, we find that vacancies exist at concentrations of about 1 at%. Based on this experimental finding, we use ab initio calculations to predict that about one fifth of vacancies in DND form N-V centers. The ability to directly detect and quantify vacancies in DND, and predict the corresponding N-V formation probability, has a significant impact to those emerging technologies where higher concentrations and better dispersion of N-V centres are critically required.Detonation nanodiamond particles (DND) contain highly-stable nitrogen-vacancy (N-V) centers, making it important for quantum-optical and biotechnology applications. However, due to the small particle size, the N-V concentrations are believed to be intrinsically very low, spawning efforts to understand the formation of N-V centers and vacancies, and increase their concentration. Here we show that vacancies in DND can be detected and quantified using simulation-aided electron energy loss spectroscopy. Despite the small particle size, we find that vacancies exist at concentrations of about 1 at%. Based on this experimental finding, we use ab initio calculations to predict that about one fifth of vacancies in DND form N-V centers. The ability to directly detect and quantify vacancies in DND, and predict the corresponding N-V formation probability, has a significant impact to those emerging technologies where higher concentrations and better dispersion of N-V centres are critically

  4. Production of defects in metals by collision cascades: TEM experiments

    SciTech Connect

    Kirk, M.A.

    1996-01-01

    This paper reviews experimental TEM data on production of dislocation loops by low energy ion bombardment to low doses, as simulations of similar collision cascades produced by fast neutrons, in various metals and alloys. Dependence of vacancy dislocation loop formation on recoil energy, temperature and metal/alloy is examined. Emphasis is placed on effects on dilute alloy additions. A model for cascade melting is used to understand these effects; this will require an examination of the role of electron-phonon coupling in cascade cooling and recrystallization. Formation of interstitial dislocation loops as cascade defects and the effect of nearby surfaces are briefly discussed.

  5. Scattering of phonons by vacancies

    SciTech Connect

    Ratsifaritana, C.A.; Klemens, P.G.

    1987-11-01

    The scattering of phonons by vacancies is estimated by a perturbation technique in terms of the missing mass and the missing linkages. An argument is given why distortion effects can be disregarded. The resonance frequency of the defect is sufficiently high so that resonance effects can be disregarded for phonons in the important frequency range for thermal conduction. The theory is applied to the thermal resistance by vacancies in cases where the vacancy concentration is known: potassium chloride with divalent cations, nonstoichiometric zirconium carbide, and tin telluride.

  6. 7 CFR 987.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Vacancies. In the event of any vacancy occasioned by the failure to qualify, declination to serve, removal... alternate member selected by the Secretary, the Committee shall promptly submit its recommendation to the... not submitted within 30 calendar days after such vacancy occurs, the Secretary may fill such vacancy...

  7. 7 CFR 987.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Vacancies. In the event of any vacancy occasioned by the failure to qualify, declination to serve, removal... alternate member selected by the Secretary, the Committee shall promptly submit its recommendation to the... not submitted within 30 calendar days after such vacancy occurs, the Secretary may fill such vacancy...

  8. Exploration of Vacancies in Solid 4^He

    NASA Astrophysics Data System (ADS)

    Clark, Bryan; Ceperley, David

    2006-03-01

    Experiments by Kim and Chan [1] have renewed interest in the understanding of supersolids and whether mechanisms exist in solid ^4He to allow for supersolid-like effects. Ground state vacancies would lead to bose condensation and superfluidity. Using Path Integral Monte Carlo we examine vacancy formation energies, vacancy-vacancy interactions and the effect of vacancies on supersolid behavior in solid ^4He. [1] E. Kim and M. H. Chan, Science 305, 1941 (2004).

  9. Facile Au catalyst loading on the inner shell of hollow SnO2 spheres using Au-decorated block copolymer sphere templates and their selective H2S sensing characteristics

    NASA Astrophysics Data System (ADS)

    Choi, Seon-Jin; Kim, Minsoo P.; Lee, Seo-Jin; Kim, Bumjoon J.; Kim, Il-Doo

    2014-09-01

    Hollow SnO2 spheres functionalized by Au catalysts were synthesized via the use of Au-decorated block copolymer (Au-BCP) sphere templates. Uniformly distributed Au nanoparticles on BCP spheres were prepared by the infiltration of Au precursors into polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) spheres. A thin SnO2 layer was coated on the Au-BCP spheres using RF sputtering at room temperature without morphological deformation of the spheres. The Au nanoparticles were uniformly transferred from the Au-BCP spheres to the inner shells of the hollow SnO2 spheres followed by decomposition of BCP spheres. The Au-loaded hollow SnO2 spheres exhibited a superior H2S sensitivity (Rair/Rgas = 17.4 at 5 ppm) with remarkably selective characteristics with a minor response (Rair/Rgas < 2.5 at 5 ppm) toward other interfering gases. Our results pave the way for a new catalyst loading method using Au-BCP spheres for the uniformly distributed Au NPs on the SnO2 layers.Hollow SnO2 spheres functionalized by Au catalysts were synthesized via the use of Au-decorated block copolymer (Au-BCP) sphere templates. Uniformly distributed Au nanoparticles on BCP spheres were prepared by the infiltration of Au precursors into polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) spheres. A thin SnO2 layer was coated on the Au-BCP spheres using RF sputtering at room temperature without morphological deformation of the spheres. The Au nanoparticles were uniformly transferred from the Au-BCP spheres to the inner shells of the hollow SnO2 spheres followed by decomposition of BCP spheres. The Au-loaded hollow SnO2 spheres exhibited a superior H2S sensitivity (Rair/Rgas = 17.4 at 5 ppm) with remarkably selective characteristics with a minor response (Rair/Rgas < 2.5 at 5 ppm) toward other interfering gases. Our results pave the way for a new catalyst loading method using Au-BCP spheres for the uniformly distributed Au NPs on the SnO2 layers. Electronic supplementary information (ESI) available. See DOI: 10

  10. Ionization-induced laser-driven QED cascade in noble gases

    NASA Astrophysics Data System (ADS)

    Artemenko, I. I.; Kostyukov, I. Yu.

    2017-09-01

    A formula for the ionization rate in an extremely intense electromagnetic field is proposed and used for numerical study of QED cascades in noble gases in the field of two counterpropagating laser pulses. It is shown that the number of the electron-positron pairs produced in the cascade increases with the atomic number of the gas, where the gas density is taken to be inversely proportional to the atomic number. While most of the electrons produced in the laser pulse front are expelled by the ponderomotive force from the region occupied by the strong laser field, there is a small portion of electrons staying in the laser field for a long time until the instance when the laser field is strong enough for cascading. This mechanism is relevant for all gases. For high-Z gases there is an additional mechanism associated with the ionization of inner shells at the instance when the laser field is strong enough for cascading. The role of both mechanisms for cascade initiation is revealed.

  11. Antioxidant effects of the chestnut (Castanea crenata) inner shell extract in t-BHP-treated HepG2 cells, and CCl4- and high-fat diet-treated mice.

    PubMed

    Noh, Jung-Ran; Gang, Gil-Tae; Kim, Yong-Hoon; Yang, Keum-Jin; Hwang, Jung-Hwan; Lee, Hyun-Sun; Oh, Won-Keun; Song, Kyung-Sik; Lee, Chul-Ho

    2010-11-01

    The antioxidant effects of chestnut inner shell extract (CISE) were investigated in a tert-butylhydroperoxide (t-BHP)-treated HepG2 cells, and in mice that were administered carbon tetrachloride (CCl(4)) and fed a high-fat diet (HFD). Pre-incubation with CISE significantly blocked the oxidative stress induced by t-BHP treatment in HepG2 cells (P<0.05) and preserved the activities of catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase compared to group treated with t-BHP only. Similarly, the CCl(4)- and HFD-induced reduction of antioxidant enzymes activities in liver was prevented by CISE treatment compared to control groups. Furthermore, hepatic lipid peroxidation were remarkably lower (P<0.05) in the CISE-treated groups with t-BHP or HFD. To determine the active compound of CISE, the fractionation of CISE has been conducted and scoparone and scopoletin were identified as main compounds. These compounds were also shown to inhibit the t-BHP-induced ROS generation and reduction in antioxidant enzyme activity in an in vitro model system. From these results, it was demonstrated that CISE has the ability to protect against damage from oxidative stressors such as t-BHP, CCl(4) and HFD in in vitro and in vivo models. The CISE might be useful for the prevention of oxidative damage in liver cells and tissues.

  12. Facile Au catalyst loading on the inner shell of hollow SnO2 spheres using Au-decorated block copolymer sphere templates and their selective H2S sensing characteristics.

    PubMed

    Choi, Seon-Jin; Kim, Minsoo P; Lee, Seo-Jin; Kim, Bumjoon J; Kim, Il-Doo

    2014-10-21

    Hollow SnO2 spheres functionalized by Au catalysts were synthesized via the use of Au-decorated block copolymer (Au-BCP) sphere templates. Uniformly distributed Au nanoparticles on BCP spheres were prepared by the infiltration of Au precursors into polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) spheres. A thin SnO2 layer was coated on the Au-BCP spheres using RF sputtering at room temperature without morphological deformation of the spheres. The Au nanoparticles were uniformly transferred from the Au-BCP spheres to the inner shells of the hollow SnO2 spheres followed by decomposition of BCP spheres. The Au-loaded hollow SnO2 spheres exhibited a superior H2S sensitivity (Rair/Rgas = 17.4 at 5 ppm) with remarkably selective characteristics with a minor response (Rair/Rgas < 2.5 at 5 ppm) toward other interfering gases. Our results pave the way for a new catalyst loading method using Au-BCP spheres for the uniformly distributed Au NPs on the SnO2 layers.

  13. Threshold collision-induced dissociation of Sr2+(H2O)x complexes (x=1-6): An experimental and theoretical investigation of the complete inner shell hydration energies of Sr2+

    NASA Astrophysics Data System (ADS)

    Carl, D. R.; Chatterjee, B. K.; Armentrout, P. B.

    2010-01-01

    The sequential bond energies of Sr2+(H2O)x complexes, where x =1-6, are determined by threshold collision-induced dissociation using a guided ion beam tandem mass spectrometer equipped with an electrospray ionization source. The electrospray source produces an initial distribution of Sr2+(H2O)x complexes, where x =6-9. Smaller Sr2+(H2O)x complexes, where x =1-5, are accessed using a recently developed in-source fragmentation technique that takes place in the high pressure region of a rf-only hexapole ion guide. This work constitutes the first experimental study for the complete inner shell of any multiply charged ion. The kinetic energy dependent cross sections are determined over a wide energy range to monitor all possible dissociation products and are modeled to obtain 0 and 298 K binding energies for loss of a single water molecule. These binding energies decrease monotonically for the Sr2+(H2O) complex to Sr2+(H2O)6. Our experimental results agree well with previous literature results obtained by equilibrium and kinetic studies for x =5 and 6. Because there has been limited theory for the hydration of Sr2+, we also present an in-depth theoretical study on the energetics of the Sr2+(H2O)x systems by employing several levels of theory with multiple effective core potentials for Sr and different basis sets for the water molecules.

  14. Annealing simulation of cascade damage in -Fe- Damage energy and temperature dependence analyses

    SciTech Connect

    Suzudo, Tomoaki; Golubov, Stanislav I; Stoller, Roger E; Yamaguchi, Masatake; Tsuru, Tomohito; Kaburaki, Hideo

    2012-01-01

    In this paper, kinetic Monte Carlo method was applied to investigate the long time evolution of cascade damage prepared by molecular dynamics simulations in -Fe up to recoil energy of more than 200 keV. We conducted thorough investigation on how the surviving defects vary with cascade damage energy and annealing temperature. The results can be used for input parameters of rate equations to simulate microstructural evolution under irradiation. The study also suggested that neighboring sub-cascades evolves almost independently during annealing, and that the temperature dependence of the annealing results can be explained by the temperature dependence of vacancy-migration and vacancy-dissociation probabilities.

  15. 7 CFR 1205.327 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE COTTON RESEARCH AND PROMOTION Cotton Research and Promotion Order Cotton Board § 1205.327 Vacancies. To fill any vacancy occasioned by...

  16. 7 CFR 1205.327 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE COTTON RESEARCH AND PROMOTION Cotton Research and Promotion Order Cotton Board § 1205.327 Vacancies. To fill any vacancy occasioned by...

  17. 7 CFR 1205.327 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE COTTON RESEARCH AND PROMOTION Cotton Research and Promotion Order Cotton Board § 1205.327 Vacancies. To fill any vacancy occasioned by...

  18. 7 CFR 932.33 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Order Regulating Handling Olive Administrative Committee § 932.33 Vacancies. To fill any vacancy occasioned by...

  19. 7 CFR 932.33 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Order Regulating Handling Olive Administrative Committee § 932.33 Vacancies. To fill any vacancy occasioned by...

  20. 7 CFR 932.33 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Order Regulating Handling Olive Administrative Committee § 932.33 Vacancies. To fill any vacancy occasioned by...

  1. 7 CFR 932.33 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Order Regulating Handling Olive Administrative Committee § 932.33 Vacancies. To fill any vacancy occasioned by...

  2. 7 CFR 932.33 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Order Regulating Handling Olive Administrative Committee § 932.33 Vacancies. To fill any vacancy occasioned by...

  3. 7 CFR 981.36 - Vacancy.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE ALMONDS GROWN IN CALIFORNIA Order Regulating Handling Almond Board of California § 981.36 Vacancy. To fill any vacancy occasioned by the death, removal...

  4. 7 CFR 981.36 - Vacancy.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE ALMONDS GROWN IN CALIFORNIA Order Regulating Handling Almond Board of California § 981.36 Vacancy. To fill any vacancy occasioned by the death, removal...

  5. 7 CFR 981.36 - Vacancy.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE ALMONDS GROWN IN CALIFORNIA Order Regulating Handling Almond Board of California § 981.36 Vacancy. To fill any vacancy occasioned by the death, removal...

  6. 7 CFR 981.36 - Vacancy.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE ALMONDS GROWN IN CALIFORNIA Order Regulating Handling Almond Board of California § 981.36 Vacancy. To fill any vacancy occasioned by the death, removal...

  7. 7 CFR 981.36 - Vacancy.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE ALMONDS GROWN IN CALIFORNIA Order Regulating Handling Almond Board of California § 981.36 Vacancy. To fill any vacancy occasioned by the death, removal...

  8. 7 CFR 1150.136 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MILK), DEPARTMENT OF AGRICULTURE DAIRY PROMOTION PROGRAM Dairy Promotion and Research Order National Dairy Promotion and Research Board § 1150.136 Vacancies. To fill any vacancy occasioned...

  9. 7 CFR 1150.136 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MILK), DEPARTMENT OF AGRICULTURE DAIRY PROMOTION PROGRAM Dairy Promotion and Research Order National Dairy Promotion and Research Board § 1150.136 Vacancies. To fill any vacancy occasioned...

  10. 7 CFR 1150.136 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... and Orders; Milk), DEPARTMENT OF AGRICULTURE DAIRY PROMOTION PROGRAM Dairy Promotion and Research Order National Dairy Promotion and Research Board § 1150.136 Vacancies. To fill any vacancy occasioned...

  11. 7 CFR 1160.205 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... and Orders; Milk), DEPARTMENT OF AGRICULTURE FLUID MILK PROMOTION PROGRAM Fluid Milk Promotion Order National Fluid Milk Processor Promotion Board § 1160.205 Vacancies. To fill any vacancy occasioned by the...

  12. 7 CFR 982.35 - Vacancy.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON Order Regulating Handling Hazelnut Control Board § 982.35 Vacancy. To fill any vacancy occasioned by...

  13. 7 CFR 982.35 - Vacancy.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON Order Regulating Handling Hazelnut Control Board § 982.35 Vacancy. To fill any vacancy occasioned by...

  14. 7 CFR 982.35 - Vacancy.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON Order Regulating Handling Hazelnut Control Board § 982.35 Vacancy. To fill any vacancy occasioned by...

  15. 7 CFR 982.35 - Vacancy.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON Order Regulating Handling Hazelnut Control Board § 982.35 Vacancy. To fill any vacancy occasioned by...

  16. 7 CFR 982.35 - Vacancy.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON Order Regulating Handling Hazelnut Control Board § 982.35 Vacancy. To fill any vacancy occasioned by...

  17. 7 CFR 7.13 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 1 2010-01-01 2010-01-01 false Vacancies. 7.13 Section 7.13 Agriculture Office of the..., COUNTY AND COMMUNITY COMMITTEES § 7.13 Vacancies. (a) In case of a vacancy in the office of chairperson... panel of alternates, except as provided in § 7.28 of this part. (d) In the event that a vacancy,...

  18. Vacancy Relaxation in Cubic Crystals

    NASA Technical Reports Server (NTRS)

    Girifalco, L. A.; Weizer, V. G.

    1960-01-01

    The configuration of the atoms surrounding a vacancy in four face-centered cubic and three body-centered cubic metals has been computed, using a pairwise, central-force model in which the energy of interaction between two atoms was taken to have the form of a Morse function. Only radial relaxations were considered. The first and second nearest-neighbor relaxations for the face-centered systems were found to be: Pb (1.42,-0.43), Ni (2.14,-0.39), Cu(2.24,-0.40) and Ca (2.73,-0.41, expressed in percentages of normal distances. For the body-centered systems the relaxations out to the fourth nearest neighbors to the vacancy were: Fe (6.07,-2.12, -0.25, -), Ba (7.85, -2.70, 0.70, -0.33) and Na (10.80, -3.14, 3.43, -0.20). The positive signs indicate relaxation toward the vacancy and the negative signs indicate relaxation away from the vacancy. The energies of relaxation (eV) are: Pb (0.162), Ni (0.626), Cu (0.560), Ca (0.400), Fe (1.410), Ba (0.950) and Na (0.172).

  19. Displacement cascades and defect annealing in tungsten, Part II: Object kinetic Monte Carlo Simulation of Tungsten Cascade Aging

    SciTech Connect

    Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

    2015-07-01

    The results of object kinetic Monte Carlo (OKMC) simulations of the annealing of primary cascade damage in bulk tungsten using a comprehensive database of cascades obtained from molecular dynamics (Setyawan et al.) are described as a function of primary knock-on atom (PKA) energy at temperatures of 300, 1025 and 2050 K. An increase in SIA clustering coupled with a decrease in vacancy clustering with increasing temperature, in addition to the disparate mobilities of SIAs versus vacancies, causes an interesting effect of temperature on cascade annealing. The annealing efficiency (the ratio of the number of defects after and before annealing) exhibits an inverse U-shape curve as a function of temperature. The capabilities of the newly developed OKMC code KSOME (kinetic simulations of microstructure evolution) used to carry out these simulations are described.

  20. Predicted vacancy cluster structures in MgO and their interaction with helium

    NASA Astrophysics Data System (ADS)

    Busker, G.; van Huis, M. A.; Grimes, R. W.; van Veen, A.

    2000-12-01

    Atomistic simulation calculations were performed to predict defect energies of vacancy clusters and dissociation energies of clusters with helium. The computation technique was based on pair potentials and the Mott-Littleton methodology was used as implemented in the CASCADE code. Both the full charge and the partial charge model were employed. The partial charge model shows better agreement with experimental data reported in the literature. The energetically most favourable spatial configurations for clusters composed of up to eight vacancies were determined and the associated formation energies calculated. The results indicate that the three-dimensional growth of vacancy clusters in MgO is energetically favourable. Next, the activation energies for dissociation of helium atoms from these vacancy clusters were calculated. The activation energy for dissociation of a helium atom from vacancy clusters larger than a monovacancy is approximately 3.6 eV for the partial charge model. Remarkably, the activation energy for dissociation of a helium atom from a monovacancy was found to be higher, 3.9 eV for the partial charge model. This last energy is enhanced by lattice relaxation around the monovacancy. The dissociation energies from large vacancy clusters is in good agreement with the permeation energy of 3.3 ± 0.3 eV obtained experimentally with a permeation experiment in which helium release was monitored with neutron depth profiling (NDP).

  1. MOLECULAR DYNAMICS OF CASCADES OVERLAP IN TUNGSTEN WITH 20-KEV PRIMARY KNOCK-ON ATOMS

    SciTech Connect

    Setyawan, Wahyu; Nandipati, Giridhar; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

    2015-04-16

    Molecular dynamics simulations are performed to investigate the mutual influence of two subsequent cascades in tungsten. The influence is studied using 20-keV primary knock-on atoms, to induce one cascade after another separated by 15 ps, in a lattice temperature of 1025 K (i.e. 0.25 of the melting temperature of the interatomic potential). The center of mass of the vacancies at the peak damage during the cascade is taken as the location of the cascade. The distance between this location to that of the next cascade is taken as the overlap parameter. Empirical fits describing the number of surviving vacancies and interstitial atoms as a function of overlap are presented.

  2. Hard-to-fill vacancies.

    PubMed

    Williams, Ruth

    2010-09-29

    Skills for Health has launched a set of resources to help healthcare employers tackle hard-to-fill entry-level vacancies and provide sustainable employment for local unemployed people. The Sector Employability Toolkit aims to reduce recruitment and retention costs for entry-level posts and repare people for employment through pre-job training programmes, and support employers to develop local partnerships to gain access to wider pools of candidates and funding streams.

  3. Further characterization of oxygen vacancies and zinc vacancies in electron-irradiated ZnO

    SciTech Connect

    Evans, S. M.; Giles, N. C.; Halliburton, L. E.; Kappers, L. A.

    2008-02-15

    Electron paramagnetic resonance (EPR) has been used to monitor oxygen vacancies and zinc vacancies in a ZnO crystal irradiated near room temperature with 1.5 MeV electrons. Out-of-phase detection at 30 K greatly enhances the EPR signals from these vacancies. Following the electron irradiation, but before illumination, Fe{sup 3+} ions and nonaxial singly ionized zinc vacancies are observed. Illumination with 325 nm laser light at low temperature eliminates the Fe{sup 3+} signal while producing spectra from singly ionized oxygen vacancies, neutral zinc vacancies, and axial singly ionized zinc vacancies. This light also produces EPR spectra from zinc vacancies having a OH{sup -} ion at an adjacent oxygen site. The low-temperature response of the irradiated crystal to illumination wavelengths between 350 and 750 nm is described. Wavelengths shorter than 600 nm convert Fe{sup 3+} ions to Fe{sup 2+} ions and convert neutral oxygen vacancies to singly ionized oxygen vacancies. Neutral zinc vacancies are formed by wavelengths shorter than 500 nm as electrons are removed from isolated singly ionized zinc vacancies. Warming above 120 K in the dark reverses the effect of the illuminations. These wavelength-dependence results suggest that the ground state of the neutral oxygen vacancy is deep, approximately 1.3 eV above the valence band, and that the ground state of the singly ionized zinc vacancy is also deep, about 0.9 eV above the valence band.

  4. Anomaly in Dependence of Radiation-induced Vacancy Accumulation on Grain Size

    SciTech Connect

    Yang, Yi; Huang, Hanchen; Zinkle, Steven J

    2010-01-01

    According to conventional steady-state rate theory predictions of displacement damage evolution in irradiated materials, the accumulation of vacancies decreases as grain size decreases. Using atomistic simulations, the authors report a transient anomaly in the dependence of radiation produced vacancy accumulation on grain size. Contrary to the conventional wisdom, the accumulation of vacancies can be higher in smaller grains than in larger grains during a transient stage. The anomaly is a result of competition between two atomic-level processes: grain boundary absorption and bulk recombination of point defects, each of which has characteristic length and time scales. A simple metal copper is used as the prototype of face-centered cubic material and electron radiation is the source of non-cascade defect production, both choices aiming at clarity for identifying physical mechanisms.

  5. Atomistic Simulation of Displacement Cascades in Zircon

    SciTech Connect

    Devanathan, Ram; Weber, William J.; Corrales, Louis R.; BP McGrail and GA Cragnolino

    2002-05-06

    Low energy displacement cascades in zircon (ZrSiO4) initiated by a Zr primary knock-on atom have been investigated by molecular dynamics simulations using a Coulombic model for long-range interactions, Buckingham potential for short-range interactions and Ziegler-Biersack potentials for close pair interactions. Displacements were found to occur mainly in the O sublattice, and O replacements by a ring mechanism were predominant. Clusters containing Si interstitials bridged by O interstitials, vacancy clusters and anti-site defects were found to occur. This Si-O-Si bridging is considerable in quenched liquid ZrSiO4.

  6. Vacancy Transport and Interactions on Metal Surfaces

    DTIC Science & Technology

    2014-03-06

    AFRL-OSR-VA-TR-2013-0317 VACANCY TRANSPORT AND INTERACTIONS ON METAL SURFACES Gert Ehrlich UNIVERSITY OF ILLINOIS CHAMPAIGN Final Report 03/06/2014...30, 2012 Gert Ehrlich , PI Abstract This proposal is a study of vacancy transport and vacancy interaction on metal surfaces. Adatom self...Trembułowicz, Gert Ehrlich , Grażyna Antczak,Surface diffusion of gold on quasihexagonal-reconstructed Au(100) ,Physical Review B 84 (2011) 245445-1

  7. Hydrogen in anion vacancies of semiconductors

    SciTech Connect

    Du, Mao-Hua; Singh, David J

    2009-01-01

    Density functional calculations show that, depending on the anion size, hydrogen in anion vacancies of various II-VI semiconductors can be either two-fold or four-fold coordinated, and has either amphoteric or shallow donor character. In general, the multi-coordination of hydrogen in an anion vacancy is the indication of an anionic H, H { ion, in the relatively ionic environment. In more covalent semiconductors, H would form a single cation-H bond in the anion vacancy.

  8. Interaction of displacement cascade with helium bubbles in alpha-iron: Computer simulation

    SciTech Connect

    Pu, Jin; Yang, Li; Gao, Fei; Heinisch, Howard L.; Kurtz, Richard J.; Zu, Xiaotao T.

    2008-09-01

    Molecular dynamics (MD) method has been performed to study the interaction of displacement cascade with He bubbles with two sets of potentials. The results show that the stability of He bubbles depends much on the initial He-vacancy (He/V) ratio and the recoil energy. For an initial He/V ratio of 3, the cascade leads to the increase in the number of vacancies in the He bubble and the decrease in the He/V ratio. For an initial He/V ratio of 0.5, the interaction of a cascade with the He/V bubble results in the decrease in the number of vacancies and the increase in the He/V ratio. For an initial He/V ratio of 1, the stability of the bubbles slightly depends on the primary knock-on atom (PKA) energy. Furthermore, a large number of self-interstitial atom clusters are formed after cascade collision for the He/V ratio of 3, while large vacancy clusters are observed for the He/V ratio of 0.5. However, some differences of defect production and clustering between the two sets of potentials are observed, which may be associated the formation energies of He-V clusters, the binding energies of vacancies and He atoms to the clusters and the probability of subcascade formation.

  9. 7 CFR 1210.324 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE WATERMELON RESEARCH AND PROMOTION PLAN Watermelon Research and Promotion Plan National Watermelon Promotion Board § 1210.324 Vacancies...

  10. 7 CFR 1210.324 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE WATERMELON RESEARCH AND PROMOTION PLAN Watermelon Research and Promotion Plan National Watermelon Promotion Board § 1210.324 Vacancies...

  11. 7 CFR 1210.324 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE WATERMELON RESEARCH AND PROMOTION PLAN Watermelon Research and Promotion Plan National Watermelon Promotion Board § 1210.324 Vacancies...

  12. 7 CFR 1260.163 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BEEF PROMOTION AND RESEARCH Beef Promotion and Research Order Beef Promotion Operating Committee § 1260.163 Vacancies. To fill any...

  13. 7 CFR 1216.44 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE PEANUT PROMOTION, RESEARCH, AND INFORMATION ORDER Peanut Promotion, Research, and Information Order National Peanut Board § 1216.44 Vacancies...

  14. 7 CFR 1216.44 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE PEANUT PROMOTION, RESEARCH, AND INFORMATION ORDER Peanut Promotion, Research, and Information Order National Peanut Board § 1216.44 Vacancies...

  15. 7 CFR 1216.44 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE PEANUT PROMOTION, RESEARCH, AND INFORMATION ORDER Peanut Promotion, Research, and Information Order National Peanut Board § 1216.44 Vacancies...

  16. 7 CFR 1216.44 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE PEANUT PROMOTION, RESEARCH, AND INFORMATION ORDER Peanut Promotion, Research, and Information Order National Peanut Board § 1216.44 Vacancies...

  17. 7 CFR 1216.44 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE PEANUT PROMOTION, RESEARCH, AND INFORMATION ORDER Peanut Promotion, Research, and Information Order National Peanut Board § 1216.44 Vacancies...

  18. 7 CFR 1220.206 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SOYBEAN PROMOTION, RESEARCH, AND CONSUMER INFORMATION Soybean Promotion and Research Order United Soybean Board § 1220.206 Vacancies....

  19. 7 CFR 1220.206 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SOYBEAN PROMOTION, RESEARCH, AND CONSUMER INFORMATION Soybean Promotion and Research Order United Soybean Board § 1220.206 Vacancies....

  20. 7 CFR 1220.206 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SOYBEAN PROMOTION, RESEARCH, AND CONSUMER INFORMATION Soybean Promotion and Research Order United Soybean Board § 1220.206 Vacancies....

  1. 7 CFR 1220.206 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SOYBEAN PROMOTION, RESEARCH, AND CONSUMER INFORMATION Soybean Promotion and Research Order United Soybean Board § 1220.206 Vacancies....

  2. 7 CFR 1220.206 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SOYBEAN PROMOTION, RESEARCH, AND CONSUMER INFORMATION Soybean Promotion and Research Order United Soybean Board § 1220.206 Vacancies....

  3. Production of defects in metals by collision cascades: TEM experiments

    SciTech Connect

    Kirk, M.A.

    1995-03-01

    This paper reviews experimental TEM data on production of dislocation loops by low energy ion bombardment to low doses, as simulations of similar collision cascades produced by fast neutron irradiation, in various metals and alloys. The dependence of vacancy dislocation loop formation on recoil energy, sample temperature, and specific metal or alloy will be examined. Special emphasis will be placed on the effects of dilute alloy additions. A model for cascade melting will be employed to understand these effects, and will require an examination of the role of electron-phonon coupling in cascade cooling and recrystallization. The formation of interstitial dislocation loops as cascade defects, and the influence of the nearby surfaces in these experiments is briefly discussed.

  4. 38 CFR 1.896 - Publicizing vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Publicizing vacancies. 1.896 Section 1.896 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS GENERAL PROVISIONS Part-Time Career Employment Program § 1.896 Publicizing vacancies. When applicants from...

  5. 38 CFR 1.896 - Publicizing vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Publicizing vacancies. 1.896 Section 1.896 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS GENERAL PROVISIONS Part-Time Career Employment Program § 1.896 Publicizing vacancies. When applicants from...

  6. 45 CFR 1176.7 - Publicizing vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 45 Public Welfare 3 2013-10-01 2013-10-01 false Publicizing vacancies. 1176.7 Section 1176.7 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL FOUNDATION ON THE ARTS AND THE HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES PART-TIME CAREER EMPLOYMENT § 1176.7 Publicizing vacancies...

  7. 45 CFR 1176.7 - Publicizing vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 45 Public Welfare 3 2011-10-01 2011-10-01 false Publicizing vacancies. 1176.7 Section 1176.7 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL FOUNDATION ON THE ARTS AND THE HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES PART-TIME CAREER EMPLOYMENT § 1176.7 Publicizing vacancies...

  8. 45 CFR 1176.7 - Publicizing vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 45 Public Welfare 3 2014-10-01 2014-10-01 false Publicizing vacancies. 1176.7 Section 1176.7 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL FOUNDATION ON THE ARTS AND THE HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES PART-TIME CAREER EMPLOYMENT § 1176.7 Publicizing vacancies...

  9. 45 CFR 1176.7 - Publicizing vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 45 Public Welfare 3 2012-10-01 2012-10-01 false Publicizing vacancies. 1176.7 Section 1176.7 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL FOUNDATION ON THE ARTS AND THE HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES PART-TIME CAREER EMPLOYMENT § 1176.7 Publicizing vacancies...

  10. 45 CFR 1176.7 - Publicizing vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Publicizing vacancies. 1176.7 Section 1176.7 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL FOUNDATION ON THE ARTS AND THE HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES PART-TIME CAREER EMPLOYMENT § 1176.7 Publicizing vacancies...

  11. 7 CFR 1150.136 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... and Orders; Milk), DEPARTMENT OF AGRICULTURE DAIRY PROMOTION PROGRAM Dairy Promotion and Research Order National Dairy Promotion and Research Board § 1150.136 Vacancies. To fill any vacancy occasioned... shall appoint a successor from the most recent list of nominations for the position or from...

  12. 22 CFR 506.6 - Publicizing vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 22 Foreign Relations 2 2012-04-01 2009-04-01 true Publicizing vacancies. 506.6 Section 506.6 Foreign Relations BROADCASTING BOARD OF GOVERNORS PART-TIME CAREER EMPLOYMENT PROGRAM § 506.6 Publicizing... Employment Offices. (c) Broadcasting Board of Governors Vacancy Announcements. (d) College and University...

  13. 22 CFR 506.6 - Publicizing vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 22 Foreign Relations 2 2014-04-01 2014-04-01 false Publicizing vacancies. 506.6 Section 506.6 Foreign Relations BROADCASTING BOARD OF GOVERNORS PART-TIME CAREER EMPLOYMENT PROGRAM § 506.6 Publicizing... Employment Offices. (c) Broadcasting Board of Governors Vacancy Announcements. (d) College and University...

  14. 22 CFR 506.6 - Publicizing vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 22 Foreign Relations 2 2013-04-01 2009-04-01 true Publicizing vacancies. 506.6 Section 506.6 Foreign Relations BROADCASTING BOARD OF GOVERNORS PART-TIME CAREER EMPLOYMENT PROGRAM § 506.6 Publicizing... Employment Offices. (c) Broadcasting Board of Governors Vacancy Announcements. (d) College and University...

  15. 22 CFR 506.6 - Publicizing vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 22 Foreign Relations 2 2011-04-01 2009-04-01 true Publicizing vacancies. 506.6 Section 506.6 Foreign Relations BROADCASTING BOARD OF GOVERNORS PART-TIME CAREER EMPLOYMENT PROGRAM § 506.6 Publicizing... Employment Offices. (c) Broadcasting Board of Governors Vacancy Announcements. (d) College and University...

  16. 22 CFR 506.6 - Publicizing vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 22 Foreign Relations 2 2010-04-01 2010-04-01 true Publicizing vacancies. 506.6 Section 506.6 Foreign Relations BROADCASTING BOARD OF GOVERNORS PART-TIME CAREER EMPLOYMENT PROGRAM § 506.6 Publicizing... Employment Offices. (c) Broadcasting Board of Governors Vacancy Announcements. (d) College and University...

  17. 7 CFR 1150.136 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Milk), DEPARTMENT OF AGRICULTURE DAIRY PROMOTION PROGRAM Dairy Promotion and Research Order National Dairy Promotion and Research Board § 1150.136 Vacancies. To fill any vacancy...

  18. 7 CFR 1160.205 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Milk), DEPARTMENT OF AGRICULTURE FLUID MILK PROMOTION PROGRAM Fluid Milk Promotion Order National Fluid Milk Processor Promotion Board § 1160.205 Vacancies. To fill any vacancy occasioned by...

  19. 7 CFR 1210.324 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 10 2011-01-01 2011-01-01 false Vacancies. 1210.324 Section 1210.324 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS... PLAN Watermelon Research and Promotion Plan National Watermelon Promotion Board § 1210.324 Vacancies...

  20. 7 CFR 993.32 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Order Regulating Handling Prune Marketing Committee § 993.32 Vacancies. In the event of any committee vacancy occasioned by the removal, resignation, disqualification, or death of any member, or in the event... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing...

  1. In-situ studies of cascade defect formation at T < 10/sup 0/K

    SciTech Connect

    Haga, K.; Baily, A.C.; King, W.E.; Merkle, K.L.; Meshii, M.

    1983-05-01

    Thin films of Ag and Au were ion-irradiated at temperature (T) < 10/sup 0/K and simultaneously observed using the Argonne National Laboratory high-voltage electron microscope (HVEM) ion-beam interface system. Displacement cascades were produced by Kr/sup +/ ion bombardment in the energy range 20 to 140 keV. For Ag, 20% of the 20-keV cascades and 100% of the 100-keV cascades produced observable contrast. Analysis of the observed dynamical black-white (BW)-contrast indicates that the clusters are of vacancy type. Subcascades were observed in the high-energy irradiations. The present results demonstrate that, during the evolution of displacement cascades in Ag and Au, extensive athermal rearrangement of vacancies occurs which gives rise to clustering and collapse to dislocation loops.

  2. Cascades frog conservation assessment

    Treesearch

    Karen Pope; Catherine Brown; Marc Hayes; Gregory Green; Diane Macfarlane

    2014-01-01

    The Cascades frog (Rana cascadae) is a montane, lentic-breeding amphibian that has become rare in the southern Cascade Range and remains relatively widespread in the Klamath Mountains of northern California. In the southern Cascades, remaining populations occur primarily in meadow habitats where the fungal disease, chytridiomycosis, and habitat...

  3. Southern cascades bioregion

    Treesearch

    Carl N. Skinner; Alan H. Taylor

    2006-01-01

    The Cascade Range extends from British Columbia, Canada, south to northern California where it meets the Sierra Nevada. The Southern Cascades bioregion in California is bounded on the west by the Sacramento Valley and the Klamath Mountains, and on the east by the Modoc Plateau and Great Basin. The bioregion encompasses the Southern Cascades section of Miles and Goudey...

  4. Computer Simulation of Cascade Damage in α-Iron with Carbon in Solution

    SciTech Connect

    Andrew, Calder F; Bacon, David J; Barashev, Aleksandr; Osetskiy, Yury N

    2008-01-01

    Molecular dynamics simulation method is used to investigate defect production by displacement cascades in iron with carbon (C) in solution. This is the first study of cascade damage in a metal containing interstitial solute. Iron is of particular interest because of the use of ferritic steels in plant for nuclear power generation. Cascades are simulated with energy in the range 5 to 20keV in iron at either 100 or 600K containing carbon with concentration in the range 0 to 1at%. C in solution has no discernible effect on the number of defects produced in cascades under any of the conditions simulated, nor on the clustered fraction of either self-interstitial atoms (SIAs) or vacancies. However, significant fractions of single SIAs and vacancies are trapped by C in the cascade process, irrespective of cascade energy. The fraction is independent of temperature for vacancies, but increases strongly with temperature for SIAs: this is a consequence of the higher mobility of the SIA.

  5. Effect of collision cascades on dislocations in tungsten: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Fu, B. Q.; Fitzgerald, S. P.; Hou, Q.; Wang, J.; Li, M.

    2017-02-01

    Tungsten (W) is the prime candidate material for the divertor and other plasma-facing components in DEMO. The point defects (i.e. vacancies and self-interstitials) produced in collision cascades caused by incident neutrons aggregate into dislocation loops (and voids), which strongly affect the mechanical properties. The point defects also interact with existing microstructural features, and understanding these processes is crucial for modelling the long term microstructural evolution of the material under fusion conditions. In this work, we performed molecular dynamics simulations of cascades interacting with initially straight edge dislocation dipoles. It was found that the residual vacancy number usually exceeds the residual interstitial number for cascades interacting with vacancy type dipoles, but for interstitial type dipoles these are close. We observed that a cascade near a dislocation promotes climb, i.e. it facilitates the movement of point defects along the climb direction. We also observed that the dislocations move easily along the glide direction, and that kinks are formed near the centre of the cascade, which then facilitate the movement of the dipoles. Some dipoles are sheared off by the cascade, and this is dependent on PKA energy, position, direction, and the width of dipole.

  6. Resonantly excited cascade x-ray emission from La

    SciTech Connect

    Moewes, A.; Wilks, R.G.; Kochur, A.G.; Kurmaev, E.Z.

    2005-08-15

    We are monitoring the intensity of the La 5p-4d emission for La metal while scanning across the deeper lying 3d-4f photoexcitation resonances of the same atom. A strong resonant enhancement in the integral intensity of the La 5p-4d fluorescence emission is observed, which is due to cascading decay of the resonantly excited 3d{sup 9}4f{sup +1} configuration. The corresponding emission spectrum features a complex satellite structure reflecting the multitude of transitions taking place in a variety of multi-vacancy configurations created by the cascade. We calculate the probability of 5p{yields}4d emission produced by the cascading decay and then take into account self-absorption of the emitted photons. This model provides good agreement with the experimental results. The number of 4d vacancies increases immensely due to electronic cascades. We also observe an enhanced integral intensity in the 5p-4d fluorescence compared to our calculations, which we attribute to intra-atomic resonance processes.

  7. Magnetic moments in graphene with vacancies.

    PubMed

    Chen, Jing-Jing; Wu, Han-Chun; Yu, Da-Peng; Liao, Zhi-Min

    2014-08-07

    Vacancies can induce local magnetic moments in graphene, paving the way to make magnetic functional graphene. Due to the interaction between magnetic moments and conduction carriers, the magnetotransport properties of graphene can be modulated. Here, the effects of vacancy induced magnetic moments on the electrical properties of graphene are studied via magnetotransport measurements and spin-polarized density functional theory calculations. We show by quantum Hall measurements that a sharp resonant Vπ state is introduced in the midgap region of graphene with vacancies, resulting in the local magnetic moment. The coupling between the localized Vπ state and the itinerant carrier is tuned by varying the carrier concentration, temperature, magnetic field, and vacancy density, which results in a transition between hopping transport and the Kondo effect and a transition between giant negative magnetoresistance (MR) and positive MR. This modulated magnetotransport is valuable for graphene based spintronic devices.

  8. 7 CFR 1207.324 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE POTATO RESEARCH AND PROMOTION PLAN Potato Research and Promotion Plan National Potato Promotion Board § 1207.324 Vacancies. To fill any...

  9. 7 CFR 1207.324 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE POTATO RESEARCH AND PROMOTION PLAN Potato Research and Promotion Plan National Potato Promotion Board § 1207.324 Vacancies. To fill any...

  10. 7 CFR 1207.324 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE POTATO RESEARCH AND PROMOTION PLAN Potato Research and Promotion Plan National Potato Promotion Board § 1207.324 Vacancies. To fill any...

  11. 7 CFR 1207.324 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE POTATO RESEARCH AND PROMOTION PLAN Potato Research and Promotion Plan National Potato Promotion Board § 1207.324 Vacancies. To fill any...

  12. 7 CFR 1207.324 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE POTATO RESEARCH AND PROMOTION PLAN Potato Research and Promotion Plan National Potato Promotion Board § 1207.324 Vacancies. To fill any...

  13. Structural relaxation of vacancies in amorphous silicon

    SciTech Connect

    Kim, E.; Lee, Y.H.; Chen, C.; Pang, T.

    1997-07-01

    The authors have studied the structural relaxation of vacancies in amorphous silicon (a-Si) using a tight-binding molecular-dynamics method. The most significant difference between vacancies in a-Si and those in crystalline silicon (c-Si) is that the deep gap states do not show up in a-Si. This difference is explained through the unusual behavior of the structural relaxation near the vacancies in a-Si, which enhances the sp{sup 2} + p bonding near the band edges. They have also observed that the vacancies do not migrate below 450 K although some of them can still be annihilated, particularly at high defect density due to large structural relaxation.

  14. 38 CFR 1.896 - Publicizing vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... PROVISIONS Part-Time Career Employment Program § 1.896 Publicizing vacancies. When applicants from outside... means, such as: (a) Federal Job Information Centers. (b) State Employment offices. (c) VA...

  15. 38 CFR 1.896 - Publicizing vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... PROVISIONS Part-Time Career Employment Program § 1.896 Publicizing vacancies. When applicants from outside... means, such as: (a) Federal Job Information Centers. (b) State Employment offices. (c) VA...

  16. 38 CFR 1.896 - Publicizing vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... PROVISIONS Part-Time Career Employment Program § 1.896 Publicizing vacancies. When applicants from outside... means, such as: (a) Federal Job Information Centers. (b) State Employment offices. (c) VA...

  17. Understanding long-time vacancy aggregation in iron: A kinetic activation-relaxation technique study

    NASA Astrophysics Data System (ADS)

    Brommer, Peter; Béland, Laurent Karim; Joly, Jean-François; Mousseau, Normand

    2014-10-01

    Vacancy diffusion and clustering processes in body-centered-cubic (bcc) Fe are studied using the kinetic activation-relaxation technique (k-ART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building capabilities. For monovacancies and divacancies, k-ART recovers previously published results while clustering in a 50-vacancy simulation box agrees with experimental estimates. Applying k-ART to the study of clustering pathways for systems containing from one to six vacancies, we find a rich set of diffusion mechanisms. In particular, we show that the path followed to reach a hexavacancy cluster influences greatly the associated mean-square displacement. Aggregation in a 50-vacancy box also shows a notable dispersion in relaxation time associated with effective barriers varying from 0.84 to 1.1 eV depending on the exact pathway selected. We isolate the effects of long-range elastic interactions between defects by comparing to simulations where those effects are deliberately suppressed. This allows us to demonstrate that in bcc Fe, suppressing long-range interactions mainly influences kinetics in the first 0.3 ms, slowing down quick energy release cascades seen more frequently in full simulations, whereas long-term behavior and final state are not significantly affected.

  18. Effects of in-cascade defect clustering on near-term defect evolution

    SciTech Connect

    Heinisch, H.L.

    1997-08-01

    The effects of in-cascade defect clustering on the nature of the subsequent defect population are being studied using stochastic annealing simulations applied to cascades generated in molecular dynamics (MD) simulations. The results of the simulations illustrates the strong influence of the defect configuration existing in the primary damage state on subsequent defect evolution. The large differences in mobility and stability of vacancy and interstitial defects and the rapid one-dimensional diffusion of small, glissile interstitial loops produced directly in cascades have been shown to be significant factors affecting the evolution of the defect distribution. In recent work, the effects of initial cluster sizes appear to be extremely important.

  19. South Cascade Glacier bibliography

    SciTech Connect

    Fountain, A.G.; Fulk, M.A.

    1984-01-01

    South Cascade Glacier, in Washington State, resides in a well-defined basin with mainly unglacierized divides making it ideal for most glaciological and hydrological studies. This bibliography is divided into three cateogories: (1) studies done about South Cascade Glacier specifically; (2) studies that use data from South Cascade Glacier but do not focus on or give insight to the glacier itself; and (3) instrumentation studies and non-glacier projects including snow studies done in the basin. (ACR)

  20. Positron trapping at vacancies in electron-irradiated Si at low temperatures

    SciTech Connect

    Maekinen, J.; Corbel, C.; Hautojaervi, P.; Moser, P.; Pierre, F.

    1989-05-15

    Experimental results on positron trapping at vacancies in electron-irradiated silicon are presented. The positron lifetimes 273 +- 3 and 248 +- 2 ps in pure Si and heavily-phosphorus-doped Si ((P) = 10/sup 20/ cm/sup -3/) are assigned to a negative monovacancy V/sup -/ and a negative vacancy-phosphorus pair (V-P)/sup -/, respectively. In pure Si, positron trapping displays a strong negative temperature dependence, and the specific trapping rate reaches very large values (10/sup 17//sup --/10/sup 18/ s/sup -1/) at low temperatures. In Si:P the trapping rate is independent of temperature. These different temperature behaviors are attributed to different positron-trapping mechanisms, a cascade of one-phonon transitions in pure Si, and an Auger process in Si:P.

  1. Cascaded automatic target recognition (Cascaded ATR)

    NASA Astrophysics Data System (ADS)

    Walls, Bradley

    2010-04-01

    The global war on terror has plunged US and coalition forces into a battle space requiring the continuous adaptation of tactics and technologies to cope with an elusive enemy. As a result, technologies that enhance the intelligence, surveillance, and reconnaissance (ISR) mission making the warfighter more effective are experiencing increased interest. In this paper we show how a new generation of smart cameras built around foveated sensing makes possible a powerful ISR technique termed Cascaded ATR. Foveated sensing is an innovative optical concept in which a single aperture captures two distinct fields of view. In Cascaded ATR, foveated sensing is used to provide a coarse resolution, persistent surveillance, wide field of view (WFOV) detector to accomplish detection level perception. At the same time, within the foveated sensor, these detection locations are passed as a cue to a steerable, high fidelity, narrow field of view (NFOV) detector to perform recognition level perception. Two new ISR mission scenarios, utilizing Cascaded ATR, are proposed.

  2. Theory of cascade refrigeration

    NASA Astrophysics Data System (ADS)

    Quack, Hans H.

    2012-06-01

    The maximum difference between the warm and cold temperature of a refrigeration cycle is limited by properties of the refrigerant and/or losses associated with the transport of the refrigerant. For larger temperature differences, one has to arrange several refrigeration cycles "above" each other, each cycle spanning a certain temperature difference. This approach is called cascade refrigeration and has played an important role in the history of cryogenics. For a theory of cascade refrigeration it is helpful to define a general one-stage non-reversible refrigeration step and to visualize it within the temperature-entropy diagram. Then one can combine several one-stage cycles to a cascade. There exist two types of cascades: "Full" cascades, where all entropy gains of a lower stage are transferred to the next higher temperature stage, and "partial" cascades, where each single cycle goes up to ambient temperature, where a part of the entropy gain is removed, and only the rest of the entropy gain is transferred to the next higher temperature stage. In cryogenic refrigeration "partial" cascades are generally more efficient than "full" cascades.

  3. Vacancy dynamics in the paramagnetic environment

    NASA Astrophysics Data System (ADS)

    Carlstrom, Johan; Svistunov, Boris; Prokofiev, Nikolay

    We consider the motion of a single vacancy in a magnetic spin-1/2 lattice. Examples of realisations of this model include vacancies in a He3 solid or holes in the t-J model with J=0. This motion is ballistic when spins exhibit ferromagnetic order, with < | r (t) | > growing linearly with time. However in the disordered paramagnet, the motion of the vacancy becomes highly nontrivial, and no exact solution to this outstanding problem is known. This scenario is known as the Brinkman-Rice problem. We report here numerical results for the spatial probability distribution of the vacancy obtained by integrating the time evolution operator through Monte Carlo and averaging over a large number of random spin realisations. We find highly counterintuitive results, with the probability of finding the vacancy at a given site oscillating in time. These results can be verified in experiments with ultra-cold fermions in optical lattice at a temperature high enough that the spins are disordered.

  4. Interstitial dislocation loop nucleation and growth and swelling produced by high-energy cascades

    SciTech Connect

    Yu, J.; Sommer, W.F.; Bradbury, J.N.

    1986-01-01

    Structural materials for advanced energy sources such as magnetically-and inertially-confined thermonuclear reactors are subjected to a radiation enviornment that produces high-energy displacement cascades and transmutation products that include helium. We address these characteristics and formulate their effect on the microstructural evolution of a material. We consider that, immediately after a high energy cascade event, a vacancy-rich region exists near the primary event site and that an interstitial-rich zone, formed by collision chains, exists some distance from the primary event site. Transmutation-product helium can diffuse into the vacancy-rich zone and stabilize bubble nuclei that will later grow if sufficient vacancies and helium atoms diffuse to the nucleus. These bubbles are the sinks for excess radiation-produced vacancies. The excess radiation-produced interstitials migrate and bond; if the binding energy is high eneough, a di-interstitial is considered to be a stable dislocation-loop nucleus. The loop nuclei grow if they receive more interstitials than vacancies; this represents material swelling since the bubbles do not cause a lattice contraction to offset the dilation caused by the growing dislocation loops.

  5. Lattice Strain Due to an Atomic Vacancy

    PubMed Central

    Li, Shidong; Sellers, Michael S.; Basaran, Cemal; Schultz, Andrew J.; Kofke, David A.

    2009-01-01

    Volumetric strain can be divided into two parts: strain due to bond distance change and strain due to vacancy sources and sinks. In this paper, efforts are focused on studying the atomic lattice strain due to a vacancy in an FCC metal lattice with molecular dynamics simulation (MDS). The result has been compared with that from a continuum mechanics method. It is shown that using a continuum mechanics approach yields constitutive results similar to the ones obtained based purely on molecular dynamics considerations. PMID:19582230

  6. 5. VIEW OF UPPER AND LOWER CASCADE BRIDGES AND CASCADE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. VIEW OF UPPER AND LOWER CASCADE BRIDGES AND CASCADE CREEK FROM 100 YARDS WEST OF THE ROSTRUM (ROCK FORMATION ON SOUTH SIDE OF MERCED RIVER). HIGHWAY 140 IS AT BOTTOM OF FRAME. HIGHWAY 120, THE BIG OAK FLAT ROAD CROSSES FRAME JUST ABOVE CENTER. - Cascade Creek Bridge, Spanning Cascade Creek on New Big Oak Flat Road, Yosemite Village, Mariposa County, CA

  7. The vacancies formation and agglomeration under centrifugal force

    NASA Astrophysics Data System (ADS)

    Wierzba, Bartek

    2017-10-01

    In this paper the vacancies formation and agglomeration under centrifugal force - sedimentation will be analyzed. The evolutionary algorithm for diffusion and vacancy evolution will be shown. The model predicts the location of vacancies agglomeration during the sedimentation process - the most probably place of voids formation. The computed results will be compared with experiments in Cu-brass diffusion couple. The influence of the centrifugal force on the vacancies migration will be presented.

  8. Biocatalysis: Chiral cascades

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Bo; Reetz, Manfred T.

    2015-12-01

    Racemic or enantiomerically pure alcohols can be converted with high yield into enantiopure chiral amines in a one-pot redox-neutral cascade process by the clever combination of an alcohol dehydrogenase and an appropriate amine dehydrogenase.

  9. 7 CFR 915.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 915.26 Section 915.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE AVOCADOS GROWN IN SOUTH FLORIDA Order...

  10. 7 CFR 984.41 - Vacancy.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancy. 984.41 Section 984.41 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order...

  11. 7 CFR 984.41 - Vacancy.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancy. 984.41 Section 984.41 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order...

  12. 7 CFR 984.41 - Vacancy.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancy. 984.41 Section 984.41 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order...

  13. 7 CFR 984.41 - Vacancy.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancy. 984.41 Section 984.41 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order...

  14. 7 CFR 984.41 - Vacancy.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancy. 984.41 Section 984.41 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order...

  15. 7 CFR 915.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 915.26 Section 915.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE AVOCADOS GROWN IN SOUTH FLORIDA...

  16. 7 CFR 915.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 915.26 Section 915.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE AVOCADOS GROWN IN SOUTH FLORIDA...

  17. 7 CFR 915.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 915.26 Section 915.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE AVOCADOS GROWN IN SOUTH FLORIDA...

  18. 7 CFR 927.29 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 927.29 Section 927.29 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE PEARS GROWN IN OREGON AND...

  19. 24 CFR 990.150 - Limited vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... THE PUBLIC HOUSING OPERATING FUND PROGRAM Eligibility for Operating Subsidy; Computation of Eligible... 24 Housing and Urban Development 4 2012-04-01 2012-04-01 false Limited vacancies. 990.150 Section 990.150 Housing and Urban Development REGULATIONS RELATING TO HOUSING AND URBAN DEVELOPMENT (CONTINUED...

  20. 24 CFR 990.150 - Limited vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... THE PUBLIC HOUSING OPERATING FUND PROGRAM Eligibility for Operating Subsidy; Computation of Eligible... 24 Housing and Urban Development 4 2014-04-01 2014-04-01 false Limited vacancies. 990.150 Section 990.150 Housing and Urban Development REGULATIONS RELATING TO HOUSING AND URBAN DEVELOPMENT (CONTINUED...

  1. 24 CFR 990.150 - Limited vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... THE PUBLIC HOUSING OPERATING FUND PROGRAM Eligibility for Operating Subsidy; Computation of Eligible... 24 Housing and Urban Development 4 2013-04-01 2013-04-01 false Limited vacancies. 990.150 Section 990.150 Housing and Urban Development REGULATIONS RELATING TO HOUSING AND URBAN DEVELOPMENT (CONTINUED...

  2. 24 CFR 990.150 - Limited vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... THE PUBLIC HOUSING OPERATING FUND PROGRAM Eligibility for Operating Subsidy; Computation of Eligible... 24 Housing and Urban Development 4 2011-04-01 2011-04-01 false Limited vacancies. 990.150 Section 990.150 Housing and Urban Development REGULATIONS RELATING TO HOUSING AND URBAN DEVELOPMENT (CONTINUED...

  3. 24 CFR 990.150 - Limited vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... THE PUBLIC HOUSING OPERATING FUND PROGRAM Eligibility for Operating Subsidy; Computation of Eligible... 24 Housing and Urban Development 4 2010-04-01 2010-04-01 false Limited vacancies. 990.150 Section 990.150 Housing and Urban Development Regulations Relating to Housing and Urban Development (Continued...

  4. 7 CFR 1260.146 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BEEF PROMOTION AND RESEARCH Beef Promotion and Research Order Cattlemen's Beef Promotion and Research Board § 1260.146 Vacancies. To fill any...

  5. 7 CFR 955.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 955.26 Section 955.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE VIDALIA ONIONS GROWN IN...

  6. 7 CFR 955.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 955.26 Section 955.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE VIDALIA ONIONS GROWN IN...

  7. 7 CFR 955.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 955.26 Section 955.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE VIDALIA ONIONS GROWN IN...

  8. 7 CFR 956.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 956.26 Section 956.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET ONIONS GROWN IN THE WALLA...

  9. 7 CFR 956.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 956.26 Section 956.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET ONIONS GROWN IN THE WALLA...

  10. 7 CFR 955.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 955.26 Section 955.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE VIDALIA ONIONS GROWN IN...

  11. 7 CFR 956.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 956.26 Section 956.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE SWEET ONIONS GROWN IN THE WALLA...

  12. 7 CFR 955.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 955.26 Section 955.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE VIDALIA ONIONS GROWN IN...

  13. 7 CFR 956.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 956.26 Section 956.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE SWEET ONIONS GROWN IN THE WALLA...

  14. 7 CFR 956.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 956.26 Section 956.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET ONIONS GROWN IN THE WALLA...

  15. 7 CFR 922.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 922.26 Section 922.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE APRICOTS GROWN IN DESIGNATED COUNTIES...

  16. 7 CFR 922.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 922.26 Section 922.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE APRICOTS GROWN IN DESIGNATED COUNTIES...

  17. 7 CFR 922.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 922.26 Section 922.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE APRICOTS GROWN IN DESIGNATED COUNTIES...

  18. 7 CFR 922.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 922.26 Section 922.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE APRICOTS GROWN IN DESIGNATED COUNTIES...

  19. 7 CFR 922.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 922.26 Section 922.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE APRICOTS GROWN IN DESIGNATED COUNTIES...

  20. 7 CFR 948.58 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 948.58 Section 948.58 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE IRISH POTATOES GROWN IN COLORADO...

  1. 7 CFR 948.58 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 948.58 Section 948.58 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE IRISH POTATOES GROWN IN COLORADO...

  2. 7 CFR 1208.43 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE PROCESSED RASPBERRY PROMOTION, RESEARCH, AND INFORMATION ORDER Processed Raspberry Promotion, Research, and Information Order National Processed Raspberry Council § 1208.43 Vacancies. (a) In the event that any member of the Council ceases to...

  3. 7 CFR 1208.43 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE PROCESSED RASPBERRY PROMOTION, RESEARCH, AND INFORMATION ORDER Processed Raspberry Promotion, Research, and Information Order National Processed Raspberry Council § 1208.43 Vacancies. (a) In the event that any member of the Council ceases to...

  4. 7 CFR 915.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 915.26 Section 915.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE AVOCADOS GROWN IN SOUTH FLORIDA...

  5. 7 CFR 930.27 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 930.27 Section 930.27 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TART CHERRIES GROWN IN THE STATES...

  6. 7 CFR 925.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 925.26 Section 925.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE GRAPES GROWN IN A DESIGNATED AREA...

  7. 7 CFR 925.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 925.26 Section 925.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE GRAPES GROWN IN A DESIGNATED AREA...

  8. 7 CFR 989.34 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 989.34 Section 989.34 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE RAISINS PRODUCED FROM GRAPES GROWN...

  9. 7 CFR 925.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 925.26 Section 925.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE GRAPES GROWN IN A DESIGNATED AREA...

  10. 7 CFR 925.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 925.26 Section 925.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE GRAPES GROWN IN A DESIGNATED AREA...

  11. 7 CFR 945.28 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 945.28 Section 945.28 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE IRISH POTATOES GROWN IN...

  12. 7 CFR 989.34 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 989.34 Section 989.34 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE RAISINS PRODUCED FROM GRAPES GROWN...

  13. 7 CFR 989.34 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 989.34 Section 989.34 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE RAISINS PRODUCED FROM GRAPES GROWN...

  14. 7 CFR 946.33 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 946.33 Section 946.33 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... event of the death, removal, resignation, or disqualification of any qualified member or alternate,...

  15. 7 CFR 948.58 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 948.58 Section 948.58 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... of any person selected as a member or as an alternate to qualify, or in the event of the...

  16. 7 CFR 924.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 924.26 Section 924.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... an alternate member of the committee to qualify, or in the event of the death, removal,...

  17. 7 CFR 945.28 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 945.28 Section 945.28 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... member or as an alternate to qualify, or in the event of the death, removal, resignation,...

  18. 7 CFR 916.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 916.26 Section 916.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... any person selected as a member or as an alternate member of the committee to qualify, or in the...

  19. 7 CFR 927.29 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 927.29 Section 927.29 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... Committee or the Processed Pear Committee to qualify, or in the event of death, removal, resignation,...

  20. 7 CFR 929.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 929.26 Section 929.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES OF...

  1. 7 CFR 929.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 929.26 Section 929.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES OF...

  2. 7 CFR 929.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 929.26 Section 929.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES OF...

  3. 7 CFR 929.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 929.26 Section 929.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES OF...

  4. 7 CFR 989.34 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 989.34 Section 989.34 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE RAISINS PRODUCED FROM GRAPES GROWN IN...

  5. 7 CFR 925.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 925.26 Section 925.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE GRAPES GROWN IN A DESIGNATED AREA OF...

  6. 7 CFR 923.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 923.26 Section 923.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET CHERRIES GROWN IN DESIGNATED...

  7. 7 CFR 930.27 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 930.27 Section 930.27 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE TART CHERRIES GROWN IN THE STATES OF...

  8. 7 CFR 923.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 923.26 Section 923.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET CHERRIES GROWN IN DESIGNATED...

  9. 7 CFR 923.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 923.26 Section 923.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET CHERRIES GROWN IN DESIGNATED...

  10. 7 CFR 930.27 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 930.27 Section 930.27 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TART CHERRIES GROWN IN THE STATES OF...

  11. 7 CFR 930.27 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 930.27 Section 930.27 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE TART CHERRIES GROWN IN THE STATES OF...

  12. 7 CFR 923.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 923.26 Section 923.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE SWEET CHERRIES GROWN IN DESIGNATED...

  13. 7 CFR 930.27 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 930.27 Section 930.27 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TART CHERRIES GROWN IN THE STATES OF...

  14. 7 CFR 923.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 923.26 Section 923.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE SWEET CHERRIES GROWN IN DESIGNATED...

  15. 7 CFR 929.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 929.26 Section 929.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... member of the committee to qualify, or in the event of the death, removal, resignation, or...

  16. 7 CFR 966.30 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 966.30 Section 966.30 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA Order...

  17. 7 CFR 966.30 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 966.30 Section 966.30 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA Order...

  18. 7 CFR 966.30 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 966.30 Section 966.30 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA Order...

  19. 7 CFR 966.30 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 966.30 Section 966.30 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA Order...

  20. 7 CFR 966.30 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 966.30 Section 966.30 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA Order...

  1. 7 CFR 920.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 920.26 Section 920.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE KIWIFRUIT GROWN IN...

  2. 7 CFR 920.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 920.26 Section 920.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE KIWIFRUIT GROWN IN...

  3. 7 CFR 920.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 920.26 Section 920.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE KIWIFRUIT GROWN IN...

  4. 7 CFR 920.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 920.26 Section 920.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE KIWIFRUIT GROWN IN...

  5. 7 CFR 920.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 920.26 Section 920.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE KIWIFRUIT GROWN IN...

  6. Ab initio calculations and rate equation simulations for vacancy and vacancy-oxygen clustering in silicon

    NASA Astrophysics Data System (ADS)

    Kissinger, G.; Dabrowski, J.; Sinno, T.; Yang, Y.; Kot, D.; Sattler, A.

    2017-06-01

    Formation energies of vacancy clusters Vn with (1≤n≤11) in crystalline Si and of their complexes VnOm (1≤m≤14) with oxygen were computed by ab initio density functional theory (DFT) within the generalized gradient approximation (GGA) and used to simulate the process of vacancy agglomeration after rapid thermal annealing (RTA) and also the formation of bulk microdefects (BMDs) in Si. Rate equation modeling of vacancy agglomeration after RTA and subsequent annealing below 1000 °C was carried out and the results were compared for binding energies obtained with different cell size. In Czochralski silicon, the interaction between vacancies and interstitial oxygen has to be taken into account. The BMD formation in Czochralski silicon was modeled by a continuum model comprised of a large system of rate equations, which accounts for the free energy of BMDs as a function of BMD size and shape, temperature and point defect concentrations.

  7. Ab initio study of the formation of vacancy and hydrogen-vacancy complexes in palladium and its hydride

    NASA Astrophysics Data System (ADS)

    Supryadkina, I. A.; Bazhanov, D. I.; Ilyushin, A. S.

    2014-01-01

    We report on the results of ab initio calculations of vacancy and hydrogen-vacancy complexes in palladium and palladium hydride. Comparative analysis of the energies of the formation of defect complexes in palladium and its hydride has revealed that the formation of vacancy clusters is easier in the palladium hydride structure. Investigation of hydrogen-vacancy complexes in bulk crystalline palladium has shown that a hydrogen atom and a vacancy interact to form a stable hydrogen-vacancy (H-Vac) defect complex with a binding energy of E b = -0.21 eV. To investigate the initial stage in the formation of hydrogen-vacancy complexes (H n -Vac m ), we consider the clusterization of defects into clusters containing H-Vac and H2-Vac complexes as a structural unit. It is found that hydrogen-vacancy complexes form 2D defect structures in palladium in the (100)-type planes.

  8. The nitrogen cascade

    SciTech Connect

    Galloway J.N.; Aber J.D.; Erisman J.W.; Seitzinger S.P.; Howarth R.W.; Cowling E.B.; Cosby B.J.

    2003-04-01

    Human production of food and energy is the dominant continental process that breaks the triple bond in molecular nitrogen (N{sub 2}) and creates reactive nitrogen (Nr) species. Circulation of anthropogenic Nr in Earth's atmosphere, hydrosphere, and biosphere has a wide variety of consequences, which are magnified with time as Nr moves along its biogeochemical pathway. The same atom of Nr can cause multiple effects in the atmosphere, in terrestrial ecosystems, in freshwater and marine systems, and on human health. We call this sequence of effects the nitrogen cascade. As the cascade progresses, the origin of Nr becomes unimportant. Reactive nitrogen does not cascade at the same rate through all environmental systems; some systems have the ability to accumulate Nr, which leads to lag times in the continuation of the cascade. These lags slow the cascade and result in Nr accumulation in certain reservoirs, which in turn can enhance the effects of Nr on that environment. The only way to eliminate Nr accumulation and stop the cascade is to convert Nr back to nonreactive N{sub 2}.

  9. Displacement cascades and defect annealing in tungsten, Part III: The sensitivity of cascade annealing in tungsten to the values of kinetic parameters

    SciTech Connect

    Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

    2015-07-01

    Object kinetic Monte Carlo (OKMC) simulations have been performed to investigate various aspects of cascade aging in bulk tungsten and to determine the sensitivity of the results to the kinetic parameters. The primary focus is on how the kinetic parameters affect the initial recombination of defects in the first few ns of a simulation. The simulations were carried out using the object kinetic Monte Carlo (OKMC) code KSOME (kinetic simulations of microstructure evolution), using a database of cascades obtained from results of molecular dynamics (MD) simulations at various primary knock-on atom (PKA) energies and directions at temperatures of 300, 1025 and 2050 K. The OKMC model was parameterized using defect migration barriers and binding energies from ab initio calculations. Results indicate that, due to the disparate mobilities of SIA and vacancy clusters in tungsten, annealing is dominated by SIA migration even at temperatures as high as 2050 K. For 100 keV cascades initiated at 300 K recombination is dominated by annihilation of large defect clusters. But for all other PKA energies and temperatures most of the recombination is due to the migration and rotation of small SIA clusters, while all the large SIA clusters escape the cubic simulation cell. The inverse U-shape behavior exhibited by the annealing efficiency as a function of temperature curve, especially for cascades of large PKA energies, is due to asymmetry in SIA and vacancy clustering assisted by the large difference in mobilities of SIAs and vacancies. This annealing behavior is unaffected by the dimensionality of SIA migration persists over a broad range of relative mobilities of SIAs and vacancies.

  10. Thermodynamics of impurity-enhanced vacancy formation in metals

    NASA Astrophysics Data System (ADS)

    Bukonte, Laura; Ahlgren, Tommy; Heinola, Kalle

    2017-01-01

    Hydrogen induced vacancy formation in metals and metal alloys has been of great interest during the past couple of decades. The main reason for this phenomenon, often referred to as the superabundant vacancy formation, is the lowering of vacancy formation energy due to the trapping of hydrogen. By means of thermodynamics, we study the equilibrium vacancy formation in fcc metals (Pd, Ni, Co, and Fe) in correlation with the H amounts. The results of this study are compared and found to be in good agreement with experiments. For the accurate description of the total energy of the metal-hydrogen system, we take into account the binding energies of each trapped impurity, the vibrational entropy of defects, and the thermodynamics of divacancy formation. We demonstrate the effect of vacancy formation energy, the hydrogen binding, and the divacancy binding energy on the total equilibrium vacancy concentration. We show that the divacancy fraction gives the major contribution to the total vacancy fraction at high H fractions and cannot be neglected when studying superabundant vacancies. Our results lead to a novel conclusion that at high hydrogen fractions, superabundant vacancy formation takes place regardless of the binding energy between vacancies and hydrogen. We also propose the reason of superabundant vacancy formation mainly in the fcc phase. The equations obtained within this work can be used for any metal-impurity system, if the impurity occupies an interstitial site in the lattice.

  11. Polaronic interactions between oxygen vacancies in rutile Ti O2

    NASA Astrophysics Data System (ADS)

    Zhao, Liang; Magyari-Köpe, Blanka; Nishi, Yoshio

    2017-02-01

    Oxygen vacancy-vacancy interactions in rutile Ti O2 are studied in conjunction with polaron formation trends using density functional theory calculations. It is found that polarons strongly enhance the formation of oxygen vacancies in this material and also mediate the interactions between existing vacancies. At distances below 1 nm, two isolated and charge-neutral vacancies exhibit attractive interactions with an equilibrium distance of about 4 Å. The attractive forces between vacancies partly arise from the polaronic transfer of excess electrons to reduce the potential energy. These discoveries provide microscopic explanations to the vacancy clustering phenomena, as well as a practical approach to stabilize the polarons at arbitrary Ti atoms in Ti O2 .

  12. Tracking Earthquake Cascades

    NASA Astrophysics Data System (ADS)

    Jordan, T. H.

    2011-12-01

    In assessing their risk to society, earthquakes are best characterized as cascades that can propagate from the natural environment into the socio-economic (built) environment. Strong earthquakes rarely occur as isolated events; they usually cluster in foreshock-mainshock-aftershock sequences, seismic swarms, and extended sequences of large earthquakes that propagate along major fault systems. These cascades are regulated by stress-mediated interactions among faults driven by tectonic loading. Within these cascades, each large event can itself cause a chain reaction in which the primary effects of faulting and ground shaking induce secondary effects, including tsunami, landslides, liquefaction, and set off destructive processes within the built environment, such as fires and radiation leakage from nuclear plants. Recent earthquakes have demonstrated how the socio-economic effects of large earthquakes can reverberate for many years. To reduce earthquake risk and improve the resiliency of communities to earthquake damage, society depends on five geotechnologies for tracking earthquake cascades: long-term probabilistic seismic hazard analysis (PSHA), short-term (operational) earthquake forecasting, earthquake early warning, tsunami warning, and the rapid production of post-event information for response and recovery (see figure). In this presentation, I describe how recent advances in earthquake system science are leading to improvements in this geotechnology pipeline. In particular, I will highlight the role of earthquake simulations in predicting strong ground motions and their secondary effects before and during earthquake cascades

  13. Hydrogenated vacancies lock dislocations in aluminium

    SciTech Connect

    Xie, Degang; Li, Suzhi; Li, Meng; Wang, Zhangjie; Gumbsch, Peter; Sun, Jun; Ma, Evan; Li, Ju; Shan, Zhiwei

    2016-11-03

    Due to its high diffusivity, hydrogen is often considered a weak inhibitor or even a promoter of dislocation movements in metals and alloys. By quantitative mechanical tests in an environmental transmission electron microscope, here we demonstrate that after exposing aluminium to hydrogen, mobile dislocations can lose mobility, with activating stress more than doubled. On degassing, the locked dislocations can be reactivated under cyclic loading to move in a stick-slip manner. However, relocking the dislocations thereafter requires a surprisingly long waiting time of ~103 s, much longer than that expected from hydrogen interstitial diffusion. Both the observed slow relocking and strong locking strength can be attributed to superabundant hydrogenated vacancies, verified by our atomistic calculations. In conclusion, vacancies therefore could be a key plastic flow localization agent as well as damage agent in hydrogen environment.

  14. Hydrogenated vacancies lock dislocations in aluminium

    DOE PAGES

    Xie, Degang; Li, Suzhi; Li, Meng; ...

    2016-11-03

    Due to its high diffusivity, hydrogen is often considered a weak inhibitor or even a promoter of dislocation movements in metals and alloys. By quantitative mechanical tests in an environmental transmission electron microscope, here we demonstrate that after exposing aluminium to hydrogen, mobile dislocations can lose mobility, with activating stress more than doubled. On degassing, the locked dislocations can be reactivated under cyclic loading to move in a stick-slip manner. However, relocking the dislocations thereafter requires a surprisingly long waiting time of ~103 s, much longer than that expected from hydrogen interstitial diffusion. Both the observed slow relocking and strongmore » locking strength can be attributed to superabundant hydrogenated vacancies, verified by our atomistic calculations. In conclusion, vacancies therefore could be a key plastic flow localization agent as well as damage agent in hydrogen environment.« less

  15. Hydrogenated vacancies lock dislocations in aluminium

    NASA Astrophysics Data System (ADS)

    Xie, Degang; Li, Suzhi; Li, Meng; Wang, Zhangjie; Gumbsch, Peter; Sun, Jun; Ma, Evan; Li, Ju; Shan, Zhiwei

    2016-11-01

    Due to its high diffusivity, hydrogen is often considered a weak inhibitor or even a promoter of dislocation movements in metals and alloys. By quantitative mechanical tests in an environmental transmission electron microscope, here we demonstrate that after exposing aluminium to hydrogen, mobile dislocations can lose mobility, with activating stress more than doubled. On degassing, the locked dislocations can be reactivated under cyclic loading to move in a stick-slip manner. However, relocking the dislocations thereafter requires a surprisingly long waiting time of ~103 s, much longer than that expected from hydrogen interstitial diffusion. Both the observed slow relocking and strong locking strength can be attributed to superabundant hydrogenated vacancies, verified by our atomistic calculations. Vacancies therefore could be a key plastic flow localization agent as well as damage agent in hydrogen environment.

  16. Vacancy-induced flow of solid helium

    NASA Astrophysics Data System (ADS)

    Benedek, Giorgio; Kalinin, Anton; Nieto, Pablo; Toennies, J. Peter

    2016-03-01

    The pulsed flow of solid 4He through a narrow capillary in a flow system which issues into vacuum is investigated at temperatures between 1.64 and 2.66 K and pressures between 54 and 104 bars. After each pulse three different capillary flow regimes are observed as the upstream pressure decreases: an oscillatory [mini-geyser (MG)] regime, a constant flow (CF) regime with a linearly decreasing pressure difference, and a nonresistant (NR) regime. A quantitative analysis of the three regimes suggests that the flow of solid 4He is driven by a counterflow of excess vacancies, which are injected downstream of the capillary at the solid/liquid interface near the micrometric orifice exposed to vacuum. The CF regime, where the flow velocity is found to be independent of the pressure difference, and the NR regime, where the solid flows as a Bernoulli fluid, suggest a new dynamic phase of solid helium induced by a steady influx of vacancies.

  17. Hydrogenated vacancies lock dislocations in aluminium

    PubMed Central

    Xie, Degang; Li, Suzhi; Li, Meng; Wang, Zhangjie; Gumbsch, Peter; Sun, Jun; Ma, Evan; Li, Ju; Shan, Zhiwei

    2016-01-01

    Due to its high diffusivity, hydrogen is often considered a weak inhibitor or even a promoter of dislocation movements in metals and alloys. By quantitative mechanical tests in an environmental transmission electron microscope, here we demonstrate that after exposing aluminium to hydrogen, mobile dislocations can lose mobility, with activating stress more than doubled. On degassing, the locked dislocations can be reactivated under cyclic loading to move in a stick-slip manner. However, relocking the dislocations thereafter requires a surprisingly long waiting time of ∼103 s, much longer than that expected from hydrogen interstitial diffusion. Both the observed slow relocking and strong locking strength can be attributed to superabundant hydrogenated vacancies, verified by our atomistic calculations. Vacancies therefore could be a key plastic flow localization agent as well as damage agent in hydrogen environment. PMID:27808099

  18. Hadron cascades produced by electromagnetic cascades

    SciTech Connect

    Nelson, W.R.; Jenkins, T.M.; Ranft, J.

    1986-12-01

    A method for calculating high energy hadron cascades induced by multi-GeV electron and photon beams is described. Using the EGS4 computer program, high energy photons in the EM shower are allowed to interact hadronically according to the vector meson dominance (VMD) model, facilitated by a Monte Carlo version of the dual multistring fragmentation model which is used in the hadron cascade code FLUKA. The results of this calculation compare very favorably with experimental data on hadron production in photon-proton collisions and on the hadron production by electron beams on targets (i.e., yields in secondary particle beam lines). Electron beam induced hadron star density contours are also presented and are compared with those produced by proton beams. This FLUKA-EGS4 coupling technique could find use in the design of secondary beams, in the determination high energy hadron source terms for shielding purposes, and in the estimation of induced radioactivity in targets, collimators and beam dumps.

  19. Resonant Cascaded Downconversion

    SciTech Connect

    Weedbrook, Christian; Parrett, Ben; Kheruntsyan, Karen; Drummond, Peter; Pooser, Raphael C; Pfister, Olivier

    2012-01-01

    We analyze an optical parametric oscillator (OPO) in which cascaded down-conversion occurs inside a cavity resonant for all modes but the initial pump. Due to the resonant cascade design, the OPO presents two {chi}{sup (2)}-level oscillation thresholds that are therefore much lower than for a {chi}{sup (3)} OPO. This is promising for reaching the regime of an effective third-order nonlinearity well above both thresholds. Such a {chi}{sup (2)} cascaded device also has potential applications in frequency conversion to far-infrared regimes. But, most importantly, it can generate novel multipartite quantum correlations in the output radiation, which represent a step beyond squeezed or entangled light. The output can be highly non-Gaussian and therefore not describable by any semiclassical model. In this paper, we derive quantum stochastic equations in the positive-P representation and undertake an analysis of steady-state and dynamical properties of this system.

  20. Critical Mandelbrot Cascades

    NASA Astrophysics Data System (ADS)

    Barral, Julien; Kupiainen, Antti; Nikula, Miika; Saksman, Eero; Webb, Christian

    2014-01-01

    We study Mandelbrot's multiplicative cascade measures at the critical temperature. As has been recently shown by Barral et al. (C R Acad Sci Paris Ser I 350:535-538, 2012), an appropriately normalized sequence of cascade measures converges weakly in probability to a nontrivial limit measure. We prove that these limit measures have no atoms and give bounds for the modulus of continuity of the cumulative distribution function of the measure. Using the earlier work of Barral and Seuret (Adv Math 214:437-468, 2007), we compute the multifractal spectrum of the measures. We also extend the result of Benjamini and Schramm (Commun Math Phys 289:653-662, 2009), in which the KPZ formula from quantum gravity is validated for the high temperature cascade measures, to the critical and low temperature cases.

  1. Collisional Cascades Revisited

    NASA Astrophysics Data System (ADS)

    Schlichting, Hilke; Pan, M.

    2013-01-01

    Collisional cascades are believed to be the primary mechanism operating in circumstellar dusty debris disks, and are thought to be important in the Kuiper and Asteroid belt. Collisional cascades transfer mass via destructive collisions from larger bodies to smaller ones. Their widespread occurrence and potential importance in understanding planet formation and planet-disk interactions have motivated detailed studies of collisional cascades. The standard theoretical treatment of collisional cascades derives a steady-state size distribution assuming a single constant velocity dispersion for all bodies regardless of size. We relax this assumption and solve self-consistently for the bodies' steady-state size and size-dependent velocity distributions. Specifically, we account for viscous stirring, dynamical friction, and collisional damping of the bodies' random velocities in addition to the mass conservation requirement typically applied to find the size distribution in a steady-state cascade. The resulting size distributions are significantly steeper than those derived without velocity evolution. For example, accounting self-consistently for the velocities can change the standard q = 3.5 power-law index of the Dohnanyi differential size spectrum to an index as large as q = 4. Similarly, for bodies held together by their own gravity, the corresponding power-law index range 2.88 < q < 3.14 of Pan & Sari (2005) can steepen to values as large as q = 3.26. These differences in the size distribution power law index are very important when estimating the total disk mass, including larger bodies, by extrapolating from the observed dust masses. Our velocity results allow quantitative predictions of the bodies' scale heights as a function of size. Together with our predictions, observations of the scale heights for different-sized bodies in, for example, extrasolar debris disks may constrain the total mass in large bodies stirring the cascade as well as the colliding bodies

  2. Deterministic Role of Concentration Surplus of Cation Vacancy over Anion Vacancy in Bipolar Memristive NiO.

    PubMed

    Sun, Zhong; Zhao, Yonggang; He, Min; Gu, Lin; Ma, Chao; Jin, Kuijuan; Zhao, Diyang; Luo, Nannan; Zhang, Qinghua; Wang, Na; Duan, Wenhui; Nan, Ce-Wen

    2016-05-11

    Migration of oxygen vacancies has been proposed to play an important role in the bipolar memristive behaviors because oxygen vacancies can directly determine the local conductivity in many systems. However, a recent theoretical work demonstrated that both migration of oxygen vacancies and coexistence of cation and anion vacancies are crucial to the occurrence of bipolar memristive switching, normally observed in the small-sized NiO. So far, experimental work addressing this issue is still lacking. In this work, with conductive atomic force microscopy and combined scanning transmission electron microscopy and electron energy loss spectroscopy, we reveal that concentration surplus of Ni vacancy over O vacancy determines the bipolar memristive switching of NiO films. Our work supports the dual-defects-based model, which is of fundamental importance for understanding the memristor mechanisms beyond the well-established oxygen-vacancy-based model. Moreover, this work provides a methodology to investigate the effect of dual defects on memristive behaviors.

  3. Triangular rogue wave cascades.

    PubMed

    Kedziora, David J; Ankiewicz, Adrian; Akhmediev, Nail

    2012-11-01

    By numerically applying the recursive Darboux transformation technique, we study high-order rational solutions of the nonlinear Schrödinger equation that appear spatiotemporally as triangular arrays of Peregrine solitons. These can be considered as rogue wave cascades and complement previously discovered circular cluster forms. In this analysis, we reveal a general parametric restriction for their existence and investigate the interplay between cascade and cluster forms. As a result, we demonstrate how to generate many more hybrid rogue wave solutions, including semicircular clusters that resemble claws.

  4. Cascades Volcano Observatory

    USGS Publications Warehouse

    Venezky, Dina Y.; Driedger, Carolyn; Pallister, John

    2008-01-01

    Washington's Mount St. Helens volcano reawakens explosively on October 1, 2004, after 18 years of quiescence. Scientists at the U.S. Geological Survey's Cascades Volcano Observatory (CVO) study and observe Mount St. Helens and other volcanoes of the Cascade Range in Washington, Oregon, and northern California that hold potential for future eruptions. CVO is one of five USGS Volcano Hazards Program observatories that monitor U.S. volcanoes for science and public safety. Learn more about Mount St. Helens and CVO at http://vulcan.wr.usgs.gov/.

  5. Computer simulation of primary damage creationin high-energy displacement cascades in copperI. Defect creation and cluster statistics

    SciTech Connect

    Voskoboinikov, Roman E; Osetskiy, Yury N; Bacon, David J

    2008-01-01

    Atomic-scale computer simulation has been used to investigate the primary damage created by displacement cascades in copper over a wide range of temperature (100 K T 900 K) and primary knock-on atom energy (5 keV EPKA 25 keV). A technique was introduced to improve computational efficiency and at least 20 cascades for each (EPKA,T) pair were simulated in order to ensure statistical reliability of the results. The total of almost 450 simulated cascades is the largest yet reported for this metal. The mean number of surviving point defects per cascade is only 15-20% of the NRT model value. It decreases with increasing T at fixed EPKA and is proportional to (EPKA)1.1 at fixed T. A high proportion (60-80%) of self-interstitial atoms (SIAs) form clusters during the cascade process. The proportion is smaller for vacancies and sensitive to T, falling from 30-60% for T 600 K to less than 20% when T = 900 K. The structure of clusters has been examined in detail. Vacancies cluster predominantly in stackingfault- tetrahedron-type configurations. SIAs tend to form either glissile dislocation loops with Burgers vector b = 1/2<110> or sessile faulted Frank loops with b = 1/3<111>. Despite the fact that cascades at a given EPKA and T exhibit a wide range of defect numbers and clustered fractions, there appears to be a correlation in the formation of vacancy clusters and SIA clusters in the same cascade. The size and spatial aspects of this are analysed in detail in part II [26]. The stability of clusters when another cascade overlaps them is also investigated in part II.

  6. DISPLACEMENT CASCADE SIMULATION IN TUNGSTEN AT 1025 K

    SciTech Connect

    Setyawan, Wahyu; Nandipati, Giridhar; Roche, Kenneth J.; Heinisch, Howard L.; Kurtz, Richard J.; Wirth, Brian D.

    2013-09-30

    Molecular dynamics simulation was employed to investigate the irradiation damage properties of bulk tungsten at 1025 K (0.25 melting temperature). A comprehensive data set of primary cascade damage was generated up to primary knock-on atom (PKA) energies 100 keV. The dependence of the number of surviving Frenkel pairs (NFP) on the PKA energy (E) exhibits three different characteristic domains presumably related to the different cascade morphologies that form. The low-energy regime < 0.2 keV is characterized by a hit-or-miss type of Frenkel pair (FP) production near the displacement threshold energy of 128 eV. The middle regime 0.3 – 30 keV exhibits a sublinear dependence of log(NFP) vs log(E) associated with compact cascade morphology with a slope of 0.73. Above 30 keV, the cascade morphology consists of complex branches or interconnected damage regions. In this extended morphology, large interstitial clusters form from superposition of interstitials from nearby damage regions. Strong clustering above 30 keV results in a superlinear dependence of log(NFP) vs log(E) with a slope of 1.365. At 100 keV, an interstitial cluster of size 92 and a vacancy cluster of size 114 were observed.

  7. Vacancies at the Cu–Nb semicoherent interface

    NASA Astrophysics Data System (ADS)

    Metsanurk, E.; Tamm, A.; Aabloo, A.; Klintenberg, M.; Caro, A.

    2017-02-01

    We present the 0 K structures and formation energies for vacancy clusters of up to four vacancies and migration barriers for a single vacancy at a semicoherent Kurdjumov–Sachs Cu–Nb interface using ab initio calculations. Two main results emerge from this study, first that the predicted vacancy structure is compact, differing notoriously with predictions based on available empirical potentials, and second that vacancy clusters containing up to four vacancies have a smaller formation energy than monovacancy in bulk. Additionally, the binding energies show that the vacancy clusters are energetically stable for clusters having up to four vacancies. Nudged elastic band calculations of migration barriers show that the migration of a vacancy from one misfit dislocation intersection to another is highly improbable due to the high barriers. These findings suggest that at nonzero temperatures the interface will be preloaded with vacancy clusters with a relatively large capture radius for interstitials in the interface plane, implying that the semicoherent Cu–Nb interface could be a highly effective sink for point defects that form due to irradiation.

  8. On the Origin of Large Interstitial Clusters in Displacement Cascades

    SciTech Connect

    Andrew, Calder F; Barashev, Aleksandr; Bacon, David J; Osetskiy, Yury N

    2010-01-01

    Displacement cascades with wide ranges of primary knock-on atom (PKA) energy and mass in iron were simulated using molecular dynamics. New visualisation techniques are introduced to show how the shock-front dynamics and internal structure of a cascade develop over time. These reveal that the nature of the final damage is determined early on in the cascade process. We define a zone (termed 'spaghetti') in which atoms are moved to new lattice sites and show how it is created by a supersonic shock-front expanding from the primary recoil event. A large cluster of self-interstitial atoms can form on the periphery of the spaghetti if a hypersonic recoil creates damage with a supersonic shock ahead of the main supersonic front. When the two fronts meet, the main one injects atoms into the low-density core of the other: these become interstitial atoms during the rapid recovery of the surrounding crystal. The hypersonic recoil occurs in less than 0.1 ps after the primary recoil and the interstitial cluster is formed before the onset of the thermal spike phase of the cascade process. The corresponding number of vacancies is then formed in the spaghetti core as the crystal cools, i.e. at times one to two orders of magnitude longer. By using the spaghetti zone to define cascade volume, the energy density of a cascade is shown to be almost independent of the PKA mass. This throws into doubt the conventional energy-density interpretation of an increased defect yield with increasing PKA mass in ion irradiation.

  9. A study of the vacancy loop formation probability in Ni-Cu and Ag-Pd alloys

    SciTech Connect

    Smalinskas, K.; Chen, Gengsheng; Haworth, J.; Robertson, I.M.; Kirk, M.A.

    1992-04-01

    The molten-zone model of vacancy loop formation from a displacement cascade predicts that the loop formation probability should scale with the melting temperature. To investigate this possibility the vacancy loop formation probability has been determined in a series of Cu-Ni and Ag-Pd alloys. The irradiations were performed at room temperature with 50 keV Kr+ ions and the resulting damage structure was examined by using transmission electron microscopy. In the Cu-Ni alloy series, the change in loop formation probability with increasing Ni concentration was complex, and at low- and high- nickel concentrations, the defect yield did not change in the predicted manner. The defect yield was higher in the Cu-rich alloys than in the Ni-rich alloys. In the Ag-Pd alloy the change in the loop formation probability followed more closely the change in melting temperature, but no simple relationship was determined.

  10. Howling about Trophic Cascades

    ERIC Educational Resources Information Center

    Kowalewski, David

    2012-01-01

    Following evolutionary theory and an agriculture model, ecosystem research has stressed bottom-up dynamics, implying that top wild predators are epiphenomenal effects of more basic causes. As such, they are assumed expendable. A more modern co-evolutionary and wilderness approach--trophic cascades--instead suggests that top predators, whose…

  11. Quantum Cascade Lasers

    DTIC Science & Technology

    2007-11-02

    predicted small linewidth enhancement factor of QC lasers was measured in outside collaboration ( Prof . Shun-Lien Chuang at UIUC) and confirmed to be...Gmachl, Michael C. Wanke, Federico Capasso, Albert L. Hutchinson, Deborah L. Sivco, Sung- Nee G. Chu, and Alfred Y. Cho “Surface plasmon quantum cascade

  12. 'Cascade Gold' raspberry

    USDA-ARS?s Scientific Manuscript database

    Cascade Gold’ is a new gold fruited, floricane fruiting raspberry cultivar (Rubus idaeus L.) jointly released by Washington State University (WSU), Oregon State University (OSU) and the U.S. Department of Agriculture (USDA). It has been evaluated at Puyallup, Wash. in plantings from 1988 to 2008. ...

  13. Cascaded thermoacoustic devices

    DOEpatents

    Swift, Gregory W.; Backhaus, Scott N.; Gardner, David L.

    2003-12-09

    A thermoacoustic device is formed with a resonator system defining at least one region of high specific acoustic impedance in an acoustic wave within the resonator system. A plurality of thermoacoustic units are cascaded together within the region of high specific acoustic impedance, where at least one of the thermoacoustic units is a regenerator unit.

  14. Inflation from flux cascades

    NASA Astrophysics Data System (ADS)

    D'Amico, Guido; Gobbetti, Roberto; Kleban, Matthew; Schillo, Marjorie L.

    2013-10-01

    When electric-type flux threads compact extra dimensions, a quantum nucleation event can break a flux line and initiate a cascade that unwinds many units of flux. Here, we present a novel mechanism for inflation based on this phenomenon. From the 4D point of view, the cascade begins with the formation of a bubble containing an open Friedmann-Robertson-Walker cosmology, but the vacuum energy inside the bubble is initially only slightly reduced, and subsequently decreases gradually throughout the cascade. If the initial flux number Q0 ≳ O (100), during the cascade the universe can undergo N ≳ 60 efolds of inflationary expansion with gradually decreasing Hubble constant, producing a nearly scale-invariant spectrum of adiabatic density perturbations with amplitude and tilt consistent with observation, and a potentially observable level of non-Gaussianity and tensor modes. The power spectrum has a small oscillatory component that does not decay away during inflation, with a period set approximately by the light-crossing time of the compact dimension(s). Since the ingredients are fluxes threading compact dimensions, this mechanism fits naturally into the string landscape, but does not appear to suffer from the eta problem or require fine-tuning (beyond the usual anthropic requirement of small vacuum energy after reheating).

  15. Howling about Trophic Cascades

    ERIC Educational Resources Information Center

    Kowalewski, David

    2012-01-01

    Following evolutionary theory and an agriculture model, ecosystem research has stressed bottom-up dynamics, implying that top wild predators are epiphenomenal effects of more basic causes. As such, they are assumed expendable. A more modern co-evolutionary and wilderness approach--trophic cascades--instead suggests that top predators, whose…

  16. Integrated Broadband Quantum Cascade Laser

    NASA Technical Reports Server (NTRS)

    Mansour, Kamjou (Inventor); Soibel, Alexander (Inventor)

    2016-01-01

    A broadband, integrated quantum cascade laser is disclosed, comprising ridge waveguide quantum cascade lasers formed by applying standard semiconductor process techniques to a monolithic structure of alternating layers of claddings and active region layers. The resulting ridge waveguide quantum cascade lasers may be individually controlled by independent voltage potentials, resulting in control of the overall spectrum of the integrated quantum cascade laser source. Other embodiments are described and claimed.

  17. Ab initio studies of isolated hydrogen vacancies in graphane

    NASA Astrophysics Data System (ADS)

    Mapasha, R. E.; Molepo, M. P.; Chetty, N.

    2016-05-01

    We present a density functional study of various hydrogen vacancies located on a single hexagonal ring of graphane (fully hydrogenated graphene) considering the effects of charge states and the position of the Fermi level. We find that uncharged vacancies that lead to a carbon sublattice balance are energetically favorable and are wide band gap systems just like pristine graphane. Vacancies that do create a sublattice imbalance introduce spin polarized states into the band gap, and exhibit a half-metallic behavior with a magnetic moment of 1.00 μB per vacancy. The results show the possibility of using vacancies in graphane for novel spin-based applications. When charging such vacancy configurations, the deep donor (+1/0) and deep acceptor (0/-1) transition levels within the band gap are noted. We also note a half-metallic to metallic transition and a significant reduction of the induced magnetic moment due to both negative and positive charge doping.

  18. Magnetometry with Ensembles of Nitrogen Vacancy Centers in Bulk Diamond

    DTIC Science & Technology

    2015-10-23

    Magnetometry with Ensembles of Nitrogen Vacancy Centers in Bulk Diamond by Carson Teale Submitted to the Department of Electrical Engineering and...Government. 2 Magnetometry with Ensembles of Nitrogen Vacancy Centers in Bulk Diamond by Carson Teale Submitted to the Department of Electrical...summarizes experiments conducted to develop a high sensitivity vector magnetometer using nitrogen vacancy (NV) centers in a bulk diamond sample. This

  19. Stiffness and strength of oxygen-functionalized graphene with vacancies

    SciTech Connect

    Zandiatashbar, A.; Ban, E.; Picu, R. C.

    2014-11-14

    The 2D elastic modulus (E{sup 2D}) and strength (σ{sup 2D}) of defective graphene sheets containing vacancies, epoxide, and hydroxyl functional groups are evaluated at 300 K by atomistic simulations. The fraction of vacancies is controlled in the range 0% to 5%, while the density of functional groups corresponds to O:C ratios in the range 0% to 25%. In-plane modulus and strength diagrams as functions of vacancy and functional group densities are generated using models with a single type of defect and with combinations of two types of defects (vacancies and functional groups). It is observed that in models containing only vacancies, the rate at which strength decreases with increasing the concentration of defects is largest, followed by models containing only epoxide groups and those with only hydroxyl groups. The effect on modulus of vacancies and epoxides present alone in the model is similar, and much stronger than that of hydroxyl groups. When the concentration of defects is large, the combined effect of the functional groups and vacancies cannot be obtained as the superposition of individual effects of the two types of defects. The elastic modulus deteriorates faster (slower) than predicted by superposition in systems containing vacancies and hydroxyl groups (vacancies and epoxide groups)

  20. Strain Relaxation and Vacancy Creation in Thin Platinum Films

    SciTech Connect

    Gruber, W.; Chakravarty, S.; Schmidt, H.; Baehtz, C.; Leitenberger, W.; Bruns, M.; Kobler, A.; Kuebel, C.

    2011-12-23

    Synchrotron based combined in situ x-ray diffractometry and reflectometry is used to investigate the role of vacancies for the relaxation of residual stress in thin metallic Pt films. From the experimentally determined relative changes of the lattice parameter a and of the film thickness L the modification of vacancy concentration and residual strain was derived as a function of annealing time at 130 deg. C. The results indicate that relaxation of strain resulting from compressive stress is accompanied by the creation of vacancies at the free film surface. This proves experimentally the postulated dominant role of vacancies for stress relaxation in thin metal films close to room temperature.

  1. Effects of oxygen vacancies on polarization stability of barium titanate

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Shen, YaoGen; Song, Fan; Ke, FuJiu; Bai, YiLong; Lu, ChunSheng

    2016-03-01

    Oxygen vacancy, a kind of native point defects in ferroelectric ceramics, usually causes an increase of the dielectric loss. Based on experimental observations, it is believed that all of the oxygen vacancies are an unfavorable factor for energy saving. By using molecular dynamics simulations, we show that the increase of coercive and saturated electric fields is due to the difficulty to switch local polarization near an oxygen vacancy, and so that a ferroelectric device has to sustain the rising consumption of energy. The simulation results also uncover how oxygen vacancies influence ferroelectric properties.

  2. Nanoscale Sensing with Nitrogen Vacancy Centers

    NASA Astrophysics Data System (ADS)

    Urbach, Elana; Lovchinsky, Igor; Sushkov, Alex; Park, Hongkun; Lukin, Mikhail

    2015-05-01

    In the last several decades Magnetic resonance imaging (MRI) has emerged as a powerful tool in science and technology. Conventional MRI technology, however, relies on measuring magnetic fields from a large (macroscopic) number of molecules, for example tissues in specific areas of the brain. Extending these techniques to the nanoscale could enable revolutionary advances in the physical, biological and medical sciences. Here we report on recent progress in using Nitrogen-Vacancy (NV) centers in diamond to detect small numbers of nuclear spins in biological molecules. In particular, we have demonstrated detection of single proteins attached to the diamond surface.

  3. Vacancy ordering in reduced barium titanate

    NASA Astrophysics Data System (ADS)

    Woodward, David I.; Reaney, Ian M.; Yang, Gaiying Y.; Dickey, Elizabeth C.; Randall, Clive A.

    2004-06-01

    A crystal structure is proposed for reduced barium titanate, BaTiO3-δ, δ≈0.33, formed during the degradation of Ni-BaTiO3 X7R multilayer ceramic capacitors. High-resolution transmission electron microscopy and selected-area electron diffraction have been used in combination with computer simulations to show that oxygen vacancies accrete on every third pseudocubic {111} plane, resulting in a cell with space group P3m1. Additionally, from electron energy loss spectroscopy, it is proposed that Ti4+ is reduced to Ti3+ as a mechanism of charge compensation within oxygen-deficient octahedra.

  4. Vacancy clusters in graphane as quantum dots.

    PubMed

    Singh, Abhishek K; Penev, Evgeni S; Yakobson, Boris I

    2010-06-22

    Complementary electronic properties and a tendency to form sharp graphene-graphane interfaces open tantalizing possibilities for two-dimensional nanoelectronics. First-principles density functional and tight-binding calculations show that graphane can serve as natural host for graphene quantum dots, clusters of vacancies in the hydrogen sublattice. Their size n, shape, and stability are governed by the aromaticity and interfaces, resulting in formation energies approximately 1/ radicaln eV/atom and preference to hexagonal clusters congruent with lattice hexagons (i.e., with armchair edge). Clusters exhibit large gaps approximately 15/ radicaln eV with size dependence typical for confined Dirac fermions.

  5. A cascade thermoacoustic engine.

    PubMed

    Gardner, D L; Swift, G W

    2003-10-01

    A cascade thermoacoustic engine is described, consisting of one standing-wave stage plus two traveling-wave stages in series. Most of the acoustic power is produced in the efficient traveling-wave stages. The straight-line series configuration is easy to build and allows no Gedeon streaming. The engine delivers up to 2 kW of acoustic power, with an efficiency (the ratio of acoustic power to heater power) of up to 20%. An understanding of the pressure and volume-velocity waves is very good. The agreement between measured and calculated powers and temperatures is reasonable. Some of the measured thermal power that cannot be accounted for by calculation can be attributed to Rayleigh streaming in the two thermal buffer tubes with the largest aspect ratios. A straightforward extension of this work should yield cascade thermoacoustic engines with efficiencies of around 35-40% of the Carnot efficiency.

  6. Electromagnetic cascades in pulsars

    NASA Technical Reports Server (NTRS)

    Daugherty, J. K.; Harding, A. K.

    1981-01-01

    The development of pair photon cascades initiated by high energy electrons above a pulsar polar cap is simulated numerically. The calculation uses the energy of the primary electron, the magnetic field strength, and the period of rotation as parameters and follows the curvature radiation emitted by the primary, the conversion of this radiation e(+) - e(-) pairs in the intense fields, and the quantized synchrotron radiation by the secondary pairs. A recursive technique allows the tracing of an indefinite number of generations using a Monte Carlo method. Gamma ray and pair spectra are calculated for cascades in different parts of the polar cap and with different acceleration models. It is found that synchrotron radiation from secondary pairs makes an important contribution to the gamma ray spectrum above 25 MeV, and that the final gamma ray and pair spectra are insensitive to the height of the accelerating region, as long as the acceleration of the primary electrons is not limited by radiation reaction.

  7. Superconducting cascade electron refrigerator

    SciTech Connect

    Camarasa-Gómez, M.; Giazotto, F.; Di Marco, A.; Hekking, F. W. J.; Winkelmann, C. B.; Courtois, H.

    2014-05-12

    The design and operation of an electronic cooler based on a combination of superconducting tunnel junctions is described. The cascade extraction of hot-quasiparticles, which stems from the energy gaps of two different superconductors, allows for a normal metal to be cooled down to about 100 mK starting from a bath temperature of 0.5 K. We discuss the practical implementation, potential performance, and limitations of such a device.

  8. Information cascade on networks

    NASA Astrophysics Data System (ADS)

    Hisakado, Masato; Mori, Shintaro

    2016-05-01

    In this paper, we discuss a voting model by considering three different kinds of networks: a random graph, the Barabási-Albert (BA) model, and a fitness model. A voting model represents the way in which public perceptions are conveyed to voters. Our voting model is constructed by using two types of voters-herders and independents-and two candidates. Independents conduct voting based on their fundamental values; on the other hand, herders base their voting on the number of previous votes. Hence, herders vote for the majority candidates and obtain information relating to previous votes from their networks. We discuss the difference between the phases on which the networks depend. Two kinds of phase transitions, an information cascade transition and a super-normal transition, were identified. The first of these is a transition between a state in which most voters make the correct choices and a state in which most of them are wrong. The second is a transition of convergence speed. The information cascade transition prevails when herder effects are stronger than the super-normal transition. In the BA and fitness models, the critical point of the information cascade transition is the same as that of the random network model. However, the critical point of the super-normal transition disappears when these two models are used. In conclusion, the influence of networks is shown to only affect the convergence speed and not the information cascade transition. We are therefore able to conclude that the influence of hubs on voters' perceptions is limited.

  9. Maxwellian cascade model

    SciTech Connect

    Macklin, R.L.

    1989-11-01

    A model for gamma-ray cascade de-excitation of a nucleus derived from the Maxwellian energy distribution function but imposing energy conservation was investigated. Energy distributions and multiplicities and their averages were found over a range of nuclear temperatures and excitation energies appropriate to neutron capture. The model was compared to existing measurements for tantalum, a case where the level density was high and thus a good approximation to the model. 7 refs., 13 figs.

  10. Cascade ICF power reactor

    SciTech Connect

    Hogan, W.J.; Pitts, J.H.

    1986-05-20

    The double-cone-shaped Cascade reaction chamber rotates at 50 rpm to keep a blanket of ceramic granules in place against the wall as they slide from the poles to the exit slots at the equator. The 1 m-thick blanket consists of layers of carbon, beryllium oxide, and lithium aluminate granules about 1 mm in diameter. The x rays and debris are stopped in the carbon granules; the neutrons are multiplied and moderated in the BeO and breed tritium in the LiAlO/sub 2/. The chamber wall is made up of SiO tiles held in compression by a network of composite SiC/Al tendons. Cascade operates at a 5 Hz pulse rate with 300 MJ in each pulse. The temperature in the blanket reaches 1600 K on the inner surface and 1350 K at the outer edge. The granules are automatically thrown into three separate vacuum heat exchangers where they give up their energy to high pressure helium. The helium is used in a Brayton cycle to obtain a thermal-to-electric conversion efficiency of 55%. Studies have been done on neutron activation, debris recovery, vaporization and recondensation of blanket material, tritium control and recovery, fire safety, and cost. These studies indicate that Cascade appears to be a promising ICF reactor candidate from all standpoints. At the 1000 MWe size, electricity could be made for about the same cost as in a future fission reactor.

  11. Graphene with vacancies: Supernumerary zero modes

    NASA Astrophysics Data System (ADS)

    Weik, Norman; Schindler, Johannes; Bera, Soumya; Solomon, Gemma C.; Evers, Ferdinand

    2016-08-01

    The density of states ϱ (E ) of graphene is investigated within the tight-binding (Hückel) approximation in the presence of vacancies. They introduce a nonvanishing density of zero modes nzm that act as midgap states, ϱ (E ) =nzmδ (E ) +smooth . As is well known, the actual number of zero modes per sample can, in principle, exceed the sublattice imbalance, Nzm≥|NA-NB| , where NA,NB denote the number of carbon atoms in each sublattice. In this paper, we establish a stronger relation that is valid in the thermodynamic limit and that involves the concentration of zero modes, nzm>|cA-cB| , where cA and cB denote the concentration of vacancies per sublattice; in particular, nzm is nonvanishing even in the case of balanced disorder, NA/NB=1 . Adopting terminology from benzoid graph theory, the excess modes associated with the current carrying backbone (percolation cluster) are called supernumerary. In the simplest cases, such modes can be associated with structural elements such as carbon atoms connected with a single bond, only. Our result suggests that the continuum limit of bipartite hopping models supports nontrivial "supernumerary" terms that escape the present continuum descriptions.

  12. Vacancy-mediated dehydrogenation of sodium alanate

    PubMed Central

    Gunaydin, Hakan; Houk, Kendall N.; Ozoliņš, Vidvuds

    2008-01-01

    Clarification of the mechanisms of hydrogen release and uptake in transition-metal-doped sodium alanate, NaAlH4, a prototypical high-density complex hydride, has fundamental importance for the development of improved hydrogen-storage materials. In this and most other modern hydrogen-storage materials, H2 release and uptake are accompanied by long-range diffusion of metal species. Using first-principles density-functional theory calculations, we have determined that the activation energy for Al mass transport via AlH3 vacancies is Q = 85 kJ/mol·H2, which is in excellent agreement with experimentally measured activation energies in Ti-catalyzed NaAlH4. The activation energy for an alternate decomposition mechanism via NaH vacancies is found to be significantly higher: Q = 112 kJ/mol·H2. Our results suggest that bulk diffusion of Al species is the rate-limiting step in the dehydrogenation of Ti-doped samples of NaAlH4 and that the much higher activation energies measured for uncatalyzed samples are controlled by other processes, such as breaking up of AlH4− complexes, formation/dissociation of H2 molecules, and/or nucleation of the product phases. PMID:18299582

  13. Molecular Dynamics Simulation of Cascade-Induced Ballistic Helium Resolutioning from Bubbles in Iron

    SciTech Connect

    Stoller, Roger E

    2013-01-01

    Molecular dynamics simulations have been used to assess the ability of atomic displacement cascades to eject helium from small bubbles in iron. This study of the ballistic resolutioning mechanism employed a recently-developed Fe-He interatomic potential in concert with an iron potential developed by Ackland and co-workers. The primary variables examined were: irradiation temperature (100 and 600K), cascade energy (5 and 20 keV), bubble radius (0.5 and 1.0 nm), and He-to-vacancy ratio in the bubble (0.25, 0.5 and 1.0). Systematic trends were observed for each of these variables. For example, ballistic resolutioning leads to a greater number of helium atoms being displaced from larger bubbles and from bubbles that have a higher He/vacancy ratio (bubble pressure). He resolutioning was reduced at 600K relative to 100K, and for 20 keV cascades relative to 5 keV cascades. Overall, the results indicate a modest level of He removal by ballistic resolutioning. The results can be used to provide guidance in selection of a resolution parameter that can be employed in cluster dynamics models to predict the bubble size distribution that evolves under irradiation.

  14. 24 CFR 880.611 - Conditions for receipt of vacancy payments.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... PROGRAM, SECTION 202 SUPPORTIVE HOUSING FOR THE ELDERLY PROGRAM AND SECTION 811 SUPPORTIVE HOUSING FOR... administrator of the vacancy or prospective vacancy and the reasons for the vacancy immediately upon learning...

  15. 24 CFR 880.611 - Conditions for receipt of vacancy payments.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... PROGRAM, SECTION 202 SUPPORTIVE HOUSING FOR THE ELDERLY PROGRAM AND SECTION 811 SUPPORTIVE HOUSING FOR... administrator of the vacancy or prospective vacancy and the reasons for the vacancy immediately upon learning...

  16. 24 CFR 880.611 - Conditions for receipt of vacancy payments.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... PROGRAM, SECTION 202 SUPPORTIVE HOUSING FOR THE ELDERLY PROGRAM AND SECTION 811 SUPPORTIVE HOUSING FOR... administrator of the vacancy or prospective vacancy and the reasons for the vacancy immediately upon learning...

  17. 24 CFR 880.611 - Conditions for receipt of vacancy payments.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... PROGRAM, SECTION 202 SUPPORTIVE HOUSING FOR THE ELDERLY PROGRAM AND SECTION 811 SUPPORTIVE HOUSING FOR... administrator of the vacancy or prospective vacancy and the reasons for the vacancy immediately upon learning...

  18. 29 CFR 511.5 - Vacancies and dissolution of committees.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false Vacancies and dissolution of committees. 511.5 Section 511.5 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR REGULATIONS WAGE ORDER PROCEDURE FOR AMERICAN SAMOA § 511.5 Vacancies and dissolution of committees....

  19. 29 CFR 511.5 - Vacancies and dissolution of committees.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 3 2014-07-01 2014-07-01 false Vacancies and dissolution of committees. 511.5 Section 511.5 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR REGULATIONS WAGE ORDER PROCEDURE FOR AMERICAN SAMOA § 511.5 Vacancies and dissolution of committees....

  20. 29 CFR 511.5 - Vacancies and dissolution of committees.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 3 2012-07-01 2012-07-01 false Vacancies and dissolution of committees. 511.5 Section 511.5 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR REGULATIONS WAGE ORDER PROCEDURE FOR AMERICAN SAMOA § 511.5 Vacancies and dissolution of committees....

  1. 29 CFR 511.5 - Vacancies and dissolution of committees.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 3 2013-07-01 2013-07-01 false Vacancies and dissolution of committees. 511.5 Section 511.5 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR REGULATIONS WAGE ORDER PROCEDURE FOR AMERICAN SAMOA § 511.5 Vacancies and dissolution of committees....

  2. 29 CFR 511.5 - Vacancies and dissolution of committees.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 3 2011-07-01 2011-07-01 false Vacancies and dissolution of committees. 511.5 Section 511.5 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR REGULATIONS WAGE ORDER PROCEDURE FOR AMERICAN SAMOA § 511.5 Vacancies and dissolution of committees....

  3. Environmental Quality Assessment of Built Areas with High Vacancy

    NASA Astrophysics Data System (ADS)

    Jiang, Y.; Yuan, Y.; Neale, A. C.

    2015-12-01

    Around the world, many urban areas are challenged by vacant and abandoned residential and business property. High vacancy areas have often been associated with increasing public safety problems and declining property values and subsequent tax base. High vacancy can lead to visible signs of city decline and significant barriers to the revitalization of cities. Addressing the problem of vacancy requires knowledge of vacancy patterns and their possible contributing factors. In this study, we evaluated the ten year (2005-2015) urban environmental changes for some high vacancy areas. Social and economic variables derived from U.S. census data such as non-white population, employment rate, housing price, and environmental variables derived from National Land Cover Data such as land cover and impervious area, were used as the basis for analysis. Correlation analysis and principle components analysis were performed at the Census Block Group level. Three components were identified and interpreted as economic status, urbanness, and greenness. A synthetic Urban Environmental Quality (UEQ) index was developed by integrating the three principle components according to their weights. Comparisons of the UEQ indices between the 2005 and 2015 in the increasingly high vacancy area provided useful information for investigating the possible associations between social, economic, and environmental factors, and the vacancy status. This study could provide useful information for understanding the complex issues leading to vacancy and facilitating future rehabilitation of vacant urban area.

  4. 29 CFR 452.25 - Vacancies in office.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 2 2010-07-01 2010-07-01 false Vacancies in office. 452.25 Section 452.25 Labor Regulations Relating to Labor OFFICE OF LABOR-MANAGEMENT STANDARDS, DEPARTMENT OF LABOR LABOR-MANAGEMENT... DISCLOSURE ACT OF 1959 Frequency and Kinds of Elections § 452.25 Vacancies in office. Title IV governs...

  5. An Optimal Sample Design for a Job Vacancy Survey.

    ERIC Educational Resources Information Center

    Gonzalez, Maria Elena

    Job vacancy statistics are useful both nationally and locally to manpower policymakers in: (1) measuring labor shortages or surpluses, (2) identifying employment trends in occupations and industries, and (3) matching persons and jobs. The purposes of this study are to analyze the reliability of vacancy estimates and to plan efficient sample…

  6. Diffusion and aggregation of oxygen vacancies in amorphous silica

    NASA Astrophysics Data System (ADS)

    Munde, Manveer S.; Gao, David Z.; Shluger, Alexander L.

    2017-06-01

    Using density functional theory (DFT) calculations, we investigated oxygen vacancy diffusion and aggregation in relation to dielectric breakdown in amorphous silicon dioxide (a-SiO2). Our calculations indicate the existence of favourable sites for the formation of vacancy dimers and trimers in the amorphous network with maximum binding energies of approximately 0.13 eV and 0.18 eV, respectively. However, an average energy barrier height for neutral vacancy diffusion is found to be about 4.6 eV, rendering this process unfeasible. At Fermi level positions above 6.4 eV with respect to the top of the valence band, oxygen vacancies can trap up to two extra electrons. Average barriers for the diffusion of negative and double negatively charged vacancies are found to be 2.7 eV and 2.0 eV, respectively. These barriers are higher than or comparable to thermal ionization energies of extra electrons from oxygen vacancies into the conduction band of a-SiO2. In addition, we discuss the competing pathways for electron trapping in oxygen deficient a-SiO2 caused by the existence of intrinsic electron traps and oxygen vacancies. These results provide new insights into the role of oxygen vacancies in degradation and dielectric breakdown in amorphous silicon oxides.

  7. 5 CFR 330.101 - Methods of filling vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Methods of filling vacancies. 330.101 Section 330.101 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS RECRUITMENT, SELECTION, AND PLACEMENT (GENERAL) Discretion in Filling Vacancies § 330.101 Methods of...

  8. 5 CFR 330.101 - Methods of filling vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 1 2011-01-01 2011-01-01 false Methods of filling vacancies. 330.101 Section 330.101 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS RECRUITMENT, SELECTION, AND PLACEMENT (GENERAL) Discretion in Filling Vacancies § 330.101 Methods of...

  9. 75 FR 10818 - Notice of Resource Advisory Council Vacancies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-09

    ... Bureau of Land Management Notice of Resource Advisory Council Vacancies AGENCY: Bureau of Land Management... the Federal Land Policy and Management Act (FLPMA), the Bureau of Land Management (BLM) is seeking... selected to fill the vacancies will complete unexpired terms ending in September 2010 and September...

  10. Pressure and density of vacancies in solid [sup 4]He

    SciTech Connect

    Bukman, D.J. ); van Leeuwen, J.M.J. )

    1994-01-01

    Crystals of [sup 4]He contain vacancies that move around by a quantum-mechanical hopping process. The density and pressure of these vacancies can be experimentally studied. The accuracy of the experiments is high enough to detect the effect of the Bose statistics of the vacancies. In this paper we examine the effect of the hard-core repulsion between the vacancies, which should also have a measurable effect on their behavior. We set up a virial expansion for a lattice gas of hard-core particles, and calculate the second virial coefficient. It turns out that the vacancies behave as ideal Bose particles at low temperatures, but that the hard-core interaction makes them behave more and more like fermions as the temperature increases.

  11. Hydrogen embrittlement of aluminum: the crucial role of vacancies.

    PubMed

    Lu, Gang; Kaxiras, Efthimios

    2005-04-22

    We report first-principles calculations which demonstrate that vacancies can combine with hydrogen impurities in bulk aluminum and play a crucial role in the embrittlement of this prototypical ductile solid. Our studies of hydrogen-induced vacancy superabundant formation and vacancy clusterization in aluminum lead to the conclusion that a large number of H atoms (up to 12) can be trapped at a single vacancy, which overcompensates the energy cost to form the defect. In the presence of trapped H atoms, three nearest-neighbor single vacancies which normally would repel each other, aggregate to form a trivacancy on the slip plane of Al, acting as embryos for microvoids and cracks and resulting in ductile rupture along these planes.

  12. Vacancy supersaturations produced by high-energy ion implantation

    SciTech Connect

    Venezia, V.C.; Eaglesham, D.J.; Jacobson, D.C.; Gossmann, H.J.; Haynes, T.E.; Agarwal, A. |; Friessnegg, T.; Nielsen, B.

    1998-01-01

    A new technique for detecting the vacancy clusters produced by high-energy ion implantation into silicon is proposed and tested. This technique takes advantage of the fact that metal impurities, such as Au, are gettered near one-half of the projected range ({1/2}R{sub p}) of MeV implants. The vacancy clustered region produced by a 2 MeV Si{sup +} implant into silicon has been labeled with Au diffused in from the front surface. The trapped Au was detected by Rutherford backscattering spectrometry (RBS) to profile the vacancy clusters. Cross section transmission electron microscopy (XTEM) analysis shows that the Au in the region of vacancy clusters is in the form of precipitates. By annealing MeV implanted samples prior to introduction of the Au, changes in the defect concentration within the vacancy clustered region were monitored as a function of annealing conditions.

  13. Probing Single Vacancies in Black Phosphorus at the Atomic Level

    NASA Astrophysics Data System (ADS)

    Kiraly, Brian; Hauptmann, Nadine; Rudenko, Alexander N.; Katsnelson, Mikhail I.; Khajetoorians, Alexander A.

    2017-06-01

    Utilizing a combination of low-temperature scanning tunneling microscopy/spectroscopy (STM/STS) and electronic structure calculations, we characterize the structural and electronic properties of single atomic vacancies within several monolayers of the surface of black phosphorus. We illustrate, with experimental analysis and tight-binding calculations, that we can depth profile these vacancies and assign them to specific sublattices within the unit cell. Measurements reveal that the single vacancies exhibit strongly anisotropic and highly delocalized charge density, laterally extended up to 20 atomic unit cells. The vacancies are then studied with STS, which reveals in-gap resonance states near the valence band edge and a strong p-doping of the bulk black phosphorus crystal. Finally, quasiparticle interference generated near these vacancies enables the direct visualization of the anisotropic band structure of black phosphorus.

  14. Probing Single Vacancies in Black Phosphorus at the Atomic Level.

    PubMed

    Kiraly, Brian; Hauptmann, Nadine; Rudenko, Alexander N; Katsnelson, Mikhail I; Khajetoorians, Alexander A

    2017-06-14

    Utilizing a combination of low-temperature scanning tunneling microscopy/spectroscopy (STM/STS) and electronic structure calculations, we characterize the structural and electronic properties of single atomic vacancies within several monolayers of the surface of black phosphorus. We illustrate, with experimental analysis and tight-binding calculations, that we can depth profile these vacancies and assign them to specific sublattices within the unit cell. Measurements reveal that the single vacancies exhibit strongly anisotropic and highly delocalized charge density, laterally extended up to 20 atomic unit cells. The vacancies are then studied with STS, which reveals in-gap resonance states near the valence band edge and a strong p-doping of the bulk black phosphorus crystal. Finally, quasiparticle interference generated near these vacancies enables the direct visualization of the anisotropic band structure of black phosphorus.

  15. Lattice vacancies in silicon film exposed to external electric field

    NASA Astrophysics Data System (ADS)

    Mao, Yuliang; Caliste, Damien; Pochet, Pascal

    2013-07-01

    Density functional calculations based on wavelet basis set are performed to investigate the structure, internal electric-charge distribution, and formation energy of lattice vacancies in silicon film under electric fields. It was found that the formation energies of vacancies both in JT⊥ (Jahn-Teller distortion orthogonal to electric field) and JT‖ (Jahn-Teller distortion parallel to electric field) distortions are decreased with the increasing of field strength, due to the charge polarization in the whole space of silicon film. For the split vacancy, it can lower its energy by moving further away from the split space to form a tetragonal JT⊥ vacancy under electric field. Our results also demonstrate the importance of the potential fluctuations induced by the electric fields on the charge redistribution within the vacancy defects.

  16. Inner-shell excitation of acetylene by electron impact

    SciTech Connect

    Michelin, S.E.; Pessoa, O.; Oliveira, H.L.; Veiteinheimer, E.; Santos, A.M.S.; Fujimoto, M.M.; Iga, I.; Lee, M.-T.

    2005-08-15

    The distorted-wave approximation (DWA) is applied to study K-shell excitation in C{sub 2}H{sub 2} by electron impact. More specifically, calculated differential and integral cross sections for the X {sup 1}{sigma}{sub g}{sup +}{yields}{sup 1,3}{pi}{sub g}(1s{sigma}{sub g}{yields}1p{pi}{sub g}) and X {sup 1}{sigma}{sub g}{sup +}{yields}{sup 1,3}{pi}{sub u}(1s{sigma}{sub u}{yields}1p{pi}{sub g}) transitions in this target in the 300-800 eV incident energy range are reported. The triplet-to-singlet ratios of respective integral cross sections, namely, RI(3:1), calculated by dividing the integral cross sections for transitions leading to the triplet core-excited states by those leading to the corresponding singlet states, are also reported as a function of incident energies. In general, our calculated sums of the generalized oscillator strength for transitions leading to the {sup 1}{pi}{sub g} and {sup 1}{pi}{sub u} excited states are in good agreement with the available experimental data. On the other hand, the present calculated integral cross sections and the corresponding data for its isoelectronic species CO are significantly different. Possible physical origins for this difference are discussed.

  17. Inner-shell and double ionization potentials of aminophenol isomers.

    SciTech Connect

    Kryzhevoi, N. V.; Santra, R.; Cederbaum, L. S.

    2011-01-01

    A comprehensive study of single and double core ionization potentials of the aminophenol molecule is reported. The role of relaxation, correlation, relativistic, and basis set effects in these potentials is clarified. Special attention is paid to the isomer dependence of the single and double core ionization potentials. Some of them are also compared with the respective values of the phenol and aniline molecules. It is shown that the core level single ionization potentials of the para-, meta-, and ortho-aminophenol molecules differ only slightly from each other, rendering these structural isomers challenging to distinguish for conventional x-ray photoelectron spectroscopy. In contrast, the energy needed to remove two core electrons from different atoms depends noticeably on the mutual arrangement and even on the relative orientations of the hydroxyl and amine groups. Together with the electrostatic repulsion between the two core holes, relaxation effects accompanying double core ionization play a crucial role here. The pronounced sensitivity of the double ionization potentials, therefore, enables a spectroscopic characterization of the electronic structure of aminophenol isomers by means of x-ray two-photon photoelectron spectroscopy.

  18. COMPACT CASCADE IMPACTS

    DOEpatents

    Lippmann, M.

    1964-04-01

    A cascade particle impactor capable of collecting particles and distributing them according to size is described. In addition the device is capable of collecting on a pair of slides a series of different samples so that less time is required for the changing of slides. Other features of the device are its compactness and its ruggedness making it useful under field conditions. Essentially the unit consists of a main body with a series of transverse jets discharging on a pair of parallel, spaced glass plates. The plates are capable of being moved incremental in steps to obtain the multiple samples. (AEC)

  19. The Ufm1 Cascade

    PubMed Central

    Daniel, Jens; Liebau, Eva

    2014-01-01

    The ubiquitin-fold modifier 1 (Ufm1) is a posttranslational modifier that belongs to the ubiquitin-like protein (UBL) family. Ufm1 is present in nearly all eukaryotic organisms, with the exception of fungi. It resembles ubiquitin in its ability to be ligated to other proteins, as well as in the mechanism of ligation. While the Ufm1 cascade has been implicated in endoplasmic reticulum functions and cell cycle control, its biological role still remains poorly understood. In this short review, we summarize the current state of Ufm1 research and its potential role in human diseases, like diabetes, ischemic heart disease and cancer. PMID:24921187

  20. Crossover behavior in driven cascades.

    PubMed

    Burridge, James

    2013-09-01

    We propose a model which explains how power-law crossover behavior can arise in a system which is capable of experiencing cascading failure. In our model the susceptibility of the system to cascades is described by a single number, the propagation power, which measures the ease with which cascades propagate. Physically, such a number could represent the density of unstable material in a system, its internal connectivity, or the mean susceptibility of its component parts to failure. We assume that the propagation power follows an upward drifting Brownian motion between cascades, and drops discontinuously each time a cascade occurs. Cascades are described by a continuous state branching process with distributional properties determined by the value of the propagation power when they occur. In common with many cascading models, pure power-law behavior is exhibited at a critical level of propagation power, and the mean cascade size diverges. This divergence constrains large systems to the subcritical region. We show that as a result, crossover behavior appears in the cascade distribution when an average is performed over the distribution of propagation power. We are able to analytically determine the exponents before and after the crossover.

  1. Cascade Mtns. Oregon

    NASA Image and Video Library

    2002-04-19

    The ground near one of the long-dormant Three Sisters volcanoes in the Cascade Mountains of west-central Oregon has risen approximately 10centimeters in a 10-by-20-km parcel since 1996, meaning that magma or underground lava is slowly flowing into the area, according to a research team from the U.S. Geological Survey. The Three Sisters area -- which contains five volcanoes -- is only about 170 miles from Mount St. Helens, which erupted in 1980. Both are part of the Cascades Range, a line of 27volcanoes stretching from British Columbia in Canada to northern California. This perspective view was created by draping a simulated natural color ASTER image over digital topography from the U.S. Geological Survey National Elevation Dataset. This image was acquired on May 28, 2000 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet. http://photojournal.jpl.nasa.gov/catalog/PIA03492

  2. Quantum dot cascade laser

    PubMed Central

    2014-01-01

    We demonstrated an unambiguous quantum dot cascade laser based on InGaAs/GaAs/InAs/InAlAs heterostructure by making use of self-assembled quantum dots in the Stranski-Krastanow growth mode and two-step strain compensation active region design. The prototype generates stimulated emission at λ ~ 6.15 μm and a broad electroluminescence band with full width at half maximum over 3 μm. The characteristic temperature for the threshold current density within the temperature range of 82 to 162 K is up to 400 K. Moreover, our materials show the strong perpendicular mid-infrared response at about 1,900 cm-1. These results are very promising for extending the present laser concept to terahertz quantum cascade laser, which would lead to room temperature operation. PACS 42.55.Px; 78.55.Cr; 78.67.Hc PMID:24666965

  3. Suppression of vacancy cluster growth in concentrated solid solution alloys

    DOE PAGES

    Zhao, Shijun; Velisa, Gihan; Xue, Haizhou; ...

    2016-12-13

    Large vacancy clusters, such as stacking-fault tetrahedra, are detrimental vacancy-type defects in ion-irradiated structural alloys. Suppression of vacancy cluster formation and growth is highly desirable to improve the irradiation tolerance of these materials. In this paper, we demonstrate that vacancy cluster growth can be inhibited in concentrated solid solution alloys by modifying cluster migration pathways and diffusion kinetics. The alloying effects of Fe and Cr on the migration of vacancy clusters in Ni concentrated alloys are investigated by molecular dynamics simulations and ion irradiation experiment. While the diffusion coefficients of small vacancy clusters in Ni-based binary and ternary solid solutionmore » alloys are higher than in pure Ni, they become lower for large clusters. This observation suggests that large clusters can easily migrate and grow to very large sizes in pure Ni. In contrast, cluster growth is suppressed in solid solution alloys owing to the limited mobility of large vacancy clusters. Finally, the differences in cluster sizes and mobilities in Ni and in solid solution alloys are consistent with the results from ion irradiation experiments.« less

  4. Persistence of strong and switchable ferroelectricity despite vacancies

    PubMed Central

    Raeliarijaona, Aldo; Fu, Huaxiang

    2017-01-01

    Vacancies play a pivotal role in affecting ferroelectric polarization and switching properties, and there is a possibility that ferroelectricity may be utterly eliminated when defects render the system metallic. However, sufficient quantitative understandings of the subject have been lacking for decades due to the fact that vacancies in ferroelectrics are often charged and polarization in charged systems is not translationally invariant. Here we perform first-principles studies to investigate the influence of vacancies on ferroelectric polarization and polarization switching in prototypical BaTiO3 of tetragonal symmetry. We demonstrate using the modern theory of polarization that, in contrast to common wisdom, defective BaTiO3 with a large concentration of vacancies (or , or ) possesses a strong nonzero electric polarization. Breaking of Ti-O bonds is found to have little effect on the magnitude of polarization, which is striking. Furthermore, a previously unrecognized microscopic mechanism, which is particularly important when vacancies are present, is proposed for polarization switching. The mechanism immediately reveals that (i) the switching barrier in the presence of is small with ΔE = 8.3 meV per bulk formula cell, and the polarization is thus switchable even when vacancies exist; (ii) The local environment of vacancy is surprisingly insignificant in polarization switching. These results provide profound new knowledge and will stimulate more theoretical and experimental interest on defect physics in FEs. PMID:28120941

  5. Suppression of vacancy cluster growth in concentrated solid solution alloys

    SciTech Connect

    Zhao, Shijun; Velisa, Gihan; Xue, Haizhou; Bei, Hongbin; Weber, William J.; Zhang, Yanwen

    2016-12-13

    Large vacancy clusters, such as stacking-fault tetrahedra, are detrimental vacancy-type defects in ion-irradiated structural alloys. Suppression of vacancy cluster formation and growth is highly desirable to improve the irradiation tolerance of these materials. In this paper, we demonstrate that vacancy cluster growth can be inhibited in concentrated solid solution alloys by modifying cluster migration pathways and diffusion kinetics. The alloying effects of Fe and Cr on the migration of vacancy clusters in Ni concentrated alloys are investigated by molecular dynamics simulations and ion irradiation experiment. While the diffusion coefficients of small vacancy clusters in Ni-based binary and ternary solid solution alloys are higher than in pure Ni, they become lower for large clusters. This observation suggests that large clusters can easily migrate and grow to very large sizes in pure Ni. In contrast, cluster growth is suppressed in solid solution alloys owing to the limited mobility of large vacancy clusters. Finally, the differences in cluster sizes and mobilities in Ni and in solid solution alloys are consistent with the results from ion irradiation experiments.

  6. Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys

    DOE PAGES

    Zhang, Z. W.; Yao, L.; Wang, X. -L.; ...

    2015-05-29

    A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. We report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using amore » combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters.« less

  7. Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys

    SciTech Connect

    Zhang, Z. W.; Yao, L.; Wang, X. -L.; Miller, M. K.

    2015-05-29

    A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. We report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using a combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters.

  8. Oxygen vacancy induced surface stabilization: (110) terminated magnetite

    NASA Astrophysics Data System (ADS)

    Walls, B.; Lübben, O.; Palotás, K.; Fleischer, K.; Walshe, K.; Shvets, I. V.

    2016-10-01

    Scanning tunneling microscopy (STM) measurements of the (110) surface of magnetite showed the coexistence of two reconstructions: the known (1 ×3 ) row reconstruction and a surprising atomic structure of high complexity which occupies a small fraction of the surface. Oxygen vacancies on the Fe3O4 (110) B-terminated surface have previously been determined to be the most energetically favorable surface termination of those considered [Li et al., Surf. Sci. 601, 876 (2007), 10.1016/j.susc.2006.10.037]. However, this study only investigated oxygen vacancies which were threefold coordinated. Here, first principles calculations indicate that twofold coordinated oxygen represents the most energetically stable oxygen vacancy on the B-terminated (110) surface of magnetite. STM simulations reveal that the structure that occupies a small fraction of the surface corresponds to this energetically favorable B-terminated Fe3O4 (110) surface. The oxygen vacancies form an ordered array: Along the [1 ¯10 ] direction, every second twofold coordinated oxygen atom is vacant, and vacancies are separated by 6 Å. In adjacent twofold coordinated oxygen rows, the vacancies are shifted in the [1 ¯10 ] direction by 3 Å. Density functional theory calculations of the spin density distributions indicate that surface and subsurface octahedrally coordinated iron atoms are charge ordered. The charge ordering and existence of oxygen vacancies act to reduce the surface charge. However, other polarity compensation mechanisms may be at play to stabilize the surface.

  9. Persistence of strong and switchable ferroelectricity despite vacancies

    NASA Astrophysics Data System (ADS)

    Raeliarijaona, Aldo; Fu, Huaxiang

    2017-01-01

    Vacancies play a pivotal role in affecting ferroelectric polarization and switching properties, and there is a possibility that ferroelectricity may be utterly eliminated when defects render the system metallic. However, sufficient quantitative understandings of the subject have been lacking for decades due to the fact that vacancies in ferroelectrics are often charged and polarization in charged systems is not translationally invariant. Here we perform first-principles studies to investigate the influence of vacancies on ferroelectric polarization and polarization switching in prototypical BaTiO3 of tetragonal symmetry. We demonstrate using the modern theory of polarization that, in contrast to common wisdom, defective BaTiO3 with a large concentration of vacancies (or , or ) possesses a strong nonzero electric polarization. Breaking of Ti-O bonds is found to have little effect on the magnitude of polarization, which is striking. Furthermore, a previously unrecognized microscopic mechanism, which is particularly important when vacancies are present, is proposed for polarization switching. The mechanism immediately reveals that (i) the switching barrier in the presence of is small with ΔE = 8.3 meV per bulk formula cell, and the polarization is thus switchable even when vacancies exist; (ii) The local environment of vacancy is surprisingly insignificant in polarization switching. These results provide profound new knowledge and will stimulate more theoretical and experimental interest on defect physics in FEs.

  10. Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys

    PubMed Central

    Zhang, Z. W.; Yao, L.; Wang, X.-L.; Miller, M. K.

    2015-01-01

    A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. Here we report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using a combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters. PMID:26023747

  11. Molecular dynamics modeling of atomic displacement cascades in 3C-SiC: Comparison of interatomic potentials

    NASA Astrophysics Data System (ADS)

    Samolyuk, G. D.; Osetsky, Y. N.; Stoller, R. E.

    2015-10-01

    We used molecular dynamics modeling of atomic displacement cascades to characterize the nature of primary radiation damage in 3C-SiC. We demonstrated that the most commonly used interatomic potentials are inconsistent with ab initio calculations of defect energetics. Both the Tersoff potential used in this work and a modified embedded-atom method potential reveal a barrier to recombination of the carbon interstitial and carbon vacancy which is much higher than the density functional theory (DFT) results. The barrier obtained with a newer potential by Gao and Weber is closer to the DFT result. This difference results in significant differences in the cascade production of point defects. We have completed both 10 keV and 50 keV cascade simulations in 3C-SiC at a range of temperatures. In contrast to the Tersoff potential, the Gao-Weber potential produces almost twice as many C vacancies and interstitials at the time of maximum disorder (∼0.2 ps) but only about 25% more stable defects at the end of the simulation. Only about 20% of the carbon defects produced with the Tersoff potential recombine during the in-cascade annealing phase, while about 60% recombine with the Gao-Weber potential. The Gao-Weber potential appears to give a more realistic description of cascade dynamics in SiC, but still has some shortcomings when the defect migration barriers are compared to the ab initio results.

  12. Cascade collapse of heavy-ion irradiated Cu-Ni alloys

    SciTech Connect

    Smalinskas, K.S.

    1988-01-01

    To evaluate the role of material properties on the probability of a displacement cascade collapsing to a vacancy dislocation loop, the alloy content in Cu-Ni has been varied over the complete composition range. Cu-90wt%Ni, Cu-80wt%Ni, Cu-60wt%Ni, Cu-40wt%Ni, Cu-20wt%Ni, and Cu-10wt%Ni were used in this investigation. The probability of vacancy loop formation in Cu-Ni alloys has been shown to vary with the concentration of Ni. Initially, the inclusion of Ni increases the defect yield but on further addition, the yield decreases to a value lower than that of Cu. The yield starts to decrease when the Ni content exceeds 40%. The maximum and average dislocation loop size also decreases with increasing Ni content. Thus the number of vacancies retained in loops is significantly lower in the high nickel alloys than in pure Cu; a ratio of 13:1 was obtained. There is good agreement between the yields and size distributions in the current data with those reported by Stathopoulos et al. The diverse effects that the addition of impurities have on the probability of forming a dislocation loop from a displacement cascade and the lack of sufficient systematic studies makes it impossible to determine the precise effect. It is likely that more than one mechanism is operative. 31 refs., 14 figs., 3 tabs.

  13. Fate of Vacancy-Induced Supersolidity in He4

    NASA Astrophysics Data System (ADS)

    Boninsegni, M.; Kuklov, A. B.; Pollet, L.; Prokof'Ev, N. V.; Svistunov, B. V.; Troyer, M.

    2006-08-01

    The supersolid state of matter, exhibiting nondissipative flow in solids, has been elusive for 35 years. The recent discovery of a nonclassical moment of inertia in solid He4 by Kim and Chan provided the first experimental evidence, although the interpretation in terms of supersolidity of the ideal crystal phase remains a subject to debate. Using quantum Monte Carlo methods we investigate the long-standing question of vacancy-induced superflow and find that vacancies in a He4 crystal phase separate instead of forming a supersolid. On the other hand, nonequilibrium vacancies relaxing on defects of polycrystalline samples could provide an explanation for the experimental observations.

  14. The Cascade Forestry Service Nursery

    Treesearch

    Don Westefer

    2002-01-01

    Cascade Forestry Service, Inc., is a private reforestation nursery and service company that has grown from a shoestring operation into an employee-owned company that both produces reforestation trees and assists landowners with forestry development and management. The Northeastern Forest and Conservation Nursery Association has proven instrumental in Cascade Forestry...

  15. Cascade sample matrix inversion arrays

    NASA Astrophysics Data System (ADS)

    Hanson, Timothy; Essman, Joseph

    It is shown that if a narrowband adaptive array is partitioned and processed as a cascade of adaptive arrays, computational complexity is reduced and performance is only slightly degraded. The sample matrix inversion (SMI) and covariance matrix estimation are discussed. Cascade SMI complexity is examined. Simulation results are presented.

  16. Cascade Distillation System Development

    NASA Technical Reports Server (NTRS)

    Callahan, Michael R.; Sargushingh, Miriam; Shull, Sarah

    2014-01-01

    NASA's Advanced Exploration Systems (AES) Life Support System (LSS) Project is chartered with de-veloping advanced life support systems that will ena-ble NASA human exploration beyond low Earth orbit (LEO). The goal of AES is to increase the affordabil-ity of long-duration life support missions, and to re-duce the risk associated with integrating and infusing new enabling technologies required to ensure mission success. Because of the robust nature of distillation systems, the AES LSS Project is pursuing develop-ment of the Cascade Distillation Subsystem (CDS) as part of its technology portfolio. Currently, the system is being developed into a flight forward Generation 2.0 design.

  17. Dynamics of cavitating cascades

    NASA Technical Reports Server (NTRS)

    Acosta, A. J.; Brennen, C.; Kim, J. H.

    1972-01-01

    Brief accounts of the theoretical research conducted on the unsteady cavitation characteristics of liquid rocket engine turbopumps are reported. The objective is to produce estimates of the cavitation compliance and other unsteady characteristics which could then be used in analysis of the pogo instability. Blade cavitation is the particular pheonomenon which is investigated and line arized free streamline methods were employed in both quasistatic and complete dynamic cascade analyses of the unsteady flow. The simpler quasistatic analysis was applied to particular turbopumps but yielded values of compliances significantly smaller than those indirectly obtained from experiments. Reasons for this discrepancy are discussed. The complete dynamic analysis presents a new problem in fundamental hydrodynamics and, though the basic solution is presented, numerical results have not as yet been obtained.

  18. Role of melting temperature on the properties of displacement cascades

    SciTech Connect

    Smalinskas, K.; Robertson, I.M.; Averback, R.S. . Dept. of Materials Science and Engineering); Kirk, M.A. )

    1990-04-01

    The defect structure produced in Cu-Ni alloys by room temperature heavy-ion irradiation have been investigated by TEM. This system exhibits complete solid solubility over the entire composition range and therefore allows the role of melting temperature on the properties of displacement cascades to be assessed. The probability of a dislocation loop forming in the Cu-Ni alloy system is highest in pure Cu and decreases with increasing Ni content. However, the change in formation probability with melting temperature is not a simple one as it is found that loops form more readily in pure nickel than in Cu-90%Ni. It was also found that the size of the dislocation loops varies markedly with alloy content. The higher the nickel content the smaller the loops. These results will be correlated with ion-beam mixing experiments to assess the role of vacancy mobility in the loop formation process. 21 refs., 4 figs., 1 tab.

  19. Unsteady turbulence cascades

    NASA Astrophysics Data System (ADS)

    Goto, Susumu; Vassilicos, J. C.

    2016-11-01

    We have run a total of 311 direct numerical simulations (DNSs) of decaying three-dimensional Navier-Stokes turbulence in a periodic box with values of the Taylor length-based Reynolds number up to about 300 and an energy spectrum with a wide wave-number range of close to -5 /3 power-law dependence at the higher Reynolds numbers. On the basis of these runs, we have found a critical time when (i) the rate of change of the square of the integral length scale turns from increasing to decreasing, (ii) the ratio of interscale energy flux to high-pass filtered turbulence dissipation changes from decreasing to very slowly increasing in the inertial range, (iii) the signature of large-scale coherent structures disappears in the energy spectrum, and (iv) the scaling of the turbulence dissipation changes from the one recently discovered in DNSs of forced unsteady turbulence and in wind tunnel experiments of turbulent wakes and grid-generated turbulence to the classical scaling proposed by G. I. Taylor [Proc. R. Soc. London, Ser. A 151, 421 (1935), 10.1098/rspa.1935.0158] and A. N. Kolmogorov [Dokl. Akad. Nauk SSSR 31, 538 (1941)]. Even though the customary theoretical basis for this Taylor-Kolmogorov scaling is a statistically stationary cascade where large-scale energy flux balances dissipation, this is not the case throughout the entire time range of integration in all our DNS runs. The recently discovered dissipation scaling can be reformulated physically as a situation in which the dissipation rates of the small and large scales evolve together. We advance two hypotheses that may form the basis of a theoretical approach to unsteady turbulence cascades in the presence of large-scale coherent structures.

  20. Unsteady turbulence cascades.

    PubMed

    Goto, Susumu; Vassilicos, J C

    2016-11-01

    We have run a total of 311 direct numerical simulations (DNSs) of decaying three-dimensional Navier-Stokes turbulence in a periodic box with values of the Taylor length-based Reynolds number up to about 300 and an energy spectrum with a wide wave-number range of close to -5/3 power-law dependence at the higher Reynolds numbers. On the basis of these runs, we have found a critical time when (i) the rate of change of the square of the integral length scale turns from increasing to decreasing, (ii) the ratio of interscale energy flux to high-pass filtered turbulence dissipation changes from decreasing to very slowly increasing in the inertial range, (iii) the signature of large-scale coherent structures disappears in the energy spectrum, and (iv) the scaling of the turbulence dissipation changes from the one recently discovered in DNSs of forced unsteady turbulence and in wind tunnel experiments of turbulent wakes and grid-generated turbulence to the classical scaling proposed by G. I. Taylor [Proc. R. Soc. London, Ser. A 151, 421 (1935)1364-502110.1098/rspa.1935.0158] and A. N. Kolmogorov [Dokl. Akad. Nauk SSSR 31, 538 (1941)]. Even though the customary theoretical basis for this Taylor-Kolmogorov scaling is a statistically stationary cascade where large-scale energy flux balances dissipation, this is not the case throughout the entire time range of integration in all our DNS runs. The recently discovered dissipation scaling can be reformulated physically as a situation in which the dissipation rates of the small and large scales evolve together. We advance two hypotheses that may form the basis of a theoretical approach to unsteady turbulence cascades in the presence of large-scale coherent structures.

  1. DISPLACEMENT CASCADE SIMULATION IN TUNGSTEN UP TO 200 KEV OF DAMAGE ENERGY AT 300, 1025, AND 2050 K

    SciTech Connect

    Setyawan, Wahyu; Nandipati, Giridhar; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

    2015-09-22

    We generated molecular dynamics database of primary defects that adequately covers the range of tungsten recoil energy imparted by 14-MeV neutrons. During this semi annual period, cascades at 150 and 200 keV at 300 and 1025 K were simulated. Overall, we included damage energy up to 200 keV at 300 and 1025 K, and up to 100 keV at 2050 K. We report the number of surviving Frenkel pairs (NF) and the size distribution of defect clusters. The slope of the NF curve versus cascade damage energy (EMD), on a log-log scale, changes at a transition energy (μ). For EMD > μ, the cascade forms interconnected damage regions that facilitate the formation of large clusters of defects. At 300 K and EMD = 200 keV, the largest size of interstitial cluster and vacancy cluster is 266 and 335, respectively. Similarly, at 1025 K and EMD = 200 keV, the largest size of interstitial cluster and vacancy cluster is 296 and 338, respectively. At 2050 K, large interstitial clusters also routinely form, but practically no large vacancy clusters do

  2. 24 CFR 891.790 - Conditions for receipt of vacancy payments for assisted units.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... vacancy payments for assisted units. (a) General. Vacancy payments under the PAC will not be made unless... leased as of the effective date of the PAC, the Borrower is entitled to vacancy payments in the amount of... violating the lease, the PAC, or any applicable law; (2) Notified HUD of the vacancy or prospective...

  3. 24 CFR 891.790 - Conditions for receipt of vacancy payments for assisted units.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... vacancy payments for assisted units. (a) General. Vacancy payments under the PAC will not be made unless... leased as of the effective date of the PAC, the Borrower is entitled to vacancy payments in the amount of... violating the lease, the PAC, or any applicable law; (2) Notified HUD of the vacancy or prospective...

  4. 24 CFR 891.790 - Conditions for receipt of vacancy payments for assisted units.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... vacancy payments for assisted units. (a) General. Vacancy payments under the PAC will not be made unless... leased as of the effective date of the PAC, the Borrower is entitled to vacancy payments in the amount of... violating the lease, the PAC, or any applicable law; (2) Notified HUD of the vacancy or prospective...

  5. 24 CFR 891.790 - Conditions for receipt of vacancy payments for assisted units.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... vacancy payments for assisted units. (a) General. Vacancy payments under the PAC will not be made unless... leased as of the effective date of the PAC, the Borrower is entitled to vacancy payments in the amount of... violating the lease, the PAC, or any applicable law; (2) Notified HUD of the vacancy or prospective...

  6. Geometric and electronic structures of monolayer hexagonal boron nitride with multi-vacancy.

    PubMed

    Kim, Do-Hyun; Kim, Hag-Soo; Song, Min Woo; Lee, Seunghyun; Lee, Sang Yun

    2017-01-01

    Hexagonal boron nitride (h-BN) is an electrical insulator with a large band gap of 5 eV and a good thermal conductor of which melting point reaches about 3000 °C. Due to these properties, much attention was given to the thermal stability rather than the electrical properties of h-BN experimentally and theoretically. In this study, we report calculations that the electronic structure of monolayer h-BN can be influenced by the presence of a vacancy defect which leads to a geometric deformation in the hexagonal lattice structure. The vacancy was varied from mono- to tri-vacancy in a supercell, and different defective structures under the same vacancy density were considered in the case of an odd number of vacancies. Consequently, all cases of vacancy defects resulted in a geometric distortion in monolayer h-BN, and new energy states were created between valence and conduction band with the Fermi level shift. Notably, B atoms around vacancies attracted one another while repulsion happened between N atoms around vacancies, irrespective of vacancy density. The calculation of formation energy revealed that multi-vacancy including more B-vacancies has much lower formation energy than vacancies with more N-vacancies. This work suggests that multi-vacancy created in monolayer h-BN will have more B-vacancies and that the presence of multi-vacancy can make monolayer h-BN electrically conductive by the new energy states and the Fermi level shift.

  7. The effects of vacancy and oxidation on black phosphorus nanoresonators.

    PubMed

    Wang, Cui-Xia; Zhang, Chao; Jiang, Jin-Wu; Rabczuk, T

    2017-03-01

    Black phosphorene (BP) is not stable at ambient conditions, so atomic defects and oxidation effects are unavoidable in BP samples in the experiment. The effects of these defects on the performance of the BP nanoresonators are still unclear. Here, we perform classical molecular dynamics to investigate the effects of the vacancy and oxidation on single-layer BP nanoresonators at different temperatures. We find that the vacancy causes a strong reduction in the quality factor of the nanoresonators, while the oxidation has a weaker effect on the nanoresonators. More specifically, a 2% concentration of randomly distributed single vacancies is able to reduce the quality factor by about 80% and 40% at 4.2 K and 50 K, respectively. We also find that the quality factor of the nanoresonators is not sensitive to the distribution pattern of the vacancy defects.

  8. 78 FR 32412 - Navigation Safety Advisory Council; Vacancies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-30

    ... the Road; navigation regulations and equipment, routing measures, marine information, diving safety... SECURITY Coast Guard Navigation Safety Advisory Council; Vacancies AGENCY: Coast Guard, DHS. ACTION... Safety Advisory Council (NAVSAC). NAVSAC provides advice and recommendations to the Secretary of Homeland...

  9. 76 FR 33773 - Navigation Safety Advisory Council; Vacancies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-09

    ... the Road, navigation regulations and equipment, routing measures, marine information, diving safety... SECURITY Coast Guard Navigation Safety Advisory Council; Vacancies AGENCY: Coast Guard, DHS. ACTION... Safety Advisory Council (NAVSAC). NAVSAC provides advice and recommendations to the Secretary, Department...

  10. 24 CFR 882.411 - Payments for vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 202 SUPPORTIVE HOUSING FOR THE ELDERLY PROGRAM AND SECTION 811 SUPPORTIVE HOUSING FOR PERSONS WITH...) of this section unless the Owner: (i) Immediately upon learning of the vacancy, has notified the...

  11. 24 CFR 882.411 - Payments for vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 202 SUPPORTIVE HOUSING FOR THE ELDERLY PROGRAM AND SECTION 811 SUPPORTIVE HOUSING FOR PERSONS WITH...) of this section unless the Owner: (i) Immediately upon learning of the vacancy, has notified the...

  12. 24 CFR 882.411 - Payments for vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 202 SUPPORTIVE HOUSING FOR THE ELDERLY PROGRAM AND SECTION 811 SUPPORTIVE HOUSING FOR PERSONS WITH...) of this section unless the Owner: (i) Immediately upon learning of the vacancy, has notified the...

  13. 24 CFR 882.411 - Payments for vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 202 SUPPORTIVE HOUSING FOR THE ELDERLY PROGRAM AND SECTION 811 SUPPORTIVE HOUSING FOR PERSONS WITH...) of this section unless the Owner: (i) Immediately upon learning of the vacancy, has notified the...

  14. 24 CFR 882.411 - Payments for vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 202 SUPPORTIVE HOUSING FOR THE ELDERLY PROGRAM AND SECTION 811 SUPPORTIVE HOUSING FOR PERSONS WITH...) of this section unless the Owner: (i) Immediately upon learning of the vacancy, has notified the...

  15. The effects of vacancy and oxidation on black phosphorus nanoresonators

    NASA Astrophysics Data System (ADS)

    Wang, Cui-Xia; Zhang, Chao; Jiang, Jin-Wu; Rabczuk, T.

    2017-03-01

    Black phosphorene (BP) is not stable at ambient conditions, so atomic defects and oxidation effects are unavoidable in BP samples in the experiment. The effects of these defects on the performance of the BP nanoresonators are still unclear. Here, we perform classical molecular dynamics to investigate the effects of the vacancy and oxidation on single-layer BP nanoresonators at different temperatures. We find that the vacancy causes a strong reduction in the quality factor of the nanoresonators, while the oxidation has a weaker effect on the nanoresonators. More specifically, a 2% concentration of randomly distributed single vacancies is able to reduce the quality factor by about 80% and 40% at 4.2 K and 50 K, respectively. We also find that the quality factor of the nanoresonators is not sensitive to the distribution pattern of the vacancy defects.

  16. 78 FR 21134 - Merchant Mariner Medical Advisory Committee; Vacancy

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-09

    ... of commercial vessels; medical examiner education; and medical research. DATES: Applicants must send... qualifications of operators of commercial vessels; medical examiner education; and medical research. The... SECURITY Coast Guard Merchant Mariner Medical Advisory Committee; Vacancy AGENCY: United States Coast...

  17. Enzymatically Controlled Vacancies in Nanoparticle Crystals

    SciTech Connect

    Barnaby, Stacey N.; Ross, Michael B.; Thaner, Ryan V.; Lee, Byeongdu; Schatz, George C.; Mirkin, Chad A.

    2016-08-01

    In atomic systems, the mixing of metals results in distinct phase behavior that depends on the identity and bonding characteristics of the atoms. In nanoscale systems, the use of oligonucleotides as programmable “bonds” that link nanoparticle “atoms” into superlattices allows for the decoupling of atom identity and bonding. While much research in atomic systems is dedicated to understanding different phase behavior of mixed metals, it is not well understood on the nanoscale how changes in the nanoscale “bond” affect the phase behavior of nanoparticle crystals. In this work, the identity of the atom is kept the same but the chemical nature of the bond is altered, which is not possible in atomic systems, through the use of DNA and RNA bonding elements. These building blocks assemble into single crystal nanoparticle superlattices with mixed DNA and RNA bonding elements throughout. The nanoparticle crystals can be dynamically changed through the selective and enzymatic hydrolysis of the RNA bonding elements, resulting in superlattices that retain their crystalline structure and habit, while incorporating up to 35% random vacancies generated from the nanoparticles removed. Therefore, the bonding elements of nanoparticle crystals can be enzymatically and selectively addressed without affecting the nature of the atom.

  18. Analysis of Army Contracting Command Contract Specialist Vacancy Announcements

    DTIC Science & Technology

    2010-09-01

    an area on its Web site where employers can post vacancy announcements for an internship posting for free, or regular job postings for a fee. NCMA...2009), states companies should develop a recruiting workforce with high interpersonal skills. Employers should develop a strong internship program...announcements. The ISM Web site provides a career center where employers can post vacancy announcements for internship postings for free, or

  19. Singular field response and singular screening of vacancies in antiferromagnets.

    PubMed

    Wollny, Alexander; Andrade, Eric C; Vojta, Matthias

    2012-10-26

    For isolated vacancies in ordered local-moment antiferromagnets we show that the magnetic-field linear-response limit is generically singular: The magnetic moment associated with a vacancy in zero field is different from that in a finite field h in the limit h→0(+). The origin is a universal and singular screening cloud, which moreover leads to perfect screening as h→0(+) for magnets which display spin-flop bulk states in the weak-field limit.

  20. Vacancy formation energies in II-VI semiconductors

    NASA Technical Reports Server (NTRS)

    Berding, M. A.; Sher, A.; Chen, A.-B.

    1987-01-01

    Cation and anion vacancy formation energies are calculated for HgTe, ZnTe, CdTe, and their dilute alloys. Harrison's tight-bonding theory is extended to a cluster embedded in an extended crystal. Only neutral vacancies have been considered, and two final states for the removed atom have been addressed: a free atom in vacuum and an atom on an ideal (111) surface.

  1. Vacancy Mechanism of the Photolysis of Aluminum Hydride

    NASA Astrophysics Data System (ADS)

    Goryaev, M. A.

    2000-01-01

    Within the framework of the thermodynamic model of formation of intrinsic defects in a lattice during the decay of photoexcitations in a solid, the formation of hydrogen vacancies in aluminum hydride is analyzed. The evolution of a system with excess vacancy concentration leads to the formation of micropores under the crystal surface. The results of calculations agree well with the experimental data on photochemically induced absorption obtained in electron-microscopic studies of AlH3 decomposition.

  2. Effect of vacancy defects on generalized stacking fault energy of fcc metals.

    PubMed

    Asadi, Ebrahim; Zaeem, Mohsen Asle; Moitra, Amitava; Tschopp, Mark A

    2014-03-19

    Molecular dynamics (MD) and density functional theory (DFT) studies were performed to investigate the influence of vacancy defects on generalized stacking fault (GSF) energy of fcc metals. MEAM and EAM potentials were used for MD simulations, and DFT calculations were performed to test the accuracy of different common parameter sets for MEAM and EAM potentials in predicting GSF with different fractions of vacancy defects. Vacancy defects were placed at the stacking fault plane or at nearby atomic layers. The effect of vacancy defects at the stacking fault plane and the plane directly underneath of it was dominant compared to the effect of vacancies at other adjacent planes. The effects of vacancy fraction, the distance between vacancies, and lateral relaxation of atoms on the GSF curves with vacancy defects were investigated. A very similar variation of normalized SFEs with respect to vacancy fractions were observed for Ni and Cu. MEAM potentials qualitatively captured the effect of vacancies on GSF.

  3. Quantum transport in graphene Hall bars: Effects of vacancy disorder

    NASA Astrophysics Data System (ADS)

    Petrović, M. D.; Peeters, F. M.

    2016-12-01

    Using the tight-binding model, we investigate the influence of vacancy disorder on electrical transport in graphene Hall bars in the presence of quantizing magnetic fields. Disorder, induced by a random distribution of monovacancies, breaks the graphene sublattice symmetry and creates states localized on the vacancies. These states are observable in the bend resistance, as well as in the total DOS. Their energy is proportional to the square root of the magnetic field, while their localization length is proportional to the cyclotron radius. At the energies of these localized states, the electron current flows around the monovacancies and, as we show, it can follow unexpected paths depending on the particular arrangement of vacancies. We study how these localized states change with the vacancy concentration, and what are the effects of including the next-nearest-neighbor hopping term. Our results are also compared with the situation when double vacancies are present in the system. Double vacancies also induce localized states, but their energy and magnetic field dependencies are different. Their localization energy scales linearly with the magnetic field, and their localization length appears not to depend on the field strength.

  4. Hydrogen-vacancy-dislocation interactions in α-Fe

    NASA Astrophysics Data System (ADS)

    Tehranchi, A.; Zhang, X.; Lu, G.; Curtin, W. A.

    2017-02-01

    Atomistic simulations of the interactions between dislocations, hydrogen atoms, and vacancies are studied to assess the viability of a recently proposed mechanism for the formation of nanoscale voids in Fe-based steels in the presence of hydrogen. Quantum-mechanics/molecular-mechanics method calculations confirm molecular statics simulations based on embedded atom method (EAM) potential showing that individual vacancies on the compressive side of an edge dislocation can be transported with the dislocation as it glides. Molecular dynamics simulations based on EAM potential then show, however, that vacancy clusters in the glide plane of an approaching dislocation are annihilated or reduced in size by the creation of a double-jog/climb process that is driven by the huge reduction in energy accompanying vacancy annihilation. The effectiveness of annihilation/reduction processes is not reduced by the presence of hydrogen in the vacancy clusters because typical V-H cluster binding energies are much lower than the vacancy formation energy, except at very high hydrogen content in the cluster. Analysis of a range of configurations indicates that hydrogen plays no special role in stabilizing nanovoids against jog formation processes that shrink voids. Experimental observations of nanovoids on the fracture surfaces of steels must be due to as-yet undetermined processes.

  5. Oxygen Vacancy Linear Clustering in a Perovskite Oxide

    DOE PAGES

    Eom, Kitae; Choi, Euiyoung; Choi, Minsu; ...

    2017-07-14

    Oxygen vacancies have been implicitly assumed isolated ones, and understanding oxide materials possibly containing oxygen vacancies remains elusive within the scheme of the isolated vacancies, although the oxygen vacancies have been playing a decisive role in oxide materials. We report the presence of oxygen vacancy linear clusters and their orientation along a specific crystallographic direction in SrTiO3, a representative of a perovskite oxide. The presence of the linear clusters and associated electron localization was revealed by an electronic structure represented in the increase in the Ti2+ valence state or corresponding Ti 3d2 electronic configuration along with divacancy cluster model analysismore » and transport measurement. The orientation of the linear clusters along the [001] direction in perovskite SrTiO3 was verified by further X-ray diffuse scattering analysis. And because SrTiO3 is an archetypical perovskite oxide, the vacancy linear clustering with the specific aligned direction and electron localization can be extended to a wide variety of the perovskite oxides.« less

  6. Lateral manipulation of atomic vacancies in ultrathin insulating films.

    PubMed

    Li, Zhe; Chen, Hsin-Yi Tiffany; Schouteden, Koen; Lauwaet, Koen; Janssens, Ewald; Van Haesendonck, Chris; Pacchioni, Gianfranco; Lievens, Peter

    2015-05-26

    During the last 20 years, using scanning tunneling microscopy (STM) and atomic force microscopy, scientists have successfully achieved vertical and lateral repositioning of individual atoms on and in different types of surfaces. Such atom manipulation allows the bottom-up assembly of novel nanostructures that can otherwise not be fabricated. It is therefore surprising that controlled repositioning of virtual atoms, i.e., atomic vacancies, across atomic lattices has not yet been achieved experimentally. Here we use STM at liquid helium temperature (4.5 K) to create individual Cl vacancies and subsequently to laterally manipulate them across the surface of ultrathin sodium chloride films. This allows monitoring the interactions between two neighboring vacancies with different separations. Our findings are corroborated by density functional theory calculations and STM image simulations. The lateral manipulation of atomic vacancies opens up a new playground for the investigation of fundamental physical properties of vacancy nanostructures of any size and shape and their coupling with the supporting substrate, and of the interaction of various deposits with charged vacancies.

  7. Gallium vacancies in β-Ga2O3 crystals

    NASA Astrophysics Data System (ADS)

    Kananen, B. E.; Halliburton, L. E.; Stevens, K. T.; Foundos, G. K.; Giles, N. C.

    2017-05-01

    The gallium vacancy, an intrinsic acceptor, is identified in β-Ga2O3 using electron paramagnetic resonance (EPR). Spectra from doubly ionized ( VG a 2 - ) and singly ionized ( VG a - ) gallium vacancies are observed at room temperature, without photoexcitation, after an irradiation with high-energy neutrons. The VG a 2 - centers (with S = 1/2) have a slight angular variation due to a small anisotropy in the g matrix (principal values are 2.0034, 2.0097, and 2.0322). The VG a 2 - centers also exhibit a resolved hyperfine structure due to equal and nearly isotropic interactions with the 69,71Ga nuclei at two Ga sites (the hyperfine parameters are 1.28 and 1.63 mT for the 69Ga and 71Ga nuclei, respectively, when the field is along the a direction). Based on these g-matrix and hyperfine results, the model for the ground state of the doubly ionized vacancy ( VG a 2 - ) has a hole localized on one threefold-coordinated oxygen ion. The vacancy is located at one of the three neighboring gallium sites, and the remaining two gallium neighbors are responsible for the equal hyperfine interactions. The singly ionized ( VG a - ) gallium vacancies are also paramagnetic. In this latter acceptor, the two holes are localized on separate oxygen ions adjacent to one gallium vacancy. Their spins align parallel to give a triplet S = 1 EPR spectrum with resolved hyperfine structure from interactions with gallium neighbors.

  8. Cascade Mtns. Oregon

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The ground near one of the long-dormant Three Sisters volcanoes in the Cascade Mountains of west-central Oregon has risen approximately 10centimeters in a 10-by-20-km parcel since 1996, meaning that magma or underground lava is slowly flowing into the area, according to a research team from the U.S. Geological Survey. The Three Sisters area -- which contains five volcanoes -- is only about 170 miles from Mount St. Helens, which erupted in 1980. Both are part of the Cascades Range, a line of 27volcanoes stretching from British Columbia in Canada to northern California. This perspective view was created by draping a simulated natural color ASTER image over digital topography from the U.S. Geological Survey National Elevation Dataset.

    This image was acquired on May 28, 2000 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet.

    ASTER is one of five Earth-observing instruments launched December 18,1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Bjorn Eng of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The Terra mission is part of NASA's Earth Science Enterprise, along-term research and technology program designed to examine Earth's land, oceans, atmosphere, ice and life as a total integrated system.

    The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical

  9. Error bounds in cascading regressions

    USGS Publications Warehouse

    Karlinger, M.R.; Troutman, B.M.

    1985-01-01

    Cascading regressions is a technique for predicting a value of a dependent variable when no paired measurements exist to perform a standard regression analysis. Biases in coefficients of a cascaded-regression line as well as error variance of points about the line are functions of the correlation coefficient between dependent and independent variables. Although this correlation cannot be computed because of the lack of paired data, bounds can be placed on errors through the required properties of the correlation coefficient. The potential meansquared error of a cascaded-regression prediction can be large, as illustrated through an example using geomorphologic data. ?? 1985 Plenum Publishing Corporation.

  10. Inferring network structure from cascades

    NASA Astrophysics Data System (ADS)

    Ghonge, Sushrut; Vural, Dervis Can

    2017-07-01

    Many physical, biological, and social phenomena can be described by cascades taking place on a network. Often, the activity can be empirically observed, but not the underlying network of interactions. In this paper we offer three topological methods to infer the structure of any directed network given a set of cascade arrival times. Our formulas hold for a very general class of models where the activation probability of a node is a generic function of its degree and the number of its active neighbors. We report high success rates for synthetic and real networks, for several different cascade models.

  11. Displacement cascades and defects annealing in tungsten, Part I: Defect database from molecular dynamics simulations

    SciTech Connect

    Setyawan, Wahyu; Nandipati, Giridhar; Roche, Kenneth J.; Heinisch, Howard L.; Wirth, Brian D.; Kurtz, Richard J.

    2015-07-01

    Molecular dynamics simulations have been used to generate a comprehensive database of surviving defects due to displacement cascades in bulk tungsten. Twenty-one data points of primary knock-on atom (PKA) energies ranging from 100 eV (sub-threshold energy) to 100 keV (~780×Ed, where Ed = 128 eV is the average displacement threshold energy) have been completed at 300 K, 1025 K and 2050 K. Within this range of PKA energies, two regimes of power-law energy-dependence of the defect production are observed. A distinct power-law exponent characterizes the number of Frenkel pairs produced within each regime. The two regimes intersect at a transition energy which occurs at approximately 250×Ed. The transition energy also marks the onset of the formation of large self-interstitial atom (SIA) clusters (size 14 or more). The observed defect clustering behavior is asymmetric, with SIA clustering increasing with temperature, while the vacancy clustering decreases. This asymmetry increases with temperature such that at 2050 K (~0.5Tm) practically no large vacancy clusters are formed, meanwhile large SIA clusters appear in all simulations. The implication of such asymmetry on the long-term defect survival and damage accumulation is discussed. In addition, <100> {110} SIA loops are observed to form directly in the highest energy cascades, while vacancy <100> loops are observed to form at the lowest temperature and highest PKA energies, although the appearance of both the vacancy and SIA loops with Burgers vector of <100> type is relatively rare.

  12. Trophic cascades across ecosystems.

    PubMed

    Knight, Tiffany M; McCoy, Michael W; Chase, Jonathan M; McCoy, Krista A; Holt, Robert D

    2005-10-06

    Predation can be intense, creating strong direct and indirect effects throughout food webs. In addition, ecologists increasingly recognize that fluxes of organisms across ecosystem boundaries can have major consequences for community dynamics. Species with complex life histories often shift habitats during their life cycles and provide potent conduits coupling ecosystems. Thus, local interactions that affect predator abundance in one ecosystem (for example a larval habitat) may have reverberating effects in another (for example an adult habitat). Here we show that fish indirectly facilitate terrestrial plant reproduction through cascading trophic interactions across ecosystem boundaries. Fish reduce larval dragonfly abundances in ponds, leading to fewer adult dragonflies nearby. Adult dragonflies consume insect pollinators and alter their foraging behaviour. As a result, plants near ponds with fish receive more pollinator visits and are less pollen limited than plants near fish-free ponds. Our results confirm that strong species interactions can reverberate across ecosystems, and emphasize the importance of landscape-level processes in driving local species interactions.

  13. Terahertz quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Koehler, Ruedeger; Tredicucci, Alessandro; Beltram, Fabio; Beere, Harvey E.; Linfield, Edmund H.; Davies, A. G.; Ritchie, David A.

    2003-07-01

    The terahertz region (1-10 THz) of the electromagnetic spectrum offers ample opportunities in spectroscopy, free space communications, remote sensing and medical imaging. Yet, the use of THz radiation in all these fields has been hampered by the lack of appropriate, convenient sources. We here report on unipolar semiconductor injection lasers that emit at THz frequencies (4.3 THz, λ ~ 69μm and 3.5 THz, λ ~ 85μm) and possess the potential for device-like implementation. They are based on the quantum cascade scheme employing interminiband transitions in the technologically mature AlGaAs/GaAs material system and feature a novel kind of waveguide loosely relying on the surface plasmon concpt. Continuous-wave laser emission is achieved with low thresholds of a few hundred A/cm2 up to 45 K heat sink temperature and maximum output powers of more than 4mW. Under pulsed excitation, peak output powers of 4.5mW at low temperatures and still 1 mW at 65 K are measured. The amximum operating temperature is 67 K.

  14. Cascading Effects Following Intervention

    PubMed Central

    Patterson, Gerald R.; Forgatch, Marion S.; DeGarmo, David S.

    2010-01-01

    Four different sources for cascade effects were examined using 9-year process and outcome data from a randomized controlled trial (RCT) of a preventive intervention using Parent Management Training – Oregon Model (PMTO™). The social interaction learning (SIL) model of child antisocial behavior serves as one basis for predicting change. A second source addresses the issue of comorbid relationships among clinical diagnoses. The third source, collateral changes, describes events in which changes in one family member correlate with changes in another. The fourth component is based on the long-term effects of reducing coercion and increasing positive interpersonal processes within the family. New findings from the 9-year follow-up show that mothers experienced benefits as measured by standard of living (i.e., income, occupation, education, and financial stress) and frequency of police arrests. It is assumed that PMTO reduces the level of coercion, which sets the stage for a massive increase in positive social interaction. In effect, PMTO alters the family environment and thereby opens doors to healthy new social environments. PMID:20883592

  15. A study of the vacancy loop formation probability in Ni-Cu and Ag-Pd alloys. [50-keV Kr sup + ions

    SciTech Connect

    Smalinskas, K.; Chen, Gengsheng; Haworth, J.; Robertson, I.M. . Dept. of Materials Science and Engineering); Kirk, M.A. )

    1992-04-01

    The molten-zone model of vacancy loop formation from a displacement cascade predicts that the loop formation probability should scale with the melting temperature. To investigate this possibility the vacancy loop formation probability has been determined in a series of Cu-Ni and Ag-Pd alloys. The irradiations were performed at room temperature with 50 keV Kr+ ions and the resulting damage structure was examined by using transmission electron microscopy. In the Cu-Ni alloy series, the change in loop formation probability with increasing Ni concentration was complex, and at low- and high- nickel concentrations, the defect yield did not change in the predicted manner. The defect yield was higher in the Cu-rich alloys than in the Ni-rich alloys. In the Ag-Pd alloy the change in the loop formation probability followed more closely the change in melting temperature, but no simple relationship was determined.

  16. One-dimensional fast migration of vacancy clusters in metals

    SciTech Connect

    Matsukawa, Yoshitaka; Zinkle, Steven J

    2007-01-01

    The migration of point defects, e.g. crystal lattice vacancies and self-interstitial atoms (SIAs), typically occurs through three-dimensional (3-D) random walk. However, when vacancies and SIAs agglomerate with like defects forming clusters, the migration mode may change. Recently, atomic-scale computer simulations using molecular dynamics (MD) codes have reported that nanometer-sized two-dimensional (2-D) clusters of SIAs exhibit one-dimensional (1-D) fast migration1-7. The 1-D migration mode transports the entire cluster containing several tens of SIAs with a mobility comparable to single SIAs3. This anisotropic migration of SIA clusters can have a significant impact on the evolution of a material fs neutron-irradiation damage microstructure, which dominates the material fs lifetime in nuclear reactor environments8-9. This is also proposed to be a key physical mechanism for the self-organization of nanometer-sized sessile vacancy cluster arrays10-13. Given these findings for SIA clusters, a fundamental question is whether the 1-D migration mode is also possible for 2-D clusters of vacancies. Preceding MD results predicted that 1-D migration of vacancy clusters is possible in body-centered cubic (bcc) iron, but not in face-centered cubic (fcc) copper2. Previous experimental studies have reported 1-D migration of SIA clusters14, but there have been no observations of 1-D vacancy cluster migration. Here we present the first experimental transmission electron microscopy (TEM) dynamic observation demonstrating the 1-D migration of vacancy clusters in fcc gold. It was found that the mobility of the vacancy clusters via the 1-D migration is much higher than single vacancies via 3-D random walk and comparable to single SIAs via 3-D random walk. Hence, the mobility of the glissile clusters is not associated with the character of their constituent point defects. Dynamic conversion of a planar vacancy loop into a 3-D stacking fault tetrahedron geometry was also observed.

  17. Shallow halogen vacancies in halide optoelectronic materials

    DOE PAGES

    Shi, Hongliang; Du, Mao -Hua

    2014-11-05

    Halogen vacancies (VH) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., CH3NH3PbI3 and TlBr. Both CH3NH3PbI3 and TlBr have been found to have shallow VH, in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., CH3NH3PbI3, CH3NH3SnI3 (photovoltaic materials), TlBr, and CsPbBr3, (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VHmore » is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of ns2 ions both play important roles in creating shallow VH in halides such as CH3NH3PbI3, CH3NH3SnI3, and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH, such as those with long cation-cation distances and low anion coordination numbers, and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH. Furthermore, the results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.« less

  18. Shallow halogen vacancies in halide optoelectronic materials

    NASA Astrophysics Data System (ADS)

    Shi, Hongliang; Du, Mao-Hua

    2014-11-01

    Halogen vacancies (VH ) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., C H3N H3Pb I3 and TlBr. Both C H3N H3Pb I3 and TlBr have been found to have shallow VH , in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., C H3N H3Pb I3 , C H3N H3Sn I3 (photovoltaic materials), TlBr, and CsPbB r3 (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VH is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of n s2 ions both play important roles in creating shallow VH in halides such as C H3N H3Pb I3 , C H3N H3Sn I3 , and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH , such as those with large cation-cation distances and low anion coordination numbers and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH . The results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.

  19. Cascade redox flow battery systems

    DOEpatents

    Horne, Craig R.; Kinoshita, Kim; Hickey, Darren B.; Sha, Jay E.; Bose, Deepak

    2014-07-22

    A reduction/oxidation ("redox") flow battery system includes a series of electrochemical cells arranged in a cascade, whereby liquid electrolyte reacts in a first electrochemical cell (or group of cells) before being directed into a second cell (or group of cells) where it reacts before being directed to subsequent cells. The cascade includes 2 to n stages, each stage having one or more electrochemical cells. During a charge reaction, electrolyte entering a first stage will have a lower state-of-charge than electrolyte entering the nth stage. In some embodiments, cell components and/or characteristics may be configured based on a state-of-charge of electrolytes expected at each cascade stage. Such engineered cascades provide redox flow battery systems with higher energy efficiency over a broader range of current density than prior art arrangements.

  20. What is a Trophic Cascade?

    PubMed

    Ripple, William J; Estes, James A; Schmitz, Oswald J; Constant, Vanessa; Kaylor, Matthew J; Lenz, Adam; Motley, Jennifer L; Self, Katharine E; Taylor, David S; Wolf, Christopher

    2016-11-01

    Few concepts in ecology have been so influential as that of the trophic cascade. Since the 1980s, the term has been a central or major theme of more than 2000 scientific articles. Despite this importance and widespread usage, basic questions remain about what constitutes a trophic cascade. Inconsistent usage of language impedes scientific progress and the utility of scientific concepts in management and conservation. Herein, we offer a definition of trophic cascade that is designed to be both widely applicable yet explicit enough to exclude extraneous interactions. We discuss our proposed definition and its implications, and define important related terms, thereby providing a common language for scientists, policy makers, conservationists, and other stakeholders with an interest in trophic cascades. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Ultrarelativistic cascades and strangeness production

    SciTech Connect

    Kahana, D.E.; Kahana, S.H.

    1998-02-01

    A two phase cascade, LUCIFER II, developed for the treatment of ultra high energy Ion-Ion collisions is applied to the production of strangeness at SPS energies. This simulation is able to simultaneously describe both hard processes such as Drell-Yan and slower, soft processes such as the production of light mesons by separating the dynamics into two steps, a fast cascade involving only the nucleons in the original colliding relativistic ions followed, after an appropriate delay, by a normal multiscattering of the resulting excited baryons and mesons produced virtually in the first step. No energy loss can take place in the short time interval over which the first cascade takes place. The chief result is a reconciliation of the important Drell-Yan measurements with the apparent success of standard cascades to describe the nucleon stopping and meson production in heavy ion experiments at the CERN SPS.

  2. The cascade high productivity language

    NASA Technical Reports Server (NTRS)

    Callahan, David; Chamberlain, Branford L.; Zima, Hans P.

    2004-01-01

    This paper describes the design of Chapel, the Cascade High Productivity Language, which is being developed in the DARPA-funded HPCS project Cascade led by Cray Inc. Chapel pushes the state-of-the-art in languages for HEC system programming by focusing on productivity, in particular by combining the goal of highest possible object code performance with that of programmability offered by a high-level user interface.

  3. Aeroelasticity in Turbomachine-Cascades.

    DTIC Science & Technology

    1982-11-10

    STABLE -180 UNSTABLE -360 ’ - ’ - -180 0. 󈧖O DIAGRAM 3 AERODYNAMIC LIFT (OENT)COEFFICIENTI AND PHASE LEADS IN DEPENDANCE OF FLOM GUANTATIES AND CASCADE...ABL -0.8 0.0 -5 0. -5 DIAGRAM ’. AERODYNAMIC NORK AND DAMPING COEFFICIENTS (FOR A RIGID NOTION) IN DEPENDANCE OF FLOW OURNTATIES AND CASCADE GEOMETRY...coefficients on blades + blade vibration + vizualization in the transonic flow domain (Schlieren) + instability dependance on flow conditions, blade

  4. Computation of inverse magnetic cascades

    NASA Technical Reports Server (NTRS)

    Montgomery, D.

    1981-01-01

    Inverse cascades of magnetic quantities for turbulent incompressible magnetohydrodynamics are reviewed, for two and three dimensions. The theory is extended to the Strauss equations, a description intermediate between two and three dimensions appropriate to Tokamak magnetofluids. Consideration of the absolute equilibrium Gibbs ensemble for the system leads to a prediction of an inverse cascade of magnetic helicity, which may manifest itself as a major disruption. An agenda for computational investigation of this conjecture is proposed.

  5. The cascade high productivity language

    NASA Technical Reports Server (NTRS)

    Callahan, David; Chamberlain, Branford L.; Zima, Hans P.

    2004-01-01

    This paper describes the design of Chapel, the Cascade High Productivity Language, which is being developed in the DARPA-funded HPCS project Cascade led by Cray Inc. Chapel pushes the state-of-the-art in languages for HEC system programming by focusing on productivity, in particular by combining the goal of highest possible object code performance with that of programmability offered by a high-level user interface.

  6. Stochastic background of atmospheric cascades

    SciTech Connect

    Wilk, G. ); Wlodarczyk, Z. )

    1993-06-15

    Fluctuations in the atmospheric cascades developing during the propagation of very high energy cosmic rays through the atmosphere are investigated using stochastic branching model of pure birth process with immigration. In particular, we show that the multiplicity distributions of secondaries emerging from gamma families are much narrower than those resulting from hadronic families. We argue that the strong intermittent like behaviour found recently in atmospheric families results from the fluctuations in the cascades themselves and are insensitive to the details of elementary interactions.

  7. Cascading gravity is ghost free

    SciTech Connect

    Rham, Claudia de; Khoury, Justin; Tolley, Andrew J.

    2010-06-15

    We perform a full perturbative stability analysis of the 6D cascading gravity model in the presence of 3-brane tension. We demonstrate that for sufficiently large tension on the (flat) 3-brane, there are no ghosts at the perturbative level, consistent with results that had previously only been obtained in a specific 5D decoupling limit. These results establish the cascading gravity framework as a consistent infrared modification of gravity.

  8. Slow relaxation of cascade-induced defects in Fe

    DOE PAGES

    Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.; ...

    2015-02-17

    On-the-fly kinetic Monte Carlo (KMC) simulations are performed to investigate slow relaxation of non-equilibrium systems. Point defects induced by 25 keV cascades in α -Fe are shown to lead to a characteristic time-evolution, described by the replenish and relax mechanism. Then, we produce an atomistically-based assessment of models proposed to explain the slow structural relaxation by focusing on the aggregation of 50 vacancies and 25 self-interstital atoms (SIA) in 10-lattice-parameter α-Fe boxes, two processes that are closely related to cascade annealing and exhibit similar time signature. Four atomistic effects explain the timescales involved in the evolution: defect concentration heterogeneities, concentration-enhancedmore » mobility, cluster-size dependent bond energies and defect-induced pressure. In conclusion, these findings suggest that the two main classes of models to explain slow structural relaxation, the Eyring model and the Gibbs model, both play a role to limit the rate of relaxation of these simple point-defect systems.« less

  9. Slow relaxation of cascade-induced defects in Fe

    SciTech Connect

    Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.; Xu, Haixuan

    2015-02-17

    On-the-fly kinetic Monte Carlo (KMC) simulations are performed to investigate slow relaxation of non-equilibrium systems. Point defects induced by 25 keV cascades in α -Fe are shown to lead to a characteristic time-evolution, described by the replenish and relax mechanism. Then, we produce an atomistically-based assessment of models proposed to explain the slow structural relaxation by focusing on the aggregation of 50 vacancies and 25 self-interstital atoms (SIA) in 10-lattice-parameter α-Fe boxes, two processes that are closely related to cascade annealing and exhibit similar time signature. Four atomistic effects explain the timescales involved in the evolution: defect concentration heterogeneities, concentration-enhanced mobility, cluster-size dependent bond energies and defect-induced pressure. In conclusion, these findings suggest that the two main classes of models to explain slow structural relaxation, the Eyring model and the Gibbs model, both play a role to limit the rate of relaxation of these simple point-defect systems.

  10. Detecting neighborhood vacancy level in Detroit city using remote sensing

    NASA Astrophysics Data System (ADS)

    Li, X.; Wang, R.; Yang, A.; Vojnovic, I.

    2015-12-01

    With the decline of manufacturing industries, many Rust Belt cities, which enjoyed prosperity in the past, are now suffering from financial stress, population decrease and urban poverty. As a consequence, urban neighborhoods deteriorate. Houses are abandoned and left to decay. Neighborhood vacancy brings on many problems. Governments and agencies try to survey the vacancy level by going through neighborhoods and record the condition of each structure, or by buying information of active mailing addresses to get approximate neighborhood vacancy rate. But these methods are expensive and time consuming. Remote sensing provides a quick and comparatively cost-efficient way to access spatial information on social and demographical attributes of urban area. In our study, we use remote sensing to detect a major aspect of neighborhood deterioration, the vacancy levels of neighborhoods in Detroit city. We compared different neighborhoods using Landsat 8 images in 2013. We calculated NDVI that indicates the greenness of neighborhoods with the image in July 2013. Then we used thermal infrared information from image in February to detect human activities. In winter, abandoned houses will not consume so much energy and therefore neighborhoods with more abandoned houses will have smaller urban heat island effect. Controlling for the differences in terms of the greenness obtained from summer time image, we used thermal infrared from winter image to determine the temperatures of urban surface. We find that hotter areas are better maintained and have lower house vacancy rates. We also compared the changes over time for neighborhoods using Landsat 7 images from 2003 to 2013. The results show that deteriorated neighborhoods have increased NDVI in summer and get colder in winter due to abandonment of houses. Our results show the potential application of remote sensing as an easily accessed and efficient way to obtain data about social conditions in cities. We used the neighborhood

  11. Interband Cascade Photovoltaic Cells

    SciTech Connect

    Yang, Rui Q.; Santos, Michael B.; Johnson, Matthew B.

    2014-09-24

    In this project, we are performing basic and applied research to systematically investigate our newly proposed interband cascade (IC) photovoltaic (PV) cells [1]. These cells follow from the great success of infrared IC lasers [2-3] that pioneered the use of quantum-engineered IC structures. This quantum-engineered approach will enable PV cells to efficiently convert infrared radiation from the sun or other heat source, to electricity. Such cells will have important applications for more efficient use of solar energy, waste-heat recovery, and power beaming in combination with mid-infrared lasers. The objectives of our investigations are to: achieve extensive understanding of the fundamental aspects of the proposed PV structures, develop the necessary knowledge for making such IC PV cells, and demonstrate prototype working PV cells. This research will focus on IC PV structures and their segments for utilizing infrared radiation with wavelengths from 2 to 5 μm, a range well suited for emission by heat sources (1,000-2,000 K) that are widely available from combustion systems. The long-term goal of this project is to push PV technology to longer wavelengths, allowing for relatively low-temperature thermal sources. Our investigations address material quality, electrical and optical properties, and their interplay for the different regions of an IC PV structure. The tasks involve: design, modeling and optimization of IC PV structures, molecular beam epitaxial growth of PV structures and relevant segments, material characterization, prototype device fabrication and testing. At the end of this program, we expect to generate new cutting-edge knowledge in the design and understanding of quantum-engineered semiconductor structures, and demonstrate the concepts for IC PV devices with high conversion efficiencies.

  12. Molecular dynamics modeling of atomic displacement cascades in 3C-SiC: Comparison of interatomic potentials

    SciTech Connect

    Samolyuk, German D.; Osetskiy, Yury N.; Stoller, Roger E.

    2015-06-03

    We used molecular dynamics modeling of atomic displacement cascades to characterize the nature of primary radiation damage in 3C-SiC. We demonstrated that the most commonly used interatomic potentials are inconsistent with ab initio calculations of defect energetics. Both the Tersoff potential used in this work and a modified embedded-atom method potential reveal a barrier to recombination of the carbon interstitial and carbon vacancy which is much higher than the density functional theory (DFT) results. The barrier obtained with a newer potential by Gao and Weber is closer to the DFT result. This difference results in significant differences in the cascade production of point defects. We have completed both 10 keV and 50 keV cascade simulations in 3C-SiC at a range of temperatures. In contrast to the Tersoff potential, the Gao-Weber potential produces almost twice as many C vacancies and interstitials at the time of maximum disorder (~0.2 ps) but only about 25% more stable defects at the end of the simulation. Only about 20% of the carbon defects produced with the Tersoff potential recombine during the in-cascade annealing phase, while about 60% recombine with the Gao-Weber potential.

  13. Effect of mass of the primary knock-on atom on displacement cascade debris in alpha-iron

    SciTech Connect

    Andrew, Calder F; Bacon, David J; Barashev, Aleksandr; Osetskiy, Yury N

    2008-01-01

    Results are presented from molecular dynamics (MD) simulations of displacement cascades created in -iron (Fe) by primary knock-on atoms (PKAs) with energy from 5 to 20 keV and mass chosen to represent C, Fe and Bi. Molecular Bi2 has also been simulated using two Bi PKAs, and PKA-Fe interaction potential has also been varied. Four effects are reported. First, the PKA mass has a major effect on cascade damage while the interaction potential has little if any. Second, the total number of point defects produced in a cascade decreases with increasing PKA mass. This fact is not accounted for in models used conventionally for estimating damage. Third, interstitial loops of <111> type and both vacancy and interstitial loops of <100> type are formed, the latter being observed in MD simulation for the first time. The probability of <100> loop appearance increases with increasing PKA mass as well as energy. Finally, there is a correlation between production of large vacancy and interstitial clusters in the same cascade.

  14. Dynamics of vacancies in two-dimensional Lennard-Jones crystals

    NASA Astrophysics Data System (ADS)

    Yao, Zhenwei; de la Cruz, Monica Olvera

    2014-12-01

    Vacancies represent an important class of crystallographic defects, and their behaviors can be strongly coupled with relevant material properties. In this work, we study the dynamics of generic n -point vacancies in two-dimensional Lennard-Jones crystals in several thermodynamic states. Simulations reveal the spectrum of distinct, size-dependent vacancy dynamics, including the nonmonotonously varying diffusive mobilities of one-, two- and three-point vacancies, and several healing routines of linear vacancies. Specifically, we numerically observe significantly faster diffusion of the two-point vacancy that can be attributed to its rotational degree of freedom. The high mobility of the two-point vacancies opens the possibility of doping two-point vacancies into atomic materials to enhance atomic migration. The rich physics of vacancies revealed in this study may have implications in the engineering of defects in extensive crystalline materials for desired properties.

  15. Vacancy relaxation in cuprous oxide (Cu2-xO1-y)

    NASA Astrophysics Data System (ADS)

    Frazer, Laszlo; Chang, Kelvin B.; Schaller, Richard D.; Poeppelmeier, Kenneth R.; Ketterson, John B.

    2017-03-01

    Phonons are produced when an excited vacancy in cuprous oxide (Cu$_2$O) relaxes. Time resolved luminescence was used to find the excited copper vacancy (acceptor) and oxygen vacancy (donor) trap levels and lifetimes. It was also used to determine the typical energy and number of phonons in the phonon pulses emitted by vacancies. The vacancy properties of cuprous oxide are controlled by several synthesis parameters and by the temperature. We directly demonstrate the absorption of light by oxygen vacancies with transient absorption. Copper and oxygen vacancies behave differently, in part because the two kinds of traps capture carriers from different states. For example, the copper vacancy luminescence lifetime is around 25 times greater at low temperature. However, both kinds of vacancy luminescence are consistent with a Poissonian multiple phonon emission model.

  16. Chemical expansion affected oxygen vacancy stability in different oxide structures from first principles calculations

    DOE PAGES

    Aidhy, Dilpuneet S.; Liu, Bin; Zhang, Yanwen; ...

    2015-01-21

    We study the chemical expansion for neutral and charged oxygen vacancies in fluorite, rocksalt, perovskite and pyrochlores materials using first principles calculations. We show that the neutral oxygen vacancy leads to lattice expansion whereas the charged vacancy leads to lattice contraction. In addition, we show that there is a window of strain within which an oxygen vacancy is stable; beyond that range, the vacancy can become unstable. Using CeO2|ZrO2 interface structure as an example, we show that the concentration of oxygen vacancies can be manipulated via strain, and the vacancies can be preferentially stabilized. Furthermore, these results could serve asmore » guiding principles in predicting oxygen vacancy stability in strained systems and in the design of vacancy stabilized materials.« less

  17. Chemical expansion affected oxygen vacancy stability in different oxide structures from first principles calculations

    SciTech Connect

    Aidhy, Dilpuneet S.; Liu, Bin; Zhang, Yanwen; Weber, William J.

    2015-01-21

    We study the chemical expansion for neutral and charged oxygen vacancies in fluorite, rocksalt, perovskite and pyrochlores materials using first principles calculations. We show that the neutral oxygen vacancy leads to lattice expansion whereas the charged vacancy leads to lattice contraction. In addition, we show that there is a window of strain within which an oxygen vacancy is stable; beyond that range, the vacancy can become unstable. Using CeO2|ZrO2 interface structure as an example, we show that the concentration of oxygen vacancies can be manipulated via strain, and the vacancies can be preferentially stabilized. Furthermore, these results could serve as guiding principles in predicting oxygen vacancy stability in strained systems and in the design of vacancy stabilized materials.

  18. Chemical expansion affected oxygen vacancy stability in different oxide structures from first principles calculations

    SciTech Connect

    Aidhy, Dilpuneet S.; Liu, Bin; Zhang, Yanwen; Weber, William J.

    2015-03-01

    We study the chemical expansion for neutral and charged oxygen vacancies in fluorite, rocksalt, perovskite and pyrochlores materials using first principles calculations. We show that the neutral oxygen vacancy leads to lattice expansion whereas the charged vacancy leads to lattice contraction. In addition, we show that there is a window of strain within which an oxygen vacancy is stable; beyond that range, the vacancy can become unstable. Using CeO2|ZrO2 interface structure as an example, we show that the concentration of oxygen vacancies can be manipulated via strain, and the vacancies can be preferentially stabilized. These results could serve as guiding principles in predicting oxygen vacancy stability in strained systems and in the design of vacancy stabilized materials.

  19. Vacancy relaxation in cuprous oxide (Cu2–xO1–y)

    DOE PAGES

    Frazer, Laszlo; Chang, Kelvin B.; Schaller, Richard D.; ...

    2016-11-14

    Phonons are produced when an excited vacancy in cuprous oxide (Cu2O) relaxes. Time resolved luminescence was used to find the excited copper vacancy (acceptor) and oxygen vacancy (donor) trap levels and lifetimes. It was also used to determine the typical energy and number of phonons in the phonon pulses emitted by vacancies. The vacancy properties of cuprous oxide are controlled by several synthesis parameters and by the temperature. We directly demonstrate the absorption of light by oxygen vacancies with transient absorption. Copper and oxygen vacancies behave differently, in part because the two kinds of traps capture carriers from different states.more » For example, the copper vacancy luminescence lifetime is around 25 times greater at low temperature. Moreover, both kinds of vacancy luminescence are consistent with a Poissonian multiple phonon emission model.« less

  20. Dynamics of vacancies in two-dimensional Lennard-Jones crystals.

    PubMed

    Yao, Zhenwei; de la Cruz, Monica Olvera

    2014-12-01

    Vacancies represent an important class of crystallographic defects, and their behaviors can be strongly coupled with relevant material properties. In this work, we study the dynamics of generic n-point vacancies in two-dimensional Lennard-Jones crystals in several thermodynamic states. Simulations reveal the spectrum of distinct, size-dependent vacancy dynamics, including the nonmonotonously varying diffusive mobilities of one-, two- and three-point vacancies, and several healing routines of linear vacancies. Specifically, we numerically observe significantly faster diffusion of the two-point vacancy that can be attributed to its rotational degree of freedom. The high mobility of the two-point vacancies opens the possibility of doping two-point vacancies into atomic materials to enhance atomic migration. The rich physics of vacancies revealed in this study may have implications in the engineering of defects in extensive crystalline materials for desired properties.

  1. Shallow halogen vacancies in halide optoelectronic materials

    SciTech Connect

    Shi, Hongliang; Du, Mao -Hua

    2014-11-05

    Halogen vacancies (VH) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., CH3NH3PbI3 and TlBr. Both CH3NH3PbI3 and TlBr have been found to have shallow VH, in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., CH3NH3PbI3, CH3NH3SnI3 (photovoltaic materials), TlBr, and CsPbBr3, (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VH is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of ns2 ions both play important roles in creating shallow VH in halides such as CH3NH3PbI3, CH3NH3SnI3, and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH, such as those with long cation-cation distances and low anion coordination numbers, and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH. Furthermore, the results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.

  2. Vacancy behavior in a compressed fcc Lennard-Jones crystal

    SciTech Connect

    Beeler, J.R. Jr.

    1981-12-01

    This computer experiment study concerns the determination of the stable vacancy configuration in a compressed fcc Lennard-Jones crystal and the migration of this defect in a compressed crystal. Isotropic and uniaxial compression stress conditions were studied. The isotropic and uniaxial compression magnitudes employed were 0.94 less than or equal to eta less than or equal to 1.5, and 1.0 less than or equal to eta less than or equal to 1.5, respectively. The site-centered vacancy (SCV) was the stable vacancy configuration whenever cubic symmetry was present. This includes all of the isotropic compression cases and the particular uniaxial compression case (eta = ..sqrt..2) that give a bcc structure. In addition, the SCV was the stable configuration for uniaxial compression eta < 1.29. The out-of-plane split vacancy (SV-OP) was the stable vacancy configuration for uniaxial compression 1.29 < eta less than or equal to 1.5 and was the saddle-point configuration for SCV migration when the SCV was the stable form. For eta > 1.20, the SV-OP is an extended defect and, therefore, a saddle point for SV-OP migration could not be determined. The mechanism for the transformation from the SCV to the SV-OP as the stable form at eta = 1.29 appears to be an alternating sign (101) and/or (011) shear process.

  3. Atomic vacancies significantly degrade the mechanical properties of phosphorene

    NASA Astrophysics Data System (ADS)

    Sha, Zhen-Dong; Pei, Qing-Xiang; Zhang, Ying-Yan; Zhang, Yong-Wei

    2016-08-01

    Due to low formation energies, it is very easy to create atomic defects in phosphorene during its fabrication process. How these atomic defects affect its mechanical behavior, however, remain unknown. Here, we report on a systematic study of the effect of atomic vacancies on the mechanical properties and failure behavior of phosphorene using molecular dynamics simulations. It is found that atomic vacancies induce local stress concentration and cause early bond-breaking, leading to a significant degradation of the mechanical properties of the material. More specifically, a 2% concentration of randomly distributed mono-vacancies is able to reduce the fracture strength by ∼40%. An increase in temperature from 10 to 400 K can further deteriorate the fracture strength by ∼60%. The fracture strength of defective phosphorene is also found to be affected by defect distribution. When the defects are patterned in a line, the reduction in fracture strength greatly depends on the tilt angle and the loading direction. Furthermore, we find that di-vacancies cause an even larger reduction in fracture strength than mono-vacancies when the loading is in an armchair direction. These findings provide important guidelines for the structural design of phosphorene in future applications.

  4. A computational study of H-Fe vacancy interaction

    NASA Astrophysics Data System (ADS)

    Pistonesi, C.; Garcia, A.; Brizuela, G.; Juan, A.

    1998-03-01

    The semi-empirical atom superposition and electron delocalization molecular orbital (ASED-MO) theory was used to study the H-Fe interaction near a Fe vacancy. Calculations were carried out using clusters of the type 0022-3727/31/5/016/img7 and simulating the absorption of a hydrogen atom near a vacancy located at the centre of the cluster. The formation of H-H pairs was also considered. Our calculations involve a system in which experiments are difficult to perform and could contribute to a better understanding or insight based on microscopic exploration. The results indicate that in general the H-Fe interaction gets stronger when the H atom is close to the vacancy but not at its centre due to a strong indirect interaction mediated by the Fe matrix. Minima regions are obtained at eccentric positions. A H-H pair is suggested to be formed near the vacancy region. The relaxation of the first neighbour Fe atoms towards the vacancy is also addressed in the presence and absence of H. For all situations studied, the most stable configuration corresponds to a cluster contraction.

  5. Role of vacancies and solute atoms on grain boundary sliding

    SciTech Connect

    Vetrano, J.S.; Henager, C.H. Jr.; Simonen, E.P.

    2000-07-01

    It is necessary for grain boundary dislocations to slide and climb during the grain boundary sliding process that dominates fine-grained superplastic deformation. The process of climb requires either an influx of vacancies to the grain boundary plane or a local generation of vacancies. Transmission electron microscopy (TEM) observations of grain boundaries in superplastically deformed Al-Mg-Mn alloys quenched under load from the deformation temperature have revealed the presence of nano-scale cavities resulting from a localized supersaturation of vacancies at the grain boundary. Compositional measurements along interfaces have also shown an effect of solute atoms on the local structure. This is shown to result from a coupling of vacancy and solute atom flows during deformation and quenching. Calculations of the localized vacancy concentration indicate that the supersaturation along the grain boundary can be as much as a factor of ten. The effects of the local supersaturation and solute atom movement on deformation rates and cavity nucleation and growth is discussed.

  6. Role of Vacancies and Solute Atoms on Grain Boundary Sliding

    SciTech Connect

    Vetrano, John S.; Henager, Charles H.; Simonen, Edward P.

    2000-10-30

    It is necessary for grain boundary dislocations to slide and climb during the grain boundary sliding process that dominates fine-grained superplastic deformation. The process of climb requires either an influx of vacancies to the grain boundary plane or a local generation of vacancies. Transmission electron microscopy (TEM) observations of grain boundaries in superplastically deformed Al-Mg-Mn alloys quenched under load from the deformation temperature have revealed the presence of nano-scale cavities resulting from a localized supersaturation of vacancies at the grain boundary. Compositional measurements along interfaces have also shown an effect of solute atoms on the local structure. This is shown to result from a coupling of vacancy and solute atom flows during deformation and quenching. Calculations of the localized vacancy concentration indicate that the supersaturation along the grain boundary can be as much as a factor of five. The effects of the local supersaturation and solute atom movement on deformation rates and cavity nucleation and growth will be discussed.

  7. Origin of Nanobubbles Electrochemically Formed in a Magnetic Field: Ionic Vacancy Production in Electrode Reaction.

    PubMed

    Aogaki, Ryoichi; Sugiyama, Atsushi; Miura, Makoto; Oshikiri, Yoshinobu; Miura, Miki; Morimoto, Ryoichi; Takagi, Satoshi; Mogi, Iwao; Yamauchi, Yusuke

    2016-07-05

    As a process complementing conventional electrode reactions, ionic vacancy production in electrode reaction was theoretically examined; whether reaction is anodic or cathodic, based on the momentum conservation by Newton's second law of motion, electron transfer necessarily leads to the emission of original embryo vacancies, and dielectric polarization endows to them the same electric charge as trans- ferred in the reaction. Then, the emitted embryo vacancies immediately receive the thermal relaxation of solution particles to develop steady-state vacancies. After the vacancy production, nanobubbles are created by the collision of the vacancies in a vertical magnetic field.

  8. Origin of Nanobubbles Electrochemically Formed in a Magnetic Field: Ionic Vacancy Production in Electrode Reaction

    PubMed Central

    Aogaki, Ryoichi; Sugiyama, Atsushi; Miura, Makoto; Oshikiri, Yoshinobu; Miura, Miki; Morimoto, Ryoichi; Takagi, Satoshi; Mogi, Iwao; Yamauchi, Yusuke

    2016-01-01

    As a process complementing conventional electrode reactions, ionic vacancy production in electrode reaction was theoretically examined; whether reaction is anodic or cathodic, based on the momentum conservation by Newton’s second law of motion, electron transfer necessarily leads to the emission of original embryo vacancies, and dielectric polarization endows to them the same electric charge as trans- ferred in the reaction. Then, the emitted embryo vacancies immediately receive the thermal relaxation of solution particles to develop steady-state vacancies. After the vacancy production, nanobubbles are created by the collision of the vacancies in a vertical magnetic field. PMID:27377532

  9. Origin of Nanobubbles Electrochemically Formed in a Magnetic Field: Ionic Vacancy Production in Electrode Reaction

    NASA Astrophysics Data System (ADS)

    Aogaki, Ryoichi; Sugiyama, Atsushi; Miura, Makoto; Oshikiri, Yoshinobu; Miura, Miki; Morimoto, Ryoichi; Takagi, Satoshi; Mogi, Iwao; Yamauchi, Yusuke

    2016-07-01

    As a process complementing conventional electrode reactions, ionic vacancy production in electrode reaction was theoretically examined; whether reaction is anodic or cathodic, based on the momentum conservation by Newton’s second law of motion, electron transfer necessarily leads to the emission of original embryo vacancies, and dielectric polarization endows to them the same electric charge as trans- ferred in the reaction. Then, the emitted embryo vacancies immediately receive the thermal relaxation of solution particles to develop steady-state vacancies. After the vacancy production, nanobubbles are created by the collision of the vacancies in a vertical magnetic field.

  10. Molecular-dynamic investigation of the interaction of vacancies with symmetrical tilt grain boundaries in aluminum

    NASA Astrophysics Data System (ADS)

    Weckman, A. V.; Demyanov, B. F.; Dragunov, A. S.

    2015-06-01

    The molecular-dynamic method has been used to study the interaction of lattice vacancies with symmetrical grain boundaries (GBs) in aluminum. The fraction of trapped vacancies has been found to depend linearly on the distance to the GB plane. The average velocity of the vacancy migration toward the boundary decreases exponentially with an increase in the distance between the GB plane and vacancy. The radius of the region of trapping of a vacancy by the boundary is limited to two to three lattice parameters and grows with an increase in temperature. Four types of boundaries, which are characterized by different capability for the trapping of vacancies, have been determined.

  11. Vacancy-rearrangement theory in the first Magnus approximation

    SciTech Connect

    Becker, R.L.

    1984-01-01

    In the present paper we employ the first Magnus approximation (M1A), a unitarized Born approximation, in semiclassical collision theory. We have found previously that the M1A gives a substantial improvement over the first Born approximation (B1A) and can give a good approximation to a full coupled channels calculation of the mean L-shell vacancy probability per electron, p/sub L/, when the L-vacancies are accompanied by a K-shell vacancy (p/sub L/ is obtained experimentally from measurements of K/sub ..cap alpha../-satellite intensities). For sufficiently strong projectile-electron interactions (sufficiently large Z/sub p/ or small v) the M1A ceases to reproduce the coupled channels results, but it is accurate over a much wider range of Z/sub p/ and v than the B1A. 27 references.

  12. Orbital reconstruction in a self-assembled oxygen vacancy nanostructure

    DOE PAGES

    Jang, H.; Kerr, G.; Lim, J. S.; ...

    2015-07-27

    We demonstrate the microscopic role of oxygen vacancies spatially confined within nanometer inter-spacing (about 1nm) in BiFeO₃, using resonant soft X-ray scattering techniques and soft X-ray spectroscopy measurements. Such vacancy confinements and total number of vacancy are controlled by substitution of Ca²⁺ for Bi³⁺ cation. We found that by increasing the substitution, the in-plane orbital bands of Fe³⁺ cations are reconstructed without any redox reaction. It leads to a reduction of the hopping between Fe atoms, forming a localized valence band, in particular Fe 3d-electronic structure, around the Fermi level. This band localization causes to decrease the conductivity of themore » doped BiFeO₃ system.« less

  13. Optical signatures of silicon-vacancy spins in diamond

    NASA Astrophysics Data System (ADS)

    Müller, Tina; Hepp, Christian; Pingault, Benjamin; Neu, Elke; Gsell, Stefan; Schreck, Matthias; Sternschulte, Hadwig; Steinmüller-Nethl, Doris; Becher, Christoph; Atatüre, Mete

    2014-02-01

    Colour centres in diamond have emerged as versatile tools for solid-state quantum technologies ranging from quantum information to metrology, where the nitrogen-vacancy centre is the most studied to date. Recently, this toolbox has expanded to include novel colour centres to realize more efficient spin-photon quantum interfaces. Of these, the silicon-vacancy centre stands out with highly desirable photonic properties. The challenge for utilizing this centre is to realize the hitherto elusive optical access to its electronic spin. Here we report spin-tagged resonance fluorescence from the negatively charged silicon-vacancy centre. Our measurements reveal a spin-state purity approaching unity in the excited state, highlighting the potential of the centre as an efficient spin-photon quantum interface.

  14. Zn vacancies creation via (2 × 2) surface reconstruction

    NASA Astrophysics Data System (ADS)

    Xie, Xiuhua; Li, Binghui; Zhang, Zhenzhong; Shen, Dezhen

    2017-08-01

    Zinc vacancies have been incorporated in ZnO via (2  ×  2) surface reconstruction during the epitaxy growth. Evolution of in situ reflection high-energy electron diffraction (RHEED) patterns indicate Zn-polar surface (2  ×  2) reconstruction was realized under extreme O-rich conditions. Atom sized triangular pits and islands were presented by the high resolution scanning tunneling microscopy (STM) images, which stand for a single Zn vacancy per (2  ×  2) surface unit cell. The neutral acceptor-bound exciton (A0,X), peak located at 3.344 eV, and red luminescence (RL), maximum emission intensity at ~1.76 eV, which related to Zn vacancy, have been studied by variable-temperature/power steady-state photoluminescence (PL) spectroscopy.

  15. Thermodynamics of vacancies and clusters in high-entropy alloys

    NASA Astrophysics Data System (ADS)

    Wang, Zhijun; Liu, C. T.; Dou, Peng

    2017-09-01

    By means of thermodynamic analyses, we provide the intriguing evidence that the equilibrium vacancy concentrations and their clusters in high entropy alloys (HEAs) are substantially larger than those in pure metals and simple binary alloys. The increased defect concentrations strongly change the thermodynamic and kinetic properties of the HEAs. With these findings, we predict a strong recombination tendency of vacancies and interstitials after excitation from radiation bombardments, and the results are favorably compatible with very recent experiments on the superior radiation resistance of HEAs. The thermodynamics of vacancies and clusters in HEAs will be of great interest to the design of advanced materials involving many thermodynamic and kinetic properties such as thermal conductivity, diffusivity, precipitation, creep, and irradiation damage.

  16. Mechanism of vacancy formation induced by hydrogen in tungsten

    SciTech Connect

    Liu, Yi-Nan; Ahlgren, T.; Bukonte, L.; Nordlund, K.; Shu, Xiaolin; Yu, Yi; Lu, Guang-Hong; Li, Xiao-Chun

    2013-12-15

    We report a hydrogen induced vacancy formation mechanism in tungsten based on classical molecular dynamics simulations. We demonstrate the vacancy formation in tungsten due to the presence of hydrogen associated directly with a stable hexagonal self-interstitial cluster as well as a linear crowdion. The stability of different self-interstitial structures has been further studied and it is particularly shown that hydrogen plays a crucial role in determining the configuration of SIAs, in which the hexagonal cluster structure is preferred. Energetic analysis has been carried out to prove that the formation of SIA clusters facilitates the formation of vacancies. Such a mechanism contributes to the understanding of the early stage of the hydrogen blistering in tungsten under a fusion reactor environment.

  17. Orbital reconstruction in a self-assembled oxygen vacancy nanostructure

    SciTech Connect

    Jang, H.; Kerr, G.; Lim, J. S.; Yang, C. -H.; Kao, C. -C.; Lee, J. -S.

    2015-07-27

    We demonstrate the microscopic role of oxygen vacancies spatially confined within nanometer inter-spacing (about 1nm) in BiFeO₃, using resonant soft X-ray scattering techniques and soft X-ray spectroscopy measurements. Such vacancy confinements and total number of vacancy are controlled by substitution of Ca²⁺ for Bi³⁺ cation. We found that by increasing the substitution, the in-plane orbital bands of Fe³⁺ cations are reconstructed without any redox reaction. It leads to a reduction of the hopping between Fe atoms, forming a localized valence band, in particular Fe 3d-electronic structure, around the Fermi level. This band localization causes to decrease the conductivity of the doped BiFeO₃ system.

  18. Electronic Structures of Clusters of Hydrogen Vacancies on Graphene.

    PubMed

    Wu, Bi-Ru; Yang, Chih-Kai

    2015-10-15

    Hydrogen vacancies in graphane are products of incomplete hydrogenation of graphene. The missing H atoms can alter the electronic structure of graphane and therefore tune the electronic, magnetic, and optical properties of the composite. We systematically studied a variety of well-separated clusters of hydrogen vacancies in graphane, including the geometrical shapes of triangles, parallelograms, hexagons, and rectangles, by first-principles density functional calculation. The results indicate that energy levels caused by the missing H are generated in the broad band gap of pure graphane. All triangular clusters of H vacancies are magnetic, the larger the triangle the higher the magnetic moment. The defect levels introduced by the missing H in triangular and parallelogram clusters are spin-polarized and can find application in optical transition. Parallelograms and open-ended rectangles are antiferromagnetic and can be used for nanoscale registration of digital information.

  19. Electronic Structures of Clusters of Hydrogen Vacancies on Graphene

    NASA Astrophysics Data System (ADS)

    Wu, Bi-Ru; Yang, Chih-Kai

    2015-10-01

    Hydrogen vacancies in graphane are products of incomplete hydrogenation of graphene. The missing H atoms can alter the electronic structure of graphane and therefore tune the electronic, magnetic, and optical properties of the composite. We systematically studied a variety of well-separated clusters of hydrogen vacancies in graphane, including the geometrical shapes of triangles, parallelograms, hexagons, and rectangles, by first-principles density functional calculation. The results indicate that energy levels caused by the missing H are generated in the broad band gap of pure graphane. All triangular clusters of H vacancies are magnetic, the larger the triangle the higher the magnetic moment. The defect levels introduced by the missing H in triangular and parallelogram clusters are spin-polarized and can find application in optical transition. Parallelograms and open-ended rectangles are antiferromagnetic and can be used for nanoscale registration of digital information.

  20. Electronic Structures of Clusters of Hydrogen Vacancies on Graphene

    PubMed Central

    Wu, Bi-Ru; Yang, Chih-Kai

    2015-01-01

    Hydrogen vacancies in graphane are products of incomplete hydrogenation of graphene. The missing H atoms can alter the electronic structure of graphane and therefore tune the electronic, magnetic, and optical properties of the composite. We systematically studied a variety of well-separated clusters of hydrogen vacancies in graphane, including the geometrical shapes of triangles, parallelograms, hexagons, and rectangles, by first-principles density functional calculation. The results indicate that energy levels caused by the missing H are generated in the broad band gap of pure graphane. All triangular clusters of H vacancies are magnetic, the larger the triangle the higher the magnetic moment. The defect levels introduced by the missing H in triangular and parallelogram clusters are spin-polarized and can find application in optical transition. Parallelograms and open-ended rectangles are antiferromagnetic and can be used for nanoscale registration of digital information. PMID:26468677

  1. Cascaded-cladding-pumped cascaded Raman fiber amplifier.

    PubMed

    Jiang, Huawei; Zhang, Lei; Feng, Yan

    2015-06-01

    The conversion efficiency of double-clad Raman fiber laser is limited by the cladding-to-core area ratio. To get high conversion efficiency, the inner-cladding-to-core area ratio has to be less than about 8, which limits the brightness enhancement. To overcome the problem, a cascaded-cladding-pumped cascaded Raman fiber laser with multiple-clad fiber as the Raman gain medium is proposed. A theoretical model of Raman fiber amplifier with multiple-clad fiber is developed, and numerical simulation proves that the proposed scheme can improve the conversion efficiency and brightness enhancement of cladding pumped Raman fiber laser.

  2. Vacancy Mediated Mechanism of Nitrogen Substitution in Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Menon, Madhu; Sadanadan, Bindu; Rao, Apparao M.

    2003-01-01

    Nitrogen substitution reaction in a graphene sheet and carbon nanotubes of different diameter are investigated using the generalized tight-binding molecular dynamics method. The formation of a vacancy in curved graphene sheet or a carbon nanotube is found to cause a curvature dependent local reconstruction of the surface. Our simulations and analysis show that vacancy mediated N substitution (rather than N chemisorption) is favored on the surface of nanotubes with diameter larger than 8 nm. This predicted value of the critical minimum diameter for N incorporation is confirmed by experimental results presented.

  3. Hydrogen saturation stabilizes vacancy-induced ferromagnetic ordering in graphene.

    PubMed

    Li, Weifeng; Zhao, Mingwen; Zhao, Xian; Xia, Yueyuan; Mu, Yuguang

    2010-11-07

    Density functional theory calculations are performed to explore vacancy-induced magnetism in graphene. The hydrogen saturation not only stabilizes the vacancy structure but also induces distinct magnetic coupling depending on the defect distribution: weak magnetic coupling between defects on different sublattices and strong coupling between defects on the same sublattice. Ferromagnetic ordering has to be accompanied with a semiconducting property. The interaction integral J between defective spins decreases linearly with the increase of the distance between them. Based on the 2D Ising model and Monte Carlo simulations, the possible highest Curie temperature T(c) of defective graphene is predicted to be lower than 500 K.

  4. Observation of Fluorine-Vacancy Complexes in Silicon

    SciTech Connect

    Jenei, Z; Simpson, P; Robison, R; Asoka-Kumar, P; Law, M

    2004-02-19

    We show direct evidence, obtained by positron annihilation spectroscopy, for the complexing of fluorine with vacancies in silicon. Both float zone and Czochralski silicon wafers were implanted with 30 keV fluorine ions to a fluence of 2x10{sup 14} ions/cm{sup 2}, and studied in the as-implanted condition, and after annealing to 650o C for 10 and for 30 minutes. The ''2-detector'' background reduction technique for positron annihilation was applied. The spectra reveal a significant concentration of fluorine-vacancy complexes after annealing, for both Czochralski and float zone material, supporting the results of computer simulations of the implantation and annealing process.

  5. Exact Model of Vacancy-Mediated Solute Transport in Magnesium

    NASA Astrophysics Data System (ADS)

    Agarwal, Ravi; Trinkle, Dallas R.

    2017-03-01

    Most substitutional solutes in solids diffuse via vacancies. However, widely used analytic models for diffusivity make uncontrolled approximations in the relations between atomic jump rates that reduce accuracy. Symmetry analysis of the hexagonal close packed crystal identifies more distinct vacancy transitions than prior models, and a Green function approach computes diffusivity exactly for solutes in magnesium. We find large differences for the solute drag of Al, Zn, and rare earth solutes, and improved diffusion activation energies—highlighting the need for exact analytic transport models.

  6. Jamming probabilities for a vacancy in the dimer model.

    PubMed

    Poghosyan, V S; Priezzhev, V B; Ruelle, P

    2008-04-01

    Following the recent proposal made by [J. Bouttier, Phys. Rev. E 76, 041140 (2007)], we study analytically the mobility properties of a single vacancy in the close-packed dimer model on the square lattice. Using the spanning web representation, we find determinantal expressions for various observable quantities. In the limiting case of large lattices, they can be reduced to the calculation of Toeplitz determinants and minors thereof. The probability for the vacancy to be strictly jammed and other diffusion characteristics are computed exactly.

  7. Vacancy distribution in a rotating solid 4He

    NASA Astrophysics Data System (ADS)

    Pushkarov, D. I.

    2012-03-01

    Vacancy distribution is considered in a rotating solid 4He immersed in a superfluid helium-II. Vacancies are considered as a quasiparticle gas of vacancions with a gap dispersion law. It is shown that the radial distribution depends on Poisson's ratio and practically not on Young's modulus. The treatment is based on a nonlinear theory unifying the elasticity theory equations and a Boltzmann-type transport equation valid for arbitrary angular velocities. The situation simulates, in a sense, the Kim and Chan rotational experiments where nonclassical inertia was observed. The model cannot be applied to solid 3He. We do not presuppose in this work any supersolid fraction.

  8. Vacancy-mediated diffusion in biaxially strained Si

    NASA Astrophysics Data System (ADS)

    Caliste, Damien; Rushchanskii, Konstantin Z.; Pochet, Pascal

    2011-01-01

    We present an analysis of stress-enhanced vacancy-mediated diffusion in biaxially deformed Si (100) films as measured by the strain derivative (Q') of the activation energy. The strain dependence of Q' is demonstrated by means of a reanalysis of previously published experimental data, which both take into account the temperature dependence of and highlight the differences between tensile and compressive stress. Based on ab initio calculations, we predict that Q' in pure silicon is higher under compressive conditions due to a broken degeneracy of the split-vacancy configuration.

  9. Influence of oxygen vacancies on the dielectric properties of hafnia: First-principles calculations

    NASA Astrophysics Data System (ADS)

    Cockayne, Eric

    2007-03-01

    First-principles calculations were used to study the effects of neutral and 2+ charged oxygen vacancies on the dielectric properties of crystalline HfO2 . In agreement with previous results, the neutral vacancy is more stable on four fold-coordinated site, while the charged vacancy is more stable on a three fold-coordinated site. For both vacancy positions, HfO2 remains insulating whether the vacancy is neutral or in the 2+ charge state. The dynamical matrix, Born effective charges, and electronic dielectric tensor were calculated for each structure. With one oxygen vacancy per 64 oxygen atoms, the static dielectric constant κs is increased by 1%-2% for neutral vacancies and suppressed by 1%-3% for 2+ charged vacancies, with the larger changes for three fold-coordinated vacancies. The exact result in the case of a charged vacancy depends on how the neutralizing charge necessary for macroscopic charge neutrality is modeled. The increase in κs for neutral oxygen vacancies arises from an enhancement of the electronic dielectric response due to a pair of electrons occupying an easily polarizable F -center defect state. The suppression in κs for charged oxygen vacancies is due to phonon hardening, which reduces the ionic response. No evidence is found for characteristic localized phonons induced by oxygen vacancies that could be detected by infrared or Raman spectroscopy.

  10. Autoregressive cascades on random networks

    NASA Astrophysics Data System (ADS)

    Iyer, Srikanth K.; Vaze, Rahul; Narasimha, Dheeraj

    2016-04-01

    A network cascade model that captures many real-life correlated node failures in large networks via load redistribution is studied. The considered model is well suited for networks where physical quantities are transmitted, e.g., studying large scale outages in electrical power grids, gridlocks in road networks, and connectivity breakdown in communication networks, etc. For this model, a phase transition is established, i.e., existence of critical thresholds above or below which a small number of node failures lead to a global cascade of network failures or not. Theoretical bounds are obtained for the phase transition on the critical capacity parameter that determines the threshold above and below which cascade appears or disappears, respectively, that are shown to closely follow numerical simulation results.

  11. Cascade Reservoirs Floodwater Resources Utilization

    NASA Astrophysics Data System (ADS)

    Wang, Y.

    2015-12-01

    A reasonable floodwater resources utilization method is put forward by dynamic controlling of cascade reservoirs flood control limited level in this paper. According to the probability distribution of the beginning time of the first flood and the ending time of the final flood from July to September, the Fuzzy Statistic Analysis was used to divide the main flood season. By fitting the flood season membership functions of each period, the cascade reservoirs flood control limited water level for each period were computed according to the characteristic data of reservoirs. In terms of the benefit maximization and risk minimum principle, the reasonable combination of flood control limited water level of cascade reservoirs was put forward.

  12. Bosonic cascades of indirect excitons

    NASA Astrophysics Data System (ADS)

    Nalitov, A. V.; De Liberato, S.; Lagoudakis, P.; Savvidis, P. G.; Kavokin, A. V.

    2017-08-01

    Recently, the concept of the terahertz bosonic cascade laser (BCL) based on a parabolic quantum well (PQW) embedded in a microcavity was proposed. We refine this proposal by suggesting transitions between indirect exciton (IX) states as a source of terahertz emission. We explicitly propose a structure containing a narrow-square QW and a wide-parabolic QW for the realisation of a bosonic cascade. Advantages of this type of structures are in large dipole matrix elements for terahertz transitions and in long exciton radiative lifetimes which are crucial for realisation of threshold and quantum efficiency BCLs.

  13. Cascading dynamics in modular networks

    NASA Astrophysics Data System (ADS)

    Galstyan, Aram; Cohen, Paul

    2007-03-01

    In this paper we study a simple cascading process in a structured heterogeneous population, namely, a network composed of two loosely coupled communities. We demonstrate that under certain conditions the cascading dynamics in such a network has a two-tiered structure that characterizes activity spreading at different rates in the communities. We study the dynamics of the model using both simulations and an analytical approach based on annealed approximation and obtain good agreement between the two. Our results suggest that network modularity might have implications in various applications, such as epidemiology and viral marketing.

  14. Nanowire terahertz quantum cascade lasers

    SciTech Connect

    Grange, Thomas

    2014-10-06

    Quantum cascade lasers made of nanowire axial heterostructures are proposed. The dissipative quantum dynamics of their carriers is theoretically investigated using non-equilibrium Green functions. Their transport and gain properties are calculated for varying nanowire thickness, from the classical-wire regime to the quantum-wire regime. Our calculation shows that the lateral quantum confinement provided by the nanowires allows an increase of the maximum operation temperature and a strong reduction of the current density threshold compared to conventional terahertz quantum cascade lasers.

  15. 24 CFR 891.445 - Conditions for receipt of vacancy payments for assisted units.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... DISABILITIES Project Management § 891.445 Conditions for receipt of vacancy payments for assisted units. (a... project rental assistance payments set forth in this section are fulfilled. (b) Vacancies during...

  16. 24 CFR 891.445 - Conditions for receipt of vacancy payments for assisted units.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... DISABILITIES Project Management § 891.445 Conditions for receipt of vacancy payments for assisted units. (a... project rental assistance payments set forth in this section are fulfilled. (b) Vacancies during...

  17. 24 CFR 891.445 - Conditions for receipt of vacancy payments for assisted units.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... DISABILITIES Project Management § 891.445 Conditions for receipt of vacancy payments for assisted units. (a... project rental assistance payments set forth in this section are fulfilled. (b) Vacancies during...

  18. 24 CFR 891.445 - Conditions for receipt of vacancy payments for assisted units.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... DISABILITIES Project Management § 891.445 Conditions for receipt of vacancy payments for assisted units. (a... project rental assistance payments set forth in this section are fulfilled. (b) Vacancies during...

  19. 24 CFR 891.445 - Conditions for receipt of vacancy payments for assisted units.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... DISABILITIES Project Management § 891.445 Conditions for receipt of vacancy payments for assisted units. (a... project rental assistance payments set forth in this section are fulfilled. (b) Vacancies during...

  20. Electronic and magnetic properties of graphene, silicene and germanene with varying vacancy concentration

    NASA Astrophysics Data System (ADS)

    Ali, Muhammad; Pi, Xiaodong; Liu, Yong; Yang, Deren

    2017-04-01

    The experimental realization of two-dimensional materials such as graphene, silicene and germanene has attracted incredible interest ranging from understanding their physical properties to device applications. During the fabrication and processing of these two-dimensional materials, structural defects such as vacancies may be produced. In this work we have systemically investigated the formation energies, electronic and magnetic properties of graphene, silicene and germanene with vacancies in the framework of spin polarized density functional theory. It is found that the magnetic moment of graphene and silicene with vacancies decreases with the increase in the concentration of vacancies. However, germanene remains non-magnetic irrespective of the vacancy concentration. Low-buckled silicene and germanene with vacancies may possess remarkable band gaps, in contrast to planar graphene with vacancies. With the formation of vacancies silicene and germanene demonstrate a transition from semimetal to semiconductor, while graphene turns to be metallic.

  1. Kinetic Monte Carlo Annealing Simulation of Cascade Damage in a-Fe

    SciTech Connect

    Suzudo, Tomoaki; Golubov, Stanislav I; Stoller, Roger E; Yamaguchi, Masatake; Tsuru, Tomohito; Kaburaki, Hideo

    2011-01-01

    Molecular dynamics is a useful tool for simulating cascade damage in metals and alloys, but the time scale accessible to molecular dynamics is only about 10-10s. Kinetic Monte Carlo can be used to simulate annealing of cascade damage to permit analysis of the longer time evolution of cascade damage. We conducted a series of such annealing simulations in -Fe. The number of surviving displacements before annealing is ~0.3 of the Norgett-Robinson-Torrens (NRT) value in the case of primary knock-on atoms with energy more than ~10 keV, and it decreased by ~30% during the annealing at 300 K because of recombination of vacancies and self-interstitial atoms. The recombination ratio increased as the annealing temperature increased. These results can be meaningfully applied in models such as mean field reaction rate theory used to simulate long-term radiation damage accumulation. We also demonstrated that 1D motion of small SIA clusters can substantially influence the long-term accumulation of cascade damage.

  2. Identification of electron and hole traps in lithium tetraborate (Li{sub 2}B{sub 4}O{sub 7}) crystals: Oxygen vacancies and lithium vacancies

    SciTech Connect

    Swinney, M. W.; McClory, J. W.; Petrosky, J. C.; Yang Shan; Brant, A. T.; Halliburton, L. E.; Adamiv, V. T.; Burak, Ya. V.; Dowben, P. A.

    2010-06-15

    Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify and characterize electrons trapped by oxygen vacancies and holes trapped by lithium vacancies in lithium tetraborate (Li{sub 2}B{sub 4}O{sub 7}) crystals. Our study includes a crystal with the natural abundances of {sup 10}B and {sup 11}B and a crystal highly enriched with {sup 10}B. The as-grown crystals contain isolated oxygen vacancies, lithium vacancies, and copper impurities, all in nonparamagnetic charge states. During an irradiation at 77 K with 60 kV x-rays, doubly ionized oxygen vacancies trap electrons while singly ionized lithium vacancies and monovalent copper impurities trap holes. The vacancies return to their preirradiation charge states when the temperature of the sample is increased to approximately 90 K. Hyperfine interactions with {sup 10}B and {sup 11}B nuclei, observed between 13 and 40 K in the radiation-induced EPR and ENDOR spectra, provide models for the two vacancy-related defects. The electron trapped by an oxygen vacancy is localized primarily on only one of the two neighboring boron ions while the hole stabilized by a lithium vacancy is localized on a neighboring oxygen ion with nearly equal interactions with the two boron ions adjacent to the oxygen ion.

  3. Vacancy complexes in Sb-doped SnO{sub 2}

    SciTech Connect

    Korhonen, E.; Tuomisto, F.; Bierwagen, O.; Speck, J. S.; White, M. E.; Galazka, Z.

    2014-02-21

    MBE-grown Sb-doped epitaxial SnO{sub 2} thin-film samples with varying doping concentrations have been measured using positron Doppler spectroscopy. Vacancies were found in varying amounts, the general trend points to a decrease in vacancy concentration as dopant concentration increases. The exact identity of the vacancy defects is not known, but results suggest complexes of Sn and O vacancies.

  4. Atomic vacancy-induced friction on the graphite surface: observation by lateral force microscopy.

    PubMed

    Paredes, J I; Martínez-Alonso, A; Tascón, J M D

    2003-05-01

    Lateral force microscopy has been employed to investigate the frictional behaviour of atomic vacancies on the graphite surface. Such a study was only made possible by the controlled expansion of originally single-atom vacancies into multiatom vacancies, employing oxygen plasma etching for this purpose. Enhanced friction was observed on the vacancy regions compared with pristine areas of graphite, the origin of which is examined and discussed.

  5. 5 CFR 7.1 - Discretion in filling vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Discretion in filling vacancies. 7.1 Section 7.1 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE RULES GENERAL PROVISIONS... fitness and without regard to political or religious affiliations, marital status, or race....

  6. 77 FR 31631 - Towing Safety Advisory Committee; Vacancies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-29

    ... SECURITY Coast Guard Towing Safety Advisory Committee; Vacancies AGENCY: Coast Guard, DHS. ACTION: Request for applications. SUMMARY: The Coast Guard seeks applications for membership on the Towing Safety... shallow-draft inland and coastal waterway navigation and towing safety. DATES: Applicants should submit...

  7. 77 FR 15784 - Navigation Safety Advisory Council; Vacancies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-16

    ... vessel navigation Rules of the Road, aids to maritime navigation, maritime law, vessel safety, port... SECURITY Coast Guard Navigation Safety Advisory Council; Vacancies AGENCY: Coast Guard, DHS. ACTION... Safety Advisory Council (NAVSAC). NAVSAC provides advice and recommendations to the Secretary of Homeland...

  8. Greatly facilitated oxygen vacancy formation in ceria nanocrystallites.

    PubMed

    Migani, Annapaola; Vayssilov, Georgi N; Bromley, Stefan T; Illas, Francesc; Neyman, Konstantin M

    2010-08-28

    The formation of oxygen vacancies in nanoparticles Ce(n)O(2n) (n < or = 80), studied using density-functional calculations, is found to be greatly facilitated compared to extended surfaces, which explains the observed spectacular reactivity of nanostructured ceria.

  9. 5 CFR 330.707 - Reporting vacancies to OPM.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Reporting vacancies to OPM. 330.707 Section 330.707 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS RECRUITMENT, SELECTION, AND PLACEMENT (GENERAL) Interagency Career Transition Assistance Plan for Displaced...

  10. 78 FR 20684 - Towing Safety Advisory Committee; Vacancies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-05

    ... SECURITY Coast Guard Towing Safety Advisory Committee; Vacancies AGENCY: United States Coast Guard. ACTION: Request for applications. SUMMARY: The United States Coast Guard (the Coast Guard) is requesting... Safety Advisory Committee (TSAC). TSAC advises the Coast Guard on matters relating to shallow-...

  11. 75 FR 49508 - Navigation Safety Advisory Council; Vacancies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-13

    ... SECURITY Coast Guard Navigation Safety Advisory Council; Vacancies AGENCY: Coast Guard, DHS. ACTION: Request for applications. SUMMARY: The Coast Guard seeks applications for membership on the Navigation... ] related to navigation safety such as the prevention of collisions, rammings, and groundings. This...

  12. Interaction mechanism of biomolecules on vacancy defected 2D materials

    NASA Astrophysics Data System (ADS)

    Gürel, Hikmet Hakan; Salmankurt, Bahadır

    2017-02-01

    In this work, we present a first principles study of the adsorption of Adenine which is a nucleobases, Histide and Leucine molecules, which are the amino acids, on vacancy defected single layer materials such as graphene and phosphorene. Among these materials, graphene, which is a single layer honeycomb structure of carbon. Also, phosphorene is recently synthesized by mechanical exfoliation of the black phosphorus. Phosphorene forming a puckered honeycomb structure similar to silicene. However, unlike zero-bandgap graphene and silicene, phosphorene is a direct band gap semiconductor, which makes it very attractive for the nanoelectronic devices. According to the studies, local defects can always exist at any temperature. The most probable defect type is the single vacancy in the single layer honeycomb structures. Vacancy defects can be emerged during growth process and they change the properties of materials significantly. In this study, we show that how to manipulate interaction and binding mechanisms of biomolecules with 2D materials with increased chemical activity by vacancy defects.

  13. Vacancy Interlayer Migration in Multi-layered Graphene

    NASA Astrophysics Data System (ADS)

    Liu, Lili; Gao, Junfeng; Zhang, Xiuyun; Yan, Tianying; Ding, Feng

    2014-03-01

    Graphene has innumerous applications due to its exceptional properties. Various defects that may be introduced into the graphene lattice during synthesis and/or post-treatments are known have significantly impact on these properties. So engineering graphene by introducing or annealing of defects is an important technology to achieve desired properties for various applications. Therefore a comprehensive understanding on the behavior of defects in graphene is critically important. Here, interlayer migration of the vacancies in multi-layered graphene (MLG) was investigated by density functional tight-binding molecular dynamic simulations and first principle calculations. Our study reveals that, although the direct vacancy migration between neighboring graphene layers (NGLs) is prohibited by a very high barrier up to ~ 7 eV, the interaction between vacancies or vacancy and holes in NGLs can greatly reduce the barrier to ~ 3 eV and expedites the migration process. Our study reveals a new mechanism of the defect self-healing in MLG and multi-walled carbon nanotubes and it can be used to engineer desired graphene materials.

  14. Growth of metalloid aluminum clusters on graphene vacancies

    NASA Astrophysics Data System (ADS)

    Alnemrat, Sufian; Mayo, Dennis H.; DeCarlo, Samantha; Hooper, Joseph P.

    2016-01-01

    Ab initio simulations are used to show that graphene vacancy sites may offer a means of templated growth of metalloid aluminum clusters from their monohalide precursors. We present density functional theory and ab initio molecular dynamics simulations of the aluminum halide AlCl interacting with a graphene surface. Unlike a bare Al adatom, AlCl physisorbs weakly on vacancy-free graphene with little charge transfer and no hybridization with carbon orbitals. The barrier for diffusion of AlCl along the surface is negligible. Covalent bonding is seen only with vacancies and results in strong chemisorption and considerable distortion of the nearby lattice. Car-Parrinello molecular dynamics simulations of AlCl liquid around a graphene single vacancy show spontaneous metalloid cluster growth via a process of repeated insertion reactions. This suggests a means of templated cluster nucleation and growth on a carbon substrate and provides some confirmation for the role of a trivalent aluminum species in nucleating a ligated metalloid cluster from AlCl and AlBr solutions.

  15. 78 FR 49544 - Great Lakes Pilotage Advisory Committee; Vacancies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-14

    ... SECURITY Coast Guard Great Lakes Pilotage Advisory Committee; Vacancies AGENCY: Coast Guard, DHS. ACTION: Request for applications. SUMMARY: The Coast Guard seeks applications for membership on the Great Lakes... of Homeland Security and the Coast Guard on matters relating to Great Lakes pilotage, including...

  16. 78 FR 42945 - Health Information Technology Policy Committee Vacancy

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-18

    ... OFFICE Health Information Technology Policy Committee Vacancy AGENCY: Government Accountability Office... Reinvestment Act of 2009 (ARRA) established the Health Information Technology Policy Committee (Health IT.... ARRA requires that one member have expertise in health information privacy and security. Due to a...

  17. 77 FR 39249 - Boston Area Maritime Security Advisory Committee; Vacancies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-02

    ... SECURITY Coast Guard Boston Area Maritime Security Advisory Committee; Vacancies AGENCY: Coast Guard, DHS... the Boston Area Maritime Security Committee (AMSC) to submit their applications for membership, to the...-223-3008. SUPPLEMENTARY INFORMATION: Authority Section 102 of the Maritime Transportation Security...

  18. 75 FR 24961 - Pittsburgh Area Maritime Security Committee; Vacancies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-06

    ... SECURITY Coast Guard Pittsburgh Area Maritime Security Committee; Vacancies AGENCY: Coast Guard, DHS... the Pittsburgh Area Maritime Security Committee (AMSC) to submit their application for membership, to... Security Act (MTSA) of 2002 (Pub. L. 107-295) added section 70112 to Title 46 of the U.S. Code,...

  19. Spin states of the silicon vacancy in silicon carbide

    NASA Astrophysics Data System (ADS)

    Bockstedte, Michel; Schuetz, Felix

    2015-03-01

    SiC as a semi conductor fulfills all necessary requirements1 for implementing qubits via defect electron spins, such as the silicon vacancy, the di-vacancy or a complex of a silicon vacancy and a nitrogen impurity. The spin-selective fluorescence in contrast to the prototypical NV-center in diamond operates in the spectral range favorable for telecom applications.Spin-manipulation of the intrinsic centers was demonstrated even at room temperature.2,3 For the silicon vacancy in SiC inter system crossings (ISCs) from high to yet unknown low spin states govern the spin-relaxation. By DFT and a DFT-based multi-reference Hamiltonian we analyze the spin physics of the defect. In 4H SiC distinct luminescence lines are obtained for the inequivalent defect sites in agreement with experiment. Our result thus establishes an assignment of the lines to the sites. Owing to the spin (S=3/2) and a stronger electron-phonon coupling in the excited state, we find ISCs distinct from the NV-center.

  20. Sustained ferromagnetism induced by H-vacancies in graphane.

    PubMed

    Berashevich, Julia; Chakraborty, Tapash

    2010-09-03

    The electronic and magnetic properties of graphane flakes with H-vacancies were investigated using quantum-chemistry methods. The hybridization of the edges is found to be absolutely crucial in defining the size of the HOMO-LUMO gap, which is increased from 3.04 to 7.51 eV when the hybridization is changed from the sp(2) to the sp(3) type. The H-vacancy defects also influence the size of the gap, which depends on the number of defects and their distribution between the two sides of the graphane plane. Further, the H-vacancy defects induced on one side of the graphane plane and placed on the neighboring carbon atoms are found to be the source of ferromagnetism which is distinguished by the high stability of the state with a large spin number in comparison to that of the singlet state and is expected to persist even at room temperatures. However, the ferromagnetic ordering of the spins is found to be limited by the concentration of H-vacancy defects and ordering would be preserved if number of defects does not exceed eight.