Science.gov

Sample records for bound defect pairs

  1. Double phase slips and bound defect pairs in parametrically driven waves

    SciTech Connect

    Riecke, H.; Granzow, G.D.

    1997-12-31

    Spatio-temporal chaos in parametrically driven waves is investigated in one and two dimensions using numerical simulations of Ginzburg-Landau equations. A regime is identified in which in one dimension the dynamics are due to double phase slips. In very small systems they are found to arise through a Hopf bifurcation off a mixed mode. In large systems they can lead to a state of localized spatio-temporal chaos, which can be understood within the framework of phase dynamics. In two dimensions the double phase slips are replaced by bound defect pairs. Our simulations indicate the possibility of an unbinding transition of these pairs, which is associated with a transition from ordered to disordered defect chaos.

  2. Topological edge states of bound photon pairs

    NASA Astrophysics Data System (ADS)

    Gorlach, Maxim A.; Poddubny, Alexander N.

    2017-05-01

    We predict the existence of interaction-driven edge states of bound two-photon quasiparticles in a dimer periodic array of nonlinear optical cavities. The energy spectrum of photon pairs is dramatically richer than in the noninteracting case or in a simple lattice, featuring collapse and revival of multiple edge and bulk modes as well as edge states in continuum. We link the edge-state existence to the two-photon quantum walk graph connectivity. Our results offer a route to control quantum entanglement and provide insights into the physics of many-body topological states.

  3. Characterizing particle pairs optically bound in "tractor beam"

    NASA Astrophysics Data System (ADS)

    Damková, Jana; Chvátal, LukáÅ.¡; Brzobohatý, Oto; Svak, Vojtěch; Å iler, Martin; Simpson, Stephen; Zemánek, Pavel

    2016-09-01

    We report on an experimental and theoretical study of optical binding of polystyrene sphere pairs illuminated by retro-reflected wide Gaussian beam, so-called "tractor beam". We show that depending on configuration of particle pairs, optically bound structure in the "tractor beam" can be pushed or pulled against the beam propagation. We employ holographic video microscopy to analyse object positions in three dimensions and their time evolution. In such a way, we investigate their dynamics in dependence on the geometrical configuration that is compared with numerical simulations. We observe strong dependence of the particle pair motion on the relative distance of the particles.

  4. Search for bound-state electron+positron pair decay

    NASA Astrophysics Data System (ADS)

    Bosch, F.; Hagmann, S.; Hillenbrand, P.-M.; Lane, G. J.; Litvinov, Yu. A.; Reed, M. W.; Sanjari, M. S.; Stöhlker, Th.; Torilov, S. Yu.; Tu, X. L.; Walke, P. M.

    2016-09-01

    The heavy ion storage rings coupled to in-flight radioactive-ion beam facilities, namely the ability to produce and store for extended periods of time radioactive nuclides in high atomic charge states, for the searchof yet unobserved decay mode - bound-state electron-positron pair decay.

  5. Approaching Tsirelson's Bound in a Photon Pair Experiment

    NASA Astrophysics Data System (ADS)

    Poh, Hou Shun; Joshi, Siddarth K.; Cerè, Alessandro; Cabello, Adán; Kurtsiefer, Christian

    2015-10-01

    We present an experimental test of the Clauser-Horne-Shimony-Holt Bell inequality on photon pairs in a maximally entangled state of polarization in which a value S =2.82759 ±0.00051 is observed. This value comes close to the Tsirelson bound of |S |≤2 √{2 } , with S -2 √{2 }=0.00084 ±0.00051 . It also violates the bound |S |≤2.82537 introduced by Grinbaum by 4.3 standard deviations. This violation allows us to exclude that quantum mechanics is only an effective description of a more fundamental theory.

  6. Synthesizing skyrmion bound pairs in Fe-Gd thin films

    SciTech Connect

    Lee, J. C. T.; Chess, J. J.; Montoya, S. A.; Shi, X.; Tamura, N.; Mishra, S. K.; Fischer, P.; McMorran, B. J.; Sinha, S. K.; Fullerton, E. E.; Kevan, S. D.; Roy, S.

    2016-07-11

    Here, we show that properly engineered amorphous Fe-Gd alloy thin films with perpendicular magnetic anisotropy exhibit bound pairs of like-polarity, opposite helicity skyrmions at room temperature. Magnetic mirror symmetry planes present in the stripe phase, instead of chiral exchange, determine the internal skyrmion structure and the net achirality of the skyrmion phase. Our study shows that stripe domain engineering in amorphous alloy thin films may enable the creation of skyrmion phases with technologically desirable properties.

  7. Synthesizing skyrmion bound pairs in Fe-Gd thin films

    NASA Astrophysics Data System (ADS)

    Lee, J. C. T.; Chess, J. J.; Montoya, S. A.; Shi, X.; Tamura, N.; Mishra, S. K.; Fischer, P.; McMorran, B. J.; Sinha, S. K.; Fullerton, E. E.; Kevan, S. D.; Roy, S.

    2016-07-01

    We show that properly engineered amorphous Fe-Gd alloy thin films with perpendicular magnetic anisotropy exhibit bound pairs of like-polarity, opposite helicity skyrmions at room temperature. Magnetic mirror symmetry planes present in the stripe phase, instead of chiral exchange, determine the internal skyrmion structure and the net achirality of the skyrmion phase. Our study shows that stripe domain engineering in amorphous alloy thin films may enable the creation of skyrmion phases with technologically desirable properties.

  8. Synthesizing skyrmion bound pairs in Fe-Gd thin films

    DOE PAGES

    Lee, J. C. T.; Chess, J. J.; Montoya, S. A.; ...

    2016-07-11

    Here, we show that properly engineered amorphous Fe-Gd alloy thin films with perpendicular magnetic anisotropy exhibit bound pairs of like-polarity, opposite helicity skyrmions at room temperature. Magnetic mirror symmetry planes present in the stripe phase, instead of chiral exchange, determine the internal skyrmion structure and the net achirality of the skyrmion phase. Our study shows that stripe domain engineering in amorphous alloy thin films may enable the creation of skyrmion phases with technologically desirable properties.

  9. Splitting of a Cooper pair by a pair of Majorana bound states.

    PubMed

    Nilsson, Johan; Akhmerov, A R; Beenakker, C W J

    2008-09-19

    We propose a method to probe the nonlocality of a pair of Majorana bound states by crossed Andreev reflection, which is the injection of an electron into one bound state followed by the emission of a hole by the other (equivalent to the splitting of a Cooper pair). We find that, at sufficiently low excitation energies, this nonlocal scattering process dominates over local Andreev reflection involving a single bound state. As a consequence, the low-temperature and low-frequency fluctuations deltaI(i) of currents into the two bound states i=1, 2 are maximally correlated: deltaI_1deltaI_2[over ]=deltaI_i(2).[over ].

  10. Splitting of a Cooper Pair by a Pair of Majorana Bound States

    SciTech Connect

    Nilsson, Johan; Akhmerov, A. R.; Beenakker, C. W. J.

    2008-09-19

    We propose a method to probe the nonlocality of a pair of Majorana bound states by crossed Andreev reflection, which is the injection of an electron into one bound state followed by the emission of a hole by the other (equivalent to the splitting of a Cooper pair). We find that, at sufficiently low excitation energies, this nonlocal scattering process dominates over local Andreev reflection involving a single bound state. As a consequence, the low-temperature and low-frequency fluctuations {delta}I{sub i} of currents into the two bound states i=1, 2 are maximally correlated: {delta}I{sub 1}{delta}I{sub 2}={delta}I{sub i}{sup 2}.

  11. Stochastic dynamics of strongly-bound magnetic vortex pairs

    NASA Astrophysics Data System (ADS)

    Bondarenko, A. V.; Holmgren, E.; Koop, B. C.; Descamps, T.; Ivanov, B. A.; Korenivski, V.

    2017-05-01

    We demonstrate that strongly-bound spin-vortex pairs exhibit pronounced stochastic behaviour. Such dynamics is due to collective magnetization states originating from purely dipolar interactions between the vortices. The resulting thermal noise exhibits telegraph-like behaviour, with random switching between different oscillation regimes observable at room temperature. The noise in the system is further studied by varying the external field and observing the related changes in the frequency of switching and the probability for different magnetic states and regimes. Monte Carlo simulations are used to replicate and explain the experimental observations.

  12. Metastable Frenkel Pair Defect in Graphite: Source of Wigner Energy?

    NASA Astrophysics Data System (ADS)

    Ewels, C. P.; Telling, R. H.; El-Barbary, A. A.; Heggie, M. I.; Briddon, P. R.

    2003-07-01

    The atomic processes associated with energy storage and release in irradiated graphite have long been subject to untested speculation. We examine structures and recombination routes for interstitial-vacancy (I-V) pairs in graphite. Interaction results in the formation of a new metastable defect (an intimate I-V pair) or a Stone-Wales defect. The intimate I-V pair, although 2.9eV more stable than its isolated constituents, still has a formation energy of 10.8eV. The barrier to recombination to perfect graphite is calculated to be 1.3eV, consistent with the experimental first Wigner energy release peak at 1.38eV. We expect similar defects to form in carbon nanostructures such as nanotubes, nested fullerenes, and onions under irradiation.

  13. Su-Schrieffer-Heeger chain with one pair of [Formula: see text]-symmetric defects.

    PubMed

    Jin, L; Wang, P; Song, Z

    2017-07-19

    The topologically nontrivial edge states induce [Formula: see text] transition in Su-Schrieffer-Heeger (SSH) chain with one pair of gain and loss at boundaries. In this study, we investigated a pair of [Formula: see text]-symmetric defects located inside the SSH chain, in particular, the defects locations are at the chain centre. The [Formula: see text] symmetry breaking of the bound states leads to the [Formula: see text] transition, the [Formula: see text]-symmetric phases and the localized states were studied. In the broken [Formula: see text]-symmetric phase, all energy levels break simultaneously in topologically trivial phase; however, two edge states in topologically nontrivial phase are free from the influence of the [Formula: see text]-symmetric defects. We discovered [Formula: see text]-symmetric bound states induced by the [Formula: see text]-symmetric local defects at the SSH chain centre. The [Formula: see text]-symmetric bound states significantly increase the [Formula: see text] transition threshold and coalesce to the topologically protected zero mode with vanishing probabilities on every other site of the left-half chain and the right-half chain, respectively.

  14. Defect pair in the elastic lattice of pancake vortices

    SciTech Connect

    Slutzky, M.; Mints, R.G.; Brandt, E.H.

    1997-07-01

    An additional pancake-antipancake vortex pair is considered in the vortex lattice of layered superconductors. Within linear elastic continuum theory, the relaxation of the background lattice screens the long-range logarithmic interaction of the defect pair, reducing the factor ln(r{sub 0}/{xi}) to ln(a/{xi}) where r{sub 0} is the pair spacing, {xi} the in-plane coherence length, and a the vortex spacing. The finite tilt modulus does not destroy this ideal two-dimensional screening, yielding a small correction {approximately}(a{sup 2}/8{pi}{lambda}{sup 2})ln(r{sub 0}/a), which in principle is of long range, but has a very small prefactor when the vortex spacing a is smaller than the in-plane penetration depth {lambda}. {copyright} {ital 1997} {ital The American Physical Society}

  15. Fermion parity flips and Majorana bound states at twist defects in superconducting fractional topological phases

    NASA Astrophysics Data System (ADS)

    Khan, Mayukh Nilay; Teo, Jeffrey C. Y.; Hughes, Taylor L.; Vishveshwara, Smitha

    2017-05-01

    In this paper, we consider a layered heterostructure of an Abelian topologically ordered state (TO), such as a fractional Chern insulator (FCI)/quantum Hall state (FQH) with an s -wave superconductor in order to explore the existence of non-Abelian defects. To uncover such defects, we note that the ground state corresponds to a charge 2 e Cooper pair, the electron can no longer be treated as a local particle, and hence we must consider a larger TO due to the presence of h /2 e flux vortices, which strictly speaking are not deconfined. Quantum dimension and species of the defects follow directly from the fusion algebra. For FCI/Laughlin states, we show the presence of three kinds of defects, two of which had been previously ignored. They owe their origin to a general anyon permutation symmetry (AS) that exists in any fermionic Abelian TO state in contact with an s -wave superconductor. Physically, this permutation corresponds to adding a fermion to odd flux vortices (in units of h /2 e ) as they travel around the associated topological (twist) defect. As such, we call it a fermion parity flip AS. We show that calculations can be handled more simply, by considering an equivalent fermion parity gauged theory, where the original TO is suitably augmented by a Z2 gauge sector coming from the s -wave SC, but with identical fusion structure. This trick makes our approach useful for analyzing a wide variety of FQH/FCI heterostructures. We give examples of the fermion parity gauging procedure for a large number of hierarchy and spin singlet states. We consider twist defects which mutate anyons according to the fermion parity flip symmetry and show that they can be realized at domain walls between distinct gapped edges or interfaces of the TO superconducting state. We analyze the properties of such defects and show that fermion parity flip twist defects are always associated with Majorana zero modes. When defects corresponding to AS which is a combination of fermion parity

  16. Bound free electron-positron pair production accompanied by giant dipole resonances

    SciTech Connect

    Senguel, M. Y.; Gueclue, M. C.

    2011-01-15

    At the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), for example, virtual photons produce many particles. At small impact parameters where the colliding nuclei make peripheral collisions, photon fluxes are very large and these are responsible for the multiple photonuclear interactions. Free pair productions, bound free pair productions, and nuclear Coulomb excitations are important examples of such interactions, and these processes play important roles in the beam luminosity at RHIC and LHC. Here we obtained the impact parameter dependence of bound free pair production cross sections and by using this probability we obtained bound free electron-positron pair production with nuclear breakup for heavy ion collisions at RHIC and LHC. We also compared our results to the other calculations.

  17. Observation of bound and antibound states of cavity polariton pairs in a CuCl microcavity

    NASA Astrophysics Data System (ADS)

    Matsuura, S.; Mitsumori, Y.; Kosaka, H.; Edamatsu, K.; Miyazaki, K.; Kim, D.; Nakayama, M.; Oohata, G.; Oka, H.; Ajiki, H.; Ishihara, H.

    2014-01-01

    We observed the antibound state, as well as the bound state, for cavity polariton pairs in a planar CuCl microcavity by spectrally resolved four-wave mixing. We obtained dispersion curves of the bound and antibound states by changing the incident angle of the pump pulses corresponding to the cavity detuning. The dispersion curve for the bound state suggests that the bound state is mainly composed of a bare biexciton and is weakly coupled to the cavity photons. The dephasing time of the bound state was faster than that of a bare biexciton in a thin sample, supporting the hypothesis that the bound state is coupled to the cavity photons. On the other hand, the antibound state consists of two lower polaritons having the same spin. The clear observation of the antibound state can be qualitatively explained by the phase-space filling, which reduces the Rabi splitting.

  18. Migration of point defects and a defect pair in zinc oxide using the dimer method

    SciTech Connect

    Chen, Dong; Gao, Fei; Dong, Mingdong; Liu, Bo

    2012-09-24

    The migration mechanism and the minimum energy path of vacancies, interstitials and an interstitial-vacancy pair in zinc oxide have been studied by the dimer method. The in-plane and out-of-plane migrations of zinc and oxygen vacancies are found to be anisotropic. The kick-out mechanism is energetically preferred to zinc and oxygen interstitials that can easily migrate through the ZnO crystal lattice. In addition, the migration process of an interstitial-vacancy pair as a complex of an octahedral oxygen interstitial and a zinc vacancy is dominated by an oxygen interstitial/zinc vacancy successive migration. The energy barriers indicate that the existence of oxygen interstitial in the defect pair can promote the mobility of zinc vacancy, whereas the migration of oxygen interstitial is slowed down due to the presence of zinc vacancy. In the end, we show a possible migration path of the interstitial-vacancy pair that can be dissociated through a set of displacement movements.

  19. Defect structures in liquid crystals bounded by microwrinkles

    NASA Astrophysics Data System (ADS)

    Ohzono, Takuya

    2013-09-01

    Spatially confined liquid crystals (LCs) exhibit non-uniform alignment, often accompanied by self-organized topological defects of non-trivial shape in response to imposed boundary conditions and geometry. Here we show that a nematic LC, when confined in a sinusoidal microwrinkle groove, exhibits a new periodic arrangement of twist deformations and a zigzag line defect. This periodic ordering results from the inherent LC elastic anisotropy and the antagonistic boundary conditions at the top flat LC and the curved LC-groove interfaces. The effect of the LC thickness on the stability of the line defect is also shown.

  20. Quantum information processing in the radical-pair mechanism: Haberkorn's theory violates the Ozawa entropy bound

    NASA Astrophysics Data System (ADS)

    Mouloudakis, K.; Kominis, I. K.

    2017-02-01

    Radical-ion-pair reactions, central for understanding the avian magnetic compass and spin transport in photosynthetic reaction centers, were recently shown to be a fruitful paradigm of the new synthesis of quantum information science with biological processes. We show here that the master equation so far constituting the theoretical foundation of spin chemistry violates fundamental bounds for the entropy of quantum systems, in particular the Ozawa bound. In contrast, a recently developed theory based on quantum measurements, quantum coherence measures, and quantum retrodiction, thus exemplifying the paradigm of quantum biology, satisfies the Ozawa bound as well as the Lanford-Robinson bound on information extraction. By considering Groenewold's information, the quantum information extracted during the reaction, we reproduce the known and unravel other magnetic-field effects not conveyed by reaction yields.

  1. Quantum information processing in the radical-pair mechanism: Haberkorn's theory violates the Ozawa entropy bound.

    PubMed

    Mouloudakis, K; Kominis, I K

    2017-02-01

    Radical-ion-pair reactions, central for understanding the avian magnetic compass and spin transport in photosynthetic reaction centers, were recently shown to be a fruitful paradigm of the new synthesis of quantum information science with biological processes. We show here that the master equation so far constituting the theoretical foundation of spin chemistry violates fundamental bounds for the entropy of quantum systems, in particular the Ozawa bound. In contrast, a recently developed theory based on quantum measurements, quantum coherence measures, and quantum retrodiction, thus exemplifying the paradigm of quantum biology, satisfies the Ozawa bound as well as the Lanford-Robinson bound on information extraction. By considering Groenewold's information, the quantum information extracted during the reaction, we reproduce the known and unravel other magnetic-field effects not conveyed by reaction yields.

  2. Pair creation induced by transitions between electronic and positronic bound states

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Lv, Q. Z.; Li, Y. T.; Grobe, R.; Su, Q.

    2015-05-01

    We study the creation process of electron-positron pairs from the quantum electrodynamical vacuum under very strong electric fields by solving the quantum field theoretical Dirac equation on a space-time grid. We investigate the role of bound-bound state mixing in such a process, which can be studied if the external force can be modeled by a combination of a potential barrier and a potential well. By increasing the magnitude of the two potentials, discrete states that originate from the positive and negative energy continua can become quasidegenerate in the mass gap region (between -mc 2 and mc 2). We show that this bound-bound state mixing is quite different from the usual bound-continuum state mixing where the particles are created until the Pauli exclusion principle inhibits this process. In the case of bound-bound mixing the particle number exhibits a characteristic oscillatory behavior that in principle can last forever. These findings can be modeled by an effective two-state model.

  3. Defect pair separation as the controlling step in homogeneous ice melting.

    PubMed

    Mochizuki, Kenji; Matsumoto, Masakazu; Ohmine, Iwao

    2013-06-20

    On being heated, ice melts into liquid water. Although in practice this process tends to be heterogeneous, it can occur homogeneously inside bulk ice. The thermally induced homogeneous melting of solids is fairly well understood, and involves the formation and growth of melting nuclei. But in the case of water, resilient hydrogen bonds render ice melting more complex. We know that the first defects appearing during homogeneous ice melting are pairs of five- and seven-membered rings, which appear and disappear repeatedly and randomly in space and time in the crystalline ice structure. However, the accumulation of these defects to form an aggregate is nearly additive in energy, and results in a steep free energy increase that suppresses further growth. Here we report molecular dynamics simulations of homogeneous ice melting that identify as a crucial first step not the formation but rather the spatial separation of a defect pair. We find that once it is separated, the defect pair--either an interstitial (I) and a vacancy (V) defect pair (a Frenkel pair), or an L and a D defect pair (a Bjerrum pair)--is entropically stabilized, or 'entangled'. In this state, defects with threefold hydrogen-bond coordination persist and grow, and thereby prepare the system for subsequent rapid melting.

  4. Investigation of bound states and transmission across orderly arranged pairs of attractive and repulsive delta potentials

    NASA Astrophysics Data System (ADS)

    Dharani, M.; Shastry, C. S.

    2017-07-01

    The pattern of bands generated by the transmission coefficient T for transmission across N ionic molecules in one dimension simulated by N alternating pairs of attractive and repulsive delta potential is studied by exploring its relation with the conditions for the occurence of threshold bound state. The number of peaks in the first band of T is found to be the difference between N and the number of negative energy bound states generated by this potential. Further we systematically study the nature of distribution of peaks in higher bands as a function of potential strength and distance parameters and compare it with the results obtained in our earlier works.

  5. Bound-free electron-positron pair production in relativistic heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Şengül, M. Y.; Güçlü, M. C.; Fritzsche, S.

    2009-10-01

    The bound-free electron-positron pair production is considered for relativistic heavy ion collisions. In particular, cross sections are calculated for the pair production with the simultaneous capture of the electron into the 1s ground state of one of the ions and for energies that are relevant for the relativistic heavy ion collider and the large hadron colliders. In the framework of perturbation theory, we applied Monte Carlo integration techniques to compute the lowest-order Feynman diagrams amplitudes by using Darwin wave functions for the bound states of the electrons and Sommerfeld-Maue wave functions for the continuum states of the positrons. Calculations were performed especially for the collision of Au+Au at 100 GeV/nucleon and Pb+Pb at 3400 GeV/nucleon.

  6. Lowest optical excitations in molecular crystals: bound excitons versus free electron-hole pairs in anthracene.

    PubMed

    Hummer, Kerstin; Puschnig, Peter; Ambrosch-Draxl, Claudia

    2004-04-09

    By solving the Bethe-Salpeter equation for the electron-hole Green function for crystalline anthracene we find the lowest absorption peak generated by strongly bound excitons or by a free electron-hole pair, depending on the polarization direction being parallel to the short or the long molecular axis, respectively. Both excitations are shifted to lower energies by pressure. The physical difference of these excitations is apparent from the electron-hole wave functions. Our findings are a major contribution to solve the long-standing puzzle about the nature of the lowest optical excitations in organic materials.

  7. Long range coupling between defect centres in inorganic nanostructures: Valence alternation pairs in nanoscale silica

    NASA Astrophysics Data System (ADS)

    Zwijnenburg, M. A.; Illas, F.; Bromley, S. T.

    2012-10-01

    Valence alternation pair (VAP) states are formed by a closed-shell combination of two space- and charge-separated topological defect centres. These pairs of defects, although historically invoked to explain the electronic properties of bulk inorganic glassy materials (e.g., amorphous silicon dioxide) via the concept of negative-U defects, have more recently been found in a number of theoretical studies of silica surfaces and nanoscale silica clusters. Using density functional theory we systematically probe the structure and internal stability of VAPs in a number of silica nanoclusters with respect to the separation of the two constituent defect centres. We find that VAP states in nanosilica are strongly stabilised by the attractive electrostatic interaction between their separated oppositely charged component defects such that VAPs can persist up to an internal separation of a least 1.5 nanometres. Beyond this distance VAPs become unstable with respect to an open-shell combination of topological defects, virtually indistinguishable from two isolated open-shell defect centres. Finally, we theoretically analyse the possibility of experimental observation of VAP states through their infra-red vibrational spectra.

  8. Transport properties of paired Majorana bound states in a parallel junction

    NASA Astrophysics Data System (ADS)

    Jiang, Cui; Gong, W. J.; Zheng, Yi-Song

    2013-12-01

    The transport properties of a paired Majorana bound states (MBSs) in a parallel junction are theoretically investigated, by considering the influence of different MBS-lead coupling manners, i.e., left-right asymmetric coupling, upper-down asymmetric coupling, and left-right upper-down asymmetric coupling. The calculation results show that the MBS-lead coupling manners affect the transport properties in a substantial way. For the former two configurations, the shot noise Fano factor in the zero-bias limit is related to the value of the conductance maximum with F0=1+1/2Tmax (conductance G =e/2hT). When both the left-right and upper-down symmetries are broken, such a relation is modified into F0=1-12/T0. These results will be helpful for describing the transport characteristics of the junction with MBSs.

  9. Topological Defects in Topological Insulators and Bound States at Topological Superconductor Vortices.

    PubMed

    Parente, Vincenzo; Campagnano, Gabriele; Giuliano, Domenico; Tagliacozzo, Arturo; Guinea, Francisco

    2014-03-04

    The scattering of Dirac electrons by topological defects could be one of the most relevant sources of resistance in graphene and at the boundary surfaces of a three-dimensional topological insulator (3D TI). In the long wavelength, continuous limit of the Dirac equation, the topological defect can be described as a distortion of the metric in curved space, which can be accounted for by a rotation of the Gamma matrices and by a spin connection inherited with the curvature. These features modify the scattering properties of the carriers. We discuss the self-energy of defect formation with this approach and the electron cross-section for intra-valley scattering at an edge dislocation in graphene, including corrections coming from the local stress. The cross-section contribution to the resistivity, ρ, is derived within the Boltzmann theory of transport. On the same lines, we discuss the scattering of a screw dislocation in a two-band 3D TI, like Bi1-xSbx, and we present the analytical simplified form of the wavefunction for gapless helical states bound at the defect. When a 3D TI is sandwiched between two even-parity superconductors, Dirac boundary states acquire superconductive correlations by proximity. In the presence of a magnetic vortex piercing the heterostructure, two Majorana states are localized at the two interfaces and bound to the vortex core. They have a half integer total angular momentum each, to match with the unitary orbital angular momentum of the vortex charge.

  10. Rare-earth defect pairs in GaN: LDA+U calculations

    NASA Astrophysics Data System (ADS)

    Sanna, Simone; Schmidt, W. G.; Frauenheim, Th.; Gerstmann, U.

    2009-09-01

    The structural and electronic properties of rare-earth (RE) (Eu, Er, and Tm) related defect pairs in GaN have been investigated theoretically. Based on LDA+U total-energy calculations, their possible role in the luminescence process is discussed. In all charge states, the lanthanides show a strong preference for the Ga-lattice site, either as isolated substitutional or complexed with intrinsic defects. With respect to the electronic valence, a proper description of correlation effects of the strongly localized 4f electrons is shown to be crucial, especially if the REGa is paired with donors like the Ga interstitial or the N vacancy. The pairs formed by REGa substitutionals and vacancies or interstitials lower the symmetry and are found to locally distort the environment. By this, they are quite effective in relaxing the selection rules for the luminescent intra- 4f -shell transitions. While for n -type GaN, the next-nearest-neighbor pair REGaVGa pair is energetically favored, for p -type GaN, the REGaVN pair provides the most stable configuration and introduces shallow levels close to the conduction band, which can act as assistant levels in the luminescence process.

  11. Possible s±-wave pairing evidenced by midgap surface bound states in Fe-pnictide superconductors

    NASA Astrophysics Data System (ADS)

    Liu, C. S.; Chang, J. Y.; Wu, W. C.; Mou, Chung-Yu

    2013-09-01

    A phenomenological theory of tunneling spectroscopy for Fe-pnictide superconductors is developed by taking into consideration asymmetric interface scattering between particle and holes. It is shown that, consistent with anti-phase s±-wave pairing, appreciable zero-energy surface bound states exist on the [100] surface of Fe-pnictide superconductors. However, in contrast to the [110] bound states in d-wave cuprate superconductors, these bound states arise as a result of non-conservation of momentum perpendicular to the interface for tunneling electrons and the s± pairing, and hence they can only exist in a small window (∼ ± 6∘) in the orientation of edges near the [100] direction. Our results explain why a zero-bias conductance peak is often observed in tunneling spectroscopy and why, when it disappears, two coherent peaks show up. These results provide unambiguous signals to test for possible s±-wave pairing in Fe-pnictide superconductors.

  12. Spin-pairing correlations and spin polarization of Majorana bound states in two-dimensional topological-insulator systems

    NASA Astrophysics Data System (ADS)

    Zhang, Kunhua; Zeng, Junjie; Ren, Yafei; Qiao, Zhenhua

    2017-08-01

    We demonstrate that a zero-energy Majorana bound state in a ferromagnetic insulator (FI)-superconductor (SC) junction formed on the edge of a two-dimensional topological insulator exhibits three types of spin-triplet pairing correlations, its spin-polarization direction is position independent in a ferromagnetic insulator, and demonstrates a spin-helix structure in a superconductor. These spin properties of Majorana bound states lead to anomalous selective equal-spin Andreev reflection. Similar behavior is found when the coupling between two Majorana bound states in a FI-SC-FI junction is invoked, though an additional weak spin-singlet pairing correlation is generated. These signatures can readily facilitate the experimental detection of spin-triplet correlations and spin polarization of Majorana bound states.

  13. Self-organised criticality in base-pair breathing in DNA with a defect

    NASA Astrophysics Data System (ADS)

    Duduială, Ciprian-Ionuţ; Wattis, Jonathan A. D.; Laughton, Charles A.

    2011-08-01

    We analyse base-pair breathing in a DNA sequence of 12 base-pairs with a defective base at its centre. We use both all-atom molecular dynamics (MD) simulations and a system of stochastic differential equations (SDEs). In both cases, Fourier analysis of the trajectories reveals self-organised critical behaviour in the breathing of base-pairs. The Fourier Transforms (FTs) of the inter-base distances show power-law behaviour with gradients close to -1. The scale-invariant behaviour we have found provides evidence for the view that base-pair breathing corresponds to the nucleation stage of large-scale DNA opening (or ‘melting’) and that this process is a (second-order) phase transition. Although the random forces in our SDE system were introduced as white noise, FTs of the displacements exhibit pink noise, as do the displacements in the AMBER/MD simulations.

  14. Repulsive bound-atom pairs in an optical lattice with two-body interaction of nearest neighbors

    SciTech Connect

    Wang, Y.-M.; Liang, J.-Q.

    2010-04-15

    Repulsively interacting particles in a periodic potential can form bound composite objects with long lifetimes, as has been observed experimentally [Winkler et al., Nature (London) 441, 853 (2006)]. In this paper, a complete two-particle solution of one-dimensional periodical potential was derived in a strong interaction regime, where the on-site approximation of a two-body interaction in the Bose-Hubbard model (BHM) is extended to include the interaction of nearest neighbors, which results in atom-pair hopping. The energy spectrum of the bound pair is drastically reshaped due to the pair-hopping term, and complex eigenenergy corresponding to metastable states is also found that has not been discovered in the usual BHM. When the absolute value of a center-of-mass quasimomentum wave vector is greater than a critical value (|K|>K{sub c}), two bound-pair solutions are found. Furthermore, the spatial and momentum distributions of the bound pair displays a crossover from dark to bright soliton-like solutions in the extended BHM. Our results reduce to that of the usual BHM in the weak interaction case.

  15. Photoinduced small polarons bound to hydrogen defects in rutile TiO2

    NASA Astrophysics Data System (ADS)

    Hupfer, A.; Vines, L.; Monakhov, E. V.; Svensson, B. G.; Herklotz, F.

    2017-08-01

    Photoinduced absorption in rutile TiO2 has been studied by means of Fourier transform infrared spectroscopy. It is shown that near-band-gap illumination results in a charge-state transition of a hydrogen defect with an O-H stretch mode at 3500 cm-1, as evidenced by the appearance of an anticorrelated vibrational mode with a blueshift of ˜1.3 cm-1 . The charge-state transition is accompanied by a broad near-infrared absorption band with maximum intensity at ˜7000 cm-1 . Our data on both the photoinduced vibrational mode and the near-infrared absorption can be conclusively explained in the framework of a model of small electron polarons bound to a Ti atom adjacent to the O-H group of the hydrogen defect.

  16. Topological Defects in Topological Insulators and Bound States at Topological Superconductor Vortices

    PubMed Central

    Parente, Vincenzo; Campagnano, Gabriele; Giuliano, Domenico; Tagliacozzo, Arturo; Guinea, Francisco

    2014-01-01

    The scattering of Dirac electrons by topological defects could be one of the most relevant sources of resistance in graphene and at the boundary surfaces of a three-dimensional topological insulator (3D TI). In the long wavelength, continuous limit of the Dirac equation, the topological defect can be described as a distortion of the metric in curved space, which can be accounted for by a rotation of the Gamma matrices and by a spin connection inherited with the curvature. These features modify the scattering properties of the carriers. We discuss the self-energy of defect formation with this approach and the electron cross-section for intra-valley scattering at an edge dislocation in graphene, including corrections coming from the local stress. The cross-section contribution to the resistivity, ρ, is derived within the Boltzmann theory of transport. On the same lines, we discuss the scattering of a screw dislocation in a two-band 3D TI, like Bi1−xSbx, and we present the analytical simplified form of the wavefunction for gapless helical states bound at the defect. When a 3D TI is sandwiched between two even-parity superconductors, Dirac boundary states acquire superconductive correlations by proximity. In the presence of a magnetic vortex piercing the heterostructure, two Majorana states are localized at the two interfaces and bound to the vortex core. They have a half integer total angular momentum each, to match with the unitary orbital angular momentum of the vortex charge. PMID:28788537

  17. Dark-polariton bound pairs in the modified Jaynes-Cummings-Hubbard model

    NASA Astrophysics Data System (ADS)

    Maggitti, A.; Radonjić, M.; Jelenković, B. M.

    2016-01-01

    We investigate a one-dimensional modified Jaynes-Cummings-Hubbard chain of N identical QED cavities with nearest-neighbor photon tunneling and periodic boundary conditions. Each cavity contains an embedded three-level atom which is coupled to a cavity mode and an external classical control field. In the case of two excitations and common large detuning of two Raman-resonant fields, we show the emergence of two different species of dark-polariton bound pairs (DPBPs) that are mutually localized in their relative spatial coordinates. Due to the high degree of controllability, we show the appearance of either one or two DPBPs, having the energies within the energy gaps between three bands of mutually delocalized eigenstates. Interestingly, in a different parameter regime with negatively detuned Raman fields, we find that the ground state of the system is a DPBP which can be utilized for the photon storage, retrieval, and controllable state preparation. Moreover, we propose an experimental realization of our model system.

  18. Research on dynamics and fault mechanism of spur gear pair with spalling defect

    NASA Astrophysics Data System (ADS)

    Ma, Rui; Chen, Yushu; Cao, Qingjie

    2012-04-01

    This study focuses on the nonlinear dynamic and vibration characteristics of spur gear pair with local spalling defect to explore the spalling mechanism. The dynamic model of the gear pair with spalling defect and time-variant mesh stiffness is established to investigate the effect of spalling defect on mesh stiffness and dynamic response. The analytical solutions of the system which is deduced into four different stages of the gear with the time-variant stiffness in a mesh period are obtained. The dynamic responses with the evolvement of sapll are analyzed by using time history, phase contrail, Poincaré section and spectrum analysis. The spalling characteristics are also evaluated by employing statistical techniques, which shows that the spalling failure is suitable to be detected under low velocity and small excitation. The gearbox with spalling defect is designed and the experiments are carried out to get the dynamic characteristics of the spalling vibration signals. The results obtained herein show the good agreement qualitatively with the theoretical analysis, which provides a theoretical basis to spalling fault diagnosis of gearbox.

  19. Excitons Bound to Nitrogen Pairs in GaAs as Seen by Photoluminescence of High Spectral and Spatial Resolution

    SciTech Connect

    Karaiskaj, D.; Mascarenhas, A.; Klem, J. F.; Volz, K.; Stolz, W.; Adamcyk, M.; Tiedje, T.

    2007-01-01

    High resolution photoluminescence (PL) spectroscopy was performed on high quality bulk GaAs, lightly doped with the nitrogen isoelectronic impurity. The shallowest nitrogen pair bound exciton center labeled as X{sub 1} revealed a total of six transitions. The photoluminescence lines from a small ensemble of nitrogen centers showed polarization dependent intensity. High spectral resolution PL spectroscopy was combined with confocal spectroscopy experiments performed on a GaAs:N/AlGaAs heterostructure. The high spatial resolution achieved by this technique enables us to localize and examine individual nitrogen bound excitons. Similar spectral structure and polarization dependence was observed for individual N-pair centers in GaAs. Both techniques support the C{sub 2v} symmetry of such isoelectronic impurity centers. The comparison between the PL spectra from an ensemble of nitrogen pairs and individual centers demonstrate the ability of the single impurity technique to lift the orientational degeneracy.

  20. Andreev bound States as a phase-sensitive probe of the pairing symmetry of the iron pnictide superconductors.

    PubMed

    Ghaemi, Pouyan; Wang, Fa; Vishwanath, Ashvin

    2009-04-17

    A leading contender for the pairing symmetry in the Fe pnictide high-temperature superconductors is extended s wave s_{+/-}, a nodeless state in which the pairing changes sign between Fermi surfaces. Verifying such a pairing symmetry requires a special phase-sensitive probe that is also momentum selective. We show that the sign structure of s_{+/-} pairing can lead to surface Andreev bound states (ABS) at the sample edge. In the clean limit they only occur when the edge is along the nearest neighbor Fe-Fe bond, but not for a diagonal edge or a surface orthogonal to the c axis. In contrast to d-wave ABS, they are not at zero energy and, in general, do not produce a zero bias tunneling peak. Consequences for tunneling measurements are derived, within a simplified two-band model and also for a more realistic five-band model. In both cases, surface ABS are obtained.

  1. Local structure investigation of oxide ion and proton defects in Ge-apatites by pair distribution function analysis.

    PubMed

    Malavasi, Lorenzo; Orera, Alodia; Slater, Peter R; Panchmatia, Pooja M; Islam, M Saiful; Siewenie, Joan

    2011-01-07

    In this communication we provide a direct insight into the local structure and defects of oxygen excess Ge-apatites, in both dry and deuterated states, by means of pair distribution function analysis.

  2. Feshbach resonances and weakly bound molecular states of boson-boson and boson-fermion NaK pairs

    NASA Astrophysics Data System (ADS)

    Viel, Alexandra; Simoni, Andrea

    2016-04-01

    We conduct a theoretical study of magnetically induced Feshbach resonances and near-threshold bound states in isotopic NaK pairs. Our calculations accurately reproduce Feshbach spectroscopy data on Na 40K and explain the origin of the observed multiplets in the p wave [Phys. Rev. A 85, 051602(R) (2012), 10.1103/PhysRevA.85.051602]. We apply the model to predict scattering and bound state threshold properties of the boson-boson Na 39K and Na 41K systems. We find that the Na 39K isotopic pair presents broad magnetic Feshbach resonances and favorable ground-state features for producing nonreactive polar molecules by two-photon association. Broad s -wave resonances are also predicted for Na 41K collisions.

  3. Robust zero-energy bound states around a pair-density-wave vortex core in locally noncentrosymmetric superconductors

    NASA Astrophysics Data System (ADS)

    Higashi, Yoichi; Nagai, Yuki; Yoshida, Tomohiro; Masaki, Yusuke; Yanase, Youichi

    2016-03-01

    We numerically investigate the electronic structures around a vortex core in a bilayer superconducting system, with s -wave pairing, Rashba spin-orbit coupling, and Zeeman magnetic field, with the use of the quasiclassical Green's function method. The BCS phase and the so-called pair-density-wave (PDW) phase appear in the temperature-magnetic-field phase diagram in a bulk uniform system [T. Yoshida et al., Phys. Rev. B 86, 134514 (2012), 10.1103/PhysRevB.86.134514]. In the low magnetic field perpendicular to the layers, the zero-energy vortex bound states in the BCS phase are split by the Zeeman magnetic field. On the other hand, the PDW state appears in the high magnetic field, and the sign of the order parameter is opposite between the layers. We find that the vortex core suddenly shrinks and the zero-energy bound states appear by increasing the magnetic field through the BCS-PDW transition. We discuss the origin of the change in the vortex-core structure between the BCS and PDW states by clarifying the relation between the vortex bound states and the bulk energy spectra. In the high-magnetic-field region, the PDW state and vortex bound states are protected by the spin-orbit coupling. These characteristic behaviors in the PDW state can be observed by scanning tunneling microscopy/spectroscopy.

  4. Simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 using four-wave mixing spectroscopy.

    PubMed

    March, Samuel A; Clegg, Charlotte; Riley, Drew B; Webber, Daniel; Hill, Ian G; Hall, Kimberley C

    2016-12-15

    Solar cells incorporating organic-inorganic perovskite, which may be fabricated using low-cost solution-based processing, have witnessed a dramatic rise in efficiencies yet their fundamental photophysical properties are not well understood. The exciton binding energy, central to the charge collection process, has been the subject of considerable controversy due to subtleties in extracting it from conventional linear spectroscopy techniques due to strong broadening tied to disorder. Here we report the simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 films using four-wave mixing (FWM) spectroscopy. Due to the high sensitivity of FWM to excitons, tied to their longer coherence decay times than unbound electron- hole pairs, we show that the exciton resonance energies can be directly observed from the nonlinear optical spectra. Our results indicate low-temperature binding energies of 13 meV (29 meV) for the free (defect-bound) exciton, with the 16 meV localization energy for excitons attributed to binding to point defects. Our findings shed light on the wide range of binding energies (2-55 meV) reported in recent years.

  5. Simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 using four-wave mixing spectroscopy

    PubMed Central

    March, Samuel A.; Clegg, Charlotte; Riley, Drew B.; Webber, Daniel; Hill, Ian G.; Hall, Kimberley C.

    2016-01-01

    Solar cells incorporating organic-inorganic perovskite, which may be fabricated using low-cost solution-based processing, have witnessed a dramatic rise in efficiencies yet their fundamental photophysical properties are not well understood. The exciton binding energy, central to the charge collection process, has been the subject of considerable controversy due to subtleties in extracting it from conventional linear spectroscopy techniques due to strong broadening tied to disorder. Here we report the simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 films using four-wave mixing (FWM) spectroscopy. Due to the high sensitivity of FWM to excitons, tied to their longer coherence decay times than unbound electron- hole pairs, we show that the exciton resonance energies can be directly observed from the nonlinear optical spectra. Our results indicate low-temperature binding energies of 13 meV (29 meV) for the free (defect-bound) exciton, with the 16 meV localization energy for excitons attributed to binding to point defects. Our findings shed light on the wide range of binding energies (2–55 meV) reported in recent years. PMID:27974815

  6. Simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 using four-wave mixing spectroscopy

    NASA Astrophysics Data System (ADS)

    March, Samuel A.; Clegg, Charlotte; Riley, Drew B.; Webber, Daniel; Hill, Ian G.; Hall, Kimberley C.

    2016-12-01

    Solar cells incorporating organic-inorganic perovskite, which may be fabricated using low-cost solution-based processing, have witnessed a dramatic rise in efficiencies yet their fundamental photophysical properties are not well understood. The exciton binding energy, central to the charge collection process, has been the subject of considerable controversy due to subtleties in extracting it from conventional linear spectroscopy techniques due to strong broadening tied to disorder. Here we report the simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 films using four-wave mixing (FWM) spectroscopy. Due to the high sensitivity of FWM to excitons, tied to their longer coherence decay times than unbound electron- hole pairs, we show that the exciton resonance energies can be directly observed from the nonlinear optical spectra. Our results indicate low-temperature binding energies of 13 meV (29 meV) for the free (defect-bound) exciton, with the 16 meV localization energy for excitons attributed to binding to point defects. Our findings shed light on the wide range of binding energies (2–55 meV) reported in recent years.

  7. Enhancement of electron-positron pair creation due to transient excitation of field-induced bound states

    NASA Astrophysics Data System (ADS)

    Jiang, M.; Lv, Q. Z.; Sheng, Z. M.; Grobe, R.; Su, Q.

    2013-04-01

    We study the creation of electron-positron pairs induced by two spatially separated electric fields that vary periodically in time. The results are based on large-scale computer simulations of the time-dependent Dirac equation in reduced spatial dimensions. When the separation of the fields is very large, the pair creation is caused by multiphoton transitions and mainly determined by the frequency of the fields. However, for small spatial separations a coherence effect can be observed that can enhance or reduce the particle yield compared to the case of two infinitely separated fields. If the travel time for a created electron or positron between both field locations becomes comparable to the period of the oscillating fields, we observe peaks in the energy spectrum which can be explained in terms of field-induced transient bound states.

  8. Fano effect and bound state in continuum in electron transport through an armchair graphene nanoribbon with line defect.

    PubMed

    Gong, Wei-Jiang; Sui, Xiao-Yan; Wang, Yan; Yu, Guo-Dong; Chen, Xiao-Hui

    2013-07-22

    : Electron transport properties in an armchair graphene nanoribbon are theoretically investigated by considering the presence of line defect. It is found that the line defect causes the abundant Fano effects and bound state in continuum (BIC) in the electron transport process, which are tightly dependent on the width of the nanoribbon. By plotting the spectra of the density of electron states of the line defect, we see that the line defect induces some localized quantum states around the Dirac point and that the different localizations of these states lead to these two kinds of transport results. Next, the Fano effect and BIC phenomenon are detailedly described via the analysis about the influence of the structure parameters. According to the numerical results, we propose such a structure to be a promising candidate for graphene nanoswitch. PACS: 81.05.Uw, 71.55.-i, 73.23.-b, 73.25.+i.

  9. Fano effect and bound state in continuum in electron transport through an armchair graphene nanoribbon with line defect

    PubMed Central

    2013-01-01

    Electron transport properties in an armchair graphene nanoribbon are theoretically investigated by considering the presence of line defect. It is found that the line defect causes the abundant Fano effects and bound state in continuum (BIC) in the electron transport process, which are tightly dependent on the width of the nanoribbon. By plotting the spectra of the density of electron states of the line defect, we see that the line defect induces some localized quantum states around the Dirac point and that the different localizations of these states lead to these two kinds of transport results. Next, the Fano effect and BIC phenomenon are detailedly described via the analysis about the influence of the structure parameters. According to the numerical results, we propose such a structure to be a promising candidate for graphene nanoswitch. PACS 81.05.Uw, 71.55.-i, 73.23.-b, 73.25.+i PMID:23870061

  10. Luttinger liquid in contact with a Kramers pair of Majorana bound states

    NASA Astrophysics Data System (ADS)

    Pikulin, Dmitry I.; Komijani, Yashar; Affleck, Ian

    2016-05-01

    We discuss the signatures of a Kramers pair of Majorana modes formed in a Josephson junction on top of a quantum spin Hall system. We show that, while ignoring interactions on the quantum spin Hall edge allows arbitrary Andreev processes in the system, moderate repulsive interactions stabilize Andreev transmission—the hole goes into the opposite lead from where the electron has arrived. We analyze the renormalization group equations and deduce the phase diagram as a function of interaction strength.

  11. Exploiting bounded signal flow for graph orientation based on cause-effect pairs.

    PubMed

    Dorn, Britta; Hüffner, Falk; Krüger, Dominikus; Niedermeier, Rolf; Uhlmann, Johannes

    2011-08-25

    We consider the following problem: Given an undirected network and a set of sender-receiver pairs, direct all edges such that the maximum number of "signal flows" defined by the pairs can be routed respecting edge directions. This problem has applications in understanding protein interaction based cell regulation mechanisms. Since this problem is NP-hard, research so far concentrated on polynomial-time approximation algorithms and tractable special cases. We take the viewpoint of parameterized algorithmics and examine several parameters related to the maximum signal flow over vertices or edges. We provide several fixed-parameter tractability results, and in one case a sharp complexity dichotomy between a linear-time solvable case and a slightly more general NP-hard case. We examine the value of these parameters for several real-world network instances. Several biologically relevant special cases of the NP-hard problem can be solved to optimality. In this way, parameterized analysis yields both deeper insight into the computational complexity and practical solving strategies.

  12. Strain effects on the behavior of isolated and paired sulfur vacancy defects in monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Sensoy, Mehmet Gokhan; Vinichenko, Dmitry; Chen, Wei; Friend, Cynthia M.; Kaxiras, Efthimios

    2017-01-01

    We investigate the behavior of sulfur vacancy defects, the most abundant type of intrinsic defect in monolayer MoS2, using first-principles calculations based on density functional theory. We consider the dependence of the isolated defect formation energy on the charge state and on uniaxial tensile and compressive strain up to 5%. We also consider the possibility of defect clustering by examining the formation energies of pairs of vacancies at various relative positions, and their dependence on charge state and strain. We find that there is no driving force for vacancy clustering, independent of strain in the material. The barrier for diffusion of S vacancies is larger than 1.9 eV in both charged and neutral states regardless of the presence of other nearby vacancies. We conclude that the formation of extended defects from S vacancies in planar monolayer MoS2 is hindered both thermodynamically and kinetically.

  13. Holes bound as small polarons to acceptor defects in oxide materials: why are their thermal ionization energies so high?

    NASA Astrophysics Data System (ADS)

    Schirmer, O. F.

    2011-08-01

    Holes bound to acceptor defects in oxide materials usually need comparatively high energies, of the order of 0.5-1.0 eV, to be ionized thermally to the valence band maximum. It is discussed that this has to be attributed to the stabilization of such holes by mainly short range interactions with the surrounding lattice, leading to the formation of small O - polarons. This is tantamount to the localization of the hole at only one of several equivalent oxygen ions next to the defect. The hole stabilizing energies can be determined experimentally from the related intense optical absorption bands. This paper exploits previous phenomenological studies of bound-hole small polarons in order to account for the large hole stabilization energies on this basis. A compilation demonstrates that bound-hole small polarons occur rather often in oxides and also in some related materials. The identification of such systems is based on EPR and optical studies and also on recent advanced electronic structure calculations.

  14. Defects activated photoluminescence in two-dimensional semiconductors: interplay between bound, charged, and free excitons.

    PubMed

    Tongay, Sefaattin; Suh, Joonki; Ataca, Can; Fan, Wen; Luce, Alexander; Kang, Jeong Seuk; Liu, Jonathan; Ko, Changhyun; Raghunathanan, Rajamani; Zhou, Jian; Ogletree, Frank; Li, Jingbo; Grossman, Jeffrey C; Wu, Junqiao

    2013-01-01

    Point defects in semiconductors can trap free charge carriers and localize excitons. The interaction between these defects and charge carriers becomes stronger at reduced dimensionalities, and is expected to greatly influence physical properties of the hosting material. We investigated effects of anion vacancies in monolayer transition metal dichalcogenides as two-dimensional (2D) semiconductors where the vacancies density is controlled by α-particle irradiation or thermal-annealing. We found a new, sub-bandgap emission peak as well as increase in overall photoluminescence intensity as a result of the vacancy generation. Interestingly, these effects are absent when measured in vacuum. We conclude that in opposite to conventional wisdom, optical quality at room temperature cannot be used as criteria to assess crystal quality of the 2D semiconductors. Our results not only shed light on defect and exciton physics of 2D semiconductors, but also offer a new route toward tailoring optical properties of 2D semiconductors by defect engineering.

  15. Towards building artificial light harvesting complexes: enhanced singlet-singlet energy transfer between donor and acceptor pairs bound to albumins.

    PubMed

    Kumar, Challa V; Duff, Michael R

    2008-12-01

    Specific donor and acceptor pairs have been assembled in bovine serum albumin (BSA), at neutral pH and room temperature, and these dye-protein complexes indicated efficient donor to acceptor singlet-singlet energy transfer. For example, pyrene-1-butyric acid served as the donor and Coumarin 540A served as the acceptor. Both the donor and the acceptor bind to BSA with affinity constants in excess of 2x10(5) M(-1), as measured in absorption and circular dichroism (CD) spectral titrations. Simultaneous binding of both the donor and the acceptor chromophores was supported by CD spectra and one chromophore did not displace the other from the protein host, even when limited concentrations of the host were used. For example, a 1:1:1 complex between the donor, acceptor and the host can be readily formed, and spectral data clearly show that the binding sites are mutually exclusive. The ternary complexes (two different ligands bound to the same protein molecule) provided opportunities to examine singlet-singlet energy transfer between the protein-bound chromophores. Donor emission was quenched by the addition of the acceptor, in the presence of limited amounts of BSA, while no energy transfer was observed in the absence of the protein host, under the same conditions. The excitation spectra of the donor-acceptor-host complexes clearly show the sensitization of acceptor emission by the donor. Protein denaturation, as induced by the addition of urea or increasing the temperature to 360 K, inhibited energy transfer, which indicate that protein structure plays an important role. Sensitization also proceeded at low temperature (77 K) and diffusion of the donor or the acceptor is not required for energy transfer. Stern-Volmer quenching plots show that the quenching constant is (3.1+/-0.2)x10(4) M(-1), at low acceptor concentrations (<35 microM). Other albumins such as human and porcine proteins also served as good hosts for the above experiments. For the first time, non

  16. Defects activated photoluminescence in two-dimensional semiconductors: interplay between bound, charged, and free excitons

    PubMed Central

    Tongay, Sefaattin; Suh, Joonki; Ataca, Can; Fan, Wen; Luce, Alexander; Kang, Jeong Seuk; Liu, Jonathan; Ko, Changhyun; Raghunathanan, Rajamani; Zhou, Jian; Ogletree, Frank; Li, Jingbo; Grossman, Jeffrey C.; Wu, Junqiao

    2013-01-01

    Point defects in semiconductors can trap free charge carriers and localize excitons. The interaction between these defects and charge carriers becomes stronger at reduced dimensionalities, and is expected to greatly influence physical properties of the hosting material. We investigated effects of anion vacancies in monolayer transition metal dichalcogenides as two-dimensional (2D) semiconductors where the vacancies density is controlled by α-particle irradiation or thermal-annealing. We found a new, sub-bandgap emission peak as well as increase in overall photoluminescence intensity as a result of the vacancy generation. Interestingly, these effects are absent when measured in vacuum. We conclude that in opposite to conventional wisdom, optical quality at room temperature cannot be used as criteria to assess crystal quality of the 2D semiconductors. Our results not only shed light on defect and exciton physics of 2D semiconductors, but also offer a new route toward tailoring optical properties of 2D semiconductors by defect engineering. PMID:24029823

  17. Solid frustrated-Lewis-pair catalysts constructed by regulations on surface defects of porous nanorods of CeO2

    PubMed Central

    Zhang, Sai; Huang, Zheng-Qing; Ma, Yuanyuan; Gao, Wei; Li, Jing; Cao, Fangxian; Li, Lin; Chang, Chun-Ran; Qu, Yongquan

    2017-01-01

    Identification on catalytic sites of heterogeneous catalysts at atomic level is important to understand catalytic mechanism. Surface engineering on defects of metal oxides can construct new active sites and regulate catalytic activity and selectivity. Here we outline the strategy by controlling surface defects of nanoceria to create the solid frustrated Lewis pair (FLP) metal oxide for efficient hydrogenation of alkenes and alkynes. Porous nanorods of ceria (PN-CeO2) with a high concentration of surface defects construct new Lewis acidic sites by two adjacent surface Ce3+. The neighbouring surface lattice oxygen as Lewis base and constructed Lewis acid create solid FLP site due to the rigid lattice of ceria, which can easily dissociate H–H bond with low activation energy of 0.17 eV. PMID:28516952

  18. Solid frustrated-Lewis-pair catalysts constructed by regulations on surface defects of porous nanorods of CeO2

    NASA Astrophysics Data System (ADS)

    Zhang, Sai; Huang, Zheng-Qing; Ma, Yuanyuan; Gao, Wei; Li, Jing; Cao, Fangxian; Li, Lin; Chang, Chun-Ran; Qu, Yongquan

    2017-05-01

    Identification on catalytic sites of heterogeneous catalysts at atomic level is important to understand catalytic mechanism. Surface engineering on defects of metal oxides can construct new active sites and regulate catalytic activity and selectivity. Here we outline the strategy by controlling surface defects of nanoceria to create the solid frustrated Lewis pair (FLP) metal oxide for efficient hydrogenation of alkenes and alkynes. Porous nanorods of ceria (PN-CeO2) with a high concentration of surface defects construct new Lewis acidic sites by two adjacent surface Ce3+. The neighbouring surface lattice oxygen as Lewis base and constructed Lewis acid create solid FLP site due to the rigid lattice of ceria, which can easily dissociate H-H bond with low activation energy of 0.17 eV.

  19. Topological defect-phase soliton and the pairing symmetry of a two-band superconductor: role of the proximity effect.

    PubMed

    Vakaryuk, Victor; Stanev, Valentin; Lee, Wei-Cheng; Levchenko, Alex

    2012-11-30

    We suggest a mechanism which promotes the existence of a phase soliton--a topological defect formed in the relative phase of superconducting gaps of a two-band superconductor with s(+-) type of pairing. This mechanism exploits the proximity effect with a conventional s-wave superconductor which favors the alignment of the phases of the two-band superconductor which, in the case of s(+-) pairing, are π shifted in the absence of proximity. In the case of a strong proximity such an effect can be used to reduce the soliton's energy below the energy of a soliton-free state, thus making the soliton thermodynamically stable. Based on this observation we consider an experimental setup, applicable for both stable and metastable solitons, which can be used to distinguish between ss(+-) and s(++) types of pairing in the iron-based multiband superconductors.

  20. Dynamics of a ±1/2 defect pair in a confined geometry: A thin hybrid aligned nematic cell

    NASA Astrophysics Data System (ADS)

    Lu, Li-Xia; Zhang, Zhi-Dong

    2015-02-01

    Confined geometry can change the defect structure and its properties. In this paper, we investigate numerically the dynamics of a dipole of ±1/2 parallel wedge disclination lines in a confined geometry: a thin hybrid aligned nematic (HAN) cell, based on the Landau-de Gennes theory. When the cell gap d is larger than a critical value of 12ξ (where ξ is the characteristic length for order-parameter change), the pair annihilates. A pure HAN configuration without defect is formed in an equilibrium state. In the confined geometry of d ≤ 12ξ, the diffusion process is discovered for the first time and an eigenvalue exchange configuration is formed in an equilibrium state. The eigenvalue exchange configuration is induced by different essential reasons. When 10ξ < d ≤ 12ξ, the two defects coalesce and annihilate. The biaxial wall is created by the inhomogeneous distortion of the director, which results in the eigenvalue exchange configuration. When d ≤ 10ξ, the defects do not collide and the eigenvalue exchange configuration originates from the biaxial seeds concentrated at the defects. Project supported by the National Natural Science Foundation of China (Grant No. 11374087) and the Key Subject Construction Project of Hebei Province University.

  1. Application of the bounds-analysis approach to arsenic and gallium antisite defects in gallium arsenide

    DOE PAGES

    Wright, A. F.; Modine, N. A.

    2015-01-23

    The As antisite in GaAs (AsGa) has been the subject of numerous experimental and theoretical studies. Recent density-functional-theory (DFT) studies report results in good agreement with experimental data for the +2, +1, and 0 charge states of the stable EL2 structure, the 0 charge state of the metastable EL2* structure, and the activation energy to transform from EL2* to EL2 in the 0 charge state. However, these studies did not report results for EL2* in the -1 charge state. In this paper, we report new DFT results for the +2, +1, 0, and -1 charge states of AsGa, obtained usingmore » a semilocal exchange-correlation functional and interpreted using a bounds-analysis approach. In good agreement with experimental data, we find a -1/0 EL2* level 0.06 eV below the conduction-band edge and an activation energy of 0.05 eV to transform from EL2* to EL2 in the -1 charge state. While the Ga antisite in GaAs (GaAs) has not been studied as extensively as AsGa, experimental studies report three charge states (-2, -1, 0) and two levels (-2/-1, -1/0) close to the valence-band edge. Recent DFT studies report the same charge states, but the levels are found to be well-separated from the valence-band edge. To resolve this disagreement, we performed new DFT calculations for GaAs and interpreted them using a bounds analysis. The analysis identified the -1 and 0 charge states as hole states weakly bound to a highly-localized -2 charge state. Moreover, the -2/-1, -1/0 levels were found to be near the valence-band edge, in good agreement with the experimental data.« less

  2. Application of the bounds-analysis approach to arsenic and gallium antisite defects in gallium arsenide

    SciTech Connect

    Wright, A. F.; Modine, N. A.

    2015-01-23

    The As antisite in GaAs (AsGa) has been the subject of numerous experimental and theoretical studies. Recent density-functional-theory (DFT) studies report results in good agreement with experimental data for the +2, +1, and 0 charge states of the stable EL2 structure, the 0 charge state of the metastable EL2* structure, and the activation energy to transform from EL2* to EL2 in the 0 charge state. However, these studies did not report results for EL2* in the -1 charge state. In this paper, we report new DFT results for the +2, +1, 0, and -1 charge states of AsGa, obtained using a semilocal exchange-correlation functional and interpreted using a bounds-analysis approach. In good agreement with experimental data, we find a -1/0 EL2* level 0.06 eV below the conduction-band edge and an activation energy of 0.05 eV to transform from EL2* to EL2 in the -1 charge state. While the Ga antisite in GaAs (GaAs) has not been studied as extensively as AsGa, experimental studies report three charge states (-2, -1, 0) and two levels (-2/-1, -1/0) close to the valence-band edge. Recent DFT studies report the same charge states, but the levels are found to be well-separated from the valence-band edge. To resolve this disagreement, we performed new DFT calculations for GaAs and interpreted them using a bounds analysis. The analysis identified the -1 and 0 charge states as hole states weakly bound to a highly-localized -2 charge state. Moreover, the -2/-1, -1/0 levels were found to be near the valence-band edge, in good agreement with the experimental data.

  3. Quasiparticle Scattering off Defects and Possible Bound States in Charge-Ordered YBa2 Cu3 Oy

    NASA Astrophysics Data System (ADS)

    Zhou, R.; Hirata, M.; Wu, T.; Vinograd, I.; Mayaffre, H.; Krämer, S.; Horvatić, M.; Berthier, C.; Reyes, A. P.; Kuhns, P. L.; Liang, R.; Hardy, W. N.; Bonn, D. A.; Julien, M.-H.

    2017-01-01

    We report the NMR observation of a skewed distribution of 17O Knight shifts when a magnetic field quenches superconductivity and induces long-range charge-density-wave (CDW) order in YBa2Cu3Oy . This distribution is explained by an inhomogeneous pattern of the local density of states N (EF) arising from quasiparticle scattering off, yet unidentified, defects in the CDW state. We argue that the effect is most likely related to the formation of quasiparticle bound states, as is known to occur, under specific circumstances, in some metals and superconductors (but not in the CDW state, in general, except for very few cases in 1D materials). These observations should provide insight into the microscopic nature of the CDW, especially regarding the reconstructed band structure and the sensitivity to disorder.

  4. First-principles calculations of momentum distributions of annihilating electron-positron pairs in defects in UO2

    NASA Astrophysics Data System (ADS)

    Wiktor, Julia; Jomard, Gérald; Torrent, Marc; Bertolus, Marjorie

    2017-01-01

    We performed first-principles calculations of the momentum distributions of annihilating electron-positron pairs in vacancies in uranium dioxide. Full atomic relaxation effects (due to both electronic and positronic forces) were taken into account and self-consistent two-component density functional theory schemes were used. We present one-dimensional momentum distributions (Doppler-broadened annihilation radiation line shapes) along with line-shape parameters S and W. We studied the effect of the charge state of the defect on the Doppler spectra. The effect of krypton incorporation in the vacancy was also considered and it was shown that it should be possible to observe the fission gas incorporation in defects in UO2 using positron annihilation spectroscopy. We suggest that the Doppler broadening measurements can be especially useful for studying impurities and dopants in UO2 and of mixed actinide oxides.

  5. Base-pairing energies of proton-bound heterodimers of cytosine and modified cytosines: implications for the stability of DNA i-motif conformations.

    PubMed

    Yang, Bo; Rodgers, M T

    2014-01-08

    The DNA i-motif conformation was discovered in (CCG)•(CGG)n trinucleotide repeats, which are associated with fragile X syndrome, the most widespread inherited cause of mental retardation in humans. The DNA i-motif is a four-stranded structure whose strands are held together by proton-bound dimers of cytosine (C(+)•C). The stronger base-pairing interactions in C(+)•C proton-bound dimers as compared to Watson-Crick G•C base pairs are the major forces responsible for stabilization of i-motif conformations. Methylation of cytosine results in silencing of the FMR1 gene and causes fragile X syndrome. However, the influence of methylation or other modifications such as halogenation of cytosine on the base-pairing energies (BPEs) in the i-motif remains elusive. To address this, proton-bound heterodimers of cytosine and 5-methylcytosine, 5-fluorocytosine, 5-bromocytosine, and 5-iodocytosine are probed in detail. Experimentally, the BPEs of proton-bound heterodimers of cytosine and modified cytosines are determined using threshold collision-induced dissociation (TCID) techniques. All modifications at the 5-position of cytosine are found to lower the BPE and therefore would tend to destabilize DNA i-motif conformations. However, the BPEs in these proton-bound heterodimers still significantly exceed those of the Watson-Crick G•C and neutral C•C base pairs, suggesting that C(+)•C mismatches are still energetically favored such that i-motif conformations are preserved. Excellent agreement between TCID measured BPEs and B3LYP calculated values is found with the def2-TZVPPD and 6-311+G(2d,2p) basis sets, suggesting that calculations at these levels of theory can be employed to provide reliable energetic predictions for related systems.

  6. Defective pairing and synaptonemal complex formation in a Sordaria mutant (spo44) with a translocated segment of the nucleolar organizer.

    PubMed

    Zickler, D; de Lares, L; Moreau, P J; Leblon, G

    1985-01-01

    The recessive meiotic mutant spo44 of Sordaria macrospora, with 90% ascospore abortion, exhibits striking effects on recombination (67% decrease), irregular segregation of the almost unpaired homologues, and a decrease in chiasma frequency in the few cases where bivalents are formed. Three-dimensional reconstructions of ten prophase nuclei indicate that pairing, as judged by the absence of fully formed synaptonemal complexes (SC), is not achieved although lateral elements (LE) assemble. The pairing failure is attributable to defects in the alignment of homologous chromosomes. The leptotene alignment seen in the wild type before SC formation was not observed in the spo44 nuclei. Dense material, considered to be precursor of SC central elements, was found scattered among the LE in two nuclei. The behaviour of spo44 substantiates the hypothesis that chromosome matching and SC formation are separable events. - The total length of the LE in the mutant is the same as in the wild type, but due to variable numbers and length of the individual LE, homologues cannot be lined up. Light microscopic observations indicate that the irregular length and number of LE is due to extensive chromosome breakage. The wild-type function corresponding to spo44 is required for both LE integrity and chromosome matching. Reconstructions of heterozygous nuclei reveal the presence of a supernumerary nucleolar organizer in one arm of chromosome 7. It is suggested that rDNA has been inserted into a gene whose function is involved in pairing or into a controlling sequence that interacts with the pairing process.

  7. Fryns syndrome: a lethal mesoectodermal birth defect with variable expression in a pair of monozygotic twins.

    PubMed

    Pratap, A; Agrawal, A; Raja, S; Khaniya, S; Tiwari, A; Kumar, A

    2007-04-01

    We report a pair of twins with variable expressions of Fryns syndrome, both of whom died in the neonatal period. The syndrome is characterised by craniofacial dysmorphism, diaphragmatic hernia and distal limb hypoplasia. With this report, there are a total of 83 cases reported in the literature and this further serves to illustrate the clinical variability of this disorder.

  8. Quantum transport through a multi-quantum-dot-pair chain side-coupled with Majorana bound states

    NASA Astrophysics Data System (ADS)

    Zhao-Tan, Jiang; Cheng-Cheng, Zhong

    2016-06-01

    We investigate the quantum transport properties through a special kind of quantum dot (QD) system composed of a serially coupled multi-QD-pair (multi-QDP) chain and side-coupled Majorana bound states (MBSs) by using the Green functions method, where the conductance can be classified into two kinds: the electron tunneling (ET) conductance and the Andreev reflection (AR) one. First we find that for the nonzero MBS-QDP coupling a sharp AR-induced zero-bias conductance peak with the height of e 2/h is present (or absent) when the MBS is coupled to the far left (or the other) QDP. Moreover, the MBS-QDP coupling can suppress the ET conductance and strengthen the AR one, and further split into two sub-peaks each of the total conductance peaks of the isolated multi-QDPs, indicating that the MBS will make obvious influences on the competition between the ET and AR processes. Then we find that the tunneling rate Γ L is able to affect the conductances of leads L and R in different ways, demonstrating that there exists a Γ L-related competition between the AR and ET processes. Finally we consider the effect of the inter-MBS coupling on the conductances of the multi-QDP chains and it is shown that the inter-MBS coupling will split the zero-bias conductance peak with the height of e 2/h into two sub-peaks. As the inter-MBS coupling becomes stronger, the two sub-peaks are pushed away from each other and simultaneously become lower, which is opposite to that of the single QDP chain where the two sub-peaks with the height of about e 2/2h become higher. Also, the decay of the conductance sub-peaks with the increase of the MBS-QDP coupling becomes slower as the number of the QDPs becomes larger. This research should be an important extension in studying the transport properties in the kind of QD systems coupled with the side MBSs, which is helpful for understanding the nature of the MBSs, as well as the MBS-related QD transport properties. Project supported by the National Natural

  9. Evidence for a pairing anti-halo effect in the odd-even staggering in reaction cross sections of weakly bound nuclei

    SciTech Connect

    Hagino, K.; Sagawa, H.

    2011-07-15

    We investigate the spatial extension of weakly bound Ne and C isotopes by taking into account the pairing correlation with the Hartree-Fock-Bogoliubov (HFB) method and a three-body model, respectively. We show that the odd-even staggering in the reaction cross sections of {sup 30,31,32}Ne and {sup 14,15,16}C are successfully reproduced, and thus the staggering can be attributed to the pairing anti-halo effect. A correlation between a one-neutron separation energy and the anti-halo effect is demonstrated for s and p waves using the HFB wave functions.

  10. Base-pairing energies of proton-bound homodimers determined by guided ion beam tandem mass spectrometry: application to cytosine and 5-substituted cytosines.

    PubMed

    Yang, Bo; Wu, R R; Rodgers, M T

    2013-11-19

    Base-pairing interactions in proton-bound dimers of cytosine (C(+)·C) are the major forces responsible for stabilization of DNA i-motif conformations. Permethylation of cytosine in extended (CCG)·(CGG)n trinucleotide repeats has been shown to cause fragile-X syndrome, the most widespread inherited cause of mental retardation in humans. Oligonucleotides containing 5-bromo- or 5-fluorocytosine can bind to proteins that selectively bind methylated DNA, suggesting that halogenated cytosine damage products can potentially mimic methylation signals. However, the influence of methylation or halogenation on the base-pairing energies (BPEs) of proton-bound dimers of cytosine and their impact on the stability of DNA i-motif conformations is presently unknown. To address this, proton-bound homodimers of cytosine and 5-methyl-, 5-fluoro-, 5-bromo-, and 5-iodocytosine are investigated in detail both experimentally and theoretically. The BPEs of proton-bound homodimers of cytosine and the modified cytosines are measured by threshold collision-induced dissociation (TCID) techniques. 5-Methylation of cytosine is found to increase the BPE and would therefore tend to stabilize DNA i-motif conformations. In contrast, 5-halogenation lowers the BPE. However, the BPEs of the proton-bound 5-halocytosine homodimers examined here still significantly exceed that of Watson-Crick G·C base pairs, such that DNA i-motif conformations should be preserved in the presence of these modifications. Excellent agreement between TCID measured and B3LYP calculated BPEs is found, suggesting that B3LYP calculations can be used to provide reliable energetic predictions for related systems.

  11. Investigating of the exclusive reaction of π⁺π⁻ pair electroproduction on a proton bound in a deuteron

    SciTech Connect

    Skorodumina, Yu. A.; Golovach, Evgeny N.; Gothe, Ralf W.; Ishkhanov, Boris S.; Isupov, Evgeny L.; Mokeev, Viktor I.; Fedotov, Gleb V.

    2015-04-01

    Preliminary results from analyzing π⁺π⁻ pair electroproduction on a proton bound in a deuteron are presented. Procedures for considering the Fermi motion of the initial proton in the deuteron and assessing the effects of interaction in the final states are developed. The yield of the reaction ep(n) → e'p'(n')π⁺π⁻ is obtained for the first time.

  12. Calculating the mean time to capture for tethered ligands and its effect on the chemical equilibrium of bound ligand pairs.

    PubMed

    Shen, Lu; Decker, Caitlin G; Maynard, Heather D; Levine, Alex J

    2016-09-01

    We present here the calculation of the mean time to capture of a tethered ligand to the receptor. This calculation is then used to determine the shift in the partitioning between (1) free, (2) singly bound, and (3) doubly bound ligands in chemical equilibrium as a function of the length of the tether. These calculations are used in the research article Fibroblast Growth Factor 2 Dimer with Superagonist in vitro Activity Improves Granulation Tissue Formation During Wound Healing (Decker et al., in press [1]) to explain quantitatively how changes in polymeric linker length in the ligand dimers modifies the efficacy of these molecules relative to that of free ligands.

  13. Crystallization and preliminary X-ray analysis of the Pax6 paired domain bound to the Pax6 gene enhancer

    SciTech Connect

    Ito, Makoto Oyama, Takuji; Okazaki, Kenji; Morikawa, Kosuke

    2005-11-01

    The mammalian Pax6 paired domain has been cocrystallizaed with a 25 bp DNA fragment of the Pax6 gene enhancer. Pax6 is a member of the Pax family of transcription factors and is essential for eye development. Pax6 has two DNA-binding domains: the paired domain and the homeodomain. The Pax6 paired domain is involved in Pax6 gene autoregulation by binding to its enhancer. In this study, crystallization and preliminary X-ray diffraction analysis of the mammalian Pax6 paired domain in complex with the Pax6 gene enhancer was attempted. The Pax6 paired domain complexed with an optimized 25 bp DNA fragment was crystallized by the hanging-drop vapour-diffusion method. The crystal diffracted synchrotron radiation to 3.0/3.7 Å resolution and belongs to the monoclinic space group P2{sub 1}, with unit-cell parameters a = 62.21, b = 70.69, c = 176.03 Å, β = 90.54°. Diffraction data were collected to 3.7 Å resolution.

  14. Multichannel HSO4- recognition promoted by a bound cation within a ferrocene-based ion pair receptor.

    PubMed

    Alfonso, María; Espinosa, Arturo; Tárraga, Alberto; Molina, Pedro

    2012-07-11

    A ferrocene-based ion pair receptor is shown only to recognise HSO(4)(-) anions in the presence of a cobound Pb(2+) or Zn(2+) cation guest species through a perturbation of the redox potential of the ferrocene unit and a remarkable enhancement of the fluorescence.

  15. Competing rearrangement reactions in small gas-phase ionic complexes: The internal SN2 and nitro-nitrite rearrangements in nitroalkane proton-bound pairs

    NASA Astrophysics Data System (ADS)

    Poon, Clement; Mayer, Paul M.

    2006-09-01

    The dissociation of metastable proton-bound pairs, (R1NO2)(R2NO2)H+ (R1 and R2 = CH3, CH3CH2, (CH3)2CH and (CH3)3C) have been investigated by mass spectrometry and density functional theory calculations. The proton-bound pairs can dissociate via hydrogen-bond cleavage into protonated and neutral nitroalkanes. Methyl substitution of the nitroalkanes (R1 and R2 = (CH3)2CH, (CH3)3C) permits a rearrangement process to compete with the H-bond cleavage on the microsecond timescale. The rearrangement reaction results in an isomer that then loses nitrous acid and involves an internal SN2-type mechanism in which (R1NO2)(R2NO2)H+ isomerizes to R1NO2...R2NO2H+ via TS1 and then subsequently to R1NO2R2+...HONO via TS2 prior to dissociation. The process is favoured by stabilization of the charge in TS2 by methyl substitution. The stability of the t-butyl ion changes the mechanism in ((CH3)3CNO2)2H+ to one that involves a two-step alkyl cation transfer. An investigation of nitro-nitrite rearrangement in protonated nitroalkanes at the B3-LYP/6-31 + G(d) level of theory found that the rearrangement barrier is lowered to the point that (CH3)3CNO2H+ can easily interconvert into (CH3)3CO(H)NO+ in the gas phase and leads to the conclusion that the proton-bound pairs involving (CH3)3CNO2 are a mixture of nitro-nitro and nitro-nitrite proton-bound pairs. The nitrite isomer can dissociate into protonated t-butyl nitrite and neutral nitroalkane via a simple hydrogen-bond cleavage. A more favourable competing dissociation process leads to the loss of t-butanol to form the ((CH3)3CNO2)(NO)+ complex.

  16. The structure of the human tRNALys3 anticodon bound to the HIV genome is stabilized by modified nucleosides and adjacent mismatch base pairs.

    PubMed

    Bilbille, Yann; Vendeix, Franck A P; Guenther, Richard; Malkiewicz, Andrzej; Ariza, Xavier; Vilarrasa, Jaume; Agris, Paul F

    2009-06-01

    Replication of human immunodeficiency virus (HIV) requires base pairing of the reverse transcriptase primer, human tRNA(Lys3), to the viral RNA. Although the major complementary base pairing occurs between the HIV primer binding sequence (PBS) and the tRNA's 3'-terminus, an important discriminatory, secondary contact occurs between the viral A-rich Loop I, 5'-adjacent to the PBS, and the modified, U-rich anticodon domain of tRNA(Lys3). The importance of individual and combined anticodon modifications to the tRNA/HIV-1 Loop I RNA's interaction was determined. The thermal stabilities of variously modified tRNA anticodon region sequences bound to the Loop I of viral sub(sero)types G and B were analyzed and the structure of one duplex containing two modified nucleosides was determined using NMR spectroscopy and restrained molecular dynamics. The modifications 2-thiouridine, s(2)U(34), and pseudouridine, Psi(39), appreciably stabilized the interaction of the anticodon region with the viral subtype G and B RNAs. The structure of the duplex results in two coaxially stacked A-form RNA stems separated by two mismatched base pairs, U(162)*Psi(39) and G(163)*A(38), that maintained a reasonable A-form helix diameter. The tRNA's s(2)U(34) stabilized the interaction between the A-rich HIV Loop I sequence and the U-rich anticodon, whereas the tRNA's Psi(39) stabilized the adjacent mismatched pairs.

  17. Simultaneous Creation of Electron-Positron Pairs and Photons in Robertson-Walker Universes with Statically Bounded Expansion

    NASA Astrophysics Data System (ADS)

    Lotze, K.-H.

    We present, based upon quantum electrodynamics in Robertson-Walker flat universes, a thorough analysis of the creation of mutually interacting electron-positron pairs and photons from vacuum. Therefore we discuss at least qualitatively all processes contributing to the number densities of created particles up to the second order in the coupling constant. For two particular expansion laws with Minkowskian in respectively in and out regions, we obtain exact solutions to the Dirac equation and investigate in detail the process of simultaneous creation of electron-positron pairs and photons and the related attenuation effect for fermionic particles. This is done for electrons and positrons which have nonrelativistic momenta at Compton time in rapidly expanding universes. The results are compared with the zeroth-order creation of electron-positron pairs. Despite being smaller by a factor of roughly e02 /4π ≈ 1 /137, the interacting-particle creation is important mainly as a source of photons even in conformally flat universes.

  18. Reliability and Validity of a Smartphone-Paired Pulse Oximeter for Screening of Critical Congenital Heart Defects in Newborns.

    PubMed

    Huizing, Maurice J; Villamor-Martínez, Eduardo; Chavagne, Ingrid A; Vanagt, Ward Y; Spaanderman, Marc A E; Villamor, Eduardo

    2017-08-03

    Barriers to widespread implementation of pulse oximetry screening of critical congenital heart defects (CCHD) in newborns include increasing trends of out-of-hospital births and cost of equipment. In recent years, smartphone-compatible pulse oximeters have appeared on the market, but the validity of such devices in the setting of CCHD screening has not been evaluated. To compare the performance in CCHD screening of a smartphone-paired pulse oximeter (Masimo iSpO2-Rx™) and a hospital-grade pulse oximeter (Masimo Radical-7™). Preductal (right hand) and postductal (either foot) saturations were determined in a population of 201 term newborns by 2 independent teams, one using the Radical-7 and the other using the iSpO2-Rx. Bland-Altman analysis was applied to calculate mean bias and 95% limits of agreement between the 2 pulse oximeters. For the preductal oxygen saturation, the mean bias (Radical-7 minus iSpO2-Rx) was -0.08 (SD 1.76) and the lower and upper limits of agreement were -3.52 and 3.36, respectively. For the postductal oxygen saturation, the mean bias was -0.11 (SD 1.68) and the lower and upper limits of agreement were -3.49 and 3.18, respectively. In addition, the iSpO2-Rx provided reliable measurements of saturations below 95% in a group of 12 infants admitted to the neonatal intensive care unit. Our data suggest that CCHD screening with the Masimo iSpO2-Rx is feasible and accurate. The use of reliable smartphone-paired pulse oximeters may contribute to the extension of CCHD screening to home births and low resource settings. © 2017 S. Karger AG, Basel.

  19. Full-length RAG1 promotes contact with coding and intersignal sequences in RAG protein complexes bound to recombination signals paired in cis

    PubMed Central

    Kumar, Sushil; Swanson, Patrick C.

    2009-01-01

    The RAG proteins initiate V(D)J recombination by mediating synapsis and cleavage of two different antigen receptor gene segments through interactions with their flanking recombination signal sequences (RSS). The protein–DNA complexes that support this process have mainly been studied using RAG–RSS complexes assembled using oligonucleotide substrates containing a single RSS that are paired in trans to promote synapsis. How closely these complexes model those formed on longer, more physiologically relevant substrates containing RSSs on the same DNA molecule (in cis) remains unclear. To address this issue, we characterized discrete core and full-length RAG protein complexes bound to RSSs paired in cis. We find these complexes support cleavage activity regulated by V(D)J recombination's ‘12/23 rule’ and exhibit plasticity in RSS usage dependent on partner RSS composition. DNA footprinting studies suggest that the RAG proteins in these complexes mediate more extensive contact with sequences flanking the RSS than previously observed, some of which are enhanced by full-length RAG1, and associated with synapsis and efficient RSS cleavage. Finally, we demonstrate that the RAG1 C-terminus facilitates hairpin formation on long DNA substrates, and full-length RAG1 promotes hairpin retention in the postcleavage RAG complex. These results provide new insights into the mechanism of physiological V(D)J recombination. PMID:19233873

  20. Full-length RAG1 promotes contact with coding and intersignal sequences in RAG protein complexes bound to recombination signals paired in cis.

    PubMed

    Kumar, Sushil; Swanson, Patrick C

    2009-04-01

    The RAG proteins initiate V(D)J recombination by mediating synapsis and cleavage of two different antigen receptor gene segments through interactions with their flanking recombination signal sequences (RSS). The protein-DNA complexes that support this process have mainly been studied using RAG-RSS complexes assembled using oligonucleotide substrates containing a single RSS that are paired in trans to promote synapsis. How closely these complexes model those formed on longer, more physiologically relevant substrates containing RSSs on the same DNA molecule (in cis) remains unclear. To address this issue, we characterized discrete core and full-length RAG protein complexes bound to RSSs paired in cis. We find these complexes support cleavage activity regulated by V(D)J recombination's '12/23 rule' and exhibit plasticity in RSS usage dependent on partner RSS composition. DNA footprinting studies suggest that the RAG proteins in these complexes mediate more extensive contact with sequences flanking the RSS than previously observed, some of which are enhanced by full-length RAG1, and associated with synapsis and efficient RSS cleavage. Finally, we demonstrate that the RAG1 C-terminus facilitates hairpin formation on long DNA substrates, and full-length RAG1 promotes hairpin retention in the post-cleavage RAG complex. These results provide new insights into the mechanism of physiological V(D)J recombination.

  1. Electronic and optical properties of Cu2XSnS4 (X = Be, Mg, Ca, Mn, Fe, and Ni) and the impact of native defect pairs

    NASA Astrophysics Data System (ADS)

    Chen, Rongzhen; Persson, Clas

    2017-05-01

    Reducing or controlling cation disorder in Cu2ZnSnS4 is a major challenge, mainly due to low formation energies of the anti-site pair ( CuZn - + ZnCu +) and the compensated Cu vacancy ( VCu - + ZnCu +). We study the electronic and optical properties of Cu2XSnS4 (CXTS, with X = Be, Mg, Ca, Mn, Fe, and Ni) and the impact of defect pairs, by employing the first-principles method within the density functional theory. The calculations indicate that these compounds can be grown in either the kesterite or stannite tetragonal phase, except Cu2CaSnS4 which seems to be unstable also in its trigonal phase. In the tetragonal phase, all six compounds have rather similar electronic band structures, suitable band-gap energies Eg for photovoltaic applications, as well as good absorption coefficients α(ω). However, the formation of the defect pairs ( C u X + X Cu) and ( V Cu + X Cu) is an issue for these compounds, especially considering the anti-site pair which has formation energy in the order of ˜0.3 eV. The ( C u X + X Cu) pair narrows the energy gap by typically ΔEg ≈ 0.1-0.3 eV, but for Cu2NiSnS4, the complex yields localized in-gap states. Due to the low formation energy of ( C u X + X Cu), we conclude that it is difficult to avoid disordering from the high concentration of anti-site pairs. The defect concentration in Cu2BeSnS4 is however expected to be significantly lower (as much as ˜104 times at typical device operating temperature) compared to the other compounds, which is partly explained by larger relaxation effects in Cu2BeSnS4 as the two anti-site atoms have different sizes. The disadvantage is that the stronger relaxation has a stronger impact on the band-gap narrowing. Therefore, instead of trying to reduce the anti-site pairs, we suggest that one shall try to compensate ( C u X + X Cu) with ( V Cu + X Cu) or other defects in order to stabilize the gap energy.

  2. Crystallization and preliminary X-ray diffraction analysis of the Pax9 paired domain bound to a DC5 enhancer DNA element.

    PubMed

    Narasimhan, Kamesh; Hilbig, Antonia; Udayasuryan, Barath; Jayabal, Sriram; Kolatkar, Prasanna R; Jauch, Ralf

    2014-10-01

    Pax genes belong to a family of metazoan transcription factors that are known to play a critical role in eye, ear, kidney and neural development. The mammalian Pax family of transcription factors is characterized by a ∼128-amino-acid DNA-binding paired domain that makes sequence-specific contacts with DNA. The diversity in Pax gene activities emerges from complex modes of interaction with enhancer regions and heterodimerization with multiple interaction partners. Based on in vitro optimal binding-site selection studies and enhancer identification assays, it has been suggested that Pax proteins may recognize and bind their target DNA elements with different binding modes/topologies, however this hypothesis has not yet been structurally explored. One of the most extensively studied DNA target elements of the Pax6 paired domain is the eye-lens specific DC5 (δ-crystallin) enhancer element. In order to shed light on Pax6-DC5 DNA interactions, the related paired-domain prototype Pax9 was crystallized with the minimal δ-crystallin DC5 enhancer element and preliminary X-ray diffraction analysis was attempted. A 3.0 Å resolution native data set was collected at the National Synchrotron Light Source (NSLS), Brookhaven from crystals grown in a solution consisting of 10%(w/v) PEG 20K, 20%(v/v) PEG 550 MME, 0.03 M NaNO3, 0.03 M Na2HPO4, 0.03 M NH2SO4, 0.1 M MES/imidazole pH 6.5. The data set was indexed and merged in space group C2221, with unit-cell parameters a = 75.74, b = 165.59, c = 70.14 Å, α = β = γ = 90°. The solvent content in the unit cell is consistent with the presence of one Pax9 paired domain bound to duplex DNA in the asymmetric unit.

  3. Defects-assisted ferromagnetism due to bound magnetic polarons in Ce into Fe, Co:ZnO nanoparticles and first-principle calculations.

    PubMed

    Verma, Kuldeep Chand; Kotnala, R K

    2016-02-21

    Zn0.94TM0.03Ce0.03O [Zn0.94Fe0.03Ce0.03O (ZFCeO) and Zn0.94Co0.03Ce0.03O (ZCCeO)] nanoparticles were synthesized by a sol-gel process. Elemental analysis of these nanoparticles detects the weight percentage of Zn, Co, Fe, Ce and O in each sample. The Rietveld refinement of the X-ray diffraction pattern obtains the occupancy of dopant atoms, Wurtzite ZnO structure, crystallinity and lattice deformation with doping. The Ce doping into ZFO and ZCO form nanoparticles than nanorods was observed in pure ZnO, ZFO and ZCO samples that described due to chemical and ionic behavior of Ce, Fe, Co and Zn ions. The Raman active modes have peak broadening, intensity changes and peak shifts with metal doping that induces lattice defects. Photoluminescence spectra show blue-shifts at near-band edges and defects that influence broad visible emission with Ce doping. An enhancement in ferromagnetism in the magnetic hysteresis at 5 K is measured. The zero-field cooling and field cooling at H = 500 Oe and T = 300-5 K could confirm antiferromagnetic interactions mediated by defect carriers. The bound magnetic polaron at defect sites is responsible for the observed ferromagnetism. The ac magnetic susceptibility measurements determine the antiferromagnetic to ferromagnetic transition with some magnetic clustered growth in the samples and reveal a frequency independent peak that shows the Neel temperature. Weak room temperature ferromagnetism and optical quenching in ZFCeO are described by valance states of Fe and Ce ions, respectively. Using first-principle calculations, we studied the occupancy of Ce (replacing Zn atoms) in the Wurtzite structure.

  4. Zero-field optical detection of magnetic resonance on a metastable sulfur-pair-related defect in silicon: Evidence for a Cu constituent

    NASA Astrophysics Data System (ADS)

    Frens, A. M.; Bennebroek, M. T.; Schmidt, J.; Chen, W. M.; Monemar, B.

    1992-11-01

    A metastable complex defect in S-doped silicon has been studied with zero-field optically-detected magnetic-resonance (ODMR) spectroscopy. The defect shows two characteristic photoluminescence (PL) spectra SA and SB, corresponding to two different geometric configurations 1 and 2. The PL spectra in both cases originate from excited-state triplet bound excitons in the neutral charge state of the defect. Previous X-band ODMR studies for SA and SB show broad spectra with unresolved hyperfine interaction. In zero-field ODMR the linewidth is reduced to about 50 MHz for SA (100 MHz for SB), and the second-order hyperfine structure of an I=32 nucleus is resolved, partly with the help of a double-resonance technique. The zero-field splitting parameters of the triplet states (i.e., the principal D-tensor components) are determined as Dxx=-2905, Dyy=-705, and Dzz=3610 MHz for SA, and Dxx=-1295, Dyy=-180, and Dzz=1475 MHz for SB. The hyperfine splitting is determined as A=175 MHz for both SA and SB, whereas the quadrupole constant Pz'z' has a value 10-20 MHz for SA and a substantially larger value, 30-40 MHz for SB. The I=32 nucleus at the core of the defect is tentatively identified as Cu. The conclusion about the different quadrupole interaction for SA and SB from these data agrees with previous ODMR X-band data in a magnetic field, which also show a different configuration (of the Cu atom) in the excited triplet states of SA and SB. It is tentatively concluded from these data that the metastability of this defect is connected to a change of the site of the Cu atom with respect to its surroundings in the silicon lattice.

  5. Association of Myopic Optic Disc Deformation with Visual Field Defects in Paired Eyes with Open-Angle Glaucoma: A Cross-Sectional Study

    PubMed Central

    Sawada, Yu; Hangai, Masanori; Ishikawa, Makoto; Yoshitomi, Takeshi

    2016-01-01

    Purpose To examine the association of myopia with the visual field (VF) defects in open-angle glaucoma (OAG) using paired eyes to eliminate the effect of unknown confounding factors that are diverse among individuals. Methods One hundred eighteen eyes of 59 subjects with myopia (spherical equivalent [SE] ≥ -2 diopter [D] and axial length ≥ 24.0 mm) whose intra-ocular pressure between paired eyes was similar and the mean deviation (MD) of the Humphrey VF test differed by more than 6 dB were included. Refractive errors (SE, axial length) and parameters associated with the papillary and parapapillary myopic deformation (tilt ratio, torsion angle, and β-zone parapapillary atrophy [PPA] area without Bruch’s membrane) were measured in each eye. The paired eyes were divided into worse and better eyes according to the MD of the VF, and parameters were compared between them. Further, multiple linear regression analysis was performed to examine the correlation of the difference in various parameters with the MD difference between paired eyes. Results The SE of all eyes was -6.39 ± 2.15 D (mean ± standard deviation) and axial length was 26.42 ± 1.07 mm. MD of the worse and better VF eyes were -13.56 ± 6.65 dB and -4.87 ± 5.32 dB, respectively. Eyes with worse VFs had significantly greater SE, axial length, tilt ratio, and PPA area without Bruch’s membrane than those with better VFs (all P < 0.05). In multiple linear regression analysis, the difference of the MD between paired eyes was significantly correlated with the difference in the tilt ratio and PPA area without Bruch’s membrane. Conclusion The myopic papillary and parapapillary deformations, but not refractive error itself, were related to the worse VF in paired eyes with OAG. This suggests that myopia influences the severity of the glaucomatous VF defects via structural deformation. PMID:27571303

  6. Defect properties of Sb- and Bi-doped CuInSe{sub 2}: The effect of the deep lone-pair s states

    SciTech Connect

    Park, Ji-Sang; Yang, Ji-Hui; Ramanathan, Kannan; Wei, Su-Huai

    2014-12-15

    Bi or Sb doping has been used to make better material properties of polycrystalline Cu{sub 2}(In,Ga)Se{sub 2} as solar cell absorbers, including the experimentally observed improved electrical properties. However, the mechanism is still not clear. Using first-principles method, we investigate the stability and electronic structure of Bi- and Sb-related defects in CuInSe{sub 2} and study their effects on the doping efficiency. Contrary to previous thinking that Bi or Sb substituted on the anion site, we find that under anion-rich conditions, the impurities can substitute on cation sites and are isovalent to In because of the formation of the impurity lone pair s states. When the impurities substitute for Cu, the defects act as shallow double donors and help remove the deep In{sub Cu} level, thus resulting in the improved carrier life time. On the other hand, under anion-poor conditions, impurities at the Se site create amphoteric deep levels that are detrimental to the device performance.

  7. Ab-initio studies on Li doping, Li-pairs, and complexes between Li and intrinsic defects in ZnO

    NASA Astrophysics Data System (ADS)

    Vidya, R.; Ravindran, P.; Fjellvâg, H.

    2012-06-01

    First-principles density functional calculations have been performed on Li-doped ZnO using all-electron projector augmented plane wave method. Li was considered at six different interstitial sites (Lii), including anti-bonding and bond-center sites and also in substitutional sites such as at Zn-site (Lizn) and at oxygen site (Lio) in the ZnO matrix. Stability of LiZn over Lii is shown to depend on synthetic condition, viz., LiZn is found to be more stable than Lii under O-rich conditions. Hybrid density functional calculations performed on LiZn indicate that it is a deep acceptor with (0/-) transition taking place at 0.74 eV above valence band maximum. The local vibrational frequencies for Li-dopants are calculated and compared with reported values. In addition, we considered the formation of Li-pair complexes and their role on electronic properties of ZnO. Present study suggests that at extreme oxygen-rich synthesis condition, a pair of acceptor type LiZn-complex is found to be stable over the compensating Lii + LiZn pair. The stability of complexes formed between Li impurities and various intrinsic defects is also investigated and their role on electronic properties of ZnO has been analyzed. We have shown that a complex between LiZn and oxygen vacancy has less formation energy and donor-type character and could compensate the holes generated by Li-doping in ZnO.

  8. Base-Pairing Energies of Proton-Bound Dimers and Proton Affinities of 1-Methyl-5-Halocytosines: Implications for the Effects of Halogenation on the Stability of the DNA i-Motif

    NASA Astrophysics Data System (ADS)

    Yang, Bo; Wu, R. R.; Rodgers, M. T.

    2015-09-01

    (CCG)n•(CGG)n trinucleotide repeats have been found to be associated with fragile X syndrome, the most widespread inherited cause of mental retardation in humans. The (CCG)n•(CGG)n repeats adopt i-motif conformations that are preferentially stabilized by base-pairing interactions of noncanonical proton-bound dimers of cytosine (C+•C). Halogenated cytosine residues are one form of DNA damage that may be important in altering the structure and stability of DNA or DNA-protein interactions and, hence, regulate gene expression. Previously, we investigated the effects of 5-halogenation and 1-methylation of cytosine on the base-pairing energies (BPEs) using threshold collision-induced dissociation (TCID) techniques. In the present study, we extend our work to include proton-bound homo- and heterodimers of cytosine, 1-methyl-5-fluorocytosine, and 1-methyl-5-bromocytosine. All modifications examined here are found to produce a decrease in the BPEs. However, the BPEs of all of the proton-bound dimers examined significantly exceed those of Watson-Crick G•C, neutral C•C base pairs, and various methylated variants such that DNA i-motif conformations should still be preserved in the presence of these modifications. The proton affinities (PAs) of the halogenated cytosines are also obtained from the experimental data by competitive analysis of the primary dissociation pathways that occur in parallel for the proton-bound heterodimers. 5-Halogenation leads to a decrease in the N3 PA of cytosine, whereas 1-methylation leads to an increase in the N3 PA. Thus, the 1-methyl-5-halocytosines exhibit PAs that are intermediate.

  9. Base-Pairing Energies of Proton-Bound Dimers and Proton Affinities of 1-Methyl-5-Halocytosines: Implications for the Effects of Halogenation on the Stability of the DNA i-Motif.

    PubMed

    Yang, Bo; Wu, R R; Rodgers, M T

    2015-09-01

    (CCG)(n)•(CGG)(n) trinucleotide repeats have been found to be associated with fragile X syndrome, the most widespread inherited cause of mental retardation in humans. The (CCG)(n)•(CGG)(n) repeats adopt i-motif conformations that are preferentially stabilized by base-pairing interactions of noncanonical proton-bound dimers of cytosine (C(+)•C). Halogenated cytosine residues are one form of DNA damage that may be important in altering the structure and stability of DNA or DNA-protein interactions and, hence, regulate gene expression. Previously, we investigated the effects of 5-halogenation and 1-methylation of cytosine on the base-pairing energies (BPEs) using threshold collision-induced dissociation (TCID) techniques. In the present study, we extend our work to include proton-bound homo- and heterodimers of cytosine, 1-methyl-5-fluorocytosine, and 1-methyl-5-bromocytosine. All modifications examined here are found to produce a decrease in the BPEs. However, the BPEs of all of the proton-bound dimers examined significantly exceed those of Watson-Crick G•C, neutral C•C base pairs, and various methylated variants such that DNA i-motif conformations should still be preserved in the presence of these modifications. The proton affinities (PAs) of the halogenated cytosines are also obtained from the experimental data by competitive analysis of the primary dissociation pathways that occur in parallel for the proton-bound heterodimers. 5-Halogenation leads to a decrease in the N3 PA of cytosine, whereas 1-methylation leads to an increase in the N3 PA. Thus, the 1-methyl-5-halocytosines exhibit PAs that are intermediate.

  10. Impurity-induced bound states inside the superconducting gap of FeSe

    NASA Astrophysics Data System (ADS)

    Jiao, Lin; Rößler, Sahana; Koz, Cevriye; Schwarz, Ulrich; Kasinathan, Deepa; Rößler, Ulrich K.; Wirth, Steffen

    2017-09-01

    We investigate the local density of states in the vicinity of a native dumbbell defect arising from an Fe vacancy in FeSe single crystals. The tunneling spectra close to the impurity display two bound states inside the superconducting gap, equally spaced with respect to zero energy but asymmetric in amplitude. Using spin-polarized density functional theory calculations on realistic slab models with an Fe vacancy, we show that such a defect does not induce a local magnetic moment. Therefore, the dumbbell defect is considered as nonmagnetic. Thus, the in-gap bound states emerging from a nonmagnetic defect-induced pair breaking suggest a sign-changing pairing state in this material.

  11. Sequence-Dependent T:G Base Pair Opening in DNA Double Helix Bound by Cren7, a Chromatin Protein Conserved among Crenarchaea

    PubMed Central

    Tian, Lei; Zhang, Zhenfeng; Wang, Hanqian; Zhao, Mohan; Dong, Yuhui; Gong, Yong

    2016-01-01

    T:G base pair arising from spontaneous deamination of 5mC or polymerase errors is a great challenge for DNA repair of hyperthermophilic archaea, especially Crenarchaea. Most strains in this phylum lack the protein homologues responsible for the recognition of the mismatch in the DNA repair pathways. To investigate whether Cren7, a highly conserved chromatin protein in Crenarchaea, serves a role in the repair of T:G mispairs, the crystal structures of Cren7-GTAATTGC and Cren7-GTGATCGC complexes were solved at 2.0 Å and 2.1 Å. In our structures, binding of Cren7 to the AT-rich DNA duplex (GTAATTGC) induces opening of T2:G15 but not T10:G7 base pair. By contrast, both T:G mispairs in the GC-rich DNA duplex (GTGATCGC) retain the classic wobble type. Structural analysis also showed DNA helical changes of GTAATTGC, especially in the steps around the open T:G base pair, as compared to GTGATCGC or the matched DNAs. Surface plasmon resonance assays revealed a 4-fold lower binding affinity of Cren7 for GTAATTGC than that for GTGATCGC, which was dominantly contributed by the decrease of association rate. These results suggested that binding of Cren7 to DNA leads to T:G mispair opening in a sequence dependent manner, and therefore propose the potential roles of Cren7 in DNA repair. PMID:27685992

  12. Sequence-Dependent T:G Base Pair Opening in DNA Double Helix Bound by Cren7, a Chromatin Protein Conserved among Crenarchaea.

    PubMed

    Tian, Lei; Zhang, Zhenfeng; Wang, Hanqian; Zhao, Mohan; Dong, Yuhui; Gong, Yong

    T:G base pair arising from spontaneous deamination of 5mC or polymerase errors is a great challenge for DNA repair of hyperthermophilic archaea, especially Crenarchaea. Most strains in this phylum lack the protein homologues responsible for the recognition of the mismatch in the DNA repair pathways. To investigate whether Cren7, a highly conserved chromatin protein in Crenarchaea, serves a role in the repair of T:G mispairs, the crystal structures of Cren7-GTAATTGC and Cren7-GTGATCGC complexes were solved at 2.0 Å and 2.1 Å. In our structures, binding of Cren7 to the AT-rich DNA duplex (GTAATTGC) induces opening of T2:G15 but not T10:G7 base pair. By contrast, both T:G mispairs in the GC-rich DNA duplex (GTGATCGC) retain the classic wobble type. Structural analysis also showed DNA helical changes of GTAATTGC, especially in the steps around the open T:G base pair, as compared to GTGATCGC or the matched DNAs. Surface plasmon resonance assays revealed a 4-fold lower binding affinity of Cren7 for GTAATTGC than that for GTGATCGC, which was dominantly contributed by the decrease of association rate. These results suggested that binding of Cren7 to DNA leads to T:G mispair opening in a sequence dependent manner, and therefore propose the potential roles of Cren7 in DNA repair.

  13. Transfer of a weakly bound electron in collisions of Rydberg atoms with neutral particles. II. Ion-pair formation and resonant quenching of the Rb(nl) and Ne(nl) States by Ca, Sr, and Ba atoms

    SciTech Connect

    Narits, A. A.; Mironchuk, E. S.; Lebedev, V. S.

    2013-10-15

    Electron-transfer processes are studied in thermal collisions of Rydberg atoms with alkaline-earth Ca(4s{sup 2}), Sr(5s{sup 2}), and Ba(6s{sup 2}) atoms capable of forming negative ions with a weakly bound outermost p-electron. We consider the ion-pair formation and resonant quenching of highly excited atomic states caused by transitions between Rydberg covalent and ionic terms of a quasi-molecule produced in collisions of particles. The contributions of these reaction channels to the total depopulation cross section of Rydberg states of Rb(nl) and Ne(nl) atoms as functions of the principal quantum number n are compared for selectively excited nl-levels with l Much-Less-Than n and for states with large orbital quantum numbers l = n - 1, n - 2. It is shown that the contribution from resonant quenching dominates at small values of n, and the ion-pair formation process begins to dominate with increasing n. The values and positions of the maxima of cross sections for both processes strongly depend on the electron affinity of an alkaline-earth atom and on the orbital angular momentum l of a highly excited atom. It is shown that in the case of Rydberg atoms in states with large l {approx} n - 1, the rate constants of ion-pair formation and collisional quenching are considerably lower than those for nl-levels with l Much-Less-Than n.

  14. Stability of a Surface-Bound Oligonucleotide Duplex Inferred from Molecular Dynamics: A Study of Single Nucleotide Defects Using DNA Microarrays

    NASA Astrophysics Data System (ADS)

    Naiser, Thomas; Kayser, Jona; Mai, Timo; Michel, Wolfgang; Ott, Albrecht

    2009-05-01

    Microarray technology uses the sequence dependent hybridization (binding) affinity of surface-bound oligonucleotide strands for the quantification of complex nucleic acid mixtures. In spite of its huge potential in life science and medicine, microarray oligonucleotide hybridization remains far from being understood. Taking advantage of microarray combinatorial possibilities we show that, although surface bound, the hybridization affinities of single-base mismatched oligonucleotides can be derived from first principles using parameters from bulk.

  15. A FRET-based probe for epidermal growth factor receptor bound non-covalently to a pair of synthetic amphipathic helixes

    SciTech Connect

    Itoh, Reina E.; Kurokawa, Kazuo; Fujioka, Aki; Sharma, Alok; Mayer, Bruce J.; Matsuda, Michiyuki . E-mail: matsudam@biken.osaka-u.ac.jp

    2005-07-01

    Epidermal growth factor (EGF) receptor plays a pivotal role in a variety of cellular functions, such as proliferation, differentiation, and migration. To monitor the EGF receptor (EGFR) activity in living cells, we developed a probe for EGFR activity based on the principle of fluorescence resonance energy transfer (FRET). Previously, we developed a probe designated as Picchu (Phosphorylation indicator of the CrkII chimeric unit), which detects the tyrosine phosphorylation of the CrkII adaptor protein. We used a pair of synthetic amphipathic helixes, WinZipA2 and WinZipB1, to bind Picchu non-covalently to the carboxyl-terminus of the EGFR. Using this modified probe named Picchu-Z, the activity of EGFR was followed in EGF-stimulated Cos7 cells. We found that a high level of tyrosine phosphorylation of Picchu-Z probe remained after endocytosis until the point when the EGFR was translocated to the perinuclear region. These findings are in agreement with the previously reported 'signaling endosome' model. Furthermore, by pulse stimulation with EGF and by acute ablation of EGFR activity with AG1478, it was suggested that the phosphorylation of Picchu-Z probe, and probably the phosphorylation of EGFR also, underwent a rapid equilibrium ({tau} {sub 1/2} < 2 min) between the phosphorylated and dephosphorylated states in the presence of EGF.

  16. Ion pair receptors†

    PubMed Central

    Kim, Sung Kuk

    2010-01-01

    Compared with simple ion receptors, which are able to bind either a cation or an anion, ion pair receptors bearing both a cation and an anion recognition site offer the promise of binding ion pairs or pairs of ions strongly as the result of direct or indirect cooperative interactions between co-bound ions. This critical review focuses on the recent progress in the design of ion pair receptors and summarizes the various binding modes that have been used to accommodate ion pairs (110 references). PMID:20737073

  17. Defect identification in the AsGa family in GaAs

    NASA Astrophysics Data System (ADS)

    Overhof, H.; Spaeth, J.-M.

    2005-09-01

    Ab initio total-energy calculations are presented for intrinsic defects in GaAs with a particular emphasis on hyperfine interactions in order to clarify the atomic structure of the various AsGa -related defects. For the AsGa-X2 defect complex the interpretation as an AsGa-VAs antisite-vacancy pair as was considered so far is challenged. An AsGa-GaAs antistructure pair is the most likely identification. It is also unlikely that the AsGa-X1 defect can be identified as a distant antistructure pair as was considered from magnetic resonance experiments. The theoretical results obtained for the isolated AsGa point defect agree with the experimental data reported for the defect identified as isolated AsGa and, with the exception of a small broadening of the nearest-neighbor lines and of a moderate splitting in the fifth shell, for the EL2 as well. We speculate that at room temperature the EL2 will be an isolated AsGa defect which lowers its symmetry attracting some other mobile defect at the low temperatures required to perform magnetic resonance experiments. We have calculated the binding energies of antisites bound to a distant shallow acceptor and the influence of the pairing on the hyperfine interactions. We show that this mechanism could explain the broadening of the nearest-neighbor lines but not the splitting in the fifth shell.

  18. Cooper Pairs in Insulators?!

    ScienceCinema

    James Valles

    2016-07-12

    Nearly 50 years elapsed between the discovery of superconductivity and the emergence of the microscopic theory describing this zero resistance state. The explanation required a novel phase of matter in which conduction electrons joined in weakly bound pairs and condensed with other pairs into a single quantum state. Surprisingly, this Cooper pair formation has also been invoked to account for recently uncovered high-resistance or insulating phases of matter. To address this possibility, we have used nanotechnology to create an insulating system that we can probe directly for Cooper pairs. I will present the evidence that Cooper pairs exist and dominate the electrical transport in these insulators and I will discuss how these findings provide new insight into superconductor to insulator quantum phase transitions. 

  19. Electronic pairing in exotic superconductors

    SciTech Connect

    Cox, D.L. ); Maple, M.B. )

    1995-02-01

    Superconductivity in heavy-fermion materials and high T[sub c] cuprates may involve electronic pairing with unconventional symmetries and mechanisms. Although there has been no smoking-gun proof, numerous pieces of circumstantial evidence combined with heuristic theoretical arguments make a compelling case that these materials have pairs with exotic symmetry bound by nonphonon glue. 20 refs., 5 figs.

  20. Outward Bound.

    ERIC Educational Resources Information Center

    Outward Bound, Inc., Andover, MA.

    The Outward Bound concept was developed in Germany and Great Britain with the saving of human life as the ultimate goal. Courses are designed to help students discover their true physical and mental limits through development of skills including emergency medical aid, firefighting, search and rescue, mountaineering, and sailing. Five Outward Bound…

  1. Effect of intrinsic point defects on ferroelectric polarization behavior of SrTiO3

    NASA Astrophysics Data System (ADS)

    Klyukin, Konstantin; Alexandrov, Vitaly

    2017-01-01

    The effect of a variety of intrinsic defects and defect clusters in bulk and thin films of SrTiO3 on ferroelectric polarization and switching mechanisms is investigated by means of density-functional-theory based calculations and the Berry phase approach. Our results show that both the titanium TiSr•• and strontium SrTi'' antisite defects induce ferroelectric polarization in SrTiO3, with the TiSr•• defect causing a more pronounced spontaneous polarization and higher activation barriers of polarization reversal than SrTi''. The presence of oxygen vacancies bound to the antisite defects can either enhance or diminish polarization depending on the configuration of the defect pair, but it always leads to larger activation barriers of polarization switching as compared to the antisite defects with no oxygen vacancies. We also show that the magnitude of spontaneous polarization in SrTiO3 can be tuned by controlling the degree of Sr/Ti nonstroichiometry. Other intrinsic point defects such as Frenkel defect pairs and electron small polarons also contribute to the emergence of ferroelectric polarization in SrTiO3.

  2. Cooper Pair Insulators

    NASA Astrophysics Data System (ADS)

    Valles, James

    One of the recent advances in the field of the Superconductor to Insulator Transition (SIT) has been the discovery and characterization of the Cooper Pair Insulator phase. This bosonic insulator, which consists of localized Cooper pairs, exhibits activated transport and a giant magneto-resistance peak. These features differ markedly from the weakly localized transport that emerges as pairs break at a ``fermionic'' SIT. I will describe how our experiments on films nano-patterned with a nearly triangular array of holes have enabled us to 1) distinguish bosonic insulators from fermionic insulators, 2) show that Cooper pairs, rather than quasi-particles dominate the transport in the Cooper Pair insulator phase, 3) demonstrate that very weak, sub nano-meter thickness inhomogeneities control whether a bosonic or fermionic insulator forms at an SIT and 4) reveal that Cooper pairs disintegrate rather than becoming more tightly bound deep in the localized phase. We have also developed a method, using a magnetic field, to tune flux disorder reversibly in these films. I will present our latest results on the influence of magnetic flux disorder and random gauge fields on phenomena near bosonic SITs. This work was performed in collaboration with M. D. Stewart, Jr., Hung Q. Nguyen, Shawna M. Hollen, Jimmy Joy, Xue Zhang, Gustavo Fernandez, Jeffrey Shainline and Jimmy Xu. It was supported by NSF Grants DMR 1307290 and DMR-0907357.

  3. Pick a Pair. Pancake Pairs

    ERIC Educational Resources Information Center

    Miller, Pat

    2005-01-01

    Cold February weather and pancakes are a traditional pairing. Pancake Day began as a way to eat up the foods that were abstained from in Lent--traditionally meat, fat, eggs and dairy products. The best-known pancake event is The Pancake Day Race in Buckinghamshire, England, which has been run since 1445. This column describes pairs of books that…

  4. Pick a Pair. Pancake Pairs

    ERIC Educational Resources Information Center

    Miller, Pat

    2005-01-01

    Cold February weather and pancakes are a traditional pairing. Pancake Day began as a way to eat up the foods that were abstained from in Lent--traditionally meat, fat, eggs and dairy products. The best-known pancake event is The Pancake Day Race in Buckinghamshire, England, which has been run since 1445. This column describes pairs of books that…

  5. Positive Root Bounds and Root Separation Bounds

    NASA Astrophysics Data System (ADS)

    Herman, Aaron Paul

    In this thesis, we study two classes of bounds on the roots of a polynomial (or polynomial system). A positive root bound of a polynomial is an upper bound on the largest positive root. A root separation bound of a polynomial is a lower bound on the distance between the roots. Both classes of bounds are fundamental tools in computer algebra and computational real algebraic geometry, with numerous applications. In the first part of the thesis, we study the quality of positive root bounds. Higher quality means that the relative over-estimation (the ratio of the bound and the largest positive root) is smaller. We find that all known positive root bounds can be arbitrarily bad. We then show that a particular positive root bound is tight for certain important classes of polynomials. In the remainder of the thesis, we turn to root separation bounds. We observe that known root separation bounds are usually very pessimistic. To our surprise, we also find that known root separation bounds are not compatible with the geometry of the roots (unlike positive root bounds). This motivates us to derive new root separation bounds. In the second part of this thesis, we derive a new root separation for univariate polynomials by transforming a known bound into a new improved bound. In the third part of this thesis, we use a similar strategy to derive a new improved root separation bound for polynomial systems.

  6. Bounding millimagnetically charged particles with magnetars

    NASA Astrophysics Data System (ADS)

    Hook, Anson; Huang, Junwu

    2017-09-01

    Millimagnetically charged particles generically appear in scenarios with kinetic mixing. We present model independent bounds on these particles coming from magnetars. Schwinger pair production discharges the magnetic field of the magnetar. Thus the existence of large magnetic fields at magnetars place strong bounds on the millimagnetic charge to be smaller than 10-18 over a large mass range.

  7. Anomalous Andreev bound state in noncentrosymmetric superconductors.

    PubMed

    Tanaka, Yukio; Mizuno, Yoshihiro; Yokoyama, Takehito; Yada, Keiji; Sato, Masatoshi

    2010-08-27

    We study edge states of noncentrosymmetric superconductors where spin-singlet d-wave pairing mixes with spin-triplet p (or f)-wave one by spin-orbit coupling. For d(xy)-wave pairing, the obtained Andreev bound state has an anomalous dispersion as compared to conventional helical edge modes. A unique topologically protected time-reversal invariant Majorana bound state appears at the edge. The charge conductance in the noncentrosymmetric superconductor junctions reflects the anomalous structures of the dispersions, particularly the time-reversal invariant Majorana bound state is manifested as a zero bias conductance peak.

  8. 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.

  9. Analysis of the accessibility of CLIP bound sites reveals that nucleation of the miRNA:mRNA pairing occurs preferentially at the 3′-end of the seed match

    PubMed Central

    Marín, Ray M.; Voellmy, Franziska; von Erlach, Thibaud; Vaníček, Jiří

    2012-01-01

    To find out whether the AGO-miRNA complex is more sensitive to the accessibility of a particular region inside the seed match, we analyze in detail the accessibility of a wide set of miRNA binding sites validated by PAR-CLIP and HITS-CLIP experiments. Our analysis reveals that nucleotides at the 3′-end of bound seed matches are significantly more accessible than nucleotides at the 5′-end as well as nucleotides at any positions in the unbound seed matches. We show that the accessibility of a single nucleotide at the 3′-end is more effective than the accessibility of several nucleotides at the 5′-end in discriminating between functional and nonfunctional binding sites. Analysis of mRNA and protein fold changes induced by miRNA overexpression demonstrates that genes with accessible nucleation regions at the 3′-end are down-regulated more strongly than genes whose accessible nucleation regions are located elsewhere within the seed match. We also observed an increase in the precision of the miRNA target prediction algorithm PACMIT when accessibility toward the 3′-end of the seed match was required. The pronounced sensitivity of the AGO–miRNA complex to the accessibility of the 3′-end of the seed match suggests that, in most cases, nucleation occurs in this region. We show that this conclusion is consistent with previous experimental studies. PMID:22915600

  10. Birth Defects

    MedlinePlus

    A birth defect is a problem that happens while a baby is developing in the mother's body. Most birth defects happen during the first 3 months of ... in the United States is born with a birth defect. A birth defect may affect how the ...

  11. Control of VO•• ˜ TiT i ' dipole pairs as well as M gTi ″ defects on dielectric properties of Mg doped (Pb0.35Sr0.65)TiO3 thin film

    NASA Astrophysics Data System (ADS)

    Hu, Tao; Wang, Zongrong; Ma, Ning; Du, Piyi

    2016-01-01

    Mg doped (Pb0.35Sr0.65)TiO3 (PST) thin films were fabricated on indium tin oxide /glass substrates by the sol-gel technique. The formation of the PST phase and control of the magnesium doping on the microstructure, defect states, and dielectric properties of the thin film were investigated by means of XRD, SEM, AFM, XPS, and impedance analysis. Results showed that the oxygen vacancies and the associated Ti3+ ions formed as VO•• ˜ TiT i ' dipole pairs, and the dipole pairs were aligned opposite to the direction of the intrinsic dipole moments in the PST thin film. The amount of dipole pairs was strongly affected by the formed M gTi ″ in the thin film. The minimum amount of the dipole pairs appeared in the PST thin film with Mg doping content of 6% in molar ratio. The thin film with Mg doping content of 6% showed high permittivity due to low offset from VO•• ˜ TiT i ' dipole pairs and low dielectric loss due to low defect electrons generated in the thin film simultaneously. The formed M gTi ″ in the oxygen octahedral contributed lower response of the dipole moments to external electric field and resulted in lower tunability of the PST thin film with increasing Mg doping content. Controlled by the substitution of Mg2+ ions for Ti4+ ions and the induced VO•• ˜ TiT i ' dipole pairs, the optimal figure of merit was obtained in the PST thin film with Mg doping content of 6% with which the thin film possessed the smallest dielectric loss and still high tunability simultaneously.

  12. Coulomb bound states of strongly interacting photons

    SciTech Connect

    Maghrebi, M. F.; Choi, S.; Martin, I.; Firstenberg, O.; Lukin, M. D.; Büchler, H. P.; Gorshkov, A. V.

    2015-09-16

    We show that two photons coupled to Rydberg states via electromagnetically induced transparency (EIT) can interact via an effective Coulomb potential. The interaction then gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasi-bound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb problem, thus obtaining a photonic analogue of the hydrogen atom. These states propagate with a negative group velocity in the medium, which allows for a simple preparation and detection scheme, before they slowly decay to pairs of bound Rydberg atoms. As a result, we verify the metastability and backward propagation of these Coulomb bound states with exact numerical simulations.

  13. Coulomb bound states of strongly interacting photons

    DOE PAGES

    Maghrebi, M. F.; Gullans, Michael J.; Bienias, P.; ...

    2015-09-16

    We show that two photons coupled to Rydberg states via electromagnetically induced transparency (EIT) can interact via an effective Coulomb potential. The interaction then gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasi-bound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb problem, thus obtaining a photonic analogue of the hydrogen atom. These states propagate with a negative group velocity in the medium, which allows for a simple preparation and detection scheme, before they slowlymore » decay to pairs of bound Rydberg atoms. As a result, we verify the metastability and backward propagation of these Coulomb bound states with exact numerical simulations.« less

  14. Sequential detection of web defects

    DOEpatents

    Eichel, Paul H.; Sleefe, Gerard E.; Stalker, K. Terry; Yee, Amy A.

    2001-01-01

    A system for detecting defects on a moving web having a sequential series of identical frames uses an imaging device to form a real-time camera image of a frame and a comparitor to comparing elements of the camera image with corresponding elements of an image of an exemplar frame. The comparitor provides an acceptable indication if the pair of elements are determined to be statistically identical; and a defective indication if the pair of elements are determined to be statistically not identical. If the pair of elements is neither acceptable nor defective, the comparitor recursively compares the element of said exemplar frame with corresponding elements of other frames on said web until one of the acceptable or defective indications occur.

  15. Hamiltonian anomalies of bound states in QED

    SciTech Connect

    Shilin, V. I.; Pervushin, V. N.

    2013-10-15

    The Bound State in QED is described in systematic way by means of nonlocal irreducible representations of the nonhomogeneous Poincare group and Dirac's method of quantization. As an example of application of this method we calculate triangle diagram Para-Positronium {yields} {gamma}{gamma}. We show that the Hamiltonian approach to Bound State in QED leads to anomaly-type contribution to creation of pair of parapositronium by two photon.

  16. Entropy Bounds and Entanglement

    NASA Astrophysics Data System (ADS)

    Fisher, Zachary

    The generalized covariant entropy bound, or Bousso bound, is a holographic bound on the entropy of a region of space in a gravitational theory. It bounds the entropy passing through certain null surfaces. The bound remains non-trivial in the weak-gravity limit, and provides non-trivial constraints on the entropy of ordinary quantum states even in a regime where gravity is negligible. In the first half of this thesis, we present a proof of the Bousso bound in the weak-gravity regime within the framework of quantum field theory. The bound uses techniques from quantum information theory which relate the energy and entropy of quantum states. We present two proofs of the bound in free and interacting field theory. In the second half, we present a generalization of the Bousso bound called the quantum focussing conjecture. Our conjecture is a bound on the rate of entropy generation in a quantum field theory coupled semiclassically to gravity. The conjecture unifies and generalizes several ideas in holography. In particular, the quantum focussing conjecture implies a bound on entropies which is similar to, but subtly different from, the Bousso bound proven in the first half. The quantum focussing conjecture implies a novel non-gravitational energy condition, the quantum null energy condition, which gives a point-wise lower bound on the null-null component of the stress tensor of quantum matter. We give a proof of this bound in the context of free and superrenormalizable bosonic quantum field theory.

  17. Ab-intitio Studies of Defects in Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Poykko, Sami

    2000-03-01

    Defects, defect complexes and domain walls in PbTiO3 have been studied using a first-principles method. Platinum is a widely used electrode material for PZT. Due to relatively high deposition temperatures a large concentration of Pt atoms diffuse into PZT, where they occupy Ti-sites and act as acceptors. Platinum impurity is shown to form a tightly bond pair with oxygen vacancy. This complex can have a significant role in fatigue, since each of these strongly polar defect also pin a polarization of a surrounding lattice. This result implies that in order to increase fatigue resistance of PZT it is extremely important to minimize especially acceptor type impurities [1]. We have shown that oxygen and lead vacancies do not form strongly bound defect complexes in PZT and therefore their creation does not seem to be directly involved in fatigue or imprint. According to our calculations a formation of a oxygen-vacancy lead-vacancy pair (close or distant) becomes exothermic under certain conditions. Therefore large number of vacancies are produced to PZT leading to resistance degradation and overall crystal quality also becomes worse [2]. An 180 degree domain wall has been shown to have an energy density of 150 erg/cm^2 and is lead-centered (ie. symmetry plane goes along Pb-atoms). A minimum width of a domain is calculated to be 4 lattice constants, narrower domains are found to be thermodynamically unstable [3]. footnote[1]S. Poykko and D. J. Chadi, "Dipolar Defect Model for Fatigue in Ferroelectric Perovskites" Physical Review Letters 83, 1231 (1999). footnote[2]S. Poykko and D. J. Chadi, "First principles study of Pb-vacancies in PbTiO_3", Applied Physics Letters, in print (2000). footnote[3]S. Poykko and D. J. Chadi, "Ab initio study of 180 degree domain wall energy and structure in PbTiO_3" Applied Physics Letters, 75, 2830 (1999).

  18. The comparative effectiveness of demineralized bone matrix, beta-tricalcium phosphate, and bovine-derived anorganic bone matrix on inflammation and bone formation using a paired calvarial defect model in rats

    PubMed Central

    Khoshzaban, Ahad; Mehrzad, Shahram; Tavakoli, Vida; Keshel, Saeed Heidari; Behrouzi, Gholam Reza; Bashtar, Maryam

    2011-01-01

    Background In this study, the effectiveness of Iranian Tissue Bank–produced demineralized bone matrix (ITB-DBM), beta-tricalcium phosphate (βTCP), and Bio-Oss® (Geistlich Pharma AG, Wolhusen, Switzerland) were evaluated and compared with double controls. The main goal was to measure the amount of new bone formation in the center of defects created in rat calvaria. Another goal was to compare the controls and evaluate the effects of each treatment material on their adjacent untreated (control) defects. Methods In this study, 40 male Wistar rats were selected and divided into four groups, In each group, there were ten rats with two defects in their calvarias; one of them is considered as control and the other one was treated with ITB-DBM (group 1), BIO-OSS (group2), and βTCP (group 3), respectively. But in group 4, both defects were considered as control. The amount of inflammation and new bone formation were evaluated at 4 and 10 weeks. In the first group, one defect was filled with ITB-DBM; in the second group, one defect was filled with Bio-Oss; in the third group, one defect was filled with βTCP; and in the fourth group, both defects were left unfilled. Zeiss microscope (Carl Zeiss AG, Oberkochen, Germany) and Image Tool® (version 3.0; University of Texas Health Science Center at San Antonio, San Antonio, TX) software were used for evaluation. SPSS Statistics (IBM Corp, Somers, NY) was used for statistical analysis. Results Maximum bone formation at 4 and 10 weeks were observed in the ITB-DBM group (46.960% ± 4.366%, 94.970% ± 0.323%), which had significant difference compared with the other groups (P < 0.001). Ranking second was the Bio-Oss group and third, the βTCP group. Bone formation in the group with two unfilled defects was much more significant than in the other controls beside the Bio-Oss and βTCP after 10 weeks (29.1 ± 2.065, 29.05 ± 1.649), while this group had the least bone formation compared with the other controls at week 4 (2.100%

  19. Locating Bound Structures in the Accelerating Universe

    NASA Astrophysics Data System (ADS)

    Pearson, David; Batuski, D. J.

    2013-01-01

    Given the overwhelming evidence of the universe’s accelerating expansion, the question of what structures are gravitationally bound becomes one of utmost interest. Dunner et al. 2006 (D06) and Busha et al. 2003 (B03) set out to answer this question analytically, and they arrived at fairly different answers owing to the differences in their assumptions of velocities at the present epoch. Applying their criteria to different superclusters, it’s possible to make predictions about what structures may be bound. We apply the criteria of D06 and B03 to the Aquarius, Microscopium, Corona Borealis, and Shapley superclusters to make predictions about what structures might be bound and compare with the results of simple N-body simulations to determine which method is a better predictor and to determine the likelihood that parts or all of the superclusters listed above are bound. We find that D06 tend to predict more structure to be bound than B03, and the results of the N-body simulations usually lie somewhere in between the two sets of predictions. Observational evidence, and simulation data suggests that pairs of clusters in Aquarius and Microscopium are gravitationally bound, and that Shapley contains a large complex of clusters that are bound, along with some additional bound pairs. The likelihood that any of the clusters in Corona Borealis are bound to one another is very small, contrary to the claims of Small et al. 1998, who claimed that the entire supercluster is likely gravitationally bound. Busha M. T., Adams F. C., Wechsler R. H., Evrard A. E., 2003, ApJ, 596, 713 Dunner R., Araya P. A., Meza A., Reisenegger A., 2006, MNRAS, 306, 803 Small T. A., Ma C., Sargent W. L. W., Hamilton D., 1998, ApJ, 492, 45

  20. Immunoglobulin K light chain deficiency: A rare, but probably underestimated, humoral immune defect.

    PubMed

    Sala, Pierguido; Colatutto, Antonio; Fabbro, Dora; Mariuzzi, Laura; Marzinotto, Stefania; Toffoletto, Barbara; Perosa, Anna R; Damante, Giuseppe

    2016-04-01

    Human immunoglobulin molecules are generated by a pair of identical heavy chains, which identify the immunoglobulin class, and a pair of identical light chains, Kappa or Lambda alternatively, which characterize the immunoglobulin type. In normal conditions, Kappa light chains represent approximately 2/3 of the light chains of total immunoglobulins, both circulating and lymphocyte surface bound. Very few cases of immunoglobulin Kappa or Lambda light chain defects have been reported. Furthermore, the genetic basis of this defect has been extensively explored only in a single case. We report a case of a patient suffering of serious recurrent bacterial infections, which was caused by a very rare form of immunoglobulin disorder, consisting of a pure defect of Kappa light chain. We evaluated major serum immunoglobulin concentrations, as well as total and free Kappa and Lambda light chain concentrations. Lymphocyte phenotyping was also performed and finally we tested the Kappa chain VJ rearrangement as well as the constant Kappa region sequence. Studies performed on VJ rearrangement showed a polyclonal genetic arrangement, whereas the gene sequencing for the constant region of Kappa chain showed a homozygous T to G substitution at the position 1288 (rs200765148). This mutation causes a substitution from Cys to Gly in the protein sequence and, therefore, determines the abnormal folding of the constant region of Kappa chain. We suggest that this defect could lead to an effective reduction of the variability of total antibody repertoire and a consequent defect of an apparently normal immunoglobulin response to common antigens.

  1. Viscosity bound versus the universal relaxation bound

    NASA Astrophysics Data System (ADS)

    Hod, Shahar

    2017-10-01

    For gauge theories with an Einstein gravity dual, the AdS/CFT correspondence predicts a universal value for the ratio of the shear viscosity to the entropy density, η / s = 1 / 4 π. The holographic calculations have motivated the formulation of the celebrated KSS conjecture, according to which all fluids conform to the lower bound η / s ≥ 1 / 4 π. The bound on η / s may be regarded as a lower bound on the relaxation properties of perturbed fluids and it has been the focus of much recent attention. In particular, it was argued that for a class of field theories with Gauss-Bonnet gravity dual, the shear viscosity to entropy density ratio, η / s, could violate the conjectured KSS bound. In the present paper we argue that the proposed violations of the KSS bound are strongly constrained by Bekenstein's generalized second law (GSL) of thermodynamics. In particular, it is shown that physical consistency of the Gauss-Bonnet theory with the GSL requires its coupling constant to be bounded by λGB ≲ 0 . 063. We further argue that the genuine physical bound on the relaxation properties of physically consistent fluids is ℑω(k > 2 πT) > πT, where ω and k are respectively the proper frequency and the wavenumber of a perturbation mode in the fluid.

  2. Pairing Learners in Pair Work Activity

    ERIC Educational Resources Information Center

    Storch, Neomy; Aldosari, Ali

    2013-01-01

    Although pair work is advocated by major theories of second language (L2) learning and research findings suggest that pair work facilitates L2 learning, what is unclear is how to best pair students in L2 classes of mixed L2 proficiency. This study investigated the nature of pair work in an English as a Foreign Language (EFL) class in a college in…

  3. Pairing Learners in Pair Work Activity

    ERIC Educational Resources Information Center

    Storch, Neomy; Aldosari, Ali

    2013-01-01

    Although pair work is advocated by major theories of second language (L2) learning and research findings suggest that pair work facilitates L2 learning, what is unclear is how to best pair students in L2 classes of mixed L2 proficiency. This study investigated the nature of pair work in an English as a Foreign Language (EFL) class in a college in…

  4. Bound states and the Bekenstein bound

    SciTech Connect

    Bousso, Raphael

    2003-10-16

    We explore the validity of the generalized Bekenstein bound, S<= pi M a. We define the entropy S as the logarithm of the number of states which have energy eigenvalue below M and are localized to a flat space region of width alpha. If boundary conditions that localize field modes are imposed by fiat, then the bound encounters well-known difficulties with negative Casimir energy and large species number, as well as novel problems arising only in the generalized form. In realistic systems, however, finite-size effects contribute additional energy. We study two different models for estimating such contributions. Our analysis suggests that the bound is both valid and nontrivial if interactions are properly included, so that the entropy S counts the bound states of interacting fields.

  5. HIM-8 binds to the X chromosome pairing center and mediateschromosome-specific meiotic synapsis

    SciTech Connect

    Phillips, Carolyn M.; Wong, Chihunt; Bhalla, Needhi; Carlton,Peter M.; Weiser, Pinky; Meneely, Philip M.; Dernburg, Abby F.

    2005-06-05

    The him-8 gene is essential for proper meiotic segregationof the X chromosomes in C. elegans. Herewe show that loss of him-8function causes profound X-chromosome-specific defects in homolog pairingand synapsis.him-8 encodes a C2H2 zinc finger protein that is expressedduring meiosis andconcentrates at a site on the X chromosome known as themeiotic Pairing Center (PC). A role for HIM-8 in PC function is supportedby genetic interactions between PC lesions and him-8 mutations.HIM-8-bound chromosome sites associate with the nuclear envelope (NE)throughout meiotic prophase. Surprisingly, a point mutation in him-8 thatretains both chromosome binding and NE localization fails to stabilizepairing or promote synapsis. These observations indicate thatstabilization of homolog pairing is an active process in which thetethering of chromosome sites to the NE may be necessary but is notsufficient.

  6. Bounded link prediction in very large networks

    NASA Astrophysics Data System (ADS)

    Cui, Wei; Pu, Cunlai; Xu, Zhongqi; Cai, Shimin; Yang, Jian; Michaelson, Andrew

    2016-09-01

    Evaluating link prediction methods is a hard task in very large complex networks due to the prohibitive computational cost. However, if we consider the lower bound of node pairs' similarity scores, this task can be greatly optimized. In this paper, we study CN index in the bounded link prediction framework, which is applicable to enormous heterogeneous networks. Specifically, we propose a fast algorithm based on the parallel computing scheme to obtain all node pairs with CN values larger than the lower bound. Furthermore, we propose a general measurement, called self-predictability, to quantify the performance of similarity indices in link prediction, which can also indicate the link predictability of networks with respect to given similarity indices.

  7. Formation energy of point defects in free surfaces and grain boundaries in MgO

    SciTech Connect

    Wolf, D.

    1982-01-01

    The computer code developed in recent years at Argonne National Laboratory for the investigation of the energy and structure of interfaces in ionic crystals has been extended to permit the consideration of neutral intrinsic point defects in such interfaces. As examples, bound Schottky pairs as well as substitutional Fe/sup 2 +/ and Ca/sup 2 +/ impurities are considered in the (100) surface and surface region. The role of isovalent impurities in the free (110) surface region and in a coincident-site twist boundary are also investigated. Results are compared and found in agreement with results obtained by means of the HADES program.

  8. Anyon pairing via phonon-mediated interaction

    NASA Astrophysics Data System (ADS)

    Kandemir, B. S.

    2006-08-01

    In this paper, we study the pairing of anyons subjected to an external uniform magnetic field and confined in a two-dimensional parabolic quantum dot within the framework of Fröhlich large bipolaron theory, motivated by the Wilczek’s prescription that treats anyons as composites having both charges and fictitious flux tubes. In this model, electrons bound to Aharanov-Bohm type flux tubes and surrounded by a cloud of virtual LO phonons interact with each other through the long range Coulomb and statistical potentials. In order to discuss the effects of both spatial confinement potential and external uniform magnetic field on the boundaries of the stability region of such a pairing in real space, we perform a self-consistent treatment of the ground-state energies of both an interacting anyon pair and two noninteracting anyons. Our results suggest that two interacting anyons can be bound into a condensate anyon pair through a phonon-mediated interaction.

  9. Coulomb Bound States of Strongly Interacting Photons

    NASA Astrophysics Data System (ADS)

    Maghrebi, M. F.; Gullans, M. J.; Bienias, P.; Choi, S.; Martin, I.; Firstenberg, O.; Lukin, M. D.; Büchler, H. P.; Gorshkov, A. V.

    2015-09-01

    We show that two photons coupled to Rydberg states via electromagnetically induced transparency can interact via an effective Coulomb potential. This interaction gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasibound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb potential, thus obtaining a photonic analogue of the hydrogen atom. Under certain conditions, the wave function resembles that of a diatomic molecule in which the two polaritons are separated by a finite "bond length." These states propagate with a negative group velocity in the medium, allowing for a simple preparation and detection scheme, before they slowly decay to pairs of bound Rydberg atoms.

  10. Morphological Processing: A Comparison between Free and Bound Stem Facilitation

    ERIC Educational Resources Information Center

    Pastizzo, Matthew J.; Feldman, Laurie B.

    2004-01-01

    Linguists distinguish between words formed from free stems (e.g., "actor": "act") and those formed from bound stems (e.g., "spectator": "spect"). In a forward masked priming task, we observed significant morphological facilitation for prime-target pairs that shared either a free (e.g., "deform"--"CONFORM") or a bound (e.g., "revive"--"SURVIVE")…

  11. Physical Uncertainty Bounds (PUB)

    SciTech Connect

    Vaughan, Diane Elizabeth; Preston, Dean L.

    2015-03-19

    This paper introduces and motivates the need for a new methodology for determining upper bounds on the uncertainties in simulations of engineered systems due to limited fidelity in the composite continuum-level physics models needed to simulate the systems. We show that traditional uncertainty quantification methods provide, at best, a lower bound on this uncertainty. We propose to obtain bounds on the simulation uncertainties by first determining bounds on the physical quantities or processes relevant to system performance. By bounding these physics processes, as opposed to carrying out statistical analyses of the parameter sets of specific physics models or simply switching out the available physics models, one can obtain upper bounds on the uncertainties in simulated quantities of interest.

  12. Superconductivity: The persistence of pairs

    SciTech Connect

    Edelman, Alex; Littlewood, Peter

    2015-05-20

    Superconductivity stems from a weak attraction between electrons that causes them to form bound pairs and behave much like bosons. These so-called Cooper pairs are phase coherent, which leads to the astonishing properties of zero electrical resistance and magnetic flux expulsion typical of superconducting materials. This coherent state may be qualitatively understood within the Bose–Einstein condensate (BEC) model, which predicts that a gas of interacting bosons will become unstable below a critical temperature and condense into a phase of matter with a macroscopic, coherent population in the lowest energy state, as happens in 4He or cold atomic gases. The successful theory proposed by Bardeen, Cooper and Schrieffer (BCS) predicts that at the superconducting transition temperature Tc, electrons simultaneously form pairs and condense, with no sign of pairing above Tc. Theorists have long surmised that the BCS and BEC models are opposite limits of a single theory and that strong interactions or low density can, in principle, drive the system to a paired state at a temperature Tpair higher than Tc, making the transition to the superconducting state BEC-like (Fig. 1). Yet most superconductors to date are reasonably well described by BCS theory or its extensions, and there has been scant evidence in electronic materials for the existence of pairing independent of the full superconducting state (though an active debate rages over the cuprate superconductors). Writing in Nature, Jeremy Levy and colleagues have now used ingenious nanostructured devices to provide evidence for electron pairing1. Perhaps surprisingly, the material they have studied is a venerable, yet enigmatic, low-temperature superconductor, SrTiO3.

  13. Bounding Species Distribution Models

    NASA Technical Reports Server (NTRS)

    Stohlgren, Thomas J.; Jarnevich, Cahterine S.; Morisette, Jeffrey T.; Esaias, Wayne E.

    2011-01-01

    Species distribution models are increasing in popularity for mapping suitable habitat for species of management concern. Many investigators now recognize that extrapolations of these models with geographic information systems (GIS) might be sensitive to the environmental bounds of the data used in their development, yet there is no recommended best practice for "clamping" model extrapolations. We relied on two commonly used modeling approaches: classification and regression tree (CART) and maximum entropy (Maxent) models, and we tested a simple alteration of the model extrapolations, bounding extrapolations to the maximum and minimum values of primary environmental predictors, to provide a more realistic map of suitable habitat of hybridized Africanized honey bees in the southwestern United States. Findings suggest that multiple models of bounding, and the most conservative bounding of species distribution models, like those presented here, should probably replace the unbounded or loosely bounded techniques currently used [Current Zoology 57 (5): 642-647, 2011].

  14. Bounding species distribution models

    USGS Publications Warehouse

    Stohlgren, T.J.; Jarnevich, C.S.; Esaias, W.E.; Morisette, J.T.

    2011-01-01

    Species distribution models are increasing in popularity for mapping suitable habitat for species of management concern. Many investigators now recognize that extrapolations of these models with geographic information systems (GIS) might be sensitive to the environmental bounds of the data used in their development, yet there is no recommended best practice for "clamping" model extrapolations. We relied on two commonly used modeling approaches: classification and regression tree (CART) and maximum entropy (Maxent) models, and we tested a simple alteration of the model extrapolations, bounding extrapolations to the maximum and minimum values of primary environmental predictors, to provide a more realistic map of suitable habitat of hybridized Africanized honey bees in the southwestern United States. Findings suggest that multiple models of bounding, and the most conservative bounding of species distribution models, like those presented here, should probably replace the unbounded or loosely bounded techniques currently used. ?? 2011 Current Zoology.

  15. Causality and Tsirelson's bounds

    SciTech Connect

    Buhrman, H.; Massar, S.

    2005-11-15

    We study the properties of no-signaling correlations that cannot be reproduced by local measurements on entangled quantum states. We say that such correlations violate Tsirelson bounds. We show that if these correlations are obtained by some reversible unitary quantum evolution U, then U cannot be written in the product form U{sub A}xU{sub B}. This implies that U can be used for signaling and for entanglement generation. This result is completely general and in fact can be viewed as a characterization of Tsirelson bounds. We then show how this result can be used as a tool to study Tsirelson bounds and we illustrate this by rederiving the Tsirelson bound of 2{radical}(2) for the Clauser-Horn-Shimony-Holt inequality, and by deriving a new Tsirelson bound for qutrits.

  16. Bounding Species Distribution Models

    NASA Technical Reports Server (NTRS)

    Stohlgren, Thomas J.; Jarnevich, Cahterine S.; Morisette, Jeffrey T.; Esaias, Wayne E.

    2011-01-01

    Species distribution models are increasing in popularity for mapping suitable habitat for species of management concern. Many investigators now recognize that extrapolations of these models with geographic information systems (GIS) might be sensitive to the environmental bounds of the data used in their development, yet there is no recommended best practice for "clamping" model extrapolations. We relied on two commonly used modeling approaches: classification and regression tree (CART) and maximum entropy (Maxent) models, and we tested a simple alteration of the model extrapolations, bounding extrapolations to the maximum and minimum values of primary environmental predictors, to provide a more realistic map of suitable habitat of hybridized Africanized honey bees in the southwestern United States. Findings suggest that multiple models of bounding, and the most conservative bounding of species distribution models, like those presented here, should probably replace the unbounded or loosely bounded techniques currently used [Current Zoology 57 (5): 642-647, 2011].

  17. A Cramer-Rao Type Lower Bound for Essentially Unbiased Parameter Estimation

    DTIC Science & Technology

    1992-01-03

    should apply to the entire class of estimators with acceptably small bias. In this report a new CR-type lower bound is derived which takes into account a...unbiased CR bound. If an upper bound on the bias gradient ot tne estimator is specified, our lower bound on estimator variance can subsequently be applied ...multiple parameters. Finally, Section 8 applies the new bound to covariance estimation for a pair of HD Gaussian sequences. 2 2. PRELIMINARIES 2.1

  18. Sculpture, perspective view looking to pair of lions positioned at ...

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

    Sculpture, perspective view looking to pair of lions positioned at top of stairs leading down into the Glen - National Park Seminary, Bounded by Capitol Beltway (I-495), Linden Lane, Woodstove Avenue, & Smith Drive, Silver Spring, Montgomery County, MD

  19. Electron-positron pairs production in a macroscopic charged core

    NASA Astrophysics Data System (ADS)

    Ruffini, Remo; Xue, She-Sheng

    2011-02-01

    Classical and semi-classical energy states of relativistic electrons bounded by a massive and charged core with the charge-mass radio Q/M and macroscopic radius R are discussed. We show that the energies of semi-classical (bound) states can be much smaller than the negative electron mass-energy (-mc2), and energy-level crossing to negative energy continuum occurs. Electron-positron pair production takes place by quantum tunneling, if these bound states are not occupied. Electrons fill into these bound states and positrons go to infinity. We explicitly calculate the rate of pair-production, and compare it with the rates of electron-positron production by the Sauter-Euler-Heisenberg-Schwinger in a constant electric field. In addition, the pair-production rate for the electro-gravitational balance ratio Q/M=10-19 is much larger than the pair-production rate due to the Hawking processes.

  20. Antihistamine Use in Early Pregnancy and Risk of Birth Defects

    PubMed Central

    Li, Qian; Mitchell, Allen A.; Werler, Martha M.; Yau, Wai-Ping; Hernández-Díaz, Sonia

    2014-01-01

    Background Several studies have reported an association between use of specific antihistamines in early pregnancy and certain specific birth defects. Objective To test 16 previously-hypothesized associations between specific antihistamines and specific birth defects, and identify possible new associations. Methods We used 1998-2010 data from the Slone Epidemiology Center Birth Defects Study, a multicenter case-control surveillance program of birth defects in North America. Mothers were interviewed within six months of delivery about demographic, reproductive, medical, and behavioral factors, and details on use of prescription and non-prescription medications. We compared 1st trimester exposure to specific antihistamines between 13,213 infants with specific malformations and 6,982 non-malformed controls, using conditional logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs), with adjustment for potential confounders, including indication for use. Results Overall, 13.7% of controls were exposed to antihistamines during the 1st trimester. The most commonly-used medications were diphenhydramine (4.2%), loratadine (3.1%), doxylamine (1.9%), and chlorpheniramine (1.7%). Where estimates were stable, none supported the previously-hypothesized associations. Among over 100 exploratory comparisons of other specific antihistamine/defect pairs, 14 had ORs ≥1.5 of which 6 had 95% CI bounds excluding 1.0 before but not after adjustment for multiple comparisons. Conclusion Our findings do not provide meaningful support for previously-posited associations between antihistamines and major congenital anomalies; at the same time, we identified associations that had not been previously suggested. We suspect that previous associations may be chance findings in the context of multiple comparisons, a situation which may also apply to our new findings. PMID:24565715

  1. Engineering the coupling between Majorana bound states

    NASA Astrophysics Data System (ADS)

    Shi, Z. C.; Shao, X. Q.; Xia, Y.; Yi, X. X.

    2017-09-01

    We study the coupling between Majorana bound states (CMBS), which is mediated by a topologically trivial chain in the presence of pairing coupling and long-range coupling. The results show that CMBS can be enhanced by the pairing coupling and long-range coupling of the trivial chain. When driving the trivial chain by periodic driving field, we deduce the analytical expressions of CMBS in the high-frequency limit, and demonstrate that CMBS can be modulated by the frequency and amplitude of driving field. Finally we exhibit the application of tunable CMBS in realizing quantum logic gates.

  2. Malabsorption of protein bound vitamin B12.

    PubMed Central

    Dawson, D W; Sawers, A H; Sharma, R K

    1984-01-01

    Patients with subnormal serum vitamin B12 concentrations were tested for absorption of protein bound vitamin B12 and compared with controls. Absorption of the protein bound vitamin appeared to decrease with increasing age in healthy subjects. Differences between the result of this test and the result of the Schilling test in patients who had undergone gastric surgery were confirmed; such differences were also seen in some patients who had iron deficiency anaemia, an excessive alcohol intake, or folate deficiency. Defective absorption was also found in six patients with an adequate dietary intake of vitamin B12, normal Schilling test results, low serum vitamin concentrations, and tissue changes responding to treatment with vitamin B12. Malabsorption of the vitamin from protein bound sources, which is not detected by the Schilling test, may produce vitamin B12 deficiency of clinical importance. PMID:6421428

  3. Organically bound tritium

    SciTech Connect

    Diabate, S.; Strack, S. )

    1993-12-01

    Tritium released into the environment may be incorporated into organic matter. Organically bound tritium in that case will show retention times in organisms that are considerably longer than those of tritiated water which has significant consequences on dose estimates. This article reviews the most important processes of organically bound tritium production and transport through food networks. Metabolic reactions in plant and animal organisms with tritiated water as a reaction partner are of great importance in this respect. The most important production process, in quantitative terms, is photosynthesis in green plants. The translocation of organically bound tritium from the leaves to edible parts of crop plants should be considered in models of organically bound tritium behavior. Organically bound tritium enters the human body on several pathways, either from the primary producers (vegetable food) or at a higher tropic level (animal food). Animal experiments have shown that the dose due to ingestion of organically bound tritium can be up to twice as high as a comparable intake of tritiated water in gaseous or liquid form. In the environment, organically bound tritium in plants and animals is often found to have higher specific tritium concentrations than tissue water. This is not due to some tritium enrichment effects but to the fact that no equilibrium conditions are reached under natural conditions. 66 refs.

  4. Asymmetric dark matter bound state

    NASA Astrophysics Data System (ADS)

    Bi, Xiao-Jun; Kang, Zhaofeng; Ko, P.; Li, Jinmian; Li, Tianjun

    2017-02-01

    We propose an interesting framework for asymmetric scalar dark matter (ADM), which has novel collider phenomenology in terms of an unstable ADM bound state (ADMonium) produced via Higgs portals. ADMonium is a natural consequence of the basic features of ADM: the (complex scalar) ADM is charged under a dark local U (1 )d symmetry which is broken at a low scale and provides a light gauge boson X . The dark gauge coupling is strong and then ADM can annihilate away into X -pair effectively. Therefore, the ADM can form a bound state due to its large self-interaction via X mediation. To explore the collider signature of ADMonium, we propose that ADM has a two-Higgs doublet portal. The ADMonium can have a sizable mixing with the heavier Higgs boson, which admits a large cross section of ADMonium production associated with b b ¯. The resulting signature at the LHC depends on the decays of X . In this paper we consider a case of particular interest: p p →b b ¯ +ADMonium followed by ADMonium→2 X →2 e+e- where the electrons are identified as (un)converted photons. It may provide a competitive explanation to heavy di-photon resonance searches at the LHC.

  5. Neural Tube Defects

    MedlinePlus

    ... Birth defects & other health conditions > Neural tube defects Neural tube defects E-mail to a friend Please ... this page It's been added to your dashboard . Neural tube defects (NTDs) are birth defects of the ...

  6. Point Defects Quenched in Nickel Aluminide and Related Intermetallic Compounds

    NASA Astrophysics Data System (ADS)

    Fan, Jiawen

    Point defects in the highly ordered B2 compounds NiAl, CoAl and FeAl were studied using the perturbed gammagamma angular correlations (PAC) technique. Quadrupole interactions detected at dilute ^{111}In probes on Al sites in NiAl and CoAl were identified with complexes containing one or two vacancies in the first atomic shell. Measurements on rapidly quenched NiAl and CoAl exhibited increases in site fractions of vacancy-probe complexes caused by formation of thermal defects. Site fractions were analyzed using the law of mass action to obtain absolute vacancy concentrations. PAC is shown to be a powerful new technique for the quantitative study of equilibrium defects in solids. For NiAl, the vacancy concentration quenched-in from a given temperature was found to be independent of composition over the range 50.4 -53.5 at.% Ni, identifying the Schottky defect (vacancy pair) as the dominant equilibrium defect, and ruling out the so-called triple defect. Formation energies and entropies of Schottky pairs were determined to be 2.66(8) and 3.48(12) eV, and 12(1) and 17(2) k_{rm B}, respectively, for NiAl and CoAl. The entropies suggest huge vacancy concentrations, 13%, at the melting temperatures of NiAl and CoAl. Migration energies of Ni and Co vacancies were found to be 1.8(2) and 2.5(2) eV, respectively. FeAl exhibited complex behavior. A low-temperature regime was detected in NiAl and CoAl within which vacancies are mobile but do not anneal out, so that the vacancy concentration remains constant. In NiAl, this "bottleneck" regime extends from 350 to 700 ^circC. Vacancies were found to be bound to the In probes with an energy very close to 0.20 eV in NiAl and CoAl. An explanation of the bottleneck is proposed in terms of saturation of all lattice sinks. This annealing bottleneck should exist in a wide range of intermetallic compounds when there is a sufficiently high vacancy concentration.

  7. Congenital Defects.

    ERIC Educational Resources Information Center

    Goldman, Allen S.; And Others

    There are two general categories (not necessarily mutually exclusive) of congenital defects: (1) abnormalities that have an hereditary basis, such as single and multiple genes, or chromosomal abberration; and (2) abnormalities that are caused by nonhereditary factors, such as malnutrition, maternal disease, radiation, infections, drugs, or…

  8. Congenital Defects.

    ERIC Educational Resources Information Center

    Goldman, Allen S.; And Others

    There are two general categories (not necessarily mutually exclusive) of congenital defects: (1) abnormalities that have an hereditary basis, such as single and multiple genes, or chromosomal abberration; and (2) abnormalities that are caused by nonhereditary factors, such as malnutrition, maternal disease, radiation, infections, drugs, or…

  9. Virial Expansion Bounds

    NASA Astrophysics Data System (ADS)

    Tate, Stephen James

    2013-10-01

    In the 1960s, the technique of using cluster expansion bounds in order to achieve bounds on the virial expansion was developed by Lebowitz and Penrose (J. Math. Phys. 5:841, 1964) and Ruelle (Statistical Mechanics: Rigorous Results. Benjamin, Elmsford, 1969). This technique is generalised to more recent cluster expansion bounds by Poghosyan and Ueltschi (J. Math. Phys. 50:053509, 2009), which are related to the work of Procacci (J. Stat. Phys. 129:171, 2007) and the tree-graph identity, detailed by Brydges (Phénomènes Critiques, Systèmes Aléatoires, Théories de Jauge. Les Houches 1984, pp. 129-183, 1986). The bounds achieved by Lebowitz and Penrose can also be sharpened by doing the actual optimisation and achieving expressions in terms of the Lambert W-function. The different bound from the cluster expansion shows some improvements for bounds on the convergence of the virial expansion in the case of positive potentials, which are allowed to have a hard core.

  10. Pairing versus quarteting coherence length

    NASA Astrophysics Data System (ADS)

    Delion, D. S.; Baran, V. V.

    2015-02-01

    We systematically analyze the coherence length in even-even nuclei. The pairing coherence length in the spin-singlet channel for the effective density-dependent delta (DDD) and Gaussian interaction is estimated. We consider in our calculations bound states as well as narrow resonances. It turns out that the pairing gaps given by the DDD interaction are similar to those of the Gaussian potential if one renormalizes the radial width to the nuclear radius. The correlations induced by the pairing interaction have, in all considered cases, a long-range character inside the nucleus and a decrease towards the surface. The mean coherence length is larger than the geometrical radius for light nuclei and approaches this value for heavy nuclei. The effect of the temperature and states in the continuum is investigated. Strong shell effects are put in evidence, especially for protons. We generalize this concept to quartets by considering similar relations, but between proton and neutron pairs. The quartet coherence length has a similar shape, but with larger values on the nuclear surface. We provide evidence of the important role of proton-neutron correlations by estimating the so-called alpha coherence length, which takes into account the overlap with the proton-neutron part of the α -particle wave function. It turns out that it does not depend on the nuclear size and has a value comparable to the free α -particle radius. We have shown that pairing correlations are mainly concentrated inside the nucleus, while quarteting correlations are connected to the nuclear surface.

  11. Validation of EMP bounds

    SciTech Connect

    Warne, L.K.; Merewether, K.O.; Chen, K.C.; Jorgenson, R.E.; Morris, M.E.; Solberg, J.E.; Lewis, J.G.; Derr, W.

    1996-07-01

    Test data on canonical weapon-like fixtures are used to validate previously developed analytical bounding results. The test fixtures were constructed to simulate (but be slightly worse than) weapon ports of entry but have known geometries (and electrical points of contact). The exterior of the test fixtures exhibited exterior resonant enhancement of the incident fields at the ports of entry with magnitudes equal to those of weapon geometries. The interior consisted of loaded transmission lines adjusted to maximize received energy or voltage but incorporating practical weapon geometrical constraints. New analytical results are also presented for bounding the energies associated with multiple bolt joints and for bounding the exterior resonant enhancement of the exciting fields.

  12. Bosonic pair creation and the Schiff-Snyder-Weinberg effect

    NASA Astrophysics Data System (ADS)

    Lv, Q. Z.; Bauke, Heiko; Su, Q.; Keitel, C. H.; Grobe, R.

    2016-01-01

    Interactions between different bound states in bosonic systems can lead to pair creation. We study this process in detail by solving the Klein-Gordon equation on space-time grids in the framework of time-dependent quantum field theory. By choosing specific external field configurations, two bound states can become pseudodegenerate, which is commonly referred to as the Schiff-Snyder-Weinberg effect. These pseudodegenerate bound states, which have complex energy eigenvalues, are related to the pseudo-Hermiticity of the Klein-Gordon Hamiltonian. In this work, the influence of the Schiff-Snyder-Weinberg effect on pair production is studied. A generalized Schiff-Snyder-Weinberg effect, where several pairs of pseudodegenerate states appear, is found in combined electric and magnetic fields. The generalized Schiff-Snyder-Weinberg effect likewise triggers pair creation. The particle number in these situations obeys an exponential growth law in time enhancing the creation of bosons, which cannot be found in fermionic systems.

  13. Electron teleportation via Majorana bound states in a mesoscopic superconductor.

    PubMed

    Fu, Liang

    2010-02-05

    Zero-energy Majorana bound states in superconductors have been proposed to be potential building blocks of a topological quantum computer, because quantum information can be encoded nonlocally in the fermion occupation of a pair of spatially separated Majorana bound states. However, despite intensive efforts, nonlocal signatures of Majorana bound states have not been found in charge transport. In this work, we predict a striking nonlocal phase-coherent electron transfer process by virtue of tunneling in and out of a pair of Majorana bound states. This teleportation phenomenon only exists in a mesoscopic superconductor because of an all-important but previously overlooked charging energy. We propose an experimental setup to detect this phenomenon in a superconductor-quantum-spin-Hall-insulator-magnetic-insulator hybrid system.

  14. Computing Graphical Confidence Bounds

    NASA Technical Reports Server (NTRS)

    Mezzacappa, M. A.

    1983-01-01

    Approximation for graphical confidence bounds is simple enough to run on programmable calculator. Approximation is used in lieu of numerical tables not always available, and exact calculations, which often require rather sizable computer resources. Approximation verified for collection of up to 50 data points. Method used to analyze tile-strength data on Space Shuttle thermal-protection system.

  15. Born Level Bound States

    NASA Astrophysics Data System (ADS)

    Hoyer, Paul

    2017-05-01

    Bound state poles in the S-matrix of perturbative QED are generated by the divergence of the expansion in α . The perturbative corrections are necessarily singular when expanding around free, {O}( α ^0 ) in and out states that have no overlap with finite-sized atomic wave functions. Nevertheless, measurables such as binding energies do have well-behaved expansions in powers of α (and log α ). It is desirable to formulate the concept of "lowest order" for gauge theory bound states such that higher order corrections vanish in the α → 0 limit. This may allow to determine a lowest order term for QCD hadrons which incorporates essential features such as confinement and chiral symmetry breaking, and thus can serve as the starting point of a useful perturbative expansion. I discuss a "Born" (no loop, lowest order in \\hbar ) approximation. Born level states are bound by gauge fields which satisfy the classical field equations. Gauss' law determines a distinct field A^0({\\varvec{x}}) for each instantaneous position of the charges. A Poincaré covariant boundary condition for the gluon field leads to a confining potential for q\\bar{q} and qqq states. In frames where the bound state is in motion the classical gauge field is obtained by a Lorentz boost of the rest frame field.

  16. Computing Graphical Confidence Bounds

    NASA Technical Reports Server (NTRS)

    Mezzacappa, M. A.

    1983-01-01

    Approximation for graphical confidence bounds is simple enough to run on programmable calculator. Approximation is used in lieu of numerical tables not always available, and exact calculations, which often require rather sizable computer resources. Approximation verified for collection of up to 50 data points. Method used to analyze tile-strength data on Space Shuttle thermal-protection system.

  17. Genetic sperm defects.

    PubMed

    Chenoweth, Peter J

    2005-08-01

    Genetic sperm defects are specific sperm defects, which have been shown to have a genetic mode of transmission. Such genetic linkage, either direct or indirect, has been associated with a number of sperm defects in different species, with this number increasing with improved diagnostic capabilities. A number of sperm defects, which have proven or suspected genetic modes of transmission are discussed herein, with particular emphasis on cattle. These include: 1. Acrosome defects (knobbed, ruffled and incomplete); 2. Head defects (abnormal condensation, decapitated, round head, rolled head, nuclear crest); 3. Midpiece abnormalities ("Dag" defect, "corkscrew" defect, "pseudo-droplet" defect); 4. Tail defects ("tail stump" defect, primary ciliary dyskinesia).

  18. Matched-pair classification

    SciTech Connect

    Theiler, James P

    2009-01-01

    Following an analogous distinction in statistical hypothesis testing, we investigate variants of machine learning where the training set comes in matched pairs. We demonstrate that even conventional classifiers can exhibit improved performance when the input data has a matched-pair structure. Online algorithms, in particular, converge quicker when the data is presented in pairs. In some scenarios (such as the weak signal detection problem), matched pairs can be generated from independent samples, with the effect not only doubling the nominal size of the training set, but of providing the structure that leads to better learning. A family of 'dipole' algorithms is introduced that explicitly takes advantage of matched-pair structure in the input data and leads to further performance gains. Finally, we illustrate the application of matched-pair learning to chemical plume detection in hyperspectral imagery.

  19. Vortex pairs on surfaces

    SciTech Connect

    Koiller, Jair

    2009-05-06

    A pair of infinitesimally close opposite vortices moving on a curved surface moves along a geodesic, according to a conjecture by Kimura. We outline a proof. Numerical simulations are presented for a pair of opposite vortices at a close but nonzero distance on a surface of revolution, the catenoid. We conjecture that the vortex pair system on a triaxial ellipsoid is a KAM perturbation of Jacobi's geodesic problem. We outline some preliminary calculations required for this study. Finding the surfaces for which the vortex pair system is integrable is in order.

  20. Petawatt laser absorption bounded

    PubMed Central

    Levy, Matthew C.; Wilks, Scott C.; Tabak, Max; Libby, Stephen B.; Baring, Matthew G.

    2014-01-01

    The interaction of petawatt (1015 W) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light f, and even the range of f is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that f exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials. PMID:24938656

  1. Cooper pairs and bipolarons

    NASA Astrophysics Data System (ADS)

    Lakhno, Victor

    2016-11-01

    It is shown that Cooper pairs are a solution of the bipolaron problem for model Fröhlich Hamiltonian. The total energy of a pair for the initial Fröhlich Hamiltonian is found. Differences between the solutions for the model and initial two-particle problems are discussed.

  2. Strongly bound excitons in anatase TiO2 single crystals and nanoparticles

    DOE PAGES

    Baldini, E.; Chiodo, L.; Dominguez, A.; ...

    2017-04-13

    Anatase TiO2 is among the most studied materials for light-energy conversion applications, but the nature of its fundamental charge excitations is still unknown. Yet it is crucial to establish whether light absorption creates uncorrelated electron-hole pairs or bound excitons and, in the latter case, to determine their character. Here, by combining steady-state angle-resolved photoemission spectroscopy and spectroscopic ellipsometry with state-of-the-art ab initio calculations, we demonstrate that the direct optical gap of single crystals is dominated by a strongly bound exciton rising over the continuum of indirect interband transitions. This exciton possesses an intermediate character between the Wannier-Mott and Frenkel regimesmore » and displays a peculiar two-dimensional wavefunction in the three-dimensional lattice. The nature of the higher-energy excitations is also identified. Furthermore, the universal validity of our results is confirmed up to room temperature by observing the same elementary excitations in defect-rich samples (doped single crystals and nanoparticles) via ultrafast two-dimensional deep-ultraviolet spectroscopy.« less

  3. Formation of asteroid pairs by rotational fission.

    PubMed

    Pravec, P; Vokrouhlický, D; Polishook, D; Scheeres, D J; Harris, A W; Galád, A; Vaduvescu, O; Pozo, F; Barr, A; Longa, P; Vachier, F; Colas, F; Pray, D P; Pollock, J; Reichart, D; Ivarsen, K; Haislip, J; Lacluyze, A; Kusnirák, P; Henych, T; Marchis, F; Macomber, B; Jacobson, S A; Krugly, Yu N; Sergeev, A V; Leroy, A

    2010-08-26

    Pairs of asteroids sharing similar heliocentric orbits, but not bound together, were found recently. Backward integrations of their orbits indicated that they separated gently with low relative velocities, but did not provide additional insight into their formation mechanism. A previously hypothesized rotational fission process may explain their formation-critical predictions are that the mass ratios are less than about 0.2 and, as the mass ratio approaches this upper limit, the spin period of the larger body becomes long. Here we report photometric observations of a sample of asteroid pairs, revealing that the primaries of pairs with mass ratios much less than 0.2 rotate rapidly, near their critical fission frequency. As the mass ratio approaches 0.2, the primary period grows long. This occurs as the total energy of the system approaches zero, requiring the asteroid pair to extract an increasing fraction of energy from the primary's spin in order to escape. We do not find asteroid pairs with mass ratios larger than 0.2. Rotationally fissioned systems beyond this limit have insufficient energy to disrupt. We conclude that asteroid pairs are formed by the rotational fission of a parent asteroid into a proto-binary system, which subsequently disrupts under its own internal system dynamics soon after formation.

  4. Universal bounds on current fluctuations

    NASA Astrophysics Data System (ADS)

    Pietzonka, Patrick; Barato, Andre C.; Seifert, Udo

    2016-05-01

    For current fluctuations in nonequilibrium steady states of Markovian processes, we derive four different universal bounds valid beyond the Gaussian regime. Different variants of these bounds apply to either the entropy change or any individual current, e.g., the rate of substrate consumption in a chemical reaction or the electron current in an electronic device. The bounds vary with respect to their degree of universality and tightness. A universal parabolic bound on the generating function of an arbitrary current depends solely on the average entropy production. A second, stronger bound requires knowledge both of the thermodynamic forces that drive the system and of the topology of the network of states. These two bounds are conjectures based on extensive numerics. An exponential bound that depends only on the average entropy production and the average number of transitions per time is rigorously proved. This bound has no obvious relation to the parabolic bound but it is typically tighter further away from equilibrium. An asymptotic bound that depends on the specific transition rates and becomes tight for large fluctuations is also derived. This bound allows for the prediction of the asymptotic growth of the generating function. Even though our results are restricted to networks with a finite number of states, we show that the parabolic bound is also valid for three paradigmatic examples of driven diffusive systems for which the generating function can be calculated using the additivity principle. Our bounds provide a general class of constraints for nonequilibrium systems.

  5. 351 New Common Proper-Motion Pairs from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Caballero, Rafael

    2012-01-01

    This paper presents 351 previously uncataloged pairs with separation under 100 arcseconds and proper motion over 70 milliseconds of arc/year. These pairs are the result of an extensive study that started with 96,205 candidate pairs from the Sloan Digital Survey (SDSS). Different criteria explained in the paper are applied to increase the probability of a physical bound between the components.

  6. Quantum Phases of Fermionic Cold Atoms Through Pairing and Dissociation

    NASA Astrophysics Data System (ADS)

    Lopez, Nicolas; Tsai, Shan-Wen; Timmermans, E.; Lin, Chi-Yong

    2011-03-01

    Cold atom experiments have realized molecule creation consisting of paired fermions and dissociation of weakly bound molecules into correlated fermions by tuning of the interactions with external fields [1,2]. We study many-body correlations in such system where molecules are weakly bound and therefore pairs of fermionic atoms convert into and dissociate from the bound molecule state. This exchange mediates a long-range interaction between the fermions. We consider a simple many-body Hamiltonian that includes the destruction of fermionic atom pairs to form single bosonic molecules and vice versa. We employ a functional renormalization-group approach to search for instabilities from the disordered quantum liquid phase that may arise from a boson mediated fermion-fermion interaction. We calculate the renormalized frequency-dependent fermion interactions vertices and renormalized molecular binding energy.

  7. Radiative recombination mechanisms in individual wurtzite ZnSe nanowires with a defect-free single-crystalline microstructure.

    PubMed

    Saxena, Ankur; Pan, Qi; Ruda, Harry E

    2013-04-07

    Photoluminescence (PL) spectroscopy performed on arrays of semiconductor nanowires (NWs) suffers from ensemble broadening of PL lines, and fails to separate the PL from NWs of different crystal structures in the ensemble. Even the results on PL from single NWs are not devoid of ambiguity. This is because the influence of structural defects in NWs, such as stacking faults, twin boundaries and dislocations, on their optical spectra cannot be accounted for since the structural characteristics of the same NW remain largely unknown. We performed low-temperature PL spectroscopy on individual wurtzite (WZ) ZnSe NWs, and confirmed a homogeneous single-crystalline microstructure without any extended defects in these NWs, thus excluding any role of structural imperfections in their optical spectra. The luminescence is shown to be dominated solely by native point defects, while no role of extrinsic impurities was found. The radiative recombination is shown to originate from excitons bound to vacancies of Zn (VZn), VZn-complexes, and their phonon replicas. The binding energies of the acceptor-bound excitons, ionization energies of the acceptors, and average number of phonons emitted for shallow donor-VZn acceptor pair related transition were determined. Distinct from previous studies on PL from arrays of ZnSe NWs, this work provides an unambiguous interpretation of the PL spectra and assignment of PL peaks to WZ ZnSe. Narrow excitonic emission of linewidths 2.9 meV indicate excellent optical quality of WZ ZnSe NWs.

  8. Electron pairing without superconductivity.

    PubMed

    Cheng, Guanglei; Tomczyk, Michelle; Lu, Shicheng; Veazey, Joshua P; Huang, Mengchen; Irvin, Patrick; Ryu, Sangwoo; Lee, Hyungwoo; Eom, Chang-Beom; Hellberg, C Stephen; Levy, Jeremy

    2015-05-14

    Strontium titanate (SrTiO3) is the first and best known superconducting semiconductor. It exhibits an extremely low carrier density threshold for superconductivity, and possesses a phase diagram similar to that of high-temperature superconductors--two factors that suggest an unconventional pairing mechanism. Despite sustained interest for 50 years, direct experimental insight into the nature of electron pairing in SrTiO3 has remained elusive. Here we perform transport experiments with nanowire-based single-electron transistors at the interface between SrTiO3 and a thin layer of lanthanum aluminate, LaAlO3. Electrostatic gating reveals a series of two-electron conductance resonances-paired electron states--that bifurcate above a critical pairing field Bp of about 1-4 tesla, an order of magnitude larger than the superconducting critical magnetic field. For magnetic fields below Bp, these resonances are insensitive to the applied magnetic field; for fields in excess of Bp, the resonances exhibit a linear Zeeman-like energy splitting. Electron pairing is stable at temperatures as high as 900 millikelvin, well above the superconducting transition temperature (about 300 millikelvin). These experiments demonstrate the existence of a robust electronic phase in which electrons pair without forming a superconducting state. Key experimental signatures are captured by a model involving an attractive Hubbard interaction that describes real-space electron pairing as a precursor to superconductivity.

  9. Rabi noise spectroscopy of individual two-level tunneling defects

    NASA Astrophysics Data System (ADS)

    Matityahu, Shlomi; Lisenfeld, Jürgen; Bilmes, Alexander; Shnirman, Alexander; Weiss, Georg; Ustinov, Alexey V.; Schechter, Moshe

    2017-06-01

    Understanding the nature of two-level tunneling defects is important for minimizing their disruptive effects in various nanodevices. By exploiting the resonant coupling of these defects to a superconducting qubit, one can probe and coherently manipulate them individually. In this work, we utilize a phase qubit to induce Rabi oscillations of single tunneling defects and measure their dephasing rates as a function of the defect's asymmetry energy, which is tuned by an applied strain. The dephasing rates scale quadratically with the external strain and are inversely proportional to the Rabi frequency. These results are analyzed and explained within a model of interacting defects, in which pure dephasing of coherent high-frequency (gigahertz) defects is caused by interaction with incoherent low-frequency thermally excited defects. Our analysis sets an upper bound for the relaxation rates of thermally excited defects interacting strongly with strain fields.

  10. Isospin Mixing and the Continuum Coupling in Weakly Bound Nuclei

    SciTech Connect

    Michel, N.; Nazarewicz, Witold; Ploszajczak, M.

    2010-01-01

    We investigate the near-threshold behavior of one-nucleon spectroscopic factors in mirror nuclei using the Gamow Shell Model, which simultaneously takes into account many-body correlations and continuum effects. We demonstrate that for weakly bound or unbound systems, the mirror symmetry-breaking effects are appreciable, and they manifest in large differences of spectroscopic factors in a mirror pair.

  11. Multifunctions of bounded variation

    NASA Astrophysics Data System (ADS)

    Vinter, R. B.

    2016-02-01

    Consider control systems described by a differential equation with a control term or, more generally, by a differential inclusion with velocity set F (t , x). Certain properties of state trajectories can be derived when it is assumed that F (t , x) is merely measurable w.r.t. the time variable t. But sometimes a refined analysis requires the imposition of stronger hypotheses regarding the time dependence. Stronger forms of necessary conditions for minimizing state trajectories can be derived, for example, when F (t , x) is Lipschitz continuous w.r.t. time. It has recently become apparent that significant addition properties of state trajectories can still be derived, when the Lipschitz continuity hypothesis is replaced by the weaker requirement that F (t , x) has bounded variation w.r.t. time. This paper introduces a new concept of multifunctions F (t , x) that have bounded variation w.r.t. time near a given state trajectory, of special relevance to control. We provide an application to sensitivity analysis.

  12. Membrane-bound selenoproteins.

    PubMed

    Liu, Jun; Rozovsky, Sharon

    2015-10-01

    Selenoproteins employ selenium to supplement the chemistry available through the common 20 amino acids. These powerful enzymes are affiliated with redox biology, often in connection with the detection, management, and signaling of oxidative stress. Among them, membrane-bound selenoproteins play prominent roles in signaling pathways, Ca(2+) regulation, membrane complexes integrity, and biosynthesis of lipophilic molecules. The number of selenoproteins whose physiological roles, protein partners, expression, evolution, and biosynthesis are characterized is steadily increasing, thus offering a more nuanced view of this specialized family. This review focuses on human membrane selenoproteins, particularly the five least characterized ones: selenoproteins I, K, N, S, and T. Membrane-bound selenoproteins are the least understood, as it is challenging to provide the membrane-like environment required for their biochemical and biophysical characterization. Hence, their studies rely mostly on biological rather than structural and biochemical assays. Another aspect that has not received much attention is the particular role that their membrane association plays in their physiological function. Findings cited in this review show that it is possible to infer the structure and the membrane-binding mode of these lesser-studied selenoproteins and design experiments to examine the role of the rare amino acid selenocysteine.

  13. Noncompeting channel approach to pair creation in supercritical fields.

    PubMed

    Lv, Q Z; Liu, Y; Li, Y J; Grobe, R; Su, Q

    2013-11-01

    The Dirac and Klein-Gordon equations are solved on a space-time grid to study the strong-field induced pair creation process for bosons and fermions from the vacuum. If the external field is sufficiently strong to induce bound states that are embedded in the negative energy continuum, a complex scaling technique of the Hamiltonian can predict the longtime behavior of the dynamics. In the case of multiple bound states this technique predicts the occurrence of a new collective time scale. The longtime behavior of the pair creation is not determined by a single (most important) channel, but collectively by the sum of all individual widths of the embedded states.

  14. Paired Straight Hearth Furnace

    SciTech Connect

    2009-04-01

    This factsheet describes a research project whose goals are to design, develop, and evaluate the scalability and commercial feasibility of the PSH Paired Straight Hearth Furnace alternative ironmaking process.

  15. Stereo Pair, Pasadena, California

    NASA Image and Video Library

    2000-03-10

    This stereoscopic image pair is a perspective view that shows the western part of the city of Pasadena, California, looking north toward the San Gabriel Mountains. Portions of the cities of Altadena and La Canada Flintridge are also shown.

  16. Stereo Pair, Honolulu, Oahu

    NASA Image and Video Library

    2000-03-10

    Honolulu, on the island of Oahu, is a large and growing urban area. This stereoscopic image pair, combining a Landsat image with topography measured by NASA Shuttle Radar Topography Mission SRTM, shows how topography controls the urban pattern.

  17. Bounded state variables and the calculus of variations

    NASA Technical Reports Server (NTRS)

    Hanafy, L. M.

    1972-01-01

    An optimal control problem with bounded state variables is transformed into a Lagrange problem by means of differentiable mappings which take some Euclidean space onto the control and state regions. Whereas all such mappings lead to a Lagrange problem, it is shown that only those which are defined as acceptable pairs of transformations are suitable in the sense that solutions to the transformed Lagrange problem will lead to solutions to the original bounded state problem and vice versa. In particular, an acceptable pair of transformations is exhibited for the case when the control and state regions are right parallelepipeds. Finally, a description of the necessary conditions for the bounded state problem which were obtained by this method is given.

  18. The Peak Pairs algorithm for strain mapping from HRTEM images.

    PubMed

    Galindo, Pedro L; Kret, Sławomir; Sanchez, Ana M; Laval, Jean-Yves; Yáñez, Andrés; Pizarro, Joaquín; Guerrero, Elisa; Ben, Teresa; Molina, Sergio I

    2007-11-01

    Strain mapping is defined as a numerical image-processing technique that measures the local shifts of image details around a crystal defect with respect to the ideal, defect-free, positions in the bulk. Algorithms to map elastic strains from high-resolution transmission electron microscopy (HRTEM) images may be classified into two categories: those based on the detection of peaks of intensity in real space and the Geometric Phase approach, calculated in Fourier space. In this paper, we discuss both categories and propose an alternative real space algorithm (Peak Pairs) based on the detection of pairs of intensity maxima in an affine transformed space dependent on the reference area. In spite of the fact that it is a real space approach, the Peak Pairs algorithm exhibits good behaviour at heavily distorted defect cores, e.g. interfaces and dislocations. Quantitative results are reported from experiments to determine local strain in different types of semiconductor heterostructures.

  19. Neural Tube Defects

    MedlinePlus

    Neural tube defects are birth defects of the brain, spine, or spinal cord. They happen in the first month ... she is pregnant. The two most common neural tube defects are spina bifida and anencephaly. In spina ...

  20. Facts about Birth Defects

    MedlinePlus

    ... Button Information For… Media Policy Makers Facts about Birth Defects Language: English (US) Español (Spanish) Recommend ... having a baby born without a birth defect. Birth Defects Are Common Every 4 ½ minutes, a ...

  1. Birth Defects (For Parents)

    MedlinePlus

    ... there is a problem with a baby's body chemistry, it is called a metabolic birth defect. Metabolic defects prevent the body from properly breaking down food to create energy. Examples of metabolic defects include ...

  2. Atrial septal defect (ASD)

    MedlinePlus

    ... other heart defects of the ventricular septum and mitral valve . Secundum defects can be a single, small ... Sometimes, open-heart surgery may be needed to repair the defect. The type of surgery is more ...

  3. Culture-bound syndromes.

    PubMed

    Levine, R E; Gaw, A C

    1995-09-01

    Since its inception, scholars have struggled with the concept of CBSs. This struggle is reflected in the continuing use of a term that is confusing and inaccurate. Most authors would agree that the term "culture-bound syndrome" was intended to describe forms of otherwise common mental illness that are rendered unusual because of the pathoplastic influence of culture. It was intended not only to describe specific syndromes, but also meanings of illness and non-Western notions of disease causation. The term has become an anachronism, for the word, "syndrome," implies specific disease entities, not illnesses of attribution of idioms of distress. Furthermore, the word "bound" implies that the entities described are restricted to a single culture. Close examination reveals that many of the so-called "culture-bound" syndromes are found in multiple cultures that have in common only that they are "non-Western." It may be unreasonable to expect one term to describe these different concepts. The most accurate of the designations offered might be "folk diagnostic categories." Perhaps the most difficult question remaining is "How can we understand (and classify) these phenomena in such a way that highlights their uniqueness but does not dismiss them as too rare and exotic to warrant attention?" The first step is to recognize that the CBSs are a heterogeneous group of conditions. We must next acknowledge that the concepts represented may be difficult for the average Western clinician to recognize but, in their respective cultures, are neither rare nor unusual. With 80% of our increasingly shrinking world coming from "non-Western" cultures, a familiarity with non-Western notions of disease causation is particularly important for modern clinicians. Many authors have recommended that those CBSs that are "true" syndromes be classified together with their Western counterparts. In order to do this, the folk labels need to be put aside and the fundamental components of each disorder

  4. Defect complexes in semiconductors and insulators

    NASA Astrophysics Data System (ADS)

    Raebiger, Hannes

    2010-03-01

    The interaction of isolated defects and impurities (concentration upto ˜10^18 cm-3) is usually rationalized as that of point charges in a dielectric medium, but as defect concentrations are in the order of atomic percent (˜10^21 cm-3), the statistical probability for two or more defects to sit on neighboring sites, forming a cluster or complex, becomes significant [1]. The formation of such clusters changes the local chemical environment, which in turn affects the electronic (and optical and magnetic) properties of the constituent defects non-trivially. To understand these changes, I study a variety of bound defect complexes in wide-gap semiconductors, composed of both deep and shallow defects, focusing on the shifting of the gap levels caused by defect--defect chemical interactions. First the electronic structure is calculated from first principles calculations, and then I will outline a simple theory that describes the level shifts due to cluster formation qualitatively and semi-quantitatively in terms local atomic shielding constants derived from local charge self-regulation [2].[4pt] [1] R. Behringer, J. Chem. Phys. 29, 537 (1958).[0pt] [2] H. Raebiger, S. Lany, and A. Zunger, Nature 453, 763 (2008).

  5. Line defects and (framed) BPS quivers

    NASA Astrophysics Data System (ADS)

    Cirafici, Michele

    2013-11-01

    The BPS spectrum of certain = 2 supersymmetric field theories can be determined algebraically by studying the representation theory of BPS quivers. We introduce methods based on BPS quivers to study line defects. The presence of a line defect opens up a new BPS sector: framed BPS states can be bound to the defect. The defect can be geometrically described in terms of laminations on a curve. To a lamination we associate certain elements of the Leavitt path algebra of the BPS quiver and use them to compute the framed BPS spectrum. We also provide an alternative characterization of line defects by introducing framed BPS quivers. Using the theory of (quantum) cluster algebras, we derive an algorithm to compute the framed BPS spectra of new defects from known ones. Line defects are generated from a framed BPS quiver by applying certain sequences of mutation operations. Framed BPS quivers also behave nicely under a set of "cut and join" rules, which can be used to study how = 2 systems with defects couple to produce more complicated ones. We illustrate our formalism with several examples.

  6. Formation of "bound

    NASA Astrophysics Data System (ADS)

    Nowak, K.; Kästner, M.; Miltner, A.

    2009-04-01

    During degradation of organic pollutants in soil, metabolites, microbial biomass, CO2and "bound" residues ("non-extractable" residues in soil organic matter) are formed. Enhanced transformation of these contaminants into "bound" residues has been proposed as an alternative remediation method for polluted soils. However, this kind of residues may pose a potential risk for the environment due to their chemical structure and possible remobilization under different conditions. Therefore particular attention is given actually to "bound" residues. Part of these non-extractable residues may be "biogenic," because microorganisms use the carbon from the pollutant to form their biomass components (fatty acids, amino acids, amino sugars), which subsequently may be incorporated into soil organic matter. Furthermore, the CO2 originating from mineralization of xenobiotics, can be re-assimilated by microorganisms and also incorporated into "biogenic residue". The hazard posed by "bound" residues may be overestimated because they are "biogenic" (contain microbial fatty acids and amino acids). The knowledge about the pathways of "biogenic residue" formation is necessary for a proper assessment of the fate of tested pollutants and their turnover in the soil environment. Moreover, these data are needed to establish the realistic degradation rates of the contaminants in soil. The main objectives of this study are: to quantify the extent of "biogenic residue" (fatty acids, amino acids, amino sugars) formation during the degradation of a model pollutant (2,4-dichlorophenoxyacetic acid = 2,4-D) and during CO2 assimilation by microorganisms and to evaluate which components are mainly incorporated into "bound" residues. To investigate the extent of "biogenic residue" formation in soil during the degradation of 2,4-D, experiments with either 14C-U-ring and 13C6-2,4-D or carboxyl-14C 2,4-D were performed. The incubation experiments were performed according to OECD test guideline 307, in the

  7. Pair distribution functions of silicon/silicon nitride interfaces

    NASA Astrophysics Data System (ADS)

    Cao, Deng; Bachlechner, Martina E.

    2006-03-01

    Using molecular dynamics simulations, we investigate different mechanical and structural properties of the silicon/silicon nitride interface. One way to characterize the structure as tensile strain is applied parallel to the interface is to calculate pair distribution functions for specific atom types. The pair distribution function gives the probability of finding a pair of atoms a distance r apart, relative to the probability expected for a completely random distribution at the same density. The pair distribution functions for bulk silicon nitride reflect the fracture of the silicon nitride film at about 8 % and the fact that the centerpiece of the silicon nitride film returns to its original structure after fracture. The pair distribution functions for interface silicon atoms reveal the formation of bonds for originally unbound atom pairs, which is indicative of the interstitial-vacancy defect that causes failure in silicon.

  8. Entropy bounds in terms of the w parameter

    NASA Astrophysics Data System (ADS)

    Abreu, Gabriel; Barceló, Carlos; Visser, Matt

    2011-12-01

    In a pair of recent articles [PRL 105 (2010) 041302; JHEP 1103 (2011) 056] two of the current authors have developed an entropy bound for equilibrium uncollapsed matter using only classical general relativity, basic thermodynamics, and the Unruh effect. An odd feature of that bound, [InlineMediaObject not available: see fulltext.], was that the proportionality constant, 1/2 , was weaker than that expected from black hole thermodynamics, 1/4 . In the current article we strengthen the previous results by obtaining a bound involving the (suitably averaged) w parameter. Simple causality arguments restrict this averaged < w> parameter to be ≤ 1. When equality holds, the entropy bound saturates at the value expected based on black hole thermodynamics. We also add some clarifying comments regarding the (net) positivity of the chemical potential. Overall, we find that even in the absence of any black hole region, we can nevertheless get arbitrarily close to the Bekenstein entropy.

  9. On Adiabatic Pair Creation

    NASA Astrophysics Data System (ADS)

    Pickl, Peter; Dürr, Detlef

    2008-08-01

    We give here a rigorous proof of the well known prediction of pair creation as it arises from the Dirac equation with an external time dependent potential. Pair creation happens with probability one if the potential changes adiabatically in time and becomes overcritical, which means that an eigenvalue curve (as a function of time) bridges the gap between the negative and positive spectral continuum. The potential can be thought of as being zero at large negative and large positive times. The rigorous treatment of this effect has been lacking since the pioneering work of Beck, Steinwedel and Süßmann [1] in 1963 and Gershtein and Zeldovich [8] in 1970.

  10. Determination of the fermion pair size in a resonantly interacting superfluid.

    PubMed

    Schunck, Christian H; Shin, Yong-Il; Schirotzek, André; Ketterle, Wolfgang

    2008-08-07

    Fermionic superfluidity requires the formation of particle pairs, the size of which varies from the femtometre scale in neutron stars and nuclei to the micrometre scale in conventional superconductors. Many properties of the superfluid depend on the pair size relative to the interparticle spacing. This is expressed in 'BCS-BEC crossover' theories, describing the crossover from a Bardeen-Cooper-Schrieffer (BCS)-type superfluid of loosely bound, large Cooper pairs to Bose-Einstein condensates (BECs) of tightly bound molecules. Such a crossover superfluid has been realized in ultracold atomic gases where high-temperature superfluidity has been observed. The microscopic properties of the fermion pairs can be probed using radio-frequency spectroscopy. However, previous work was difficult to interpret owing to strong final-state interactions that were not well understood. Here we realize a superfluid spin mixture in which such interactions have negligible influence and present fermion pair dissociation spectra that reveal the underlying pairing correlations. This allows us to determine that the spectroscopic pair size in the resonantly interacting gas is 20 per cent smaller than the interparticle spacing. These are the smallest pairs so far observed in fermionic superfluids, highlighting the importance of small fermion pairs for superfluidity at high critical temperatures. We have also identified transitions from fermion pairs to bound molecular states and to many-body bound states in the case of strong final-state interactions.

  11. Bound Rationality and Organizational Learning.

    DTIC Science & Technology

    1989-09-23

    8217 . 90 0 8 0.. O 4 BOUNDED RATIONALITY AND ORGANIZATIONAL LEARNING Technical Report AlP - 107 Herbert A. Simon Department of Psychology Carnegie Mellon...ACCESSION No N/A N/A N/A N/A 1 1 TITLE (include Security Classificarnon) Bounded rationality and organizational learning 12 PERSONAL AUTHOR(S) HretA io 13a...organizations organizational psychology organizational learning bounded rationality cognitive psychology 𔄃 ABSTRACT (Continue on reverse if necessary

  12. Physical Mechanism of Photon Pairing in a Kerr Nonlinear Medium

    NASA Astrophysics Data System (ADS)

    Cheng, Ze

    2017-01-01

    We establish that Cooper instability of the ground state of a normal blackbody triggers the attractive photons to form the pairs. We next find that however small the effective interphoton attraction V 0 is, Cooper pairs of photon always exist in the ground state of a Kerr nonlinear blackbody. It has been pointed out that there are the three fundamental properties of the Cooper pair of photon: the extremely large binding energy, the extremely small radius, and the extremely high critical temperature. These properties are reflected in the many-photon bound state described by the optical superfluid theory.

  13. Physical Mechanism of Photon Pairing in a Kerr Nonlinear Medium

    NASA Astrophysics Data System (ADS)

    Cheng, Ze

    2017-05-01

    We establish that Cooper instability of the ground state of a normal blackbody triggers the attractive photons to form the pairs. We next find that however small the effective interphoton attraction V 0 is, Cooper pairs of photon always exist in the ground state of a Kerr nonlinear blackbody. It has been pointed out that there are the three fundamental properties of the Cooper pair of photon: the extremely large binding energy, the extremely small radius, and the extremely high critical temperature. These properties are reflected in the many-photon bound state described by the optical superfluid theory.

  14. Aerodynamics of intermittent bounds in flying birds

    NASA Astrophysics Data System (ADS)

    Tobalske, Bret W.; Hearn, Jason W. D.; Warrick, Douglas R.

    Flap-bounding is a common flight style in small birds in which flapping phases alternate with flexed-wing bounds. Body lift is predicted to be essential to making this flight style an aerodynamically attractive flight strategy. To elucidate the contributions of the body and tail to lift and drag during the flexed-wing bound phase, we used particle image velocimetry (PIV) and measured properties of the wake of zebra finch (Taeniopygia guttata, N = 5), flying at 6-10 m s- 1 in a variable speed wind tunnel as well as flow around taxidermically prepared specimens (N = 4) mounted on a sting instrumented with force transducers. For the specimens, we varied air velocity from 2 to 12 m s- 1 and body angle from -15∘ to 50∘. The wake of bounding birds and mounted specimens consisted of a pair of counterrotating vortices shed into the wake from the tail, with induced downwash in the sagittal plane and upwash in parasagittal planes lateral to the bird. This wake structure was present even when the tail was entirely removed. We observed good agreement between force measures derived from PIV and force transducers over the range of body angles typically used by zebra finch during forward flight. Body lift:drag (L:D) ratios averaged 1.4 in live birds and varied between 1 and 1.5 in specimens at body angles from 10∘ to 30∘. Peak (L:D) ratio was the same in live birds and specimens (1.5) and was exhibited in specimens at body angles of 15∘ or 20∘, consistent with the lower end of body angles utilized during bounds. Increasing flight velocity in live birds caused a decrease in CL and CD from maximum values of 1.19 and 0.95 during flight at 6 m s- 1 to minimum values of 0.70 and 0.54 during flight at 10 m s- 1. Consistent with delta-wing theory as applied to birds with a graduated-tail shape, trimming the tail to 0 and 50% of normal length reduced L:D ratios and extending tail length to 150% of normal increased L:D ratio. As downward induced velocity is present in the

  15. Aerodynamics of intermittent bounds in flying birds

    NASA Astrophysics Data System (ADS)

    Tobalske, Bret W.; Hearn, Jason W. D.; Warrick, Douglas R.

    2009-05-01

    Flap-bounding is a common flight style in small birds in which flapping phases alternate with flexed-wing bounds. Body lift is predicted to be essential to making this flight style an aerodynamically attractive flight strategy. To elucidate the contributions of the body and tail to lift and drag during the flexed-wing bound phase, we used particle image velocimetry (PIV) and measured properties of the wake of zebra finch ( Taeniopygia guttata, N = 5), flying at 6-10 m s-1 in a variable speed wind tunnel as well as flow around taxidermically prepared specimens ( N = 4) mounted on a sting instrumented with force transducers. For the specimens, we varied air velocity from 2 to 12 m s-1 and body angle from -15° to 50°. The wake of bounding birds and mounted specimens consisted of a pair of counter-rotating vortices shed into the wake from the tail, with induced downwash in the sagittal plane and upwash in parasagittal planes lateral to the bird. This wake structure was present even when the tail was entirely removed. We observed good agreement between force measures derived from PIV and force transducers over the range of body angles typically used by zebra finch during forward flight. Body lift:drag ( L: D) ratios averaged 1.4 in live birds and varied between 1 and 1.5 in specimens at body angles from 10° to 30°. Peak ( L: D) ratio was the same in live birds and specimens (1.5) and was exhibited in specimens at body angles of 15° or 20°, consistent with the lower end of body angles utilized during bounds. Increasing flight velocity in live birds caused a decrease in C L and C D from maximum values of 1.19 and 0.95 during flight at 6 m s-1 to minimum values of 0.70 and 0.54 during flight at 10 m s-1. Consistent with delta-wing theory as applied to birds with a graduated-tail shape, trimming the tail to 0 and 50% of normal length reduced L: D ratios and extending tail length to 150% of normal increased L: D ratio. As downward induced velocity is present in the

  16. Schwinger pair production with ultracold atoms

    NASA Astrophysics Data System (ADS)

    Kasper, V.; Hebenstreit, F.; Oberthaler, M. K.; Berges, J.

    2016-09-01

    We consider a system of ultracold atoms in an optical lattice as a quantum simulator for electron-positron pair production in quantum electrodynamics (QED). For a setup in one spatial dimension, we investigate the nonequilibrium phenomenon of pair production including the backreaction leading to plasma oscillations. Unlike previous investigations on quantum link models, we focus on the infinite-dimensional Hilbert space of QED and show that it may be well approximated by experiments employing Bose-Einstein condensates interacting with fermionic atoms. Numerical calculations based on functional integral techniques give a unique access to the physical parameters required to realize QED phenomena in a cold atom experiment. In particular, we use our approach to consider quantum link models in a yet unexplored parameter regime and give bounds for their ability to capture essential features of the physics. The results suggest a paradigmatic change towards realizations using coherent many-body states for quantum simulations of high-energy particle physics phenomena.

  17. Direct Cavity Detection of Majorana Pairs

    NASA Astrophysics Data System (ADS)

    Dartiailh, Matthieu C.; Kontos, Takis; Douçot, Benoit; Cottet, Audrey

    2017-03-01

    No experiment could directly test the particle-antiparticle duality of Majorana fermions, so far. However, this property represents a necessary ingredient towards the realization of topological quantum computing schemes. Here, we show how to complete this task by using microwave techniques. The direct coupling between a pair of overlapping Majorana bound states and the electric field from a microwave cavity is extremely difficult to detect due to the self-adjoint character of Majorana fermions which forbids direct energy exchanges with the cavity. We show theoretically how this problem can be circumvented by using photoassisted tunneling to fermionic reservoirs. The absence of a direct microwave transition inside the Majorana pair in spite of the light-Majorana coupling would represent a smoking gun for the Majorana self-adjoint character.

  18. Minimal Pairs: Minimal Importance?

    ERIC Educational Resources Information Center

    Brown, Adam

    1995-01-01

    This article argues that minimal pairs do not merit as much attention as they receive in pronunciation instruction. There are other aspects of pronunciation that are of greater importance, and there are other ways of teaching vowel and consonant pronunciation. (13 references) (VWL)

  19. Anchored paired comparisons

    NASA Astrophysics Data System (ADS)

    Dalal, E. N.; Handley, J. C.; Wu, W.; Wang, J.

    2008-01-01

    The method of paired comparisons is often used in image quality evaluations. Psychometric scale values for quality judgments are modeled using Thurstone's Law of Comparative Judgment in which distance in a psychometric scale space is a function of the probability of preference. The transformation from psychometric space to probability is a cumulative probability distribution. The major drawback of a complete paired comparison experiment is that every treatment is compared to every other, thus the number of comparisons grows quadratically. We ameliorate this difficulty by performing paired comparisons in two stages, by precisely estimating anchors in the psychometric scale space which are spaced apart to cover the range of scale values and comparing treatments against those anchors. In this model, we employ a generalized linear model where the regression equation has a constant offset vector determined by the anchors. The result of this formulation is a straightforward statistical model easily analyzed using any modern statistics package. This enables model fitting and diagnostics. This method was applied to overall preference evaluations of color pictorial hardcopy images. The results were found to be compatible with complete paired comparison experiments, but with significantly less effort.

  20. Two Pairs of Storms

    NASA Image and Video Library

    2004-06-04

    Two pairs of dark spots, or storms, in Saturn atmosphere squeeze past each other as they dance around the planet. In this group of four storms, the top left and lower right storms are fringed with white clouds as seen by NASA Cassini spacecraft.

  1. Sculpture, view looking to pair of lions, positioned at top ...

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

    Sculpture, view looking to pair of lions, positioned at top of stairs leading down into the Glen from DeWitt Circle, just north of the American Bungalow (note: Windmill in background) - National Park Seminary, Bounded by Capitol Beltway (I-495), Linden Lane, Woodstove Avenue, & Smith Drive, Silver Spring, Montgomery County, MD

  2. Defect properties of ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Stehr, J. E.; Devika, M.; Reddy, N. Koteeswara; Tu, C. W.; Chen, W. M.; Buyanova, I. A.

    2014-02-01

    In this work we examined optical and defect properties of as-grown and Ni-coated ZnO nanowires (NWs) grown by rapid thermal chemical vapor deposition by means of optically detected magnetic resonance (ODMR). Several grown-in defects are revealed by monitoring visible photoluminescence (PL) emissions and are attributed to Zn vacancies, O vacancies, a shallow (but not effective mass) donor and exchange-coupled pairs of a Zn vacancy and a Zn interstitial. It is also found that the same ODMR signals are detected in the as-grown and Ni-coated NWs, indicating that metal coatings does not significantly affect formation of the aforementioned defects and that the observed defects are located in the bulk of the NWs.

  3. Superrotations and black hole pair creation

    NASA Astrophysics Data System (ADS)

    Strominger, Andrew; Zhiboedov, Alexander

    2017-03-01

    Recent work has shown that the symmetries of classical gravitational scattering in asymptotically flat spacetimes include, at the linearized level, infinitesimal superrotations. These act like Virasoro generators on the celestial sphere at null infinity. However, due to the singularities in these generators, the physical status of finite superrotations has remained unclear. Here we address this issue in the context of the breaking of a cosmic string via quantum black hole pair nucleation. This process is described by a gravitational instanton known as the C-metric. After pair production, the black holes are pulled by the string to null infinity with a constant acceleration. At late times the string decays and the spacetime settles into a vacuum state. We show that the early and late spacetimes before and after string decay differ by a finite superrotation. This provides a physical interpretation of superrotations. They act on spacetimes which are asymptotically flat everywhere except at isolated singularities with cosmic string defects.

  4. Point defects quenched in NiAl and related intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Fan, Jiawen

    1991-08-01

    Point defects in the highly ordered B2 compounds NiAl, CoAl and FeAl were studied using the perturbed gamma-gamma angular correlations (PAC) technique. Quadrupole interactions detected at dilute In-111 probes on Al sites in NiAl and CoAl were identified with complexes containing one or two vacancies in the first atomic shell. Measurements on rapidly quenched NiAl and CoAl exhibited increases in site fractions of vacancy-probe complexes caused by formation of thermal defects. Site fractions were analyzed using the law of mass action to obtain absolute vacancy concentrations. PAC is shown to be a powerful new technique for the quantitative study of equilibrium defects in solids. For NiAl, the vacancy concentration quenched-in from a given temperature was found to be independent of composition over the range 50.4 to 53.5 at. pct. Ni, identifying the Schottky defect (vacancy pair) as the dominant equilibrium defect, and ruling out the so-called triple defect. Formation energies and entropies of Schottky pairs were determined to be 2.66(8) and 3.48(12) eV, and 12(1) and 17(2) k sub B, respectively, for NiAl and CoAl. The entropies suggest huge vacancy concentrations, 13 pct. at the melting temperatures of NiAl and CoAl. Migration energies of Ni and Co vacancies were found to be 1.8(2) and 2.5(2) eV, respectively. FeAl exhibited complex behavior. A low temperature regime was detected in NiAl and CoAl within which vacancies are mobile but do not anneal out, so that the vacancy concentration remains constant. In NiAl, this 'bottleneck' regime extends from 350 to 700 C. Vacancies were found to be bound to the In probes with an energy very close to 0.20 eV in NiAl and CoAl. An explanation of the bottleneck is proposed in terms of saturation of all lattice sinks. This annealing bottleneck should exist in a wide range of intermetallic compounds when there is a sufficiently high vacancy concentration.

  5. Anaphoric Pronouns and Bound Variables

    ERIC Educational Resources Information Center

    Wasow, Thomas

    1975-01-01

    Deals with certain problems inherent in deriving anaphoric pronouns from bound variables. Syntactic rules applied to determine anaphora relations cannot be applied if anaphoric pronouns and their antecedents have identical underlying forms. An approach to anaphora which preserves some advantages of the bound-variable theory without the problems is…

  6. Northwest Outward Bound Instructor's Manual.

    ERIC Educational Resources Information Center

    Northwest Outward Bound School, Portland, OR.

    Instructor responsibilities, procedures for completing activities safely, and instructional methods and techniques are outlined to assist instructors in the Northwest Outward Bound School (Portland, Oregon) as they strive for teaching excellence. Information is organized into six chapters addressing: history and philosophy of Outward Bound; course…

  7. Bounds for Asian basket options

    NASA Astrophysics Data System (ADS)

    Deelstra, Griselda; Diallo, Ibrahima; Vanmaele, Michèle

    2008-09-01

    In this paper we propose pricing bounds for European-style discrete arithmetic Asian basket options in a Black and Scholes framework. We start from methods used for basket options and Asian options. First, we use the general approach for deriving upper and lower bounds for stop-loss premia of sums of non-independent random variables as in Kaas et al. [Upper and lower bounds for sums of random variables, Insurance Math. Econom. 27 (2000) 151-168] or Dhaene et al. [The concept of comonotonicity in actuarial science and finance: theory, Insurance Math. Econom. 31(1) (2002) 3-33]. We generalize the methods in Deelstra et al. [Pricing of arithmetic basket options by conditioning, Insurance Math. Econom. 34 (2004) 55-57] and Vanmaele et al. [Bounds for the price of discrete sampled arithmetic Asian options, J. Comput. Appl. Math. 185(1) (2006) 51-90]. Afterwards we show how to derive an analytical closed-form expression for a lower bound in the non-comonotonic case. Finally, we derive upper bounds for Asian basket options by applying techniques as in Thompson [Fast narrow bounds on the value of Asian options, Working Paper, University of Cambridge, 1999] and Lord [Partially exact and bounded approximations for arithmetic Asian options, J. Comput. Finance 10 (2) (2006) 1-52]. Numerical results are included and on the basis of our numerical tests, we explain which method we recommend depending on moneyness and time-to-maturity.

  8. Fractional diffusion on bounded domains

    DOE PAGES

    Defterli, Ozlem; D'Elia, Marta; Du, Qiang; ...

    2015-03-13

    We found that the mathematically correct specification of a fractional differential equation on a bounded domain requires specification of appropriate boundary conditions, or their fractional analogue. In this paper we discuss the application of nonlocal diffusion theory to specify well-posed fractional diffusion equations on bounded domains.

  9. Fractional diffusion on bounded domains

    SciTech Connect

    Defterli, Ozlem; D'Elia, Marta; Du, Qiang; Gunzburger, Max Donald; Lehoucq, Richard B.; Meerschaert, Mark M.

    2015-03-13

    We found that the mathematically correct specification of a fractional differential equation on a bounded domain requires specification of appropriate boundary conditions, or their fractional analogue. In this paper we discuss the application of nonlocal diffusion theory to specify well-posed fractional diffusion equations on bounded domains.

  10. Northwest Outward Bound Instructor's Manual.

    ERIC Educational Resources Information Center

    Northwest Outward Bound School, Portland, OR.

    Instructor responsibilities, procedures for completing activities safely, and instructional methods and techniques are outlined to assist instructors in the Northwest Outward Bound School (Portland, Oregon) as they strive for teaching excellence. Information is organized into six chapters addressing: history and philosophy of Outward Bound; course…

  11. TOPICAL REVIEW: O- bound small polarons in oxide materials

    NASA Astrophysics Data System (ADS)

    Schirmer, O. F.

    2006-11-01

    Holes bound to acceptor defects in oxide crystals are often localized by lattice distortion at just one of the equivalent oxygen ligands of the defect. Such holes thus form small polarons in symmetric clusters of a few oxygen ions. An overview on mainly the optical manifestations of those clusters is given. The article is essentially divided into two parts: the first one covers the basic features of the phenomena and their explanations, exemplified by several paradigmatic defects; in the second part numerous oxide materials are presented which exhibit bound small polaron optical properties. The first part starts with summaries on the production of bound hole polarons and the identification of their structure. It is demonstrated why they show strong, wide absorption bands, usually visible, based on polaron stabilization energies of typically 1 eV. The basic absorption process is detailed with a fictitious two-well system. Clusters with four, six and twelve equivalent ions are realized in various oxide compounds. In these cases several degenerate optically excited polaron states occur, leading to characteristic final state resonance splittings. The peak energies of the absorption bands as well as the sign of the transfer energy depend on the topology of the clusters. A special section is devoted to the distinction between interpolaron and intrapolaron optical transitions. The latter are usually comparatively weak. The oxide compounds exhibiting bound hole small polaron absorptions include the alkaline earth oxides (e.g. MgO), BeO and ZnO, the perovskites BaTiO3 and KTaO3, quartz, the sillenites (e.g. Bi12TiO20), Al2O3, LiNbO3, topaz and various other materials. There are indications that the magnetic crystals NiO, doped with Li, and LaMnO3, doped with Sr, also show optical features caused by bound hole polarons. Beyond being elementary paradigms for the properties of small polarons in general, the defect species treated can be used to explain radiation and light

  12. Wind effects on bounding flight.

    PubMed

    Sachs, Gottfried

    2013-01-07

    The effects of the wind on the energy expenditure of bounding flight and on the travelling speed are dealt with. For this purpose, a mathematical model of bounding flight in moving air is developed. Introducing an appropriate non-dimensionalization, results and findings of generally valid nature are derived. It is shown that bounding flight yields a flight mechanical advantage in headwinds when compared with continuous flapping flight. This is because the minimum energy expenditure is lower and the associated travelling speed is higher. The body lift in the bound phase has an advantageous influence. The effects of tailwinds yield less differences between bounding flight and continuous flapping flight. Copyright © 2012. Published by Elsevier Ltd.

  13. Metabolism of organically bound tritium

    SciTech Connect

    Travis, C.C.

    1984-01-01

    The classic methodology for estimating dose to man from environmental tritium ignores the fact that organically bound tritium in foodstuffs may be directly assimilated in the bound compartment of tissues without previous oxidation. We propose a four-compartment model consisting of a free body water compartment, two organic compartments, and a small, rapidly metabolizing compartment. The utility of this model lies in the ability to input organically bound tritium in foodstuffs directly into the organic compartments of the model. We found that organically bound tritium in foodstuffs can increase cumulative total body dose by a factor of 1.7 to 4.5 times the free body water dose alone, depending on the bound-to-loose ratio of tritium in the diet. Model predictions are compared with empirical measurements of tritium in human urine and tissue samples, and appear to be in close agreement. 10 references, 4 figures, 3 tables.

  14. Therapeutic drugs in early pregnancy and congenital defects.

    PubMed

    McDonald, A D

    1994-01-01

    In a study of occupation and pregnancy outcome, information was collected on certain non-occupational factors including therapeutic drugs taken in the first trimester, reported by some 17% of women. A case-referent analysis was made of data from pregnancies leading to 787 major (class 1) and 2386 miscellaneous minor (class 2) congenital defects compared with pregnancies without defects, matched for hospital, maternal age and educational level. In pairs discordant for one of seven drug groups, ratios of positive pairs (case with drug) to negative pairs (referent with drug) were for class 1 defects 164:148, relative risk (RR) 1.11 and for class 2 defects 433:383, RR 1.13. Only anti-infective drugs showed an increased RR: 1.70 (p = 0.06). This was mainly with nervous/sensory defects (10:2; RR 5.0, p = 0.04) but no one type of defect or type of drug was identified; the infections for which the drugs were given might have been responsible. For class 1 defects two pairs were positive for anti-convulsant drugs and two negative; no increase in risk was found for any specific drugs including doxylamine succinate (Bendectin).

  15. Majorana Kramers pair in a nematic vortex

    DOE PAGES

    Wu, Fengcheng; Martin, Ivar

    2017-06-05

    A time-reversal (TR) invariant topological superconductor is characterized by a Kramers pair of Majorana zero-energy modes on boundaries and in a core of a TR invariant vortex. A vortex defect that preserves TR symmetry has remained primarily of theoretical interest, since typically a magnetic field, which explicitly breaks TR, needs to be applied to create vortices in superconductors. In this paper, we show that an odd-parity topological superconductor with a nematic pairing order parameter can host a nematic vortex that preserves TR symmetry and binds a Majorana Kramers pair. Such a nematic superconductor could be realized in metal-doped Bi2Se3, asmore » suggested by recent experiments. We provide an analytic solution for the zero modes in a continuous nematic vortex. In lattice, crystalline anisotropy can pin the two-component order parameter along high-symmetry directions. We show that a discrete nematic vortex, which forms when three nematic domains meet, also supports a TR pair of Majorana modes. Lastly, we discuss possible experiments to probe the zero modes.« less

  16. Majorana Kramers pair in a nematic vortex

    NASA Astrophysics Data System (ADS)

    Wu, Fengcheng; Martin, Ivar

    2017-06-01

    A time-reversal (TR) invariant topological superconductor is characterized by a Kramers pair of Majorana zero-energy modes on boundaries and in a core of a TR invariant vortex. A vortex defect that preserves TR symmetry has remained primarily of theoretical interest, since typically a magnetic field, which explicitly breaks TR, needs to be applied to create vortices in superconductors. In this paper, we show that an odd-parity topological superconductor with a nematic pairing order parameter can host a nematic vortex that preserves TR symmetry and binds a Majorana Kramers pair. Such a nematic superconductor could be realized in metal-doped Bi2Se3 , as suggested by recent experiments. We provide an analytic solution for the zero modes in a continuous nematic vortex. In lattice, crystalline anisotropy can pin the two-component order parameter along high-symmetry directions. We show that a discrete nematic vortex, which forms when three nematic domains meet, also supports a TR pair of Majorana modes. Finally, we discuss possible experiments to probe the zero modes.

  17. Pumping Electron-Positron Pairs from a Well Potential

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Liu, Jie; Fu, Li-Bin

    2016-04-01

    In the presence of very deep well potential, electrons will spontaneously occupy the empty embedded bound states and electron-positron pairs are created by means of a non-perturbative tunneling process. In this work, by slowly oscillating the width or depth, the population transfer channels are opened and closed periodically. We find and clearly show that by the non-synchronous ejections of particles, the saturation of pair number in a static super-critical well can be broken, and electrons and positrons can be pumped inexhaustibly from vacuum with a constant production rate. In the adiabatic limit, final pair number after a single cycle has quantized values as a function of the upper boundary of the oscillating, and the critical upper boundaries indicate the diving points of the bound states.

  18. Pumping Electron-Positron Pairs from a Well Potential

    PubMed Central

    Wang, Qiang; Liu, Jie; Fu, Li-bin

    2016-01-01

    In the presence of very deep well potential, electrons will spontaneously occupy the empty embedded bound states and electron-positron pairs are created by means of a non-perturbative tunneling process. In this work, by slowly oscillating the width or depth, the population transfer channels are opened and closed periodically. We find and clearly show that by the non-synchronous ejections of particles, the saturation of pair number in a static super-critical well can be broken, and electrons and positrons can be pumped inexhaustibly from vacuum with a constant production rate. In the adiabatic limit, final pair number after a single cycle has quantized values as a function of the upper boundary of the oscillating, and the critical upper boundaries indicate the diving points of the bound states. PMID:27125998

  19. Protected Flux Pairing Qubit

    NASA Astrophysics Data System (ADS)

    Bell, Matthew; Zhang, Wenyuan; Ioffe, Lev; Gershenson, Michael

    2014-03-01

    We have studied the coherent flux tunneling in a qubit containing two submicron Josephson junctions shunted by a superinductor (a dissipationless inductor with an impedance much greater than the resistance quantum). The two low energy quantum states of this device, 0 and 1, are represented by even and odd number of fluxes in the loop, respectively. This device is dual to the charge pairing Josephson rhombi qubit. The spectrum of the device, studied by microwave spectroscopy, reflects the interference between coherent quantum phase slips in the two junctions (the Aharonov-Casher effect). The time domain measurements demonstrate the suppression of the qubit's energy relaxation in the protected regime, which illustrates the potential of this flux pairing device as a protected quantum circuit. Templeton Foundation, NSF, and ARO.

  20. Junctionless Cooper pair transistor

    NASA Astrophysics Data System (ADS)

    Arutyunov, K. Yu.; Lehtinen, J. S.

    2017-02-01

    Quantum phase slip (QPS) is the topological singularity of the complex order parameter of a quasi-one-dimensional superconductor: momentary zeroing of the modulus and simultaneous 'slip' of the phase by ±2π. The QPS event(s) are the dynamic equivalent of tunneling through a conventional Josephson junction containing static in space and time weak link(s). Here we demonstrate the operation of a superconducting single electron transistor (Cooper pair transistor) without any tunnel junctions. Instead a pair of thin superconducting titanium wires in QPS regime was used. The current-voltage characteristics demonstrate the clear Coulomb blockade with magnitude of the Coulomb gap modulated by the gate potential. The Coulomb blockade disappears above the critical temperature, and at low temperatures can be suppressed by strong magnetic field.

  1. The Hg isoelectronic defect in ZnO

    SciTech Connect

    Cullen, J.; McGlynn, E. Henry, M. O.; Johnston, K.; Dunker, D.; Bayer, M.; Yakovlev, D. R.

    2013-11-21

    We report a study of the luminescence due to Hg in ZnO, concentrating on the main zero phonon line (ZPL) at 3.2766(1) eV and its associated phonon sidebands. For a sample implanted with radioactive {sup 192}Hg, the ZPL intensity, normalised to that of shallow bound exciton emission, is observed to decrease with an equivalent half-life of 4.5(1) h, very close to the 4.85(20) h half-life of {sup 192}Hg. ZnO implanted with stable Hg impurities produces the same luminescence spectrum. Temperature dependent measurements confirm that the zero phonon line is a thermalizing doublet involving one allowed and one largely forbidden transition from excited states separated by 0.91(1) meV to a common ground state. Uniaxial stress measurements show that the allowed transition takes place from an orbitally degenerate excited state to a non-degenerate ground state in a centre of trigonal (C{sub 3v}) symmetry while the magneto-optical properties are characteristic of electron-hole pair recombination at an isoelectronic defect. The doublet luminescence is assigned to bound exciton recombination involving exchange-split Γ{sub 5} and Γ{sub 1,2} excited states (using C{sub 6v} symmetry labels; Γ{sub 3} and Γ{sub 1,2} using C{sub 3v} labels) at isoelectronic Hg impurities substituting for Zn in the crystal. The electron and hole g values deduced from the magneto-optical data indicate that this Hg impurity centre in ZnO is hole-attractive.

  2. Defect coarsening in a biological system: the vascular cambium of cottonwood trees.

    PubMed

    Kramer, Eric M; Groves, Joseph V

    2003-04-01

    We present micrographic evidence for the annihilation of topological defect pairs and defect-mediated coarsening in the vascular cambium of cottonwood trees (Populus deltoides). We also show that a recently published mathematical model of cell orientation dynamics in the cambium reproduces many qualitative features of the defect coarsening process.

  3. Structure of the weakly bound triatomic He2Li and He2Na molecules

    NASA Astrophysics Data System (ADS)

    Suno, Hiroya

    2017-07-01

    We study the structure of triatomic molecules containing two helium atoms and one alkali-metal atom X (X = Li, Na). The three-body Schrödinger equation is solved in hyperspherical coordinates using the He-He and He-X pair van der Waals potentials available in the literature. We calculate the structural properties of the He2Li and He2Na bound states, and analyze one-dimensional pair and angle distribution functions as well as two-dimensional pair-pair and angle-angle distribution functions. These bound states are characterized by so peculiar weakly bound structures that classifying them into particular sizes and geometrical shapes appears to be elusive. Particularly, the JΠ=0+ excited states of He426Li and He427Li are found to constitute giant triatomic molecules with their size amounting to several hundred bohrs.

  4. Optical identification of sulfur vacancies: Bound excitons at the edges of monolayer tungsten disulfide

    PubMed Central

    Carozo, Victor; Wang, Yuanxi; Fujisawa, Kazunori; Carvalho, Bruno R.; McCreary, Amber; Feng, Simin; Lin, Zhong; Zhou, Chanjing; Perea-López, Néstor; Elías, Ana Laura; Kabius, Bernd; Crespi, Vincent H.; Terrones, Mauricio

    2017-01-01

    Defects play a significant role in tailoring the optical properties of two-dimensional materials. Optical signatures of defect-bound excitons are important tools to probe defective regions and thus interrogate the optical quality of as-grown semiconducting monolayer materials. We have performed a systematic study of defect-bound excitons using photoluminescence (PL) spectroscopy combined with atomically resolved scanning electron microscopy and first-principles calculations. Spatially resolved PL spectroscopy at low temperatures revealed bound excitons that were present only on the edges of monolayer tungsten disulfide and not in the interior. Optical pumping of the bound excitons was sublinear, confirming their bound nature. Atomic-resolution images reveal that the areal density of monosulfur vacancies is much larger near the edges (0.92 ± 0.45 nm−2) than in the interior (0.33 ± 0.11 nm−2). Temperature-dependent PL measurements found a thermal activation energy of ~36 meV; surprisingly, this is much smaller than the bound-exciton binding energy of ~300 meV. We show that this apparent inconsistency is related to a thermal dissociation of the bound exciton that liberates the neutral excitons from negatively charged point defects. First-principles calculations confirm that sulfur monovacancies introduce midgap states that host optical transitions with finite matrix elements, with emission energies ranging from 200 to 400 meV below the neutral-exciton emission line. These results demonstrate that bound-exciton emission induced by monosulfur vacancies is concentrated near the edges of as-grown monolayer tungsten disulfide. PMID:28508048

  5. Excited state dependent electron transfer of a rhenium-dipyridophenazine complex intercalated between the base pairs of DNA: a time-resolved UV-visible and IR absorption investigation into the photophysics of fac-[Re(CO)3(F2dppz)(py)]+ bound to either [poly(dA-dT)]2 or [poly(dG-dC)]2.

    PubMed

    Cao, Qian; Creely, Caitriona M; Davies, E Stephen; Dyer, Joanne; Easun, Timothy L; Grills, David C; McGovern, David A; McMaster, Jonathan; Pitchford, Jonathan; Smith, Jayden A; Sun, Xue-Zhong; Kelly, John M; George, Michael W

    2011-08-01

    The transient species formed following excitation of fac-[Re(CO)(3)(F(2)dppz)(py)](+) (F(2)dppz = 11,12-difluorodipyrido[3,2-a:2',3'-c]phenazine) bound to double-stranded polynucleotides [poly(dA-dT)](2) or [poly(dG-dC)](2) have been studied by transient visible and infra-red spectroscopy in both the picosecond and nanosecond time domains. The latter technique has been used to monitor both the metal complex and the DNA by monitoring the regions 1900-2100 and 1500-1750 cm(-1) respectively. These data provide direct evidence for electron transfer from guanine to the excited state of the metal complex, which proceeds both on a sub-picosecond time scale and with a lifetime of 35 ps, possibly due to the involvement of two excited states. No electron transfer is found for the [poly(dA-dT)](2) complex, although characteristic changes are seen in the DNA-region TRIR consistent with changes in the binding of the bases in the intercalation site upon excitation of the dppz-complex. This journal is © The Royal Society of Chemistry and Owner Societies 2011

  6. Atrioventricular Canal Defect

    MedlinePlus

    ... birth (congenital). The condition is often associated with Down syndrome. Atrioventricular canal defect allows extra blood to flow ... baby's heart is developing. Some factors, such as Down syndrome, might increase the risk of atrioventricular canal defect. ...

  7. Birth Defects (For Parents)

    MedlinePlus

    ... to create energy. Examples of metabolic defects include Tay-Sachs disease , a fatal disease that affects the central nervous ... called recessive inheritance and includes conditions such as Tay-Sachs disease and cystic fibrosis . A disease or defect also ...

  8. Effects of QCD bound states on dark matter relic abundance

    NASA Astrophysics Data System (ADS)

    Liew, Seng Pei; Luo, Feng

    2017-02-01

    We study scenarios where there exists an exotic massive particle charged under QCD in the early Universe. We calculate the formation and dissociation rates of bound states formed by pairs of these particles, and apply the results in dark matter (DM) coannihilation scenarios, including also the Sommerfeld effect. We find that on top of the Sommerfeld enhancement, bound-state effects can further significantly increase the largest possible DM masses which can give the observed DM relic abundance, by ˜ 30-100% with respect to values obtained by considering the Sommerfeld effect only, for the color triplet or octet exotic particles we consider. In particular, it indicates that the Bino DM mass in the right-handed stop-Bino coannihilation scenario in the Minimal Supersymmetric extension of the Standard Model (MSSM) can reach ˜ 2.5 TeV, even though the potential between the stop and antistop prior to forming a bound state is repulsive. We also apply the bound-state effects in the calculations of relic abundance of long-lived or metastable massive colored particles, and discuss the implications on the BBN constraints and the abundance of a super-weakly interacting DM. The corrections for the bound-state effect when the exotic massive colored particles also carry electric charges, and the collider bounds are also discussed.

  9. Duralumin - Defects and Failures

    NASA Technical Reports Server (NTRS)

    Nelson, WM

    1927-01-01

    It is proposed in this paper to identify some of the defects and failures in duralumin most frequently encountered by the aircraft industry with a view to indicate their importance. The defects and failures in duralumin may be classified into the following groups: 1) defects produced during manufacture; 2) defects produced during fabrication; 3) corrosion and erosion; and 4) fatigue failures. Only the first two will be covered in this report.

  10. Nonuniversal BBN bounds on electromagnetically decaying particles

    NASA Astrophysics Data System (ADS)

    Poulin, Vivian; Serpico, Pasquale Dario

    2015-05-01

    In Poulin and Serpico [Phys. Rev. Lett. 114, 091101 (2015)] we recently argued that when the energy of a photon injected in the primordial plasma falls below the pair-production threshold the universality of the nonthermal photon spectrum from the standard theory of electromagnetic cascades onto a photon background breaks down. We showed that this could reopen or widen the parameter space for an exotic solution to the "lithium problem." Here we discuss another application, namely the impact that this has on nonthermal big bang nucleosynthesis constraints from He 4 , He 3 , and H 2 , using the parametric example of monochromatic photon injection of different energies. Typically, we find tighter bounds than those existing in the literature, up to more than 1 order of magnitude. As a consequence of the nonuniversality of the spectrum, the energy dependence of the photodissociation cross sections is important. We also compare the constraints obtained with current level and future reach of cosmic microwave background spectral distortion bounds.

  11. Spin susceptibility of Andreev bound states

    NASA Astrophysics Data System (ADS)

    Rosemeyer, B. M.; Vorontsov, Anton B.

    2016-10-01

    We calculate the electronic spin susceptibility and spin-lattice relaxation rate in a singlet superconductor near a pair-breaking surface, or in a domain wall of the order parameter. We directly link the presence of high-density Andreev bound states in the inhomogeneous region, combined with coherence factors, to the enhancement of the susceptibility above the normal state's value for certain q vectors. Besides the dominant peak at ferromagnetic vector q =0 , we find significant enhancement of antiferromagnetic correlations at vectors q ≲2 kf , with q along the domain wall in an S -wave superconductor, and across the domain wall in D -wave (nodes along the wall). These features are destroyed by applying a moderate Zeeman field that splits the zero-energy peak. We solve Bogoliubov-de Gennes equations in momentum space and discuss the deviation of our results from the lattice models investigated previously. Large enhancement of the spin-lattice relaxation rate T1-1 at the domain wall provides a clear signature of the quasiparticle bound states, and is in good agreement with recent experiment in organic superconductor κ -(BEDT-TTF ) 2Cu (NCS) 2 .

  12. Etravirine in CSF is highly protein bound

    PubMed Central

    Nguyen, Anh; Rossi, Steven; Croteau, David; Best, Brookie M.; Clifford, David; Collier, Ann C.; Gelman, Benjamin; Marra, Christina; McArthur, Justin; McCutchan, J. Allen; Morgello, Susan; Simpson, David; Ellis, Ronald J.; Grant, Igor; Capparelli, Edmund; Letendre, Scott; Ellis, Ronald J.; Letendre, Scott; Abramson, Ian; Al-Lozi, Muhammad; Atkinson, J. Hampton; Capparelli, Edmund; Clifford, David; Collier, Ann C.; Fennema-Notestine, Christine; Gamst, Anthony C.; Gelman, Benjamin; Heaton, Robert K.; Marcotte, Thomas D.; Marra, Christina; McCutchan, J. Allen; McArthur, Justin; Morgello, Susan; Simpson, David; Smith, Davey M.; Taylor, Michael J.; Theilmann, Rebecca; Vaida, Florin; Paul Woods, Steven; Cushman, Clint; Dawson, Matthew; Franklin, Donald; Jones, Trudy; Lewis, Kristen; Mintz, Letty; Teshome, Mengesha; Toperoff, Will

    2013-01-01

    Objectives Etravirine has high affinity for plasma drug-binding proteins, such as albumin and α1-acid glycoprotein, which limits the amount of unbound etravirine available to enter the CNS. The objective of this study was to compare total and unbound etravirine concentrations in CSF with plasma concentrations and the in vitro median inhibitory concentration (IC50) for wild-type HIV (0.9 ng/mL). Methods Total and bound etravirine concentrations were measured in 17 CSF and plasma pairs by isotope-dilution liquid chromatography tandem mass spectroscopy, radioligand displacement and ultracentrifugation. Unbound etravirine concentrations were calculated from the bound fraction. The dynamic range of the assay was 7.8–2000 (plasma) and 0.78–200 (CSF) ng/mL. Results Subjects were mostly middle-aged (median 43 years) white (78%) men (89%). All CSF etravirine concentrations were above the limit of quantification. Total and unbound median etravirine concentrations in CSF were 9.5 (IQR 6.4, 26.4) and 0.13 (IQR 0.08, 0.27) ng/mL, respectively. Etravirine was 96% (IQR 94.5, 97.2) protein bound in plasma and 98.4% (IQR 97.8, 98.8) in CSF. Total etravirine in CSF was 4.3% (IQR 3, 5.9) of total and 101% (IQR 76, 160) of unbound etravirine in plasma. There were no significant correlations between unbound etravirine concentrations and concentrations of albumin in plasma or CSF. Unbound etravirine concentrations in CSF did not reach the wild-type IC50 in any of the specimens. Conclusions Unbound etravirine may not achieve optimal concentrations to inhibit HIV replication in the CNS. PMID:23335197

  13. Pair of Craters

    NASA Technical Reports Server (NTRS)

    2005-01-01

    14 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.5 meters per pixel (5 ft/pixel) view of a pair of small meteor impact craters in the Arena Colles region of Mars, located north of Isidis Planitia.

    Location near: 22.7oN, 278.5oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  14. Bound states in string nets

    NASA Astrophysics Data System (ADS)

    Schulz, Marc Daniel; Dusuel, Sébastien; Vidal, Julien

    2016-11-01

    We discuss the emergence of bound states in the low-energy spectrum of the string-net Hamiltonian in the presence of a string tension. In the ladder geometry, we show that a single bound state arises either for a finite tension or in the zero-tension limit depending on the theory considered. In the latter case, we perturbatively compute the binding energy as a function of the total quantum dimension. We also address this issue in the honeycomb lattice where the number of bound states in the topological phase depends on the total quantum dimension. Finally, the internal structure of these bound states is analyzed in the zero-tension limit.

  15. Finding Bounded Rational Equilibria. Part 1; Iterative Focusing

    NASA Technical Reports Server (NTRS)

    Wolpert, David H.

    2004-01-01

    A long-running difficulty with conventional game theory has been how to modify it to accommodate the bounded rationality characterizing all real-world players. A recurring issue in statistical physics is how best to approximate joint probability distributions with decoupled (and therefore far more tractable) distributions. It has recently been shown that the same information theoretic mathematical structure, known as Probability Collectives (PC) underlies both issues. This relationship between statistical physics and game theory allows techniques and insights from the one field to be applied to the other. In particular, PC provides a formal model-independent definition of the degree of rationality of a player and of bounded rationality equilibria. This pair of papers extends previous work on PC by introducing new computational approaches to effectively find bounded rationality equilibria of common-interest (team) games.

  16. Donor-vacancy pairs in irradiated n-Ge: A searching look at the problem

    SciTech Connect

    Emtsev, Vadim; Oganesyan, Gagik

    2014-02-21

    The present situation concerning the identification of vacancy-donor pairs in irradiated n-Ge is discussed. The challenging points are the energy states of these defects deduced from DLTS spectra. Hall effect data seem to be at variance with some important conclusions drawn from DLTS measurements. Critical points of the radiation-produced defect modeling in n-Ge are highlighted.

  17. Defects in liquid crystal nematic shells

    NASA Astrophysics Data System (ADS)

    Fernandez-Nieves, A.; Utada, A. S.; Vitelli, V.; Link, D. R.; Nelson, D. R.; Weitz, D. A.

    2006-03-01

    We generate water/liquid crystal (LC)/water double emulsions via recent micro-capillary fluidic devices [A. S. Utada, et.al. Science 308, 537 (2005)]. The resultant objects are stabilized against coalescence by using surfactants or adequate polymers; these also fix the boundary conditions for the director field n. We use 4-pentyl-4-cyanobiphenyl (5CB) and impose tangential boundary conditions at both water/LC interfaces by having polyvinyl alcohol (PVA) dispersed in the inner and outer water phases. We confirm recent predictions [D. R. Nelson, NanoLetters 2, 1125 (2002)] and find that four strength s=+1/2 defects are present; this is in contrast to the two s=+1 defect bipolar configuration observed for bulk spheres [A. Fernandez-Nieves, et.al. Phys. Rev. Lett. 92, 105503 (2004)]. However, these defects do not lie in the vertices of a tetrahedron but are pushed towards each other until certain equilibration distance is reached. In addition to the four defect shells, we observe shells with two s=+1 defects and even with three defects, a s=+1 and two s=+1/2. We argue these configurations arise from nematic bulk distortions that become important as the shell thickness increases. Finally, by adding a different surfactant, sodium dodecyl sulphate (SDS), to the outer phase, we can change the director boundary conditions at the outermost interface from parallel to homeotropic, to induce coalescing of the two pair of defects in the four defect shell configuration to yield two defect bipolar shells.

  18. Congenital defects of sheep.

    PubMed

    Dennis, S M

    1993-03-01

    With increasing incrimination of viruses, plants, and drugs as causes of ovine congenital defects, concerted efforts are required to identify environmental teratogens. Expanding knowledge of congenital defects requires studying as many defective lambs as possible; recording and documenting; detailed diagnostic examinations; genetic analyses and chromosomal examinations, whenever possible; and field investigations. Adopting standardized classification, terminology, and diagnostic procedures should improve descriptions, diagnoses, and interdisciplinary exchange of information. That, in turn, should improve our knowledge of and diagnosis of congenital defects of sheep in the future. Finally, veterinary clinicians and diagnosticians are encouraged to take an interest in congenital defects and teratology.

  19. Defect production in ceramics

    SciTech Connect

    Zinkle, S.J.; Kinoshita, C.

    1997-08-01

    A review is given of several important defect production and accumulation parameters for irradiated ceramics. Materials covered in this review include alumina, magnesia, spinel silicon carbide, silicon nitride, aluminum nitride and diamond. Whereas threshold displacement energies for many ceramics are known within a reasonable level of uncertainty (with notable exceptions being AIN and Si{sub 3}N{sub 4}), relatively little information exists on the equally important parameters of surviving defect fraction (defect production efficiency) and point defect migration energies for most ceramics. Very little fundamental displacement damage information is available for nitride ceramics. The role of subthreshold irradiation on defect migration and microstructural evolution is also briefly discussed.

  20. Topological defect lasers

    NASA Astrophysics Data System (ADS)

    Knitter, Sebastian; Fatt Liew, Seng; Xiong, Wen; Guy, Mikhael I.; Solomon, Glenn S.; Cao, Hui

    2016-01-01

    We introduce a topological defect to a regular photonic crystal defect cavity with anisotropic unit cell. Spatially localized resonances are formed and have high quality factor. Unlike the regular photonic crystal defect states, the localized resonances in the topological defect structures support powerflow vortices. Experimentally we realize lasing in the topological defect cavities with optical pumping. This work shows that the spatially inhomogeneous variation of the unit cell orientation adds another degree of freedom to the control of lasing modes, enabling the manipulation of the field pattern and energy flow landscape.

  1. Type III burst pair

    NASA Astrophysics Data System (ADS)

    Ning, Zongjun; Fu, Qijun; Lu, Quankang

    2000-05-01

    We present a special solar radio burst detected on 5 January 1994 using the multi-channel (50) spectrometer (1.0-2.0 GHz) of the Beijing Astronomical Observatory (BAO). Sadly, the whole event could not be recorded since it had a broader bandwidth than the limit range of the instrument. The important part was obtained, however. The event is composed of a normal drift type III burst on the lower frequency side and a reverse drift type III burst appearing almost simultaneously on the high side. We call the burst type III a burst pair. It is a typical characteristic of two type III bursts that they are morphologically symmetric about some frequency from 1.64 GHz to 1.78 GHz on the dynamic spectra records, which indicates that there are two different electron beams from the same acceleration region travelling simultaneously in opposite directions (upward and downward). A magnetic reconnection mode is a nice interpretation of type III burst pair since the plasma beta β~=0.01 is much less than 1 and the beams have velocity of about 1.07×10^8 cm s^-1 after leaving the reconnection region if we assume that the ambient magnetic field strength is about 100 G.

  2. Type III burst pair.

    NASA Astrophysics Data System (ADS)

    Zongjun, Ning; Fu, Qijun; Quankang, Lu

    2000-05-01

    Presents a special solar radio burst detected on 5 January 1994 using the multi-channel (50) spectrometer (1.0 - 2.0 GHz) of the Beijing Astronomical Observatory. Sadly, the whole event could not be recorded since it had a broader bandwidth than the limit range of the instrument. The important part was obtained, however. The event is composed of a normal drift type III burst on the lower frequency side and a reverse drift type III burst appearing almost simultaneously on the high side. The authors call the burst type III a burst pair. It is a typical characteristic of two type III bursts that they are morphologically symmetric about some frequency from 1.64 GHz to 1.78 GHz on the dynamic spectra records, which indicates that there are two different electron beams from the same acceleration region travelling simultaneously in opposite directions (upward and downward). A magnetic reconnection mode is an interpretation of type III burst pair.

  3. Swelling Mechanisms of UO2 Lattices with Defect Ingrowths

    PubMed Central

    Günay, Seçkin D.

    2015-01-01

    The swelling that occurs in uranium dioxide as a result of radiation-induced defect ingrowth is not fully understood. Experimental and theoretical groups have attempted to explain this phenomenon with various complex theories. In this study, experimental lattice expansion and lattice super saturation were accurately reproduced using a molecular dynamics simulation method. Based on their resemblance to experimental data, the simulation results presented here show that fission induces only oxygen Frenkel pairs while alpha particle irradiation results in both oxygen and uranium Frenkel pair defects. Moreover, in this work, defects are divided into two sub-groups, obstruction type defects and distortion type defects. It is shown that obstruction type Frenkel pairs are responsible for both fission- and alpha-particle-induced lattice swelling. Relative lattice expansion was found to vary linearly with the number of obstruction type uranium Frenkel defects. Additionally, at high concentrations, some of the obstruction type uranium Frenkel pairs formed diatomic and triatomic structures with oxygen ions in their octahedral cages, increasing the slope of the linear dependence. PMID:26244777

  4. Postdevelopment defect evaluation

    NASA Astrophysics Data System (ADS)

    Miyahara, Osamu; Kiba, Yukio; Ono, Yuko

    2001-08-01

    Reduction of defects after development is a critical issue in photolithography. A special category of post development defects is the satellite defect which is located in large exposed areas generally in proximity to large unexposed regions of photoresist. We have investigated the formation of this defect type on ESCAP and ACETAL DUV resists with and without underlying organic BARCs, In this paper, we will present AFM and elemental analysis data to determine the origin of the satellite defect. Imaging was done on a full-field Nikon 248nm stepper and resist processing was completed on a TEL CLEAN TRACK ACT 8 track. Defect inspection and review were performed on a KLA-Tencor and Hitachi SEM respectively. Results indicate that the satellite defect is generated on both BARC and resist films and defect counts are dependent on the dark erosion. Elemental analysis indicates that the defects are composed of sulfur and nitrogen compounds. We suspect that the defect is formed as a result of a reaction between PAG, quencher and TMAH. This defect type is removed after a DIW re-rinse.

  5. Restricted Defect Dynamics in Colloidal Peanut Crystals

    NASA Astrophysics Data System (ADS)

    Gerbode, Sharon; Lee, Stephanie; John, Bettina; Wolfgang, Angie; Liddell, Chekesha; Escobedo, Fernando; Cohen, Itai

    2008-03-01

    We report that monolayers of hard peanut-shaped colloidal particles consisting of two connected spherical lobes order into a crystalline phase at high area fractions. In this ``lobe-close-packed'' (LCP) crystal, the peanut particle lobes occupy triangular lattice sites, much like close-packed spheres, while the connections between lobe pairs are randomly oriented, uniformly populating the three crystalline directions of the underlying lattice. Using optical microscopy, we directly observe defect nucleation and dynamics in sheared LCP crystals. We find that many particle configurations form obstacles blocking dislocation glide. Consequently, in stark contrast to colloidal monolayers of close-packed spheres, single dislocation pair nucleation is not the only significant energetic barrier to relieving an imposed shear strain. Dislocation propagation beyond such obstructions can proceed only through additional mechanisms such as dislocation reactions. We discuss the implications of such restricted defect mobility for the plasticity of LCP crystals.

  6. Restricted Defect Dynamics in Colloidal Peanut Crystals

    NASA Astrophysics Data System (ADS)

    Gerbode, Sharon; Lee, Stephanie; John, Bettina; Wolfgang, Angie; Liddell, Chakesha; Escobedo, Fernando; Cohen, Itai

    2008-03-01

    We report that monolayers of hard peanut-shaped colloidal particles consisting of two connected spherical lobes order into a crystalline phase at high area fractions. In this ``lobe- close-packed'' (LCP) crystal, the peanut particle lobes occupy triangular lattice sites, much like close-packed spheres, while the connections between lobe pairs are randomly oriented, uniformly populating the three crystalline directions of the underlying lattice. Using optical microscopy, we directly observe defect nucleation and dynamics in sheared LCP crystals. We find that many particle configurations form obstacles blocking dislocation glide. Consequently, in stark contrast to colloidal monolayers of close-packed spheres, single dislocation pair nucleation is not the only significant energetic barrier to relieving an imposed shear strain. Dislocation propagation beyond such obstructions can proceed only through additional mechanisms such as dislocation reactions. We discuss the implications of such restricted defect mobility for the plasticity of LCP crystals.

  7. Ventricular Septal Defect (For Parents)

    MedlinePlus

    ... Atrial Septal Defect Ventricular Septal Defect Heart and Circulatory System ECG (Electrocardiogram) Anesthesia - What to Expect Tetralogy of ... Atrial Septal Defect Ventricular Septal Defect Heart and Circulatory System Contact Us Print Resources Send to a friend ...

  8. Ventricular Septal Defect (For Parents)

    MedlinePlus

    ... Atrial Septal Defect Ventricular Septal Defect Heart and Circulatory System ECG (Electrocardiogram) Anesthesia - What to Expect Tetralogy of ... Atrial Septal Defect Ventricular Septal Defect Heart and Circulatory System Contact Us Print Resources Send to a Friend ...

  9. Topology optimization of compliant mechanisms using pairs of curves

    NASA Astrophysics Data System (ADS)

    Wang, N. F.; Zhang, X. M.

    2015-11-01

    The structural topology optimization approach can be used to generate compliant mechanisms for some desired input-output requirements. The success of the optimization depends on the structural geometry representation scheme used. In this paper, a novel representation scheme is proposed. The representation scheme is characterized by pairs of curves that are used to connect Input/Ouput (I/O) regions of the structure. Each pair of curves includes a normal curve and a fat curve. The areas bounded by the pair of curves define the material distribution between them. All I/O regions are connected to one another (either directly or indirectly) by pairs of curves in order to form one single connected load-bearing structure. A genetic algorithm for constrained and multiobjective optimization is then applied with the representation scheme of the structure in the form of a graph. Simulation results from a displacement inverter and a displacement redirector indicate that the presented representation scheme is appropriate.

  10. Squark pair production in the MSSM with explicit CP violation

    SciTech Connect

    Alan, Ahmet T.; Cankocak, Kerem; Demir, Durmus A.

    2007-05-01

    We analyze effects of the CP-odd soft phases in the MSSM on the pair productions of colored superpartners in pp collisions at the LHC energies. We find that, among all pair-production processes, those of the scalar quarks in the first and second generations are particularly sensitive to the CP-odd phases, more precisely, to the phases of the gluinos and neutralinos. We compute pair-production cross sections, classify various production modes according to their dependencies on the gluino and neutralino phases, perform a detailed numerical analysis to determine individual as well as total cross sections, and give a detailed discussion of 2. electric dipole moment (EDM) bounds. We find that pair productions of first and second generation squarks serve as a viable probe of the CP violation sources in the gaugino sector of the theory even if experiments cannot determine chirality, flavor and electric charge of the squarks produced.

  11. Pairing mechanism in the ferromagnetic superconductor UCoGe

    PubMed Central

    Wu, Beilun; Bastien, Gaël; Taupin, Mathieu; Paulsen, Carley; Howald, Ludovic; Aoki, Dai; Brison, Jean-Pascal

    2017-01-01

    Superconductivity is a unique manifestation of quantum mechanics on a macroscopic scale, and one of the rare examples of many-body phenomena that can be explained by predictive, quantitative theories. The superconducting ground state is described as a condensate of Cooper pairs, and a major challenge has been to understand which mechanisms could lead to a bound state between two electrons, despite the large Coulomb repulsion. An even bigger challenge is to identify experimentally this pairing mechanism, notably in unconventional superconductors dominated by strong electronic correlations, like in high-Tc cuprates, iron pnictides or heavy-fermion compounds. Here we show that in the ferromagnetic superconductor UCoGe, the field dependence of the pairing strength influences dramatically its macroscopic properties like the superconducting upper critical field, in a way that can be quantitatively understood. This provides a simple demonstration of the dominant role of ferromagnetic spin fluctuations in the pairing mechanism. PMID:28230099

  12. Effective response theory for zero-energy Majorana bound states in three spatial dimensions

    NASA Astrophysics Data System (ADS)

    Lopes, Pedro L. e. S.; Teo, Jeffrey C. Y.; Ryu, Shinsei

    2015-05-01

    We propose a gravitational response theory for point defects (hedgehogs) binding Majorana zero modes in (3 + 1)-dimensional superconductors. Starting in 4 + 1 dimensions, where the point defect is extended into a line, a coupling of the bulk defect texture with the gravitational field is introduced. Diffeomorphism invariance then leads to an S U (2) 2 Kac-Moody current running along the defect line. The S U (2) 2 Kac-Moody algebra accounts for the non-Abelian nature of the zero modes in 3 + 1 dimensions. It is then shown to also encode the angular momentum density which permeates throughout the bulk between hedgehog-antihedgehog pairs.

  13. Single-point position and transition defects in continuous time quantum walks

    PubMed Central

    Li, Z. J.; Wang, J. B.

    2015-01-01

    We present a detailed analysis of continuous time quantum walks (CTQW) with both position and transition defects defined at a single point in the line. Analytical solutions of both traveling waves and bound states are obtained, which provide valuable insight into the dynamics of CTQW. The number of bound states is found to be critically dependent on the defect parameters, and the localized probability peaks can be readily obtained by projecting the state vector of CTQW on to these bound states. The interference between two bound states are also observed in the case of a transition defect. The spreading of CTQW probability over the line can be finely tuned by varying the position and transition defect parameters, offering the possibility of precision quantum control of the system. PMID:26323855

  14. Octagonal Defects at Carbon Nanotube Junctions

    PubMed Central

    Jaskólski, W.; Pelc, M.; Chico, Leonor; Ayuela, A.

    2013-01-01

    We investigate knee-shaped junctions of semiconductor zigzag carbon nanotubes. Two dissimilar octagons appear at such junctions; one of them can reconstruct into a pair of pentagons. The junction with two octagons presents two degenerate localized states at Fermi energy (EF). The reconstructed junction has only one state near EF, indicating that these localized states are related to the octagonal defects. The inclusion of Coulomb interaction splits the localized states in the junction with two octagons, yielding an antiferromagnetic system. PMID:24089604

  15. Quantum conductance of carbon nanotubes with defects

    SciTech Connect

    Chico, L.; Benedict, L.X.; Louie, S.G.; Cohen, M.L. |

    1996-07-01

    We study the conductance of metallic carbon nanotubes with vacancies and pentagon-heptagon pair defects within the Landauer formalism. Using a tight-binding model and a Green{close_quote}s function technique to calculate the scattering matrix, we examine the one-dimensional to two-dimensional crossover in these systems and show the existence of metallic tube junctions in which the conductance is suppressed for symmetry reasons. {copyright} {ital 1996 The American Physical Society.}

  16. Point Defects in Two-Dimensional Layered Semiconductors: Physics and Its Applications

    NASA Astrophysics Data System (ADS)

    Suh, Joonki

    thermoelectric materials are thoroughly investigated. Point defects can potentially beat the undesired coupling, often term "thermoelectric Bermuda triangle", among electrical conductivity, thermal conductivity and thermopower. The maximum thermoelectric performance is demonstrated with an intermediate density of defects when they beneficially and multi-functionally act as electron donors, as well as strongly energy-dependent electron and phonon scatterers. Therefore, this is a good example of how fundamental defect physics can be applied for practical devices toward renewable energy technology. Another interesting field of layered nanomaterials is on transition-metal dichalcogenides (TMDs), sensational candidates for 2D semiconductor physics and applications. At the reduced dimensionality of 2D where a far stronger correlation between point defects and charge carriers is expected, it is studied how chalcogen vacancies alter optical properties of monolayer TMDs. A new, sub-bandgap broad emission lines as well as increase in the overall photoluminescence intensity at low temperatures are reported as a result of high quantum efficiency of excitons, i.e., bound electron-hole pairs, localized at defect sites. On electrical transport, both n- and p-type materials are needed to form junctions and support bipolar carrier conduction while typically only one type of doping is stable for a particular TMD. For example, MoS2 is natively n-type, thus the lack of p-type doping hampers the development of charge-splitting p-n junctions of MoS2. To address this issue, we demonstrate stable p-type conduction in MoS2 by substitutional Nb doping up to the degenerate level. Proof-of-concept, van der Waals p-n homo-junctions based on vertically stacked MoS2 layers are also fabricated which enable gate-tuneable current rectification. Various electronic devices fabricated are stable in ambient air even without additional treatment such as capping layer protection, thanks to the substitutionality nature

  17. Mechanics of Miura-ori Origami Lattice Defects

    NASA Astrophysics Data System (ADS)

    Silverberg, Jesse; McLeod, Lauren; Evans, Arthur; Ginepro, Jessica; Santangelo, Christian; Hull, Thomas; Cohen, Itai

    2014-03-01

    The mechanical properties of origami-inspired materials show remarkable potential for responsive, tunable next-generation materials. For example, the Miura-ori fold is predicted to have negative Poisson ratio and anisotropic compressive properties. Using a custom mechanical testing device and 3D laser profilometry, we investigate the moduli and the role of curvature in setting these material properties. Because defects are known to dramatically alter the bulk properties in other periodic materials, we introduce defects into the folding pattern to investigate their effects on the macroscopic mechanical properties. Interestingly, we find that a single defect increases the overall material stiffness, but the introduction of a second defect in the opposite direction can cancel out the first, tending to restore the original material properties. Moreover, these defect pairs can be arranged to form edge dislocations, grain boundaries, and many other topological configurations familiar from the study of crystallographic lattice defects.

  18. Upper bounds on the error probabilities and asymptotic error exponents in quantum multiple state discrimination

    SciTech Connect

    Audenaert, Koenraad M. R.; Mosonyi, Milán

    2014-10-01

    We consider the multiple hypothesis testing problem for symmetric quantum state discrimination between r given states σ₁, …, σ{sub r}. By splitting up the overall test into multiple binary tests in various ways we obtain a number of upper bounds on the optimal error probability in terms of the binary error probabilities. These upper bounds allow us to deduce various bounds on the asymptotic error rate, for which it has been hypothesized that it is given by the multi-hypothesis quantum Chernoff bound (or Chernoff divergence) C(σ₁, …, σ{sub r}), as recently introduced by Nussbaum and Szkoła in analogy with Salikhov's classical multi-hypothesis Chernoff bound. This quantity is defined as the minimum of the pairwise binary Chernoff divergences min{sub jbound is actually achieved. It was known to be achieved, in particular, when the state pair that is closest together in Chernoff divergence is more than 6 times closer than the next closest pair. Our results improve on this in two ways. First, we show that the optimal asymptotic rate must lie between C/2 and C. Second, we show that the Chernoff bound is already achieved when the closest state pair is more than 2 times closer than the next closest pair. We also show that the Chernoff bound is achieved when at least r - 2 of the states are pure, improving on a previous result by Nussbaum and Szkoła. Finally, we indicate a number of potential pathways along which a proof (or disproof) may eventually be found that the multi-hypothesis quantum Chernoff bound is always achieved.

  19. Bound states of fractionalized excitations in a modulated Kitaev spin liquid

    NASA Astrophysics Data System (ADS)

    Théveniaut, Hugo; Vojta, Matthias

    2017-08-01

    Fractionalization is a hallmark of spin-liquid behavior; it typically leads to response functions consisting of continua instead of sharp modes. However, microscopic processes can enable the formation of short-distance bound states of fractionalized excitations, despite asymptotic deconfinement. Here we study such bound-state formation for the Z2 spin liquid realized in Kitaev's honeycomb compass model, supplemented by a kekulé distortion of the lattice. Bound states between flux pairs and Majorana fermions form in the Majorana band gaps. We calculate the dynamic spin susceptibility and show that bound states lead to sharp modes in the magnetic response of the spin liquid, with the momentum dependence of the corresponding spectral weight encoding the internal symmetry of the bound state. As a byproduct, we also show that isolated fluxes may produce Majorana bound states at exactly zero energy. Generalizations and implications of the results are discussed.

  20. Absence of bound states for waveguides in two-dimensional periodic structures

    SciTech Connect

    Hoang, Vu E-mail: hoang@math.wisc.edu; Radosz, Maria

    2014-03-15

    We study a Helmholtz-type spectral problem in a two-dimensional medium consisting of a fully periodic background structure and a perturbation in form of a line defect. The defect is aligned along one of the coordinate axes, periodic in that direction (with the same periodicity as the background), and bounded in the other direction. This setting models a so-called “soft-wall” waveguide problem. We show that there are no bound states, i.e., the spectrum of the operator under study contains no point spectrum.

  1. Prospective very young asteroid pairs

    NASA Astrophysics Data System (ADS)

    Galád, A.; Vokrouhlický, D.; Zizka, J.

    2014-07-01

    Several tens of asteroid pairs can be discerned from the background main-belt asteroids. The majority of them are thought to have formed within only the last few 10^6 yr. The youngest recognized pairs have formed more than ≈ 10 kyr ago. As some details of pair formation are still not understood well, the study of young pairs is of great importance. It is mainly because the conditions at the time of the pair formation could be deduced much more reliably for young pairs. For example, space weathering on the surfaces of the components, or changes in their rotational properties (in spin rates, tumbling, coordinates of rotational pole) could be negligible since the formation of young pairs. Also, possible strong perturbations by main-belt bodies on pair formation can be reliably studied only for extremely young pairs. Some pairs can quickly blend in with the background asteroids, so even the frequency of asteroid pair formation could be determined more reliably based on young pairs (though only after a statistically significant sample is at disposal). In our regular search for young pairs in the growing asteroid database, only multiopposition asteroids with very similar orbital and proper elements are investigated. Every pair component is represented by a number of clones within orbital uncertainties and drifting in semimajor axis due to the Yarkovsky effect. We found that, if the previously unrecognized pairs (87887) 2000 SS_{286} - 2002 AT_{49} and (355258) 2007 LY_{4} - 2013AF_{40} formed at the recent very close approach of their components, they could become the youngest known pairs. In both cases, the relative encounter velocities of the components were only ˜ 0.1 m s^{-1}. However, the minimum distances between some clones are too large and a few clones of the latter pair did not encounter recently (within ≈ 10 kyr). The age of some prospective young pairs cannot be determined reliably without improved orbital properties (e.g., the second component of a pair

  2. Multiprocessor switch with selective pairing

    DOEpatents

    Gara, Alan; Gschwind, Michael K; Salapura, Valentina

    2014-03-11

    System, method and computer program product for a multiprocessing system to offer selective pairing of processor cores for increased processing reliability. A selective pairing facility is provided that selectively connects, i.e., pairs, multiple microprocessor or processor cores to provide one highly reliable thread (or thread group). Each paired microprocessor or processor cores that provide one highly reliable thread for high-reliability connect with a system components such as a memory "nest" (or memory hierarchy), an optional system controller, and optional interrupt controller, optional I/O or peripheral devices, etc. The memory nest is attached to a selective pairing facility via a switch or a bus

  3. Microstructure and point defects in CdTe nanowires for photovoltaic applications.

    PubMed

    Williams, B L; Halliday, D P; Mendis, B G; Durose, K

    2013-04-05

    Defects in Au-catalysed CdTe nanowires vapour-liquid-solid-grown on polycrystalline underlayers have been critically evaluated. Their low-temperature photoluminescence spectra were dominated by excitonic emission with rarely observed above-gap emission also being recorded. While acceptor bound exciton lines due to monovalent metallic impurities (Ag, Cu or Na) were seen, only deeper, donor-acceptor-pair emission could be attributed to the Au contamination that is expected from the catalyst. Annealing under nitrogen acted to enhance the single crystal-like PL emission, whilst oxidizing and reducing anneals of the type that is used in solar cell device processing caused it to degrade. The incidence of stacking faults, polytypes and twins was related only to the growth axes of the wires (<111> 50%, <112> 30% and <110> 20%), and was not influenced by annealing. The potential electrical activity of the point and extended defects, and the suitability of these nanowire materials (including processing steps) for solar cell applications, is discussed. Overall they have a quality that is superior to that of thin polycrystalline films, although questions remain about recombination due to Au.

  4. Paired twins and [112] morphology in GaP nanowires.

    PubMed

    Algra, Rienk E; Verheijen, Marcel A; Feiner, Lou-Fé; Immink, George G W; Theissmann, Ralf; van Enckevort, Willem J P; Vlieg, Elias; Bakkers, Erik P A M

    2010-07-14

    Formation of random as well as periodic planar defects can occur during vapor-liquid-solid growth of nanowires with the zinc-blende crystal structure. Here we investigate the formation of pairs of twin planes in GaP nanowires. In such pairs, the first twin plane is formed at a random position, rapidly followed by the formation of a second twin plane of which the position is directly related to that of the first one. We show that the triangular [112] morphology of the nanowire is a key element in the formation of these twin pairs. We have extended our previous kinetic nucleation model and show that this describes the development of the nanowire morphology and its relation with the formation of single and paired twin planes.

  5. Fuzzy Logic Connectivity in Semiconductor Defect Clustering

    SciTech Connect

    Gleason, S.S.; Kamowski, T.P.; Tobin, K.W.

    1999-01-24

    In joining defects on semiconductor wafer maps into clusters, it is common for defects caused by different sources to overlap. Simple morphological image processing tends to either join too many unrelated defects together or not enough together. Expert semiconductor fabrication engineers have demonstrated that they can easily group clusters of defects from a common manufacturing problem source into a single signature. Capturing this thought process is ideally suited for fuzzy logic. A system of rules was developed to join disconnected clusters based on properties such as elongation, orientation, and distance. The clusters are evaluated on a pair-wise basis using the fuzzy rules and are joined or not joined based on a defuzzification and threshold. The system continuously re-evaluates the clusters under consideration as their fuzzy memberships change with each joining action. The fuzzy membership functions for each pair-wise feature, the techniques used to measure the features, and methods for improving the speed of the system are all developed. Examples of the process are shown using real-world semiconductor wafer maps obtained from chip manufacturers. The algorithm is utilized in the Spatial Signature Analyzer (SSA) software, a joint development project between Oak Ridge National Lab (ORNL) and SEMATECH.

  6. The entangled triplet pair state in acene and heteroacene materials

    PubMed Central

    Yong, Chaw Keong; Musser, Andrew J.; Bayliss, Sam L.; Lukman, Steven; Tamura, Hiroyuki; Bubnova, Olga; Hallani, Rawad K.; Meneau, Aurélie; Resel, Roland; Maruyama, Munetaka; Hotta, Shu; Herz, Laura M.; Beljonne, David; Anthony, John E.; Clark, Jenny; Sirringhaus, Henning

    2017-01-01

    Entanglement of states is one of the most surprising and counter-intuitive consequences of quantum mechanics, with potent applications in cryptography and computing. In organic materials, one particularly significant manifestation is the spin-entangled triplet-pair state, which mediates the spin-conserving fission of one spin-0 singlet exciton into two spin-1 triplet excitons. Despite long theoretical and experimental exploration, the nature of the triplet-pair state and inter-triplet interactions have proved elusive. Here we use a range of organic semiconductors that undergo singlet exciton fission to reveal the photophysical properties of entangled triplet-pair states. We find that the triplet pair is bound with respect to free triplets with an energy that is largely material independent (∼30 meV). During its lifetime, the component triplets behave cooperatively as a singlet and emit light through a Herzberg–Teller-type mechanism, resulting in vibronically structured photoluminescence. In photovoltaic blends, charge transfer can occur from the bound triplet pairs with >100% photon-to-charge conversion efficiency. PMID:28699637

  7. The entangled triplet pair state in acene and heteroacene materials

    NASA Astrophysics Data System (ADS)

    Yong, Chaw Keong; Musser, Andrew J.; Bayliss, Sam L.; Lukman, Steven; Tamura, Hiroyuki; Bubnova, Olga; Hallani, Rawad K.; Meneau, Aurélie; Resel, Roland; Maruyama, Munetaka; Hotta, Shu; Herz, Laura M.; Beljonne, David; Anthony, John E.; Clark, Jenny; Sirringhaus, Henning

    2017-07-01

    Entanglement of states is one of the most surprising and counter-intuitive consequences of quantum mechanics, with potent applications in cryptography and computing. In organic materials, one particularly significant manifestation is the spin-entangled triplet-pair state, which mediates the spin-conserving fission of one spin-0 singlet exciton into two spin-1 triplet excitons. Despite long theoretical and experimental exploration, the nature of the triplet-pair state and inter-triplet interactions have proved elusive. Here we use a range of organic semiconductors that undergo singlet exciton fission to reveal the photophysical properties of entangled triplet-pair states. We find that the triplet pair is bound with respect to free triplets with an energy that is largely material independent (~30 meV). During its lifetime, the component triplets behave cooperatively as a singlet and emit light through a Herzberg-Teller-type mechanism, resulting in vibronically structured photoluminescence. In photovoltaic blends, charge transfer can occur from the bound triplet pairs with >100% photon-to-charge conversion efficiency.

  8. Experimental many-pairs nonlocality

    NASA Astrophysics Data System (ADS)

    Poh, Hou Shun; Cerè, Alessandro; Bancal, Jean-Daniel; Cai, Yu; Sangouard, Nicolas; Scarani, Valerio; Kurtsiefer, Christian

    2017-08-01

    Collective measurements on large quantum systems together with a majority voting strategy can lead to a violation of the Clauser-Horne-Shimony-Holt Bell inequality. In the presence of many entangled pairs, this violation decreases quickly with the number of pairs and vanishes for some critical pair number that is a function of the noise present in the system. Here we show that a different binning strategy can lead to a more substantial Bell violation when the noise is sufficiently small. Given the relation between the critical pair number and the source noise, we then present an experiment where the critical pair number is used to quantify the quality of a high visibility photon pair source. Our results demonstrate nonlocal correlations using collective measurements operating on clusters of more than 40 photon pairs.

  9. Effective diffusion coefficients of point defects in impure materials

    SciTech Connect

    Mansur, L.K.

    1980-03-01

    Effective diffusion coefficients of vacancies and interstitials in a material containing impurities are derived in terms of impurity and point defect concentrations and reaction parameters. Irradiation and thermal conditions are considered. Several expressions presented earlier are reviewed. These are found to be limiting or approximate forms to a more general result. The regimes of importance of the point defect processes of thermal dissociation, trapping, recombination with bound point defects of the opposite type, and impurity-associated transport to sinks are evaluated in terms of the structure of the effective diffusion coefficients.

  10. Maximum common subgraph: some upper bound and lower bound results

    PubMed Central

    Huang, Xiuzhen; Lai, Jing; Jennings, Steven F

    2006-01-01

    Background Structure matching plays an important part in understanding the functional role of biological structures. Bioinformatics assists in this effort by reformulating this process into a problem of finding a maximum common subgraph between graphical representations of these structures. Among the many different variants of the maximum common subgraph problem, the maximum common induced subgraph of two graphs is of special interest. Results Based on current research in the area of parameterized computation, we derive a new lower bound for the exact algorithms of the maximum common induced subgraph of two graphs which is the best currently known. Then we investigate the upper bound and design techniques for approaching this problem, specifically, reducing it to one of finding a maximum clique in the product graph of the two given graphs. Considering the upper bound result, the derived lower bound result is asymptotically tight. Conclusion Parameterized computation is a viable approach with great potential for investigating many applications within bioinformatics, such as the maximum common subgraph problem studied in this paper. With an improved hardness result and the proposed approaches in this paper, future research can be focused on further exploration of efficient approaches for different variants of this problem within the constraints imposed by real applications. PMID:17217524

  11. Modeling agreement on bounded scales.

    PubMed

    Vanbelle, Sophie; Lesaffre, Emmanuel

    2017-01-01

    Agreement is an important concept in medical and behavioral sciences, in particular in clinical decision making where disagreements possibly imply a different patient management. The concordance correlation coefficient is an appropriate measure to quantify agreement between two scorers on a quantitative scale. However, this measure is based on the first two moments, which could poorly summarize the shape of the score distribution on bounded scales. Bounded outcome scores are common in medical and behavioral sciences. Typical examples are scores obtained on visual analog scales and scores derived as the number of positive items on a questionnaire. These kinds of scores often show a non-standard distribution, like a J- or U-shape, questioning the usefulness of the concordance correlation coefficient as agreement measure. The logit-normal distribution has shown to be successful in modeling bounded outcome scores of two types: (1) when the bounded score is a coarsened version of a latent score with a logit-normal distribution on the [0,1] interval and (2) when the bounded score is a proportion with the true probability having a logit-normal distribution. In the present work, a model-based approach, based on a bivariate generalization of the logit-normal distribution, is developed in a Bayesian framework to assess the agreement on bounded scales. This method permits to directly study the impact of predictors on the concordance correlation coefficient and can be simply implemented in standard Bayesian softwares, like JAGS and WinBUGS. The performances of the new method are compared to the classical approach using simulations. Finally, the methodology is used in two different medical domains: cardiology and rheumatology.

  12. Stereo Pair, Honolulu, Oahu

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Honolulu, on the island of Oahu, is a large and growing urban area. This stereoscopic image pair, combining a Landsat image with topography measured by the Shuttle Radar Topography Mission (SRTM), shows how topography controls the urban pattern. This color image can be viewed in 3-D by viewing the left image with the right eye and the right image with the left eye (cross-eyed viewing), or by downloading and printing the image pair, and viewing them with a stereoscope.

    Features of interest in this scene include Diamond Head (an extinct volcano near the bottom of the image), Waikiki Beach (just above Diamond Head), the Punchbowl National Cemetary (another extinct volcano, near the image center), downtown Honolulu and Honolulu harbor (image left-center), and offshore reef patterns. The slopes of the Koolau mountain range are seen in the right half of the image. Clouds commonly hang above ridges and peaks of the Hawaiian Islands, but in this synthesized stereo rendition appear draped directly on the mountains. The clouds are actually about 1000 meters (3300 feet) above sea level.

    This stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with a Landsat 7 Thematic Mapper image collected at the same time as the SRTM flight. The topography data were used to create two differing perspectives, one for each eye. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions. The United States Geological Survey's Earth Resources Observations Systems (EROS) Data Center, Sioux Falls, South Dakota, provided the Landsat data.

    The Shuttle Radar Topography Mission (SRTM), launched on February 11, 2000, used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission was designed to collect three-dimensional measurements of the

  13. Repair of Auricular Defects.

    PubMed

    Watson, Deborah; Hecht, Avram

    2017-08-01

    Repairing defects of the auricle requires an appreciation of the underlying 3-dimensional framework, the flexible properties of the cartilages, and the healing contractile tendencies of the surrounding soft tissue. In the analysis of auricular defects and planning of their reconstruction, it is helpful to divide the auricle into subunits for which different techniques may offer better functional and aesthetic outcomes. This article reviews many of the reconstructive options for defects of the various auricular subunits. Published by Elsevier Inc.

  14. Holographic bounds and finite inflation

    NASA Astrophysics Data System (ADS)

    Phillips, Daniel; Scacco, Andrew; Albrecht, Andreas

    2015-02-01

    We compare two holographic arguments that impose especially strong bounds on the amount of inflation. One comes from the de Sitter equilibrium cosmology and the other from the work of Banks and Fischler. We find that simple versions of these two approaches yield the same bound on the number of e-foldings. A careful examination reveals that while these pictures are similar in spirit, they are not necessarily identical prescriptions. We apply the two pictures to specific cosmologies which expose potentially important differences and which also demonstrate ways these seemingly simple proposals can be tricky to implement in practice.

  15. Uncertainty bounds using sector theory

    NASA Technical Reports Server (NTRS)

    Waszak, Martin R.; Schmidt, David K.

    1989-01-01

    An approach based on sector-stability theory can furnish a description of the uncertainty associated with the frequency response of a model, given sector-bounds on the individual parameters of the model. The application of the sector-based approach to the formulation of useful uncertainty descriptions for linear, time-invariant multivariable systems is presently explored, and the approach is applied to two generic forms of parameter uncertainty in order to investigate its advantages and limitations. The results obtained show that sector-uncertainty bounds can be used to evaluate the impact of parameter uncertainties on the frequency response of the design model.

  16. Stereo Pair, Pasadena, California

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This stereoscopic image pair is a perspective view that shows the western part of the city of Pasadena, California, looking north toward the San Gabriel Mountains. Portions of the cities of Altadena and La Canada Flintridge are also shown. The cluster of large buildings left of center, at the base of the mountains, is the Jet Propulsion Laboratory. This image shows the power of combining data from different sources to create planning tools to study problems that affect large urban areas. In addition to the well-known earthquake hazards, Southern California is affected by a natural cycle of fire and mudflows. Data shown in this image can be used to predict both how wildfires spread over the terrain and how mudflows are channeled down the canyons.

    The image was created from three datasets: the Shuttle Radar Topography Mission (SRTM) supplied the elevation, U. S. Geological Survey digital aerial photography provided the image detail, and the Landsat Thematic Mapper provided the color. The United States Geological Survey's Earth Resources Observations Systems (EROS) Data Center, Sioux Falls, South Dakota, provided the Landsat data and the aerial photography. The image can be viewed in 3-D by viewing the left image with the right eye and the right image with the left eye (cross-eyed viewing), or by downloading and printing the image pair, and viewing them with a stereoscope.

    The Shuttle Radar Topography Mission (SRTM), launched on February 11, 2000, used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, an additional C-band imaging antenna and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration

  17. Stereo Pair, Pasadena, California

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This stereoscopic image pair is a perspective view that shows the western part of the city of Pasadena, California, looking north toward the San Gabriel Mountains. Portions of the cities of Altadena and La Canada Flintridge are also shown. The cluster of large buildings left of center, at the base of the mountains, is the Jet Propulsion Laboratory. This image shows the power of combining data from different sources to create planning tools to study problems that affect large urban areas. In addition to the well-known earthquake hazards, Southern California is affected by a natural cycle of fire and mudflows. Data shown in this image can be used to predict both how wildfires spread over the terrain and how mudflows are channeled down the canyons.

    The image was created from three datasets: the Shuttle Radar Topography Mission (SRTM) supplied the elevation, U. S. Geological Survey digital aerial photography provided the image detail, and the Landsat Thematic Mapper provided the color. The United States Geological Survey's Earth Resources Observations Systems (EROS) Data Center, Sioux Falls, South Dakota, provided the Landsat data and the aerial photography. The image can be viewed in 3-D by viewing the left image with the right eye and the right image with the left eye (cross-eyed viewing), or by downloading and printing the image pair, and viewing them with a stereoscope.

    The Shuttle Radar Topography Mission (SRTM), launched on February 11, 2000, used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, an additional C-band imaging antenna and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration

  18. A novel ciliopathic skull defect arising from excess neural crest.

    PubMed

    Tabler, Jacqueline M; Rice, Christopher P; Liu, Karen J; Wallingford, John B

    2016-09-01

    The skull is essential for protecting the brain from damage, and birth defects involving disorganization of skull bones are common. However, the developmental trajectories and molecular etiologies by which many craniofacial phenotypes arise remain poorly understood. Here, we report a novel skull defect in ciliopathic Fuz mutant mice in which only a single bone pair encases the forebrain, instead of the usual paired frontal and parietal bones. Through genetic lineage analysis, we show that this defect stems from a massive expansion of the neural crest-derived frontal bone. This expansion occurs at the expense of the mesodermally-derived parietal bones, which are either severely reduced or absent. A similar, though less severe, phenotype was observed in Gli3 mutant mice, consistent with a role for Gli3 in cilia-mediated signaling. Excess crest has also been shown to drive defective palate morphogenesis in ciliopathic mice, and that defect is ameliorated by reduction of Fgf8 gene dosage. Strikingly, skull defects in Fuz mutant mice are also rescued by loss of one allele of fgf8, suggesting a potential route to therapy. In sum, this work is significant for revealing a novel skull defect with a previously un-described developmental etiology and for suggesting a common developmental origin for skull and palate defects in ciliopathies. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Pygmy stars: first pair.

    PubMed

    Zwicky, F

    1966-07-01

    The binary LP 101-15/16 having the proper motion of 1.62 seconds of arc per year has been studied with the prime-focus spectrograph of the 200-inch (508 cm) telescope. Indications are that LP 101-15/16 is the first pair of pygmy stars ever discovered. One of its components, LP 101-16, is probably a blue pygmy star which is at least four magnitudes fainter than the ordinary white dwarfs. Also, two of the Balmer lines in absorption appear to be displaced toward the red by amounts which indicate the existence of an Einstein gravitational red shift corresponding to about 1000 km sec-1. On the other hand LP 101-15 is red and shows an entirely new type of spectrum, which suggests that it may be a first representative of a type of red pygmy star which is 2.5 magnitudes fainter than the M-type dwarf stars of the main sequence.

  20. Cooperon condensation and intravalley pairing states in honeycomb Dirac systems

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Shunji; Goryo, Jun; Arahata, Emiko; Sigrist, Manfred

    2016-09-01

    Motivated by recent developments in the experimental study of superconducting graphene and transition metal dichalcogenides, we investigate superconductivity of the Kane-Mele (KM) model with short-range attractive interactions on the two-dimensional honeycomb lattice. We show that intravalley spin-triplet pairing arises from nearest-neighbor (NN) attractive interaction and the intrinsic spin-orbit coupling. We demonstrate this in two independent approaches: We study superconducting instability driven by condensation of Cooperons, which are in-gap bound states of two conduction electrons, within the T -matrix approximation and also study the superconducting ground state within the mean-field theory. We find that Cooperons with antiparallel spins condense at the K and K' points. This leads to the emergence of an intravalley spin-triplet pairing state belonging to the irreducible representation A1 of the point group C6 v. The fact that this pairing state has opposite chirality for K and K' identifies this state as a "helical" valley-triplet state, the valley analog to the 3He -B phase in two dimensions. Because of the finite center of mass momentum of Cooper pairs, the pair amplitude in NN bonds exhibits spatial modulation on the length scale of lattice constant, such that this pairing state may be viewed as a pair-density wave state. We find that the pair amplitude spontaneously breaks the translational symmetry and exhibits a p -Kekulé pattern. We also discuss the selection rule for pairing states focusing the characteristic band structure of the KM model and the Berry phase effects to the emergence of the intravalley pairing state.

  1. Observation of 3D defect mediated dust acoustic wave turbulence with fluctuating defects and amplitude hole filaments

    SciTech Connect

    Chang, Mei-Chu; Tsai, Ya-Yi; I, Lin

    2013-08-15

    We experimentally demonstrate the direct observation of defect mediated wave turbulence with fluctuating defects and low amplitude hole filaments, from a 3D self-excited plane dust acoustic wave in a dusty plasma by reducing dissipation. The waveform undulation is found to be the origin for the amplitude and the phase modulations of the local dust density oscillation, the broadening of the sharp peaks in the frequency spectrum, and the fluctuating defects. The corrugated wave crest surface also causes the observed high and low density patches in the transverse (xy) plane. Low oscillation amplitude spots (holes) share the same positions with the defects. Their trajectories in the xyt space appear in the form of chaotic filaments without long term predictability, through uncertain pair generation, propagation, and pair annihilation.

  2. Successfully Serving the College Bound

    ERIC Educational Resources Information Center

    Hands, Africa S.

    2015-01-01

    Whether they are students taking the traditional path of entering college from high school, or adult first-time or re-entry students, navigating the admissions and financial aid process can be overwhelming for the college bound. Public libraries can help provide information and guidance for a successful start, and this book shows how to do it.…

  3. Pieter Paul Rubens, "Prometheus Bound."

    ERIC Educational Resources Information Center

    Shoemaker, Marla K.

    1986-01-01

    Provides a full-color reproduction of Pieter Paul Rubens' painting, "Prometheus Bound," and a lesson plan for using it with students in grades 10 through 12. The goal of the lesson is to introduce students to the techniques of design and execution used by Rubens. (JDH)

  4. Wronskian Method for Bound States

    ERIC Educational Resources Information Center

    Fernandez, Francisco M.

    2011-01-01

    We propose a simple and straightforward method based on Wronskians for the calculation of bound-state energies and wavefunctions of one-dimensional quantum-mechanical problems. We explicitly discuss the asymptotic behaviour of the wavefunction and show that the allowed energies make the divergent part vanish. As illustrative examples we consider…

  5. Wronskian Method for Bound States

    ERIC Educational Resources Information Center

    Fernandez, Francisco M.

    2011-01-01

    We propose a simple and straightforward method based on Wronskians for the calculation of bound-state energies and wavefunctions of one-dimensional quantum-mechanical problems. We explicitly discuss the asymptotic behaviour of the wavefunction and show that the allowed energies make the divergent part vanish. As illustrative examples we consider…

  6. Teacher Education in Outward Bound.

    ERIC Educational Resources Information Center

    Robinson, Richard A.

    A series of Outward Bound programs and experiences was planned for El Paso County, Colorado, school teachers to increase their awareness of their personal characteristics, especially those that might enhance learning on the part of their students. Part of the planning for the program involved a survey of county high school teachers, counselors,…

  7. Variational Bounds for Creeping Composites

    NASA Astrophysics Data System (ADS)

    Procházka, Petr

    2010-05-01

    In the paper time dependent variational bounds are derived based on Extended Hashin-Shtrikman variational principles. Direct calculation leads to explicit formulas to be presented in the text. For various mechanical properties easy coding in Excel, say, can be used and verification of accuracy for numerical procedures is available using the derived formulas.

  8. Loosely-Bound Diatomic Molecules.

    ERIC Educational Resources Information Center

    Balfour, W. J.

    1979-01-01

    Discusses concept of covalent bonding as related to homonuclear diatomic molecules. Article draws attention to the existence of bound rare gas and alkaline earth diatomic molecules. Summarizes their molecular parameters and offers spectroscopic data. Strength and variation with distance of interatomic attractive forces is given. (Author/SA)

  9. Pieter Paul Rubens, "Prometheus Bound."

    ERIC Educational Resources Information Center

    Shoemaker, Marla K.

    1986-01-01

    Provides a full-color reproduction of Pieter Paul Rubens' painting, "Prometheus Bound," and a lesson plan for using it with students in grades 10 through 12. The goal of the lesson is to introduce students to the techniques of design and execution used by Rubens. (JDH)

  10. Loosely-Bound Diatomic Molecules.

    ERIC Educational Resources Information Center

    Balfour, W. J.

    1979-01-01

    Discusses concept of covalent bonding as related to homonuclear diatomic molecules. Article draws attention to the existence of bound rare gas and alkaline earth diatomic molecules. Summarizes their molecular parameters and offers spectroscopic data. Strength and variation with distance of interatomic attractive forces is given. (Author/SA)

  11. Teacher Education in Outward Bound.

    ERIC Educational Resources Information Center

    Robinson, Richard A.

    A series of Outward Bound programs and experiences was planned for El Paso County, Colorado, school teachers to increase their awareness of their personal characteristics, especially those that might enhance learning on the part of their students. Part of the planning for the program involved a survey of county high school teachers, counselors,…

  12. Titania bound sodium titanate ion exchanger

    DOEpatents

    DeFilippi, Irene C. G.; Yates, Stephen Frederic; Shen, Jian-Kun; Gaita, Romulus; Sedath, Robert Henry; Seminara, Gary Joseph; Straszewski, Michael Peter; Anderson, David Joseph

    1999-03-23

    This invention is method for preparing a titania bound ion exchange composition comprising admixing crystalline sodium titanate and a hydrolyzable titanium compound and, thereafter drying the titania bound crystalline sodium titanate and subjecting the dried titania bound ion exchange composition to optional compaction and calcination steps to improve the physical strength of the titania bound composition.

  13. Three carbon pairs in Si

    NASA Astrophysics Data System (ADS)

    Docaj, A.; Estreicher, S. K.

    2012-08-01

    Carbon impurities in Si are common in floating-zone and cast-Si materials. The simplest and most discussed carbon complex is the interstitial-substitutional CiCs pair, which readily forms when self-interstitials are present in the material. This pair has three possible configurations, each of which is electrically active. The less common CsCs pair has been studied in irradiated material but has also recently been seen in as-grown C-rich cast-Si, which is commonly used to fabricate solar cells. The third pair consists of two interstitial C atoms: CiCi. Although its formation probability is low for several reasons, the CiCi pair is very stable and electrically inactive. In this contribution, we report preliminary results of first-principles calculations of these three C pairs in Si. The structures, binding energies, vibrational spectra, and electrical activity are predicted.

  14. Kink pair production and dislocation motion

    NASA Astrophysics Data System (ADS)

    Fitzgerald, S. P.

    2016-12-01

    The motion of extended defects called dislocations controls the mechanical properties of crystalline materials such as strength and ductility. Under moderate applied loads, this motion proceeds via the thermal nucleation of kink pairs. The nucleation rate is known to be a highly nonlinear function of the applied load, and its calculation has long been a theoretical challenge. In this article, a stochastic path integral approach is used to derive a simple, general, and exact formula for the rate. The predictions are in excellent agreement with experimental and computational investigations, and unambiguously explain the origin of the observed extreme nonlinearity. The results can also be applied to other systems modelled by an elastic string interacting with a periodic potential, such as Josephson junctions in superconductors.

  15. Kink pair production and dislocation motion

    PubMed Central

    Fitzgerald, S. P.

    2016-01-01

    The motion of extended defects called dislocations controls the mechanical properties of crystalline materials such as strength and ductility. Under moderate applied loads, this motion proceeds via the thermal nucleation of kink pairs. The nucleation rate is known to be a highly nonlinear function of the applied load, and its calculation has long been a theoretical challenge. In this article, a stochastic path integral approach is used to derive a simple, general, and exact formula for the rate. The predictions are in excellent agreement with experimental and computational investigations, and unambiguously explain the origin of the observed extreme nonlinearity. The results can also be applied to other systems modelled by an elastic string interacting with a periodic potential, such as Josephson junctions in superconductors. PMID:28004834

  16. SDSS DR2 Merging pairs

    NASA Astrophysics Data System (ADS)

    Allam, S. S.; Tucker, D. L.; SDSS Collaboration

    2004-05-01

    We present and analyze a catalog of 9,000 Merging pairs candidates to g=21 from the imaging data of the Sloan Digital Sky Survey (SDSS) Second Data Release (DR2). Candidates were selected using an automated algorithm (Allam et al. 2004) that is efficient in its selection of galaxy pairs. We highlight possible science applications of such a large photometric sample of merging pais and discuss future improvements, including incorporating magnitudes and pushing to higher redshifts and fainter pairs.

  17. Hamiltonian dynamics on matched pairs

    NASA Astrophysics Data System (ADS)

    Esen, Oğul; Sütlü, Serkan

    2016-08-01

    The cotangent bundle of a matched pair Lie group, and its trivialization, are shown to be a matched pair Lie group. The explicit matched pair decomposition on the trivialized bundle is presented. On the trivialized space, the canonical symplectic two-form and the canonical Poisson bracket are explicitly written. Various symplectic and Poisson reductions are perfomed. The Lie-Poisson bracket is derived. As an example, Lie-Poisson equations on 𝔰𝔩(2, ℂ)∗ are obtained.

  18. Multiple focused EMAT designs for improved surface breaking defect characterization

    NASA Astrophysics Data System (ADS)

    Thring, C. B.; Fan, Y.; Edwards, R. S.

    2017-02-01

    Ultrasonic Rayleigh waves can be employed for the detection of surface breaking defects such as rolling contact fatigue and stress corrosion cracking. Electromagnetic Acoustic Transducers (EMATs) are well suited to this technique as they can directly generate Rayleigh waves within the sample without the requirement for wedges, and they are robust and inexpensive compared to laser ultrasonics. Three different EMAT coil types have been developed, and these are compared to assess their ability to detect and characterize small (down to 0.5 mm depth, 1 mm diameter) surface breaking defects in aluminium. These designs are: a pair of linear meander coils used in a pseudo-pulse-echo mode, a pair of focused meander coils also used in pseudo-pulse-echo mode, and a pair of focused racetrack coils used in pitch-catch mode. The linear meander coils are able to detect most of the defects tested, but have a much lower signal to noise ratio and give limited sizing information. The focused meander coils and the focused racetrack coils can detect all defects tested, but have the advantage that they can also characterize the defect sizes on the sample surface, and have a stronger sensitivity at their focal point. Measurements using all three EMAT designs are presented and compared for high resolution imaging of surface-breaking defects.

  19. Light-induced defects in hybrid lead halide perovskite

    NASA Astrophysics Data System (ADS)

    Sharia, Onise; Schneider, William

    One of the main challenges facing organohalide perovskites for solar application is stability. Solar cells must last decades to be economically viable alternatives to traditional energy sources. While some causes of instability can be avoided through engineering, light-induced defects can be fundamentally limiting factor for practical application of the material. Light creates large numbers of electron and hole pairs that can contribute to degradation processes. Using ab initio theoretical methods, we systematically explore first steps of light induced defect formation in methyl ammonium lead iodide, MAPbI3. In particular, we study charged and neutral Frenkel pair formation involving Pb and I atoms. We find that most of the defects, except negatively charged Pb Frenkel pairs, are reversible, and thus most do not lead to degradation. Negative Pb defects create a mid-gap state and localize the conduction band electron. A minimum energy path study shows that, once the first defect is created, Pb atoms migrate relatively fast. The defects have two detrimental effects on the material. First, they create charge traps below the conduction band. Second, they can lead to degradation of the material by forming Pb clusters.

  20. Defects in hardwood timber

    Treesearch

    Roswell D. Carpenter; David L. Sonderman; Everette D. Rast; Martin J. Jones

    1989-01-01

    Includes detailed information on all common defects that may aRect hardwood trees and logs. Relationships between manufactured products and those forms of round material to be processed from the tree for conversion into marketable products are discussed. This handbook supersedes Agriculture Handbook No. 244, Grade defects in hardwood timber and logs, by C.R. Lockard, J...

  1. Controversies in kidney paired donation.

    PubMed

    Gentry, Sommer E; Montgomery, Robert A; Segev, Dorry L

    2012-07-01

    Kidney paired donation represented 10% of living kidney donation in the United States in 2011. National registries around the world and several separate registries in the United States arrange paired donations, although with significant variations in their practices. Concerns about ethical considerations, clinical advisability, and the quantitative effectiveness of these approaches in paired donation result in these variations. For instance, although donor travel can be burdensome and might discourage paired donation, it was nearly universal until convincing analysis showed that living donor kidneys can sustain many hours of cold ischemia time without adverse consequences. Opinions also differ about whether the last donor in a chain of paired donation transplants initiated by a nondirected donor should donate immediately to someone on the deceased donor wait-list (a domino or closed chain) or should be asked to wait some length of time and donate to start another sequence of paired donations later (an open chain); some argue that asking the donor to donate later may be coercive, and others focus on balancing the probability that the waiting donor withdraws versus the number of additional transplants if the chain can be continued. Other controversies in paired donation include simultaneous versus nonsimultaneous donor operations, whether to enroll compatible pairs, and interactions with desensitization protocols. Efforts to expand public awareness of and participation in paired donation are needed to generate more transplant opportunities.

  2. Transversely bounded DFB lasers. [bounded distributed-feedback lasers

    NASA Technical Reports Server (NTRS)

    Elachi, C.; Evans, G.; Yeh, C.

    1975-01-01

    Bounded distributed-feedback (DFB) lasers are studied in detail. Threshold gain and field distribution for a number of configurations are derived and analyzed. More specifically, the thin-film guide, fiber, diffusion guide, and hollow channel with inhomogeneous-cladding DFB lasers are considered. Optimum points exist and must be used in DFB laser design. Different-modes feedback and the effects of the transverse boundaries are included. A number of applications are also discussed.

  3. Detection of oocyte perivitelline membrane-bound sperm: a tool for avian collection management

    PubMed Central

    Croyle, Kaitlin E.; Durrant, Barbara S.; Jensen, Thomas

    2015-01-01

    The success and sustainability of an avian breeding programme depend on managing productive and unproductive pairs. Given that each breeding season can be of immeasurable importance, it is critical to resolve pair fertility issues quickly. Such problems are traditionally diagnosed through behavioural observations, egg lay history and hatch rates, with a decision to re-pair generally taking one or more breeding seasons. In pairs producing incubated eggs that show little or no signs of embryonic development, determining fertility is difficult. Incorporating a technique to assess sperm presence on the oocyte could, in conjunction with behaviour and other data, facilitate a more timely re-pair decision. Detection of perivitelline membrane-bound (PVM-bound) sperm verifies successful copulation, sperm production and sperm functionality. Alternatively, a lack of detectable sperm, at least in freshly laid eggs, suggests no mating, lack of sperm production/function or sperm–oviduct incompatibility. This study demonstrated PVM-bound sperm detection by Hoechst staining in fresh to 24-day-incubated exotic eggs from 39 species representing 13 orders. However, a rapid and significant time-dependent loss of detectable PVM-bound sperm was observed following incubation of chicken eggs. The PCR detection of sperm in seven species, including two bacterially infected eggs, demonstrated that this method was not as reliable as visual detection using Hoechst staining. The absence of amplicons in visually positive PVMs was presumably due to large PVM size and low sperm count, resulting in DNA concentrations too low for standard PCR detection. In summary, this study demonstrated the feasibility and limitations of using PVM-bound sperm detection as a management tool for exotic avian species. We verified that sperm presence or absence on fluorescence microscopy can aid in the differentiation of fertile from infertile eggs to assist breeding managers in making prompt decisions for pair

  4. Detection of oocyte perivitelline membrane-bound sperm: a tool for avian collection management.

    PubMed

    Croyle, Kaitlin E; Durrant, Barbara S; Jensen, Thomas

    2015-01-01

    The success and sustainability of an avian breeding programme depend on managing productive and unproductive pairs. Given that each breeding season can be of immeasurable importance, it is critical to resolve pair fertility issues quickly. Such problems are traditionally diagnosed through behavioural observations, egg lay history and hatch rates, with a decision to re-pair generally taking one or more breeding seasons. In pairs producing incubated eggs that show little or no signs of embryonic development, determining fertility is difficult. Incorporating a technique to assess sperm presence on the oocyte could, in conjunction with behaviour and other data, facilitate a more timely re-pair decision. Detection of perivitelline membrane-bound (PVM-bound) sperm verifies successful copulation, sperm production and sperm functionality. Alternatively, a lack of detectable sperm, at least in freshly laid eggs, suggests no mating, lack of sperm production/function or sperm-oviduct incompatibility. This study demonstrated PVM-bound sperm detection by Hoechst staining in fresh to 24-day-incubated exotic eggs from 39 species representing 13 orders. However, a rapid and significant time-dependent loss of detectable PVM-bound sperm was observed following incubation of chicken eggs. The PCR detection of sperm in seven species, including two bacterially infected eggs, demonstrated that this method was not as reliable as visual detection using Hoechst staining. The absence of amplicons in visually positive PVMs was presumably due to large PVM size and low sperm count, resulting in DNA concentrations too low for standard PCR detection. In summary, this study demonstrated the feasibility and limitations of using PVM-bound sperm detection as a management tool for exotic avian species. We verified that sperm presence or absence on fluorescence microscopy can aid in the differentiation of fertile from infertile eggs to assist breeding managers in making prompt decisions for pair

  5. Nuclear and bound nucleon structure studies using GlueX

    NASA Astrophysics Data System (ADS)

    Patsyuk, Maria; Hen, Or; Williams, Mike

    2016-09-01

    We propose extending the physics program of the GlueX detector at Jefferson Lab to study structure of bound nucleon and short range correlations (SRC) in nuclei. Many important properties of nuclear systems are significantly influenced by the existence of SRC-pairs, which are high- momentum nucleons in a nucleus with considerably overlapping wave functions. Using the new JLab high-energy high-intensity photon beam, we will study exclusive meson photo-production on the nucleon in nuclei from Deuterium to Lead. We will compare the branching ratio of these reactions on semi-free nucleons in deuterium, deeply bound nucleons in heavier nuclei, and nucleons belonging to SRC pairs (by tagging the spectator recoil nucleon in the GlueX Barrel Calorimeter) in order to learn about short range structure of nuclei and the possible modification of the internal structure of bound nucleons. In this talk, we will present a brief summary of the physics goals and a data-driven determination of the neutron-detection efficiency using the so-called tag and probe technique.

  6. Pairs of promoter pairs in a web of transcription.

    PubMed

    Kaplan, Craig D

    2016-08-30

    A new analysis has characterized a fundamental building block of complex transcribed loci. Constellations of core promoters can generally be reduced to pairs of divergent transcription units, where the distance between the pairs of transcription units correlates with constraints on genomic context, which in turn contribute to transcript fate.

  7. Asymptotic behavior of impurity-induced bound states in low-dimensional topological superconductors

    NASA Astrophysics Data System (ADS)

    Kaladzhyan, V.; Bena, C.; Simon, P.

    2016-12-01

    We study theoretically the asymptotic behavior of the Shiba bound states associated with magnetic impurities embedded in both 2D and 1D anomalous superconductors. We calculate analytically the spatial dependence of the local density of states together with the spin polarization associated with the Shiba bound states. We show that the latter quantity exhibits drastic differences between s-wave and different types of p-wave superconductors. Such properties, which could be measured using spin-polarized STM, offer therefore a way to discriminate between singlet and triplet pairing in low-dimensional superconductors, as well as a way to estimate the amplitude of the triplet pairing in these systems.

  8. Asymptotic behavior of impurity-induced bound states in low-dimensional topological superconductors.

    PubMed

    Kaladzhyan, V; Bena, C; Simon, P

    2016-12-07

    We study theoretically the asymptotic behavior of the Shiba bound states associated with magnetic impurities embedded in both 2D and 1D anomalous superconductors. We calculate analytically the spatial dependence of the local density of states together with the spin polarization associated with the Shiba bound states. We show that the latter quantity exhibits drastic differences between s-wave and different types of p-wave superconductors. Such properties, which could be measured using spin-polarized STM, offer therefore a way to discriminate between singlet and triplet pairing in low-dimensional superconductors, as well as a way to estimate the amplitude of the triplet pairing in these systems.

  9. Performance Bounds on Two Concatenated, Interleaved Codes

    NASA Technical Reports Server (NTRS)

    Moision, Bruce; Dolinar, Samuel

    2010-01-01

    A method has been developed of computing bounds on the performance of a code comprised of two linear binary codes generated by two encoders serially concatenated through an interleaver. Originally intended for use in evaluating the performances of some codes proposed for deep-space communication links, the method can also be used in evaluating the performances of short-block-length codes in other applications. The method applies, more specifically, to a communication system in which following processes take place: At the transmitter, the original binary information that one seeks to transmit is first processed by an encoder into an outer code (Co) characterized by, among other things, a pair of numbers (n,k), where n (n > k)is the total number of code bits associated with k information bits and n k bits are used for correcting or at least detecting errors. Next, the outer code is processed through either a block or a convolutional interleaver. In the block interleaver, the words of the outer code are processed in blocks of I words. In the convolutional interleaver, the interleaving operation is performed bit-wise in N rows with delays that are multiples of B bits. The output of the interleaver is processed through a second encoder to obtain an inner code (Ci) characterized by (ni,ki). The output of the inner code is transmitted over an additive-white-Gaussian- noise channel characterized by a symbol signal-to-noise ratio (SNR) Es/No and a bit SNR Eb/No. At the receiver, an inner decoder generates estimates of bits. Depending on whether a block or a convolutional interleaver is used at the transmitter, the sequence of estimated bits is processed through a block or a convolutional de-interleaver, respectively, to obtain estimates of code words. Then the estimates of the code words are processed through an outer decoder, which generates estimates of the original information along with flags indicating which estimates are presumed to be correct and which are found to

  10. Upper bound for induced gravitation

    SciTech Connect

    Khuri, N.N.

    1982-08-23

    Given the assumption that G/sub ind.//sup ts-1/ from the Adler-Zee formula is positive, an explicit and rigorous upper bound is derived for it. For pure SU(N) gauge theory, (16..pi..G)/sup -1/< or =(25/12..pi../sup 2/)(N/sup 2/-1) ..lambda../sub N//sup ts2/ is obtained, where ..lambda../sub N/ is the mass scale. In general the bound (16..pi..G)/sup -1/< or =25(..pi../sup 2//144)C/sub psi/..lambda../sup 2/ obtained, where C/sub psi/ is the coefficient of the most singular anomaly contribution in x space, a constant easily determined by low-order perturbation theory for any gauge group.

  11. Secure Key from Bound Entanglement

    NASA Astrophysics Data System (ADS)

    Horodecki, Karol; Horodecki, Michał; Horodecki, Paweł; Oppenheim, Jonathan

    2005-04-01

    We characterize the set of shared quantum states which contain a cryptographically private key. This allows us to recast the theory of privacy as a paradigm closely related to that used in entanglement manipulation. It is shown that one can distill an arbitrarily secure key from bound entangled states. There are also states that have less distillable private keys than the entanglement cost of the state. In general, the amount of distillable key is bounded from above by the relative entropy of entanglement. Relationships between distillability and distinguishability are found for a class of states which have Bell states correlated to separable hiding states. We also describe a technique for finding states exhibiting irreversibility in entanglement distillation.

  12. Computing an upper bound on contact stress with surrogate duality

    NASA Astrophysics Data System (ADS)

    Xuan, Zhaocheng; Papadopoulos, Panayiotis

    2016-07-01

    We present a method for computing an upper bound on the contact stress of elastic bodies. The continuum model of elastic bodies with contact is first modeled as a constrained optimization problem by using finite elements. An explicit formulation of the total contact force, a fraction function with the numerator as a linear function and the denominator as a quadratic convex function, is derived with only the normalized nodal contact forces as the constrained variables in a standard simplex. Then two bounds are obtained for the sum of the nodal contact forces. The first is an explicit formulation of matrices of the finite element model, derived by maximizing the fraction function under the constraint that the sum of the normalized nodal contact forces is one. The second bound is solved by first maximizing the fraction function subject to the standard simplex and then using Dinkelbach's algorithm for fractional programming to find the maximum—since the fraction function is pseudo concave in a neighborhood of the solution. These two bounds are solved with the problem dimensions being only the number of contact nodes or node pairs, which are much smaller than the dimension for the original problem, namely, the number of degrees of freedom. Next, a scheme for constructing an upper bound on the contact stress is proposed that uses the bounds on the sum of the nodal contact forces obtained on a fine finite element mesh and the nodal contact forces obtained on a coarse finite element mesh, which are problems that can be solved at a lower computational cost. Finally, the proposed method is verified through some examples concerning both frictionless and frictional contact to demonstrate the method's feasibility, efficiency, and robustness.

  13. Optical binding of particle pairs in retro-reflected beam geometry

    NASA Astrophysics Data System (ADS)

    Damková, Jana; Chvátal, Lukáš; Brzobohatý, Oto; Zemánek, Pavel

    2016-12-01

    Optical binding of polystyrene microparticle pairs in retro-reflected wide Gaussian beam, called "tractor beam", is studied experimentally and the results are compared with the numerical calculations based on the multiple-particle Mie scattering theory. To investigate the dynamics of optically bound particle pairs in three dimensions we employ holographic video microscopy technique. We show that the particle pair motion is strongly dependent on the relative distances of the particles and the switching between applying pushing and pulling force on particle pairs can be achieved only by changing their configuration even though the "tractor-beam" parameters remain unchanged.

  14. Lower Bounds on Paraclique Density.

    PubMed

    Hagan, Ronald D; Langston, Michael A; Wang, Kai

    2016-05-11

    The scientific literature teems with clique-centric clustering strategies. In this paper we analyze one such method, the paraclique algorithm. Paraclique has found practical utility in a variety of application domains, and has been successfully employed to reduce the effects of noise. Nevertheless, its formal analysis and worst-case guarantees have remained elusive. We address this issue by deriving a series of lower bounds on paraclique densities.

  15. Assessment Strategies for Pair Programming

    ERIC Educational Resources Information Center

    Hahn, Jan Hendrik; Mentz, Elsa; Meyer, Lukas

    2009-01-01

    Although pair programming has proved its usefulness in teaching and learning programming skills, it is difficult to assess the individual roles and abilities of students whilst programming in pairs. (Note that within this manuscript, the term assessment refers to evaluating individual student performance.) Assessing only the outcomes of a pair…

  16. Oxygen defects in GaAs: A hybrid functional study

    NASA Astrophysics Data System (ADS)

    Colleoni, Davide; Pasquarello, Alfredo

    2016-03-01

    Using hybrid density functional calculations, we address the structural properties, formation energies, and charge transition levels of a variety of oxygen defects in GaAs. The set of considered defects comprises the bridging O atom in a As-O-Ga configuration, interstitial O atoms in tetrahedral sites, and O atoms substitutional to either Ga (OGa) or As atoms (OAs). In addition, we consider an As vacancy containing two O atoms, for which the most stable configurations are found through the use of molecular dynamics simulations, and defect complexes involving a OAs defect bound to either one or two AsGa antisites, denoted AsGa-OAs and (AsGa)2-OAs , respectively. We find that the bridging O defect and the AsGa-OAs and (AsGa)2-OAs complexes are the most stable oxygen defects in GaAs. The actual occurrence of these defects is examined against two criteria. The first criterion concerns the stability against O dissociation and is evaluated via the calculation of dissociation energies. The second criterion involves the defect formation at thermodynamic equilibrium and is inferred from the comparison between the formation energy of the oxygen defect and that of its O-related dissociation product (bridging O defect). Both the AsGa-OAs and (AsGa)2-OAs complexes satisfy these criteria and are stable against O dissociation. Further analysis in cooled-down conditions leads us to dismiss the AsGa-OAs defect due to the more favorable bonding of two rather than one AsGa antisites. The conclusion that only the bridging O defect and the (AsGa)2-OAs complex are expected to occur is in accord with experimental observations.

  17. Defects and Ion-Solid Interactions in Silicon Carbide

    SciTech Connect

    Weber, William J.; Gao, Fei; Devanathan, Ram; Jiang, Weilin; Zhang, Yanwen

    2005-01-03

    Atomic-level simulations are used to determine defect production, cascade-overlap effects, and defect migration energies in SiC. Energetic C and Si collision cascades primarily produce single interstitials, mono-vacancies, antisite defects, and small defect clusters, while amorphous clusters are produced within 25% of Au cascades. Cascade overlap results in defect stimulated cluster growth that produces amorphization. The good agreement of disordering behavior and changes in volume and elastic modulus obtained computationally and experimentally provides atomic-level interpretation of experimentally observed features. Simulations indicate that close-pair recombination activation energies range from 0.24 to 0.38 eV, and long-range migration energies for interstitials and vacancies have been determined.

  18. Stereo Pair: Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This view of northern Patagonia, near El Cain, Argentina shows complexly eroded volcanic terrain, with basalt mesas, sinkholes, landslide debris, playas, and relatively few integrated drainage channels. Surrounding this site (but also extending far to the east) is a broad plateau capped by basalt, the Meseta de Somuncura. Here, near the western edge of the plateau, erosion has broken through the basalt cap in a variety of ways. On the mesas, water-filled sinkholes (lower left) are most likely the result of the collapse of old lava tubes. Along the edges of the mesas (several locations) the basalt seems to be sliding away from the plateau in a series of slices. Water erosion by overland flow is also evident, particularly in canyons where vegetation blankets the drainage channels (green patterns, bottom of image). However, overland water flow does not extend very far at any location. This entire site drains to local playas, some of which are seen here (blue). While the water can reach the playas and then evaporate, what becomes of the eroded rock debris? Wind might excavate some of the finer eroded debris, but the fate of much of the missing bedrock remains mysterious.

    This cross-eyed stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with an enhanced Landsat 7 satellite color image. The topography data are used to create two differing perspectives of a single image, one perspective for each eye. In doing so, each point in the image is shifted slightly, depending on its elevation. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The

  19. Stereo Pair: Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This view of northern Patagonia, near El Cain, Argentina shows complexly eroded volcanic terrain, with basalt mesas, sinkholes, landslide debris, playas, and relatively few integrated drainage channels. Surrounding this site (but also extending far to the east) is a broad plateau capped by basalt, the Meseta de Somuncura. Here, near the western edge of the plateau, erosion has broken through the basalt cap in a variety of ways. On the mesas, water-filled sinkholes (lower left) are most likely the result of the collapse of old lava tubes. Along the edges of the mesas (several locations) the basalt seems to be sliding away from the plateau in a series of slices. Water erosion by overland flow is also evident, particularly in canyons where vegetation blankets the drainage channels (green patterns, bottom of image). However, overland water flow does not extend very far at any location. This entire site drains to local playas, some of which are seen here (blue). While the water can reach the playas and then evaporate, what becomes of the eroded rock debris? Wind might excavate some of the finer eroded debris, but the fate of much of the missing bedrock remains mysterious.

    This cross-eyed stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with an enhanced Landsat 7 satellite color image. The topography data are used to create two differing perspectives of a single image, one perspective for each eye. In doing so, each point in the image is shifted slightly, depending on its elevation. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The

  20. Stereo Pair, Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This view of northern Patagonia, at Los Menucos, Argentina shows remnants of relatively young volcanoes built upon an eroded plain of much older and contorted volcanic, granitic, and sedimentary rocks. The large purple, brown, and green 'butterfly' pattern is a single volcano that has been deeply eroded. Large holes on the volcano's flanks indicate that they may have collapsed soon after eruption, as fluid molten rock drained out from under its cooled and solidified outer shell. At the upper left, a more recent eruption occurred and produced a small volcanic cone and a long stream of lava, which flowed down a gully. At the top of the image, volcanic intrusions permeated the older rocks resulting in a chain of small dark volcanic peaks. At the top center of the image, two halves of a tan ellipse pattern are offset from each other. This feature is an old igneous intrusion that has been split by a right-lateral fault. The apparent offset is about 6.6 kilometers (4 miles). Color, tonal, and topographic discontinuities reveal the fault trace as it extends across the image to the lower left. However, young unbroken basalt flows show that the fault has not been active recently.

    This cross-eyed stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with an enhanced Landsat 7satellite color image. The topography data are used to create two differing perspectives of a single image, one perspective for each eye. In doing so, each point in the image is shifted slightly, depending on its elevation. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive

  1. Information bounds for Gaussian copulas

    PubMed Central

    Hoff, Peter D.; Niu, Xiaoyue; Wellner, Jon A.

    2013-01-01

    Often of primary interest in the analysis of multivariate data are the copula parameters describing the dependence among the variables, rather than the univariate marginal distributions. Since the ranks of a multivariate dataset are invariant to changes in the univariate marginal distributions, rank-based estimators are natural candidates for semiparametric copula estimation. Asymptotic information bounds for such estimators can be obtained from an asymptotic analysis of the rank likelihood, i.e. the probability of the multivariate ranks. In this article, we obtain limiting normal distributions of the rank likelihood for Gaussian copula models. Our results cover models with structured correlation matrices, such as exchangeable or circular correlation models, as well as unstructured correlation matrices. For all Gaussian copula models, the limiting distribution of the rank likelihood ratio is shown to be equal to that of a parametric likelihood ratio for an appropriately chosen multivariate normal model. This implies that the semiparametric information bounds for rank-based estimators are the same as the information bounds for estimators based on the full data, and that the multivariate normal distributions are least favorable. PMID:25313292

  2. Homologous pairing and the role of pairing centers in meiosis.

    PubMed

    Tsai, Jui-He; McKee, Bruce D

    2011-06-15

    Homologous pairing establishes the foundation for accurate reductional segregation during meiosis I in sexual organisms. This Commentary summarizes recent progress in our understanding of homologous pairing in meiosis, and will focus on the characteristics and mechanisms of specialized chromosome sites, called pairing centers (PCs), in Caenorhabditis elegans and Drosophila melanogaster. In C. elegans, each chromosome contains a single PC that stabilizes chromosome pairing and initiates synapsis of homologous chromosomes. Specific zinc-finger proteins recruited to PCs link chromosomes to nuclear envelope proteins--and through them to the microtubule cytoskeleton--thereby stimulating chromosome movements in early prophase, which are thought to be important for homolog sorting. This mechanism appears to be a variant of the 'telomere bouquet' process, in which telomeres cluster on the nuclear envelope, connect chromosomes through nuclear envelope proteins to the cytoskeleton and lead chromosome movements that promote homologous synapsis. In Drosophila males, which undergo meiosis without recombination, pairing of the largely non-homologous X and Y chromosomes occurs at specific repetitive sequences in the ribosomal DNA. Although no other clear examples of PC-based pairing mechanisms have been described, there is evidence for special roles of telomeres and centromeres in aspects of chromosome pairing, synapsis and segregation; these roles are in some cases similar to those of PCs.

  3. F-wave pairing of cold atoms in optical lattices

    SciTech Connect

    Lee, Wei-Cheng; Wu Congjun; Das Sarma, S.

    2010-11-15

    The tremendous development of cold atom physics has opened up a whole new opportunity to study novel states of matter which are not easily accessible in solid-state systems. Here we propose to realize the f-wave pairing superfluidity of spinless fermions in p{sub x,y}-orbital bands of two-dimensional honeycomb optical lattices. The nontrivial orbital band structure, rather than strong correlation effects, gives rise to the unconventional pairing with the nodal lines of the f-wave symmetry. With a confining harmonic trap, zero-energy Andreev bound states appear around the circular boundary with a sixfold symmetry. The experimental realization and detection of this novel pairing state are feasible.

  4. Diabetes mellitus and birth defects

    PubMed Central

    Correa, Adolfo; Gilboa, Suzanne M.; Besser, Lilah M.; Botto, Lorenzo D.; Moore, Cynthia A.; Hobbs, Charlotte A.; Cleves, Mario A.; Riehle-Colarusso, Tiffany J.; Waller, D. Kim; Reece, E. Albert

    2016-01-01

    OBJECTIVE The purpose of this study was to examine associations between diabetes mellitus and 39 birth defects. STUDY DESIGN This was a multicenter case-control study of mothers of infants who were born with (n = 13,030) and without (n = 4895) birth defects in the National Birth Defects Prevention Study (1997–2003). RESULTS Pregestational diabetes mellitus (PGDM) was associated significantly with noncardiac defects (isolated, 7/23 defects; multiples, 13/23 defects) and cardiac defects (isolated, 11/16 defects; multiples, 8/16 defects). Adjusted odds ratios for PGDM and all isolated and multiple defects were 3.17 (95% CI, 2.20–4.99) and 8.62 (95% CI, 5.27–14.10), respectively. Gestational diabetes mellitus (GDM) was associated with fewer noncardiac defects (isolated, 3/23 defects; multiples, 3/23 defects) and cardiac defects (isolated, 3/16 defects; multiples, 2/16 defects). Odds ratios between GDM and all isolated and multiple defects were 1.42 (95% CI, 1.17–1.73) and 1.50 (95% CI, 1.13–2.00), respectively. These associations were limited generally to offspring of women with prepregnancy body mass index ≥25 kg/m2. CONCLUSION PGDM was associated with a wide range of birth defects; GDM was associated with a limited group of birth defects. PMID:18674752

  5. Magnetic Pair Creation Transparency in Gamma-Ray Pulsars

    NASA Astrophysics Data System (ADS)

    Story, Sarah A.; Baring, Matthew G.

    2014-07-01

    Magnetic pair creation, γ → e + e -, has been at the core of radio pulsar paradigms and central to polar cap models of gamma-ray pulsars for over three decades. The Fermi gamma-ray pulsar population now exceeds 140 sources and has defined an important part of Fermi's science legacy, providing rich information for the interpretation of young energetic pulsars and old millisecond pulsars. Among the population characteristics well established is the common occurrence of exponential turnovers in their spectra in the 1-10 GeV range. These turnovers are too gradual to arise from magnetic pair creation in the strong magnetic fields of pulsar inner magnetospheres. By demanding insignificant photon attenuation precipitated by such single-photon pair creation, the energies of these turnovers for Fermi pulsars can be used to compute lower bounds for the typical altitude of GeV band emission. This paper explores such pair transparency constraints below the turnover energy and updates earlier altitude bound determinations that have been deployed in various Fermi pulsar papers. For low altitude emission locales, general relativistic influences are found to be important, increasing cumulative opacity, shortening the photon attenuation lengths, and also reducing the maximum energy that permits escape of photons from a neutron star magnetosphere. Rotational aberration influences are also explored, and are found to be small at low altitudes, except near the magnetic pole. The analysis presented in this paper clearly demonstrates that including near-threshold physics in the pair creation rate is essential to deriving accurate attenuation lengths and escape energies. The altitude bounds are typically in the range of 2-7 stellar radii for the young Fermi pulsar population, and provide key information on the emission altitude in radio quiet pulsars that do not possess double-peaked pulse profiles. The bound for the Crab pulsar is at a much higher altitude, with the putative detection

  6. Magnetic pair creation transparency in gamma-ray pulsars

    SciTech Connect

    Story, Sarah A.; Baring, Matthew G. E-mail: baring@rice.edu

    2014-07-20

    Magnetic pair creation, γ → e {sup +} e {sup –}, has been at the core of radio pulsar paradigms and central to polar cap models of gamma-ray pulsars for over three decades. The Fermi gamma-ray pulsar population now exceeds 140 sources and has defined an important part of Fermi's science legacy, providing rich information for the interpretation of young energetic pulsars and old millisecond pulsars. Among the population characteristics well established is the common occurrence of exponential turnovers in their spectra in the 1-10 GeV range. These turnovers are too gradual to arise from magnetic pair creation in the strong magnetic fields of pulsar inner magnetospheres. By demanding insignificant photon attenuation precipitated by such single-photon pair creation, the energies of these turnovers for Fermi pulsars can be used to compute lower bounds for the typical altitude of GeV band emission. This paper explores such pair transparency constraints below the turnover energy and updates earlier altitude bound determinations that have been deployed in various Fermi pulsar papers. For low altitude emission locales, general relativistic influences are found to be important, increasing cumulative opacity, shortening the photon attenuation lengths, and also reducing the maximum energy that permits escape of photons from a neutron star magnetosphere. Rotational aberration influences are also explored, and are found to be small at low altitudes, except near the magnetic pole. The analysis presented in this paper clearly demonstrates that including near-threshold physics in the pair creation rate is essential to deriving accurate attenuation lengths and escape energies. The altitude bounds are typically in the range of 2-7 stellar radii for the young Fermi pulsar population, and provide key information on the emission altitude in radio quiet pulsars that do not possess double-peaked pulse profiles. The bound for the Crab pulsar is at a much higher altitude, with the

  7. Base pairing and base mis-pairing in nucleic acids

    NASA Technical Reports Server (NTRS)

    Wang, A. H. J.; Rich, A.

    1986-01-01

    In recent years we have learned that DNA is conformationally active. It can exist in a number of different stable conformations including both right-handed and left-handed forms. Using single crystal X-ray diffraction analysis we are able to discover not only additional conformations of the nucleic acids but also different types of hydrogen bonded base-base interactions. Although Watson-Crick base pairings are the predominant type of interaction in double helical DNA, they are not the only types. Recently, we have been able to examine mismatching of guanine-thymine base pairs in left-handed Z-DNA at atomic resolution (1A). A minimum amount of distortion of the sugar phosphate backbone is found in the G x T pairing in which the bases are held together by two hydrogen bonds in the wobble pairing interaction. Because of the high resolution of the analysis we can visualize water molecules which fill in to accommodate the other hydrogen bonding positions in the bases which are not used in the base-base interactions. Studies on other DNA oligomers have revealed that other types of non-Watson-Crick hydrogen bonding interactions can occur. In the structure of a DNA octamer with the sequence d(GCGTACGC) complexed to an antibiotic triostin A, it was found that the two central AT base pairs are held together by Hoogsteen rather than Watson-Crick base pairs. Similarly, the G x C base pairs at the ends are also Hoogsteen rather than Watson-Crick pairing. Hoogsteen base pairs make a modified helix which is distinct from the Watson-Crick double helix.

  8. Base pairing and base mis-pairing in nucleic acids

    NASA Technical Reports Server (NTRS)

    Wang, A. H. J.; Rich, A.

    1986-01-01

    In recent years we have learned that DNA is conformationally active. It can exist in a number of different stable conformations including both right-handed and left-handed forms. Using single crystal X-ray diffraction analysis we are able to discover not only additional conformations of the nucleic acids but also different types of hydrogen bonded base-base interactions. Although Watson-Crick base pairings are the predominant type of interaction in double helical DNA, they are not the only types. Recently, we have been able to examine mismatching of guanine-thymine base pairs in left-handed Z-DNA at atomic resolution (1A). A minimum amount of distortion of the sugar phosphate backbone is found in the G x T pairing in which the bases are held together by two hydrogen bonds in the wobble pairing interaction. Because of the high resolution of the analysis we can visualize water molecules which fill in to accommodate the other hydrogen bonding positions in the bases which are not used in the base-base interactions. Studies on other DNA oligomers have revealed that other types of non-Watson-Crick hydrogen bonding interactions can occur. In the structure of a DNA octamer with the sequence d(GCGTACGC) complexed to an antibiotic triostin A, it was found that the two central AT base pairs are held together by Hoogsteen rather than Watson-Crick base pairs. Similarly, the G x C base pairs at the ends are also Hoogsteen rather than Watson-Crick pairing. Hoogsteen base pairs make a modified helix which is distinct from the Watson-Crick double helix.

  9. Defects in Calcite.

    DTIC Science & Technology

    1991-05-13

    AD-A245 645 A TRIDENT SCHOLAR PROJECT REPORT NO. 181 "DEFECTS IN CALCITE " DTTC %N FEB 5-1912 UNITED STATES NAVAL ACADEMY ANNAPOLIS, MARYLAND 92-02841...report; no. 181 (1991) "DEFECTS IN CALCITE " A Trident Scholar Project Report by Midshipman Anthony J. Kotarski, Class of 1991 U. S. Naval Academy Annapolis...REPORT TYPE AND DATES COVERED 13 May 1991 Final 1990/91 . TITLE AND SUBTITLE s. FUNDING NUMBERS DEFECTS IN CALCITE 6. AUTHOR(S) Anthony J. Kotarski 7

  10. Bound state, phase separation and superconductivity in presence of Rashba spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Kapri, Priyadarshini; Basu, Saurabh

    2017-06-01

    We have investigated the phase diagram for the t - J model at low electronic densities in presence of Rashba spin-orbit coupling (RSOC). We have rigorously derived a bound state criterion which arises out of a competition between the kinetic energy of the electrons and the exchange coupling between them. Further, we have obtained that the phase diagram consists of three phases, namely, a gas of electrons, a gas of bound pairs, and a fully phase separated state. Subsequently an extension of the pairing scenario is done at finite densities by solving a BCS gap equation. Finite superconducting correlations are observed for J values much lower than that required for the formation of a single bound pair, thereby indicating that pairing in a many particle environment requires weaker interaction strengths than that in the dilute case. We have further obtained that the RSOC increases the transition temperature for a p-wave pairing state, while it diminishes the same for an s-wave pairing correlations.

  11. Pairing in Luttinger Liquids and Quantum Hall States

    NASA Astrophysics Data System (ADS)

    Kane, Charles L.; Stern, Ady; Halperin, Bertrand I.

    2017-07-01

    We study spinless electrons in a single-channel quantum wire interacting through attractive interaction, and the quantum Hall states that may be constructed by an array of such wires. For a single wire, the electrons may form two phases, the Luttinger liquid and the strongly paired phase. The Luttinger liquid is gapless to one- and two-electron excitations, while the strongly paired state is gapped to the former and gapless to the latter. In contrast to the case in which the wire is proximity coupled to an external superconductor, for an isolated wire there is no separate phase of a topological, weakly paired superconductor. Rather, this phase is adiabatically connected to the Luttinger liquid phase. The properties of the one-dimensional topological superconductor emerge when the number of channels in the wire becomes large. The quantum Hall states that may be formed by an array of single-channel wires depend on the Landau-level filling factors. For odd-denominator fillings ν =1 /(2 n +1 ), wires at the Luttinger phase form Laughlin states, while wires in the strongly paired phase form a bosonic fractional quantum Hall state of strongly bound pairs at a filling of 1 /(8 n +4 ). The transition between the two is of the universality class of Ising transitions in three dimensions. For even-denominator fractions ν =1 /2 n , the two single-wire phases translate into four quantum Hall states. Two of those states are bosonic fractional quantum Hall states of weakly and strongly bound pairs of electrons. The other two are non-Abelian quantum Hall states, which originate from coupling wires close to their critical point. One of these non-Abelian states is the Moore-Read state. The transitions between all of these states are of the universality class of Majorana transitions. We point out some of the properties that characterize the different phases and the phase transitions.

  12. Lower bound for quantum phase estimation

    SciTech Connect

    Bessen, Arvid J.

    2005-04-01

    We obtain a query lower bound for quantum algorithms solving the phase estimation problem. Our analysis generalizes existing lower-bound approaches to the case where the oracle Q is given by controlled powers Q{sup p} of Q, as it is, for example, in Shor's order-finding algorithm. In this setting we will prove a {omega}(log 1/{epsilon}) lower bound for the number of applications of Q{sup p{sub 1}}, Q{sup p{sub 2}},.... This bound is tight due to a matching upper bound. We obtain the lower bound using a technique based on frequency analysis.

  13. Role of Topological Defects in the Phase Transition of the Three-Dimensional Heisenberg Model.

    NASA Astrophysics Data System (ADS)

    Lau, Manhot

    The role of topological point defects (hedgehogs) in the phase transition of the classical Heisenberg model in three dimensions is investigated by using Monte Carlo simulations. Simulations of the behavior of the defects near the phase transition show that the number density of defects increases sharply and defect pairs with separations comparable to the sample size begin to appear as the temperature is increased through the transition temperature. In simulations in a restricted ensemble in which spin configurations containing defects are not allowed, the system appears to remain ordered at all temperatures. Simulations in which the spin-spin interaction is set equal to zero and the number density of defects is controlled by varying a 'chemical potential' term indicate that the system is ordered if the number density of defect pairs is sufficiently small. These results show that topological defects play a crucial role in the three-dimensional Heisenberg transition in the sense that configurations containing defect pairs are necessary for the transition from the ferromagnetic to paramagnetic phase to occur. Such a conclusion is also consistent with a Renormalization Group study of the O(n) model, which suggests that topological defects should be explicitly taken into account for a correct description of the critical behavior in models including the three-dimensional Heisenberg model.

  14. Shell closures, loosely bound structures, and halos in exotic nuclei

    SciTech Connect

    Saxena, G.; Singh, D.

    2013-04-15

    Inspired by the recent experiments indicating doubly magic nuclei that lie near the drip-line and encouraged by the success of our relativistic mean-field (RMF) plus state-dependent BCS approach to the description of the ground-state properties of drip-line nuclei, we develop this approach further, across the entire periodic table, to explore magic nuclei, loosely bound structures, and halo formation in exotic nuclei. In our RMF+BCS approach, the single-particle continuum corresponding to the RMF is replaced by a set of discrete positive-energy states for the calculations of pairing energy. Detailed analysis of the single-particle spectrum, pairing energies, and densities of the nuclei predict the unusual proton shell closures at proton numbers Z = 6, 14, 16, 34, and unusual neutron shell closures at neutron numbers N = 6, 14, 16, 34, 40, 70, 112. Further, in several nuclei like the neutron-rich isotopes of Ca, Zr, Mo, etc., the gradual filling of lowlying single-particle resonant state together with weakly bound single-particle states lying close to the continuum threshold helps accommodate more neutrons but with an extremely small increase in the binding energy. This gives rise to the occurrence of loosely bound systems of neutron-rich nuclei with a large neutron-to-proton ratio. In general, the halo-like formation, irrespective of the existence of any resonant state, is seen to be due to the large spatial extension of the wave functions for the weakly bound single-particle states with low orbital angular momentum having very small or no centrifugal barriers.

  15. Birth Defects: Cerebral Palsy

    MedlinePlus

    ... unit (NICU) Birth defects & other health conditions Loss & grief Tools & Resources Frequently asked health questions Ask our ... experts Calculating your due date Ovulation calendar Order bereavement materials News Moms Need Blog News & Media News ...

  16. Ventricular Septal Defect (VSD)

    MedlinePlus

    ... specially sized mesh device to close the hole. Hybrid procedure. A hybrid procedure uses surgical and catheter-based techniques. Access ... clinicalkey.com. Accessed Sept. 15, 2014. Konetti NR. Hybrid muscular ventricular defect closure: Surgeon or physician. Indian ...

  17. Ventricular Septal Defect (VSD)

    MedlinePlus

    ... you exert yourself or when you lie down Rapid or irregular heartbeat Fatigue or weakness Causes Congenital heart defects arise from problems early in the heart's development, but there's often no clear cause. Genetics and ...

  18. Single Ventricle Defects

    MedlinePlus

    ... artery and blood reaches the aorta through a patent ductus arteriosus (see diagram). How does the defect ... only source of lung blood flow is the patent ductus arteriosus (PDA), an open passageway between the ...

  19. Detecting Speech Defects

    ERIC Educational Resources Information Center

    Kryza, Frank T., II

    1976-01-01

    Discusses the importance of early detection of speech defects and briefly describes the activities of the Pre-School Diagnostic Center for Severe Communication Disorders in New Haven, Connecticut. (ED)

  20. Neural Tube Defects

    MedlinePlus

    ... unit (NICU) Birth defects & other health conditions Loss & grief Tools & Resources Frequently asked health questions Ask our ... experts Calculating your due date Ovulation calendar Order bereavement materials News Moms Need Blog News & Media News ...

  1. Birth Defects: Cerebral Palsy

    MedlinePlus

    ... unit (NICU) Birth defects & other health conditions Loss & grief Tools & Resources Frequently asked health questions Ask our ... experts Calculating your due date Ovulation calendar Order bereavement materials News Moms Need Blog News & Media News ...

  2. Congenital Heart Defects

    MedlinePlus

    ... Treatment can include medicines, catheter procedures, surgery, and heart transplants. The treatment depends on the type of the defect, how severe it is, and a child's age, size, and general health. NIH: National Heart, Lung, and Blood Institute

  3. Birth defects monitoring

    SciTech Connect

    Klingberg, M.A.; Papier, C.M.; Hart, J.

    1983-01-01

    Population monitoring of birth defects provides a means for detecting relative changes in their frequency. Many varied systems have been developed throughout the world since the thalidomide tragedy of the early 1960s. Although it is difficult to pinpoint specific teratogenic agents based on rises in rates of a particular defect or a constellation of defects, monitoring systems can provide clues for hypothesis testing in epidemiological investigations. International coordination of efforts in this area resulted in the founding of the International Clearinghouse for Birth Defects Monitoring Systems (ICBDMS) in 1974. In this paper we will describe the functions and basic requirements of monitoring systems in general, and look at the development and activities of the ICBDMS. A review of known and suspected environmental teratogenic agents (eg, chemical, habitual, biological, physical, and nutritional) is also presented.

  4. DNA as membrane-bound ligand-receptor pairs: duplex stability is tuned by intermembrane forces.

    PubMed

    Beales, Paul A; Vanderlick, T Kyle

    2009-02-18

    We use membrane-anchored DNA as model adhesion receptors between lipid vesicles. By studying the thermal stability of DNA duplex formation, which tethers the vesicles into superstructures, we show that the melting temperature of a 10-base DNA sequence is dependent on the lipid composition of the tethered vesicles. We propose a simple model that describes how the intermembrane interactions tilt the free energy landscape for DNA binding. From our model, we estimate the area per DNA in the binding sites between vesicles and also the total area of the adhesion plaques. We find that vesicles containing a small proportion of cationic lipid that are modified with membrane-anchored DNA can be reversibly tethered by specific DNA interactions and that the DNA also induces a small attraction between these membranes, which stabilizes the DNA duplex. By increasing the equilibrium intermembrane distance on binding, we show that intermembrane interactions become negligible for the binding thermodynamics of the DNA and hence the thermal stability of vesicle aggregates becomes independent of lipid composition at large enough intervesicle separations. We discuss the implications of our findings with regards to cell adhesion and fusion receptors, and the programmable self-assembly of nano-structured materials by DNA hybridization.

  5. Defect Physics of Structural Materials under Extreme Conditions

    NASA Astrophysics Data System (ADS)

    Stocks, G. Malcolm

    2010-03-01

    ``Crystals are like people: it is the defects in them that make them interesting.'' This oft quoted quip of Sir Charles Frank speaks to the heart of structural alloys. Indeed, the extent to which the collective effects of defects can be manipulated and controlled determines the combination of structural materials properties that underpins modern energy and transportation technologies. Furthermore, the bounds on performance of current structural materials generally result from limitations in our understanding of defects, rather than insurmountable physical principles. I will describe research in the Center for Defect PhysicsfootnotetextThe CDP is an Energy Frontier Research Center (EFRC), DOE Office of Basic Energy Sciences. in three thrust areas: *Fundamental Physics of Defect Formation and Evolution during Irradiation *Fundamental Physics of Defect Interactions during Deformation *Quantum Theory of Defects and Interactions Specifically, I will described ongoing and planned research that is based on the realization that we are on the verge of a new era of ``quantitative measurement'' and ``direct quantum simulation'' of defects and their interactions enabled by major national facilities (APS, SNS, and LCLS) and the PFlop/s computing (NCCS and NERSC).

  6. Discrete family of dissipative soliton pairs in mode-locked fiber lasers

    SciTech Connect

    Zavyalov, Aleksandr; Iliew, Rumen; Egorov, Oleg; Lederer, Falk

    2009-05-15

    We numerically investigate the formation of soliton pairs (bound states) in mode-locked fiber ring lasers. In the distributed model (complex cubic-quintic Ginzburg-Landau equation) we observe a discrete family of soliton pairs with equidistantly increasing peak separation. This family was identified by two alternative numerical schemes and the bound state instability was disclosed by a linear stability analysis. Moreover, similar families of unstable bound state solutions have been found in a more realistic lumped laser model with an idealized saturable absorber (instantaneous response). We show that a stabilization of these bound states can be achieved when the finite relaxation time of the saturable absorber is taken into account. The domain of stability can be controlled by varying this relaxation time.

  7. Discrete family of dissipative soliton pairs in mode-locked fiber lasers

    NASA Astrophysics Data System (ADS)

    Zavyalov, Aleksandr; Iliew, Rumen; Egorov, Oleg; Lederer, Falk

    2009-05-01

    We numerically investigate the formation of soliton pairs (bound states) in mode-locked fiber ring lasers. In the distributed model (complex cubic-quintic Ginzburg-Landau equation) we observe a discrete family of soliton pairs with equidistantly increasing peak separation. This family was identified by two alternative numerical schemes and the bound state instability was disclosed by a linear stability analysis. Moreover, similar families of unstable bound state solutions have been found in a more realistic lumped laser model with an idealized saturable absorber (instantaneous response). We show that a stabilization of these bound states can be achieved when the finite relaxation time of the saturable absorber is taken into account. The domain of stability can be controlled by varying this relaxation time.

  8. TOPICAL REVIEW: W = 0 pairing in Hubbard and related models of low-dimensional superconductors

    NASA Astrophysics Data System (ADS)

    Balzarotti, Adalberto; Cini, Michele; Perfetto, Enrico; Stefanucci, Gianluca

    2004-12-01

    Lattice Hamiltonians with on-site interaction W have W = 0 solutions, that is, many-body singlet eigenstates without double occupation. In particular, W = 0 pairs give a clue to understand the pairing force in repulsive Hubbard models. These eigenstates are found in systems with high enough symmetry, like the square, hexagonal or triangular lattices. By a general theorem, we propose a systematic way to construct all the W = 0 pairs of a given Hamiltonian. We also introduce a canonical transformation to calculate the effective interaction between the particles of such pairs. In geometries appropriate for the CuO2 planes of cuprate superconductors, armchair carbon nanotubes, or cobalt oxide planes, the dressed pair becomes a bound state in a physically relevant range of parameters. We also show that W = 0 pairs quantize the magnetic flux as superconducting pairs do. The pairing mechanism breaks down in the presence of strong distortions. The W = 0 pairs are also the building blocks for the antiferromagnetic ground state of the half-filled Hubbard model at weak coupling. Our analytical results for the 4 × 4 Hubbard square lattice, compared to available numerical data, demonstrate that the method, besides providing an intuitive grasp on pairing, also has quantitative predictive power. We also consider including phonon effects in this scenario. Preliminary calculations with small clusters indicate that vector phonons hinder pairing while half-breathing modes are synergic with the W = 0 pairing mechanism both at weak coupling and in the polaronic regime.

  9. Lower bounds for randomized Exclusive Write PRAMs

    SciTech Connect

    MacKenzie, P.D.

    1995-05-02

    In this paper we study the question: How useful is randomization in speeding up Exclusive Write PRAM computations? Our results give further evidence that randomization is of limited use in these types of computations. First we examine a compaction problem on both the CREW and EREW PRAM models, and we present randomized lower bounds which match the best deterministic lower bounds known. (For the CREW PRAM model, the lower bound is asymptotically optimal.) These are the first non-trivial randomized lower bounds known for the compaction problem on these models. We show that our lower bounds also apply to the problem of approximate compaction. Next we examine the problem of computing boolean functions on the CREW PRAM model, and we present a randomized lower bound, which improves on the previous best randomized lower bound for many boolean functions, including the OR function. (The previous lower bounds for these functions were asymptotically optimal, but we improve the constant multiplicative factor.) We also give an alternate proof for the randomized lower bound on PARITY, which was already optimal to within a constant additive factor. Lastly, we give a randomized lower bound for integer merging on an EREW PRAM which matches the best deterministic lower bound known. In all our proofs, we use the Random Adversary method, which has previously only been used for proving lower bounds on models with Concurrent Write capabilities. Thus this paper also serves to illustrate the power and generality of this method for proving parallel randomized lower bounds.

  10. Pairing Correlations at High Spins

    NASA Astrophysics Data System (ADS)

    Ma, Hai-Liang; Dong, Bao-Guo; Zhang, Yan; Fan, Ping; Yuan, Da-Qing; Zhu, Shen-Yun; Zhang, Huan-Qiao; Petrache, C. M.; Ragnarsson, I.; Carlsson, B. G.

    The pairing correcting energies at high spins in 161Lu and 138Nd are studied by comparing the results of the cranked-Nilsson-Strutinsky (CNS) and cranked-Nilsson-Strutinsky-Bogoliubov (CNSB) models. It is concluded that the Coriolis effect rather than the rotational alignment effect plays a major role in the reduction of the pairing correlations in the high spin region. Then we proposed an average pairing correction method which not only better reproduces the experimental data comparing with the CNS model but also enables a clean-cut tracing of the configurations thus the full-spin-range discussion on the various rotating bands.

  11. Bound Anionic States of Aadenine

    SciTech Connect

    Haranczyk, Maciej; Gutowski, Maciej S.; Li, Xiang; Bowen, Kit H.

    2007-03-20

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases are thought to be adiabatically unbound. Contrary to this expectation,wehave demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the newfound anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The new valence states observed here, unlike the dipole-bound state, could exist in condensed phases and might be relevant to radiobiological damage. The discovery of these valence anionic states of adenine was facilitated by the development of (i) an experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (ii) a combinatorial/quantum chemical approach for identification of the most stable tautomers of organic molecules.

  12. Bound Anionic States of Adenine

    SciTech Connect

    Haranczyk, Maciej; Gutowski, Maciej S.; Li, Xiang; Bowen, Kit H.

    2007-03-20

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the newfound anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The new valence states observed here, unlike the dipole-bound state, could exist in condensed phases and might be relevant to radiobiological damage. The discovery of these valence anionic states of adenine was facilitated by the development of (i) an experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (it) a combinatorial/quantum chemical approach for identification of the most stable tautomers of organic molecules.

  13. Pair 2-electron reduced density matrix theory using localized orbitals

    NASA Astrophysics Data System (ADS)

    Head-Marsden, Kade; Mazziotti, David A.

    2017-08-01

    Full configuration interaction (FCI) restricted to a pairing space yields size-extensive correlation energies but its cost scales exponentially with molecular size. Restricting the variational two-electron reduced-density-matrix (2-RDM) method to represent the same pairing space yields an accurate lower bound to the pair FCI energy at a mean-field-like computational scaling of O (r3) where r is the number of orbitals. In this paper, we show that localized molecular orbitals can be employed to generate an efficient, approximately size-extensive pair 2-RDM method. The use of localized orbitals eliminates the substantial cost of optimizing iteratively the orbitals defining the pairing space without compromising accuracy. In contrast to the localized orbitals, the use of canonical Hartree-Fock molecular orbitals is shown to be both inaccurate and non-size-extensive. The pair 2-RDM has the flexibility to describe the spectra of one-electron RDM occupation numbers from all quantum states that are invariant to time-reversal symmetry. Applications are made to hydrogen chains and their dissociation, n-acene from naphthalene through octacene, and cadmium telluride 2-, 3-, and 4-unit polymers. For the hydrogen chains, the pair 2-RDM method recovers the majority of the energy obtained from similar calculations that iteratively optimize the orbitals. The localized-orbital pair 2-RDM method with its mean-field-like computational scaling and its ability to describe multi-reference correlation has important applications to a range of strongly correlated phenomena in chemistry and physics.

  14. Voronoi Diagrams Without Bounding Boxes

    NASA Astrophysics Data System (ADS)

    Sang, E. T. K.

    2015-10-01

    We present a technique for presenting geographic data in Voronoi diagrams without having to specify a bounding box. The method restricts Voronoi cells to points within a user-defined distance of the data points. The mathematical foundation of the approach is presented as well. The cell clipping method is particularly useful for presenting geographic data that is spread in an irregular way over a map, as for example the Dutch dialect data displayed in Figure 2. The automatic generation of reasonable cell boundaries also makes redundant a frequently used solution to this problem that requires data owners to specify region boundaries, as in Goebl (2010) and Nerbonne et al (2011).

  15. Exchange of carbon-bound hydrogen atoms ortho to the hydroxyl group in tyrosine.

    PubMed

    Martin, R B; Morlino, V J

    1965-10-22

    The carbon-bound hydrogen atoms of tyrosine that exchange with solvent protons in strongly acid solutions at about 100 degrees C are not the methylene hydrogen atoms but a pair on the aromatic ring. Of the two pairs of protons on the aromatic ring, observed in the proton magnetic resonance spectra, the pair at higher field undergoes exchange in 2.4N DCI at 100 degrees C. Other hydrogen atoms, attached either to aliphatic or aromatic carbon atoms, exhibit no noticeable exchange under the same conditions. From a chemicalshift analysis the exchanging protons are assigned as those ortho to the hydroxyl group on the aromatic ring.

  16. Bounds on multipartite concurrence and tangle

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Li, Ming; Li, Hongfang; Fei, Shao-Ming; Li-Jost, Xianqing

    2016-10-01

    We present an analytical lower bound of multipartite concurrence based on the generalized Bloch representations of density matrices. It is shown that the lower bound can be used as an effective entanglement witness of genuine multipartite entanglement. Tight lower and upper bounds for multipartite tangles are also derived. Since the lower bounds depend on just part of the correlation tensors, the result is experimentally feasible.

  17. Finite Element Output Bounds for Hyperbolic Problems

    SciTech Connect

    Machiels, L.

    2000-03-27

    We propose a Neumann-subproblem a posteriori finite element error bound technique for linear stationary scalar advection problems. The method is similar in many respects to the previous output bound technique developed for elliptic problems. In the new approach, however, the primal residual is enhanced with a streamline diffusion term. We first formulate the bound algorithm, with particular emphasis on the proof of the bounding properties; then, we provide numerical results for an illustrative example.

  18. Some Educational Implications & Contributions of Outward Bound.

    ERIC Educational Resources Information Center

    Australian Outward Bound School, Sydney.

    The development of Outward Bound, from the early beginnings in Britain through expansion in over 30 locations throughout the world, is outlined, and Outward Bound educational aspects are analyzed in terms of the Australian Outward Bound School. The concepts of experiential education, lifelong education, and the broader Australian educational scene…

  19. Determining Normal-Distribution Tolerance Bounds Graphically

    NASA Technical Reports Server (NTRS)

    Mezzacappa, M. A.

    1983-01-01

    Graphical method requires calculations and table lookup. Distribution established from only three points: mean upper and lower confidence bounds and lower confidence bound of standard deviation. Method requires only few calculations with simple equations. Graphical procedure establishes best-fit line for measured data and bounds for selected confidence level and any distribution percentile.

  20. The Acquisition of Bound and Free Anaphora.

    ERIC Educational Resources Information Center

    Koster, Jan; Koster, Charlotte

    Most linguists assume that bound anaphors such as "himself" are connected with their antecedents in a different way from free anaphors such as "him." Bound anaphora resolution is deterministic, based on Principle A of Chomsky's binding theory. Free anaphors, pronominals, cannot be bound in the domain of reflexives (principle…

  1. Consistent Tolerance Bounds for Statistical Distributions

    NASA Technical Reports Server (NTRS)

    Mezzacappa, M. A.

    1983-01-01

    Assumption that sample comes from population with particular distribution is made with confidence C if data lie between certain bounds. These "confidence bounds" depend on C and assumption about distribution of sampling errors around regression line. Graphical test criteria using tolerance bounds are applied in industry where statistical analysis influences product development and use. Applied to evaluate equipment life.

  2. Resonances from QCD bound states and the 750 GeV diphoton excess

    NASA Astrophysics Data System (ADS)

    Kats, Yevgeny; Strassler, Matthew J.

    2016-05-01

    Pair production of colored particles is in general accompanied by production of QCD bound states (onia) slightly below the pair-production threshold. Bound state annihilation leads to resonant signals, which in some cases are easier to see than the decays of the pair-produced constituents. In a previous paper ( arXiv:1204.1119 ) we estimated the bound state signals, at leading order and in the Coulomb approximation, for particles with various spins, color representations and electric charges, and used 7 TeV ATLAS and CMS resonance searches to set rough limits. Here we update our results to include 8 and 13 TeV data. We find that the recently reported diphoton excesses near 750 GeV could indeed be due to a bound state of this kind. A narrow resonance of the correct size could be obtained for a color-triplet scalar with electric charge -4/3 and mass near 375GeV, if (as a recent lattice computation suggests) the wave function at the origin is somewhat larger than anticipated. Pair production of this particle could have evaded detection up to now. Other candidates may include a triplet scalar of charge 5/3, a triplet fermion of charge -4/3, and perhaps a sextet scalar of charge -2/3.

  3. Quantum correlations beyond Tsirelson's bound

    NASA Astrophysics Data System (ADS)

    Berry, Dominic; Ringbauer, Martin; Fedrizzi, Alessandro; White, Andrew

    2014-03-01

    Violations of Bell inequalities show that there are correlations that cannot explained by any classical theory. Further violation, beyond Tsirelson's bound, shows that there are correlations that are not explained by quantum mechanics. Such super-quantum correlations would enable violation of information causality, where communication of one bit provides more than one bit of information [Nature 461, 1101 (2009)]. An unavoidable feature of all realistic Bell inequality experiments is loss. If one postselects on successful measurements, unentangled states can violate Bell inequalities. On the other hand, loss can be used to enhance the violation of Bell inequalities for entangled states. This can improve the ability to distinguish between entangled and unentangled states, despite loss. Here we report an optical experiment providing maximal violation of the CHSH-Bell inequality with entangled states. Due to loss and postselection, Tsirelson's bound is also violated. This enables us to more easily distinguish between entangled and unentangled states. In addition, it provides violation of information causality for the postselected data.

  4. Endurance bounds of aerial systems

    NASA Astrophysics Data System (ADS)

    Harrington, Aaron M.; Kroninger, Christopher M.

    2014-06-01

    Within the past few years micro aerial vehicles (MAVs) have received much more attention and are starting to proliferate into military as well as civilian roles. However, one of the major drawbacks for this technology currently, has been their poor endurance, usually below 10 minutes. This is a direct result of the inefficiencies inherent in their design. Often times, designers do not consider the various components in the vehicle design and match their performance to the desired mission for the vehicle. These vehicles lack a prescribed set of design guidelines or empirically derived design equations which often limits their design to selection of commercial off-the-shelf components without proper consideration of their affect on vehicle performance. In the current study, the design space for different vehicle configurations has been examined including insect flapping, avian flapping, rotary wing, and fixed wing, and their performance bounds are established. The propulsion system typical of a rotary wing vehicle is analyzed to establish current baselines for efficiency of vehicles at this scale. The power draw from communications is analyzed to determine its impact on vehicle performance. Finally, a representative fixed wing MAV is examined and the effects of adaptive structures as a means for increasing vehicle endurance and range are examined. This paper seeks to establish the performance bounds for micro air vehicles and establish a path forward for future designs so that efficiency may be maximized.

  5. Birth Defects. Matrix No. 2.

    ERIC Educational Resources Information Center

    Brent, Robert L.

    This report discusses the magnitude of the problem of birth defects, outlines advances in the birth defects field in the past decade, and identifies those areas where research is needed for the prevention, treatment, and management of birth defects. The problem of birth defects has consumed a greater portion of our health care resources because of…

  6. Effects of stoichiometry on the defect clustering in uranium dioxide

    NASA Astrophysics Data System (ADS)

    Ngayam-Happy, Raoul; Krack, Matthias; Pautz, Andreas

    2015-11-01

    This study addresses the on-going topic of point defects and point defect clusters in uranium dioxide. Molecular statics simulation using an extended pair potential model that accounts for disproportionation equilibrium as charge compensation has been applied to assess the effect of disproportionation on structural properties and clustering in non-stoichiometric uranium dioxide. The defective structures are scanned in minute detail using a powerful and versatile analysing tool, called ASTRAM, developed in-house for the purpose. Unlike pair potential models ignoring disproportionation effects, our model reproduces volume changes observed experimentally in non-stoichiometric ~\\text{U}{{\\text{O}}\\text{2-\\text{x}}} and ~\\text{U}{{\\text{O}}\\text{2+x}} . The oxygen defect energetics computed is in good agreement with data in the literature. The model is used to assess the clustering that occurs in bulk samples of non-stoichiometric uranium dioxide. This study confirms the generation of split-interstitial clusters as the dominant defect type in non-stoichiometric uranium dioxide. A new key mechanism for defect clustering in hyper-stoichiometric uranium dioxide is proposed that is based on the progressive aggregation of primitive blocks identified as 1-vacancy split-interstitial clusters.

  7. Negative U-centers and defect superconductivity

    NASA Astrophysics Data System (ADS)

    Dzhumanov, S.; Yavidov, B.; Makhmudov, N. A.

    1997-04-01

    A connection between the formation of defect bipolarons (i.e. U-centers or U-bipolarons) and superconductivity in high-Tcsuperconductors (HTSC) is considered in two pairing limits of carriers in realr- andk-spaces. The irrelevance ofr-space U-bipolarons to superconductivity is motivated. It is shown that the formation ofk-space U-bipolarons and their subsequent attractive single particle and pair condensation lead to depressed (in comparison with lattice bipolarons) superconductivity due to a large mass of such U-bipolarons. It is argued that the coexistence ofk-space lattice bipolarons andr-space U-bipolarons leads to the shift of the maximum of the concentration dependenceTc(n)to higher carrier concentrations, in accordance with the observations in HTSC.

  8. Relativistic description of pair production of doubly heavy baryons in e{sup +}e{sup −} annihilation

    SciTech Connect

    Martynenko, A. P.; Trunin, A. M.

    2015-05-15

    Relativistic corrections in the pair production of S-wave doubly heavy diquarks in electron-positron annihilation were calculated on the basis of perturbative QCD and the quark model. The relativistic corrections to the wave functions for quark bound states were taken into account with the aid of the Breit potential in QCD. Relativistic effects change substantially the nonrelativistic cross sections for pair diquark production. The yield of pairs of (ccq) doubly heavy baryons at B factories was estimated.

  9. Structural birth defects associated with neural tube defects in Hawai'i from 1986 until 2001.

    PubMed

    Forrester, Mathias B; Merz, Ruth D

    2007-09-01

    Using birth defects registry data, this study identified birth defects associated with anencephaly, spina bifida, and encephalocele. Musculoskeletal defects were associated with anencephaly; central nervous system defects, gastrointestinal atresia/stenosis, genitourinary system defects, and musculoskeletal system defects with spina bifida; and central nervous system defects, respiratory defects, oral clefts, genitourinary system defects, and musculoskeletal system defects with encephalocele.

  10. Unitary photoassociation: One-step production of ground-state bound molecules

    SciTech Connect

    Kallush, S.; Kosloff, R.

    2008-02-15

    Bound-state molecules can be photoassociated directly from ultracold free-atom pairs by excitation to a purely repulsive electronic state. The process is explained on the basis of quantum unitarity: the initially free-scattering state is transformed by an impulsive light pulse to a deformed superposition which contains bound-state components. For pulse durations which are short compared to the ultracold dynamics, the maximal rate of photoassociation was found to be determined by the initial stationary distribution of scattering states of the atom pairs. The process was simulated for an ultracold gas of {sup 87}Rb with a temperature of T=44 {mu}K and a density of {approx_equal}10{sup 11} cm{sup -3}. Transform-limited pulses maximize the photoassociation, yielding {approx}1 bound molecule per pulse. Coherent control calculated by a local control scheme can increase the photoassociation yield by two orders of magnitude.

  11. Self-confined particle pairs in complex plasmas.

    PubMed

    Lisina, I I; Lisin, E A; Vaulina, O S; Petrov, O F

    2017-01-01

    The liquid-crystal type of phase transition in complex plasmas has been observed repeatedly. However, more studies need to be done on the liquid-vapor transition in complex plasmas. In this paper, the phenomenon of coupling (condensation) of particles into self-confined particle pairs in an anisotropic plasma medium with ion flow is considered analytically and numerically using the Langevin molecular dynamics method. We obtain the stability conditions of the pair (bound) state depending on the interaction parameters and particle kinetic energy. It was shown that the breakup of the particle pair is very sensitive to the ratio of particle charges; for example, it is determined by the influence of the upper particle on the ion flow around the lower one. We also show that a self-confined pair of particles exists even if their total kinetic energy is much greater than the potential well depth for the pair state. This phenomenon occurs due to velocity correlation of particles, which arises with the nonreciprocity of interparticle interaction.

  12. Self-confined particle pairs in complex plasmas

    NASA Astrophysics Data System (ADS)

    Lisina, I. I.; Lisin, E. A.; Vaulina, O. S.; Petrov, O. F.

    2017-01-01

    The liquid-crystal type of phase transition in complex plasmas has been observed repeatedly. However, more studies need to be done on the liquid-vapor transition in complex plasmas. In this paper, the phenomenon of coupling (condensation) of particles into self-confined particle pairs in an anisotropic plasma medium with ion flow is considered analytically and numerically using the Langevin molecular dynamics method. We obtain the stability conditions of the pair (bound) state depending on the interaction parameters and particle kinetic energy. It was shown that the breakup of the particle pair is very sensitive to the ratio of particle charges; for example, it is determined by the influence of the upper particle on the ion flow around the lower one. We also show that a self-confined pair of particles exists even if their total kinetic energy is much greater than the potential well depth for the pair state. This phenomenon occurs due to velocity correlation of particles, which arises with the nonreciprocity of interparticle interaction.

  13. Creating multiphoton-polarization bound entangled states

    SciTech Connect

    Wei, Tzu-Chieh; Lavoie, Jonathan; Kaltenbaek, Rainer

    2011-03-15

    Bound entangled states are the exotic objects in the entangled world. They require entanglement to create them, but once they are formed, it is not possible to locally distill any free entanglement from them. It is only until recently that a few bound entangled states were realized in the laboratory. Motivated by these experiments, we propose schemes for creating various classes of bound entangled states with photon polarization. These include Acin-Bruss-Lewenstein-Sanpara states, Duer's states, Lee-Lee-Kim bound entangled states, and an unextendible-product-basis bound entangled state.

  14. Defect behavior of polycrystalline solar cell silicon

    SciTech Connect

    Schroder, D.K.; Park, S.H.; Hwang, I.G.; Mohr, J.B.; Hanly, M.P.

    1993-05-01

    The major objective of this study, conducted from October 1988 to September 1991, was to gain an understanding of the behavior of impurities in polycrystalline silicon and the influence of these impurities on solar cell efficiency. The authors studied edge-defined film-fed growth (EFG) and cast poly-Si materials and solar cells. With EFG Si they concentrated on chromium-doped materials and cells to determine the role of Cr on solar cell performance. Cast poly-Si samples were not deliberately contaminated. Samples were characterized by cell efficiency, current-voltage, deep-level transient spectroscopy (DLTS), surface photovoltage (SPV), open-circuit voltage decay, secondary ion mass spectrometry, and Fourier transform infrared spectroscopy measurements. They find that Cr forms Cr-B pairs with boron at room temperature and these pairs dissociate into Cr{sub i}{sup +} and B{sup {minus}} during anneals at 210{degrees}C for 10 min. Following the anneal, Cr-B pairs reform at room temperature with a time constant of 230 h. Chromium forms CrSi{sub 2} precipitates in heavily contaminated regions and they find evidence of CrSi{sub 2} gettering, but a lack of chromium segregation or precipitation to grain boundaries and dislocations. Cr-B pairs have well defined DLTS peaks. However, DLTS spectra of other defects are not well defined, giving broad peaks indicative of defects with a range of energy levels in the band gap. In some high-stress, low-efficiency cast poly-Si they detect SiC precipitates, but not in low-stress, high-efficiency samples. SPV measurements result in nonlinear SPV curves in some materials that are likely due to varying optical absorption coefficients due to locally varying stress in the material.

  15. Numerical investigation of the role of topological defects in the three-dimensional Heisenberg transition

    NASA Astrophysics Data System (ADS)

    Lau, Man-Hot; Dasgupta, Chandan

    1989-04-01

    The role of topological point defects (hedgehogs) in the phase transition of the classical Heisenberg model in three dimensions is investigated by using Monte Carlo simulations. Simulations of the behavior of the defects near the phase transition show that the number density of defects increases sharply and defect pairs with separations comparable to the sample size begin to appear as the temperature is increased through the transition temperature. In simulations in a restricted ensemble in which spin configurations containing defects are not allowed, the system appears to remain ordered at all temperatures. Simulations in which the spin-spin interaction is set equal to zero and the number density of defects is controlled by varying a ``chemical potential'' term indicate that the system is ordered if the number density of defect pairs is sufficiently small. These results show that topological defects play a crucial role in the three-dimensional Heisenberg transition in the sense that configurations containing defect pairs are necessary for the transition from the ferromagnetic to the paramagnetic phase to occur.

  16. Reconstruction of Mandibular Defects

    PubMed Central

    Chim, Harvey; Salgado, Christopher J.; Mardini, Samir; Chen, Hung-Chi

    2010-01-01

    Defects requiring reconstruction in the mandible are commonly encountered and may result from resection of benign or malignant lesions, trauma, or osteoradionecrosis. Mandibular defects can be classified according to location and extent, as well as involvement of mucosa, skin, and tongue. Vascularized bone flaps, in general, provide the best functional and aesthetic outcome, with the fibula flap remaining the gold standard for mandible reconstruction. In this review, we discuss classification and approach to reconstruction of mandibular defects. We also elaborate upon four commonly used free osteocutaneous flaps, inclusive of fibula, iliac crest, scapula, and radial forearm. Finally, we discuss indications and use of osseointegrated implants as well as recent advances in mandibular reconstruction. PMID:22550439

  17. Wire insulation defect detector

    NASA Technical Reports Server (NTRS)

    Greulich, Owen R. (Inventor)

    2004-01-01

    Wiring defects are located by detecting a reflected signal that is developed when an arc occurs through the defect to a nearby ground. The time between the generation of the signal and the return of the reflected signal provides an indication of the distance of the arc (and therefore the defect) from the signal source. To ensure arcing, a signal is repeated at gradually increasing voltages while the wire being tested and a nearby ground are immersed in a conductive medium. In order to ensure that the arcing occurs at an identifiable time, the signal whose reflection is to be detected is always made to reach the highest potential yet seen by the system.

  18. Polaron pair mediated triplet generation in polymer/fullerene blends

    PubMed Central

    Dimitrov, Stoichko D.; Wheeler, Scot; Niedzialek, Dorota; Schroeder, Bob C.; Utzat, Hendrik; Frost, Jarvist M.; Yao, Jizhong; Gillett, Alexander; Tuladhar, Pabitra S.; McCulloch, Iain; Nelson, Jenny; Durrant, James R.

    2015-01-01

    Electron spin is a key consideration for the function of organic semiconductors in light-emitting diodes and solar cells, as well as spintronic applications relying on organic magnetoresistance. A mechanism for triplet excited state generation in such systems is by recombination of electron-hole pairs. However, the exact charge recombination mechanism, whether geminate or nongeminate and whether it involves spin-state mixing is not well understood. In this work, the dynamics of free charge separation competing with recombination to polymer triplet states is studied in two closely related polymer-fullerene blends with differing polymer fluorination and photovoltaic performance. Using time-resolved laser spectroscopic techniques and quantum chemical calculations, we show that lower charge separation in the fluorinated system is associated with the formation of bound electron-hole pairs, which undergo spin-state mixing on the nanosecond timescale and subsequent geminate recombination to triplet excitons. We find that these bound electron-hole pairs can be dissociated by electric fields. PMID:25735188

  19. Assessing EUV mask defectivity

    NASA Astrophysics Data System (ADS)

    Okoroanyanwu, Uzodinma; Tchikoulaeva, Anna; Ackmann, Paul; Wood, Obert; La Fontaine, Bruno; Bubke, Karsten; Holfeld, Christian; Peters, Jan Hendrik; Kini, Sumanth; Watson, Sterling; Lee, Isaac; Mu, Bo; Lim, Phillip; Raghunathan, Sudhar; Boye, Carol

    2010-04-01

    This paper assesses the readiness of EUV masks for pilot line production. The printability of well characterized reticle defects, with particular emphasis on those reticle defects that cause electrical errors on wafer test chips, is investigated. The reticles are equipped with test marks that are inspected in a die-to-die mode (using DUV inspection tool) and reviewed (using a SEM tool), and which also comprise electrically testable patterns. The reticles have three modules comprising features with 32 nm ground rules in 104 nm pitch, 22 nm ground rules with 80 nm pitch, and 16 nm ground rules with 56 nm pitch (on the wafer scale). In order to determine whether specific defects originate from the substrate, the multilayer film, the absorber stack, or from the patterning process, the reticles were inspected after each fabrication step. Following fabrication, the reticles were used to print wafers on a 0.25 NA full-field ASML EUV exposure tool. The printed wafers were inspected with state of the art bright-field and Deep UV inspection tools. It is observed that the printability of EUV mask defects down to a pitch of 56 nm shows a trend of increased printability as the pitch of the printed pattern gets smaller - a well established trend at larger pitches of 80 nm and 104 nm, respectively. The sensitivity of state-of-the-art reticle inspection tools is greatly improved over that of the previous generation of tools. There appears to be no apparent decline in the sensitivity of these state-of-the-art reticle inspection tools for higher density (smaller) patterns on the mask, even down to 56nm pitch (1x). Preliminary results indicate that a blank defect density of the order of 0.25 defects/cm2 can support very early learning on EUV pilot line production at the 16nm node.

  20. Lifetimes of Bound Excited States of Si^-

    NASA Astrophysics Data System (ADS)

    O'Malley, Steven M.; Beck, Donald R.

    2003-05-01

    The bound excited states of Si^- lie 6955 cm-1 (^2D_3/2), 6969 cm-1 (M. Scheer et al, Phys. Rev. Lett. 80), 2562 (1998). (^2D_5/2), and 10 977 cm-1 (A. Kasden et al, J. Chem. Phys. 62), 541 (1975). (^2P_1/2) above the ^4S_3/2 ground state. Transitions from each of the bottom three levels to the ^2P_1/2 level are LS allowed (both E2 and M1) and thus relatively uncomplicated calculations, resulting in a lifetime for the ^2P_1/2 level of ˜25 s. The ^4S/^2D/^2P mixing is critical for the ^4S arrow ^2D LS forbidden transitions, and LS purity is greater than 99.5% for such a light (nonrelativistic) system. At the Dirac-Fock level we find the most important factor in the ^4S_3/2 arrow ^2D_3/2 transition is the amount of ^4S mixing in the ^2D_3/2 level. With no such ^4S component in the ^2D_5/2 level, its lifetime is over 100 000 s. Important correlation configurations which act to lower the ^2D_3/2 lifetime include the valence excitations 3p arrow p and 3p^2 arrow p^2 and the core-valence 3s,3p and 2p,3p pair excitations. Our current ^2D_3/2 lifetime in an ongoing series of calculations is ˜200 s.

  1. Scanning electron microscope automatic defect classification of process induced defects

    NASA Astrophysics Data System (ADS)

    Wolfe, Scott; McGarvey, Steve

    2017-03-01

    With the integration of high speed Scanning Electron Microscope (SEM) based Automated Defect Redetection (ADR) in both high volume semiconductor manufacturing and Research and Development (R and D), the need for reliable SEM Automated Defect Classification (ADC) has grown tremendously in the past few years. In many high volume manufacturing facilities and R and D operations, defect inspection is performed on EBeam (EB), Bright Field (BF) or Dark Field (DF) defect inspection equipment. A comma separated value (CSV) file is created by both the patterned and non-patterned defect inspection tools. The defect inspection result file contains a list of the inspection anomalies detected during the inspection tools' examination of each structure, or the examination of an entire wafers surface for non-patterned applications. This file is imported into the Defect Review Scanning Electron Microscope (DRSEM). Following the defect inspection result file import, the DRSEM automatically moves the wafer to each defect coordinate and performs ADR. During ADR the DRSEM operates in a reference mode, capturing a SEM image at the exact position of the anomalies coordinates and capturing a SEM image of a reference location in the center of the wafer. A Defect reference image is created based on the Reference image minus the Defect image. The exact coordinates of the defect is calculated based on the calculated defect position and the anomalies stage coordinate calculated when the high magnification SEM defect image is captured. The captured SEM image is processed through either DRSEM ADC binning, exporting to a Yield Analysis System (YAS), or a combination of both. Process Engineers, Yield Analysis Engineers or Failure Analysis Engineers will manually review the captured images to insure that either the YAS defect binning is accurately classifying the defects or that the DRSEM defect binning is accurately classifying the defects. This paper is an exploration of the feasibility of the

  2. Bound states in the continuum

    NASA Astrophysics Data System (ADS)

    Hsu, Chia Wei; Zhen, Bo; Stone, A. Douglas; Joannopoulos, John D.; Soljačić, Marin

    2016-09-01

    Bound states in the continuum (BICs) are waves that remain localized even though they coexist with a continuous spectrum of radiating waves that can carry energy away. Their very existence defies conventional wisdom. Although BICs were first proposed in quantum mechanics, they are a general wave phenomenon and have since been identified in electromagnetic waves, acoustic waves in air, water waves and elastic waves in solids. These states have been studied in a wide range of material systems, such as piezoelectric materials, dielectric photonic crystals, optical waveguides and fibres, quantum dots, graphene and topological insulators. In this Review, we describe recent developments in this field with an emphasis on the physical mechanisms that lead to BICs across seemingly very different materials and types of waves. We also discuss experimental realizations, existing applications and directions for future work.

  3. Supersymmetric k-defects

    DOE PAGES

    Koehn, Michael; Trodden, Mark

    2016-03-03

    In supersymmetric theories, topological defects can have nontrivial behaviors determined purely by whether or not supersymmetry is restored in the defect core. A well-known example of this is that some supersymmetric cosmic strings are automatically superconducting, leading to important cosmological effects and constraints. We investigate the impact of nontrivial kinetic interactions, present in a number of particle physics models of interest in cosmology, on the relationship between supersymmetry and supercurrents on strings. Furthermore, we find that in some cases it is possible for superconductivity to be disrupted by the extra interactions.

  4. Supersymmetric k-defects

    NASA Astrophysics Data System (ADS)

    Koehn, Michael; Trodden, Mark

    2016-04-01

    In supersymmetric theories, topological defects can have nontrivial behaviors determined purely by whether or not supersymmetry is restored in the defect core. A well-known example of this is that some supersymmetric cosmic strings are automatically superconducting, leading to important cosmological effects and constraints. We investigate the impact of nontrivial kinetic interactions, present in a number of particle physics models of interest in cosmology, on the relationship between supersymmetry and supercurrents on strings. We find that in some cases it is possible for superconductivity to be disrupted by the extra interactions.

  5. Pair extended coupled cluster doubles

    SciTech Connect

    Henderson, Thomas M.; Scuseria, Gustavo E.; Bulik, Ireneusz W.

    2015-06-07

    The accurate and efficient description of strongly correlated systems remains an important challenge for computational methods. Doubly occupied configuration interaction (DOCI), in which all electrons are paired and no correlations which break these pairs are permitted, can in many cases provide an accurate account of strong correlations, albeit at combinatorial computational cost. Recently, there has been significant interest in a method we refer to as pair coupled cluster doubles (pCCD), a variant of coupled cluster doubles in which the electrons are paired. This is simply because pCCD provides energies nearly identical to those of DOCI, but at mean-field computational cost (disregarding the cost of the two-electron integral transformation). Here, we introduce the more complete pair extended coupled cluster doubles (pECCD) approach which, like pCCD, has mean-field cost and reproduces DOCI energetically. We show that unlike pCCD, pECCD also reproduces the DOCI wave function with high accuracy. Moreover, pECCD yields sensible albeit inexact results even for attractive interactions where pCCD breaks down.

  6. Molecular Dynamics Simulation of Defect Production in Collision Cascades in Zircon

    SciTech Connect

    Devanathan, Ram; Corrales, Louis R.; Weber, William J.; Chartier, Alain; Meis, Constantin

    2005-01-01

    Defect production in collision cascades in zircon has been examined by molecular dynamics simulations using a partial charge model combined with the Ziegler-Biersack-Littmark potential. U, Zr, Si and O recoils with energies ranging from 250 eV to 5 keV were simulated in the NVE ensemble. To obtain good statistics, 5-10 cascades in randomly chosen directions were simulated for each ion and energy. The damage consists of mainly Si and O Frenkel pairs, a smaller number of Zr Frenkel pairs, and Zr on Si antisite defects. Defect production, interstitial clustering, ion beam mixing and Si-O-Si polymerization increase with PKA mass and energy.

  7. Annealing bounds to prevent further Charge Transfer Inefficiency increase of the Chandra X-ray CCDs

    NASA Astrophysics Data System (ADS)

    Monmeyran, Corentin; Patel, Neil S.; Bautz, Mark W.; Grant, Catherine E.; Prigozhin, Gregory Y.; Agarwal, Anuradha; Kimerling, Lionel C.

    2016-12-01

    After the front-illuminated CCDs on board the X-ray telescope Chandra were damaged by radiation after launch, it was decided to anneal them in an effort to remove the defects introduced by the irradiation. The annealing led to an unexpected increase of the Charge Transfer Inefficiency (CTI). The performance degradation is attributed to point defect interactions in the devices. Specifically, the annealing at 30 °C activated the diffusion of the main interstitial defect in the device, the carbon interstitial, which led to its association with a substitutional impurity, ultimately resulting in a stable and electrically active defect state. Because the formation reaction of this carbon interstitial and substitutional impurity associate is diffusion limited, we recommend a higher upper bound for the annealing temperature and duration of any future CCD anneals, that of -50 °C for one day or -60 °C for a week, to prevent further CTI increase.

  8. Correlated defect nanoregions in a metal-organic framework

    NASA Astrophysics Data System (ADS)

    Cliffe, Matthew J.; Wan, Wei; Zou, Xiaodong; Chater, Philip A.; Kleppe, Annette K.; Tucker, Matthew G.; Wilhelm, Heribert; Funnell, Nicholas P.; Coudert, François-Xavier; Goodwin, Andrew L.

    2014-06-01

    Throughout much of condensed matter science, correlated disorder is a key to material function. While structural and compositional defects are known to exist within a variety of metal-organic frameworks (MOFs), the prevailing understanding is that these defects are only ever included in a random manner. Here we show—using a combination of diffuse scattering, electron microscopy, anomalous X-ray scattering and pair distribution function measurements—that correlations between defects can in fact be introduced and controlled within a hafnium terephthalate MOF. The nanoscale defect structures that emerge are an analogue of correlated Schottky vacancies in rocksalt-structured transition metal monoxides and have implications for storage, transport, optical and mechanical responses. Our results suggest how the diffraction behaviour of some MOFs might be reinterpreted, and establish a strategy of exploiting correlated nanoscale disorder as a targetable and desirable motif in MOF design.

  9. Defect-Stabilized Phases in Extensile Active Nematics

    NASA Astrophysics Data System (ADS)

    Redner, Gabriel; Decamp, Stephen; Dogic, Zvonimir; Hagan, Michael

    2015-03-01

    Active nematics are liquid crystals which are driven out of equilibrium by energy-dissipating active stresses. The equilibrium nematic state is unstable in these materials, leading to beautiful and surprising behaviors including the spontaneous generation of topological defect pairs which stream through the system and later annihilate, yielding a complex, seemingly chaotic dynamical steady-state. In this talk, I will describe the emergence of order from this chaos in the form of previously unknown broken-symmetry phases in which the topological defects themselves undergo orientational ordering. We have identified these defect-ordered phases in two realizations of an active nematic: first, a suspension of extensile bundles of microtubules and molecular motor proteins, and second, a computational model of extending hard rods. I will describe the defect-stabilized phases that manifest in these systems, our current understanding of their origins, and discuss whether such phases may be a general feature of extensile active nematics.

  10. Pair-Starved Pulsar Magnetospheres

    NASA Technical Reports Server (NTRS)

    Muslimov, Alex G.; Harding, Alice K.

    2009-01-01

    We propose a simple analytic model for the innermost (within the light cylinder of canonical radius, approx. c/Omega) structure of open-magnetic-field lines of a rotating neutron star (NS) with relativistic outflow of charged particles (electrons/positrons) and arbitrary angle between the NS spin and magnetic axes. We present the self-consistent solution of Maxwell's equations for the magnetic field and electric current in the pair-starved regime where the density of electron-positron plasma generated above the pulsar polar cap is not sufficient to completely screen the accelerating electric field and thus establish thee E . B = 0 condition above the pair-formation front up to the very high altitudes within the light cylinder. The proposed mode1 may provide a theoretical framework for developing the refined model of the global pair-starved pulsar magnetosphere.

  11. Rapid thermal co-annihilation through bound states in QCD

    NASA Astrophysics Data System (ADS)

    Kim, Seyong; Laine, M.

    2016-07-01

    The co-annihilation rate of heavy particles close to thermal equilibrium, which plays a role in many classic dark matter scenarios, can be "simulated" in QCD by considering the pair annihilation rate of a heavy quark and antiquark at a temperature of a few hundred MeV. We show that the so-called Sommerfeld factors, parameterizing the rate, can be defined and measured non-perturbatively within the NRQCD framework. Lattice measurements indicate a modest suppression in the octet channel, in reasonable agreement with perturbation theory, and a large enhancement in the singlet channel, much above the perturbative prediction. The additional enhancement is suggested to originate from bound state formation and subsequent decay. Making use of a Green's function based method to incorporate thermal corrections in perturbative co-annihilation rate computations, we show that qualitative agreement with lattice data can be found once thermally broadened bound states are accounted for. We suggest that our formalism may also be applicable to specific dark matter models which have complicated bound state structures.

  12. Reconstruction of complex abdominal wall defects.

    PubMed

    Leppäniemi, A; Tukiainen, E

    2013-01-01

    Complex abdominal wall defects refer to situations where simple ventral hernia repair is not feasible because the defect is very large, there is a concomitant infection or failed previous re-pair attempt, or if there is not enough original skin to cover the repair. Usually a complex abdominal wall repair is preceded by a period of temporary abdominal closure where the short-term aims include closure of the catabolic drain, protection of the viscera and preventing fistula formation, preventing bowel adherence to the abdominal wall, and enabling future fascial and skin closure. Currently the best way to achieve these goals is the vacuum- and mesh-mediated fascial traction method achieving close to 90% fascial closure rates. The long-term aims of an abdominal closure following a planned hernia strategy include intact skin cover, fascial closure at midline (if possible), good functional outcome with innervated abdominal musculature, no pain and good cosmetic result. The main methods of abdominal wall reconstruction include the use of prosthetic (mesh) or autologous material (tissue flaps). In patients with original skin cover over the fascial defect (simple ventral hernia), the most commonly used method is hernia repair with an artificial mesh. For more complex defects, our first choice of reconstruction is the component separation technique, sometimes combined with a mesh. In contaminated fields where component separation alone is not feasible, a combination with a biological mesh can be used. In large defects with grafted skin, a free TFL flap is the best option, sometimes reinforced with a mesh and enhanced with components separation.

  13. Turbulent Inertial Particle Pair Diffusion

    NASA Astrophysics Data System (ADS)

    Usama, Syed; Malik, Nadeem

    2017-04-01

    Inertial particle pair diffusion has received much less attention than fluid particle pair diffusion, even though it is arguably more relevant to real world applications, such as sand storms, and pollen dispersion. Only the DNS work of Bec et al [1] has been reported. A non-local theory of fluid particle pair diffusion has recently been proposed [2,3]; but the question is, can non-locality be extended to inertial particle pair diffusion? Here, we investigate it using Kinematic Simulations [4,5], in the limit of Stokes' drag where the transport is given by, d{x}/dt={v}(t), \\qquad; d{v}/dt = -1/τ({v}(t)-{u}) {x}(t) is the particle position at time t, {v}(t) is the particle velocity, {u}({x},t) is the Eulerian velocity field generated by the KS model, τ is the particle response time. The Stokes number is, St=τ/t_η, where t_η is the Kolmogorov time scale, σ_l(t)=< l(t)^2>1/2, where l(t)=|{x}_1(t)-{x}_2(t)| is the distance between particles in a pair, in an ensemble of particle pairs released at time t=0 such that l(t=0) =l0 2/3. KS was used in a frame of reference moving with the (virtual) large scale sweeping velocities with spectrum, E(k)˜ k-5/3, for 1≤ k ≤10^4, and E(k)=0, for k

  14. First-Principles Study of Defects in GaN, AlN and Their Alloys

    DTIC Science & Technology

    2010-08-31

    studied the similar type of pairs in GaN, i.e. Gai -VGa. These types of defect complexes are called Frenkel pairs which are believed to form when the...defects have been carried out.[17-21] In our previous program, we studied the GaGa i V− pairs in GaN. We found that Gai can occur in 3+, 2+, and 1...charge states, depending on the Fermi energy of the sample. VGa can occur in 3−, 2−, 1−, and neutral charge states. Because Gai and VGa have

  15. Using tolerance bounds in scientific investigations

    SciTech Connect

    Wendelberger, J.R.

    1996-07-01

    Assessment of the variability in population values plays an important role in the analysis of scientific data. Analysis of scientific data often involves developing a bound on a proportion of a population. Sometimes simple probability bounds are obtained using formulas involving known mean and variance parameters and replacing the parameters by sample estimates. The resulting bounds are only approximate and fail to account for the variability in the estimated parameters. Tolerance bounds provide bounds on population proportions which account for the variation resulting from the estimated mean and variance parameters. A beta content, gamma confidence tolerance interval is constructed so that a proportion beta of the population lies within the region bounded by the interval with confidence gamma. An application involving corrosion measurements is used to illustrate the use of tolerance bounds for different situations. Extensions of standard tolerance intervals are applied to generate regression tolerance bounds, tolerance bounds for more general models of measurements collected over time, and tolerance intervals for varying precision data. Tolerance bounds also provide useful information for designing the collection of future data.

  16. Quantum computing with defects.

    PubMed

    Weber, J R; Koehl, W F; Varley, J B; Janotti, A; Buckley, B B; Van de Walle, C G; Awschalom, D D

    2010-05-11

    Identifying and designing physical systems for use as qubits, the basic units of quantum information, are critical steps in the development of a quantum computer. Among the possibilities in the solid state, a defect in diamond known as the nitrogen-vacancy (NV(-1)) center stands out for its robustness--its quantum state can be initialized, manipulated, and measured with high fidelity at room temperature. Here we describe how to systematically identify other deep center defects with similar quantum-mechanical properties. We present a list of physical criteria that these centers and their hosts should meet and explain how these requirements can be used in conjunction with electronic structure theory to intelligently sort through candidate defect systems. To illustrate these points in detail, we compare electronic structure calculations of the NV(-1) center in diamond with those of several deep centers in 4H silicon carbide (SiC). We then discuss the proposed criteria for similar defects in other tetrahedrally coordinated semiconductors.

  17. Quantum computing with defects

    PubMed Central

    Weber, J. R.; Koehl, W. F.; Varley, J. B.; Janotti, A.; Buckley, B. B.; Van de Walle, C. G.; Awschalom, D. D.

    2010-01-01

    Identifying and designing physical systems for use as qubits, the basic units of quantum information, are critical steps in the development of a quantum computer. Among the possibilities in the solid state, a defect in diamond known as the nitrogen-vacancy (NV-1) center stands out for its robustness—its quantum state can be initialized, manipulated, and measured with high fidelity at room temperature. Here we describe how to systematically identify other deep center defects with similar quantum-mechanical properties. We present a list of physical criteria that these centers and their hosts should meet and explain how these requirements can be used in conjunction with electronic structure theory to intelligently sort through candidate defect systems. To illustrate these points in detail, we compare electronic structure calculations of the NV-1 center in diamond with those of several deep centers in 4H silicon carbide (SiC). We then discuss the proposed criteria for similar defects in other tetrahedrally coordinated semiconductors. PMID:20404195

  18. Defects in flexoelectric solids

    NASA Astrophysics Data System (ADS)

    Mao, Sheng; Purohit, Prashant K.

    2015-11-01

    A solid is said to be flexoelectric when it polarizes in proportion to strain gradients. Since strain gradients are large near defects, we expect the flexoelectric effect to be prominent there and decay away at distances much larger than a flexoelectric length scale. Here, we quantify this expectation by computing displacement, stress and polarization fields near defects in flexoelectric solids. For point defects we recover some well known results from strain gradient elasticity and non-local piezoelectric theories, but with different length scales in the final expressions. For edge dislocations we show that the electric potential is a maximum in the vicinity of the dislocation core. We also estimate the polarized line charge density of an edge dislocation in an isotropic flexoelectric solid which is in agreement with some measurements in ice. We perform an asymptotic analysis of the crack tip fields in flexoelectric solids and show that our results share some features from solutions in strain gradient elasticity and piezoelectricity. We also compute the energy release rate for cracks using simple crack face boundary conditions and use them in classical criteria for crack growth to make predictions. Our analysis can serve as a starting point for more sophisticated analytic and computational treatments of defects in flexoelectric solids which are gaining increasing prominence in the field of nanoscience and nanotechnology.

  19. Invisibly Sanitizable Signature without Pairings

    NASA Astrophysics Data System (ADS)

    Yum, Dae Hyun; Lee, Pil Joong

    Sanitizable signatures allow sanitizers to delete some pre-determined parts of a signed document without invalidating the signature. While ordinary sanitizable signatures allow verifiers to know how many subdocuments have been sanitized, invisibly sanitizable signatures do not leave any clue to the sanitized subdocuments; verifiers do not know whether or not sanitizing has been performed. Previous invisibly sanitizable signature scheme was constructed based on aggregate signature with pairings. In this article, we present the first invisibly sanitizable signature without using pairings. Our proposed scheme is secure under the RSA assumption.

  20. Enhancing EUV mask blanks usability through smart shift and blank-design pairing optimization

    NASA Astrophysics Data System (ADS)

    Soni, Rakesh Kumar; Paninjath, Sankaranarayanan; Pereira, Mark; Buck, Peter; Thwaite, Peter

    2016-10-01

    EUV Defect avoidance techniques will play a vital role in extreme ultraviolet lithography (EUVL) photomask fabrication with the anticipation that defect free mask blanks won't be available and that cost effective techniques will not be available for defect repairing. In addition, mask shops may not have a large inventory of expensive EUV mask blanks. Given these facts, defect avoidance can be used as cost effective technique to optimize the mask blank and design data (mask data) pair selection across mask blank manufacturers and mask shops so that overall mask blank utilization can be enhanced. In previous work, it was determined that the pattern shift based solution increases the chance that a defective mask blank can be used that would otherwise be discarded [1]. In pattern shift, design data is shifted such that defects are either moved to isolated regions or hidden under the patterns that are written. However pattern shifts techniques don't perform well with masks with higher defect counts. Pattern shift techniques in this form assume all defects to be equally critical. In addition, a defect is critical or important only if it lands on the main pattern. A defect landing on fill, sub-resolution assist feature (SRAF) or fiducial areas may not be critical. In this paper we assess the performance of pattern shift techniques assuming defects that are not critical based upon size or type, as well as defects landing in non-critical areas (smart shift) can be ignored. In a production mask manufacturing environment it is necessary to co-optimize and prioritize blank-design pairing for multiple mask layouts in the queue with the available blanks. A blank-design pairing tool maximizes the utilization of blanks by finding the best pairing between blanks and design data so that the maximum number of mask blanks can be used. In this paper we also propose a novel process which would optimize the usage of costly EUV mask blanks across mask blank manufacturers and mask shops

  1. Conjugate quasilinear Dirichlet and Neumann problems and a posteriori error bounds

    NASA Technical Reports Server (NTRS)

    Lavery, J. E.

    1976-01-01

    Quasilinear Dirichlet and Neumann problems on a rectangle D with boundary D prime are considered. Using these concepts, conjugate problems, that is, a pair of one Dirichlet and one Neumann problem, the minima of the energies of which add to zero, are introduced. From the concept of conjugate problems, two-sided bounds for the energy of the exact solution of any given Dirichlet or Neumann problem are constructed. These two-sided bounds for the energy at the exact solution are in turn used to obtain a posteriori error bounds for the norm of the difference of the approximate and exact solutions of the problem. These bounds do not involve the unknown exact solution and are easily constructed numerically.

  2. Scattering and bound states of fermions in a mixed vector–scalar smooth step potential

    SciTech Connect

    Castilho, W.M. Castro, A.S. de

    2014-07-15

    The scattering of a fermion in the background of a smooth step potential is considered with a general mixing of vector and scalar Lorentz structures with the scalar coupling stronger than or equal to the vector coupling. Charge-conjugation and chiral-conjugation transformations are discussed and it is shown that a finite set of intrinsically relativistic bound-state solutions appears as poles of the transmission amplitude. It is also shown that those bound solutions disappear asymptotically as one approaches the conditions for the realization of the so-called spin and pseudospin symmetries in a four-dimensional space–time. - Highlights: • Scattering and bound states of fermions in a kink-like potential. • No pair production despite the high localization. • No bounded solution under exact spin and pseudospin symmetries.

  3. Bound anionic states of adenine

    SciTech Connect

    Haranczyk, Maciej; Gutowski, Maciej S; Li, Xiang; Bowen, Kit H

    2007-03-20

    Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases, are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the new-found anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The discovery of these valence anionic states of adenine was facilitated by the development of: (i) a new experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (ii) a new combinatorial/ quantum chemical approach for identification of the most stable tautomers of organic molecules. The computational portion of this work was supported by the: (i) Polish State Committee for Scientific Research (KBN) Grants: DS/8000-4-0140-7 (M.G.) and N204 127 31/2963 (M.H.), (ii) European Social Funds (EFS) ZPORR/2.22/II/2.6/ARP/U/2/05 (M.H.), and (iii) US DOE Office of Biological and Environmental Research, Low Dose Radiation Research Program (M.G.). M.H. holds the Foundation for Polish Science (FNP) award for young scientists. The calculations were performed at the Academic

  4. Competing Pairing Symmetries in a Generalized Two-Orbital Model for the Pnictide Superconductors

    SciTech Connect

    Nicholson, Andrew D; Ge, Weihao; Zhang, Xiaotian; Riera, J. A.; Daghofer, M.; Olés, Andrzej M.; Martins, G. B.; Moreo, Adriana; Dagotto, Elbio R

    2011-01-01

    We introduce and study an extended t-U-J two-orbital model for the pnictides that includes Heisenberg terms deduced from the strong coupling expansion. Including these J terms explicitly allows us to enhance the strength of the %;0 - 0;% spin order which favors the presence of tightly bound pairing states even in the small clusters that are here exactly diagonalized. The A1g and B2g pairing symmetries are found to compete in the realistic spin-ordered and metallic regime. The dynamical pairing susceptibility additionally unveils low-lying B1g states, suggesting that small changes in parameters may render any of the three channels stable.

  5. Relativistic and quantum electrodynamics effects in the helium pair potential.

    PubMed

    Przybytek, M; Cencek, W; Komasa, J; Łach, G; Jeziorski, B; Szalewicz, K

    2010-05-07

    The helium pair potential was computed including relativistic and quantum electrodynamics contributions as well as improved accuracy adiabatic ones. Accurate asymptotic expansions were used for large distances R. Error estimates show that the present potential is more accurate than any published to date. The computed dissociation energy and the average R for the (4)He(2) bound state are 1.62+/-0.03 mK and 47.1+/-0.5 A. These values can be compared with the measured ones: 1.1(-0.2)(+0.3) mK and 52+/-4 A [R. E. Grisenti, Phys. Rev. Lett. 85, 2284 (2000)].

  6. Defect states in perovskite solar cells associated with hysteresis and performance

    NASA Astrophysics Data System (ADS)

    Miller, D. Westley; Eperon, Giles E.; Roe, Ellis T.; Warren, Charles W.; Snaith, Henry J.; Lonergan, Mark C.

    2016-10-01

    External quantum efficiency and transient photocapacitance (TPC) spectra were obtained for perovskite solar cells with methylammonium lead triiodide perovskite absorbers formed by either dip or vapor conversion. These measurements reveal an extended band of sub-gap states in all of the devices studied. The defect band is best fit by a pair of defects, and the appearance of the defect signal in the transient photocapacitance spectra indicates that at least one of the observed defects is in the perovskite absorber. The cells with the largest density of defect states show the lowest short-circuit current density and open-circuit voltage for slow, quasi-steady-state, current density-voltage sweeps and the largest hysteresis in short-circuit current density for fast sweeps. This suggests that defect states in the perovskite absorber limit steady-state device performance, and that these defects or associated mobile charges play a role in the hysteresis observed in current density-voltage measurements.

  7. Plane-wave pseudopotential study of point defects in uranium dioxide

    NASA Astrophysics Data System (ADS)

    Crocombette, J. P.; Jollet, F.; Nga, L. Thien; Petit, T.

    2001-09-01

    A study on uranium and oxygen point defects in uranium dioxide using the ab initio plane-wave pseudopotential method in the local density approximation of the density functional theoretical framework is presented. Norm conserving pseudopotentials are used to describe oxygen and uranium atoms. The uranium pseudopotential is specifically described. Its validity is ascertained thanks to a detailed structural study of uranium dioxide and of three phases of metallic uranium (fcc, bcc, and α phase). The free energies of formation of both intrinsic (Frenkel pairs and Schottky defect) and extrinsic (single vacancies or interstitials) defects are calculated. The obtained values form a reliable set of numerical data that are analyzed in the framework of the point defect model which is commonly used to assess defect concentrations in uranium dioxide and their variation with stoichiometry. From the obtained results, the ability of the point defect model to accurately reproduce defect concentrations in uranium dioxide is discussed.

  8. Random waves in the brain: Symmetries and defect generation in the visual cortex

    NASA Astrophysics Data System (ADS)

    Schnabel, M.; Kaschube, M.; Löwel, S.; Wolf, F.

    2007-06-01

    How orientation maps in the visual cortex of the brain develop is a matter of long standing debate. Experimental and theoretical evidence suggests that their development represents an activity-dependent self-organization process. Theoretical analysis [1] exploring this hypothesis predicted that maps at an early developmental stage are realizations of Gaussian random fields exhibiting a rigorous lower bound for their densities of topological defects, called pinwheels. As a consequence, lower pinwheel densities, if observed in adult animals, are predicted to develop through the motion and annihilation of pinwheel pairs. Despite of being valid for a large class of developmental models this result depends on the symmetries of the models and thus of the predicted random field ensembles. In [1] invariance of the orientation map's statistical properties under independent space rotations and orientation shifts was assumed. However, full rotation symmetry appears to be broken by interactions of cortical neurons, e.g. selective couplings between groups of neurons with collinear orientation preferences [2]. A recently proposed new symmetry, called shift-twist symmetry [3], stating that spatial rotations have to occur together with orientation shifts in order to be an appropriate symmetry transformation, is more consistent with this organization. Here we generalize our random field approach to this important symmetry class. We propose a new class of shift-twist symmetric Gaussian random fields and derive the general correlation functions of this ensemble. It turns out that despite strong effects of the shift-twist symmetry on the structure of the correlation functions and on the map layout the lower bound on the pinwheel densities remains unaffected, predicting pinwheel annihilation in systems with low pinwheel densities.

  9. Nonadditivity of Rains' bound for distillable entanglement

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Duan, Runyao

    2017-06-01

    Rains' bound is arguably the best known upper bound of the distillable entanglement by operations completely preserving positivity of partial transpose (PPT) and was conjectured to be additive and coincide with the asymptotic relative entropy of entanglement. We disprove both conjectures by explicitly constructing a special class of mixed two-qubit states. We then introduce an additive semidefinite programming lower bound (EM) for the asymptotic Rains' bound, and it immediately becomes a computable lower bound for entanglement cost of bipartite states. Furthermore, EM is also proved to be the best known upper bound of the PPT-assisted deterministic distillable entanglement and gives the asymptotic rates for all pure states and some class of genuinely mixed states.

  10. Watson-Crick pairing, the Heisenberg group and Milnor invariants.

    PubMed

    Gadgil, Siddhartha

    2009-07-01

    We study the secondary structure of RNA determined by Watson-Crick pairing without pseudo-knots using Milnor invariants of links. We focus on the first non-trivial invariant, which we call the Heisenberg invariant. The Heisenberg invariant, which is an integer, can be interpreted in terms of the Heisenberg group as well as in terms of lattice paths. We show that the Heisenberg invariant gives a lower bound on the number of unpaired bases in an RNA secondary structure. We also show that the Heisenberg invariant can predict allosteric structures for RNA. Namely, if the Heisenberg invariant is large, then there are widely separated local maxima (i.e., allosteric structures) for the number of Watson-Crick pairs found.

  11. Pairing symmetry and vortex zero mode for superconducting Dirac fermions

    SciTech Connect

    Lu, C.-K.; Herbut, Igor F.

    2010-10-01

    We study vortex zero-energy bound states in presence of pairing between low-energy Dirac fermions on the surface of a topological insulator. The pairing symmetries considered include the s-wave, p-wave, and, in particular, the mixed-parity symmetry, which arises in absence of the inversion symmetry on the surface. The zero mode is analyzed within the generalized Jackiw-Rossi-Dirac Hamiltonian that contains a momentum-dependent mass term, and includes the effects of the electromagnetic gauge field and the Zeeman coupling as well. At a finite chemical potential, as long as the spectrum without the vortex is fully gapped, the presence of a single Fermi surface with a definite helicity always leads to one Majorana zero mode, in which both electron's spin projections participate. In particular, the critical effects of the Zeeman coupling on the zero mode are discussed.

  12. Pairing Linguistic and Music Intelligences

    ERIC Educational Resources Information Center

    DiEdwardo, MaryAnn Pasda

    2005-01-01

    This article describes how music in the language classroom setting can be a catalyst for developing reading, writing, and understanding skills. Studies suggest that pairing music and linguistic intelligences in the college classroom improves students' grades and abilities to compose theses statements for research papers in courses that emphasize…

  13. Missing energies at pair creation

    NASA Technical Reports Server (NTRS)

    El-Ela, A. A.; Hassan, S.; Bagge, E. R.

    1985-01-01

    Wilson cloud chamber measurements of the separated spectra of positrons and electrons produced by gamma quanta of 6.14 MeV differ considerably from the theoretically predicted spectra by BETHE and HEITLER, but are in good agreement with those of a modified theory of pair creation.

  14. Pick a Pair. Being Bony

    ERIC Educational Resources Information Center

    Miller, Pat

    2004-01-01

    This column suggests pairings of fiction and nonfiction books to meet curricular needs and help students to compare/contrast the texts as they may be asked on state tests. The author of this paper focuses on activities surrounding Halloween. Since many schools are discouraged from teaching about Halloween, this can be a great time to investigate…

  15. Pairing Linguistic and Music Intelligences

    ERIC Educational Resources Information Center

    DiEdwardo, MaryAnn Pasda

    2005-01-01

    This article describes how music in the language classroom setting can be a catalyst for developing reading, writing, and understanding skills. Studies suggest that pairing music and linguistic intelligences in the college classroom improves students' grades and abilities to compose theses statements for research papers in courses that emphasize…

  16. Pick a Pair. Being Bony

    ERIC Educational Resources Information Center

    Miller, Pat

    2004-01-01

    This column suggests pairings of fiction and nonfiction books to meet curricular needs and help students to compare/contrast the texts as they may be asked on state tests. The author of this paper focuses on activities surrounding Halloween. Since many schools are discouraged from teaching about Halloween, this can be a great time to investigate…

  17. Matched pair conical spiral antennas

    NASA Technical Reports Server (NTRS)

    Metzler, R. E.

    1972-01-01

    A matched pair of VHF (220-260 MHz) conical spiral antennas for use in a rocket-tracking interferometer array was designed and tested. While gain, bandwidth, impedance, and pattern measurements met specifications, the phase match between antennas at low elevations was not equal to the design goal.

  18. Using defects to store energy in materials - a computational study.

    PubMed

    Lu, I-Te; Bernardi, Marco

    2017-06-13

    Energy storage occurs in a variety of physical and chemical processes. In particular, defects in materials can be regarded as energy storage units since they are long-lived and require energy to be formed. Here, we investigate energy storage in non-equilibrium populations of materials defects, such as those generated by bombardment or irradiation. We first estimate upper limits and trends for energy storage using defects. First-principles calculations are then employed to compute the stored energy in the most promising elemental materials, including tungsten, silicon, graphite, diamond and graphene, for point defects such as vacancies, interstitials and Frenkel pairs. We find that defect concentrations achievable experimentally (~0.1-1 at.%) can store large energies per volume and weight, up to ~5 MJ/L and 1.5 MJ/kg for covalent materials. Engineering challenges and proof-of-concept devices for storing and releasing energy with defects are discussed. Our work demonstrates the potential of storing energy using defects in materials.

  19. Trace Impurities and Radiation Defects in Optical Materials

    NASA Astrophysics Data System (ADS)

    Malovichko, Galina; Grachev, Valentin; Meyer, Martin; Munro, Mark; Pankratov, Vladimir

    2007-05-01

    Trace impurities and radiation defects lead to inevitable performance degradation of devices based on optical materials. The results of the Electron Paramagnetic Resonance (EPR) study of defects in as grown and irradiated single crystals are reported. Among investigated optical materials are LiNbO3, Li2B4O7, KTiOPO4 etc. Crystals from different vendors or grown by different ways have different concentrations of non-controlled impurities and, as a result, different physical properties, including radiation resistance. Intrinsic defects (vacancies and antisites), usually present in congruent non-stoichiometric crystals like lithium niobate and tantalate. Many EPR lines of non-controlled impurities were found in KTiOPO4 crystals. We found that dominating types of defects formed under visible, UV and gamma photon irradiation are centers created by defects trapped electron or hole. The neutron and high energy electron irradiation creates stable Frenkel pairs - interstitial ions and vacancies. Computer simulation of observed spectra allowed us to determine spectroscopic characteristics and models for more than dozen trace impurities and radiation defects. Obtained data about atomic defects can be used for a selection of materials suitable for various applications. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.NWS07.B1.2

  20. Triplet pairing in neutron matter

    NASA Astrophysics Data System (ADS)

    Khodel, V. V.; Khodel, V. A.; Clark, J. W.

    2001-01-01

    The separation method developed earlier by us [Nucl. Phys. A 598 390 (1996)] to calculate and analyze solutions of the BCS gap equation for 1S 0 pairing is extended and applied to 3P 2- 3F 2 pairing in pure neutron matter. The pairing matrix elements are written as a separable part plus a remainder that vanishes when either momentum variable is on the Fermi surface. This decomposition effects a separation of (i) the problem of determining the dependence of the gap components in a spin-angle representation on the magnitude of the momentum (described by a set of functions independent of magnetic quantum number) from (ii) the problem of determining the dependence of the gap on angle or magnetic projection. The former problem is solved through a set of nonsingular, quasilinear integral equations, providing inputs for solution of the latter problem through a coupled system of algebraic equations for a set of numerical coefficients. An incisive criterion is given for finding the upper critical density for closure of the triplet gap. The separation method and its development for triplet pairing exploit the existence of a small parameter, given by a gap-amplitude measure divided by the Fermi energy. The revised BCS equations admit analysis revealing universal properties of the full set of solutions for 3P 2 pairing in the absence of tensor coupling, referring especially to the energy degeneracy and energetic order of these solutions. The angle-average approximation introduced by Baldo et al. is illuminated in terms of the separation-transformed BCS problem and the small parameter expansion. Numerical calculations of 3P 2 pairing parameters and gap functions, with and without coupling to the 3F 2 state, are carried out for pairing matrix elements supplied by (vacuum) two-neutron interactions that fit nucleon-nucleon scattering data. It is emphasized that ab initio evaluation of the in-medium particle-particle interaction and associated single-particle energies will be

  1. Lower bound for the multifield bounce action

    NASA Astrophysics Data System (ADS)

    Aravind, Aditya; Lorshbough, Dustin; Paban, Sonia

    2014-05-01

    We present a lower bound for the multifield bounce action with a quartic potential with bounded coefficients in the absence of gravity. We find that for a large number of fields the lower bound decreases with the number of fields as N-3. This work clarifies previous statements made in numerical studies which found that the bounce action scales as N-2.66 and discusses some subtleties of studying field space trajectories.

  2. Optimized Live Heap Bound Analysis

    DTIC Science & Technology

    2003-01-01

    Optimized Live Heap Bound Analysis Leena Unnikrishnan ∗ Scott D. Stoller∗ Yanhong A. Liu∗ Abstract This paper describes a general approach for...insertion sort selection sort merge sort n S B Bopt n S B Bopt n S B Bopt n S B Bopt 101 1.0 m 0 1.0 m 101 1.0 m 1.0 M 9.0 m 101 0 37.3 s 10.0 m 101 2.0 m 0.9...s 0.7 s 102 0.1 s 0.3 s 0.1 s 102 0.1 s 5.1 s 102 0.2 s 5.0 s 102 40.0 m 103 10.7 s 3.5 M 11.9 s 103 12.8 s 1.5 H 103 27.3 s 1.5 H 103 0.7 s binomial

  3. Radial oscillations of color superconducting self-bound quark stars

    SciTech Connect

    Vasquez Flores, C.; Lugones, G.

    2010-09-15

    We investigate the effect of the color-flavor locking pairing pattern on the adiabatic radial oscillations of pure self-bound quark stars using an equation of state in the framework of the MIT bag model. We integrate the equations of relativistic radial oscillations to determine the fundamental and the first excited oscillation modes for several parameterizations of the equation of state. For low mass stars we find that the period of the fundamental mode is typically {approx}0.1 ms and has a small dependence on the parameters of the equation of state. For large mass stars the effect of color-flavor locking is related to the rise of the maximum mass with increasing {Delta}. As for unpaired quark stars, the period of the fundamental mode becomes divergent at the maximum mass but now the divergence is shifted to large masses for large values of the pairing gap {Delta}. As a consequence, the oscillation period is strongly affected by color superconductivity for stars with M > or approx. 1.5 M{sub {center_dot}}. We fit the period of the fundamental mode with appropriate analytical functions of the gravitational redshift of the star and the pairing gap {Delta}. We further discuss the excitation and damping of the modes and their potential detectability during violent transient phenomena.

  4. Radial oscillations of color superconducting self-bound quark stars

    NASA Astrophysics Data System (ADS)

    Vásquez Flores, C.; Lugones, G.

    2010-09-01

    We investigate the effect of the color-flavor locking pairing pattern on the adiabatic radial oscillations of pure self-bound quark stars using an equation of state in the framework of the MIT bag model. We integrate the equations of relativistic radial oscillations to determine the fundamental and the first excited oscillation modes for several parameterizations of the equation of state. For low mass stars we find that the period of the fundamental mode is typically ˜0.1ms and has a small dependence on the parameters of the equation of state. For large mass stars the effect of color-flavor locking is related to the rise of the maximum mass with increasing Δ. As for unpaired quark stars, the period of the fundamental mode becomes divergent at the maximum mass but now the divergence is shifted to large masses for large values of the pairing gap Δ. As a consequence, the oscillation period is strongly affected by color superconductivity for stars with M≳1.5M⊙. We fit the period of the fundamental mode with appropriate analytical functions of the gravitational redshift of the star and the pairing gap Δ. We further discuss the excitation and damping of the modes and their potential detectability during violent transient phenomena.

  5. Andreev bound state at a strongly correlated oxide interface

    NASA Astrophysics Data System (ADS)

    Cheng, Guanglei; Tomczyk, Michelle; Tacla, Alexandre; Daley, Andrew; Lu, Shicheng; Veazey, Josh; Huang, Mengchen; Irvin, Patrick; Ryu, Sangwoo; Lee, Hyungwoo; Eom, Chang-Beom; Pekker, David; Levy, Jeremy

    Strongly correlated electrons at oxide interfaces give rise to a set of novel physics phenomena including superconductivity and magnetism. At the LaAlO3/SrTiO3 (LAO/STO) interface, signatures of strong electron pairing persist even for conditions where superconductivity is suppressed. Meanwhile, an Andreev bound state (ABS) is a single quasiparticle excitation that mediates pair transport in confined superconductor-normal systems. Here we report a transition from pair resonant transport to ABS in sketched single electron transistors at the LAO/STO interface. This transition is consistent with a change of electron-electron interaction from attractive to repulsive, occurring at or near the Lifshitz transition. Such new electronically tunable electron-electron interaction may be useful for quantum simulation and engineering of novel quantum states in oxide materials. We gratefully acknowledge support from AFOSR FA9550-10-1-0524 (JL, CBE), AFOSR FA9550-12-1-0057 (JL, CBE, AD), NSF DMR-1104191 (JL), ONR N00014-15-1-2847 (JL).

  6. Sharpening bounds on principal effects with covariates.

    PubMed

    Long, Dustin M; Hudgens, Michael G

    2013-12-01

    Estimation of treatment effects in randomized studies is often hampered by possible selection bias induced by conditioning on or adjusting for a variable measured post-randomization. One approach to obviate such selection bias is to consider inference about treatment effects within principal strata, that is, principal effects. A challenge with this approach is that without strong assumptions principal effects are not identifiable from the observable data. In settings where such assumptions are dubious, identifiable large sample bounds may be the preferred target of inference. In practice these bounds may be wide and not particularly informative. In this work we consider whether bounds on principal effects can be improved by adjusting for a categorical baseline covariate. Adjusted bounds are considered which are shown to never be wider than the unadjusted bounds. Necessary and sufficient conditions are given for which the adjusted bounds will be sharper (i.e., narrower) than the unadjusted bounds. The methods are illustrated using data from a recent, large study of interventions to prevent mother-to-child transmission of HIV through breastfeeding. Using a baseline covariate indicating low birth weight, the estimated adjusted bounds for the principal effect of interest are 63% narrower than the estimated unadjusted bounds. © 2013, The International Biometric Society.

  7. Error-correcting pairs for a public-key cryptosystem

    NASA Astrophysics Data System (ADS)

    Pellikaan, Ruud; Márquez-Corbella, Irene

    2017-06-01

    Code-based Cryptography (CBC) is a powerful and promising alternative for quantum resistant cryptography. Indeed, together with lattice-based cryptography, multivariate cryptography and hash-based cryptography are the principal available techniques for post-quantum cryptography. CBC was first introduced by McEliece where he designed one of the most efficient Public-Key encryption schemes with exceptionally strong security guarantees and other desirable properties that still resist to attacks based on Quantum Fourier Transform and Amplitude Amplification. The original proposal, which remains unbroken, was based on binary Goppa codes. Later, several families of codes have been proposed in order to reduce the key size. Some of these alternatives have already been broken. One of the main requirements of a code-based cryptosystem is having high performance t-bounded decoding algorithms which is achieved in the case the code has a t-error-correcting pair (ECP). Indeed, those McEliece schemes that use GRS codes, BCH, Goppa and algebraic geometry codes are in fact using an error-correcting pair as a secret key. That is, the security of these Public-Key Cryptosystems is not only based on the inherent intractability of bounded distance decoding but also on the assumption that it is difficult to retrieve efficiently an error-correcting pair. In this paper, the class of codes with a t-ECP is proposed for the McEliece cryptosystem. Moreover, we study the hardness of distinguishing arbitrary codes from those having a t-error correcting pair.

  8. Defect Tolerance in Methylammonium Lead Triiodide Perovskite

    SciTech Connect

    Steirer, K. Xerxes; Schulz, Philip; Teeter, Glenn; Stevanovic, Vladan; Yang, Mengjin; Zhu, Kai; Berry, Joseph J.

    2016-08-12

    Photovoltaic applications of perovskite semiconductor material systems have generated considerable interest in part because of predictions that primary defect energy levels reside outside the bandgap. We present experimental evidence that this enabling material property is present in the halide-lead perovskite, CH3NH3PbI3 (MAPbI3), consistent with theoretical predictions. By performing X-ray photoemission spectroscopy, we induce and track dynamic chemical and electronic transformations in the perovskite. These data show compositional changes that begin immediately with exposure to X-ray irradiation, whereas the predominant electronic structure of the thin film on compact TiO2 appears tolerant to the formation of compensating defect pairs of VI and VMA and for a large range of I/Pb ratios. Changing film composition is correlated with a shift of the valence-band maximum only as the halide-lead ratio drops below 2.5. This delay is attributed to the invariance of MAPbI3 electronic structure to distributed defects that can significantly transform the electronic density of states only when in high concentrations.

  9. Congenital heart defect - corrective surgery

    MedlinePlus

    ... repair; Tetralogy of Fallot repair; Coarctation of the aorta repair; Atrial septal defect repair; Ventricular septal defect ... the pulmonary valve and removing the thickened muscle (stenosis). Placing a patch on the right ventricle and ...

  10. Birth Defects Data and Statistics

    MedlinePlus

    ... this? Submit Button Information For… Media Policy Makers Data & Statistics Recommend on Facebook Tweet Share Compartir On ... of birth defects in the United States. For data on specific birth defects, please visit the specific ...

  11. Guidance for Preventing Birth Defects

    MedlinePlus

    ... Prevention. Commit to Healthy Choices to Help Prevent Birth Defects Language: English (US) Español (Spanish) Recommend on ... Tweet Share Compartir We know that not all birth defects can be prevented. But, we also know ...

  12. Atrial Septal Defect (For Parents)

    MedlinePlus

    ... Defect Preparing Your Child for Surgery Heart and Circulatory System Anesthesia Basics Congenital Heart Defects Activity: The Heart ... EKG (Video) Going to the Hospital Your Heart & Circulatory System Quiz: Heart & Circulatory System EKG (Video) What's It ...

  13. Neural tube defects.

    PubMed

    Greene, Nicholas D E; Copp, Andrew J

    2014-01-01

    Neural tube defects (NTDs), including spina bifida and anencephaly, are severe birth defects of the central nervous system that originate during embryonic development when the neural tube fails to close completely. Human NTDs are multifactorial, with contributions from both genetic and environmental factors. The genetic basis is not yet well understood, but several nongenetic risk factors have been identified as have possibilities for prevention by maternal folic acid supplementation. Mechanisms underlying neural tube closure and NTDs may be informed by experimental models, which have revealed numerous genes whose abnormal function causes NTDs and have provided details of critical cellular and morphological events whose regulation is essential for closure. Such models also provide an opportunity to investigate potential risk factors and to develop novel preventive therapies.

  14. Controversies in Parotid Defect Reconstruction.

    PubMed

    Tamplen, Matthew; Knott, P Daniel; Fritz, Michael A; Seth, Rahul

    2016-08-01

    Reconstruction of the parotid defect is a complex topic that encompasses restoration of both facial form and function. The reconstructive surgeon must consider facial contour, avoidance of Frey syndrome, skin coverage, tumor surveillance, potential adjuvant therapy, and facial reanimation when addressing parotid defects. With each defect there are several options within the reconstructive ladder, creating controversies regarding optimal management. This article describes surgical approaches to reconstruction of parotid defects, highlighting areas of controversy.

  15. Molecular defects in the chondrodysplasias

    SciTech Connect

    Rimoin, D.L.

    1996-05-03

    There has been a recent explosion of knowledge concerning the biochemical and molecular defects in the skeletal dysplasia. Through both the candidate gene approach and positional cloning, specific gene defects that produce the skeletal dysplasia have been identified and may be classified into several general categories: (1) qualitative or quantitative abnormalities in the structural proteins of cartilage; (2) inborn errors of cartilage metabolism; (3) defects in local regulators of cartilage growth; and (4) systemic defects influencing cartilage development. 35 refs., 1 tab.

  16. Composite Defect Significance.

    DTIC Science & Technology

    1982-07-13

    A12i 299 COMPOSITE DEFECT SIGNIFICANCE(U) MATERIALS SCIENCES 1/1 \\ CORP SPRING HOUSE PA S N CHATTERJEE ET AL. 13 JUL 82 MSC/TFR/1288/il87 NADC-80848...Directorate 30 Sensors & Avionics Technology Directorate 40 Communication & Navigation Technology Directorate 50 Software Computer Directorate 60 Aircraft ...instructions concerning commercial products herein do not constitute an endorsement by the Government nor do they convey or imply the license or right to use

  17. Defective pyrite (100) surface: An ab initio study

    SciTech Connect

    Stirling, Andras; Bernasconi, Marco; Parrinello, Michele

    2007-04-15

    The structural and electronic properties of sulfur monomeric defects at the FeS{sub 2}(100) surface have been studied by periodic density-functional calculations. We have shown that for a monomeric sulfur bound to an originally fivefold coordinated surface Fe site, the defect core features a triplet electronic ground state with unpaired spins localized on the exposed Fe-S unit. At this site, the iron and sulfur ions have oxidation states +4 and -2, respectively. This defect can be seen as produced via heterolytic bond breaking of the S-S sulfur dimer followed by a Fe-S redox reaction. The calculated sulfur 2p core-level shifts of the monomeric defects are in good agreement with experimental photoemission spectra, which allow a compelling assignment of the different spectroscopic features. The effect of water on the stability of the defective surface has also been studied, and it has been shown that the triplet state is stable against the wetting of the surface. The most important implications of the presence of the monomeric sulfur defect on the reactivity are also discussed.

  18. Defect mapping system

    DOEpatents

    Sopori, B.L.

    1995-04-11

    Apparatus for detecting and mapping defects in the surfaces of polycrystalline materials in a manner that distinguishes dislocation pits from grain boundaries includes a laser for illuminating a wide spot on the surface of the material, a light integrating sphere with apertures for capturing light scattered by etched dislocation pits in an intermediate range away from specular reflection while allowing light scattered by etched grain boundaries in a near range from specular reflection to pass through, and optical detection devices for detecting and measuring intensities of the respective intermediate scattered light and near specular scattered light. A center blocking aperture or filter can be used to screen out specular reflected light, which would be reflected by nondefect portions of the polycrystalline material surface. An X-Y translation stage for mounting the polycrystalline material and signal processing and computer equipment accommodate rastor mapping, recording, and displaying of respective dislocation and grain boundary defect densities. A special etch procedure is included, which prepares the polycrystalline material surface to produce distinguishable intermediate and near specular light scattering in patterns that have statistical relevance to the dislocation and grain boundary defect densities. 20 figures.

  19. Defect mapping system

    DOEpatents

    Sopori, Bhushan L.

    1995-01-01

    Apparatus for detecting and mapping defects in the surfaces of polycrystalline materials in a manner that distinguishes dislocation pits from grain boundaries includes a laser for illuminating a wide spot on the surface of the material, a light integrating sphere with apertures for capturing light scattered by etched dislocation pits in an intermediate range away from specular reflection while allowing light scattered by etched grain boundaries in a near range from specular reflection to pass through, and optical detection devices for detecting and measuring intensities of the respective intermediate scattered light and near specular scattered light. A center blocking aperture or filter can be used to screen out specular reflected light, which would be reflected by nondefect portions of the polycrystalline material surface. An X-Y translation stage for mounting the polycrystalline material and signal processing and computer equipment accommodate rastor mapping, recording, and displaying of respective dislocation and grain boundary defect densities. A special etch procedure is included, which prepares the polycrystalline material surface to produce distinguishable intermediate and near specular light scattering in patterns that have statistical relevance to the dislocation and grain boundary defect densities.

  20. Defects at semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Henzler, Martin

    1985-04-01

    Low Energy Electron Diffraction (LEED) is widely used for detection of periodicity at the surface and of atom arrangement within the unit cell. Experiments and results, however, are increasing, which use the spot profile analysis (SPA-LEED) for the study of nonperiodic surfaces. Here the kinematical approximation provides a wider range of validity than expected. For semiconductors defects are especially important, since the surface states in the gap are determined or strongly influenced by almost any kind of defects at the surface. Atomic steps at the interface {Si}/{SiO2} have been shown to be correlated with many electronic properties of MOS devices like mobility, interface states and fixed charge. The epitaxy on Si and GaAs has been studied with LEED and RHEED, showing the density of the nuclei during formation of a layer and the layer-by-layer growth. The formation of metal suicides in the monolayer range is accompanied by many different superstructures and other rearrangements. It is demonstrated, that the new high resolution instruments provide additional qualitative and quantitative informations on any kind of surface defects.

  1. Mask Blank Defect Detection

    SciTech Connect

    Johnson, M A; Sommargren, G E

    2000-02-04

    Mask blanks are the substrates that hold the master patterns for integrated circuits. Integrated circuits are semiconductor devices, such as microprocessors (mPs), dynamic random access memory (DRAMs), and application specific integrated circuits (ASICs) that are central to the computer, communication, and electronics industries. These devices are fabricated using a set of master patterns that are sequentially imaged onto light-sensitive coated silicon wafers and processed to form thin layers of insulating and conductive materials on top of the wafer. These materials form electrical paths and transistors that control the flow of electricity through the device. For the past forty years the semiconductor industry has made phenomenal improvements in device functionality, compactness, speed, power, and cost. This progress is principally due to the exponential decrease in the minimum feature size of integrated circuits, which has been reduced by a factor of {radical}2 every three years. Since 1992 the Semiconductor Industry Association (SIA) has coordinated the efforts of producing a technology roadmap for semiconductors. In the latest document, ''The International Technology Roadmap for Semiconductors: 1999'', future technology nodes (minimum feature sizes) and targeted dates were specified and are summarized in Table 1. Lithography is the imaging technology for producing a de-magnified image of the mask on the wafer. A typical de-magnification factor is 4. Mask blank defects as small as one-eighth the equivalent minimum feature size are printable and may cause device failure. Defects might be the result of the surface preparation, such as polishing, or contamination due to handling or the environment. Table 2 shows the maximum tolerable defect sizes on the mask blank for each technology node. This downward trend puts a tremendous burden on mask fabrication, particularly in the area of defect detection and reduction. A new infrastructure for mask inspection will be

  2. Impurity bound states in fully gapped d-wave superconductors with subdominant order parameters

    NASA Astrophysics Data System (ADS)

    Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica M.

    2017-03-01

    Impurities in superconductors and their induced bound states are important both for engineering novel states such as Majorana zero-energy modes and for probing bulk properties of the superconducting state. The high-temperature cuprates offer a clear advantage in a much larger superconducting order parameter, but the nodal energy spectrum of a pure d-wave superconductor only allows virtual bound states. Fully gapped d-wave superconducting states have, however, been proposed in several cuprate systems thanks to subdominant order parameters producing d + is- or d + id‧-wave superconducting states. Here we study both magnetic and potential impurities in these fully gapped d-wave superconductors. Using analytical T-matrix and complementary numerical tight-binding lattice calculations, we show that magnetic and potential impurities behave fundamentally different in d + is- and d + id‧-wave superconductors. In a d + is-wave superconductor, there are no bound states for potential impurities, while a magnetic impurity produces one pair of bound states, with a zero-energy level crossing at a finite scattering strength. On the other hand, a d + id‧-wave symmetry always gives rise to two pairs of bound states and only produce a reachable zero-energy level crossing if the normal state has a strong particle-hole asymmetry.

  3. Impurity bound states in fully gapped d-wave superconductors with subdominant order parameters

    PubMed Central

    Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica M.

    2017-01-01

    Impurities in superconductors and their induced bound states are important both for engineering novel states such as Majorana zero-energy modes and for probing bulk properties of the superconducting state. The high-temperature cuprates offer a clear advantage in a much larger superconducting order parameter, but the nodal energy spectrum of a pure d-wave superconductor only allows virtual bound states. Fully gapped d-wave superconducting states have, however, been proposed in several cuprate systems thanks to subdominant order parameters producing d + is- or d + id′-wave superconducting states. Here we study both magnetic and potential impurities in these fully gapped d-wave superconductors. Using analytical T-matrix and complementary numerical tight-binding lattice calculations, we show that magnetic and potential impurities behave fundamentally different in d + is- and d + id′-wave superconductors. In a d + is-wave superconductor, there are no bound states for potential impurities, while a magnetic impurity produces one pair of bound states, with a zero-energy level crossing at a finite scattering strength. On the other hand, a d + id′-wave symmetry always gives rise to two pairs of bound states and only produce a reachable zero-energy level crossing if the normal state has a strong particle-hole asymmetry. PMID:28281570

  4. Impurity bound states in fully gapped d-wave superconductors with subdominant order parameters.

    PubMed

    Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica M

    2017-03-10

    Impurities in superconductors and their induced bound states are important both for engineering novel states such as Majorana zero-energy modes and for probing bulk properties of the superconducting state. The high-temperature cuprates offer a clear advantage in a much larger superconducting order parameter, but the nodal energy spectrum of a pure d-wave superconductor only allows virtual bound states. Fully gapped d-wave superconducting states have, however, been proposed in several cuprate systems thanks to subdominant order parameters producing d + is- or d + id'-wave superconducting states. Here we study both magnetic and potential impurities in these fully gapped d-wave superconductors. Using analytical T-matrix and complementary numerical tight-binding lattice calculations, we show that magnetic and potential impurities behave fundamentally different in d + is- and d + id'-wave superconductors. In a d + is-wave superconductor, there are no bound states for potential impurities, while a magnetic impurity produces one pair of bound states, with a zero-energy level crossing at a finite scattering strength. On the other hand, a d + id'-wave symmetry always gives rise to two pairs of bound states and only produce a reachable zero-energy level crossing if the normal state has a strong particle-hole asymmetry.

  5. Study of lattice defect vibration

    NASA Technical Reports Server (NTRS)

    Elliott, R. J.

    1969-01-01

    Report on the vibrations of defects in crystals relates how defects, well localized in a crystal but interacting strongly with the other atoms, change the properties of a perfect crystal. The methods used to solve defect problems relate the properties of an imperfect lattice to the properties of a perfect lattice.

  6. Classification of two-dimensional topological crystalline superconductors and Majorana bound states at disclinations

    NASA Astrophysics Data System (ADS)

    Benalcazar, Wladimir A.; Teo, Jeffrey C. Y.; Hughes, Taylor L.

    2014-06-01

    We classify discrete-rotation symmetric topological crystalline superconductors (TCS) in two dimensions and provide the criteria for a zero-energy Majorana bound state (MBS) to be present at composite defects made from magnetic flux, dislocations, and disclinations. In addition to the Chern number that encodes chirality, discrete rotation symmetry further divides TCS into distinct stable topological classes according to the rotation eigenspectrum of Bogoliubov-de Gennes quasiparticles. Conical crystalline defects are shown to be able to accommodate robust MBS when a certain combination of these bulk topological invariants is nontrivial as dictated by the index theorems proved within. The number parity of MBS is counted by a Z2-valued index that solely depends on the disclination and the topological class of the TCS. We also discuss the implications for corner-bound Majorana modes on the boundary of topological crystalline superconductors.

  7. Soliton-like defects in nematic liquid crystal thin layers

    NASA Astrophysics Data System (ADS)

    Chuvyrov, A. N.; Krekhov, A. P.; Lebedev, Yu. A.; Timirov, Yu. I.

    2016-11-01

    The nonsingular soliton-like defects in plane nematic liquid crystal (NLC) layers and spherical NLC drops are experimentally detected and studied when the interaction of NLC molecules with a bounding surface is varied. The dynamics and the annihilation of nonsingular defects of opposite signs on a plane surface are investigated. Periodic transformations of the soliton-like defects in NLC drops in an electric field are detected. The theory of elasticity is used to show that the surface energy taken into account in the total free energy of NLC in the case of weak anchoring leads to the possibility of nonsingular solutions of a director equilibrium equation. The calculated pictures of director distribution in a plane NLC layer and in a spherical NLC drop characterized by weak surface anchoring agree well with the results of polarized light optical observations.

  8. Soliton-like defects in nematic liquid crystal thin layers

    SciTech Connect

    Chuvyrov, A. N.; Krekhov, A. P.; Lebedev, Yu. A. Timirov, Yu. I.

    2016-11-15

    The nonsingular soliton-like defects in plane nematic liquid crystal (NLC) layers and spherical NLC drops are experimentally detected and studied when the interaction of NLC molecules with a bounding surface is varied. The dynamics and the annihilation of nonsingular defects of opposite signs on a plane surface are investigated. Periodic transformations of the soliton-like defects in NLC drops in an electric field are detected. The theory of elasticity is used to show that the surface energy taken into account in the total free energy of NLC in the case of weak anchoring leads to the possibility of nonsingular solutions of a director equilibrium equation. The calculated pictures of director distribution in a plane NLC layer and in a spherical NLC drop characterized by weak surface anchoring agree well with the results of polarized light optical observations.

  9. On the recombination centers of iron-gallium pairs in Ga-doped silicon

    NASA Astrophysics Data System (ADS)

    Nærland, Tine Uberg; Bernardini, Simone; Haug, Halvard; Grini, Sigbjørn; Vines, Lasse; Stoddard, Nathan; Bertoni, Mariana

    2017-08-01

    Gallium (Ga) doped silicon (Si) is becoming a relevant player in solar cell manufacturing thanks to its demonstrated low light-induced degradation, yet little is known about Ga-related recombination centers. In this paper, we study iron (Fe)-related recombination centers in as-grown, high quality, directionally solidified, monocrystalline Ga-doped Si. While no defect states could be detected by deep level transient spectroscopy, lifetime spectroscopy analysis shows that the minority carrier lifetime in as-grown wafers is dominated by low levels of FeGa related defect complexes. FeGa pairs have earlier been shown to occur in two different structural configurations. Herein, we show that in terms of recombination strength, the orthorhombic pair-configuration is dominant over the trigonal pair-configuration for FeGa. Furthermore, the defect energy level in the band gap for the orthorhombic defect center is determined to be EV + 0.09 eV, and the capture cross-section ratio of the same defect center is determined to be 220.

  10. Exploring Subclinical Phenotypic Features in Twin Pairs Discordant for Cleft Lip and Palate

    PubMed Central

    Leslie, Elizabeth J.; Carlson, Jenna C.; Cooper, Margaret E.; Christensen, Kaare; Weinberg, Seth M.; Marazita, Mary L.

    2016-01-01

    Objective Monozygotic twins of an individual with an orofacial cleft have a significantly elevated risk for orofacial cleft compared with the general population, but still the concordance rate for orofacial cleft in monozygotic twins is about 40% to 50%. The goal of this study was to determine whether unaffected cotwins have an increased frequency of orbicularis oris muscle defects, a subclinical form of orofacial cleft. The presence of such defects may reduce the overall rate of discordance. Method A total of 63 discordant monozygotic and dizygotic twin pairs, 262 unaffected nontwin siblings, and 543 controls with no history of orofacial clefts were assessed for orbicularis oris defects by high-resolution ultrasound. Frequencies were compared by the Fisher exact test. Results Unaffected cotwins from discordant monozygotic pairs had a higher frequency of defects (12.5%) than the other test groups (6.38% to 6.99%), but the difference was not statistically significant (P = .74). Conclusions In this study, orbicularis oris defects were not statistically significantly more common among the unaffected twins from orofacial cleft discordant twin pairs. The trends in the results warrant future studies with larger sample sizes and additional subclinical phenotypes. PMID:26882109

  11. Exploring Subclinical Phenotypic Features in Twin Pairs Discordant for Cleft Lip and Palate.

    PubMed

    Leslie, Elizabeth J; Carlson, Jenna C; Cooper, Margaret E; Christensen, Kaare; Weinberg, Seth M; Marazita, Mary L

    2017-01-01

      Monozygotic twins of an individual with an orofacial cleft have a significantly elevated risk for orofacial cleft compared with the general population, but still the concordance rate for orofacial cleft in monozygotic twins is about 40% to 50%. The goal of this study was to determine whether unaffected cotwins have an increased frequency of orbicularis oris muscle defects, a subclinical form of orofacial cleft. The presence of such defects may reduce the overall rate of discordance.   A total of 63 discordant monozygotic and dizygotic twin pairs, 262 unaffected nontwin siblings, and 543 controls with no history of orofacial clefts were assessed for orbicularis oris defects by high-resolution ultrasound. Frequencies were compared by the Fisher exact test.   Unaffected cotwins from discordant monozygotic pairs had a higher frequency of defects (12.5%) than the other test groups (6.38% to 6.99%), but the difference was not statistically significant (P = .74).   In this study, orbicularis oris defects were not statistically significantly more common among the unaffected twins from orofacial cleft discordant twin pairs. The trends in the results warrant future studies with larger sample sizes and additional subclinical phenotypes.

  12. Collisions of Vortex Filament Pairs

    NASA Astrophysics Data System (ADS)

    Banica, Valeria; Faou, Erwan; Miot, Evelyne

    2014-12-01

    We consider the problem of collisions of vortex filaments for a model introduced by Klein et al. (J Fluid Mech 288:201-248, 1995) and Zakharov (Sov Phys Usp 31(7):672-674, 1988, Lect. Notes Phys 536:369-385, 1999) to describe the interaction of almost parallel vortex filaments in three-dimensional fluids. Since the results of Crow (AIAA J 8:2172-2179, 1970) examples of collisions are searched as perturbations of antiparallel translating pairs of filaments, with initial perturbations related to the unstable mode of the linearized problem; most results are numerical calculations. In this article, we first consider a related model for the evolution of pairs of filaments, and we display another type of initial perturbation leading to collision in finite time. Moreover, we give numerical evidence that it also leads to collision through the initial model. We finally study the self-similar solutions of the model.

  13. Origin of transionospheric pulse pairs

    NASA Astrophysics Data System (ADS)

    Wu, H.-C.

    2017-03-01

    Transionospheric pulse pairs, associated with lightning, are the most powerful natural radio signals on Earth. Although they were discovered over two decades ago by satellites, their origin remains elusive. Here we attribute these radio signals to relativistic electrons generated by cloud-to-ground lightning. When these electrons strike the ground, radio bursts are emitted toward space within a narrow cone. This model naturally explains the interval, duration, polarization, coherence, and bimodal feature of the pulse pairs. Based on electron parameters inferred from X-ray observations of lightning, we find that the calculated signal intensity agrees with satellite measurements. Our results can be applied to the development of a global warning system for storms and hurricanes using GPS satellites.

  14. Properties of the zero-energy Andreev bound state in a two-sublattice SNS junction

    NASA Astrophysics Data System (ADS)

    Setty, Chandan; Hu, Jiangping

    2016-05-01

    We study properties of the zero energy Andreev bound state in a superconductor-normal metal-superconductor (SNS) junction consisting of two intrinsic degrees of freedom. The superconductors on either sides of the normal metal are assumed to have two sublattices with an intra-sublattice pairing with a phase equal to zero or π between the two sublattices. In addition, we add a uniform inter-sublattice pairing and study its effect on the local density of states (LDOS). In particular, we find that as the inter-sublattice pairing is turned on, the zero-bias peak (ZBP) is unstable (robust) when the phase difference across the sublattices is π (zero). We discuss the relevance of our results to the recently proposed odd-parity η pairing ground states in iron-based superconductors (FeSCs).

  15. Asymmetric Ion-Pairing Catalysis

    PubMed Central

    Brak, Katrien

    2014-01-01

    Charged intermediates and reagents are ubiquitous in organic transformations. The interaction of these ionic species with chiral neutral, anionic, or cationic small molecules has emerged as a powerful strategy for catalytic, enantioselective synthesis. This review describes developments in the burgeoning field of asymmetric ion-pairing catalysis with an emphasis on the insights that have been gleaned into the structural and mechanistic features that contribute to high asymmetric induction. PMID:23192886

  16. Septin pairs, a complex choreography.

    PubMed

    Ewers, Helge

    2011-06-13

    Septins form a filamentous collar at the mother-bud neck in budding yeast. In cytokinesis, this collar splits into two rings and the septin complexes undergo a dramatic reorientation. Using fluorescence polarization microscopy, DeMay et al. (2011. J. Cell Biol. doi:10.1083/jcb.201012143) now demonstrate that septin complexes assemble as paired filaments in vivo and reveal new insights into septin organization during cytokinesis.

  17. Conductivity bound from dirty black holes

    NASA Astrophysics Data System (ADS)

    Bitaghsir Fadafan, Kazem

    2016-11-01

    We propose a lower bound of the dc electrical conductivity in strongly disordered, strongly interacting quantum field theories using holography. We study linear response of black holes with broken translational symmetry in Einstein-Maxwell-dilaton theories of gravity. Using the generalized Stokes equations at the horizon, we derive the lower bound of the electrical conductivity for the dual two dimensional disordered field theory.

  18. THE HOPF BIFURCATION WITH BOUNDED NOISE

    PubMed Central

    Botts, Ryan T.; Homburg, Ale Jan; Young, Todd R.

    2012-01-01

    We study Hopf-Andronov bifurcations in a class of random differential equations (RDEs) with bounded noise. We observe that when an ordinary differential equation that undergoes a Hopf bifurcation is subjected to bounded noise then the bifurcation that occurs involves a discontinuous change in the Minimal Forward Invariant set. PMID:24748762

  19. Outward Bound: an Experience in Human Development

    ERIC Educational Resources Information Center

    Danenburg, William; Gaggi, Silvio

    1974-01-01

    Two authors describe how their participation in an outward bound program has helped them develop a greater degree of general self confidence, greater ease in dealing with complex and frustrating problems, and a greater appreciation of man's place in the natural environment. They also describe Outward Bound courses that have been especially…

  20. Outward Bound: An Innovative Patient Education Program.

    ERIC Educational Resources Information Center

    Stich, Thomas F.; Gaylor, Michael S.

    A 1975 Dartmouth Outward Bound Mental Health Project, begun with a pilot project for disturbed adolescents, has evolved into an ongoing treatment option in three separate clinical settings for psychiatric patients and recovering alcoholics. Outward Bound consists of a series of prescribed physical and social tasks where the presence of stress,…

  1. Generalized upper bound for inelastic diffraction

    NASA Astrophysics Data System (ADS)

    Troshin, S. M.; Tyurin, N. E.

    2017-01-01

    For inelastic diffraction, we obtain an upper bound valid for the whole range of the elastic scattering amplitude variation allowed by unitarity. We discuss the energy dependence of the inelastic diffractive cross-section on the base of this bound and recent Large Hadron Collider (LHC) data.

  2. THE HOPF BIFURCATION WITH BOUNDED NOISE.

    PubMed

    Botts, Ryan T; Homburg, Ale Jan; Young, Todd R

    2012-08-01

    We study Hopf-Andronov bifurcations in a class of random differential equations (RDEs) with bounded noise. We observe that when an ordinary differential equation that undergoes a Hopf bifurcation is subjected to bounded noise then the bifurcation that occurs involves a discontinuous change in the Minimal Forward Invariant set.

  3. Outward Bound: An Innovative Patient Education Program.

    ERIC Educational Resources Information Center

    Stich, Thomas F.; Gaylor, Michael S.

    A 1975 Dartmouth Outward Bound Mental Health Project, begun with a pilot project for disturbed adolescents, has evolved into an ongoing treatment option in three separate clinical settings for psychiatric patients and recovering alcoholics. Outward Bound consists of a series of prescribed physical and social tasks where the presence of stress,…

  4. A lower bound for the QRQW PRAM

    SciTech Connect

    MacKenzie, P.D.

    1995-05-02

    The queue-read, queue-write (QRQW) parallel random access machine (PRAM) model is a shared memory model which allows concurrent reading and writing with a time cost proportional to the contention. This is designed to model currently available parallel machines more accurately than either the CRCW PRAM or EREW PRAM models. Many algorithmic results have been developed for the QRQW PRAM. However, the only lower bound results have been fairly simple reductions from lower bounds for other models, such as the EREW PRAM or the ``few-write`` CREW PRAM. Here we present a lower bound specific to the QRQW PRAM. This lower bound is on the problem of Linear Approximate Compaction (LAC), whose input consists of at most m marked items in an array of size n, and whose output consists of the rn marked items in an array of size 0(m). There is an O({radical}log n), expected time randomized algorithm for LAC on the QRQW PRAM. We prove a lower bound of {Omega}(log log log n) expected time for any randomized algorithm for LAC. This bound applies regardless of the number of processors and memory cells of the QRQW PRAM. The previous best lower bound was {Omega}(log* n) time, taken from the known lower bound for LAC on the CRCW PRAM.

  5. Experimental Evidence for Bounds on Quantum Correlations

    NASA Astrophysics Data System (ADS)

    Bovino, F. A.; Castagnoli, G.; Degiovanni, I. P.; Castelletto, S.

    2004-02-01

    We implemented the experiment proposed by Cabello in the preceding Letter to test the bounds of quantum correlation. As expected from the theory we found that, for certain choices of local observables, Tsirelson's bound of the Clauser-Horne-Shimony-Holt inequality (2√(2)) is not reached by any quantum states.

  6. Weakly bound states of the He-He-Ca triatomic system

    NASA Astrophysics Data System (ADS)

    Gou, Qingdong; Li, Yong

    2012-01-01

    We investigate for the existence of the weakly bound He-He-Ca molecules. By employing the best empirical interaction between each pair of particles, the Schrödinger equation for the triatomic system is solved using hyperspherical coordinates in the adiabatic approximation. The bound states are found for each of the 3He-3He-40Ca, 3He-4He-40Ca, and 4He-4He-40Ca trimers, respectively. The binding energies of such molecules are estimated. We discuss the features of the channel functions associated with the hyperspherical potential curves of each system to obtain insight into the geometry of the molecules.

  7. Mediators of homologous DNA pairing.

    PubMed

    Zelensky, Alex; Kanaar, Roland; Wyman, Claire

    2014-10-09

    Homologous DNA pairing and strand exchange are at the core of homologous recombination. These reactions are promoted by a DNA-strand-exchange protein assembled into a nucleoprotein filament comprising the DNA-pairing protein, ATP, and single-stranded DNA. The catalytic activity of this molecular machine depends on control of its dynamic instability by accessory factors. Here we discuss proteins known as recombination mediators that facilitate formation and functional activation of the DNA-strand-exchange protein filament. Although the basics of homologous pairing and DNA-strand exchange are highly conserved in evolution, differences in mediator function are required to cope with differences in how single-stranded DNA is packaged by the single-stranded DNA-binding protein in different species, and the biochemical details of how the different DNA-strand-exchange proteins nucleate and extend into a nucleoprotein filament. The set of (potential) mediator proteins has apparently expanded greatly in evolution, raising interesting questions about the need for additional control and coordination of homologous recombination in more complex organisms. Copyright © 2014 Cold Spring Harbor Laboratory Press; all rights reserved.

  8. Mediators of Homologous DNA Pairing

    PubMed Central

    Zelensky, Alex; Kanaar, Roland; Wyman, Claire

    2014-01-01

    Homologous DNA pairing and strand exchange are at the core of homologous recombination. These reactions are promoted by a DNA-strand-exchange protein assembled into a nucleoprotein filament comprising the DNA-pairing protein, ATP, and single-stranded DNA. The catalytic activity of this molecular machine depends on control of its dynamic instability by accessory factors. Here we discuss proteins known as recombination mediators that facilitate formation and functional activation of the DNA-strand-exchange protein filament. Although the basics of homologous pairing and DNA-strand exchange are highly conserved in evolution, differences in mediator function are required to cope with differences in how single-stranded DNA is packaged by the single-stranded DNA-binding protein in different species, and the biochemical details of how the different DNA-strand-exchange proteins nucleate and extend into a nucleoprotein filament. The set of (potential) mediator proteins has apparently expanded greatly in evolution, raising interesting questions about the need for additional control and coordination of homologous recombination in more complex organisms. PMID:25301930

  9. Covariant entropy bound and loop quantum cosmology

    SciTech Connect

    Ashtekar, Abhay; Wilson-Ewing, Edward

    2008-09-15

    We examine Bousso's covariant entropy bound conjecture in the context of radiation filled, spatially flat, Friedmann-Robertson-Walker models. The bound is violated near the big bang. However, the hope has been that quantum gravity effects would intervene and protect it. Loop quantum cosmology provides a near ideal setting for investigating this issue. For, on the one hand, quantum geometry effects resolve the singularity and, on the other hand, the wave function is sharply peaked at a quantum corrected but smooth geometry, which can supply the structure needed to test the bound. We find that the bound is respected. We suggest that the bound need not be an essential ingredient for a quantum gravity theory but may emerge from it under suitable circumstances.

  10. Upper bounds on sequential decoding performance parameters

    NASA Technical Reports Server (NTRS)

    Jelinek, F.

    1974-01-01

    This paper presents the best obtainable random coding and expurgated upper bounds on the probabilities of undetectable error, of t-order failure (advance to depth t into an incorrect subset), and of likelihood rise in the incorrect subset, applicable to sequential decoding when the metric bias G is arbitrary. Upper bounds on the Pareto exponent are also presented. The G-values optimizing each of the parameters of interest are determined, and are shown to lie in intervals that in general have nonzero widths. The G-optimal expurgated bound on undetectable error is shown to agree with that for maximum likelihood decoding of convolutional codes, and that on failure agrees with the block code expurgated bound. Included are curves evaluating the bounds for interesting choices of G and SNR for a binary-input quantized-output Gaussian additive noise channel.

  11. Mutually unbiased bases and bound entanglement

    NASA Astrophysics Data System (ADS)

    Hiesmayr, Beatrix C.; Löffler, Wolfgang

    2014-04-01

    In this contribution we relate two different key concepts: mutually unbiased bases (MUBs) and entanglement. We provide a general toolbox for analyzing and comparing entanglement of quantum states for different dimensions and numbers of particles. In particular we focus on bound entanglement, i.e. highly mixed states which cannot be distilled by local operations and classical communications. For a certain class of states—for which the state-space forms a ‘magic’ simplex—we analyze the set of bound entangled states detected by the MUB criterion for different dimensions d and number of particles n. We find that the geometry is similar for different d and n, consequently the MUB criterion opens possibilities to investigate the typicality of positivity under partial transposition (PPT)-bound and multipartite bound entanglement more deeply and provides a simple experimentally feasible tool to detect bound entanglement.

  12. Rigorous bounds for optimal dynamical decoupling

    SciTech Connect

    Uhrig, Goetz S.; Lidar, Daniel A.

    2010-07-15

    We present rigorous performance bounds for the optimal dynamical decoupling pulse sequence protecting a quantum bit (qubit) against pure dephasing. Our bounds apply under the assumption of instantaneous pulses and of bounded perturbing environment and qubit-environment Hamiltonians such as those realized by baths of nuclear spins in quantum dots. We show that if the total sequence time is fixed the optimal sequence can be used to make the distance between the protected and unperturbed qubit states arbitrarily small in the number of applied pulses. If, on the other hand, the minimum pulse interval is fixed and the total sequence time is allowed to scale with the number of pulses, then longer sequences need not always be advantageous. The rigorous bound may serve as a testbed for approximate treatments of optimal decoupling in bounded models of decoherence.

  13. Disclinations, dislocations, and continuous defects: A reappraisal

    NASA Astrophysics Data System (ADS)

    Kleman, M.; Friedel, J.

    2008-01-01

    Disclinations were first observed in mesomorphic phases. They were later found relevant to a number of ill-ordered condensed-matter media involving continuous symmetries or frustrated order. Disclinations also appear in polycrystals at the edges of grain boundaries; but they are of limited interest in solid single crystals, where they can move only by diffusion climb and, owing to their large elastic stresses, mostly appear in close pairs of opposite signs. The relaxation mechanisms associated with a disclination in its creation, motion, and change of shape involve an interplay with continuous or quantized dislocations and/or continuous disclinations. These are attached to the disclinations or are akin to Nye’s dislocation densities, which are particularly well suited for consideration here. The notion of an extended Volterra process is introduced, which takes these relaxation processes into account and covers different situations where this interplay takes place. These concepts are illustrated by a variety of applications in amorphous solids, mesomorphic phases, and frustrated media in their curved habit space. These often involve disclination networks with specific node conditions. The powerful topological theory of line defects considers only defects stable against any change of boundary conditions or relaxation processes compatible with the structure considered. It can be seen as a simplified case of the approach considered here, particularly suited for media of high plasticity or/and complex structures. It cannot analyze the dynamical properties of defects nor the elastic constants involved in their static properties; topological stability cannot guarantee energetic stability, and sometimes cannot distinguish finer details of the structure of defects.

  14. Thermal properties of defective fullerene

    NASA Astrophysics Data System (ADS)

    Li, Jian; Zheng, Dong-Qin; Zhong, Wei-Rong

    2016-09-01

    We have investigated the thermal conductivity of defective fullerene (C60) by using the nonequilibrium molecular dynamics (MD) method. It is found that the thermal conductivity of C60 with one defect is lower than the thermal conductivity of perfect C60. However, double defects in C60 have either positive or negative influence on the thermal conductivity, which depends on the positions of the defects. The phonon spectra of perfect and defective C60 are also provided to give corresponding supports. Our results can be extended to long C60 chains, which is helpful for the thermal management of C60.

  15. Germination-defective mutant of Neurospora crassa that responds to siderophores

    NASA Technical Reports Server (NTRS)

    Charlang, G.; Williams, N. P.

    1977-01-01

    A conditionally germination-defective mutant of Neurospora crassa has been found to be partially curable by ferricrocin and other siderophores. The mutant conidia rapidly lose their membrane-bound siderophores when suspended in buffer or growth media. Germination is consequently delayed unless large numbers of conidia are present (positive population effect). This indicates that the mutant has a membrane defect involving the siderophore attachment site.

  16. Germination-defective mutant of Neurospora crassa that responds to siderophores

    NASA Technical Reports Server (NTRS)

    Charlang, G.; Williams, N. P.

    1977-01-01

    A conditionally germination-defective mutant of Neurospora crassa has been found to be partially curable by ferricrocin and other siderophores. The mutant conidia rapidly lose their membrane-bound siderophores when suspended in buffer or growth media. Germination is consequently delayed unless large numbers of conidia are present (positive population effect). This indicates that the mutant has a membrane defect involving the siderophore attachment site.

  17. Stabilization of primary mobile radiation defects in MgF2 crystals

    NASA Astrophysics Data System (ADS)

    Lisitsyn, V. M.; Lisitsyna, L. A.; Popov, A. I.; Kotomin, E. A.; Abuova, F. U.; Akilbekov, A.; Maier, J.

    2016-05-01

    Non-radiative decay of the electronic excitations (excitons) into point defects (F-H pairs of Frenkel defects) is main radiation damage mechanism in many ionic (halide) solids. Typical time scale of the relaxation of the electronic excitation into a primary, short-lived defect pair is about 1-50 ps with the quantum yield up to 0.2-0.8. However, only a small fraction of these primary defects are spatially separated and survive after transformation into stable, long-lived defects. The survival probability (or stable defect accumulation efficiency) can differ by orders of magnitude, dependent on the material type; e.g. ∼10% in alkali halides with f.c.c. or b.c.c. structure, 0.1% in rutile MgF2 and <0.001% in fluorides MeF2 (Me: Ca, Sr, Ba). The key factor determining accumulation of stable radiation defects is stabilization of primary defects, first of all, highly mobile hole H centers, through their transformation into more complex immobile defects. In this talk, we present the results of theoretical calculations of the migration energies of the F and H centers in poorely studied MgF2 crystals with a focus on the H center stabilization in the form of the interstitial F2 molecules which is supported by presented experimental data.

  18. Bound-free Spectra for Diatomic Molecules

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.

    2012-01-01

    It is now recognized that prediction of radiative heating of entering space craft requires explicit treatment of the radiation field from the infrared (IR) to the vacuum ultra violet (VUV). While at low temperatures and longer wavelengths, molecular radiation is well described by bound-bound transitions, in the short wavelength, high temperature regime, bound-free transitions can play an important role. In this work we describe first principles calculations we have carried out for bound-bound and bound-free transitions in N2, O2, C2, CO, CN, NO, and N2+. Compared to bound ]bound transitions, bound-free transitions have several particularities that make them different to deal with. These include more complicated line shapes and a dependence of emission intensity on both bound state diatomic and atomic concentrations. These will be discussed in detail below. The general procedure we used was the same for all species. The first step is to generate potential energy curves, transition moments, and coupling matrix elements by carrying out ab initio electronic structure calculations. These calculations are expensive, and thus approximations need to be made in order to make the calculations tractable. The only practical method we have to carry out these calculations is the internally contracted multi-reference configuration interaction (icMRCI) method as implemented in the program suite Molpro. This is a widely used method for these kinds of calculations, and is capable of generating very accurate results. With this method, we must first of choose which electrons to correlate, the one-electron basis to use, and then how to generate the molecular orbitals.

  19. Topological Defects by Size Polydispersity

    NASA Astrophysics Data System (ADS)

    Yao, Zhenwei; Olvera de La Cruz, Monica

    2014-03-01

    The engineering of defects in crystalline matter introduces entirely new physical properties of materials. The fascinating possible applications of defects, known as topological defects, provide great motivations to perform fundamental investigations to uncover their role on the physical properties of various systems. Here we investigate topological defects in size polydispersity on flat surfaces. Our simulations show that in polydispersed systems topological defects play the role of order-restoring. The perfect hexagonal lattice beyond a small defective region around the impurity particle is well protected. Moreover, size polydispersity is shown numerically here to be an essential ingredient to understand short-range attractions between like-charge disclinations. Our study suggests the promising potential of size polydispersity to engineer defects in real systems. We thank the support of the Office of the Secretary of Defense under the NSSEFF program award number FA9550-10-1-0167.

  20. Biomechanical characteristics of osteochondral defects of the humeral capitellum.

    PubMed

    Mihata, Teruhisa; Quigley, Ryan; Robicheaux, Grant; McGarry, Michelle H; Neo, Masashi; Lee, Thay Q

    2013-08-01

    The repetitive, excessive compression forces in the radiocapitellar joint caused by elbow valgus stresses during throwing motions can result in osteochondritis dissecans (OCD) of the humeral capitellum in adolescent athletes. To assess the effect of elbow valgus torque on contact pressure in the radiocapitellar joint and that of central and lateral capitellar osteochondral defects on radiocapitellar joint contact pressure, elbow valgus laxity, and ulnar collateral ligament (UCL) strain. Controlled laboratory study. In 8 matched pairs of fresh-frozen cadaveric upper limbs, lateral osteochondral defects of the humeral capitellum (5-, 10-, 15-, and 20-mm diameters) were evaluated in one side, and central defects were evaluated in the contralateral side. Radiocapitellar joint contact pressure, elbow valgus laxity, and UCL strain were all measured with and without 2 N·m of valgus torque at 30°, 60°, and 90° of elbow flexion in neutral forearm rotation. Applying valgus torque increased contact pressure in radiocapitellar joints with intact or damaged capitula. Contact pressure in joints with 15-mm (90° of elbow flexion) and 20-mm (60° and 90° of elbow flexion) lateral capitellar defects was greater than that in joints with intact capitula. Radiocapitellar contact pressure was greater with a 20-mm lateral capitellar defect than in the same-sized central defect at 60° and 90° of elbow flexion. In both central and lateral defect groups, elbow valgus laxity increased as the size of the capitellar defect increased, and UCL strain remained unchanged regardless of the size of the capitellar defect. Elbow valgus torque increases contact pressure in the radiocapitellar joint. Capitellar osteochondral defects increase elbow valgus laxity and contact pressure without increasing UCL strain. When valgus torque is applied, contact pressure in the radiocapitellar joint is greater with a lateral defect than with a central defect. Adolescent baseball players with capitellar OCD

  1. Tunable odd-frequency triplet pairing states and skyrmion modes in chiral p-wave superconductor.

    PubMed

    Lou, Yu-Feng; Wen, Lin; Zha, Guo-Qiao; Zhou, Shi-Ping

    2017-08-29

    Bogliubov-de Gennes equations are solved self-consistently to investigate the properties of bound states in chiral p-wave superconductive disks. It shows that either an s-wave or the mixed d- and s-wave state with odd-frequency and spin-triplet symmetry is induced at the vortex core, depending both on the chirality of the pairing states and on the vortex topology. It is also found that the odd-frequency triplet even parity (OTE) bound state can be manipulated with a local non-magnetic potential. Interestingly, with an appropriate potential amplitude, the zero-energy OTE bound state can be stabilized at a distance from the vortex core and from the local potential. Possible existences of the Majorana fermion modes are expected if the particle-hole symmetry property is applied to the zero-energy OTE bound state. Moreover, skyrmion modes with an integer topological charge have been found to exist.

  2. Single ventricle cardiac defect.

    PubMed

    Eren, Bulent; Turkmen, Nursel; Turkmen, Nurset; Fedakar, Recep; Senel, Berna; Cetin, Volkan; Cetin, Volkn

    2010-05-01

    Single ventricle heart is defined as a rare cardiac abnormality with a single ventricle chamber involving diverse functional and physiological defects. Our case is of a ten month-old baby boy who died shortly after admission to the hospital due to vomiting and diarrhoea. Autopsy findings revealed cyanosis of finger nails and ears. Internal examination revealed; large heart, weighing 60 grams, single ventricle, without a septum and upper membranous part. Single ventricle is a rare pathology, hence, this paper aims to discuss this case from a medico-legal point of view.

  3. Dynamic nuclear polarization of membrane proteins: covalently bound spin-labels at protein-protein interfaces.

    PubMed

    Wylie, Benjamin J; Dzikovski, Boris G; Pawsey, Shane; Caporini, Marc; Rosay, Melanie; Freed, Jack H; McDermott, Ann E

    2015-04-01

    We demonstrate that dynamic nuclear polarization of membrane proteins in lipid bilayers may be achieved using a novel polarizing agent: pairs of spin labels covalently bound to a protein of interest interacting at an intermolecular interaction surface. For gramicidin A, nitroxide tags attached to the N-terminal intermolecular interface region become proximal only when bimolecular channels forms in the membrane. We obtained signal enhancements of sixfold for the dimeric protein. The enhancement effect was comparable to that of a doubly tagged sample of gramicidin C, with intramolecular spin pairs. This approach could be a powerful and selective means for signal enhancement in membrane proteins, and for recognizing intermolecular interfaces.

  4. Theoretical study of transition-metal ions bound to benzene

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Langhoff, Stephen R.

    1992-01-01

    Theoretical binding energies are reported for all first-row and selected second-row transition metal ions (M+) bound to benzene. The calculations employ basis sets of at least double-zeta plus polarization quality and account for electron correlation using the modified coupled-pair functional method. While the bending is predominantly electrostatic, the binding energies are significantly increased by electron correlation, because the donation from the metal d orbitals to the benzene pi* orbitals is not well described at the self-consistent-field level. The uncertainties in the computed binding energies are estimated to be about 5 kcal/mol. Although the calculated and experimental binding energies generally agree to within their combined uncertainties, it is likely that the true binding energies lie in the lower portion of the experimental range. This is supported by the very good agreement between the theoretical and recent experimental binding energies for AgC6H6(+).

  5. Bound {mu}{sup +}{mu}{sup {minus}} system

    SciTech Connect

    Jentschura, U.D.; Soff, G.; Ivanov, V.G.; Karshenboim, S.G.

    1997-12-01

    We consider the hyperfine structure, the atomic spectrum, and the decay channels of the bound {mu}{sup +}{mu}{sup {minus}} system (dimuonium). The annihilation lifetimes of low-lying atomic states of the system lie in the 10{sup {minus}12} s range. The decay rates could be measured by detection of the decay products (high-energy photons or electron-positron pairs). The hyperfine-structure splitting of the dimuonic system and its decay rate are influenced by electronic vacuum polarization effects in the far timelike asymptotic region. This constitutes a previously unexplored kinematic regime. We evaluate next-to-leading-order radiative corrections to the decay rate of low-lying atomic states. We also obtain order {alpha}{sup 5}m{sub {mu}} corrections to the hyperfine splitting of the 1S and 2S levels. {copyright} {ital 1997} {ital The American Physical Society}

  6. Alu pair exclusions in the human genome

    PubMed Central

    2011-01-01

    Background The human genome contains approximately one million Alu elements which comprise more than 10% of human DNA by mass. Alu elements possess direction, and are distributed almost equally in positive and negative strand orientations throughout the genome. Previously, it has been shown that closely spaced Alu pairs in opposing orientation (inverted pairs) are found less frequently than Alu pairs having the same orientation (direct pairs). However, this imbalance has only been investigated for Alu pairs separated by 650 or fewer base pairs (bp) in a study conducted prior to the completion of the draft human genome sequence. Results We performed a comprehensive analysis of all (> 800,000) full-length Alu elements in the human genome. This large sample size permits detection of small differences in the ratio between inverted and direct Alu pairs (I:D). We have discovered a significant depression in the full-length Alu pair I:D ratio that extends to repeat pairs separated by ≤ 350,000 bp. Within this imbalance bubble (those Alu pairs separated by ≤ 350,000 bp), direct pairs outnumber inverted pairs. Using PCR, we experimentally verified several examples of inverted Alu pair exclusions that were caused by deletions. Conclusions Over 50 million full-length Alu pairs reside within the I:D imbalance bubble. Their collective impact may represent one source of Alu element-related human genomic instability that has not been previously characterized. PMID:21943335

  7. Charge Aspects of Composite Pair Superconductivity

    NASA Astrophysics Data System (ADS)

    Flint, Rebecca

    2014-03-01

    Conventional Cooper pairs form from well-defined electronic quasiparticles, making the internal structure of the pair irrelevant. However, in the 115 family of superconductors, the heavy electrons are forming as they pair and the internal pair structure becomes as important as the pairing mechanism. Conventional spin fluctuation mediated pairing cannot capture the direct transition from incoherent local moments to heavy fermion superconductivity, but the formation of composite pairs favored by the two channel Kondo effect can. These composite pairs are local d-wave pairs formed by two conduction electrons in orthogonal Kondo channels screening the same local moment. Composite pairing shares the same symmetries as magnetically mediated pairing, however, only composite pairing necessarily involves a redistribution of charge within the unit cell originating from the internal pair structure, both as a monopole (valence change) and a quadrupole effect. This redistribution will onset sharply at the superconducting transition temperature. A smoking gun test for composite pairing is therefore a sharp signature at Tc - for example, a cusp in the Mossbauer isomer shift in NpPd5Al2 or in the NQR shift in (Ce,Pu)CoIn5.

  8. Curvature-driven stability of defects in nematic textures over spherical disks

    NASA Astrophysics Data System (ADS)

    Duan, Xiuqing; Yao, Zhenwei

    2017-06-01

    Stabilizing defects in liquid-crystal systems is crucial for many physical processes and applications ranging from functionalizing liquid-crystal textures to recently reported command of chaotic behaviors of active matters. In this work, we perform analytical calculations to study the curvature-driven stability mechanism of defects based on the isotropic nematic disk model that is free of any topological constraint. We show that in a growing spherical disk covering a sphere the accumulation of curvature effect can prevent typical +1 and +1/2 defects from forming boojum textures where the defects are repelled to the boundary of the disk. Our calculations reveal that the movement of the equilibrium position of the +1 defect from the boundary to the center of the spherical disk occurs in a very narrow window of the disk area, exhibiting the first-order phase-transition-like behavior. For the pair of +1/2 defects by splitting a +1 defect, we find the curvature-driven alternating repulsive and attractive interactions between the two defects. With the growth of the spherical disk these two defects tend to approach and finally recombine towards a +1 defect texture. The sensitive response of defects to curvature and the curvature-driven stability mechanism demonstrated in this work in nematic disk systems may have implications towards versatile control and engineering of liquid-crystal textures in various applications.

  9. Match-bounded String Rewriting Systems

    NASA Technical Reports Server (NTRS)

    Geser, Alfons; Hofbauer, Dieter; Waldmann, Johannes

    2003-01-01

    We introduce a new class of automated proof methods for the termination of rewriting systems on strings. The basis of all these methods is to show that rewriting preserves regular languages. To this end, letters are annotated with natural numbers, called match heights. If the minimal height of all positions in a redex is h+1 then every position in the reduct will get height h+1. In a match-bounded system, match heights are globally bounded. Using recent results on deleting systems, we prove that rewriting by a match-bounded system preserves regular languages. Hence it is decidable whether a given rewriting system has a given match bound. We also provide a sufficient criterion for the abence of a match-bound. The problem of existence of a match-bound is still open. Match-boundedness for all strings can be used as an automated criterion for termination, for match-bounded systems are terminating. This criterion can be strengthened by requiring match-boundedness only for a restricted set of strings, for instance the set of right hand sides of forward closures.

  10. Fluorophore-Quencher Pair For Monitoring Protein Motion

    PubMed Central

    Tahmassebi, Deborah C.; Millar, David P.

    2009-01-01

    A fluorophore/quencher pair capable of detecting conformational changes of DNA-protein complexes is described. The system employs a fluorescent nucleoside analog 1,3-diaza-2-oxophenothiazine (tC) within duplex DNA and a non-fluorescent quencher (TEMPO) attached to an engineered cysteine residue of the protein. The straightforward labeling methodology allows for the placement of the fluorophore and quencher moieties at specific positions suited to studying the conformational change of interest. To illustrate the utility of the tC-TEMPO pair, we have monitored nucleotide-induced conformational changes of the Klenow fragment (KF) polymerase bound to duplex DNA. In this system, tC was incorporated in the primer strand of the duplex, adjacent to the 3’ end, while TEMPO was positioned at the end of the O-helix within the fingers domain of KF. Using steady-state fluorescence spectroscopy, we measured the quenching efficiency in a binary complex of tC-modified DNA and TEMPO-labeled KF and in ternary complexes containing cognate or non-cognate dNTP substrates. The quenching efficiency is significantly enhanced in the presence of a cognate dNTP, indicating that the O-helix has moved closer towards the DNA. In contrast, no significant tC quenching is observed in the presence of a non-cognate dNTP, indicating that the O-helix remains in a position that is beyond the distance reporting range of the tC-TEMPO pair. These results demonstrate that a cognate dNTP substrate induces a large conformational change of the O-helix, which can be sensitively detected using the tC-TEMPO pair. This fluorophore/quencher pair may be useful to study conformational changes associated with other DNA-enzyme complexes. PMID:19167347

  11. Phenomenology of transionospheric pulse pairs

    NASA Astrophysics Data System (ADS)

    Massey, R. S.; Holden, D. N.

    1995-09-01

    Recent observations of transient radio impulses by an Earth-orbiting satellite appear to be quite unlike any previously reported. They appear as pairs of brief (a few microseconds), noiselike bursts, separated by a few tens of microseconds, and are dispersed in a way that implies subionospheric origin. Over 300 of these events have now been observed. These "transionospheric pulse pairs" (TIPPs) have not yet been associated with any known source, although thunderstorms are suspected. The observations, made by the Blackbeard instrument on the ALEXIS satellite, are digitized records of the electric field in a passband from about 25 to 100 MHz. Ground-based observations of lightning in this band appear quite different, even accounting for ionospheric dispersion: bursts of short pulses last hundreds of microseconds and have much lower power (when propagated to the satellite) than TIPP events. Signals that resemble the ground-based data have been observed by Blackbeard but, being much weaker, are much less likely to trigger the instrument than are the strong pulse pair events. In this paper we analyze 97 of the early TIPP observations. We compute several parameters that describe the events: the location of the satellite at the time of reception, the energy in each pulse, the separation between pulses, the duration of each pulse, and the dispersion of each pulse. The statistical distributions of these parameters provide clues to and constraints on possible source mechanisms. The possibility that the pulses might be the direct and reflected signals from a high-altitude source is considered and cannot be rejected by the data.

  12. Ultrasound anal sphincter defects and 3D anal pressure defects.

    PubMed

    Mion, F; Garros, A; Damon, H; Roman, S

    2017-04-13

    We read with interest the paper by Rezaie et al. on the use of 3D high definition anorectal manometry (3DARM) to detect anal sphincter defects in patients with faecal incontinence [1]. In their series of 39 patients, they described a new metrics to define anal pressure defect (defect of at least 18° of the 25 mmHg isobaric contour on anal resting pressures), and then compared the results of pressure defects determined by 3DARM and 3D anal ultrasound results. They found a rather good negative predictive value of manometry to eliminate the presence of ultrasound anal sphincter defects (92%), and suggested the possibility to use 3DARM to rule out anal sphincter defects and avoid the need of anal ultrasound in selected patients. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  13. Paired circularly polarized heterodyne ellipsometer

    SciTech Connect

    Yu, C.-J.; Lin, C.-E.; Yu, L.-P.; Chou, C

    2009-02-01

    We develop a paired circularly polarized heterodyne ellipsometer (PCPHE), in which a heterodyne interferometer based on a two-frequency circularly polarized laser beam is set up. It belongs to an amplitude-sensitive ellipsometer that is able to provide not only a wider dynamic range of polarization modulation frequency but also a higher detection sensitivity than that of a conventional photometric ellipsometer. A real-time and precise measurement of ellipsometric parameters, which demonstrated an accuracy of less than 1 nm on thickness measurement of SiO2 thin film deposited on silicon substrate, can be applied with the PCPHE.

  14. Effects of Sleep on Word Pair Memory in Children - Separating Item and Source Memory Aspects.

    PubMed

    Wang, Jing-Yi; Weber, Frederik D; Zinke, Katharina; Noack, Hannes; Born, Jan

    2017-01-01

    Word paired-associate learning is a well-established task to demonstrate sleep-dependent memory consolidation in adults as well as children. Sleep has also been proposed to benefit episodic features of memory, i.e., a memory for an event (item) bound into the spatiotemporal context it has been experienced in (source). We aimed to explore if sleep enhances word pair memory in children by strengthening the episodic features of the memory, in particular. Sixty-one children (8-12 years) studied two lists of word pairs with 1 h in between. Retrieval testing comprised cued recall of the target word of each word pair (item memory) and recalling in which list the word pair had appeared in (source memory). Retrieval was tested either after 1 h (short retention interval) or after 11 h, with this long retention interval covering either nocturnal sleep or daytime wakefulness. Compared with the wake interval, sleep enhanced separate recall of both word pairs and the lists per se, while recall of the combination of the word pair and the list it had appeared in remained unaffected by sleep. An additional comparison with adult controls (n = 37) suggested that item-source bound memory (combined recall of word pair and list) is generally diminished in children. Our results argue against the view that the sleep-induced enhancement in paired-associate learning in children is a consequence of sleep specifically enhancing the episodic features of the memory representation. On the contrary, sleep in children might strengthen item and source representations in isolation, while leaving the episodic memory representations (item-source binding) unaffected.

  15. First-principles DFT+U modeling of defect behaviors in anti-ferromagnetic uranium mononitride

    SciTech Connect

    Lan, Jian-Hui; Zhao, Zi-Chen; Wu, Qiong; Zhao, Yu-Liang; Shi, Wei-Qun; Chai, Zhi-Fang

    2013-12-14

    A series of point defects in uranium mononitride (UN) have been studied by first-principles DFT+U calculations. The influence of intrinsic defects on the properties of UN was explored by considering the anti-ferromagnetic (AFM) order along the [001] direction. Our results show that all the point defects lead to obvious volume swelling of UN crystal. Energetically, the interstitial nitrogen defect is the most favorable one among single-point defects in UN crystal with the formation energy of 4.539 eV, while the N-Frenkel pair becomes the most preferable one among double-point defects. The AFM order induces obvious electron spin polarization of uranium towards neighboring uranium atoms with opposite spin orientations in UN crystal.

  16. Protein packing defects "heat up" interfacial water.

    PubMed

    Sierra, María Belén; Accordino, Sebastián R; Rodriguez-Fris, J Ariel; Morini, Marcela A; Appignanesi, Gustavo A; Fernández Stigliano, Ariel

    2013-06-01

    Ligands must displace water molecules from their corresponding protein surface binding site during association. Thus, protein binding sites are expected to be surrounded by non-tightly-bound, easily removable water molecules. In turn, the existence of packing defects at protein binding sites has been also established. At such structural motifs, named dehydrons, the protein backbone is exposed to the solvent since the intramolecular interactions are incompletely wrapped by non-polar groups. Hence, dehydrons are sticky since they depend on additional intermolecular wrapping in order to properly protect the structure from water attack. Thus, a picture of protein binding is emerging wherein binding sites should be both dehydrons rich and surrounded by easily removable water. In this work we shall indeed confirm such a link between structure and dynamics by showing the existence of a firm correlation between the degree of underwrapping of the protein chain and the mobility of the corresponding hydration water molecules. In other words, we shall show that protein packing defects promote their local dehydration, thus producing a region of "hot" interfacial water which might be easily removed by a ligand upon association.

  17. Anomalous Defects and Their Quantized Transverse Conductivities

    NASA Astrophysics Data System (ADS)

    Balachandran, A. P.; John, Varghese; Momen, Arshad; Moraes, Fernando

    Using a description of defects in solids in terms of three-dimensional gravity, we study the propagation of electrons in the background of disclinations and screw dislocations. We study the situations where there are bound states that are effectively localized on the defect and hence can be described in terms of an effective (1+1)-dimensional field theory for the low energy excitations. In the case of screw dislocations, we find that these excitations are chiral and can be described by an effective field theory of chiral fermions. Fermions of both chirality occur even for a given direction of the magnetic field. The "net" chirality of the system however is not always the same for a given direction of the magnetic field, but changes from one sign of the chirality through zero to the other sign as the Fermi momentum or the magnitude of the magnetic flux is varied. On coupling to an external electromagnetic field, the latter becomes anomalous and predicts novels conduction properties for these material.

  18. [Congenital defects and incapacity].

    PubMed

    Jouve de la Barreda, Nicolás

    2009-01-01

    As a whole the congenital defects constitute an important section of the medical attention affecting near 3% of the population. A 15% of spontaneous abortions take place of which the greater frequency corresponds to the chromosome anomalies (25%) and the monogenic mutations (20%) and in a lesser extent to the effects of teratogenic agents. Between the genetic causes determining the congenital defects the mutations that affect genes acting in the early stages of development occupy a main place. These alterations can affect to homeotic genes or monogenic systems that act during the critical phases of the organogenesis. It seems evident that an alteration in the expression of a necessary gene for the appearance of a morphogenetic change constitutes the angular stone to understand resurging of a malformation or discapacity. In the last years has been demonstrated the importance of the teratogenic or environmental agents on the delicate internal physiological balance during the critical stages of the development. In this context must be included the inductive environmental factors inducing epigenetic modifications in the early stage of the development of the embryos produced by fertilization in vitro.

  19. Dipole defects in beryl

    NASA Astrophysics Data System (ADS)

    Holanda, B. A.; Cordeiro, R. C.; Blak, A. R.

    2010-11-01

    Dipole defects in gamma irradiated and thermally treated beryl (Be3Al2Si6O18) samples have been studied using the Thermally Stimulated Depolarization Currents (TSDC) technique. TSDC experiments were performed in pink (morganite), green (emerald), blue (aquamarine) and colourless (goshenite) natural beryl. TSDC spectra present dipole peaks at 190K, 220K, 280K and 310K that change after gamma irradiation and thermal treatments. In morganite samples, for thermal treatments between 700K and 1100K, the 280K peak increase in intensity and the band at 220K disappears. An increase of the 280K peak and a decrease of the 190K peak were observed in the TSDC spectra of morganite after a gamma irradiation of 25kGy performed after the thermal treatments. In the case of emerald samples, thermal treatments enhanced the 280K peak and gamma irradiation partially destroyed this band. The goshenite TSDC spectra present only one band at 280K that is not affected either by thermal treatments or by gamma irradiation. All the observed peaks are of dipolar origin because the intensity of the bands is linearly dependent on the polarization field, behaviour of dipole defects. The systematic study, by means of TSDC measurements, of ionizing irradiation effects and thermal treatments in these crystals makes possible a better understanding of the role played by the impurities in beryl crystals.

  20. Reconstruction of perineal defects

    PubMed Central

    Baker, RJ; Muneer, A; Mosahebi, A

    2013-01-01

    Introduction Perineal defects are commonly encountered in an oncological setting although they may also present as a result of trauma and infection (eg following Fournier’s gangrene). Reconstruction of these poses functional as well as aesthetic challenges. Skin coverage and tissue volume may both be required in addition to anogenital preservation or reconstruction. General prerequisites of an adequate reconstruction of perineal defects include provision of skin cover, well vascularised tissue to fill the dead space (reducing fluid collection and infection), vulvovaginal reconstruction and no faecal or urinary contamination. Methods A literature search was performed using PubMed and MEDLINE®. The search terms included ‘perineal defects’, ‘perineal reconstruction’, ‘perforator flaps for perineum’, ‘vulval flaps’, ‘secondary healing of wound’ and ‘vacuum assisted closure’. Backward chaining of reference lists from retrieved papers was also used to expand the search. Findings Modern developments have led to an increased expectation in improved quality of life as the main goal of reconstruction, therefore necessitating surgery with less morbidity and early return to normal activity. Progress in microsurgical procedures has been the main recent advance in perineal reconstruction and, in future, refinements in perforator flap design and tissue engineering techniques will lead to even better reconstructions. PMID:24165333