Interpolation solution of the single-impurity Anderson model
International Nuclear Information System (INIS)
Kuzemsky, A.L.
1990-10-01
The dynamical properties of the single-impurity Anderson model (SIAM) is studied using a novel Irreducible Green's Function method (IGF). The new solution for one-particle GF interpolating between the strong and weak correlation limits is obtained. The unified concept of relevant mean-field renormalizations is indispensable for strong correlation limit. (author). 21 refs
Unbinding slave spins in the Anderson impurity model
Guerci, Daniele; Fabrizio, Michele
2017-11-01
We show that a generic single-orbital Anderson impurity model, lacking, for instance, any kind of particle-hole symmetry, can be exactly mapped without any constraint onto a resonant level model coupled to two Ising variables, which reduce to one if the hybridization is particle-hole symmetric. The mean-field solution of this model is found to be stable to unphysical spontaneous magnetization of the impurity, unlike the saddle-point solution in the standard slave-boson representation. Remarkably, the mean-field estimate of the Wilson ratio approaches the exact value RW=2 in the Kondo regime.
Substitutional impurity in single-layer graphene: The Koster–Slater and Anderson models
Energy Technology Data Exchange (ETDEWEB)
Davydov, S. Yu., E-mail: sergei-davydov@mail.ru [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)
2016-06-15
The Koster–Slater and Anderson models are used to consider substitutional impurities in free-standing single-layer graphene. The density of states of graphene is described using a model (the M model). For the nitrogen and boron impurities, the occupation numbers and the parameter η which defines the fraction of delocalized electrons of the impurity are determined. In this case, experimental data are used for both determination of the model parameters and comparison with the results of theoretical estimations. The general features of the Koster–Slater and Anderson models and the differences between the two models are discussed. Specifically, it is shown that the band contributions to the occupation numbers of a nitrogen atom in both models are comparable, whereas the local contributions are substantially different: the local contributions are decisive in the Koster–Slater model and negligible in the Anderson model. The asymptotic behavior of the wave functions of a defect is considered in the Koster–Slater model, and the electron states of impurity dimers are considered in the Anderson model.
CT-QMC-simulations on the single impurity Anderson model with a superconducting bath
Energy Technology Data Exchange (ETDEWEB)
Sohn, Florian; Pruschke, Thomas [Institut fuer theoretische Physik, Universitaet Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany)
2016-07-01
Coupling a heavy fermion impurity to a superconducting lead induces a competition between the Kondo effect and superconductivity in the low temperature regime. This situation has been modeled with a single impurity Anderson model, where the normal state bath is replaced by a BCS-type superconducting bath in mean field approximation. We study this model using a continuous-time quantum Monte Carlo hybridization expansion algorithm. Results include the impurity Green's functions as well as the corresponding spectral functions obtained from analytic continuation. Two side bands are observed which we discuss in the light of Yu-Shiba-Rusinov states.
Electronic structure of vitamin B12 within the framework of the Haldane-Anderson impurity model
Kandemir, Zafer; Mayda, Selma; Bulut, Nejat
2015-03-01
We study the electronic structure of vitamin B12 (cyanocobalamine C63H88CoN14O14P) by using the framework of the multi-orbital single-impurity Haldane-Anderson model of a transition-metal impurity in a semiconductor host. Here, our purpose is to understand the many-body effects originating from the transition-metal impurity. In this approach, the cobalt 3 d orbitals are treated as the impurity states placed in a semiconductor host which consists of the rest of the molecule. The parameters of the resulting effective Haldane-Anderson model are obtained within the Hartree-Fock approximation for the electronic structure of the molecule. The quantum Monte Carlo technique is then used to calculate the one-electron and magnetic correlation functions of this effective Haldane-Anderson model for vitamin B12. We find that new states form inside the semiconductor gap due to the on-site Coulomb interaction at the impurity 3 d orbitals and that these states become the highest occupied molecular orbitals. In addition, we present results on the charge distribution and spin correlations around the Co atom. We compare the results of this approach with those obtained by the density-functional theory calculations.
International Nuclear Information System (INIS)
Guang-Ming Zhang; Lu Yu
1998-10-01
We consider the symmetric single-impurity Anderson model in the presence of pairing fluctuations. In the isotropic limit, the degrees of freedom of the local impurity are separated into hybridizing and non-hybridizing modes. The self-energy for the hybridizing modes can be obtained exactly, leading to two subbands centered at ±U/2. For the non-hybridizing modes, the second order perturbation yields a singular resonance of the marginal Fermi liquid form. By multiplicative renormalization, the self-energy is derived exactly, showing the resonance is pinned at the Fermi level, while its strength is weakened by renormalization. (author)
Symmetry breaking and physical properties of the bosonic single-impurity Anderson model
Warnes, J. H.; Miranda, E.
2012-10-01
We show how exact diagonalization of small clusters can be used as a fast and reliable impurity solver by determining the phase diagram and physical properties of the bosonic single-impurity Anderson model. This is specially important for applications which require the solution of a large number of different single-impurity problems, such as the bosonic dynamical mean field theory of disordered systems. In particular, we investigate the connection between spontaneous global gauge symmetry breaking and the occurrence of Bose-Einstein condensation (BEC). We show how BEC is accurately signaled by the appearance of broken symmetry, even when a fairly modest number of states is retained. The occurrence of symmetry breaking can be detected both by adding a small conjugate field or, as in generic quantum critical points, by the divergence of the associated phase susceptibility. Our results show excellent agreement with the considerably more demanding numerical renormalization group (NRG) method. We also investigate the mean impurity occupancy and its fluctuations, identifying an asymmetry in their critical behavior across the quantum phase transitions between BEC and `Mott' phases.
Effects of correlated hybridization in the single-impurity Anderson model
Líbero, Valter; Veiga, Rodrigo
2013-03-01
The development of new materials often dependents on the theoretical foundations which study the microscopic matter, i.e., the way atoms interact and create distinct configurations. Among the interesting materials, those with partially filled d or f orbitals immersed in nonmagnetic metals have been described by the Anderson model, which takes into account Coulomb correlation (U) when a local level (energy Ed) is doubled occupied, and an electronic hybridization between local levels and conduction band states. In addition, here we include a correlated hybridization term, which depends on the local-level occupation number involved. This term breaks particle-hole symmetry (even when U + 2Ed = 0), enhances charge fluctuations on local levels and as a consequence strongly modifies the crossover between the Hamiltonian fixed-points, even suppressing one or other. We exemplify these behaviors showing data obtained from the Numerical Renormalization Group (NRG) computation for the impurity temperature-dependent specific heat, entropy and magnetic susceptibility. The interleaving procedure is used to recover the continuum spectrum after the NRG-logarithmic discretization of the conduction band. Fundação de Amparo à Pesquisa do Estado de São Paulo - FAPESP.
Spectral properties of a two-orbital Anderson impurity model across anon-Fermi-liquid fixed point
Leo, Lorenzo De; Fabrizio, Michele
2004-06-01
We study by Wilson numerical renormalization group the spectral properties of a two-orbital Anderson impurity model in the presence of an exchange splitting that follows either regular or inverted Hund’s rules. The phase diagram contains a non-Fermi-liquid fixed point separating a screened phase, where conventional Kondo effect occurs, from an unscreened one, where the exchange splitting takes care of quenching the impurity degrees of freedom. On the Kondo screened side close to this fixed point the impurity density of states shows a narrow Kondo peak on top of a broader resonance. This narrow peak transforms in the unscreened phase into a narrow pseudogap inside the broad resonance. Right at the fixed point only the latter survives. The fixed point is therefore identified by a jump of the density of states at the chemical potential. We also consider the effect of several particle-hole symmetry-breaking terms. We show that particle-hole perturbations that simply shift the orbital energies do not wash out the fixed point, unlike those perturbations that hybridize the two orbitals. Consequently the density-of-state jump at the chemical potential remains finite even away from particle-hole symmetry. In other words, the pseudogap stays pinned at the chemical potential, although it is partially filled in. We also discuss the relevance of these results for lattice models that map onto this Anderson impurity model in the limit of large lattice coordination. Upon approaching the Mott metal-insulator transition, these lattice models necessarily enter a region with a local criticality that reflects the impurity non-Fermi-liquid fixed point. However, unlike the impurity, the lattice can get rid of the single-impurity fixed-point instability by spontaneously developing bulk coherent symmetry-broken phases, which we identify for different lattice models.
Czech Academy of Sciences Publication Activity Database
Pokorný, Vladislav; Žonda, M.; Kauch, Anna; Janiš, Václav
2017-01-01
Roč. 131, č. 4 (2017), s. 1042-1044 ISSN 0587-4246 R&D Projects: GA ČR GA15-14259S Institutional support: RVO:68378271 Keywords : Anderson model * parquet equations * numerical renormalization group Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 0.469, year: 2016
An interacting multielectron Anderson model
Zenk, H
2003-01-01
This article is a first tiny step towards a rigorous description of an interacting multielectron system in a random potential of Anderson type. Deterministic spectrum and a Wegner estimate for this model are proven.
Effect of Anderson magnetic impurities on superconducting alloys
International Nuclear Information System (INIS)
Ahmed, M.; Rashid, R.I.M.A.
1983-06-01
A model which consists of a BCS Hamiltonian and a periodic Anderson Hamiltonian for a lattice of magnetic ions is studied using the Green functions equation of motion method. It is found that the Cooper pairing on the site-localized magnetic electrons with antiferromagnetic coupling is capable of destroying superconductivity at a lower critical temperature and thus predicting a reentrant behaviour of the superconducting transition temperature. (author)
Exact interacting Green's function for the Anderson impurity at high bias voltages
Oguri, Akira; Sakano, Rui
2013-10-01
We describe some exact high-energy properties of a single Anderson impurity connected to two noninteracting leads in a nonequilibrium steady state. In the limit of high bias voltages, and also in the high-temperature limit at thermal equilibrium, the model can be mapped onto an effective non-Hermitian Hamiltonian consisting of two sites, which correspond to the original impurity and its image that is defined in a doubled Hilbert space referred to as Liouville-Fock space. For this, we provide a heuristic derivation using a path-integral representation of the Keldysh contour and the thermal field theory, in which the time evolution along the backward contour is replicated by extra degrees of freedom corresponding to the image. We find that the effective Hamiltonian can also be expressed in terms of charges and currents. From this, it can be deduced that the dynamic susceptibilities for the charges and the current fluctuations become independent of the Coulomb repulsion U in the high bias limit. Furthermore, the equations of motion for the Green's function and two other higher-order correlation functions constitute a closed system. The exact solution obtained from the three coupled equations extends the atomic-limit solution such that the self-energy correctly captures the imaginary part caused by the relaxation processes at high energies. The spectral weights of the upper and lower Hubbard levels depend sensitively on the asymmetry in the tunneling couplings to the left and right leads.
Comment on Theory of impure superconductors: Anderson versus Abrikosov and Gor'kov''
Energy Technology Data Exchange (ETDEWEB)
Abrikosov, A.A. (Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)); Gor' kov, L.P. (National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306 (United States) L.D. Landau Institute for Theoretical Physics, Moscow (Russian Federation))
1994-05-01
A response is given to a criticism in a paper by Kim and Overhauser of an earlier work by Abrikosov and Gor'kov on superconductors with impurities. The criticism is based on a primitive misunderstanding of the nature of the attraction of electrons achieved by phonons. As it was explained by the present authors in several publications, there exists a complete equivalence of their results with the later work by Anderson.
Mott transitions in the periodic Anderson model
International Nuclear Information System (INIS)
Logan, David E; Galpin, Martin R; Mannouch, Jonathan
2016-01-01
The periodic Anderson model (PAM) is studied within the framework of dynamical mean-field theory, with particular emphasis on the interaction-driven Mott transition it contains, and on resultant Mott insulators of both Mott–Hubbard and charge-transfer type. The form of the PAM phase diagram is first deduced on general grounds using two exact results, over the full range of model parameters and including metallic, Mott, Kondo and band insulator phases. The effective low-energy model which describes the PAM in the vicinity of a Mott transition is then shown to be a one-band Hubbard model, with effective hoppings that are not in general solely nearest neighbour, but decay exponentially with distance. This mapping is shown to have a range of implications for the physics of the problem, from phase boundaries to single-particle dynamics; all of which are confirmed and supplemented by NRG calculations. Finally we consider the locally degenerate, non-Fermi liquid Mott insulator, to describe which requires a two-self-energy description. This is shown to yield a number of exact results for the associated local moment, charge, and interaction-renormalised levels, together with a generalisation of Luttinger’s theorem to the Mott insulator. (paper)
Mobile impurities in integrable models
Directory of Open Access Journals (Sweden)
Andrew S. Campbell, Dimitri M. Gangardt
2017-08-01
Full Text Available We use a mobile impurity or depleton model to study elementary excitations in one-dimensional integrable systems. For Lieb-Liniger and bosonic Yang-Gaudin models we express two phenomenological parameters characterising renormalised inter- actions of mobile impurities with superfluid background: the number of depleted particles, $N$ and the superfluid phase drop $\\pi J$ in terms of the corresponding Bethe Ansatz solution and demonstrate, in the leading order, the absence of two-phonon scattering resulting in vanishing rates of inelastic processes such as viscosity experienced by the mobile impurities
Spectra of Anderson type models with decaying randomness
Indian Academy of Sciences (India)
Springer Verlag Heidelberg #4 2048 1996 Dec 15 10:16:45
There have been but few models in higher dimensional random operators of the Anderson model type in which presence ... The models we consider in this paper are related to the discrete Laplacian ( u)(n) = ∑. |i|=1 u(n + i) on l2( ν). .... identically distributed real valued random variables with distribution µ. The operator H0.
Eigenfunction statistics for Anderson model with Hölder continuous ...
Indian Academy of Sciences (India)
continuous (0 < α ≤ 1) single site distribution. In localized regime, we study the distri- bution of eigenfunctions in space and energy simultaneously. In a certain scaling limit, we prove limit points are Poisson. Keywords. Anderson model; Hölder continuous measure; Poisson statistics. 2010 Mathematics Subject Classification ...
Dynamic greedy algorithms for the Edwards-Anderson model
Schnabel, Stefan; Janke, Wolfhard
2017-11-01
To provide a novel tool for the investigation of the energy landscape of the Edwards-Anderson spin-glass model we introduce an algorithm that allows an efficient execution of a greedy optimization based on data from a previously performed optimization for a similar configuration. As an application we show how the technique can be used to perform higher-order greedy optimizations and simulated annealing searches with improved performance.
Transverse Ising model with multi-impurity
International Nuclear Information System (INIS)
Huang, Xuchu; Yang, Zhihua
2015-01-01
We study the transverse Ising spin model with spin-1 impurities under the exact solution. We develop a universal method to deal with the multi-impurity problem by introducing a displacement quantity in the wave function and get a recursive formula to simplify the calculation of the partition function. This allows us to rigorously determine the impurity effects for a specific distribution of impurity in the thermodynamic limit. The low temperature behaviors are governed by the interplay between host and impurity excitations, and the quantum critical fluctuations around the critical point of the transverse Ising model are tuned by the transverse field and the concentration of impurity. However the impurity effects are limited, which depends on the host–impurity exchange interaction and the coupling strength of impurities. - Highlights: • A universal method is proposed to exactly resolve the transverse Ising model with many impurities. • The phase diagram of the ground state is obtained for different impurity concentrations. • The thermodynamic properties can be determined rigorously by a recursive formula in the thermodynamic limit
Oguri, Akira; Hewson, A. C.
2018-01-01
We study the low-energy behavior of the vertex function of a single Anderson impurity away from half filling for finite magnetic fields, using the Ward identities with careful consideration of the antisymmetry and analytic properties. The asymptotic form of the vertex function Γσσ';σ'σ(i ω ,i ω';i ω',i ω ) is determined up to terms of linear order with respect to the two frequencies ω and ω', as well as the ω2 contribution for antiparallel spins σ'≠σ at ω'=0 . From these results, we also obtain a series of the Fermi-liquid relations beyond those of Yamada-Yosida [Prog. Theor. Phys. 54, 316 (1975), 10.1143/PTP.54.316]. The ω2 real part of the self-energy Σσ(i ω ) is shown to be expressed in terms of the double derivative ∂2Σσ(0 ) /∂ ɛdσ 2 with respect to the impurity energy level ɛdσ, and agrees with the formula obtained recently by Filippone, Moca, von Delft, and Mora (FMvDM) in the Nozières phenomenological Fermi-liquid theory [Phys. Rev. B 95, 165404 (2017), 10.1103/PhysRevB.95.165404]. We also calculate the T2 correction of the self-energy and find that the real part can be expressed in terms of the three-body correlation function ∂ χ↑↓/∂ ɛd,-σ , where χ↑↓ is the static susceptibility between antiparallel spins. We also provide an alternative derivation of the asymptotic form of the vertex function. Specifically, we calculate the skeleton diagrams for the vertex function Γσσ ;σ σ(i ω ,0 ;0 ,i ω ) for parallel spins up to order U4 in the Coulomb repulsion U . It directly clarifies the fact that the analytic components of order ω vanish as a result of the cancellation of four related Feynman diagrams, which are related to each other through the antisymmetry operation.
A variational study of superconducting correlations within periodic Anderson model
International Nuclear Information System (INIS)
Dua, Piyush; Panwar, Sunil; Singh, Ishwar
2005-01-01
In this work we present the study of heavy fermion (HF) systems represented by the extended periodic Anderson model (PAM). A term, which contains the superconducting correlations, has been included in the conventional PAM. The study has been carried out at finite U. We have used the variational method. The variational wavefunction contains two variational parameters A kσ and B kσ . We have found that both the variational parameters are mutually dependent. We have studied ground state as well as finite temperature properties. We have found that T c increases, as J increases
Classical mapping for Hubbard operators: Application to the double-Anderson model
International Nuclear Information System (INIS)
Li, Bin; Miller, William H.; Levy, Tal J.; Rabani, Eran
2014-01-01
A classical Cartesian mapping for Hubbard operators is developed to describe the nonequilibrium transport of an open quantum system with many electrons. The mapping of the Hubbard operators representing the many-body Hamiltonian is derived by using analogies from classical mappings of boson creation and annihilation operators vis-à-vis a coherent state representation. The approach provides qualitative results for a double quantum dot array (double Anderson impurity model) coupled to fermionic leads for a range of bias voltages, Coulomb couplings, and hopping terms. While the width and height of the conduction peaks show deviations from the master equation approach considered to be accurate in the limit of weak system-leads couplings and high temperatures, the Hubbard mapping captures all transport channels involving transition between many electron states, some of which are not captured by approximate nonequilibrium Green function closures
d-wave superconductivity in the frustrated two-dimensional periodic Anderson model
Directory of Open Access Journals (Sweden)
Wei Wu
2015-02-01
Full Text Available Superconductivity in heavy-fermion materials can sometimes appear in the incoherent regime and in proximity to an antiferromagnetic quantum critical point. Here, we study these phenomena using large-scale determinant quantum Monte Carlo simulations and the dynamical cluster approximation with various impurity solvers for the periodic Anderson model with frustrated hybridization. We obtain solid evidence for a d_{x^{2}−y^{2}} superconducting phase arising from an incoherent normal state in the vicinity of an antiferromagnetic quantum critical point. There is a coexistence region, and the width of the superconducting dome increases with frustration. Through a study of the pairing dynamics, we find that the retarded spin fluctuations give the main contribution to the pairing glue. These results are relevant for unconventional superconductivity in the Ce-115 family of heavy fermions.
The parabolic Anderson model random walk in random potential
König, Wolfgang
2016-01-01
This is a comprehensive survey on the research on the parabolic Anderson model – the heat equation with random potential or the random walk in random potential – of the years 1990 – 2015. The investigation of this model requires a combination of tools from probability (large deviations, extreme-value theory, e.g.) and analysis (spectral theory for the Laplace operator with potential, variational analysis, e.g.). We explain the background, the applications, the questions and the connections with other models and formulate the most relevant results on the long-time behavior of the solution, like quenched and annealed asymptotics for the total mass, intermittency, confinement and concentration properties and mass flow. Furthermore, we explain the most successful proof methods and give a list of open research problems. Proofs are not detailed, but concisely outlined and commented; the formulations of some theorems are slightly simplified for better comprehension.
Spin-liquid state in an inhomogeneous periodic Anderson model
Caro, R. C.; Franco, R.; Silva-Valencia, J.
2018-02-01
We studied the ground state of alkaline-earth-metal atoms confined in one-dimensional optical lattices with an effective hybridization generated by a suitable laser field. This system is modeled by the periodic Anderson model plus a quadratic confining potential, and we adopted the density-matrix renormalization group to calculate its ground state. We found a one-to-one correspondence between the local variance, the local von Neumann entropy, and the on-site spin-spin correlation. For low global densities, we observed the formation of local singlets between delocalized and localized atoms and found Kondo spin-liquid domains that can be tuned with the confining potential, the hybridization, and the local repulsion. Band insulator, metallic, phase separation, and Kondo spin-liquid regions coexist in the ground state.
Superconductivity in the periodic Anderson model with anisotropic hybridization
International Nuclear Information System (INIS)
Sarasua, L.G.; Continentino, Mucio A.
2003-01-01
In this work we study superconductivity in the periodic Anderson model with both on-site and intersite hybridization, including the interband Coulomb repulsion. We show that the presence of the intersite hybridization together with the on-site hybridization significantly affects the superconducting properties of the system. The symmetry of the hybridization has a strong influence in the symmetry of the superconducting order parameter of the ground state. The interband Coulomb repulsion may increase or decrease the superconducting critical temperature at small values of this interaction, while is detrimental to superconductivity for strong values. We show that the present model can give rise to positive or negative values of dT c /dP, depending on the values of the system parameters
Compressible ferrimagnetism in the depleted periodic Anderson model
Costa, N. C.; Araújo, M. V.; Lima, J. P.; Paiva, T.; dos Santos, R. R.; Scalettar, R. T.
2018-02-01
Tight-binding Hamiltonians with single and multiple orbitals exhibit an intriguing array of magnetic phase transitions. In most cases the spin ordered phases are insulating, while the disordered phases may be either metallic or insulating. In this paper we report a determinant quantum Monte Carlo study of interacting electrons in a geometry which can be regarded as a two-dimensional periodic Anderson model with depleted interacting (f ) orbitals. For a single depletion, we observe an enhancement of antiferromagnetic correlations and formation of localized states. For half of the f orbitals regularly depleted, the system exhibits a ferrimagnetic ground state. We obtain a quantitative determination of the nature of magnetic order, which we discuss in the context of Tsunetsugu's theorem, and show that, although the dc conductivity indicates insulating behavior at half filling, the compressibility remains finite.
X-slave boson approach to the periodic Anderson model
International Nuclear Information System (INIS)
Franco, R.; Figueira, M.S.; Foglio, M.E.
2001-01-01
The periodic anderson model (PAM) in the limit U=∞, can be studied by employing the Hubbard X operators to project out the unwanted states. In a previous work, we have studied the cumulant expansion of this Hamiltonian employing the hybridization as a perturbation, but probability conservation of the local states (completeness) is not usually satisfied when partial expansions like the 'chain approximation (CHA)' are employed. To consider this problem, we use a technique similar to the one employed by Coleman to treat the same problem with slave-bosons in the mean-field approximation. Assuming a particular renormalization for hybridization, we obtain a description that avoids an unwanted phase transition that appears in the mean-field slave-boson method at intermediate temperatures
The topological Anderson insulator phase in the Kane-Mele model
Orth, Christoph P.; Sekera, Tibor; Bruder, Christoph; Schmidt, Thomas L.
2016-04-01
It has been proposed that adding disorder to a topologically trivial mercury telluride/cadmium telluride (HgTe/CdTe) quantum well can induce a transition to a topologically nontrivial state. The resulting state was termed topological Anderson insulator and was found in computer simulations of the Bernevig-Hughes-Zhang model. Here, we show that the topological Anderson insulator is a more universal phenomenon and also appears in the Kane-Mele model of topological insulators on a honeycomb lattice. We numerically investigate the interplay of the relevant parameters, and establish the parameter range in which the topological Anderson insulator exists. A staggered sublattice potential turns out to be a necessary condition for the transition to the topological Anderson insulator. For weak enough disorder, a calculation based on the lowest-order Born approximation reproduces quantitatively the numerical data. Our results thus considerably increase the number of candidate materials for the topological Anderson insulator phase.
Attractive Hubbard model with disorder and the generalized Anderson theorem
International Nuclear Information System (INIS)
Kuchinskii, E. Z.; Kuleeva, N. A.; Sadovskii, M. V.
2015-01-01
Using the generalized DMFT+Σ approach, we study the influence of disorder on single-particle properties of the normal phase and the superconducting transition temperature in the attractive Hubbard model. A wide range of attractive potentials U is studied, from the weak coupling region, where both the instability of the normal phase and superconductivity are well described by the BCS model, to the strong-coupling region, where the superconducting transition is due to Bose-Einstein condensation (BEC) of compact Cooper pairs, formed at temperatures much higher than the superconducting transition temperature. We study two typical models of the conduction band with semi-elliptic and flat densities of states, respectively appropriate for three-dimensional and two-dimensional systems. For the semi-elliptic density of states, the disorder influence on all single-particle properties (e.g., density of states) is universal for an arbitrary strength of electronic correlations and disorder and is due to only the general disorder widening of the conduction band. In the case of a flat density of states, universality is absent in the general case, but still the disorder influence is mainly due to band widening, and the universal behavior is restored for large enough disorder. Using the combination of DMFT+Σ and Nozieres-Schmitt-Rink approximations, we study the disorder influence on the superconducting transition temperature T c for a range of characteristic values of U and disorder, including the BCS-BEC crossover region and the limit of strong-coupling. Disorder can either suppress T c (in the weak-coupling region) or significantly increase T c (in the strong-coupling region). However, in all cases, the generalized Anderson theorem is valid and all changes of the superconducting critical temperature are essentially due to only the general disorder widening of the conduction band
Shiba states and zero-bias anomalies in the hybrid normal-superconductor Anderson model
Žitko, Rok; Lim, Jong Soo; López, Rosa; Aguado, Ramón
2015-01-01
Hybrid semiconductor-superconductor systems are interesting melting pots where various fundamental effects in condensed-matter physics coexist. For example, when a quantum dot is coupled to a superconducting electrode two very distinct phenomena, superconductivity and the Kondo effect, compete. As a result of this competition, the system undergoes a quantum phase transition when the superconducting gap Δ is of the order of the Kondo temperature TK. The underlying physics behind such transition ultimately relies on the physics of the Anderson model where the standard metallic host is replaced by a superconducting one, namely the physics of a (quantum) magnetic impurity in a superconductor. A characteristic feature of this hybrid system is the emergence of subgap bound states, the so-called Yu-Shiba-Rusinov (YSR) states, which cross zero energy across the quantum phase transition, signaling a switching of the fermion parity and spin (doublet or singlet) of the ground state. Interestingly, similar hybrid devices based on semiconducting nanowires with spin-orbit coupling may host exotic zero-energy bound states with Majorana character. Both parity crossings and Majorana bound states (MBSs) are experimentally marked by zero-bias anomalies in transport, which are detected by coupling the hybrid device with an extra normal contact. We here demonstrate theoretically that this extra contact, usually considered as a nonperturbing tunneling weak probe, leads to nontrivial effects. This conclusion is supported by numerical renormalization-group calculations of the phase diagram of an Anderson impurity coupled to both superconducting and normal-state leads. We obtain this phase diagram for an arbitrary ratio Δ/TK, which allows us to analyze relevant experimental scenarios, such as parity crossings as well as Kondo features induced by the normal lead, as this ratio changes. Spectral functions at finite temperatures and magnetic fields, which can be directly linked to
Spin-spin correlations of magnetic impurities in graphene
Guclu, A. D.; Bulut, Nejat
2014-01-01
We study the interaction between two magnetic adatom impurities in graphene using the Anderson model. The two-impurity Anderson Hamiltonian is solved numerically by using the quantum Monte Carlo technique. We find that the inter-impurity spin susceptibility is strongly enhanced at low temperatures, significantly diverging from the well-known Ruderman-Kittel-Kasuya-Yoshida (RKKY) result which decays as $R^{-3}$.
Mott Transition of Cerium Compound CeCu2Si2 in the Anderson ...
African Journals Online (AJOL)
The Exact-Diagonalization (ED) technique is applied to the Single Site Impurity Anderson Model (SIAM) and the Periodic Anderson Model (PAM) to elucidate the nature of the ground-state energy and the phase diagram of the two models. The results obtained show a smooth phase transition from an antiferromagnetic ...
Balseiro, C A; Usaj, G; Sánchez, M J
2010-10-27
We study non-equilibrium electron transport through a quantum impurity coupled to metallic leads using the equation of motion technique at finite temperature T. Assuming that the interactions are taking place solely in the impurity and focusing on the infinite Hubbard limit, we compute the out of equilibrium density of states and the differential conductance G(2)(T, V) in order to test several scaling laws. We find that G(2)(T, V)/G(2)(T, 0) is a universal function of both eV/T(K) and T/T(K), T(K) being the Kondo temperature. The effect of an in-plane magnetic field on the splitting of the zero bias anomaly in the differential conductance is also analyzed. For a Zeeman splitting Δ, the computed differential conductance peak splitting depends only on Δ/T(K), and for large fields approaches the value of 2Δ. Besides studying the traditional two leads setup, we also consider other configurations that mimic recent experiments, namely, an impurity embedded in a mesoscopic wire and the presence of a third weakly coupled lead. In these cases, a double peak structure of the Kondo resonance is clearly obtained in the differential conductance while the amplitude of the highest peak is shown to decrease as ln(eV/T(K)). Several features of these results are in qualitative agreement with recent experimental observations reported on quantum dots.
Brownian motion and parabolic Anderson model in a renormalized Poisson potential
Chen, Xia; Kulik, Alexey M.
2012-01-01
A method known as renormalization is proposed for constructing some more physically realistic random potentials in a Poisson cloud. The Brownian motion in the renormalized random potential and related parabolic Anderson models are modeled. With the renormalization, for example, the models consistent to Newton’s law of universal attraction can be rigorously constructed.
A functional integral approach without slave bosons to the Anderson model
International Nuclear Information System (INIS)
Nguyen Ngoc Thuan; Nguyen Toan Thang; Coqblin, B.; Bhattacharjee, A.; Hoang Anh Tuan.
1994-06-01
We developed the technique of the functional integral method without slave bosons for the Periodic Anderson Model (PAM) suggested by Sarker for treating the Hubbard Model. This technique allowed us to obtain an analytical expression of Green functions containing U-dependence that is omitted in the formalism with slave bosons. (author). 9 refs
Combining Anderson's Model in the Teaching of Art Appreciation for Undergraduate Students
Subramaniam, Maithreyi; Basaree, Ruzaika Omar; Hanafi, Jaffri; Putih, Abu Talib
2016-01-01
This study utilized 33 students taking creative communication design 3 in the third year of the graphic design and multimedia program, using an Anderson's model in teaching art appreciation. The quantitative research design and procedures were employed in this study. An experimental research using the quasi-experimental design, a single-group…
Parametrization of Transfer Matrix: for One-Dimensional Anderson Model with Diagonal Disorder
International Nuclear Information System (INIS)
Kang Kai; Qin Shaojing; Wang Chuilin
2010-01-01
In this paper, we developed a new parametrization method to calculate the localization length in one-dimensional Anderson model with diagonal disorder. This method can avoid the divergence difficulty encountered in the conventional methods, and significantly save computing time as well. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
DEFF Research Database (Denmark)
Opper, Manfred; Winther, Ole
2001-01-01
We develop an advanced mean held method for approximating averages in probabilistic data models that is based on the Thouless-Anderson-Palmer (TAP) approach of disorder physics. In contrast to conventional TAP. where the knowledge of the distribution of couplings between the random variables...
Ginzburg-Landau expansion in strongly disordered attractive Anderson-Hubbard model
Kuchinskii, E. Z.; Kuleeva, N. A.; Sadovskii, M. V.
2017-07-01
We have studied disordering effects on the coefficients of Ginzburg-Landau expansion in powers of superconducting order parameter in the attractive Anderson-Hubbard model within the generalized DMFT+Σ approximation. We consider the wide region of attractive potentials U from the weak coupling region, where superconductivity is described by BCS model, to the strong coupling region, where the superconducting transition is related with Bose-Einstein condensation (BEC) of compact Cooper pairs formed at temperatures essentially larger than the temperature of superconducting transition, and a wide range of disorder—from weak to strong, where the system is in the vicinity of Anderson transition. In the case of semielliptic bare density of states, disorder's influence upon the coefficients A and B of the square and the fourth power of the order parameter is universal for any value of electron correlation and is related only to the general disorder widening of the bare band (generalized Anderson theorem). Such universality is absent for the gradient term expansion coefficient C. In the usual theory of "dirty" superconductors, the C coefficient drops with the growth of disorder. In the limit of strong disorder in BCS limit, the coefficient C is very sensitive to the effects of Anderson localization, which lead to its further drop with disorder growth up to the region of the Anderson insulator. In the region of BCS-BEC crossover and in BEC limit, the coefficient C and all related physical properties are weakly dependent on disorder. In particular, this leads to relatively weak disorder dependence of both penetration depth and coherence lengths, as well as of related slope of the upper critical magnetic field at superconducting transition, in the region of very strong coupling.
Adaptive and self-averaging Thouless-Anderson-Palmer mean-field theory for probabilistic modeling
DEFF Research Database (Denmark)
Opper, Manfred; Winther, Ole
2001-01-01
We develop a generalization of the Thouless-Anderson-Palmer (TAP) mean-field approach of disorder physics. which makes the method applicable to the computation of approximate averages in probabilistic models for real data. In contrast to the conventional TAP approach, where the knowledge of the d...... distributions in the thermodynamic limit. On the other hand, simulations on a real data model demonstrate that the method achieves more accurate predictions as compared to conventional TAP approaches....
Photoemission in the Anderson model for rare earth compounds with floating valences
International Nuclear Information System (INIS)
Frota, H.O. da.
1985-01-01
X-ray photoemission spectra (XPS) are calculated for the spin-degenerate Anderson model of valence fluctuation compounds. Based on the renormalization group technique originally introduced by Wilson to calculate the magnetic susceptibility for the Kondo model, the numerical calculation has uniform accuracy over the entire parameter space of the Anderson model; at any given photoelectron energy, a maximum error of 4% is estimated for the calculated photoemission current. The calculated spectra display two peaks associated with the two possible x-ray induced transitions between the n f = 0,1 or 2 occupations of the f-orbital: a first ionization peak corresponding to the n f = 2 → n f = 1 transition and a second ionization peak due to the n f 1 → n f = 0 transition. (author)
Modeling of impurity transport in the core plasma
International Nuclear Information System (INIS)
Hulse, R.A.
1992-01-01
This paper presents a brief overview of computer modeling of impurity transport in the core region of controlled thermonuclear fusion plasmas. The atomic processes of importance in these high temperature plasmas and the numerical formulation of the model are described. Selected modeling examples are then used to highlight some features of the physics of impurity behavior in large tokamak fusion devices, with an emphasis on demonstrating the sensitivity of such modeling to uncertainties in the rate coefficients used for the atomic processes. This leads to a discussion of current requirements and opportunities for generating the improved sets of comprehensive atomic data needed to support present and future fusion impurity modeling studies
On Absence of Pure Singular Spectrum of Random Perturbations and in Anderson Model at Low Disorde
Grinshpun, V
2006-01-01
Absence of singular component, with probability one, in the conductivity spectra of bounded random perturbations of multidimensional finite-difference Hamiltonians, is for the first time rigorously established under certain conditions ensuring either absence of pure point, or absence of pure absolutely continuous component in the corresponding regions of spectra. The main technical tool applied is the theory of rank-one perturbations of singular spectra. The respective new result (the non-mixing property) is applied to establish existence and bounds of the (non-empty) pure absolutely continuous component in the spectrum of the Anderson model with bounded random potential in dimension 2 at low disorder. The new (1999) result implies, via the trace-class perturbation analysis, the Anderson model with the unbounded potential to have only pure point spectrum (complete system of localized wave-functions) with probability one in arbitrary dimension. The new technics, based on the resolvent reduction formula, and ex...
Impurity modes in the one-dimensional XXZ Heisenberg model
International Nuclear Information System (INIS)
Sousa, J.M.; Leite, R.V.; Landim, R.R.; Costa Filho, R.N.
2014-01-01
A Green's function formalism is used to calculate the energy of impurity modes associated with one and/or two magnetic impurities in the one-dimensional Heisenberg XXZ magnetic chain. The system can be tuned from the Heisenberg to the Ising model varying a parameter λ. A numerical study is performed showing two types of localized modes (s and p). The modes depend on λ and the degeneracy of the acoustic modes is broken.
Non-ergodic delocalized phase in Anderson model on Bethe lattice and regular graph
Kravtsov, V. E.; Altshuler, B. L.; Ioffe, L. B.
2018-02-01
We develop a novel analytical approach to the problem of single particle localization in infinite dimensional spaces such as Bethe lattice and random regular graph models. The key ingredient of the approach is the notion of the inverted order thermodynamic limit (IOTL) in which the coupling to the environment goes to zero before the system size goes to infinity. Using IOTL and Replica Symmetry Breaking (RSB) formalism we derive analytical expressions for the fractal dimension D1 that distinguishes between the extended ergodic, D1 = 1, and extended non-ergodic (multifractal), 0 graphs with the branching number K. We also employ RSB formalism to derive the analytical expression ln Styp-1 = - 〈 ln S 〉 ∼(Wc - W) - 1 for the typical imaginary part of self-energy Styp in the non-ergodic phase close to the Anderson transition in the conventional thermodynamic limit. We prove the existence of an extended non-ergodic phase in a broad range of disorder strength and energy and establish the phase diagrams of the models as a function of disorder and energy. The results of the analytical theory are compared with large-scale population dynamics and with the exact diagonalization of Anderson model on random regular graphs. We discuss the consequences of these results for the many body localization.
Boutet de Monvel, A.; Chulaevsky, V.; Stollmann, P.; Suhov, Y.
2010-03-01
We consider an N-particle quantum systems in ℝ d , with interaction and in presence of a random external alloy-type potential (a continuous N-particle Anderson model). We establish Wegner-type bounds (inequalities) for such models, giving upper bounds for the probability that random spectra of Hamiltonians in finite volumes intersect a given set.
Kettemann, S.; Mucciolo, E. R.; Varga, I.; Slevin, K.
2012-03-01
Dilute magnetic impurities in a disordered Fermi liquid are considered close to the Anderson metal-insulator transition (AMIT). Critical power-law correlations between electron wave functions at different energies in the vicinity of the AMIT result in the formation of pseudogaps of the local density of states. Magnetic impurities can remain unscreened at such sites. We determine the density of the resulting free magnetic moments in the zero-temperature limit. While it is finite on the insulating side of the AMIT, it vanishes at the AMIT, and decays with a power law as function of the distance to the AMIT. Since the fluctuating spins of these free magnetic moments break the time-reversal symmetry of the conduction electrons, we find a shift of the AMIT, and the appearance of a semimetal phase. The distribution function of the Kondo temperature TK is derived at the AMIT, in the metallic phase, and in the insulator phase. This allows us to find the quantum phase diagram in an external magnetic field B and at finite temperature T. We calculate the resulting magnetic susceptibility, the specific heat, and the spin relaxation rate as a function of temperature. We find a phase diagram with finite-temperature transitions among insulator, critical semimetal, and metal phases. These new types of phase transitions are caused by the interplay between Kondo screening and Anderson localization, with the latter being shifted by the appearance of the temperature-dependent spin-flip scattering rate. Accordingly, we name them Kondo-Anderson transitions.
Matrix product state calculations for one-dimensional quantum chains and quantum impurity models
Energy Technology Data Exchange (ETDEWEB)
Muender, Wolfgang
2011-09-28
involving a Kondo exciton and population switching in quantum dots. It turns out that both phenomena rely on the various manifestations of Anderson orthogonality (AO), which describes the fact that the response of the Fermi sea to a quantum quench (i.e. an abrupt change of some property of the impurity or quantum dot) is a change of the scattering phase shifts of all the single-particle wave functions, therefore drastically changing the system. In this context, we demonstrate that NRG, a highly accurate method for quantum impurity models, allows for the calculation of all static and dynamic quantities related to AO and present an extensive NRG study for population switching in quantum dots. (orig.)
Foglio, M. E.; Lobo, T.; Figueira, M. S.
2012-09-01
We consider the cumulant expansion of the periodic Anderson model (PAM) in the case of a finite electronic correlation U, employing the hybridization as perturbation, and obtain a formal expression of the exact one-electron Green's function (GF). This expression contains effective cumulants that are as difficult to calculate as the original GF, and the atomic approach consists in substituting the effective cumulants by the ones that correspond to the atomic case, namely by taking a conduction band of zeroth width and local hybridization. In a previous work (T. Lobo, M. S. Figueira, and M. E. Foglio, Nanotechnology 21, 274007 (2010), 10.1088/0957-4484/21/27/274007) we developed the atomic approach by considering only one variational parameter that is used to adjust the correct height of the Kondo peak by imposing the satisfaction of the Friedel sum rule. To obtain the correct width of the Kondo peak in the present work, we consider an additional variational parameter that guarantees this quantity. The two constraints now imposed on the formalism are the satisfaction of the Friedel sum rule and the correct Kondo temperature. In the first part of the work, we present a general derivation of the method for the single impurity Anderson model (SIAM), and we calculate several density of states representative of the Kondo regime for finite correlation U, including the symmetrical case. In the second part, we apply the method to study the electronic transport through a quantum dot (QD) embedded in a quantum wire (QW), which is realized experimentally by a single electron transistor (SET). We calculate the conductance of the SET and obtain a good agreement with available experimental and theoretical results.
The physics of Kondo impurities in graphene.
Fritz, Lars; Vojta, Matthias
2013-03-01
This article summarizes our understanding of the Kondo effect in graphene, primarily from a theoretical perspective. We shall describe different ways to create magnetic moments in graphene, either by adatom deposition or via defects. For dilute moments, the theoretical description is in terms of effective Anderson or Kondo impurity models coupled to graphene's Dirac electrons. We shall discuss in detail the physics of these models, including their quantum phase transitions and the effect of carrier doping, and confront this with existing experimental data. Finally, we will point out connections to other quantum impurity problems, e.g., in unconventional superconductors, topological insulators, and quantum spin liquids.
Anderson localization for a random vector potential model at high dimensions
Nakano, F
2005-01-01
We prove that Anderson localization holds on the spectral edge of the Schroedinger operator with a uniformly distributed random vector potential on ${\\bf Z}^d$, if d is sufficiently large. The key ingredient is the proof of a Wegner estimate which is reduced to the problem of counting the number of paths on ${\\bf Z}^d$ with ``no loops".
Magnetic states of single impurity in disordered environment
Directory of Open Access Journals (Sweden)
G.W. Ponedilok
2013-01-01
Full Text Available The charged and magnetic states of isolated impurities dissolved in amorphous metallic alloy are investigated. The Hamiltonian of the system under study is the generalization of Anderson impurity model. Namely, the processes of elastic and non-elastic scattering of conductive electrons on the ions of a metal and on a charged impurity are included. The configuration averaged one-particle Green's functions are obtained within Hartree-Fock approximation. A system of self-consistent equations is given for calculation of an electronic spectrum, the charged and the spin-polarized impurity states. Qualitative analysis of the effect of the metallic host structural disorder on the observed values is performed. Additional shift and broadening of virtual impurity level is caused by a structural disorder of impurity environment.
Erhard, D; Hollander, den, WTF Frank; Maillard, G Gregory
2014-01-01
In this paper we study the parabolic Anderson equation $\\partial u(x,t)/\\partial t=\\kappa\\varDelta u(x,t)+\\xi(x,t)u(x,t)$, $x\\in\\mathbb{Z}^{d}$, $t\\geq0$, where the $u$-field and the $\\xi$-field are $\\mathbb{R}$-valued, $\\kappa\\in[0,\\infty)$ is the diffusion constant, and $\\varDelta $ is the discrete Laplacian. The $\\xi$-field plays the role of a dynamic random environment that drives the equation. The initial condition $u(x,0)=u_{0}(x)$, $x\\in\\mathbb{Z}^{d}$, is taken to be non-negative and ...
Mano, Tomohiro; Ohtsuki, Tomi
2017-11-01
The three-dimensional Anderson model is a well-studied model of disordered electron systems that shows the delocalization-localization transition. As in our previous papers on two- and three-dimensional (2D, 3D) quantum phase transitions [https://doi.org/10.7566/JPSJ.85.123706" xlink:type="simple">J. Phys. Soc. Jpn. 85, 123706 (2016), https://doi.org/10.7566/JPSJ.86.044708" xlink:type="simple">86, 044708 (2017)], we used an image recognition algorithm based on a multilayered convolutional neural network. However, in contrast to previous papers in which 2D image recognition was used, we applied 3D image recognition to analyze entire 3D wave functions. We show that a full phase diagram of the disorder-energy plane is obtained once the 3D convolutional neural network has been trained at the band center. We further demonstrate that the full phase diagram for 3D quantum bond and site percolations can be drawn by training the 3D Anderson model at the band center.
Modeling of the Microchemistry for Diffusion of Selected Impurities in Uranium
International Nuclear Information System (INIS)
Kirkpatrick, J. R.; Bullock, J.S. IV
2001-01-01
Unalloyed metallic uranium used in some work done at Y-12 contains small quantities of impurities, the three most significant of which are carbon, iron, and silicon. During metallurgical processing, as the metal cools from a molten condition towards room temperature, the metallic matrix solution becomes supersaturated in each of the impurities whose concentration exceeds the solubility limit. Many impurity atoms form compounds with uranium that precipitate out of the solution, thus creating and growing inclusions. The objective of the present work is to study the distribution of impurity atoms about some of the inclusions, with a view toward examining the effect of the interaction between inclusions on the impurity atom distribution. The method used is time-dependent mass diffusion from the supersaturated solution to the surfaces of the inclusions. Micrographs of metal samples suggest that the inclusions form in successive stages. After each inclusion forms, it begins to draw impurity atoms from its immediate vicinity, thus altering the amounts and distributions of impurity atoms available for formation and growth of later inclusions. In the present work, a one-dimensional spherical approximation was used to simulate inclusions and their regions of influence. A first set of calculations was run to simulate the distribution of impurity atoms about the largest inclusions. Then, a second set of calculations was run to see how the loss of impurity atoms to the largest inclusions might affect the distribution of impurity atoms around the next stage of inclusions. Plots are shown for the estimated distributions of impurity atoms in the region of influence about the inclusions for the three impurities studied. The authors believe that these distributions are qualitatively correct. However, there is enough uncertainty about precisely when inclusions nucleate and begin to grow that one should not put too much reliance on the quantitative results. This work does provide a
Hyperfine Fields on Actinide Impurities in Ferromagnetic Fe and Ni Hosts
International Nuclear Information System (INIS)
Oliveira, A.L. de; Oliveira, N.A. de; Troper, A.
2003-01-01
We discuss the local magnetic moments and magnetic hyperfine fields on actinide impurities diluted in Fe and Ni hosts. One adopts a Anderson- Moriya model in which a localized 5f level is hybridized with a spin polarized and charge perturbed d-conduction band. Our self-consistent numerical calculations for the hyperfine fields on the impurity sites are in good agreement with the available experimental data. (author)
Self-consistent modeling of plasma response to impurity spreading from intense localized source
International Nuclear Information System (INIS)
Koltunov, Mikhail
2012-07-01
Non-hydrogen impurities unavoidably exist in hot plasmas of present fusion devices. They enter it intrinsically, due to plasma interaction with the wall of vacuum vessel, as well as are seeded for various purposes deliberately. Normally, the spots where injected particles enter the plasma are much smaller than its total surface. Under such conditions one has to expect a significant modification of local plasma parameters through various physical mechanisms, which, in turn, affect the impurity spreading. Self-consistent modeling of interaction between impurity and plasma is, therefore, not possible with linear approaches. A model based on the fluid description of electrons, main and impurity ions, and taking into account the plasma quasi-neutrality, Coulomb collisions of background and impurity charged particles, radiation losses, particle transport to bounding surfaces, is elaborated in this work. To describe the impurity spreading and the plasma response self-consistently, fluid equations for the particle, momentum and energy balances of various plasma components are solved by reducing them to ordinary differential equations for the time evolution of several parameters characterizing the solution in principal details: the magnitudes of plasma density and plasma temperatures in the regions of impurity localization and the spatial scales of these regions. The results of calculations for plasma conditions typical in tokamak experiments with impurity injection are presented. A new mechanism for the condensation phenomenon and formation of cold dense plasma structures is proposed.
Energy Technology Data Exchange (ETDEWEB)
Patel, Niravkumar D. [The Univ. of Tennessee, Knoxville, TN (United States); Mukherjee, Anamitra [National Institute of Science Education and Research, Jatni (India); Kaushal, Nitin [The Univ. of Tennessee, Knoxville, TN (United States); Moreo, Adriana [The Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Dagotto, Elbio R. [The Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2017-08-24
Here, we employ a recently developed computational many-body technique to study for the first time the half-filled Anderson-Hubbard model at finite temperature and arbitrary correlation U and disorder V strengths. Interestingly, the narrow zero temperature metallic range induced by disorder from the Mott insulator expands with increasing temperature in a manner resembling a quantum critical point. Our study of the resistivity temperature scaling T^{α} for this metal reveals non-Fermi liquid characteristics. Moreover, a continuous dependence of α on U and V from linear to nearly quadratic is observed. We argue that these exotic results arise from a systematic change with U and V of the “effective” disorder, a combination of quenched disorder and intrinsic localized spins.
Anomalies in the 1D Anderson model: Beyond the band-centre and band-edge cases
Tessieri, L.; Izrailev, F. M.
2018-03-01
We consider the one-dimensional Anderson model with weak disorder. Using the Hamiltonian map approach, we analyse the validity of the random-phase approximation for resonant values of the energy, E = 2 cos(πr) , with r a rational number. We expand the invariant measure of the phase variable in powers of the disorder strength and we show that, contrary to what happens at the centre and at the edges of the band, for all other resonant energies the leading term of the invariant measure is uniform. When higher-order terms are taken into account, a modulation of the invariant measure appears for all resonant values of the energy. This implies that, when the localisation length is computed within the second-order approximation in the disorder strength, the Thouless formula is valid everywhere except at the band centre and at the band edges.
Modeling of soluble impurities distribution in the steam generator secondary water
International Nuclear Information System (INIS)
Matal, O.; Simo, T.; Kucak, L.; Urban, F.
1997-01-01
A model was developed to compute concentration of impurities in the WWER 440 steam generator (SG) secondary water along the tube bundle. Calculated values were verified by concentration values obtained from secondary water sample chemical analysis. (orig.)
Modeling of soluble impurities distribution in the steam generator secondary water
Energy Technology Data Exchange (ETDEWEB)
Matal, O.; Simo, T. [Energovyzkum s.r.o., Brno (Switzerland); Kucak, L.; Urban, F. [Slovak Technical Univ., Bratislava (Slovakia)
1997-12-31
A model was developed to compute concentration of impurities in the WWER 440 steam generator (SG) secondary water along the tube bundle. Calculated values were verified by concentration values obtained from secondary water sample chemical analysis. (orig.). 2 refs.
Modeling impurity-assisted chain creation in noble-metal break junctions
International Nuclear Information System (INIS)
Di Napoli, S; Thiess, A; Blügel, S; Mokrousov, Y
2012-01-01
In this work we present the generalization of the model for chain formation in break junctions, introduced by Thiess et al (2008 Nano Lett. 8 2144), to zigzag transition-metal chains with s and p impurities. We apply this extended model to study the producibility trends for noble-metal chains with impurities, often present in break junction experiments, namely, Cu, Ag and Au chains with H, C, O and N adatoms. Providing the material-specific parameters for our model from systematic full-potential linearized augmented plane-wave first-principles calculations, we find that the presence of such impurities crucially affects the binding properties of the noble-metal chains. We reveal that both the impurity-induced bond strengthening and the formation of zigzag bonds can lead to a significantly enhanced probability for chain formation in break junctions. (paper)
Investigation of Anderson lattice behavior in Yb1-xLuxAl3
International Nuclear Information System (INIS)
Bauer, E.D.; Booth, C.H.; Lawrence, J.M.; Hundley, M.F.; Sarrao, J.L.; Thompson, J.D.; Riseborough, P.S.; Ebihara, T.
2003-01-01
Measurements of magnetic susceptibility χ(T), specific heat C(T), Hall coefficient R H (T), and Yb valence ν = 2 + n f [f-occupation number n f (T) determined from Yb L 3 x-ray absorption measurements] were carried out on single crystals of Yb 1-x Lu x Al 3 . The low temperature anomalies observed in χ(T) and C(T) corresponding to an energy scale T coh ∼ 40 K in the intermediate valence, Kondo lattice compound YbAl 3 are suppressed by Lu concentrations as small as 5% suggesting these low-T anomalies are extremely sensitive to disorder and, therefore, are a true coherence effect. By comparing the temperature dependence of various physical quantities to the predictions of the Anderson Impurity Model, the slow crossover behavior observed in YbAl 3 , in which the data evolve from a low-temperature coherent, Fermi-liquid regime to a high temperature local moment regime more gradually than predicted by the Anderson Impurity Model, appears to evolve to fast crossover behavior at x ∼ 0.7 where the evolution is more rapid than predicted. These two phenomena found in Yb 1-x Lu x Al 3 , i.e., the low-T anomalies and the slow/fast crossover behavior are discussed in relation to recent theories of the Anderson lattice
Visualization and modeling of impurity atom migration for superdiffusion in semiconductors
Energy Technology Data Exchange (ETDEWEB)
Wada, T. [Nagoya Sangyo University, Aichi (Japan); Kojiguchi, K. [Nagoya Sangyo University, Aichi (Japan); Nagao, H. [Graduate School of information Science, Nagoya University (Japan); Fujimoto, H. [Daido institute of Technology, Nagoya (Japan)]. E-mail: fujimoto@daido-it.ac.jp
2006-04-01
Radiation-enhanced superdiffusion in two-layered structures, comprised of an impurity overlayer and a semiconductor substrate, subjected to electron beam irradiation is modeled and visualized using computer graphics animation. The important and experimentally observed large sticking probabilities of impurities at the wafer surface were modeled in the algorithm, and the animation was found to behave as expected under irradiation. Programming of the animation algorithm was performed using an object modeling technique. The animation generated a continuous display of radiation-enhanced superdiffusion that was qualitatively consistent with experimental observations, thereby facilitating understanding of the superdiffusion process.
Directory of Open Access Journals (Sweden)
Ivanova-Stanik Irena
2017-03-01
Full Text Available Numerical simulations with the COREDIV code of JET H-mode discharges with 25 MW of auxiliary heating in the ITER-like wall (ILW configuration with different impurity seedings – nitrogen (N, neon (Ne, argon (Ar and krypton (Kr – are presented. All simulations have been performed with the same transport model and input discharge parameters like auxiliary heating, volume average plasma density, confinement factor. Only the seeded impurity puff rate was changed in the calculations. It appears that for the considered heating power of 25 MW and relatively low volume electron average density = 6.2 × 1019 m−3, impurity seeding is necessary. It has been found that for every gas at the maximum level of the seeding rate, allowed by the code convergence, the power to the plate is reduced up to 2–4 MW, with electron temperature at the plate of about 2 eV, indicating semi-detached conditions in the divertor region. It should be noted, however, that in cases with low and medium Z impurity (N, Ne and Ar, tungsten radiation is a significant part of radiation losses and stays above 22–32% of the total energy losses, but for high Z impurity (Kr it is reduced up to 10% of the total losses. The maximum of the Kr radiation is between the pedestal region and separatrix, showing that radiative mantle can be created, which might have a strong influence on the plasma parameters in the pedestal region.
Johnson, T H; Yuan, Y; Bao, W; Clark, S R; Foot, C; Jaksch, D
2016-06-17
We investigate cold bosonic impurity atoms trapped in a vortex lattice formed by condensed bosons of another species. We describe the dynamics of the impurities by a bosonic Hubbard model containing occupation-dependent parameters to capture the effects of strong impurity-impurity interactions. These include both a repulsive direct interaction and an attractive effective interaction mediated by the Bose-Einstein condensate. The occupation dependence of these two competing interactions drastically affects the Hubbard model phase diagram, including causing the disappearance of some Mott lobes.
Indian Academy of Sciences (India)
Home; Fellowship. Fellow Profile. Elected: 1978 Honorary. Anderson, Prof. John Stuart. Date of birth: 9 January 1908. Date of death: 25 December 1990. YouTube; Twitter; Facebook; Blog. Academy News. IAS Logo. 29th Mid-year meeting. Posted on 19 January 2018. The 29th Mid-year meeting of the Academy will be held ...
Anderson, Prof. Basil Williams
Indian Academy of Sciences (India)
Home; Fellowship. Fellow Profile. Elected: 1964 Honorary. Anderson, Prof. Basil Williams. Date of birth: 3 July 1901. Date of death: 24 February 1984. YouTube; Twitter; Facebook; Blog. Academy News. IAS Logo. 29th Mid-year meeting. Posted on 19 January 2018. The 29th Mid-year meeting of the Academy will be held ...
Indian Academy of Sciences (India)
Home; Fellowship. Fellow Profile. Elected: 1978 Honorary. Anderson, Prof. John Stuart. Date of birth: 9 January 1908. Date of death: 25 December 1990. YouTube; Twitter; Facebook; Blog. Academy News. IAS Logo. Theory Of Evolution. Posted on 23 January 2018. Joint Statement by the Three Science Academies of India ...
Anderson, Prof. Basil Williams
Indian Academy of Sciences (India)
Home; Fellowship. Fellow Profile. Elected: 1964 Honorary. Anderson, Prof. Basil Williams. Date of birth: 3 July 1901. Date of death: 24 February 1984. YouTube; Twitter; Facebook; Blog. Academy News. IAS Logo. Theory Of Evolution. Posted on 23 January 2018. Joint Statement by the Three Science Academies of India on ...
Study of impurity effects on CFETR steady-state scenario by self-consistent integrated modeling
Shi, Nan; Chan, Vincent S.; Jian, Xiang; Li, Guoqiang; Chen, Jiale; Gao, Xiang; Shi, Shengyu; Kong, Defeng; Liu, Xiaoju; Mao, Shifeng; Xu, Guoliang
2017-12-01
Impurity effects on fusion performance of China fusion engineering test reactor (CFETR) due to extrinsic seeding are investigated. An integrated 1.5D modeling workflow evolves plasma equilibrium and all transport channels to steady state. The one modeling framework for integrated tasks framework is used to couple the transport solver, MHD equilibrium solver, and source and sink calculations. A self-consistent impurity profile constructed using a steady-state background plasma, which satisfies quasi-neutrality and true steady state, is presented for the first time. Studies are performed based on an optimized fully non-inductive scenario with varying concentrations of Argon (Ar) seeding. It is found that fusion performance improves before dropping off with increasing {{Z}\\text{eff}} , while the confinement remains at high level. Further analysis of transport for these plasmas shows that low-k ion temperature gradient modes dominate the turbulence. The decrease in linear growth rate and resultant fluxes of all channels with increasing {{Z}\\text{eff}} can be traced to impurity profile change by transport. The improvement in confinement levels off at higher {{Z}\\text{eff}} . Over the regime of study there is a competition between the suppressed transport and increasing radiation that leads to a peak in the fusion performance at {{Z}\\text{eff}} (~2.78 for CFETR). Extrinsic impurity seeding to control divertor heat load will need to be optimized around this value for best fusion performance.
International Nuclear Information System (INIS)
Valerio, Luis G.; Cross, Kevin P.
2012-01-01
Control and minimization of human exposure to potential genotoxic impurities found in drug substances and products is an important part of preclinical safety assessments of new drug products. The FDA's 2008 draft guidance on genotoxic and carcinogenic impurities in drug substances and products allows use of computational quantitative structure–activity relationships (QSAR) to identify structural alerts for known and expected impurities present at levels below qualified thresholds. This study provides the information necessary to establish the practical use of a new in silico toxicology model for predicting Salmonella t. mutagenicity (Ames assay outcome) of drug impurities and other chemicals. We describe the model's chemical content and toxicity fingerprint in terms of compound space, molecular and structural toxicophores, and have rigorously tested its predictive power using both cross-validation and external validation experiments, as well as case studies. Consistent with desired regulatory use, the model performs with high sensitivity (81%) and high negative predictivity (81%) based on external validation with 2368 compounds foreign to the model and having known mutagenicity. A database of drug impurities was created from proprietary FDA submissions and the public literature which found significant overlap between the structural features of drug impurities and training set chemicals in the QSAR model. Overall, the model's predictive performance was found to be acceptable for screening drug impurities for Salmonella mutagenicity. -- Highlights: ► We characterize a new in silico model to predict mutagenicity of drug impurities. ► The model predicts Salmonella mutagenicity and will be useful for safety assessment. ► We examine toxicity fingerprints and toxicophores of this Ames assay model. ► We compare these attributes to those found in drug impurities known to FDA/CDER. ► We validate the model and find it has a desired predictive performance.
Yamoto, S.; Bonnin, X.; Homma, Y.; Inoue, H.; Hoshino, K.; Hatayama, A.; Pitts, R. A.
2017-11-01
In order to obtain a better understanding of tungsten (W) transport processes, we are developing the Monte-Carlo W transport code IMPGYRO. The code has the following characteristics which are important for calculating W transport: (1) the exact Larmor motion of W ions is computed so that the effects of drifts are automatically taken into account; (2) Coulomb collisions between W impurities and background plasma ions are modelled using the Binary Collision Model which provides more precise kinetic calculations of the friction and thermal forces. By using the IMPGYRO code, the W production/transport in the ITER geometry has been calculated under two different divertor operation modes (Case A: partially detached state and Case B: high recycling state) obtained from the SOLPS-ITER code suite calculation without the effect of drifts. The results of the W-density in the upstream SOL (scrape-off layer) strongly depend on the divertor operation mode. From the comparison of the W impurity transport between Case A and Case B, obtaining a partially detached state is shown to be effective to reduce W-impurities in the upstream SOL. The limitations of the employed model and the validity of the above results are discussed and future problems are summarized for further applications of IMPGYRO code to ITER plasmas.
Magnetic impurity in a system of interacting electrons
International Nuclear Information System (INIS)
Huynh Thanh Duc; Nguyen Toan Thang
1999-04-01
The Kondo effect of the Anderson impurity in a correlated conduction electron system is studied within the slave boson mean-field theory. The interacting conduction electrons are described by a Hubbard model with an interaction of strength U. It is shown that the Kondo temperature T K decreases with an increase of U. In the intermediate regime at half-filling the exponential scale of the Kondo temperature T K is lost already at the saddle-point level of slave boson formulation. (author)
Atomistic modeling of an impurity element and a metal-impurity system: pure P and Fe-P system
International Nuclear Information System (INIS)
Ko, Won-Seok; Lee, Byeong-Joo; Kim, Nack J
2012-01-01
An interatomic potential for pure phosphorus, an element that has van der Waals, covalent and metallic bonding character, simultaneously, has been developed for the purpose of application to metal-phosphorus systems. As a simplification, the van der Waals interaction, which is less important in metal-phosphorus systems, was omitted in the parameterization process and potential formulation. On the basis of the second-nearest-neighbor modified embedded-atom method (2NN MEAM) interatomic potential formalism applicable to both covalent and metallic materials, a potential that can describe various fundamental physical properties of a wide range of allotropic or transformed crystalline structures of pure phosphorus could be developed. The potential was then extended to the Fe-P binary system describing various physical properties of intermetallic compounds, bcc and liquid alloys, and also the segregation tendency of phosphorus on grain boundaries of bcc iron, in good agreement with experimental information. The suitability of the present potential and the parameterization process for atomic scale investigations about the effects of various non-metallic impurity elements on metal properties is demonstrated. (paper)
Brambila, Danilo
2012-01-01
We have theoretically studied Anderson localization in a 2D+1 nonlinear kicked rotor model. The system shows a very rich dynamical behavior, where the Anderson localization is suppressed and soliton wave-particles undergo a superdiffusive motion.
Evaluation of Thermodynamic Models for Predicting Phase Equilibria of CO2 + Impurity Binary Mixture
Shin, Byeong Soo; Rho, Won Gu; You, Seong-Sik; Kang, Jeong Won; Lee, Chul Soo
2018-03-01
For the design and operation of CO2 capture and storage (CCS) processes, equation of state (EoS) models are used for phase equilibrium calculations. Reliability of an EoS model plays a crucial role, and many variations of EoS models have been reported and continue to be published. The prediction of phase equilibria for CO2 mixtures containing SO2, N2, NO, H2, O2, CH4, H2S, Ar, and H2O is important for CO2 transportation because the captured gas normally contains small amounts of impurities even though it is purified in advance. For the design of pipelines in deep sea or arctic conditions, flow assurance and safety are considered priority issues, and highly reliable calculations are required. In this work, predictive Soave-Redlich-Kwong, cubic plus association, Groupe Européen de Recherches Gazières (GERG-2008), perturbed-chain statistical associating fluid theory, and non-random lattice fluids hydrogen bond EoS models were compared regarding performance in calculating phase equilibria of CO2-impurity binary mixtures and with the collected literature data. No single EoS could cover the entire range of systems considered in this study. Weaknesses and strong points of each EoS model were analyzed, and recommendations are given as guidelines for safe design and operation of CCS processes.
Energy Technology Data Exchange (ETDEWEB)
Ding, L.J., E-mail: dinglinjie82@126.com; Zhong, Y.
2017-07-15
Highlights: • The quantum critical scaling is investigated by Green’s function theory. • The obtained power-law critical exponents (β, δ and α) obey the critical scaling relation α + β(1 + δ) = 2. • The scaling hypothesis equations are proposed to verify the scaling analysis. - Abstract: The quantum phase transition and thermodynamics of a periodic Anderson-like polymer chain in a magnetic field are investigated by Green’s function theory. The T-h phase diagram is explored, wherein a crossover temperature T{sup ∗} denoting the gapless phase crossover into quantum critical regimes, smoothly connects near the critical fields to the universal linear line T{sup ∗} ∼ (h − h{sub c,s}), and ends at h{sub c,s}, providing a new route to capture quantum critical point (QCP). The quantum critical scaling around QCPs is demonstrated by analyzing magnetization, specific heat and Grüneisen parameter Γ{sub h}, which provide direct access to distill the power-law critical exponents (β, δ and α) obeying the critical scaling relation α + β(1 + δ) = 2, analogous to the quantum spin system. Furthermore, scaling hypothesis equations are proposed to check the scaling analysis, for which all the data collapse onto a single curve or two independent branches for the plot against an appropriate scaling variable, indicating the self-consistency and reliability of the obtained critical exponents.
International Nuclear Information System (INIS)
Tolpin, A.E.
1992-01-01
A new approach toward understanding the heavy-fermion systems (HFS) within a framework of the almost-degenerate lattice Anderson Hamiltonian in the Kondo regime is proposed. In the coherent low-temperature regime, operators in the effective Hamiltonian are found to belong to an SU(2J + 3) dynamical algebra. A canonical transformation is employed to decouple the quasiparticle branches, thereby setting up the decoupling equation. It is found that this decoupling equation has a solution of the symmetry-altering type. The thermodynamic response functions and other quantities are calculated for this new state. This solution is a consequence of the degeneracy of the uncoupled f-orbitals. It is characterized by the interatomic hopping of f-electrons, which produces the spin-delocalization regime and with the renormalized f-level pinned close to the Fermi level. This is also found to be the source of the apparent spin-compensation regime, which is accompanied by large enhancement of the thermodynamic response functions. In addition, the calculated phase coherence length is found to be much greater than a lattice constant, thereby showing a many-body character of this new state. It is believed that this new state provides an accurate description of the heavy-fermion state at low temperatures. The stability conditions for the new regime are also discussed
Sharma, P; Mišković, Z L
2015-10-07
We present a model describing the electrostatic interactions across a structure that consists of a single layer of graphene with large area, lying above an oxide substrate of finite thickness, with its surface exposed to a thick layer of liquid electrolyte containing salt ions. Our goal is to analyze the co-operative screening of the potential fluctuation in a doped graphene due to randomness in the positions of fixed charged impurities in the oxide by the charge carriers in graphene and by the mobile ions in the diffuse layer of the electrolyte. In order to account for a possibly large potential drop in the diffuse later that may arise in an electrolytically gated graphene, we use a partially linearized Poisson-Boltzmann (PB) model of the electrolyte, in which we solve a fully nonlinear PB equation for the surface average of the potential in one dimension, whereas the lateral fluctuations of the potential in graphene are tackled by linearizing the PB equation about the average potential. In this way, we are able to describe the regime of equilibrium doping of graphene to large densities for arbitrary values of the ion concentration without restrictions to the potential drop in the electrolyte. We evaluate the electrostatic Green's function for the partially linearized PB model, which is used to express the screening contributions of the graphene layer and the nearby electrolyte by means of an effective dielectric function. We find that, while the screened potential of a single charged impurity at large in-graphene distances exhibits a strong dependence on the ion concentration in the electrolyte and on the doping density in graphene, in the case of a spatially correlated two-dimensional ensemble of impurities, this dependence is largely suppressed in the autocovariance of the fluctuating potential.
Horvat, Alen; Žitko, Rok; Mravlje, Jernej
2017-08-01
We investigate the effects of spin-orbit coupling (SOC) in a three-orbital impurity model with a Kanamori interaction using the numerical renormalization group method. We focus on the impurity occupancy Nd=2 relevant to the dynamical mean-field theory studies of Hund's metals. Depending on the strength of SOC λ , we identify three regimes: the usual Hund's impurity for |λ |λc , and a J =2 impurity for λ <-λc . They all correspond to a Fermi liquid but with very different quasiparticle phase shifts and different physical properties. The crossover between these regimes is controlled by an emergent scale, the orbital Kondo temperature λc=TKorb , that drops with increasing interaction strength. This implies that oxides with strong electronic correlations are more prone to the effects of spin-orbit coupling.
Effect of coulomb interaction on Anderson localization
International Nuclear Information System (INIS)
Waintal, X.
1999-01-01
We study the quantum mechanics of interacting particles in a disordered system, and in particular, what happens to Anderson localisation when interaction is taken into account. In the first part, one looks at the excited states of two particles in one dimension. For this model, it has been shown (Shepelyansky 1994) that a local repulsive interaction can partially destroy Anderson localisation. Here, we show that this model has similarities with the three-dimensional Anderson model at the metal-insulator transition. In particular, the maximum of rigidity obtained in the spectral statistics correspond to some intermediary statistics that cannot be described by random matrix theory neither by a Poisson statistics. The wave functions show a multifractal behaviour and the spreading of the center of mass of a wave packet is logarithmic in time. The second part deals with the ground state of a finite density of spinless fermions in two dimensions. After the scaling theory of localisation, it was commonly accepted that there was no metal in two dimensions. This idea has been challenged by the observation of a metal-insulator transition in low density electron gas (Kravchenko et al. 1994). We propose a scenario in which a metallic phase occurs between the Anderson insulator and the pinned Wigner crystal. This intermediate phase is characterized by an alignment of the local currents flowing in the system. (author)
Directory of Open Access Journals (Sweden)
C. Bréant
2017-07-01
Full Text Available The transformation of snow into ice is a complex phenomenon that is difficult to model. Depending on surface temperature and accumulation rate, it may take several decades to millennia for air to be entrapped in ice. The air is thus always younger than the surrounding ice. The resulting gas–ice age difference is essential to documenting the phasing between CO2 and temperature changes, especially during deglaciations. The air trapping depth can be inferred in the past using a firn densification model, or using δ15N of air measured in ice cores. All firn densification models applied to deglaciations show a large disagreement with δ15N measurements at several sites in East Antarctica, predicting larger firn thickness during the Last Glacial Maximum, whereas δ15N suggests a reduced firn thickness compared to the Holocene. Here we present modifications of the LGGE firn densification model, which significantly reduce the model–data mismatch for the gas trapping depth evolution over the last deglaciation at the coldest sites in East Antarctica (Vostok, Dome C, while preserving the good agreement between measured and modelled modern firn density profiles. In particular, we introduce a dependency of the creep factor on temperature and impurities in the firn densification rate calculation. The temperature influence intends to reflect the dominance of different mechanisms for firn compaction at different temperatures. We show that both the new temperature parameterization and the influence of impurities contribute to the increased agreement between modelled and measured δ15N evolution during the last deglaciation at sites with low temperature and low accumulation rate, such as Dome C or Vostok. We find that a very low sensitivity of the densification rate to temperature has to be used in the coldest conditions. The inclusion of impurity effects improves the agreement between modelled and measured δ15N at cold East Antarctic sites during the last
Tunneling effect in superconductors with magnetic impurities
International Nuclear Information System (INIS)
Ahmed, M.
1985-07-01
We investigate the influence of transition metal impurities on the amplitude of the Josephson tunneling current. We consider a junction made up of two identical superconductors containing transition metal impurities and define a parameter K which is the normalised difference of the derivative of Josephson currents for superconducting pairs with and without magnetic impurities. We find K=0 for U/πGAMMA >1 in the Abrikosov-Gorkov theory, as well as large deviations of K from this value for 1< U/πGAMMA<3, where U/πGAMMA is the parameter of the Anderson theory. (author)
Monte Carlo impurity transport modeling in the DIII-D transport
International Nuclear Information System (INIS)
Evans, T.E.; Finkenthal, D.F.
1998-04-01
A description of the carbon transport and sputtering physics contained in the Monte Carlo Impurity (MCI) transport code is given. Examples of statistically significant carbon transport pathways are examined using MCI's unique tracking visualizer and a mechanism for enhanced carbon accumulation on the high field side of the divertor chamber is discussed. Comparisons between carbon emissions calculated with MCI and those measured in the DIII-D tokamak are described. Good qualitative agreement is found between 2D carbon emission patterns calculated with MCI and experimentally measured carbon patterns. While uncertainties in the sputtering physics, atomic data, and transport models have made quantitative comparisons with experiments more difficult, recent results using a physics based model for physical and chemical sputtering has yielded simulations with about 50% of the total carbon radiation measured in the divertor. These results and plans for future improvement in the physics models and atomic data are discussed
Modeling and data analysis of a palladium membrane reactor for tritiated impurities cleanup
International Nuclear Information System (INIS)
Birdsell, S.A.; Willms, R.S.
1995-01-01
A Palladium Membrane Reactor (PMR) is under consideration for the tritium plant for the International Thermonuclear Experimental Reactor (ITER). The ITER reactor exhaust will contain tritiated impurities such as water and methane. Tritium will need to be recovered from these impurities for environmental and economic reasons. For this purpose a promising device, PMR, has been proposed. The PMR is a combined permeator and catalytic reactor. Shift catalysts are used to foster reactions such as water-gas shift, H 2 O + CO → H 2 + CO 2 , and methane steam reforming, CH 4 + H 2 O → 3H 2 + CO. Due to thermodynamic limitations these reactions only proceed to partial completion. Thus, a Pd/Ag membrane, which is exclusively permeable to hydrogen isotopes, is incorporated into the reactor. By maintaining a vacuum on the permeate, product hydrogen isotopes are removed, enabling the reactions to proceed to completion. A model has been developed to study the complex interactions in a PMR so that the optimal design can be determined. The model accounts for the coupled effects of transport-limited permeation of hydrogen isotopes and chemical reactions. The permeation model is an extension of previous models that include the effects of temperature, wall thickness, reaction-side pressure, and permeate-side pressure. Reaction rates for methane steam reforming and the water-gas shift reaction are incorporated into the model along with the respective reverse reactions. The model is compared to PMR data and used to investigate the concentration and pressure profiles in the reactor. Due to the interactions of permeation and reaction complex profiles can be produced in a PMR. For example, the water concentration often increases after the inlet to the PMR to a maximum value, and then decreases to the low values expected with a PMR. Detailed information like this is required for the design and optimization of PMRs for the ITER tritium plant
Competitive heterogeneous nucleation onto a microscopic impurity in a Potts model
Asuquo, Cletus C.; McArthur, Danielle; Bowles, Richard K.
2016-08-01
Many metastable systems can nucleate to multiple competing stable or intermediate metastable states. In this work, a Potts model, subject to external fields, is used to study the competitive nucleation of two phases attempting to grow on a microscopic impurity. Monte Carlo simulations are used to calculate the free energy surfaces for the system under different conditions, where the relative stability of the phases is adjusted by changing the interaction parameters, and the nucleation rates obtained using multicomponent transition state theory (TST) are compared with the rates measured using the survival probability method. We find that the two methods predict similar nucleation rates when the free energy barrier used in the transition state theory is defined as the work required to form a critical embryo from the metastable phase. An analysis of the free energy surfaces also reveals that the competition between the nucleating phases leads to an effective drying of the impurity which slows down the nucleation rate compared to the single phase case.
Resonant Scattering by Magnetic Impurities as a Model for Spin Relaxation in Bilayer Graphene.
Kochan, Denis; Irmer, Susanne; Gmitra, Martin; Fabian, Jaroslav
2015-11-06
We propose that the observed spin relaxation in bilayer graphene is due to resonant scattering by magnetic impurities. We analyze a resonant scattering model due to adatoms on both dimer and nondimer sites, finding that only the former give narrow resonances at the charge neutrality point. Opposite to single-layer graphene, the measured spin-relaxation rate in the graphene bilayer increases with carrier density. Although it has been commonly argued that a different mechanism must be at play for the two structures, our model explains this behavior rather naturally in terms of different broadening scales for the same underlying resonant processes. Not only do our results-using robust and first-principles inspired parameters-agree with experiment, they also predict an experimentally testable sharp decrease of the spin-relaxation rate at high carrier densities.
Lithuania 1940 / Herbert Foster Anderson
Foster Anderson, Herbert
2004-01-01
Stseenid Leedu ennesõjaaegsest pealinnast Kaunasest briti ärimehe H. Foster Andersoni silme läbi 1940. aastal. Lühikokkuvõte raamatust: Foster Anderson, Herbert. Borderline Russia. London : Cresset press, 1942
International Nuclear Information System (INIS)
Jones, R.
2000-01-01
The Price-Anderson Act establishes nuclear liability law in the United States. First passed in 1957, it has influenced other nuclear liability legislation around the world. The insurer response the nuclear accident at Three Mile Island in 1979 demonstrates the application of the Act in a real life situation. The Price-Anderson Act is scheduled to be renewed in 2002, and the future use of commercial nuclear power in tge United States will be influenced by this renewal. (author)
Tuzet, Francois; Dumont, Marie; Lafaysse, Matthieu; Picard, Ghislain; Arnaud, Laurent; Voisin, Didier; Lejeune, Yves; Charrois, Luc; Nabat, Pierre; Morin, Samuel
2017-11-01
Light-absorbing impurities (LAIs) decrease snow albedo, increasing the amount of solar energy absorbed by the snowpack. Its most intuitive and direct impact is to accelerate snowmelt. Enhanced energy absorption in snow also modifies snow metamorphism, which can indirectly drive further variations of snow albedo in the near-infrared part of the solar spectrum because of the evolution of the near-surface snow microstructure. New capabilities have been implemented in the detailed snowpack model SURFEX/ISBA-Crocus (referred to as Crocus) to account for impurities' deposition and evolution within the snowpack and their direct and indirect impacts. Once deposited, the model computes impurities' mass evolution until snow melts out, accounting for scavenging by meltwater. Taking advantage of the recent inclusion of the spectral radiative transfer model TARTES (Two-stream Analytical Radiative TransfEr in Snow model) in Crocus, the model explicitly represents the radiative impacts of light-absorbing impurities in snow. The model was evaluated at the Col de Porte experimental site (French Alps) during the 2013-2014 snow season against in situ standard snow measurements and spectral albedo measurements. In situ meteorological measurements were used to drive the snowpack model, except for aerosol deposition fluxes. Black carbon (BC) and dust deposition fluxes used to drive the model were extracted from simulations of the atmospheric model ALADIN-Climate. The model simulates snowpack evolution reasonably, providing similar performances to our reference Crocus version in terms of snow depth, snow water equivalent (SWE), near-surface specific surface area (SSA) and shortwave albedo. Since the reference empirical albedo scheme was calibrated at the Col de Porte, improvements were not expected to be significant in this study. We show that the deposition fluxes from the ALADIN-Climate model provide a reasonable estimate of the amount of light-absorbing impurities deposited on the
On the Anderson localization conjecture in Dusty Plasma
Liaw, Constanze; Busse, Kyle; Matthews, Lorin; Hyde, Truell
2015-11-01
In 1958, Anderson suggested that sufficiently large impurities in a semi-conductor could lead to spatial localization of electrons. This idea unfolded into the field of Anderson Localization, one of the most fascinating phenomena in solid-state physics as it plays a major role in the conductive properties of imperfectly ordered materials. The Anderson Localization Conjecture claims that random disorder of any strength causes localization of electrons in the medium. The problem has proven to be highly non-trivial. Over the years the community has argued whether spatial localization occurs in 2D for small impurities. From a mathematical standpoint, the conjecture is still considered an open question. In 2013, Liaw challenged the commonly held assumption that localization holds in 2D by introducing a new mathematically more rigorous method to test for extended states, and applying it to the discrete random Schrödinger operator. One of the advantages of the underlying method is its versatility. It can be applied to any ordered system such as colloids, crystals, and atomic lattices. In a cross-disciplinary effort we merge this method with a numerical code used to simulate 2D physics systems, in preparation for experimentally testing the theory against complex plasma crystals.
Alamdari, Abdolmohammad; Nourafkan, Ehsan; Jahanmiri, Abdolhosein
2010-07-01
A deactivation mechanism was developed to present the influence of 4-tert-butylphenol as a sample impurity on the bisphenol-A (BPA) adduct particles during the crystallization process. 4-tert-butylphenol is an organic sample impurity generally present in the reaction mixture of the industrial production of BPA. Kinetic parameters of growth, nucleation, agglomeration, and deactivation were estimated using the technique of model fitting to experimental data. The population and mass balances were used to model the adductive crystallization of BPA. Experiments were carried out in several plastic bottles as crystallizers in a rotating bath. Liquid and solid phase information during the course of experiments was provided using the methods of gas chromatography, sieve analysis, and scanning electron microscopy. The impurity influence on the solution thermodynamics was investigated by measuring the width of metastable zone in the presence and in the absence of 4-tert-butylphenol. Consistency of the model predictions of size distributions with the experimental data beyond the range where the parameters were optimized revealed the validity of the model and the accuracy of the parameter values. The results showed that traces of impurity would reduce the BPA solubility, widen the metastability zone, increase agglomeration, and deactivate the growth and nucleation sites on the crystals.
Simulating graphene impurities
Szyniszewski, Marcin
2013-01-01
We study a model of magnetic impurities deposited onto a graphene lattice, interacting via exchange of conduction electrons. Our objective is to look for the long-range ordering of the impurities, which would lead to drastic changes in the transport properties of graphene. Numerical simulations are performed and we indeed observe the ordered phase. We also estimate the critical temperature of a transition between disordered and ordered phases.
50 Years of Anderson Localization
Abrahams, Elihu
2010-01-01
In his groundbreaking paper Absence of diffusion in certain random lattices (1958), Philip W. Anderson originated, described and developed the physical principles underlying the phenomenon of the localization of quantum objects due to disorder. Anderson's 1977 Nobel Prize citation featured that paper, which was fundamental for many subsequent developments in condensed matter theory and technical applications. After more than a half century, the subject continues to be of fundamental importance. In particular, in the last 25 years, the phenomenon of localization has proved to be crucial for the
Self-consistent gyrokinetic modeling of neoclassical and turbulent impurity transport
Estève , D. ,; Sarazin , Y.; Garbet , X.; Grandgirard , V.; Breton , S. ,; Donnel , P. ,; Asahi , Y. ,; Bourdelle , C.; Dif-Pradalier , G; Ehrlacher , C.; Emeriau , C.; Ghendrih , Ph; Gillot , C.; Latu , G.; Passeron , C.
2018-01-01
International audience; Trace impurity transport is studied with the flux-driven gyrokinetic GYSELA code [V. Grandgirard et al., Comp. Phys. Commun. 207, 35 (2016)]. A reduced and linearized multi-species collision operator has been recently implemented, so that both neoclassical and turbulent transport channels can be treated self-consistently on an equal footing. In the Pfirsch-Schlüter regime likely relevant for tungsten, the standard expression of the neoclassical impurity flux is shown t...
Computer simulation model of the structure of ion implanted impurities in semiconductors
International Nuclear Information System (INIS)
Roman, E.; Majlis, N.
1983-02-01
A system of ion implanted impurities in a semiconductor is described by a Monte Carlo simulation of a non-equilibrium system of random distributed hard spheres. The radial distribution function of this system is found. The comparison is made with the fluid hard sphere case. The assumption of the absence either of annealing or diffusion of the impurities after the implantation process is also made. (author)
Energy Technology Data Exchange (ETDEWEB)
Gong, Longyan, E-mail: lygong@njupt.edu.cn [Information Physics Research Center and Department of Applied Physics, Nanjing University of Posts and Telecommunications, Nanjing, 210003 (China); Institute of Signal Processing and Transmission, Nanjing University of Posts and Telecommunications, Nanjing, 210003 (China); National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Feng, Yan; Ding, Yougen [Information Physics Research Center and Department of Applied Physics, Nanjing University of Posts and Telecommunications, Nanjing, 210003 (China); Institute of Signal Processing and Transmission, Nanjing University of Posts and Telecommunications, Nanjing, 210003 (China)
2017-02-12
Highlights: • Quasiperiodic lattice models with next-nearest-neighbor hopping are studied. • Shannon information entropies are used to reflect state localization properties. • Phase diagrams are obtained for the inverse bronze and golden means, respectively. • Our studies present a more complete picture than existing works. - Abstract: We explore the reduced relative Shannon information entropies SR for a quasiperiodic lattice model with nearest- and next-nearest-neighbor hopping, where an irrational number is in the mathematical expression of incommensurate on-site potentials. Based on SR, we respectively unveil the phase diagrams for two irrationalities, i.e., the inverse bronze mean and the inverse golden mean. The corresponding phase diagrams include regions of purely localized phase, purely delocalized phase, pure critical phase, and regions with mobility edges. The boundaries of different regions depend on the values of irrational number. These studies present a more complete picture than existing works.
Self-consistent gyrokinetic modeling of neoclassical and turbulent impurity transport
Estève, D.; Sarazin, Y.; Garbet, X.; Grandgirard, V.; Breton, S.; Donnel, P.; Asahi, Y.; Bourdelle, C.; Dif-Pradalier, G.; Ehrlacher, C.; Emeriau, C.; Ghendrih, Ph.; Gillot, C.; Latu, G.; Passeron, C.
2018-03-01
Trace impurity transport is studied with the flux-driven gyrokinetic GYSELA code (Grandgirard et al 2016 Comput. Phys. Commun. 207 35). A reduced and linearized multi-species collision operator has been recently implemented, so that both neoclassical and turbulent transport channels can be treated self-consistently on an equal footing. In the Pfirsch-Schlüter regime that is probably relevant for tungsten, the standard expression for the neoclassical impurity flux is shown to be recovered from gyrokinetics with the employed collision operator. Purely neoclassical simulations of deuterium plasma with trace impurities of helium, carbon and tungsten lead to impurity diffusion coefficients, inward pinch velocities due to density peaking, and thermo-diffusion terms which quantitatively agree with neoclassical predictions and NEO simulations (Belli et al 2012 Plasma Phys. Control. Fusion 54 015015). The thermal screening factor appears to be less than predicted analytically in the Pfirsch-Schlüter regime, which can be detrimental to fusion performance. Finally, self-consistent nonlinear simulations have revealed that the tungsten impurity flux is not the sum of turbulent and neoclassical fluxes computed separately, as is usually assumed. The synergy partly results from the turbulence-driven in-out poloidal asymmetry of tungsten density. This result suggests the need for self-consistent simulations of impurity transport, i.e. including both turbulence and neoclassical physics, in view of quantitative predictions for ITER.
International Nuclear Information System (INIS)
Roth, J.
1982-01-01
The contact of the plasma with the surrounding walls leads to surface erosion and production of impurity atoms. Obvious signs of erosion in today's high temperature plasma experiments are the characteristic cathode are tracks and local melting spots from overheated areas. Impurity production by sputtering is not so readily observed. It can, however, be deduced from mass and energy analysis of impurity atoms leaving the wall and divertor plates. The mechanism of sputtering, evaporation and arcing will be outlined. The conditions found in the boundary layer of today's tokamaks, i.e. the particle fluxes and energies, will be presented and estimates for the erosion rates will be made for the erosion rates will be made for the different erosion processes. (orig.)
Modeling of neutral transport and impurity generation in the Tore Supra pump limiter
International Nuclear Information System (INIS)
Klepper, C.C.; Owen, L.W.; Mioduszewski, P.K.; Grosman, A.
1989-01-01
A system of modular pump limiters is employed in Tore Supra for particle control. It includes one large outboard module which is instrumented with an optical multi-channel analyzer viewing the neutralizer plate, in addition to pressure, temperature and particle diagnostics. The transport of neutrals in both the particle scoop mode and in the pump limiter mode with active pumping is modeled with the DEGAS code. Equilibrium neutral pressure and density, H α -intensity at the neutralizer plate, and particle back-flow into the scrape-off layer are calculated for typical projected plasma edge conditions. Effects on neutral particle transport of varying the length of the ''shelf'' separating the throat region from the pumping chamber are investigated. The generation and transport of carbon impurities arising from ion impact sputtering at the neutralizer plate are estimated. The short mean-free-path for ionization of sputtered carbon atoms suggests the possibility of spectroscopically measuring the effects of poloidal flux variations arising from shadowing of the modular limiter system. (orig.)
Anderson's Relevant Deontic and Eubouliatic Systems
Lokhorst, G.J.C.
2008-01-01
We present axiomatizations of the deontic fragment of Anderson's relevant deontic logic (the logic of obligation and related concepts) and the eubouliatic fragment of Anderson's eubouliatic logic (the logic of prudence, safety, risk, and related concepts).
Phil Anderson and Gauge Symmetry Breaking
Witten, Edward
In this article, I describe the celebrated paper that Phil Anderson wrote in 1962 with early contributions to the idea of gauge symmetry breaking in particle physics. To set the stage, I describe the work of Julian Schwinger to which Anderson was responding, and also some of Anderson's own work on superconductivity that provided part of the context. After describing Anderson's work I describe the later work of others, leading to the modern understanding of gauge symmetry breaking in weak interactions...
The Consultancy Activity on In Silico Models for Genotoxic Prediction of Pharmaceutical Impurities.
Pavan, Manuela; Kovarich, Simona; Bassan, Arianna; Broccardo, Lorenza; Yang, Chihae; Fioravanzo, Elena
2016-01-01
The toxicological assessment of DNA-reactive/mutagenic or clastogenic impurities plays an important role in the regulatory process for pharmaceuticals; in this context, in silico structure-based approaches are applied as primary tools for the evaluation of the mutagenic potential of the drug impurities. The general recommendations regarding such use of in silico methods are provided in the recent ICH M7 guideline stating that computational (in silico) toxicology assessment should be performed using two (Q)SAR prediction methodologies complementing each other: a statistical-based method and an expert rule-based method.Based on our consultant experience, we describe here a framework for in silico assessment of mutagenic potential of drug impurities. Two main applications of in silico methods are presented: (1) support and optimization of drug synthesis processes by providing early indication of potential genotoxic impurities and (2) regulatory evaluation of genotoxic potential of impurities in compliance with the ICH M7 guideline. Some critical case studies are also discussed.
Muñoz Burgos, J. M.; Tritz, K.; Stutman, D.; Bell, R. E.; LeBlanc, B. P.; Sabbagh, S. A.
2015-12-01
An advanced kinetic collisional radiative model is used to predict beam into plasma charge-exchange visible and extreme UV (XUV ∽ 50 -700 Å ) light emission to quantify impurity density profiles on NSTX. This kinetic model is first benchmarked by predicting line-of-sight integrated emission for the visible λ = 5292.0 Å line of carbon (C VI n = 8 → 7), and comparing these predictions to absolute calibrated measurements from the active CHarge-Exchange Recombination Spectroscopy diagnostic (CHERS) on NSTX. Once benchmarked, the model is used to predict charge-exchange emission for the 182.1 Å line of carbon (C VI n = 3 → 2) that is used to scale Bremsstrahlung continuum emission in the UV/XUV region. The scaled Bremsstrahlung emission is used as a base to estimate an absolute intensity calibration curve of a XUV Transmission Grating-based Imaging Spectrometer (TGIS) diagnostic installed on the National Spherical Torus Experiment (NSTX and upgrade NSTX-U). The TGIS diagnostic operates in the wavelength region ∽ 50 -700 Å , and it is used to measure impurity spectra from charge-exchange emission. Impurity densities are estimated by fitting synthetic emission from the kinetic charge-exchange model to TGIS spectral measurements.
Czech Academy of Sciences Publication Activity Database
Casson, F.J.; Angioni, C.; Belli, E.A.; Bilato, R.; Mantica, P.; Odstrčil, T.; Pütterich, T.; Valisa, M.; Garzotti, L.; Giroud, C.; Hobirk, J.; Maggi, C.F.; Mlynář, Jan; Reinke, M.L.
2015-01-01
Roč. 57, č. 1 (2015), č. článku 014031. ISSN 0741-3335 Institutional support: RVO:61389021 Keywords : tokamak * impurity * transport * neoclassical * validation * modelling * tungsten Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.404, year: 2015 http://iopscience.iop.org/article/10.1088/0741-3335/57/1/014031/meta
Panwar, Sunil; Kumar, Vijay; Singh, Ishwar
2017-10-01
An anomalous Hall constant RH has been observed in various rare earth manganites doped with alkaline earths namely Re1-xAxMnO3 (where Re = La, Pr, Nd etc., and A = Ca, Sr, Ba etc.) which exhibit colossal magnetoresistance (CMR), metal- insulator transition and many other poorly understood phenomena. We show that this phenomenon of anomalous Hall constant can be understood using two band (ℓ-b) Anderson lattice model Hamiltonian alongwith (ℓ-b) hybridization recently studied by us for manganites in the strong electron-lattice Jahn-Teller (JT) coupling regime an approach similar to the two - fluid models. We use a variational method in this work to study the temperature variation of Hall constant RH (T) in these compounds. We have already used this variational method to study the zero field electrical resistivity ρ (T) and magnetic susceptibility of doped CMR manganites. In the present study, we find that the Hall constant RH (T) reduces with increasing magnetic field parameters h&m and the metal-insulator transition temperature (Tρ) shifts towards higher temperature region. We have also observed the role of the model parameters e.g. local Coulomb repulsion U, Hund's rule coupling JH between eg spins and t2g spins, ferromagnetic nearest neighbor exchange coupling JF between t2g core spins and hybridization Vk between ℓ-polarons and d-electrons on Hall constant RH (T) of these materials at different magnetic fields. Here we find that RH (T) for a particular value of h and m shows a rapid initial increase, followed by a sharp peak at low temperature say 50 K in our case and a slow decrease at high temperatures, resembling with the key feature of many CMR compounds like La0.8Ba0.2 MnO3.The magnitude of RH (T) reduces and the anomaly (sharp peak) in RH becomes broader and shifts towards higher temperature region on increasing Vk or JH or doping x and even vanishes on further increasing these parameters. Our results of anomalous Hall constant (RH) have same
Dynamic behavior of impurities and native components in model LSM microelectrodes on YSZ
DEFF Research Database (Denmark)
Norrman, Kion; Hansen, Karin Vels; Jacobsen, Torben
2015-01-01
behavior of the native components (La, Sr, Mn) and selected impurities (Si, K, Na) both laterally and in-depth. Manganese was found to be especially mobile and showed both segregation onto the electrolyte as a result of temperature and polarization and dissolution into the electrolyte below...
Zeroth order phase transition in a holographic superconductor with single impurity
Zeng, Hua Bi; Zhang, Hai-Qing
We investigate the single normal impurity effect in a superconductor by the holographic method. When the size of impurity is much smaller than the host superconductor, we can reproduce the Anderson theorem, which states that a conventional s-wave superconductor is robust to a normal (non-magnetic)
International Nuclear Information System (INIS)
Okabe, Y.; Nagi, A.D.S.
1983-01-01
The Shiba-Rusinov theory of magnetic impurities in a superconductor is investigated, with special attention paid to the role of the potential scattering term in the electron-impurity interaction. The meaning of Anderson's theorem in the Shiba-Rusinov theory is discussed
International Nuclear Information System (INIS)
Valencia, Antoni; Prous, Josep; Mora, Oscar; Sadrieh, Nakissa; Valerio, Luis G.
2013-01-01
As indicated in ICH M7 draft guidance, in silico predictive tools including statistically-based QSARs and expert analysis may be used as a computational assessment for bacterial mutagenicity for the qualification of impurities in pharmaceuticals. To address this need, we developed and validated a QSAR model to predict Salmonella t. mutagenicity (Ames assay outcome) of pharmaceutical impurities using Prous Institute's Symmetry℠, a new in silico solution for drug discovery and toxicity screening, and the Mold2 molecular descriptor package (FDA/NCTR). Data was sourced from public benchmark databases with known Ames assay mutagenicity outcomes for 7300 chemicals (57% mutagens). Of these data, 90% was used to train the model and the remaining 10% was set aside as a holdout set for validation. The model's applicability to drug impurities was tested using a FDA/CDER database of 951 structures, of which 94% were found within the model's applicability domain. The predictive performance of the model is acceptable for supporting regulatory decision-making with 84 ± 1% sensitivity, 81 ± 1% specificity, 83 ± 1% concordance and 79 ± 1% negative predictivity based on internal cross-validation, while the holdout dataset yielded 83% sensitivity, 77% specificity, 80% concordance and 78% negative predictivity. Given the importance of having confidence in negative predictions, an additional external validation of the model was also carried out, using marketed drugs known to be Ames-negative, and obtained 98% coverage and 81% specificity. Additionally, Ames mutagenicity data from FDA/CFSAN was used to create another data set of 1535 chemicals for external validation of the model, yielding 98% coverage, 73% sensitivity, 86% specificity, 81% concordance and 84% negative predictivity. - Highlights: • A new in silico QSAR model to predict Ames mutagenicity is described. • The model is extensively validated with chemicals from the FDA and the public domain. • Validation tests
Energy Technology Data Exchange (ETDEWEB)
Valencia, Antoni; Prous, Josep; Mora, Oscar [Prous Institute for Biomedical Research, Rambla de Catalunya, 135, 3-2, Barcelona 08008 (Spain); Sadrieh, Nakissa [Office of Pharmaceutical Science, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, MD 20993-0002 (United States); Valerio, Luis G., E-mail: luis.valerio@fda.hhs.gov [Office of Pharmaceutical Science, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, MD 20993-0002 (United States)
2013-12-15
As indicated in ICH M7 draft guidance, in silico predictive tools including statistically-based QSARs and expert analysis may be used as a computational assessment for bacterial mutagenicity for the qualification of impurities in pharmaceuticals. To address this need, we developed and validated a QSAR model to predict Salmonella t. mutagenicity (Ames assay outcome) of pharmaceutical impurities using Prous Institute's Symmetry℠, a new in silico solution for drug discovery and toxicity screening, and the Mold2 molecular descriptor package (FDA/NCTR). Data was sourced from public benchmark databases with known Ames assay mutagenicity outcomes for 7300 chemicals (57% mutagens). Of these data, 90% was used to train the model and the remaining 10% was set aside as a holdout set for validation. The model's applicability to drug impurities was tested using a FDA/CDER database of 951 structures, of which 94% were found within the model's applicability domain. The predictive performance of the model is acceptable for supporting regulatory decision-making with 84 ± 1% sensitivity, 81 ± 1% specificity, 83 ± 1% concordance and 79 ± 1% negative predictivity based on internal cross-validation, while the holdout dataset yielded 83% sensitivity, 77% specificity, 80% concordance and 78% negative predictivity. Given the importance of having confidence in negative predictions, an additional external validation of the model was also carried out, using marketed drugs known to be Ames-negative, and obtained 98% coverage and 81% specificity. Additionally, Ames mutagenicity data from FDA/CFSAN was used to create another data set of 1535 chemicals for external validation of the model, yielding 98% coverage, 73% sensitivity, 86% specificity, 81% concordance and 84% negative predictivity. - Highlights: • A new in silico QSAR model to predict Ames mutagenicity is described. • The model is extensively validated with chemicals from the FDA and the public domain.
Breatherlike impurity modes in discrete nonlinear lattices
DEFF Research Database (Denmark)
Hennig, D.; Rasmussen, Kim; Tsironis, G. P.
1995-01-01
We investigate the properties of a disordered generalized discrete nonlinear Schrodinger equation, containing both diagonal and nondiagonal nonlinear terms. The equation models a Linear host lattice doped with nonlinear impurities. We find different types of impurity states that form itinerant...
On Properties of Impurity Spectrum in the Disordered Exactly Solvable Model
Grinshpun, V
2006-01-01
The random point interaction Hamiltonian (H) is considered on L^2(R^d), d=2, or d=3. Existence and certain bounds of the non-empty pure point component and exponential decay of the corresponding eigenfunctions with probability 1, within region of impurity spectrum of H, are rigorously established. In order to prove the localization result, the structure of the generalized eigenfunctions of H is explicitly described, and the relation between its spectral properties, and the properties of spectra of finite-difference infinite-order operators on l^2(Z^d), is established. The multiscale analysis scheme is applied to investigate the point spectrum of finite-difference operators. In addition, the generalized spectral theorem, and absolute continuity of the integrated density of states of H at the negative (impurity) part of the spectrum, rigorously proved. Applications of the new approximation scheme include straightforward analysis of absolutely continuous conductivity spectrum, subject to a possible separate publ...
DEFF Research Database (Denmark)
Henriksen, Jonas Rosager; Sabra, Mads Christian; Mouritsen, Ole G.
2000-01-01
The nonequilibrium, steady-state phase transitions and the structure of the different phases of a two-dimensional system with two thermodynamic temperatures are studied via a simple lattice-gas model with mobile active impurities ("hot/cold spots'') whose activity is controlled by an external drive....... The properties of the model are calculated by Monte Carlo computer-simulation techniques. The two temperatures and the external drive on the system lead to a rich phase diagram including regions of microstructured phases in addition to macroscopically ordered (phase-separated) and disordered phases. Depending...
Modelling of impurity deposition in gaps of castellated surfaces with the 3D-GAPS code
Czech Academy of Sciences Publication Activity Database
Matveev, D.; Kirschner, A.; Litnovsky, A.; Borodin, D.; Philipps, V.; Van Oost, G.; Komm, Michael
2010-01-01
Roč. 52, č. 7 (2010), 075007-075007 ISSN 0741-3335 R&D Projects: GA ČR GA202/07/0044 Institutional research plan: CEZ:AV0Z20430508 Keywords : TEXTOR * simulation * PIC * impurity * transport * gap * divertor * limiter * retention Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.466, year: 2010 http://iopscience.iop.org/0741-3335/52/7/075007/pdf/0741-3335_52_7_075007.pdf
Modeling study of radiation characteristics with different impurity species seeding in EAST
Liu, X. J.; Deng, G. Z.; Wang, L.; Liu, S. C.; Zhang, L.; Li, G. Q.; Gao, X.
2017-12-01
A critical issue for EAST and future tokamak machines such as ITER and China Fusion Engineering Testing Reactor is the handling of excessive heat load on the divertor target plates. As an effective means of actively reducing and controlling the power fluxes to the target plates, localized impurity (N, Ne, and Ar) gas puffing from the lower dome is investigated by using SOLPS5.0 for an L-mode discharge on EAST with double null configuration. The radiative efficiency and distribution of different impurities are compared. The effect of N, Ne, and Ar seeding on target power load, the power entering into scrape-off layer (SOL), Psep, and their concentration in SOL along the poloidal length and edge effective ion charge number (Zeff) which are closely related to core plasma performance are presented. The simulation results indicate that N, Ne, and Ar seeding can effectively reduce the peak heat load and electron temperature at divertor targets similarly. N seeding can reach the highest radiative loss fraction and both N and Ar strongly radiate power in the divertor region, while the radiative power inside the separatrix for Ar seeding is also significant. Ne radiates power mainly around the separatrix and X-point. Ne and Ar impurities' puffing results in a faster decrease of Psep than N seeding case; the reduction of Psep can eventually degrade the core performance of fusion plasma. Additionally, seeding with Ne has a totally larger concentration at the outer midplane and edge Zeff than those in N and Ar seeding cases; it suggests that N and Ar impurities are more acceptable than Ne in terms of fuel dilution for this discharge.
Directory of Open Access Journals (Sweden)
Ibrahim A. Naguib
2015-01-01
Full Text Available A comparison between partial least squares regression and support vector regression chemometric models is introduced in this study. The two models are implemented to analyze cefoperazone sodium in presence of its reported impurities, 7-aminocephalosporanic acid and 5-mercapto-1-methyl-tetrazole, in pure powders and in pharmaceutical formulations through processing UV spectroscopic data. For best results, a 3-factor 4-level experimental design was used, resulting in a training set of 16 mixtures containing different ratios of interfering moieties. For method validation, an independent test set consisting of 9 mixtures was used to test predictive ability of established models. The introduced results show the capability of the two proposed models to analyze cefoperazone in presence of its impurities 7-aminocephalosporanic acid and 5-mercapto-1-methyl-tetrazole with high trueness and selectivity (101.87 ± 0.708 and 101.43 ± 0.536 for PLSR and linear SVR, resp.. Analysis results of drug products were statistically compared to a reported HPLC method showing no significant difference in trueness and precision, indicating the capability of the suggested multivariate calibration models to be reliable and adequate for routine quality control analysis of drug product. SVR offers more accurate results with lower prediction error compared to PLSR model; however, PLSR is easy to handle and fast to optimize.
International Nuclear Information System (INIS)
Drawin, H.W.
1976-11-01
In high-temperature low-density plasmas radiation cooling by impurity atoms can be an important energy loss mechanism, since the radiation is not reabsorbed. In a brief historical survey it is shown that the problem is not new but was discussed since the first beginning of controlled thermonuclear fusion research. It is then shown radiation losses enter into the general power balance equation of a plasma containing impurities. The equations for the different types of radiation losses are given as a function of the atomic quantities. In a special section simplifications due to the corona model assumption are discussed. It follows a detailed survey of the results obtained by several authors for the ionization balance and power losses of impurity elements observed in present high-temperature plasma machines used in CTR, especially in TOKAMAKS. In the conclusion a survey is given of the atomic data which experimentalists and theorists need for current research on impurities in fusion-like plasmas. (86 references)
Renormalization group approach to the Fröhlich polaron model: application to impurity-BEC problem.
Grusdt, F; Shchadilova, Y E; Rubtsov, A N; Demler, E
2015-07-17
When a mobile impurity interacts with a many-body system, such as a phonon bath, a polaron is formed. Despite the importance of the polaron problem for a wide range of physical systems, a unified theoretical description valid for arbitrary coupling strengths is still lacking. Here we develop a renormalization group approach for analyzing a paradigmatic model of polarons, the so-called Fröhlich model, and apply it to a problem of impurity atoms immersed in a Bose-Einstein condensate of ultra cold atoms. Polaron energies obtained by our method are in excellent agreement with recent diagrammatic Monte Carlo calculations for a wide range of interaction strengths. They are found to be logarithmically divergent with the ultra-violet cut-off, but physically meaningful regularized polaron energies are also presented. Moreover, we calculate the effective mass of polarons and find a smooth crossover from weak to strong coupling regimes. Possible experimental tests of our results in current experiments with ultra cold atoms are discussed.
Benedict Andersons forestillede fællesskaber
DEFF Research Database (Denmark)
Ivarsson, Søren
2007-01-01
Artiklen diskuterer Benedict Andersons analyse af nationalismens opståen i en kolonial kontekst og den kritik som Partha Chatterjee har rejst mod denne. Udgivelsesdato: Januar 2008......Artiklen diskuterer Benedict Andersons analyse af nationalismens opståen i en kolonial kontekst og den kritik som Partha Chatterjee har rejst mod denne. Udgivelsesdato: Januar 2008...
Interplay of Anderson localization and strong interaction in disordered systems
Energy Technology Data Exchange (ETDEWEB)
Henseler, Peter
2010-01-15
We study the interplay of disorder localization and strong local interactions within the Anderson-Hubbard model. Taking into account local Mott-Hubbard physics and static screening of the disorder potential, the system is mapped onto an effective single-particle Anderson model, which is studied within the self-consistent theory of electron localization. For fermions, we find rich nonmonotonic behavior of the localization length {xi}, particularly in two-dimensional systems, including an interaction-induced exponential enhancement of {xi} for small and intermediate disorders and a strong reduction of {xi} due to hopping suppression by strong interactions. In three dimensions, we identify for half filling a Mott-Hubbard-assisted Anderson localized phase existing between the metallic and the Mott-Hubbard-gapped phases. For small U there is re-entrant behavior from the Anderson localized phase to the metallic phase. For bosons, the unrestricted particle occupation number per lattice site yields a monotonic enhancement of {xi} as a function of decreasing interaction, which we assume to persist until the superfluid Bose-Einstein condensate phase is entered. Besides, we study cold atomic gases expanding, by a diffusion process, in a weak random potential. We show that the density-density correlation function of the expanding gas is strongly affected by disorder and we estimate the typical size of a speckle spot, i.e., a region of enhanced or depleted density. Both a Fermi gas and a Bose-Einstein condensate (in a mean-field approach) are considered. (orig.)
Interplay of Anderson localization and strong interaction in disordered systems
International Nuclear Information System (INIS)
Henseler, Peter
2010-01-01
We study the interplay of disorder localization and strong local interactions within the Anderson-Hubbard model. Taking into account local Mott-Hubbard physics and static screening of the disorder potential, the system is mapped onto an effective single-particle Anderson model, which is studied within the self-consistent theory of electron localization. For fermions, we find rich nonmonotonic behavior of the localization length ξ, particularly in two-dimensional systems, including an interaction-induced exponential enhancement of ξ for small and intermediate disorders and a strong reduction of ξ due to hopping suppression by strong interactions. In three dimensions, we identify for half filling a Mott-Hubbard-assisted Anderson localized phase existing between the metallic and the Mott-Hubbard-gapped phases. For small U there is re-entrant behavior from the Anderson localized phase to the metallic phase. For bosons, the unrestricted particle occupation number per lattice site yields a monotonic enhancement of ξ as a function of decreasing interaction, which we assume to persist until the superfluid Bose-Einstein condensate phase is entered. Besides, we study cold atomic gases expanding, by a diffusion process, in a weak random potential. We show that the density-density correlation function of the expanding gas is strongly affected by disorder and we estimate the typical size of a speckle spot, i.e., a region of enhanced or depleted density. Both a Fermi gas and a Bose-Einstein condensate (in a mean-field approach) are considered. (orig.)
Matt, F.; Burkhart, J. F.
2017-12-01
Light absorbing impurities in snow and ice (LAISI) originating from atmospheric deposition enhance snow melt by increasing the absorption of solar radiation. The consequences are a shortening of the snow cover duration due to increased snow melt and, with respect to hydrologic processes, a temporal shift in the discharge generation. However, the effects as simulated in numerical models have large uncertainties. These uncertainties originate mainly from uncertainties in the wet and dry deposition of light absorbing aerosols, limitations in the model representation of the snowpack, and the lack of observable variables required to estimate model parameters. This leads to high uncertainties in the additional energy absorbed by the snow due to the presence of LAISI (the so called radiative forcing of LAISI), a key variable in understanding snowpack energy-balance dynamics. In this study, we present an approach combining distributed model simulations on the catchment scale and remotely sensed radiative forcing from LAISI in order to evaluate and improve model predictions. In a case study, we assess the effect of LAISI on snow melt and discharge generation in a high mountain catchment located in the western Himalaya using the distributed hydrologic model, Shyft. The snow albedo is hereby calculated from a radiative transfer model for snow, taking the increased absorption of solar radiation by LAISI into account. LAISI mixing ratios in snow are determined from atmospheric aerosol deposition rates. To asses the quality of our simulations, we model the instantaneous clear sky radiative forcing at MODIS overpass times, and compare it to the MODIS Dust Radiative Forcing in Snow (MODDRFS) satellite product. By scaling the deposition input to the model, we can optimize the simulated radiative forcing towards the satellite observations.
Schemata, Cognitive Structure, and Advance Organizers: A Reply to Anderson, Spiro, and Anderson.
Ausubel, David P.
1980-01-01
Anderson, Spiro, and Anderson (EJ 189 658) assert that the author's assimilation theory of meaningful learning and retention is "hopelessly vague." Documented examination of these assertions indicates that they are unspecified, unsubstantiated, undocumented, and based on indisputable misrepresentation of published material and on logical…
Exact diagonalization library for quantum electron models
Iskakov, Sergei; Danilov, Michael
2018-04-01
We present an exact diagonalization C++ template library (EDLib) for solving quantum electron models, including the single-band finite Hubbard cluster and the multi-orbital impurity Anderson model. The observables that can be computed using EDLib are single particle Green's functions and spin-spin correlation functions. This code provides three different types of Hamiltonian matrix storage that can be chosen based on the model.
Depolarization of diffusing spins by paramagnetic impurities
International Nuclear Information System (INIS)
Schillaci, M.E.; Hutson, R.L.; Heffner, R.H.; Leon, M.; Dodds, S.A.; Estle, T.L.
1980-01-01
The depolarization of diffusing spins (muons) interacting with dilute paramagnetic impurities in a solid was studied using a simple computational model which properly treats the muon motion and preserves correct muon-impurity distances. Long-range (dipolar) and nearest-neighbor (contact) interactions are treated together. Diffusion parameters are deduced and model comparisons made for AuGd
Graphene plasmons: Impurities and nonlocal effects
Viola, Giovanni; Wenger, Tobias; Kinaret, Jari; Fogelström, Mikael
2018-02-01
This work analyzes how impurities and vacancies on the surface of a graphene sample affect its optical conductivity and plasmon excitations. The disorder is analyzed in the self-consistent Green's function formulation and nonlocal effects are fully taken into account. It is shown that impurities modify the linear spectrum and give rise to an impurity band whose position and width depend on the two parameters of our model, the density and the strength of impurities. The presence of the impurity band strongly influences the electromagnetic response and the plasmon losses. Furthermore, we discuss how the impurity-band position can be obtained experimentally from the plasmon dispersion relation and discuss this in the context of sensing.
Wegner estimates, Lifshitz tails, and Anderson localization for Gaussian random magnetic fields
Ueki, Naomasa
2016-07-01
The Wegner estimate for the Hamiltonian of the Anderson model for the special Gaussian random magnetic field is extended to more general magnetic fields. The Lifshitz tail upper bounds of the integrated density of states as analyzed by Nakamura are reviewed and extended so that Gaussian random magnetic fields can be treated. By these and multiscale analysis, the Anderson localization at low energies is proven.
Random nanolasing in the Anderson localized regime
DEFF Research Database (Denmark)
Liu, Jin; Garcia, P. D.; Ek, Sara
2014-01-01
multiple scattering. The applicability of random lasers has been limited due to multidirectional emission, lack of tunability, and strong mode competition with chaotic fluctuations due to a weak mode confinement. The regime of Anderson localization of light has been proposed for obtaining stable multimode...... random lasing, and initial work concerned macroscopic one-dimensional layered media. Here, we demonstrate on-chip random nanolasers where the cavity feedback is provided by the intrinsic disorder. The strong confinement achieved by Anderson localization reduces the spatial overlap between lasing modes...
MD Anderson's Population Health Approaches to Cancer Prevention.
Foxhall, Lewis; Moreno, Mark; Hawk, Ernest
2018-02-01
Texas's size and unique population demographics present challenges to addressing the state's cancer burden. The University of Texas MD Anderson Cancer Center is one of 69 National Cancer Institute-designated cancer centers across the United States. While these centers traditionally have focused on research, education and training, and providing research-driven patient care, they are in a unique position to collaboratively advance population health through cancer control. Unlike the traditional academic model of a three-legged stool representing research, education, and patient care, MD Anderson's mission includes a fourth leg that incorporates population health approaches. MD Anderson has leveraged state- and national-level data and freely available resources to develop population-health priorities and a set of evidence-based actions across policy, public and professional education, and community-based clinical service domains to address these priorities. Population health approaches complement dissemination and implementation research and treatment, and will be increasingly needed to address the growing cancer burden in Texas and the nation.
International Nuclear Information System (INIS)
Al-Jibbouri, Sattar; Ulrich, Joachim
2004-01-01
A fluidized bed crystallizer is employed to investigate the growth and dissolution rates of MgSO 4 .7H 2 O from aqueous solutions in the presence of borax as impurity at 25 C. By adding 0.5, 1, 2 and 5 wt % of impurity the pH value changes from 6.7 to 7.11, while the saturation temperature shifts to 24.8, 24.4, 24 and 23.1 C, respectively. The data on crystal growth rates from aqueous solutions as a function of impurity concentration are discussed from the standpoint of Cabrera and Vermileya, and Kubota and Mullin. The value of the impurity effect, αθ eq , determined from analysis of the data on growth kinetics was found to be in good agreement with the value obtained from direct adsorption experiments. The estimated value of the average spacing between the adjacent adsorption active sites and the average distance between the neighbouring impurity-adsorbed sites are also reported. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Fluid and gyrokinetic simulations of impurity transport at JET
DEFF Research Database (Denmark)
Nordman, H; Skyman, A; Strand, P
2011-01-01
Impurity transport coefficients due to ion-temperature-gradient (ITG) mode and trapped-electron mode turbulence are calculated using profile data from dedicated impurity injection experiments at JET. Results obtained with a multi-fluid model are compared with quasi-linear and nonlinear gyrokinetic...... simulation results obtained with the code GENE. The sign of the impurity convective velocity (pinch) and its various contributions are discussed. The dependence of the impurity transport coefficients and impurity peaking factor −∇nZ/nZ on plasma parameters such as impurity charge number Z, ion logarithmic...
Linear Rashba Model of a Hydrogenic Donor Impurity in GaAs/GaAlAs Quantum Wells
Directory of Open Access Journals (Sweden)
Li Shu-Shen
2008-01-01
Full Text Available Abstract The Rashba spin-orbit splitting of a hydrogenic donor impurity in GaAs/GaAlAs quantum wells is investigated theoretically in the framework of effective-mass envelope function theory. The Rashba effect near the interface between GaAs and GaAlAs is assumed to be a linear relation with the distance from the quantum well side. We find that the splitting energy of the excited state is larger and less dependent on the position of the impurity than that of the ground state. Our results are useful for the application of Rashba spin-orbit coupling to photoelectric devices.
Energy Technology Data Exchange (ETDEWEB)
Tong, David; Wong, Kenny [Department of Applied Mathematics and Theoretical Physics,University of Cambridge, Cambridge (United Kingdom)
2014-01-17
We describe the BPS dynamics of vortices in the presence of impurities. We argue that a moduli space of solitons survives the addition of both electric and magnetic impurities. However, dynamics on the moduli space is altered. In the case of electric impurities, the metric remains unchanged but the dynamics is accompanied by a connection term, acting as an effective magnetic field over the moduli space. We give an expression for this connection and compute the vortex-impurity bound states in simple cases. In contrast, magnetic impurities distort the metric on the moduli space. We show that magnetic impurities can be viewed as vortices associated to a second, frozen, gauge group. We provide a D-brane description of the dynamics of vortices in product gauge groups and show how one can take the limit such that a subset of the vortices freeze.
Theory of s-wave superconductor containing impurities with retarded interaction with quasiparticles
International Nuclear Information System (INIS)
K V Grigorishin
2014-01-01
We propose a perturbation theory and diagram technique for a disordered metal when scattering of quasiparticles by nonmagnetic impurities is caused with a retarded interaction. The perturbation theory generalizes a case of elastic scattering in a disordered metal. Eliashberg equations for s-wave superconductivity are generalized for such a disordered superconductor. Anderson's theorem is found to be violated in the sense that embedding of the impurities into an s-wave superconductor increases its critical temperature. We show that the amplification of superconducting properties is a result of nonelastic effects in a scattering by the impurities. (paper)
Haile, Lydia A; Puig, Montserrat; Polumuri, Swamy K; Ascher, Jill; Verthelyi, Daniela
2017-03-01
Unwanted immune responses to therapeutic proteins can severely impact their safety and efficacy. Studies show that the presence of trace amounts of host cells and process-related impurities that stimulate pattern recognition receptors (PRR) can cause local inflammation and enhance product immunogenicity. Here we used purified PRR agonists as model impurities to assess the minimal level of individual innate immune response modulating impurities (IIRMIs) that could activate a local immune response. We show that levels of endotoxin as low as 10 pg (0.01 EU), 1 ng for polyinosinic:polycytidylic acid (PolyI:C), 100 ng for synthetic diacylated liopprotein, thiazoloquinolone compound, or muramyl dipeptide, 1 μg for flagellin or β-glucan, or 5 μg for CpG-oligodeoxynucleotide increased expression of genes linked to innate immune activation and inflammatory processes in the skin of rhesus macaques. Furthermore, spiking studies using rasburicase as a model therapeutic showed that the levels of PRR agonists that induced detectable gene upregulation in the skin were associated with increased immunogenicity for rasburicase. This study underscores the need for testing multiple IIRMIs in biologics, strengthening the connection between the local mRNA induction in skin, innate immune activation, and antibody development in primates, and provides an indication of the levels of IIRMI in therapeutic products that could impact product immunogenicity. Published by Elsevier Inc.
Quantum Monte Carlo method for models of molecular nanodevices
Arrachea, Liliana; Rozenberg, Marcelo J.
2005-07-01
We introduce a quantum Monte Carlo technique to calculate exactly at finite temperatures the Green function of a fermionic quantum impurity coupled to a bosonic field. While the algorithm is general, we focus on the single impurity Anderson model coupled to a Holstein phonon as a schematic model for a molecular transistor. We compute the density of states at the impurity in a large range of parameters, to demonstrate the accuracy and efficiency of the method. We also obtain the conductance of the impurity model and analyze different regimes. The results show that even in the case when the effective attractive phonon interaction is larger than the Coulomb repulsion, a Kondo-like conductance behavior might be observed.
Energy Technology Data Exchange (ETDEWEB)
Guessi, L.H.; Leandro, S.C.; Seridonio, A.C.; Siqueira, E.C. [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Ilha Solteira, SP (Brazil). Dept. de Fisico Quimica; Souza, F.M.; Vernek, E. [Universidade Federal de Uberlandia (UFU), MG (Brazil). Inst. de Fisica; Yoshida, M. [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Rio Claro, SP (Brazil); Figueira, M.S. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Fisica
2012-07-01
Full text: In this work, we report a theoretical description of the differential conductance in the low bias regime, for a normal scanning tunneling microscope (STM) probe in the presence of ferromagnetic (FM) hosts with impurities. The hosts are treated as a spin-polarized electron gas hybridized to a pair of side-coupled impurities. Two setups of different dimensionalities are considered, a quantum wire (QW) and a metallic surface (MS). In order to deal with the non-interacting and the Coulomb blockade regimes of these systems, the analysis is done in the framework of the two-impurity Anderson model (TIAM) in combination with the equation of motion (EOM) approach for the Hamiltonian Green functions (GFs). The Fano effect appears in such setups, due to the quantum interference between the transport channels composed by the spin-polarized conduction bands and the electron tunneling into (or out of) the impurities. Thus the conductance of the STM reveals as a function of the probe position, a Fano interference strong dependent on the host dimensionality. It leads to the emergence of spin-polarized quantum beats in the Friedel oscillations for the conductance signal, which are uniform in the QW system in opposite to those found in the MS case, characterized by a long-range damped behavior. We remark that, the energy levels of the impurities and the Coulomb repulsion, modulate these beats. As a result, they establish a scenario where the interplay between the Coulomb blockade and the ferromagnetism of a metallic environment, can be useful for future quantum computation devices. (author)
In Situ STM Observation of Nonmagnetic Impurity Effect in MBE-grown CeCoIn5 Films
Haze, Masahiro; Torii, Yohei; Peters, Robert; Kasahara, Shigeru; Kasahara, Yuichi; Shibauchi, Takasada; Terashima, Takahito; Matsuda, Yuji
2018-03-01
Local electronic effects in the vicinity of an impurity provide pivotal insight into the origin of unconventional superconductivity, especially when the materials are located on the edge of magnetic instability. In high-temperature cuprate superconductors, a strong suppression of superconductivity and appearance of low-energy bound states are clearly observed near nonmagnetic impurities. However, whether these features are common to other strongly correlated superconductors has not been established experimentally. Here, we report the in situ scanning tunneling microscopy observation of electronic structure around a nonmagnetic Zn impurity in heavy-fermion CeCo(In1-xZnx)5 films, which are epitaxially grown by the state-of-the-art molecular beam epitaxy technique. The films have very wide atomically flat terraces and Zn atoms residing on two different In sites are clearly resolved. Remarkably, no discernible change is observed for the superconducting gap at and around the Zn atoms. Moreover, the local density of states around Zn atoms shows little change inside the c-f hybridization gap, which is consistent with calculations for a periodic Anderson model without local magnetic order. These results indicate that no nonsuperconducting region is induced around a Zn impurity and do not support the scenario of antiferromagnetic droplet formation suggested by indirect measurements in Cd-doped CeCoIn5. These results also highlight a significant difference of the impurity effect between cuprates and CeCoIn5, in both of which d-wave superconductivity arises from the non-Fermi liquid normal state near antiferromagnetic instabilities.
Tsuruta, Atsushi; Miyake, Kazumasa
2015-11-01
We theoretically investigate electronic states and physical properties in a two-channel Anderson lattice model to understand the non-Fermi liquid behaviors observed in PrV2Al20 and PrIr2Zn20, whose ground state of the crystalline electric field for a local f-electron is the Γ3 non-Kramers doublet of f2-configuration and whose excited state is the Γ7 Kramers doublet of f1-configuration. We use the expansion from the limit of the large degeneracy N of the ground state (1/N-expansion), with N being the spin-orbital degeneracy. The inclusion of the self-energy of conduction electrons up to the order of O(1/N) leads to heavy electrons with channel and spin-orbit degeneracies. We find that the electrical resistivity is proportional to the temperature T in the limit T → 0 and follows the √{T} -law in a wide temperature region, i.e., Tx < T < T0, where the typical values of Tx and T0 are Tx ˜ 10-3TK and T0 ˜ 10-2TK, respectively, TK being the Kondo temperature of the model. We also find non-Fermi liquid behaviors at T ≪ TK in a series of physical quantities; chemical potential, specific heat, and magnetic susceptibility, which explain the non-Fermi liquid behaviors observed in PrV2Al20 and PrIr2Zn20. At the same time, we find that the Fermi liquid behavior becomes prominent for the system with a small hybridization between f- and conduction electrons, explaining the Fermi liquid behaviors observed in PrTi2Al20.
Anderson introduces a new biomass baler
Energy Technology Data Exchange (ETDEWEB)
D' amour, L.; Lavoie, F. [Anderson Group Co., Chesterville, PQ (Canada)
2010-07-01
Canadian-based Anderson Group Company has developed an innovative round baler for harvesting a large variety of woody biomass. The baler was initially developed in 2005 in collaboration with the University Laval and Agriculture and Agri-Food Canada. The third generation BIOBALER{sup TM} is currently built, engineered and commercialized by Anderson. It can produce up to 40 bales/hr in short rotations woody crops such as willow and hybrid poplar. The unit can harvest brushes up to 125 mm in diameter. A standard tractor can pull the BIOBALER in fallow or abandoned land, under power transmission lines, and between planted trees. The patented BIOBALER includes a mulcher head attachment, a choice of long or short swivel tongue, a fixed chamber and an undercarriage frame.
Anderson localization in bipartite lattices
International Nuclear Information System (INIS)
Fabrizio, Michele; Castellani, Claudio
2000-01-01
We study the localization properties of a disordered tight-binding Hamiltonian on a generic bipartite lattice close to the band center. By means of a fermionic replica trick method, we derive the effective non-linear σ-model describing the diffusive modes, which we analyse by using the Wilson-Polyakov renormalization group. In addition to the standard parameters which define the non-linear σ-model, namely, the conductance and the external frequency, a new parameter enters, which may be related to the fluctuations of the staggered density of states. We find that, when both the regular hopping and the disorder only couple one sublattice to the other, the quantum corrections to the Kubo conductivity vanish at the band center, thus implying the existence of delocalized states. In two dimensions, the RG equations predict that the conductance flows to a finite value, while both the density of states and the staggered density of states fluctuations diverge. In three dimensions, we find that, sufficiently close to the band center, all states are extended, independently of the disorder strength. We also discuss the role of various symmetry breaking terms, as a regular hopping between same sublattices, or an on-site disorder
Anderson localization in bipartite lattices
International Nuclear Information System (INIS)
Fabrizio, M.; Castellani, C.
2000-04-01
We study the localization properties of a disordered tight-binding Hamiltonian on a generic bipartite lattice close to the band center. By means of a fermionic replica trick method, we derive the effective non-linear σ-model describing the diffusive modes, which we analyse by using the Wilson-Polyakov renormalization group. In addition to the standard parameters which define the non-linear σ-model, namely the conductance and the external frequency, a new parameter enters, which may be related to the fluctuations of the staggered density of states. We find that, when both the regular hopping and the disorder only couple one sublattice to the other, the quantum corrections to the Kubo conductivity vanish at the band center, thus implying the existence of delocalized states. In two dimensions, the RG equations predict that the conductance flows to a finite value, while both the density of states and the staggered density of states fluctuations diverge. In three dimensions, we find that, sufficiently close to the band center, all states are extended, independently of the disorder strength. We also discuss the role of various symmetry breaking terms, as a regular hopping between same sublattices, or an on-site disorder. (author)
Divertor retention for recycling impurities
International Nuclear Information System (INIS)
Krieger, K.; Roth, J.; Fussmann, G.
1992-01-01
As an important issue for fusion devices with divertor configurations the retention capability for both recycling and non-recycling impurities receives increasing interest. In the case of recycling, gaseous, impurities the retention capability is usually investigated by means of short impurity gas puffs into the plasma vessel and the analysis of the time dependence of the observed line radiation. The detailed understanding of the impurity transport processes related to the retention capability of a certain divertor structure will require modelling of the experimental results with 2D or 3D transport code simulations. However, for the comparison of the global behavior of different configurations a much simpler description of the divertor retention in terms of global time constants may be sufficient. We will give a summary of experimental results from ASDEX for the dependence of the retention capability on parameters like divertor plasma density and temperature and the distance along field lines between main plasma and divertor. In addition we will compare some of these results with similar experiments on DIIID. (author) 8 refs., 2 figs., 2 tabs
Impurity study experiment proposal
International Nuclear Information System (INIS)
1975-05-01
ISX is a modest tokamak which emphasizes the production of a predictable test plasma, experimental flexibility, ease of assembly and disassembly, and good diagnostic access. Its plasma models the outer cooler layers in EPR like plasmas. In addition, provisions will be made for long discharge times which may be necessary to observe some impurity effects. These machine characteristics will enable one to study the collisional transport of impurities in the plasma, perform systematic studies of wall and limiter materials and geometries, study methods of cleaning the walls, and develop and test new diagnostic techniques. ISX will employ water-cooled copper coils to produce a maximum toroidal magnetic field of 20 kG at the plasma axis, which is 77 cm from the major axis. The plasma minor radius will be about 15 cm, and the maximum plasma current will be 100 kA which will be induced by an iron core transformer with a capability of up to 0.9 volt-sec for long discharges. An aspect ratio of five and the modest magnetic field permit a design with ample space for thick wall structures such as honeycomb walls. The ''picture frame'' toroidal field coil provides additional space, while removable coil top sections allow easy replacement of the vacuum chamber. The 72-turn toroidal field coil is grouped into 24 sections for increased access. Absence of a conducting shell and placement of the vertical field and transformer primary coils away from the plasma allow easy viewing of the plasma and good diagnostic access. (U.S.)
Spectral Approach to Anderson Localization in a Disordered 2D Complex Plasma Crystal
Kostadinova, Eva; Liaw, Constanze; Matthews, Lorin; Busse, Kyle; Hyde, Truell
2016-10-01
In condensed matter, a crystal without impurities acts like a perfect conductor for a travelling wave-particle. As the level of impurities reaches a critical value, the resistance in the crystal increases and the travelling wave-particle experiences a transition from an extended to a localized state, which is called Anderson localization. Due to its wide applicability, the subject of Anderson localization has grown into a rich field in both physics and mathematics. Here, we introduce the mathematics behind the spectral approach to localization in infinite disordered systems and provide physical interpretation in context of both quantum mechanics and classical physics. We argue that the spectral analysis is an important contribution to localization theory since it avoids issues related to the use of boundary conditions, scaling, and perturbation. To test accuracy and applicability we apply the spectral approach to the case of a 2D hexagonal complex plasma crystal used as a macroscopic analog for a graphene-like medium. Complex plasma crystals exhibit characteristic distance and time scales, which are easily observable by video microscopy. As such, these strongly coupled many-particle systems are ideal for the study of localization phenomena. The goal of this research is to both expand the spectral method into the classical regime and show the potential of complex plasma as a macroscopic tool for localization experiments. NSF / DOE funding is gratefully acknowledged - PHY1414523 & PHY1262031.
Energy Technology Data Exchange (ETDEWEB)
Waintal, X
1999-09-10
We study the quantum mechanics of interacting particles in a disordered system, and in particular, what happens to Anderson localisation when interaction is taken into account. In the first part,one looks at the excited states of two particles in one dimension. For this model, it has been shown (Shepelyansky 1994) that a local repulsive interaction can partially destroy Anderson localisation. Here, we show that this model has similarities with the three-dimensional Anderson model at the metal-insulator transition. In particular, the maximum of rigidity obtained in the spectral statistics correspond to some intermediary statistics that cannot be described by random matrix theory neither by a Poisson statistics. The wave functions show a multifractal behaviour and the spreading of the center of mass of a wave packet is logarithmic in time. The second part deals with the ground state of a finite density of spinless fermions in two dimensions. After the scaling theory of localisation, it was commonly accepted that there was no metal in two dimensions. This idea has been challenged by the observation of a metal-insulator transition in low density electron gas (Kravchenko et al. 1994). We propose a scenario in which a metallic phase occurs between the Anderson insulator and the pinned Wigner crystal. This intermediate phase is characterized by an alignment of the local currents flowing in the system. (author)
Phonon scattering by isotopic impurities
International Nuclear Information System (INIS)
Dacol, D.K.
1974-06-01
The effects upon vibrations of a perfect crystal lattice due to the replacement of some of its atoms by isotopes of these atoms are studied. The approach consists in considering the isotopic impurities as scattering centres for the quanta of the elastic waves the objective is to obtain the scattering amplitudes. These amplitudes are obtained through a canonical transformation method which was introduced by Chevalier and Rideau in the study of the Wentzel's model in quantum field theory
Price-Anderson Act and nuclear insurance
International Nuclear Information System (INIS)
Long, J.D.; Long, D.P.
1979-01-01
The nuclear incident at Three Mile Island has served to intensify debate about elimination of the federal limit on liability of utilities (and others) for operation of private nuclear reactions and about elimination of possible federal indemnification of utilities (or others) for claims paid in nuclear incidents. Not all those who debate these issues appear to be fully informed about the present nuclear liability and insurance system. This paper provides a brief description of the Price-Anderson Act, as amended, and of the operation of the nuclear insurance pools. It also includes a comment on the recent federal district court award against the Kerr-McGee Corporation
Anderson localization and Mott insulator phase in the time domain
Sacha, Krzysztof
2015-01-01
Particles in space periodic potentials constitute standard models for investigation of crystalline phenomena in solid state physics. Time periodicity of periodically driven systems is a close analogue of space periodicity of solid state crystals. There is an intriguing question if solid state phenomena can be observed in the time domain. Here we show that wave-packets localized on resonant classical trajectories of periodically driven systems are ideal elements to realize Anderson localization or Mott insulator phase in the time domain. Uniform superpositions of the wave-packets form stationary states of a periodically driven particle. However, an additional perturbation that fluctuates in time results in disorder in time and Anderson localization effects emerge. Switching to many-particle systems we observe that depending on how strong particle interactions are, stationary states can be Bose-Einstein condensates or single Fock states where definite numbers of particles occupy the periodically evolving wave-packets. Our study shows that non-trivial crystal-like phenomena can be observed in the time domain. PMID:26074169
Persistence of Anderson localization in Schrodinger operators with decaying random potentials
Figotin, A; Klein, A; Müller, P
2006-01-01
We show persistence of both Anderson and dynamical localization in Schrodinger operators with non-positive (attractive) random decaying potential. We consider an Anderson-type Schr\\"odinger operator with a non-positive ergodic random potential, and multiply the random potential by a decaying envelope function. If the envelope function decays slower than $|x|^{-2}$ at infinity, we prove that the operator has infinitely many eigenvalues below zero. For envelopes decaying as $|x|^{-\\alpha}$ at infinity, we determine the number of bound states below a given energy $E<0$, asymptotically as $\\alpha\\downarrow 0$. To show that bound states located at the bottom of the spectrum are related to the phenomenon of Anderson localization in the corresponding ergodic model, we prove: ~(a)~ these states are exponentially localized with a localization length that is uniform in the decay exponent $\\alpha$; (b)~ dynamical localization holds uniformly in $\\alpha$.
International Nuclear Information System (INIS)
Young, G.A. Jr.; Najafabadi, R.; Strohmayer, W.; Baldrey, D.G.; Hamm, B.; Harris, J.; Sticht, J.; Wimmer, E.
2003-01-01
Atomistic modeling methods were employed to investigate the effects of impurity elements on the metallurgy, irradiation embrittlement, and environmentally assisted cracking of nickel-base alloys exposed to nuclear environments. Calculations were performed via ab initio atomistic modeling methods to ensure the accuracy and reliability of the results. A Griffith-type fracture criterion was used to quantitatively assess the effect of elements or element pairs on the grain boundary cohesive strength. In order of most embrittling to most strengthening, the elements are ranked as: He, Li, S, H, C, Zr, P, Fe, Mn, Nb, Cr, and B. Helium is strongly embrittling (-2.04 eV/atom lowering of the Griffith energy), phosphorus has little effect on the grain boundary (0.1 eV/atom), and boron offers appreciable strengthening (1.03 eV/atom increase in the Griffith energy). Calculations for pairs of elements (H-Li, H-B, H-C, H-P, and H-S) show little interaction on the grain boundary cohesive energy, so that for the conditions studied, linear superposition of elemental effects is a good approximation. These calculations help explain metallurgical effects (e.g. why boron can strengthen grain boundaries), irradiation embrittlement (e.g. how boron transmutation results in grain boundary embrittlement), as well as how grain boundary impurity elements can affect environmentally assisted cracking (i.e. low temperature crack propagation and stress corrosion cracking) of nickel-base alloys
Typical-medium multiple-scattering theory for disordered systems with Anderson localization
Terletska, H.; Zhang, Y.; Chioncel, L.; Vollhardt, D.; Jarrell, M.
2017-04-01
The typical medium dynamical cluster approximation (TMDCA) is reformulated in the language of multiple scattering theory to make possible first-principles calculations of the electronic structure of substitutionally disordered alloys including the effect of Anderson localization. The TMDCA allows for a systematic inclusion of nonlocal multisite correlations and at the same time provides an order parameter, the typical density of states, for the Anderson localization transition. The relation between the dynamical cluster approximation and the multiple scattering theory is analyzed, and is illustrated for a tight-binding model.
Lopez, Matthias; Clément, Jean-François; Lemarié, Gabriel; Delande, Dominique; Szriftgiser, Pascal; Garreau, Jean Claude
2013-06-01
We realize experimentally a cold-atom system, the quasiperiodic kicked rotor, equivalent to the three-dimensional Anderson model of disordered solids where the anisotropy between the x direction and the y-z plane can be controlled by adjusting an experimentally accessible parameter. This allows us to study experimentally the disorder versus anisotropy phase diagram of the Anderson metal-insulator transition. Numerical and experimental data compare very well with each other and a theoretical analysis based on the self-consistent theory of localization correctly describes the observed behavior, illustrating the flexibility of cold-atom experiments for the study of transport phenomena in complex quantum systems.
Simulation of impurity transport in tokamaks, 1
International Nuclear Information System (INIS)
Amano, T.; Mizuno, J.; Kako, M.
1982-11-01
A computer code to simulate impurity transport in tokamaks are described. The code solves the coupled rate and diffusion equations for a set of plasma ions, hydrogen isotopes plus several charge states of one or more impurity elements. Neoclassical transport for all ion species including both density gradient and temperature gradient effects is used. Impurity ions and plasma ions can be either in Pfirsch-Schluter or plateau-banana regime. Anomalous transport is also considered. Several models are used for atomic rates. The source of impurity is calculated from the sputtering of limiter and wall. The rate and diffusion equations are solved by Cranck-Nicholson's implicit scheme. The Crank-Nicholson's method is compared with more accurate Gear's method and a fairly good agreement is found between the two methods. (author)
Numerical Studies of Impurities in Fusion Plasmas
Hulse, R. A.
1982-09-01
The coupled partial differential equations used to describe the behavior of impurity ions in magnetically confined controlled fusion plasmas require numerical solution for cases of practical interest. Computer codes developed for impurity modeling at the Princeton Plasma Physics Laboratory are used as examples of the types of codes employed for this purpose. These codes solve for the impurity ionization state densities and associated radiation rates using atomic physics appropriate for these low-density, high-temperature plasmas. The simpler codes solve local equations in zero spatial dimensions while more complex cases require codes which explicitly include transport of the impurity ions simultaneously with the atomic processes of ionization and recombination. Typical applications are discussed and computational results are presented for selected cases of interest.
Kuldkepp, M.; Brunsell, P. R.; Cecconello, M.; Dux, R.; Menmuir, S.; Rachlew, E.
2006-09-01
Radial impurity profiles of oxygen in the rebuilt reversed field pinch EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Control. Fusion 43, 1457 (2001)] have been measured with a multichannel spectrometer. Absolute ion densities for oxygen peak between 1-4×1010cm-3 for a central electron density of 1×1013cm-3. Transport simulations with the one-dimensional transport code STRAHL with a diffusion coefficient of 20m2 s-1 yield density profiles similar to those measured. Direct measurement of the ion profile evolution during pulsed poloidal current drive suggests that the diffusion coefficient is reduced by a factor ˜2 in the core but remains unaffected toward the edge. Core transport is not significantly affected by the radial magnetic field growth seen at the edge in discharges without feedback control. This indicates that the mode core amplitude remains the same while the mode eigenfunction increases at the edge.
International Nuclear Information System (INIS)
Cecchi, J.L.
1980-06-01
The control of impurities in TFTR will be a particularly difficult problem due to the large energy and particle fluxes expected in the device. As part of the TFTR Flexibility Modification (TEM) project, a program has been implemented to address this problem. Transport code simulations are used to infer an impurity limit criterion as a function of the impurity atomic number. The configurational designs of the limiters and associated protective plates are discussed along with the consideration of thermal and mechanical loads due to normal plasma operation, neutral beams, and plasma disruptions. A summary is given of the materials-related research, which has been a collaborative effort involving groups at Argonne National Laboratory, Sandia Laboratories, and Princeton Plasma Physics Laboratory. Conceptual designs are shown for getterng systems capable of regenerating absorbed tritium. Research on this topic by groups at the previously mentioned laboratories and SAES Research Laboratory is reviewed
Bell, Adam Patrick
2017-01-01
What does it mean to experience disability in music? Based on interviews with Patrick Anderson--arguably the greatest wheelchair basketball player of all time--this article presents insights into the complexities of the experience of disability in sports and music. Contrasted with music education's tendency to adhere to a medicalized model of…
Purifying Impure Virtue Epistemology
DEFF Research Database (Denmark)
Broncano-Berrocal, Fernando
2018-01-01
A notorious objection to robust virtue epistemology—the view that an agent knows a proposition if and only if her cognitive success is because of her intellectual virtues—is that it fails to eliminate knowledge-undermining luck. Modest virtue epistemologists agree with robust virtue epistemologists...... instances of impure virtue epistemology. The aim of the paper is to argue, firstly, that such a move lacks adequate motivation; secondly, that the resulting impure accounts equally fail to handle knowledge-undermining luck. On a more positive note, these results bolster a more orthodox virtue...
Anderson Exploration Ltd. 1998 annual report
International Nuclear Information System (INIS)
1999-01-01
In 1998, Anderson Exploration's undeveloped land inventory in the western provinces decreased 7% to 3,183,000 net acres largely due to lease expiries and drilling activity. The undeveloped land base is located 63% in Alberta, 19% in British Columbia, 17% in Saskatchewan, and 1% in Manitoba. During 1998, Anderson Exploration participated in drilling 446 wells for oil and gas vs. 669 for 1997. The average working interest in the wells was 63% vs. 64% in 1997. In 1998, the company spent $109 million on the construction of field gathering systems and production facilities vs. $123 million in 1997. In 1998, the company's gas sales increased to 555 million cubic feet per day from 549 million cubic feet per day in 1997. Crude oil sales averaged 29,808 barrels per day in 1998, an increase of 9% over the 1997 production. In 1998, the company replaced 148% of production with proven reserve additions, net of revisions, by spending 163% of cash flow from operations on capital spending. After a volatile year in 1 997, natural gas prices stabilized somewhat in 1998. A modest price increase was experienced in 1997. The company's average plant gate natural gas price increased modestly in 1998 to $1.94 per thousand cubic feet, marking the 3rd consecutive price increase. The company owns an average interest of 10.4% in two straddle plants at Empress, Alberta. The company operates and is a 50% owner of Federated Pipe Lines Ltd. The company is committed to protecting the health and safety of all employees and the public, as well as preserving the quality of the environment
Gattenlöhner, S; Hannes, W-R; Ostrovsky, P M; Gornyi, I V; Mirlin, A D; Titov, M
2014-01-17
We explore the longitudinal conductivity of graphene at the Dirac point in a strong magnetic field with two types of short-range scatterers: adatoms that mix the valleys and "scalar" impurities that do not mix them. A scattering theory for the Dirac equation is employed to express the conductance of a graphene sample as a function of impurity coordinates; an averaging over impurity positions is then performed numerically. The conductivity σ is equal to the ballistic value 4e2/πh for each disorder realization, provided the number of flux quanta considerably exceeds the number of impurities. For weaker fields, the conductivity in the presence of scalar impurities scales to the quantum-Hall critical point with σ≃4×0.4e2/h at half filling or to zero away from half filling due to the onset of Anderson localization. For adatoms, the localization behavior is also obtained at half filling due to splitting of the critical energy by intervalley scattering. Our results reveal a complex scaling flow governed by fixed points of different symmetry classes: remarkably, all key manifestations of Anderson localization and criticality in two dimensions are observed numerically in a single setup.
Controlling Anderson localization in disordered photonic crystal waveguides
DEFF Research Database (Denmark)
Garcia-Fernández, David; Smolka, Stephan; Stobbe, Søren
2010-01-01
In most experiments on Anderson localization so far, only completely random systems without any long-range correlation between the scattering sites have been used, meaning that the Anderson localized modes cannot be controlled. Strongly confined modes were recently observed in the slow-light regime...... of a disordered photonic crystal waveguide and attributed to Anderson localization. We have tested this hypothesis by measuring the light localization length, ξloc, in a disordered photonic crystal waveguide and checked explicitly the criterion of one dimensional Anderson localization that ξloc is shorter than...... the waveguide length LS. Our measurements demonstrate for the first time the close relation between light localization and density of states, which can be used ultimately for controlling Anderson localized modes....
Fractal growth in impurity-controlled solidification in lipid monolayers
DEFF Research Database (Denmark)
Fogedby, Hans C.; Sørensen, Erik Schwartz; Mouritsen, Ole G.
1987-01-01
A simple two-dimensional microscopic model is proposed to describe solidifcation processes in systems with impurities which are miscible only in the fluid phase. Computer simulation of the model shows that the resulting solids are fractal over a wide range of impurity concentrations and impurity...... diffusional constants. A fractal-forming mechanism is suggested for impurity-controlled solidification which is consistent with recent experimental observations of fractal growth of solid phospholipid domains in monolayers. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....
Gong, Mingyang
With demand over green energy economy, fuel cells have been developed as a promising energy conversion technology with higher efficiency and less emission. Solid oxide fuel cells (SOFC) can utilize various fuels in addition to hydrogen including coal derived sygas, and thus are favored for future power generation due to dependence on coal in electrical industry. However impurities such as sulfur and phosphorous present in coal syngas in parts per million (p.p.m.) levels can severely poison SOFC anode typically made of Ni/yttria-stabilized-zirconia (Ni-YSZ) and limit SOFC applicability in economically derivable fuels. The focus of the research is to develop strategy for application of high performance SOFC in coal syngas with tolerance against trace impurities such as H2S and PH3. To realize the research goal, the experimental study on sulfur tolerant anode materials and examination of various fuel impurity effects on SOFC anode are combined with electrochemical modeling of SOFC cathode kinetics in order to benefit design of direct-coal-syngas SOFC. Tolerant strategy for SOFC anode against sulfur is studied by using alternative materials which can both mitigate sulfur poisoning and function as active anode components. The Ni-YSZ anode was modified by incorporation of lanthanum doped ceria (LDC) nano-coatings via impregnation. Cell test in coal syngas containing 20 ppm H2S indicated the impregnated LDC coatings inhibited on-set of sulfur poisoning by over 10hrs. Cell analysis via X-ray photon spectroscopy (XPS), X-ray diffraction (XRD) and electrochemistry revealed LDC coatings reacted with H2S via chemisorptions, resulting in less sulfur blocking triple--phase-boundary and minimized performance loss. Meanwhile the effects of PH3 impurity on SOFC anode is examined by using Ni-YSZ anode supported SOFC. Degradation of cell is found to be irreversible due to adsorption of PH3 on TPB and further reaction with Ni to form secondary phases with low melting point. The
International Nuclear Information System (INIS)
Pacella, D.; Fournier, K. B.; Zerbini, M.; Finkenthal, M.; Mattioli, M.; May, M. J.; Goldstein, W. H.
2000-01-01
This work presents and interprets, by means of detailed atomic calculations, observations of L-shell (n=3→n=2) transitions in highly ionized molybdenum, the main intrinsic heavy impurity in the Frascati tokamak upgrade plasmas. These hot plasmas were obtained by additional electron cyclotron resonance heating (ECRH), at the frequency of 140 Ghz, during the current ramp-up phase of the discharge. Injecting 400 kW on axis and 800 kW slightly off axis, the peak central electron temperature reached 8.0 and 7.0 keV, respectively, for a time much longer than the ionization equilibrium time of the molybdenum ions. X-ray emissions from rarely observed high charge states, Mo 30+ to Mo 39+ , have been studied with moderate spectral resolution (λ/Δλ∼150) and a time resolution of 5 ms. A sophisticated collisional-radiative model for the study of molybdenum ions in plasmas with electron temperature in the range 4-20 keV is presented. The sensitivity of the x-ray emission to the temperature and to impurity transport processes is discussed. This model has been then used to investigate two different plasma scenarios. In the first regime the ECRH heating occurs on axis during the current ramp up phase, when the magnetic shear is evolving from negative to zero up to the half radius. The spectrum is well reproduced with the molybdenum ions in coronal equilibrium and with a central impurity peaking. In the second regime, at the beginning of the current flat top when magnetic shear is monotonic and sawtoothing activity is appearing, the lowest charge states (Mo 33+ to Mo 30+ ), populated off axis, are affected by anomalous transport and the total molybdenum profile is found to be flat up to the half radius. We conclude with the presentation of ''synthetic spectra'' computed for even higher temperature plasmas that are expected in future experiments with higher ECRH power input. (c) 2000 The American Physical Society
Impurity solitons with quadratic nonlinearities
DEFF Research Database (Denmark)
Clausen, Carl A. Balslev; Torres, Juan P-; Torner, Lluis
1998-01-01
We fmd families of solitary waves mediated by parametric mixing in quadratic nonlinear media that are localized at point-defect impurities. Solitons localized at attractive impurities are found to be dynamically stable. It is shown that localization at the impurity modifies strongly the soliton...
Impurity screening of scrape-off plasma in a tokamak
International Nuclear Information System (INIS)
Kishimoto, Hiroshi; Tani, Keiji; Nakamura, Hiroo
1981-11-01
Impurity screening effect of a scrape-off layer has been studied in a tokamak, based on a simple model of wall-released impurity behavior. Wall-sputtered impurities are stopped effectively by the scrape-off plasma for a medium-Z or high-Z wall system while major part of impurities enters the main plasma in a low-Z wall system. The screening becomes inefficient with increase of scrape-off plasma temperature. Successive multiplication of recycling impurities in the scrape-off layer is large for a high-Z wall and is enhanced by a rise of scrape-off plasma temperature. The stability of plasma-wall interaction is determined by a multiplication factor of recycling impurities. (author)
Anomalous diffusion, clustering, and pinch of impurities in plasma edge turbulence
DEFF Research Database (Denmark)
Priego, M.; Garcia, O.E.; Naulin, V.
2005-01-01
The turbulent transport of impurity particles in plasma edge turbulence is investigated. The impurities are modeled as a passive fluid advected by the electric and polarization drifts, while the ambient plasma turbulence is modeled using the two-dimensional Hasegawa-Wakatani paradigm for resistive......-diffusion analysis of the evolution of impurity puffs. Additional effects appear for inertial impurities as a consequence of compressibility. First, the density of inertial impurities is found to correlate with the vorticity of the electric drift velocity, that is, impurities cluster in vortices of a precise...
Cavity quantum electrodynamics in the Anderson-localized regime
DEFF Research Database (Denmark)
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren
2010-01-01
We experimentally measure, by means of time-resolved photoluminescence spectroscopy, a 15-fold enhancement of the spontaneous emission decay rate of single semiconductor quantum dots coupled to disorder-induced Anderson-localized modes with efficiencies reaching 94%....
Martin Anderson valis "Joonase lähetamise" / Priit Kuusk
Kuusk, Priit, 1938-
2000-01-01
M. Anderson kommenteeris ameerika muusikaajakirjas "Fanfare" viit talle kõige enam mõju avaldanud heliplaati, sh. R. Tobiase oratooriumi "Joonase lähetamine" CD-plaati (BIS). M. Andersoni huvist eesti muusika vastu
Controlling Anderson localization in disordered photonic crystal waveguides
DEFF Research Database (Denmark)
Garcia-Fernández, David; Smolka, Stephan; Stobbe, Søren
structures [1,2]. Originally proposed for electrons by P. W. Anderson [3], only completely random systems without any long-range correlation between the scattering sites have been used so far, meaning that the Anderson-localized modes cannot be controlled. In disordered photonic crystals, these modes...... are predicted to appear at frequencies in or near a band gap [4] providing a possible way to control Anderson-localized modes. We have tested this hypothesis by measuring the light localization length, ξ, in a disordered photonic crystal waveguide (PCW) as a function of the dispersive slowdown factor of light...... of the waveguide. Our measurements demonstrate for the first time the close relation between light localization and density of states [5], which can be used ultimately for controlling the extension and spectral position of Anderson-localized modes....
Probing the statistical properties of Anderson localization with quantum emitters
DEFF Research Database (Denmark)
Smolka, Stephan; Nielsen, Henri Thyrrestrup; Sapienza, Luca
2011-01-01
Wave propagation in disordered media can be strongly modified by multiple scattering and wave interference. Ultimately, the so-called Anderson-localized regime is reached when the waves become strongly confined in space. So far, Anderson localization of light has been probed in transmission...... experiments by measuring the intensity of an external light source after propagation through a disordered medium. However, discriminating between Anderson localization and losses in these experiments remains a major challenge. In this paper, we present an alternative approach where we use quantum emitters...... embedded in disordered photonic crystal waveguides as light sources. Anderson-localized modes are efficiently excited and the analysis of the photoluminescence spectra allows us to explore their statistical properties, for example the localization length and average loss length. With increasing the amount...
Steady-state organization of binary mixtures by active impurities
DEFF Research Database (Denmark)
Sabra, Mads Christian; Gilhøj, Henriette; Mouritsen, Ole G.
1998-01-01
The structural reorganization of a phase-separated binary mixture in the presence of an annealed dilution of active impurities is studied by computer-simulation techniques via a simple two-dimensional lattice-gas model. The impurities, each of which has two internal states with different affinity...
Strong Anderson localization in cold atom quantum quenches
Micklitz, T.; Müller, C. A.; Altland, A.
2013-01-01
Signatures of strong Anderson localization in the momentum distribution of a cold atom cloud after a quantum quench are studied. We consider a quasi one-dimensional cloud initially prepared in a well defined momentum state, and expanding for some time in a disorder speckle potential. Anderson localization leads to a formation of a coherence peak in the \\emph{forward} scattering direction (as opposed to the common weak localization backscattering peak). We present a microscopic, and fully time...
Controlling Anderson localization in disordered photonic crystal waveguides
DEFF Research Database (Denmark)
Smolka, Stephan; Garcia, Pedro D.; Lodahl, Peter
2010-01-01
We prove Anderson localization in the slow-light regime of a photonic crystal waveguide by measuring the ensemble-averaged localization length which is controlled by the dispersion of the disordered photonic crystal waveguide.......We prove Anderson localization in the slow-light regime of a photonic crystal waveguide by measuring the ensemble-averaged localization length which is controlled by the dispersion of the disordered photonic crystal waveguide....
Study by nuclear techniques of the impurity-defect interaction in implanted metals
International Nuclear Information System (INIS)
Thome, Lionel.
1978-01-01
The properties of out equilibrium alloys formed by impurity implantation are strongly influenced by radiation damage created during implantation. This work presents a study, via hyperfine interaction and lattice location experiments, of the impurity-defect interaction in ion implanted metals. When the impurity and defect concentrations in the implanted layer are small, i.e. when impurities are uniformly recoil implanted in the whole crystal volume following a nuclear reaction (Aq In experiments), the impurity interacts with its own damage cascade. In this case, a vacancy is found to be trapped by a fraction of impurities during an athermal process. The value of this fraction does not seem to depend critically on impurity and host. When the impurity and defect concentrations are such that defect cascades interact, i.e. when impurities are implanted with an isotope separator (Fe Yb experiments), the observed impurity-vacancy (or vacancy cluster) interactions depend then strongly on the nature of impurity and host. An empirical relation, which indicates the importance of elastic effects, has been found between the proportion of impurities interacting with defects and the difference between impurity and host atom radii. At implantation temperature such that vacancies are mobile, the impurity-defect interaction depends essentially on vacancy migration. A model based on chemical kinetics has been developed to account for the variation with temperature of measured quantities [fr
Energy bands and gaps near an impurity
Czech Academy of Sciences Publication Activity Database
Mihóková, Eva; Schulman, L. S.
2016-01-01
Roč. 380, č. 41 (2016), s. 3430-3433 ISSN 0375-9601 R&D Projects: GA ČR GA13-09876S Institutional support: RVO:68378271 Keywords : crystal structure * impurity * modeling * energy bands Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.772, year: 2016
Anderson transition in one-dimension using Wegner's Flow equations
Bhattacharjee, Paraj; Quito, Victor; Pekker, David; Refael, Gil
2015-03-01
We study the Anderson transition in one-dimensional random single-particle Hamiltonians with long-range hoppings decaying in a power-law. Explicitly, we consider the single particle tight-binding model in the spin representation with disorder both in the fields and hoppings. It has been shown by Mirlin et. al. that this model shows an extended-to-localized transition as a function of the power-law exponent with a critical multi-fractal regime when the decay exponent is equal to one. We generalize the flow equation technique, first introduced by Wegner, to the disordered system and use it to study the model and elucidate the character of this transition. This method allows us to efficiently compute the eigenvalues and local observables. We follow, analytically and numerically, the flow of the coupling distributions for the different exponents as a function of the flow-time and look for signatures of the two distinct phases as well as a characterization of the critical point.
Matt, Felix; Burkhart, John F.
2017-04-01
Light absorbing impurities in snow and ice (LAISI) originating from atmospheric deposition enhance snow melt by increasing the absorption of short wave radiation. The consequences are a shortening of the snow cover duration due to increased snow melt and, with respect to hydrologic processes, a temporal shift in the discharge generation. However, the magnitude of these effects as simulated in numerical models have large uncertainties, originating mainly from uncertainties in the wet and dry deposition of light absorbing aerosols, limitations in the model representation of the snowpack, and the lack of observable variables required to estimate model parameters and evaluate the simulated variables connected with the representation of LAISI. This leads to high uncertainties in the additional energy absorbed by the snow due to the presence of LAISI, a key variable in understanding snowpack energy-balance dynamics. In this study, we assess the effect of LAISI on snow melt and discharge generation and the involved uncertainties in a high mountain catchment located in the western Himalayas by using a distributed hydrological catchment model with focus on the representation of the seasonal snow pack. The snow albedo is hereby calculated from a radiative transfer model for snow, taking the increased absorption of short wave radiation by LAISI into account. Meteorological forcing data is generated from an assimilation of observations and high resolution WRF simulations, and LAISI mixing ratios from deposition rates of Black Carbon simulated with the FLEXPART model. To asses the quality of our simulations and the related uncertainties, we compare the simulated additional energy absorbed by the snow due to the presence of LAISI to the MODIS Dust Radiative Forcing in Snow (MODDRFS) algorithm satellite product.
International Nuclear Information System (INIS)
Legros, F.
2008-01-01
In GEN IV studies on future fission nuclear reactors, two concepts using helium as a coolant have been selected: GFR and VHTR. Among radioactive impurities and dusts, helium can contain H 2 , CO, CH 4 , CO 2 , H 2 O, O 2 , as well as nitrogenous species. To optimize the reactor functioning and lifespan, it is necessary to control the coolant chemical composition using a dedicated purification system. A pilot designed at the CEA allows studying this purification system. Its design includes three unit operations: H 2 and CO oxidation on CuO, then two adsorption steps. This study aims at providing a detailed analysis of the first and second purification steps, which have both been widely studied experimentally at laboratory scale. A first modelling based on a macroscopic approach was developed to represent the behaviour of the reactor and has shown that the CuO fixed bed conversion is dependent on the chemistry (mass transfer is not an issue) and is complete. The results of the structural analysis of the solids allow considering the CuO as particles made of 200 nm diameter grains. Hence, a new model at grain scale is proposed. It is highlighted that the kinetic constants from these two models are related with a scale factor which depends on geometry. A competition between carbon monoxide and hydrogen oxidation has been shown. Activation energies are around 30 kJ.mol-1. Simulation of the simultaneous oxidations leads to consider CO preferential adsorption. A similar methodology has been applied for CO 2 and H 2 O adsorption. The experimental isotherms showed a Langmuir type adsorption. Using this model, experimental and theoretical results agree. (author) [fr
Potential fluctuations in graphene due to correlated charged impurities in substrate
Anicic, Rastko; Miskovic, Zoran
2013-01-01
We evaluate the autocorrelation function of the electrostatic potential in doped graphene due to nearby charged impurities. The screening of those impurities is described by a combination of the polarization function for graphene in random phase approximation with the electrostatic Green's function of the surrounding dielectrics. Using the hard-disk model for a two-dimensional distribution of impurities, we show that large correlation lengths between impurities can give rise to anti-correlati...
Neo-classical impurity transport
International Nuclear Information System (INIS)
Stringer, T.E.
The neo-classical theory for impurity transport in a toroidal plasma is outlined, and the results discussed. A general account is given of the impurity behaviour and its dependence on collisionality. The underlying physics is described with special attention to the role of the poloidal rotation
International Nuclear Information System (INIS)
Evans, T.E.; Loh, Y.S.; West, W.P.; Finkenthal, D.F.
1997-11-01
The MCI transport model was used to compare chemical and physical sputtering for a DIII-D divertor plasma near detachment. With physical sputtering alone the integrated carbon influx was 8.4 x 10 19 neutral/s while physical plus chemical sputtering produced an integrated carbon influx of 1.7 x 10 21 neutrals/s. The average carbon concentration in the computational volume increased from 0.012% with only physical sputtering to 0.182% with both chemical and physical sputtering. This increase in the carbon inventory produced more radiated power which is in better agreement with experimental measurements
Strong Anderson localization in cold atom quantum quenches.
Micklitz, T; Müller, C A; Altland, A
2014-03-21
Signatures of Anderson localization in the momentum distribution of a cold atom cloud after a quantum quench are studied. We consider a quasi-one-dimensional cloud initially prepared in a well-defined momentum state, and expanding for some time in a disorder speckle potential. Quantum interference generates a peak in the forward scattering amplitude which, unlike the common weak localization backscattering peak, is a signature of strong Anderson localization. We present a nonperturbative, and fully time resolved description of the phenomenon, covering the entire diffusion-to-localization crossover. Our results should be observable by present day experiments.
Kleibergen, F.R.
2002-01-01
We extend the novel pivotal statistics for testing the parameters in the instrumental variables regression model. We show that these statistics result from a decomposition of the Anderson-Rubin statistic into two independent pivotal statistics. The first statistic is a score statistic that tests
Mobile impurities in ferromagnetic liquids
Kantian, Adrian; Schollwoeck, Ulrich; Giamarchi, Thierry
2011-03-01
Recent work has shown that mobile impurities in one dimensional interacting systems may exhibit behaviour that differs strongly from that predicted by standard Tomonaga-Luttinger liquid theory, with the appearance of power-law divergences in the spectral function signifying sublinear diffusion of the impurity. Using time-dependent matrix product states, we investigate a range of cases of mobile impurities in systems beyond the analytically accessible examples to assess the existence of a new universality class of low-energy physics in one-dimensional systems. Correspondence: Adrian.Kantian@unige.ch This work was supported in part by the Swiss SNF under MaNEP and division II.
Impurity states in two and three dimensional disordered system S
International Nuclear Information System (INIS)
Silva, A.F. da; Fabbri, M.
1984-01-01
We investigate the microscopic structure of the impurity states in two-and three-dimensional (2D and 3D) disordered system. A cluster model is outlined for the donor impurity density of states (DIDS) of doped semiconductors. It is shown that the impurity states are very sensitive to a change in the dimensionality of the system, i.e., from 3D to 2D system. It is found that all eigenstates become localized in 2D disordered system for a large range of concentration. (author) [pt
Laser Ablation Plume Expansion In The Presence Of Charged Impurities
International Nuclear Information System (INIS)
Djebli, M.
2008-01-01
The expansion of plasma created by laser ablation is investigated using the fluid model. At the first stage of the expansion, electrons are considered in thermal equilibrium. The presence of highly charged impurities is considered through Poisson's equation. The set of nonlinear differential equations is solved using a moving boundary and taken into account the charge separation effect. The uniformly distributed impurities can accelerate or decelerate the ion motion depending on their charge and concentration. It is also found that the separation of the charge is valid for a specific time which depends on the impurities parameters.
Magnetic field nanosensor based on Mn impurities
Directory of Open Access Journals (Sweden)
Daniela ENCIU
2014-06-01
Full Text Available Nanosensors based on graphene nanoribbon, studied in the present work, could provide a special interest in (aero space applications. More specifically, the paper proposes the construction of a nanosensor based on Mn (Manganese impurities. Different spin configurations of the Mn atoms are considered. The mathematical model used to determine the spin transport is based on Kohn-Sham equations. The spin-dependent transmission functions are calculated using the formalism of the nonequilibrium Green’s functions. The implementation of the mathematical model is performed in the SIESTA package. The spin transport properties are determined using the first principle calculations using density functional theory. The graphene nanoribbon with transition metal impurities is based on active element – the system of spins – which is influenced by the external perturbation field. Such nanostructures may serve as spatial applications. The differences between different excited states are determined and it is established that the energy range overlaps the mid-infrared wavelengths.
Quantum criticality of quasi one-dimensional topological Anderson insulators
Altland, A.; Bagrets, D.; Fritz, L.; Kamenev, A.; Schmiedt, H.
2014-01-01
We present an analytic theory of quantum criticality in the quasi one-dimensional topological Anderson insulators of class AIII and BDI. We describe the systems in terms of two parameters (g,χ) representing localization and topological properties, respectively. Surfaces of half-integer valued χ
Coordination of lanthanide cation to an Anderson type ...
Indian Academy of Sciences (India)
Home; Journals; Journal of Chemical Sciences; Volume 126; Issue 5. Coordination of lanthanide cation to an Anderson type polyoxometalate anion ... and spectroscopy. Vaddypally Shivaiah Tanmay Chatterjee Samar K Das. Special issue on Chemical Crystallography Volume 126 Issue 5 September 2014 pp 1525-1533 ...
Controlling Anderson localization in disordered photonic crystal waveguides
DEFF Research Database (Denmark)
Garcia-Fernández, David; Smolka, Stephan; Stobbe, Søren
2010-01-01
are predicted to appear at frequencies in or near a band gap [4] providing a possible way to control Anderson-localized modes. We have tested this hypothesis by measuring the light localization length, ξ, in a disordered photonic crystal waveguide (PCW) as a function of the dispersive slowdown factor of light...
Impurities confined in quantum structures
Holtz, Per Olof
2004-01-01
The introduction of impurities, even in very small concentrations, in a semiconductor can change its optical and electrical properties entirely. This attribute of the semiconductor is utilized in the manifoldness of their applications. In this book, the progress on elucidating the physical properties of impurities confined in quantum structures are reviewed with an emphasis on the experimental aspects. The major results of various kinds of characterization, such as infrared spectroscopy, Raman measurements, luminescence characterization, perturbation spectroscopy and dynamical studies of the confined impurities are reviewed, but also the theoretical basis to calculate the electronic structure of the confined donors and acceptors are presented. This monograph also describes more specific aspects of the confined impurities such as the properties in the high doping regime and the effects of hydrogen passivation.
Impurities in Holography and Transport Coefficients
Hashimoto, Koji
2012-01-01
We present a way to include impurities in AdS/CFT correspondence, in view of its application to condensed matter physics. Examples of these are the current impurity and spin impurity. We calculate electric conductivity and spin susceptibility of holographic superconductors, with doping of density/spin impurities.
Elliott, Perry; Baker, Robert; Pasquale, Ferdinando; Quarta, Giovanni; Ebrahim, Hatim; Mehta, Atul B.; Hughes, Derralynn A.; Anastasakis, Aristides; Autore, Camillo; Musumeci, Maria Beatrice; Frenneaux, Michael; Gimeno, Juan; Tiina, Heliö; Kuusisto, Johanna; Aalto-Setäla, Katriina; McKeown, Pascal; Monserrat, Lorenzo; Fernandez, Xusto; Pacileo, Giuseppe; Limongelli, Giuseppe; Rapezzi, Claudio; Biagini, Elena; ten Cate, Folkert J.; Wilde, Arthur A. M.; Pinto, Yigal M.; Christiaans, Imke; Zachara, Elisabetta
2011-01-01
The prevalence of Anderson-Fabry disease (AFD) in patients presenting with unexplained left ventricular hypertrophy (LVH) is controversial. The aim of this study was to determine the prevalence of AFD in a large, consecutive cohort of patients with hypertrophic cardiomyopathy (HCM) using rapid
2010-06-16
... Employment and Training Administration Plastic Omnium Automotive Exteriors, LLC, Anderson, SC; Plastic Omnium... Assistance on March 18, 2010, applicable to workers of Plastic Omnium Automotive Exteriors, LLC, Anderson... have occurred involving workers in support of the Anderson, South Carolina location of Plastic Omnium...
Impurities of oxygen in silicon
International Nuclear Information System (INIS)
Gomes, V.M.S.
1985-01-01
The electronic structure of oxygen complex defects in silicon, using molecular cluster model with saturation by watson sphere into the formalism of Xα multiple scattering method is studied. A systematic study of the simulation of perfect silicon crystal and an analysis of the increasing of atom number in the clusters are done to choose the suitable cluster for the calculations. The divacancy in three charge states (Si:V 2 + , Si:V 2 0 , Si:V 2 - ), of the oxygen pair (Si:O 2 ) and the oxygen-vacancy pair (Si:O.V) neighbours in the silicon lattice, is studied. Distortions for the symmetry were included in the Si:V 2 + and Si:O 2 systems. The behavior of defect levels related to the cluster size of Si:V 2 0 and Si:O 2 systems, the insulated oxygen impurity of silicon in interstitial position (Si:O i ), and the complexes involving four oxygen atoms are analysed. (M.C.K.) [pt
Efficient implementation of the continuous-time hybridization expansion quantum impurity solver
Hafermann, Hartmut; Werner, Philipp; Gull, Emanuel
2013-04-01
Strongly correlated quantum impurity problems appear in a wide variety of contexts ranging from nanoscience and surface physics to material science and the theory of strongly correlated lattice models, where they appear as auxiliary systems within dynamical mean-field theory. Accurate and unbiased solutions must usually be obtained numerically, and continuous-time quantum Monte Carlo algorithms, a family of algorithms based on the stochastic sampling of partition function expansions, perform well for such systems. With the present paper we provide an efficient and generic implementation of the hybridization expansion quantum impurity solver, based on the segment representation. We provide a complete implementation featuring most of the recently developed extensions and optimizations. Our implementation allows one to treat retarded interactions and provides generalized measurement routines based on improved estimators for the self-energy and for vertex functions. The solver is embedded in the ALPS-DMFT application package. Catalogue identifier: AEOL_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOL_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Use of the hybridization expansion impurity solvers requires citation of this paper. Use of any ALPS program requires citation of the ALPS [1] paper. No. of lines in distributed program, including test data, etc.: 650044 No. of bytes in distributed program, including test data, etc.: 20553265 Distribution format: tar.gz Programming language: C++/Python. Computer: Desktop PC, high-performance computers. Operating system: Unix, Linux, OSX, Windows. Has the code been vectorized or parallelized?: Yes, MPI parallelized. RAM: 1 GB Classification: 7.3. External routines: ALPS [1, 2, 3], BLAS [4, 5], LAPACK [6], HDF5 [7] Nature of problem: Quantum impurity models were originally introduced to describe a magnetic transition metal ion in a non
Elemental Impurities in Pharmaceutical Excipients.
Li, Gang; Schoneker, Dave; Ulman, Katherine L; Sturm, Jason J; Thackery, Lisa M; Kauffman, John F
2015-12-01
Control of elemental impurities in pharmaceutical materials is currently undergoing a transition from control based on concentrations in components of drug products to control based on permitted daily exposures in drug products. Within the pharmaceutical community, there is uncertainty regarding the impact of these changes on manufactures of drug products. This uncertainty is fueled in part by a lack of publically available information on elemental impurity levels in common pharmaceutical excipients. This paper summarizes a recent survey of elemental impurity levels in common pharmaceutical excipients as well as some drug substances. A widely applicable analytical procedure was developed and was shown to be suitable for analysis of elements that are subject to United States Pharmacopoeia Chapter and International Conference on Harmonization's Q3D Guideline on Elemental Impurities. The procedure utilizes microwave-assisted digestion of pharmaceutical materials and inductively coupled plasma mass spectrometry for quantitative analysis of these elements. The procedure was applied to 190 samples from 31 different excipients and 15 samples from eight drug substances provided through the International Pharmaceutical Excipient Council of the Americas. The results of the survey indicate that, for the materials included in the study, relatively low levels of elemental impurities are present. © 2015 The Authors. Journal of Pharmaceutical Sciences published by Wiley Periodicals, Inc. and the American Pharmacists Association.
Timmermans, Eddy; Blinova, Alina; Boshier, Malcolm
2013-05-01
Polarons (particles that interact with the self-consistent deformation of the host medium that contains them) self-localize when strongly coupled. Dilute Bose-Einstein condensates (BECs) doped with neutral distinguishable atoms (impurities) and armed with a Feshbach-tuned impurity-boson interaction provide a unique laboratory to study self-localized polarons. In nature, self-localized polarons come in two flavors that exhibit qualitatively different behavior: In lattice systems, the deformation is slight and the particle is accompanied by a cloud of collective excitations as in the case of the Landau-Pekar polarons of electrons in a dielectric lattice. In natural fluids and gases, the strongly coupled particle radically alters the medium, e.g. by expelling the host medium as in the case of the electron bubbles in superfluid helium. We show that BEC-impurities can self-localize in a bubble, as well as in a Landau-Pekar polaron state. The BEC-impurity system is fully characterized by only two dimensionless coupling constants. In the corresponding phase diagram the bubble and Landau-Pekar polaron limits correspond to large islands separated by a cross-over region. The same BEC-impurity species can be adiabatically Feshbach steered from the Landau-Pekar to the bubble regime. This work was funded by the Los Alamos LDRD program.
Calculations of neoclassical impurity transport in stellarators
Mollén, Albert; Smith, Håkan M.; Langenberg, Andreas; Turkin, Yuriy; Beidler, Craig D.; Helander, Per; Landreman, Matt; Newton, Sarah L.; García-Regaña, José M.; Nunami, Masanori
2017-10-01
The new stellarator Wendelstein 7-X has finished the first operational campaign and is restarting operation in the summer 2017. To demonstrate that the stellarator concept is a viable candidate for a fusion reactor and to allow for long pulse lengths of 30 min, i.e. ``quasi-stationary'' operation, it will be important to avoid central impurity accumulation typically governed by the radial neoclassical transport. The SFINCS code has been developed to calculate neoclassical quantities such as the radial collisional transport and the ambipolar radial electric field in 3D magnetic configurations. SFINCS is a cutting-edge numerical tool which combines several important features: the ability to model an arbitrary number of kinetic plasma species, the full linearized Fokker-Planck collision operator for all species, and the ability to calculate and account for the variation of the electrostatic potential on flux surfaces. In the present work we use SFINCS to study neoclassical impurity transport in stellarators. We explore how flux-surface potential variations affect the radial particle transport, and how the radial electric field is modified by non-trace impurities and flux-surface potential variations.
Defect-impurity interactions in irradiated germanium
International Nuclear Information System (INIS)
Cleland, J.W.; James, F.J.; Westbrook, R.D.
1975-07-01
Results of experiments are used to formulate a better model for the structures of lattice defects and defect-impurity complexes in irradiated n-type Ge. Single crystals were grown by the Czochralski process from P, As, or Sb-doped melts, and less than or equal to 10 15 to greater than or equal to 10 17 oxygen cm -3 was added to the furnace chamber after approximately 1 / 3 of the crystal had been solidified. Hall coefficient and resistivity measurements (at 77 0 K) were used to determine the initial donor concentration due to the dopant and clustered oxygen, and infrared absorption measurements (at 11.7 μ) were used to determine the dissociated oxygen concentration. Certain impurity and defect-impurity interactions were then investigated that occurred as a consequence of selected annealing, quenching, Li diffusion, and irradiation experiments at approximately 300 0 K with 60 Co photons, 1.5 to 2.0 MeV electrons, or thermal energy neutrons. Particular attention was given to determining the electrical role of the irradiation produced interstitial and vacancy, and to look for any evidence from electrical and optical measurements of vacancy--oxygen, lithium--oxygen, and lithium--vacancy interactions. (U.S.)
Schmidt, Richard; Knap, Michael; Ivanov, Dmitri A; You, Jhih-Shih; Cetina, Marko; Demler, Eugene
2018-02-01
In this report we discuss the dynamical response of heavy quantum impurities immersed in a Fermi gas at zero and at finite temperature. Studying both the frequency and the time domain allows one to identify interaction regimes that are characterized by distinct many-body dynamics. From this theoretical study a picture emerges in which impurity dynamics is universal on essentially all time scales, and where the high-frequency few-body response is related to the long-time dynamics of the Anderson orthogonality catastrophe by Tan relations. Our theoretical description relies on different and complementary approaches: functional determinants give an exact numerical solution for time- and frequency-resolved responses, bosonization provides accurate analytical expressions at low temperatures, and the theory of Toeplitz determinants allows one to analytically predict response up to high temperatures. Using these approaches we predict the thermal decoherence rate of the fermionic system and prove that within the considered model the fastest rate of long-time decoherence is given by [Formula: see text]. We show that Feshbach resonances in cold atomic systems give access to new interaction regimes where quantum effects can prevail even in the thermal regime of many-body dynamics. The key signature of this phenomenon is a crossover between different exponential decay rates of the real-time Ramsey signal. It is shown that the physics of the orthogonality catastrophe is experimentally observable up to temperatures [Formula: see text] where it leaves its fingerprint in a power-law temperature dependence of thermal spectral weight and we review how this phenomenon is related to the physics of heavy ions in liquid [Formula: see text]He and the formation of Fermi polarons. The presented results are in excellent agreement with recent experiments on LiK mixtures, and we predict several new phenomena that can be tested using currently available experimental technology.
Universal many-body response of heavy impurities coupled to a Fermi sea: a review of recent progress
Schmidt, Richard; Knap, Michael; Ivanov, Dmitri A.; You, Jhih-Shih; Cetina, Marko; Demler, Eugene
2018-02-01
In this report we discuss the dynamical response of heavy quantum impurities immersed in a Fermi gas at zero and at finite temperature. Studying both the frequency and the time domain allows one to identify interaction regimes that are characterized by distinct many-body dynamics. From this theoretical study a picture emerges in which impurity dynamics is universal on essentially all time scales, and where the high-frequency few-body response is related to the long-time dynamics of the Anderson orthogonality catastrophe by Tan relations. Our theoretical description relies on different and complementary approaches: functional determinants give an exact numerical solution for time- and frequency-resolved responses, bosonization provides accurate analytical expressions at low temperatures, and the theory of Toeplitz determinants allows one to analytically predict response up to high temperatures. Using these approaches we predict the thermal decoherence rate of the fermionic system and prove that within the considered model the fastest rate of long-time decoherence is given by γ=π k_BT/4 . We show that Feshbach resonances in cold atomic systems give access to new interaction regimes where quantum effects can prevail even in the thermal regime of many-body dynamics. The key signature of this phenomenon is a crossover between different exponential decay rates of the real-time Ramsey signal. It is shown that the physics of the orthogonality catastrophe is experimentally observable up to temperatures T/T_F≲ 0.2 where it leaves its fingerprint in a power-law temperature dependence of thermal spectral weight and we review how this phenomenon is related to the physics of heavy ions in liquid {\\hspace{0pt}}3 He and the formation of Fermi polarons. The presented results are in excellent agreement with recent experiments on LiK mixtures, and we predict several new phenomena that can be tested using currently available experimental technology.
Studying Online Behavior: Comment on Anderson et al. 2014
Directory of Open Access Journals (Sweden)
Kevin Lewis
2015-01-01
Full Text Available As social scientists increasingly employ data from online sources, it is important that we acknowledge both the advantages an limitations of this research. The latter have received comparatively little public attention. In this comment, I argue that a recent article by Anderson and colleagues: 1 inadequately describes the study sample; 2 inadequately describes how the website operates; and 3 inadequately develops the paper’s central measures — such that it is difficult to evaluate the generalizability, veracity, and importance of their claims and impossible to replicate their findings. These limitations are not unique to the Anderson et al. article; rather, they point to a set of concerns that all researchers in this growing and important line of study need to address if our work is to have enduring impact.
Dynamical Localization for Discrete Anderson Dirac Operators
Prado, Roberto A.; de Oliveira, César R.; Carvalho, Silas L.
2017-04-01
We establish dynamical localization for random Dirac operators on the d-dimensional lattice, with d\\in { 1, 2, 3} , in the three usual regimes: large disorder, band edge and 1D. These operators are discrete versions of the continuous Dirac operators and consist in the sum of a discrete free Dirac operator with a random potential. The potential is a diagonal matrix formed by different scalar potentials, which are sequences of independent and identically distributed random variables according to an absolutely continuous probability measure with bounded density and of compact support. We prove the exponential decay of fractional moments of the Green function for such models in each of the above regimes, i.e., (j) throughout the spectrum at larger disorder, (jj) for energies near the band edges at arbitrary disorder and (jjj) in dimension one, for all energies in the spectrum and arbitrary disorder. Dynamical localization in theses regimes follows from the fractional moments method. The result in the one-dimensional regime contrast with one that was previously obtained for 1D Dirac model with Bernoulli potential.
Wegner Estimate and Anderson Localization for Random Magnetic Fields
Erdős, László; Hasler, David
2012-01-01
We consider a two dimensional magnetic Schrödinger operator with a spatially stationary random magnetic field. We assume that the magnetic field has a positive lower bound and that it has Fourier modes on arbitrarily short scales. We prove the Wegner estimate at arbitrary energy, i.e. we show that the averaged density of states is finite throughout the whole spectrum. We also prove Anderson localization at the bottom of the spectrum.
Experimental Test of Universality of the Anderson Transition
Lopez, Matthias; Clément, Jean-François; Szriftgiser, Pascal; Garreau, Jean Claude; Delande, Dominique
2012-03-01
We experimentally test the universality of the Anderson three dimensional metal-insulator transition, using a quasiperiodic atomic kicked rotor. Nine sets of parameters controlling the microscopic details have been tested. Our observation indicates that the transition is of second order, with a critical exponent independent of the microscopic details; the average value 1.63±0.05 agrees very well with the numerically predicted value ν=1.58.
Wu Hua
2003-01-01
The transverse-field Ising model is successfully applied to the Ba sub x Sr sub 1 sub - sub x TiO sub 3 system. An impurity-induced paraelectric-ferroelectric phase transition is found for proper parameters. An explanation is offered for the results of the susceptibility chi(x, T), the transition temperature T sub m (x), the spontaneous polarization (P ) versus x and versus T, the field dependence of chi(x, T) and that of the polarization (P ) versus E for x, 0.2 <= x <= 0.95.
Nuclear liability and the Price--Anderson Act
International Nuclear Information System (INIS)
Wilson, R.
1977-01-01
The Price-Anderson Act is viewed as meeting public needs in a unique and responsible way, reflecting the far-sightedness of those involved in the early development of nuclear power who saw the importance of building safety into each step of the program. An extension of the Act is advised as a first step in recognizing that many potential and real disasters (e.g., dam breaks, floods, etc.) are man-made rather than ''Acts of God''. Rather than abolish the Price-Anderson Act because it is unique, the case is made for extending it to cover these other situations. Provisions of the Act are examined in terms of the role of negligence in nuclear accidents, and the conclusion is reached that public concern for reactor safety should not be affected. Limited assets on the part of insurers and insurance pools have made government involvement important but not a real subsidy because of high premiums. Premiums in the new amendment are paid retroactively when there is an accident, which relieves the problem of anticipating what premiums may be needed in the future. This limits government liability and, combined with the waiver of defenses against liability, offers better protection for the public. Recommendations for allowing tort law to operate above the $560 million Price-Anderson limits are criticized, and a counter proposal is made for reassessing the figure at an appropriate limit and extending insurance to competitive industries
Time of Anderson-Fabry Disease Detection and Cardiovascular Presentation
Directory of Open Access Journals (Sweden)
K. Selthofer-Relatic
2018-01-01
Full Text Available Background. Anderson-Fabry disease is an X-linked inherited disease, which manifests in a different manner depending on gender and genotype. Making a working diagnosis of Anderson-Fabry disease is difficult because of several reasons: (a that it is a multiorgan disease with wide variety of phenotypes, (b different timelines of presentation, (c gender differences, and (d possible coexistence with other comorbidities. Late-onset/cardiac type of presentation with minimal involvement of other organs can additionally make diagnosis difficult. Aim. To describe different cardiac manifestations at different time points in the course of the disease: (1 72-year-old female (echocardiography detection, heterozygote, significant left and mild right ventricular hypertrophy; (2 62-year-old male (echocardiography detection, hemizygote, left ventricular hypertrophy, implanted cardiac pacemaker, a performed percutaneous coronary intervention after myocardial infarction, degenerative medium degree aortic valve stenosis; (3 45-year-old female (asymptomatic/family screening, heterozygote, thickened mitral papillary muscle, mild left ventricular hypertrophy, first degree diastolic dysfunction; and (4 75-year-old female (symptomatic/family screening, heterozygote, cardiomyopathy with reduced left ventricular ejection fraction after heart surgery (mitral valve annuloplasty and plastic repair of the tricuspid valve. Conclusion. All patients have Anderson-Fabry disease but with different clinical presentations depending on the gender, the type of mutation, and the time of detection. All these features can make the patients’ profiles unique and delay the time of detection.
Conductance distribution near the Anderson transition
Suslov, I. M.
2017-05-01
Using a modification of the Shapiro approach, we introduce the two-parameter family of conductance distributions W( g), defined by simple differential equations, which are in the one-to-one correspondence with conductance distributions for quasi-one-dimensional systems of size L d-1 × L z , characterizing by parameters L/ξ and L z / L (ξ is the correlation length, d is the dimension of space). This family contains the Gaussian and log-normal distributions, typical for the metallic and localized phases. For a certain choice of parameters, we reproduce the results for the cumulants of conductance in the space dimension d = 2 + ɛ obtained in the framework of the σ-model approach. The universal property of distributions is existence of two asymptotic regimes, log-normal for small g and exponential for large g. In the metallic phase they refer to remote tails, in the critical region they determine practically all distribution, in the localized phase the former asymptotics forces out the latter. A singularity at g = 1, discovered in numerical experiments, is admissible in the framework of their calculational scheme, but related with a deficient definition of conductance. Apart of this singularity, the critical distribution for d = 3 is well described by the present theory. One-parameter scaling for the whole distribution takes place under condition, that two independent parameters characterizing this distribution are functions of the ratio L/ξ.
Properties of magnetic impurities embedded into an anisotropic Heisenberg chain with spin gap
International Nuclear Information System (INIS)
Schlottmann, P.
2000-01-01
We consider a U(1)-invariant model consisting of the integrable anisotropic easy-axis Heisenberg chain of arbitrary spin S embedding an impurity of spin S'. The host chain has a spin gap for all values of S. The ground state properties and the elementary excitations of the host are studied as a function of the anisotropy and the magnetic field. The impurity is located on a link of the chain and interacts only with both neighboring sites. The coupling of the impurity to the lattice can be tuned by the impurity rapidity p 0 (usually playing the role of the Kondo coupling). The impurity model is then integrable as a function of two continuous parameters (the anisotropy and the impurity rapidity) and two discrete variables (the spins S and S'). The Bethe ansatz equations are derived and used to obtain the magnetization of the impurity. The impurity magnetization is non-universal as a function of p 0 . For small fields the impurity magnetization is determined by the spin gap and the van Hove singularity of the rapidity band. For an overcompensated impurity (S'< S) at intermediate fields there is a crossover to non-Fermi-liquid behavior remnant from the suppressed quantum critical point
Numerical analysis of the Anderson localization
International Nuclear Information System (INIS)
Markos, P.
2006-01-01
The aim of this paper is to demonstrate, by simple numerical simulations, the main transport properties of disordered electron systems. These systems undergo the metal insulator transition when either Fermi energy crosses the mobility edge or the strength of the disorder increases over critical value. We study how disorder affects the energy spectrum and spatial distribution of electronic eigenstates in the diffusive and insulating regime, as well as in the critical region of the metal-insulator transition. Then, we introduce the transfer matrix and conductance, and we discuss how the quantum character of the electron propagation influences the transport properties of disordered samples. In the weakly disordered systems, the weak localization and anti-localization as well as the universal conductance fluctuation are numerically simulated and discussed. The localization in the one dimensional system is described and interpreted as a purely quantum effect. Statistical properties of the conductance in the critical and localized regimes are demonstrated. Special attention is given to the numerical study of the transport properties of the critical regime and to the numerical verification of the single parameter scaling theory of localization. Numerical data for the critical exponent in the orthogonal models in dimension 2 < d ≤ 5 are compared with theoretical predictions. We argue that the discrepancy between the theory and numerical data is due to the absence of the self-averaging of transmission quantities. This complicates the analytical analysis of the disordered systems. Finally, theoretical methods of description of weakly disordered systems are explained and their possible generalization to the localized regime is discussed. Since we concentrate on the one-electron propagation at zero temperature, no effects of electron-electron interaction and incoherent scattering are discussed in the paper (Author)
Investigation of impurity defects in α-iron by molecular dynamics method
International Nuclear Information System (INIS)
Kevorkyan, Yu.R.
1986-01-01
Investigation of the configuration of impurity defects in α-iron by the molecular dynamics method is presented. The Jhonson model potential has been used to calculate the interaction of matrix atoms. The impurity-matrix atom interaction is described by the same form of the potential shifted along the axis of interatomic distances for a definite value. The correspondence between the shift value and change in the radius of the impurity defect is established on the basis of calculation of the relaxation volume. Possible configurations of the impurity - interstitial matrix atom complexes are obtained for the given model of the impurity defect, dimensional boundaries of possible transitions between different configurations are determined. Formation and bound energies, relaxation volumes of impurity defects are calculated
Impurity doping processes in silicon
Wang, FFY
1981-01-01
This book introduces to non-experts several important processes of impurity doping in silicon and goes on to discuss the methods of determination of the concentration of dopants in silicon. The conventional method used is the discussion process, but, since it has been sufficiently covered in many texts, this work describes the double-diffusion method.
Tokamak impurity-control techniques
International Nuclear Information System (INIS)
Schmidt, J.A.
1980-01-01
A brief review is given of the impurity-control functions in tokamaks, their relative merits and disadvantages and some prominent edge-interaction-control techniques, and there is a discussion of a new proposal, the particle scraper, and its potential advantages. (author)
The influence of magnetic impurities in the vortex core dynamics in magnetic nano-disks
International Nuclear Information System (INIS)
Silva, J.H.; Toscano, D.; Sato, F.; Coura, P.Z.; Costa, B.V.; Leonel, S.A.
2012-01-01
In this work we have used spin dynamics simulations to study the gyrotropic frequency behavior in nano-disks of Permalloy with magnetic impurities. We consider the effect of attractive impurity and repulsive impurity placed near the vortex core gyrotropic trajectory. We observed that the gyrotropic frequency is affected by the presence of impurity. The gyrotropic frequency shift depends on the relative position between the impurity and the vortex core gyrotropic trajectory and if impurity is attractive or repulsive. Our results agree with the analytical model and with experimental behavior for the gyrotropic frequency shown in the literature. - Highlights: ► Study of the gyrotropic frequency behavior in nano-disks with magnetic impurities. ► The gyrotropic frequency is affected by the presence of magnetic impurity. ► The frequency shift ΔF depends on if magnetic impurity is attractive or repulsive. ► The ΔF depends on the relative position of the impurity and gyrotropic trajectory.
Energy Technology Data Exchange (ETDEWEB)
G.A. Young Jr.; R. Najafabadi; W. Strohmayer; D.G. Baldrey; B. Hamm; J. Harris; J. Sticht; E. Wimmer
2003-06-16
Atomistic modeling methods were employed to investigate the effects of impurity elements on the metallurgy, irradiation embrittlement, and environmentally assisted cracking of nickel-base alloys exposed to nuclear environments. Calculations were performed via ab initio atomistic modeling methods to ensure the accuracy and reliability of the results. A Griffith-type fracture criterion was used to quantitatively assess the effect of elements or element pairs on the grain boundary cohesive strength. In order of most embrittling to most strengthening, the elements are ranked as: He, Li, S, H, C, Zr, P, Fe, Mn, Nb, Cr, and B. Helium is strongly embrittling (-2.04 eV/atom lowering of the Griffith energy), phosphorus has little effect on the grain boundary (0.1 eV/atom), and boron offers appreciable strengthening (1.03 eV/atom increase in the Griffith energy). Calculations for pairs of elements (H-Li, H-B, H-C, H-P, and H-S) show little interaction on the grain boundary cohesive energy, so that for the conditions studied, linear superposition of elemental effects is a good approximation. These calculations help explain metallurgical effects (e.g. why boron can strengthen grain boundaries), irradiation embrittlement (e.g. how boron transmutation results in grain boundary embrittlement), as well as how grain boundary impurity elements can affect environmentally assisted cracking (i.e. low temperature crack propagation and stress corrosion cracking) of nickel-base alloys.
Multi-particle Anderson Localisation: Induction on the Number of Particles
International Nuclear Information System (INIS)
Chulaevsky, Victor; Suhov, Yuri
2009-01-01
This paper is a follow-up of our recent papers Chulaevsky and Suhov (Commun Math Phys 283:479-489, 2008) and Chulaevsky and Suhov (Commun Math Phys in press, 2009) covering the two-particle Anderson model. Here we establish the phenomenon of Anderson localisation for a quantum N-particle system on a lattice with short-range interaction and in presence of an IID external potential with sufficiently regular marginal cumulative distribution function (CDF). Our main method is an adaptation of the multi-scale analysis (MSA; cf. Froehlich and Spencer, Commun Math Phys 88:151-184, 1983; Froehlich et al., Commun Math Phys 101:21-46, 1985; von Dreifus and Klein, Commun Math Phys 124:285-299, 1989) to multi-particle systems, in combination with an induction on the number of particles, as was proposed in our earlier manuscript (Chulaevsky and Suhov 2007). Recently, Aizenman and Warzel (2008) proved spectral and dynamical localisation for N-particle lattice systems with a short-range interaction, using an extension of the Fractional-Moment Method (FMM) developed earlier for single-particle models in Aizenman and Molchanov (Commun Math Phys 157:245-278, 1993) and Aizenman et al. (Commun Math Phys 224:219-253, 2001) (see also references therein) which is also combined with an induction on the number of particles
Numerical calculation of impurity charge state distributions
International Nuclear Information System (INIS)
Crume, E.C.; Arnurius, D.E.
1977-09-01
The numerical calculation of impurity charge state distributions using the computer program IMPDYN is discussed. The time-dependent corona atomic physics model used in the calculations is reviewed, and general and specific treatments of electron impact ionization and recombination are referenced. The complete program and two examples relating to tokamak plasmas are given on a microfiche so that a user may verify that his version of the program is working properly. In the discussion of the examples, the corona steady-state approximation is shown to have significant defects when the plasma environment, particularly the electron temperature, is changing rapidly
Numerical calculation of impurity charge state distributions
Energy Technology Data Exchange (ETDEWEB)
Crume, E. C.; Arnurius, D. E.
1977-09-01
The numerical calculation of impurity charge state distributions using the computer program IMPDYN is discussed. The time-dependent corona atomic physics model used in the calculations is reviewed, and general and specific treatments of electron impact ionization and recombination are referenced. The complete program and two examples relating to tokamak plasmas are given on a microfiche so that a user may verify that his version of the program is working properly. In the discussion of the examples, the corona steady-state approximation is shown to have significant defects when the plasma environment, particularly the electron temperature, is changing rapidly.
Huesmann, L. Rowell
2010-01-01
Over the past half-century the mass media, including video games, have become important socializers of children. Observational learning theory has evolved into social-cognitive information processing models that explain that what a child observes in any venue has both short-term and long-term influences on the child's behaviors and cognitions. Anderson's (2010) extensive meta-analysis of the effects of violent video games confirms what these theories predict and what prior research about othe...
Observation of impurity accumulation and concurrent impurity influx in PBX
International Nuclear Information System (INIS)
Sesnic, S.S.; Fonck, R.J.; Ida, K.
1986-07-01
Impurity studies in L- and H-mode discharges in PBX have shown that both types of discharges can evolve into either an impurity accumulative or nonaccumulative case. In a typical accumulative discharge, Zeff peaks in the center to values of about 5. The central metallic densities can be high, n/sub met//n/sub e/ ≅ 0.01, resulting in central radiated power densities in excess of 1 W/cm 3 , consistent with bolometric estimates. The radial profiles of metals obtained independently from the line radiation in the soft x-ray and the VUV regions are very peaked. Concurrent with the peaking, an increase in the impurity influx coming from the edge of the plasma is observed. At the beginning of the accumulation phase the inward particle flux for titanium has values of 6 x 10 10 and 10 x 10 10 particles/cm 2 s at minor radii of 6 and 17 cm. At the end of the accumulation phase, this particle flux is strongly increased to values of 3 x 10 12 and 1 x 10 12 particles/cm 2 s. This increased flux is mainly due to influx from the edge of the plasma and to a lesser extent due to increased convective transport. Using the measured particle flux, an estimate of the diffusion coefficient D and the convective velocity v is obtained
Observation of impurity accumulation and concurrent impurity influx in PBX
International Nuclear Information System (INIS)
Sesnic, S.S.; Fonck, R.J.; Ida, K.; Couture, P.; Kaita, R.; Kaye, S.; Kugel, H.; LeBlanc, B.; Okabayashi, M.; Paul, S.; Powell, E.T.; Reusch, M.; Takahashi, H.; Gammel, G.; Morris, W.
1987-01-01
Impurity studies in L- and H-mode discharges in PBX have shown that both types of discharges can evolve into either an impurity accumulative or nonaccumulative case. In a typical accumulative discharge, Z eff peaks in the center to values of about 5. The central metallic densities can be high, n met /n e ≅ 0.01, resulting in central radiated power densities in excess of 1 W/cm 3 , consistent with bolometric estimates. The radial profiles of metals obtained independently from the line radiation in the soft X-ray and the VUV regions are very peaked. Concurrent with the peaking, an increase in the impurity influx coming from the edge of the plasma is observed. At the beginning of the accumulation phase the inward particle flux for titanium has values of 6x10 10 and 10x10 10 particles/cm 2 s at minor radii of 6 and 17 cm. At the end of the accumulation phase, this particle flux is strongly increased to values of 3x10 12 and 1x10 12 particles/cm 2 s. This increased flux is mainly due to influx from the edge of the plasma and to a lesser extent due to increased convective transport. Using the measured particle flux, an estimate of the diffusion coefficient D and the convective velocity v is obtained. (orig.)
Remembering Joan (Jan) Mary Anderson (1932-2015).
Chow, Wah Soon; Horton, Peter; Barrett, Martin; Osmond, Charles Barry
2016-08-01
Joan Mary Anderson, known to most people as Jan, was born on May 12, 1932 in Dunedin, New Zealand. She died on August 28, 2015 in Canberra, Australia. To celebrate her life, we present here a brief biography, some comments on her discoveries in photosynthesis during a career spanning more than half a century, and reminiscences from family and friends. We remember this wonderful person who had an unflagging curiosity, creative ability to think laterally, enthusiasm, passion, generosity and love of color and culture.
Signatures of Anderson localization excited by an optical frequency comb
Gentilini, S.
2010-01-25
We investigate Anderson localization of light as occurring in ultrashort excitations. A theory based on time dependent coupled-mode equations predicts universal features in the spectrum of the transmitted pulse. In particular, the process of strong localization of light is shown to correspond to the formation of peaks in both the amplitude and in the group delay of the transmitted pulse. Parallel ab initio simulations made with finite-difference time-domain codes and molecular dynamics confirm theoretical predictions, while showing that there exists an optimal degree of disorder for the strong localization. © 2010 The American Physical Society.
Price-Anderson Nuclear Safety Enforcement Program. 1996 Annual report
International Nuclear Information System (INIS)
1996-01-01
This first annual report on DOE's Price Anderson Amendments Act enforcement program covers the activities, accomplishments, and planning for calendar year 1996. It also includes the infrastructure development activities of 1995. It encompasses the activities of the headquarters' Office of Enforcement in the Office of Environment, Safety and Health (EH) and Investigation and the coordinators and technical advisors in DOE's Field and Program Offices and other EH Offices. This report includes an overview of the enforcement program; noncompliances, investigations, and enforcement actions; summary of significant enforcement actions; examples where enforcement action was deferred; and changes and improvements to the program
Effect of impurities in the electrothermic instability
International Nuclear Information System (INIS)
Azevedo, M.T. de.
1982-04-01
It is proposed a model for a ''impure'' plasma based on the homogenous hydrogen plasma used in the theory formulated by Tomimura and Haines to explain the increasing of instable electrothermal modes with wave vector perpendicular to the applyed magnetic field. The impurities are implicity introduced in the transport coeficients of the model of two fluids through the effective charge number Z eff as suggested by Duechs et al., Furth etc... The results obtained are: (i) the greatest increasing ratio for the absolute mode (non-convective) decreases with the increasing of Z eff going to zero for a given value of these parameter which is denominated Z crit ; (ii) the wavelenght associated with that greatest ratio of increasing decreases with the increasing of Z eff ; (iii) Z crit x T eo /T io curves, where T eo and T io are the electronic and ionic temperatures of equilibri um show that, for each value of T eo (used as a parameter) there is a limiting value Z crit from which the plasma is stable, independently of the temperature ratio. The correlation of these results with that of a difuse pinch model, which shows the tendency in assume in the stationary state a filamental current structure is inconclusive with respect to the Z eff dependence. (M.W.O.) [pt
Strong impact of impurity bands on domain formation in superlattices
DEFF Research Database (Denmark)
Wacker, Andreas; Jauho, Antti-Pekka
1998-01-01
The formation of electric field domains in doped semiconductor superlattices is described within a microscopic model. Due to the presence of impurity bands in low-doped samples the current-voltage characteristic is essentially different compared to medium-doped samples. (C) 1998 Published by Else...... by Elsevier Science B.V. All rights reserved.......The formation of electric field domains in doped semiconductor superlattices is described within a microscopic model. Due to the presence of impurity bands in low-doped samples the current-voltage characteristic is essentially different compared to medium-doped samples. (C) 1998 Published...
Multi-photon Rabi oscillations in high spin paramagnetic impurity
International Nuclear Information System (INIS)
Bertaina, S; Groll, N; Chen, L; Chiorescu, I
2011-01-01
We report on multiple photon monochromatic quantum oscillations (Rabi oscillations) observed by pulsed EPR (Electron Paramagnetic Resonance) of Mn 2+ (S = 5/2) impurities in MgO. We find that when the microwave magnetic field is similar or large than the anisotropy splitting, the Rabi oscillations have a spectrum made of many frequencies not predicted by the S = l/2 Rabi model. We show that these new frequencies come from multiple photon coherent manipulation of the multi-level spin impurity. We develop a model based on the crystal field theory and the rotating frame approximation, describing the observed phenomenon with a very good agreement.
Anderson-Mott transition in a disordered Hubbard chain with correlated hopping
Battista, Francesca; Camjayi, Alberto; Arrachea, Liliana
2017-07-01
We study the ground-state phase diagram of the Anderson-Hubbard model with correlated hopping at half-filling in one dimension. The Hamiltonian has a local Coulomb repulsion U and a disorder potential with local energies randomly distributed in the interval (-W ,+W ) with equal probability, acting on the singly occupied sites. The hopping process which modifies the number of doubly occupied sites is forbidden. The hopping between nearest-neighbor singly occupied and empty sites or between singly occupied and doubly occupied sites has the same amplitude t . We identify three different phases as functions of the disorder amplitude W and Coulomb interaction strength U >0 . When U 4 t the Anderson-localized phase survives as long as disorder effects dominate on the interaction effects, otherwise a Mott-insulator phase (iii) arises. Phases (i) and (ii) are characterized by a finite density of doublons and a vanishing charge gap among the ground state and the excited states. Phase (iii) is characterized by the vanishing density of doublons and a finite gap for the charge excitations.
Controlling dynamical thermal transport of biased bilayer graphene by impurity atoms
Energy Technology Data Exchange (ETDEWEB)
Rezania, Hamed, E-mail: rezania.hamed@gmail.com [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of); Yarmohammadi, Mohsen [Young Researchers and Elit Club, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of)
2016-07-15
We address the dynamical thermal conductivity of biased bilayer graphene doped with acceptor impurity atoms for AA-stacking in the context of tight binding model Hamiltonian. The effect of scattering by dilute charged impurities is discussed in terms of the self-consistent Born approximation. Green’s function approach has been exploited to find the behavior of thermal conductivity of bilayer graphene within the linear response theory. We have found the frequency dependence of thermal conductivity for different values of concentration and scattering strength of dopant impurity. Also the dependence of thermal conductivity on the impurity concentration and bias voltage has been investigated in details.
International Nuclear Information System (INIS)
Leite, R.V.; Oliveira Filho, L.O. de; Milton Pereira, J.; Cottam, M.G.; Costa Filho, R.N.
2009-01-01
A Green's function method is used to obtain the spectrum of spin excitations associated with a linear array of magnetic impurities implanted in a ferromagnetic thin film. The equations of motion for the Green's functions of the anisotropic film are written in the framework of the Ising model in a transverse field. The frequencies of localized modes are calculated as a function of the interaction parameters for the exchange coupling between impurity-spin pairs, host-spin pairs, and impurity-host neighbors, as well as the effective field parameter at the impurity sites.
Parametric dependences of impurity transport in the Tore Supra tokamak
International Nuclear Information System (INIS)
Parisot, Th.
2007-09-01
During this Ph.D. work, a full setup of tools for an experimental investigation of impurity transport has been developed on the Tore Supra tokamak. It includes a laser blow-off system for metallic impurity injections and developments for ITC (Impurity Transport Code), a transport code which allows the extraction of the experimental impurity transport coefficients (diffusion and convection velocity). This tool has been used to perform and analyse several experiments, to evidence parametric dependences of impurity transport. In a first experiment, a confinement time law for nickel in Tore Supra has been obtained as a function of collisionality ν * and normalized Larmor radius ρ * . Then the impurity charge Z role has been investigated in various conditions: ohmic regime with or without sawteeth, and sawtooth less L-mode with LH power. No Z effect is observed, consistently with theoretical predictions, whether neoclassical (NCLASS) or for turbulent transport with both non linear gyro-fluid (TRB) and quasilinear gyrokinetic (QuaLiKiz) simulations. An exception is found for LH heated plasmas where the confinement time seems to decrease for the heaviest impurities. This is not explained by any model available. The observed transport is close to neoclassical between sawtooth relaxations, in the centre (r q-1 ) of ohmic plasmas, turbulent outside. Without sawteeth, it is turbulent in the whole plasma, for ohmic or L mode discharges. The profile shape of the diffusion coefficient is here qualitatively different, with a stronger and deeper transition between the low diffusion central region and a more turbulent peripheral region for LH heated plasmas. (author)
Spin polarization of electrons in a magnetic impurity doped ...
Indian Academy of Sciences (India)
Abstract. A theoretical model is presented in this paper for degree of spin polarization in a light emitting diode (LED) whose epitaxial region contains quantum dots doped with magnetic impurity. The model is then used to investigate the effect of electron–phonon interaction on degree of spin polarization at different ...
Spin polarization of electrons in a magnetic impurity doped ...
Indian Academy of Sciences (India)
A theoretical model is presented in this paper for degree of spin polarization in alight emitting diode (LED) whose epitaxial region contains quantum dots doped with magnetic impurity. The model is then used to investigate the effect of electron–phonon interaction on degree of spin polarization at different temperatures and ...
International Nuclear Information System (INIS)
Stangeby, P.C.; Toronto Univ., ON
1990-01-01
Most divertor impurity modelling gives the result that negligible leakage occurs of impurities produced at the plates, to the confined plasma and that negligible impurity radiation occurs, even in the divertor plasma. This is not, however, found experimentally. A Monte Carlo impurity code has been employed in exploratory studies aimed at identifying possible leakage pathways to the main plasma. It was found that for a substantial range of divertor plasma densities and temperatures, the friction force dominated all other forces on the impurities, including the temperature gradient forces which are generally directed away from the plates. Thus, if it was assumed that the deuterium plasma flow was everywhere directed toward the plates, negligible leakage to the confined plasma occurred. The possibility of deuterium flow reversal was also considered where it was assumed that over some radial fraction of the SOL, the deuterium plasma flow was directed away from the plates, starting at a distance from the plates equal to the deuterium average ionization distance. The spatial distribution of impurity (carbon) physically sputtered neutrals was modelled and it was found that a fraction of the impurity neutrals were ionized in the deuterium flow reversal zone. When these impurity particles were then tracked through further ionization, and their parallel and cross-field transport was followed, significant impurity radiation resulted and a substantial impurity density was found in the confined plasma with Z eff values of 3 or more. It was thus concluded that flow reversal of the deuterium plasma is a promising possible explanation of impurity radiation and of the leakage of divertor plate impurities to the confined plasma
The Effects of Impurities on Protein Crystal Growth and Nucleation: A Preliminary Study
Schall, Constance A.
1998-01-01
Kubota and Mullin (1995) devised a simple model to account for the effects of impurities on crystal growth of small inorganic and organic molecules in aqueous solutions. Experimentally, the relative step velocity and crystal growth of these molecules asymptotically approach zero or non-zero values with increasing concentrations of impurities. Alternatively, the step velocity and crystal growth can linearly approach zero as the impurity concentration increases. The Kubota-Mullin model assumes that the impurity exhibits Langmuirian adsorption onto the crystal surface. Decreases in step velocities and subsequent growth rates are related to the fractional coverage (theta) of the crystal surface by adsorbed impurities; theta = Kx / (I +Kx), x = mole fraction of impurity in solution. In the presence of impurities, the relative step velocity, V/Vo, and the relative growth rate of a crystal face, G/Go, are proposed to conform to the following equations: V/Vo approx. = G/Go = 1 - (alpha)(theta). The adsorption of impurity is assumed to be rapid and in quasi-equilibrium with the crystal surface sites available. When the value of alpha, an effectiveness factor, is one the growth will asymptotically approach zero with increasing concentrations of impurity. At values less than one, growth approaches a non-zero value asymptotically. When alpha is much greater than one, there will be a linear relationship between impurity concentration and growth rates. Kubota and Mullin expect alpha to decrease with increasing supersaturation and shrinking size of a two dimensional nucleus. It is expected that impurity effects on protein crystal growth will exhibit behavior similar to that of impurities in small molecule growth. A number of proteins were added to purified chicken egg white lysozyme, the effect on crystal nucleation and growth assessed.
International Nuclear Information System (INIS)
West, W.P.; Evans, T.E.; Brooks, N.H.
1996-10-01
NEWT1D, a one dimensional multifluid model of the scrape-off layer and divertor plasma, has been used to model the plasma including the distribution of carbon ionization states in the SOL and divertor of ELMing H-mode at two injected power levels in DIII-D. Comparison of the code predictions to the measured divertor and scrape-off layer (SOL) plasma density and temperature shows good agreement. Comparison of the predicted line emissions to the spectroscopic data suggests that physically sputtered carbon from the strike point is not transported up the flux tube; a distributed source of carbon a few centimeters up the flux tube is required to achieve reasonable agreement
Sodium sampling and impurities determination
International Nuclear Information System (INIS)
Docekal, J.; Kovar, C.; Stuchlik, S.
1980-01-01
Samples may be obtained from tubes in-built in the sodium facility and further processed or they are taken into crucibles, stored and processed later. Another sampling method is a method involving vacuum distillation of sodium, thus concentrating impurities. Oxygen is determined by malgamation, distillation or vanadium balance methods. Hydrogen is determined by the metal diaphragm extraction, direct extraction or amalgamation methods. Carbon is determined using dry techniques involving burning a sodium sample at 1100 degC or using wet techniques by dissolving the sample with an acid. Trace amounts of metal impurities are determined after dissolving sodium in ethanol. The trace metals are concentrated and sodium excess is removed. (M.S.)
La importancia de Comunidades imaginadas y de Benedict Anderson
Directory of Open Access Journals (Sweden)
Craig Calhoun
2017-01-01
Full Text Available El remarcable libro Comunidades imaginadas de Benedict Anderson reconfiguró el estudio de las naciones y el nacionalismo. Sorprendentemente original, rompió con el excesivo énfasis que hasta el momento se ponía en el continente europeo y con los argumentos falsamente polarizados sobre si las naciones existían desde siempre o eran meros epifenómenos de los estados modernos. Comunidades imaginadas dirige la atención a la dinámica de la imaginación organizada social y culturalmente como proceso que se encuentra en el corazón de la cultura política, la comprensión de uno mismo y la solidaridad, idea que, como innovación de primer orden en la comprensión de los ‘imaginarios sociales’, tuvo una influencia que va más allá del estudio del nacionalismo. Sin embargo, el enfoque de Anderson conservó el incapié en las condiciones materiales que configuran la cultura y en las instituciones que facilitan su reproducción, desde periódicos y novelas a censos, mapas y museos.
Permittivity disorder induced Anderson localization in magnetophotonic crystals
Energy Technology Data Exchange (ETDEWEB)
Abdi-Ghaleh, R., E-mail: r.abdi@bonabu.ac.ir [Department of Laser and Optical Engineering, University of Bonab, 5551761167 Bonab (Iran, Islamic Republic of); Namdar, A. [Faculty of Physics, University of Tabriz, 5166614766 Tabriz (Iran, Islamic Republic of)
2016-11-15
This theoretical study was carried out to investigate the permittivity disorder induced Anderson localization of light in one-dimensional magnetophotonic crystals. It was shown that the disorder create the resonant transmittance modes associated with enhanced Faraday rotations inside the photonic band gap. The average localization length of the right- and left-handed circular polarizations (RCP and LCP), the total transmittance together with the ensemble average of the RCP and LCP phases, and the Faraday rotation of the structure were also investigated. For this purpose, the off-diagonal elements of the permittivity tensor were varied for various wavelengths of incident light. The obtained results revealed the nonreciprocal property of circular eigen modes. This study can potentially open up a new aspect for utilizing the disorder magnetophotonic structures in nonreciprocal systems such as isolators and circulators. - Highlights: • We theoretically investigated the permittivity disorder induced Anderson localization of light in magnetophotonic crystals. • The disorder considered in the diagonal elements of the permittivity tensor of magneto-optical layers. • The disorder create the resonant transmittance modes associated with enhanced Faraday rotations in the photonic band gap. • The average localization length of the circular polarizations and the ensemble average of their phases were investigated. • The obtained results revealed the nonreciprocal property of circular eigen modes.
Price-Anderson Act - the third decade. Report to Congress
International Nuclear Information System (INIS)
Saltzman, J.
1983-12-01
Subsection 170p. of the Atomic Energy Act of 1954, as amended, requires that the Commission submit to the Congress by August 1, 1983, a detailed report on the need for continuation or modification of Section 170 of the Act, the Price-Anderson provisions. The report is divided into four sections with detailed subject reports appended to the main report. Sections I through III include an examination of issues that the Commission was required by statute to study (i.e., condition of the nuclear industry, state of knowledge of nuclear safety, and availability of private insurance), and discussion of other issues of interest and importance to the Congress and to the public. The subjects covered are as follows: (1) overview of the Price-Anderson system; (2) the state of knowledge of nuclear safety; (3) availability of private insurance; (4) conditions of the nuclear industry; (5) causality and proof of damages; (6) limitation of liability and subsidy; and (7) a proposal that would provide for removal of the limitation of liability but with limited annual liability payments. Section IV of the report contains conclusions and recommendations. Section V contains a bibliography
Design of a Municipal Yard Waste Composting Facility for Anderson County, South Carolina
National Research Council Canada - National Science Library
Klapmeyer, Michael
2003-01-01
.... Large-scale composting is a proven method by which Anderson County can demonstrate sound environmental stewardship while drastically reducing the volume of waste entering county landfills, thereby...
Many-body Anderson localization of strongly interacting bosons in random lattices
International Nuclear Information System (INIS)
Katzer, Roman
2015-05-01
In the present work, we investigate the problem of many-body localization of strongly interacting bosons in random lattices within the disordered Bose-Hubbard model. This involves treating both the local Mott-Hubbard physics as well as the non-local quantum interference processes, which give rise to the phenomenon of Anderson localization, within the same theory. In order to determine the interaction induced transition to the Mott insulator phase, it is necessary to treat the local particle interaction exactly. Therefore, here we use a mean-field approach that approximates only the kinetic term of the Hamiltonian. This way, the full problem of interacting bosons on a random lattice is reduced to a local problem of a single site coupled to a particle bath, which has to be solved self-consistently. In accordance to previous works, we find that a finite disorder width leads to a reduced size of the Mott insulating regions. The transition from the superfluid phase to the Bose glass phase is driven by the non-local effect of Anderson localization. In order to describe this transition, one needs to work within a theory that is non-local as well. Therefore, here we introduce a new approach to the problem. Based on the results for the local excitation spectrum obtained within the mean-field theory, we reduce the full, interacting model to an effective, non-interacting model by applying a truncation scheme to the Hilbert space. Evaluating the long-ranged current density within this approximation, we identify the transition from the Bose glass to the superfluid phase with the Anderson transition of the effective model. Resolving this transition using the self-consistent theory of localization, we obtain the full phase diagram of the disordered Bose-Hubbard model in the regime of strong interaction and larger disorder. In accordance to the theorem of inclusions, we find that the Mott insulator and the superfluid phase are always separated by the compressible, but insulating
EFFECT OF FUEL IMPURITIES ON FUEL CELL PERFORMANCE AND DURABILITY
Energy Technology Data Exchange (ETDEWEB)
Colon-Mercado, H.
2010-09-28
A fuel cell is an electrochemical energy conversion device that produces electricity during the combination of hydrogen and oxygen to produce water. Proton exchange membranes fuel cells are favored for portable applications as well as stationary ones due to their high power density, low operating temperature, and low corrosion of components. In real life operation, the use of pure fuel and oxidant gases results in an impractical system. A more realistic and cost efficient approach is the use of air as an oxidant gas and hydrogen from hydrogen carriers (i.e., ammonia, hydrocarbons, hydrides). However, trace impurities arising from different hydrogen sources and production increases the degradation of the fuel cell. These impurities include carbon monoxide, ammonia, sulfur, hydrocarbons, and halogen compounds. The International Organization for Standardization (ISO) has set maximum limits for trace impurities in the hydrogen stream; however fuel cell data is needed to validate the assumption that at those levels the impurities will cause no degradation. This report summarizes the effect of selected contaminants tested at SRNL at ISO levels. Runs at ISO proposed concentration levels show that model hydrocarbon compound such as tetrahydrofuran can cause serious degradation. However, the degradation is only temporary as when the impurity is removed from the hydrogen stream the performance completely recovers. Other molecules at the ISO concentration levels such as ammonia don't show effects on the fuel cell performance. On the other hand carbon monoxide and perchloroethylene shows major degradation and the system can only be recovered by following recovery procedures.
Choice of capillary electrophoresis systems for the impurity profiling of drugs
Hilhorst, M.J; Somsen, G.W; de Jong, G.J.
In order to develop a strategy for the impurity profiling of drugs, the possibilities of some capillary electrophoresis systems were investigated. A mixture containing a drug and some of its possible impurities has been used as a model problem. The test compounds were investigated by capillary zone
Effects of quenched impurities on surface diffusion, spreading, and ordering of O/W(110)
DEFF Research Database (Denmark)
Nikunen, P.; Vattulainen, Ilpo Tapio; Ala-Nissila, T.
2002-01-01
We study how quenched impurities affect the surface diffusion and ordering of strongly interacting adsorbate atoms on surfaces. To this end, we carry out Monte Carlo simulations for a lattice-gas model of O/W(110), including small concentrations of immobile impurities which block their adsorption...
Impurity transport in a collision-dominated rotating tokamak plasma
International Nuclear Information System (INIS)
Eriksson, G.; Liljegren, A.
1981-04-01
The flux of heavy impurities is an axisymmetric, toroidal plasma with all particles in the collision-dominated regime is considered. Plasma rotation and charge-exchange with neutrals are taken into account. A hydrodynamic model employing Braginskii's transport equations is used. The theorry is extended to higher collision freqencies as compared to previous treatments. It is found that the Pfirsch-Schlueter flux is significantly reduced as compared to the value given by Rutherford and that it is of the same order of magnitude, or less, than the classical flux in all regimes considered. It is also shown that the impurity flux can be influenced by charge-exchange with neutrals. (author)
Deep impurity levels in n-type copper oxides
International Nuclear Information System (INIS)
Ovchinnikov, S.G.
1994-01-01
The density of Nd 2-x Ce x CuO 4 monoparticle states was calculated by the method of precise diagonalization of multielectron hamiltonian of 6-zone model for CuO cluster. Emergence of a deep impurity state of a symmetry in the middle of dielectric slit, which is a mixture of d z 2-states of copper and a 1 -molecular orbital of oxygen, is shown. Fluctuation of parameters of p-d jump and energies of charge transfer provide additional fine impurity levels near the bottom of conductivity zone and ceiling of valency zone. 30 refs., 4 figs
Fermi liquid and non-Fermi liquid in M-channel N fold degenerate anderson lattice
International Nuclear Information System (INIS)
Tsuruta, Atsushi; Ono, Yoshiaki; Matsuura, Tamifusa; Kuroda, Yoshihiro; Kobayashi, Akito; Deguchi, Ken
1999-01-01
We investigate Fermi liquid in the single-channel U-infinite N fold degenerate Anderson lattice with use of the expansion from the large limit of the spin-orbital degeneracy N. By collecting all diagrams up to O(N -2 ) of the imaginary part of the self-energy of the conduction electrons, the sum of those is shown to be given by a form proportional to ω 2 + π 2 T 2 up to O(N -2 ) in the single-channel model. On the other hand, the imaginary part of the self-energy of O(N -1 ) in the multichannel model has more singular frequency-/temperature-dependence, so the system is regarded as non-Fermi liquid. (author)
Eigenfunction statistics for Anderson model with Hölder continuous ...
Indian Academy of Sciences (India)
We consider random Schrödinger operators on l 2 ( Z d ) with α -Hölder continuous ( 0 < α ≤ 1 ) single site distribution. In localized regime, we study the distribution of eigenfunctions in space and energy simultaneously. In a certain scaling limit, we prove limit points are Poisson.
Spectra of Anderson type models with decaying randomness
Indian Academy of Sciences (India)
Springer Verlag Heidelberg #4 2048 1996 Dec 15 10:16:45
existence of absolutely continuous spectrum, the results of Jaksic–Last [14] to show its purity and those of .... Then, the spectra of both H0 and H0+ are purely absolutely continuous and σ (H0) = [E−,E+], and σ ..... We use this fact and do integration by parts twice with respect to the variable θ1 to obtain. T = {. ∑. |n1|≤ vφ s. 4.
Eigenfunction statistics for Anderson model with Hölder continuous ...
Indian Academy of Sciences (India)
In general, left and right α-derivatives do not coincide with symmetric α-derivative, while in case of usual derivative, all three are the same. It is also hard to determine the set {x : Dα ν (x) > 0}, so we have kept. Dα ν (λ) > 0 in the hypothesis and considered the case of symmetric intervals only. To compute the limit of ξω.
The CTD2 Center at the University of Texas MD Anderson Cancer Center utilized an established and operational MCF10A normal breast epithelial cell model to assess the ability of candidate driver aberrations to promote cell grow in anchorage-independent conditions (soft agar assay) and proliferate in the absence of insulin and epidermal growth factor (EGF).
Lipopolysaccharide contamination in intradermal DNA vaccination : toxic impurity or adjuvant?
Berg, J.H. van den; Quaak, S.G.L.; Beijnen, J.H.; Hennink, W.E.; Storm, G.; Schumacher, T.N.; Haanen, J.B.A.G.; Nuijen, B.
Purpose: Lipopolysaccharides (LPS) are known both as potential adjuvants for vaccines and as toxic impurity in pharmaceutical preparations. The aim of this study was to assess the role of LPS in intradermal DNA vaccination administered by DNA tattooing. Method: Micewere vaccinated with a model DNA
Impurity diffusion activation energies in Al from first principles
Simonovic, D.; Sluiter, M.H.
2009-01-01
Activation energies for vacancy-mediated impurity diffusion in face-centered-cubic aluminum have been computed ab initio for all technologically important alloying elements, as well as for most of the lanthanides. The so-called five-frequency rate model is used to establish the limiting vacancy
Monovalent impurities on graphene: midgap states and migration barriers
Wehling, T. O.; Katsnelson, M. I.; Lichtenstein, A. I.
2009-01-01
Monovalent impurities on graphene can be divided into ionically and covalently bond impurities. The covalent impurities cause universal midgap states as the carbon atom next to the impurity is effectively decoupled from the graphene pi-bands. The electronic structure of graphene suppresses migration of these impurities and making the universal midgap very stable. This effect is strongest for neutral covalently bond impurities. The ionically bond impurities have migration barriers of typically...
Void growth suppression by dislocation impurity atmospheres
International Nuclear Information System (INIS)
Weertman, J.; Green, W.V.
1976-01-01
A detailed calculation is given of the effect of an impurity atmosphere on void growth under irradiation damage conditions. Norris has proposed that such an atmosphere can suppress void growth. The hydrostatic stress field of a dislocation that is surrounded by an impurity atmosphere was found and used to calculate the change in the effective radius of a dislocation line as a sink for interstitials and vacancies. The calculation of the impurity concentration in a Cottrell cloud takes into account the change in hydrostatic pressure produced by the presence of the cloud itself. It is found that void growth is eliminated whenever dislocations are surrounded by a condensed atmosphere of either oversized substitutional impurity atoms or interstitial impurity atoms. A condensed atmosphere will form whenever the average impurity concentration is larger than a critical concentration
Moessbauer Studies of Implanted Impurities in Solids
2002-01-01
Moessbauer studies were performed on implanted radioactive impurities in semiconductors and metals. Radioactive isotopes (from the ISOLDE facility) decaying to a Moessbauer isotope were utilized to investigate electronic and vibrational properties of impurities and impurity-defect structures. This information is inferred from the measured impurity hyperfine interactions and Debye-Waller factor. In semiconductors isoelectronic, shallow and deep level impurities have been implanted. Complex impurity defects have been produced by the implantation process (correlated damage) or by recoil effects from the nuclear decay in both semiconductors and metals. Annealing mechanisms of the defects have been studied. \\\\ \\\\ In silicon amorphised implanted layers have been recrystallized epitaxially by rapid-thermal-annealing techniques yielding highly supersaturated, electrically-active donor concentrations. Their dissolution and migration mechanisms have been investigated in detail. The electronic configuration of Sb donors...
Impure placebo is a useless concept.
Louhiala, Pekka; Hemilä, Harri; Puustinen, Raimo
2015-08-01
Placebos are allegedly used widely in general practice. Surveys reporting high level usage, however, have combined two categories, 'pure' and 'impure' placebos. The wide use of placebos is explained by the high level usage of impure placebos. In contrast, the prevalence of the use of pure placebos has been low. Traditional pure placebos are clinically ineffective treatments, whereas impure placebos form an ambiguous group of diverse treatments that are not always ineffective. In this paper, we focus on the impure placebo concept and demonstrate problems related to it. We also show that the common examples of impure placebos are not meaningful from the point of view of clinical practice. We conclude that the impure placebo is a scientifically misleading concept and should not be used in scientific or medical literature. The issues behind the concept, however, deserve serious attention in future research.
Price-Anderson Nuclear Safety Enforcement Program. 1997 annual report
International Nuclear Information System (INIS)
1998-01-01
This report summarizes activities in the Department of Energy's Price-Anderson Amendments Act (PAAA) Enforcement Program in calendar year 1997 and highlights improvements planned for 1998. The DOE Enforcement Program involves the Office of Enforcement and Investigation in the DOE Headquarters Office of Environment, Safety and Health, as well as numerous PAAA Coordinators and technical advisors in DOE Field and Program Offices. The DOE Enforcement Program issued 13 Notices of Violation (NOV's) in 1997 for cases involving significant or potentially significant nuclear safety violations. Six of these included civil penalties totaling $440,000. Highlights of these actions include: (1) Brookhaven National Laboratory Radiological Control Violations / Associated Universities, Inc.; (2) Bioassay Program Violations at Mound / EG ampersand G, Inc.; (3) Savannah River Crane Operator Uptake / Westinghouse Savannah River Company; (4) Waste Calciner Worker Uptake / Lockheed-Martin Idaho Technologies Company; and (5) Reactor Scram and Records Destruction at Sandia / Sandia Corporation (Lockheed-Martin). Sandia / Sandia Corporation (Lockheed-Martin)
Classical diffusion, Anderson localization, and spectral statistics in billiard chains
International Nuclear Information System (INIS)
Dittrich, T.; Doron, E.; Smilansky, U.
1993-03-01
We study spectral properties of quasi one-dimensional extended systems that show deterministic diffusion on the classical level and Anderson localization in the quantal description. Using semiclassical arguments, we relate to universal aspects of the spectral fluctuations to features of the set of classical periodic orbits, expressed in terms of probability to perform periodic motion, that are likewise universal. This allows to derive an analytical expression for the spectral form factor which reflects the diffusive nature of the corresponding classical dynamics. It defines a novel spectral universality class which covers the transition between GOE statistics in the limit of a small ratio of the system size to the localization length, corresponding to the metallic regime of disordered systems, to Poissonian level fluctuations in the opposite limit. Our semiclassical predictions are illustrated and confirmed by a numerical investigation of aperiodic chains of chaotic billiards. (authors)
Unconstitutionality of Section 170 (e) of the price Anderson Act
International Nuclear Information System (INIS)
1977-01-01
Several environmental protection groups in the State of North Carolina have recently contested the conformity with the United States Constitution of Section 170 (e) of the Atomic Energy Act (Price-Anderson Act). The court seized of the question (the United States District Court for the western district of North Carolina, Charlotte Division) held in March 1977 that this Section and the other provisions of the Atomic Energy Act concerning implementation of the $560 million limitation of liability for nuclear damage were unconstitutional and unenforceable insofar as they applied to nuclear incidents occurring inside the United States. The defendants, the former United States Atomic Energy Commission and its then Commissioners as well as the Duke Power Company (the local electricity company) will appeal this decision. The note on case law analyses the arguments retained by the court. (NEA) [fr
Effect of impurities on kinetic transport processes in fusion plasmas
Energy Technology Data Exchange (ETDEWEB)
Braun, Stefanie
2010-12-10
Within the framework of this thesis, different problems arising in connection with impurities have been investigated. Collisional damping of zonal flows in tokamaks: Since the Coulomb collision frequency increases with increasing ion charge, heavy, highly charged impurities play an important role in this process. The effect of such impurities on the linear response of the plasma to an external potential perturbation, as caused by zonal flows, is calculated with analytical methods. In comparison with a pure plasma, the damping of the flows occurs, as expected, considerably faster; for experimentally relevant parameters, the enhancement exceeds the effective charge Z{sub eff} of the plasma. Impurity transport driven by microturbulence in tokamaks: With regard to impurities, it is especially important whether the resulting flows are directed inwards or outwards, since they are deleterious for core energy confinement on the one hand, but on the other hand help protecting plasma-facing components from too high energy fluxes in the edge region. A semi-analytical model is presented describing the resulting impurity fluxes and the stability boundary of the underlying mode. The main goal is to bridge the gap between, on the one hand, costly numerical simulations, which are applicable to a broad range of problems but yield scarcely traceable results, and, on the other hand, analytical theory, which might ease the interpretation of the results but is so far rather rudimentary. The model is based on analytical formulae whenever possible but resorts to a numerical treatment when the approximations necessary for an analytical solution would lead to a substantial distortion of the results. Both the direction of the impurity flux and the stability boundary are found to depend sensitively on the plasma parameters such as the impurity density and the temperature gradient. Pfirsch-Schlueter transport in stellarators: Due to geometry effects, collisional transport plays a much more
All-solid-state cavity QED using Anderson-localized modes in disordered photonic crystal waveguides
DEFF Research Database (Denmark)
Lodahl, Peter; Sapienza, Luca; Nielsen, Henri Thyrrestrup
2010-01-01
We employ Anderson-localized modes in deliberately disordered photonic crystal waveguides to confine light and enhance the interaction with matter. A 15-fold enhancement of the decay rate of a single quantum dot is observed meaning that 94% of the emitted single photons are coupled to an Anderson...
Impurity study of TMX using ultraviolet spectroscopy
International Nuclear Information System (INIS)
Allen, S.L.; Strand, O.T.; Moos, H.W.; Fortner, R.J.; Nash, T.J.; Dietrich, D.D.
1981-01-01
An extreme ultraviolet (EUV) study of the emissions from intrinsic and injected impurities in TMX is presented. Two survey spectrographs were used to determine that the major impurities present were oxygen, nitrogen, carbon, and titanium. Three absolutely-calibrated monochromators were used to measure the time histories and radial profiles of these impurity emissions in the central cell and each plug. Two of these instruments were capable of obtaining radial profiles as a function of time in a single shot
Method for detecting trace impurities in gases
Freund, S.M.; Maier, W.B. II; Holland, R.F.; Beattie, W.H.
A technique for considerably improving the sensitivity and specificity of infrared spectrometry as applied to quantitative determination of trace impurities in various carrier or solvent gases is presented. A gas to be examined for impurities is liquefied and infrared absorption spectra of the liquid are obtained. Spectral simplification and number densities of impurities in the optical path are substantially higher than are obtainable in similar gas-phase analyses. Carbon dioxide impurity (approx. 2 ppM) present in commercial Xe and ppM levels of Freon 12 and vinyl chloride added to liquefied air are used to illustrate the method.
PWA90 Workshop : Marking the Scientific Accomplishments of Philip W. Anderson
Coleman, PIers; Kotliar, Gabi; Ong, Phuan; Stein, Daniel L; Yu, Clare; PWA90 : a lifetime of emergence
2016-01-01
In a remarkable career spanning more than six decades, Philip W Anderson has made many fundamental contributions to physics. As codified in his oft-quoted phrase "More is Different", Anderson has been the most forceful and persuasive proponent of the radical, but now ubiquitous, viewpoint of emergent phenomena: truly fundamental concepts that can and do emerge from studies of Nature at each layer of complexity or energy scale. Anderson's ideas have also extended deeply into other areas of physics, including the Anderson–Higgs mechanism and the dynamics of pulsars. PWA90: A Lifetime of Emergence is a volume of original scientific essays and personal reminiscences of Philip W Anderson by experts in the field, that were presented as part of "PWA90: Emergent Frontiers of Condensed Matter" meeting held at Princeton in December 2013 to highlight Anderson's contributions to physics.
Impurity transport studies on the FTU tokamak
International Nuclear Information System (INIS)
Pacella, D.; Romanelli, F.; Gregory, B.
1999-01-01
In this work, the radial profile of the diffusion coefficient D and the convective velocity V in the plasma core (0 2 /s and V ∼ 100 m/s. A model for the anomalous transport induced by electrostatic turbulence is developed. With a typical fluctuation spectrum (ω = 10 5 -2x10 5 Hz), calculations can reproduce very well the experimental results. To investigate the impurity behavior in a non-stationary phase, Kr gas was injected into the plasma. It is found that the total flux of Kr gas flowing into the core is also driven by diffusion but the magnitude is much lower than the single ion fluxes derived for Mo ions. The effect of the turbulence on the single ion is very strong but it is reduced when averaged over many charge states. (author)
STM tunneling through a quantum wire with a side-attached impurity
International Nuclear Information System (INIS)
Kwapinski, T.; Krawiec, M.; Jalochowski, M.
2008-01-01
The STM tunneling through a quantum wire (QW) with a side-attached impurity (atom, island) is investigated using a tight-binding model and the non-equilibrium Keldysh Green function method. The impurity can be coupled to one or more QW atoms. The presence of the impurity strongly modifies the local density of states of the wire atoms, thus influences the STM tunneling through all the wire atoms. The transport properties of the impurity itself are also investigated mainly as a function of the wire length and the way it is coupled to the wire. It is shown that the properties of the impurity itself and the way it is coupled to the wire strongly influence the STM tunneling, the density of states and differential conductance
Measurements of Impurity Particle Transport Associated with Drift-Wave Turbulence in MST
Nishizawa, Takashi; Nornberg, Mark; Boguski, John; Craig, Darren; den Hartog, Daniel; Pueschel, M. J.; Sarff, John; Terry, Paul; Williams, Zach; Xing, Zichuan
2017-10-01
Understanding and controlling impurity transport in a toroidal magnetized plasma is one of the critical issues that need to be addressed in order to achieve controlled fusion. Gyrokinetic modeling shows turbulence can drive impurity transport, but direct measurements of the turbulent flux have not been made. Particle balance is typically used to infer the presence of turbulent impurity transport. We report, for the first time in a toroidal plasma, direct measurements of turbulence-driven impurity transport. Trapped electron mode (TEM) turbulence appears in MST plasmas when MHD tearing fluctuations are suppressed. Impurity ion-Doppler spectroscopy is used to correlate impurity density and radial velocity fluctuations associated with TEM. Small Doppler shifts associated with the radial velocity fluctuations (rms 1km/s) are resolved with the use of a new linearized spectrum correlation analysis method, which improves the rejection of Poisson noise. The method employs frequency-domain correlation analysis to expose the fluctuation and transport spectrum. The C+ 2 impurity transport velocity driven by turbulence is found to be 48m/s (inward), which is sufficiently large to impact an impurity flux balance in MST improved-confinement plasmas. This work is supported by the US DOE.
Plasma Interactions with Mixed Materials and Impurity Transport
Energy Technology Data Exchange (ETDEWEB)
Rognlien, T. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Beiersdorfer, Peter [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chernov, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Frolov, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Magee, E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rudd, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Umansky, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-10-28
The project brings together three discipline areas at LLNL to develop advanced capability to predict the impact of plasma/material interactions (PMI) on metallic surfaces in magnetic fusion energy (MFE) devices. These areas are (1) modeling transport of wall impurity ions through the edge plasma to the core plasma, (2) construction of a laser blow-off (LBO) system for injecting precise amounts of metallic atoms into a tokamak plasma, and (3) material science analysis of fundamental processes that modify metallic surfaces during plasma bombardment. The focus is on tungsten (W), which is being used for the ITER divertor and in designs of future MFE devices. In area (1), we have worked with the University of California, San Diego (UCSD) on applications of the UEDGE/DUSTT coupled codes to predict the influx of impurity ions from W dust through the edge plasma, including periodic edge-plasma oscillations, and revived a parallel version of UEDGE to speed up these simulations. In addition, the impurity transport model in the 2D UEDGE code has been implemented into the 3D BOUT++ turbulence/transport code to allow fundamental analysis of the impact of strong plasma turbulence on the impurity transport. In area (2), construction and testing of the LBO injection system has been completed. The original plan to install the LBO on the National Spherical Torus Experiment Upgrade (NSTX-U) at Princeton and its use to validate the impurity transport simulations is delayed owing to NSTX-U being offline for substantial magnetic coil repair period. In area (3), an analytic model has been developed to explain the growth of W tendrils (or fuzz) observed for helium-containing plasmas. Molecular dynamics calculations of W sputtering by W and deuterium (D) ions shows that a spatial blending of interatomic potentials is needed to describe the near-surface and deeper regions of the material.
Plasma Interactions with Mixed Materials and Impurity Transport
International Nuclear Information System (INIS)
Rognlien, T. D.; Beiersdorfer, Peter; Chernov, A.; Frolov, T.; Magee, E.; Rudd, R.; Umansky, M.
2016-01-01
The project brings together three discipline areas at LLNL to develop advanced capability to predict the impact of plasma/material interactions (PMI) on metallic surfaces in magnetic fusion energy (MFE) devices. These areas are (1) modeling transport of wall impurity ions through the edge plasma to the core plasma, (2) construction of a laser blow-off (LBO) system for injecting precise amounts of metallic atoms into a tokamak plasma, and (3) material science analysis of fundamental processes that modify metallic surfaces during plasma bombardment. The focus is on tungsten (W), which is being used for the ITER divertor and in designs of future MFE devices. In area (1), we have worked with the University of California, San Diego (UCSD) on applications of the UEDGE/DUSTT coupled codes to predict the influx of impurity ions from W dust through the edge plasma, including periodic edge-plasma oscillations, and revived a parallel version of UEDGE to speed up these simulations. In addition, the impurity transport model in the 2D UEDGE code has been implemented into the 3D BOUT++ turbulence/transport code to allow fundamental analysis of the impact of strong plasma turbulence on the impurity transport. In area (2), construction and testing of the LBO injection system has been completed. The original plan to install the LBO on the National Spherical Torus Experiment Upgrade (NSTX-U) at Princeton and its use to validate the impurity transport simulations is delayed owing to NSTX-U being offline for substantial magnetic coil repair period. In area (3), an analytic model has been developed to explain the growth of W tendrils (or fuzz) observed for helium-containing plasmas. Molecular dynamics calculations of W sputtering by W and deuterium (D) ions shows that a spatial blending of interatomic potentials is needed to describe the near-surface and deeper regions of the material.
Nonlinear screening of charge impurities in graphene
Katsnelson, M. I.
2006-01-01
It is shown that a ``vacuum polarization'' induced by Coulomb potential in graphene leads to a strong suppression of electric charges even for undoped case (no charge carriers). A standard linear response theory is therefore not applicable to describe the screening of charge impurities in graphene. In particular, it overestimates essentially the contributions of charge impurities into the resistivity of graphene.
Role of impurity ions in the impurity influx into the plasma of a fusion device
International Nuclear Information System (INIS)
Voitsenya, V.S.
1989-01-01
Experimental data on the fluxes of impurity and hydrogen (deuterium) ions outside the confinement volume of magnetic-confinement fusion devices are analyzed. The sputtering coefficients of a stainless steel surface for sputtering by deuterium ions and also by ions of light impurities (C) and metal impurities are calculated as a function of the electron temperature of the plasma near the wall. The potential difference near the wall is taken into account. It is concluded from a comparison of the relative magnitudes of the fluxes and the sputtering coefficients that the sputtering caused by multiply charged impurity ions plays a leading role in the impurity flux in existing fusion devices
Hopkins, R. H.; Davis, J. R.; Rohatgi, A.; Hanes, M. H.; Rai-Choudhury, P.; Mollenkopf, H. C.
1982-01-01
The effects of impurities and processing on the characteristics of silicon and terrestrial silicon solar cells were defined in order to develop cost benefit relationships for the use of cheaper, less pure solar grades of silicon. The amount of concentrations of commonly encountered impurities that can be tolerated in typical p or n base solar cells was established, then a preliminary analytical model from which the cell performance could be projected depending on the kinds and amounts of contaminants in the silicon base material was developed. The impurity data base was expanded to include construction materials, and the impurity performace model was refined to account for additional effects such as base resistivity, grain boundary interactions, thermal processing, synergic behavior, and nonuniform impurity distributions. A preliminary assessment of long term (aging) behavior of impurities was also undertaken.
Uranium analysis. Impurities determination by spark mass spectrometry
International Nuclear Information System (INIS)
Anon.
Determination of impurities in uranium, suitable for atomic content greater than 10 -8 , particularly adapted for a low content. The method is quantitative for metallic impurities and qualitative for non metallic impurities [fr
Energy Technology Data Exchange (ETDEWEB)
Post, D.E.; Goldston, R.J.; Grimm, R.C.
1978-09-01
Computational models have been constructed for the Princeton Large Torus (PLT), the Poloidal Divertor Experiment (PDX), and the Tokamak Fusion Test Reactor (TFTR). These models have been calibrated by comparison with current experiments and used to predict plasma parameters and delineate favorable modes of operation for future experiments. The models for PLT emphasize plasma transport and neutral beam injection heating. The models for PDX emphasize the capability of divertors for impurity and recycling control in intense neutral-beam-heated tokamaks, as well as optimization of the MHD properties of divertor-equipped tokamaks. The TFTR calculations stress the fusion aspects of a large, circular cross-section D-T tokamak with intense neutral beam injection.
Continuous-time quantum Monte Carlo impurity solvers
Gull, Emanuel; Werner, Philipp; Fuchs, Sebastian; Surer, Brigitte; Pruschke, Thomas; Troyer, Matthias
2011-04-01
Continuous-time quantum Monte Carlo impurity solvers are algorithms that sample the partition function of an impurity model using diagrammatic Monte Carlo techniques. The present paper describes codes that implement the interaction expansion algorithm originally developed by Rubtsov, Savkin, and Lichtenstein, as well as the hybridization expansion method developed by Werner, Millis, Troyer, et al. These impurity solvers are part of the ALPS-DMFT application package and are accompanied by an implementation of dynamical mean-field self-consistency equations for (single orbital single site) dynamical mean-field problems with arbitrary densities of states. Program summaryProgram title: dmft Catalogue identifier: AEIL_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEIL_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: ALPS LIBRARY LICENSE version 1.1 No. of lines in distributed program, including test data, etc.: 899 806 No. of bytes in distributed program, including test data, etc.: 32 153 916 Distribution format: tar.gz Programming language: C++ Operating system: The ALPS libraries have been tested on the following platforms and compilers: Linux with GNU Compiler Collection (g++ version 3.1 and higher), and Intel C++ Compiler (icc version 7.0 and higher) MacOS X with GNU Compiler (g++ Apple-version 3.1, 3.3 and 4.0) IBM AIX with Visual Age C++ (xlC version 6.0) and GNU (g++ version 3.1 and higher) compilers Compaq Tru64 UNIX with Compq C++ Compiler (cxx) SGI IRIX with MIPSpro C++ Compiler (CC) HP-UX with HP C++ Compiler (aCC) Windows with Cygwin or coLinux platforms and GNU Compiler Collection (g++ version 3.1 and higher) RAM: 10 MB-1 GB Classification: 7.3 External routines: ALPS [1], BLAS/LAPACK, HDF5 Nature of problem: (See [2].) Quantum impurity models describe an atom or molecule embedded in a host material with which it can exchange electrons. They are basic to nanoscience as
Anderson's considerations on the flow of superfluid helium: Some offshoots
Varoquaux, Eric
2015-07-01
Nearly five decades have elapsed since the seminal 1966 paper of P. W. Anderson on the flow of superfluid helium, 4He at that time. Some of his "considerations"—the role of the quantum phase as a dynamical variable, the interplay between the motion of quantized vortices and potential superflow, its incidence on dissipation in the superfluid and the appearance of critical velocities, the quest for the hydrodynamic analogs of the Josephson effects in helium—and the way they have evolved over the past half century are recounted in this review. But it is due to key advances on the experimental front that phase slippage could be harnessed in the laboratory, leading to a deeper understanding of superflow, vortex nucleation, the various intrinsic and extrinsic dissipation mechanisms in superfluids, macroscopic quantum effects, and the superfluid analog of both ac and dc Josephson effects—pivotal concepts in superfluid physics—have been performed. Some of the experiments that have shed light on the more intimate effect of quantum mechanics on the hydrodynamics of the dense heliums are surveyed, including the nucleation of quantized vortices both by Arrhenius processes and by macroscopic quantum tunneling, the setting up of vortex mills, and superfluid interferometry.
Magnetic flux creep in HTSC and Anderson-Kim theory
International Nuclear Information System (INIS)
Lykov, A.N.
2014-01-01
The theoretical and experimental data on flux creep in high-temperature superconductors (HTSC) were analyzed in the review paper. On the one hand, the main attention is paid to the most striking experimental results which have had a significant influence on the investigations of flux creep in HTSC. On the other hand, the analysis of theoretical studies is concentrated on the works, which explain the features of flux creep on the basis of the Anderson-Kim (AK) theory modifications, and received previously unsufficient attention. However, it turned out that the modified AK theory could explain a lot of features of flux creep in HTSC: the scaling behaviour of current-voltage curves of HTSC, the finite rate of flux creep at ultra low temperatures, the logarithmic dependence of effective pinning potential as a function of transport current and its decrease with temperature. The harmonic potential field which is used in this approach makes it possible to solve accurately the both problems: viscous vortex motion and flux creep in this field. Moreover the distribution of pinning potential and the interaction of vortices with each other are taken into account in the approach. Thus, the modification of the AK theory consists, essentially, in its detailed elaboration and approaching to real situations in superconductors
What should the Price--Anderson Act accomplish
International Nuclear Information System (INIS)
Kane, G.L.
1977-01-01
A historical review of the Price-Anderson Act's goals is followed by recommendations for amendments to improve guarantees of public safety. Failures of the original Act are identified as its failure to cover some accident situations appropriately and to provide incentives for promoting public safety. Legislation should correct these problems and be extended to all energy areas. Legislation based on worst-case situations is not found to be meaningful in terms of increasing safety or estimating comprehensive compensation because it relies on invalidated assumptions, which are still useful in safety awareness. Legislation could take the direction of putting 1.5 percent of the reactor cost into a fund, with the vendor and licensee contributing equal parts. When an incident occurs at any reactor, another one percent is put in by every reactor plus a $1 million penalty proportioned among those responsible. The Federal government would cover amounts above the fund, which would have no limit. Compensation to public funds by the industry would be a social decision based on the social and economic impact
Influence of iron impurities on defected graphene
International Nuclear Information System (INIS)
Faccio, Ricardo; Pardo, Helena; Araújo-Moreira, Fernando M.; Mombrú, Alvaro W.
2015-01-01
Highlights: • The interaction among a multivacancy graphene system and iron impurities is studied. • The studied iron impurities were single atom and tetrahedral and octahedral clusters. • DFT calculations using the VASP code were performed. • The embedding of Fe affects the structure and electronic behavior in the graphene. • Half metal or semimetal behavior can be obtained, depending on the Fe impurities. - Abstract: The aim of this work is to study the interaction of selected iron cluster impurities and a multivacancy graphene system, in terms of the structural distortion that the impurities cause as well as their magnetic response. While originally, the interaction has been limited to vacancies and isolated metallic atoms, in this case, we consider small iron clusters. This study was undertaken using Density Functional Theory (DFT) calculations. The influence of the iron impurities in the electronic structure of the vacant graphene system is discussed. The main conclusion of this work is that the presence of iron impurities acts lowering the magnetic signal due to the occurrence of spin pairing between carbon and iron, instead of enhancing the possible intrinsic carbon magnetism
Effect of light impurities on the early stage of swelling in austenitic stainless steel
International Nuclear Information System (INIS)
Igata, N.
1998-01-01
The objective of this study is to analyse the early stage of swelling and clarify the role of light impurities (nitrogen) in swelling of austenitic stainless steel. Recent results show that light impurities affect the swelling of 316 stainless steel under HVEM irradiation up to 10 dpa. At low concentration of light impurities the radiation swelling increases then decreases through the maximum as the concentration of light impurities increases. In the present paper the theoretical model is presented for the explanation of this effect. The model is based on the two factors: the influence of absorbed impurities on the voids caused by the production of an additional gas pressure in voids for their stabilization and the effect of impurities segregated around the surface of voids by the lowering of surface tension. These two affects are taken into account in the calculations of the critical size and the growth rate of cavities. The theoretical predictions on the radiation swelling rate dependent on the impurity concentration and temperature coincided with the experimental results on 316 stainless steel irradiated by HVEM. (orig.)
Final Report - Effects of Impurities on Fuel Cell Performance and Durability
Energy Technology Data Exchange (ETDEWEB)
Trent Molter
2012-08-18
This program is focused on the experimental determination of the effects of key hydrogen side impurities on the performance of PEM fuel cells. Experimental data has been leveraged to create mathematical models that predict the performance of PEM fuel cells that are exposed to specific impurity streams. These models are validated through laboratory experimentation and utilized to develop novel technologies for mitigating the effects of contamination on fuel cell performance. Results are publicly disseminated through papers, conference presentations, and other means.
Resonant scattering by realistic impurities in graphene.
Wehling, T O; Yuan, S; Lichtenstein, A I; Geim, A K; Katsnelson, M I
2010-07-30
We develop a first-principles theory of resonant impurities in graphene and show that a broad range of typical realistic impurities leads to the characteristic sublinear dependence of the conductivity on the carrier concentration. By means of density functional calculations various organic groups as well as adatoms such as H absorbed to graphene are shown to create midgap states within ±0.03 eV around the neutrality point. A low energy tight-binding description is mapped out. Boltzmann transport theory as well as a numerically exact Kubo formula approach yield the conductivity of graphene contaminated with these realistic impurities in accordance with recent experiments.
International Nuclear Information System (INIS)
Dubois, S.
2007-05-01
This study aims at understanding the influence of the impurity - defect interaction on the silicon solar cell performances. We studied first the case of single-crystalline silicon. We combined numerical simulations and experimental data providing new knowledge concerning metal impurities in silicon, to quantify the evolution of the conversion efficiency with the impurity concentration. Mainly due to the gettering effects, iron appears to be quite well tolerated. It is not the case for gold, diffusing too slowly. Hydrogenation effects were limited. We transposed then this study toward multi-crystalline silicon. Iron seems rather well tolerated, due to the gettering effects but also due to the efficiency of the hydrogenation. When slow diffusers are present, multi crystalline silicon is sensitive to thermal degradation. n-type silicon could solve this problem, this material being less sensitive to metal impurities. (author)
2010-02-24
... From the Federal Register Online via the Government Publishing Office ENVIRONMENTAL PROTECTION AGENCY Proposed CERCLA Administrative Settlement; Anderson-Calhoun Mine and Mill Site, Leadpoint, WA AGENCY: Environmental Protection Agency (EPA). ACTION: Notice; request for public comment. SUMMARY: In...
Steady-State Anderson Accelerated Coupling of Lattice Boltzmann and Navier–Stokes Solvers
Atanasov, Atanas
2016-10-17
We present an Anderson acceleration-based approach to spatially couple three-dimensional Lattice Boltzmann and Navier–Stokes (LBNS) flow simulations. This allows to locally exploit the computational features of both fluid flow solver approaches to the fullest extent and yields enhanced control to match the LB and NS degrees of freedom within the LBNS overlap layer. Designed for parallel Schwarz coupling, the Anderson acceleration allows for the simultaneous execution of both Lattice Boltzmann and Navier–Stokes solver. We detail our coupling methodology, validate it, and study convergence and accuracy of the Anderson accelerated coupling, considering three steady-state scenarios: plane channel flow, flow around a sphere and channel flow across a porous structure. We find that the Anderson accelerated coupling yields a speed-up (in terms of iteration steps) of up to 40% in the considered scenarios, compared to strictly sequential Schwarz coupling.
Modified Anderson orthogonality catastrophe power law in the presence of shell structure
Bandopadhyay, Swarnali; Hentschel, Martina
2011-01-01
We study Anderson orthogonality catastrophe (AOC) for parabolic quantum dots and focus on the effects of degeneracies, realized through the inherent shell structure of their energy levels that can be lifted through an external magnetic field, on the Anderson overlap. We find rich and interesting behaviors as a function of the strength and position of the perturbation, the system size, and the applied magnetic field. In particular, even for weak perturbations, we observe a pronounced AOC that is related to the degeneracy of energy levels. Most importantly, the power-law decay of the Anderson overlap as a function of the number of particles is modified in comparison to the metallic case due to the rearrangement of the energy-level shell structure. We support our analytical results by numerical calculations and also study the distribution of Anderson overlaps.
Non-Fermi-liquid behavior: Exact results for ensembles of magnetic impurities
Zvyagin, A A
2002-01-01
In this work we consider several exactly solvable models of magnetic impurities in critical quantum antiferromagnetic spin chains and multichannel Kondo impurities. Their ground state properties are studied and the finite set of nonlinear integral equations, which exactly describe the thermodynamics of the models, is constructed. We obtain several analytic low-energy expressions for the temperature, magnetic field, and frequency dependences of important characteristics of exactly solvable disordered quantum spin models and disordered multichannel Kondo impurities with essential many-body interactions. We show that the only low-energy parameter that gets renormalized is the velocity of the low-lying excitations (or the effective crossover scale connected with each impurity); the others appear to be universal. In our study several kinds of strong disorder important for experiments were used. Some of them produce low divergences in certain characteristics of our strongly disordered critical systems (compared wit...
Anderson localization for 2D discrete Schrödinger operator with random vector potential
Klopp, F
2002-01-01
We prove the Anderson localization near the bottom of the spectrum for two dimensional discrete Schr{\\"o}dinger operators with a class of random vector potentials and no scalar potentials. Main lemmas are the Lifshitz tail and the Wegner estimate on the integrated density of states. Then, the Anderson localization, i.e., the pure point spectrum with exponentially decreasing eigenfunctions, is proved by the standard multiscale argument.
Impurity states in two-and three-dimensional disordered systems
International Nuclear Information System (INIS)
Silva, A.F. da; Fabbri, M.
1984-04-01
The microscopic structure of the impurity states in two-and three-dimensional (2D and 3D) disordered systems is investigated. A cluster model is outlined for the donor impurity density of states (DIDS) of doped semiconductors. It is shown that the impurity states are very sensitive to a change in the dimensionality of the system, i.e., from 3D to 2D system. It is found that all eigenstates become localized in 2D disordered system for a large range of concentration. (Author) [pt
FLAPW Study of the EFG Tensor at Cd Impurities in In2O3
International Nuclear Information System (INIS)
Errico, L. A.; Renteria, M.; Fabricius, G.; Darriba, G. N.
2004-01-01
We report an ab initio study of the electric-field gradient tensor (EFG) at Cd impurities located at both nonequivalent cationic sites in the semiconductor In 2 O 3 . Calculations were performed with the FLAPW method that allows us to treat the electronic structure of the doped system and the atomic relaxations introduced by the impurities in the host in a fully self-consistent way. From our results for the EFG (in excellent agreement with the experiments), it is clear that the problem of the EFG at Cd impurities in In 2 O 3 cannot be described by the point-charge model and antishielding factors.
Impurity and quaternions in nonrelativistic scattering from a quantum memory
International Nuclear Information System (INIS)
Margetis, Dionisios; Grillakis, Manoussos G
2008-01-01
Models of quantum computing rely on transformations of the states of a quantum memory. We study mathematical aspects of a model proposed by Wu in which the memory state is changed via the scattering of incoming particles. This operation causes the memory content to deviate from a pure state, i.e. induces impurity. For nonrelativistic particles scattered from a two-state memory and sufficiently general interaction potentials in (1+1) dimensions, we express impurity in terms of quaternionic commutators. In this context, pure memory states correspond to null hyperbolic quaternions. In the case with point interactions, the scattering process amounts to appropriate rotations of quaternions in the frequency domain. Our work complements previous analyses by Margetis and Myers (2006 J. Phys. A 39 11567)
Impurity and quaternions in nonrelativistic scattering from a quantum memory
Energy Technology Data Exchange (ETDEWEB)
Margetis, Dionisios; Grillakis, Manoussos G [Department of Mathematics, University of Maryland, College Park, MD 20742 (United States)], E-mail: dio@math.umd.edu, E-mail: mng@math.umd.edu
2008-02-15
Models of quantum computing rely on transformations of the states of a quantum memory. We study mathematical aspects of a model proposed by Wu in which the memory state is changed via the scattering of incoming particles. This operation causes the memory content to deviate from a pure state, i.e. induces impurity. For nonrelativistic particles scattered from a two-state memory and sufficiently general interaction potentials in (1+1) dimensions, we express impurity in terms of quaternionic commutators. In this context, pure memory states correspond to null hyperbolic quaternions. In the case with point interactions, the scattering process amounts to appropriate rotations of quaternions in the frequency domain. Our work complements previous analyses by Margetis and Myers (2006 J. Phys. A 39 11567)
Glycolic acid physical properties and impurities assessment
Energy Technology Data Exchange (ETDEWEB)
Lambert, D. P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Pickenheim, B. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hay, M. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); BIBLER, N. E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2017-08-09
This document has been revised to add analytical data for fresh, 1 year old, and 4 year old glycolic acid as recommended in Revision 2 of this document. This was needed to understand the concentration of formaldehyde and methoxyacetic acid, impurities present in the glycolic acid used in Savannah River National Laboratory (SRNL) experiments. Based on this information, the concentration of these impurities did not change during storage. These impurities were in the glycolic acid used in the testing included in this report and in subsequent testing using DuPont (now called Chemours) supplied Technical Grade 70 wt% glycolic acid. However, these impurities were not reported in the first two versions of this report. The Defense Waste Processing Facility (DWPF) is planning to implement a nitric-glycolic acid flowsheets to increase attainment to meet closure commitment dates during Sludge Batch 9. In fiscal year 2009, SRNL was requested to determine the physical properties of formic and glycolic acid blends.
Hydrogenic impurity in double quantum dots
International Nuclear Information System (INIS)
Wang, X.F.
2007-01-01
The ground state binding energy and the average interparticle distances for a hydrogenic impurity in double quantum dots with Gaussian confinement potential are studied by the variational method. The probability density of the electron is calculated, too. The dependence of the binding energy on the impurity position is investigated for GaAs quantum dots. The result shows that the binding energy has a minimum as a function of the distance between the two quantum dots when the impurity is located at the center of one quantum dot or at the center of the edge of one quantum dot. When the impurity is located at the center of the two dots, the binding energy decreases monotonically
An atomic impurity in a high density plasma
International Nuclear Information System (INIS)
Das, M.P.
1981-07-01
We present a self-consistent theory based on the local density functional approach to study the electron structure of an atom imbedded in a high density plasma. We consider a neon atom as an impurity relevant to high compression laser fusion experiments for our analysis and indicate the usefulness of this approach to study level shifts where linear theories like Debye-Hueckel or Thomas-Fermi model will fail. (author)
Ab initio study of the EFG tensor at Cd impurities in Sc2O3 semiconductor
International Nuclear Information System (INIS)
Munoz, E.L.; Richard, D.; Errico, L.A.; Renteria, M.
2009-01-01
We present an ab initio study of diluted Cd impurities localized at both cation sites of the semiconductor Sc 2 O 3 . The electric-field-gradient (EFG) tensor at Cd impurities located at both cationic sites of the host structure was determined from the calculation of the electronic structure of the doped system. Calculations were performed with the full-potential augmented-plane wave plus local orbitals (APW+lo) method within the framework of the density functional theory. We studied the atomic structural relaxations and the perturbation of the electronic charge density induced by the impurities in the host system in a fully self-consistent way. We showed that the Cd impurity introduces an increase of 8% in the nearest oxygen neighbors bond-lengths, changing the EFG sign for probes located at the asymmetric cation site. The APW+lo predictions for the charged state of the Cd impurity were compared with EFG results existent in the literature, coming from time-differential γ-γ perturbed-angular-correlations experiments performed on 111 Cd-implanted Sc 2 O 3 powder samples. From the excellent agreement between theory and experiment, we can strongly suggest that the Cd acceptor impurities are ionized at room temperature. Finally, we showed that simple calculations like those performed within the point-charge model with antishielding factors do not correctly describe the problem of a Cd impurity in Sc 2 O 3 .
Effects of helium impurities on superalloys
Energy Technology Data Exchange (ETDEWEB)
Selle, J.E.
1977-07-01
A review of the literature on the effects of helium impurities on superalloys at elevated temperatures was undertaken. The actual effects of these impurities vary depending on the alloy, composition of the gas atmosphere, and temperature. In general, exposure in helium produces significant but not catastrophic changes in the structure and properties of the alloys. The effects of these treatments on the structure, creep, fatigue, and mechanical properties of the various alloys are reviewed and discussed. Suggestions for future work are presented.
Effects of helium impurities on superalloys
International Nuclear Information System (INIS)
Selle, J.E.
1977-07-01
A review of the literature on the effects of helium impurities on superalloys at elevated temperatures was undertaken. The actual effects of these impurities vary depending on the alloy, composition of the gas atmosphere, and temperature. In general, exposure in helium produces significant but not catastrophic changes in the structure and properties of the alloys. The effects of these treatments on the structure, creep, fatigue, and mechanical properties of the various alloys are reviewed and discussed. Suggestions for future work are presented
Mechanisms of impurity diffusion in rutile
International Nuclear Information System (INIS)
Peterson, N.L.; Sasaki, J.
1984-01-01
Tracer diffusion of 46 Sc, 51 Cr, 54 Mn, 59 Fe, 60 Co, 63 Ni, and 95 Zr, was measured as functions of crystal orientation, temperature, and oxygen partial pressure in rutile single crystals using the radioactive tracer sectioning technique. Compared to cation self-diffusion, divalent impurities (e.g., Co and Ni) diffuse extremely rapidly in TiO 2 and exhibit a large anisotropy in the diffusion behavior; divalent-impurity diffusion parallel to the c-axis is much larger than it is perpendicular to the c-axis. The diffusion of trivalent impurity ions (Sc and Cr) and tetravalent impurity ions (Zr) is similar to cation self-diffusion, as a function of temperature and of oxygen partial pressure. The divalent impurity ions Co and Ni apparently diffuse as interstitial ions along open channels parallel to the c-axis. The results suggest that Sc, Cr, and Zr ions diffuse by an interstitialcy mechanism involving the simultaneous and cooperative migration of tetravalent interstitial titanium ions and the tracer-impurity ions. Iron ions diffused both as divalent and as trivalent ions. 8 figures
On impurities transport in a tokamak
International Nuclear Information System (INIS)
Rozhanskij, V.A.
1980-01-01
Transport of impurity ions is analitically analized in the case when main plasma is in plateau or banana regimes but impurity ions - in the Pfirsch-Schlutter mode. It is shown that in the large region of parameters the impUrity transport represents a drift in a p oloidal electric field, averaged from magnetic surface with provision for disturbance of concentration on it. Therefore, transport velocity does not depend on Z value and impurity type, as well as collision frequency both in the plateau and banana regimes. A value of flows is determined by the value of poloidal rotation velocity. At the rotation velocity corresponding to the electric field directed from the centre to periphery impurities are thrown out of a discharge, in the reverse case the flow is directed inside. Refusal from the assumption that Zsub(eff) > approximately 2, does not considerably change the results of work. The approach developed in the process of work can be applied to the case when impurity ions are in the plateau or banana modes
Lectard, A.; Nicolas, F.
Precipitation yields of alamina trihydrate from different sodium aluminate solutions, synthetic or industrial, with variable content in mineral and organic impurities, have been determined at different soda concentrations. The conditions of precipitation were the same for all the solutions. A mathematical model of experimental results, taking into account possible interactions between impurities, has been established, allowing to predict specific effect of each mineral impurity and overall effet of organic content. With the kinetic equation of precipitations, the use of the mathematical model permits the calculation of equilibrium composition of the aluminate solution as a function of the content of impurities. Calculated and experimental values are in agreement. So, with equilibrium values and the kinetic equation, it is possible to predict the precipitation yield of any liquor knowing its chemical composition and condition of precipitation (temperature, seed charge, retention time).
The impurity transport in HT-6M tokamak
International Nuclear Information System (INIS)
Xu Wei; Wan Baonian; Xie Jikang
2003-01-01
The space-time profile of impurities has been measured with a multichannel visible spectroscopic detect system and UV rotation-mirror system in the HT-6M tokamak. An ideal impurity transport code has been used to simulate impurities (carbon and oxygen) behaviour during the OHM discharge. The profiles of impurities diffusion and convection coefficient, impurities ion densities in different ionized state, loss power density and effective charge number have been derived. The impurity behaviour during low-hybrid current drive has also been analyzed, the results show that the confinement of particles, impurities and energy has been improved, and emission power and effective charge number have been reduced
Influence of impurities on the fuel retention in fusion reactors
International Nuclear Information System (INIS)
Reinhart, Michael
2015-01-01
The topic of this thesis is the influence of plasma impurities on the hydrogen retention in metals, in the scope of plasma-wall-interaction research for fusion reactors. This is addressed experimentally and by modelling. The mechanisms of the hydrogen retention are influenced by various parameters like the wall temperature, ion energy, flux and fluence as well as the plasma composition. The plasma composition is a relevant factor for hydrogen retention in fusion reactors, as their plasma will also contain impurities like helium or seeded impurities like argon. The experiments treated in this thesis were performed in the linear plasma generator PSI-2 at Forschungszentrum Juelich, and are divided in 3 parts: The first experiments cover the plasma diagnostics, most importantly the measurement of the impurity ion concentration in the plasma by optical emission spectroscopy. This is a requirement for the later experiments with mixed plasmas. Diagnostics like Langmuir probe measurements are not applicable for this task because they do not distinguish different ionic species. The results also show that the impurity ion concentrations cannot be simply concluded from the neutral gas input to the plasma source, because the relation between the neutral gas concentration and impurity ion concentration is not linear. The second and main part of the experiments covers the exposure of tungsten samples to deuterium plasmas. In the experiments, the impurity ion type and concentration is variated, to verify the general influence of helium and argon on the deuterium retention in tungsten samples exposed at low temperatures. It shows that helium impurities reduce the amount of retained deuterium by a factor of 3, while argon impurities slightly increase the total retention, compared to exposures to a pure deuterium plasma. Cross-sections of the exposed tungsten surfaces via TEM-imaging reveal a 12-15 nm deep helium nanobubble layer at the surface of the sample, while for the cases of
Aničić, Rastko; Mišković, Zoran L.
2013-01-01
We investigate the conductivity of doped graphene in the semiclassical Boltzmann limit, as well as the conductivity minimum within the self-consistent transport theory. Using the hard-disk model for a two-dimensional distribution of impurities gives rise to both strong increase in the slope of conductivity at low charge carrier densities in graphene and a strongly sub-linear behavior of the conductivity at high charge carrier densities when the correlation distance between the impurities is l...
Co-ordination of heterovalent cation impurities in molten salts
International Nuclear Information System (INIS)
Andreoni, W.; Rovere, M.; Tosi, M.P.
1982-01-01
The local liquid structure around heterovalent cation impurities in molten chlorides is discussed in relation to spectroscopic data on solutions of transition metal ions. A tightly packed, low co-ordination shell is shown to be favoured by Coulomb ionic interactions for physically reasonable values of the size of the impurity. A competition between these forces and ''crystal field'' interactions favouring octahedral co-ordination is thus to be expected for many transition metal ions, as suggested by Gruen and McBeth. The transition observed for some transition metal ions from higher to lower co-ordination with increasing temperature is attributed primarily to entropy differences, that are roughly estimated in a solid-like model. (author)
Isotope effect of impurity diffusion of cadmium in silver
International Nuclear Information System (INIS)
Rockosch, H.J.; Herzig, C.
1984-01-01
The isotope effect of impurity diffusion of cadmium in silver single crystals was measured with the radioisotopes 115 Cd/ 109 Cd by gamma spectrometry. As a mean value E = 0.37 at T = 1060 K was obtained. The correlation factor f /SUB Cd/ = 0.41 is in disagreement with previous results of other investigators due to their unfavourable experimental approach. The present value of f /SUB Cd/ , however, is consistent with those of In and Sn in Ag. A comparison with the corresponding correlation factors in the copper solvent reveals a distinct influence of lattice perturbations because of the different atomic volumes of the solvents. Since the size effect is neglected in the electrostatic diffusion model, the agreement with this model is only qualitative. The frequency ratios for vacancy jumps were calculated. The free binding enthalpy of the vacancy-impurity complex was estimated to be Δg /SUB Cd/ = -0.064 eV. This value is smaller than those for In and Sn in Ag and complies with the relative diffusivities of these impurities in Ag
Studies of Impurities in the Pegasus Spherical Tokamak
Rodriguez Sanchez, C.; Bodner, G. M.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Perry, J. M.; Reusch, J. A.; Weberski, J. D.
2017-10-01
Local Helicity Injection (LHI) is used to initiate ST plasmas without a solenoid. Testing predictive models for the evolution of Ip(t) during LHI requires measurement of the plasma resistivity to quantify the dissipation of helicity. To that end, three diagnostic systems are coupled with an impurity transport model to quantify plasma contaminants. These are: visible bremsstrahlung (VB) spectroscopy; bolometry; and VUV spectroscopy. A spectral survey has been performed to identify line-free regions for VB measurements in the visible. Initial VB measurements are obtained with a single sightline through the plasma, and will be expanded to an imaging array to provide spatial resolution. A SPRED multichannel VUV spectrometer is being upgraded to provide high-speed ( 0.2 ms) spectral surveys for ion species identification, with a high-resolution grating installed for metallic line identification. A 16-channel thinistor bolometer array is planned. Absolutely calibrated VB, bolometer measurements, and qualitative ion species identification from SPRED are used as constraints in an impurity transport code to estimate absolute impurity content. Earlier work using this general approach indicated Zeff < 3 , before the edge current sources were shielded to reduce plasma-injector interactions. Work supported by US DOE Grant DE-FG02-96ER54375.
Theory of charged impurity scattering in two dimensional graphene
Adam, S.; Hwang, E. H.; Rossi, E.; Sarma, S. Das
2008-01-01
We review the physics of charged impurities in the vicinity of graphene. The long-range nature of Coulomb impurities affects both the nature of the ground state density profile as well as graphene's transport properties. We discuss the screening of a single Coulomb impurity and the ensemble averaged density profile of graphene in the presence of many randomly distributed impurities. Finally, we discuss graphene's transport properties due to scattering off charged impurities both at low and hi...
Impurity Trapping of Positive Muons in Metals
2002-01-01
Polarized positive muons are implanted into metal samples. In an applied magnetic field the muon spin precession is studied. The line width in the precession frequency spectrum gives information about the static and dynamic properties of muons in a metal lattice. At temperatures where the muon is immobile within its lifetime the line width gives information about the site of location. At temperatures where the muon is mobile, the line width gives information on the diffusion process. It is known from experiments on quasi-elastic neutron scattering on hydrogen in niobium that interstitial impurities like nitrogen tend to act as traps for hydrogen. These trapping effects have now been studied systematically for muons in both f.c.c. metals (aluminium and copper) and b.c.c. metals (mainly niobium). Direct information on the trapping rates and the nature of the diffusion processes can be obtained since the muonic lifetime covers a time range where many of these processes occur.\\\\ \\\\ Mathematical models are set up ...
Gamble, Ronald S., Jr.
Thin film YBa2Cu3O7--delta (YBCO) samples with added non-superconducting nanodot defects of CeO 2 and BaSnO2 are the focus of recent high-temperature superconductor studies. These nanodots allow magnetic flux to penetrate at these sites of the superconducting lattice thus creating a magnetic flux vortex state. Examining the structure shows that these quantized magnetic flux vortices arrange themselves in a self-assembled lattice. The nanodots, with non-superconducting properties, serve to present structural properties to restrict motion of these vorticies under a pinning-force and to enhance the critical current density. A formulation of a new model for the system by a variation in the electron pair velocity via the virtual work from the nanodot defects in accordance to the well-known Superconductivity theories is tested. A solution to the expression for the magnetic flux, zero net force and pair velocity will generate a setting for the optimal deposition parameters of number density, growth geometry and mass density of these nanodot structures. With a calculation of pair velocities from a similar work, a comparison is made between experimental and theoretical velocity calculations using growth geometry and chemical potential. This will yield insight into how the current density for a doped high-temperature superconductor will be modified and tuned based on the dynamics and density of the nanodots themselves.
On the radiative effects of light-absorbing impurities on snowpack evolution
Dumont, M.; Tuzet, F.; Lafaysse, M.; Arnaud, L.; Picard, G.; Lejeune, Y.; Lamare, M.; Morin, S.; Voisin, D.; Di Mauro, B.
2017-12-01
The presence of light absorbing impurities in snow strongly decreases snow reflectance leading to an increase in the amount of solar energy absorbed by the snowpack. This effect is also known as impurities direct radiative effect. The change in the amount of energy absorbed by the snowpack modifies the temperature profile inside the snowpack and in turn snow metamorphism (impurities indirect radiative effects). In this work, we used the detailed snowpack model SURFEX/ISBA-Crocus with an explicit representation of snow light-absorbing impurities content (Tuzet et al., 2017) fed by medium-resolution ALADIN-Climate atmospheric model to represent dust and black carbon atmospheric deposition fluxes. The model is used at two sites: Col de Porte (medium elevation site in the French Alps) and Torgnon (high elevation site in the Italian Alps). The simulations are compared to in-situ observations and used to quantify the effects of light-absorbing impurities on snow melt rate and timing. The respective parts of the direct and indirect radiative effects of light-absorbing impurities in snow are also computed for the two sites, emphasizing the need to account for the interactions between snow metamorphism and LAI radiative properties, to accurately predict the effects of light-absorbing impurities in snow. Moreover, we describe how automated hyperspectral reflectance can be used to estimate effective impurities surface content in snow. Finally we demonstrate how these reflectances measurements either from in situ or satellite data can be used via an assimilation scheme to constrain snowpack ensemble simulations and better predict the snowpack state and evolution.
Huesmann, L Rowell
2010-03-01
Over the past half century the mass media, including video games, have become important socializers of children. Observational learning theory has evolved into social-cognitive information processing models that explain that what a child observes in any venue has both short-term and long-term influences on the child's behaviors and cognitions. C. A. Anderson et al.'s (2010) extensive meta-analysis of the effects of violent video games confirms what these theories predict and what prior research about other violent mass media has found: that violent video games stimulate aggression in the players in the short run and increase the risk for aggressive behaviors by the players later in life. The effects occur for males and females and for children growing up in Eastern or Western cultures. The effects are strongest for the best studies. Contrary to some critics' assertions, the meta-analysis of C. A. Anderson et al. is methodologically sound and comprehensive. Yet the results of meta-analyses are unlikely to change the critics' views or the public's perception that the issue is undecided because some studies have yielded null effects, because many people are concerned that the implications of the research threaten freedom of expression, and because many people have their identities or self-interests closely tied to violent video games.
Frandsen, Benjamin A.; Brunelli, Michela; Page, Katharine; Uemura, Yasutomo J.; Staunton, Julie B.; Billinge, Simon J. L.
2016-05-01
We present a temperature-dependent atomic and magnetic pair distribution function (PDF) analysis of neutron total scattering measurements of antiferromagnetic MnO, an archetypal strongly correlated transition-metal oxide. The known antiferromagnetic ground-state structure fits the low-temperature data closely with refined parameters that agree with conventional techniques, confirming the reliability of the newly developed magnetic PDF method. The measurements performed in the paramagnetic phase reveal significant short-range magnetic correlations on a ˜1 nm length scale that differ substantially from the low-temperature long-range spin arrangement. Ab initio calculations using a self-interaction-corrected local spin density approximation of density functional theory predict magnetic interactions dominated by Anderson superexchange and reproduce the measured short-range magnetic correlations to a high degree of accuracy. Further calculations simulating an additional contribution from a direct exchange interaction show much worse agreement with the data. The Anderson superexchange model for MnO is thus verified by experimentation and confirmed by ab initio theory.
Frandsen, Benjamin A; Brunelli, Michela; Page, Katharine; Uemura, Yasutomo J; Staunton, Julie B; Billinge, Simon J L
2016-05-13
We present a temperature-dependent atomic and magnetic pair distribution function (PDF) analysis of neutron total scattering measurements of antiferromagnetic MnO, an archetypal strongly correlated transition-metal oxide. The known antiferromagnetic ground-state structure fits the low-temperature data closely with refined parameters that agree with conventional techniques, confirming the reliability of the newly developed magnetic PDF method. The measurements performed in the paramagnetic phase reveal significant short-range magnetic correlations on a ∼1 nm length scale that differ substantially from the low-temperature long-range spin arrangement. Ab initio calculations using a self-interaction-corrected local spin density approximation of density functional theory predict magnetic interactions dominated by Anderson superexchange and reproduce the measured short-range magnetic correlations to a high degree of accuracy. Further calculations simulating an additional contribution from a direct exchange interaction show much worse agreement with the data. The Anderson superexchange model for MnO is thus verified by experimentation and confirmed by ab initio theory.
FP-LAPW Calculations of the EFG at Cd Impurities in Rutile SnO2
International Nuclear Information System (INIS)
Errico, L. A.; Fabricius, G.; Renteria, M.
2001-01-01
We report an ab initio study of the electric-field gradient (EFG) at Cd impurities located at the cation site in the semiconductor SnO 2 (rutile phase). The study was performed with the WIEN97 implementation of the FP-LAPW method. In order to simulate the diluted Cd-impurity in the SnO 2 host and to calculate the electronic structure of the system we used a 72-atoms super-cell, studying the relaxation introduced by the impurity in the lattice. The free-relaxation process performed shows that the relaxations of the oxygen nearest-neighbors of the impurity are not isotropic. Our prediction for the EFG tensor are compared with experimental results and point-charge model predictions
i QIST: An open source continuous-time quantum Monte Carlo impurity solver toolkit
Huang, Li; Wang, Yilin; Meng, Zi Yang; Du, Liang; Werner, Philipp; Dai, Xi
2015-10-01
Quantum impurity solvers have a broad range of applications in theoretical studies of strongly correlated electron systems. Especially, they play a key role in dynamical mean-field theory calculations of correlated lattice models and realistic materials. Therefore, the development and implementation of efficient quantum impurity solvers is an important task. In this paper, we present an open source interacting quantum impurity solver toolkit (dubbed i QIST). This package contains several highly optimized quantum impurity solvers which are based on the hybridization expansion continuous-time quantum Monte Carlo algorithm, as well as some essential pre- and post-processing tools. We first introduce the basic principle of continuous-time quantum Monte Carlo algorithm and then discuss the implementation details and optimization strategies. The software framework, major features, and installation procedure for i QIST are also explained. Finally, several simple tutorials are presented in order to demonstrate the usage and power of i QIST.
International Nuclear Information System (INIS)
Santos, Robinson A. dos; Hamada, Margarida M.; Costa, Fabio E. da; Gennari, Roseli F.; Martins, Joao F.T.; Marcondes, Renata M.; Mesquita, Carlos H. de
2011-01-01
TlBr crystals were purified and grown by the repeated Bridgman method from two commercial TlBr salts and characterized to be used as radiation detectors. To evaluate the purification efficiency, measurements of the impurity concentration were made after each growth, analyzing the trace impurities by inductively coupled plasma mass spectroscopy (ICP-MS). A significant decrease of the impurity concentration resulting from the purification number was observed. To evaluate the crystal as a radiation semiconductor detector, measurements of its resistivity and gamma-ray spectroscopy were carried out. The radiation response depended on the crystal purity. The repeated Bridgman technique improved the TlBr crystal quality used as a radiation detector. A compartmental model was proposed to fit the impurity concentration as a function of the repetition number of the Bridgman growth. (author)
Fractal dimension of interfaces in Edwards-Anderson spin glasses for up to six space dimensions
Wang, Wenlong; Moore, M. A.; Katzgraber, Helmut G.
2018-03-01
The fractal dimension of domain walls produced by changing the boundary conditions from periodic to antiperiodic in one spatial direction is studied using both the strong-disorder renormalization group algorithm and the greedy algorithm for the Edwards-Anderson Ising spin-glass model for up to six space dimensions. We find that for five or fewer space dimensions, the fractal dimension is lower than the space dimension. This means that interfaces are not space filling, thus implying that replica symmetry breaking is absent in space dimensions fewer than six. However, the fractal dimension approaches the space dimension in six dimensions, indicating that replica symmetry breaking occurs above six dimensions. In two space dimensions, the strong-disorder renormalization group results for the fractal dimension are in good agreement with essentially exact numerical results, but the small difference is significant. We discuss the origin of this close agreement. For the greedy algorithm there is analytical expectation that the fractal dimension is equal to the space dimension in six dimensions and our numerical results are consistent with this expectation.
Satellite Water Impurity Marker (SWIM) for predicting seasonal cholera outbreaks
Jutla, A. S.; Akanda, A. S.; Islam, S.
2011-12-01
Prediction of outbreaks of cholera, a deadly water related disease, remains elusive. Since coastal brackish water provides a natural ecological niche for cholera bacteria and because a powerful evidence of new biotypes is emerging, it is highly unlikely that cholera will be fully eradicated. Therefore, it is necessary to develop cholera prediction model with several months' of lead time. Satellite based estimates of chlorophyll, a surrogate for phytoplankton abundance, has been associated with proliferation of cholera bacteria. However, survival of cholera bacteria in a variety of coastal ecological environment put constraints on predictive abilities of chlorophyll algorithm since it only measures greenness in coastal waters. Here, we propose a new remote sensing reflectance based statistical index: Satellite Water Impurity Marker, or SWIM. This statistical index estimates impurity levels in the coastal waters and is based on the variability observed in the difference between the blue (412nm) and green (555nm) wavelengths in coastal waters. The developed index is bounded between clear and impure water and shows the ability to predict cholera outbreaks in the Bengal Delta with a predicted r2 of 78% with two months lead time. We anticipate that a predictive system based on SWIM will provide essential lead time allowing effective intervention and mitigation strategies to be developed for other cholera endemic regions of the world.
Experimental study of impurity production in the Tokapole II tokamak
International Nuclear Information System (INIS)
Brickhouse, N.S.
1984-01-01
The release mechanism for low-Z impurities in Tokapole II has been characterized through impurity doping and isotopic exchange experiments. The desorption mechanism responsible for the low-Z impurity concentrations during the rise phase of the plasma current depends on the mass of the plasma ions. Doping with small amounts of any gas studied (H 2 , D 2 , He, N 2 , O 2 , Ne, Ar, Kr, and Xe) increases the early-time radiation of O, C, and N. For exotic gas doping this increase is linear with the dopant concentration, and proportional to the mass of the dopant, as expected for a momentum transfer process. Isotopic exchange experiments confirm the mass-dependence of oxygen production. A time-dependent coronal model is compared with the vacuum ultraviolet spectroscopic signals of the ionizing oxygen. The quantity sigma/tau (desorption cross section divided by particle confinement time) is determined to be 4 x 10 13 cm 2 /msec. The oxygen influx has a large peak early in the start-up
Energy Technology Data Exchange (ETDEWEB)
Datta, Nirmal Kumar [Department of Physics, Suri Vidyasagar College, Suri, Birbhum 731 101, West Bengal (India); Ghosh, Manas, E-mail: pcmg77@rediffmail.com [Department of Chemistry, Physical Chemistry Section, Visva Bharati University, Santiniketan, Birbhum 731 235, West Bengal (India)
2010-06-16
Graphical abstract: The pattern of time evolution of eigenstates of a repulsive impurity doped quantum dot is explored. We have considered Gaussian impurity centers. Under a periodically fluctuating impurity potential, the system reveals a long time dynamics that is undulatory in nature. Coupled to the dopant location, the domain of influence of the impurity potential affects the separation between the eigenstates of the unperturbed system. The investigation points to a threshold value of spatial extension of impurity potential. Above this threshold value, the dopant location becomes important in monitoring the minimum value of impurity potential required to cause excitation. - Abstract: We explore the pattern of time evolution of eigenstates of a repulsive impurity doped quantum dot. The quantum dot is 2-dimensional and contains one electron which is harmonically confined. We have considered Gaussian impurity centers. A static transverse magnetic field is also present. Under a periodically fluctuating impurity potential, the system reveals a long time dynamics that is undulatory in nature. Coupled to the dopant location, the domain of influence of the impurity potential affects the separation between the eigenstates of the unperturbed system. The investigation points to a threshold value of spatial extension of impurity potential. Above this threshold value, the dopant location becomes important in monitoring the minimum value of impurity potential required to cause excitation.
Nikcevic, Irena; Wyrzykiewicz, Tadeusz K.; Limbach, Patrick A.
2010-01-01
Summary An LC-MS method based on the use of high resolution Fourier transform ion cyclotron resonance mass spectrometry (FTIRCMS) for profiling oligonucleotides synthesis impurities is described. Oligonucleotide phosphorothioatediesters (phosphorothioate oligonucleotides), in which one of the non-bridging oxygen atoms at each phosphorus center is replaced by a sulfur atom, are now one of the most popular oligonucleotide modifications due to their ease of chemical synthesis and advantageous pharmacokinetic properties. Despite significant progress in the solid-phase oligomerization chemistry used in the manufacturing of these oligonucleotides, multiple classes of low-level impurities always accompany synthetic oligonucleotides. Liquid chromatography-mass spectrometry has emerged as a powerful technique for the identification of these synthesis impurities. However, impurity profiling, where the entire complement of low-level synthetic impurities is identified in a single analysis, is more challenging. Here we present an LC-MS method based the use of high resolution-mass spectrometry, specifically Fourier transform ion cyclotron resonance mass spectrometry (FTIRCMS or FTMS). The optimal LC-FTMS conditions, including the stationary phase and mobile phases for the separation and identification of phosphorothioate oligonucleotides, were found. The characteristics of FTMS enable charge state determination from single m/z values of low-level impurities. Charge state information then enables more accurate modeling of the detected isotopic distribution for identification of the chemical composition of the detected impurity. Using this approach, a number of phosphorothioate impurities can be detected by LC-FTMS including failure sequences carrying 3′-terminal phosphate monoester and 3′-terminal phosphorothioate monoester, incomplete backbone sulfurization and desulfurization products, high molecular weight impurities, and chloral, isobutyryl, and N3 (2-cyanoethyl) adducts
Impurity production and acceleration in CTIX
Energy Technology Data Exchange (ETDEWEB)
Buchenauer, D. [Sandia National Laboratories, MS-9161, P.O. Box 969, Livermore, CA 94550 (United States)], E-mail: dabuche@sandia.gov; Clift, W.M. [Sandia National Laboratories, MS-9161, P.O. Box 969, Livermore, CA 94550 (United States); Klauser, R.; Horton, R.D. [CTIX Group, University of California at Davis, Davis, CA 95616 (United States); Howard, S.J. [General Fusion Inc., Burnaby, BC V5A 3H4 (Canada); Brockington, S.J. [HyperV Technologies Corp., Chantilly, VA 20151 (United States); Evans, R.W.; Hwang, D.Q. [CTIX Group, University of California at Davis, Davis, CA 95616 (United States)
2009-06-15
The Compact Toroid Injection Experiment (CTIX) produces a high density, high velocity hydrogen plasma that maintains its configuration in free space on a MHD resistive time scale. In order to study the production and acceleration of impurities in the injector, several sets of silicon collector probes were exposed to spheromak-like CT's exiting the accelerator. Elemental analysis by Auger Electron Spectroscopy indicated the presence of O, Al, Fe, and Cu in films up to 200 A thickness (1000 CT interactions). Using a smaller number of CT interactions (10-20), implantation of Fe and Cu was measured by Auger depth profiling. The amount of impurities was found to increase with accelerating voltage and number of CT interactions while use of a solenoidal field reduced the amount. Comparison of the implanted Fe and Cu with TRIM simulations indicated that the impurities were traveling more slowly than the hydrogen CT.
Spectroscopic impurity survey in Wendelstein 7-X
Energy Technology Data Exchange (ETDEWEB)
Buttenschoen, Birger; Burhenn, Rainer; Thomsen, Henning [Max-Planck-Institut fuer Plasmaphysik, Greifswald (Germany); Biel, Wolfgang; Assmann, Jochen; Hollfeld, Klaus-Peter [Forschungszentrum Juelich GmbH, Juelich (Germany); Collaboration: the Wendelstein 7-X Team
2016-07-01
The High Efficiency eXtreme ultraviolet Overview Spectrometer (HEXOS) has been developed specifically for impurity identification and survey purposes on the Wendelstein 7-X stellarator. This spectrometer system, consisting of four individual spectrometers, covers the wavelength range between λ=2.5 nm and λ=160 nm, observing the intense resonance lines of relevant Mg-, Na-, Be- and Li-like impurity ions as well as the high-Z W/Ta quasi-continua. During the first operation phase of W7-X, commissioning of HEXOS was finished by providing an in-situ wavelength calibration. The permanently acquired spectra are evaluated to monitor the overall impurity content in the plasma, and serve as an indicator for unintended plasma-wall contact possibly leading to machine damage. HEXOS results from the first operation phase of W7-X are presented and discussed with respect to future scientific exploitation of the available data.
Impurity dependence of superconductivity in niobium
International Nuclear Information System (INIS)
Laa, C.
1984-04-01
Jump temperatures, the critical fields Hsubc and Hsubc 2 and specific heats were measured on niobium samples where the impurity content was systematically varied by loading with nitrogen. Quantities could thus be extrapolated to lattice perfection and absolute purity. Comparisons with theories were made and some parameters extracted. Agreement was found with Gorkov theory for small impurities. A new value of the Ginsburg-Landau parameter Ko was determined to be just above 1/sqrt2 which proves that niobium is an elementary Type II semiconductor. By comparisons with the BCS and the CLAC theory the values of the mean Fermi velocity, the London penetration depth, the BCS coherence length and the impurity parameter were extracted. (G.Q.)
Magnetic impurity coupled to interacting conduction electrons
International Nuclear Information System (INIS)
Schork, T.
1996-01-01
We consider a magnetic impurity which interacts by hybridization with a system of weakly correlated electrons and determine the energy of the ground state by means of a 1/N f expansion. The correlations among the conduction electrons are described by a Hubbard Hamiltonian and are treated to the lowest order in the interaction strength. We find that their effect on the Kondo temperature, T K , in the Kondo limit is twofold: first, the position of the impurity level is shifted due to the reduction of charge fluctuations, which reduces T K . Secondly, the bare Kondo exchange coupling is enhanced as spin fluctuations are enlarged. In total, T K increases. Both corrections require intermediate states beyond the standard Varma-Yafet ansatz. This shows that the Hubbard interaction does not just provide quasiparticles, which hybridize with the impurity, but also renormalizes the Kondo coupling. copyright 1996 The American Physical Society
Impurity and particle control for INTOR
International Nuclear Information System (INIS)
Post, D.
1985-02-01
The INTOR impurity control system studies have been focused on the development of an impurity control system which would be able to provide the necessary heat removal and He pumping while satisfying the requirements for (1) minimum plasma contamination by impurities, (2) reasonable component lifetime (approx. 1 year), and (3) minimum size and cost. The major systems examined were poloidal divertors and pumped limiters. The poloidal divertor was chosen as the reference option since it offered the possibility of low sputtering rates due to the formation of a cool, dense plasma near the collector plates. Estimates of the sputtering rates associated with pumped limiters indicated that they would be too high for a reasonable system. Development of an engineering design concept was done for both the poloidal divertor and the pumped limiter
Effect of impurity radiation on tokamak equilibrium
International Nuclear Information System (INIS)
Rebut, P.H.; Green, B.J.
1977-01-01
The energy loss from a tokamak plasma due to the radiation from impurities is of great importance in the overall energy balance. Taking the temperature dependence of this loss for two impurities characteristic of those present in existing tokamak plasmas, the condition for radial power balance is derived. For the impurities considered (oxygen and iron) it is found that the radiation losses are concentrated in a thin outer layer of the plasma and the equilibrium condition places an upper limit on the plasma paraticle number density in this region. This limiting density scales with mean current density in the same manner as is experimentally observed for the peak number density of tokamak plasmas. The stability of such equilibria is also discussed. (author)
Wigner-like crystallization of Anderson-localized electron systems with low electron densities
Slutskin, A A; Pepper, M
2002-01-01
We consider an electron system under conditions of strong Anderson localization, taking into account interelectron long-range Coulomb repulsion. We establish that at sufficiently low electron densities and sufficiently low temperatures the Coulomb electron interaction brings about ordering of the Anderson-localized electrons into a structure that is close to an ideal (Wigner) crystal lattice, provided the dimension of the system is > 1. This Anderson-Wigner glass (AWG) is a new macroscopic electron state that, on the one hand, is beyond the conventional Fermi glass concept, and on the other hand, qualitatively differs from the known 'plain' Wigner glass (inherent in self-localized electron systems) in that the random slight electron displacements from the ideal crystal sites essentially depend on the electron density. With increasing electron density the AWG is found to turn into the plain Wigner glass or Fermi glass, depending on the width of the random spread of the electron levels. It is shown that the res...
Image transport through a disordered optical fibre mediated by transverse Anderson localization.
Karbasi, Salman; Frazier, Ryan J; Koch, Karl W; Hawkins, Thomas; Ballato, John; Mafi, Arash
2014-02-25
Transverse Anderson localization of light allows localized optical-beam-transport through a transversely disordered and longitudinally invariant medium. Its successful implementation in disordered optical fibres recently resulted in the propagation of localized beams of radii comparable to that of conventional optical fibres. Here we demonstrate optical image transport using transverse Anderson localization of light. The image transport quality obtained in the polymer disordered optical fibre is comparable to or better than some of the best commercially available multicore image fibres with less pixelation and higher contrast. It is argued that considerable improvement in image transport quality can be obtained in a disordered fibre made from a glass matrix with near wavelength-size randomly distributed air-holes with an air-hole fill-fraction of 50%. Our results open the way to device-level implementation of the transverse Anderson localization of light with potential applications in biological and medical imaging.
John Anderson's development of (situational) realism and its bearing on psychology today.
Hibberd, Fiona J
2009-10-01
In 1927, the Scottish philosopher John Anderson arrived in Australia to take up the chair of Philosophy at the University of Sydney. By the late 1930s, the "macrostructure" of his realist system was in place. It includes a theory of process and a substantial metaphysics, one that opposes positivism, linguistic philosophy and all forms of idealism. However, beyond Australia it remains largely unknown, despite its bearing on a number of current issues in psychology and the social sciences generally. This article outlines Anderson's transition from Hegelian idealism to realism, describes aspects of his ontology and epistemology, compares some of Anderson's ideas with Dewey's pragmatism and explains their relevance to present-day psychology.
Image transport through a disordered optical fibre mediated by transverse Anderson localization
Karbasi, Salman; Frazier, Ryan J.; Koch, Karl W.; Hawkins, Thomas; Ballato, John; Mafi, Arash
2014-02-01
Transverse Anderson localization of light allows localized optical-beam-transport through a transversely disordered and longitudinally invariant medium. Its successful implementation in disordered optical fibres recently resulted in the propagation of localized beams of radii comparable to that of conventional optical fibres. Here we demonstrate optical image transport using transverse Anderson localization of light. The image transport quality obtained in the polymer disordered optical fibre is comparable to or better than some of the best commercially available multicore image fibres with less pixelation and higher contrast. It is argued that considerable improvement in image transport quality can be obtained in a disordered fibre made from a glass matrix with near wavelength-size randomly distributed air-holes with an air-hole fill-fraction of 50%. Our results open the way to device-level implementation of the transverse Anderson localization of light with potential applications in biological and medical imaging.
The electronic structure of impurities in semiconductors
Nylandsted larsen, A; Svane, A
2002-01-01
The electronic structure of isolated substitutional or interstitial impurities in group IV, IV-IV, and III-V compound semiconductors will be studied. Mössbauer spectroscopy will be used to investigate the incorporation of the implanted isotopes on the proper lattice sites. The data can be directly compared to theoretical calculations using the LMTO scheme. Deep level transient spectroscopy will be used to identify the band gap levels introduced by metallic impurities, mainly in Si~and~Si$ _{x}$Ge$_{1-x}$. \\\\ \\\\
Impurity screening in strongly coupled plasma systems
Kyrkos, S
2003-01-01
We present an overview of the problem of screening of an impurity in a strongly coupled one-component plasma within the framework of the linear response (LR) theory. We consider 3D, 2D and quasi-2D layered systems. For a strongly coupled plasma the LR can be determined by way of the known S(k) structure functions. In general, an oscillating screening potential with local overscreening and antiscreening regions emerges. In the case of the bilayer, this phenomenon becomes global, as overscreening develops in the layer of the impurity and antiscreening in the adjacent layer. We comment on the limitations of the LR theory in the strong coupling situation.
Correlations between locked modes and impurity influxes
Energy Technology Data Exchange (ETDEWEB)
Fishpool, G.M. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Lawson, K.D. [UKAEA Culham Lab., Abingdon (United Kingdom)
1994-07-01
An analysis of pulses that were disturbed by medium Z impurity influxes (Cl, Cr, Fe and Ni) recorded during the 91/92 JET operations, has demonstrated that such influxes can result in MHD modes which subsequently ``lock``. A correlation is found between the power radiated by the influx and the time difference between the start of the influx and the beginning of the locked mode. The growth in the amplitude of the locked mode itself can lead to further impurity influxes. A correlation is noted between intense influxes (superior to 10 MW) and the mode ``unlocking``. (authors). 4 refs., 4 figs.
Periodic trends governing the interactions between impurity atoms [H-Ar] and (alpha)-U
Energy Technology Data Exchange (ETDEWEB)
Taylor, Christopher David [Los Alamos National Laboratory
2008-01-01
The binding energies, geometries, charges and electronic structures of a series of impurity atoms [H-Ar] interacting with the {alpha}-U lattice in various configurations were assessed by means of density functional theory calculations. Periodic trends governing the binding energy were highlighted and related to the electronic properties of the impurity atoms, with some consideration given to the band-structure of {alpha}-U. The strongest bound impurity atoms include [C, N, O] and [Si, P, S]. The general trends in the binding energy can be reproduced by a simple parameterisation in terms of the electronegativity (charge-transfer) and covalent radius (elasticity theory) of the impurity atom. The strongest bound atoms deviate from this model, due to their ability to bind with an optimum mixture of covalency and ionicity. This last point is evidenced by the partial overlap of the impurity atom p-band with the hybrid d-/f-band of {alpha}-U. It is expected that the trends and general behaviour reported in this work can be extended to the interactions of impurity atoms with other metallic systems.
The influence of a homologous protein impurity on lysozyme crystal growth
Bhamidi, V.; Hanson, B. L.; Edmundson, A.; Skrzypczak-Jankun, E.; Schall, C.
1999-08-01
The effect of a structurally similar protein impurity, turkey ( Meleagris gallopavo) egg-white lysozyme (TEWL) on crystallization of the host protein, hen-egg-white lysozyme (HEWL) from chicken ( Gallus gallus) was studied under varying impurity and host solution concentrations. A change in morphology is observed when crystals of HEWL are grown in the presence of TEWL. As the relative amount of TEWL increases, HEWL crystals become more elongated in the [0 0 1] direction. Elongation is more pronounced in samples with lower initial concentrations of HEWL than in samples with higher initial concentrations. This behavior is consistent with that of impurities in small molecule crystal growth and with predictions based on the Kubota-Mullin model. The observed effect on the growth process can be attributed to the apparent inhibition in the [1 1 0] crystal growth direction of HEWL by TEWL since slowly growing faces become dominant faces in crystal growth. Incorporation of TEWL into HEWL crystals grown in a sitting drop batch method was measured using cation exchange chromatography. The results indicate that impurity incorporation is associated with increasing supersaturation. This conclusion is consistent with a kinetically controlled process of impurity incorporation. The observed impurity effects are most probably associated with the interchange of glutamine in position 41 of HEWL by histidine in TEWL.
Anomalous temperature behavior of Sn impurities
International Nuclear Information System (INIS)
Haskel, D.; Shechter, H.; Stern, E.A.; Newville, M.; Yacoby, Y.
1993-01-01
Sn impurities in Pb and Ag hosts have been investigated by Moessbauer effect and in Pb by x-ray-absorption fine-structure (XAFS) studies. The Sn atoms are dissolved up to at least 2 at. % in Pb and up to at least 8 at. % in Ag for the temperature ranges investigated. The concentration limit for Sn-Sn interactions is 1 at. % for Pb and 2 at. % for Ag as determined experimentally by lowering the Sn concentration until no appreciable change occurs in the Moessbauer effect. XAFS measurements verify that the Sn impurities in Pb are dissolved and predominantly at substitutional sites. For both hosts the temperature dependence of the spectral intensities of isolated Sn impurities below a temperature T 0 is as expected for vibrating about a lattice site. Above T 0 the Moessbauer spectral intensity exhibits a greatly increased rate of drop-off with temperature without appreciable broadening. This drop-off is too steep to be explained by ordinary anharmonic effects and can be explained by a liquidlike rapid hopping of the Sn, localized about a lattice site. Higher-entropy-density regions of radii somewhat more than an atomic spacing surround such impurities, and can act as nucleation sites for three-dimensional melting
Detection of mineral impurities in diatomite ores
Guatame Garcia, L.A.; Buxton, M.W.N.; Fiore, Saverio
2017-01-01
Diatomaceous Earth (DE) is commonly used in the industry for the manufacturing of filters, where diatomite is preferred due to its low chemical reactivity and high porosity. Diatomite deposits with major amounts of mineral impurities, such as carbonates, present a problem in the production DE. In
Zirconium analysis. Impurities determination by spark mass specrometry
International Nuclear Information System (INIS)
Anon.
Determination of impurities in zirconium, suitable for atomic content greater than 10 -8 but particularly adapted for low contents. The method is quantitative only if a reference sample is available (metallic impurities) [fr
Covalent magnetism and magnetic impurities.
Gruber, C; Bedolla, P O; Mohn, P
2013-05-08
We use the model of covalent magnetism and its application to magnetic insulators applied to the case of insulating carbon doped BaTiO3. Since the usual Stoner mechanism is not applicable we study the possibility of the formation of magnetic order based on a mechanism favoring singly occupied orbitals. On the basis of our model parameters we formulate a criterion similar to the Stoner criterion but also valid for insulators. We describe the model of covalent magnetism using a molecular orbital picture and determine the occupation numbers for spin-up and spin-down states. Our model allows a simulation of the results of our ab initio calculations for E(ℳ) which are found to be in very good agreement.
Financial analysis of potential retrospective premium assessments under the Price-Anderson system
International Nuclear Information System (INIS)
Wood, R.S.
1985-04-01
Ten representative nuclear utilities have been analyzed over the period 1981 to 1983 to evaluate the effects of three levels of retrospective premiums on various financial indicators. This analysis continues and expands on earlier analyses prepared as background for deliberations by the US Congress for possible extension or modification of the Price-Anderson Act
Ilu võitlus koleduse välja vastu / Rebekka Lotman ; kommenteerinud Mart Anderson
Lotman, Rebekka, 1978-
2009-01-01
Konkursside "25 kauneimat Eesti raamatut" ja "Viis kauneimat Eesti lasteraamatut" võidutööde näitus Eesti Rahvusraamatukogus. Võidutööde valikut kommenteerib žürii esimees Mart Anderson. Loetletud 2008. aasta 25 kaunimat raamatut. Nimekiri: 2008. aasta 25 kauneimat raamatut
Page 1 Graded subrings of C[X, Y] 215 References {1} Anderson ...
Indian Academy of Sciences (India)
{1} Anderson D. F. Subrings of k[X, Y] generated by monomials, Can. J. Math, Vol. XXX, No. 1 (1978). 2 : 5. 224. [2] Bourbaki N, Commutative Algebra. Hermann, Addison Wesley Publishers. L3] Gurjar R V and Shastri A R, The fundamental group at infinity of affine surfaces, Commen, Math. Heleetici 59 (1984) 459–484.
E. N. Anderson: Caring for place: ecology, ideology, and emotion in traditional landscape management
Susan Stevens Hummel
2016-01-01
Anderson is deeply concerned with inadequate responses to ongoing global environmental degradation. Accordingly, he offers cases of traditional societies that survived over long time periods without destroying their environments. His focus is on ways humans think about plants, animals, and landscapes because of his conviction that stories about them are what make us...
78 FR 41835 - Inflation Adjustments to the Price-Anderson Act Financial Protection Regulations
2013-07-12
... Price-Anderson Act Financial Protection Regulations AGENCY: Nuclear Regulatory Commission. ACTION: Final rule. SUMMARY: The Atomic Energy Act of 1954, as amended (AEA), requires the U.S. Nuclear Regulatory.... Congressional Review Act I. Background Section 604 of the Energy Policy Act of 2005, Public Law 109-58, amended...
Directory of Open Access Journals (Sweden)
Averbukh I. Sh.
2013-03-01
Full Text Available We show that molecules kicked periodically by laser pulses currently used in molecular alignment experiments allow to observe effects of the periodically kicked quantum rotor in a real rotational system. Among these effects are Anderson localisation in angular momentum and the scaling of the quantum resonance. Based on this, we propose a new scheme for selective molecular rotational excitation.
Alternative reality and art: the creative world of Walter Inglis Anderson.
Rodenhauser, Paul
2005-01-01
Both mental illness and creativity run in families. This observation suggests the possibility of genetic predisposition; in light of the known dynamic interrelationships among the environment, the personality, and the brain, however, it does not diminish the possibility of significant environmental influence on personal development. An examination of the biological, psychological, and social forces impacting the life of Walter Inglis Anderson (1903-1965), the South's most important artist, serves as a case in point. Anderson's upbringing, including his mother's determination that her sons become artists and her beliefs about the shamanistic role of artists in society, might have played a large part in establishing an unusual and indelible frame of reference in a family whose history insinuated the possibility of untoward outcomes. Walter Anderson's life as an artist--one who lived at times in an alternative reality--raises questions about how a different set of circumstances might have affected his mental state as well as his talent. This essay discusses some of the important relationships, events, and circumstances in Walter Anderson's life from a biopsychosocial perspective, with emphasis on psychodynamic implications of his illness and its questionable diagnosis as schizophrenia.
Evaluation of the train signal and rail systems for the Anton Anderson Memorial Tunnel.
2014-07-01
The Whittier Access Project was completed in 2000. One phase of the project was to convert the 2.5 mile long Anton Anderson : Memorial Tunnel (Whittier Tunnel) into the worlds only dual-use highway/railroad tunnel with one way reversible highway t...
Financial analysis of potential retrospective premium assessments under the Price-Anderson system
Energy Technology Data Exchange (ETDEWEB)
Wood, R.S.
1985-04-01
Ten representative nuclear utilities have been analyzed over the period 1981 to 1983 to evaluate the effects of three levels of retrospective premiums on various financial indicators. This analysis continues and expands on earlier analyses prepared as background for deliberations by the US Congress for possible extension or modification of the Price-Anderson Act.
Spin-Polarized Semiconductor Induced by Magnetic Impurities in Graphene
Daghofer, Maria; Zheng, Nan; Moreo, Adriana
2010-01-01
Magnetic impurities adsorbed on graphene are coupled magnetically via the itinerant electrons. This interaction opens a gap in the band structure of graphene. The result strongly depends on how the magnetic impurities are distributed. While random doping produces a semiconductor, if all or most impurities are located in the same sublattice, the spin degeneracy is removed and a spin-polarized semiconductor arises.
In vitro genotoxicity of piperacillin impurity-A | Vijayan | African ...
African Journals Online (AJOL)
Since no report of genotoxicity data is available on the impurities of piperacillin, further studies were designed and conducted to provide information for establishing the safety profile and qualification of the piperacillin impurity-A. Salmonella typhimurium strains were exposed to Piperacillin impurity-A for Ames tests. Neither ...
Impurity diagnostics in the GAMMA 10 tandem mirror
Energy Technology Data Exchange (ETDEWEB)
Yoshikawa, M.; Okamoto, Y.; Kawamori, E.; Ito, T.; Watabe, C.; Watanabe, Y.; Tamano, T. [Plasma Research Center, University of Tsukuba, Tsukuba, Ibaraki (Japan); Ikeda, K. [National Inst. for Fusion Science, Toki, Gifu (Japan); Yamaguchi, N. [Toyota Technological Institute, Nagoya, Aichi (Japan)
2000-01-01
We have constructed spectroscopic measurement systems in the wavelength range from soft X-ray to visible lights. We observed absolute impurity line intensities, Doppler line broadenings and Doppler shifts of impurity lines and time dependent radial profiles of the impurity lines in the GAMMA 10 tandem mirror. (author)
Impurity and trace tritium transport in tokamak edge turbulence
DEFF Research Database (Denmark)
Naulin, V.
2005-01-01
The turbulent transport of impurity or minority species, as for example tritium, is investigated in drift-Alfven edge turbulence. The full effects of perpendicular and parallel convection are kept for the impurity species. The impurity density develops a granular structure with steep gradients...
Air impurity in holographic photonic crystals made with dichromated gelatin
Ren, Zhi; Li, Songtao; Liu, Dahe
2010-11-01
The physical mechanism of the air impurity in volume holographic photonic crystals was investigated in this paper. The photonic forbidden band with the air impurity was analyzed and calculated by the transfer matrix method. Verifications were carried out using one dimensional holographic photonic crystals made with Dichromated Gelatin (DCG), and the impurity modes were observed.
International Nuclear Information System (INIS)
Thome, L.; Bernas, H.; Cohen, C.
1978-01-01
The relation between the hyperfine interaction (HFI) and the lattice location of heavy impurities in iron is discussed in the light of results (see companion papers) on 169 Yb, 175 Yb and Au in Fe. A compilation of all known results in Fe and Cu reveals a simple correlation between the difference in atomic radii of implanted and host atoms and the corrected extinction ratio in lattice location experiments. A simple model is developed to account simultaneously for the annealing -and implantation- temperature dependence of the impurity HFI and lattice location in Fe between room temperature and 800K. It is based on existing information concerning the nature and evolution of radiation damage in Fe: impurity evolution is described in terms of a two-stage process involving (i) vacancy migration towards the impurity and (ii) migration of the impurity-vacancy complex, with the latter stage being much faster than the former. Quantitative agreement is found with our experimental results, as well as with results obtained on other impurities in Fe. It is suggested that the model is applicable in all cases where vacancy motion determines impurity evolution
Effects of magnetic impurities on transport in 2D topological insulators
Dang, Xiaoqian; Burton, J. D.; Tsymbal, Evgeny
Understanding the transport properties of topological insulators could bring such materials from fundamental research to potential applications. Here we report on the theoretical investigations of the effects of magnetic impurities on transport properties of model two-dimensional (2D) topological insulators (TIs). We utilize the tight-binding form of the Bernevig-Hughes-Zhang model and investigate the transport properties by employing the Landauer-Büttiker formalism. We explore the current distribution in 2D TIs resulting from scattering by a magnetic impurity which breaks time-reversal symmetry. We find that a magnetic impurity could drive anti-resonant behavior of the conductance, as revealed from full backscattering of the electron current flowing at one of the edges of the TI. This phenomenon occurs due to spin-flip scattering when the Fermi energy matches the impurity state and the magnetic moment of the impurity is aligned along the TI edge. Additionally, we explore the effect of an external magnetic gate attached to the system and show that changing the magnetization orientation within the gate allows the control of conductance. This geometric setup could be realized experimentally providing the opportunity to tune transport properties of 2D TIs by a magnetic gate.
On an layer-by-layer analysis of impurity profiles by ions of chemically active gases
International Nuclear Information System (INIS)
Kornich, G.V.; Kornilova, L.O.; Teplov, S.V.
1992-01-01
A phenomenological model of layer-by-layer analysis by oxygen ions has been described with account taken of the chemical interaction of the bombarding ions with the matrix impurity atoms. The results of the layer-by-layer analysis for a two-layer system of impurity Mg in the Si matrix have been calculated in the framework of the model. It has been concluded that the use of oxygen ions for profiles of Mg and Ca in Si improves the resolvability and increases the sensitivity of the layer-by-layer analysis method
A Spectroscopic Study of Impurity Behavior in Neutral-beam and Ohmically Heated TFTR Discharges
Stratton, B. C.; Ramsey, A. T.; Boody, F. P.; Bush, C. E.; Fonck, R. J.; Groenbner, R. J.; Hulse, R. A.; Richards, R. K.; Schivell, J.
1987-02-01
Quantitative spectroscopic measurements of Z{sub eff}, impurity densities, and radiated power losses have been made for ohmic- and neutral-beam-heated TFTR discharges at a plasma current of 2.2 MA and toroidal field of 4.7 T. Variations in these quantities with line-average plasma density (anti n{sub e}) and beam power up to 5.6 MW are presented for discharges on a graphite movable limiter. A detailed discussion of the use of an impurity transport model to infer absolute impurity densities and radiative losses from line intensity and visible continuum measurements is given. These discharges were dominated by low-Z impurities with carbon having a considerably higher density than oxygen, except in high-anti n{sub e} ohmic discharges, where the densities of carbon and oxygen were comparable. Metallic impurity concentrations and radiative losses were small, resulting in hollow radiated power profiles and fractions of the input power radiated being 30 to 50% for ohmic heating and 30% or less with beam heating. Spectroscopic estimates of the radiated power were in good agreement with bolometrically measured values. Due to an increase in the carbon density, Z{sub eff} rose from 2.0 to 2.8 as the beam power increased from 0 to 5.6 MW, pointing to a potentially serious dilution of the neutron-producing plasma ions as the beam power increased. Both the low-Z and metallic impurity concentrations were approximately constant with minor radius, indicating no central impurity accumulation in these discharges.
Energy Technology Data Exchange (ETDEWEB)
Montoya, R., E-mail: rodrigo.montoya@cenim.csic.es [Centro Nacional de Investigaciones Metalurgicas, CENIM, CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain); Departamento de Matematicas, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, UNAM, Ciudad Universitaria, 04510 Mexico D.F. (Mexico); Departamento de Ingenieria Metalurgica, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, UNAM, Ciudad Universitaria, 04510 Mexico D.F. Mexico (Mexico); Escudero, M.L., E-mail: escudero@cenim.csic.es [Centro Nacional de Investigaciones Metalurgicas, CENIM, CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain); Garcia-Alonso, M.C., E-mail: crisga@cenim.csic.es [Centro Nacional de Investigaciones Metalurgicas, CENIM, CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain)
2011-12-15
Highlights: Black-Right-Pointing-Pointer Degradation of Mg due to the presence of impurities by finite element method. Black-Right-Pointing-Pointer A thin film of electrolyte causes galvanic corrosion focused only close on impurities. Black-Right-Pointing-Pointer A thick layer of electrolyte provokes galvanic corrosion extended the whole surface. Black-Right-Pointing-Pointer A higher number of impurities causes galvanic corrosion on the Mg surface independently of electrolyte thickness. Black-Right-Pointing-Pointer The electrolyte thickness is an important variable that affects the in vivo degradation. - Abstract: The aim of this work is to study the degradation of magnesium due to the presence of impurities, by finite element method (FEM), when different thickness of physiological medium bathes the surface. The electrochemical experimental data obtained from polarization curves are used to model mathematically the corrosion process by solving the Laplace equation and the proper boundary conditions by means of FEM. The results show that when Mg is covered by a thin film of electrolyte, galvanic corrosion is focused only on the areas located really close to the cathodic sites, and far from the impurities, the Mg matrix remains near to its corrosion potential with a natural corrosion process. However, if the Mg matrix is completely covered by a thick layer of electrolyte the potentials obtained in the Mg surface far from the impurity are higher than its corrosion potential, so the Mg suffers more severe galvanic corrosion. On the other hand, when a higher number of impurities is considered, the Mg matrix is anodically polarized and it suffers severe galvanic corrosion, independently of h. The thickness of the electrolyte h must be considered as an important variable that affects the in vivo degradation.
Bernal, S R; Murrieta, H
1998-01-01
The amount of first stage coloration in NaCl doped with Sn has been investigated as a function of the gamma-irradiation dose rate and impurity concentration. It was ascertained that in all cases the amount of first stage coloration is proportional to the square root of gamma-irradiation dose rate as well as the square root of the impurity concentration in agreement with the theoretical models developed by Comins and Carragher and our group for F-center production in the alkali halides doped with divalent impurities.
Kinetic neoclassical calculations of impurity radiation profiles
Directory of Open Access Journals (Sweden)
D.P. Stotler
2017-08-01
Full Text Available Modifications of the drift-kinetic transport code XGC0 to include the transport, ionization, and recombination of individual charge states, as well as the associated radiation, are described. The code is first applied to a simulation of an NSTX H-mode discharge with carbon impurity to demonstrate the approach to coronal equilibrium. The effects of neoclassical phenomena on the radiated power profile are examined sequentially through the activation of individual physics modules in the code. Orbit squeezing and the neoclassical inward pinch result in increased radiation for temperatures above a few hundred eV and changes to the ratios of charge state emissions at a given electron temperature. Analogous simulations with a neon impurity yield qualitatively similar results.
Quantitative spectrographic analysis of impurities in antimonium
International Nuclear Information System (INIS)
Brito, J. de; Gomes, R.P.
1978-01-01
An emission spectrographic method is describe for the determination of Ag, Al, As, Be, Bi, Cd, Cr, Cu, Ga, Ni, Pb, Sn, Si, and Zn in high purity antimony metal. The metal sample ia dissolved in nitric acid(1:1) and converted tp oxide by calcination at 900 0 C for one hour. The oxide so obtained is mixed with graphite, which is used as a spectroscopic buffer, and excited by a direct current arc. Many parameters are studied optimum conditions are selected for the determination of the impurities mentioned. The spectrum is photographed in the second order of a 15.000 lines per inch grating and the most sensitive lines for the elements are selected. The impurities are determined in the concentration range of 1 - 0,01% with a precision of approximately 10% [pt
Impurities enhance caking in lactose powder
DEFF Research Database (Denmark)
Carpin, M.; Bertelsen, H.; Dalberg, A.
2017-01-01
Caking of lactose and other dry ingredients is a common problem in the dairy and food industries. The lactose production process includes different purification steps, depending on the type of lactose produced. The aim of this study was therefore to investigate how the remaining impurities (i.......e. non-lactose components) affect the caking tendency of the final powder. The results from a combination of different methods, including dynamic vapor sorption, characterization of the physicochemical composition and assessment of caking with a ring shear tester, suggested humidity caking. Larger...... amounts of impurities in the lactose powder resulted in enhanced moisture sorption and greater caking tendency. These findings emphasize the importance of controlling the washing and purification steps throughout the production process in order to limit caking in the final product...
Influence of impurities on silicide contact formation
International Nuclear Information System (INIS)
Kazdaev, Kh.R.; Meermanov, G.B.; Kazdaev, R.Kh.
2002-01-01
Research objectives of this work are to investigate the influence of light impurities implantation on peculiarities of the silicides formation in molybdenum monocrystal implanted by silicon, and in molybdenum films sputtered on silicon substrate at subsequent annealing. Implantation of the molybdenum samples was performed with silicon ions (90 keV, 5x10 17 cm -2 ). Phase identification was performed by X ray analysis with photographic method of registration. Analysis of the results has shown the formation of the molybdenum silicide Mo 3 Si at 900 deg. C. To find out the influence of impurities present in the atmosphere (C,N,O) on investigated processes we have applied combined implantation. At first, molybdenum was implanted with ions of the basic component (silicon) and then -- with impurities ions. Acceleration energies (40keV for C, 45 keV for N and 50 keV for O) were chosen to obtain the same distribution profiles for basic and impurities ions. Ion doses were 5x10 17 cm -2 for Si-ions and 5x10 16 cm -2 - for impurities. The most important results are reported here. The first, for all three kinds of impurities the decreased formation temperatures of the phase Mo 3 Si were observed; in the case of C and N it was ∼100 deg. and in the case of nitrogen - ∼200 deg. Further, simultaneously with the Mo 3 Si phase, the appearance of the rich-metal phase Mo 5 Si 3 was registered (not observed in the samples without additional implantation). In case of Mo/Si-structure, the implantation of the impurities (N,O) was performed to create the peak concentration (∼4at/%) located in the middle of the molybdenum film (∼ 150nm) deposited on silicon substrate. Investigation carried out on unimplanted samples showed the formation of the silicide molybdenum MoSi 2 , observed after annealing at temperatures 900/1000 deg. C, higher than values 500-600 deg. C reported in other works. It is discovered that electrical conductivity of Mo 5 Si 3 -films synthesized after impurities
INTOR impurity control and first wall system
International Nuclear Information System (INIS)
Abdou, M.A.
1983-04-01
The highlights of the recent INTOR effort on examining the key issues of the impurity control/first wall system are summarized. The emphasis of the work was an integrated study of the edge-region physics, plasma-wall interaction, materials, engineering and magnetic considerations associated with the poloidal divertor and pump limiter. The development of limiter and divertor collector plate designs with an acceptable lifetime was a major part of the work
Hopkins, R. H.; Davis, J. R.; Rohatgi, A.; Campbell, R. B.; Blais, P. D.; Rai-Choudhury, P.; Stapleton, R. E.; Mollenkopf, H. C.; Mccormick, J. R.
1980-01-01
Two major topics are treated: methods to measure and evaluate impurity effects in silicon and comprehensive tabulations of data derived during the study. Discussions of deep level spectroscopy, detailed dark I-V measurements, recombination lifetime determination, scanned laser photo-response, conventional solar cell I-V techniques, and descriptions of silicon chemical analysis are presented and discussed. The tabulated data include lists of impurity segregation coefficients, ingot impurity analyses and estimated concentrations, typical deep level impurity spectra, photoconductive and open circuit decay lifetimes for individual metal-doped ingots, and a complete tabulation of the cell I-V characteristics of nearly 200 ingots.
Evaluation of determinative methods for sodium impurities
International Nuclear Information System (INIS)
Molinari, Marcelo; Guido, Osvaldo; Botbol, Jose; Ares, Osvaldo
1988-01-01
Sodium, universally accepted as heat transfer fluid in fast breeder reactors, requires a special technology for every operation involved in any applicable methodology, due to its well known chemical reactivity. The purpose of this work is: a) to study the sources and effects of chemical species which, as traces, accompany sodium used in the nuclear field; b) to classify, taking into account, the present requirements and resources of the National Atomic Energy Commission (CNEA), the procedures found in the literature for determination of the most important impurities which exist in experimental liquid sodium systems and c) to describe the principles of the methods and to evaluate them in order to make a selection. It was concluded the convenience to develop, as a first stage, laboratory procedures to determine carbon, oxygen, hydrogen and non-volatile impurities, which besides serving present needs, will be referential for direct methods with undeferred response. The latter are needed in liquid sodium experimental loops and require, primarily, more complex and extended development. Additionally, a description is made of experimental work performed up-to-now in this laboratory, consisting of a transfer device for sodium sampling and a sodium distillation device, adapted from a previous design, with associated vacuum and inert gas systems. It is intended as a separative technique for indirect determination of oxygen and non-volatile impurities. (Author) [es
Metal impurity release in diverted tokamak discharges
International Nuclear Information System (INIS)
Staudenmaier, G.; Wampler, W.R.
1987-01-01
Plasma-materials interaction at the wall of the main plasma chamber of the divertor tokamak ASDEX was investigated by a combined probe, allowing simultaneous measurements of the erosion rate by neutral particles, and the flux and average energy of neutrals. The erosion was measured by collecting part of the released material which was analysed subsequently by electron induced X-ray analysis. The flux and energy of the impinging neutral particles were measured after each single discharge with an energy resolving carbon resistance probe. The carbon probe is an excellent detector not only for deuterium but also for energetic neutral helium atoms. Wall sputtering by CX neutrals is the dominant iron impurity source in ohmically heated deuterium discharges. However, during discharges in helium not only CX neutral sputtering but also sputtering by helium ions is an important impurity release mechanism. But during auxiliary heating by neutral beams and radio frequency in deuterium, impurity generation by CX neutrals was found to increase with heating power. (orig.)
Nag, Tanay; Rajak, Atanu
2018-04-01
We investigate the effect of a time-reversal-breaking impurity term (of strength λd) on both the equilibrium and nonequilibrium critical properties of entanglement entropy (EE) in a three-spin-interacting transverse Ising model, which can be mapped to a p -wave superconducting chain with next-nearest-neighbor hopping and interaction. Importantly, we find that the logarithmic scaling of the EE with block size remains unaffected by the application of the impurity term, although, the coefficient (i.e., central charge) varies logarithmically with the impurity strength for a lower range of λd and eventually saturates with an exponential damping factor [˜exp(-λd) ] for the phase boundaries shared with the phase containing two Majorana edge modes. On the other hand, it receives a linear correction in term of λd for an another phase boundary. Finally, we focus to study the effect of the impurity in the time evolution of the EE for the critical quenching case where the impurity term is applied only to the final Hamiltonian. Interestingly, it has been shown that for all the phase boundaries, contrary to the equilibrium case, the saturation value of the EE increases logarithmically with the strength of impurity in a certain regime of λd and finally, for higher values of λd, it increases very slowly dictated by an exponential damping factor. The impurity-induced behavior of EE might bear some deep underlying connection to thermalization.
Ab initio study of the EFG tensor at Cd impurities in Sc{sub 2}O{sub 3} semiconductor
Energy Technology Data Exchange (ETDEWEB)
Munoz, E.L.; Richard, D. [Departamento de Fisica and IFLP (CONICET-UNLP), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CC 67, 1900 La Plata (Argentina); Errico, L.A. [Departamento de Fisica and IFLP (CONICET-UNLP), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CC 67, 1900 La Plata (Argentina); Universidad Nacional del Noroeste Bonaerense (UNNOBA), Monteagudo 2772, Pergamino, CP 2700 Buenos Aires (Argentina); Renteria, M., E-mail: renteria@fisica.unlp.edu.a [Departamento de Fisica and IFLP (CONICET-UNLP), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CC 67, 1900 La Plata (Argentina)
2009-10-01
We present an ab initio study of diluted Cd impurities localized at both cation sites of the semiconductor Sc{sub 2}O{sub 3}. The electric-field-gradient (EFG) tensor at Cd impurities located at both cationic sites of the host structure was determined from the calculation of the electronic structure of the doped system. Calculations were performed with the full-potential augmented-plane wave plus local orbitals (APW+lo) method within the framework of the density functional theory. We studied the atomic structural relaxations and the perturbation of the electronic charge density induced by the impurities in the host system in a fully self-consistent way. We showed that the Cd impurity introduces an increase of 8% in the nearest oxygen neighbors bond-lengths, changing the EFG sign for probes located at the asymmetric cation site. The APW+lo predictions for the charged state of the Cd impurity were compared with EFG results existent in the literature, coming from time-differential gamma-gamma perturbed-angular-correlations experiments performed on {sup 111}Cd-implanted Sc{sub 2}O{sub 3} powder samples. From the excellent agreement between theory and experiment, we can strongly suggest that the Cd acceptor impurities are ionized at room temperature. Finally, we showed that simple calculations like those performed within the point-charge model with antishielding factors do not correctly describe the problem of a Cd impurity in Sc{sub 2}O{sub 3}.
Impurities in a non-axisymmetric plasma: Transport and effect on bootstrap current
Energy Technology Data Exchange (ETDEWEB)
Mollén, A., E-mail: albertm@chalmers.se [Department of Applied Physics, Chalmers University of Technology, Göteborg (Sweden); Max-Planck-Institut für Plasmaphysik, 17491 Greifswald (Germany); Landreman, M. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States); Smith, H. M.; Helander, P. [Max-Planck-Institut für Plasmaphysik, 17491 Greifswald (Germany); Braun, S. [Max-Planck-Institut für Plasmaphysik, 17491 Greifswald (Germany); German Aerospace Center, Institute of Engineering Thermodynamics, Pfaffenwaldring 38-40, D-70569 Stuttgart (Germany)
2015-11-15
Impurities cause radiation losses and plasma dilution, and in stellarator plasmas the neoclassical ambipolar radial electric field is often unfavorable for avoiding strong impurity peaking. In this work we use a new continuum drift-kinetic solver, the SFINCS code (the Stellarator Fokker-Planck Iterative Neoclassical Conservative Solver) [M. Landreman et al., Phys. Plasmas 21, 042503 (2014)] which employs the full linearized Fokker-Planck-Landau operator, to calculate neoclassical impurity transport coefficients for a Wendelstein 7-X (W7-X) magnetic configuration. We compare SFINCS calculations with theoretical asymptotes in the high collisionality limit. We observe and explain a 1/ν-scaling of the inter-species radial transport coefficient at low collisionality, arising due to the field term in the inter-species collision operator, and which is not found with simplified collision models even when momentum correction is applied. However, this type of scaling disappears if a radial electric field is present. We also use SFINCS to analyze how the impurity content affects the neoclassical impurity dynamics and the bootstrap current. We show that a change in plasma effective charge Z{sub eff} of order unity can affect the bootstrap current enough to cause a deviation in the divertor strike point locations.
Li, Jun; Ji, Min; Schwarz, Tobias; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Yuan, Jie; Pereira, Paulo J.; Huang, Ya; Zhang, Gufei; Feng, Hai-Luke; Yuan, Ya-Hua; Hatano, Takeshi; Kleiner, Reinhold; Koelle, Dieter; Chibotaru, Liviu F.; Yamaura, Kazunari; Wang, Hua-Bing; Wu, Pei-Heng; Takayama-Muromachi, Eiji; Vanacken, Johan; Moshchalkov, Victor V.
2015-01-01
The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors. Here we demonstrate the local destruction of superconductivity by non-magnetic zinc impurities in Ba0.5K0.5Fe2As2 by exploring phase-slip phenomena in a mesoscopic structure with 119 × 102 nm2 cross-section. The impurities suppress superconductivity in a three-dimensional ‘Swiss cheese'-like pattern with in-plane and out-of-plane characteristic lengths slightly below ∼1.34 nm. This causes the superconducting order parameter to vary along abundant narrow channels with effective cross-section of a few square nanometres. The local destruction of superconductivity can be related to Cooper pair breaking by non-magnetic impurities. PMID:26139568
Li, Jun; Ji, Min; Schwarz, Tobias; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Yuan, Jie; Pereira, Paulo J; Huang, Ya; Zhang, Gufei; Feng, Hai-Luke; Yuan, Ya-Hua; Hatano, Takeshi; Kleiner, Reinhold; Koelle, Dieter; Chibotaru, Liviu F; Yamaura, Kazunari; Wang, Hua-Bing; Wu, Pei-Heng; Takayama-Muromachi, Eiji; Vanacken, Johan; Moshchalkov, Victor V
2015-07-03
The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors. Here we demonstrate the local destruction of superconductivity by non-magnetic zinc impurities in Ba0.5K0.5Fe2As2 by exploring phase-slip phenomena in a mesoscopic structure with 119 × 102 nm(2) cross-section. The impurities suppress superconductivity in a three-dimensional 'Swiss cheese'-like pattern with in-plane and out-of-plane characteristic lengths slightly below ∼1.34 nm. This causes the superconducting order parameter to vary along abundant narrow channels with effective cross-section of a few square nanometres. The local destruction of superconductivity can be related to Cooper pair breaking by non-magnetic impurities.
Radiated Power and Impurity Concentrations in the EXTRAP-T2R Reversed-Field Pinch
Corre, Y.; Rachlew, E.; Cecconello, M.; Gravestijn, R. M.; Hedqvist, A.; Pégourié, B.; Schunke, B.; Stancalie, V.
2005-01-01
A numerical and experimental study of the impurity concentration and radiation in the EXTRAP-T2R device is reported. The experimental setup consists of an 8-chord bolometer system providing the plasma radiated power and a vacuum-ultraviolet spectrometer providing information on the plasma impurity content. The plasma emissivity profile as measured by the bolometric system is peaked in the plasma centre. A one dimensional Onion Skin Collisional-Radiative model (OSCR) has been developed to compute the density and radiation distributions of the main impurities. The observed centrally peaked emissivity profile can be reproduced by OSCR simulations only if finite particle confinement time and charge-exchange processes between plasma impurities and neutral hydrogen are taken into account. The neutral hydrogen density profile is computed with a recycling code. Simulations show that recycling on metal first wall such as in EXTRAP-T2R (stainless steel vacuum vessel and molybdenum limiters) is compatible with a rather high neutral hydrogen density in the plasma centre. Assuming an impurity concentration of 10% for oxygen and 3% for carbon compared with the electron density, the OSCR calculation including lines and continuum emission reproduces about 60% of the total radiated power with a similarly centrally peaked emissivity profile. The centrally peaked emissivity profile is due to low ionisation stages and strongly radiating species in the plasma core, mainly O4+ (Be-like) and C3+ Li-like.
Scaling with toroidal current of impurity transport in ATC
International Nuclear Information System (INIS)
Marmar, E.S.; Cohen, S.A.; Cecchi, J.L.
1976-06-01
An experiment measuring the scaling with changing plasma conditions of a parameter characteristic of the transport of aluminum injected into the ATC tokamak is discussed. This parameter is the time after injection at which the photon signal from Al XI reaches its maximum. It is found that the data are in agreement with the predictions of a computer code which uses neoclassical theory in the Pfirsch-Schluter regime. An approximate model describing impurity transport in ATC is also presented. This model is utilized to calculate the expected scaling with current of the aluminum transport assuming classical, neoclassical and pseudoclassical forms for the diffusion coefficient. The data are in agreement with both the neoclassical and pseudoclassical results from this model
First-principles study on Ni3Al (111 ) antiphase boundary with Ti and Hf impurities
Sun, Ruoshi; Woodward, Christopher; van de Walle, Axel
2017-06-01
The effect of Ti and Hf impurities on the (111 ) antiphase boundary (APB) energy of Ni3Al is investigated via ab initio calculations. Cluster expansion is performed to predict supercell total energies sampled in a Monte Carlo approach that accounts for nondilute point defects at finite temperature, obtaining APB energies as a function of impurity concentration and temperature. Of the two ternary elements, Hf is more effective in increasing the APB energy. While the (111 ) APB energy of a pure L1 2 material requires at least second-nearest-neighbor interactions, we observe a strong correlation between impurity-induced APB energy enhancement and formation of first-nearest-neighbor Ni-Ni bonds across the APB due to symmetry breaking. Using a linear-chain model and effective bond energies derived from effective cluster interactions, we propose a mechanism that explains why Hf is more effective than Ti.
Enhanced impurity-limited mobility in ultra-scaled Si nanowire junctionless field-effect transistors
Ueda, Akiko; Luisier, Mathieu; Sano, Nobuyuki
2015-12-01
We examine the transport properties of heavily doped ultra-scaled Si junctionless nanowire field-effect transistors, by means of atomistic quantum transport simulations based on the s p 3 d 5 s ∗ tight-binding model, the nonequilibrium Green's function formalism, and including electron-phonon scattering. Each individual doping atom is treated explicitly and its potential is determined by solving the Poisson equation. The impurity atoms are assumed to be aligned along a single line or to slightly vary from this well-ordered configuration. We find that the impurity-limited mobility enhances as the carrier concentration increases due to the screening effect. The mobility also improves with the doping concentration because closely placed impurities induce resonant tunneling states that positively affect the current magnitude. This behavior is found to persist even in the case of slight disorder.
Nozato, Hideaki; Morita, Shigeru; Goto, Motoshi
2005-07-01
Recycling coefficients of carbon, aluminum, and titanium were evaluated using a new technique combining impurity pellet injection with high-spatial resolution bremsstrahlung measurement in hydrogen and helium plasmas on the large helical device. The recycling coefficient of impurities was investigated by measuring absolute intensities with the visible bremsstrahlung array. The time evolution of the bremsstrahlung signals was modeled by an impurity transport code adjusting the diffusion coefficient, convective velocity, and recycling coefficient. As a result, a finite value of the recycling coefficient was required in the case of carbon, whereas aluminum and titanium were explained as nonrecycled particles. It was also clarified that the recycling coefficient of carbon had a larger value in hydrogen plasmas (R =0.5 -0.65 ) than in helium plasmas (R =0 -0.2 ) , suggesting the formation of hydrogen molecules.
Crossover physics in the nonequilibrium dynamics of quenched quantum impurity systems.
Vasseur, Romain; Trinh, Kien; Haas, Stephan; Saleur, Hubert
2013-06-14
A general framework is proposed to tackle analytically local quantum quenches in integrable impurity systems, combining a mapping onto a boundary problem with the form factor approach to boundary-condition-changing operators introduced by Lesage and Saleur [Phys. Rev. Lett. 80, 4370 (1998)]. We discuss how to compute exactly the following two central quantities of interest: the Loschmidt echo and the distribution of the work done during the quantum quench. Our results display an interesting crossover physics characterized by the energy scale T(b) of the impurity corresponding to the Kondo temperature. We discuss in detail the noninteracting case as a paradigm and benchmark for more complicated integrable impurity models and check our results using numerical methods.
Impurity-related nonlinear optical properties in delta-doped quantum rings: Electric field effects
International Nuclear Information System (INIS)
Restrepo, R.L.; Morales, A.L.; Martínez-Orozco, J.C.; Baghramyan, H.M.; Barseghyan, M.G.; Mora-Ramos, M.E.; Duque, C.A.
2014-01-01
Using a variational procedure within the effective mass approximation, we have calculated the donor impurity binding energy for the ground (1s-like) and the excited (2p z -like) states as well as the impurity-related nonlinear optical absorption and relative changes in the refraction index in a GaAs single quantum ring with axial n-type delta-doping. The delta-like potential along the z-direction is an approximate model analytically described using a Lorentzian function with two parameters. Additionally we consider the application of an electric field along the z-direction. It is found that the changes in the geometry of the quantum ring, the change in the 2D impurity density of the delta-like doping, and different values of the electric field lead to a shifting of the resonant peaks of the optical responses spectrum
Direct observation of Anderson localization of matter waves in a controlled disorder.
Billy, Juliette; Josse, Vincent; Zuo, Zhanchun; Bernard, Alain; Hambrecht, Ben; Lugan, Pierre; Clément, David; Sanchez-Palencia, Laurent; Bouyer, Philippe; Aspect, Alain
2008-06-12
In 1958, Anderson predicted the localization of electronic wavefunctions in disordered crystals and the resulting absence of diffusion. It is now recognized that Anderson localization is ubiquitous in wave physics because it originates from the interference between multiple scattering paths. Experimentally, localization has been reported for light waves, microwaves, sound waves and electron gases. However, there has been no direct observation of exponential spatial localization of matter waves of any type. Here we observe exponential localization of a Bose-Einstein condensate released into a one-dimensional waveguide in the presence of a controlled disorder created by laser speckle. We operate in a regime of pure Anderson localization, that is, with weak disorder-such that localization results from many quantum reflections of low amplitude-and an atomic density low enough to render interactions negligible. We directly image the atomic density profiles as a function of time, and find that weak disorder can stop the expansion and lead to the formation of a stationary, exponentially localized wavefunction-a direct signature of Anderson localization. We extract the localization length by fitting the exponential wings of the profiles, and compare it to theoretical calculations. The power spectrum of the one-dimensional speckle potentials has a high spatial frequency cutoff, causing exponential localization to occur only when the de Broglie wavelengths of the atoms in the expanding condensate are greater than an effective mobility edge corresponding to that cutoff. In the opposite case, we find that the density profiles decay algebraically, as predicted in ref. 13. The method presented here can be extended to localization of atomic quantum gases in higher dimensions, and with controlled interactions.
ALONE, UNARMED, AND UNAFRAID OVER CUBA: THE STORY OF MAJOR RUDY ANDERSON
2017-06-01
invasion which would include the use of US 2 Ted Shelton, “The Major Flew Into the Page of History ...President worried aloud that any type of retaliatory airstrike would spiral into a global nuclear war: “It isn’t the first step that concerns me...yes sir”12 and official SAC history and USAF accounts of the crisis gave Heyser and Anderson equal credit for taking the first photos.13
Directory of Open Access Journals (Sweden)
Frederico Carlos Jaña Neto
2016-04-01
Full Text Available OBJECTIVE: To analyze the characteristics of patients with Gustilo-Anderson Type III open tibial fractures treated at a tertiary care hospital in São Paulo between January 2013 and August 2014. METHODS: This was a cross-sectional retrospective study. The following data were gathered from the electronic medical records: age; gender; diagnosis; trauma mechanism; comorbidities; associated fractures; Gustilo and Anderson, Tscherne and AO classifications; treatment (initial and definitive; presence of compartment syndrome; primary and secondary amputations; MESS (Mangled Extremity Severity Score index; mortality rate; and infection rate. RESULTS: 116 patients were included: 81% with fracture type IIIA, 12% IIIB and 7% IIIC; 85% males; mean age 32.3 years; and 57% victims of motorcycle accidents. Tibial shaft fractures were significantly more prevalent (67%. Eight patients were subjected to amputation: one primary case and seven secondary cases. Types IIIC (75% and IIIB (25% predominated among the patients subjected to secondary amputation. The MESS index was greater than 7 in 88% of the amputees and in 5% of the limb salvage group. CONCLUSION: The profile of patients with open tibial fracture of Gustilo and Anderson Type III mainly involved young male individuals who were victims of motorcycle accidents. The tibial shaft was the segment most affected. Only 7% of the patients underwent amputation. Given the current controversy in the literature about amputation or salvage of severely injured lower limbs, it becomes necessary to carry out prospective studies to support clinical decisions.
Emerce, Esra; Cok, Ismet; Degim, I Tuncer
2015-10-14
Impurities affecting safety, efficacy, and quality of pharmaceuticals are of increasing concern for regulatory agencies and pharmaceutical industries, since genotoxic impurities are understood to play important role in carcinogenesis. The study aimed to analyse impurities of montelukast chronically used in asthma theraphy and perform genotoxicological assessment considering regulatory approaches. Impurities (sulfoxide, cis-isomer, Michael adducts-I&II, methylketone, methylstyrene) were quantified using RP-HPLC analysis on commercial products available in Turkish market. For sulfoxide impurity, having no toxicity data and found to be above the qualification limit, in silico mutagenicity prediction analysis, miniaturized bacterial gene mutation test, mitotic index determination and in vitro chromosomal aberration test w/wo metabolic activation system were conducted. In the analysis of different batches of 20 commercial drug products from 11 companies, only sulfoxide impurity exceeded qualification limit in pediatric tablets from 2 companies and in adult tablets from 7 companies. Leadscope and ToxTree programs predicted sulfoxide impurity as nonmutagenic. It was also found to be nonmutagenic in Ames MPF Penta I assay. Sulfoxide impurity was dose-dependent cytotoxic in human peripheral lymphocytes, however, it was found to be nongenotoxic. It was concluded that sulfoxide impurity should be considered as nonmutagenic and can be classified as ordinary impurity according to guidelines. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
Zn vacancy-donor impurity complexes in ZnO
Frodason, Y. K.; Johansen, K. M.; Bjørheim, T. S.; Svensson, B. G.; Alkauskas, A.
2018-03-01
Results from hybrid density functional theory calculations on the thermodynamic stability and optical properties of the Zn vacancy (VZn) complexed with common donor impurities in ZnO are reported. Complexing VZn with donors successively removes its charge-state transition levels in the band gap, starting from the most negative one. Interestingly, the presence of a donor leads only to modest shifts in the positions of the VZn charge-state transition levels, the sign and magnitude of which can be interpreted from a polaron energetics model by taking hole-donor repulsion into account. By employing a one-dimensional configuration coordinate model, luminescence lineshapes and positions were calculated. Due to the aforementioned effects, the isolated VZn gradually changes from a mainly nonradiative defect with transitions in the infrared region in n -type material, to a radiative one with broad emission in the visible range when complexed with shallow donors.
Impurity-controlled recrystallization in natural fluorite
Duschl, Florian; Wischhöfer, Philipp; Vollbrecht, Axel
2017-04-01
Microfabrics in natural fluorite from stratiform fluorite occurrences in Zechstein carbonate rocks (Ca2) near Eschwege (Germany) exhibit complex recrystallization features with different stages of accretive crystallization. Thin sections were studied using standard petrographic microscopy and hot-cathodoluminescence microscopy (CL); to identify fluid inclusion composition microthermometric analysis was applied. Though fluorite occurs in various forms at the locality, the focus of this study lies on early-diagenetic fluorite that replaced aragonitic ooids in the Zechstein carbonate. It can be subdivided into three groups: (I) brown or violet, impurity-rich replacement fluorite, (II) aggregates of parallel, bar-shaped or fibrous crystals with brown to violet grain boundaries, and (III) white fluorite grains with rectangular to mostly polygonal grain boundaries. Type (III) is the product of merged type (II) crystal aggregates. Artificial decoration of fluorite grain surfaces due to CL-induced electron irradiation (acceleration voltage: 14 kV) helped to visualize otherwise invisible crystallographic features. This technique revealed a strong crystallographic control on bar-shaped fluorite (type II) at an early stage of recrystallization. Parallel bundles of type (II) crystals show a crystallographic preferred orientation after {100}, that is no longer apparent after consumption by type (III) fluorite and formation of polygonal grains. Impurities such as fluid and solid inclusions in type (I) fluorite were segregated during progressive recrystallization; subsequently, solid and fluid inclusions accumulated along newly formed grain boundaries. Increase in grain size due to recrystallization is locally hindered by the concentration of impurities along grain boundaries. Therefore, we assume that impurity-controlled recrystallization not only influenced the formation of bar-shaped crystals prior to the development of a polygonal fabric, but locally also strongly affected
Spectrophotometric determination of zinc in impure solutions
International Nuclear Information System (INIS)
Rodriguez Hernandez, B.; Reyes Tamaral, A.
1972-01-01
A dithizone colorimetric method is described for determining zinc concentrations of 0.001 to 5 g/l in aqueous solutions from Rio Tinto Mines, containing copper, iron and other impurities. Citrate, cyanide and bis-2hydroxyethyl)-dithiocarbamate are added to the aqueous sample of masking several metals, and zinc is extracted at pH 5 with a solution of dithizone in carbon tetrachloride. Excess of dithizone is removed with sodium sulphide, and optical density of zinc dithionate in organic solution is measured at 5.35 nm. Calibration curves obey Beer's law up to 0.5 micro Zn/ml. (Author) 5 refs
Enhanced ionized impurity scattering in nanowires
Oh, Jung Hyun; Lee, Seok-Hee; Shin, Mincheol
2013-06-01
The electronic resistivity in silicon nanowires is investigated by taking into account scattering as well as the donor deactivation from the dielectric mismatch. The effects of poorly screened dopant atoms from the dielectric mismatch and variable carrier density in nanowires are found to play a crucial role in determining the nanowire resistivity. Using Green's function method within the self-consistent Born approximation, it is shown that donor deactivation and ionized impurity scattering combined with the charged interface traps successfully to explain the increase in the resistivity of Si nanowires while reducing the radius, measured by Björk et al. [Nature Nanotech. 4, 103 (2009)].
Impurity beam-trapping instability in tokamaks
International Nuclear Information System (INIS)
Hogan, J.T.; Howe, H.C.
1976-01-01
The sensitivity of neutron energy production to the impurity trapping of injected neutral beams is considered. This process is affected by inherent low-Z contamination of the tritium pre-heat plasma, by the species composition of the neutral beam, and by the entrance angle of the beam. The sensitivities of the process to these variables, and to the variation of wall material are compared. One finds that successful use of a low-Z, low-sputtering material can appreciably lengthen the useful pulse length
Impurity beam-trapping instability in tokamaks
International Nuclear Information System (INIS)
Hogan, J.T.; Howe, H.C.
1976-12-01
The sensitivity of neutron energy production to the trapping by impurities by injected neutral beams is considered. The beam-trapping process is affected by inherent low-Z contamination of the tritium plasma, by the species composition of the neutral beam, and by the entrance angle of the beam. The sensitivities of the process are compared to these variables and to the variation with wall material. One finds that use of a low-Z, low sputtering material could retard a possible beam trapping instability
Transitions and excitations in a superfluid stream passing small impurities
Pinsker, Florian
2014-05-08
We analyze asymptotically and numerically the motion around a single impurity and a network of impurities inserted in a two-dimensional superfluid. The criticality for the breakdown of superfluidity is shown to occur when it becomes energetically favorable to create a doublet—the limiting case between a vortex pair and a rarefaction pulse on the surface of the impurity. Depending on the characteristics of the potential representing the impurity, different excitation scenarios are shown to exist for a single impurity as well as for a lattice of impurities. Depending on the lattice characteristics it is shown that several regimes are possible: dissipationless flow, excitations emitted by the lattice boundary, excitations created in the bulk, and the formation of large-scale structures.
Macromolecule Crystal Quality Improvement in Microgravity: The Role of Impurities
Judge, Russell A.; Snell, Edward H.; Pusey, Marc L.; Sportiello, Michael G.; Todd, Paul; Bellamy, Henry; Borgstahl, Gloria E.; Pokros, Matt; Cassanto, John M.
2000-01-01
While macromolecule impurities may affect crystal size and morphology the over-riding question is; "How do macromolecule impurities effect crystal X-ray quality and diffraction resolution?" In the case of chicken egg white lysozyme, crystals can be grown in the presence of a number of impurities without affecting diffraction resolution. One impurity however, the lysozyme dimer, does negatively impact the X-ray crystal properties. Crystal quality improvement as a result of better partitioning of this impurity during crystallization in microgravity has been reported'. In our recent experimental work dimer partitioning was found to be not significantly different between the two environments. Mosaicity analysis of pure crystals showed a reduced mosaicity and increased signal to noise for the microgravity grown crystals. Dimer incorporation however, did greatly reduce the resolution limit in both ground and microgravity grown crystals. These results indicate that impurity effects in microgravity are complex and may rely on the conditions or techniques employed.
FP-LAPW Calculations of the EFG at Cd Impurities in Rutile SnO{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Errico, L. A.; Fabricius, G.; Renteria, M. [Universidad Nacional de La Plata, Instituto de Fisica La Plata (IFLP-CONICET) - Departamento de Fisica, Facultad de Ciencias Exactas (Argentina)
2001-11-15
We report an ab initio study of the electric-field gradient (EFG) at Cd impurities located at the cation site in the semiconductor SnO{sub 2}(rutile phase). The study was performed with the WIEN97 implementation of the FP-LAPW method. In order to simulate the diluted Cd-impurity in the SnO{sub 2} host and to calculate the electronic structure of the system we used a 72-atoms super-cell, studying the relaxation introduced by the impurity in the lattice. The free-relaxation process performed shows that the relaxations of the oxygen nearest-neighbors of the impurity are not isotropic. Our prediction for the EFG tensor are compared with experimental results and point-charge model predictions.
Impurity injection into tokamak plasmas by erosion probes
International Nuclear Information System (INIS)
Hildebrandt, D.; Bakos, J.S.; Buerger, G.; Paszti, F.; Petravich, G.
1987-08-01
Exposing special erosion probes into the edge plasma of MT-1 the impurities Li and Ti were released and contaminated the plasma. By the use of collector probes the torodial transport of these impurities were investigated. The results indicate a preferential impurity flow into codirection of the plasma current. However, the asymmetric component of this flow is much larger than expected from the toroidal drift correlated to the plasma current. (author)
Investigation of Impurity Dynamics at GOL-3 Facility
International Nuclear Information System (INIS)
Polosatkin, S.V.; Burdako, A.V.; Piffl, V.; Postupaev, V.V.; Weinzettl, V.
2005-01-01
Dynamics of light impurities at multimirror trap GOL-3 was studied using imaging spectroscopy diagnostics in VUV and visible spectral range. The results of impurity balance and transport simulation as well as comparison with measurements are presented in this paper. Concentration of impurities in plasma and diffusion coefficient are found out from the measurements. Suitability using VUV and XUV spectroscopy for measuring main plasma parameters is considered
Recommended methods for purification of solvents and tests for impurities
Coetzee, J F
1982-01-01
Recommended Methods for Purification of Solvents and Tests for Impurities is a compilation of recommended procedures for purification of solvents and tests for solvent impurities. Ten solvents are covered: acetonitrile, sulfolane, propylene carbonate, dimethyl sulfoxide, dimethylformamide, hexamethylphosphoramide, pyridine, ethylenediamine, N-methylacetamide, and N-methylpropionamide. This book is comprised of 12 chapters and opens with an introduction to general aspects of impurity effects. The rationale for the selection of solvent is explained, and the relative reactivities of solutes in di
Impurity binding energy for δ-doped quantum well structures
Indian Academy of Sciences (India)
Administrator
Abstract. The binding energy of an impurity delta layer situated either in the centre or at the edge of a quantum well (QW) is theoretically considered for the example of n-type Si0∙8Ge0∙2/Si/Si0∙8Ge0∙2 QW doped with phosphorus. Calculations are made for the case of not so big impurity concentrations, when impurity.
The screening of charged impurities in bilayer graphene
International Nuclear Information System (INIS)
Zhang Wenjing; Li, Lain-Jong
2010-01-01
Positively charged impurities were introduced into a bilayer graphene (BLG) transistor by n-doping with dimethylformamide. Subsequent exposure of the BLG device to moisture resulted in a positive shift of the Dirac point and an increase of hole mobility, suggesting that moisture could reduce the scattering strength of the existing charged impurities. In other words, moisture screened off the 'effective density' of charged impurities. At the early stage of moisture screening the scattering of hole carriers is dominated by long-range Coulomb scatter, but an alternative scattering mechanism should also be taken into consideration when the effective density of impurities is further lowered on moisture exposure.
Isotope effect in impure high T_c superconductors
Mierzynska, M.; Wysokinski, K. I.
2003-01-01
The influence of various kinds of impurities on the isotope shift exponent \\alpha of high temperature superconductors has been studied. In these materials the dopant impurities, like Sr in La_{2-x}Sr_xCuO_4, play different role and usually occupy different sites than impurities like Zn, Fe, Ni {\\it etc} intentionally introduced into the system to study its superconducting properties. In the paper the in-plane and out-of-plane impurities present in layered superconductors have been considered....
Local chemistry of Al and P impurities in silica
DEFF Research Database (Denmark)
Lægsgaard, Jesper; Stokbro, Kurt
2000-01-01
The local structure around Al and P impurities in silica is investigated using density-functional theory. Two distinct cases are considered: impurities substituting for a Si atom in alpha quartz, and impurities implanted in a stoichiometric alpha-quartz crystal. Both impurity elements are found...... to have similar stable substitutional configurations; however, when they are implanted the geometries are quite different: While P prefers to stay in the interstitial region, Al tends to substitute for a Si atom, which in this way is forced into the interstitial region. The underlying chemical origin...
Collective impurity effects in the Heisenberg triangular antiferromagnet
International Nuclear Information System (INIS)
Maryasin, V S; Zhitomirsky, M E
2015-01-01
We theoretically investigate the Heisenberg antiferromagnet on a triangular lattice doped with nonmagnetic impurities. Two nontrivial effects resulting from collective impurity behavior are predicted. The first one is related to presence of uncompensated magnetic moments localized near vacancies as revealed by the low-temperature Curie tail in the magnetic susceptibility. These moments exhibit an anomalous growth with the impurity concentration, which we attribute to the clustering mechanism. In an external magnetic field, impurities lead to an even more peculiar phenomenon lifting the classical ground-state degeneracy in favor of the conical state. We analytically demonstrate that vacancies spontaneously generate a positive biquadratic exchange, which is responsible for the above degeneracy lifting
Particle fueling and impurity control in PDX
International Nuclear Information System (INIS)
Fonck, R.J.; Bell, M.; Bol, K.
1984-12-01
Fueling requirements and impurity levels in neutral-beam-heated discharges in the PDX tokamak have been compared for plasmas formed with conventional graphite rail limiters, a particle scoop limiter, and an open or closed poloidal divertor. Gas flows necessary to obtain a given density are highest for diverted discharges and lowest for the scoop limiter. Hydrogen pellet injection provides an efficient alternate fueling technique, and a multiple pellet injector has produced high density discharges for an absorbed neutral beam power of up to 600 kW, above which higher speeds or more massive pellets are required for penetration to the plasma core. Power balance studies indicate that 30 to 40% of the total input power is radiated while approx. 15% is absorbed by the limiting surface, except in the open divertor case, where 60% flows to the neutralizer plate. In all operating configurations, Z/sub eff/ usually rises at the onset of neutral beam injection. Both open divertor plasmas and those formed on a well conditioned water-cooled limiter have Z/sub eff/ less than or equal to 2 at the end of neutral injection. A definitive comparison of divertors and limiters for impurity control purposes requires longer beam pulses or higher power levels than available on present machines
Effects of impurities on silicon solar-cell performance
Hopkins, R. H.
1986-01-01
Model analyses indicate that sophisticated solar cell designs (back surface fields, optical reflectors, surface passivation, and double layer antireflective coatings) can produce devices with conversion efficiencies above 20%. To realize this potential, the quality of the silicon from which the cells are made must be improved; and these excellent electrical properties must be maintained during device processing. As the cell efficiency rises, the sensitivity to trace contaminants also increases. For example, the threshold Ti impurity concentraion at which cell performance degrades is more than an order of magnitude lower for an 18% cell than for a 16% cell. Similar behavior occurs for numerous other metal species which introduce deep level traps that stimulate the recombination of photogenerated carriers in silicon. Purification via crystal growth in conjunction with gettering steps to preserve the large diffusion length of the as grown material can lead to the production of devices with efficiencies above 18%, as verified experimentally.
Impurity effects in silicon for high efficiency solar cells
Hopkins, R. H.; Rohatgi, A.
1986-01-01
Model analyses indicate that sophisticated solar cell designs including, e.g., back surface fields, optical reflectors, surface passivation, and double layer antireflective coatings can produce devices with conversion efficiencies above 20 percent (AM1). To realize this potential, the quality of the silicon from which the cells are made must be improved; and these excellent electrical properties must be maintained during device processing. As the cell efficiency rises, the sensitivity to trace contaminants also increases. For example, the threshold Ti impurity concentration at which cell performance degrades is more than an order of magnitude lower for an 18-percent cell. Similar behavior occurs for numerous other metal species which introduce deep level traps that stimulate the recombination of photogenerated carriers in silicon. Purification via crystal growth in conjunction with gettering steps to preserve the large diffusion length of the as-grown material can lead to the production of devices with efficiencies aboved 18 percent, as has been verified experimentally.
THE EFFICIENCY OF IMPURITIES EXTRACTION DURING THE PROCESS OF ETHANOL EPURATION
Directory of Open Access Journals (Sweden)
S. Yu. Nikitina
2015-01-01
Full Text Available The static model of the hydroselection column that describes the concentration variation of the main components was proposed. The purpose of this work is an optimization of the shared mixture input-position and evaluation of efficiency of the digestion and the impurity compound concentration during the epuration process. To this end, the author developed a static model of epuration columns, which allows to reveal the dependence of the degree of digestion and the degree of concentration of the main impurities in the column of the number of plates in each of these parts. It’s proved that with the increasing of theoretical plates number in the concentration part of the column the concentration effect tends to the limit value. The effects of the head impurities digestion increase indefinitely with the growth of exhausting part. The proportion of the output from the condenser impurities depends more from the digestion effect than from the condensation effect. The effect of alcohol cleaning from the fusel oil components depends strongly from the ratio of the number of plates in the digestion and concentration parts (the optimal ratio for isopropanol, isoamyl, butanol is 1.5, for the propanol, isobutanol is 0.45.
Polarons and Mobile Impurities Near a Quantum Phase Transition
Shadkhoo, Shahriar
This dissertation aims at improving the current understanding of the physics of mobile impurities in highly correlated liquid-like phases of matter. Impurity problems pose challenging and intricate questions in different realms of many-body physics. For instance, the problem of ''solvation'' of charged solutes in polar solvents, has been the subject of longstanding debates among chemical physicists. The significant role of quantum fluctuations of the solvent, as well as the break down of linear response theory, render the ordinary treatments intractable. Inspired by this complicated problem, we first attempt to understand the role of non-specific quantum fluctuations in the solvation process. To this end, we calculate the dynamic structure factor of a model polar liquid, using the classical Molecular Dynamics (MD) simulations. We verify the failure of linear response approximation in the vicinity of a hydrated electron, by comparing the outcomes of MD simulations with the predictions of linear response theory. This nonlinear behavior is associated with the pronounced peaks of the structure factor, which reflect the strong fluctuations of the local modes. A cavity picture is constructed based on heuristic arguments, which suggests that the electron, along with the surrounding polarization cloud, behave like a frozen sphere, for which the linear response theory is broken inside and valid outside. The inverse radius of the spherical region serves as a UV momentum cutoff for the linear response approximation to be applicable. The problem of mobile impurities in polar liquids can be also addressed in the framework of the ''polaron'' problem. Polaron is a quasiparticle that typically acquires an extended state at weak couplings, and crossovers to a self-trapped state at strong couplings. Using the analytical fits to the numerically obtained charge-charge structure factor, a phenomenological approach is proposed within the Leggett's influence functional formalism, which
Power load reduction due to impurity radiation in ITER-like reactor
International Nuclear Information System (INIS)
Stankiewicz, R.; Zagorski, R.
2001-01-01
The reduction of power load to divertor target plates is a critical issue for long pulse and high power operation regime for magnetic confinement fusion devices. Thus additional losses are required to spread the power load over a wider area. Significant reduction of the heat load to the divertor plates can be achieved by strong impurities radiation in the SOL (Scrape-off Layer) and the core region. In order to asses correctly the heat load to the divertor plates the core region and SOL have to be treated self-consistently. In recent years the necessity of the self-consistent modelling of the plasma dynamics in the core and the scrape-off layer (SOL) has been widely recognised. In the paper the simple self-consistent model for the core and the SOL has been used. The model consists of 1-D analytical model for SOL plasma and 1-D core radial transport model for heat, bulk ions and impurities and is suitable to fast scans of the parameter space of the tokamak type reactor. The SOL model takes into account the strong variation of plasma parameters along the magnetic fields lines. The energy losses due to Bremsstrahlung and line radiation of sputtered and added impurities as well as alpha particles heating are included into the model. The sputtering phenomena and radiation cooling in the SOL and the core are treated in self-consistent way in the model. The heat transport has been described by the simple local transport model proposed by Mandrekas and Stacey reproducing the global confinement predictions or by the simple mixed Bohm and gyro Bohm model. Calculations have been performed to analyse the influence of the core-SOL coupling due to the production of sputtered impurities and its cooling effect in the new ITER-FEAT design. The problem of the choice of suitable materials for the plasma facing components in the ITER type reactor is also addressed. Analysis have been performed to investigate operating regimes of the reactor with deferent diverter plate materials and
Glycolic acid physical properties and impurities assessment
Energy Technology Data Exchange (ETDEWEB)
Lambert, D. P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pickenheim, B. R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bibler, N. E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hay, M. S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-06-08
This document has been revised due to recent information that the glycolic acid used in Savannah River National Laboratory (SRNL) experiments contains both formaldehyde and methoxyacetic acid. These impurities were in the glycolic acid used in the testing included in this report and in subsequent testing using DuPont (now called Chemours) supplied Technical Grade 70 wt% glycolic acid. However, these impurities were not reported in earlier revisions. Additional data concerning the properties of glycolic acid have also been added to this report. The Defense Waste Processing Facility (DWPF) is planning to implement a nitric-glycolic acid flowsheets to increase attainment to meet closure commitment dates during Sludge Batch 9. In fiscal year 2009, SRNL was requested to determine the physical properties of formic and glycolic acid blends. Blends of formic acid in glycolic acid were prepared and their physical properties tested. Increasing amounts of glycolic acid led to increases in blend density, viscosity and surface tension as compared to the 90 wt% formic acid that is currently used at DWPF. These increases are small, however, and are not expected to present any difficulties in terms of processing. The effect of sulfur impurities in Technical Grade glycolic acid was studied for its impact on DWPF glass quality. While the glycolic acid specification allows for more sulfate than the current formic acid specification, the ultimate impact is expected to be on the order of 0.033 wt% sulfur in glass. Note that lower sulfur content glycolic acid could likely be procured at some increased cost if deemed necessary. A paper study on the effects of radiation on glycolic acid was performed. The analysis indicates that substitution of glycolic acid for formic acid would not increase the radiolytic production rate of H2 and cause an adverse effect in the Slurry Receipt and Adjustment Tank (SRAT) or Slurry Mix Evaporator (SME) process. It has been cited that glycolic acid
Impurity-seeded plasma experiments on JET
Maddison, G. P.; Brix, M.; Budny, R.; Charlet, M.; Coffey, I.; Cordey, J. G.; Dumortier, P.; Erents, S. K.; Hawkes, N. C.; von Hellermann, M.; Hillis, D. L.; Hogan, J.; Horton, L. D.; Ingesson, L. C.; Jachmich, S.; Jackson, G. L.; Kallenbach, A.; Koslowski, H. R.; Lawson, K. D.; Loarte, A.; Matthews, G. F.; McDonald, D.; McKee, G. R.; Meigs, A.; Messiaen, A. M.; Milani, F.; Monier-Garbet, P.; Murakami, M.; Nave, M. F. F.; Ongena, J.; Puiatti, M. E.; Rachlew, E.; Rapp, J.; Sharapov, S.; Staebler, G. M.; Stamp, M.; Strachan, J. D.; Suttrop, W.; Telesca, G.; Tokar, M. Z.; Unterberg, B.; Valisa, M.; Zastrow, K.-D.; 2000 workprogramme contributors, EFDA-JET
2003-01-01
Scaling to larger tokamaks of high confinement plasmas with radiating edges, induced by impurities, is being studied through internationally collaborative experiments on JET. In campaigns till the end of 2000, three different regimes have been explored. A small number of limiter L-mode discharges seeded with neon have most closely repeated the approach used on TEXTOR-94, but different collisionality and particle transport in JET impede central peaking of the density associated with improved confinement. Divertor L-modes at intermediate density, again with neon injection, have pursued transiently enhanced states found on DIII-D. Confinement up to H-mode quality, together with radiation fractions of approx40%, have briefly been obtained, though central Zeff quickly increases. Most effectively, neon and argon seeding of higher density ELMy H-modes formed mainly at low triangularity on the septum of the MkIIGB divertor, resembling a pumped-limiter arrangement, have been examined. Good confinement has been sustained at densities close to the Greenwald level in `afterpuff' (AP) phases following the end of main gas fuelling, for little change of central Zeff but up to approx60% radiation. Outstanding normalized properties up to H97 = 0.99 at fGwd = 0.94 have thus been achieved, above the conventional H-mode density limit for diverted plasmas. Stationarity of states has also been extended to many energy confinement times by including low, extra gas inputs in the `AP', suggestive of an optimized fuelling scheme. Further development in 2001 is reported separately in [1]. Accompanying ELMs are generally reduced in frequency though not evidently in size, electron pedestal pressure being almost unchanged from unseeded behaviour. There are indications of the most favourable impurity species scaling with plasma parameters, performance, radiation and its concentration within a mantle all increasing with argon compared to neon in JET. These benefits in terms of integrated
Simulation of runaway electron generation during plasma shutdown by impurity injection
Energy Technology Data Exchange (ETDEWEB)
Feher, Tamas
2011-03-15
Disruptions are dangerous instabilities in tokamaks that should be avoided or mitigated. One possible disruption mitigation method is to inject impurities into the plasma to shut it down in a controlled way. Runaway Electrons (REs) can be generated after the plasma is cooled down by the impurities and these electrons can damage the tokamak. In this work a simulation code is developed to investigate different disruption mitigation scenarios. The response of the bulk plasma, more precisely the temperature evolution of electrons, deuterium and impurity ions are described by energy balance equations in a 1D cylindrical plasma model. The induction and resistive diffusion of electric field is calculated. RE generation rates are used to calculate the runaway current. The Dreicer, hot-tail and avalanche effect is taken into account and a simple model for RE losses is also included. RE generation is studied in JET-like plasmas during pellet injection. Carbon pellets cause effective cooling but these scenarios are prone to runaway generation. A mixture of argon and deuterium gas could be used for safe shutdown without RE generation. In ITER the hot-tail RE generation process becomes important, and the simulation is therefore extended to take this into account. Shutdown scenarios with different concentration of neon and argon impurities were tested in ITER-like plasmas. To simplify the problem the impurity injection into the plasma is not modeled in these cases, only the response of the bulk plasma. The avalanche process cannot be suppressed in a simple way and would produce high runaway current. It can be avoided if some runaway loss phenomenon is included in the simulations, like diffusion due to magnetic perturbations
Strain field due to self-interstitial impurity in Ni
Indian Academy of Sciences (India)
metals due to substitutional impurities using Kanzaki lattice static method based on discrete lattice theory. This method ... lattice under applied external forces is expanded in powers series of the displacements which in the .... Since the interstitial impurity interacts with short-range interactions, the external force is expected to ...
In vitro genotoxicity of piperacillin impurity-A
African Journals Online (AJOL)
SERVER
2007-09-19
Sep 19, 2007 ... The manufacturing and storage of the piperacillin produce different impurities of various concentrations, which may influence the efficacy and safety of the drug. Since no report of genotoxicity data is available on the impurities of piperacillin, further studies were designed and conducted to.
Effects of electronically neutral impurities on muonium in germanium
International Nuclear Information System (INIS)
Clawson, C.W.; Crowe, K.M.; Haller, E.E.; Rosenblum, S.S.; Brewer, J.H.
1983-04-01
Low-temperature measurements of muonium parameters in various germanium crystals have been performed. We have measured crystals with different levels of neutral impurities, with and without dislocations, and with different annealing histories. The most striking result is the apparent trapping of Mu by silicon impurities in germanium
The effects of naturally occurring impurities in rock salt
Indian Academy of Sciences (India)
In this paper we investigate the effect that naturally occurring impurities in salt mines have both on effective permittivity of the medium and on radio wave propagation at ∼200 MHz. The effective permittivity is determined based on the dielectric properties of salt and the characteristics of the main impurities. We conclude that ...
Boulmier, Amandine; Vacher, Antoine; Zang, Dejin; Yang, Shu; Saad, Ali; Marrot, Jérôme; Oms, Olivier; Mialane, Pierre; Ledoux, Isabelle; Ruhlmann, Laurent; Lorcy, Dominique; Dolbecq, Anne
2018-04-02
Three polyoxometalates (POMs) functionalized by tetrathiafulvalene (TTF) molecules have been synthesized by a coupling reaction between the Anderson-type POMs [MnMo 6 O 18 {(OCH 2 ) 3 CNH 2 } 2 ] 3- or [AlMo 6 O 18 (OH) 3 {(OCH 2 ) 3 CNH 2 }] 3- and the TTF carboxylic acid derivative (MeS) 3 TTF(S-CH 2 -CO 2 H). The monofunctionalized TTF-AlMo 6 POM contains one TTF group covalently grafted on an Al Anderson platform. The symmetrical TTF-MnMo 6 -TTF POM possesses two TTF groups grafted on each side of a Mn Anderson derivative while the asymmetrical TTF-MnMo 6 -SP POM contains a TTF and a spiropyran groups. These three trianionic species have been characterized by elemental analysis, 1 H and 13 C NMR, FT-IR spectroscopy, ESI-MS spectrometry, and single-crystal X-ray diffraction (for TTF-MnMo 6 -TTF). In the solid state, the grafted TTF molecules of TTF-MnMo 6 -TTF POMs interact via S···S and π···π interactions and form chains. The electrochemical properties of the complexes reflect the contributions of both the inorganic POM and the TTF moieties. Despite adsorption of the oxidized hybrid species on the Pt grid working electrode, UV-vis-NIR spectroelectrochemical investigations evidence peaks characteristic of the oxidation of the TTF units. Finally, hyper-Rayleigh scattering (HRS) measurements show that the three novel TTF derivatives exhibit β values between 20 and 37 × 10 -30 esu. Moreover it is observed that the oxidation of the TTF moieties by Fe 3+ ions increases the NLO response. These values are in the order of magnitude of that found for the well-known 4-dimethylamino- N-methyl-4-stilbazolium (DAS + ) cation (β = 60 × 10 -30 esu).
Metal impurity release in diverted tokamak discharges
International Nuclear Information System (INIS)
Staudenmaier, G.; Wampler, W.R.
1986-01-01
Plasma materials interaction at the wall of the main plasma chamber of the divertor tokamak ASDEX was investigated by a combined probe, allowing simultaneous measurements of the erosion rate by neutral particles, and the flux and average energy of neutrals. The erosion was measured by collecting part of the released material on a carbon strip. Subsequent surface analysis was performed by electron induced x-ray analysis. Flux and energy of the impinging neutral particles were measured after each single discharge with an energy resolving carbon resistance probe. Such combined measurements yield the erosion yield being characteristic for the erosion process. Data for ohmic discharges in deuterium and helium are compared. It turns out that the carbon resistance probe is a simple but powerful means to study the metal impurity release from the tokamak walls by charge exchange neutrals
Spectrographic determination of impurities in magnesium metal
International Nuclear Information System (INIS)
Capdevila, C.; Diaz-Guerra, J. P.
1979-01-01
The spectrographic determination of trace quantities of Al, B, Cd, Co, Cr, Cu, Fe, Li, Hn, Mo, Ni and Si in magnesium metal is described. Samples are dissolved with HNO 3 and calcinate into MgO. In order to avoid losses of boron NH 4 OH is added to the nitric solution. Except for aluminium and chromium the analysis is performed through the use of the carrier distillation technique. These two impurities are determined by burning to completion the MgO. Among the compounds studied as carriers (AgCl, AgF, CsCl, CuF 2 , KCl and SrF 2 ) AgCl allows, In general, the best volatilization efficiency. Lithium determination is achieved by using KC1 or CsCl. Detection limits, on the basis of MgO, are in the range 0,1 to 30 ppm, depending on the element. (Author) 8 refs
Viscoelasticity of colloidal polycrystals doped with impurities
Louhichi, Ameur; Tamborini, Elisa; Oberdisse, Julian; Cipelletti, Luca; Ramos, Laurence
2015-09-01
We investigate how the microstructure of a colloidal polycrystal influences its linear visco-elasticity. We use thermosensitive copolymer micelles that arrange in water in a cubic crystalline lattice, yielding a colloidal polycrystal. The polycrystal is doped with a small amount of nanoparticles, of size comparable to that of the micelles, which behave as impurities and thus partially segregate in the grain boundaries. We show that the shear elastic modulus only depends on the packing of the micelles and varies neither with the presence of nanoparticles nor with the crystal microstructure. By contrast, we find that the loss modulus is strongly affected by the presence of nanoparticles. A comparison between rheology data and small-angle neutron-scattering data suggests that the loss modulus is dictated by the total amount of nanoparticles in the grain boundaries, which in turn depends on the sample microstructure.
Spectroscopical determination of impurities in nuclear graphite
International Nuclear Information System (INIS)
Lordello, A.R.; Tognini, R.P.
1975-01-01
A spectrochemical method for the direct determination of B, Cd, Si, Hg, Fe, Mg, Mn, Cr, Ni, Al, Mo, Ti, Sr, Na, Zn, and As in nuclear grade graphite is described. A 9:1 ratio of graphite to copper difluoride is used in the preparation of samples and standards. The excitation is carried out in a d-c at 10 amperes. The copper fluoride used as spectrographic buffer serves to increase the volatilization rate of the impurities and to diminish the differences in the nature of the analytical and calibration samples. The relative standard deviations for the determination of the 16 trace elements, except Sr, Fe, Cd, Al and Si, are in the range of 8 - 20% in their appropriate calibration levels. For the latter five elements they are approximately 20-40%
Recycling of gaseous impurities in ASDEX
International Nuclear Information System (INIS)
Poschenrieder, W.; Desinger, K.
1990-01-01
The closed divertor configuration of ASDEX isolates the zone of dominant plasma-wall interaction in a rather well defined manner from the plasma in the main chamber. Studies have shown that for recycling gases the effective conductance between divertor and plasma chamber is closely represented by the values for molecular flow also during a discharge. Hence, from partial pressure measurements of contaminant gases in the divertor impurity recycling fluxes can be obtained. In deuterium discharges the problem of mass peak interferences, especially for methane and watervapour, has to be resolved. Data are shown for various ASDEX scenarios: stainless steel walls, carbon wall elements, Ti-gettering and boronization. The results expose the production of CO as main culprit, as long as no gettering or boronization is employed. Then, however, with carbon still present in the machine, the hydrocarbons limit the attainment of optimum performance parameters. What are the conclusions? (orig.)
Electrically Driven Spin Dynamics of Paramagnetic Impurities
Saha, D.; Siddiqui, L.; Bhattacharya, P.; Datta, S.; Basu, D.; Holub, M.
2008-05-01
The spin dynamics of dilute paramagnetic impurities embedded in a semiconductor GaAs channel of a conventional lateral spin valve has been investigated. It is observed that the electron spin of paramagnetic Mn atoms can be polarized electrically when driven by a spin valve in the antiparallel configuration. The transient current through the MnAs/GaAs/MnAs spin valve bears the signature of the underlying spin dynamics driven by the exchange interaction between the conduction band electrons in GaAs and the localized Mn electron spins. The time constant for this interaction is observed to be dependent on temperature and is estimated to be 80 ns at 15 K.
APA/Psi Chi Edwin B. Newman Graduate Research Award: Samantha F. Anderson.
2017-12-01
The Edwin B. Newman Graduate Research Award is given jointly by Psi Chi and the American Psychological Association. The award was established to recognize young researchers at the beginning of their professional lives and to commemorate both the 50th anniversary of Psi Chi and the 100th anniversary of psychology as a science (dating from the founding of Wundt's laboratory). The 2017 recipient is Samantha F. Anderson, who was chosen for "an exceptional research paper that responds to psychology's 'replication crisis' by outlining a broader view of success in replication." Her award citation, biography, and a selected bibliography are presented here. (PsycINFO Database Record (c) 2017 APA, all rights reserved).
DEFF Research Database (Denmark)
Jacobsen, Finn
2011-01-01
The effect known as ‘weak Anderson localisation’, ‘coherent backscattering’ or ‘enhanced backscattering’ is a physical phenomenon that occurs in random systems, e.g., disordered media and linear wave systems, including reverberation rooms: the mean square response is increased at the drive point...... position it is obviously very difficult to measure the effect directly. The ‘concentration factor’ is usually assumed to be 2, and the ‘modal kurtosis’ is assumed to be 3. This paper presents the results of an indirect experimental estimation of these two parameters, and discusses implications...... for the uncertainty of sound power measurements....
Yamamoto, Saori; Suzuki, Hideaki; Sugimura, Koichiro; Tatebe, Shunsuke; Aoki, Tatsuo; Miura, Masanobu; Yaoita, Nobuhiro; Sato, Haruka; Kozu, Katuya; Ota, Hideki; Takanami, Kentaro; Takase, Kei; Shimokawa, Hiroaki
2016-11-25
It remains to be elucidated whether cardiac sympathetic nervous activity is impaired in patients with Anderson-Fabry disease (AFD).Methods and Results:We performed 123 I-meta-iodobenzylguanidine (MIBG) scintigraphy and gadolinium-enhanced cardiovascular magnetic resonance (CMR) in 5 AFD patients. MIBG uptake in the inferolateral wall, where wall thinning and delayed enhancement were noted on CMR, was significantly lower compared with the anteroseptal wall. The localized reduction in MIBG uptake was also noted in 2 patients with no obvious abnormal findings on CMR. Cardiac sympathetic nervous activity is impaired in AFD before development of structural myocardial abnormalities. (Circ J 2016; 80: 2550-2551).
Density of states controls Anderson localization in disordered photonic crystal waveguides
DEFF Research Database (Denmark)
Garcia-Fernández, David; Smolka, Stephan; Stobbe, Søren
2010-01-01
-of-plane losses are non-negligible, ℓe can be approximated to be the localization length ξ. The extinction mean-free path shows a fivefold variation between the low- and the high-DOS regime, and it becomes shorter than the sample length thus giving rise to strongly confined modes. The dispersive behavior of ℓe......We prove Anderson localization in a disordered photonic crystal waveguide by measuring the ensemble-averaged extinction mean-free path, ℓe, which is controlled by the dispersion in the photon density of states (DOS) of the photonic crystal waveguide. Except for the very low DOS case, where out...
Clinton P. Anderson Meson Physics Facility and its operational safety program
International Nuclear Information System (INIS)
Putnam, T.M.
1975-01-01
The Clinton P. Anderson Meson Physics Facility (LAMPF) at the Los Alamos Scientific Laboratory consists of/ (1) a medium-energy, high-intensity linear proton accelerator; (2) experimental areas designed to support a multidisciplined program of research and practical applications; and (3) support facilities for accelerator operations and the experimental program. The high-intensity primary and secondary beams at LAMPF and the varied research program create many interesting and challenging problems for the Health Physics staff. A brief overview of LAMPF is presented, and the Operational Safety Program is discussed, with emphasis on the radiological safety and health physics aspects
DEFF Research Database (Denmark)
Jacobsen, Finn
2011-01-01
The effect known as ‘weak Anderson localisation’, ‘coherent backscattering’ or ‘enhanced backscattering’ is a physical phenomenon that occurs in random systems, e.g., disordered media and linear wave systems, including reverberation rooms: the mean square response is increased at the drive point....... In a reverberation room this means that one can expect an increase of the reverberant sound field at the position of the source that generates the sound field. This affects the sound power output of the source and is therefore of practical concern. However, because of the stronger direct sound field at the source...... for the uncertainty of sound power measurements....
Energy Technology Data Exchange (ETDEWEB)
Metzger, I.; Van Geet, O.
2014-06-01
This report summarizes the results from the data center energy efficiency and renewable energy site assessment conducted for the Oregon Army National Guard in Salem, Oregon. A team led by NREL conducted the assessment of the Anderson Readiness Center data centers March 18-20, 2014 as part of ongoing efforts to reduce energy use and incorporate renewable energy technologies where feasible. Although the data centers in this facility account for less than 5% of the total square footage, they are estimated to be responsible for 70% of the annual electricity consumption.
Anderson phase-slip theory and loss mechanism of the motion of vortices in superconductors
International Nuclear Information System (INIS)
Xu, L.K.; Shan, L.; Tang, Y.L.; Wang, F.; Xu, X.N.; Jin, X.; Nanjing Univ.
2001-01-01
The loss mechanism of the super-current is discussed in the frame of Anderson phase-slip theory and G-L theory. In the discussion we also use vortex conservation equations instead of Maxwell equations. It is found that this method is more reasonable to apply the vortex motion induced energy loss in type II superconductors than the traditional deduction in terms of Maxwell equations. Moreover, we propose a new method to determine the effective pinning energy of vortex lines in type II superconductors. (orig.)
Diagnostics of heavy impurities at GOL-3 facility
Sorokina, N.; Burdakov, A.; Ivanov, I.; Kuklin, K.; Polosatkin, S.; Popov, S.; Postupaev, V.; Rovenskikh, A.; Shoshin, A.; Schudlo, I.
2010-11-01
Multimirror approach to plasma confinement for fusion is studied at GOL-3 facility in the Budker Institute of Nuclear Physics (Novosibirsk, Russia). The presented work is devoted to diagnostics of heavy impurities in plasma of this facility. The main purpose is quantitative measurement of density, degree of ionization of the main heavy impurities in plasma and their contribution to an effective charge of plasma at the GOL-3 facility. Density of interested elements was measured by optical spectroscopy and mass-spectroscopy of residual vacuum. A number of spectroscopic diagnostics has been developed for this purpose. Experimental data were compared with results of numerical calculations of impurities dynamics. As a result it is revealed that the contribution of heavy impurities to effective charge of plasma does not exceed 20%; thus the presence of impurities in plasma of the GOL-3 facility does not influence essentially the plasma confinement at the multimirror trap.
Diagnostics of heavy impurities at GOL-3 facility
International Nuclear Information System (INIS)
Sorokina, N.; Burdakov, A.; Ivanov, I.; Kuklin, K.; Polosatkin, S.; Popov, S.; Postupaev, V.; Rovenskikh, A.; Shoshin, A.; Schudlo, I.
2010-01-01
Multimirror approach to plasma confinement for fusion is studied at GOL-3 facility in the Budker Institute of Nuclear Physics (Novosibirsk, Russia). The presented work is devoted to diagnostics of heavy impurities in plasma of this facility. The main purpose is quantitative measurement of density, degree of ionization of the main heavy impurities in plasma and their contribution to an effective charge of plasma at the GOL-3 facility. Density of interested elements was measured by optical spectroscopy and mass-spectroscopy of residual vacuum. A number of spectroscopic diagnostics has been developed for this purpose. Experimental data were compared with results of numerical calculations of impurities dynamics. As a result it is revealed that the contribution of heavy impurities to effective charge of plasma does not exceed 20%; thus the presence of impurities in plasma of the GOL-3 facility does not influence essentially the plasma confinement at the multimirror trap.
Perturbation theory for an Anderson quantum dot asymmetrically attached to two superconducting leads
Czech Academy of Sciences Publication Activity Database
Žonda, M.; Pokorný, Vladislav; Janiš, Václav; Novotný, T.
2016-01-01
Roč. 93, č. 2 (2016), 1-18, č. článku 024523. ISSN 2469-9950 Institutional support: RVO:68378271 Keywords : numerical renormalization-group * carbon nanotubes * josephson-junction * phase-transition * impurity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016
Hydrocyclones for the separation of impurities in pretreated biowaste.
Jank, Anna; Müller, Wolfgang; Waldhuber, Sebastian; Gerke, Frédéric; Ebner, Christian; Bockreis, Anke
2017-06-01
The aim of the mechanical pretreatment in case of anaerobic digestion of biowaste is to produce a substrate without impurities. To facilitate a failure free operation of the anaerobic digestion process even small impurities like stones or sand should be separated. As a result of an insufficient pretreatment or impurities separation, plant malfunctions, increased equipment wear or pipe clogging are reported. Apart from grit chambers or pulper systems, a hydrocyclone is a cost-efficient and space-saving option to remove impurities. The aim of this work was to investigate the efficiency of hydrocyclones for the separation of impurities. Two hydrocyclones at two different plants were investigated regarding their capability to separate the small inert impurities from pretreated source separated biowaste. In plant A, the hydrocyclone is part of the digester system. In plant B, the hydrocyclone is part of the biowaste pretreatment line (after milling and sieving the biowaste) before digestion. Separation rates of inert impurities such as stones, glass and sand were determined as well as the composition of the concentrated solids separated by the hydrocyclone. Due to the heterogeneity of the biowaste the impurity separation rates showed variations, therefore the following mean results were obtained in average: the investigated hydrocyclones of plant B, part of the biowaste treatment, separated more than 80% of the inert impurities in the waste stream before anaerobic digestion. These impurities had a size range of 0.5-4mm. The hydrocyclone integrated in the digester system of plant A showed separation rates up to 80% only in the size range of 2-4mm. Copyright © 2017 Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Errico, L.A.; Fabricius, G.; Renteria, M. [Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CC 67, 1900 La Plata (Argentina)
2004-08-01
We report an ab-initio comparative study of the electric-field-gradient tensor (EFG) and structural relaxations introduced by acceptor (Cd) and donor (Ta) impurities when they replace cations in a series of binary oxides: TiO{sub 2}, SnO{sub 2}, and In{sub 2}O{sub 3}. Calculations were performed with the Full-Potential Linearized-Augmented Plane Waves method that allows us to treat the electronic structure and the atomic relaxations in a fully self-consistent way. We considered different charge states for each impurity and studied the dependence on these charge states of the electronic properties and the structural relaxations. Our results are compared with available data coming from PAC experiments and previous calculations, allowing us to obtain a new insight on the role that metal impurities play in oxide semiconductors. It is clear from our results that simple models can not describe the measured EFGs at impurities in oxides even approximately. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Liu, Cuimei; Hua, Zhendong; Bai, Yanping
2015-12-01
The illicit manufacture of heroin results in the formation of trace levels of acidic and neutral manufacturing impurities that provide valuable information about the manufacturing process used. In this work, a new ultra performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC-Q-TOF) method; that features high resolution, mass accuracy and sensitivity for profiling neutral and acidic heroin manufacturing impurities was developed. After the UPLC-Q-TOF analysis, the retention times and m/z data pairs of acidic and neutral manufacturing impurities were detected, and 19 peaks were found to be evidently different between heroin samples from "Golden Triangle" and "Golden Crescent". Based on the data set of these 19 impurities in 150 authentic heroin samples, classification of heroin geographic origins was successfully achieved utilizing partial least squares discriminant analysis (PLS-DA). By analyzing another data set of 267 authentic heroin samples, the developed discrimiant model was validated and proved to be accurate and reliable. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
Repartitioning of NaCl and Protein Impurities in Lysozyme Crystallization
Vekilov, Peter G.; Monaco, Lisa A.; Thomas, Bill R.; Stojanoff, Vivian; Rosenberger, Franz
1996-01-01
Nonuniform precipitant and impurity incorporation in protein crystals can cause lattice strain and, thus, possibly decrease the X-ray diffraction resolution. To address this issue, a series of crystallization experiments were carried out, in which initial supersaturation, NaCl concentration, protein purity level and crystallized fraction were varied. Lysozyme and protein impurities, as well as sodium and chloride were independently determined in the initial solution, supernatant and crystals. The segregation coefficients for Na(+) and Cl(-) were found to be independent of supersaturation and NaCl concentration, and decreased with crystallized fraction/crystal size. Numerical evaluation of the extensive body of data, based on a nucleation-growth- repartitioning model, suggests a core of approx. 40 microns in which salt is incorporated in much greater concentrations than during later growth. Small crystals containing higher amounts of incorporated NaCl also had higher protein impurity contents. This suggests that the excess salt is associated with the protein impurities in the core. X-ray topography revealed strain fields in the center of the crystals comparable in size to the inferred core. The growth rates of crystals smaller than 30-40 pm in size were consistently 1.5-2 times lower than those of larger crystals, presumably due to higher chemical potentials in the core.
Helium localization around the microscopic impurities embedded to liquid helium
International Nuclear Information System (INIS)
Gordon, E.B.; Shestakov, A.F.
2000-01-01
The structure and properties of the environment round the impurity atoms (Im) embedded in liquid helium are considered. It is shown that there are two qualitatively different types of structure of the He atom layer next to Im - attraction and repulsion structures. For the center attraction structure (strong Im-He interaction) the Im-He separation is longer than the equilibrium one for the pair Im-He potential, and the density and localization of He atoms are higher than in the bulk. It this case the He atom content in the layer, n, is almost independent of applied pressure. In the repulsion structure realized for alkaline metal atoms the Im-He separation is shorter than the equilibrium one and the density is lower than in the helium bulk. At T approx 1 K occupied are several states with different n and their energies differ only by approx 0.1 K, an increase in pressure resulting in a considerable reduction of n. The optical and EPR spectra of the atoms embedded to liquid and solid helium are interpreted on the basis of the analysis carried out. A simple model is proposed to evaluate the helium surroundings characteristics from the experimental pressure dependences of atomic line shifts in the absorption and emission spectra. The attraction structures in 3 He - 4 He mixtures are suggested to be highly enriched by 4 He atoms which the repulsion structures - by 3 He atoms. a possibility for existence of phase transitions in helium shells surrounding impurity atoms is considered
Huesmann, L. Rowell
2010-01-01
Over the past half-century the mass media, including video games, have become important socializers of children. Observational learning theory has evolved into social-cognitive information processing models that explain that what a child observes in any venue has both short-term and long-term influences on the child's behaviors and cognitions. Anderson's (2010) extensive meta-analysis of the effects of violent video games confirms what these theories predict and what prior research about other violent mass media has found – that violent video games stimulate aggression in the players in the short run and increase the risk for aggressive behaviors by the players later in life. The effects occur for males and females and for children growing up in Eastern or Western cultures. The effects are strongest for the best studies. Contrary to some critics' assertions, the meta-analysis is methodologically sound and comprehensive. Yet the results are unlikely to change the critics' views or the public's perception that the issue is undecided because there are some studies that have yielded null effects, because many people are concerned that the implications of the research threaten freedom of expression, and because many people have their identities or self-interests closely tied to violent video games. PMID:20192555
Center deviation of localized modes in a one-dimension anharmonic single impurity chain
Chen, Xuan-Lin; Zhu, Gang-Bei; Jiang, Ze-Hui; Yang, Yan-Qiang
2018-04-01
A 1D anharmonic chain with a single impurity particle is used to study the center deviation and stability of the localized modes. The displacement patterns of the localized modes for a variable impurity mass and anharmonic parameter are studied. The pattern center is shifted away from the impurity with decreasing anharmonic parameter for both symmetric and asymmetric anharmonic impurity modes. In the limit of a heavy-mass impurity, the energy localization is constrained to the three particles nearest to the impurity.
Directory of Open Access Journals (Sweden)
Suvajit Pal
2013-01-01
Full Text Available Excitation in quantum dots is an important phenomenon. Realizing the importance we investigate the excitation behavior of a repulsive impurity-doped quantum dot induced by simultaneous oscillations of impurity potential and spatial stretch of impurity domain. The impurity potential has been assumed to have a Gaussian nature. The ratio of two oscillations (η has been exploited to understand the nature of excitation rate. Indeed it has been found that the said ratio could fabricate the excitation in a remarkable way. The present study also indicates attainment of stabilization in the excitation rate as soon as η surpasses a threshold value regardless of the dopant location. However, within the stabilization zone we also observe maximization in the excitation rate at some typical location of dopant incorporation. The critical analysis of pertinent impurity parameters provides important perception about the physics behind the excitation process.
[Results of Boyd and Anderson reconstruction of distal biceps brachii tendon rupture].
Franiel, Jan; Zorychta, Daniel; Szalewicz, Joanna
2009-01-01
The aim of this work has been retrospective evaluation of flexion and supination strength as well as range of motion after reinsertion of biceps tendon using Boyd and Anderson method. In the years 2000-2005 this method was used in therapy of 9 men. All them had the right limb dominant. The average age of patients in the moment of injury was 48 years (from 27 to 58). The observation period was 3 years and 7 months. 7 of them showed up for the check examination. One of the patients a complication in the form of radioulnar syntostosis and complete loss of forearm rotation. The rest of patients did not exhibit the significant funcional limits of extension and flexion movement rates and forearm rotation. In those six patients the flexion strength and movement of supination strength were measured using dynamometer of own construction. Four patients had the right limb operated, two of them had the left one. The control group constituted 30 healthy, randomly chosen, right-handed men. Statistical assessment concerning quantity was only possible for the right limbs. Statistical difference between control group and tested group as for flexion strength and moment of supination strength was not observed. Operation of early anatomic reinsertion of ruptured biceps tendon using Boyd and Anderson method enables full recovery of the forearm flexion and supination strength.
International Nuclear Information System (INIS)
Cabello, Carmen I.; Munoz, Mercedes; Botto, Irma L.; Payen, Edmond
2006-01-01
The influence of Rh heteroatom on the molybdenum reducibility in the Anderson-type heteropolyoxomolybdate structure of formula (NH 4 ) 3 [RhMo 6 O 24 H 6 ].7H 2 O was investigated by means of TPR technique. With comparative purposes, the thermal behavior in non-reducing conditions was also carried out by means of TGA-DTA studies. The study was performed by XRD, SEM, EDAX and FTIR-Raman techniques. Results were related to those preliminary measurements over other XMo 6 Anderson phases. Likewise, Rh(III)-Al(III) formal replacement in the RhMo 6 structural arrangement was proved. The formation of a solid solution in a limited range of composition (up to 0.25 Rh) was established in order to explore the catalytic performance of γ-Al 2 O 3 supported planar heteropolyoxomolybdate, aiming at optimizing the noble metal content in the catalytic system. Preliminary measurements of RhMo 6 /γ-Al 2 O 3 and (Rh, Al)Mo 6 /γ-Al 2 O 3 activity for HDS and HYD processes were also performed. These results were compared to those obtained for CoMo 6 /γ-Al 2 O 3 system in similar operating conditions and other conventional catalytic systems. The potentiality and scope of RhMo 6 catalytic system for the HDS and HYD processes were analyzed
Scaling analysis of transverse Anderson localization in a disordered optical waveguide
Abaie, Behnam; Mafi, Arash
2016-08-01
The intention of this paper is twofold. First, the mode-width probability density function (PDF) is introduced as a powerful statistical tool to study and compare the transverse Anderson localization properties of a disordered quasi-one-dimensional optical waveguide. Second, by analyzing the scaling properties of the mode-width PDF with the transverse size of the waveguide, it is shown that the mode-width PDF gradually converges to a terminal configuration. Therefore, it may not be necessary to study a real-sized disordered structure in order to obtain its statistical localization properties and the same PDF can be obtained for a substantially smaller structure. This observation is important because it can reduce the often demanding computational effort that is required to study the statistical properties of Anderson localization in disordered waveguides. Using the mode-width PDF, substantial information about the impact of the waveguide parameters on its localization properties is extracted. This information is generally obscured when disordered waveguides are analyzed using other techniques such as the beam propagation method. As an example of the utility of the mode-width PDF, it is shown that the cladding refractive index can be used to quench the number of extended modes, hence improving the contrast in image transport properties of disordered waveguides.
Portuguese validation of the Symptom Inventory of the M.D. Anderson Cancer Center
Directory of Open Access Journals (Sweden)
Adriane Cristina Bernat Kolankiewicz
2014-12-01
Full Text Available Objective To analyze the reliability and validity of the psychometric properties of the Brazilian version of the instrument for symptom assessment, titled MD Anderson Symptom Inventory - core. Method A cross-sectional study with 268 cancer patients in outpatient treatment, in the municipality of Ijuí, state of Rio Grande do Sul, Brazil. Results The Cronbach’s alpha for the MDASI general, symptoms and interferences was respectively (0.857, (0.784 and (0.794. The factor analysis showed adequacy of the data (0.792. In total, were identified four factors of the principal components related to the symptoms. Factor I: sleep problems, distress (upset, difficulties in remembering things and sadness. Factor II: dizziness, nausea, lack of appetite and vomiting. Factor III: drowsiness, dry mouth, numbness and tingling. Factor IV: pain, fatigue and shortness of breath. A single factor was revealed in the component of interferences with life (0.780, with prevalence of activity in general (59.7%, work (54.9% and walking (49.3%. Conclusion The Brazilian version of the MD Anderson Symptom Inventory - core showed adequate psychometric properties in the studied population.
Hoggard, Jamin C; Wahl, Jon H; Synovec, Robert E; Mong, Gary M; Fraga, Carlos G
2010-01-15
In this report we present the feasibility of using analytical and chemometric methodologies to reveal and exploit the chemical impurity profiles from commercial dimethyl methylphosphonate (DMMP) samples to illustrate the type of forensic information that may be obtained from chemical-attack evidence. Using DMMP as a model compound of a toxicant that may be used in a chemical attack, we used comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC x GC/TOF-MS) to detect and identify trace organic impurities in six samples of commercially acquired DMMP. The GC x GC/TOF-MS data was analyzed to produce impurity profiles for all six DMMP samples using 29 analyte impurities. The use of PARAFAC for the mathematical resolution of overlapped GC x GC peaks ensured clean spectra for the identification of many of the detected analytes by spectral library matching. The use of statistical pairwise comparison revealed that there were trace impurities that were quantitatively similar and different among five of the six DMMP samples. Two of the DMMP samples were revealed to have identical impurity profiles by this approach. The use of nonnegative matrix factorization indicated that there were five distinct DMMP sample types as illustrated by the clustering of the multiple DMMP analyses into five distinct clusters in the scores plots. The two indistinguishable DMMP samples were confirmed by their chemical supplier to be from the same bulk source. Sample information from the other chemical suppliers supported the idea that the other four DMMP samples were likely from different bulk sources. These results demonstrate that the matching of synthesized products from the same source is possible using impurity profiling. In addition, the identified impurities common to all six DMMP samples provide strong evidence that basic route information can be obtained from impurity profiles. Finally, impurities that may be unique to the sole bulk manufacturer of DMMP were
Spectroscopic system for impurity measurements in the TJ-1 Tokamak of JEN
International Nuclear Information System (INIS)
Navas, G.; Zurro, B.
1982-01-01
we describe a spectroscopic system with spatial resolution capability that has been configured for plasma diagnostic in the TJ-1 Tokamak of JEN. The experimental system, based on a one meter monochromator, has been absolutely calibrated using a tungsten-halogen lamp. The calibration procedures and the absolute spectral sensitivity are presented as well as its dependence with the polarization. A simplified spectroscopic model of the radiation emitted by the intrinsic plasma impurities (C, 0, . . . ) has been developed. A one dimensional model of the temporal evolution of various ionization stages in coronal equilibrium is used to predict the electron temperature and impurity concentration. This model has been applied to experimental data from several Tokamaks. (Author) 23 refs
Impurity induced neutralization of MeV energy protons in JET plasmas
Energy Technology Data Exchange (ETDEWEB)
Gondhalekar, A. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Korotkov, A.A. [AF Ioffe Institute, Saint Petersburg (Russian Federation)
1994-07-01
A model elucidating the role of carbon and beryllium, the main impurities in JET plasmas, in neutralizing MeV energy protons, which arise during ICRF heating of deuterium plasmas in the hydrogen minority heating mode D(H), and from D-D fusion reactions, is presented. The model establishes charge transfer from hydrogen-like impurity ions to protons as the main process for neutralization. Calculations for deducing the proton energy distribution function from measured hydrogen flux are described. The validity of the model is tested by using it to described the measured flux in different conditions of plasma heating and fueling. Further, it is used to deduce the background thermal deuterium atom density at the plasma center. 9 refs., 6 figs.
Spin-1 two-impurity Kondo problem on a lattice
Allerdt, A.; Žitko, R.; Feiguin, A. E.
2018-01-01
We present an extensive study of the two-impurity Kondo problem for spin-1 adatoms on a square lattice using an exact canonical transformation to map the problem onto an effective one-dimensional system that can be numerically solved using the density matrix renormalization group method. We provide a simple intuitive picture and identify the different regimes, depending on the distance between the two impurities, Kondo coupling JK, longitudinal anisotropy D , and transverse anisotropy E . In the isotropic case, two impurities on opposite (the same) sublattices have a singlet (triplet) ground state. However, the energy difference between the triplet ground state and the singlet excited state is very small and we expect an effectively fourfold-degenerate ground state, i.e., two decoupled impurities. For large enough JK the impurities are practically uncorrelated forming two independent underscreened states with the conduction electrons, a clear nonperturbative effect. When the impurities are entangled in an RKKY-like state, Kondo correlations persist and the two effects coexist: the impurities are underscreened, and the dangling spin-1 /2 degrees of freedom are responsible for the interimpurity entanglement. We analyze the effects of magnetic anisotropy in the development of quasiclassical correlations.
Recent trends in the impurity profile of pharmaceuticals
Directory of Open Access Journals (Sweden)
Kavita Pilaniya
2010-01-01
Full Text Available Various regulatory authorities such as the International Conference on Harmonization (ICH, the United States Food and Drug administration (FDA, and the Canadian Drug and Health Agency (CDHA are emphasizing on the purity requirements and the identification of impurities in Active Pharmaceutical Ingredients (APIs. The various sources of impurity in pharmaceutical products are - reagents, heavy metals, ligands, catalysts, other materials like filter aids, charcoal, and the like, degraded end products obtained during \\ after manufacturing of bulk drugs from hydrolysis, photolytic cleavage, oxidative degradation, decarboxylation, enantiomeric impurity, and so on. The different pharmacopoeias such as the British Pharmacopoeia, United State Pharmacopoeia, and Indian Pharmacopoeia are slowly incorporating limits to allowable levels of impurities present in APIs or formulations. Various methods are used to isolate and characterize impurities in pharmaceuticals, such as, capillary electrophoresis, electron paramagnetic resonance, gas-liquid chromatography, gravimetric analysis, high performance liquid chromatography, solid-phase extraction methods, liquid-liquid extraction method, Ultraviolet Spectrometry, infrared spectroscopy, supercritical fluid extraction column chromatography, mass spectrometry, Nuclear magnetic resonance (NMR spectroscopy, and RAMAN spectroscopy. Among all hyphenated techniques, the most exploited techniques for impurity profiling of drugs are Liquid Chromatography (LC-Mass Spectroscopy (MS, LC-NMR, LC-NMR-MS, GC-MS, and LC-MS. This reveals the need and scope of impurity profiling of drugs in pharmaceutical research.
Impurity production and transport at the JET belt limiter
International Nuclear Information System (INIS)
Pitcher, C.S.; McCracken, G.M.; Strangeby, P.C.; Toronto Univ., ON; Summers, D.D.R.
1989-01-01
Under certain operating conditions in JET the impurity content of the discharge can be high, thus reducing the fusion reaction rate through the dilution of the hydrogenic fuel. The dilution in most discharges is predominantly due to carbon impurities. In order to understand how carbon impurities are produced and transported into the plasma, detailed measurements with interference filters centered on intense spectral lines of the low ionization states of carbon (C I, C II, C III) as well as the fuel species (Dα) and helium (He I). (author) 6 refs., 4 figs
Studies of impurity recycling by the collector probe technique
International Nuclear Information System (INIS)
Hildebrandt, D.; Grote, H.; Herrmann, A.; Laux, M.; Pech, P.; Reiner, H.D.; Wolff, H.
1987-01-01
In order to study recycling effects of the nonintrinsic impurity Li discharges with and without LiD-pellet injection were investigated. The observed maximum impurity level of Li in the SOL plasma of discharges without injection reaches less than 10% of that observed in discharges with injection. The measurements offer the possibility to distinguish between influxes from the wall and those which reach the collector probe via the core plasma. The time evolution, orientation and radial dependence of the impurity fluxes are characteristic features of their origin. The consideration of all these features facilitates a better understanding of collector probe measurements in the SOL-plasma. (orig.)
Electronic structure of deep impurity centers in silicon
International Nuclear Information System (INIS)
Oosten, A.B. van.
1989-01-01
This thesis reports an experimental study of deep level impurity centers in silicon, with much attention for theoretical interpretation of the data. A detailed picture of the electronic structure of several centers was obtained by magnetic resonance techniques, such as electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR) and field scanned ENDOR (FSE). The thesis consists of two parts. The first part deals with chalcogen (sulfur, selenium and tellurium) related impurities, which are mostly double donors. The second part is about late transition metal (nickel, palladium and platinum) impurities, which are single (Pd,Pt) or double (Ni) acceptor centers. (author). 155 refs.; 51 figs.; 23 tabs
Extraction process for removing metallic impurities from alkalide metals
Royer, Lamar T.
1988-01-01
A development is described for removing metallic impurities from alkali metals by employing an extraction process wherein the metallic impurities are extracted from a molten alkali metal into molten lithium metal due to the immiscibility of the alkali metals in lithium and the miscibility of the metallic contaminants or impurities in the lithium. The purified alkali metal may be readily separated from the contaminant-containing lithium metal by simple decanting due to the differences in densities and melting temperatures of the alkali metals as compared to lithium.
Kecili, Rustem; Billing, Johan; Nivhede, David; Sellergren, Börje; Rees, Anthony; Yilmaz, Ecevit
2014-04-25
This study describes the identification and evaluation of molecularly imprinted polymers (MIPs) for the selective removal of potentially genotoxic aminopyridine impurities from pharmaceuticals. Screening experiments were performed using existing MIP resin libraries to identify resins selective towards those impurities in the presence of model pharmaceutical compounds. A hit resin with a considerable imprinting effect was found in the screening and upon further investigation, the resin was found to show a broad selectivity towards five different aminopyridines in the presence of the two model active pharmaceutical ingredients (APIs) piroxicam and tenoxicam. Copyright © 2014 Elsevier B.V. All rights reserved.
1999-01-01
In 1936, at age 31, Carl David Anderson became the second youngest Nobel laureate for his discovery of antimatter when he observed positrons in a cloud chamber.He is responsible for developing rocket power weapons that were used in World War II.He was born in New York City in 1905 and was educated in Los Angeles. He served for many years as a physics professor at California Institute of Technology. Prior to Oppenheimer, Anderson was offered the job of heading the Los Alamos atomic bomb program but could not assume the role because of family obligations.He was a pioneer in studying cosmic rays
Determination of trace impurities in materials
International Nuclear Information System (INIS)
Parashar, D.C.
1991-01-01
Research work done at the National Physical Laboratory to develop new methods which are more specific and/or more sensitive has been reviewed. These methods are based on the use of existing facilities viz. atomic absorption spectrophotometry, uv-visible spectrophotometry, gas chromatography and conventional chemical methods. It is possible to determine impurities like boron at 5ppb level, phosphorus at 100 ppb and oxygen non-stoichiometry in 1:2:3 compounds with higher accuracy. Boron is determined spectrophotometrically by forming a complex with curcumin and phosphorus is determined indirectly by atomic absorption spectrophotometry by forming phosphomolybdate complex with antimony or bismuth which have 1:1 ratio with phosphorus in the complex. Gas chromatographic technique has been used to evaluate the oxygen non-stoichiometry in high temperature superconductors (1:2:3 compound) where the HTc sample is dissolved in dilute nitric acid in helium environment and the oxygen released is determined using thermal conductivity detector. (author). 19 refs., 3 figs., 4 tabs
Impurity effects on the band structure of one-dimensional photonic crystals: experiment and theory
Energy Technology Data Exchange (ETDEWEB)
Luna-Acosta, G A [Instituto de Fisica, BUAP Apartado Postal J-48, 72570 Puebla (Mexico); Schanze, H; Kuhl, U; Stoeckmann, H-J [Fachbereich Physik der Philipps-Universitaet Marburg, Renthof 5, D-35032 (Germany)], E-mail: gluna@sirio.ifuap.buap.mx
2008-04-15
We study the effects of single impurities on the transmission in microwave realizations of the photonic Kronig-Penney model, consisting of arrays of Teflon pieces alternating with air spacings in a microwave guide. As only the first propagating mode is considered, the system is essentially one-dimensional (1D) obeying the Helmholtz equation. We derive analytical closed form expressions from which the band structure, frequency of defect modes and band profiles can be determined. These agree very well with experimental data for all types of single defects considered (e.g. interstitial and substitutional) and show that our experimental set-up serves to explore some of the phenomena occurring in more sophisticated experiments. Conversely, based on the understanding provided by our formulae, information about the unknown impurity can be determined by simply observing certain features in the experimental data for the transmission. Further, our results are directly applicable to the closely related quantum 1D Kronig-Penney model.
Effect of impurity on electronic properties of carbon nano tubes
International Nuclear Information System (INIS)
Jalili, S.; Jafari, M.; Habibian, J.
2008-01-01
We have studied the effect of impurity on electronic properties of single-walled carbon nano tubes using Density Functional Theory. Electronic band structures and density of states of (4, 4) and (7, 0) carbon nano tubes in the presence of different amount of B and N impurities were calculated. It was found that these impurities have significant effect on the conductivity of carbon nano tubes. The metallic (4, 4) nano tube remains to be metallic after doping with B and N. The electronic properties of small gap semiconducting (7, 0) tube can extensively change in the presence of impurity. Our results indicate that B-doped and N-doped (7, 0) carbon nano tubes can be p-type and n-type semiconductors, respectively
Investigation of impurity states in AlSb
International Nuclear Information System (INIS)
Agaev, Ya.; Bekmedova, N.G.; Mikhailov, A.P.
1976-01-01
The spectra of infrared absorption and the Hall effect have been investigated in the impurity region of aluminium antimonide crystals doped with sulphur and tellurium. By the measurements of the Hall effect temperature dependence in n-AlSb(S) and n-AlSb(Te) crystals determined is the activation energy of an impurity level equal to 0.24 eV and 0.068 eV respectively. The ionization energy for n-AlSb(S), equal to 0.22 eV, and for n-AlSb(Te) equal to 0.09 eV has been found from the infrared absorption curves. The absorption bands caused by the ionized impurity-band transition have been shown to be well described by the Callouway formula. Deep impurity centers have been revealed
International Nuclear Information System (INIS)
Komarov, F.F.; Komarov, A.F.; Mironov, A.M.; Makarevich, Yu.V.; Miskevich, S.A.; Zayats, G.M.
2011-01-01
Physical and mathematical models and numerical simulation of the diffusion of implanted impurities during rapid thermal treatment of silicon structures are discussed. The calculation results correspond to the experimental results with a sufficient accuracy. A simulation software system has been developed that is integrated into ATHENA simulation system developed by Silvaco Inc. This program can simulate processes of the low-energy implantation of B, BF 2 , P, As, Sb, C ions into the silicon structures and subsequent rapid thermal annealing. (authors)
Sensitivity of graphene flakes and nanorings to impurities
Energy Technology Data Exchange (ETDEWEB)
Konobeeva, N.N., E-mail: yana_nn@volsu.ru [Volgograd State University, University Avenue 100, Volgograd 400062 (Russian Federation); Belonenko, M.B. [Volgograd State University, University Avenue 100, Volgograd 400062 (Russian Federation); Volgograd Institute of Business, Uzhno-Ukrainskaya Str., Volgograd 400048 (Russian Federation)
2017-06-01
In this paper, we consider the influence of impurity on the graphene flakes and nanorings conductance. Based on the jumping Hamiltonian for graphene electrons with its direct diagonalization, we obtain the density of states. Further, the tunneling current is calculated for the following contacts: graphene flake-metal, graphene flake-quantum dots, graphene nanoring-quantum dots. We analyze the effect of the flake dimensions and the positions of the adsorbed molecule of impurity on the characteristic properties of the tunneling current.
Engineering and material aspects of impurity control systems
International Nuclear Information System (INIS)
Koski, J.A.
1985-01-01
The design of impurity control devices for fusion energy devices is discussed from the engineering and materials viewpoint. First, examples of impurity control devices are presented, and the plasma edge environment for which they are designed is briefly described. Materials concerns related to the design of the components are discussed and some currently proposed designs presented. Engineering tools available to the designer are listed, and some commonly encountered engineering analysis problems described
INVESTIGATION OF IMPURITY DYNAMICS AT GOL-3 FACILITY
Czech Academy of Sciences Publication Activity Database
Polosatkin, S.; Burdakov, A. V.; Piffl, Vojtěch; Postupaev, V. V.; Weinzettl, Vladimír
2005-01-01
Roč. 47, 1T (2005), s. 267-269 ISSN 0748-1896. [International Conference on Open Magnetic Systems for Plasma Confinement/5th./. Novosibirsk, 5.7.2005-9.7.2005] R&D Projects: GA AV ČR(CZ) KSK2043105 Institutional research plan: CEZ:AV0Z20430508 Keywords : UV spectroscopy * plasma impurities * impurity transport Subject RIV: BL - Plasma and Gas Discharge Physics
Impurity-defect induced noncentrosymmetricity in nonlinear optical processes
International Nuclear Information System (INIS)
Miah, M. Idrish
2009-01-01
Noncentrosymmetric nanosize-material processes in cadmium iodide are formed by doping it with the impurity copper. The noncentrosymmetricity in the processes are probed by the observation of the second-order optical susceptibility χ ijk (2) . The value of χ ijk (2) is found to depend fashionably on the impurity content of the nanomaterials. The results also show that a significant enhancement in the noncentrosymmetric response is achieved in nanomaterials with reduced sizes and at low temperatures.
Nuclear relaxation in semiconductors doped with magnetic impurities
International Nuclear Information System (INIS)
Mel'nichuk, S.V.; Tovstyuk, N.K.
1984-01-01
The temperature and concentration dependences are investigated of the nuclear spin-lattice relaxation time with account of spin diffusion for degenerated and non-degenerated semicon- ductors doped with magnetic impurities. In case of the non-degenerated semiconductor the time is shown to grow with temperature, while in case of degenerated semiconductor it is practically independent of temperature. The impurity concentration growth results in decreasing the spin-lattice relaxation time
Thermal Conductivity of Nanotubes: Effects of Chirality and Isotope Impurity
Gang, Zhang; Li, Baowen
2005-01-01
We study the dependence of thermal conductivity of single walled nanotubes (SWNT) on chirality and isotope impurity by nonequilibrium molecular dynamics method with accurate potentials. It is found that, contrary to electronic conductivity, the thermal conductivity is insensitive to the chirality. The isotope impurity, however, can reduce the thermal conductivity up to 60% and change the temperature dependence behavior. We also study the dependence of thermal conductivity on tube length for t...
Arrhythmia and Clinical Cardiac Findings in Children With Anderson-Fabry Disease.
Wilson, Hunter C; Hopkin, Robert J; Madueme, Peace C; Czosek, Richard J; Bailey, Laurie A; Taylor, Michael D; Jefferies, John L
2017-07-15
Anderson-Fabry Disease (AFD) is a lysosomal storage disorder that results in progressive cardiovascular hypertrophy, scarring, and arrhythmia burden; yet, the early cardiac phenotype of AFD is still poorly defined. To further characterize early cardiac features in AFD, we evaluated electrocardiographic and clinical findings contained in a local cohort of pediatric AFD patients and arrhythmia data in children enrolled in the Fabry Registry. Twenty-six local patients aged Fabry Registry, sinus bradycardia, defined as heart rate Fabry cardiomyopathy. Bradycardia, common in adults, is frequent even among children with AFD. Given the potential for early initiation of enzyme replacement therapy to reduce cardiovascular morbidity, continued work to develop paradigms of therapy and longitudinal cardiovascular surveillance is warranted. Copyright © 2017 Elsevier Inc. All rights reserved.
A Bitslice Implementation of Anderson's Attack on A5/1
Bulavintsev, Vadim; Semenov, Alexander; Zaikin, Oleg; Kochemazov, Stepan
2018-03-01
The A5/1 keystream generator is a part of Global System for Mobile Communications (GSM) protocol, employed in cellular networks all over the world. Its cryptographic resistance was extensively analyzed in dozens of papers. However, almost all corresponding methods either employ a specific hardware or require an extensive preprocessing stage and significant amounts of memory. In the present study, a bitslice variant of Anderson's Attack on A5/1 is implemented. It requires very little computer memory and no preprocessing. Moreover, the attack can be made even more efficient by harnessing the computing power of modern Graphics Processing Units (GPUs). As a result, using commonly available GPUs this method can quite efficiently recover the secret key using only 64 bits of keystream. To test the performance of the implementation, a volunteer computing project was launched. 10 instances of A5/1 cryptanalysis have been successfully solved in this project in a single week.
VizieR Online Data Catalog: Radio observations of Galactic WISE HII regions (Anderson+, 2015)
Anderson, L. D.; Armentrout, W. P.; Johnstone, B. M.; Bania, T. M.; Balser, D. S.; Wenger, T. V.; Cunningham, V.
2016-01-01
We draw our targets from the MIR objects in the WISE catalog of Anderson+, 2014, J/ApJS/212/1. We also include in our sample Sharpless H II regions (Sharpless 1959, VII/20). See section 2 for further details. Our observations were made with the GBT 100m telescope from 2012 July through 2014 August. There are seven radio recombination lines (RRLs) that can be cleanly observed simultaneously with the GBT in the X-band: H87α to H93α. We average these seven RRLs (each at two orthogonal polarizations) to create a single average RRL spectrum. We followed the same GBT observational procedure as in the original HRDS (Green Bank Telescope H II Region Discovery Survey (GBT HRDS; Bania et al. 2010ApJ...718L.106B). (3 data files).
Modified Anderson-Darling Test-Based Target Detector in Non-Homogenous Environments
Directory of Open Access Journals (Sweden)
Yang Li
2014-08-01
Full Text Available A constant false alarm rate (CFAR target detector in non-homogenous backgrounds is proposed. Based on K-sample Anderson-Darling (AD tests, the method re-arranges the reference cells by merging homogenous sub-blocks surrounding the cell under test (CUT into a new reference window to estimate the background statistics. Double partition test, clutter edge refinement and outlier elimination are used as an anti-clutter processor in the proposed Modified AD (MAD detector. Simulation results show that the proposed MAD test based detector outperforms cell-averaging (CA CFAR, greatest of (GO CFAR, smallest of (SO CFAR, order-statistic (OS CFAR, variability index (VI CFAR, and CUT inclusive (CI CFAR in most non-homogenous situations.
Modified Anderson-Darling test-based target detector in non-homogenous environments.
Li, Yang; Wei, Yinsheng; Li, Bingfei; Alterovitz, Gil
2014-08-29
A constant false alarm rate (CFAR) target detector in non-homogenous backgrounds is proposed. Based on K-sample Anderson-Darling (AD) tests, the method re-arranges the reference cells by merging homogenous sub-blocks surrounding the cell under test (CUT) into a new reference window to estimate the background statistics. Double partition test, clutter edge refinement and outlier elimination are used as an anti-clutter processor in the proposed Modified AD (MAD) detector. Simulation results show that the proposed MAD test based detector outperforms cell-averaging (CA) CFAR, greatest of (GO) CFAR, smallest of (SO) CFAR, order-statistic (OS) CFAR, variability index (VI) CFAR, and CUT inclusive (CI) CFAR in most non-homogenous situations.
Maximilien Brice
2005-01-01
At a ceremony on 26 September at CERN, W Cleon Anderson, president of the Institute of Electrical and Electronics Engineers (IEEE), formally dedicated a "Milestone" plaque in recognition of the invention of electronic particle detectors at CERN. The plaque was unveiled by Anderson and Georges Charpak, the Nobel-prize winning inventor of wire-chamber technology at CERN.
Energy Technology Data Exchange (ETDEWEB)
Cabello, Carmen I. [Centro de Investigacion y Desarrollo en Ciencias Aplicadas Dr. Jorge J. Ronco, CINDECA - CONICET-Universidad Nacional de La Plata, Calle 47 No 257 (1900) La Plata, Buenos Aires (Argentina)]. E-mail: ccabello@quimica.unlp.edu.ar; Munoz, Mercedes [Centro de Investigacion y Desarrollo en Ciencias Aplicadas Dr. Jorge J. Ronco, CINDECA - CONICET-Universidad Nacional de La Plata, Calle 47 No 257 (1900) La Plata, Buenos Aires (Argentina); Botto, Irma L. [Centro de Quimica Inorganica CEQUINOR - CONICET-Universidad Nacional de La Plata (1900) La Plata, Buenos Aires (Argentina); Payen, Edmond [Unite de Catalyse et de Chimie du Solide, UCCS UMR CNRS 8181, Universite des Sciences et Technologies de Lille, Bat. C3, 59655 Villeneuve d' Ascq Cedex (France)
2006-08-01
The influence of Rh heteroatom on the molybdenum reducibility in the Anderson-type heteropolyoxomolybdate structure of formula (NH{sub 4}){sub 3}[RhMo{sub 6}O{sub 24}H{sub 6}].7H{sub 2}O was investigated by means of TPR technique. With comparative purposes, the thermal behavior in non-reducing conditions was also carried out by means of TGA-DTA studies. The study was performed by XRD, SEM, EDAX and FTIR-Raman techniques. Results were related to those preliminary measurements over other XMo{sub 6} Anderson phases. Likewise, Rh(III)-Al(III) formal replacement in the RhMo{sub 6} structural arrangement was proved. The formation of a solid solution in a limited range of composition (up to 0.25 Rh) was established in order to explore the catalytic performance of {gamma}-Al{sub 2}O{sub 3} supported planar heteropolyoxomolybdate, aiming at optimizing the noble metal content in the catalytic system. Preliminary measurements of RhMo{sub 6}/{gamma}-Al{sub 2}O{sub 3} and (Rh, Al)Mo{sub 6}/{gamma}-Al{sub 2}O{sub 3} activity for HDS and HYD processes were also performed. These results were compared to those obtained for CoMo{sub 6}/{gamma}-Al{sub 2}O{sub 3} system in similar operating conditions and other conventional catalytic systems. The potentiality and scope of RhMo{sub 6} catalytic system for the HDS and HYD processes were analyzed.
Bilateral testicular germ cell tumors: twenty-year experience at M. D. Anderson Cancer Center.
Che, Mingxin; Tamboli, Pheroze; Ro, Jae Y; Park, Dong Soo; Ro, Jung Sil; Amato, Robert J; Ayala, Alberto G
2002-09-15
The incidence of testicular carcinoma in the United States has increased significantly over the last two decades. Germ cell tumors form the majority of malignant testicular tumors. With advances in diagnosis and therapeutic approaches, germ cell tumors are now highly sensitive to treatment, providing long-term survival. It has been speculated that the incidence of bilateral germ cell tumors may increase due to the improved survival of patients with unilateral germ cell tumors. In this report, the authors present a study of bilateral germ cell tumors of the testis in men who were treated at The University of Texas M. D. Anderson Cancer Center over a 20-year period with emphasis on their incidence, histologic features, and clinical features. Between 1978 and 1999, 2431 patients with testicular germ cell tumors were treated at The University of Texas M. D. Anderson Cancer Center. Among these, 24 patients with bilateral germ cell tumors were identified. Clinical records and all available pathology slides of the tumors were reviewed. The overall incidence of bilateral germ cell tumors in the patients with testicular germ cell tumors was 1% (24 of 2431 patients). The incidence was 1.8% (14 of 776 patients) in patients with seminoma and 0.6% (10 of 1655 patients) in patients with nonseminomatous germ cell tumors. Patients with seminoma who were age presentation in patients with seminoma. Thus, patients in the second or third decade of life who presented with seminomas as their initial tumor were more likely to develop a second germ cell tumor compared with patients in the fourth or fifth decade of life. These findings have potentially important implications for clinical management by identifying a population of patients with germ cell tumors who are at risk of developing a second tumor and also for studying risk factors of bilateral germ cell tumors of the testis. Copyright 2002 American Cancer Society.
Spectroscopic studies of carbon impurities in PISCES-A
International Nuclear Information System (INIS)
Ra, Y.; Hirooka, Y.; Leung, W.K.; Conn, R.W.; Pospieszczyk, A.
1989-08-01
The graphite used for the limiter of the tokamak reactor produces carbon-containing molecular impurities as a result of the interactions with the edge plasma. The behavior of these molecular impurities has been studied using emission spectroscopy. The present study includes: finding molecular bands and atomic lines in the visible spectral range which can be used for the study of the molecular impurities, studying the breakup processes of the molecular impurities on their way from the source into the plasma, developing a spectroscopic diagnostic method for the absolute measurement of the molecular impurity flux resulting from graphite erosion. For these studies, carbon-containing molecules such as CH 4 , C 2 H 2 , C 2 H 4 , and CO 2 were injected into the tokamak-boundary,like plasma generated by PISCES-A. The spectrograms of these gases were taken. Many useful bands and lines were determined from the spectrograms. The breakup processes of these gases were studied by observing the spatial profiles of the emission of the molecules and their radicals for different plasma conditions. For the absolute measurement of the eroded molecular impurity flux, the photon efficiency of the lines and bands were found by measuring the absolute number of the emitted photons and injected gas molecules. The chemical sputtering yield of graphite by hydrogen plasma was spectroscopically measured using the previously obtained photon efficiencies. It showed good agreement with results obtained by weight loss measurements. 16 refs., 7 figs., 1 tab
Toroidal asymmetries in divertor impurity influxes in NSTX
Directory of Open Access Journals (Sweden)
F. Scotti
2017-08-01
Full Text Available Toroidal asymmetries in divertor carbon and lithium influxes were observed in NSTX, due to toroidal differences in surface composition, tile leading edges, externally-applied three-dimensional (3D fields and toroidally-localized edge plasma modifications due to radio frequency heating. Understanding toroidal asymmetries in impurity influxes is critical for the evaluation of total impurity sources, often inferred from measurements with a limited toroidal coverage. The toroidally-asymmetric lithium deposition induced asymmetries in divertor lithium influxes. Enhanced impurity influxes at the leading edge of divertor tiles were the main cause of carbon toroidal asymmetries and were enhanced during edge localized modes. Externally-applied 3D fields led to strike point splitting and helical lobes observed in divertor impurity emission, but marginal changes to the toroidally-averaged impurity influxes. Power coupled to the scrape-off layer SOL plasma during radio frequency (RF heating of H-mode discharges enhanced impurity influxes along the non-axisymmetric divertor footprint of flux tubes connecting to plasma in front of the RF antenna.
Van Hove singularities in the paramagnetic phase of the Hubbard model: DMFT study
Žitko, Rok; Bonča, Janez; Pruschke, Thomas
2009-12-01
Using the dynamical mean-field theory (DMFT) with the numerical renormalization-group impurity solver we study the paramagnetic phase of the Hubbard model with the density of states (DOS) corresponding to the three-dimensional (3D) cubic lattice and the two-dimensional (2D) square lattice, as well as a DOS with inverse square-root singularity. We show that the electron correlations rapidly smooth out the square-root van Hove singularities (kinks) in the spectral function for the 3D lattice and that the Mott metal-insulator transition (MIT) as well as the magnetic-field-induced MIT differ only little from the well-known results for the Bethe lattice. The consequences of the logarithmic singularity in the DOS for the 2D lattice are more dramatic. At half filling, the divergence pinned at the Fermi level is not washed out, only its integrated weight decreases as the interaction is increased. While the Mott transition is still of the usual kind, the magnetic-field-induced MIT falls into a different universality class as there is no field-induced localization of quasiparticles. In the case of a power-law singularity in the DOS at the Fermi level, the power-law singularity persists in the presence of interaction, albeit with a different exponent, and the effective impurity model in the DMFT turns out to be a pseudogap Anderson impurity model with a hybridization function which vanishes at the Fermi level. The system is then a generalized Fermi liquid. At finite doping, regular Fermi-liquid behavior is recovered.
Energy Technology Data Exchange (ETDEWEB)
Posske, Thore Hagen
2016-02-26
Topological insulators are electronic phases that insulate in the bulk and accommodate a peculiar, metallic edge liquid with a spin-dependent dispersion. They are regarded to be of considerable future use in spintronics and for quantum computation. Besides determining the intrinsic properties of this rather novel electronic phase, considering its combination with well-known physical systems can generate genuinely new physics. In this thesis, we report on such combinations including topological insulators. Specifically, we analyze an attached Rashba impurity, a Kondo dot in the two channel setup, magnetic impurities on the surface of a strong three-dimensional topological insulator, the proximity coupling of the latter system to a superconductor, and hybrid systems consisting of a topological insulator and a semimetal. Let us summarize our primary results. Firstly, we determine an analytical formula for the Kondo cloud and describe its possible detection in current correlations far away from the Kondo region. We thereby rely on and extend the method of refermionizable points. Furthermore, we find a class of gapless topological superconductors and semimetals, which accommodate edge states that behave similarly to the ones of globally gapped topological phases. Unexpectedly, we also find edge states that change their chirality when affected by sufficiently strong disorder. We regard the presented research helpful in future classifications and applications of systems containing topological insulators, of which we propose some examples.
Energetics of halogen impurities in thorium dioxide
Kuganathan, Navaratnarajah; Ghosh, Partha S.; Arya, Ashok K.; Dey, Gautam K.; Grimes, Robin W.
2017-11-01
Defect energies for halogen impurity atoms (Cl, Br and I) in thoria are calculated using the generalized gradient approximation and projector augmented plane wave potentials under the framework of density functional theory. The energy to place a halogen atom at a pre-existing lattice site is the incorporation energy. Seven sites are considered: octahedral interstitial, O vacancy, Th vacancy, Th-O di-vacancy cluster (DV) and the three O-Th-O tri-vacancy cluster (NTV) configurations. For point defects and vacancy clusters, neutral and all possible defect charge states up to full formal charge are considered. The most favourable incorporation site for Cl is the singly charged positive oxygen vacancy while for Br and I it is the NTV1 cluster. By considering the energy to form the defect sites, solution energies are generated. These show that in both ThO2-x and ThO2 the most favourable solution equilibrium site for halides is the single positively charged oxygen vacancy (although in ThO2, I demonstrates the same solubility in the NTV1 and DV clusters). Solution energies are much lower in ThO2-x than in ThO2 indicating that stoichiometry is a significant factor in determining solubility. In ThO2, all three halogens are highly insoluble and in ThO2-x Br and I remain insoluble. Although ½Cl2 is soluble in ThO2-x alternative phases such as ZrCl4 exist which are of lower energy.
Synthesis, Isolation and Characterization of Process-Related Impurities in Oseltamivir Phosphate
Directory of Open Access Journals (Sweden)
Yogesh Kumar Sharma
2012-01-01
Full Text Available Three known impurities in oseltamivir phosphate bulk drug at level 0.1% (ranging from 0.05-0.1% were detected by gradient reverse phase high performance liquid chromatography. These impurities were preliminarily identified by the mass number of the impurities. Different experiments were conducted and finally the known impurities were synthesized and characterized.
Shiino, Masatoshi; Yamana, Michiko
2004-01-01
We study the statistical mechanical aspects of stochastic analog neural network models for associative memory with correlation type learning. We take three approaches to derive the set of the order parameter equations for investigating statistical properties of retrieval states: the self-consistent signal-to-noise analysis (SCSNA), the Thouless-Anderson-Palmer (TAP) equation, and the replica symmetric calculation. On the basis of the cavity method the SCSNA can be generalized to deal with stochastic networks. We establish the close connection between the TAP equation and the SCSNA to elucidate the relationship between the Onsager reaction term of the TAP equation and the output proportional term of the SCSNA that appear in the expressions for the local fields.
DEFF Research Database (Denmark)
Fakhri, Yama; Sejersten, Maria; Schoos, Mikkel Malby
2016-01-01
Background: The Anderson-Wilkins score (AW-score) is based on quantitative 12-lead electrocardiogram (ECG) criteria to estimate acuteness of ischemia in patients with ST elevation myocardial infarction (STEMI). The score identifies patients with a substantial salvage potential after primary percu...
Directory of Open Access Journals (Sweden)
Hirokazu Takai
2016-01-01
Full Text Available Purpose. Anderson type III odontoid fractures have traditionally been considered stable and treated conservatively. However, unstable cases with unfavorable results following conservative treatment have been reported. Methods. We present the cases of two patients who sustained minimally displaced Anderson type III fractures with a characteristic fracture pattern that we refer to as “oblique type axis body fracture.” Results. The female patients aged 90 and 72 years, respectively, were both diagnosed with minimally displaced Anderson type III fractures. Both fractures had a characteristic “oblique type” fracture pattern. The first patient was treated conservatively with cervical spine immobilization in a semirigid collar. However, gross displacement was noted at the 6-week follow-up visit. The second patient was therefore treated operatively by C1–C3/4 posterior fusion and the course was uneventful. Conclusions. Oblique type axis body fractures resemble a highly unstable subtype of Anderson type III fractures with the potential of severe secondary deformity following conservative treatment, irrespective of initial grade of displacement. The authors therefore warrant a high index of suspicion for this injury and suggest early operative stabilization.
Scully : võin ka lolli mängida / Gillian Anderson ; tõlk. Triin Tael
Anderson, Gillian
2008-01-01
USA sarjale "The X-Files" põhinev teine järjefilm "Salatoimikud: Ma tahan uskuda" ("The X-Files: I Want to Believe") : režissöör Chris Carter : peaosades David Duchovny, Gillian Anderson : Ameerika Ühendriigid - Kanada 2008. Intervjuu ilmus juulis portaalis USA Weekend
Geertsma, W; Khomskii, D
1996-01-01
A mechanism is suggested which can modify in certain cases the Goodenough-Kanamori-Anderson rules determining the character of superexchange in magnetic insulators; namely, side groups coupled to ligands, which are often present but are usually ignored, may contribute significantly, and may in
Energy Technology Data Exchange (ETDEWEB)
Korytar, Richard; Pruneda, Miguel; Ordejon, Pablo; Lorente, Nicolas [Centre d' Investigacio en Nanociencia i Nanotecnologia (CSIC-ICN), Campus de la UAB, E-08193 Bellaterra (Spain); Junquera, Javier, E-mail: rkorytar@cin2.e [Departamento de Ciencias de la Tierra y Fisica de la Materia Condensada, Universidad de Cantabria, E-39005 Santander (Spain)
2010-09-29
We have adapted the maximally localized Wannier function approach of Souza et al (2002 Phys. Rev. B 65 035109) to the density functional theory based SIESTA code (Soler et al 2002 J. Phys.: Condens. Mater. 14 2745) and applied it to the study of Co substitutional impurities in bulk copper as well as to the Cu(111) surface. In the Co impurity case, we have reduced the problem to the Co d-electrons and the Cu sp-band, permitting us to obtain an Anderson-like Hamiltonian from well defined density functional parameters in a fully orthonormal basis set. In order to test the quality of the Wannier approach to surfaces, we have studied the electronic structure of the Cu(111) surface by again transforming the density functional problem into the Wannier representation. An excellent description of the Shockley surface state is attained, permitting us to be confident in the application of this method to future studies of magnetic adsorbates in the presence of an extended surface state.
FLAPW Study of the EFG Tensor at Cd Impurities in In{sub 2}O{sub 3}
Energy Technology Data Exchange (ETDEWEB)
Errico, L. A., E-mail: errico@fisica.unlp.edu.ar; Renteria, M.; Fabricius, G.; Darriba, G. N. [Universidad Nacional de La Plata, Departamento de Fisica, Facultad de Ciencias Exactas (Argentina)
2004-11-15
We report an ab initio study of the electric-field gradient tensor (EFG) at Cd impurities located at both nonequivalent cationic sites in the semiconductor In{sub 2}O{sub 3}. Calculations were performed with the FLAPW method that allows us to treat the electronic structure of the doped system and the atomic relaxations introduced by the impurities in the host in a fully self-consistent way. From our results for the EFG (in excellent agreement with the experiments), it is clear that the problem of the EFG at Cd impurities in In{sub 2}O{sub 3} cannot be described by the point-charge model and antishielding factors.
Lowest excited-state impurity binding energy in InGaN/GaN parabolic QWW: magnetic field effect
International Nuclear Information System (INIS)
Haddou El Ghazi; Anouar Jorio; Izeddine Zorkani
2013-01-01
In this paper, we have investigated the magnetic field effect on the lowest excited-state binding energy of hydrogenic shallow-donor impurity in wurtzite (In,Ga)N/GaN parabolic transversal-section quantum-well wire (PQWW) using the finite-difference method within the quasi-one-dimensional effective potential model. The calculations are performed within the framework of the effective mass approximation. A cylindrical QWW effective radius is taken into account to describe the lateral confinement strength. The numerical results show that: (i) the probability density is the largest on a circularity whose radius is the effective radius and (ii) the lowest excited-state binding energy is the largest when an impurity is located on this circularity while it starts to decrease as the impurity is away from the circularity. (author)
Dynamics of Impurity and Valence Bands in Ga1-xMnxAs Within the Dynamical Mean-Field Approximation
International Nuclear Information System (INIS)
Majidi, M.A.; Moreno, Juana; Jarrell, Mark; Fishman, Randy Scott; Aryanpour, K.A.
2006-01-01
We calculate the density-of-states and the spectral function of Ga 1-x Mn x As within the dynamical mean-field approximation. Our model includes the competing effects of the strong spin-orbit coupling on the J=3/2 GaAs hole bands and the exchange interaction between the magnetic ions and the itinerant holes. We study the quasiparticle and impurity bands in the paramagnetic and ferromagnetic phases for different values of impurity-hole coupling J c at a Mn doping of x=0.05. By analyzing the anisotropic angular distribution of the impurity band carriers at T=0, we conclude that the carrier polarization is optimal when the carriers move along the direction parallel to the average magnetization.