Anderson localization of composite excitations in disordered optomechanical arrays
NASA Astrophysics Data System (ADS)
Figueiredo Roque, Thales; Peano, Vittorio; Yevtushenko, Oleg M.; Marquardt, Florian
2017-01-01
Optomechanical (OMA) arrays are a promising future platform for studies of transport, many-body dynamics, quantum control and topological effects in systems of coupled photon and phonon modes. We introduce disordered OMA arrays, focusing on features of Anderson localization of hybrid photon-phonon excitations. It turns out that these represent a unique disordered system, where basic parameters can be easily controlled by varying the frequency and the amplitude of an external laser field. We show that the two-species setting leads to a non-trivial frequency dependence of the localization length for intermediate laser intensities. This could serve as a convincing evidence of localization in a non-equilibrium dissipative situation.
Local theory for Mott-Anderson localization
NASA Astrophysics Data System (ADS)
Sen, Sudeshna; Terletska, Hanna; Moreno, Juana; Vidhyadhiraja, N. S.; Jarrell, Mark
2016-12-01
The paramagnetic metallic phase of the Anderson-Hubbard model (AHM) is investigated using a nonperturbative local moment approach within the framework of dynamical mean-field theory with a typical medium. Our focus is on the breakdown of the metallic phase near the metal-insulators transition as seen in the single-particle spectra, scattering rates, and the associated distribution of Kondo scales. We demonstrate the emergence of a universal, underlying low-energy scale, TKpeak. This lies close to the peak of the distribution of Kondo scales obtained within the metallic phase of the paramagnetic AHM. Spectral dynamics for energies ω ≲TKpeak display Fermi liquid universality crossing over to an incoherent universal dynamics for ω ≫TKpeak in the scaling regime. Such universal dynamics indicate that within a local theory the low to moderately low-energy physics is governed by an effective, disorder renormalized Kondo screening.
Anderson localization in the time domain
NASA Astrophysics Data System (ADS)
Sacha, Krzysztof; Delande, Dominique
2016-08-01
In analogy with the usual Anderson localization taking place in time-independent disordered quantum systems where the disorder acts in configuration space, systems exposed to temporally disordered potentials can display Anderson localization in the time domain. We demonstrate this phenomenon with one-dimensional examples where a temporally disordered potential induces localization during the quantum evolution of wave packets, in contrast with a fully delocalized classical dynamics. This is an example of a time crystal phenomenon, i.e., a crystalline behavior in the time domain.
Anderson localization for chemically realistic systems
NASA Astrophysics Data System (ADS)
Terletska, Hanna
2015-03-01
Disorder which is ubiquitous for most materials can strongly effect their properties. It may change their electronic structures or even cause their localization, known as Anderson localization. Although, substantial progress has been achieved in the description of the Anderson localization, a proper mean-field theory of this phenomenon for more realistic systems remains elusive. Commonly used theoretical methods such as the coherent potential approximation and its cluster extensions fail to describe the Anderson transition, as the average density of states (DOS) employed in such theories is not critical at the transition. However, near the transition, due to the spatial confinement of carriers, the local DOS becomes highly skewed with a log-normal distribution, for which the most probable and the typical values differ noticeably from the average value. Dobrosavljevic et.al., incorporated such ideas in their typical medium theory (TMT), and showed that the typical (not average) DOS is critical at the transition. While the TMT is able to capture the localized states, as a local single site theory it still has several drawbacks. For the disorder Anderson model in three dimension it underestimates the critical disorder strength, and fails to capture the re-entrance behavior of the mobility edge. We have recently developed a cluster extension of the TMT, which addresses these drawbacks by systematically incorporating non-local corrections. This approach converges quickly with cluster size and allows us to incorporate the effect of interactions and realistic electronic structure. As the first steps towards realistic material modeling, we extended our TMDCA formalisms to systems with the off diagonal disorder and multiple bands structures. We also applied our TMDCA scheme to systems with both disorder and interactions and found that correlations effects tend to stabilize the metallic behavior even in two dimensions. This work was supported by DOE SciDAC Grant No. DE-FC02
Distribution of critical temperature at Anderson localization
NASA Astrophysics Data System (ADS)
Gammag, Rayda; Kim, Ki-Seok
2016-05-01
Based on a local mean-field theory approach at Anderson localization, we find a distribution function of critical temperature from that of disorder. An essential point of this local mean-field theory approach is that the information of the wave-function multifractality is introduced. The distribution function of the Kondo temperature (TK) shows a power-law tail in the limit of TK→0 regardless of the Kondo coupling constant. We also find that the distribution function of the ferromagnetic transition temperature (Tc) gives a power-law behavior in the limit of Tc→0 when an interaction parameter for ferromagnetic instability lies below a critical value. However, the Tc distribution function stops the power-law increasing behavior in the Tc→0 limit and vanishes beyond the critical interaction parameter inside the ferromagnetic phase. These results imply that the typical Kondo temperature given by a geometric average always vanishes due to finite density of the distribution function in the TK→0 limit while the typical ferromagnetic transition temperature shows a phase transition at the critical interaction parameter. We propose that the typical transition temperature serves a criterion for quantum Griffiths phenomena vs smeared transitions: Quantum Griffiths phenomena occur above the typical value of the critical temperature while smeared phase transitions result at low temperatures below the typical transition temperature. We speculate that the ferromagnetic transition at Anderson localization shows the evolution from quantum Griffiths phenomena to smeared transitions around the critical interaction parameter at low temperatures.
Quantum non-Markovianity induced by Anderson localization
Lorenzo, Salvatore; Lombardo, Federico; Ciccarello, Francesco; Palma, G. Massimo
2017-01-01
As discovered by P. W. Anderson, excitations do not propagate freely in a disordered lattice, but, due to destructive interference, they localise. As a consequence, when an atom interacts with a disordered lattice, one indeed observes a non-trivial excitation exchange between atom and lattice. Such non-trivial atomic dynamics will in general be characterised also by a non-trivial quantum information backflow, a clear signature of non-Markovian dynamics. To investigate the above scenario, we consider a quantum emitter, or atom, weakly coupled to a uniform coupled-cavity array (CCA). If initially excited, in the absence of disorder, the emitter undergoes a Markovian spontaneous emission by releasing all its excitation into the CCA (initially in its vacuum state). By introducing static disorder in the CCA the field normal modes become Anderson-localized, giving rise to a non-Markovian atomic dynamics. We show the existence of a functional relationship between a rigorous measure of quantum non-Markovianity and the CCA localization. We furthermore show that the average non-Markovianity of the atomic dynamics is well-described by a phenomenological model in which the atom is coupled, at the same time, to a single mode and to a standard - Markovian - dissipative bath. PMID:28205542
Quantum non-Markovianity induced by Anderson localization
NASA Astrophysics Data System (ADS)
Lorenzo, Salvatore; Lombardo, Federico; Ciccarello, Francesco; Palma, G. Massimo
2017-02-01
As discovered by P. W. Anderson, excitations do not propagate freely in a disordered lattice, but, due to destructive interference, they localise. As a consequence, when an atom interacts with a disordered lattice, one indeed observes a non-trivial excitation exchange between atom and lattice. Such non-trivial atomic dynamics will in general be characterised also by a non-trivial quantum information backflow, a clear signature of non-Markovian dynamics. To investigate the above scenario, we consider a quantum emitter, or atom, weakly coupled to a uniform coupled-cavity array (CCA). If initially excited, in the absence of disorder, the emitter undergoes a Markovian spontaneous emission by releasing all its excitation into the CCA (initially in its vacuum state). By introducing static disorder in the CCA the field normal modes become Anderson-localized, giving rise to a non-Markovian atomic dynamics. We show the existence of a functional relationship between a rigorous measure of quantum non-Markovianity and the CCA localization. We furthermore show that the average non-Markovianity of the atomic dynamics is well-described by a phenomenological model in which the atom is coupled, at the same time, to a single mode and to a standard - Markovian - dissipative bath.
Quantum non-Markovianity induced by Anderson localization.
Lorenzo, Salvatore; Lombardo, Federico; Ciccarello, Francesco; Palma, G Massimo
2017-02-16
As discovered by P. W. Anderson, excitations do not propagate freely in a disordered lattice, but, due to destructive interference, they localise. As a consequence, when an atom interacts with a disordered lattice, one indeed observes a non-trivial excitation exchange between atom and lattice. Such non-trivial atomic dynamics will in general be characterised also by a non-trivial quantum information backflow, a clear signature of non-Markovian dynamics. To investigate the above scenario, we consider a quantum emitter, or atom, weakly coupled to a uniform coupled-cavity array (CCA). If initially excited, in the absence of disorder, the emitter undergoes a Markovian spontaneous emission by releasing all its excitation into the CCA (initially in its vacuum state). By introducing static disorder in the CCA the field normal modes become Anderson-localized, giving rise to a non-Markovian atomic dynamics. We show the existence of a functional relationship between a rigorous measure of quantum non-Markovianity and the CCA localization. We furthermore show that the average non-Markovianity of the atomic dynamics is well-described by a phenomenological model in which the atom is coupled, at the same time, to a single mode and to a standard - Markovian - dissipative bath.
Floß, Johannes; Averbukh, Ilya Sh
2016-05-19
We describe a universal behavior of linear molecules excited by a periodic train of short laser pulses under conditions close to the quantum resonance. The quantum resonance effect causes an unlimited ballistic growth of the angular momentum. We show that a disturbance of the quantum resonance, either by the centrifugal distortion of the rotating molecules or a controlled detuning of the pulse train period from the so-called rotational revival time, eventually halts the growth by causing Anderson localization beyond a critical value of the angular momentum, the Anderson wall. Below the wall, the rotational excitation oscillates with the number of pulses due to a mechanism similar to Bloch oscillations in crystalline solids. We suggest optical experiments capable of observing the rotational Anderson wall and Bloch oscillations at near-ambient conditions with the help of existing laser technology.
On the Anderson localization conjecture in Dusty Plasma
NASA Astrophysics Data System (ADS)
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.
Super-diffusion in optical realizations of Anderson localization
NASA Astrophysics Data System (ADS)
Krivolapov, Yevgeny; Levi, Liad; Fishman, Shmuel; Segev, Mordechai; Wilkinson, Michael
2012-04-01
We discuss the dynamics of particles in one dimension in potentials that are random in both space and time. The results are applied to recent optics experiments on Anderson localization, in which the transverse spreading of a beam is suppressed by random fluctuations in the refractive index. If the refractive index fluctuates along the direction of the paraxial propagation of the beam, the localization is destroyed. We analyze this broken localization in terms of the spectral decomposition of the potential. When the potential has a discrete spectrum, the spread is controlled by the overlap of Chirikov resonances in phase space. As the number of Fourier components is increased, the resonances merge into a continuum, which is described by a Fokker-Planck equation. We express the diffusion coefficient in terms of the spectral intensity of the potential. For a general class of potentials that are commonly used in optics, the solutions to the Fokker-Planck equation exhibit anomalous diffusion in phase space, implying that when Anderson localization is broken by temporal fluctuations of the potential, the result is transport at a rate similar to a ballistic one or even faster. For a class of potentials which arise in some existing realizations of Anderson localization, atypical behavior is found.
The optical Anderson localization in three-dimensional percolation system
NASA Astrophysics Data System (ADS)
Burlak, G.; Martinez-Sánchez, E.
2017-03-01
We study the optical Anderson localization associated with the properties of three-dimensional (3D) disordered percolation system, where the percolating clusters are filled by active media composed by light noncoherent emitters. In such a non-uniformly spatial structure the radiating and scattering of field occur by incoherent way. We numerically study 3D field structures where the wave localization takes place and propose the criterion of field localization based on conception of a mean photon free path in such system. The analysis of a mean free path and the Inverse participation ratio (IPR) shows that the localization arises closely to the threshold of 3D percolation phase transition.
Experimental observation of Anderson localization in laser-kicked molecular rotors
NASA Astrophysics Data System (ADS)
Bitter, Martin; Milner, Valery
2016-05-01
For the first time, the phenomenon of Anderson localization is observed and studied in a system of true quantum kicked rotors. Nitrogen molecules in a supersonic molecular jet are cooled down to 27 K and are rotationally excited by a periodic train of 24 high-intensity femtosecond pulses. Exponential distribution of the molecular angular momentum - the most unambiguous signature of Anderson localization - is measured directly by means of coherent Raman scattering. We demonstrate the suppressed growth of the molecular rotational energy with the number of laser kicks and study the dependence of the localization length on the kick strength. Both timing and amplitude noise in the pulse train is shown to destroy the localization and revive the diffusive growth of angular momentum.
Cavity quantum electrodynamics with Anderson-localized modes.
Sapienza, Luca; Thyrrestrup, Henri; Stobbe, Søren; Garcia, Pedro David; Smolka, Stephan; Lodahl, Peter
2010-03-12
A major challenge in quantum optics and quantum information technology is to enhance the interaction between single photons and single quantum emitters. This requires highly engineered optical cavities that are inherently sensitive to fabrication imperfections. We have demonstrated a fundamentally different approach in which disorder is used as a resource rather than a nuisance. We generated strongly confined Anderson-localized cavity modes by deliberately adding disorder to photonic crystal waveguides. The emission rate of a semiconductor quantum dot embedded in the waveguide was enhanced by a factor of 15 on resonance with the Anderson-localized mode, and 94% of the emitted single photons coupled to the mode. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering an approach to inherently disorder-robust quantum information devices.
Centrifugal Distortion Causes Anderson Localization in Laser Kicked Molecules
NASA Astrophysics Data System (ADS)
Floss, Johannes; Averbukh, Ilya Sh.
2014-05-01
The periodically kicked 2D rotor is a textbook model in nonlinear dynamics. The classical kicked rotor can exhibit truly chaotic motion, whilst in the quantum regime this chaotic motion is suppressed by a mechanism similar to Anderson Localization. Up to now, these effects have been mainly observed in an atom optics analogue of a quantum rotor: cold atoms in a standing light wave. We demonstrate that common linear molecules (like N2, O2, CO2, ...), kicked by a train of short linearly polarized laser pulses, can exhibit a new mechanism for dynamical Anderson Localization due to their non-rigidity. When the pulses are separated by the rotational revival time trev = πℏ / B , the angular momentum J grows ballistically (Quantum Resonance). We show that, due to the centrifugal distortion of fast spinning molecules, above some critical value J =Jcr the Quantum Resonance is suppressed via the mechanism of Anderson Localization. This leads to a non-sinusoidal oscillation of the angular momentum distribution, which may be experimentally observed even at ambient conditions by using current techniques for laser molecular alignment.
Integrals of motion for one-dimensional Anderson localized systems
NASA Astrophysics Data System (ADS)
Modak, Ranjan; Mukerjee, Subroto; Yuzbashyan, Emil A.; Shastry, B. Sriram
2016-03-01
Anderson localization is known to be inevitable in one-dimension for generic disordered models. Since localization leads to Poissonian energy level statistics, we ask if localized systems possess ‘additional’ integrals of motion as well, so as to enhance the analogy with quantum integrable systems. We answer this in the affirmative in the present work. We construct a set of nontrivial integrals of motion for Anderson localized models, in terms of the original creation and annihilation operators. These are found as a power series in the hopping parameter. The recently found Type-1 Hamiltonians, which are known to be quantum integrable in a precise sense, motivate our construction. We note that these models can be viewed as disordered electron models with infinite-range hopping, where a similar series truncates at the linear order. We show that despite the infinite range hopping, all states but one are localized. We also study the conservation laws for the disorder free Aubry-Andre model, where the states are either localized or extended, depending on the strength of a coupling constant. We formulate a specific procedure for averaging over disorder, in order to examine the convergence of the power series. Using this procedure in the Aubry-Andre model, we show that integrals of motion given by our construction are well-defined in localized phase, but not so in the extended phase. Finally, we also obtain the integrals of motion for a model with interactions to lowest order in the interaction.
Integrals of motion for one-dimensional Anderson localized systems
Modak, Ranjan; Mukerjee, Subroto; Yuzbashyan, Emil A.; Shastry, B. Sriram
2016-03-02
Anderson localization is known to be inevitable in one-dimension for generic disordered models. Since localization leads to Poissonian energy level statistics, we ask if localized systems possess ‘additional’ integrals of motion as well, so as to enhance the analogy with quantum integrable systems. Weanswer this in the affirmative in the present work. We construct a set of nontrivial integrals of motion for Anderson localized models, in terms of the original creation and annihilation operators. These are found as a power series in the hopping parameter. The recently found Type-1 Hamiltonians, which are known to be quantum integrable in a precise sense, motivate our construction.Wenote that these models can be viewed as disordered electron models with infinite-range hopping, where a similar series truncates at the linear order.Weshow that despite the infinite range hopping, all states but one are localized.Wealso study the conservation laws for the disorder free Aubry–Andre model, where the states are either localized or extended, depending on the strength of a coupling constant.Weformulate a specific procedure for averaging over disorder, in order to examine the convergence of the power series. Using this procedure in the Aubry–Andre model, we show that integrals of motion given by our construction are well-defined in localized phase, but not so in the extended phase. Lastly, we also obtain the integrals of motion for a model with interactions to lowest order in the interaction.
Multi-Scale Jacobi Method for Anderson Localization
NASA Astrophysics Data System (ADS)
Imbrie, John Z.
2015-11-01
A new KAM-style proof of Anderson localization is obtained. A sequence of local rotations is defined, such that off-diagonal matrix elements of the Hamiltonian are driven rapidly to zero. This leads to the first proof via multi-scale analysis of exponential decay of the eigenfunction correlator (this implies strong dynamical localization). The method has been used in recent work on many-body localization (Imbrie in On many-body localization for quantum spin chains,
Transversal Anderson localization of sound in acoustic waveguide arrays.
Ye, Yangtao; Ke, Manzhu; Feng, Junheng; Wang, Mudi; Qiu, Chunyin; Liu, Zhengyou
2015-04-22
We present designs of one-dimensional acoustic waveguide arrays and investigate wave propagation inside. Under the condition of single identical waveguide mode and weak coupling, the acoustic wave motion in waveguide arrays can be modeled with a discrete mode-coupling theory. The coupling constants can be retrieved from simulations or experiments as the function of neighboring waveguide separations. Sound injected into periodic arrays gives rise to the discrete diffraction, exhibiting ballistic or extended transport in transversal direction. But sound injected into randomized waveguide arrays readily leads to Anderson localization transversally. The experimental results show good agreement with simulations and theoretical predictions.
Recurrent Scattering and Memory Effect at the Anderson Localization Transition
NASA Astrophysics Data System (ADS)
Aubry, A.; Cobus, L. A.; Skipetrov, S. E.; van Tiggelen, B. A.; Derode, A.; Page, J. H.
2014-01-01
We report on ultrasonic measurements of the propagation operator in a strongly scattering mesoglass. The backscattered field is shown to display a deterministic spatial coherence due to a remarkably large memory effect induced by long recurrent trajectories. Investigation of the recurrent scattering contribution directly yields the probability for a wave to come back close to its starting spot. The decay of this quantity with time is shown to change dramatically near the Anderson localization transition. The singular value decomposition of the propagation operator reveals the dominance of very intense recurrent scattering paths near the mobility edge.
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
Integrals of motion for one-dimensional Anderson localized systems
Modak, Ranjan; Mukerjee, Subroto; Yuzbashyan, Emil A.; ...
2016-03-02
Anderson localization is known to be inevitable in one-dimension for generic disordered models. Since localization leads to Poissonian energy level statistics, we ask if localized systems possess ‘additional’ integrals of motion as well, so as to enhance the analogy with quantum integrable systems. Weanswer this in the affirmative in the present work. We construct a set of nontrivial integrals of motion for Anderson localized models, in terms of the original creation and annihilation operators. These are found as a power series in the hopping parameter. The recently found Type-1 Hamiltonians, which are known to be quantum integrable in a precisemore » sense, motivate our construction.Wenote that these models can be viewed as disordered electron models with infinite-range hopping, where a similar series truncates at the linear order.Weshow that despite the infinite range hopping, all states but one are localized.Wealso study the conservation laws for the disorder free Aubry–Andre model, where the states are either localized or extended, depending on the strength of a coupling constant.Weformulate a specific procedure for averaging over disorder, in order to examine the convergence of the power series. Using this procedure in the Aubry–Andre model, we show that integrals of motion given by our construction are well-defined in localized phase, but not so in the extended phase. Lastly, we also obtain the integrals of motion for a model with interactions to lowest order in the interaction.« less
Perfect transmission through Anderson localized systems mediated by a cluster of localized modes.
Choi, Wonjun; Park, Q-Han; Choi, Wonshik
2012-08-27
In a strongly scattering medium where Anderson localization takes place, constructive interference of local non-propagating waves dominate over the incoherent addition of propagating waves. This results in the disappearance of propagating waves within the medium, which significantly attenuates energy transmission. In this numerical study performed in the optical regime, we systematically found resonance modes, called eigenchannels, of a 2-D Anderson localized system that allow for the near-perfect energy transmission. We observed that the internal field distribution of these eigenchannels exhibit dense clustering of localized modes. This strongly suggests that the clustered resonance modes facilitate long-range energy flow of local waves. Our study explicitly elucidates the interplay between wave localization and transmission enhancement in the Anderson localization regime.
Anomalous Anderson localization behaviors in disordered pseudospin systems.
Fang, A; Zhang, Z Q; Louie, Steven G; Chan, C T
2017-04-04
We discovered unique Anderson localization behaviors of pseudospin systems in a 1D disordered potential. For a pseudospin-1 system, due to the absence of backscattering under normal incidence and the presence of a conical band structure, the wave localization behaviors are entirely different from those of conventional disordered systems. We show that there exists a critical strength of random potential ([Formula: see text]), which is equal to the incident energy ([Formula: see text]), below which the localization length [Formula: see text] decreases with the random strength [Formula: see text] for a fixed incident angle [Formula: see text] But the localization length drops abruptly to a minimum at [Formula: see text] and rises immediately afterward. The incident angle dependence of the localization length has different asymptotic behaviors in the two regions of random strength, with [Formula: see text] when [Formula: see text] and [Formula: see text] when [Formula: see text] The existence of a sharp transition at [Formula: see text] is due to the emergence of evanescent waves in the systems when [Formula: see text] Such localization behavior is unique to pseudospin-1 systems. For pseudospin-1/2 systems, there is also a minimum localization length as randomness increases, but the transition from decreasing to increasing localization length at the minimum is smooth rather than abrupt. In both decreasing and increasing regions, the [Formula: see text] dependence of the localization length has the same asymptotic behavior [Formula: see text].
Permittivity disorder induced Anderson localization in magnetophotonic crystals
NASA Astrophysics Data System (ADS)
Abdi-Ghaleh, R.; Namdar, A.
2016-11-01
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.
Anderson localization and ergodicity on random regular graphs
NASA Astrophysics Data System (ADS)
Tikhonov, K. Â. S.; Mirlin, A. Â. D.; Skvortsov, M. Â. A.
2016-12-01
A numerical study of Anderson transition on random regular graphs (RRGs) with diagonal disorder is performed. The problem can be described as a tight-binding model on a lattice with N sites that is locally a tree with constant connectivity. In a certain sense, the RRG ensemble can be seen as an infinite-dimensional (d →∞ ) cousin of the Anderson model in d dimensions. We focus on the delocalized side of the transition and stress the importance of finite-size effects. We show that the data can be interpreted in terms of the finite-size crossover from a small (N ≪Nc ) to a large (N ≫Nc ) system, where Nc is the correlation volume diverging exponentially at the transition. A distinct feature of this crossover is a nonmonotonicity of the spectral and wave-function statistics, which is related to properties of the critical phase in the studied model and renders the finite-size analysis highly nontrivial. Our results support an analytical prediction that states in the delocalized phase (and at N ≫Nc ) are ergodic in the sense that their inverse participation ratio scales as 1 /N .
Ferrimagnetism and single-particle excitations in a periodic Anderson model on the honeycomb lattice
NASA Astrophysics Data System (ADS)
Seki, Kazuhiro; Shirakawa, Tomonori; Zhang, Qinfang; Li, Tao; Yunoki, Seiji
2015-04-01
By using the variationalcluster approximation and cluster perturbation theory, we investigate the magnetism and single-particle excitations of a periodic Anderson model on the honeycomb lattice as an effective model for the single-side hydrogenated graphene, namely, graphone. We calculate the magnetic moment as a function of U (Coulomb interaction on impurity sites) with showing that the ground state is ferrimagneticfor any U > 0. We then calculate the single-particle excitations and show that the single-particle excitations are gapless and exhibit quadratic dispersion relation near the Fermi energy.
Anomalously suppressed localization in the two-channel Anderson model.
Nguyen, Ba Phi; Kim, Kihong
2012-04-04
We study numerically the localization properties of a two-channel quasi-one-dimensional Anderson model with uncorrelated diagonal disorder within the nearest-neighbor tight-binding approximation. We calculate and analyze the disorder-averaged transmittance and the Lyapunov exponent. We find that the localization of the entire system is enhanced by increasing the interchain hopping strength t̃. From the numerical investigation of the energy dependence of the Lyapunov exponent for many different interchain hopping strengths, we find that apart from the band center anomaly, which usually occurs in strictly one-dimensional disordered systems, additional anomalies appear at special spectral points. They are found to be associated with the interchain hopping strength and occur at E = ± t̃/2 and ± t̃. We find that the anomalies at E = ± t̃ are associated with the π-coupling occurring within one energy band and those at E = ± t̃/2 are associated with the π-coupling occurring between two different energy bands. Despite having a similar origin, these two anomalies have distinct characteristics in their dependence on the strength of disorder. We also show that for a suitable range of parameter values, effectively delocalized states are observed in finite-size systems.
NASA Astrophysics Data System (ADS)
Natale, Joseph; Hentschel, George
Firing-rate networks offer a coarse model of signal propagation in the brain. Here we analyze sparse, 2D planar firing-rate networks with no synapses beyond a certain cutoff distance. Additionally, we impose Dale's Principle to ensure that each neuron makes only or inhibitory outgoing connections. Using spectral methods, we find that the number of neurons participating in excitations of the network becomes insignificant whenever the connectivity cutoff is tuned to a value near or below the average interneuron separation. Further, neural activations exceeding a certain threshold stay confined to a small region of space. This behavior is an instance of Anderson localization, a disorder-induced phase transition by which an information channel is rendered unable to transmit signals. We discuss several potential implications of localization for both local and long-range computation in the brain. This work was supported in part by Grants JSMF/ 220020321 and NSF/IOS/1208126.
NASA Astrophysics Data System (ADS)
Ekuma, C. E.; Terletska, H.; Tam, K.-M.; Meng, Z.-Y.; Moreno, J.; Jarrell, M.
2014-02-01
We develop a systematic typical medium dynamical cluster approximation that provides a proper description of the Anderson localization transition in three dimensions (3D). Our method successfully captures the localization phenomenon both in the low and large disorder regimes, and allows us to study the localization in different momenta cells, which renders the discovery that the Anderson localization transition occurs in a cell-selective fashion. As a function of cluster size, our method systematically recovers the reentrance behavior of the mobility edge and obtains the correct critical disorder strength for Anderson localization in 3D.
Anderson localization to enhance light-matter interaction (Conference Presentation)
NASA Astrophysics Data System (ADS)
Garcia, Pedro David
2016-04-01
Deliberately introducing disorder in low-dimensional nanostructures like photonic crystal waveguides (PCWs) [1] or photonic crystals (PCs) [2] leads to Anderson localization where light is efficiently trapped by random multiple scattering with the lattice imperfections. These disorder-induced optical modes hace been demonstrated to be very promising for cavity-quantum electrodynamics (QED) experiments where the radiative emission rate of single quantum emitters can be controlled when tuned through resonance with one of these random cavities. Our statistical analysis of the emission dynamics from single quantum dots embeded in disordered PCWs [3] provides detailed insigth about the statistical properties of QED in these complex nanostructures. In addition, using internal light sources reveals new physics in the form of nonuniversal intensity correlations between the different scattered paths within the structure which imprint the local QED properties deep inside the complex structure onto the far-field intensity pattern [2]. Finally, increasing the optical gain in PCWs allows on-chip random nanolasing where the cavity feedback is provided by the intrinsic disorder which enables highly efficient, stable, and broadband tunable lasers with very small mode volumes [4]. The figure of merit of these disorder-induced cavities is their localization length which determines to a large degree the coupling efficiency of a quantum emitter to a disorder-induced cavity as well as the efficiency of random lasing and reveals a strongly dispersive behavior and a non-trivial dependence on disorder in PCWs [5]. [1] L. Sapienza, H. Thyrrestrup, S. Stobbe, P.D. Garcia, S. Smolka, and P. Lodahl, Science 327, 1352 (2010). [2] P. D. García, S. Stobbe, I. Soellner and P. Lodahl, Physical Review Letters 109, 253902 (2012). [3] A. Javadi, S. Maibom, L. Sapienza, H. Thyrrestrup, P.D. Garcia, and P. Lodahl, Opt. Express 22, 30992 (2014). [4] J. Liu, P. D. Garcia, S. Ek, N. Gregersen, T. Suhr, M
Anderson attractors in active arrays
Laptyeva, Tetyana V.; Tikhomirov, Andrey A.; Kanakov, Oleg I.; Ivanchenko, Mikhail V.
2015-01-01
In dissipationless linear media, spatial disorder induces Anderson localization of matter, light, and sound waves. The addition of nonlinearity causes interaction between the eigenmodes, which results in a slow wave diffusion. We go beyond the dissipationless limit of Anderson arrays and consider nonlinear disordered systems that are subjected to the dissipative losses and energy pumping. We show that the Anderson modes of the disordered Ginsburg-Landau lattice possess specific excitation thresholds with respect to the pumping strength. When pumping is increased above the threshold for the band-edge modes, the lattice dynamics yields an attractor in the form of a stable multi-peak pattern. The Anderson attractor is the result of a joint action by the pumping-induced mode excitation, nonlinearity-induced mode interactions, and dissipative stabilization. The regimes of Anderson attractors can be potentially realized with polariton condensates lattices, active waveguide or cavity-QED arrays. PMID:26304462
Transverse Anderson localization of light near Dirac points of photonic nanostructures.
Deng, Hanying; Chen, Xianfeng; Malomed, Boris A; Panoiu, Nicolae C; Ye, Fangwei
2015-10-26
We perform a comparative study of the Anderson localization of light beams in disordered layered photonic nanostructures that, in the limit of periodic layer distribution, possess either a Dirac point or a Bragg gap in the spectrum of the wavevectors. In particular, we demonstrate that the localization length of the Anderson modes increases when the width of the Bragg gap decreases, such that in the vanishingly small bandgap limit, namely when a Dirac point is formed, even extremely high levels of disorder are unable to localize the optical modes residing near the Dirac point. A comparative analysis of the key features of the propagation of Anderson modes formed in the Bragg gap or near the Dirac point is also presented. Our findings could provide valuable guidelines in assessing the influence of structural disorder on the functionality of a broad array of optical nanodevices.
Transverse Anderson localization of light near Dirac points of photonic nanostructures
Deng, Hanying; Chen, Xianfeng; Malomed, Boris A.; Panoiu, Nicolae C.; Ye, Fangwei
2015-01-01
We perform a comparative study of the Anderson localization of light beams in disordered layered photonic nanostructures that, in the limit of periodic layer distribution, possess either a Dirac point or a Bragg gap in the spectrum of the wavevectors. In particular, we demonstrate that the localization length of the Anderson modes increases when the width of the Bragg gap decreases, such that in the vanishingly small bandgap limit, namely when a Dirac point is formed, even extremely high levels of disorder are unable to localize the optical modes residing near the Dirac point. A comparative analysis of the key features of the propagation of Anderson modes formed in the Bragg gap or near the Dirac point is also presented. Our findings could provide valuable guidelines in assessing the influence of structural disorder on the functionality of a broad array of optical nanodevices. PMID:26498634
Finite-size effects in Anderson localization of one-dimensional Bose-Einstein condensates
Cestari, J. C. C.; Foerster, A.; Gusmao, M. A.
2010-12-15
We investigate the disorder-induced localization transition in Bose-Einstein condensates for the Anderson and Aubry-Andre models in the noninteracting limit using exact diagonalization. We show that, in addition to the standard superfluid fraction, other tools such as the entanglement and fidelity can provide clear signatures of the transition. Interestingly, the fidelity exhibits good sensitivity even for small lattices. Effects of the system size on these quantities are analyzed in detail, including the determination of a finite-size-scaling law for the critical disorder strength in the case of the Anderson model.
Analytical description of the transverse Anderson localization of light
NASA Astrophysics Data System (ADS)
Schirmacher, Walter; Leonetti, Marco; Ruocco, Giancarlo
2017-04-01
We develop an analytical theory for describing the transverse localization properties of light beams in optical fibers with lateral disorder. This theory, which starts from the widely used paraxial approximation for the Helmholtz equation of the electric field, is a combination of an effective-medium theory for transverse disorder with the self-consistent localization theory of Vollhardt and Wölfle. We obtain explicit expressions for the dependence of the transverse localization length on the direction along the fiber. These results are in agreement with simulational data published recently by Karbasi et al. In particular we explain the focussing mechanism leading to the establishment of narrow transparent channels along the sample.
Linear and Nonlinear Anderson Localization in a Curved Potential
NASA Astrophysics Data System (ADS)
Claudio, Conti
2014-03-01
Disorder induced localization in the presence of nonlinearity and curvature is investigated. The time-resolved three-dimensional expansion of a wave packet in a bent cigar shaped potential with a focusing Kerr-like interaction term and Gaussian disorder is numerically analyzed. A self-consistent analytical theory, in which randomness, nonlinearity and geometry are determined by a single scaling parameter, is reported, and it is shown that curvature enhances localization.
NASA Astrophysics Data System (ADS)
Shiina, Ryousuke
2017-03-01
An interplay of valence fluctuation and orbital occupancy is studied for a two-orbital impurity Anderson model having f2 singlet ground and triplet excited states in the localized limit. Employing the numerical renormalization group method, we identify the existence of a quantum phase transition between the local-singlet and the Kondo-singlet states in a variation of the c-f hybridization, and clarify how it depends on the f2 singlet-triplet energy splitting. It is found that the transition takes place definitely at a finite strength of the hybridization even when the singlet-triplet splitting is infinitely large. It is also found that as the splitting becomes small, the occupancies of the singlet and triplet states display a drastic change in the vicinity of the transition point. The origin of these findings is discussed in view of the features of valence fluctuation from the local many-body singlet state.
Interplay between Anderson and Stark Localization in 2D Lattices
Kolovsky, A. R.
2008-11-07
This Letter studies the dynamics of a quantum particle in 2D lattices with on-site disorder in the presence of a static field. It is shown that the particle is localized along the field direction, while in the orthogonal direction to the field it shows diffusive dynamics for algebraically large times. For weak disorder an analytical expression for the diffusion coefficient is obtained by mapping the problem to a band random matrix. This expression is confirmed by numerical simulations of the particle's dynamics, which also indicate the existence of a universal equation for the diffusion coefficient, valid for an arbitrary disorder strength.
Effect of Anderson localization on light emission from gold nanoparticle aggregates
Abdellatif, Mohamed H; Abdelrasoul, Gaser N; Liakos, Ioannis; Scarpellini, Alice; Marras, Sergio; Diaspro, Alberto
2016-01-01
The localization of light known as Anderson localization is a common phenomenon characterizing aggregates of metallic nanostructures. The electromagnetic energy of visible light can be localized inside nanostructures below the diffraction limit by converting the optical modes into nonradiative surface plasmon resonances. The energy of the confined photons is correlated to the size and shape of the nanostructured system. In this work, we studied the photoluminescence dependence of aggregates of 14 nm diameter gold nanoparticles (AuNPs) synthesized by drop-casting a liquid suspension on two different substrates of glass and quartz. The AuNP aggregates were characterized by electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The dielectric constant of the surrounding medium plays a crucial role in determining the aggregate geometry, which affects the Anderson localization of light in the aggregates and hence causes a red-shift in the plasmonic resonance and in the photoluminescence emission. The geometry of the gold nanoparticle aggregates determine the strength of the Anderson localization, and hence, the light emission from the aggregates. The photoluminescence lifetime was found to be dependent on the AuNP aggregate geometry and the dielectric constant of the medium. PMID:28144549
Anderson localization and Brewster anomalies in photonic disordered quasiperiodic lattices
Reyes-Gomez, E.; Bruno-Alfonso, A.; Cavalcanti, S. B.; Oliveira, L. E.
2011-09-15
A comprehensive study of the properties of light propagation through one-dimensional photonic disordered quasiperiodic superlattices, composed of alternating layers with random thicknesses of air and a dispersive metamaterial, is theoretically performed. The superlattices consist of the successive stacking of N quasiperiodic Fibonacci or Thue-Morse heterostructures. The width of the slabs in the photonic superlattice may randomly fluctuate around its mean value, which introduces a structural disorder into the system. It is assumed that the left-handed layers have a Drude-type dispersive response for both the dielectric permittivity and magnetic permeability, and Maxwell's equations are solved for oblique incidence by using the transfer-matrix formalism. The influence of both quasiperiodicity and structural disorder on the localization length and Brewster anomalies are thoroughly discussed.
Non-compact local excitations in spin-glasses
NASA Astrophysics Data System (ADS)
Lamarcq, J.; Bouchaud, J.-P.; Martin, O. C.; Mézard, M.
2002-05-01
We study numerically the local low-energy excitations in the 3d Edwards-Anderson model for spin-glasses. Given the ground state, we determine the lowest-lying connected cluster of flipped spins with a fixed volume containing one given spin. These excitations are not compact, having a fractal dimension close to two, suggesting an analogy with lattice animals. Also, their energy does not grow with their size; the associated exponent is slightly negative whereas the one for compact clusters is positive. These findings call for a modification of the basic hypotheses underlying the droplet model.
Light focusing in the Anderson regime
NASA Astrophysics Data System (ADS)
Leonetti, Marco; Karbasi, Salman; Mafi, Arash; Conti, Claudio
2014-07-01
Anderson localization is a regime in which diffusion is inhibited and waves (also electromagnetic waves) get localized. Here we exploit adaptive optics to achieve focusing in disordered optical fibres in the Anderson regime. By wavefront shaping and optimization, we observe the generation of a propagation-invariant beam, where light is trapped transversally by disorder, and show that Anderson localizations can be also excited by extended speckled beams. We demonstrate that disordered fibres allow a more efficient focusing action with respect to standard fibres in a way independent of their length, because of the propagation-invariant features and cooperative action of transverse localizations.
Anderson localization of electrons in single crystals: LixFe7Se8
Ying, Tianping; Gu, Yueqiang; Chen, Xiao; Wang, Xinbo; Jin, Shifeng; Zhao, Linlin; Zhang, Wei; Chen, Xiaolong
2016-01-01
Anderson (disorder-induced) localization, proposed more than half a century ago, has inspired numerous efforts to explore the absence of wave diffusions in disordered media. However, the proposed disorder-induced metal-insulator transition (MIT), associated with the nonpropagative electron waves, has hardly been observed in three-dimensional (3D) crystalline materials, let alone single crystals. We report the observation of an MIT in centimeter-size single crystals of LixFe7Se8 induced by lattice disorder. Both specific heat and infrared reflectance measurements reveal the presence of considerable electronic states in the vicinity of the Fermi level when the MIT occurs, suggesting that the transition is not due to Coulomb repulsion mechanism. The 3D variable range hopping regime evidenced by electrical transport measurements at low temperatures indicates the localized nature of the electronic states on the Fermi level. Quantitative analyses of carrier concentration, carrier mobility, and simulated density of states (DOS) fully support that LixFe7Se8 is an Anderson insulator. On the basis of these results, we provide a unified DOS picture to explain all the experimental results, and a schematic diagram for finding other potential Anderson insulators. This material will thus serve as a rich playground for both theoretical and experimental investigations on MITs and disorder-induced phenomena. PMID:26989781
Critical properties of the Anderson localization transition and the high-dimensional limit
NASA Astrophysics Data System (ADS)
Tarquini, E.; Biroli, G.; Tarzia, M.
2017-03-01
In this paper we present a thorough study of transport, spectral, and wave-function properties at the Anderson localization critical point in spatial dimensions d =3 , 4, 5, 6. Our aim is to analyze the dimensional dependence and to assess the role of the d →∞ limit provided by Bethe lattices and treelike structures. Our results strongly suggest that the upper critical dimension of Anderson localization is infinite. Furthermore, we find that dU=∞ is a much better starting point compared to dL=2 to describe even three-dimensional systems. We find that critical properties and finite-size scaling behavior approach by increasing d those found for Bethe lattices: the critical state becomes an insulator characterized by Poisson statistics and corrections to the thermodynamics limit become logarithmic in the number N of lattice sites. In the conclusion, we present physical consequences of our results, propose connections with the nonergodic delocalized phase suggested for the Anderson model on infinite-dimensional lattices, and discuss perspectives for future research studies.
Simulation of Anderson localization in two-dimensional ultracold gases for pointlike disorder
NASA Astrophysics Data System (ADS)
Morong, W.; DeMarco, B.
2015-08-01
Anderson localization has been observed for a variety of media, including ultracold atomic gases with speckle disorder in one and three dimensions. However, observation of Anderson localization in a two-dimensional geometry for ultracold gases has been elusive. We show that a cause of this difficulty is the relatively high percolation threshold of a speckle potential in two dimensions, resulting in strong classical localization. We propose a realistic pointlike disorder potential that circumvents this percolation limit with localization lengths that are experimentally observable. The percolation threshold is evaluated for experimentally realistic parameters, and a regime of negligible classical trapping is identified. Localization lengths are determined via scaling theory, using both exact scattering cross sections and the Born approximation, and by direct simulation of the time-dependent Schrödinger equation. We show that the Born approximation can underestimate the localization length by four orders of magnitude at low energies, while exact cross sections and scaling theory provide an upper bound. Achievable experimental parameters for observing localization in this system are proposed.
Spectral Approach to Anderson Localization in a Disordered 2D Complex Plasma Crystal
NASA Astrophysics Data System (ADS)
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.
NASA Astrophysics Data System (ADS)
Cossu, Guido; Hashimoto, Shoji
2016-06-01
We investigate the properties of the background gauge field configurations that act as disorder for the Anderson localization mechanism in the Dirac spectrum of QCD at high temperatures. We compute the eigenmodes of the Möbius domain-wall fermion operator on configurations generated for the SU(3) gauge theory with two flavors of fermions, in the temperature range [0.9, 1.9]T c . We identify the source of localization of the eigenmodes with gauge configurations that are self-dual and support negative fluctuations of the Polyakov loop P L , in the high temperature sea of P L ˜ 1. The dependence of these observations on the boundary conditions of the valence operator is studied. We also investigate the spatial overlap of the left-handed and right-handed projected eigenmodes in correlation with the localization and the corresponding eigenvalue. We discuss an interpretation of the results in terms of monopole-instanton structures.
NASA Astrophysics Data System (ADS)
Kuzovkov, V. N.
2011-12-01
The goal of this paper is twofold. First, based on the interpretation of a quantum tight-binding model in terms of a classical Hamiltonian map, we consider the Anderson localization (AL) problem as the Fermi-Pasta-Ulam (FPU) effect in a modified dynamical system containing both stable and unstable (inverted) modes. Delocalized states in the AL are analogous to the stable quasi-periodic motion in FPU, whereas localized states are analogous to thermalization, respectively. The second aim is to use the classical Hamilton map for a simplified derivation of exact equations for the localization operator H(z). The latter was presented earlier (Kuzovkov et al 2002 J. Phys.: Condens. Matter 14 13777) treating the AL as a generalized diffusion in a dynamical system. We demonstrate that counter-intuitive results of our studies of the AL are similar to the FPU counter-intuitivity.
Perfect absorption in nanotextured thin films via Anderson-localized photon modes
NASA Astrophysics Data System (ADS)
Aeschlimann, Martin; Brixner, Tobias; Differt, Dominik; Heinzmann, Ulrich; Hensen, Matthias; Kramer, Christian; Lükermann, Florian; Melchior, Pascal; Pfeiffer, Walter; Piecuch, Martin; Schneider, Christian; Stiebig, Helmut; Strüber, Christian; Thielen, Philip
2015-10-01
The enhancement of light absorption in absorber layers is crucial in a number of applications, including photovoltaics and thermoelectrics. The efficient use of natural resources and physical constraints such as limited charge extraction in photovoltaic devices require thin but efficient absorbers. Among the many different strategies used, light diffraction and light localization at randomly nanotextured interfaces have been proposed to improve absorption. Although already exploited in commercial devices, the enhancement mechanism for devices with nanotextured interfaces is still subject to debate. Using coherent two-dimensional nanoscopy and coherent light scattering, we demonstrate the existence of localized photonic states in nanotextured amorphous silicon layers as used in commercial thin-film solar cells. Resonant absorption in these states accounts for the enhanced absorption in the long-wavelength cutoff region. Our observations establish that Anderson localization—that is, strong localization—is a highly efficient resonant absorption enhancement mechanism offering interesting opportunities for the design of efficient future absorber layers.
Kravtsov, V. E.; Yudson, V. I.
2009-05-14
The statistics of normalized wavefunctions in the one-dimensional (1d) Anderson model of localization is considered. It is shown that at any energy that corresponds to a rational filling factor f = (p/q) there is a statistical anomaly which is seen in expansion of the generating function (GF) to the order q-2 in the disorder parameter. We study in detail the principle anomaly at f = (1/2) that appears in the leading order. The transfer-matrix equation of the Fokker-Planck type with a two-dimensional internal space is derived for GF. It is shown that the zero-mode variant of this equation is integrable and a solution for the generating function is found in the thermodynamic limit.
Simulation of Anderson localization in a random fiber using a fast Fresnel diffraction algorithm
NASA Astrophysics Data System (ADS)
Davis, Jeffrey A.; Cottrell, Don M.
2016-06-01
Anderson localization has been previously demonstrated both theoretically and experimentally for transmission of a Gaussian beam through long distances in an optical fiber consisting of a random array of smaller fibers, each having either a higher or lower refractive index. However, the computational times were extremely long. We show how to simulate these results using a fast Fresnel diffraction algorithm. In each iteration of this approach, the light passes through a phase mask, undergoes Fresnel diffraction over a small distance, and then passes through the same phase mask. We also show results where we use a binary amplitude mask at the input that selectively illuminates either the higher or the lower index fibers. Additionally, we examine imaging of various sized objects through these fibers. In all cases, our results are consistent with other computational methods and experimental results, but with a much reduced computational time.
Tarasov, Yu.V. Shostenko, L.D.
2015-05-15
coexist in waveguide-like systems with randomly corrugated boundaries, specifically, the entropic localization and the one-dimensional Anderson (disorder-driven) localization. If the particular mode propagates across the rough segment ballistically, the Fabry–Pérot-type oscillations should be observed in the conductance, which are suppressed for the mode transferred in the Anderson-localized regime.
Kravtsov, V.E.; Yudson, V.I.
2011-07-15
Highlights: > Statistics of normalized eigenfunctions in one-dimensional Anderson localization at E = 0 is studied. > Moments of inverse participation ratio are calculated. > Equation for generating function is derived at E = 0. > An exact solution for generating function at E = 0 is obtained. > Relation of the generating function to the phase distribution function is established. - Abstract: The one-dimensional (1d) Anderson model (AM), i.e. a tight-binding chain with random uncorrelated on-site energies, has statistical anomalies at any rational point f=(2a)/({lambda}{sub E}) , where a is the lattice constant and {lambda}{sub E} is the de Broglie wavelength. We develop a regular approach to anomalous statistics of normalized eigenfunctions {psi}(r) at such commensurability points. The approach is based on an exact integral transfer-matrix equation for a generating function {Phi}{sub r}(u, {phi}) (u and {phi} have a meaning of the squared amplitude and phase of eigenfunctions, r is the position of the observation point). This generating function can be used to compute local statistics of eigenfunctions of 1d AM at any disorder and to address the problem of higher-order anomalies at f=p/q with q > 2. The descender of the generating function P{sub r}({phi}){identical_to}{Phi}{sub r}(u=0,{phi}) is shown to be the distribution function of phase which determines the Lyapunov exponent and the local density of states. In the leading order in the small disorder we derived a second-order partial differential equation for the r-independent ('zero-mode') component {Phi}(u, {phi}) at the E = 0 (f=1/2 ) anomaly. This equation is nonseparable in variables u and {phi}. Yet, we show that due to a hidden symmetry, it is integrable and we construct an exact solution for {Phi}(u, {phi}) explicitly in quadratures. Using this solution we computed moments I{sub m} = N< vertical bar {psi} vertical bar {sup 2m}> (m {>=} 1) for a chain of the length N {yields} {infinity} and found an
Localization of electrons and excitations
NASA Astrophysics Data System (ADS)
Larsson, Sven
2006-07-01
Electrons, electron holes, or excitations in finite or infinite 'multimer systems' may be localized or delocalized. In the theory of Hush, localization depends on the ratio Δ/ λ ( Δ/2 = coupling; λ = reorganization energy). The latter theory has been extended to the infinite system [S. Larsson, A. Klimkāns, Mol. Cryst. Liq. Cryst. 355 (2000) 217]. The metal/insulator transition often takes place abruptly as a function of Δ/ λ. It is argued that localization in a system with un-filled bands cannot be determined on the basis of Mott-Hubbard U alone, but depends on the number of accessible valence states, reorganization energy λ and coupling Δ (=2t). In fact U = 0 does not necessarily imply delocalization. The analysis here shows that there are many different situations for an insulator to metal transition. Charge transfer in doped NiO is characterized by Ni 2+ - Ni 3+ exchange while charge transfer in pure NiO is characterized by a disproportionation 2Ni 2+ → Ni + + Ni 3+. In spite of the great differences between these two cases, U has been applied without discrimination to both. The relevant localization parameters appear to be Δ and λ in the first case, with only two oxidation states, and U, Δ and λ in the second case with three oxidation states. The analysis is extended to insulator-metal transitions, giant magnetic resistance (GMR) and high Tc superconductivity (SC). λ and Δ can be determined quite accurately in quantum mechanical calculations involving only one and two monomers, respectively.
NASA Astrophysics Data System (ADS)
Monthus, Cécile
2016-03-01
The generalization of the Dyson Brownian motion approach of random matrices to Anderson localization (AL) models (Chalker et al 1996 Phys. Rev. Lett. 77 554) and to many-body localization (MBL) Hamiltonians (Serbyn and Moore 2015 arXiv:1508.07293) is revisited to extract the level repulsion exponent β, where β =1 in the delocalized phase governed by the Wigner-Dyson statistics, β =0 , in the localized phase governed by the Poisson statistics, and 0<{βc}<1 at the critical point. The idea is that the Gaussian disorder variables h i are promoted to Gaussian stationary processes h i (t) in order to sample the disorder stationary distribution with some time correlation τ. The statistics of energy levels can then be studied via Langevin and Fokker-Planck equations. For the MBL quantum spin Hamiltonian with random fields h i , we obtain β =2qn,n+1\\text{EA}(N)/qn,n\\text{EA}(N) in terms of the Edwards-Anderson matrix qnm\\text{EA}(N)\\equiv \\frac{1}{N}{\\sum}i=1N|< {φn}|σ iz|{φm}> {{|}2} for the same eigenstate m = n and for consecutive eigenstates m = n + 1. For the Anderson localization tight-binding Hamiltonian with random on-site energies h i , we find β =2{{Y}n,n+1}(N)/≤ft({{Y}n,n}(N)-{{Y}n,n+1}(N)\\right) in terms of the density correlation matrix {{Y}nm}(N)\\equiv {\\sum}i=1N|< {φn}|i> {{|}2}|< i|{φm}> {{|}2} for consecutive eigenstates m = n + 1, while the diagonal element m = n corresponds to the inverse participation ratio {{Y}nn}(N)\\equiv {\\sum}i=1N|< {φn}|i> {{|}4} of the eigenstate |{φn}> .
NASA Astrophysics Data System (ADS)
Monthus, Cécile; Garel, Thomas
2011-04-01
In contrast to finite dimensions where disordered systems display multifractal statistics only at criticality, the tree geometry induces multifractal statistics for disordered systems also off criticality. For the Anderson tight-binding localization model defined on a tree of branching ratio K = 2 with N generations, we consider the Miller-Derrida scattering geometry (1994 J. Stat. Phys. 75 357), where an incoming wire is attached to the root of the tree, and where KN outcoming wires are attached to the leaves of the tree. In terms of the KN transmission amplitudes tj, the total Landauer transmission is T ≡ ∑j|tj|2, so that each channel j is characterized by the weight wj = |tj|2/T. We numerically measure the typical multifractal singularity spectrum f(α) of these weights as a function of the disorder strength W and we obtain the following conclusions for its left termination point α+(W). In the delocalized phase W < Wc, α+(W) is strictly positive α+(W) > 0 and is associated with a moment index q+(W) > 1. At criticality, it vanishes α+(Wc) = 0 and is associated with the moment index q+(Wc) = 1. In the localized phase W > Wc, α+(W) = 0 is associated with some moment index q+(W) < 1. We discuss the similarities with the exact results concerning the multifractal properties of the directed polymer on the Cayley tree.
Successive superconducting transitions and Anderson localization effect in Ta2 S2 C
NASA Astrophysics Data System (ADS)
Walter, Jürgen; Suzuki, Itsuko S.; Suzuki, Masatsugu
2004-08-01
A complex carbide Ta2S2C consists of van der Waals (vdw)-bonded layers with a stacking sequence along the c axis: ⋯C-Ta-S-vdw-S-Ta-C-⋯ . The magnetic properties of this compound have been studied from dc and ac magnetic susceptibility. Ta2S2C undergoes successive superconducting transitions of a hierachical nature at Tcl=3.61±0.01K [ Hc1(l)(0)=28±2Oe and Hc2(l)(0)=7.7±0.2kOe ] and Tcu=8.9±0.1K [ Hc2(u)(0)=14.0±0.5kOe ]. The intermediate phase between Tcu and Tcl is an intragrain superconductive state occurring in the Ta-C layers in Ta2S2C . The low temperature phase below Tcl is an intergrain superconductive state. The magnetic susceptibility at H well above 10kOe is described by a sum of a diamagnetic susceptibility and a Curie-type behavior. The latter is due to the localized magnetic moments of conduction electrons associated with the Anderson localization effect, occurring in the 1T-TaS2 type structure in Ta2S2C .
Anderson Localization for Schrödinger Operators on with Strongly Mixing Potentials
NASA Astrophysics Data System (ADS)
Bourgain, Jean; Schlag, Wilhelm
In this paper we show that for a.e. x∈[ 0,2 π) the operators defined on as
NASA Astrophysics Data System (ADS)
Monthus, Cécile
2017-03-01
For Anderson localization models with multifractal eigenvectors on disordered samples containing N sites, we analyze in a unified framework the consequences for the statistical properties of the Green function. We focus in particular on the imaginary part of the Green function at coinciding points GxxI≤ft(E-\\text{i}η \\right) and study the scaling with the size N of the moments of arbitrary indices q when the broadening follows the scaling η =\\frac{c}{{{N}δ}} . For the standard scaling regime δ =1 , we find in the two limits c\\ll 1 and c\\gg 1 that the moments are governed by the anomalous exponents Δ (q) of individual eigenfunctions, without the assumption of strong correlations between the weights of consecutive eigenstates at the same point. For the non-standard scaling regimes 0<δ <1 , we obtain that the imaginary Green function follows some Fréchet distribution in the typical region, while rare events are important to obtain the scaling of the moments. We describe the application to the case of Gaussian multifractality and to the case of linear multifractality.
Local pair natural orbitals for excited states.
Helmich, Benjamin; Hättig, Christof
2011-12-07
We explore how in response calculations for excitation energies with wavefunction based (e.g., coupled cluster) methods the number of double excitation amplitudes can be reduced by means of truncated pair natural orbital (PNO) expansions and localized occupied orbitals. Using the CIS(D) approximation as a test model, we find that the number of double excitation amplitudes can be reduced dramatically with minor impact on the accuracy if the excited state wavefunction is expanded in state-specific PNOs generated from an approximate first-order guess wavefunction. As for ground states, the PNO truncation error can also for excitation energies be controlled by a single threshold related to generalized natural occupation numbers. The best performance is found with occupied orbitals which are localized by the Pipek-Mezey localization. For a large test set of excited states we find with this localization that already a PNO threshold of 10(-8)-10(-7), corresponding to an average of only 40-80 PNOs per pair, is sufficient to keep the PNO truncation error for vertical excitation energies below 0.01 eV. This is a significantly more rapid convergence with the number doubles amplitudes than in domain-based local response approaches. We demonstrate that the number of significant excited state PNOs scales asymptotically linearly with the system size in the worst case of completely delocalized excitations and sub-linearly whenever the chromophore does not increase with the system size. Moreover, we observe that the flexibility of state-specific PNOs to adapt to the character of an excitation allows for an almost unbiased treatment of local, delocalized and charge transfer excited states.
Local pair natural orbitals for excited states
NASA Astrophysics Data System (ADS)
Helmich, Benjamin; Hättig, Christof
2011-12-01
We explore how in response calculations for excitation energies with wavefunction based (e.g., coupled cluster) methods the number of double excitation amplitudes can be reduced by means of truncated pair natural orbital (PNO) expansions and localized occupied orbitals. Using the CIS(D) approximation as a test model, we find that the number of double excitation amplitudes can be reduced dramatically with minor impact on the accuracy if the excited state wavefunction is expanded in state-specific PNOs generated from an approximate first-order guess wavefunction. As for ground states, the PNO truncation error can also for excitation energies be controlled by a single threshold related to generalized natural occupation numbers. The best performance is found with occupied orbitals which are localized by the Pipek-Mezey localization. For a large test set of excited states we find with this localization that already a PNO threshold of 10-8-10-7, corresponding to an average of only 40-80 PNOs per pair, is sufficient to keep the PNO truncation error for vertical excitation energies below 0.01 eV. This is a significantly more rapid convergence with the number doubles amplitudes than in domain-based local response approaches. We demonstrate that the number of significant excited state PNOs scales asymptotically linearly with the system size in the worst case of completely delocalized excitations and sub-linearly whenever the chromophore does not increase with the system size. Moreover, we observe that the flexibility of state-specific PNOs to adapt to the character of an excitation allows for an almost unbiased treatment of local, delocalized and charge transfer excited states.
Kondo correlations formation and the local magnetic moment dynamics in the Anderson model
NASA Astrophysics Data System (ADS)
Maslova, N. S.; Arseyev, P. I.; Mantsevich, V. N.
2017-02-01
We investigated the typical time scales of the Kondo correlations formation for the single-state Anderson model, when coupling to the reservoir is switched on at the initial time moment. The influence of the Kondo effect appearance on the system non-stationary characteristics was analyzed and discussed.
NASA Astrophysics Data System (ADS)
Daley, P.; Wortis, R.
2016-05-01
Non-interacting systems with bounded disorder have been shown to exhibit sharp density of state peaks at the band edge which coincide with an energy range of abruptly suppressed localization. Recent work has shown that these features also occur in the presence of on-site interactions in ensembles of two-site Anderson-Hubbard systems at half filling. Here we demonstrate that this effect in interacting systems persists away from half filling, and moreover that energy regions with suppressed localization continue to appear in ensembles of larger systems despite a loss of sharp features in the density of states.
Photothermal measurements using a localized excitation source
NASA Astrophysics Data System (ADS)
Aamodt, L. C.; Murphy, J. C.
1981-08-01
Optical-beam deflection (OBD) photothermal imaging uses spatially localized excitation to observe spatial variations in the sample surface temperature. This paper analyzes OBD signals produced by localized excitation in terms of three-dimensional thermal diffusion in the sample and in the fluid region in contact with the sample. The dependence of the signals on the local optical absorption coefficient, on gas/sample thermal properties, on modulation frequency, and on the probe/excitation beam radii are discussed with special attention being given to determining the spatial resolution possible for OBD imaging. A criterion for photothermal ''saturation'' appropriate to localized optical absorption is developed. Finally, a new variant of the OBD technique is introduced, which is especially adapted to studying optical and thermal boundaries in the plane of the sample. Some comparisons between theory and experiment are provided which illustrate transverse thermal diffusion.
NASA Astrophysics Data System (ADS)
Kravtsov, V. E.; Yudson, V. I.
2010-11-01
An exact solution is found for the problem of the center-of-band (E=0) anomaly in the one-dimensional Anderson model of localization. By deriving and solving an equation for the generating function Φ(u,ϕ) we obtained an exact expression in quadratures for statistical moments Iq=⟨|ψE(r)|2q⟩ of normalized wave functions ψE(r) which show violation of one-parameter scaling and emergence of an additional length scale at E≈0 .
NASA Astrophysics Data System (ADS)
Maslova, N. S.; Mantsevich, V. N.; Arseyev, P. I.
2017-02-01
We perform theoretical investigation of the localized state dynamics in the presence of interaction with the reservoir and Coulomb correlations. We analyze kinetic equations for electron occupation numbers with different spins taking into account high order correlation functions for the localized electrons. We reveal that in the stationary state electron occupation numbers with the opposite spins always have the same value - the stationary state is a "paramagnetic" one. "Magnetic" properties can appear only in the non-stationary characteristics of the single-impurity Anderson model and in the dynamics of the localized electrons second order correlation functions. We found, that for deep energy levels and strong Coulomb correlations, relaxation time for initial "magnetic" state can be several orders larger than for "paramagnetic" one. So, long-living "magnetic" moment can exist in the system. We also found non-stationary spin polarized currents flowing in opposite directions for the different spins in the particular time interval.
NASA Astrophysics Data System (ADS)
Roundy, R. C.; Nemirovsky, D.; Kagalovsky, V.; Raikh, M. E.
2014-06-01
Motivated by recent experiments, where the tunnel magnetoresitance (TMR) of a spin valve was measured locally, we theoretically study the distribution of TMR along the surface of magnetized electrodes. We show that, even in the absence of interfacial effects (like hybridization due to donor and acceptor molecules), this distribution is very broad, and the portion of area with negative TMR is appreciable even if on average the TMR is positive. The origin of the local sign reversal is quantum interference of subsequent spin-rotation amplitudes in the course of incoherent transport of carriers between the source and the drain. We find the distribution of local TMR exactly by drawing upon formal similarity between evolution of spinors in time and of the reflection coefficient along a 1D chain in the Anderson model. The results obtained are confirmed by the numerical simulations.
NASA Astrophysics Data System (ADS)
Kolodiazhnyi, Taras; Charoonsuk, Thitirat; Seo, Yu-Seong; Chang, Suyong; Vittayakorn, Naratip; Hwang, Jungseek
2017-01-01
We report magnetic susceptibility, electrical conductivity and optical absorption of Ce1 -xMxO2 where M = Nb,Ta and 0 ≤x ≤0.03 . The dc conductivity follows a simple thermally activated Arrhenius-type behavior in the T =70 -700 K range with a change in slope at T*≈155 K. The high-temperature activation energy shows gradual increase from ≈170 to 220 meV as the dopant concentration increases. The activation energy of the low-temperature conductivity shows a broad minimum of ≈77 meV at x ≈0.01 . Electron transport and localization mechanisms are analyzed in the framework of the Holstein small polaron, Anderson localization, and Jahn-Teller distortion models. The fit to the small polaron mobility is dramatically improved when, instead of the longitudinal phonons, the transverse optical phonons are considered in the phonon-assisted electron transport. This serves as an indirect evidence of a strong 4 f1 orbital interaction with the oxygen ligands, similar to the case of PrO2. Based on comparison of the experimental data to the models, it is proposed that the defect-induced random electric fields make the dominant contribution to the electron localization in donor-doped ceria.
Probing Anderson localization of light via decay rate statistics in aperiodic Vogel spirals
NASA Astrophysics Data System (ADS)
Christofi, Aristi; Pinheiro, Felipe A.; Dal Negro, Luca
We systematically investigate the spectral properties of different types of two-dimensional aperiodic Vogel spiral arrays of pointlike scatterers and three-dimensional metamaterials with Vogel spiral chirality using rigorous Green's function spectral method. We considered an efficient T-matrix approach to analyze multiple-scattering effects, including all scattering orders, and to understand localization properties through the statistics of the Green's matrix eigenvalues. The knowledge of the spectrum of the Green matrix of multi-particle scattering systems provides important information on the character of light propagation and localization in chiral media with deterministic aperiodic geometry. In particular, we analyze for the first time the statistics of the eigenvalues and eigenvectors of the Green matrix and extract the decay rates of the eigenmodes, their inverse participation ratio (IPR), the Wigner delay times and their quality factors. We emphasize the unique properties of aperiodic Vogel spirals with respect to random scattering media, which have been investigated so far. This work was supported by the Army Research Laboratory under Cooperative Agreement Number W911NF-12-2-0023.
Typical density of states as an order parameter for the Anderson localization
NASA Astrophysics Data System (ADS)
Tam, Ka-Ming; Moore, Conrad; Moreno, Juana; Jarrell, Mark
2015-03-01
The typical medium theory and its recently proposed extensions for models with off-diagonal disorder and multiple bands are significant progress towards the study of localization phenomenon in real materials. The fundamental assumption of these methods is that the typical density of states can be treated as an order parameter. However, its justifications in lattice model is largely lacking. This is predominantly due to two factors. First, the lattice sizes amenable for exact diagonalization is rather limited. Second, the small lattice sizes lead to a very sensitive dependence on the broadening factor. In this work, we use the kernel polynomial method to perform simulation for large system sizes. By adapting the method for the study of criticality, we find that the typical density of states has a well defined finite size scaling behavior. In particular, from the kurtosis, Binder ratio, of the distribution of the density of states for different lattice sizes, we find a clear crossing to identify the critical point. This provides further support that the typical density of states can be used as an order parameter for the localization transition.
M.H. Redi; J.L. Johnson; S. Klasky; J. Canik; R.L. Dewar; W.A. Cooper
2001-10-31
The radially local magnetohydrodynamic (MHD) ballooning stability of a compact, quasiaxially symmetric stellarator (QAS), is examined just above the ballooning beta limit with a method that can lead to estimates of global stability. Here MHD stability is analyzed through the calculation and examination of the ballooning mode eigenvalue isosurfaces in the 3-space [s, alpha, theta(subscript ''k'')]; s is the edge normalized toroidal flux, alpha is the field line variable, and q(subscript ''k'') is the perpendicular wave vector or ballooning parameter. Broken symmetry, i.e., deviations from axisymmetry, in the stellarator magnetic field geometry causes localization of the ballooning mode eigenfunction, and gives rise to new types of nonsymmetric eigenvalue isosurfaces in both the stable and unstable spectrum. For eigenvalues far above the marginal point, isosurfaces are topologically spherical, indicative of strong ''quantum chaos.'' The complexity of QAS marginal isosurfaces suggests that finite Larmor radius stabilization estimates will be difficult and that fully three-dimensional, high-n MHD computations are required to predict the beta limit.
Basko, D.M.
2011-07-15
Research Highlights: > In a one-dimensional disordered chain of oscillators all normal modes are localized. > Nonlinearity leads to chaotic dynamics. > Chaos is concentrated on rare chaotic spots. > Chaotic spots drive energy exchange between oscillators. > Macroscopic transport coefficients are obtained. - Abstract: The subject of this study is the long-time equilibration dynamics of a strongly disordered one-dimensional chain of coupled weakly anharmonic classical oscillators. It is shown that chaos in this system has a very particular spatial structure: it can be viewed as a dilute gas of chaotic spots. Each chaotic spot corresponds to a stochastic pump which drives the Arnold diffusion of the oscillators surrounding it, thus leading to their relaxation and thermalization. The most important mechanism of equilibration at long distances is provided by random migration of the chaotic spots along the chain, which bears analogy with variable-range hopping of electrons in strongly disordered solids. The corresponding macroscopic transport equations are obtained.
Intermittent movement of localized excitations of a nonlinear lattice.
Rumpf, Benno
2004-01-01
The mobility of localized high-amplitude excitations of the discrete nonlinear Schrödinger equation is studied. The excitations can either be pinned at the lattice or they can propagate depending on their energy and particle number. Such localized excitation can emit or absorb waves with a low amplitude which changes the amount of these quantities in the excitation. For statistical reasons, the excitations absorb a high amount of energy per particle through their interaction with low-amplitude waves. They can only move if their energy decreases temporarily either by a random fluctuation or by an external force.
Emergence of Asynchronous Local Clocks in Excitable Media.
Gerum, Richard Carl; Fabry, Ben; Metzner, Claus
2015-01-01
Excitable media such as the myocardium or the brain consist of arrays of coupled excitable elements, in which the local excitation of a single element can propagate to its neighbors in the form of a non-linear autowave. Since each element has to pass through a refractory period immediately after excitation, the frequency of autowaves is self-limiting. In this work, we consider the case where each element is spontaneously excited at a fixed average rate and thereby initiates a new autowave. Although these spontaneous self-excitation events are modelled as independent Poisson point processes with exponentially distributed waiting times, the travelling autowaves lead collectively to a non-exponential, unimodal waiting time distribution for the individual elements. With increasing system size, a global 'clock' period T emerges as the most probable waiting time for each element, which fluctuates around T with an increasingly small but non-zero variance. This apparent synchronization between asynchronous, temporally uncorrelated point processes differs from synchronization effects between perfect oscillators interacting in a phase-aligning manner. Finally, we demonstrate that asynchronous local clocks also emerge in non-homogeneous systems in which the rates of self-excitation are different for all individuals, suggesting that this novel mechanism can occur in a wide range of excitable media.
Emergence of Asynchronous Local Clocks in Excitable Media
Gerum, Richard Carl; Fabry, Ben; Metzner, Claus
2015-01-01
Excitable media such as the myocardium or the brain consist of arrays of coupled excitable elements, in which the local excitation of a single element can propagate to its neighbors in the form of a non-linear autowave. Since each element has to pass through a refractory period immediately after excitation, the frequency of autowaves is self-limiting. In this work, we consider the case where each element is spontaneously excited at a fixed average rate and thereby initiates a new autowave. Although these spontaneous self-excitation events are modelled as independent Poisson point processes with exponentially distributed waiting times, the travelling autowaves lead collectively to a non-exponential, unimodal waiting time distribution for the individual elements. With increasing system size, a global ‘clock’ period T emerges as the most probable waiting time for each element, which fluctuates around T with an increasingly small but non-zero variance. This apparent synchronization between asynchronous, temporally uncorrelated point processes differs from synchronization effects between perfect oscillators interacting in a phase-aligning manner. Finally, we demonstrate that asynchronous local clocks also emerge in non-homogeneous systems in which the rates of self-excitation are different for all individuals, suggesting that this novel mechanism can occur in a wide range of excitable media. PMID:26559528
Localized excitations in hydrogen-bonded molecular crystals
NASA Astrophysics Data System (ADS)
Alexander, D. M.; Krumhansl, J. A.
1986-05-01
Localized excitations analogous to the small Holstein polaron, to localized modes in alkali halides, and to localized excitonic states, are postulated for a set of internal vibrational modes in crystalline acetanilide. The theoretical framework in which one can describe the characteristics of the ir and Raman spectroscopy peaks associated with these localized states is adequately provided by the Davydov model (formally equivalent to the Holstein polaron model). The possible low-lying excitations arising from this model are determined using a variational approach. Hence, the contribution to the spectral function due to each type of excitation can be calculated. The internal modes of chief concern here are the amide-I (CO stretch) and the N-H stretch modes for which we demonstrate consistency of the theoretical model with the available ir data. Past theoretical approaches will be discussed and reasons why one should prefer one description over another will be examined.
Quantum dimensions from local operator excitations in the Ising model
NASA Astrophysics Data System (ADS)
Caputa, Paweł; Rams, Marek M.
2017-02-01
We compare the time evolution of entanglement measures after local operator excitation in the critical Ising model with predictions from conformal field theory. For the spin operator and its descendants we find that Rényi entropies of a block of spins increase by a constant that matches the logarithm of the quantum dimension of the conformal family. However, for the energy operator we find a small constant contribution that differs from the conformal field theory answer equal to zero. We argue that the mismatch is caused by the subtleties in the identification between the local operators in conformal field theory and their lattice counterpart. Our results indicate that evolution of entanglement measures in locally excited states not only constraints this identification, but also can be used to extract non-trivial data about the conformal field theory that governs the critical point. We generalize our analysis to the Ising model away from the critical point, states with multiple local excitations, as well as the evolution of the relative entropy after local operator excitation and discuss universal features that emerge from numerics.
NASA Astrophysics Data System (ADS)
Cao, Zhenwei
Over the years, people have found Quantum Mechanics to be extremely useful in explaining various physical phenomena from a microscopic point of view. Anderson localization, named after physicist P. W. Anderson, states that disorder in a crystal can cause non-spreading of wave packets, which is one possible mechanism (at single electron level) to explain metal-insulator transitions. The theory of quantum computation promises to bring greater computational power over classical computers by making use of some special features of Quantum Mechanics. The first part of this dissertation considers a 3D alloy-type model, where the Hamiltonian is the sum of the finite difference Laplacian corresponding to free motion of an electron and a random potential generated by a sign-indefinite single-site potential. The result shows that localization occurs in the weak disorder regime, i.e., when the coupling parameter lambda is very small, for energies E ≤ --Clambda 2. The second part of this dissertation considers adiabatic quantum computing (AQC) algorithms for the unstructured search problem to the case when the number of marked items is unknown. In an ideal situation, an explicit quantum algorithm together with a counting subroutine are given that achieve the optimal Grover speedup over classical algorithms, i.e., roughly speaking, reduce O(2n) to O(2n/2), where n is the size of the problem. However, if one considers more realistic settings, the result shows this quantum speedup is achievable only under a very rigid control precision requirement (e.g., exponentially small control error).
Energy transport in the Anderson insulator
NASA Astrophysics Data System (ADS)
Gutman, D. B.; Protopopov, I. V.; Burin, A. L.; Gornyi, I. V.; Santos, R. A.; Mirlin, A. D.
2016-06-01
We study the heat conductivity in Anderson insulators in the presence of a power-law interaction. Particle-hole excitations built on localized electron states are viewed as two-level systems randomly distributed in space and energy and coupled due to electron-electron interaction. A small fraction of these states form resonant pairs that in turn build a complex network allowing for energy propagation. We identify the character of energy transport through this network and evaluate the thermal conductivity. For physically relevant cases of two-dimensional and three-dimensional spin systems with 1 /r3 dipole-dipole interaction (originating from the conventional 1 /r Coulomb interaction between electrons), the found thermal conductivity κ scales with temperature as κ ∝T3 and κ ∝T4 /3 , respectively. Our results may be of relevance also to other realizations of random spin Hamiltonians with long-range interactions.
NASA Astrophysics Data System (ADS)
Perera, J.; Wortis, R.
2015-08-01
After Anderson's prediction of disorder-induced insulating behavior, extensive work found no singularities in the density of states of localized systems. However, Johri and Bhatt [Phys. Rev. Lett. 109, 076402 (2012), 10.1103/PhysRevLett.109.076402 and Phys. Rev. B 86, 125140 (2012), 10.1103/PhysRevB.86.125140] recently uncovered the existence of a nonanalyticity in the density of states near the band edge of noninteracting systems with bounded disorder, in an energy range outside that captured by previous work. Moreover, this feature marks the boundary of an energy range in which the localization is sharply suppressed. Given strong current interest in the effect of interactions on disordered systems, we explore here the effect of a Hubbard U interaction on this behavior. We find that in ensembles of small systems a cusp in the density of states persists and continues to be associated with a sharp suppression of the localization. We explore the origins of this behavior and discuss its connection with many-body localization.
NASA Astrophysics Data System (ADS)
Wortis, Rachel; Perera, Jayanayana
2015-03-01
We explore the effect of interactions on novel features found in non-interacting disordered systems. Johri and Bhatt [PRL 109 076402 (2012), PRB 86 125140 (2012)] showed that for non-interacting particles moving in a disordered potential Lifshitz states lead to a decrease in localization at the band edges. This is reflected in an abrupt decline in the inverse participation ratio following a sharp peak. We consider an ensemble of two-site Anderson-Hubbard systems and study a generalization of the inverse participation ratio applicable to interacting systems. With on-site Coulomb repulsion U, two types of resonances can occur: As in the non-interacting case, the potentials at the two sites may be similar. In addition, the potential at one site may differ from its neighbor by U. We demonstrate that these two types of resonance and the diversity of transitions in the interacting case result in much more varied dependence of localization on energy, with multiple local minima, including a strong suppression and more structure near the Fermi level. Opportunities for experimental observation are considered. NSERC of Canada.
Electrically excited, localized infrared emission from single carbon nanotubes.
Freitag, Marcus; Tsang, James C; Kirtley, John; Carlsen, Autumn; Chen, Jia; Troeman, Aico; Hilgenkamp, Hans; Avouris, Phaedon
2006-07-01
Carbon nanotube field-effect transistors (CNTFETs) produce band gap derived infrared emission under both ambipolar and unipolar transport conditions. We demonstrate here that heterogeneities/defects in the local environment of a CNTFET perturb the local potentials and, as a result, the characteristic bias dependent motion of the ambipolar light emission. Such defects can also introduce localized infrared emission due to impact excitation by carriers accelerated by a voltage drop at the defect. The correlation of the change in the motion of the ambipolarlight emission and of the stationary electroluminescence with the electrical characteristics of the CNTFETs shows that stationaryelectroluminescence can identify "environmental defects" in carbon nanotubes and help evaluate their influence on electrical transport and device operation. A number of different defects are studied involving local dielectric environment changes (partially polymer-covered nanotubes), nanotube-nanotube contacts in looped nanotubes, and nanotube segments close to the electronic contacts. Random defects due to local charging are also observed.
Exciting and probing plasmons in graphene by local defects
NASA Astrophysics Data System (ADS)
Efimov, Anatoly; Velizhanin, Kirill
2012-02-01
The short wavelength of collective excitations, i.e., plasmons, in doped graphene (˜10-20 nm) is very attractive for multiple applications. However, the same short wavelength makes photoexcitation of plasmons in graphene a very challenging task. In this work, we discuss various types of local defects including semiconductor quantum dots, metallic nanoclusters, edges and holes in graphene as means to ``squeeze'' the large wavelength of optical excitation down to the nanometer scale, thus, providing an effective coupling between free photons and plasmons in graphene. In the case of semiconductor quantum dots, we show how plasmons in graphene can be excited and probed by Forster resonance energy transfer from the optically excited quantum dot to the graphene sheet. Specifically, we demonstrate how the calculated dispersion relation of plasmons in graphene as well as of other electronic excitations can be accurately extracted by controlling the backgate voltage and the distance between the quantum dot and graphene [1]. [4pt] [1] K. A. Velizhanin, A. Efimov``Probing plasmons in graphene by resonance energy transfer,'' Phys. Rev. B, 085401, 84 (2011).
NASA Astrophysics Data System (ADS)
Zhou, Lu; Pu, Han; Zhang, Weiping
2013-02-01
We theoretically investigate the localization properties of a spin-orbit-coupled spin-1/2 particle moving in a one-dimensional quasiperiodic potential, which can be experimentally implemented using cold atoms trapped in a quasiperiodic optical lattice potential and external laser fields. We present the phase diagram in the parameter space of the disorder strength and those related to the spin-orbit coupling. The phase diagram is verified via multifractal analysis of the atomic wave functions and the numerical simulation of diffusion dynamics. We found that spin-orbit coupling can lead to spectra mixing (coexistence of extended and localized states) and the appearance of mobility edges.
Local photo-excitation of shift current in noncentrosymmetric systems
NASA Astrophysics Data System (ADS)
Ishizuka, Hiroaki; Nagaosa, Naoto
2017-03-01
Photocurrent in solids is an important phenomenon with many applications including the solar cells. In conventional photoconductors, the electrons and holes created by light irradiation are separated by the external electric field, resulting in a current flowing into electrodes. Shift current in noncentrosymmetric systems is distinct from this conventional photocurrent in the sense that no external electric field is needed and, more remarkably, is driven by the Berry phase inherent to the Bloch wavefunction. It is analogous to the polarization current in the ground state but is a dc current continuously supported by the nonequilibrium steady state under the pumping by light. Here we show theoretically, by employing Keldysh–Floquet formalism applied to a simple one-dimensional model, that the local photo excitation can induce the shift current which is independent of the position and width of the excited region and also the length of the system. This feature is in stark contrast to the conventional photocurrent, which is suppressed when the sample is excited locally at the middle and increases towards the electrodes. This finding reveals the unconventional nature of shift current and will pave a way to design a highly efficient photovoltaic effect in solids.
Raj, S; Hashimoto, D; Matsui, H; Souma, S; Sato, T; Takahashi, T; Sarma, D D; Mahadevan, Priya; Oishi, S
2006-04-14
The electronic structure of the insulating sodium tungsten bronze, Na(0.025)WO(3), is investigated by high-resolution angle-resolved photoemission spectroscopy. We find that near-E(F) states are localized due to the strong disorder arising from random distribution of Na+ ions in the WO(3) lattice, which makes the system insulating. The temperature dependence of photoemission spectra provides direct evidence for polaron formation. The remnant Fermi surface of the insulator is found to be the replica of the real Fermi surface in the metallic system.
NASA Astrophysics Data System (ADS)
Gong, Longyan; Feng, Yan; Ding, Yougen
2017-02-01
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.
Yamada, Hiroaki; Ikeda, Kensuke S
2002-04-01
It was shown that localization in one-dimensional disordered (quantum) electronic system is destroyed against coherent harmonic perturbations and the delocalized electron exhibits an unlimited diffusive motion [Yamada and Ikeda, Phys. Rev. E 59, 5214 (1999)]. The appearance of diffusion implies that the system has potential for irreversibility and dissipation. In the present paper, we investigate dissipative property of the dynamically delocalized state, and we show that an irreversible quasistationary energy flow indeed appears in the form of a "heat" flow when we couple the system with another dynamical degree of freedom. In the concrete we numerically investigate dissipative properties of a one-dimensional tight-binding electronic system perturbed by time-dependent harmonic forces, by coupling it with a quantum harmonic oscillator or a quantum anharmonic oscillator. It is demonstrated that if the on-site potential is spatially irregular an irreversible energy transfer from the scattered electron to the test oscillator occurs. Moreover, the test oscillator promptly approaches a thermalized state characterized by a well-defined time-dependent temperature. On the contrary, such a relaxation process cannot be observed at all for periodic potential systems. Our system is one of the minimal quantum systems in which a distinct nonequilibrium statistical behavior is self-induced.
Local excitation and collection in polymeric fluorescent microstructures
NASA Astrophysics Data System (ADS)
Henrique, Franciele Renata; Mendonca, Cleber Renato
2016-04-01
Integrated photonics has gained attention in recent years due to its wide range of applications which span from biology to optical communications. The use of polymer-based platforms for photonic devices is of great interest because organic compounds can be easily incorporated to polymers, enabling modifications to the system physical properties. The two-photon polymerization technique has emerged as an interesting tool for the production of three-dimensional polymeric microstructures. However, for their further incorporation in photonic devices it is necessary to develop methods to perform optical excitation and signal collection on such microstructures. With such purpose, we demonstrate approaches to perform local excitation and collection in polymeric microstructures doped with fluorescent dyes, employing tapered fibers. The obtained results indicate that fiber tapers are suitable to couple light in and out of fluorescent polymeric microstructures, paving the way for their incorporation in photonic devices. We also show that microstructures doped with more than one dye can be used as built-in broadband light sources to photonic circuits and their emission spectrum can be tuned by the right choice of the excitation position.
Quantum entanglement of locally excited states in Maxwell theory
NASA Astrophysics Data System (ADS)
Nozaki, Masahiro; Watamura, Naoki
2016-12-01
In 4 dimensional Maxwell gauge theory, we study the changes of (Rényi) entanglement entropy which are defined by subtracting the entropy for the ground state from the one for the locally excited states, generated by acting with gauge invariant local operators on the state. The changes for the operators which we consider in this paper reflect the electric-magnetic duality. The late-time value of changes can be interpreted in terms of electromagnetic quasi-particles. When the operator constructed of both electric and magnetic fields acts on the ground state, it shows that the operator acts on the late-time structure of quantum entanglement differently from free scalar fields.
Lasting depression in corticomotor excitability associated with local scalp cooling.
Tremblay, François; Remaud, Anthony; Mekonnen, Abeye; Gholami-Boroujeny, Shiva; Racine, Karl-Édouard; Bolic, Miodrag
2015-07-23
In this study, we investigated the effect of local scalp cooling on corticomotor excitability with transcranial magnetic simulation (TMS). Participants (healthy male adults, n=12) were first assessed with TMS to derive baseline measure of excitability from motor evoked potentials (MEPs) using the right first dorsal interosseous as the target muscle. Then, local cooling was induced on the right hemi-scalp (upper frontal region ∼ 15 cm(2)) by means of a cold wrap. The cooling was maintained for 10-15 min to get a decrease of at least 10°C from baseline temperature. In the post-cooling period, both scalp temperature and MEPs were reassessed at specific time intervals (i.e., T0, T10, T20 and T30 min). Scalp surface temperatures dropped on average by 12.5°C from baseline at T0 (p<0.001) with partial recovery at T10 (p<0.05) and full recovery at T20. Parallel analysis of post-cooling variations in MEP amplitude revealed significant reductions relative to baseline at T0, T10 and T20. No concurrent change in MEP latency was observed. A secondary control experiment was performed in a subset of participants (n=5) to account for the mild discomfort associated with the wrapping procedure without the cooling agent. Results showed no effect on any of the dependent variables (temperature, MEP amplitude and latency). To our knowledge, this report provides the first neurophysiological evidence linking changes in scalp temperature with lasting changes in corticomotor excitability.
Local treatment of electron excitations in the EOM-CCSD method
NASA Astrophysics Data System (ADS)
Korona, Tatiana; Werner, Hans-Joachim
2003-02-01
The Equation-of-Motion coupled cluster method restricted to single and double excitations (EOM-CCSD) and singlet excited states is formulated in a basis of nonorthogonal local orbitals. In the calculation of excited states only electron promotions from localized molecular orbitals into subspaces (excitation domains) of the local basis are allowed, which strongly reduces the number of EOM-CCSD amplitudes to be optimized. Furthermore, double excitations are neglected unless the excitation domains of the corresponding localized occupied orbitals are close to each other. Unlike in the local methods for the ground state, the excitation domains cannot be simply restricted to the atomic orbitals that are spatially close to the localized occupied orbitals. In the present paper the choice of the excitation domains is based on the analysis of wave functions computed by more approximate (and cheaper) methods like, e.g., configuration-interaction singles. The effect of various local approximations is investigated in detail, and it is found that a balanced description of the local configuration spaces describing the ground and excited states is essential to obtain accurate results. Using a single set of parameters for a given basis set, test calculations with the local EOM-CCSD method were performed for 14 molecules and 49 electronically excited states. The excitation energies computed by the local EOM-CCSD method reproduce the conventional EOM-CCSD excitation energies with an average error of 0.06 eV.
Probing the Locality of Excited States with Linear Algebra.
Etienne, Thibaud
2015-04-14
This article reports a novel theoretical approach related to the analysis of molecular excited states. The strategy introduced here involves gathering two pieces of physical information, coming from Hilbert and direct space operations, into a general, unique quantum mechanical descriptor of electronic transitions' locality. Moreover, the projection of Hilbert and direct space-derived indices in an Argand plane delivers a straightforward way to visually probe the ability of a dye to undergo a long- or short-range charge-transfer. This information can be applied, for instance, to the analysis of the electronic response of families of dyes to light absorption by unveiling the trend of a given push-pull chromophore to increase the electronic cloud polarization magnitude of its main transition with respect to the size extension of its conjugated spacer. We finally demonstrate that all the quantities reported in this article can be reliably approximated by a linear algebraic derivation, based on the contraction of detachment/attachment density matrices from canonical to atomic space. This alternative derivation has the remarkable advantage of a very low computational cost with respect to the previously used numerical integrations, making fast and accurate characterization of large molecular systems' excited states easily affordable.
Parametric excitation of multiple resonant radiations from localized wavepackets
Conforti, Matteo; Trillo, Stefano; Mussot, Arnaud; Kudlinski, Alexandre
2015-01-01
Fundamental physical phenomena such as laser-induced ionization, driven quantum tunneling, Faraday waves, Bogoliubov quasiparticle excitations, and the control of new states of matter rely on time-periodic driving of the system. A remarkable property of such driving is that it can induce the localized (bound) states to resonantly couple to the continuum. Therefore experiments that allow for enlightening and controlling the mechanisms underlying such coupling are of paramount importance. We implement such an experiment in a special optical fiber characterized by a dispersion oscillating along the propagation coordinate, which mimics “time”. The quasi-momentum associated with such periodic perturbation is responsible for the efficient coupling of energy from the localized wave-packets (solitons in anomalous dispersion and shock fronts in normal dispersion) sustained by the fiber nonlinearity, into free-running linear dispersive waves (continuum) at multiple resonant frequencies. Remarkably, the observed resonances can be explained by means of a unified approach, regardless of the fact that the localized state is a soliton-like pulse or a shock front. PMID:25801054
Parametric excitation of multiple resonant radiations from localized wavepackets
NASA Astrophysics Data System (ADS)
Conforti, Matteo; Trillo, Stefano; Mussot, Arnaud; Kudlinski, Alexandre
2015-03-01
Fundamental physical phenomena such as laser-induced ionization, driven quantum tunneling, Faraday waves, Bogoliubov quasiparticle excitations, and the control of new states of matter rely on time-periodic driving of the system. A remarkable property of such driving is that it can induce the localized (bound) states to resonantly couple to the continuum. Therefore experiments that allow for enlightening and controlling the mechanisms underlying such coupling are of paramount importance. We implement such an experiment in a special optical fiber characterized by a dispersion oscillating along the propagation coordinate, which mimics ``time''. The quasi-momentum associated with such periodic perturbation is responsible for the efficient coupling of energy from the localized wave-packets (solitons in anomalous dispersion and shock fronts in normal dispersion) sustained by the fiber nonlinearity, into free-running linear dispersive waves (continuum) at multiple resonant frequencies. Remarkably, the observed resonances can be explained by means of a unified approach, regardless of the fact that the localized state is a soliton-like pulse or a shock front.
Optical Excitation of Carbon Nanotubes Drives Localized Diazonium Reactions.
Powell, Lyndsey R; Piao, Yanmei; Wang, YuHuang
2016-09-15
Covalent chemistries have been widely used to modify carbon nanomaterials; however, they typically lack the precision and efficiency required to directly engineer their optical and electronic properties. Here, we show, for the first time, that visible light which is tuned into resonance with carbon nanotubes can be used to drive their functionalization by aryldiazonium salts. The optical excitation accelerates the reaction rate 154-fold (±13) and makes it possible to significantly improve the efficiency of covalent bonding to the sp(2) carbon lattice. Control experiments suggest that the reaction is dominated by a localized photothermal effect. This light-driven reaction paves the way for precise nanochemistry that can directly tailor carbon nanomaterials at the optical and electronic levels.
Validation of local hybrid functionals for TDDFT calculations of electronic excitation energies
NASA Astrophysics Data System (ADS)
Maier, Toni M.; Bahmann, Hilke; Arbuznikov, Alexei V.; Kaupp, Martin
2016-02-01
The first systematic evaluation of local hybrid functionals for the calculation of electronic excitation energies within linear-response time-dependent density functional theory (TDDFT) is reported. Using our recent efficient semi-numerical TDDFT implementation [T. M. Maier et al., J. Chem. Theory Comput. 11, 4226 (2015)], four simple, thermochemically optimized one-parameter local hybrid functionals based on local spin-density exchange are evaluated against a database of singlet and triplet valence excitations of organic molecules, and against a mixed database including also Rydberg, intramolecular charge-transfer (CT) and core excitations. The four local hybrids exhibit comparable performance to standard global or range-separated hybrid functionals for common singlet valence excitations, but several local hybrids outperform all other functionals tested for the triplet excitations of the first test set, as well as for relative energies of excited states. Evaluation for the combined second test set shows that local hybrids can also provide excellent Rydberg and core excitations, in the latter case rivaling specialized functionals optimized specifically for such excitations. This good performance of local hybrids for different excitation types could be traced to relatively large exact-exchange (EXX) admixtures in a spatial region intermediate between valence and asymptotics, as well as close to the nucleus, and lower EXX admixtures in the valence region. In contrast, the tested local hybrids cannot compete with the best range-separated hybrids for intra- and intermolecular CT excitation energies. Possible directions for improvement in the latter category are discussed. As the used efficient TDDFT implementation requires essentially the same computational effort for global and local hybrids, applications of local hybrid functionals to excited-state problems appear promising in a wide range of fields. Influences of current-density dependence of local kinetic
Ramasamy, P R
2017-01-01
Background: Open fractures of tibia have posed great difficulty in managing both the soft tissue and the skeletal components of the injured limb. Gustilo Anderson III B open tibial fractures are more difficult to manage than I, II, and III A fractures. Stable skeletal fixation with immediate soft tissue cover has been the key to the successful outcome in treating open tibial fractures, in particular, Gustilo Anderson III B types. If the length of the open wound is larger and if the exposed surface of tibial fracture and tibial shaft is greater, then the management becomes still more difficult. Materials and Methods: Thirty six Gustilo Anderson III B open tibial fractures managed between June 2002 and December 2013 with “fix and shift” technique were retrospectively reviewed. All the 36 patients managed by this technique had open wounds measuring >5 cm (post debridement). Under fix and shift technique, stable fixation involved primary external fixator application or primary intramedullary nailing of the tibial fracture and immediate soft tissue cover involved septocutaneous shift, i.e., shifting of fasciocutaneous segments based on septocutaneous perforators. Results: Primary fracture union rate was 50% and reoperation rate (bone stimulating procedures) was 50%. Overall fracture union rate was 100%. The rate of malunion was 14% and deep infection was 16%. Failure of septocutaneous shift was 2.7%. There was no incidence of amputation. Conclusion: Management of Gustilo Anderson III B open tibial fractures with “fix and shift” technique has resulted in better outcome in terms of skeletal factors (primary fracture union, overall union, and time for union and malunion) and soft tissue factors (wound healing, flap failure, access to secondary procedures, and esthetic appearance) when compared to standard methods adopted earlier. Hence, “fix and shift” could be recommended as one of the treatment modalities for open III B tibial fractures. PMID:28216752
Interview with Philip W. Anderson
Anderson, P.W.
1988-08-01
Phil Anderson, Professor of Physics at Princeton University, has devoted his career to research in theoretical physics. He is a member of the National Academy of Science and the American Academy of Arts and Sciences, a foreign member of the Royal Society, and a foreign associate of the Accademia Lincei in Rome. The Americal Physical Society awarded him the Oliver E. Buckley Solid State Physics Prize in 1964. In 1977 he won the Nobel Prize in Physics with J.H. van Vleck and N.F. Mott. His work has encompassed a broad range of subjects: quantum theory of condensed matter, broken symmetry, transport theory and localization, random statistical systems, spectral line broadening, superfluidity in helium and neutron stars, magnetism, and superconductivity. His avocations include ''hiking, the game of GO, Romanesque architecture, and the human condition.'' In this interview he explains his RVB theory of the oxide superconductors and its historical context.
NASA Astrophysics Data System (ADS)
He, James Jun; Zhou, Tong; Gu, Z. C.; Law, K. T.
When a magnetic field is applied to a quantum spin Hall insulator (QSHI) without inversion symmetry, the edge states become gapful due to the breaking of time reversal symmetry (TRS) and the QSHI becomes a trivial spin Hall insulator (SHI) whose Chern number is N = 0 . In this work we show that disorder can drive such a SHI to a Chern insulator (CI) with N = 1 which supports a gapless chiral edge state. This CI exists in a finite range of disorder strength. Interestingly, the edge state is protected by the bulk mobility gap instead of an energy gap. For this reason, the new phase is called an Anderson Chern insulator (ACI).
Quantifying Anderson's fault types
Simpson, R.W.
1997-01-01
Anderson [1905] explained three basic types of faulting (normal, strike-slip, and reverse) in terms of the shape of the causative stress tensor and its orientation relative to the Earth's surface. Quantitative parameters can be defined which contain information about both shape and orientation [Ce??le??rier, 1995], thereby offering a way to distinguish fault-type domains on plots of regional stress fields and to quantify, for example, the degree of normal-faulting tendencies within strike-slip domains. This paper offers a geometrically motivated generalization of Angelier's [1979, 1984, 1990] shape parameters ?? and ?? to new quantities named A?? and A??. In their simple forms, A?? varies from 0 to 1 for normal, 1 to 2 for strike-slip, and 2 to 3 for reverse faulting, and A?? ranges from 0?? to 60??, 60?? to 120??, and 120?? to 180??, respectively. After scaling, A?? and A?? agree to within 2% (or 1??), a difference of little practical significance, although A?? has smoother analytical properties. A formulation distinguishing horizontal axes as well as the vertical axis is also possible, yielding an A?? ranging from -3 to +3 and A?? from -180?? to +180??. The geometrically motivated derivation in three-dimensional stress space presented here may aid intuition and offers a natural link with traditional ways of plotting yield and failure criteria. Examples are given, based on models of Bird [1996] and Bird and Kong [1994], of the use of Anderson fault parameters A?? and A?? for visualizing tectonic regimes defined by regional stress fields. Copyright 1997 by the American Geophysical Union.
NASA Astrophysics Data System (ADS)
Lee, Myeong H.; Troisi, Alessandro
2017-02-01
It has been reported in recent years that vibronic resonance between vibrational energy of the intramolecular nuclear mode and excitation-energy difference is crucial to enhance excitation energy transport in light harvesting proteins. Here we investigate how vibronic enhancement induced by vibronic resonance is influenced by the details of local and non-local exciton-phonon interactions. We study a heterodimer model with parameters relevant to the light-harvesting proteins with the surrogate Hamiltonian quantum dynamics method in a vibronic basis. In addition, the impact of field-driven excitation on the efficiency of population transfer is compared with the instantaneous excitation, and the effect of multi-mode vibronic coupling is presented in comparison with the coupling to a single effective vibrational mode. We find that vibronic enhancement of site population transfer is strongly suppressed with the increase of non-local exciton-phonon interaction and increasing the number of strongly coupled high-frequency vibrational modes leads to a further decrease in vibronic enhancement. Our results indicate that vibronic enhancement is present but may be much smaller than previously thought and therefore care needs to be taken when interpreting its role in excitation energy transport. Our results also suggest that non-local exciton-phonon coupling, which is related to the fluctuation of the excitonic coupling, may be as important as local exciton-phonon coupling and should be included in any quantum dynamics model.
Plasmonic local heating beyond diffraction limit by the excitation of magnetic polariton
NASA Astrophysics Data System (ADS)
Alshehri, Hassan; Wang, Hao; Ma, Yanchao; Wang, Liping
2015-08-01
In recent years, optical local heating in the nanoscale has attracted great attention due to its unique features of small hot spot size and high energy density. Plasmonic local heating can provide solutions to several challenges in data storage and cancer treatment. Research conducted in this field to achieve plasmonic local heating has mainly utilized the excitation of localized surface plasmon (LSP) or surface plasmon resonance (SPR). However, achieving plasmonic local heating by the excitation of magnetic polariton (MP) has not been researched extensively yet. We numerically investigate the optical response of a nanostructure composed of a gold nanowire on a gold surface separated by a polymer spacer using the ANSYS High Frequency Structural Simulator (HFSS). The structure exhibits a strong absorption peak at the wavelength of 750 nm, and the underlying physical mechanism is verified by the local electromagnetic field distribution to be the magnetic resonance excitation. By incorporating the volume loss density due to the strong local optical energy confinement as the heat generation, nanoscale temperature distribution within the structure is numerically obtained with a thermal solver after assigning proper boundary conditions. The results show a maximum temperature of 158.5°C confined in a local area on the order of 35 nm within the ultrathin polymer layer, which clearly demonstrates the plasmonic local heating effect beyond diffraction limit by excitation of MP.
Bayati, Mehdi; Valizadeh, Alireza; Abbassian, Abdolhossein; Cheng, Sen
2015-01-01
Many experimental and theoretical studies have suggested that the reliable propagation of synchronous neural activity is crucial for neural information processing. The propagation of synchronous firing activity in so-called synfire chains has been studied extensively in feed-forward networks of spiking neurons. However, it remains unclear how such neural activity could emerge in recurrent neuronal networks through synaptic plasticity. In this study, we investigate whether local excitation, i.e., neurons that fire at a higher frequency than the other, spontaneously active neurons in the network, can shape a network to allow for synchronous activity propagation. We use two-dimensional, locally connected and heterogeneous neuronal networks with spike-timing dependent plasticity (STDP). We find that, in our model, local excitation drives profound network changes within seconds. In the emergent network, neural activity propagates synchronously through the network. This activity originates from the site of the local excitation and propagates through the network. The synchronous activity propagation persists, even when the local excitation is removed, since it derives from the synaptic weight matrix. Importantly, once this connectivity is established it remains stable even in the presence of spontaneous activity. Our results suggest that synfire-chain-like activity can emerge in a relatively simple way in realistic neural networks by locally exciting the desired origin of the neuronal sequence.
NASA Astrophysics Data System (ADS)
Yu, Xiongjie; Pekker, David; Clark, Bryan K.
2017-01-01
A key property of many-body localized Hamiltonians is the area law entanglement of even highly excited eigenstates. Matrix product states (MPS) can be used to efficiently represent low entanglement (area law) wave functions in one dimension. An important application of MPS is the widely used density matrix renormalization group (DMRG) algorithm for finding ground states of one-dimensional Hamiltonians. Here, we develop two algorithms, the shift-and-invert MPS (SIMPS) and excited state DMRG which find highly excited eigenstates of many-body localized Hamiltonians. Excited state DMRG uses a modified sweeping procedure to identify eigenstates, whereas SIMPS applies the inverse of the shifted Hamiltonian to a MPS multiple times to project out the targeted eigenstate. To demonstrate the power of these methods, we verify the breakdown of the eigenstate thermalization hypothesis in the many-body localized phase of the random field Heisenberg model, show the saturation of entanglement in the many-body localized phase, and generate local excitations.
Investigation of RF excited CW CO2 waveguide lasers local oscillator - RF excitation
NASA Technical Reports Server (NTRS)
Hochuli, U.
1988-01-01
A new local oscillator housing was built which seems to have improved laser life. Laser cooling was changed from internal water cooling to the more convenient thermal contact cooling. At the present time, a conclusion can not be made if the 20 percent reduction in power output is the result of poorer cooling or poorer grating alignment. The coupling-starting network was improved from 55 to about 90 percent. It can be adjusted by varying trimmers C sub 1 and C sub 2 to match RF power levels between 10 and 30 W. If the laser admittance changes greatly with laser life rematching will have to be achieved by remote control for space applications. The same holds true if the RF power level has to be changed with a maximum efficiency constraint.
Schrauben, Joel N.; Akdag, Akin; Wen, Jin; Havlas, Zdenek; Ryerson, Joseph L.; Smith, Millie B.; Michl, Josef; Johnson, Justin C.
2016-05-26
Two isomers of both the lowest excited singlet (S1) and triplet (T1) states of the directly para, para'-connected covalent dimer of the singlet-fission chromophore 1,3-diphenylisobenzofuran have been observed. In one isomer, excitation is delocalized over both halves of the dimer, and in the other, it is localized on one or the other half. For a covalent dimer in solution, such 'excitation isomerism' is extremely rare. The vibrationally relaxed isomers do not interconvert, and their photophysical properties, including singlet fission, differ significantly.
Polarons in π-Conjugated Polymers: Anderson or Landau?
Barford, William; Marcus, Max; Tozer, Oliver Robert
2016-02-04
Using both analytical expressions and the density matrix renormalization group method, we study the fully quantized disordered Holstein model to investigate the localization of charges and excitons by vibrational or torsional modes-i.e., the formation of polarons-in conformationally disordered π-conjugated polymers. We identify two distinct mechanisms for polaron formation, namely Anderson localization via disorder (causing the formation of Anderson polarons) and self-localization by self-trapping via normal modes (causing the formation of Landau polarons). We identify the regimes where either description is more valid. The key distinction between Anderson and Landau polarons is that for the latter the particle wave function is a strong function of the normal coordinates, and hence the "vertical" and "relaxed" wave functions are different. This has theoretical and experimental consequences for Landau polarons. Theoretically, it means that the Condon approximation is not valid, and so care needs to be taken when evaluating transition rates. Experimentally, it means that the self-localization of the particle as a consequence of its coupling to the normal coordinates may lead to experimental observables, e.g., ultrafast fluorescence depolarization. We apply these ideas to poly(p-phenylenevinylene). We show that the high frequency C-C bond oscillation only causes Landau polarons for a very narrow parameter regime; generally we expect disorder to dominate and Anderson polarons to be a more applicable description. Similarly, for the low frequency torsional fluctuations we show that Anderson polarons are expected for realistic parameters.
NASA Astrophysics Data System (ADS)
Nayyar, Iffat; Batista, Enrique; Tretiak, Sergei; Saxena, Avadh; Smith, Darryl; Martin, Richard
2012-02-01
Organic polymers find varied applications in optoelectronic devices such as solar cells, light emitting diodes and lasers. Detailed understanding of charge carrier transport by polarons and excitonic energy transfer producing singlet and triplet excitations is critical to improve their efficiency. We benchmarked the ability of current functional models to describe the spatial extent of self-trapped neutral and charged excitations for MEH-PPV owing to its superior luminescence and experimental evidence. Now we are interested in distinguishing between two distinct origins leading to localization; spatial localization of the wavefunction by itself on the undistorted geometry and localization of the wavefunction assured by distortion of the structure during its relaxation. We suggest localization is produced by electronic rearrangements and character of the functional. We also observe that different functionals place the highest occupied and lowest virtual orbitals at different positions in the energy band diagram based on their ability to predict the extent of localization of these states.
Plasmonic localized heating beyond the diffraction limit via magnetic polariton excitation
NASA Astrophysics Data System (ADS)
Alshehri, Hassan; Ying, Xiaoyan; Wang, Hao; Wang, Liping
2016-09-01
Optical localized heating in the nanoscale has recently attracted great attention due to its unique small hot spot size with high energy. However, the hot spot size is conventionally constrained by the diffraction limit. Plasmonic localized heating can provide solutions to this limitation in nanoscale patterning, cancer treatment, and data storage. Plasmonic approaches to overcome the diffraction limit in hot spot size have mainly utilized the excitation of surface plasmon or localized surface plasmon resonance. However, achieving plasmonic localized heating by the excitation of magnetic polariton has not been researched extensively yet. In this work, we numerically investigated the optical response of a nanoscale metamaterial composed of a gold nanowire array and a gold film separated by an ultrathin polymer spacer using ANSYS High Frequency Structural Simulator. A strong absorption peak at the wavelength of 760 nm was exhibited, and the underlying physical mechanism for the strong absorption was verified via the local electromagnetic field distribution to be magnetic resonance excitation. An inductor-capacitor circuit model was used to predict the magnetic resonance wavelength and compare with the numerical results for varied geometrical parameters. Volume loss density due to the strong local optical energy confinement was transferred as heat generation to an ANSYS thermal solver to obtain the local temperature profile. The steady state temperature profile shows an average temperature of 145 °C confined in a local area as small as 33 nm within the spacer, with a full-width at half-maximum of 50 nm along the x-direction. Moreover, the temperature rise from ambient drops to half its maximum value at a distance of 5 nm from the top of the spacer along the z-direction. This clearly demonstrates plasmonic localized heating beyond the diffraction limit via magnetic polariton excitation. Furthermore, the transient temperature profile shows that the system reached
Nagesh, Jayashree; Frisch, Michael J; Brumer, Paul; Izmaylov, Artur F
2016-12-28
We extend the localized operator partitioning method (LOPM) [J. Nagesh, A. F. Izmaylov, and P. Brumer, J. Chem. Phys. 142, 084114 (2015)] to the time-dependent density functional theory framework to partition molecular electronic energies of excited states in a rigorous manner. A molecular fragment is defined as a collection of atoms using Becke's atomic partitioning. A numerically efficient scheme for evaluating the fragment excitation energy is derived employing a resolution of the identity to preserve standard one- and two-electron integrals in the final expressions. The utility of this partitioning approach is demonstrated by examining several excited states of two bichromophoric compounds: 9-((1- naphthyl)- methyl)- anthracene and 4-((2- naphthyl)- methyl)- benzaldehyde. The LOPM is found to provide nontrivial insights into the nature of electronic energy localization that is not accessible using a simple density difference analysis.
NASA Astrophysics Data System (ADS)
Zhou, Lu; Pu, Han; Zhang, Weiping
2013-03-01
We theoretically investigate the localization properties of a noninteracting atomic Bose-Einstein condensate moving in a one-dimensional quasiperiodic optical lattice potential in the tight-binding regime. The atoms are subject to effective spin-orbit coupling induced by external laser fields. We present the phase diagram in the parameter space of the disorder strength and those related to the effective spin-orbit coupling. The phase diagram are verified via multifractal analysis of the atomic wavefunctions. We found that spin-orbit coupling can lead to the spectra mixing (coexistence of extended and localized states) and the appearance of mobility edges. We acknowledge National Natural Science Foundation of China under Grant No 11004057, Shanghai Rising-Star Program under Grant No. 12QA1401000 and the ``Chen Guang'' project under Grant No 10CG24 for financial supports.
Excitation by Axon Terminal GABA Spillover in a Sound Localization Circuit
Weisz, Catherine J.C.; Rubio, Maria E.; Givens, Richard S.
2016-01-01
Synapses from neurons of the medial nucleus of the trapezoid body (MNTB) onto neurons of the lateral superior olive (LSO) in the auditory brainstem are glycinergic in maturity, but also GABAergic and glutamatergic in development. The role for this neurotransmitter cotransmission is poorly understood. Here we use electrophysiological recordings in brainstem slices from P3-P21 mice to demonstrate that GABA release evoked from MNTB axons can spill over to neighboring MNTB axons and cause excitation by activating GABAAR. This spillover excitation generates patterns of staggered neurotransmitter release from different MNTB axons resulting in characteristic “doublet” postsynaptic currents in LSO neurons. Postembedding immunogold labeling and electron microscopy provide evidence that GABAARs are localized at MNTB axon terminals. Photolytic uncaging of p-hydroxyphenacyl (pHP) GABA demonstrates backpropagation of GABAAR-mediated depolarizations from MNTB axon terminals to the soma, some hundreds of microns away. These somatic depolarizations enhanced somatic excitability by increasing the probability of action potential generation. GABA spillover excitation between MNTB axon terminals may entrain neighboring MNTB neurons, which may play a role in the developmental refinement of the MNTB-LSO pathway. Axonal spillover excitation persisted beyond the second postnatal week, suggesting that this mechanism may play a role in sound localization, by providing new avenues of communication between MNTB neurons via their distal axonal projections. SIGNIFICANCE STATEMENT In this study, a new mechanism of neuronal communication between auditory synapses in the mammalian sound localization pathway is described. Evidence is provided that the inhibitory neurotransmitter GABA can spill over between axon terminals to cause excitation of nearby synapses to further stimulate neurotransmitter release. Excitatory GABA spillover between inhibitory axon terminals may have important
Localized and propagating excitations in gapped phases of spin systems with bond disorder
NASA Astrophysics Data System (ADS)
Utesov, O. I.; Sizanov, A. V.; Syromyatnikov, A. V.
2014-10-01
Using the conventional T-matrix approach, we discuss gapped phases in one-, two-, and three-dimensional (3D) spin systems (both with and without a long-range magnetic order) with bond disorder and with weakly interacting bosonic elementary excitations. This work is motivated by recent experimental and theoretical activity in spin-liquid-like systems with disorder and in the disordered interacting boson problem. In particular, we apply our theory to both paramagnetic low-field and fully polarized high-field phases in dimerized spin-1/2 systems and in integer-spin magnets with large single-ion easy-plane anisotropy D with disorder in exchange coupling constants (and/or D). The elementary excitation spectrum and the density of states are calculated in the first order in defects concentration c ≪1. In 2D and 3D systems, the scattering on defects leads to a finite damping of all propagating excitations in the band except for states lying near its edges. We demonstrate that the analytical approach is inapplicable for states near the band edges and our numerical calculations reveal their localized nature. We find that the damping of propagating excitations can be much more pronounced in considered systems than in magnetically ordered gapless magnets with impurities. In 1D systems, the disorder leads to localization of all states in the band, while those lying far from the band edges (short-wavelength excitations) can look like conventional wave packets.
Excitation of unsteady Görtler vortices by localized surface nonuniformities
NASA Astrophysics Data System (ADS)
Boiko, A. V.; Ivanov, A. V.; Kachanov, Yu. S.; Mischenko, D. A.; Nechepurenko, Yu. M.
2017-02-01
A combined theoretical and numerical analysis of an experiment devoted to the excitation of Görtler vortices by localized stationary or vibrating surface nonuniformities in a boundary layer over a concave surface is performed. A numerical model of generation of small-amplitude disturbances and their downstream propagation based on parabolic equations is developed. In the framework of this model, the optimal and the modal parts of excited disturbance are defined as solutions of initial-value problems with initial values being, respectively, the optimal disturbance and the leading local mode at the location of the source. It is shown that a representation of excited disturbance as a sum of the optimal part and a remainder makes it possible to describe its generation and downstream propagation, as well as to predict satisfactorily the corresponding receptivity coefficient. In contrast, the representation based on the modal part provides only coarse information about excitation and propagation of disturbance in the range of parameters under investigation. However, it is found that the receptivity coefficients estimated using the modal parts can be reinterpreted to preserve their practical significance. A corresponding procedure was developed. The theoretical and experimental receptivity coefficients are estimated and compared. It is found that the receptivity magnitudes grow significantly with the disturbance frequency. Variation of the span-wise scale of the nonuniformities affects weakly the receptivity characteristics at zero frequency. However, at high frequencies, the efficiency of excitation of Görtler vortices depends substantially on the span-wise scale.
Galindo, Johan F; Atas, Evrim; Altan, Aysun; Kuroda, Daniel G; Fernandez-Alberti, Sebastian; Tretiak, Sergei; Roitberg, Adrian E; Kleiman, Valeria D
2015-09-16
Solar energy conversion starts with the harvest of light, and its efficacy depends on the spatial transfer of the light energy to where it can be transduced into other forms of energy. Harnessing solar power as a clean energy source requires the continuous development of new synthetic materials that can harvest photon energy and transport it without significant losses. With chemically-controlled branched architectures, dendrimers are ideally suited for these initial steps, since they consist of arrays of chromophores with relative positioning and orientations to create energy gradients and to spatially focus excitation energies. The spatial localization of the energy delimits its efficacy and has been a point of intense research for synthetic light harvesters. We present the results of a combined theoretical experimental study elucidating ultrafast, unidirectional, electronic energy transfer on a complex molecule designed to spatially focus the initial excitation onto an energy sink. The study explores the complex interplay between atomic motions, excited-state populations, and localization/delocalization of excitations. Our findings show that the electronic energy-transfer mechanism involves the ultrafast collapse of the photoexcited wave function due to nonadiabatic electronic transitions. The localization of the wave function is driven by the efficient coupling to high-frequency vibrational modes leading to ultrafast excited-state dynamics and unidirectional efficient energy funneling. This work provides a long-awaited consistent experiment-theoretical description of excited-state dynamics in organic conjugated dendrimers with atomistic resolution, a phenomenon expected to universally appear in a variety of synthetic conjugated materials.
Baudin, Pablo; Bykov, Dmytro; Liakh, Dmitry I.; ...
2017-02-22
Here, the recently developed Local Framework for calculating Excitation energies (LoFEx) is extended to the coupled cluster singles and doubles (CCSD) model. In the new scheme, a standard CCSD excitation energy calculation is carried out within a reduced excitation orbital space (XOS), which is composed of localised molecular orbitals and natural transition orbitals determined from time-dependent Hartree–Fock theory. The presented algorithm uses a series of reduced second-order approximate coupled cluster singles and doubles (CC2) calculations to optimise the XOS in a black-box manner. This ensures that the requested CCSD excitation energies have been determined to a predefined accuracy compared tomore » a conventional CCSD calculation. We present numerical LoFEx-CCSD results for a set of medium-sized organic molecules, which illustrate the black-box nature of the approach and the computational savings obtained for transitions that are local compared to the size of the molecule. In fact, for such local transitions, the LoFEx-CCSD scheme can be applied to molecular systems where a conventional CCSD implementation is intractable.« less
2010-01-01
Background One of the major challenges in evolutionary biology is identifying rare species and devising management plans to protect them while also sustaining their genetic diversity. However, in attempting a broad understanding of rarity, single-species studies provide limited insights because they do not reveal whether the factors that affect rare species differ from those that affect more common species. To illustrate this important concept and to arrive at a better understanding of the form of rarity characterizing the rare Gerbillus henleyi, we explored its population genetic structure alongside that of the locally common Gerbillus andersoni allenbyi. We trapped gerbils in several locations in Israel's western and inner Negev sand dunes. We then extracted DNA from ear samples, and amplified two mitochondrial sequences: the control region (CR) and the cytochrome oxidase 2 gene (CO2). Results Nucleotide diversity was low for all sequences, especially for the CR of G. a. allenbyi, which showed no diversity. We could not detect any significant population genetic structure in G. henleyi. In contrast, G. a. allenbyi's CO2 sequence showed significant population genetic structure. Pairwise PhiPT comparisons showed low values for G. henleyi but high values for G. a. allenbyi. Analysis of the species' demographic history indicated that G. henleyi's population size has not changed recently, and is under the influence of an ongoing bottleneck. The same analysis for G. a. allenbyi showed that this species has undergone a recent population expansion. Conclusions Comparing the two species, the populations of G. a. allenbyi are more isolated from each other, likely due to the high habitat specificity characterizing this species. The bottleneck pattern found in G. henleyi may be the result of competition with larger gerbil species. This result, together with the broad habitat use and high turnover rate characterizing G. henleyi, may explain the low level of differentiation
Dual-fermion approach to the Anderson-Hubbard model
NASA Astrophysics Data System (ADS)
Haase, P.; Yang, S.-X.; Pruschke, T.; Moreno, J.; Jarrell, M.
2017-01-01
We apply the recently developed dual-fermion algorithm for disordered interacting systems to the Anderson-Hubbard model. This algorithm is compared with dynamical cluster approximation calculations for a one-dimensional system to establish the quality of the approximation in comparison with an established cluster method. We continue with a three-dimensional (3D) system and look at the antiferromagnetic, Mott, and Anderson localization transitions. The dual-fermion approach leads to quantitative as well as qualitative improvement of the dynamical mean-field results, and it allows one to calculate the hysteresis in the double occupancy in 3D, taking into account nonlocal correlations.
Anderson Transition for Classical Transport in Composite Materials
NASA Astrophysics Data System (ADS)
Murphy, N. Benjamin; Cherkaev, Elena; Golden, Kenneth M.
2017-01-01
The Anderson transition in solids and optics is a wave phenomenon where disorder induces localization of the wave functions. We find here that the hallmarks of the Anderson transition are exhibited by classical transport at a percolation threshold—without wave interference or scattering effects. As long range order or connectedness develops, the eigenvalue statistics of a key random matrix governing transport cross over toward universal statistics of the Gaussian orthogonal ensemble, and the field eigenvectors delocalize. The transition is examined in resistor networks, human bone, and sea ice structures.
Spin susceptibility of Anderson impurities in arbitrary conduction bands
NASA Astrophysics Data System (ADS)
Fang, Tie-Feng; Tong, Ning-Hua; Cao, Zhan; Sun, Qing-Feng; Luo, Hong-Gang
2015-10-01
Spin susceptibility of Anderson impurities is a key quantity in understanding the physics of Kondo screening. Traditional numerical renormalization group (NRG) calculation of the impurity contribution χimp to susceptibility, defined originally by Wilson in a flat wide band, has been generalized before to structured conduction bands. The results brought about non-Fermi-liquid and diamagnetic Kondo behaviors in χimp, even when the bands are not gapped at the Fermi energy. Here, we use the full density-matrix (FDM) NRG to present high-quality data for the local susceptibility χloc and to compare them with χimp obtained by the traditional NRG. Our results indicate that those exotic behaviors observed in χimp are unphysical. Instead, the low-energy excitations of the impurity in arbitrary bands only without gap at the Fermi energy are still a Fermi liquid and paramagnetic. We also demonstrate that unlike the traditional NRG yielding χloc less accurate than χimp, the FDM method allows a high-precision dynamical calculation of χloc at much reduced computational cost, with an accuracy at least one order higher than χimp. Moreover, artifacts in the FDM algorithm to χimp and origins of the spurious non-Fermi-liquid and diamagnetic features are clarified. Our work provides an efficient high-precision algorithm to calculate the spin susceptibility of impurity for arbitrary structured bands, while negating the applicability of Wilson's definition to such cases.
Vura-Weis, Josh; Newton, M. D.; Wasielewski, Michael R; Subotnik, J.E.
2010-12-09
A common strategy to calculate electronic coupling matrix elements for charge or energy transfer is to take the adiabatic states generated by electronic structure computations and rotate them to form localized diabatic states. In this paper, we show that, for intermolecular transfer of singlet electronic excitation, usually we cannot fully localize the electronic excitations in this way. Instead, we calculate putative initial and final states with small excitation tails caused by weak interactions with high energy excited states in the electronic manifold. These tails do not lead to substantial changes in the total diabatic coupling between states, but they do lead to a different partitioning of the total coupling between Coulomb (Förster), exchange (Dexter), and one-electron components. The tails may be reduced by using a multistate diabatic model or eliminated entirely by truncation (denoted as “chopping”). Without more information, we are unable to conclude with certainty whether the observed diabatic tails are a physical reality or a computational artifact. This research suggests that decomposition of the diabatic coupling between chromophores into Coulomb, exchange, and one-electron components may depend strongly on the number of states considered, and such results should be treated with caution.
Anderson testifies on Planet Earth
NASA Astrophysics Data System (ADS)
Wainger, Lisa A.
AGU president Don Anderson joined former astronaut Sally Ride and National Aeronautics and Space Administration official Lennard Fisk March 8 in testifying before the Senate committee on Commerce, Science, and Transportation. The three had been asked to speak on the future of the Mission to Planet Earth, proposed both in a National Academy of Sciences report and a NASA study.Anderson was chairman of the National Academy of Science's Task Group on Earth Sciences, which prepared the report Mission to Planet Earth as part of the series Space Science in the Twenty-First Century. In his testimony, Anderson highlighted parts of the report and quoted the frontispiece “We now have the technology and the incentive to move boldly forward on a Mission to Planet Earth. We call on the nation to implement an integrated global program using both spaceborne and earth-based instrumentation for fundamental research on the origin, evolution and nature of our planet, its place in our solar system, and its interaction with living things, including mankind.”
Valence transition in the periodic Anderson model
NASA Astrophysics Data System (ADS)
Hübsch, A.; Becker, K. W.
2006-08-01
A very rich phase diagram has recently been found in CeCu2Si2 from high pressure experiments where, in particular, a transition between an intermediate valence configuration and an integral valent heavy fermion state has been observed. We show that such a valence transition can be understood in the framework of the periodic Anderson model. In particular, our results show a breakdown of a mixed-valence state which is accompanied by a drastic change in the f occupation in agreement with experiment. This valence transition can possibly be interpreted as a collapse of the large Fermi surface of the heavy fermion state which incorporates not only the conduction electrons but also the localized f electrons. The theoretical approach used in this paper is based on the novel projector-based renormalization method (PRM). With respect to the periodic Anderson model, the method was before only employed in combination with the basic approximations of the well-known slave-boson mean-field theory. In this paper, the PRM treatment is performed in a more sophisticated manner where both mixed as well as integral valent solutions have been obtained. Furthermore, we argue that the presented PRM approach might be a promising starting point to study the competing interactions in CeCu2Si2 and related compounds.
Khait, Vadim D; Bernus, Olivier; Mironov, Sergey F; Pertsov, Arkady M
2006-01-01
This study explores the possibility of localizing the excitation centers of electrical waves inside the heart wall using voltage-sensitive dyes (fluorescent or absorptive). In the present study, we propose a method for the 3-D localization of excitation centers from pairs of 2-D images obtained in two modes of observation: reflection and transillumination. Such images can be obtained using high-speed charge-coupled device (CCD) cameras and photodiode arrays with time resolution up to 0.5 ms. To test the method, we simulate optical signals produced by point sources and propagating ellipsoidal waves in 1-cm-thick slabs of myocardial tissue. Solutions of the optical diffusion equation are constructed by employing the method of images with Robin boundary conditions. The coordinates of point sources as well as of the centers of expanding waves can be accurately determined using the proposed algorithm. The method can be extended to depth estimations of the outer boundaries of the expanding wave. The depth estimates are based on ratios of spatially integrated images. The method shows high tolerance to noise and can give accurate results even at relatively low signal-to-noise ratios. In conclusion, we propose a novel and efficient algorithm for the localization of excitation centers in 3-D cardiac tissue.
NASA Astrophysics Data System (ADS)
Ye, ChuanXiang; Zhao, Yi; Liang, WanZhen
2015-10-01
The time-dependent correlation function approach for the calculations of absorption and resonance Raman spectra (RRS) of organic molecules absorbed on semiconductor surfaces [Y. Zhao and W. Z. Liang, J. Chem. Phys. 135, 044108 (2011)] is extended to include the contribution of the intermolecular charge transfer (CT) excitation from the absorbers to the semiconducting nanoparticles. The results demonstrate that the bidirectionally interfacial CT significantly modifies the spectral line shapes. Although the intermolecular CT excitation makes the absorption spectra red shift slightly, it essentially changes the relative intensities of mode-specific RRS and causes the oscillation behavior of surface enhanced Raman spectra with respect to interfacial electronic couplings. Furthermore, the constructive and destructive interferences of RRS from the localized molecular excitation and CT excitation are observed with respect to the electronic coupling and the bottom position of conductor band. The interferences are determined by both excitation pathways and bidirectionally interfacial CT.
LES of a Jet Excited by the Localized Arc Filament Plasma Actuators
NASA Technical Reports Server (NTRS)
Brown, Clifford A.
2011-01-01
The fluid dynamics of a high-speed jet are governed by the instability waves that form in the free-shear boundary layer of the jet. Jet excitation manipulates the growth and saturation of particular instability waves to control the unsteady flow structures that characterize the energy cascade in the jet.The results may include jet noise mitigation or a reduction in the infrared signature of the jet. The Localized Arc Filament Plasma Actuators (LAFPA) have demonstrated the ability to excite a high-speed jets in laboratory experiments. Extending and optimizing this excitation technology, however, is a complex process that will require many tests and trials. Computational simulations can play an important role in understanding and optimizing this actuator technology for real-world applications. Previous research has focused on developing a suitable actuator model and coupling it with the appropriate computational fluid dynamics (CFD) methods using two-dimensional spatial flow approximations. This work is now extended to three-dimensions (3-D) in space. The actuator model is adapted to a series of discrete actuators and a 3-D LES simulation of an excited jet is run. The results are used to study the fluid dynamics near the actuator and in the jet plume.
Non-Landau damping of magnetic excitations in systems with localized and itinerant electrons.
Chubukov, Andrey V; Betouras, Joseph J; Efremov, Dmitry V
2014-01-24
We discuss the form of the damping of magnetic excitations in a metal near a ferromagnetic instability. The paramagnon theory predicts that the damping term should have the form γ(q,Ω)∝Ω/Γ(q), with Γ(q)∝q (the Landau damping). However, the experiments on uranium metallic compounds UGe2 and UCoGe showed that Γ(q) is essentially independent of q. A nonzero γ(q=0,Ω) is impossible in systems with one type of carrier (either localized or itinerant) because it would violate the spin conservation. It has been conjectured recently that a near-constant Γ(q) in UGe2 and UCoGe may be due to the presence of both localized and itinerant electrons in these materials, with ferromagnetism involving predominantly localized spins. We present the microscopic analysis of the damping of near-critical localized excitations due to interaction with itinerant carriers. We show explicitly how the presence of two types of electrons breaks the cancellation between the contributions to Γ(0) from the self-energy and vertex correction insertions into the spin polarization bubble. We compare our theory with the available experimental data.
Anderson Mobility Gap Probed by Dynamic Coherent Backscattering.
Cobus, L A; Skipetrov, S E; Aubry, A; van Tiggelen, B A; Derode, A; Page, J H
2016-05-13
We use dynamic coherent backscattering to study one of the Anderson mobility gaps in the vibrational spectrum of strongly disordered three-dimensional mesoglasses. Comparison of experimental results with the self-consistent theory of localization allows us to estimate the localization (correlation) length as a function of frequency in a wide spectral range covering bands of diffuse transport and a mobility gap delimited by two mobility edges. The results are corroborated by transmission measurements on one of our samples.
Regular and irregular patterns of self-localized excitation in arrays of coupled phase oscillators
NASA Astrophysics Data System (ADS)
Wolfrum, Matthias; Omel'chenko, Oleh E.; Sieber, Jan
2015-05-01
We study a system of phase oscillators with nonlocal coupling in a ring that supports self-organized patterns of coherence and incoherence, called chimera states. Introducing a global feedback loop, connecting the phase lag to the order parameter, we can observe chimera states also for systems with a small number of oscillators. Numerical simulations show a huge variety of regular and irregular patterns composed of localized phase slipping events of single oscillators. Using methods of classical finite dimensional chaos and bifurcation theory, we can identify the emergence of chaotic chimera states as a result of transitions to chaos via period doubling cascades, torus breakup, and intermittency. We can explain the observed phenomena by a mechanism of self-modulated excitability in a discrete excitable medium.
Suppression of Spiral Breakup in Excitable Media by Local Periodic Forcing
NASA Astrophysics Data System (ADS)
Liu, Guiquan; Ying, Heping; Luo, Honglei; Liu, Xiaoxia; Yang, Jinghua
2016-12-01
Lowered excitability leads to unstable meandering of spiral tip, which result in breakup of spiral waves into chaotic states induced by Doppler effects. This phenomenon is responsible for the transition from tachycardia to ventricular fibrillation in cardiac tissues. Numerical simulations show that low-energy local periodic forcing (LPF) applied around spiral tip can efficiently suppress the meandering behavior and consequently prevent spiral breakup. The controllable phase diagrams that describe the amplitude and period of LPF against excitability parameter are presented to illustrate the control region. The underlying mechanism of suppressing spiral meandering behavior is explored by greatly decreasing the radius of the meandering tip. The proposed scheme can potentially contribute to controlling cardiac arrhythmia.
Regular and irregular patterns of self-localized excitation in arrays of coupled phase oscillators
Wolfrum, Matthias; Omel'chenko, Oleh E.; Sieber, Jan
2015-05-15
We study a system of phase oscillators with nonlocal coupling in a ring that supports self-organized patterns of coherence and incoherence, called chimera states. Introducing a global feedback loop, connecting the phase lag to the order parameter, we can observe chimera states also for systems with a small number of oscillators. Numerical simulations show a huge variety of regular and irregular patterns composed of localized phase slipping events of single oscillators. Using methods of classical finite dimensional chaos and bifurcation theory, we can identify the emergence of chaotic chimera states as a result of transitions to chaos via period doubling cascades, torus breakup, and intermittency. We can explain the observed phenomena by a mechanism of self-modulated excitability in a discrete excitable medium.
Relativistic Coulomb excitation within the time dependent superfluid local density approximation
Stetcu, I.; Bertulani, C. A.; Bulgac, A.; Magierski, P.; Roche, K. J.
2015-01-06
Within the framework of the unrestricted time-dependent density functional theory, we present for the first time an analysis of the relativistic Coulomb excitation of the heavy deformed open shell nucleus ^{238}U. The approach is based on the superfluid local density approximation formulated on a spatial lattice that can take into account coupling to the continuum, enabling self-consistent studies of superfluid dynamics of any nuclear shape. We compute the energy deposited in the target nucleus as a function of the impact parameter, finding it to be significantly larger than the estimate using the Goldhaber-Teller model. The isovector giant dipole resonance, the dipole pygmy resonance, and giant quadrupole modes are excited during the process. As a result, the one-body dissipation of collective dipole modes is shown to lead a damping width Γ↓≈0.4 MeV and the number of preequilibrium neutrons emitted has been quantified.
Hydrodynamics of local excitations after an interaction quench in 1D cold atomic gases
NASA Astrophysics Data System (ADS)
Franchini, Fabio; Kulkarni, Manas; Trombettoni, Andrea
2016-11-01
We discuss the hydrodynamic approach to the study of the time evolution—induced by a quench—of local excitations in one dimension. We focus on interaction quenches: the considered protocol consists of creating a stable localized excitation propagating through the system, and then operating a sudden change of the interaction between the particles. To highlight the effect of the quench, we take the initial excitation to be a soliton. The quench splits the excitation into two packets moving in opposite directions, whose characteristics for short times can be expressed in a universal way. Our treatment allows for the description of the internal dynamics of these two packets in terms of the different velocities of their components. We confirm our analytical predictions through numerical simulations performed with the Gross-Pitaevskii equation and with the Calogero model (as an example of long range interactions and solvable with a parabolic confinement). Through the Calogero model we also discuss the effect of an external trapping on the protocol. The hydrodynamic approach shows that there is a difference between the bulk velocities of the propagating packets and the velocities of their peaks: it is possible to discriminate the two quantities, as we show through the comparison between numerical simulations and analytical estimates. We show that our analytical results capture with remarkable precision the findings of the numerical simulations also for intermediate times and we provide predictions for the time at which the two packets becomes distinguishable. In the realizations of the discussed quench protocol in a cold atom experiment, these different velocities are accessible through different measurement procedures.
Local excitation of strongly coupled exciton-surface plasmons polaritons by a single nanoantenna
Eizner, E. Ellenbogen, T.
2014-06-02
We demonstrate experimentally local coupling of light from free space to exciton-surface plasmon polaritons (X-SPPs). This is achieved by using a single, sub-wavelength gold nanowire on top of a thin silver film which is covered with a 30 nm thick layer of J-aggregating dyes in polyvinyl alcohol. We show that the nanowire acts as an antenna that resonantly scatters light to X-SPPs states with a Rabi splitting of 0.1 eV. The locally excited X-SPPs properties are studied by angle resolved spectroscopy of the far-field leaky photons and are compared to the large-scale response through Kretschmann reflection measurements and to theoretical calculations. The nanowire scattering properties are studied by dark-field scattering measurements and finite-difference time-domain simulations. This method to locally excite X-SPPs can potentially be useful for future applications of hybrid light matter states.
NASA Astrophysics Data System (ADS)
Han, Ruixue; Wang, Jiang; Yu, Haitao; Deng, Bin; Wei, Xilei; Qin, Yingmei; Wang, Haixu
2015-04-01
Reliable signal propagation across distributed brain areas is an essential requirement for cognitive function, and it has been investigated extensively in computational studies where feed-forward network (FFN) is taken as a generic model. But it is still unclear how distinct local network states, which are intrinsically generated by synaptic interactions within each layer, would affect the ability of FFN to transmit information. Here we investigate the impact of such network states on propagating transient synchrony (synfire) and firing rate by a combination of numerical simulations and analytical approach. Specifically, local network dynamics is attributed to the competition between excitatory and inhibitory neurons within each layer. Our results show that concomitant with different local network states, the performance of signal propagation differs dramatically. For both synfire propagation and firing rate propagation, there exists an optimal local excitability state, respectively, that optimizes the performance of signal propagation. Furthermore, we find that long-range connections strongly change the dependence of spiking activity propagation on local network state and propose that these two factors work jointly to determine information transmission across distributed networks. Finally, a simple mean field approach that bridges response properties of long-range connectivity and local subnetworks is utilized to reveal the underlying mechanism.
Han, Ruixue; Wang, Jiang; Yu, Haitao; Deng, Bin; Wei, Xilei; Qin, Yingmei; Wang, Haixu
2015-04-01
Reliable signal propagation across distributed brain areas is an essential requirement for cognitive function, and it has been investigated extensively in computational studies where feed-forward network (FFN) is taken as a generic model. But it is still unclear how distinct local network states, which are intrinsically generated by synaptic interactions within each layer, would affect the ability of FFN to transmit information. Here we investigate the impact of such network states on propagating transient synchrony (synfire) and firing rate by a combination of numerical simulations and analytical approach. Specifically, local network dynamics is attributed to the competition between excitatory and inhibitory neurons within each layer. Our results show that concomitant with different local network states, the performance of signal propagation differs dramatically. For both synfire propagation and firing rate propagation, there exists an optimal local excitability state, respectively, that optimizes the performance of signal propagation. Furthermore, we find that long-range connections strongly change the dependence of spiking activity propagation on local network state and propose that these two factors work jointly to determine information transmission across distributed networks. Finally, a simple mean field approach that bridges response properties of long-range connectivity and local subnetworks is utilized to reveal the underlying mechanism.
The optical theorem for local source excitation of a particle near a plane interface
NASA Astrophysics Data System (ADS)
Eremin, Yuri; Wriedt, Thomas
2015-11-01
Based on classic Maxwell's theory and the Gauss Theorem we extended the Optical Theorem to the case of a penetrable particle excited by a local source deposited near a plane interface. We demonstrate that the derived Extinction Cross-Section involves the total point source radiating cross-section and some definite integrals responsible for the scattering by the interface. The derived extinction cross-section can be employed to estimate the quantum yield and the optical antenna efficiency without computation of the absorption cross-section.
NASA Astrophysics Data System (ADS)
Angeles Izquierdo, M.; Bell, Toby D. M.; Habuchi, Satoshi; Fron, Eduard; Pilot, Roberto; Vosch, Tom; De Feyter, Steven; Verhoeven, Jan; Jacob, Josemon; Müllen, Klaus; Hofkens, Johan; De Schryver, Frans C.
2005-01-01
A novel perylene imide and oligo-pentaphenyl bisfluorene containing molecule is shown to undergo electron transfer to form an emissive charge transfer state in di-benzyl ether and THF. At the single molecule level in a PMMA film, fluorescence spectra characteristic of both emissive states (locally excited and charge transfer) are observed with 44% of the molecules studied showing switching between the two states. These results demonstrate that charge transfer fluorescence from single molecules can be used to report on the properties and dynamics of a molecule's immediate surroundings or nano-environment.
Magnetic Excitations in the Nearly Localized, Itinerant Magnet Gd, Studied by Neutron Spectroscopy
NASA Astrophysics Data System (ADS)
Graroth, G. E.; Aczel, A. A.; Fernandez-Baca, J. A.; Nagler, S. E.
2012-02-01
Many of the current questions about magnetic superconductors are present when these complex materials are in the normal state. Therefore studies of simpler itinerant magnets may help provide understanding of these phenomena. We chose to study an Itinerant magnet near to the fully localized limit. The system of choice, Gd has a total moment size of ˜7.6 μB of which ˜0.6μB of that is itinerant. We used the SEQUOIA spectrometer, at the Spallation Neutron Source at Oak Ridge National Laboratory, to measure the magnetic excitations in a 12 gm ^160Gd single crystal. The fine resolution Fermi chopper was spun at 360 Hz and phased for Ei = 50 meV. The crystal was mounted with the h0l plane horizontal and then rotated around the vertical axis in 1^o steps. This method, and the large out of plane detector coverage of SEQUOIA, provided continuous coverage of a large region of reciprocal space allowing us to map the magnetic excitations. This map provides a measured structure factor for comparison to spin wave models with and without itinerancy effects. There measurements also more clearly resolve the excitations along the h00 direction than in previous studies (J. W. Cable, R. M. Nicklow and N. Wakabayashi Phys. Rev. B 32, 1710 (1985)).
An Anderson-like model of the QCD chiral transition
NASA Astrophysics Data System (ADS)
Giordano, Matteo; Kovács, Tamás G.; Pittler, Ferenc
2016-06-01
We study the problems of chiral symmetry breaking and eigenmode localisation in finite-temperature QCD by looking at the lattice Dirac operator as a random Hamiltonian. We recast the staggered Dirac operator into an unconventional three-dimensional Anderson Hamiltonian ("Dirac-Anderson Hamiltonian") carrying internal degrees of freedom, with disorder provided by the fluctuations of the gauge links. In this framework, we identify the features relevant to chiral symmetry restoration and localisation of the low-lying Dirac eigenmodes in the ordering of the local Polyakov lines, and in the related correlation between spatial links across time slices, thus tying the two phenomena to the deconfinement transition. We then build a toy model based on QCD and on the Dirac-Anderson approach, replacing the Polyakov lines with spin variables and simplifying the dynamics of the spatial gauge links, but preserving the above-mentioned relevant dynamical features. Our toy model successfully reproduces the main features of the QCD spectrum and of the Dirac eigenmodes concerning chiral symmetry breaking and localisation, both in the ordered (deconfined) and disordered (confined) phases. Moreover, it allows us to study separately the roles played in the two phenomena by the diagonal and the off-diagonal terms of the Dirac-Anderson Hamiltonian. Our results support our expectation that chiral symmetry restoration and localisation of the low modes are closely related, and that both are triggered by the deconfinement transition.
Chirp- and random-based coded ultrasonic excitation for localized blood-brain barrier opening.
Kamimura, H A S; Wang, S; Wu, S-Y; Karakatsani, M E; Acosta, C; Carneiro, A A O; Konofagou, E E
2015-10-07
Chirp- and random-based coded excitation methods have been proposed to reduce standing wave formation and improve focusing of transcranial ultrasound. However, no clear evidence has been shown to support the benefits of these ultrasonic excitation sequences in vivo. This study evaluates the chirp and periodic selection of random frequency (PSRF) coded-excitation methods for opening the blood-brain barrier (BBB) in mice. Three groups of mice (n = 15) were injected with polydisperse microbubbles and sonicated in the caudate putamen using the chirp/PSRF coded (bandwidth: 1.5–1.9 MHz, peak negative pressure: 0.52 MPa, duration: 30 s) or standard ultrasound (frequency: 1.5 MHz, pressure: 0.52 MPa, burst duration: 20 ms, duration: 5 min) sequences. T1-weighted contrast-enhanced MRI scans were performed to quantitatively analyze focused ultrasound induced BBB opening. The mean opening volumes evaluated from the MRI were mm3, mm3and mm3 for the chirp, random and regular sonications, respectively. The mean cavitation levels were V.s, V.s and V.s for the chirp, random and regular sonications, respectively. The chirp and PSRF coded pulsing sequences improved the BBB opening localization by inducing lower cavitation levels and smaller opening volumes compared to results of the regular sonication technique. Larger bandwidths were associated with more focused targeting but were limited by the frequency response of the transducer, the skull attenuation and the microbubbles optimal frequency range. The coded methods could therefore facilitate highly localized drug delivery as well as benefit other transcranial ultrasound techniques that use higher pressure levels and higher precision to induce the necessary bioeffects in a brain region while avoiding damage to the surrounding healthy tissue.
Localization of bleomycin in a single living cell using three-photon excitation microscopy
NASA Astrophysics Data System (ADS)
Abraham, Anil T.; Brautigan, David L.; Hecht, Sidney M.; Periasamy, Ammasi
2001-04-01
Bleomycin has been used in the clinic as a chemotherapeutic agent for the treatment of several neoplasms, including non-Hodgkins lymphomas, squamous cell carcinomas, and testicular tumors. The effectiveness of bleomycin is believed to be derived from its ability to bind and oxidatively cleave DNA in the presence of a iron cofactor in vivo. A substantial amount of data on BLM has been collected, there is little information concerning the effects of bleomycin in living cells. In order to obtain data pertinent to the effects of BLM in intact cells, we have exploited the intrinsic fluorescence property of bleomycin to monitor the uptake of the drug in mammalian cells. We employed two light microscopy techniques, a wide-field and three-photon excitation (760 nm) fluorescence microscopy. Treatment of HeLa cells with bleomycin resulted in rapid to localization within the cells. In addition data collected from the wide field experiments, three-photon excitation of BLM which considerably reduced the phototoxic effect compared with UV light excitation in the wide-field microscopy indicated co-localization of the drug to regions of the cytoplasm occupied by the endoplasmic reticulum probe, DiOC5. The data clearly indicates that the cellular uptake of bleomycin after one minute includes the nucleus as well as in cytoplasm. Contrary to previous studies, which indicate chromosomal DNA as the target of bleomycin, the current findings suggest that the drug is distributed to many areas within the cell, including the endoplasmic reticulum, an organelle that is known to contain ribonucleic acids.
Leske, Sabine; Ruhnau, Philipp; Frey, Julia; Lithari, Chrysa; Müller, Nadia; Hartmann, Thomas; Weisz, Nathan
2015-12-01
An ever-increasing number of studies are pointing to the importance of network properties of the brain for understanding behavior such as conscious perception. However, with regards to the influence of prestimulus brain states on perception, this network perspective has rarely been taken. Our recent framework predicts that brain regions crucial for a conscious percept are coupled prior to stimulus arrival, forming pre-established pathways of information flow and influencing perceptual awareness. Using magnetoencephalography (MEG) and graph theoretical measures, we investigated auditory conscious perception in a near-threshold (NT) task and found strong support for this framework. Relevant auditory regions showed an increased prestimulus interhemispheric connectivity. The left auditory cortex was characterized by a hub-like behavior and an enhanced integration into the brain functional network prior to perceptual awareness. Right auditory regions were decoupled from non-auditory regions, presumably forming an integrated information processing unit with the left auditory cortex. In addition, we show for the first time for the auditory modality that local excitability, measured by decreased alpha power in the auditory cortex, increases prior to conscious percepts. Importantly, we were able to show that connectivity states seem to be largely independent from local excitability states in the context of a NT paradigm.
LTP is accompanied by an enhanced local excitability of pyramidal neuron dendrites.
Frick, Andreas; Magee, Jeffrey; Johnston, Daniel
2004-02-01
The propagation and integration of signals in the dendrites of pyramidal neurons is regulated, in part, by the distribution and biophysical properties of voltage-gated ion channels. It is thus possible that any modification of these channels in a specific part of the dendritic tree might locally alter these signaling processes. Using dendritic and somatic whole-cell recordings, combined with calcium imaging in rat hippocampal slices, we found that the induction of long-term potentiation (LTP) was accompanied by a local increase in dendritic excitability that was dependent on the activation of NMDA receptors. These changes favored the back-propagation of action potentials into this dendritic region with a subsequent boost in the Ca(2+) influx. Dendritic cell-attached patch recordings revealed a hyperpolarized shift in the inactivation curve of transient, A-type K(+) currents that can account for the enhanced excitability. These results suggest an important mechanism associated with LTP for shaping signal processing and controlling dendritic function.
NASA Technical Reports Server (NTRS)
Wilson, J. W.; Xu, Y. J.; Kamaratos, E.; Chang, C. K.
1984-01-01
The basic model of Lindhard and Scharff, known as the local plasma model, is used to study the effects on stopping power of the chemical and physical state of the medium. Unlike previous work with the local plasma model, in which individual electron shifts in the plasma frequency were estimated empirically, he Pines correction derived for a degenerate Fermi gas is shown herein to provide a reasonable estimate, even on the atomic scale. Thus, the model is moved to a complete theoretical base requiring no empirical adjustments, as characteristic of past applications. The principal remaining error is in the overestimation of the low-energy absorption properties that are characteristic of the plasma model in the region of the atomic discrete spectrum, although higher-energy phenomena are accurately represented, and even excitation-to-ionization ratios are given to fair accuracy. Mean excitation energies for covalent-bonded gases and solids, for ionic gases and crystals, and for metals are calculated using first-order models of the bonded states.
Leske, Sabine; Ruhnau, Philipp; Frey, Julia; Lithari, Chrysa; Müller, Nadia; Hartmann, Thomas; Weisz, Nathan
2015-01-01
An ever-increasing number of studies are pointing to the importance of network properties of the brain for understanding behavior such as conscious perception. However, with regards to the influence of prestimulus brain states on perception, this network perspective has rarely been taken. Our recent framework predicts that brain regions crucial for a conscious percept are coupled prior to stimulus arrival, forming pre-established pathways of information flow and influencing perceptual awareness. Using magnetoencephalography (MEG) and graph theoretical measures, we investigated auditory conscious perception in a near-threshold (NT) task and found strong support for this framework. Relevant auditory regions showed an increased prestimulus interhemispheric connectivity. The left auditory cortex was characterized by a hub-like behavior and an enhanced integration into the brain functional network prior to perceptual awareness. Right auditory regions were decoupled from non-auditory regions, presumably forming an integrated information processing unit with the left auditory cortex. In addition, we show for the first time for the auditory modality that local excitability, measured by decreased alpha power in the auditory cortex, increases prior to conscious percepts. Importantly, we were able to show that connectivity states seem to be largely independent from local excitability states in the context of a NT paradigm. PMID:26408799
Fermi-liquid theory for the single-impurity Anderson model
NASA Astrophysics Data System (ADS)
Mora, Christophe; Moca, Cǎtǎlin Paşcu; von Delft, Jan; Zaránd, Gergely
2015-08-01
We generalize Nozières' Fermi-liquid theory for the low-energy behavior of the Kondo model to that of the single-impurity Anderson model. In addition to the electrons' phase shift at the Fermi energy, the low-energy Fermi-liquid theory is characterized by four Fermi-liquid parameters: the two given by Nozières that enter to first order in the excitation energy, and two additional ones that enter to second order and are needed away from particle-hole symmetry. We express all four parameters in terms of zero-temperature physical observables, namely the local charge and spin susceptibilities and their derivatives with respect to the local level position. We determine these in terms of the bare parameters of the Anderson model using Bethe ansatz and numerical renormalization group (NRG) calculations. Our low-energy Fermi-liquid theory applies throughout the crossover from the strong-coupling Kondo regime via the mixed-valence regime to the empty-orbital regime. From the Fermi-liquid theory, we determine the conductance through a quantum dot symmetrically coupled to two leads in the regime of small magnetic field, low temperature, and small bias voltage, and compute the coefficients of the ˜B2 , ˜T2 , and ˜V2 terms exactly in terms of the Fermi-liquid parameters. The coefficients of T2, V2, and B2 are found to change sign during the Kondo to empty-orbital crossover. The crossover becomes universal in the limit that the local interaction is much larger than the level width. For completeness, we also compute the shot noise and discuss the resulting Fano factor.
Mott transitions in the periodic Anderson model
NASA Astrophysics Data System (ADS)
Logan, David E.; Galpin, Martin R.; Mannouch, Jonathan
2016-11-01
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.
NASA Astrophysics Data System (ADS)
Closser, Kristina Danielle
superpositions of atomic states with surface states appearing close to the atomic excitation energies and interior states being blue shifted by up to ≈2 eV. The dynamics resulting from excitation of He_7 were subsequently explored using ab initio molecular dynamics (AIMD). These simulations were performed with classical adiabatic dynamics coupled to a new state-following algorithm on CIS potential energy surfaces. Most clusters were found to completely dissociate and resulted in a single excited atomic state (90%), however, some trajectories formed bound, He*2 (3%), and a few yielded excited trimers (<0.5%). Comparisons were made with available experimental information on much larger clusters. Various applications of this state following algorithm are also presented. In addition to AIMD, these include excited-state geometry optimization and minimal energy path finding via the growing string method. When using state following we demonstrate that more physical results can be obtained with AIMD calculations. Also, the optimized geometries of three excited states of cytosine, two of which were not found without state following, and the minimal energy path between the lowest two singlet excited states of protonated formaldimine are offered as example applications. Finally, to address large clusters, a local variation of CIS was developed. This method exploits the properties of absolutely localized molecular orbitals (ALMOs) to limit the total number of excitations to scaling only linearly with cluster size, which results in formal scaling with the third power of the system size. The derivation of the equations and design of the algorithm are discussed in detail, and computational timings as well as a pilot application to the size dependence of the helium cluster spectrum are presented.
NASA Astrophysics Data System (ADS)
Koroloff, Sophie N.; Nevzorov, Alexander A.
2017-01-01
Spectroscopic assignment of NMR spectra for oriented uniformly labeled membrane proteins embedded in their native-like bilayer environment is essential for their structure determination. However, sequence-specific assignment in oriented-sample (OS) NMR is often complicated by insufficient resolution and spectral crowding. Therefore, the assignment process is usually done by a laborious and expensive "shotgun" method involving multiple selective labeling of amino acid residues. Presented here is a strategy to overcome poor spectral resolution in crowded regions of 2D spectra by selecting resolved "seed" residues via soft Gaussian pulses inserted into spin-exchange separated local-field experiments. The Gaussian pulse places the selected polarization along the z-axis while dephasing the other signals before the evolution of the 1H-15N dipolar couplings. The transfer of magnetization is accomplished via mismatched Hartmann-Hahn conditions to the nearest-neighbor peaks via the proton bath. By optimizing the length and amplitude of the Gaussian pulse, one can also achieve a phase inversion of the closest peaks, thus providing an additional phase contrast. From the superposition of the selective spin-exchanged SAMPI4 onto the fully excited SAMPI4 spectrum, the 15N sites that are directly adjacent to the selectively excited residues can be easily identified, thereby providing a straightforward method for initiating the assignment process in oriented membrane proteins.
Storoniak, Piotr; Rak, Janusz; Polska, Katarzyna; Blancafort, Lluís
2011-04-21
The UV electronic transition energies and their oscillator strengths for two stacked dimers having B-DNA geometries and consisting of 5-bromouracil ((Br)U) and a purine base were studied at the MS-CASPT2/6-311G(d) level with an active space of 12 orbitals and 12 electrons. The calculated energy of the first vertical (π,π*) transitions for the studied dimers remain in fair agreement with the maxima in the difference spectra measured for duplexes with the 5'-A(Br)U-3' or 5'-G(Br)U-3' sequences. Our MS-CASPT2 results show that the charge transfer (CT) states in which an electron is transferred from A/G to (Br)U are located at much higher energies than the first (π,π*) transitions, which involve local excitation (LE) of (Br)U. Moreover, CT transitions are characterized by small oscillator strengths, which implies that they could not be excited directly. The results of the current studies suggest that the formation of the reactive uracil-5-yl radical in DNA is preceded by the formation of the highly oxidative LE state of (Br)U, which is followed by electron transfer, presumably from guanine.
Natural triple excitations in local coupled cluster calculations with pair natural orbitals
NASA Astrophysics Data System (ADS)
Riplinger, Christoph; Sandhoefer, Barbara; Hansen, Andreas; Neese, Frank
2013-10-01
In this work, the extension of the previously developed domain based local pair-natural orbital (DLPNO) based singles- and doubles coupled cluster (DLPNO-CCSD) method to perturbatively include connected triple excitations is reported. The development is based on the concept of triples-natural orbitals that span the joint space of the three pair natural orbital (PNO) spaces of the three electron pairs that are involved in the calculation of a given triple-excitation contribution. The truncation error is very smooth and can be significantly reduced through extrapolation to the zero threshold. However, the extrapolation procedure does not improve relative energies. The overall computational effort of the method is asymptotically linear with the system size O(N). Actual linear scaling has been confirmed in test calculations on alkane chains. The accuracy of the DLPNO-CCSD(T) approximation relative to semicanonical CCSD(T0) is comparable to the previously developed DLPNO-CCSD method relative to canonical CCSD. Relative energies are predicted with an average error of approximately 0.5 kcal/mol for a challenging test set of medium sized organic molecules. The triples correction typically adds 30%-50% to the overall computation time. Thus, very large systems can be treated on the basis of the current implementation. In addition to the linear C150H302 (452 atoms, >8800 basis functions) we demonstrate the first CCSD(T) level calculation on an entire protein, Crambin with 644 atoms, and more than 6400 basis functions.
Fletcher, Patrick; Bertram, Richard; Tabak, Joel
2016-06-01
Models of electrical activity in excitable cells involve nonlinear interactions between many ionic currents. Changing parameters in these models can produce a variety of activity patterns with sometimes unexpected effects. Further more, introducing new currents will have different effects depending on the initial parameter set. In this study we combined global sampling of parameter space and local analysis of representative parameter sets in a pituitary cell model to understand the effects of adding K (+) conductances, which mediate some effects of hormone action on these cells. Global sampling ensured that the effects of introducing K (+) conductances were captured across a wide variety of contexts of model parameters. For each type of K (+) conductance we determined the types of behavioral transition that it evoked. Some transitions were counterintuitive, and may have been missed without the use of global sampling. In general, the wide range of transitions that occurred when the same current was applied to the model cell at different locations in parameter space highlight the challenge of making accurate model predictions in light of cell-to-cell heterogeneity. Finally, we used bifurcation analysis and fast/slow analysis to investigate why specific transitions occur in representative individual models. This approach relies on the use of a graphics processing unit (GPU) to quickly map parameter space to model behavior and identify parameter sets for further analysis. Acceleration with modern low-cost GPUs is particularly well suited to exploring the moderate-sized (5-20) parameter spaces of excitable cell and signaling models.
Relativistic Coulomb excitation within the time dependent superfluid local density approximation
Stetcu, I.; Bertulani, C. A.; Bulgac, A.; ...
2015-01-06
Within the framework of the unrestricted time-dependent density functional theory, we present for the first time an analysis of the relativistic Coulomb excitation of the heavy deformed open shell nucleus 238U. The approach is based on the superfluid local density approximation formulated on a spatial lattice that can take into account coupling to the continuum, enabling self-consistent studies of superfluid dynamics of any nuclear shape. We compute the energy deposited in the target nucleus as a function of the impact parameter, finding it to be significantly larger than the estimate using the Goldhaber-Teller model. The isovector giant dipole resonance, themore » dipole pygmy resonance, and giant quadrupole modes are excited during the process. As a result, the one-body dissipation of collective dipole modes is shown to lead a damping width Γ↓≈0.4 MeV and the number of preequilibrium neutrons emitted has been quantified.« less
Gogan, P; Schmiedel-Jakob, I; Chitti, Y; Tyc-Dumont, S
1995-01-01
The spatial distribution of depolarized patches of membrane during the excitation of single neurons in culture has been recorded with a high spatial resolution (1 micron2/pixel) imaging system based on a liquid-nitrogen-cooled astronomical camera mounted on an inverted microscope. Images were captured from rat nodose neurons stained with the voltage-sensitive dye RH237. Conventional intracellular microelectrode recordings were made in synchrony with the images. During an action potential the fluorescence changes occurred in localized, unevenly distributed membrane areas, which formed clusters of depolarized sites of different sizes and intensities. When fast conductances were blocked by the addition of tetrodotoxin, a reduction in the number and the intensities of the depolarized sites was observed. The blockade by tetrodotoxin of voltage-clamped neurons also reduced the number of depolarized sites, although the same depolarizing voltage step was applied. Similarly, when a voltage-clamped neuron was depolarized by a constant-amplitude voltage step, the number of depolarized sites varied according to the degree of activation of the voltage-sensitive channels, which was modified by changing the holding potential. These results suggest that the spatial patterns of depolarization observed during excitation are related to the operations of ionic channels in the membrane. Images FIGURE 1 FIGURE 2 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 PMID:8527643
Spoof localized surface plasmons in corrugated ring structures excited by microstrip line.
Yang, Bao Jia; Zhou, Yong Jin; Xiao, Qian Xun
2015-08-10
We have investigated the fundamental and high-order spoof localized surface plasmons (LSPs) modes in the proposed corrugated ring resonator printed on a thin dielectric substrate with or without ground plane. An efficient and ease-of-integration method to excite spoof LSPs in the textured ring resonator has been adopted to suppress unwanted high-order modes and enhance fundamental modes. A multi-band-pass filter has been proposed and numerically demonstrated. Experimental results at the microwave frequencies verify the high performances of the corrugated ring resonator and the filter, showing great agreements with the simulation results. We have also shown that the fabricated device is sensitive to the variation of the refraction index of materials under test, even when the material is as thin as paper.
NASA Astrophysics Data System (ADS)
Wang, Xiaonan; Lu, Ying; Jiang, Minxi; Ouyang, Qi
2004-05-01
Trapping and untrapping of spiral tips in a two-dimensional homogeneous excitable medium with local small-world connections are studied by numerical simulation. In a homogeneous medium which can be simulated with a lattice of regular neighborhood connections, the spiral wave is in the meandering regime. When changing the topology of a small region from regular connections to small-world connections, the tip of the spiral waves is attracted by the small-world region, where the average path length declines with the introduction of long distant connections. The “trapped” phenomenon also occurs in regular lattices where the diffusion coefficient of the small region is increased. The above results can be explained by the eikonal equation, the Luther equation, and the relation between the core radius and the diffusion coefficient.
NASA Astrophysics Data System (ADS)
Österlind, Tomas; Kari, Leif; Nicolescu, Cornel Mihai
2017-02-01
Rotor vibration and stationary displacement patterns observed in rotating machineries subject to local harmonic excitation are analysed for improved understanding and dynamic characterization. The analysis stresses the importance of coordinate transformation between rotating and stationary frame of reference for accurate results and estimation of dynamic properties. A generic method which can be used for various rotor applications such as machine tool spindle and turbo machinery vibration is presented. The phenomenon shares similarities with stationary waves in rotating disks though focuses on vibration in shafts. The paper further proposes a graphical tool, the displacement map, which can be used for selection of stable rotational speed for rotating machinery. The results are validated through simulation of dynamic response of a milling cutter, which is a typical example of a variable speed rotor operating under different load conditions.
Entanglement scaling of excited states in large one-dimensional many-body localized systems
NASA Astrophysics Data System (ADS)
Kennes, D. M.; Karrasch, C.
2016-06-01
We study the properties of excited states in one-dimensional many-body localized (MBL) systems using a matrix product state algorithm. First, the method is tested for a large disordered noninteracting system, where for comparison we compute a quasiexact reference solution via a Monte Carlo sampling of the single-particle levels. Thereafter, we present extensive data obtained for large interacting systems of L ˜100 sites and large bond dimensions χ ˜1700 , which allows us to quantitatively analyze the scaling behavior of the entanglement S in the system. The MBL phase is characterized by a logarithmic growth S (L )˜log(L ) over a large scale separating the regimes where volume and area laws hold. We check the validity of the eigenstate thermalization hypothesis. Our results are consistent with the existence of a mobility edge.
Excitation of XPS spectra from nanoscaled particles by local generation of x-rays
Mallinson, Christopher F.; Castle, James E.
2015-09-15
In preliminary work, the authors have shown that use of an aluminum substrate to support a distribution of copper particles enables their characteristic photoelectrons to be observed within the Auger electron spectrum generated by an incident electron beam. This observation raises the possibility of the use of chemical shifts and the corresponding Auger parameter to identify the chemical states present on the surface of individual submicrometer particles within a mixture. In this context, the technique has an advantage in that, unlike conventional Auger electron spectroscopy, the electron beam does not dwell on the particle but on the substrate adjacent to it. Given the importance, for both medical and toxicological reasons, of the surface composition of such particles, the authors have continued to explore the potential of this development. In this contribution, the authors show that proximal excitation of x-rays is equally successful with magnesium substrates. In some regions of the x-ray photoelectron spectrum, the much larger Auger peaks generated by the electron beam can cause inconvenient clustering of Auger and photoelectron peaks. As in conventional x-ray photoelectron spectroscopy, the ability to switch between Al and Mg sources is useful in such situations. In this context, the authors have extended the studies to iron particles where the authors show that use of Al or Mg substrates, as necessary, can make a contribution to clear identification of individual components in the Fe 2p peaks. For this development in electron spectroscopy to achieve its full potential, it is necessary to optimize the beam conditions used to generate the local x-ray to give good selectivity of a given particle. Measurements made in support of this will be given. Of greater concern is a possible problem of local heating associated with x-ray generation. The authors continue to explore this problem and report some progress in minimizing heating of the particle while maintaining
Chirp- and random-based coded ultrasonic excitation for localized blood-brain barrier opening
NASA Astrophysics Data System (ADS)
Kamimura, H. A. S.; Wang, S.; Wu, S.-Y.; Karakatsani, M. E.; Acosta, C.; Carneiro, A. A. O.; Konofagou, E. E.
2015-10-01
Chirp- and random-based coded excitation methods have been proposed to reduce standing wave formation and improve focusing of transcranial ultrasound. However, no clear evidence has been shown to support the benefits of these ultrasonic excitation sequences in vivo. This study evaluates the chirp and periodic selection of random frequency (PSRF) coded-excitation methods for opening the blood-brain barrier (BBB) in mice. Three groups of mice (n = 15) were injected with polydisperse microbubbles and sonicated in the caudate putamen using the chirp/PSRF coded (bandwidth: 1.5-1.9 MHz, peak negative pressure: 0.52 MPa, duration: 30 s) or standard ultrasound (frequency: 1.5 MHz, pressure: 0.52 MPa, burst duration: 20 ms, duration: 5 min) sequences. T1-weighted contrast-enhanced MRI scans were performed to quantitatively analyze focused ultrasound induced BBB opening. The mean opening volumes evaluated from the MRI were 9.38+/- 5.71 mm3, 8.91+/- 3.91 mm3and 35.47+/- 5.10 mm3 for the chirp, random and regular sonications, respectively. The mean cavitation levels were 55.40+/- 28.43 V.s, 63.87+/- 29.97 V.s and 356.52+/- 257.15 V.s for the chirp, random and regular sonications, respectively. The chirp and PSRF coded pulsing sequences improved the BBB opening localization by inducing lower cavitation levels and smaller opening volumes compared to results of the regular sonication technique. Larger bandwidths were associated with more focused targeting but were limited by the frequency response of the transducer, the skull attenuation and the microbubbles optimal frequency range. The coded methods could therefore facilitate highly localized drug delivery as well as benefit other transcranial ultrasound techniques that use higher pressure levels and higher precision to induce the necessary bioeffects in a brain region while avoiding damage to the surrounding healthy tissue.
Chirp- and random-based coded ultrasonic excitation for localized blood-brain barrier opening
Kamimura, HAS; Wang, S; Wu, S-Y; Karakatsani, ME; Acosta, C; Carneiro, AAO; Konofagou, EE
2015-01-01
Chirp- and random-based coded excitation methods have been proposed to reduce standing wave formation and improve focusing of transcranial ultrasound. However, no clear evidence has been shown to support the benefits of these ultrasonic excitation sequences in vivo. This study evaluates the chirp and periodic selection of random frequency (PSRF) coded-excitation methods for opening the blood-brain barrier (BBB) in mice. Three groups of mice (n=15) were injected with polydisperse microbubbles and sonicated in the caudate putamen using the chirp/PSRF coded (bandwidth: 1.5-1.9 MHz, peak negative pressure: 0.52 MPa, duration: 30 s) or standard ultrasound (frequency: 1.5 MHz, pressure: 0.52 MPa, burst duration: 20 ms, duration: 5 min) sequences. T1-weighted contrast-enhanced MRI scans were performed to quantitatively analyze focused ultrasound induced BBB opening. The mean opening volumes evaluated from the MRI were 9.38±5.71 mm3, 8.91±3.91 mm3 and 35.47 ± 5.10 mm3 for the chirp, random and regular sonications, respectively. The mean cavitation levels were 55.40±28.43 V.s, 63.87±29.97 V.s and 356.52±257.15 V.s for the chirp, random and regular sonications, respectively. The chirp and PSRF coded pulsing sequences improved the BBB opening localization by inducing lower cavitation levels and smaller opening volumes compared to results of the regular sonication technique. Larger bandwidths were associated with more focused targeting but were limited by the frequency response of the transducer, the skull attenuation and the microbubbles optimal frequency range. The coded methods could therefore facilitate highly localized drug delivery as well as benefit other transcranial ultrasound techniques that use higher pressure levels and higher precision to induce the necessary bioeffects in a brain region while avoiding damage to the surrounding healthy tissue. PMID:26394091
NASA Astrophysics Data System (ADS)
Rescigno, T. N.; Trevisan, C. S.; McCurdy, C. W.
2015-02-01
Asymmetry in the molecular-frame photoelectron angular distributions from core-hole- or core-valence-excited polyatomic targets with symmetry-equivalent atoms can provide direct evidence for core-hole localization. Using acetylene as an example, we contrast the small asymmetry that can be seen in direct core-level ionization, due to the competition between two competing pathways to the continuum, with ionization from core-valence-excited HCCH, which offers the prospect of observing markedly greater asymmetry.
Taking on Titan: Meet Carrie Anderson
When she was a little girl, Carrie Anderson dreamed of becoming an astronomer. Now, as a space scientist at NASA Goddard Space Flight Center, Carrie studies the atmosphere on Titan: one of Saturn's...
Encoding the structure of many-body localization with matrix product operators
NASA Astrophysics Data System (ADS)
Pekker, David; Clark, Bryan K.
2017-01-01
Anderson insulators are noninteracting disordered systems which have localized single-particle eigenstates. The interacting analog of Anderson insulators are the many-body localized (MBL) phases. The spectrum of the many-body eigenstates of an Anderson insulator is efficiently represented as a set of product states over the single-particle modes. We show that product states over matrix product operators of small bond dimension is the corresponding efficient description of the spectrum of an MBL insulator. In this language all of the many-body eigenstates are encoded by matrix product states (i.e., density matrix renormalization group wave functions) consisting of only two sets of low bond dimension matrices per site: the Gi matrices corresponding to the local ground state on site i and the Ei matrices corresponding to the local excited state. All 2n eigenstates can be generated from all possible combinations of these sets of matrices.
Encoding the structure of many-body localization with matrix product operators
NASA Astrophysics Data System (ADS)
Pekker, David; Clark, Bryan K.
2015-03-01
Anderson insulators are non-interacting disordered systems which have localized single particle eigenstates. The interacting analogue of Anderson insulators are the Many-Body Localized (MBL) phases. The natural language for representing the spectrum of the Anderson insulator is that of product states over the single-particle modes. We show that product states over Matrix Product Operators of small bond dimension is the corresponding natural language for describing the MBL phases. In this language all of the many-body eigenstates are encode by Matrix Product States (i.e. DMRG wave function) consisting of only two sets of low bond-dimension matrices per site: the Gi matrix corresponding to the local ground state on site i and the Ei matrix corresponding to the local excited state. All 2 n eigenstates can be generated from all possible combinations of these matrices.
Energy exchange and localization in a modular metastructure under impulsive excitation
NASA Astrophysics Data System (ADS)
Wu, Z.; Harne, R. L.; Wang, K. W.
2016-04-01
Recent investigations on the concept of modular metastructures have demonstrated remarkable adaptivity of properties as a synergistic product of assembling together metastable modules, modules that exhibit coexisting states for the same topology. It has been found that such modularity provides an accessible pathway for unprecedented massive property adaptation. Despite the extensive report on the static or quasistatic characteristics of modular metastructures, much remains to be explored regarding their dynamic characteristics. This research initiates the study on transient response of a modular metastructure under impulsive excitation. Numerical studies characterize the adaptability of energy exchange and localization characteristics afforded by metastable states. It is found that responses of internal bistable masses of the metastable modules play an important role in determining energy distribution of the overall system. It is discovered that low internal bistable mass and high impulsive energy level are beneficial for energy to be localized and dissipated internally. Additionally, mechanism behind effective energy absorption is disclosed. Overall, this investigation provides opportunities to tailor dynamical responses using modular metastructures and opens potential avenues for designing transient vibration absorbers.
Khemani, Vedika; Pollmann, Frank; Sondhi, S L
2016-06-17
The eigenstates of many-body localized (MBL) Hamiltonians exhibit low entanglement. We adapt the highly successful density-matrix renormalization group method, which is usually used to find modestly entangled ground states of local Hamiltonians, to find individual highly excited eigenstates of MBL Hamiltonians. The adaptation builds on the distinctive spatial structure of such eigenstates. We benchmark our method against the well-studied random field Heisenberg model in one dimension. At moderate to large disorder, the method successfully obtains excited eigenstates with high accuracy, thereby enabling a study of MBL systems at much larger system sizes than those accessible to exact-diagonalization methods.
NASA Astrophysics Data System (ADS)
Khemani, Vedika; Pollmann, Frank; Sondhi, S. L.
2016-06-01
The eigenstates of many-body localized (MBL) Hamiltonians exhibit low entanglement. We adapt the highly successful density-matrix renormalization group method, which is usually used to find modestly entangled ground states of local Hamiltonians, to find individual highly excited eigenstates of MBL Hamiltonians. The adaptation builds on the distinctive spatial structure of such eigenstates. We benchmark our method against the well-studied random field Heisenberg model in one dimension. At moderate to large disorder, the method successfully obtains excited eigenstates with high accuracy, thereby enabling a study of MBL systems at much larger system sizes than those accessible to exact-diagonalization methods.
Fan, Jianzhong; Cai, Lei; Lin, Lili; Wang, Chuan-Kui
2016-12-01
The highly efficient organic light-emitting diodes (OLEDS) based on fluorescent emitters with hybridized local and charge-transfer (HLCT) excited state have attracted great attention recently. The excited-state dynamics of the fluorescent molecule with consideration of molecular interaction are studied using the hybrid quantum mechanics/molecular mechanics method. The results show that, in solid state, the internal conversion rate (KIC) between the first singlet excited state (S1) and the ground state (S0) is smaller than the fluorescent rate (Kr), while in gas phase KIC is much larger than Kr. By analyzing the Huang-Rhys (HR) factor and reorganization energy (λ), we find that these two parameters in solid state are much smaller than those in gas phase due to the suppression of the vibration modes in low-frequency regions (<200 cm(-1)) related with dihedral angles between donor and acceptor groups. This is further demonstrated by the geometrical analysis that variation of the dihedral angle between geometries of S1 and S0 is smaller in solid state than that in gas phase. Moreover, combining the dynamics of the excited states and the adiabatic energy structures calculated in solid state, we illustrate the suggested "hot-exciton" mechanism of the HLCT emitters in OLEDs. Our work presents a rational explanation for the experimental results and demonstrates the importance of molecular interaction for theoretical simulation of the working principle of OLEDs.
Kubo-Anderson Mixing in the Turbulent Boundary Layer
NASA Astrophysics Data System (ADS)
Dekker, H.; de Leeuw, G.; Brink, A. Maassen Van Den
A novel ab initio analysis of the Reynolds stress is presented in order to model non-local turbulence transport. The theory involves a sample path space and a stochastic hypothesis. A scaling relation maps the path space onto the boundary layer. Analytical sampling rates are shown to model mixing by exchange. Nonlocal mixing involves a scaling exponent ɛ≈0.58 (ɛ→∞ in the diffusion limit). The resulting transport equation represents a nondiffusive (Kubo-Anderson or kangaroo) type stochastic process.
Quantum Criticality of Quasi-One-Dimensional Topological Anderson Insulators
NASA Astrophysics Data System (ADS)
Altland, Alexander; Bagrets, Dmitry; Fritz, Lars; Kamenev, Alex; Schmiedt, Hanno
2014-05-01
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 define phase boundaries between distinct topological sectors. Upon increasing system size, the two parameters exhibit flow similar to the celebrated two-parameter flow describing the class A quantum Hall insulator. However, unlike the quantum Hall system, an exact analytical description of the entire phase diagram can be given. We check the quantitative validity of our theory by comparison to numerical transfer matrix computations.
NASA Astrophysics Data System (ADS)
Nogajewski, K.; Łusakowski, J.; Knap, W.; Popov, V. V.; Teppe, F.; Rumyantsev, S. L.; Shur, M. S.
2011-11-01
Magnetotransport and magnetooptics investigations of plasmon excitations in large-area grating-gate terahertz modulators based on AlGaN/GaN high-electron-mobility transistors with different grating-gate duty cycle are reported. We demonstrate that the effect of the gate potential on the ungated region extends beyond the conventional fringing effect distance, ranging over 250-350 nm instead of expected 26-30 nm. This phenomenon enables excitation of the localized gated magnetoplasmon modes only if the inter-finger spacing in the grating gate exceeds 350 nm. For narrower slits, only the collective gated magnetoplasmon modes extending over the entire period of the structure can be excited.
Nonlocal and local magnetization dynamics excited by an RF magnetic field in magnetic multilayers
NASA Astrophysics Data System (ADS)
Moriyama, Takahiro
A microwave study in spintronic devices has been actively pursued in the past several years due to the fertile physics and potential applications. On one hand, a passive use of microwave can be very helpful to analyze and understand the magnetization dynamics in spintronic devices. Examples include ferromagnetic resonance (FMR) measurements, and various microwave spectrum analyses in ferromagnetic materials. The most important chrematistic parameter for the phenomenological analysis on the magnetization dynamics is, so called, the Gilbert damping constant. In this work, a relatively new measurement technique, a flip-chip FMR measurement, to conduct the ferromagnetic resonance measurements has been developed. The measurement technique is equally comparable to a conventional FMR measurement. The Gilbert damping constants were extracted for single ferromagnetic layer, spin vale structures, and magnetic tunnel junctions (MTJs). On the other hand, an active use of microwave yields a great potential for interesting phenomena which give new functionalities into spintronic devices. For instance, a spin wave excitation by an rf field can be used to reduce the switching field of a ferromagnet, i.e. microwave assisted magnetization reversal, which could be a potential application in advanced recording media. More interestingly, a precessing magnetization driven by an rf field can generate a pure spin current into a neighboring layer, i.e. spin pumping effect, which is one of the candidates for generating a pure spin current. A ferromagnetic tunnel junction (MTJ) is one of the important devices in spintronics, which is also the key device to investigate the local and nonlocal magnetization dynamics in this work. Therefore, it is also important to develop high quality MTJs. My work starts from the development of MTJ with AlOx and MgO tunnel barriers where it was found it is crucial to find the proper condition for forming a few nanometers thick tunnel barrier. After obtaining
Newton, M.D.; Vura-Weis, J.; Wasielewski, M.R.; Subotnik, J.E.
2010-10-19
A common strategy to calculate electronic coupling matrix elements for charge or energy transfer is to take the adiabatic states generated by electronic structure computations and rotate them to form localized diabatic states. In this paper, we show that, for intermolecular transfer of singlet electronic excitation, usually we cannot fully localize the electronic excitations in this way. Instead, we calculate putative initial and final states with small excitation tails caused by weak interactions with high energy excited states in the electronic manifold. These tails do not lead to substantial changes in the total diabatic coupling between states, but they do lead to a different partitioning of the total coupling between Coulomb (Forster), exchange (Dexter), and one-electron components. The tails may be reduced by using a multistate diabatic model or eliminated entirely by truncation (denoted as 'chopping'). Without more information, we are unable to conclude with certainty whether the observed diabatic tails are a physical reality or a computational artifact. This research suggests that decomposition of the diabatic coupling between chromophores into Coulomb, exchange, and one-electron components may depend strongly on the number of states considered, and such results should be treated with caution.
27 CFR 9.86 - Anderson Valley.
Code of Federal Regulations, 2014 CFR
2014-04-01
... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Anderson Valley. 9.86 Section 9.86 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas §...
Curchod, Basile F E; Penfold, Thomas J; Rothlisberger, Ursula; Tavernelli, Ivano
2015-07-20
The application of local control theory combined with nonadiabatic ab initio molecular dynamics to study the photoinduced intramolecular proton transfer reaction in 4-hydroxyacridine was investigated. All calculations were performed within the framework of linear-response time-dependent density functional theory. The computed pulses revealed important information about the underlying excited-state nuclear dynamics highlighting the involvement of collective vibrational modes that would normally be neglected in a study performed on model systems constrained to a subset of the full configuration space. This study emphasizes the strengths of local control theory for the design of pulses that can trigger chemical reactions associated with the population of a given molecular excited state. In addition, analysis of the generated pulses can help to shed new light on the photophysics and photochemistry of complex molecular systems.
NASA Astrophysics Data System (ADS)
Smirnov, M. S.; Buganov, O. V.; Shabunya-Klyachkovskaya, E. V.; Tikhomirov, S. A.; Ovchinnikov, O. V.; Vitukhnovsky, A. G.; Perepelitsa, A. S.; Matsukovich, A. S.; Katsaba, A. V.
2016-10-01
Dynamics of the 1Se-1S3/2 exciton in colloidal CdS quantum dots with diameter of 3.1 ÷ 4.5 nm in gelatin with involvement of localized states was studied by means of femtosecond photoinduced absorption spectroscopy (pump-probe), thermally stimulated luminescence (TSL) observed under permanently excited luminescence. It was found that the bleaching band occurs in the energy region of exciton ground state under excitation by femtosecond laser pulses. The complex dynamics of bleaching recovery is caused by the capture of electron on localized states, found using TSL. The stochastic model describing the dynamics of bleaching recovery is discussed. It is shown that the low efficiency of exciton luminescence is caused by the rapid capture of holes by luminescence centers.
Ultrahigh-field MRI whole-slice and localized RF field excitations using the same RF transmit array.
Ibrahim, Tamer S
2006-10-01
In this paper, a multiport driving mechanism is numerically implemented at ultra high-field (UHF) magnetic resonance imaging (MRI) to provide 1) homogenous whole-slice (axial, sagittal, or coronal) and 2) highly localized radio frequency (RF) field excitation within the same slices, all with the same RF transmit array (here chosen to be a standard transverse electromagnetic (TEM) resonator/coil). The method is numerically tested using a full-wave model of a TEM coil loaded with a high-resolution/18-tissue/anatomically detailed human head mesh. The proposed approach is solely based on electromagnetic and phased array antenna theories. The results demonstrate that both homogenous whole-slice as well as localized RF excitation can be achieved within any slice of the head at 7 T (298 MHz for proton imaging).
NASA Astrophysics Data System (ADS)
Santos, Lea F.; Távora, Marco; Pérez-Bernal, Francisco
2016-07-01
Excited-state quantum phase transitions (ESQPTs) are generalizations of quantum phase transitions to excited levels. They are associated with local divergences in the density of states. Here, we investigate how the presence of an ESQPT can be detected from the analysis of the structure of the Hamiltonian matrix, the level of localization of the eigenstates, the onset of bifurcation, and the speed of the system evolution. Our findings are illustrated for a Hamiltonian with infinite-range Ising interaction in a transverse field. This is a version of the Lipkin-Meshkov-Glick (LMG) model and the limiting case of the one-dimensional spin-1/2 system with tunable interactions realized with ion traps. From our studies for the dynamics, we uncover similarities between the LMG and the noninteracting XX models.
NASA Astrophysics Data System (ADS)
Hren, Rok
1998-06-01
Using computer simulations, we systematically investigated the limitations of an inverse solution that employs the potential distribution on the epicardial surface as an equivalent source model in localizing pre-excitation sites in Wolff-Parkinson-White syndrome. A model of the human ventricular myocardium that features an anatomically accurate geometry, an intramural rotating anisotropy and a computational implementation of the excitation process based on electrotonic interactions among cells, was used to simulate body surface potential maps (BSPMs) for 35 pre-excitation sites positioned along the atrioventricular ring. Two individualized torso models were used to account for variations in torso boundaries. Epicardial potential maps (EPMs) were computed using the L-curve inverse solution. The measure for accuracy of the localization was the distance between a position of the minimum in the inverse EPMs and the actual site of pre-excitation in the ventricular model. When the volume conductor properties and lead positions of the torso were precisely known and the measurement noise was added to the simulated BSPMs, the minimum in the inverse EPMs was at 12 ms after the onset on average within cm of the pre-excitation site. When the standard torso model was used to localize the sites of onset of the pre-excitation sequence initiated in individualized male and female torso models, the mean distance between the minimum and the pre-excitation site was cm for the male torso and cm for the female torso. The findings of our study indicate that a location of the minimum in EPMs computed using the inverse solution can offer non-invasive means for pre-interventional planning of the ablative treatment.
Describing excited state relaxation and localization in TiO2 nanoparticles using TD-DFT
Berardo, Enrico; Hu, Han -Shi; van Dam, Hubertus J. J.; ...
2014-02-26
We have investigated the description of excited state relaxation in naked and hydrated TiO2 nanoparticles using Time-Dependent Density Functional Theory (TD-DFT) with three common hybrid exchange-correlation (XC) potentials; B3LYP, CAM-B3LYP and BHLYP. Use of TD-CAM-B3LYP and TD-BHLYP yields qualitatively similar results for all structures, which are also consistent with predictions of coupled cluster theory for small particles. TD-B3LYP, in contrast, is found to make rather different predictions; including apparent conical intersections for certain particles that are not observed with TD-CAM-B3LYP nor with TD-BHLYP. In line with our previous observations for vertical excitations, the issue with TD-B3LYP appears to be themore » inherent tendency of TD-B3LYP, and other XC potentials with no or a low percentage of Hartree-Fock Like Exchange, to spuriously stabilize the energy of charge-transfer (CT) states. Even in the case of hydrated particles, for which vertical excitations are generally well described with all XC potentials, the use of TD-B3LYP appears to result in CT-problems for certain particles. We hypothesize that the spurious stabilization of CT-states by TD-B3LYP even may drive the excited state optimizations to different excited state geometries than those obtained using TD-CAM-B3LYP or TD-BHLYP. In conclusion, focusing on the TD-CAM-B3LYP and TD-BHLYP results, excited state relaxation in naked and hydrated TiO2 nanoparticles is predicted to be associated with a large Stokes’ shift.« less
Li, Qian; Jesse, Stephen; Tselev, Alexander; Collins, Liam; Yu, Pu; Kravchenko, Ivan; Kalinin, Sergei V.; Balke, Nina
2015-01-05
In this paper, nanomechanical properties are closely related to the states of matter, including chemical composition, crystal structure, mesoscopic domain configuration, etc. Investigation of these properties at the nanoscale requires not only static imaging methods, e.g., contact resonance atomic force microscopy (CR-AFM), but also spectroscopic methods capable of revealing their dependence on various external stimuli. Here we demonstrate the voltage spectroscopy of CR-AFM, which was realized by combining photothermal excitation (as opposed to the conventional piezoacoustic excitation method) with the band excitation technique. We applied this spectroscopy to explore local bias-induced phenomena ranging from purely physical to surface electromechanical and electrochemical processes. Our measurements show that the changes in the surface properties associated with these bias-induced transitions can be accurately assessed in a fast and dynamic manner, using resonance frequency as a signature. Finally, with many of the advantages offered by photothermal excitation, contact resonance voltage spectroscopy not only is expected to find applications in a broader field of nanoscience but also will provide a basis for future development of other nanoscale elastic spectroscopies.
Li, Qian; Jesse, Stephen; Tselev, Alexander; ...
2015-01-05
In this paper, nanomechanical properties are closely related to the states of matter, including chemical composition, crystal structure, mesoscopic domain configuration, etc. Investigation of these properties at the nanoscale requires not only static imaging methods, e.g., contact resonance atomic force microscopy (CR-AFM), but also spectroscopic methods capable of revealing their dependence on various external stimuli. Here we demonstrate the voltage spectroscopy of CR-AFM, which was realized by combining photothermal excitation (as opposed to the conventional piezoacoustic excitation method) with the band excitation technique. We applied this spectroscopy to explore local bias-induced phenomena ranging from purely physical to surface electromechanical andmore » electrochemical processes. Our measurements show that the changes in the surface properties associated with these bias-induced transitions can be accurately assessed in a fast and dynamic manner, using resonance frequency as a signature. Finally, with many of the advantages offered by photothermal excitation, contact resonance voltage spectroscopy not only is expected to find applications in a broader field of nanoscience but also will provide a basis for future development of other nanoscale elastic spectroscopies.« less
Entanglement Area Law in Disordered Free Fermion Anderson Model in One, Two, and Three Dimensions
Pouranvari, Mohammad; Zhang, Yuhui; Yang, Kun
2015-01-01
We calculate numerically the entanglement entropy of free fermion ground states in one-, two-, and three-dimensional Anderson models and find that it obeys the area law as long as the linear size of the subsystem is sufficiently larger than the mean free path. This result holds in the metallic phase of the three-dimensional Anderson model, where the mean free path is finite although the localization length is infinite. Relation between the present results and earlier ones on area law violation in special one-dimensional models that support metallic phases is discussed.
Diagram theory for the twofold-degenerate Anderson impurity model
NASA Astrophysics Data System (ADS)
Moskalenko, V. A.; Dohotaru, L. A.; Digor, D. F.; Cebotari, I. D.
2014-02-01
We develop a diagram technique for investigating the twofold-degenerate Anderson impurity model in the normal state with the strong electronic correlations of d electrons of the impurity ion taken into account. We discuss the properties of the Slater-Kanamori model of d electrons. After finding the eigenfunctions and eigenvalues of all 16 local states, we determine the local one-particle propagator. We construct the perturbation theory around the atomic limit of the impurity ion and obtain a Dyson-type equation establishing the relation between the impurity electron propagator and the normal correlation function. As a result of summing infinite series of ladder diagrams, we obtain an approximation for the correlation function.
NASA Astrophysics Data System (ADS)
Widom, Julia R.
Biological systems present many challenges to researchers attempting to study them using spectroscopy. Low specificity, low sensitivity, and broad and overlapping lineshapes limit the amount of information that can be obtained in experiments. Two-dimensional fluorescence spectroscopy (2D FS) is a highly sensitive and information-rich spectroscopic technique that was developed to study the conformations and excited state dynamics of systems exhibiting exciton coupling. In this dissertation, I describe a variety of extensions of 2D FS that further increase its utility for the study of biological systems. I describe experiments on a dimer of zinc tetraphenylporphyrin embedded in a membrane, in which the signals from two conformational subpopulations were separated in order to study the thermodynamics of their interconversion. I present proof-of-principle experiments on nucleic acids that utilize fluorescence resonance energy transfer to separate signals from different subpopulations. I also describe experiments in which 2D FS was performed using ultraviolet excitation to determine the conformation of a dinucleotide of a fluorescent analogue of the nucleic acid base adenine. I discuss experiments on porphyrin dimers in which 2D FS was used as a probe of excited state dynamics. Finally, I present model calculations for a proposed variation of 2D FS in which entangled photons would be used as the excitation source. These calculations suggest that this approach has the potential to yield significantly narrower spectral lineshapes than conventional 2D FS. These experiments and calculations yield new insight into the systems investigated and establish a `toolbox' of variations of 2D FS that can be used to gain as much information as possible from experiments on challenging systems such as protein-DNA complexes.
Phase relaxed localized excitation pulses for inner volume fast spin echo imaging
Hajnal, Joseph V.
2015-01-01
Purpose To design multidimensional spatially selective radiofrequency (RF) pulses for inner volume imaging (IVI) with three‐dimensional (3D) fast spin echo (FSE) sequences. Enhanced background suppression is achieved by exploiting particular signal properties of FSE sequences. Theory and Methods The CPMG condition dictates that echo amplitudes will rapidly decrease if a 90° phase difference between excitation and refocusing pulses is not present, and refocusing flip angles are not precisely 180°. This mechanism is proposed as a means for generating additional background suppression for spatially selective excitation, by biasing residual excitation errors toward violating the CPMG condition. 3D RF pulses were designed using this method with a 3D spherical spiral trajectory, under‐sampled by factor 5.6 for an eight‐channel PTx system, at 3 Tesla. Results 3D‐FSE IVI with pulse durations of approximately 12 ms was demonstrated in phantoms and for T2‐weighted brain imaging in vivo. Good image quality was obtained, with mean background suppression factors of 103 and 82 ± 6 in phantoms and in vivo, respectively. Conclusion Inner Volume Imaging with 3D‐FSE has been demonstrated in vivo with tailored 3D‐RF pulses. The proposed design methods are also applicable to 2D pulses. Magn Reson Med 76:848–861, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine PMID:26451691
Wang, Zhiqiang; Wen, Bo; Hao, Qunqing; Liu, Li-Min; Zhou, Chuanyao; Mao, Xinchun; Lang, Xiufeng; Yin, Wen-Jin; Dai, Dongxu; Selloni, Annabella; Yang, Xueming
2015-07-22
In reduced TiO2, electronic transitions originating from the Ti(3+)-induced states in the band gap are known to contribute to the photoabsorption, being in fact responsible for the material's blue color, but the excited states accessed by these transitions have not been characterized in detail. In this work we investigate the excited state electronic structure of the prototypical rutile TiO2(110) surface using two-photon photoemission spectroscopy (2PPE) and density functional theory (DFT) calculations. Using 2PPE, an excited resonant state derived from Ti(3+) species is identified at 2.5 ± 0.2 eV above the Fermi level (EF) on both the reduced and hydroxylated surfaces. DFT calculations reveal that this excited state is closely related to the gap state at ∼1.0 eV below EF, as they both result from the Jahn-Teller induced splitting of the 3d orbitals of Ti(3+) ions in reduced TiO2. Localized excitation of Ti(3+) ions via 3d → 3d transitions from the gap state to this empty resonant state significantly increases the TiO2 photoabsorption and extends the absorbance to the visible region, consistent with the observed enhancement of the visible light induced photocatalytic activity of TiO2 through Ti(3+) self-doping. Our work reveals the physical origin of the Ti(3+) related photoabsorption and visible light photocatalytic activity in prototypical TiO2 and also paves the way for the investigation of the electronic structure and photoabsorption of other metal oxides.
NASA Astrophysics Data System (ADS)
Kazlauskas, K.; Tamulaitis, G.; Mickevičius, J.; Kuokštis, E.; Žukauskas, A.; Cheng, Yung-Chen; Wang, Hsiang-Cheng; Huang, Chi-Feng; Yang, C. C.
2005-01-01
Excitation-power dynamics of near-band-edge photoluminescence (PL) peak position in InxGa1-xN/GaN multiple quantum wells (x˜0.15) was analyzed as a function of well width. The analysis was based on energy reference provided by photoreflectance (PR) spectra. The difference in spectral position of the PR feature and low-excitation PL band (the Stokes Shift) revealed carrier localization energy, which exhibited a remarkable sensitivity to the well width, increasing from 75meV in 2nm wells to about 250meV in 4nm wells. Meanwhile collating of the PR data with the flat-band model for the optical transition energy in quantum wells rendered a relatively weak (0.5MV/cm) built-in piezoelectric field. The blueshift of the PL peak position with increasing photoexcitation power density was shown to be in qualitative agreement with the model of filling of the band-tail states with some contribution from screening of built-in field in the thickest (4nm) wells. Increased incident photon energy resulted in an additional blueshift of the PL peak, which was explained by a nonthermalized distribution of localized carriers and/or carrier localization in the interface region. Our results are consistent with a concept of emission from partially relaxed large In-rich regions with internal band potential fluctuations, which are enhanced with increasing the growth time.
Zachariasse, Klaas A; Druzhinin, Sergey I; Galievsky, Victor A; Demeter, Attila; Allonas, Xavier; Kovalenko, Sergey A; Senyushkina, Tamara A
2010-12-23
Pentacyano-N,N-dimethylaniline (PCDMA) does not undergo an intramolecular charge transfer (ICT) reaction, even in the strongly polar solvent acetonitrile (MeCN), in clear contrast to 4-(dimethylamino)benzonitrile (DMABN). Within the twisted ICT (TICT) model, this is unexpected, as the electron affinity of the pentacyanobenzene moiety of PCDMA is much larger than that of the benzonitrile subgroup in DMABN. According to the TICT model, the energy of the ICT state of PCDMA would be 2.05 eV (∼16550 cm(-1)) lower than that of DMABN, on the basis of the reduction potentials E(A(-)/A) of pentacyanobenzene (-0.29 V vs saturated calomel electrode (SCE)) and benzonitrile (-2.36 V vs SCE), more than enough to compensate for the decrease in energy of the locally excited (LE) state of PCDMA (E(S(1)) = 19990 cm(-1)) relative to that of DMABN (E(S(1)) = 29990 cm(-1)). This absence of a LE → ICT reaction shows that the TICT hypothesis does not hold for PCDMA in the singlet excited state, similar to what was found for DMABN, N-phenylpyrrole, and their derivatives. In this connection, the six dicyano-substituted dimethylanilines are also discussed. The energy gap ΔE(S(1),S(2)) between the two lowest singlet excited states is, at 7170 cm(-1) for PCDMA in MeCN, considerably larger than that for DMABN (2700 cm(-1) in n-hexane, smaller in MeCN). The absence of ICT is therefore in accord with the planar ICT (PICT) model, which considers a sufficiently small ΔE(S(1),S(2)) to be an important condition determining whether an ICT reaction will take place. The fluorescence quantum yield of PCDMA is very small: Φ(LE) = 0.0006 in MeCN at 25 °C, predominantly due to LE → S(0) internal conversion (IC), as the intersystem crossing yield Φ(ISC) is practically zero (<0.01). From the LE fluorescence decay time of 27 ps for PCDMA in MeCN at 25 °C, a radiative rate constant k(f)(LE) = 2 × 10(7) s(-1) results, comparable to the k(f)(LE) of DMABN (6.5 × 10(7) s(-1)) and 2,4,6-tricyano
Atomic mean excitation energies for stopping powers from local plasma oscillator strengths
NASA Technical Reports Server (NTRS)
Wilson, J. W.; Xu, Y. J.; Chang, C. K.; Kamaratos, E.
1984-01-01
The stopping of a charged particle by isolated atoms is investigated theoretically using an 'atomic plasma' model in which atomic oscillator strengths are replaced by the plasma frequency spectrum. The plasma-frequency correction factor for individual electron motion proposed by Pines (1953) is incorporated, and atomic mean excitation energies are calculated for atoms through Sr. The results are compared in a graph with those obtained theoretically by Inokuti et al. (1978, 1981) and Dehmer et al. (1975) and with the experimental values compiled by Seltzer and Berger (1982): good agreement is shown.
NASA Astrophysics Data System (ADS)
Tsuchida, Yuji; Kudo, Yuki; Enokizono, Masato
2017-02-01
This paper presents our proposed frequency sweeping excitation and spectrogram method (FSES method) by a magnetic sensor for non-destructive testing of hardened low carbon steels. This method can evaluate the magnetic properties of low carbon steels which were changed after induction heating treatment. It was examined by our proposed method that the degrees of yield strength of low carbon steels were varied depending on hardened conditions. Moreover, it was made clear that the maximum magnetic field strength, Hmax, derived from the measured B-H loops was very sensitive to the hardening if the surface of the samples were flat.
Dual effect of local anesthetics on the function of excitable rod outer segment disk membrane
Mashimo, T.; Abe, K.; Yoshiya, I.
1986-04-01
The effects of local anesthetics and a divalent cation, Ca2+, on the function of rhodopsin were estimated from the measurements of light-induced proton uptake. The light-induced proton uptake by rhodopsin in the rod outer segment disk membrane was enhanced at lower pH (4) but depressed at higher pHs (6 to 8) by the tertiary amine local anesthetics lidocaine, bupivacaine, tetracaine, and dibucaine. The order of local anesthetic-induced depression of the proton uptake followed that of their clinical anesthetic potencies. The depression of the proton uptake versus the concentration of the uncharged form of local anesthetic nearly describes the same curve for small and large dose of added anesthetic. Furthermore, a neutral local anesthetic, benzocaine, depressed the proton uptake at all pHs between 4 and 7. These results indicate that the depression of the proton uptake is due to the effect of only the uncharged form. It is hypothesized that the uncharged form of local anesthetics interacts hydrophobically with the rhodopsin in the disk membrane. The dual effect of local anesthetics on the proton uptake, on the other hand, suggests that the activation of the function of rhodopsin may be caused by the charged form. There was no significant change in the light-induced proton uptake by rhodopsin when 1 mM of Ca2+ was introduced into the disk membrane at varying pHs in the absence or presence of local anesthetics. This fact indicates that Ca2+ ion does not influence the diprotonating process of metarhodopsin; neither does it interfere with the local anesthetic-induced changes in the rhodopsin molecule.
Superdiffusive transport and energy localization in disordered granular crystals
Martinez, Alejandro J.; Kevrekidis, Panagiotis G.; Porter, Mason A.
2016-02-12
We study the spreading of initially localized excitations in one-dimensional disordered granular crystals. We thereby investigate localization phenomena in strongly nonlinear systems, which we demonstrate to be fundamentally different from localization in linear and weakly nonlinear systems. We conduct a thorough comparison of wave dynamics in chains with three different types of disorder: an uncorrelated (Anderson-like) disorder and two types of correlated disorders (which are produced by random dimer arrangements), and for two families of initial conditions: displacement perturbations and velocity perturbations. We find for strongly precompressed (i.e., weakly nonlinear) chains that the dynamics strongly depends on the initial condition. Furthermore, for displacement perturbations, the long-time asymptotic behavior of the second moment m^{~}2 has oscillations that depend on the type of disorder, with a complex trend that is markedly different from a power law and which is particularly evident for an Anderson-like disorder.
Superdiffusive transport and energy localization in disordered granular crystals
Martinez, Alejandro J.; Kevrekidis, Panagiotis G.; Porter, Mason A.
2016-02-12
We study the spreading of initially localized excitations in one-dimensional disordered granular crystals. We thereby investigate localization phenomena in strongly nonlinear systems, which we demonstrate to be fundamentally different from localization in linear and weakly nonlinear systems. We conduct a thorough comparison of wave dynamics in chains with three different types of disorder: an uncorrelated (Anderson-like) disorder and two types of correlated disorders (which are produced by random dimer arrangements), and for two families of initial conditions: displacement perturbations and velocity perturbations. We find for strongly precompressed (i.e., weakly nonlinear) chains that the dynamics strongly depends on the initial condition.more » Furthermore, for displacement perturbations, the long-time asymptotic behavior of the second moment m~2 has oscillations that depend on the type of disorder, with a complex trend that is markedly different from a power law and which is particularly evident for an Anderson-like disorder.« less
Fidler, Andrew F.; Singh, Ved P.; Long, Phillip D.; Dahlberg, Peter D.; Engel, Gregory S.
2014-01-01
Time-resolved ultrafast optical probes of chiral dynamics provide a new window allowing us to explore how interactions with such structured environments drive electronic dynamics. Incorporating optical activity into time-resolved spectroscopies has proven challenging due to the small signal and large achiral background. Here, we demonstrate that two-dimensional electronic spectroscopy can be adapted to detect chiral signals and that these signals reveal how excitations delocalize and contract following excitation. We dynamically probe the evolution of chiral electronic structure in the light harvesting complex 2 of purple bacteria following photoexcitation by creating a chiral two-dimensional mapping. The dynamics of the chiral two-dimensional signal directly reports on changes in the degree of delocalization of the excitonic state following photoexcitation. The mechanism of energy transfer in this system may enhance transfer probability due to the coherent coupling among chromophores while suppressing fluorescence that arises from populating delocalized states. This generally applicable spectroscopy will provide an incisive tool to probe ultrafast transient molecular fluctuations that are obscured in non-chiral experiments. PMID:24504144
Lisman, John
2011-01-01
What causes the positive, negative, and cognitive symptoms of schizophrenia? The importance of circuits is underscored by the finding that no single gene contributes strongly to the disease. Thus, some circuit abnormality to which many proteins can contribute is the likely cause. There are several major hypotheses regarding the circuitry involved: 1) a change in the balance of excitation/inhibition in the PFC; 2) abnormal EEG oscillations in the gamma range; 3) an increase in theta/delta EEG power related to changes in the thalamus (particularly midline nuclei); 4) hyperactivity in the hippocampus and consequent dopamine hyperfunction; or 5) deficits in corollary discharge. Evidence for these hypotheses will be reviewed. PMID:22079494
Fountaine, Katherine T; Kendall, Christian G; Atwater, Harry A
2014-05-05
We report design methods for achieving near-unity broadband light absorption in sparse nanowire arrays, illustrated by results for visible absorption in GaAs nanowires on Si substrates. Sparse (<5% fill fraction) nanowire arrays achieve near unity absorption at wire resonant wavelengths due to coupling into 'leaky' radial waveguide modes of individual wires and wire-wire scattering processes. From a detailed conceptual development of radial mode resonant absorption, we demonstrate two specific geometric design approaches to achieve near unity broadband light absorption in sparse nanowire arrays: (i) introducing multiple wire radii within a small unit cell array to increase the number of resonant wavelengths, yielding a 15% absorption enhancement relative to a uniform nanowire array and (ii) tapering of nanowires to introduce a continuum of diameters and thus resonant wavelengths excited within a single wire, yielding an 18% absorption enhancement over a uniform nanowire array.
Huang, Hong-Lei; Cendan, Cruz-Miguel; Roza, Carolina; Okuse, Kenji; Cramer, Rainer; Timms, John F; Wood, John N
2008-01-01
Neuropathic pain may arise following peripheral nerve injury though the molecular mechanisms associated with this are unclear. We used proteomic profiling to examine changes in protein expression associated with the formation of hyper-excitable neuromas derived from rodent saphenous nerves. A two-dimensional difference gel electrophoresis (2D-DIGE) profiling strategy was employed to examine protein expression changes between developing neuromas and normal nerves in whole tissue lysates. We found around 200 proteins which displayed a >1.75-fold change in expression between neuroma and normal nerve and identified 55 of these proteins using mass spectrometry. We also used immunoblotting to examine the expression of low-abundance ion channels Nav1.3, Nav1.8 and calcium channel α2δ-1 subunit in this model, since they have previously been implicated in neuronal hyperexcitability associated with neuropathic pain. Finally, S35methionine in vitro labelling of neuroma and control samples was used to demonstrate local protein synthesis of neuron-specific genes. A number of cytoskeletal proteins, enzymes and proteins associated with oxidative stress were up-regulated in neuromas, whilst overall levels of voltage-gated ion channel proteins were unaffected. We conclude that altered mRNA levels reported in the somata of damaged DRG neurons do not necessarily reflect levels of altered proteins in hyper-excitable damaged nerve endings. An altered repertoire of protein expression, local protein synthesis and topological re-arrangements of ion channels may all play important roles in neuroma hyper-excitability. PMID:18700027
Collective excitations of dipolar gases based on local tunneling in superlattices
NASA Astrophysics Data System (ADS)
Cao, Lushuai; Mistakidis, Simeon I.; Deng, Xing; Schmelcher, Peter
2017-01-01
The collective dynamics of a dipolar fermionic quantum gas confined in a one-dimensional double-well superlattice is explored. The fermionic gas resides in a paramagnetic-like ground state in the weak interaction regime, upon which a new type of collective dynamics is found when applying a local perturbation. This dynamics is composed of the local tunneling of fermions in separate supercells, and is a pure quantum effect, with no classical counterpart. Due to the presence of the dipolar interactions the local tunneling transports through the entire superlattice, giving rise to a collective dynamics. A well-defined momentum-energy dispersion relation is identified in the ab-initio simulations demonstrating the phonon-like behavior. The phonon-like characteristic is also confirmed by an analytical description of the dynamics within a semiclassical picture.
X-slave boson approach to the periodic Anderson model
NASA Astrophysics Data System (ADS)
Franco, R.; Figueira, M. S.; Foglio, M. E.
2001-05-01
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.
X-boson cumulant approach to the periodic Anderson model
NASA Astrophysics Data System (ADS)
Franco, R.; Figueira, M. S.; Foglio, M. E.
2002-07-01
The periodic Anderson model can be studied in the limit U=∞ by employing the Hubbard X operators to project out the unwanted states. We had already studied this problem by employing the cumulant expansion with the hybridization as perturbation, but the probability conservation of the local states (completeness) is not usually satisfied when partial expansions like the ``chain approximation'' (CHA) are employed. To rectify this situation, we modify the CHA by employing a procedure that was used in the mean-field approximation of Coleman's slave-boson method. Our technique reproduces the features of that method in its region of validity, but avoids the unwanted phase transition that appears in the same method both when μ>>Ef at low T and for all values of the parameters at intermediate temperatures. Our method also has a dynamic character that is absent from the mean-field slave-boson method.
Universal Knight shift anomaly in the periodic Anderson model
NASA Astrophysics Data System (ADS)
Jiang, M.; Curro, N. J.; Scalettar, R. T.
2014-12-01
We report a determinant Quantum Monte Carlo investigation which quantifies the behavior of the susceptibility and the entropy in the framework of the periodic Anderson model, focusing on the evolution with different degree of conduction electron (c )-local moment (f ) hybridization. These results capture the behavior observed in several experiments, including the universal behavior of the NMR Knight shift anomaly below the crossover temperature T*. We find that T* is a measure of the onset of c - f correlations and grows with increasing hybridization. These results suggest that the NMR Knight shift and spin-lattice relaxation rate measurements in non-Fermi-liquid materials are strongly influenced by the temperature dependence of the c - f kinetic energy. Our results provide a microscopic basis for the phenomenological two-fluid model of Kondo lattice behavior, and its evolution with pressure and temperature.
Topological Anderson insulators in systems without time-reversal symmetry
NASA Astrophysics Data System (ADS)
Su, Ying; Avishai, Y.; Wang, X. R.
2016-06-01
Occurrence of the topological Anderson insulator (TAI) in a HgTe quantum well suggests that when time-reversal symmetry (TRS) is maintained, the pertinent topological phase transition, marked by re-entrant 2 e2/h quantized conductance contributed by helical edge states, is driven by disorder. Here we show that when TRS is broken, the physics of the TAI becomes even richer. The pattern of longitudinal conductance and nonequilibrium local current distribution displays novel TAI phases characterized by nonzero Chern numbers, indicating the occurrence of multiple chiral edge modes. Tuning either disorder or Fermi energy (in both topologically trivial and nontrivial phases), drives transitions between these distinct TAI phases, characterized by jumps of the quantized conductance from 0 to e2/h and from e2/h to 2 e2/h . An effective medium theory based on the Born approximation yields an accurate description of different TAI phases in parameter space.
Universal Knight shift anomaly in the periodic Anderson model
Jiang, M.; Curro, N. J.; Scalettar, R. T.
2014-12-12
Here, we report a Determinant Quantum Monte Carlo investigation which quantifies the behavior of the susceptibility and the entropy in the framework of the periodic Anderson model (PAM), focussing on the evolution with different degree of conduction electron (c) -local moment (f) hybridization. These results capture the behavior observed in several experiments, including the universal behavior of the NMR Knight shift anomaly below the crossover temperature, T*. We find that T* is a measure of the onset of c-f correlations and grows with increasing hybridization. Our results suggest that the NMR Knight shift and spin-lattice relaxation rate measurements in non-Fermi liquid materials are strongly influenced by temperature-dependent hybridization processes. Furthermore, our results provide a microscopic basis for the phenomenological two-fluid model of Kondo lattice behavior, and its evolution with pressure and temperature.
Universal Knight shift anomaly in the periodic Anderson model
Jiang, M.; Curro, N. J.; Scalettar, R. T.
2014-12-12
Here, we report a Determinant Quantum Monte Carlo investigation which quantifies the behavior of the susceptibility and the entropy in the framework of the periodic Anderson model (PAM), focussing on the evolution with different degree of conduction electron (c) -local moment (f) hybridization. These results capture the behavior observed in several experiments, including the universal behavior of the NMR Knight shift anomaly below the crossover temperature, T*. We find that T* is a measure of the onset of c-f correlations and grows with increasing hybridization. Our results suggest that the NMR Knight shift and spin-lattice relaxation rate measurements in non-Fermimore » liquid materials are strongly influenced by temperature-dependent hybridization processes. Furthermore, our results provide a microscopic basis for the phenomenological two-fluid model of Kondo lattice behavior, and its evolution with pressure and temperature.« less
Facilitation Dynamics and Localization Phenomena in Rydberg Lattice Gases with Position Disorder
NASA Astrophysics Data System (ADS)
Marcuzzi, Matteo; Minář, Jiří; Barredo, Daniel; de Léséleuc, Sylvain; Labuhn, Henning; Lahaye, Thierry; Browaeys, Antoine; Levi, Emanuele; Lesanovsky, Igor
2017-02-01
We explore the dynamics of Rydberg excitations in an optical tweezer array under antiblockade (or facilitation) conditions. Because of the finite temperature the atomic positions are randomly spread, an effect that leads to quenched correlated disorder in the interatomic interaction strengths. This drastically affects the facilitation dynamics as we demonstrate experimentally on the elementary example of two atoms. To shed light on the role of disorder in a many-body setting we show that here the dynamics is governed by an Anderson-Fock model, i.e., an Anderson model formulated on a lattice with sites corresponding to many-body Fock states. We first consider a one-dimensional atom chain in a limit that is described by a one-dimensional Anderson-Fock model with disorder on every other site, featuring both localized and delocalized states. We then illustrate the effect of disorder experimentally in a situation in which the system maps on a two-dimensional Anderson-Fock model on a trimmed square lattice. We observe a clear suppression of excitation propagation, which we ascribe to the localization of the many-body wave functions in Hilbert space.
Facilitation Dynamics and Localization Phenomena in Rydberg Lattice Gases with Position Disorder.
Marcuzzi, Matteo; Minář, Jiří; Barredo, Daniel; de Léséleuc, Sylvain; Labuhn, Henning; Lahaye, Thierry; Browaeys, Antoine; Levi, Emanuele; Lesanovsky, Igor
2017-02-10
We explore the dynamics of Rydberg excitations in an optical tweezer array under antiblockade (or facilitation) conditions. Because of the finite temperature the atomic positions are randomly spread, an effect that leads to quenched correlated disorder in the interatomic interaction strengths. This drastically affects the facilitation dynamics as we demonstrate experimentally on the elementary example of two atoms. To shed light on the role of disorder in a many-body setting we show that here the dynamics is governed by an Anderson-Fock model, i.e., an Anderson model formulated on a lattice with sites corresponding to many-body Fock states. We first consider a one-dimensional atom chain in a limit that is described by a one-dimensional Anderson-Fock model with disorder on every other site, featuring both localized and delocalized states. We then illustrate the effect of disorder experimentally in a situation in which the system maps on a two-dimensional Anderson-Fock model on a trimmed square lattice. We observe a clear suppression of excitation propagation, which we ascribe to the localization of the many-body wave functions in Hilbert space.
NASA Technical Reports Server (NTRS)
Mcpeak, W. L.
1975-01-01
A new exciter switch assembly has been installed at the three DSN 64-m deep space stations. This assembly provides for switching Block III and Block IV exciters to either the high-power or 20-kW transmitters in either dual-carrier or single-carrier mode. In the dual-carrier mode, it provides for balancing the two drive signals from a single control panel located in the transmitter local control and remote control consoles. In addition to the improved switching capabilities, extensive monitoring of both the exciter switch assembly and Transmitter Subsystem is provided by the exciter switch monitor and display assemblies.
Astronaut Clay Anderson Speaks With S.C. Students
From NASA's International Space Station Mission Control Center, NASA astronaut Clay Anderson participates in a Digital Learning Network (DLN) event with students at Crayton Middle School, Columbia,...
Superconducting parity effect across the Anderson limit
Vlaic, Sergio; Pons, Stéphane; Zhang, Tianzhen; Assouline, Alexandre; Zimmers, Alexandre; David, Christophe; Rodary, Guillemin; Girard, Jean-Christophe; Roditchev, Dimitri; Aubin, Hervé
2017-01-01
How small can superconductors be? For isolated nanoparticles subject to quantum size effects, P.W. Anderson in 1959 conjectured that superconductivity could only exist when the electronic level spacing δ is smaller than the superconducting gap energy Δ. Here we report a scanning tunnelling spectroscopy study of superconducting lead (Pb) nanocrystals grown on the (110) surface of InAs. We find that for nanocrystals of lateral size smaller than the Fermi wavelength of the 2D electron gas at the surface of InAs, the electronic transmission of the interface is weak; this leads to Coulomb blockade and enables the extraction of electron addition energy of the nanocrystals. For large nanocrystals, the addition energy displays superconducting parity effect, a direct consequence of Cooper pairing. Studying this parity effect as a function of nanocrystal volume, we find the suppression of Cooper pairing when the mean electronic level spacing overcomes the superconducting gap energy, thus demonstrating unambiguously the validity of the Anderson criterion. PMID:28240294
The atomic approach to the Anderson model for the finite U case: application to a quantum dot.
Lobo, T; Figueira, M S; Foglio, M E
2010-07-09
In the present work we apply the atomic approach to the single-impurity Anderson model (SIAM). A general formulation of this approach, that can be applied both to the impurity and to the lattice Anderson Hamiltonian, was developed in a previous work (Foglio et al 2009 arxiv: 0903.0139v2 [cond-mat.str-el]). The method starts from the cumulant expansion of the periodic Anderson model, employing the hybridization as a perturbation. The atomic Anderson limit is analytically solved and its sixteen eigenenergies and eigenstates are obtained. This atomic Anderson solution, which we call the AAS, has all the fundamental excitations that generate the Kondo effect, and in the atomic approach is employed as a 'seed' to generate the approximate solutions for finite U. The width of the conduction band is reduced to zero in the AAS, and we choose its position such that the Friedel sum rule is satisfied, close to the chemical potential mu. We perform a complete study of the density of states of the SIAM over the whole relevant range of parameters: the empty dot, intermediate valence, Kondo and magnetic regimes. In the Kondo regime we obtain a density of states that characterizes well the structure of the Kondo peak. To show the usefulness of the method we have calculated the conductance of a quantum dot, side-coupled to a conduction band.
Density Functional Theory for Excited States in a Quasi Local Density Approximation.
1986-02-10
In the present note we develop a quasi-local approximation for M Exc, closely related to the LDA for thermal ensembles. As shown by Theophllou4 ), the...the equt-ensemble and corresponding KS ensemble are equal, S. However, the relations between entropy and temperature are different for interacting...and C() Ss(e) - T de’ (non-interacting) (18) 0 * .*.’ . with unequal heat capacities C and Cs. In general, referring to the tableau, S and 6 are related
Non-local dynamics of weakly nonlinear spin excitations in thin ferromagnetic films
NASA Astrophysics Data System (ADS)
Kiseliev, V. V.; Tankeyev, A. P.
1996-12-01
Effective integro-differential equations of weakly nonlinear dynamics describing the interaction of quasi-one-dimensional exchange-dipole spin-waves are derived for a thin ferromagnetic slab (film). The non-local part of the magnetostatic dispersion of these waves has been taken into account. Algebraic soliton-like states have been predicted. The conditions of their existence and their dynamic properties are investigated depending on the film thickness and on the magnitude and orientation of the external magnetic field. The role of crystallographic magnetic anisotropy in the formation of these states is analysed.
Krah, Tim; Ben Amor, Nadia; Maynau, Daniel; Berger, J A; Robert, Vincent
2014-07-01
Based on localized molecular orbitals, the proposed method reduces large configuration interaction (CI) spaces while maintaining agreement with reference values. Our strategy concentrates the numerical effort on physically pertinent CI-contributions and is to be considered as a tool to tackle large systems including numerous open-shells. To show the efficiency of our method we consider two 4-electron parent systems. First, we illustrate our approach by describing the van der Waals interactions in the (H2)2 system. By systematically including local correlation, dispersion and charge transfer mechanisms, we show that 90% of the reference full CI dissociation energy of the H2 dimer is reproduced using only 3% of the full CI space. Second, the conformational cis/trans rotation barrier of the butadiene molecule is remarkably reproduced (97% of the reference value) with less than 1% of the reference space. This work paves the way to numerical strategies which afford the electronic structure determination of large open-shell systems avoiding the exponential limitation. At the same time, a physical analysis of the contents of the wave function is offered.
Generalized local-frame-transformation theory for excited species in external fields
NASA Astrophysics Data System (ADS)
Giannakeas, P.; Greene, Chris H.; Robicheaux, F.
2016-07-01
A rigorous theoretical framework is developed for a generalized local-frame-transformation theory (GLFT). The GLFT is applicable to the following systems: Rydberg atoms or molecules in an electric field and negative ions in any combination of electric and/or magnetic fields. A first test application to the photoionization spectra of Rydberg atoms in an external electric field demonstrates dramatic improvement over the first version of the local-frame-transformation theory developed initially by U. Fano [Phys. Rev. A 24, 619 (1981), 10.1103/PhysRevA.24.619] and D. A. Harmin [Phys. Rev. A 26, 2656 (1982), 10.1103/PhysRevA.26.2656]. This revised GLFT theory yields nontrivial corrections because it now includes the full on-shell Hilbert space without adopting the truncations in the original theory. Comparisons of the semianalytical GLFT Stark spectra with ab initio numerical simulations yield errors in the range of a few tens of MHz, an improvement over the original Fano-Harmin theory, whose errors are 10-100 times larger. Our analysis provides a systematic pathway to precisely describe the corresponding photoabsorption spectra that should be accurate enough to meet most modern experimental standards.
NASA Astrophysics Data System (ADS)
Rasmussen, K. Ø.; Christiansen, P. L.; Johansson, M.; Gaididei, Yu. B.; Mingaleev, S. F.
1998-03-01
A one-dimensional discrete nonlinear Schrödinger (DNLS) model with the power dependence, r- s on the distance r, of dispersive interactions is proposed. The stationary states of the system are studied both analytically and numerically. Two kinds of trial functions, exp-like and sech-like are exploited and the results of both approaches are compared. Both on-site and inter-site stationary states are investigated. It is shown that for s sufficiently large all features of the model are qualitatively the same as in the DNLS model with nearest-neighbor interaction. For s less than some critical value, scr, there is an interval of bistability where two stable stationary states exist at each excitation number. The bistability of on-site solitons may occur for dipole-dipole dispersive interaction ( s = 3), while scr for inter-site solitions is close to 2.1. In the framework of the DNLS equation with nearest-neighbor coupling we discuss the stability of highly localized, “breather-like”, excitations under the influence of thermal fluctuations. Numerical analysis shows that the lifetime of the breather is always finite and in a large parameter region inversely proportional to the noise variance for fixed damping and nonlinearity. We also find that the decay rate of the breather decreases with increasing nonlinearity and with increasing damping.
NASA Astrophysics Data System (ADS)
Gokhale, Shreyas; Hima Nagamanasa, K.; Sood, A. K.; Ganapathy, Rajesh
2016-07-01
Elucidating the nature of the glass transition has been the holy grail of condensed matter physics and statistical mechanics for several decades. A phenomenological aspect that makes glass formation a conceptually formidable problem is that structural and dynamic correlations in glass-forming liquids are too subtle to be captured at the level of conventional two-point functions. As a consequence, a host of theoretical techniques, such as quenched amorphous configurations of particles, have been devised and employed in simulations and colloid experiments to gain insights into the mechanisms responsible for these elusive correlations. Very often, though, the analysis of spatio-temporal correlations is performed in the context of a single theoretical framework, and critical comparisons of microscopic predictions of competing theories are thereby lacking. Here, we address this issue by analysing the distribution of localized excitations, which are building blocks of relaxation as per the dynamical facilitation (DF) theory, in the presence of an amorphous wall, a construct motivated by the random first-order transition theory (RFOT). We observe that spatial profiles of the concentration of excitations exhibit complex features such as non-monotonicity and oscillations. Moreover, the smoothly varying part of the concentration profile yields a length scale {ξc} , which we compare with a previously computed length scale {ξ\\text{dyn}} . Our results suggest a method to assess the role of dynamical facilitation in governing structural relaxation in glass-forming liquids.
Powell, B J
2015-06-30
There is longstanding fundamental interest in 6-fold coordinated d(6) (t(2g)(6)) transition metal complexes such as [Ru(bpy)3](2+) and Ir(ppy)3, particularly their phosphorescence. This interest has increased with the growing realisation that many of these complexes have potential uses in applications including photovoltaics, imaging, sensing, and light-emitting diodes. In order to design new complexes with properties tailored for specific applications a detailed understanding of the low-energy excited states, particularly the lowest energy triplet state, T1, is required. Here we describe a model of pseudo-octahedral complexes based on a pseudo-angular momentum representation and show that the predictions of this model are in excellent agreement with experiment - even when the deviations from octahedral symmetry are large. This model gives a natural explanation of zero-field splitting of T1 and of the relative radiative rates of the three sublevels in terms of the conservation of time-reversal parity and total angular momentum modulo two. We show that the broad parameter regime consistent with the experimental data implies significant localization of the excited state.
NASA Astrophysics Data System (ADS)
Hosford, A.; Ryan, S. G.; García Pérez, A. E.; Norris, J. E.; Olive, K. A.
2009-01-01
Context: The discovery of the Spite plateau in the abundances of 7Li for metal-poor stars led to the determination of an observationally deduced primordial lithium abundance. However, after the success of the Wilkinson Microwave Anisotropy Probe (WMAP) in determining the baryon density, Ω_Bh2, there was a discrepancy between observationally determined and theoretically determined abundances in the case of 7Li. One of the most important uncertain factors in the calculation of the stellar 7Li abundance is the effective temperature, T_eff. Aims: We use sixteen metal-poor halo dwarfs to calculate new T_eff values using the excitation energy method. With this temperature scale we then calculate new Li abundances for this group of stars in an attempt to resolve the 7Li discrepancy. Methods: Using high signal-to-noise (S/N ≈ 100) spectra of 16 metal-poor halo dwarfs, obtained with the UCLES spectrograph on the AAT, measurements of equivalent widths from a set of unblended Fe I lines are made. These equivalent widths are then used to calculate new T_eff values with the use of the single line radiative transfer program WIDTH6, where we have constrained the gravity using either theoretical isochrones or the Hipparcos parallax, rather than the ionization balance. The lithium abundances of the stars are calculated with these temperatures. Results: The physical parameters are derived for the 16 programme stars, and two standards. These include T_eff, log g, [Fe/H], microturbulence and 7Li abundances. A comparison between the temperature scale of this work and those adopted by others has been undertaken. We find good consistency with the temperatures derived from the Hα line by Asplund et al. (2006, ApJ, 644, 229), but not with the hotter scale of Meléndez & Ramírez (2004, ApJ, 615, L33). We also present results of the investigation into whether any trends between 7Li and metallicity or temperature are present in these metal-poor stars. Appendix A is only available in
NASA Astrophysics Data System (ADS)
Hosford, A.; García Pérez, A. E.; Collet, R.; Ryan, S. G.; Norris, J. E.; Olive, K. A.
2010-02-01
Context. The plateau in the abundance of 7Li in metal-poor stars was initially interpreted as an observational indicator of the primordial lithium abundance. However, this observational value is in disagreement with that deduced from calculations of Big Bang nucleosynthesis (BBN), when using the Wilkinson microwave anisotropy probe (WMAP) baryon density measurements. One of the most important factors in determining the stellar lithium abundance is the effective temperature. In a previous study by the authors, new effective temperatures (Teff) for sixteen metal-poor halo dwarfs were derived using a local thermodynamic equilibrium (LTE) description of the formation of Fe lines. This new Teff scale reinforced the discrepancy. Aims: For six of the stars from our previous study we calculate revised temperatures using a non-local thermodynamic equilibrium (NLTE) approach. These are then used to derive a new mean primordial lithium abundance in an attempt to solve the lithium discrepancy. Methods: Using the code MULTI we calculate NLTE corrections to the LTE abundances for the Fe i lines measured in the six stars, and determine new Teff's. We keep other physical parameters, i.e. log g, [Fe/H] and ξ, constant at the values calculated in Paper I. With the revised Teff scale we derive new Li abundances. We compare the NLTE values of Teff with the photometric temperatures of Ryan et al. (1999, ApJ, 523, 654), the infrared flux method (IRFM) temperatures of Meléndez & Ramírez (2004, ApJ, 615, L33), and the Balmer line wing temperatures of Asplund et al. (2006, ApJ, 644, 229). Results: We find that our temperatures are hotter than both the Ryan et al. and Asplund et al. temperatures by typically ~110-160 K, but are still cooler than the temperatures of Meléndez & Ramírez by typically ~190 K. The temperatures imply a primordial Li abundance of 2.19 dex or 2.21 dex, depending on the magnitude of collisions with hydrogen in the calculations, still well below the value of 2
Slow Relaxation in Anderson Critical Systems
NASA Astrophysics Data System (ADS)
Choi, Soonwon; Yao, Norman; Choi, Joonhee; Kucsko, Georg; Lukin, Mikhail
2016-05-01
We study the single particle dynamics in disordered systems with long range hopping, focusing on the critical cases, i.e., the hopping amplitude decays as 1 /rd in d-dimension. We show that with strong on-site potential disorder, the return probability of the particle decays as power-law in time. As on-site potential disorder decreases, the temporal profile smoothly changes from a simple power-law to the sum of multiple power-laws with exponents ranged from 0 to νmax. We analytically compute the decay exponents using a simple resonance counting argument, which quantitatively agrees with exact numerical results. Our result implies that the dynamics in Anderson Critical systems are dominated by resonances. Harvard-MIT CUA, Kwanjeong Educational Fellowship, AFOSR MURI, Samsung Scholarship.
The Knight shift anomaly in the disordered periodic Anderson model
NASA Astrophysics Data System (ADS)
Dos Santos, Raimundo; Costa, Natanael; Paiva, Thereza; Curro, Nicholas; Scalettar, Richard
In some materials, the coherence temperature T* signals the regime in which one has a heavy-electron fluid and `dissolved' local moments. An experimental signature of T* is provided by the Knight shift anomaly in NMR measurements. Further, the contribution of the heavy-electron fluid to the Knigh shift, KHF, displays universal character over a wide range of temperatures. An important probe of the physical mechanisms at play is the random substitution of say, La for Ce in CeRhIn5: this amounts to removing local moments at random sites, and one may wonder whether these universal features are sensitive to the presence of disorder. The Periodic Anderson Model (PAM) captures many aspects of heavy-fermion materials, so here we consider the two-dimensional PAM with a fraction x of the f-sites removed at random. Through Determinant Quantum Monte Carlo simulations we find that universality of KHF persists even in the presence of disorder, which, in turn, allows us to establish that T* decreases monotonically with x, in agreement with available experimental data. Our simulations also shed light into the low temperature behavior of the disordered PAM at low temperatures: the spin liquid phase of the local moments is suppressed upon dilution.
ERIC Educational Resources Information Center
Albert, Marc K.
2008-01-01
M. Singh and B. L. Anderson proposed a perceptual theory of achromatic transparency in which the perceived transmittance of a perceived transparent filter is determined by the ratio of the Michelson contrast seen in the region of transparency to that of the background seen directly. Subsequently, B. L. Anderson, M. Singh, and J. Meng proposed that…
Numerical results for the Edwards-Anderson spin-glass model at low temperature
NASA Astrophysics Data System (ADS)
Fernández, Julio F.; Alonso, Juan J.
2013-04-01
We have simulated Edwards-Anderson (EA) as well as Sherrington-Kirkpatrick systems of L3 spins. After averaging over large sets of EA system samples of 3≤L≤10, we obtain accurate numbers for distributions p(q) of the overlap parameter q at very low-temperature T. We find p(0)/T→0.233(4) as T→0. This is in contrast with the droplet scenario of spin glasses. We also study the number of mismatched links—between replica pairs—that come with large scale excitations. Contributions from small scale excitations are discarded. We thus obtain for the fractal dimension of outer surfaces of q˜0 excitations in the EA model ds→2.59(3) as T→0. This is in contrast with ds→3 as T→0 that is predicted by mean-field theory for the macroscopic limit.
Hall, Jeremy; Renger, Thomas; Picorel, Rafael; Krausz, Elmars
2016-01-01
Circularly polarized luminescence (CPL) spectroscopy is an established but relatively little-used technique that monitors the chirality of an emission. When applied to photosynthetic pigment assemblies, we find that CPL provides sensitive and detailed information on low-energy exciton states, reflecting the interactions, site energies and geometries of interacting pigments. CPL is the emission analog of circular dichroism (CD) and thus spectra explore the optical activity only of fluorescent states of the pigment-protein complex and consequently the nature of the lowest-energy excited states (trap states), whose study is a critical area of photosynthesis research. In this work, we develop the new approach of temperature-dependent CPL spectroscopy, over the 2-120 K temperature range, and apply it to the CP43 proximal antenna protein of photosystem II. Our results confirm strong excitonic interactions for at least one of the two well-established emitting states of CP43 named "A" and "B". Previous structure-based models of CP43 spectra are evaluated in the light of the new CPL data. Our analysis supports the assignments of Shibata et al. [Shibata et al. J. Am. Chem. Soc. 135 (2013) 6903-6914], particularly for the highly-delocalized B-state. This state dominates CPL spectra and is attributed predominantly to chlorophyll a's labeled Chl 634 and Chl 636 (alternatively labeled Chl 43 and 45 by Shibata et al.). The absence of any CPL intensity in intramolecular vibrational sidebands associated with the delocalized "B" excited state is attributed to the dynamic localization of intramolecular vibronic transitions.
Optomechanical coupling in the Anderson-localization regime
NASA Astrophysics Data System (ADS)
García, P. D.; Bericat-Vadell, R.; Arregui, G.; Navarro-Urrios, D.; Colombano, M.; Alzina, F.; Sotomayor-Torres, C. M.
2017-03-01
Optomechanical crystals, purposely designed and fabricated semiconductor nanostructures, are used to enhance the coupling between the electromagnetic field and the mechanical vibrations of matter at the nanoscale. However, in real optomechanical crystals, imperfections open extra channels where the transfer of energy is lost, reducing the optomechanical coupling efficiency. Here, we quantify the role of disorder in a paradigmatic one-dimensional optomechanical crystal with full phononic and photonic band gaps. We show how disorder can be exploited as a resource to enhance the optomechanical coupling beyond engineered structures, thus providing a new tool set for optomechanics.
Passive control of buckling deformation via Anderson Localization Phenomenon
NASA Technical Reports Server (NTRS)
Elishakoff, Isaac; Li, Y. W.; Starnes, J. H., Jr.
1998-01-01
Buckling problems of two types of multi-span elastic plates with transverse stiffeners are considered using a method based on the finite difference calculus. The discreteness of the stiffeners is accounted for. It is found that the torsional rigidity of the stiffener plays an important role in the buckling mode pattern. When the torsional rigidity is properly adjusted, the stiffener can act as an isolator of deformation for the structure at buckling so that the deflection is only limited to a small area.
Critical exponent for the Anderson transition in the three-dimensional orthogonal universality class
NASA Astrophysics Data System (ADS)
Slevin, Keith; Ohtsuki, Tomi
2014-01-01
We report a careful finite size scaling study of the metal-insulator transition in Anderson's model of localization. We focus on the estimation of the critical exponent ν that describes the divergence of the localization length. We verify the universality of this critical exponent for three different distributions of the random potential: box, normal and Cauchy. Our results for the critical exponent are consistent with the measured values obtained in experiments on the dynamical localization transition in the quantum kicked rotor realized in a cold atomic gas.
Engineering extended Hubbard models with Zeeman excitations of ultracold Dy atoms
NASA Astrophysics Data System (ADS)
Vargas-Hernández, R. A.; Krems, R. V.
2016-12-01
We show that Zeeman excitations of ultracold Dy atoms trapped in an optical lattice can be used to engineer extended Hubbard models with tunable inter-site and particle number-non-conserving interactions. We show that the ratio of the hopping amplitude and inter-site interactions in these lattice models can be tuned in a wide range by transferring the atoms to different Zeeman states. We propose to use the resulting controllable models for the study of the effects of direct particle interactions and particle number-non-conserving terms on Anderson localization.
NASA Astrophysics Data System (ADS)
Feng, Lei; Yi, Xiaohua; Zhu, Dapeng; Xie, Xiongyao; Wang, Yang
2015-08-01
In a modern metropolis, metro rail systems have become a dominant mode for mass transportation. The structural health of a metro tunnel is closely related to public safety. Many vibration-based techniques for detecting and locating structural damage have been developed in the past several decades. However, most damage detection techniques and validation tests are focused on bridge and building structures; very few studies have been reported on tunnel structures. Among these techniques, transmissibility function and cross correlation analysis are two well-known diagnostic approaches. The former operates in frequency domain and the latter in time domain. Both approaches can be applied to detect and locate damage through acceleration data obtained from sensor arrays. Furthermore, the two approaches can directly utilize structural response data without requiring excitation measurement, which offers advantages in field testing on a large structure. In this research, a numerical finite element model of a metro tunnel is built and different types of structural defects are introduced at multiple locations of the tunnel. Transmissibility function and cross correlation analysis are applied to perform structural damage detection and localization, based on simulated structural vibration data. Numerical results demonstrate that the introduced defects can be successfully identified and located. The sensitivity and feasibility of the two approaches have been verified when sufficient distribution of measurement locations is available. Damage detection results of the two different approaches are compared and discussed.
Anderson-Fabry disease in children.
Sestito, Simona; Ceravolo, Ferdinando; Concolino, Daniela
2013-01-01
Although clinical evidence of major organ damage is typical of adulthood, many of the signs and symptoms of Anderson Fabry Disease (AFD) occur frequently in childhood. The clinical phenotype of AFD in pediatric patients has been described in several studies which show a higher incidence and an earlier onset of symptoms in male patients than in females. These include neurological manifestations (acroparaesthesias, chronic neuropathic pain, hypo-anhidrosis, tinnitus, hearing, loss), gastrointestinal (GI) symptoms (abdominal pain and diarrhea), angiokeratomas, ocular abnormalities (cornea verticillata, tortuous retinal vessels and subcapsular cataracts). Such manifestations may impair quality of life and, because of their unspecific nature, rarely lead to an early diagnosis. In addition, signs of major organ damage (microalbuminuria or proteinuria, urinary hyperfiltration, impaired heart rate variability, left ventricular hypertrophy, stroke) are encountered in children with AFD. Clinical trials of enzyme replacement therapy (ERT) with agalsidase alfa and agalsidase beta have been conducted in children, with clinical and pharmacodinamc effects proved by both enzyme formulations, whereas differences in safety profile and administration were found. Although several studies suggest that ERT should be started before irreversible damage in critical organs have occurred, the issue of when to initiate it has not yet been resolved. More controlled trials must be done in order to demonstrate that an early start of ERT could prevent adult complications and to assess the optimal timing of treatment in children with AFD. This review aims to provide an update of the current understanding for a better approach of pediatric AFD.
Geology of the Anderson Mesa quadrangle, Colorado
Cater, Fred W.; Withington, C.F.
1953-01-01
The Anderson Mesa quadrangle is one of the eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of the southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteenth quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quarternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults, and northwest-tending folds. Conspicuous among the folds are large anticlines having cores of intrusive slat and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing many thousands of tons. The ore consists of largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.
2007-10-08
self- localized nonlinear bullet mode: large precession angle, strong spatial localization, and low frequency below the fer- romagnetic resonance FMR ...bullet mode with the fre- quency lower than the FMR frequency of the free layer is excited, in full agreement with the results of previous simulations...through it is varied. FORMULATION OF THE PROBLEM We studied current-induced spin-wave dynamics in a magnetic multilayered system consisting of a thick
Wescott, Andrew P; Jafri, M Saleet; Lederer, W J; Williams, George S B
2016-03-01
Calcium-induced calcium release is the principal mechanism that triggers the cell-wide [Ca(2+)]i transient that activates muscle contraction during cardiac excitation-contraction coupling (ECC). Here, we characterize this process in mouse cardiac myocytes with a novel mathematical action potential (AP) model that incorporates realistic stochastic gating of voltage-dependent L-type calcium (Ca(2+)) channels (LCCs) and sarcoplasmic reticulum (SR) Ca(2+) release channels (the ryanodine receptors, RyR2s). Depolarization of the sarcolemma during an AP stochastically activates the LCCs elevating subspace [Ca(2+)] within each of the cell's 20,000 independent calcium release units (CRUs) to trigger local RyR2 opening and initiate Ca(2+) sparks, the fundamental unit of triggered Ca(2+) release. Synchronization of Ca(2+) sparks during systole depends on the nearly uniform cellular activation of LCCs and the likelihood of local LCC openings triggering local Ca(2+) sparks (ECC fidelity). The detailed design and true SR Ca(2+) pump/leak balance displayed by our model permits investigation of ECC fidelity and Ca(2+) spark fidelity, the balance between visible (Ca(2+) spark) and invisible (Ca(2+) quark/sub-spark) SR Ca(2+) release events. Excess SR Ca(2+) leak is examined as a disease mechanism in the context of "catecholaminergic polymorphic ventricular tachycardia (CPVT)", a Ca(2+)-dependent arrhythmia. We find that that RyR2s (and therefore Ca(2+) sparks) are relatively insensitive to LCC openings across a wide range of membrane potentials; and that key differences exist between Ca(2+) sparks evoked during quiescence, diastole, and systole. The enhanced RyR2 [Ca(2+)]i sensitivity during CPVT leads to increased Ca(2+) spark fidelity resulting in asynchronous systolic Ca(2+) spark activity. It also produces increased diastolic SR Ca(2+) leak with some prolonged Ca(2+) sparks that at times become "metastable" and fail to efficiently terminate. There is a huge margin of safety for
Pressure dependence of the magnetic order on the Anderson lattice
NASA Astrophysics Data System (ADS)
Bernhard, B. H.; Aguiar, C.; Coqblin, B.
2006-05-01
The Anderson lattice model is employed in the description of several rare-earth compounds exhibiting charge fluctuations. Here we address the model by means of Green's function technique introduced in [B.H. Bernhard, C. Lacroix, Phys. Rev. B 60 (1999) 12149]. The description of the magnetic phase is obtained from the analysis of the self-consistent magnetization curves. Calculations are performed specifically on a cubic lattice. The competition between the antiferromagnetic (AF) order and the Kondo effect is tuned by the control parameter V/Ef which simulates the effect of pressure. The T- p diagram of the model is obtained for different values of the ratio V/t. By accompanying the evolution of the quantum critical point (QCP), we are able to draw the phase diagram at T=0. The model admits the coexistence of AF order and Kondo behavior, with a clear reduction of the local Kondo correlation function
Anderson metal-insulator transitions with classical magnetic impurities
Jung, Daniel; Kettemann, Stefan
2014-08-20
We study the effects of classical magnetic impurities on the Anderson metal-insulator transition (AMIT) numerically. In particular we find that while a finite concentration of Ising impurities lowers the critical value of the site-diagonal disorder amplitude W{sub c}, in the presence of Heisenberg impurities, W{sub c} is first increased with increasing exchange coupling strength J due to time-reversal symmetry breaking. The resulting scaling with J is compared to analytical predictions by Wegner [1]. The results are obtained numerically, based on a finite-size scaling procedure for the typical density of states [2], which is the geometric average of the local density of states. The latter can efficiently be calculated using the kernel polynomial method [3]. Although still suffering from methodical shortcomings, our method proves to deliver results close to established results for the orthogonal symmetry class [4]. We extend previous approaches [5] by combining the KPM with a finite-size scaling analysis. We also discuss the relevance of our findings for systems like phosphor-doped silicon (Si:P), which are known to exhibit a quantum phase transition from metal to insulator driven by the interplay of both interaction and disorder, accompanied by the presence of a finite concentration of magnetic moments [6].
Conduction in quasiperiodic and quasirandom lattices: Fibonacci, Riemann, and Anderson models
NASA Astrophysics Data System (ADS)
Varma, V. K.; Pilati, S.; Kravtsov, V. E.
2016-12-01
We study the ground state conduction properties of noninteracting electrons in aperiodic but nonrandom one-dimensional models with chiral symmetry and make comparisons against Anderson models with nondeterministic disorder. The first model we consider is the Fibonacci lattice, which is a paradigmatic model of quasicrystals; the second is the Riemann lattice, which we define inspired by Dyson's proposal on the possible connection between the Riemann hypothesis and a suitably defined quasicrystal. Our analysis is based on Kohn's many-particle localization tensor defined within the modern theory of the insulating state. In the Fibonacci quasicrystal, where all single-particle eigenstates are critical (i.e., intermediate between ergodic and localized), the noninteracting electron gas is found to be an insulator, due to spectral gaps, at various specific fillings ρ , including the values ρ =1 /gn , where g is the golden ratio and n is any integer; however away from these spectral anomalies, the system is found to be a conductor, including the half-filled case. In the Riemann lattice metallic behavior is found at half filling as well; however, in contrast to the Fibonacci quasicrystal, the Riemann lattice is generically an insulator due to single-particle eigenstate localization, likely at all other fillings. Its behavior turns out to be alike that of the off-diagonal Anderson model, albeit with different system-size scaling of the band-center anomalies. The advantages of analyzing the Kohn's localization tensor instead of other measures of localization familiar from the theory of Anderson insulators (such as the participation ratio or the Lyapunov exponent) are highlighted.
The magnetocaloric effect with critical behavior of a periodic Anderson-like organic polymer.
Ding, L J; Zhong, Y; Fan, S W; Zhu, L Y
2016-01-07
We study the magnetocaloric effect and the critical behavior of a periodic Anderson-like organic polymer using Green's function theory, in which the localized f orbitals hybridize with the conduction orbitals at even sites. The field-induced metal-insulator transitions with the magnetic Grüneisen parameter showing |Γh|∼T(-1) power-law critical behaviour are revealed, which provides a new thermodynamic means for probing quantum phase transitions. It is found that the competition of up-spin and down-spin hole excitations is responsible for the double peak structure of magnetic entropy change (-ΔS) for the dominant Kondo coupling case, implying a double magnetic cooling process via demagnetization, which follows a power law dependence of the magnetic field h: -ΔS∼h(n). The local exponent n tends to 1 and 2 below and above TC, while has a minimum of 0.648 at TC, which is in accordance with the experimental observation of perovskite manganites Pr0.55Sr0.45MnO3 and Nd0.55Sr0.45MnO3 (J. Y. Fan et al., Appl. Phys. Lett., 2011, 98, 072508; Europhys. Lett., 2015, 112, 17005) corresponding to the conventional ferromagnets within the mean field theory -ΔS∼h(2/3). At TC, the -ΔS∼h curves with a convex curvature superpose each other for small V values, which are separated by the large V case, distinguishing the RKKY interaction and Kondo coupling explicitly. Furthermore, the critical scaling law n(TC) = 1 + (β- 1)/(β + γ) = 1 + 1/δ(1 - 1/β) is related to the critical exponents (β, γ, and δ) extracted from the Arrott-Noakes equation of state and the Kouvel-Fisher method, which fulfill the Widom scaling relation δ = 1 + γβ(-1), indicating the self-consistency and reliability of the obtained results. In addition, based on the scaling hypothesis through checking the scaling analysis of magnetization, the M-T-h curves collapse into two independent universal branches below and above TC.
Guérin, Bastien; Gebhardt, Matthias; Serano, Peter; Adalsteinsson, Elfar; Hamm, Michael; Pfeuffer, Josef; Nistler, Juergen; Wald, Lawrence L.
2014-01-01
Purpose We compare the performance of 8 parallel transmit (pTx) body arrays with up to 32 channels and a standard birdcage design. Excitation uniformity, local SAR, global SAR and power metrics are analyzed in the torso at 3 T for RF-shimming and 2-spoke excitations. Methods We used a fast co-simulation strategy for field calculation in the presence of coupling between transmit channels. We designed spoke pulses using magnitude least squares (MLS) optimization with explicit constraint of SAR and power and compared the performance of the different pTx coils using the L-curve method. Results PTx arrays outperformed the conventional birdcage coil in all metrics except peak and average power efficiency. The presence of coupling exacerbated this power efficiency problem. At constant excitation fidelity, the pTx array with 24 channels arranged in 3 z-rows could decrease local SAR more than 4-fold (2-fold) for RF-shimming (2-spoke) compared to the birdcage coil for pulses of equal duration. Multi-row pTx coils had a marked performance advantage compared to single row designs, especially for coronal imaging. Conclusion PTx coils can simultaneously improve the excitation uniformity and reduce SAR compared to a birdcage coil when SAR metrics are explicitly constrained in the pulse design. PMID:24752979
Soh, Wee Tee Ong, C. K.; Peng, Bin
2015-04-21
We demonstrate the localized excitation and dc electrical detection of magnetostatic surface spin waves (MSSWs) in yttrium iron garnet (YIG) by a shorted coaxial probe. Thin films of NiFe and Pt are patterned at different regions onto a common bulk YIG substrate. A shorted coaxial probe is used to excite spin precession locally near various patterned regions. The dc voltages across the corresponding regions are recorded. For excitation of the Pt regions, the dc voltage spectra are dominated by the spin pumping of MSSWs from YIG, where various modes can be clearly distinguished. For the NiFe region, it is also found that spin pumping from MSSWs generated in YIG dominated the spectra, indicating that the spin pumped currents are dissipated into charge currents via the inverse Spin Hall effect (ISHE) in NiFe. For all regions, dc signals from YIG MSSWs are observed to be much stronger than the ferromagnetic resonance (FMR) uniform mode, likely due to the nature of the microwave excitation. The results indicate the potential of this probe for microwave imaging via dc detection of spin dynamics in continuous and patterned films.
Modified Anderson Model——Dynamics of Brittle Faulting
NASA Astrophysics Data System (ADS)
Tong, H.
2014-12-01
Anderson's model has been a basic theory of fault mechanical analysis in one century. However, because of the assumptions, there are some major limitations in Anderson model, and it does not account for frequently observed oblique slips, complicated fault cases in nature and the slips occurring on pre-existing planes of weakness. On the basis of Reactivation Tendency Analysis theory proposed by Tong and Yin (2011), we proposed Modified Anderson model and extended Anderson model from 1) homogeneous media to Inhomogeneous media with pre-existing weakness(es); 2) Andersonian stress state to arbitrary stress state; 3) transient activity trend analysis to fault formation and evolution, and verified with sandbox experiments and natural cases. With Modified Anderson model, we can predict 1) the sequence of fault formation; 2) fault orientations and distribution; 3) slip directions (dip slip, oblique-dip slip, oblique slip, oblique strike slip and strike sip) of different fault when the directions of principal stress, orientations and mechanical properties (cohesion and frictional coefficient) of pre-existing weakness(es) are given. The origin of the complicated fault systems in nature can be explained reasonably. There will be a wide applications for oil and gas exploration and development, coal mining, earthquake risk evaluation, etc.
Louisa Garrett Anderson (1873-1943), surgeon and suffragette.
Geddes, Jennian F
2008-11-01
Louisa Garrett Anderson, daughter of Britain's first woman doctor, has been largely forgotten today despite the fact that her contribution to the women's movement was as great as that of her mother. Recognized by her contemporaries as an important figure in the suffrage campaign, Anderson chose to lend her support through high-profile action, being one of the few women doctors in her generation who risked their professional as well as their personal reputation in the fight for women's rights by becoming a suffragette - in her case, even going so far as to spend a month in prison for breaking a window on a demonstration. On the outbreak of war, with only the clinical experience she had gained as outpatient surgeon in a women's hospital, Anderson established a series of women-run military hospitals where she was a Chief Surgeon. The most successful was the Endell Street Military Hospital in London, funded by the Royal Army Medical Corps and the only army hospital ever to be run and staffed entirely by women. Believing that a doctor had an obligation to take a lead in public affairs, Anderson continued campaigning for women's issues in the unlikely setting of Endell Street, ensuring that their activities remained in the public eye through constant press coverage. Anderson's achievement was that her work played no small part in expunging the stigma of the militant years in the eyes of the public and - more importantly - was largely instrumental in putting women doctors on equal terms with their male colleagues.
The M. D. Anderson proton therapy system
Smith, Alfred; Gillin, Michael; Bues, Martin; Zhu, X. Ronald; Suzuki, Kazumichi; Mohan, Radhe; Woo, Shiao; Lee, Andrew; Komaki, Ritsko; Cox, James; Hiramoto, Kazuo; Akiyama, Hiroshi; Ishida, Takayuki; Sasaki, Toshie; Matsuda, Koji
2009-09-15
Purpose: The purpose of this study is to describe University of Texas M. D. Anderson proton therapy system (PTC-H) including the accelerator, beam transport, and treatment delivery systems, the functionality and clinical parameters for passive scattering and pencil beam scanning treatment modes, and the results of acceptance tests. Methods: The PTC-H has a synchrotron (70-250 MeV) and four treatment rooms. An overall control system manages the treatment, physics, and service modes of operation. An independent safety system ensures the safety of patients, staff, and equipment. Three treatment rooms have isocentric gantries and one room has two fixed horizontal beamlines, which include a large-field treatment nozzle, used primarily for prostate treatments, and a small-field treatment nozzle for ocular treatments. Two gantry treatment rooms and the fixed-beam treatment room have passive scattering nozzles. The third gantry has a pencil beam scanning nozzle for the delivery of intensity modulated proton treatments (IMPT) and single field uniform dose (SFUD) treatments. The PTC-H also has an experimental room with a fixed horizontal beamline and a passive scattering nozzle. The equipment described above was provided by Hitachi, Ltd. Treatment planning is performed using the Eclipse system from Varian Medical Systems and data management is handled by the MOSAIQ system from IMPAC Medical Systems, Inc. The large-field passive scattering nozzles use double scattering systems in which the first scatterers are physically integrated with the range modulation wheels. The proton beam is gated on the rotating range modulation wheels at gating angles designed to produce spread-out-Bragg peaks ranging in size from 2 to 16 g/cm{sup 2}. Field sizes of up to 25x25 cm{sup 2} can be achieved with the double scattering system. The IMPT delivery technique is discrete spot scanning, which has a maximum field size of 30x30 cm{sup 2}. Depth scanning is achieved by changing the energy
Describing excited state relaxation and localization in TiO_{2} nanoparticles using TD-DFT
Berardo, Enrico; Hu, Han -Shi; van Dam, Hubertus J. J.; Shevlin, Stephen A.; Woodley, Scott M.; Kowalski, Karol; Zwijnenburg, Martijn A.
2014-02-26
We have investigated the description of excited state relaxation in naked and hydrated TiO_{2} nanoparticles using Time-Dependent Density Functional Theory (TD-DFT) with three common hybrid exchange-correlation (XC) potentials; B3LYP, CAM-B3LYP and BHLYP. Use of TD-CAM-B3LYP and TD-BHLYP yields qualitatively similar results for all structures, which are also consistent with predictions of coupled cluster theory for small particles. TD-B3LYP, in contrast, is found to make rather different predictions; including apparent conical intersections for certain particles that are not observed with TD-CAM-B3LYP nor with TD-BHLYP. In line with our previous observations for vertical excitations, the issue with TD-B3LYP appears to be the inherent tendency of TD-B3LYP, and other XC potentials with no or a low percentage of Hartree-Fock Like Exchange, to spuriously stabilize the energy of charge-transfer (CT) states. Even in the case of hydrated particles, for which vertical excitations are generally well described with all XC potentials, the use of TD-B3LYP appears to result in CT-problems for certain particles. We hypothesize that the spurious stabilization of CT-states by TD-B3LYP even may drive the excited state optimizations to different excited state geometries than those obtained using TD-CAM-B3LYP or TD-BHLYP. In conclusion, focusing on the TD-CAM-B3LYP and TD-BHLYP results, excited state relaxation in naked and hydrated TiO_{2} nanoparticles is predicted to be associated with a large Stokes’ shift.
France, Kevin; Nell, Nicholas; Kane, Robert; Green, James C.; Burgh, Eric B.
2013-07-20
We present the first science results from the Sub-orbital Local Interstellar Cloud Experiment (SLICE): moderate resolution 1020-1070 A spectroscopy of four sightlines through the local interstellar medium. High signal-to-noise (S/N) spectra of {eta} Uma, {alpha} Vir, {delta} Sco, and {zeta} Oph were obtained during a 2013 April 21 rocket flight. The SLICE observations constrain the density, molecular photoexcitation rates, and physical conditions present in the interstellar material toward {delta} Sco and {zeta} Oph. Our spectra indicate a factor of two lower total N(H{sub 2}) than previously reported for {delta} Sco, which we attribute to higher S/N and better scattered light control in the new SLICE observations. We find N(H{sub 2}) = 1.5 Multiplication-Sign 10{sup 19} cm{sup -2} on the {delta} Sco sightline, with kinetic and excitation temperatures of 67 and 529 K, respectively, and a cloud density of n{sub H} = 56 cm{sup -3}. Our observations of the bulk of the molecular sightline toward {zeta} Oph are consistent with previous measurements (N(H{sub 2}) Almost-Equal-To 3 Multiplication-Sign 10{sup 20} cm{sup -2} at T{sub 01}(H{sub 2}) = 66 K and T{sub exc} = 350 K). However, we detect significantly more rotationally excited H{sub 2} toward {zeta} Oph than previously observed. We infer a cloud density in the rotationally excited component of n{sub H} Almost-Equal-To 7600 cm{sup -3} and suggest that the increased column densities of excited H{sub 2} are a result of the ongoing interaction between {zeta} Oph and its environment; also manifest as the prominent mid-IR bowshock observed by WISE and the presence of vibrationally excited H{sub 2} molecules observed by the Hubble Space Telescope.
DMFT Study for Valence Fluctuations in the Extended Periodic Anderson Model
NASA Astrophysics Data System (ADS)
Shinzaki, Ryu; Nasu, Joji; Koga, Akihisa
2016-02-01
We study valence fluctuations at finite temperatures in the extended periodic Anderson model, where the Coulomb interaction between conduction and localized f-electrons is taken into account, using dynamical mean-field theory combined with the continuous-time quantum Monte Carlo (CT-QMC) method. The valence transition with the hysteresis is clearly found, indicating the first-order phase transition between the Kondo and mixed-valence states. We demonstrate that spin correlation rapidly develops when the system approaches the valence transition point. The comparison of the impurity solvers, the CT-QMC, non-crossing approximation, and one-crossing approximation, is also addressed.
NASA Astrophysics Data System (ADS)
Figueira, M. S.; Foglio, M. E.
1996-07-01
The approximate Green's functions of the localized electrons, obtained by the cumulant expansion of the periodic Anderson model in the limit of infinite Coulomb repulsion, do not satisfy completeness even for the simplest families of diagrams, like the chain approximation. The idea that employing 0953-8984/8/27/012/img6-derivable approximations would solve this difficulty is shown to be false by proving that the chain approximation is 0953-8984/8/27/012/img6-derivable and does not satisfy completeness. After finding a family of diagrams with Green's functions that satisfy completeness, we put forward a conjecture that shows how to select families of diagrams with this property.
Towards the Realization of Self-Consistent Effective Medium Theory for Anderson Disorder Model
NASA Astrophysics Data System (ADS)
Ekuma, Chinedu; Terletska, Hanna; Tam, Ka Ming; Meng, Zi Yang; Moreno, Juana; Jarrell, Mark
2014-03-01
A mean-field theory that properly characterizes the Anderson localization transition in three dimensions has remain elusive. Here, we present a systematic typical medium dynamical cluster approximation that provides a proper description of this phenomenon. Our method accurately provides a proper way to treat the different energy scales (close to the criticality) such that the characteristic re-entrant behavior of the mobility edge is obtained. This allows us to study the localization in different momenta cells, which renders the discovery that the Anderson localization transition occurs in a momentum cell-selective fashion. As a function of cluster size, our method systematically recovers the re-entrance behavior of the mobility edge and obtains the correct critical disorder strength with great improvement on the critical exponent of the order parameter (β > 1 . 4). This work is supported by the NSF EPSCoR EPS-1003897; and DOE BES DE-AC02-98CH10886 and SciDAC DE-SC0005274. Supercomputer support is provided by LONI and HPC@LSU.
Anderson-Fabry cardiomyopathy: prevalence, pathophysiology, diagnosis and treatment.
Putko, Brendan N; Wen, Kevin; Thompson, Richard B; Mullen, John; Shanks, Miriam; Yogasundaram, Haran; Sergi, Consolato; Oudit, Gavin Y
2015-03-01
Anderson-Fabry disease (AFD) is a lysosomal storage disease caused by the inappropriate accumulation of globotriaosylceramide in tissues due to a deficiency in the enzyme α-galactosidase A (α-Gal A). Anderson-Fabry cardiomyopathy is characterized by structural, valvular, vascular and conduction abnormalities, and is now the most common cause of mortality in patients with AFD. Large-scale metabolic and genetic screening studies have revealed AFD to be prevalent in populations of diverse ethnic origins, and the variant form of AFD represents an unrecognized health burden. Anderson-Fabry disease is an X-linked disorder, and genetic testing is critical for the diagnosis of AFD in women. Echocardiography with strain imaging and cardiac magnetic resonance imaging using late enhancement and T1 mapping are important imaging tools. The current therapy for AFD is enzyme replacement therapy (ERT), which can reverse or prevent AFD progression, while gene therapy and the use of molecular chaperones represent promising novel therapies for AFD. Anderson-Fabry cardiomyopathy is an important and potentially reversible cause of heart failure that involves LVH, increased susceptibility to arrhythmias and valvular regurgitation. Genetic testing and cardiac MRI are important diagnostic tools, and AFD cardiomyopathy is treatable if ERT is introduced early.
Measuring the Edwards-Anderson order parameter of the Bose glass: A quantum gas microscope approach
NASA Astrophysics Data System (ADS)
Thomson, S. J.; Walker, L. S.; Harte, T. L.; Bruce, G. D.
2016-11-01
With the advent of spatially resolved fluorescence imaging in quantum gas microscopes, it is now possible to directly image glassy phases and probe the local effects of disorder in a highly controllable setup. Here we present numerical calculations using a spatially resolved local mean-field theory, show that it captures the essential physics of the disordered system, and use it to simulate the density distributions seen in single-shot fluorescence microscopy. From these simulated images we extract local properties of the phases which are measurable by a quantum gas microscope and show that unambiguous detection of the Bose glass is possible. In particular, we show that experimental determination of the Edwards-Anderson order parameter is possible in a strongly correlated quantum system using existing experiments. We also suggest modifications to the experiments which will allow further properties of the Bose glass to be measured.
NASA Astrophysics Data System (ADS)
Taguchi, T.; Ohno, T.; Nozue, Y.
A multiple LO-phonon emission process related to the relaxation of excitons of Cd xZn 1- xS/ZnS strained-layer superlattices ( x = 0.3), has been observed in the photoluminescence excitation spectra. The localization of excitons has been found to be the dominant cause of the linewidth broadening. In electric field dependent photocurrent spectra, a significant blueshift of the peak energy and photocurrent enhancement take place with increasing applied field. These results may be fully explained by assuming that this strained superlattice system exhibits a type II band lineup.
NASA Astrophysics Data System (ADS)
Stenzel, O.; Stendal, A.; Röder, M.; Wilbrandt, S.; Drews, D.; Werninghaus, T.; von Borczyskowski, C.; Zahn, D. R. T.
1998-03-01
Thin film sandwich samples have been prepared of copper phthalocyanine ultrathin solid films with incorporated metal (silver, indium) nanoclusters, surrounded by an amorphous silicon environment. The samples were investigated by transmission electron microscopy in both lateral and cross-sectional geometries. In view of the optical properties, we observed a gradual blue wavelength shift of the localized metal cluster plasmon excitation for about 300 nm accompanying an equivalent copper phthalocyanine thickness increase from `zero' to a threshold thickness of about 4 nm. We attribute this behaviour to the formation of bulk-like optical properties of the copper phthalocyanine film, which is completed at the observed equivalent threshold thickness.
Federal Register 2010, 2011, 2012, 2013, 2014
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...
Halpin, Yvonne; Dini, Danilo; Ahmed, Hamid M Younis; Cassidy, Lynda; Browne, Wesley R; Vos, Johannes G
2010-03-15
The synthesis of two asymmetric dinuclear complexes with the formula [M(bpy)(2)(bpt)Ru(tpy)Cl](2+), where M = Ru (1a), Os(2a); bpy = 2,2'-bipyridyl; Hbpt = 3,5-bis(pyridin-2-yl)1,2,4-triazole and tpy = 2,2',6',2''-terpyridine, is reported. The compounds obtained are characterized by mass spectrometry, (1)H NMR, UV/vis/NIR absorption, luminescence, and resonance Raman spectroscopy. Deuterium isotope labeling facilitates assignment of the (1)H NMR and resonance Raman spectra. The interaction between the two metal centers, mediated by the bridging 1,2,4-triazolato moiety in the mixed valent state, is assigned as type II based on the observation of metal to metal charge transfer absorption bands at 7090 and 5990 cm(-1) for 1a and 2a, respectively. The extent of localization of the emissive excited state was determined by transient resonance Raman and emission spectroscopy. Both 1a and 2a show phosphorescence at the same wavelengths; however, whereas for compound 1a the emission is based on the Ru(tpy)Cl- center, for 2a the emissive state is localized on the Os(bpy)(2)- unit. This indicates that also in the excited state there is efficient interaction between the two metal centers.
NASA Astrophysics Data System (ADS)
Kang, Kai; Qin, Shao-Jing; Wang, Chui-Lin
2010-10-01
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.
Phase Shift of the Asymmetric Friedel-Anderson Impurity
NASA Astrophysics Data System (ADS)
Bergmann, Gerd
2013-04-01
The ground state of the asymmetric Friedel-Anderson (aFA) impurity is calculated within the FAIR (Friedel artificially inserted resonance) theory. Its properties are investigated by means of the fidelity with different Friedel impurities and by its Friedel oscillations. Friedel impurities with a specific phase shift δ at the Fermi level possess a finite fidelity with the aFA impurity. This phase shift δ determines other properties of the aFA impurity such as the amplitude and displacement of its Friedel oscillations. One can find the parameters of a Friedel impurity which coincides in its Friedel oscillations almost perfectly with the aFA impurity, thereby avoiding an Anderson orthogonality catastrophe.
STS-107 Crew Interviews: Michael Anderson, Mission Specialist
NASA Technical Reports Server (NTRS)
2002-01-01
STS-107 Mission Specialist 3 and Payload Commander Michael Anderson is seen during this preflight interview, where he gives a quick overview of the mission before answering questions about his inspiration to become an astronaut and his career path. He outlines his role in the mission in general, and specifically in conducting onboard science experiments. He discusses the following instruments and sets of experiments in detail: CM2 (Combustion Module 2), FREESTAR (Fast Reaction Enabling Science Technology and Research, MEIDEX (Mediterranean Israeli Dust Experiment) and MGM (Mechanics of Granular Materials). Anderson also mentions on-board activities and responsibilities during launch and reentry, mission training, and microgravity research. In addition, he touches on the dual work-shift nature of the mission, the use of crew members as research subjects including pre and postflight monitoring activities, the emphasis on crew safety during training and the value of international cooperation.
STS-107 Crew Interviews: Michael Anderson, Mission Specialist
NASA Astrophysics Data System (ADS)
2002-06-01
STS-107 Mission Specialist 3 and Payload Commander Michael Anderson is seen during this preflight interview, where he gives a quick overview of the mission before answering questions about his inspiration to become an astronaut and his career path. He outlines his role in the mission in general, and specifically in conducting onboard science experiments. He discusses the following instruments and sets of experiments in detail: CM2 (Combustion Module 2), FREESTAR (Fast Reaction Enabling Science Technology and Research, MEIDEX (Mediterranean Israeli Dust Experiment) and MGM (Mechanics of Granular Materials). Anderson also mentions on-board activities and responsibilities during launch and reentry, mission training, and microgravity research. In addition, he touches on the dual work-shift nature of the mission, the use of crew members as research subjects including pre and postflight monitoring activities, the emphasis on crew safety during training and the value of international cooperation.
Markovian Anderson Model: Bounds for the Rate of Propagation
NASA Astrophysics Data System (ADS)
Tcheremchantsev, Serguei
We consider the Anderson model in with potentials whose values at any site of the lattice are Markovian independent random functions of time. For solutions to the time-dependent Schrödinger equation we show under some conditions that with probability 1
Solar hot water system installed at Anderson, South Carolina
NASA Technical Reports Server (NTRS)
1978-01-01
A description is given of the solar energy hot water system installed in the Days Inns of America, Inc., at Anderson, South Carolina. The building is a low-rise, two-story 114-room motel. The solar system was designed to provide 40 percent of the total hot water demand. The collector is a flat plate, liquid with an area of 750 square feet. Operation of this system was begun in November 1977, and has performed flawlessly for one year.
The effect of the exhaustion on the magnetic and optical properties of the periodic Anderson model
NASA Astrophysics Data System (ADS)
Figueira, M. S.; Silva-Valencia, J.; Franco, R.
We are interested in the study of the "exhaustion problem", as originally introduced by Nozières, in the Kondo regime, and its manifestations on the magnetic and optical properties of the periodic Anderson model (PAM). In the case of the impurity problem there is only one single energy scale governed by the Kondo temperature TK, below which the local moment is screened by the conduction electrons. In the lattice case, there is the emergence of another energy scale governed by the coherence temperature T*, below which the system forms a Fermi liquid. The "exhaustion problem" becomes especially relevant when few conduction electrons nc≪1 are available to screen the local spins. To solve the model we employ the X-boson approach. We computed numerically the evolution of the magnetic susceptibility and the optical conductivity, in the heavy fermion Kondo-exhaustion regime, as a function of the temperature T, when the total occupation number Nt was kept constant.
A Suitable Option for Gustilo and Anderson Grade III Injury
Yang, Ronghua; Wang, Zhijun; Huang, Wenzhu; Zhao, Yuhuan; Xu, Lusheng; Yu, Shaobin
2016-01-01
Background The management of Gustilo and Anderson grade III injury remains difficult, particularly due to the incidence of wound infections, delayed fracture union, and traumatic extremity amputation. However, little data is available on delayed skin graft or flap reconstructions of Gustilo grade III injury, especially using new technologies of wound coverage, such as vacuum sealing drainage (VSD) combined with limited internal and/or external fixation. Material/Methods Between June 2008 and May 2013, we performed the VSD technique combined with limited internal and/or external fixation on 38 patients (22 males and 16 females, with a mean age of 36.5 years) with Gustilo and Anderson grade III injury. VSD was regularly changed and delayed skin grafts or flaps were used to cover the defect. Two patients were lost to follow-up, and the remaining 36 were available for evaluation. The complications, wound healing, infections, and bony union were assessed for a mean duration of 2.5 years (range, 1–4 years). Results Complications were seen in 5 of the 36 cases: 2 cases had infection alone, 1 case had delayed union or nonunion, 1 case had infection and delayed union, and 1 case had wound necrosis, infection, and nonunion. VSD was regularly changed 2–6 times. Morphological appearance and functional recovery were satisfactory in all cases. Conclusions Using VSD before skin grafts or flaps coverage, combined with limited internal and/or external fixation, is a suitable option for Gustilo and Anderson grade III injury. PMID:27564219
Topological Anderson insulator induced by inter-cell hopping disorder
Lv, Shu-Hui; Song, Juntao Li, Yu-Xian
2013-11-14
We have studied in detail the influence of same-orbit and different-orbit hopping disorders in HgTe/CdTe quantum wells. Intriguingly, similar to the behavior of the on-site Anderson disorder, a phase transition from a topologically trivial phase to a topological phase is induced at a proper strength of the same-orbit hopping disorder. For different-orbit hopping disorder, however, the phase transition does not occur. The results have been analytically verified by using effective medium theory. A consistent conclusion can be obtained by comparing phase diagrams, conductance, and conductance fluctuations. In addition, the influence of Rashba spin-orbit interaction (RSOI) on the system has been studied for different types of disorder, and the RSOI shows different influence on topological phase at different disorders. The topological phase induced by same-orbit hopping disorder is more robust against the RSOI than that induced by on-site Anderson disorder. For different-orbit hopping disorder, no matter whether the RSOI is included or not, the phase transition does not occur. The results indicate, whether or not the topological Anderson insulator can be observed depends on a competition between the different types of the disorder as well as the strength of the RSOI in a system.
Chen, Bin; Peng, Ming-Li; Wu, Li-Zhu; Zhang, Li-Ping; Tung, Chen-Ho
2006-10-01
The absorption and fluorescence spectra of a Hantzsch 1,4-dihydropyridine derivative bearing a N,N-dimethylaminophenyl group at 4-position (H(2)Py-PhN(CH(3))(2)) in aprotic solvents have been examined and compared to model compounds 4-phenyl- and 4-methyl-substituted Hantzsch 1,4-dihydropyridines (H(2)Py-Ph and H(2)Py-Me). While H(2)Py-Ph and H(2)Py-Me show fluorescence around 420 nm from the local excited state of the dihydropyridine chromophore, H(2)Py-PhN(CH(3))(2) exhibits fluorescence around 520 nm from the intramolecular charge transfer (ICT) state involving the aniline and dihydropyridine groups as donor and acceptor, respectively. Upon addition of an acid to the solution of H(2)Py-PhN(CH(3))(2), the amino group in the aniline is protonated. Thus, the photoinduced intramolecular charge transfer is prevented, and only the fluorescence from the local excited state of the dihydropyridine chromophore can be detected. These changes in the fluorescence behavior are fully reversible: subsequent addition of a base to the acidic solution leads to the recovery of the ICT fluorescence and the quenching of the local fluorescence. Transition metal ions also can switch the fluorescence of H(2)Py-PhN(CH(3))(2). Evidence for the interaction between transition metal ions and the amino group in the dimethylaniline have been provided by absorption and emission spectrum as well as NMR studies.
NASA Technical Reports Server (NTRS)
Hoshino, M.
1991-01-01
A forced magnetic reconnection process with a temporal evolution of resistivity is studied for a plasma sheet with a nonuniform resistivity profile based on the nonlocal mode structure of the lower hybrid drift type instability. The growth rate of the mode found is almost independent of the resistivity at the neutral sheet, but depends on the resistivity of the region of maximum density gradient away from the neutral sheet. This is studied by using both a nonlinear numerical MHD simulation and a linear theory. The mode may be relevant to the prevalent theoretical concept of MHD reconnection and the localized anomalous resistivity profile based on the lower hybrid drift instability.
NASA Astrophysics Data System (ADS)
Grasselli, Federico; Bertoni, Andrea; Goldoni, Guido
2016-09-01
When composite particles—such as small molecules, nuclei, or photogenerated excitons in semiconductors—are scattered by an external potential, energy may be transferred between the c.m. and the internal degrees of freedom. An accurate dynamical modeling of this effect is pivotal in predicting diverse scattering quantities and reaction cross sections, and allows us to rationalize time-resolved energy and localization spectra. Here, we show that time-dependent scattering of a quantum composite particle with an arbitrary, nonperturbative external potential can be obtained by propagating the c.m. degrees of freedom with a properly designed local self-energy potential. The latter embeds the effect of internal virtual transitions and can be obtained by the knowledge of the stationary internal states. The case is made by simulating Wannier-Mott excitons in one- and two-dimensional semiconductor heterostructures. The self-energy approach shows very good agreement with numerically exact Schrödinger propagation for scattering potentials where a mean-field model cannot be applied, at a dramatically reduced computational cost.
Bolt, H; Hemel, V; Koch, F; Nickel, H
1996-06-01
Space resolved optical emission spectroscopy has been applied to determine the distribution of excited species in dense plasmas which are used for the deposition of thin coatings. Typical electron densities and electron temperatures in the plasma facility PETRA ( Plasma Engineering and Technology Research Assembly) are in the range of n(e) = 10(12) cm(-3) and T(e) = 10 eV. During the deposition process material (Al) is evaporated from a vapour cell under controlled conditions. The vapour stream is guided into a dense plasma which is composed of inert gas, Ar or He, and hydrocarbon species produced from the dissociation of C(2)H(2). The evaporated Al-stream which travels with thermal velocity into a plasma of high electron density, is nearly completely ionized due to the short mean free path for electron impact ionization in the above mentioned parameter range. Optical emission spectroscopy has been applied to investigate the interaction processes between the vapour stream and the plasma as well as the transport of the ionized Al along the applied magnetic field. For the measurements space resolved optical emission spectroscopy with an in-situ translation mechanism of the optical fibre has been used to measure the local concentrations of excited Al neutrals and ions as well as the concentration of the background plasma species.
NASA Astrophysics Data System (ADS)
Kovalenko, S. A.; Ernsting, N. P.; Ruthmann, J.
1996-08-01
Transient spectra of the styryl dyM (4-dicyanomethylene-2-methyl-6- p-dimethylaminostyryl-4H-pyran) in methanol were studied by the pump-supercontinuum probe technique with 40 fs time resolution. A theory of measurements with a supercontinuum probe is presented. Gain and absorption spectra were measured from 400 to 800 nm with 1.5 nm resolution. Before 70 fs, prominent spectral structure is observed which is mainly due to resonant Raman processes. At longer times the spectrum undergoes a red shift and change of shape (time constant 140 fs) with a well-defined isosbestic point. After 300 fs solvation becomes apparent. The early transient spectrum is assigned to the locally excited state of DCM.
Li, Ying; Gao, Xiao Bing; Sakurai, Takeshi; van den Pol, Anthony N
2002-12-19
Neurons that release hypocretin/orexin modulate sleep, arousal, and energy homeostasis; the absence of hypocretin results in narcolepsy. Here we present data on the physiological characteristics of these cells, identified with GFP in transgenic mouse brain slices. Hypocretin-1 and -2 depolarized hypocretin neurons by 15mV and evoked an increase in spike frequency (+366% from a 1-3 Hz baseline). The mechanism for this appears to be hypocretin-mediated excitation of local glutamatergic neurons that regulate hypocretin neuron activity, in part by presynaptic facilitation of glutamate release. This represents a possible mechanism for orchestrating the output of the diffuse hypothalamic arousal system. No direct effect of hypocretin on membrane properties of hypocretin cells was detected. Norepinephrine and serotonin, transmitters of other arousal systems, decreased spike frequency and evoked outward currents, whereas acetylcholine and histamine had little effect.
NASA Astrophysics Data System (ADS)
Ning, Jun; Nagata, Kotaro; Ainai, Akira; Hasegawa, Hideki; Kano, Hiroshi
2013-08-01
We report on a method to determine subtype of influenza viruses by using surface plasmons localized in microscopic region on a flat metal surface. In this method, refractive index variation arisen from interactions between viruses and their monoclonal antibodies is measured. The developed sensor shows stability of refractive index in the order of 10-4 against sample exchange. In our experiment, A/H1N1 viruses are distinguished from A/H3N2 viruses by using monoclonal antibodies immobilized on the metal surface. Since the measurement probe has the volume of ˜6 al, the method has potential to handle multiple subtypes in the measurement of a sample with ultra small volume.
Spin waves and magnetic excitations
Borovik-Romanov, A.S.; Sinha, S.K.
1988-01-01
This book describes both simple spin waves (magnons) and complicated excitations in magnetic systems. The following subjects are covered: - various methods of magnetic excitation investigations such as neutron scattering on magnetic excitations, spin-wave excitation by radio-frequency, power light scattering on magnons and magnetic excitation observation within the light-absorption spectrum; - oscillations of magnetic electron systems coupled with phonons, nuclear spin systems and localized impurity modes: - low-dimensional magnetics, amorphous magnetics and spin glasses.
Thermodynamic properties of the periodic Anderson model: X-boson treatment
NASA Astrophysics Data System (ADS)
Franco, R.; Figueira, M. S.; Foglio, M. E.
2003-11-01
We study the specific-heat dependence of the periodic Anderson model (PAM) in the limit of U=∞ employing the X-boson treatment in two different regimes of the PAM: the heavy fermion Kondo (HF-K) and the local magnetic moment regime (HF-LMM). We obtain a multiple peak structure for the specific heat in agreement with the experimental results as well as the increase of the electronic effective mass at low temperatures associated with the HF-K regime. The entropy per site at low T tends to zero in the HF-K regime, corresponding to a singlet ground state, and it tends to kBln 2 in the HF-LMM, corresponding to a doublet ground state at each site. The linear coefficient γ(T)=Cv(T)/T of the specific heat qualitatively agrees with the experimental results obtained for different materials in the two regimes considered here.
Note: Work function change measurement via improved Anderson method
Sabik, A. Gołek, F.; Antczak, G.
2015-05-15
We propose the modification to the Anderson method of work function change (Δϕ) measurements. In this technique, the kinetic energy of the probing electrons is already low enough for non-destructive investigation of delicate molecular systems. However, in our implementation, all electrodes including filament of the electron gun are polarized positively. As a consequence, electron bombardment of any elements of experimental system is eliminated. Our modification improves cleanliness of the ultra-high vacuum system. As an illustration of the solution capabilities, we present Δϕ of the Ag(100) surface induced by cobalt phthalocyanine layers.
The S=1 Underscreened Anderson Lattice model for Uranium compounds
NASA Astrophysics Data System (ADS)
Thomas, C.; Simões, A. S. R.; Iglesias, J. R.; Lacroix, C.; Perkins, N. B.; Coqblin, B.
2011-01-01
Magnetic properties of uranium and neptunium compounds showing coexistence of the Kondo effect and ferromagnetic order are investigated within the degenerate Anderson Lattice Hamiltonian, describing a 5f2 electronic configuration with S = 1 spins. Through the Schrieffer-Wolff transformation, both an exchange Kondo interaction for the S = 1 f-spins and an effective f-band term are obtained, allowing to describe the coexistence of Kondo effect and ferromagnetic ordering and a weak delocalization of the 5f-electrons. We calculate the Kondo and Curie temperatures and we can account for the pressure dependence of the Curie temperature of UTe.
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.
Applying a southern solvent: an interview with Warwick Anderson.
Anderson, Warwick; Cueto, Marcos; Santos, Ricardo Ventura
2016-12-01
An interview by the editor and a member of the scientific board of História, Ciências, Saúde - Manguinhos with Warwick Anderson, a leading historian of science and race from Australia. He talks about his training, positions he held at US universities, his publications, and his research at the University of Sydney. He discusses his current concern with the circulation of racial knowledge and biological materials as well as with the construction of networks of racial studies in the global south during the twentieth century. He also challenges the traditional historiography of science, which conventionally has been told from a Eurocentric perspective.
Collective Kondo effect in the Anderson-Hubbard lattice
NASA Astrophysics Data System (ADS)
Fazekas, P.; Itai, K.
1997-02-01
The periodic Anderson model is extended by switching on a Hubbard U for the conduction electrons. We use the Gutzwiller variational method to study the nearly integral valent limit. The lattice Kondo energy contains the U-dependent chemical potential of the Hubbard subsystem in the exponent, and the correlation-induced band narrowing in the prefactor. Both effects tend to suppress the Kondo scale, which can be understood to result from the blocking of hybridization. At half-filling, we find a Brinkman-Rice-type transition from a Kondo insulator to a Mott insulator.
Price-Anderson Nuclear Safety Enforcement Program. 1996 Annual report
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.
Giant charge relaxation resistance in the Anderson model.
Filippone, Michele; Le Hur, Karyn; Mora, Christophe
2011-10-21
We investigate the dynamical charge response of the Anderson model viewed as a quantum RC circuit. Applying a low-energy effective Fermi liquid theory, a generalized Korringa-Shiba formula is derived at zero temperature, and the charge relaxation resistance is expressed solely in terms of static susceptibilities which are accessible by Bethe ansatz. We identify a giant charge relaxation resistance at intermediate magnetic fields related to the destruction of the Kondo singlet. The scaling properties of this peak are computed analytically in the Kondo regime. We also show that the resistance peak fades away at the particle-hole symmetric point.
Note: Work function change measurement via improved Anderson method.
Sabik, A; Gołek, F; Antczak, G
2015-05-01
We propose the modification to the Anderson method of work function change (Δϕ) measurements. In this technique, the kinetic energy of the probing electrons is already low enough for non-destructive investigation of delicate molecular systems. However, in our implementation, all electrodes including filament of the electron gun are polarized positively. As a consequence, electron bombardment of any elements of experimental system is eliminated. Our modification improves cleanliness of the ultra-high vacuum system. As an illustration of the solution capabilities, we present Δϕ of the Ag(100) surface induced by cobalt phthalocyanine layers.
Probability Density Function at the 3D Anderson Transition
NASA Astrophysics Data System (ADS)
Rodriguez, Alberto; Vasquez, Louella J.; Roemer, Rudolf
2009-03-01
The probability density function (PDF) for the wavefunction amplitudes is studied at the metal-insulator transition of the 3D Anderson model, for very large systems up to L^3=240^3. The implications of the multifractal nature of the state upon the PDF are presented in detail. A formal expression between the PDF and the singularity spectrum f(α) is given. The PDF can be easily used to carry out a numerical multifractal analysis and it appears as a valid alternative to the more usual approach based on the scaling law of the general inverse participation rations.
STS-118 Astronauts Rick Mastracchio and Clay Anderson Perform EVA
NASA Technical Reports Server (NTRS)
2007-01-01
As the construction continued on the International Space Station (ISS), STS-118 astronaut and mission specialist Rick Mastracchio was anchored on the foot restraint of the Canadarm2 as he participated in the third session of Extra Vehicular Activity (EVA) for the mission. Assisting Mastracchio was Expedition 15 flight engineer Clay Anderson (out of frame). During the 5 hour, 28 minute space walk, the two relocated the S-band Antenna Sub-Assembly from the Port 6 (P6) truss to the Port 1 (P1) truss, installed a new transponder on P1 and retrieved the P6 transponder.
NASA Astrophysics Data System (ADS)
Gálisová, Lucia; Strečka, Jozef
2015-02-01
A hybrid spin-electron system defined on a one-dimensional double-tetrahedral chain, in which the localized Ising spin regularly alternates with two mobile electrons delocalized over a triangular plaquette, is exactly solved with the help of generalized decoration-iteration transformation. It is shown that a macroscopic degeneracy of ferromagnetic and ferrimagnetic ground states arising from chiral degrees of freedom of the mobile electrons cannot be lifted by a magnetic field in contrast to a macroscopic degeneracy of the frustrated ground state, which appears due to a kinetically driven frustration of the localized Ising spins. An anomalous behavior of all basic thermodynamic quantities can be observed on account of massive thermal excitations, which mimic a temperature-driven first-order phase transition from the nondegenerate frustrated state to the highly degenerate ferrimagnetic state at nonzero magnetic fields. A substantial difference in the respective degeneracies is responsible for an immense low-temperature peak of the specific heat and very abrupt (almost discontinuous) thermal variations of the entropy and sublattice magnetizations.
Giovannini, L.; Montoncello, F.; Nizzoli, F.; Vavassori, P.; Grimsditch, M.
2011-11-04
The authors reported in their letter some outstanding experimental results of spin excitations in nano-particles investigated by near-field Brillouin scattering. They conclude from their observations that existing theories -- in particular micromagnetic simulations -- do not correctly describe the behavior of the spin modes. Since excellent agreement has been reported between spin-wave mode frequencies obtained from Brillouin scattering experiments and those obtained from micromagnetic-based simulations, it is somewhat surprising that the simulations should fail for the particles investigated in Ref. 1. In the literature, there is also evidence of various kinds and degrees of mode localization when exchange competes with dipolar interactions. When dipolar long-range interactions are taken into account, the eigenmodes can be seen as the superposition of plane waves, leading to different localizations and in particular to the appearence of bulk-dead modes. We have simulated the normal modes of the particles used in Ref. 1, with the dynamical matrix method; the results are shown in Fig. 1 for different values of the applied field. In addition to the lowest frequency non-localized mode (1-BA), several localized modes are present. Large particles exhibit modes with oscillations along the field direction;8 for such modes, we use the label n-BA-loc, with n the number of nodes. While the profile of the pure end-mode, i.e., 0-BA-loc, has its maximum at the edge with the amplitude monotonously decreasing toward the interior of the ellipse, as correctly described by the authors, the localized modes with n > 0, not considered by them, do not have this characteristic: see inset of Fig. 1. Based on Fig. 1, we believe that the assumption that the mode they observe is 'the' localized spin mode is not correct. Instead, we believe that the mode detected in the experiment at H > 700 Oe is a combinations (due to non-linear excitation conditions of the experiment) of several n
Bray, James William [Niskayuna, NY; Garces, Luis Jose [Niskayuna, NY
2012-03-13
The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.
Effects of correlated hybridization in the single-impurity Anderson model
NASA Astrophysics Data System (ADS)
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.
Otton, J.K.; Bradbury, J.P.; Forester, R.M.; Hanley, J.H.
1990-01-01
The Tertiary sedimentary sequence of the Date Creek basin area of Arizona is composed principally of intertonguing alluvial-fan and lacustrine deposits. The lacustrine rocks contain large intermediate- to, locally, high-grade uranium deposits that form one of the largest uranium resources in the United States (an estimated 670,000 tons of U3O8 at an average grade of 0.023% is indicated by drilling to date). At the Anderson mine, about 50,000 tons of U3O8 occurs in lacustrine carbonaceous siltstones and mudstones (using a cutoff grade of 0.01%). The Anderson mine constitutes a new class of ore deposit, a lacustrine carbonaceous uranium deposit. Floral and faunal remains at the Anderson mine played a critical role in creating and documenting conditions necessary for uranium mineralization. Organic-rich, uraniferous rocks at the Anderson mine contain plant remains and ostracodes having remarkably detailed preservation of internal features because of infilling by opaline silica. This preservation suggests that the alkaline lake waters in the mine area contained high concentrations of dissolved silica and that silicification occurred rapidly, before compaction or cementation of the enclosing sediment. Uranium coprecipitated with the silica. Thinly laminated, dark-colored, siliceous beds contain centric diatoms preserved with carbonaceous material suggesting that lake waters at the mine were locally deep and anoxic. These alkaline, silica-charged waters and a stagnant, anoxic environment in parts of the lake were necessary conditions for the precipitation of large amounts of uranium in the lake-bottom sediments. Sediments at the Anderson mine contain plant remains and pollen that were derived from diverse vegetative zones suggesting about 1500 m of relief in the area at the time of deposition. The pollen suggests that the valley floor was semiarid and subtropical, whereas nearby mountains supported temperate deciduous forests. ?? 1990.
Danzer, Steve C; McNamara, James O
2004-12-15
Hippocampal dentate granule cells directly excite and indirectly inhibit CA3 pyramidal cells via distinct presynaptic terminal specializations of their mossy fiber axons. This mossy fiber pathway contains the highest concentration of brain-derived neurotrophic factor (BDNF) in the CNS, yet whether BDNF is positioned to regulate the excitatory and/or inhibitory pathways is unknown. To localize BDNF, confocal microscopy of green fluorescent protein transgenic mice was combined with BDNF immunohistochemistry. Approximately half of presynaptic granule cell-CA3 pyramidal cell contacts were found to contain BDNF. Moreover, enhanced neuronal activity virtually doubled the percentage of BDNF-immunoreactive terminals contacting CA3 pyramidal cells. To our surprise, BDNF was also found in mossy fiber terminals contacting inhibitory neurons. These studies demonstrate that mossy fiber BDNF is poised to regulate both direct excitatory and indirect feedforward inhibitory inputs to CA3 pyramdal cells and reveal that seizure activity increases the pool of BDNF-expressing granule cell presynaptic terminals contacting CA3 pyramidal cells.
Award for Distinguished Scientific Early Career Contributions to Psychology: Adam K. Anderson
ERIC Educational Resources Information Center
American Psychologist, 2009
2009-01-01
Adam K. Anderson, recipient of the Award for Distinguished Scientific Early Career Contributions to Psychology, is cited for his outstanding contribution to understanding the representation of emotion and its influence on cognition. By combining psychological and neuroscience techniques with rigorous and creative experimental designs, Anderson has…
Finite-size corrections for ground states of Edwards-Anderson spin glasses
NASA Astrophysics Data System (ADS)
Boettcher, Stefan; Falkner, Stefan
2012-05-01
Extensive computations of ground-state energies of the Edwards-Anderson spin glass on bond-diluted, hypercubic lattices are conducted in dimensions d=3, ..., 7. Results are presented for bond densities exactly at the percolation threshold, p=pc, and deep within the glassy regime, p>pc, where finding ground states is one of the hardest combinatorial optimization problems. Finite-size corrections of the form 1/Nω are shown to be consistent throughout with the prediction ω=1-y/d, where y refers to the "stiffness" exponent that controls the formation of domain wall excitations at low temperatures. At p=pc, an extrapolation for d→∞ appears to match our mean-field results for these corrections. In the glassy phase, however, ω does not approach its anticipated mean-field value of 2/3, obtained from simulations of the Sherrington-Kirkpatrick spin glass on an N-clique graph. Instead, the value of ω reached at the upper critical dimension matches another type of mean-field spin glass models, namely those on sparse random networks of regular degree called Bethe lattices.
NASA Astrophysics Data System (ADS)
Hübsch, A.; Becker, K. W.
2005-04-01
In this paper a recently developed projector-based renormalization method (PRM) for many-particle Hamiltonians is applied to the periodic Anderson model with the aim to describe heavy-fermion behavior. In this method high-energetic excitation operators instead of high energetic states are eliminated. We arrive at an effective Hamiltonian for a quasifree system which consists of two noninteracting heavy-quasiparticle bands. The resulting renormalization equations for the parameters of the Hamiltonian are valid for large as well as small degeneracy νf of the angular momentum. An expansion in 1/νf is avoided. Within an additional approximation which adapts the idea of a fixed renormalized f level ɛ˜f , we obtain coupled equations for ɛ˜f and the averaged f occupation ⟨nf⟩ . These equations resemble to a certain extent those of the usual slave boson mean-field (SB) treatment. In particular, for large νf the results for the PRM and the SB approach agree perfectly whereas considerable differences are found for small νf .
Renormalization flow of the hierarchical Anderson model at weak disorder
NASA Astrophysics Data System (ADS)
Metz, F. L.; Leuzzi, L.; Parisi, G.
2014-02-01
We study the flow of the renormalized model parameters obtained from a sequence of simple transformations of the 1D Anderson model with long-range hierarchical hopping. Combining numerical results with a perturbative approach for the flow equations, we identify three qualitatively different regimes at weak disorder. For a sufficiently fast decay of the hopping energy, the Cauchy distribution is the only stable fixed point of the flow equations, whereas for sufficiently slowly decaying hopping energy the renormalized parameters flow to a δ-peak fixed-point distribution. In an intermediate range of the hopping decay, both fixed-point distributions are stable and the stationary solution is determined by the initial configuration of the random parameters. We present results for the critical decay of the hopping energy separating the different regimes.
Nonequilibrium Anderson model made simple with density functional theory
NASA Astrophysics Data System (ADS)
Kurth, S.; Stefanucci, G.
2016-12-01
The single-impurity Anderson model is studied within the i-DFT framework, a recently proposed extension of density functional theory (DFT) for the description of electron transport in the steady state. i-DFT is designed to give both the steady current and density at the impurity, and it requires the knowledge of the exchange-correlation (xc) bias and on-site potential (gate). In this work we construct an approximation for both quantities which is accurate in a wide range of temperatures, gates, and biases, thus providing a simple and unifying framework to calculate the differential conductance at negligible computational cost in different regimes. Our results mark a substantial advance for DFT and may inform the construction of functionals applicable to other correlated systems.
Multi-level Algorithm for the Anderson Impurity Model
NASA Astrophysics Data System (ADS)
Chandrasekharan, S.; Yoo, J.; Baranger, H. U.
2004-03-01
We develop a new quantum Monte Carlo algorithm to solve the Anderson impurity model. Instead of integrating out the Fermions, we work in the Fermion occupation number basis and thus have direct access to the Fermionic physics. The sign problem that arises in this formulation can be solved by a multi-level technique developed by Luscher and Weisz in the context of lattice QCD [JHEP, 0109 (2001) 010]. We use the directed-loop algorithm to update the degrees of freedom. Further, this algorithm allows us to work directly in the Euclidean time continuum limit for arbitrary values of the interaction strength thus avoiding time discretization errors. We present results for the impurity susceptibility and the properties of the screening cloud obtained using the algorithm.
The topological Anderson insulator phase in the Kane-Mele model
Orth, Christoph P.; Sekera, Tibor; Bruder, Christoph; Schmidt, Thomas L.
2016-01-01
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. PMID:27045779
Path to poor coherence in the periodic Anderson model from Mott physics and hybridization
NASA Astrophysics Data System (ADS)
Amaricci, A.; de'Medici, L.; Sordi, G.; Rozenberg, M. J.; Capone, M.
2012-06-01
We investigate the anomalous metal arising from hole-doping the Mott insulating state in the periodic Anderson model. Using dynamical mean-field theory we show that, as opposed to the electron-doped case, in the hole-doped regime the hybridization between localized and delocalized orbitals leads to the formation of composite quasiparticles reminiscent of the Zhang-Rice singlets. We compute the coherence temperature of this state, showing its extremely small value at low doping. As a consequence the weakly doped Mott state deviates from the predictions of Fermi-liquid theory already at small temperatures. The onset of the Zhang-Rice state and of the consequent poor coherence is due to the electronic structure in which both localized and itinerant carriers have to be involved in the formation of the conduction states and to the proximity to the Mott state. By investigating the magnetic properties of this state, we discuss the relation between the anomalous metallic properties and the behavior of the magnetic degrees of freedom.
Quantum Monte Carlo investigation of Knight shift anomaly in Periodic Anderson model
NASA Astrophysics Data System (ADS)
Jiang, Mi; Curro, Nicholas; Scalettar, Richard; UC Davis Team; UC Davis Team
2014-03-01
We report a Determinant Quantum Monte Carlo investigation of the Knight shift anomaly observed in nuclear magnetic resonance (NMR) of heavy fermion materials. As opposed to normal Fermi liquids, the Knight shift in heavy fermion materials deviates from the total susceptibility χ below a crossover temperature T*. This deviation is believed to originate in the different temperature dependence of the conduction electron and local moment components of the total susceptibility χ. Here we quantify the behavior of χcc(T) ,χcf(T) , and χff(T) in the framework of periodic Anderson model (PAM), focussing on the evolution with different degree of conduction electron-local moment hybridization. These results confirm several predictions of the two-fluid theory of the Knight shift anomaly, including the demonstration of a universal logarithmic divergence of the contribution of the heavy electrons to the Knight shift. This universal behavior, which occurs with decreasing temperature below T* in the paramagnetic state, agrees well with experimental findings, and indicates that different heavy fermion materials exhibit a common scaling, differing only in the coherence temperature scale, T*.
Correlation Effects in One-Dimensional Quasiperiodic Anderson-Lattice Model
NASA Astrophysics Data System (ADS)
Matsuda, Fuyuki; Tezuka, Masaki; Kawakami, Norio
We consider the one-dimensional (1D) quasiperiodic Anderson-lattice model, which has quasiperiodically ordered impurities. The sites with an f-orbital are ordered as a "Fibonacci word", one way to form 1D quasiperiodic orderings. To treat the correlation effect precisely, we use the density matrix renormalization group (DMRG) method. We show that the spin correlation function in the quasiperiodic system gives a characteristic pattern. Also, by analyzing the f-electron number and its fluctuation, we find that a valence transition, which usually occurs in the periodic Anderson model when the on-site interorbital interaction is large, is not sharp in the quasiperiodic system. Finally, we discuss the properties of the quasiperiodic Anderson-lattice model, comparing them against the Anderson-lattice model with randomly located f-orbitals. We find that the quasiperiodic Anderson-lattice model has a similar property to the periodic Anderson model for spin correlation, but also has a similar property to the Anderson-lattice model with randomly located f-orbitals for the valence fluctuation.
Random Walks in Anderson's Garden: A Journey from Cuprates to Cooper Pair Insulators and Beyond
NASA Astrophysics Data System (ADS)
Baskaran, G.
Anderson's Garden is a drawing presented to Philip W. Anderson on the eve of his 60th birthday celebration, in 1983, by a colleague (author unknown). This cartoon (Fig. 1) succinctly depicts some of Anderson's pre-1983 works. As an avid reader of Anderson's papers, a random walk in Anderson's garden had become a part of my routine since graduate school days. This was of immense help and prepared me for a wonderful collaboration with Anderson on the theory of high-Tc cuprates and quantum spin liquids at Princeton. Here I narrate this story, ending with a brief summary of my ongoing theoretical efforts to extend Anderson's RVB theory for superconductivity to encompass the recently observed high-temperature (Tc ~ 203K) superconductivity in solid H2S at pressure ~200GPa. In H2S molecule, four valence electrons form two saturated covalent bonds, H-S-H. These bond singlets are confined Cooper pairs close to chemical potential. Solid H2S is a Cooper pair insulator. Pressure changes the structure and not the number of valence electrons. Bond singlet pairing tendency continues and new S-S and H-H bonds are formed. S-S bonds are mostly saturated. However, hydrogen sublattice has unsaturated H-H bonds. It prepares ground for a RVB superconducting state.
Front interaction induces excitable behavior
NASA Astrophysics Data System (ADS)
Parra-Rivas, P.; Matías, M. A.; Colet, P.; Gelens, L.; Walgraef, D.; Gomila, D.
2017-02-01
Spatially extended systems can support local transient excitations in which just a part of the system is excited. The mechanisms reported so far are local excitability and excitation of a localized structure. Here we introduce an alternative mechanism based on the coexistence of two homogeneous stable states and spatial coupling. We show the existence of a threshold for perturbations of the homogeneous state. Subthreshold perturbations decay exponentially. Superthreshold perturbations induce the emergence of a long-lived structure formed by two back to back fronts that join the two homogeneous states. While in typical excitability the trajectory follows the remnants of a limit cycle, here reinjection is provided by front interaction, such that fronts slowly approach each other until eventually annihilating. This front-mediated mechanism shows that extended systems with no oscillatory regimes can display excitability.
The completeness problem in the impurity Anderson model
NASA Astrophysics Data System (ADS)
Lobo, T.; Figueira, M. S.; Franco, R.; Silva-Valencia, J.; Foglio, M. E.
2007-09-01
With the recent development of the nanoscopic technology, the impurity Anderson model (AIM) was experimentally realized in quantum dot devices, and there is renewed interest in the study of the Kondo physics of the AIM. Several Green's functions approximations by the equation of motion method (EOM), that incorporates the Kondo effect through a digamma function, have been presented in the literature as an adequate tool to describe, at least qualitatively, the Kondo effect. However, these approximations present several drawbacks: they are no longer valid as the temperature decreases below the Kondo temperature, because the logarithmic divergence of the digamma function makes the spectral density at the chemical potential to vanish, and the Friedel sum rule and the completeness in the occupation numbers are not fulfilled. In this work we present a critical discussion comparing the results of digamma approximations GF with the atomic approach, recently developed by some of us, that satisfy the completeness and the Friedel sum rule. We present results for the density of states, the Friedel sum rule and the completeness.
Magnetic susceptibility for a two-channel Anderson model
NASA Astrophysics Data System (ADS)
Líbero, Valter L.; Ferreira, João V. B.; Oliveira, Luiz N.; Cox, Daniel L.
2001-03-01
Non-Fermi-liquid magnetic properties are studied using a generalized two-channel Anderson model suitable for compounds like U_xTh_1-xRu_2Si2 or La_1-xCe_xCu_2.2Si2 in the low concentration regime, for which single-site characteristics of the f-electrons are experimentally evident^1. The model encompasses a spin doublet and two (degenerate) channel doublets as impurity levels, opening two channels in the conduction band, with hybridization strength V1 and V_2. The interleaving Numerical Renormalization Group procedure^2,3 determines the temperature-dependent susceptibility \\chi. For the isotropic case V_1=V2 non-Fermi liquid behavior, \\chi ≈ -ln T, is obtained. This non-trivial fixed-point, however, is unstable against channel anisotropy: for V1 ne V2 normal-Fermi liquid behavior is recovered. 1- Tae-Suk Kim and D. L. Cox, Phys. Rev. Lett. 75, 1622 (1995). 2- S. C. Costa, C. A. Paula, V. L. Líbero and L. N. Oliveira, Phys. Rev. B 55, 30 (1997). 3- J. V. B. Ferreira and V. L. Líbero, Phys. Rev. B 61, 10615 (2000).
Sohn, Woon Yong; Brenner, Valérie; Gloaguen, Eric; Mons, Michel
2016-11-02
Conformer-selective IR gas phase spectroscopy and high level quantum chemistry methods have been used to characterise the diversity of local NH-π interactions between the π ring of a phenylalanine aromatic residue and the nearby main chain amide groups. The study of model systems shows how the amide NH stretch vibrational features, in the 3410-3460 cm(-1) frequency range, can be used to monitor the strength of these local π H-bonds, which is found to depend on both the backbone conformation and the aromatic side chain orientation. This is rationalized in terms of partial electron transfer between the π cloud and the main chain NH bonds, with the help of analysis tools based on Natural Bonding Orbitals and Non-Covalent Interactions plots. The experimental study, extended to the NH-π interactions when the Phe residue is excited in its first ππ* electronic state, also demonstrates the principle of the ππ* labelling technique, i.e. a selective labelling of those NH bonds in a peptide molecule that are in close contact with an aromatic ring, as an elegant tool for IR spectroscopic assignments. The validation of theoretical predictions against experimental data (frequency change upon excitation) eventually qualifies the use of the CC2 method for the description of the ππ* excited states of systems having a phenyl ring, both in terms of structure, vibrational modes and nature of excited states.
Benjamin A. Frandsen; Brunelli, Michela; Page, Katharine; ...
2016-05-11
Here, 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 dominatedmore » 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. Furthermore, the Anderson superexchange model for MnO is thus verified by experimentation and confirmed by ab initio theory.« less
NASA Astrophysics Data System (ADS)
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.
Hormonal profile and fertility in patients with Anderson-Fabry disease.
Hauser, A C; Gessl, A; Harm, F; Wiesholzer, M; Kleinert, J; Wallner, M; Voigtländer, T; Bieglmayer, C; Sunder-Plassmann, G
2005-09-01
Anderson-Fabry disease is a glycosphingolipid storage disorder with an X-linked recessive inheritance. The alpha-galactosidase A deficiency leads to a progressive accumulation of globotriaosylceramide in the endothelium and tissue cells of various organs. The kidney, heart and brain are predominantly affected. Reports on endocrine function and fertility rates in patients with Anderson-Fabry disease are sparse. In the present study, we assessed ovarian, testicular and adrenal function in a cohort of patients with Anderson-Fabry disease. Plasma follicle-stimulating hormone, luteinizing hormone, prolactin, estradiol, testosterone, sex hormone-binding globulin, somatotropin, insulin-like growth factor-I and serum cortisol were measured in 13 patients (six female and seven male), currently observed in an outpatient clinic. The profile revealed an undisturbed hormonal function and a normal fertility rate in both male and female Anderson-Fabry patients when compared with the corresponding Austrian population.
Anderson localisation and optical-event horizons in rogue-soliton generation
NASA Astrophysics Data System (ADS)
Saleh, Mohammed F.; Conti, Claudio; Biancalana, Fabio
2017-03-01
We unveil the relation between the linear Anderson localisation process and nonlinear modulation instability. Anderson localised modes are formed in certain temporal intervals due to the random background noise. Such localised modes seed the formation of solitary waves that will appear during the modulation instability process at those preferred intervals. Afterwards, optical-event horizon effects between dispersive waves and solitons produce an artificial collective acceleration that favours the collision of solitons, which could eventually lead to a rogue-soliton generation.
Adaptive Thouless-Anderson-Palmer approach to inverse Ising problems with quenched random fields
NASA Astrophysics Data System (ADS)
Huang, Haiping; Kabashima, Yoshiyuki
2013-06-01
The adaptive Thouless-Anderson-Palmer equation is derived for inverse Ising problems in the presence of quenched random fields. We test the proposed scheme on Sherrington-Kirkpatrick, Hopfield, and random orthogonal models and find that the adaptive Thouless-Anderson-Palmer approach allows accurate inference of quenched random fields whose distribution can be either Gaussian or bimodal. In particular, another competitive method for inferring external fields, namely, the naive mean field method with diagonal weights, is compared and discussed.
A new dataset of Wood Anderson magnitude from the Trieste (Italy) seismic station
NASA Astrophysics Data System (ADS)
Sandron, Denis; Gentile, G. Francesco; Gentili, Stefania; Rebez, Alessandro; Santulin, Marco; Slejko, Dario
2014-05-01
The standard torsion Wood Anderson (WA) seismograph owes its fame to the fact that historically it has been used for the definition of the magnitude of an earthquake (Richter, 1935). With the progress of the technology, digital broadband (BB) seismographs replaced it. However, for historical consistency and homogeneity with the old seismic catalogues, it is still important continuing to compute the so called Wood Anderson magnitude. In order to evaluate WA magnitude, the synthetic seismograms WA equivalent are simulated convolving the waveforms recorded by a BB instrument with a suitable transfer function. The value of static magnification that should be applied in order to simulate correctly the WA instrument is debated. The original WA instrument in Trieste operated from 1971 to 1992 and the WA magnitude (MAW) estimates were regularly reported in the seismic station bulletins. The calculation of the local magnitude was performed following the Richter's formula (Richter, 1935), using the table of corrections factor unmodified from those calibrated for California and without station correction applied (Finetti, 1972). However, the WA amplitudes were computed as vector sum rather than arithmetic average of the horizontal components, resulting in a systematic overestimation of approximately 0.25, depending on the azimuth. In this work, we have retrieved the E-W and N-S components of the original recordings and re-computed MAW according to the original Richter (1935) formula. In 1992, the WA recording were stopped, due to the long time required for the daily development of the photographic paper, the costs of the photographic paper and the progress of the technology. After a decade of interruption, the WA was recovered and modernized by replacing the recording on photographic paper with an electronic device and it continues presently to record earthquakes. The E-W and N-S components records were memorized, but not published till now. Since 2004, next to the WA (few
Magnetic order and Kondo effect in the Anderson-lattice model
NASA Astrophysics Data System (ADS)
Bernhard, B. H.; Aguiar, C.; Kogoutiouk, I.; Coqblin, B.
The Anderson-lattice model has been extensively developed to account for the properties of many anomalous rare-earth compounds and in particular for the competition between the Kondo effect and an antiferromagnetic (AF) phase in a cubic lattice. Here we apply the higher-order decoupling of the equations of motion for the Green Functions (GF) introduced in [H.G. Luo, S.J. Wang, Phys. Rev. B 62 (2000) 1485]. We obtain an improved description of the phase diagram, where the AF phase subsists in a smaller range of the model parameters. As higher-order GF are included in the chain of equations, we are able to calculate directly the local spin-flip correlation function
Superconducting pairing of interacting electrons: implications from the two-impurity Anderson model
NASA Astrophysics Data System (ADS)
Zhu, Lijun; Zhu, Jian-Xin
2011-03-01
We study the non-local superconducting pairing of two interacting Anderson impurities, which has an instability near the quantum critical point from the competition between the Kondo effect and an antiferromagnetic inter-impurity spin exchange interaction. As revealed by the dynamics over the whole energy range, the superconducting pairing fluctuations acquire considerable strength from an energy scale much higher than the characteristic spin fluctuation scale while the low energy behaviors follow those of the staggered spin susceptibility. We argue that the superconducting pairing might not need the spin fluctuations as the glue, but rather originated from the effective Coulomb interaction. On the other hand, critical spin fluctuations in the vicinity of quantum criticality are also crucial to a superconducting pairing instability, by preventing a Fermi liquid fixed point being reached to keep the superconducting pairing fluctuations finite at low energies. A superconducting order, to reduce the accumulated entropy carried by the critical degrees of freedom, may arise favorably from this instability. This work is supported by the U.S. DOE through the LANL/LDRD program.
Parabolic Anderson Model in a Dynamic Random Environment: Random Conductances
NASA Astrophysics Data System (ADS)
Erhard, D.; den Hollander, F.; Maillard, G.
2016-06-01
The parabolic Anderson model is defined as the partial differential equation ∂ u( x, t)/ ∂ t = κ Δ u( x, t) + ξ( x, t) u( x, t), x ∈ ℤ d , t ≥ 0, where κ ∈ [0, ∞) is the diffusion constant, Δ is the discrete Laplacian, and ξ is a dynamic random environment that drives the equation. The initial condition u( x, 0) = u 0( x), x ∈ ℤ d , is typically taken to be non-negative and bounded. The solution of the parabolic Anderson equation describes the evolution of a field of particles performing independent simple random walks with binary branching: particles jump at rate 2 d κ, split into two at rate ξ ∨ 0, and die at rate (- ξ) ∨ 0. In earlier work we looked at the Lyapunov exponents λ p(κ ) = limlimits _{tto ∞} 1/t log {E} ([u(0,t)]p)^{1/p}, quad p in {N} , qquad λ 0(κ ) = limlimits _{tto ∞} 1/2 log u(0,t). For the former we derived quantitative results on the κ-dependence for four choices of ξ : space-time white noise, independent simple random walks, the exclusion process and the voter model. For the latter we obtained qualitative results under certain space-time mixing conditions on ξ. In the present paper we investigate what happens when κΔ is replaced by Δ𝓚, where 𝓚 = {𝓚( x, y) : x, y ∈ ℤ d , x ˜ y} is a collection of random conductances between neighbouring sites replacing the constant conductances κ in the homogeneous model. We show that the associated annealed Lyapunov exponents λ p (𝓚), p ∈ ℕ, are given by the formula λ p({K} ) = {sup} {λ p(κ ) : κ in {Supp} ({K} )}, where, for a fixed realisation of 𝓚, Supp(𝓚) is the set of values taken by the 𝓚-field. We also show that for the associated quenched Lyapunov exponent λ 0(𝓚) this formula only provides a lower bound, and we conjecture that an upper bound holds when Supp(𝓚) is replaced by its convex hull. Our proof is valid for three classes of reversible ξ, and for all 𝓚
ERIC Educational Resources Information Center
Wright, Bradford L.
1975-01-01
Advocates the creation of swimming pool oscillations as part of a general investigation of mechanical oscillations. Presents the equations, procedure for deriving the slosh modes, and methods of period estimation for exciting swimming pool oscillations. (GS)
Attractive Hubbard model with disorder and the generalized Anderson theorem
Kuchinskii, E. Z. Kuleeva, N. A. Sadovskii, M. V.
2015-06-15
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{sub 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{sub c} (in the weak-coupling region) or significantly increase T{sub 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.
Localization of Bogoliubov quasiparticles in interacting Bose gases with correlated disorder
Lugan, P.; Sanchez-Palencia, L.
2011-07-15
We study the Anderson localization of Bogoliubov quasiparticles (elementary many-body excitations) in a weakly interacting Bose gas of chemical potential {mu} subjected to a disordered potential V. We introduce a general mapping (valid for weak inhomogeneous potentials in any dimension) of the Bogoliubov-de Gennes equations onto a single-particle Schroedinger-like equation with an effective potential. For disordered potentials, the Schroedinger-like equation accounts for the scattering and localization properties of the Bogoliubov quasiparticles. We derive analytically the localization lengths for correlated disordered potentials in the one-dimensional geometry. Our approach relies on a perturbative expansion in V/{mu}, which we develop up to third order, and we discuss the impact of the various perturbation orders. Our predictions are shown to be in very good agreement with direct numerical calculations. We identify different localization regimes: For low energy, the effective disordered potential exhibits a strong screening by the quasicondensate density background, and localization is suppressed. For high-energy excitations, the effective disordered potential reduces to the bare disordered potential, and the localization properties of quasiparticles are the same as for free particles. The maximum of localization is found at intermediate energy when the quasicondensate healing length is of the order of the disorder correlation length. Possible extensions of our work to higher dimensions are also discussed.
NASA Astrophysics Data System (ADS)
Hager, Gordon D.; Rotondaro, Matthew D.; Perram, Glen P.
2012-11-01
A mathematical method is described to compute the pressure dependent spectrum of the D1 and D2 lines of atomic cesium in the presence of argon. The method is based on the Anderson Tallman unified theory of pressure broadening in which the spectrum is determined form the Fourier transform of the auto-correlation function. The method uses modified potential energy surfaces of the ground and excited states that correlate to the 2S1/2 ground state and the 2P1/2 and 2P3/2excited states at large inter-nuclear separation. These surfaces are used to form interaction difference potentials to determine the auto-correlation function. In addition to being able to compute pressure dependent spectra that exhibit symmetry and far wing structure the method also allows us to compute the low pressure shift and broadening rates of the Lorentzian line core.
Localization oscillation in antidot lattices
NASA Astrophysics Data System (ADS)
Uryu, S.; Ando, T.
1998-06-01
The Anderson localization in square and hexagonal antidot lattices is numerically studied with the use of a Thouless number method. It is revealed that localization is very sensitive to the aspect ratio between the antidot diameter and the lattice constant. In a hexagonal lattice, both the Thouless number and the localization length oscillate with the period equal to the Al’tshuler-Aronov-Spivak oscillation. The oscillation is quite weak in a square lattice.
Shielding and localization in the presence of long-range hopping
NASA Astrophysics Data System (ADS)
Celardo, G. L.; Kaiser, R.; Borgonovi, F.
2016-10-01
We investigate a paradigmatic model for quantum transport with both nearest-neighbor and infinite-range hopping coupling (independent of the position). Due to long-range homogeneous hopping, a gap between the ground state and the excited states can be induced, which is mathematically equivalent to the superconducting gap. In the gapped regime, the dynamics within the excited-state subspace is shielded from long-range hopping, namely it occurs as if long-range hopping would be absent. This is a cooperative phenomenon since shielding is effective over a time scale that diverges with the system size. We named this effect cooperative shielding. We also discuss the consequences of our findings on Anderson localization. Long-range hopping is usually thought to destroy localization due to the fact that it induces an infinite number of resonances. Contrary to this common lore we show that the excited states display strong localized features when shielding is effective even in the regime of strong long-range coupling. A brief discussion on the extension of our results to generic power-law decaying long-range hopping is also given. Our preliminary results confirm that the effects found for the infinite-range case are generic.
Zhou, L.; Callcott, T.A.; Jia, J.J.
1997-04-01
Zn M{sub 2,3} soft x-ray fluorescence (SXF) spectra of ZnS and ZnS{sub .5}Se{sub .5} excited near threshold show strong inelastic scattering effects that can be explained using a simple model and an inelastic scattering theory based on second order perturbation theory. This scattering is often called electronic resonance Raman scattering. Tulkki and Aberg have developed this theory in detail for atomic systems, but their treatment can be applied to solid systems by utilizing electronic states characteristic of solids rather than of atomic systems.
NASA Astrophysics Data System (ADS)
Hidajatullah-Maksoed, Widastra
2015-04-01
Arthur Cayley at least investigate by creating the theory of permutation group[F:∖∖Group_theory.htm] where in cell elements addressing of the lattice Qmf used a Cayley tree, the self-afine object Qmf is described by the combination of the finite groups of rotation & inversion and the infinite groups of translation & dilation[G Corso & LS Lacena: ``Multifractal lattice and group theory'', Physica A: Statistical Mechanics &Its Applications, 2005, v 357, issue I, h 64-70; http://www.sciencedirect.com/science/articel/pii/S0378437105005005 ] hence multifractal can be related to group theory. Many grateful Thanks to HE. Mr. Drs. P. SWANTORO & HE. Mr. Ir. SARWONO KUSUMAATMADJA.
beta-Function of Anderson localization transition in three dimensions at unitary symmetry
NASA Astrophysics Data System (ADS)
Neogi, Sanghamitra
In recent years, with the advances in experimental techniques, the characteristic length scales of the materials synthesized, are becoming increasingly small. Many of these microscopic structures found their places in important commercial applications. However, the thermal loads imposed on these devices and structures create a major obstacle toward their applicability. This challenge is driving a renewed interest among researchers from various disciplines, toward the topic of thermal management. The interest in the topic of thermal transport in small scale structures, served as the motivation for the work performed in this dissertation. More specifically, the following topics were investigated: • Transport in One-Dimensional Nonlinear Systems: Thermal transport in materials can be explained in terms of the diffusive motion of the heat carriers at the microscopic level. An important and surprising situation emerges in some low dimensional model systems; the thermal conductivity diverges with system size. It was shown (Toda, 1979) that nonlinearity has an important effect on the heat transport in low dimensional systems. We investigate the transport of energy in a nonlinear one-dimensional chain. We show that solitons are spontaneous generated when we apply forcing functions at the end of the chain. We investigate the different characteristics of these solitons generated in the chain. • Transport in Fluids --- Study of Pair Distribution Function: Thermal transport in fluids depends on the distribution of particles in the fluid. It is well known that the two-particle distribution function can describe most of the thermodynamic properties for classical fluids in thermal equilibrium. We review the approximate integral equation theories (Percus-Yevick, Hypernetted chain approximation) to obtain the pair distribution functions of classical fluids. We find that these methods are highly dependent on the choice of the thermodynamic parameters of the fluid. We solve several Lennard-Jones fluid systems with different density and temperature values and prepare a density-temperature compressibility diagram. This diagram shows the region of applicability of these theories and helps us obtain the pair distribution function for a Lennard-Jones fluid with known thermodynamic parameters. We also suggest a modification of the integral-equation theories to obtain the pair distribution functions of quantum fluids. • Thermal Transport Across Interfaces: When thermal energy is transported from one material to another, there is a discontinuity in temperature at the interface between them. This thermal boundary resistance is known as Kapitza resistance. The scattering of phonons at interfaces is one of the main reasons behind the presence of thermal boundary resistance. We explore the scattering of acoustic waves at several solid-solid interfaces using lattice dynamical methods. We derive matrix equations to obtain the reflection and transmission coefficients for an acoustic wave incident on the interface. These coefficients can reproduce the familiar expressions in the continuum limit and are consistent with the conservation relations. We discuss a method to obtain the thermal boundary resistance for neutral solid-fluid interfaces. The acoustic mismatch theory works poorly for solid-fluid interfaces. One reason is that this theory only includes the long wavelength acoustic phonons. Our theory includes all the phonon modes in the solid and all the sound modes in the fluid, in the calculation of the thermal boundary resistance. We provide an application of this method to obtain the thermal boundary resistance at the interface between solid Argon and liquid Neon. Our method yields the value for Kapitza conductance for solid Argon-fluid Neon interface as 0.0374GW/Km2.
Mukhopadhyay, N.C.
1986-01-01
The status of the theory of the low-energy approach to hadron structure is reviewed briefly by surveying a few relevant models. A few examples of tests needed to sort out the predictions of different models pertaining to the quark-gluon structure of hadrons are discussed, and given the resulting physics objectives, a few experimental options for excited baryon research at CFBAF are suggested. (LEW)
Meuleman, G. Allyn
1986-05-01
This report presents an analysis of impacts on wildlife and their habitats as a result of construction and operation of the US Bureau of Reclamation's Anderson Ranch, Black Canyon, and Boise Diversion Projects in Idaho. The objectives were to: (1) determine the probable impacts of development and operation of the Anderson Ranch, Black Canyon, and Boise Diversion Projects to wildlife and their habitats; (2) determine the wildlife and habitat impacts directly attributable to hydroelectric development and operation; (3) briefly identify the current major concerns for wildlife in the vicinities of the hydroelectric projects; and (4) provide for consultation and coordination with interested agencies, tribes, and other entities expressing interest in the project.
Interaction effect in the Kondo energy of the periodic Anderson-Hubbard model
NASA Astrophysics Data System (ADS)
Itai, K.; Fazekas, P.
1996-07-01
We extend the periodic Anderson model by switching on a Hubbard U for the conduction band. The nearly integral valent limit of the Anderson-Hubbard model is studied with the Gutzwiller variational method. The lattice Kondo energy shows U dependence both in the prefactor and the exponent. Switching on U reduces the Kondo scale, which can be understood to result from the blocking of hybridization. At half filling, we find a Brinkman-Rice-type transition from a Kondo insulator to a Mott insulator. Our findings should be relevant for a number of correlated two-band models of recent interest.
NASA Astrophysics Data System (ADS)
Adamatzky, Andrew
2012-11-01
Excitable cellular automata with dynamical excitation interval exhibit a wide range of space-time dynamics based on an interplay between propagating excitation patterns which modify excitability of the automaton cells. Such interactions leads to formation of standing domains of excitation, stationary waves and localized excitations. We analyzed morphological and generative diversities of the functions studied and characterized the functions with highest values of the diversities. Amongst other intriguing discoveries we found that upper boundary of excitation interval more significantly affects morphological diversity of configurations generated than lower boundary of the interval does and there is no match between functions which produce configurations of excitation with highest morphological diversity and configurations of interval boundaries with highest morphological diversity. Potential directions of future studies of excitable media with dynamically changing excitability may focus on relations of the automaton model with living excitable media, e.g. neural tissue and muscles, novel materials with memristive properties and networks of conductive polymers.
Pajón-Suárez, Pedro; Rojas-Lorenzo, Germán A; Rubayo-Soneira, Jesús; Hernández-Lamoneda, Ramón; Larrégaray, Pascal
2009-12-31
The local relaxation of solid neon subsequent to the impulsive excitation of the NO chromophore to its A(3s sigma) Ryberg state is investigated using molecular dynamics simulations. This study makes use of empirical NO(X,A)-Ne isotropic pair potentials as well as a recently developed ab initio triatomic potential energy surface for the excited state. The role of these interaction potentials is analyzed, including many-body effects. In particular, empirical potentials, designed to reproduce correctly both the NO X-A steady-state absorption and emission bands, are shown to lead to a good description of the subpicosecond relaxation dynamics. The 600 fs expansion of the electronic bubble fairly agrees with experimental data. This relatively long time scale with respect to solid Argon, which was previously attributed to the range of the NO(A)-Ne interaction, is presumably related to the quantum nature of the medium. The time-resolved local relaxation of the Ne solid is understandably intermediate between that of classical solids (e.g., Ar) and that of quantum solids (e.g., H(2)).
Federal Register 2010, 2011, 2012, 2013, 2014
2010-02-24
... AGENCY Proposed CERCLA Administrative Settlement; Anderson-Calhoun Mine and Mill Site, Leadpoint, WA..., as amended (CERCLA), 42 U.S.C. 9622(i), notice is hereby given of a proposed administrative... 107(a) of CERCLA, 42 U.S.C. 9606 or 9607(a), for recovery of past costs and for the performance of...
Melissa L. Anderson: APA/APAGS Award for Distinguished Graduate Student in Professional Psychology
ERIC Educational Resources Information Center
American Psychologist, 2012
2012-01-01
Presents a short biography of the winner of the American Psychological Association/American Psychological Association of Graduate Students Award for Distinguished Graduate Student in Professional Psychology. The 2012 winner is Melissa L. Anderson for her ongoing commitment to understanding, treating, and preventing domestic violence in Deaf women…
Dystopian Visions of Global Capitalism: Philip Reeve's "Mortal Engines" and M.T Anderson's "Feed"
ERIC Educational Resources Information Center
Bullen, Elizabeth; Parsons, Elizabeth
2007-01-01
This article examines Philip Reeve's novel for children, "Mortal Engines", and M.T. Anderson's young adult novel, "Feed", by assessing these dystopias as prototypical texts of what Ulrich Beck calls risk society. Through their visions of a fictional future, the two narratives explore the hazards created by contemporary techno-economic progress,…
78 FR 41835 - Inflation Adjustments to the Price-Anderson Act Financial Protection Regulations
Federal Register 2010, 2011, 2012, 2013, 2014
2013-07-12
... Federal Regulations is sold by the Superintendent of Documents. #0;Prices of new books are listed in the... 3150-AJ25 Inflation Adjustments to the Price-Anderson Act Financial Protection Regulations AGENCY: Nuclear Regulatory Commission. ACTION: Final rule. SUMMARY: The Atomic Energy Act of 1954, as amended...
Adolescent Identities and Sexual Behavior: An Examination of Anderson's Player Hypothesis
ERIC Educational Resources Information Center
Giordano, Peggy C.; Longmore, Monica A.; Manning, Wendy D.; Northcutt, Miriam J.
2009-01-01
We investigate the social and behavioral characteristics of male adolescents who self-identify as players, focusing particularly on Anderson's claim that this social role is inextricably linked with poverty and minority status. Results indicate that black respondents, those affiliated with liberal peers and young men who initially report a…
Nonperturbative spectral-density function for the Anderson model at arbitrary temperatures
NASA Technical Reports Server (NTRS)
Neal, Henry L.
1991-01-01
Using a nonperturbative self-energy solution for the nondegenerate Anderson model, the temperature-dependent spectral-density function is calculated in the symmetric limit. The function is found to give reliable results for all values of the parameter u and inverse temperature beta.
High prevalence of subclinical hypothyroidism in patients with Anderson-Fabry disease.
Hauser, A C; Gessl, A; Lorenz, M; Voigtländer, T; Födinger, M; Sunder-Plassmann, G
2005-01-01
Anderson-Fabry disease is a rare lysosomal storage disorder. It results from a deficiency of the lysosomal alpha-galactosidase A and leads to progressive accumulation of globotriaosylceramide in the endothelium and tissue cells of various organs. Some of the typical clinical findings such as tiredness, dry skin, myalgia and arthralgia as well as vague gastrointestinal complaints are also symptoms of hypothyroidism. Therefore, we studied the thyroid function in patients with Anderson-Fabry disease. Thyroid function was studied in 11 patients (6 female, 5 male) with Anderson-Fabry disease by measuring thyroid-stimulating hormone (TSH) and free thyroxine serum levels. Nine patients had chronic kidney disease with stage 1 and two with stage 5. Subclinical hypothyroidism (normal serum free thyroxine concentrations along with elevated serum TSH levels) was found in 4 of 11 patients (36.4%). Subclinical hypothyroidism was observed in both male and female patients as well as in patients with stage 1 and stage 5 kidney disease. Subclinical hypothyroidism is a common finding in patients with Anderson-Fabry disease, showing an excess prevalence as compared to the normal population. The high frequency seems to be relevant regarding the potential consequences of a hypothyroid state.
Stoller, R J
1976-08-01
Sexual excitement depends on a scenario the person to be aroused has been writing since childhood. The story is an adventure, an autobiography disguised as fiction, in which the hero/heroine hides crucial intrapsychic conflicts, mysteries, screen memories of actual traumatic events and the resolution of these elements into a happy ending, best celebrated by orgasm. The function of the fantasy is to take these painful experiences and convert them to pleasure-triumph. In order to sharpen excitement-the vibration between the fear of original traumas repeating and the hope of a pleasurable conclusion this time-one introduces into the story elements of risk (approximations of the trauma) meant to prevent boredom and safety factors (sub-limnal signals to the storyteller that the risk are not truly dangerous). Sexual fantasy can be studied by means of a person's daydreams (including those chosen in magazines, books, plays, television, movies, and outright pornography), masturbatory behavior, object choice, foreplay, techniques of intercourse, or postcoital behavior.
Anderson transition in ultracold atoms: Signatures and experimental feasibility
Garcia-Garcia, Antonio M.; Wang Jiao
2006-12-15
Kicked rotators with certain nonanalytic potentials avoid dynamical localization and undergo a metal-insulator transition. We show that typical properties of this transition are still present as the nonanalyticity is progressively smoothed out provided that the smoothing is less than a certain limiting value. We have identified a smoothing-dependent time scale such that full dynamical localization is absent and the quantum momentum distribution develops power-law tails with anomalous decay exponents as in the case of a conductor at the metal-insulator transition. We discuss under what conditions these findings may be verified experimentally by using ultracold atom techniques. It is found that ultracold atoms can indeed be utilized for the experimental investigation of the metal-insulator transition.
A self-consistent theory of localization in nonlinear random media
NASA Astrophysics Data System (ADS)
Cherroret, Nicolas
2017-01-01
The self-consistent theory of localization is generalized to account for a weak quadratic nonlinear potential in the wave equation. For spreading wave packets, the theory predicts the destruction of Anderson localization by the nonlinearity and its replacement by algebraic subdiffusion, while classical diffusion remains unaffected. In 3D, this leads to the emergence of a subdiffusion-diffusion transition in place of the Anderson transition. The accuracy and the limitations of the theory are discussed.
Negative pressure wound therapy for Gustilo Anderson grade IIIb open tibial fractures
Park, Chul Hyun; Shon, Oog Jin; Kim, Gi Beom
2016-01-01
Background: Traditionally, Gustilo Anderson grade IIIb open tibial fractures have been treated by initial wide wound debridement, stabilization of fracture with external fixation, and delayed wound closure. The purpose of this study is to evaluate the clinical and radiological results of staged treatment using negative pressure wound therapy (NPWT) for Gustilo Anderson grade IIIb open tibial fractures. Materials and Methods: 15 patients with Gustilo Anderson grade IIIb open tibial fractures, treated using staged protocol by a single surgeon between January 2007 and December 2011 were reviewed in this retrospective study. The clinical results were assessed using a Puno scoring system for severe open fractures of the tibia at the last followup. The range of motion (ROM) of the knee and ankle joints and postoperative complication were evaluated at the last followup. The radiographic results were assessed using time to bone union, coronal and sagittal angulations and a shortening at the last followup. Results: The mean score of Puno scoring system was 87.4 (range 67–94). The mean ROM of the knee and ankle joints was 121.3° (range 90°–130°) and 37.7° (range 15°–50°), respectively. Bone union developed in all patients and the mean time to union was 25.3 weeks (range 16–42 weeks). The mean coronal angulation was 2.1° (range 0–4°) and sagittal was 2.7° (range 1–4°). The mean shortening was 4.1 mm (range 0–8 mm). Three patients had partial flap necrosis and 1 patient had total flap necrosis. There was no superficial and deep wound infection. Conclusion: Staged treatment using NPWT decreased the risks of infection and requirement of flap surgeries in Gustilo Anderson grade IIIb open tibial fractures. Therefore, staged treatment using NPWT could be a useful treatment option for Gustilo Anderson grade IIIb open tibial fractures. PMID:27746498
Meuleman, G. Allyn
1987-06-01
Under direction of the Pacific Northwest Electric Power Planning and Conservation Act of 1980, and the subsequent Northwest Power Planning Council's Columbia River Basin Fish and Wildlife Program, projects have been developed in Idaho to mitigate the impacts to wildlife habitat and production due to the development and operation of the Anderson Ranch and Black Canyon Facilities (i.e., dam, power plant, and reservoir areas). The Anderson Ranch Facility covered about 4812 acres of wildlife habitat while the Black Canyon Facility covered about 1115 acres. These acreages include dam and power plant staging areas. A separate mitigation plan has been developed for each facility. A modified Habitat Evaluation Procedure (HEP) was used to assess the benefits of the mitigation plans to wildlife. The interagency work group used the target species Habitat Units (HU's) lost at each facility as a guideline during the mitigation planning process, while considering the needs of wildlife in the areas. Totals of 9619 and 2238 target species HU's were estimated to be lost in the Anderson Ranch and Black Canyon Facility areas, respectively. Through a series of projects, the mitigation plans will provide benefits of 9620 target species HU's to replace Anderson Ranch wildlife impacts and benefits of 2195 target species HU's to replace Black Canyon wildlife impacts. Target species to be benefited by the Anderson Ranch and/or Black Canyon mitigation plans include the mallard, Canada goose, mink, yellow warbler, black-capped chickadee, ruffed grouse, mule deer, blue grouse, sharp-tailed grouse, ring-necked pheasant, and peregrine falcon.
NASA Astrophysics Data System (ADS)
Hatta, Kohei; Nakajima, Yohei; Isoda, Erika; Itoh, Mariko; Yamamoto, Tamami
The brain is one of the most complicated structures in nature. Zebrafish is a useful model to study development of vertebrate brain, because it is transparent at early embryonic stage and it develops rapidly outside of the body. We made a series of transgenic zebrafish expressing green-fluorescent protein related molecules, for example, Kaede and KikGR, whose green fluorescence can be irreversibly converted to red upon irradiation with ultra-violet (UV) or violet light, and Dronpa, whose green fluorescence is eliminated with strong blue light but can be reactivated upon irradiation with UV or violet-light. We have recently shown that infrared laser evoked gene operator (IR-LEGO) which causes a focused heat shock could locally induce these fluorescent proteins and the other genes. Neural cell migration and axonal pattern formation in living brain could be visualized by this technique. We also can express channel rhodopsine 2 (ChR2), a photoactivatable cation channel, or Natronomonas pharaonis halorhodopsin (NpHR), a photoactivatable chloride ion pump, locally in the nervous system by IR. Then, behaviors of these animals can be controlled by activating or silencing the local neurons by light. This novel strategy is useful in discovering neurons and circuits responsible for a wide variety of animal behaviors. We proposed to call this method ‘multi-stepped optogenetics’.
NASA Astrophysics Data System (ADS)
Chichinadze, Dmitry V.; Ribeiro, Pedro; Shchadilova, Yulia E.; Rubtsov, Alexey N.
2016-08-01
The exact description of the time evolution of open correlated quantum systems remains one of the major challenges of condensed matter theory, especially for asymptotic long times where most numerical methods fail. Here, the post-quench dynamics of the N -component Bose-Anderson impurity model is studied in the N →∞ limit. The equilibrium phase diagram is similar to that of the Bose-Hubbard model in that it contains local versions of Mott and Bose phases. Using a numerically exact procedure, we are able to study the real-time evolution including asymptotic long-time regimes. The formation of long-lived transient phases is observed for quench paths crossing foreign phases. For quenches inside the local Bose condensed phase, a dynamical phase transition is reported that separates the evolution towards a new equilibrium state and a regime characterized at large times by a persistent phase rotation of the order parameter. We explain how such nondecaying modes can exist in the presence of a dissipative bath. We discuss the extension of our results to the experimental relevant finite-N case and their implication for the existence of nondecaying modes in generic quantum systems in the presence of a bath.
Localization in Open Quantum Systems
NASA Astrophysics Data System (ADS)
Yusipov, I.; Laptyeva, T.; Denisov, S.; Ivanchenko, M.
2017-02-01
In an isolated single-particle quantum system, a spatial disorder can induce Anderson localization. Being a result of interference, this phenomenon is expected to be fragile in the face of dissipation. Here we show that a proper dissipation can drive a disordered system into a steady state with tunable localization properties. This can be achieved with a set of identical dissipative operators, each one acting nontrivially on a pair of sites. Operators are parametrized by a uniform phase, which controls the selection of Anderson modes contributing to the state. On the microscopic level, quantum trajectories of a system in the asymptotic regime exhibit intermittent dynamics consisting of long-time sticking events near selected modes interrupted by intermode jumps.
Evidence of Non-Mean-Field-Like Low-Temperature Behavior in the Edwards-Anderson Spin-Glass Model
NASA Astrophysics Data System (ADS)
Yucesoy, B.; Katzgraber, Helmut G.; Machta, J.
2012-10-01
The three-dimensional Edwards-Anderson and mean-field Sherrington-Kirkpatrick Ising spin glasses are studied via large-scale Monte Carlo simulations at low temperatures, deep within the spin-glass phase. Performing a careful statistical analysis of several thousand independent disorder realizations and using an observable that detects peaks in the overlap distribution, we show that the Sherrington-Kirkpatrick and Edwards-Anderson models have a distinctly different low-temperature behavior. The structure of the spin-glass overlap distribution for the Edwards-Anderson model suggests that its low-temperature phase has only a single pair of pure states.
Santos, Jose; Graves, David R.; Data, Przemyslaw; Nobuyasu, Roberto S.; Fox, Mark A.; Batsanov, Andrei S.; Palmeira, Tiago; Berberan‐Santos, Mário N.; Bryce, Martin R.; Monkman, Andrew P.
2016-01-01
Here, a comprehensive photophysical investigation of a the emitter molecule DPTZ‐DBTO2, showing thermally activated delayed fluorescence (TADF), with near‐orthogonal electron donor (D) and acceptor (A) units is reported. It is shown that DPTZ‐DBTO2 has minimal singlet–triplet energy splitting due to its near‐rigid molecular geometry. However, the electronic coupling between the local triplet (3LE) and the charge transfer states, singlet and triplet, (1CT, 3CT), and the effect of dynamic rocking of the D–A units about the orthogonal geometry are crucial for efficient TADF to be achieved. In solvents with low polarity, the guest emissive singlet 1CT state couples directly to the near‐degenerate 3LE, efficiently harvesting the triplet states by a spin orbit coupling charge transfer mechanism (SOCT). However, in solvents with higher polarity the emissive CT state in DPTZ‐DBTO2 shifts below (the static) 3LE, leading to decreased TADF efficiencies. The relatively large energy difference between the 1CT and 3LE states and the extremely low efficiency of the 1CT to 3CT hyperfine coupling is responsible for the reduction in TADF efficiency. Both the electronic coupling between 1CT and 3LE, and the (dynamic) orientation of the D–A units are thus critical elements that dictate reverse intersystem crossing processes and thus high efficiency in TADF. PMID:27981000
The exhaustion problem in the periodic Anderson model: An X-boson approach
NASA Astrophysics Data System (ADS)
Franco, R.; Silva-Valencia, J.; Figueira, M. S.
2006-10-01
We study the thermodynamical properties of the periodic Anderson model (PAM), within the X-boson approach. The exhaustion problem is studied and we calculate the entropy and the specific heat for the heavy fermion Kondo regime (HF-K) of the PAM. We compute numerically the evolution of the Kondo lattice TKL and the Fermi liquid T* temperatures as function of the conduction electron occupation number nc. The results obtained are consistent with others reported in the literature for the Kondo lattice.
Magnetic frustration in the three-band Anderson lattice model for high-temperature superconductors
Ihle, D.; Kasner, M. )
1990-09-01
The three-band Anderson lattice model for the CuO{sub 2} planes in high-{Tc} superconductors is established. Treating this model by perturbation theory, the effective spin interactions are derived. The antiferromagnetic superexchange integrals are calculated as functions of the direct oxygen transfer and the hole concentration. It is found that frustration in the superexchange occurs, even in the undoped case, which increases with oxygen trnasfer and decreases with hole concentration.
Xie, Wenrui; Strong, Judith A.; Zhang, Jun-Ming
2015-01-01
In the spinal nerve ligation model of neuropathic pain, as in other pain models, abnormal spontaneous activity of myelinated sensory neurons occurs early and is essential for establishing pain behaviors and other pathologies. Sympathetic sprouting into the dorsal root ganglion (DRG) is observed after spinal nerve ligation, and sympathectomy reduces pain behavior. Sprouting and spontaneous activity may be mutually reinforcing: blocking neuronal activity reduces sympathetic sprouting, and sympathetic spouts functionally increase spontaneous activity in vitro. However, most studies in this field have used nonspecific methods to block spontaneous activity, methods that also block evoked and normal activity. In this study, we injected small inhibitory RNA directed against the NaV1.6 sodium channel isoform into the DRG before spinal nerve ligation. This isoform can mediate high frequency repetitive firing, like that seen in spontaneously active neurons. Local knockdown of NaV1.6 markedly reduced mechanical pain behaviors induced by spinal nerve ligation, reduced sympathetic sprouting into the ligated sensory ganglion, and blocked abnormal spontaneous activity and other measures of hyperexcitability in myelinated neurons in the ligated sensory ganglion. Immunohistochemical experiments showed that sympathetic sprouting preferentially targeted NaV1.6-positive neurons. Under these experimental conditions, NaV1.6 knockdown did not prevent or strongly alter single evoked action potentials, unlike previous less specific methods used to block spontaneous activity. NaV1.6 knockdown also reduced pain behaviors in another pain model, chronic constriction of the sciatic nerve, provided the model was modified so that the lesion site was relatively close to the siRNA-injected lumbar DRGs. The results highlight the relative importance of abnormal spontaneous activity in establishing both pain behaviors and sympathetic sprouting, and suggest that the NaV1.6 isoform may have value as a
Kondo physics of the Anderson impurity model by distributional exact diagonalization
NASA Astrophysics Data System (ADS)
Motahari, S.; Requist, R.; Jacob, D.
2016-12-01
The distributional exact diagonalization (DED) scheme is applied to the description of Kondo physics in the Anderson impurity model. DED maps Anderson's problem of an interacting impurity level coupled to an infinite bath onto an ensemble of finite Anderson models, each of which can be solved by exact diagonalization. An approximation to the self-energy of the original infinite model is then obtained from the ensemble-averaged self-energy. Using Friedel's sum rule, we show that the particle number constraint, a central ingredient of the DED scheme, ultimately imposes Fermi liquid behavior on the ensemble-averaged self-energy, and thus is essential for the description of Kondo physics within DED. Using the numerical renormalization group (NRG) method as a benchmark, we show that DED yields excellent spectra, both inside and outside the Kondo regime for a moderate number of bath sites. Only for very strong correlations (U /Γ ≫10 ) does the number of bath sites needed to achieve good quantitative agreement become too large to be computationally feasible.
Electronic structure of vitamin B12 within the framework of the Haldane-Anderson impurity model
NASA Astrophysics Data System (ADS)
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.
Jaña Neto, Frederico Carlos; de Paula Canal, Marina; Alves, Bernardo Aurélio Fonseca; Ferreira, Pablício Martins; Ayres, Jefferson Castro; Alves, Robson
2016-01-01
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. PMID:27069881
Janik, Cathy J.; Goff, Fraser; Walter, Stephen R.; Sorey, Michael L.; Counce, Dale; Colvard, Elizabeth M.
2000-01-01
The Anderson Springs area is located about 90 miles (145 kilometers) north of San Francisco, California, in the southwestern part of Lake County. The area was first developed in the late 1800s as a health resort, which was active until the 1930s. Patrons drank a variety of cool to hot mineral waters from improved springs, swam in various baths and pools, and hiked in the rugged hills flanking Anderson Creek and its tributaries. In the bluffs to the south of the resort were four small mercury mines of the eastern Mayacmas quicksilver district. About 1,260 flasks of mercury were produced from these mines between 1909 and 1943. By the early 1970s, the higher ridges south and west of Anderson Springs became part of the southeast sector of the greater Geysers geothermal field. Today, several electric power plants are built on these ridges, producing energy from a vapor-dominated 240 °C reservoir. Only the main hot spring at Anderson Springs has maintained a recognizable identity since the 1930s. The hot spring is actually a cluster of seeps and springs that issue from a small fault in a ravine southwest of Anderson Creek. Published and unpublished records show that the maximum temperature (Tm) of this cluster fell gradually from 63°C in 1889 to 48°C in 1992. However, Tm of the cluster climbed to 77°C in 1995 and neared boiling (98°C) in 1998. A new cluster of boiling vents and small fumaroles (Tm = 99.3°C) formed in 1998 about 30 m north of the old spring cluster. Several evergreen trees on steep slopes immediately above these vents apparently were killed by the new activity. Thermal waters at Anderson Hot Springs are mostly composed of near-surface ground waters with some added gases and condensed steam from The Geysers geothermal system. Compared to gas samples from Southeast Geysers wells, the hot spring gases are higher in CO2 and lower in H2S and NH3. As the springs increased in temperature, however, the gas composition became more like the mean composition
Effect of wave localization on plasma instabilities. Ph.D. Thesis
NASA Technical Reports Server (NTRS)
Levedahl, William Kirk
1987-01-01
The Anderson model of wave localization in random media is involved to study the effect of solar wind density turbulence on plasma processes associated with the solar type III radio burst. ISEE-3 satellite data indicate that a possible model for the type III process is the parametric decay of Langmuir waves excited by solar flare electron streams into daughter electromagnetic and ion acoustic waves. The threshold for this instability, however, is much higher than observed Langmuir wave levels because of rapid wave convection of the transverse electromagnetic daughter wave in the case where the solar wind is assumed homogeneous. Langmuir and transverse waves near critical density satisfy the Ioffe-Reigel criteria for wave localization in the solar wind with observed density fluctuations -1 percent. Numerical simulations of wave propagation in random media confirm the localization length predictions of Escande and Souillard for stationary density fluctations. For mobile density fluctuations localized wave packets spread at the propagation velocity of the density fluctuations rather than the group velocity of the waves. Computer simulations using a linearized hybrid code show that an electron beam will excite localized Langmuir waves in a plasma with density turbulence. An action principle approach is used to develop a theory of non-linear wave processes when waves are localized. A theory of resonant particles diffusion by localized waves is developed to explain the saturation of the beam-plasma instability. It is argued that localization of electromagnetic waves will allow the instability threshold to be exceeded for the parametric decay discussed above.
Benjamin A. Frandsen; Brunelli, Michela; Page, Katharine; Uemura, Yasutomo J.; Staunton, Julie B.; Billinge, Simon J. L.
2016-05-11
Here, 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. Furthermore, the Anderson superexchange model for MnO is thus verified by experimentation and confirmed by ab initio theory.
Zhang, Jiangwei; Liu, Zhenhua; Huang, Yichao; zhang, Jin; Hao, Jian; Wei, Yongge
2015-06-04
The μ2-O atom in Anderson polyoxometalates was regioselectively activated by the introduction of protons, which, upon functionalization with triol ligands, could afford a series of unique χ isomers of the organically-derived Anderson cluster {[RCC(CH2O)3]MMo6O18(OH)3}(3-). Herein proton-controlled isomer transformation between the δ and χ isomer was observed by using the fingerprint region in the IR spectra and (13)C NMR spectra.
Wu, Tsan-Pei; Wang, Xiao-Qun; Guo, Guang-Yu; Anders, Frithjof; Chung, Chung-Hou
2016-05-05
The quantum criticality of the two-lead two-channel pseudogap Anderson impurity model is studied. Based on the non-crossing approximation (NCA) and numerical renormalization group (NRG) approaches, we calculate both the linear and nonlinear conductance of the model at finite temperatures with a voltage bias and a power-law vanishing conduction electron density of states, ρc(ω) proportional |ω − μF|(r) (0 < r < 1) near the Fermi energy μF. At a fixed lead-impurity hybridization, a quantum phase transition from the two-channel Kondo (2CK) to the local moment (LM) phase is observed with increasing r from r = 0 to r = rc < 1. Surprisingly, in the 2CK phase, different power-law scalings from the well-known [Formula: see text] or [Formula: see text] form is found. Moreover, novel power-law scalings in conductances at the 2CK-LM quantum critical point are identified. Clear distinctions are found on the critical exponents between linear and non-linear conductance at criticality. The implications of these two distinct quantum critical properties for the non-equilibrium quantum criticality in general are discussed.
Kobori, Yasuhiro; Fuki, Masaaki; Murai, Hisao
2010-11-18
We present a theoretical model of analysis of the time-resolved electron paramagnetic resonance (TREPR) spectrum of the charge-separated (CS) state generated by the photoinduced electron transfer (ET) reaction via the locally excited triplet state in an electron donor-acceptor (D-A) system with a fixed molecular orientation. We show, by the stochastic-Liouville equation, that chemically induced dynamic electron polarization (CIDEP) of the triplet mechanism is explained by lack of transfer of quantum coherence terms in the primary triplet spin state, resulting in net emissive or absorptive electron spin polarization (ESP) which is dependent on anisotropy of the singlet-triplet intersystem crossing in the precursor excited state. This disappearance of the coherence is clearly shown to occur when the photoinduced ET rate is smaller than the angular frequency of the Zeeman splitting: the transferred coherence terms are averaged to be zero due to effective quantum oscillations during the time that the chemical reaction proceeds. The above theory has been applied to elucidate the molecular geometries and spin-spin exchange interactions (2J) of the CS states for both folded and extended conformers by computer simulations of TREPR spectra of the zinc porphyrin-fullerene dyad (ZnP-C(60)) bridged by diphenyldisilane. On the extended conformation, the electronic coupling is estimated from the 2J value. It has been revealed that the coupling term is smaller than the reported electronic interactions of the porphyrin-C(60) systems bridged by diphenylamide spacers. The difference in the electronic couplings has been explained by the difference in the LUMO levels of the bridge moieties that mediate the superexchange coupling for the long-range ET reaction.
Band Excitation Kelvin probe force microscopy utilizing photothermal excitation
Collins, Liam; Jesse, Stephen; Balke, Nina; Rodriguez, Brian J.; Kalinin, Sergei; Li, Qian
2015-03-13
A multifrequency open loop Kelvin probe force microscopy (KPFM) approach utilizing photothermal as opposed to electrical excitation is developed. Photothermal band excitation (PthBE)-KPFM is implemented here in a grid mode on a model test sample comprising a metal-insulator junction with local charge-patterned regions. Unlike the previously described open loop BE-KPFM, which relies on capacitive actuation of the cantilever, photothermal actuation is shown to be highly sensitive to the electrostatic force gradient even at biases close to the contact potential difference (CPD). PthBE-KPFM is further shown to provide a more localized measurement of true CPD in comparison to the gold standard ambient KPFM approach, amplitude modulated KPFM. In conclusion, PthBE-KPFM data contain information relating to local dielectric properties and electronic dissipation between tip and sample unattainable using conventional single frequency KPFM approaches.
Band Excitation Kelvin probe force microscopy utilizing photothermal excitation
Collins, Liam; Jesse, Stephen; Balke, Nina; ...
2015-03-13
A multifrequency open loop Kelvin probe force microscopy (KPFM) approach utilizing photothermal as opposed to electrical excitation is developed. Photothermal band excitation (PthBE)-KPFM is implemented here in a grid mode on a model test sample comprising a metal-insulator junction with local charge-patterned regions. Unlike the previously described open loop BE-KPFM, which relies on capacitive actuation of the cantilever, photothermal actuation is shown to be highly sensitive to the electrostatic force gradient even at biases close to the contact potential difference (CPD). PthBE-KPFM is further shown to provide a more localized measurement of true CPD in comparison to the gold standardmore » ambient KPFM approach, amplitude modulated KPFM. In conclusion, PthBE-KPFM data contain information relating to local dielectric properties and electronic dissipation between tip and sample unattainable using conventional single frequency KPFM approaches.« less
Causation's nuclear future: applying proportional liability to the Price-Anderson Act.
O'Connell, William D
2014-11-01
For more than a quarter century, public discourse has pushed the nuclear-power industry in the direction of heavier regulation and greater scrutiny, effectively halting construction of new reactors. By focusing on contemporary fear of significant accidents, such discourse begs the question of what the nation's court system would actually do should a major nuclear incident cause radiation-induced cancers. Congress's attempt to answer that question is the Price-Anderson Act, a broad statute addressing claims by the victims of a major nuclear accident. Lower courts interpreting the Act have repeatedly encountered a major stumbling block: it declares that judges must apply the antediluvian preponderance-of-the-evidence logic of state tort law, even though radiation science insists that the causes of radiation-induced cancers are more complex. After a major nuclear accident, the Act's paradoxically outdated rules for adjudicating "causation" would make post-incident compensation unworkable. This Note urges that nuclear-power-plant liability should not turn on eighteenth-century tort law. Drawing on modern scientific conclusions regarding the invariably "statistical" nature of cancer, this Note suggests a unitary federal standard for the Price-Anderson Act--that a defendant be deemed to have "caused" a plaintiff's injury in direct proportion to the increased risk of harm the defendant has imposed. This "proportional liability" rule would not only fairly evaluate the costs borne by injured plaintiffs and protect a reawakening nuclear industry from the prospect of bank-breaking litigation, but would prove workable with only minor changes to the Price-Anderson Act's standards of "injury" and "fault."
RESONANT CAVITY EXCITATION SYSTEM
Baker, W.R.; Kerns, Q.A.; Riedel, J.
1959-01-13
An apparatus is presented for exciting a cavity resonator with a minimum of difficulty and, more specifically describes a sub-exciter and an amplifier type pre-exciter for the high-frequency cxcitation of large cavities. Instead of applying full voltage to the main oscillator, a sub-excitation voltage is initially used to establish a base level of oscillation in the cavity. A portion of the cavity encrgy is coupled to the input of the pre-exciter where it is amplified and fed back into the cavity when the pre-exciter is energized. After the voltage in the cavity resonator has reached maximum value under excitation by the pre-exciter, full voltage is applied to the oscillator and the pre-exciter is tunned off. The cavity is then excited to the maximum high voltage value of radio frequency by the oscillator.
Machine learning for many-body physics: The case of the Anderson impurity model
NASA Astrophysics Data System (ADS)
Arsenault, Louis-François; Lopez-Bezanilla, Alejandro; von Lilienfeld, O. Anatole; Millis, Andrew J.
2014-10-01
Machine learning methods are applied to finding the Green's function of the Anderson impurity model, a basic model system of quantum many-body condensed-matter physics. Different methods of parametrizing the Green's function are investigated; a representation in terms of Legendre polynomials is found to be superior due to its limited number of coefficients and its applicability to state of the art methods of solution. The dependence of the errors on the size of the training set is determined. The results indicate that a machine learning approach to dynamical mean-field theory may be feasible.
Topolska, G
2001-01-01
Varroa jacobsoni was noted for the first time in 1904, in the nest ofApis cerana. In Apis mellifera nests the first Varroa mites were probably found in Korea (1950), next in Japan (1958). In the following years they have spread all over the world. All the time they were regarded as V. jacobsoni. Recently Anderson and Trueman have proved that Varroa jacobsoni is more than one species. They gave the new name Varroa destructor n. sp. to the group of six haplotypes. Mites, which became pests ofA. mellifera worldwide, belong to V. destructor.
Anderson transition in low-dimensional disordered systems driven by long-range nonrandom hopping.
Rodríguez, A; Malyshev, V A; Sierra, G; Martín-Delgado, M A; Rodríguez-Laguna, J; Domínguez-Adame, F
2003-01-17
The single-parameter scaling hypothesis predicts the absence of delocalized states for noninteracting quasiparticles in low-dimensional disordered systems. We show analytically, using a supersymmetric method combined with a renormalization group analysis, as well as numerically that extended states may occur in the one- and two-dimensional Anderson model with a nonrandom hopping falling off as some power of the distance between sites. The different size scaling of the bare level spacing and the renormalized magnitude of the disorder seen by the quasiparticles finally results in the delocalization of states at one of the band edges of the quasiparticle energy spectrum.
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.
Localization of a Bose-Fermi mixture in a bichromatic optical lattice
Cheng Yongshan; Adhikari, S. K.
2011-08-15
We study the localization of a cigar-shaped superfluid Bose-Fermi mixture in a quasiperiodic bichromatic optical lattice (OL) for interspecies attraction and intraspecies repulsion. The mixture is described by the Gross-Pitaevskii equation for the bosons, coupled to a hydrodynamic mean-field equation for fermions at unitarity. We confirm the existence of the symbiotic localized states in the Bose-Fermi mixture and Anderson localization of the Bose component in the interacting Bose-Fermi mixture on a bichromatic OL. The phase diagram in boson and fermion numbers showing the regions of the symbiotic and Anderson localization of the Bose component is presented. Finally, the stability of symbiotic and Anderson localized states is established under small perturbations.
On the possibility of many-body localization in a doped Mott insulator
NASA Astrophysics Data System (ADS)
He, Rong-Qiang; Weng, Zheng-Yu
2016-10-01
Many-body localization (MBL) is currently a hot issue of interacting systems, in which quantum mechanics overcomes thermalization of statistical mechanics. Like Anderson localization of non-interacting electrons, disorders are usually crucial in engineering the quantum interference in MBL. For translation invariant systems, however, the breakdown of eigenstate thermalization hypothesis due to a pure many-body quantum effect is still unclear. Here we demonstrate a possible MBL phenomenon without disorder, which emerges in a lightly doped Hubbard model with very strong interaction. By means of density matrix renormalization group numerical calculation on a two-leg ladder, we show that whereas a single hole can induce a very heavy Nagaoka polaron, two or more holes will form bound pair/droplets which are all localized excitations with flat bands at low energy densities. Consequently, MBL eigenstates of finite energy density can be constructed as composed of these localized droplets spatially separated. We further identify the underlying mechanism for this MBL as due to a novel ‘Berry phase’ of the doped Mott insulator, and show that by turning off this Berry phase either by increasing the anisotropy of the model or by hand, an eigenstate transition from the MBL to a conventional quasiparticle phase can be realized.
On the possibility of many-body localization in a doped Mott insulator
He, Rong-Qiang; Weng, Zheng-Yu
2016-01-01
Many-body localization (MBL) is currently a hot issue of interacting systems, in which quantum mechanics overcomes thermalization of statistical mechanics. Like Anderson localization of non-interacting electrons, disorders are usually crucial in engineering the quantum interference in MBL. For translation invariant systems, however, the breakdown of eigenstate thermalization hypothesis due to a pure many-body quantum effect is still unclear. Here we demonstrate a possible MBL phenomenon without disorder, which emerges in a lightly doped Hubbard model with very strong interaction. By means of density matrix renormalization group numerical calculation on a two-leg ladder, we show that whereas a single hole can induce a very heavy Nagaoka polaron, two or more holes will form bound pair/droplets which are all localized excitations with flat bands at low energy densities. Consequently, MBL eigenstates of finite energy density can be constructed as composed of these localized droplets spatially separated. We further identify the underlying mechanism for this MBL as due to a novel ‘Berry phase’ of the doped Mott insulator, and show that by turning off this Berry phase either by increasing the anisotropy of the model or by hand, an eigenstate transition from the MBL to a conventional quasiparticle phase can be realized. PMID:27752064
Janik, C.J.; Goff, F.; Sorey, M.L.; Rytuba, J.J.; Counce, D.; Colvard, E.M.; Huebner, M.; White, L.D.; Foster, A.
1999-01-01
Anderson Springs is located about 90 miles (145 kilometers) north of San Francisco, California, in the southwestern part of Lake County. The area was first developed in the late 1800s as a health resort, which was active until the 1930s. In the rugged hills to the south of the resort were four small mercury mines of the eastern Mayacmas quicksilver district. About 1,260 flasks of mercury were produced from these mines between 1909 and 1943. In the 1970s, the high-elevation areas surrounding Anderson Springs became part of The Geysers geothermal field. Today, several electric powerplants are located on the ridges above Anderson Springs, utilizing steam produced from a 240°C vapor-dominated reservoir. The primary purpose of this report is to provide physical, chemical, and isotopic data on samples collected in the Anderson Springs area during 1998 and 1999, in response to a Freedom of Information Act request. In July 1998, drainage from the Schwartz adit of the abandoned Anderson mercury mine increased substantially over a 2-day period, transporting a slurry of water and precipitates down a tributary and into Anderson Creek. In August 1998, J.J. Rytuba and coworkers sampled the Schwartz adit drainage and water from the Anderson Springs Hot Spring for base metal and methylmercury analysis. They measured a maximum temperature (Tm) of 85°C in the Hot Spring. Published records show that the temperature of the Anderson Springs Hot Spring (main spring) was 63°C in 1889, 42–52°C from 1974 through 1991, and 77°C in March 1995. To investigate possible changes in thermal spring activity and to collect additional samples for geochemical analysis, C.J. Janik and coworkers returned to the area in September and December 1998. They determined that a cluster of springs adjacent to the main spring had Tm=98°C, and they observed that a new area of boiling vents and small fumaroles (Tm=99.3°C) had formed in an adjacent gully about 20 meters to the north of the main spring
Analysis of Anderson Acceleration on a Simplified Neutronics/Thermal Hydraulics System
Toth, Alex; Kelley, C. T.; Slattery, Stuart R; Hamilton, Steven P; Clarno, Kevin T; Pawlowski, R. P. P.
2015-01-01
ABSTRACT A standard method for solving coupled multiphysics problems in light water reactors is Picard iteration, which sequentially alternates between solving single physics applications. This solution approach is appealing due to simplicity of implementation and the ability to leverage existing software packages to accurately solve single physics applications. However, there are several drawbacks in the convergence behavior of this method; namely slow convergence and the necessity of heuristically chosen damping factors to achieve convergence in many cases. Anderson acceleration is a method that has been seen to be more robust and fast converging than Picard iteration for many problems, without significantly higher cost per iteration or complexity of implementation, though its effectiveness in the context of multiphysics coupling is not well explored. In this work, we develop a one-dimensional model simulating the coupling between the neutron distribution and fuel and coolant properties in a single fuel pin. We show that this model generally captures the convergence issues noted in Picard iterations which couple high-fidelity physics codes. We then use this model to gauge potential improvements with regard to rate of convergence and robustness from utilizing Anderson acceleration as an alternative to Picard iteration.
Nutritional influences on early white matter development: response to Anderson and Burggren.
Deoni, Sean C L; Dean, Douglas C; Walker, Lindsay; Dirks, Holly; O'Muircheartaigh, Jonathan
2014-10-15
Does breastfeeding alter early brain development? In a recent retrospective study, our group examined the cross-sectional relationship between early infant feeding practice and white matter maturation and cognitive development. In groups matched for child and mother age, gestation duration, birth weight, gender distribution, and socio-economic status; we observed that children who were breastfed exclusively for at least 3 months showed, on average, increased white matter myelin development compared to children who either were exclusively formula-fed, or received a mixture of breast milk and formula. In secondary analysis on sub-sets of these children, again matched for important confounding variables, we found improved cognitive test scores of receptive language in the exclusively breast-fed children compared to formula or formula+breast-fed children; and that prolonged breastfeeding was associated with increased motor, language, and visual functioning in exclusively breast-fed children. In response to this work, Anderson and Burggren have questioned our methodology and, by association, our findings. Further, they use their critique as a platform for advancing an alternative interpretation of our findings: that observed results were not associated with prolonged breast-feeding, but rather delayed the introduction of cow's milk. In this response, we address and clarify some of the misconceptions presented by Anderson and Burggren.
NASA Astrophysics Data System (ADS)
Kandemir, Zafer; Mayda, Selma; Bulut, Nejat
2016-04-01
We study the electronic structure and correlations of vitamin B12 (cyanocobalamine) by using the framework of the multi-orbital single-impurity Haldane-Anderson model of a transition-metal impurity in a semiconductor host. The parameters of the effective Haldane-Anderson model are obtained within the Hartree-Fock (HF) approximation. The quantum Monte Carlo (QMC) technique is then used to calculate the one-electron and magnetic correlation functions of this effective model. We observe that new states form inside the semiconductor gap found by HF due to the intra-orbital Coulomb interaction at the impurity 3d orbitals. In particular, the lowest unoccupied states correspond to an impurity bound state, which consists of states from mainly the CN axial ligand and the corrin ring as well as the Co eg-like orbitals. We also observe that the Co (3d) orbitals can develop antiferromagnetic correlations with the surrounding atoms depending on the filling of the impurity bound states. In addition, we make comparisons of the HF+QMC data with the density functional theory calculations. We also discuss the photoabsorption spectrum of cyanocobalamine.
Dr Walter Henry Anderson (1870-1937) and the mission hospital at Safed, Palestine.
Stokes, Gordon S
2013-02-01
Walter Henry Anderson, a brewer's clerk in Burton-upon-Trent, became a missionary doctor, supported by a society promoting welfare and evangelism in Jewish communities abroad. His family background was rich in pastoral ministry at home and adventure abroad. Arguably, this background played a part in his decision to serve the Jews of Safed. His life in Palestine entailed much enterprise and hardship as he raised a family, fought disease and set up a mission hospital serving not only the Jewish community but persons of all faiths. His years in Palestine, from 1894 to 1915, were times of peace in the Middle East before the turmoil unleashed by the Great War. Jews from the Diaspora were gaining an increasing foothold in Palestine, their 'Promised Land'. Themes of that era - the rise of Zionism, confrontation between Judaism and evangelical Christianity, conflict between immigrant Jew and Palestinian Arab and the remarkable travels of Lawrence of Arabia were interwoven with the lives of Dr Anderson and his family.
Evidence of Non-Mean-Field-Like Low-Temperature Behavior in the Edwards-Anderson Spin-Glass Model
NASA Astrophysics Data System (ADS)
Yucesoy, Burcu; Katzgraber, Helmut G.; Machta, Jonathan
2013-03-01
The three and four-dimensional Edwards-Anderson and mean-field Sherrington-Kirkpatrick Ising spin glasses are studied via large-scale Monte Carlo simulations at low temperatures, deep within the spin-glass phase. Performing a careful statistical analysis of several thousand independent disorder realizations and using an observable that detects peaks in the overlap distribution, we show that the Sherrington-Kirkpatrick and Edwards-Anderson models have a distinctly different low-temperature behavior. The structure of the spin-glass overlap distribution for the Edwards-Anderson model suggests that its low-temperature phase has only a single pair of pure states. J. M. and B. Y. are supported in part by the NSF (Grant No. DMR-0907235 and DMR-1208046).
Butler, J.N.; Shukla, S.
1995-05-01
The experimental status of excited charmed mesons is reviewed and is compared to theoretical expectations. Six states have been observed and their properties are consistent with those predicted for excited charmed states with orbital angular momentum equal to one.
NASA Technical Reports Server (NTRS)
Beecher, L. C.; Williams, F. T.
1970-01-01
Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.
NASA Astrophysics Data System (ADS)
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.
Calculation of molecular excitation rates
NASA Technical Reports Server (NTRS)
Flynn, George
1993-01-01
State-to-state collisional excitation rates for interstellar molecules observed by radio astronomers continue to be required to interpret observed line intensities in terms of local temperatures and densities. A problem of particular interest is collisional excitation of water which is important for modeling the observed interstellar masers. In earlier work supported by a different NASA Grant, excitation of water in collisions with He atoms was studied; after many years of successively more refined calculations that problem now seems to be well understood, and discrepancies with earlier experimental data for related (pressure broadening) phenomena are believed to reflect experimental errors. Because of interstellar abundances, excitation by H2, the dominant interstellar species, is much more important than excitation by He, although it has been argued that rates for excitation by these are similar. Under the current grant theoretical study of this problem has begun which is greatly complicated by the additional degrees of freedom which must be included both in determining the interaction potential and also in the molecular scattering calculation. We have now computed the interaction forces for nearly a thousand molecular geometries and are close to having an acceptable global fit to these points which is necessary for the molecular dynamics calculations. Also, extensive modifications have been made to the molecular scattering code, MOLSCAT. These included coding the rotational basis sets and coupling matrix elements required for collisions of an asymmetric top with a linear rotor. A new method for numerical solution of the coupled equations has been incorporated. Because of the long-ranged nature of the water-hydrogen interaction it is necessary to integrate the equations to rather large intermolecular separations, and the integration methods previously available in MOLSCAT are not ideal for such cases. However, the method used by Alexander in his HIBRIDON code is
ERIC Educational Resources Information Center
Horning, Kathleen
2006-01-01
This article presents an interview with 38-year-old writer Matthew Tobin Anderson. In the interview, Anderson talks about his experiences, passion for writing, teenage interests, and his relation to the distinguished writer Mark Twain. He also states the importance of liberty and what it takes to be a patriot and a loyalist. Furthermore, Matthew…
Acoustically excited heated jets. 1: Internal excitation
NASA Technical Reports Server (NTRS)
Lepicovsky, J.; Ahuja, K. K.; Brown, W. H.; Salikuddin, M.; Morris, P. J.
1988-01-01
The effects of relatively strong upstream acoustic excitation on the mixing of heated jets with the surrounding air are investigated. To determine the extent of the available information on experiments and theories dealing with acoustically excited heated jets, an extensive literature survey was carried out. The experimental program consisted of flow visualization and flowfield velocity and temperature measurements for a broad range of jet operating and flow excitation conditions. A 50.8-mm-diam nozzle was used for this purpose. Parallel to the experimental study, an existing theoretical model of excited jets was refined to include the region downstream of the jet potential core. Excellent agreement was found between theory and experiment in moderately heated jets. However, the theory has not yet been confirmed for highly heated jets. It was found that the sensitivity of heated jets to upstream acoustic excitation varies strongly with the jet operating conditions and that the threshold excitation level increases with increasing jet temperature. Furthermore, the preferential Strouhal number is found not to change significantly with a change of the jet operating conditions. Finally, the effects of the nozzle exit boundary layer thickness appear to be similar for both heated and unheated jets at low Mach numbers.
A Cartesian quasi-classical model to nonequilibrium quantum transport: the Anderson impurity model.
Li, Bin; Levy, Tal J; Swenson, David W H; Rabani, Eran; Miller, William H
2013-03-14
We apply the recently proposed quasi-classical approach for a second quantized many-electron Hamiltonian in Cartesian coordinates [B. Li and W. H. Miller, J. Chem. Phys. 137, 154107 (2012)] to correlated nonequilibrium quantum transport. The approach provides accurate results for the resonant level model for a wide range of temperatures, bias, and gate voltages, correcting the flaws of our recently proposed mapping using action-angle variables. When electron-electron interactions are included, a Gaussian function scheme is required to map the two-electron integrals, leading to quantitative results for the Anderson impurity model. In particular, we show that the current mapping is capable of capturing quantitatively the Coulomb blockade effect and the temperature dependence of the current below and above the blockade.
NASA Astrophysics Data System (ADS)
Stokes, James; Konik, Robert
2014-03-01
Using the Numerical Renormalization Group (NRG), the low energy sector of the Anderson Hamiltonian with two impurities in parallel has been previously argued to be consistent with an underscreened spin-1 Kondo effect (R. Zitko and J. Bonca, Phys. Rev. B 76, 241305 (2007); Logan et al., Phys. Rev. B 80, 125117 (2009)). Bethe Ansatz and slave boson calculations have given the ground state as a singlet (M. Kulkarni and R. M. Konik, Phys. Rev. B 83, 245121 (2011)). As an attempt to understand these differences, we have developed a modified NRG routine that takes into account the multiple channels arising from the logarithmic discretization of the Fermi sea. This could conceivably allow for more complicated screening processes suggested by the Bethe ansatz computations. Results of studies using this code for various numbers of impurities and channels will be presented and discussed in relationship to these conflicting views.
High-energy neutron dosimetry at the Clinton P. Anderson Meson Physics Facility
Mallett, M.W.; Vasilik, D.G.; Littlejohn, G.J.; Cortez, J.R.
1990-01-01
Neutron energy spectrum measurements performed at the Clinton P. Anderson Meson Physics Facility indicated potential areas for high energy neutron exposure to personnel. The low sensitivity of the Los Alamos thermoluminescent dosimeter (TLD) to high energy neutrons warranted issuing a NTA dosimeter in addition to the TLD badge to employees entering these areas. The dosimeter consists of a plastic holder surrounding NTA film that has been desiccated and sealed in a dry nitrogen environment. A study of the fading of latent images in NTA film demonstrated the success of this packaging method to control the phenomenon. The Los Alamos NTA dosimeter is characterized and the fading study discussed. 10 refs., 4 figs., 2 tabs.
Physical characteristics of the M.D. Anderson Hospital clinical neutron beam.
Horton, J L; Otte, V A; Schultheiss, T E; Stafford, P M; Sun, T; Zermeno, A
1988-09-01
The physical characteristics of the M.D. Anderson Hospital (MDAH) clinical neutron beam are presented. The central-axis percent depth-dose values are intermediate between a 4 and 6 MV X-ray beam. The build-up curves reach a depth of maximum dose at 1.2 cm and have surface dose values of approximately 30%. Teflon flattening filters are employed to flatten the beam at the depth of the 75% dose level. Two wedges are available for shaping the beam; they are made of Teflon and produce wedge angles of 31 degrees and 45 degrees as defined by the ICRU. Output factors ranged from 0.88 for a 4 x 4 cm field to 1.12 for a 20 x 20 cm field. Tungsten blocks reduced the dose received at Dmax to 25% of the unblocked value but only 52% of the unblocked value at a depth of 22.8 cm.
GW approach to Anderson model in and out of equilibrium : scaling properties in the Kondo regime.
Spataru, Dan Catalin
2010-03-01
The low-energy properties of the Anderson model for a single impurity coupled to two leads are studied using the GW approximation. We find that quantities such as the spectral function at zero temperature, the linear-response conductance as function of temperature or the differential conductance as function of bias voltage exhibit universal scaling behavior in the Kondo regime. We show how the form of the GW scaling functions relates to the form of the scaling functions obtained from the exact solution at equilibrium. We also compare the energy scale that goes inside the GW scaling functions with the exact Kondo temperature, for a broad range of the Coulomb interaction strength in the asymptotic regime. This analysis allows to clarify a presently suspended question in the literature, namely whether or not the GW solution captures the Kondo resonance.
Doping-induced perturbation and percolation in the two-dimensional Anderson lattice
Wei, Lan-ying; Yang, Yi-feng
2017-01-01
We examine the doping effects in the two-dimensional periodic Anderson model using the determinant Quantum Monte Carlo (DQMC) method. We observe bound states around the Kondo hole site and find that the heavy electron states are destroyed at the nearest-neighbor sites. Our results show no clear sign of hybridization oscillation predicted in previous mean-field calculations. We further study the electron transport with increasing doping and as a function of temperature and obtain a critical doping xc ≈ 0.6 that marks a transition from the Kondo insulator regime to the single-ion Kondo regime. The value of xc is in good agreement with the predicted threshold for the site percolation. Our results confirm the percolative nature of the insulator-metal transition widely observed in doped Kondo insulators. PMID:28383021
Intrafamilial phenotypic variability in four families with Anderson-Fabry disease.
Rigoldi, M; Concolino, D; Morrone, A; Pieruzzi, F; Ravaglia, R; Furlan, F; Santus, F; Strisciuglio, P; Torti, G; Parini, R
2014-09-01
We analysed the clinical history of 16 hemizygous males affected by Anderson-Fabry Disease, from four families, to verify their intrafamilial phenotypic variability. Seven male patients, ranging from 26 to 61 years of age, died, whereas nine (age range 23-55) are alive. Eleven patients have undergone enzyme replacement therapy (ERT) for a period of 5-10 years. We have found a wide range of intrafamilial phenotypic variability in these families, both in terms of target-organs and severity of the disease. Overall, our findings confirm previous data from the literature showing a high degree of intrafamilial phenotypic variability in patients carrying the same mutation. Furthermore, our results underscore the difficulty in giving accurate prognostic information to patients during genetic counselling, both in terms of rate of disease progression and involvement of different organs, when such prognosis is solely based on the patient's family history.
VizieR Online Data Catalog: Radio observations of Galactic WISE HII regions (Anderson+, 2015)
NASA Astrophysics Data System (ADS)
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).
Doping-induced perturbation and percolation in the two-dimensional Anderson lattice.
Wei, Lan-Ying; Yang, Yi-Feng
2017-04-06
We examine the doping effects in the two-dimensional periodic Anderson model using the determinant Quantum Monte Carlo (DQMC) method. We observe bound states around the Kondo hole site and find that the heavy electron states are destroyed at the nearest-neighbor sites. Our results show no clear sign of hybridization oscillation predicted in previous mean-field calculations. We further study the electron transport with increasing doping and as a function of temperature and obtain a critical doping xc ≈ 0.6 that marks a transition from the Kondo insulator regime to the single-ion Kondo regime. The value of xc is in good agreement with the predicted threshold for the site percolation. Our results confirm the percolative nature of the insulator-metal transition widely observed in doped Kondo insulators.
Decay of a nonlinear impurity in a structured continuum from a nonlinear Fano-Anderson model
Longhi, Stefano
2007-05-01
The decay dynamics of a nonlinear impurity mode embedded in a linear structured continuum is theoretically investigated in the framework of a nonlinear Fano-Anderson model. A gradient flow dynamics for the survival probability is derived in the Van Hove ({lambda}{sup 2}t) limit by a multiple-scale asymptotic analysis, and the role of nonlinearity on the decay law is discussed. In particular, it is shown that the existence of bound states embedded in the continuum acts as transient trapping states which slow down the decay. The dynamical behavior predicted in the {lambda}{sup 2}t limit is studied in detail for a simple tight-binding one-dimensional lattice model, which may describe electron or photon transport in condensed matter or photonic systems. Numerical simulations of the underlying equations confirm, in particular, the trapping effect in the decay process due to bound states embedded in the continuum.
The Ce 4{ital f} surface shift: A test for the Anderson-impurity Hamiltonian
Duo, L.; De Rossi, S.; Vavassori, P.; Ciccacci, F.; Olcese, G.L.; Chiaia, G.; Lindau, I.
1996-12-01
Evidence is provided of the role of the different hybridization strengths between the surface and the bulk in determining the magnitude of the surface shift for the shallow Ce 4{ital f} levels, with respect to the deeper core levels. This was achieved by comparing the photoemission core levels for a weakly hybridized case (CeAl) to a case of intermediate hybridization ({gamma}-Ce). For CeAl a 4{ital f} surface shift of 0.45 eV was observed, similar to that for the 5{ital p} core level, whereas a smaller (if any) 4{ital f} surface shift was observed for {gamma}-Ce. Model calculations based on the Anderson impurity Hamiltonian are shown to give a correct evaluation of this effect, which can be exploited as a way of testing the results of such a description for the Ce {ital f} states. {copyright} {ital 1996 The American Physical Society.}
Classical mapping for Hubbard operators: Application to the double-Anderson model
Li, Bin; Miller, William H.; Levy, Tal J.; Rabani, Eran
2014-05-28
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.
Measuring service quality at the University of Texas M.D. Anderson Cancer Center.
Anderson, E A; Zwelling, L A
1996-01-01
Evaluates the service quality of four clinics at the University of Texas M.D. Anderson Cancer Center using a questionnaire methodology. The SERVQUAL instrument was administered to patients of the Medical Breast, Leukemia, Medical Gastroenterology and Bone Marrow Aspiration clinics. Results show that, according to the service gap methodology of comparing expectations and perceptions, across all four clinics the issues of billing accuracy and waiting times are deemed by patients as significant problems. In comparing the individual clinics, the Medical Gastroenterology and Leukemia clinics are best performers and the Medical Breast clinic is the worst. However, these differences in performance are due to differences in patients' expectations of service quality, rather than differences in perceptions. Concludes that customer expectations can have a strong impact on a firm's evaluation of its service quality.
Willert, Jeffrey; Taitano, William T.; Knoll, Dana
2014-09-15
In this note we demonstrate that using Anderson Acceleration (AA) in place of a standard Picard iteration can not only increase the convergence rate but also make the iteration more robust for two transport applications. We also compare the convergence acceleration provided by AA to that provided by moment-based acceleration methods. Additionally, we demonstrate that those two acceleration methods can be used together in a nested fashion. We begin by describing the AA algorithm. At this point, we will describe two application problems, one from neutronics and one from plasma physics, on which we will apply AA. We provide computational results which highlight the benefits of using AA, namely that we can compute solutions using fewer function evaluations, larger time-steps, and achieve a more robust iteration.
Twisting Anderson pseudospins with light: Quench dynamics in terahertz-pumped BCS superconductors
NASA Astrophysics Data System (ADS)
Chou, Yang-Zhi; Liao, Yunxiang; Foster, Matthew S.
2017-03-01
We study the preparation (pump) and the detection (probe) of far-from-equilibrium BCS superconductor dynamics in THz pump-probe experiments. In a recent experiment [R. Matsunaga, Y. I. Hamada, K. Makise, Y. Uzawa, H. Terai, Z. Wang, and R. Shimano, Phys. Rev. Lett. 111, 057002 (2013), 10.1103/PhysRevLett.111.057002], an intense monocycle THz pulse with center frequency ω ≃Δ was injected into a superconductor with BCS gap Δ ; the subsequent postpump evolution was detected via the optical conductivity. It was argued that nonlinear coupling of the pump to the Anderson pseudospins of the superconductor induces coherent dynamics of the Higgs (amplitude) mode Δ (t ) . We validate this picture in a two-dimensional BCS model with a combination of exact numerics and the Lax reduction method, and we compute the nonequilibrium phase diagram as a function of the pump intensity. The main effect of the pump is to scramble the orientations of Anderson pseudospins along the Fermi surface by twisting them in the x y plane. We show that more intense pump pulses can induce a far-from-equilibrium phase of gapless superconductivity ("phase I"), originally predicted in the context of interaction quenches in ultracold atoms. We show that the THz pump method can reach phase I at much lower energy densities than an interaction quench, and we demonstrate that Lax reduction (tied to the integrability of the BCS Hamiltonian) provides a general quantitative tool for computing coherent BCS dynamics. We also calculate the Mattis-Bardeen optical conductivity for the nonequilibrium states discussed here.
Volcanic ash dispersed in the Wyodak-Anderson coal bed, Powder River Basin, Wyoming
Triplehorn, D.M.; Stanton, R.W.; Ruppert, L.F.; Crowley, S.S.
1991-01-01
Minerals derived from air-fall volcanic ash were found in two zones in the upper Paleocene Wyodak-Anderson coal bed of the Fort Union Formation in the Powder River Basin of Wyoming, and are the first reported evidence of such volcanic material in this thick (> 20 m) coal bed. The volcanic minerals occur in zones that are not visually obvious because they contain little or no clay. These zones were located by geophysical logs of the boreholes and X-ray radiography of the cores. The zones correspond to two of a series of incremental core samples of the coal bed that have anomalous concentrations of Zr, Ba, Nb, Sr, and P2O5. Two suites of minerals were found in both of the high-density zones. A primary suite (not authigenic) consists of silt-sized quartz grains, biotite, and minor zircon. A minor suite consists of authigenic minerals, including calcite, pyrite, kaolinite, quartz, anatase, barite, and an alumino-phosphate (crandallite?). The original volcanic ash is inferred to have consisted of silica glass containing phenocrysts of quartz, biotite, zircon, and possibly, associated feldspars, pyroxenes, and amphiboles. The glass, as well as the less stable minerals, probably dissolved relatively quickly and contributed to the minor authigenic mineral suite or was removed from the peat as a result of the prevailing hydrologic conditions present in a raised peat formation. This type of volcanic ash suggests that suggests that volcanic material could have rained on the peat; this fallout may have also had a fertilizing effect on the peat by providing nutrients essential for plant growth thus contributing to the thick accumulations of the Wyodak-Anderson bed. Notwithstanding, the presence of these minerals provides evidence for the contribution by volcanic sources to the mineral content of coal, but not as tonsteins. ?? 1991.
Transport across an Anderson quantum dot in the intermediate coupling regime
NASA Astrophysics Data System (ADS)
Kern, Johannes; Grifoni, Milena
2013-09-01
We describe linear and nonlinear transport across a strongly interacting single impurity Anderson model quantum dot with intermediate coupling to the leads, i.e. with tunnel coupling Γ of the order of the thermal energy k B T. The coupling is large enough that sequential tunneling processes (second order in the tunneling Hamiltonian) alone do not suffice to properly describe the transport characteristics. Upon applying a density matrix approach, the current is expressed in terms of rates obtained by considering a very small class of diagrams which dress the sequential tunneling processes by charge fluctuations. We call this the "dressed second order" (DSO) approximation. One advantage of the DSO is that, still in the Coulomb blockade regime, it can describe the crossover from thermally broadened to tunneling broadened conductance peaks. When the temperature is decreased even further ( k B T < Γ), the DSO captures Kondesque behaviours of the Anderson quantum dot qualitatively: we find a zero bias anomaly of the differential conductance versus applied bias, an enhancement of the conductance with decreasing temperature as well as universality of the shape of the conductance as function of the temperature. We can without complications address the case of a spin degenerate level split energetically by a magnetic field. In case spin dependent chemical potentials are assumed and only one of the four chemical potentials is varied, the DSO yields in principle only one resonance. This seems to be in agreement with experiments with pseudo spin [U. Wilhelm, J. Schmid, J. Weis, K.V. Klitzing, Physica E 14, 385 (2002)]. Furthermore, we get qualitative agreement with experimental data showing a cross-over from the Kondo to the empty orbital regime.
10 CFR 8.2 - Interpretation of Price-Anderson Act, section 170 of the Atomic Energy Act of 1954.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 10 Energy 1 2010-01-01 2010-01-01 false Interpretation of Price-Anderson Act, section 170 of the Atomic Energy Act of 1954. 8.2 Section 8.2 Energy NUCLEAR REGULATORY COMMISSION INTERPRETATIONS § 8.2... in Nuclear Energy 75 (1959). In the testimony before the Joint Committee last year, Professor...
Federal Register 2010, 2011, 2012, 2013, 2014
2012-12-06
... Surface Transportation Board Chessie Logistics Co., LLC--Acquisition and Operation Exemption-- J. Emil Anderson & Son, Inc. Chessie Logistics Co., LLC (Chessie), a noncarrier, has filed a verified notice of... copy of each pleading must be served on Ariel A. Erbacher, Legal Counsel, Chessie Logistics Co.,...
10 CFR 8.2 - Interpretation of Price-Anderson Act, section 170 of the Atomic Energy Act of 1954.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 10 Energy 1 2012-01-01 2012-01-01 false Interpretation of Price-Anderson Act, section 170 of the Atomic Energy Act of 1954. 8.2 Section 8.2 Energy NUCLEAR REGULATORY COMMISSION INTERPRETATIONS § 8.2... in Nuclear Energy 75 (1959). In the testimony before the Joint Committee last year, Professor...
10 CFR 8.2 - Interpretation of Price-Anderson Act, section 170 of the Atomic Energy Act of 1954.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 10 Energy 1 2011-01-01 2011-01-01 false Interpretation of Price-Anderson Act, section 170 of the Atomic Energy Act of 1954. 8.2 Section 8.2 Energy NUCLEAR REGULATORY COMMISSION INTERPRETATIONS § 8.2... in Nuclear Energy 75 (1959). In the testimony before the Joint Committee last year, Professor...
ERIC Educational Resources Information Center
Newman, Michael K.
A study identified and analyzed the learning preferences of 17 seriously and chronically mentally ill adults participating in the rehabilitative psychosocial therapy program at the Toxaway Church Site of the Anderson Mental Health Center. Staff perceived as boring and unfocused the traditional treatment approach that relied mainly upon…
NASA Astrophysics Data System (ADS)
Sposetti, C. N.; Manuel, L. O.; Roura-Bas, P.
2016-08-01
The Anderson impurity model is studied by means of the self-consistent hybridization expansions in its noncrossing (NCA) and one-crossing (OCA) approximations. We have found that for the one-channel spin-1 /2 particle-hole symmetric Anderson model, the NCA results are qualitatively wrong for any temperature, even when the approximation gives the exact threshold exponents of the ionic states. Actually, the NCA solution describes an overscreened Kondo effect, because it is the same as for the two-channel infinite-U single-level Anderson model. We explicitly show that the NCA is unable to distinguish between these two very different physical systems, independently of temperature. Using the impurity entropy as an example, we show that the low-temperature values of the NCA entropy for the symmetric case yield the limit Simp(T =0 ) →ln√{2 }, which corresponds to the zero temperature entropy of the overscreened Kondo model. Similar pathologies are predicted for any other thermodynamic property. On the other hand, we have found that the OCA approach lifts the artificial mapping between the models and restores correct properties of the ground state, for instance, a vanishing entropy at low enough temperatures Simp(T =0 ) →0 . Our results indicate that the very well known NCA should be used with caution close to the symmetric point of the Anderson model.
Rayman, M K; Aris, B
1981-01-01
Comparison of the Anderson--Baird-Parker direct plating method (DP) and the North American most probable number procedure (MPN) for enumerating Escherichia coli in frozen meats revealed that the DP method is more precise and yields higher counts of E. coli than the MPN procedure. Any of three brands of membrane filters tested was suitable for use in the DP method.
Receiver-exciter controller design
NASA Technical Reports Server (NTRS)
Jansma, P. A.
1982-01-01
A description of the general design of both the block 3 and block 4 receiver-exciter controllers for the Deep Space Network (DSN) Mark IV-A System is presented along with the design approach. The controllers are designed to enable the receiver-exciter subsystem (RCV) to be configured, calibrated, initialized and operated from a central location via high level instructions. The RECs are designed to be operated under the control of the DMC subsystem. The instructions are in the form of standard subsystem blocks (SSBs) received via the local area network (LAN). The centralized control provided by RECs and other DSCC controllers in Mark IV-A is intended to reduce DSN operations costs from the Mark III era.
Quantum transport localization through graphene.
Srivastava, Saurabh; Kino, Hiori; Nakaharai, Shu; Verveniotis, Elisseos; Okawa, Yuji; Ogawa, Shinichi; Joachim, Christian; Aono, Masakazu
2017-01-20
Localization of atomic defect-induced electronic transport through a single graphene layer is calculated using a full-valence electronic structure description as a function of the defect density and taking into account the atomic-scale deformations of the layer. The elementary electronic destructive interferences leading to Anderson localization are analyzed. The low-voltage current intensity decreases with increasing length and defect density, with a calculated localization length ζ = 3.5 nm for a defect density of 5%. The difference from the experimental defect density of 0.5% required for an oxide surface-supported graphene to obtain the same ζ is discussed, pointing out how interactions of the graphene supporting surface and surface chemical modifications also control electronic transport localization.
Quantum transport localization through graphene
NASA Astrophysics Data System (ADS)
Srivastava, Saurabh; Kino, Hiori; Nakaharai, Shu; Verveniotis, Elisseos; Okawa, Yuji; Ogawa, Shinichi; Joachim, Christian; Aono, Masakazu
2017-01-01
Localization of atomic defect-induced electronic transport through a single graphene layer is calculated using a full-valence electronic structure description as a function of the defect density and taking into account the atomic-scale deformations of the layer. The elementary electronic destructive interferences leading to Anderson localization are analyzed. The low-voltage current intensity decreases with increasing length and defect density, with a calculated localization length ζ = 3.5 nm for a defect density of 5%. The difference from the experimental defect density of 0.5% required for an oxide surface-supported graphene to obtain the same ζ is discussed, pointing out how interactions of the graphene supporting surface and surface chemical modifications also control electronic transport localization.
8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER ...
8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER No. 2., AND GENERATOR UNITS BEHIND EXCITER No. 2 IN BACKGROUND. EXCITER No. 1 GENERATOR HAS A COVER OVER TOP HALF OF COMMUTATOR ELEMENT. VIEW TO NORTHWEST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA
Thermodynamic potential of the periodic Anderson model with the X-boson method: chain approximation
NASA Astrophysics Data System (ADS)
Franco, R.; Figueira, M. S.; Foglio, M. E.
2002-05-01
The periodic Anderson model (PAM) in the U→∞ limit has been studied in a previous work employing the cumulant expansion with the hybridization as perturbation (Figueira et al., Phys. Rev. B 50 (1994) 17 933). When the total number of electrons Nt is calculated as a function of the chemical potential μ in the “chain approximation” (CHA), there are three values of the chemical potential μ for each Nt in a small interval of Nt at low T (Physica A 208 (1994) 279). We have recently introduced the “X-boson” method, inspired in the slave boson technique of Coleman, that solves the problem of nonconservation of probability (completeness) in the CHA as well as removing the spurious phase transitions that appear with the slave boson method in the mean field approximation. In the present paper, we show that the X-boson method solves also the problem of the multiple roots of Nt( μ) that appear in the CHA.
Application of the S=1 underscreened Anderson lattice model to Kondo uranium and neptunium compounds
NASA Astrophysics Data System (ADS)
Thomas, Christopher; da Rosa Simões, Acirete S.; Iglesias, J. R.; Lacroix, C.; Perkins, N. B.; Coqblin, B.
2011-01-01
Magnetic properties of uranium and neptunium compounds showing the coexistence of the Kondo screening effect and ferromagnetic order are investigated within the Anderson lattice Hamiltonian with a two-fold degenerate f level in each site, corresponding to 5f2 electronic configuration with S=1 spins. A derivation of the Schrieffer-Wolff transformation is presented and the resulting Hamiltonian has an effective f-band term, in addition to the regular exchange Kondo interaction between the S=1 f spins and the s=1/2 spins of the conduction electrons. The resulting effective Kondo lattice model can describe both the Kondo regime and a weak delocalization of the 5f electrons. Within this model we compute the Kondo and Curie temperatures as a function of model parameters, namely the Kondo exchange interaction constant JK, the magnetic intersite exchange interaction JH, and the effective f bandwidth. We deduce, therefore, a phase diagram of the model which yields the coexistence of the Kondo effect and ferromagnetic ordering and also accounts for the pressure dependence of the Curie temperature of uranium compounds such as UTe.
Dental findings and rehabilitation in familial osteodysplasia (Anderson type): a case report.
Deger, S; Tabar, G; Sermet, B; Tanyeri, H; Kurklu, E
2006-03-01
Familial osteodysplasia is a disorder of osteogenesis with an autosomal recessive pattern of inheritance which predominantly affects facial bones. No recent case had been reported, particularly from a dental point of view since the syndrome was first described by Anderson et al (JAMA 1972;220:1687-93). A 23-year-old male with familial osteodysplasia was presented in maxillofacial and dental aspects with clinical and radiological manifestations including malocclusion, abnormal teeth alignment, impacted teeth, shape disturbances including uncompleted coronal formation, root shortening with bulbous form, high angled mandible and elongation of the corpus of mandible. Recognition of the syndromal features prior to any dental intervention is of paramount importance because of increased inclination to spontaneous mandibular fractures. Hence, no surgical intervention was performed for impacted teeth. Following the extractions of severely mobile teeth, a definitive restoration was fabricated as distal-extension removable partial dentures with conus crown telescopic system. The aesthetic and functional outcome was satisfactory for the patient. In conclusion, dentists appear to play an important role in the recognition of familial osteodysplasia, based on maxillofacial and dentoalveolar findings. Awareness of the syndromal features, especially of spontaneous fractures, would detect the limitations for dental interventions and treatment planning.
Verdam, Maria Christina dos Santos; de Andrade, Kleyton Cardoso; Fernandes, Karina Lorena Meira; Machado, Tallita Marques; de Souza, Mayane Pereira; Koolen, Hector Henrique Ferreira; Miyazaki, Cristina Mayumi Sasaki; Kalegari, Milena; Miguel, Marilis Dallarmi; Stuelp-Campelo, Patricia Maria; Miguel, Obdulio Gomes
2017-01-01
Background. Byrsonima is a promising neotropical genus, rich in flavonoids and triterpenes, with several proven pharmacological properties. Nevertheless, Byrsonima duckeana W. R. Anderson is an Amazonian species almost not studied. Objective. To assess the antioxidant, anti-inflammatory, and analgesic activities of Byrsonima duckeana leaves. Materials and Methods. We analyzed an ethanol extract and its fractions for polyphenol content and UHPLC-MS/MS, phosphomolybdenum, DPPH, TBARS antioxidant tests, formalin-induced pain, carrageenan-induced peritonitis, acetic acid-induced abdominal writhings, and hot plate assays. Results. All the samples showed high polyphenol content and antioxidant capacity in the phosphomolybdenum, DPPH, and TBARS tests. We identified ethyl gallate, quinic acid, gallic acid, catechin, epicatechin, quercetrin, and quercetin in the samples. B. duckeana was able to reduce leukocyte migration in the carrageenan-induced peritonitis by 43% and the licking time in the formalin test by 57%. In the acetic acid-induced writhing test, the chloroform (FCL) and ethyl acetate (FEA) fractions were the most active samples. FEA was selected for the hot plate test, where all the dosages tested (5, 50, and 200 mg·kg−1) showed significant analgesic activity. Conclusion. B. duckeana has interesting analgesic and antioxidant activities, due to its high phenolic content, especially phenolic acids. PMID:28367492
Basic Properties of Conductivity and Normal Hall Effect in the Periodic Anderson Model
NASA Astrophysics Data System (ADS)
Watanabe, Shinji; Miyake, Kazumasa
2016-04-01
Exact formulas of diagonal conductivity σxx and Hall conductivity σxy are derived from the Kubo formula in hybridized two-orbital systems with arbitrary band dispersions. On the basis of the theoretical framework for the Fermi liquid based on these formulas, the ground-state properties of the periodic Anderson model with electron correlation and weak impurity scattering are studied on the square lattice. It is shown that imbalance of the mass-renormalization factors causes remarkable increase in σxx and σxy in the valence-fluctuation regime as the f level increases while the cancellation of the renormalization factors causes slight increase in σxx and σxy in the Kondo regime. The Hall coefficient RH shows almost constant behavior in both the regimes. Near half filling, RH is expressed by the total hole density as R{H} = 1/(bar{n}{hole}e) while RH approaches zero near quarter filling, which reflects the curvature of the Fermi surface. These results hold as far as the damping rate for f electrons is less than about 10% of the renormalized hybridization gap. From these results we discuss pressure dependence of residual resistivity and normal Hall effect in Ce- and Yb-based heavy electron systems.
Anderson lattice in the intermediate valence compound Ce3Ni2B2N3-δ
NASA Astrophysics Data System (ADS)
Ali, Tahir; Bauer, Ernst; Hilscher, Gerfried; Michor, Herwig
2011-03-01
We have studied magnetic, thermodynamic, and transport properties of Ce3Ni2B2N3-δ and its solid solution with the Tc≃13 K superconductor La3Ni2B2N3-δ. The solid solution (La,Ce)3Ni2B2N3-δ reveals a rapid reduction of Tc by increasing the Ce content with a complete suppression of superconductivity at the composition La2.85Ce0.15Ni2B2N3-δ. The low-temperature properties characterize Ce3Ni2B2N3-δ as an intermediate valence system with a moderately enhanced Sommerfeld value γ≃54 mJ/mol K2 and a susceptibility χ0≃1.6×10-3 emu/mol, increased by about one order of magnitude as compared to the respective value χ0≃0.2×10-3 emu/mol of superconducting La3Ni2B2N3-δ (γ=26 mJ/mol K2) which serves as reference with a nonmagnetic rare earth ion. The electrical resistivity and thermoelectric power of Ce3Ni2B2N3-δ are analyzed in terms of the degenerate Anderson lattice model revealing a characteristic Kondo temperature TKALM~1100 K.
Non-equilibrium STLS approach to transport properties of single impurity Anderson model
NASA Astrophysics Data System (ADS)
Rezai, Raheleh; Ebrahimi, Farshad
2014-04-01
In this work, using the non-equilibrium Keldysh formalism, we study the effects of the electron-electron interaction and the electron-spin correlation on the non-equilibrium Kondo effect and the transport properties of the symmetric single impurity Anderson model (SIAM) at zero temperature by generalizing the self-consistent method of Singwi, Tosi, Land, and Sjolander (STLS) for a single-band tight-binding model with Hubbard type interaction to out of equilibrium steady-states. We at first determine in a self-consistent manner the non-equilibrium spin correlation function, the effective Hubbard interaction, and the double-occupancy at the impurity site. Then, using the non-equilibrium STLS spin polarization function in the non-equilibrium formalism of the iterative perturbation theory (IPT) of Yosida and Yamada, and Horvatic and Zlatic, we compute the spectral density, the current-voltage characteristics and the differential conductance as functions of the applied bias and the strength of on-site Hubbard interaction. We compare our spectral densities at zero bias with the results of numerical renormalization group (NRG) and depict the effects of the electron-electron interaction and electron-spin correlation at the impurity site on the aforementioned properties by comparing our numerical result with the order U2 IPT. Finally, we show that the obtained numerical results on the differential conductance have a quadratic universal scaling behavior and the resulting Kondo temperature shows an exponential behavior.
1992-12-01
An inventory of wetlands within the floodplain of East Fork Poplar Creek (EFPC) in Anderson and Roane Counties, Tennessee was conducted during October, 1991 through May, 1992 for the US Department of Energy (DOE) by the US Army Corps of Engineers, Nashville District. About 15 miles of EFPC channel and 500 acres of its floodplain are contaminated with mercury and other contaminants released from the Y-12 Plant on the DOE Oak Ridge Reservation. The wetland inventory will serve as baseline information for DOE`s remedial action planning and National Environmental Policy Act compliance efforts related to the contamination. In order to provide broad wetland determinations beyond which future wetland definitions are unlikely to expand, the 1989 Federal Manual for Identifying And Delineating Jurisdictional Wetlands was utilized. Using the manual`s methodology in a contaminated system under the approved health and safety plan presented some unique problems, resulting in intrusive sampling for field indicators of hydric soils being accomplished separately from observation of other criteria. Beginning with wetland areas identified on National Wetland Inventory Maps, the entire floodplain was examined for presence of wetland criteria, and 17 wetlands were identified ranging from 0.01 to 2.81 acres in size. The majority of wetlands identified were sized under 1 acre. Some of the wetlands identified were not delineated on the National Wetland Inventory Maps, and much of the wetland area delineated on the maps did not meet the criteria under the 1989 manual.
The three-dimensional Edwards-Anderson spin glass in an external magnetic field
NASA Astrophysics Data System (ADS)
Yllanes, David; Janus Collaboration
2014-03-01
Spin glasses are a longstanding model for the sluggish dynamics that appears at the glass transition. However, in order for spin glasses to be a faithful model for general glassy physics, we need to introduce an external magnetic field to eliminate their time-reversal symmetry. Unfortunately, little is known about the critical behavior of a spin glass in a field in three spatial dimensions. We have carried out a dynamical study combining equilibrium and non-equilibrium data. In particular, using the Janus computer, we have been able to simulate one thousand samples, each with half a million spins, along a time window spanning ten orders of magnitude for several magnetic fields and temperature protocols. Our main conclusion is that the system has a clearly identifiable dynamical transition, which we discuss in terms of different possibilities for the underlying physics (from a thermodynamical spin-glass transition to a mode-coupling crossover). In fact, we are able to make quantitative connections between the Edwards-Anderson spin glass and the physics of supercooled liquids. We also discuss ongoing work in equilibrium from parallel tempering simulations. Supported by the ERC, grant agreement no. 247328.
Numerical evidence against both mean field and droplet scenarios of the Edwards-Anderson model
NASA Astrophysics Data System (ADS)
Fernandez, Julio F.; Alonso, Juan J.
2013-03-01
From tempered Monte Carlo simulations, we have obtained accurate probability distributions p (q) of the spin-overlap parameter q for finite Edwards-Anderson (EA) and Sherrington-Kirkpatrick (SK) spin-glass systems at low temperatures. Our results for p (q) follow from averages over 105 disordered samples of linear sizes L = 4 - 8 and over 15 000 samples for L = 10 . In both the SK and EA models, at temperatures as low as 0 . 2Tsg , where Tsg is the transition temperature, p (q) varies insignificantly with L. This does not fit the trend that the droplet model predicts for large L. We have also calculated correlation functions, F (q1 ,q2) , from which rms deviations, δp , over different realizations of quenched disorder, as well as thermal fluctuations, w, of q values, follow. Our numerical results for δp and w scale as √{ L} and 1 / L , respectively, in the SK model. This fits in well with mean field predictions. On the other hand, our data for w and δp vary little, if at all, for the EA model.
Jiang, Cheng-Wei; Ni, I-Chih; Tzeng, Shien-Der; Wu, Cen-Shawn; Kuo, Watson
2014-06-07
How the interparticle tunnelling affects the charge conduction of self-assembled gold nanoparticles is studied by three means: tuning the tunnel barrier width by different molecule modification and by substrate bending, and tuning the barrier height by high-dose electron beam exposure. All approaches indicate that the metal-Mott insulator transition is governed predominantly by the interparticle coupling strength, which can be quantified by the room temperature sheet resistance. The Hubbard gap, following the prediction of quantum fluctuation theory, reduces to zero rapidly as the sheet resistance decreases to the quantum resistance. At very low temperature, the fate of devices near the Mott transition depends on the strength of disorder. The charge conduction is from nearest-neighbour hopping to co-tunnelling between nanoparticles in Mott insulators whereas it is from variable-range hopping through charge puddles in Anderson insulators. When the two-dimensional nanoparticle network is under a unidirectional strain, the interparticle coupling becomes anisotropic so the average sheet resistance is required to describe the charge conduction.
Nonequilibrium transport in the Anderson-Holstein model with interfacial screening
NASA Astrophysics Data System (ADS)
Perfetto, Enrico; Stefanucci, Gianluca
Image charge effects in nanoscale junctions with strong electron-phonon coupling open the way to unexplored physical scenarios. Here we present a comprehensive study of the transport properties of the Anderson-Holstein model in the presence of dot-lead repulsion. We propose an accurate many-body approach to deal with the simultaneous occurrence of the Franck-Condon blockade and the screening-induced enhancement of the polaron mobility. Remarkably, we find that a novel mechanism of negative differential conductance origins from the competition between the charge blocking due to the electron-phonon interaction and the charge deblocking due to the image charges. An experimental setup to observe this phenomenon is discussed. References [1]E. Perfetto, G. Stefanucci and M. Cini, Phys. Rev. B 85, 165437 (2012). [2] E. Perfetto and G. Stefanucci, Phys. Rev. B 88, 245437 (2013). [3] E. Perfetto and G. Stefanucci, Journal of Computational Electronics 14, 352 (2015). E.P. and G.S. acknowledge funding by MIUR FIRB Grant No. RBFR12SW0J.
Animal model of Sar1b deficiency presents lipid absorption deficits similar to Anderson Disease
Levic, Daniel S.; Minkel, JR; Wang, Wen-Der; Rybski, Witold M.; Melville, David B.; Knapik, Ela W.
2015-01-01
Anderson Disease (ANDD) or Chylomicron Retention Disease (CMRD) is a rare, hereditary lipid malabsorption syndrome associated with mutations in the SAR1B gene that is characterized by failure to thrive and hypocholesterolemia. Although the SAR1B structure has been resolved and its role in formation of coat protein II (COPII) coated carriers is well established, little is known about the requirement for SAR1B during embryogenesis. To address this question, we have developed a zebrafish model of Sar1b deficiency based on antisense oligonucleotide knockdown. We show that zebrafish sar1b is highly conserved among vertebrates, broadly expressed during development, and enriched in the digestive tract organs, brain and craniofacial skeleton. Consistent with ANDD symptoms of chylomicron retention, we found that dietary lipids in Sar1b deficient embryos accumulate in enterocytes. Transgenic expression analysis revealed that Sar1b is required for growth of exocrine pancreas and liver. Furthermore, we found abnormal differentiation and maturation of craniofacial cartilage associated with defects in procollagen II secretion, and absence of select, neuroD-positive neurons of the midbrain and hindbrain. The model presented here will help to systematically dissect developmental roles of Sar1b and to discover molecular and cellular mechanisms leading to organ-specific ANDD pathology. PMID:25559265
Low-lying excitations in a strongly interacting Fermi gas
NASA Astrophysics Data System (ADS)
Vale, Christopher; Hoinka, Sascha; Dyke, Paul; Lingham, Marcus
2016-05-01
We present measurements of the low-lying excitation spectrum of a strongly interacting Fermi gas across the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) crossover using Bragg spectroscopy. By focussing the Bragg lasers onto the central volume of the cloud we can probe atoms at near-uniform density allowing measurement of the homogeneous density-density response function. The Bragg wavevector is set to be approximately half of the Fermi wavevector to probe the collective response. Below the superfluid transition temperature the Bragg spectra dominated by the Bogoliubov-Anderson phonon mode. Single particle excitations become visible at energies greater than twice the pairing gap. As interactions are tuned from the BCS to BEC regime the phonon and single particle modes separate apart and both the pairing gap and speed of sound can be directly read off in certain regions of the crossover. Single particle pair-breaking excitations become heavily suppressed as interactions are tuned from the BCS to BEC regimes.
Quantum transport through disordered 1D wires: Conductance via localized and delocalized electrons
Gopar, Víctor A.
2014-01-14
Coherent electronic transport through disordered systems, like quantum wires, is a topic of fundamental and practical interest. In particular, the exponential localization of electron wave functions-Anderson localization-due to the presence of disorder has been widely studied. In fact, Anderson localization, is not an phenomenon exclusive to electrons but it has been observed in microwave and acoustic experiments, photonic materials, cold atoms, etc. Nowadays, many properties of electronic transport of quantum wires have been successfully described within a scaling approach to Anderson localization. On the other hand, anomalous localization or delocalization is, in relation to the Anderson problem, a less studied phenomenon. Although one can find signatures of anomalous localization in very different systems in nature. In the problem of electronic transport, a source of delocalization may come from symmetries present in the system and particular disorder configurations, like the so-called Lévy-type disorder. We have developed a theoretical model to describe the statistical properties of transport when electron wave functions are delocalized. In particular, we show that only two physical parameters determine the complete conductance distribution.
Sala, Francesco; Albisetti, Walter; Capitani, Dario
2010-11-01
Taylor Spatial Frame (TSF) combines a multiplanar external fixator and software accuracy for reduction of acute long-bone fractures. The frame gives stability, soft-tissue preservation, adjustability and functionality allowing bone to realize its full osteogenic potential. Three patients with multiple injuries and femoral Gustilo-Anderson type III C have been treated in our center. Initial surgery was performed within 6 h of injury with help of vascular surgeon. We used TSF as definitive fixation method. The results were assessed using the functional and radiological scoring system described by Paley and Maar. Fracture union occurred in all limbs and average fixation time was 151.6 days. All three patients had excellent outcome in terms of bony and functional ASAMI criteria. The TSF is a valuable tool. It is a definitive method of femoral Gustilo-Anderson type III C fracture care using external fixation with several advantages over previously used devices.
The aeronomy of vibrationally excited ozone
NASA Technical Reports Server (NTRS)
Frederick, J. E.; Allen, J. E., Jr.
1980-01-01
Theoretical calculations show that above 80 km in the earth's atmosphere the production of vibrationally excited ozone by chemical processes leads to number densities which are usually larger than those expected for local thermodynamic equilibrium. Quenching of highly excited molecules produced in O+O2+M, O3+M provided a significant source of the lower lying states above the mesopause while the 9.6 microns emission of O3 (0,0,1) was a major sink. Analysis of available laboratory results implied that reactions involving excited ozone play a significant role in the global ozone balance despite the relatively small abundance of the molecule. However, this effect is implicit in many of the rate coefficients currently used in stratospheric calculations. In the upper mesosphere and lower thermosphere, where the excited state populations differ from those for thermal equilibrium, published reaction rate data are not necessarily applicable to aeronomic calculations.
Ultrafast optical excitation of magnetic skyrmions
Ogawa, N.; Seki, S.; Tokura, Y.
2015-01-01
Magnetic skyrmions in an insulating chiral magnet Cu2OSeO3 were studied by all-optical spin wave spectroscopy. The spins in the conical and skyrmion phases were excited by the impulsive magnetic field from the inverse-Faraday effect, and resultant spin dynamics were detected by using time-resolved magneto-optics. Clear dispersions of the helimagnon were observed, which is accompanied by a distinct transition into the skyrmion phase, by sweeping temperature and magnetic field. In addition to the collective excitations of skyrmions, i.e., rotation and breathing modes, several spin precession modes were identified, which would be specific to optical excitation. The ultrafast, nonthermal, and local excitation of the spin systems by photons would lead to the efficient manipulation of nano-magnetic structures. PMID:25897634
Excitability dependent pattern formation
NASA Astrophysics Data System (ADS)
Prabhakara, Kaumudi; Gholami, Azam; Bodenschatz, Eberhard
2014-03-01
On starvation, the amoebae Dictyostelium discoideum emit the chemo-attractant cyclic adenosine monophosphate (cAMP) at specific frequencies. The neighboring amoebae sense cAMP through membrane receptors and produce their own cAMP. Soon the cells synchronize and move via chemotaxis along the gradient of cAMP. The response of the amoebae to the emission of cAMP is seen as spiral waves or target patterns under a dark field microscope. The causal reasons for the selection of one or the other patterns are still unclear. Here we present a possible explanation based on excitability. The excitability of the amoebae depends on the starvation time because the gene expression changes with starvation. Cells starved for longer times are more excitable. In this work, we mix cells of different excitabilities to study the dependence of the emergent patterns on the excitability. Preliminary results show a transition from spirals to target patterns for specific excitabilities. A phase map of the patterns for different combinations of excitability and number densities is obtained. We compare our findings with numerical simulations of existing theoretical models.
NASA Astrophysics Data System (ADS)
Brückner, Charlotte; Engels, Bernd
2017-01-01
Vertical and adiabatic singlet and triplet excitation energies of molecular p-type semiconductors calculated with various DFT functionals and wave-function based approaches are benchmarked against MS-CASPT2/cc-pVTZ reference values. A special focus lies on the singlet-triplet gaps that are very important in the process of singlet fission. Singlet fission has the potential to boost device efficiencies of organic solar cells, but the scope of existing singlet-fission compounds is still limited. A computational prescreening of candidate molecules could enlarge it; yet it requires efficient methods accurately predicting singlet and triplet excitation energies. Different DFT formulations (Tamm-Dancoff approximation, linear response time-dependent DFT, Δ-SCF) and spin scaling schemes along with several ab initio methods (CC2, ADC(2)/MP2, CIS(D), CIS) are evaluated. While wave-function based methods yield rather reliable singlet-triplet gaps, many DFT functionals are shown to systematically underestimate triplet excitation energies. To gain insight, the impact of exact exchange and correlation is in detail addressed.
Closser, Kristina D; Ge, Qinghui; Mao, Yuezhi; Shao, Yihan; Head-Gordon, Martin
2015-12-08
We develop a local excited-state method, based on the configuration interaction singles (CIS) wave function, for large atomic and molecular clusters. This method exploits the properties of absolutely localized molecular orbitals (ALMOs), which strictly limits the total number of excitations, and results in formal scaling with the third power of the system size for computing the full spectrum of ALMO-CIS excited states. The derivation of the equations and design of the algorithm are discussed in detail, with particular emphasis on the computational scaling. Clusters containing ∼500 atoms were used in evaluating the scaling, which agrees with the theoretical predictions, and the accuracy of the method is evaluated with respect to standard CIS. A pioneering application to the size dependence of the helium cluster spectrum is also presented for clusters of 25-231 atoms, the largest of which results in the computation of 2310 excited states per sampled cluster geometry.
Panda, Shasanka Shekhar; Bajpai, Minu; Jana, Manisha; Baidya, Dalim Kumar; Kumar, Rakesh
2014-01-01
Objective: The objective of this study was to evaluate the results of Anderson-Hynes pyeloplasty with isthmotomy and lateropexy in horseshoe kidney with pelviureteric junction obstruction (PUJO). Materials and Methods: Medical records of patients of horseshoe kidney with PUJO operated in our institute between June 1998 and June 2012 were reviewed. Anderson-Hynes pyeloplasty with isthmotomy and lateropexy was performed in all patients. The surgical outcome was evaluated with emphasis on the changes in degree of hydronephrosis by ultrasonography, renal drainage and function assessed by diuretic renal scans. Results: We studied the records of eight children of horseshoe kidney having unilateral PUJO. Obstruction was caused by a crossing lower-pole vessel in two cases, a high ureteral insertion in three and narrowing of the PUJ in three cases. Post-operative follow-up (median 4.4 years, range 18 months to 10 years) revealed improved renal function and good drainage in all cases. Hydronephrosis disappeared in 3, 4 showed Grade 1 and one showed Grade 2 hydronephrosis. All children are doing well and have no symptoms. Conclusion: Anderson-Hynes pyeloplasty with isthmotomy and lateropexy is a highly effective and safe procedure for treating PUJO in horseshoe kidney in children. PMID:24744513
Pieruzzi, Federico; Pieroni, Maurizio; Zachara, Elisabetta; Marziliano, Nicola; Morrone, Amelia; Cecchi, Franco
2015-11-01
Anderson-Fabry disease is a rare X-linked lysosomal storage disorder caused by mutations of the GLA gene that encodes alpha-galactosidase A. It is characterized by a multisystemic involvement: the renal, neurological, heart, cochleovestibular and cutaneous systems are the most damaged. Morbidity and mortality of Anderson-Fabry disease depend on renal insufficiency, heart failure and nervous system involvement. Left ventricular hypertrophy is the most common cardiac manifestation followed by conduction system disease, valve dysfunction, and arrhythmias. Mild to moderate left ventricular hypertrophy may simulate a non-obstructive hypertrophic cardiomyopathy. Management of Anderson-Fabry disease starting from the diagnosis of cardiac involvement, the prevention of complications, the therapeutic aspects, up to appropriate clinical follow-up, requires a multidisciplinary approach. According to recent management guidelines, only few evidence-based data are available to guide the clinical and therapeutic approach to this rare disease. An Italian Board, composed by nephrologists, cardiologists, geneticists, pediatricians and neurologists has been established in order to approve by consensus a diagnostic and therapeutic management protocol. The authors report the results of this cardiologic management consensus.
Warwick, P.D.; Stanton, R.W.
1988-01-01
Six lithofacies of the thick ( > 30 m) Wyodak-Anderson subbituminous coal bed of the Fort Union Formation (Paleocene), Powder River Basin, Wyoming, can be delimited using megascopic and petrographic data. Previous lithofacies analysis of the rock types associated with the Wyodak-Anderson bed suggested that raised peat accumulated in restricted parts of an inland flood plain. The peat bodies were separated by deposits of contemporaneous, possibly anastomosed channels. In this study, megascopic descriptions from four mine highwalls of the Wyodak-Anderson coal bed were found to be similar to facies defined by microscopic data from core and highwall samples. The data indicate that the upper and lower parts of the coal bed are rich in preserved wood remains (for instance, humotelinite), whereas the middle part of the bed contains comparatively larger amounts of material that resulted from degradation and comminution of the peat (e.g. eugelinite). The facies are interpreted to be the result of different chemical and biological environments at the time of peat formation. ?? 1988.
15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. ...
15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. 1 BEHIND. OVERHEAD CRANE DANGLES AT TOP OF PHOTO. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA
Asymptotic wave propagation in excitable media.
Bernus, Olivier; Vigmond, Edward
2015-07-01
Wave shape and velocity are important issues in reaction-diffusion systems, and are often the result of competition in media with heterogeneous conduction properties. Asymptotic wave front propagation at maximal conduction velocity has been previously reported in the context of anisotropic cardiac tissue, but it is unknown whether this is a universal property of excitable tissues where conduction velocity can be locally modulated by mechanisms other than anisotropy. Here, we investigate the impact of conduction heterogeneities and boundary effects on wave propagation in excitable media. Following a theoretical analysis, we find that wave-front cusps occur where local velocity is reduced and that asymptotic wave fronts propagate at the maximal translational conduction velocity. Simulations performed in different reaction-diffusion systems, including cardiac tissue, confirm our theoretical findings. We conclude that this property can be found in a wide range of reaction-diffusion systems with excitable dynamics and that asymptotic wave-front shapes can be predicted.
ATLANTA - United States Attorney Bill Nettles stated late yesterday that Nancy Marie Stein, age 62, of Anderson, South Carolina , was sentenced by Senior United States District Judge Henry M. Herlong in federal court in Greenville, to a total of 73
Supersolitons: Solitonic Excitations in Atomic Soliton Chains
Novoa, David; Michinel, Humberto; Perez-Garcia, Victor M.
2008-10-03
We show that, by tuning interactions in nonintegrable vector nonlinear Schroedinger equations modeling Bose-Einstein condensates and other relevant physical systems, it is possible to achieve a regime of elastic particlelike collisions between solitons. This would allow one to construct a Newton's cradle with solitons and supersolitons: localized collective excitations in solitary-wave chains.
Geomagnetic excitation of nutation
NASA Astrophysics Data System (ADS)
Ron, C.; Vondrák, J.
2015-08-01
We tested the hypothesis of Malkin (2013), who demonstrated that the observed changes of Free Core Nutation parameters (phase, amplitude) occur near the epochs of geomagnetic jerks. We found that if the numerical integration of Brzeziński broad-band Liouville equations of atmospheric/oceanic excitations is re-initialized at the epochs of geomagnetic jerks, the agreement between the integrated and observed celestial pole offsets is improved (Vondrák & Ron, 2014). Nevertheless, this approach assumes that the influence of geomagnetic jerks leads to a stepwise change in the position of celestial pole, which is physically not acceptable. Therefore we introduce a simple continuous excitation function that hypothetically describes the influence of geomagnetic jerks, and leads to rapid but continuous changes of pole position. The results of numerical integration of atmospheric/oceanic excitations and this newly introduced excitation are then compared with the observed celestial pole offsets, and prove that the agreement is improved significantly.
Arjomandy, Bijan; Sahoo, Narayan; Zhu, X. Ronald; Zullo, John R.; Wu, Richard Y.; Zhu Mingping; Ding Xiaoning; Martin, Craig; Ciangaru, George; Gillin, Michael T.
2009-06-15
The number of proton and carbon ion therapy centers is increasing; however, since the publication of the International Commission on Radiation Units and Measurements report, there has been no dedicated report dealing with proton therapy quality assurance. The purpose of this article is to describe the quality assurance procedures performed on the passively scattered proton therapy beams at The University of Texas M. D. Anderson Cancer Center Proton Therapy Center in Houston. The majorities of these procedures are either adopted from procedures outlined in the American Association of Physicists in Medical Task Group (TG) 40 report or are a modified version of the TG 40 procedures. In addition, new procedures, which were designed specifically to be applicable to the synchrotron at the author's center, have been implemented. The authors' procedures were developed and customized to ensure patient safety and accurate operation of synchrotron to within explicit limits. This article describes these procedures and can be used by others as a guideline for developing QA procedures based on particle accelerator specific parameters and local regulations pertinent to any new facility.
The pioneer woman's view of migraine: Elizabeth Garrett Anderson's thesis "Sur la migraine".
Wilkinson, M; Isler, H
1999-01-01
This is a presentation of a doctoral thesis of 1870. The author was English but the thesis and the examinations were in French. Elizabeth Garrett Anderson, usually referred to as E.G.A., was the first woman in Britain to obtain the title of M.D., but not the first in Europe. Nadeshda Prokofevna Suslova, a Russian, received her M.D. in 1867 in Zurich, the most liberal university at that time, soon to be flooded by female students from Russia. E.G.A. had been applying to the few possible European universities but she settled for Paris after the Empress Eugenie had decided that she should be accepted there. This meant that she could succeed without having to be a Paris resident, just by writing a thesis and passing a series of examinations presided over by Paul Broca. This was important as she was already conducting private and dispensary practice, and could not find a locum (she insisted on a woman). E.G.A. had suffered many setbacks, for being a woman, as such being unacceptable in dissection rooms and operating theatres, and generally in a professional career where women were unheard of. She was finally permitted to receive her medical diploma from the Worshipful Society of Apothecaries of London. She wrote about her thesis: "I have chosen Headache as its subject. I had to find a subject which could be well studied without post-mortem observations, of which I can have but very few in either private or dispensary practice; and I wished also to take a large subject, one that demanded some insight into the harmony that exists between the main physiological functions." Marcia Wilkinson (M.W.), who worked in the Elizabeth Garrett Anderson Hospital in London for 35 years, heard there of E.G.A.'s thesis on migraine and sent for it from Paris. In 1966 she translated it into English from the original French, being interested both in the subject and in the person of this resolute and lucid woman. When H. Isler found the French thesis in the British Library he intended to
On Planetary Evolution and the Evolution of Planetary Science During the Career of Don Anderson
NASA Astrophysics Data System (ADS)
Solomon, S. C.
2003-12-01
The planets of our solar system have long been viewed by Don Anderson as laboratories for testing general aspects of planetary evolution and as points of comparison to the Earth. I was fortunate to have been a student 39 years ago in a course at Caltech that Don taught with Bob Kovach on the interiors of the Earth and the planets. At that time, Mariner 4 had not yet flown by Mars, the lunar Ranger program was still in progress, and it was permissible to entertain the hypothesis that all of the terrestrial planets were identical in bulk composition. In the last four decades spacecraft have visited every planet from Mercury to Neptune; samples from the Moon, Mars, asteroids, and comets reside in our laboratories; and more than 100 planets have been discovered orbiting other stars. More importantly, traditionally distinct fields have merged to the point where planetary scientists must be conversant with the findings and modes of thinking from astronomy and biology as well as the geosciences. A few examples illustrate this confluence. Theoretical models for the structure of the atmospheres of gas-giant planets led to the first astronomical detection of an extrasolar planetary atmosphere for the transiting planet HD209458b. Although the atmospheric models were based on those for solar-system gas giants, the 3.5-day orbital period means that this planet is 100 times closer to its star than Jupiter is to the Sun, its effective temperature is 1100 K, and the detected signature of the planetary atmosphere was absorption by neutral sodium. Sodium in Mercury's exosphere, detected astronomically from Earth, figures into the question of how the terrestrial planets came to have distinct bulk compositions. Hypotheses to account for Mercury's high uncompressed density, and by inference its high ratio of metal to silicate, range from chemical gradients in the early solar nebula to preferential removal of silicates from a differentiated protoplanet by nebular heating or giant impact
Wang, Zhijie; Shi, Naiyi; Naing, Aung; Janku, Filip; Subbiah, Vivek; Araujo, Dejka M; Patel, Shreyaskumar R; Ludwig, Joseph A; Ramondetta, Lois M; Levenback, Charles F; Ramirez, Pedro T; Piha-Paul, Sarina A; Hong, David; Karp, Daniel D; Tsimberidou, Apostolia M; Meric-Bernstam, Funda; Fu, Siqing
2016-12-01
Advanced stage leiomyosarcoma (LMS) is incurable with current systemic antitumor therapies. Therefore, there is clinical interest in exploring novel therapeutic regimens to treat LMS. We reviewed the medical records of 75 consecutive patients with histologically confirmed metastatic LMS, who had been referred to the Clinical Center for Targeted Therapy at MD Anderson Cancer Center. To lay the foundation for potential phase I trials for the treatment of advanced LMS, we analyzed tumor response and survival outcome data. The frequent hotspot gene aberrations that we observed were the TP53 mutation (65%) and RB1 loss/mutation (45%) detected by Sequenom or next-generation sequencing. Among patients treated with gene aberration-related phase I trial therapy, the median progression-free survival was 5.8 months and the median overall survival was 15.9 months, significantly better than in patients without therapy (1.9 months, P = 0.001; and 8.7 months, P = 0.013, respectively). Independent risk factors that predicted shorter overall survival included hemoglobin <10 g/dL, body mass index <30 kg/m(2) , serum albumin <3.5 g/dL, and neutrophil above upper limit of normal. The median survivals were 19.9, 7.6, and 0.9 months for patients with 0, 1 or 2, and ≥3 of the above risk factors, respectively (P < 0.001). A prognostic scoring system that included four independent risk factors might predict survival in patients with metastatic LMS who were treated in a phase I trial. Gene aberration-related therapies led to significantly better clinical benefits, supporting that further exploration with novel mechanism-driven therapeutic regimens is warranted.
Anderson-Stuart Model to Analyze DC Conductivity of Fluormica Glassceramics
NASA Astrophysics Data System (ADS)
Jogad, Mahantappa S.; Krishnamurthy, B. S.; Saraswati, V.
2001-03-01
The Glassceramics (GC) are essentially polycrystalline solids in the matrix of residual glass phase. They are interesting in view of the scientific and technological importance. The fluormica glass system (K2O MgO Al2O3 MgF2 B2O3 SiO2) was prepared for a specific composition by melt quench technique, and the fluormica GC phase was obtained by giving heat treatment at 1123 K to the glass sample [1]. The transition from glass to GC was confirmed using XRD. The fluormica are structural analogues of natural mica. Here the K+ ions are weakly cross-bonded in tetrahedral sheet. Fluormica exhibits an unusual combination of properties like machinability, resistance to withstand high temperatures, high dielectric constant with low loss, and high DC resistivity [2]. We have measured the DC conductivity (s) as a function of temperature (T) using the two-probe method. These measurements have been analyzed using the Anderson-Stuart (AS) model [3]. The Arrhenius plots of s vs T exhibit two linear regions, and the activation energy of the GC is found to be larger than that of glass [1]. The physical parameters selected to fit s vs T using the AS model which describes fairly well the ionic conduction in the fluormica glass system, are found to be reasonable. However, it appeared that a distribution of activation energies instead of single activation energy is necessary, to explain the experimental data. Dr Mahntappa S Jogad would like to acknowledge the American Physical Society’s Kilambi Ramavataram Committee and the Fulbright Foreign Scholarship Board, for a visiting fellowship. References: 1. M S Jogad, B S Krishnamurthy and V Saraswati, Asian Journal of Physics, 6, Nos, 142, 158 (1997) 2. Mahantappa S Jogad, B S Krishnamurthy and V Saraswati, J Non Crystalline Solids (Communicated). 3. M. D. Ingram, Phys. Chem. Glasses, 28, 215 (1987).
The University of Texas M.D. Anderson Cancer Center Proton Therapy Facility
Smith, Alfred; Newhauser, Wayne; Latinkic, Mitchell; Hay, Amy; Cox, James; McMaken, Bruce; Styles, John
2003-08-26
The University of Texas M.D. Anderson Cancer Center (MDACC), in partnership with Sanders Morris Harris Inc., a Texas-based investment banking firm, and The Styles Company, a developer and manager of hospitals and healthcare facilities, is building a proton therapy facility near the MDACC main complex at the Texas Medical Center in Houston, Texas USA. The MDACC Proton Therapy Center will be a freestanding, investor-owned radiation oncology center offering state-of-the-art proton beam therapy. The facility will have four treatment rooms: three rooms will have rotating, isocentric gantries and the fourth treatment room will have capabilities for both large and small field (e.g. ocular melanoma) treatments using horizontal beam lines. There will be an additional horizontal beam room dedicated to physics research and development, radiation biology research, and outside users who wish to conduct experiments using proton beams. The first two gantries will each be initially equipped with a passive scattering nozzle while the third gantry will have a magnetically swept pencil beam scanning nozzle. The latter will include enhancements to the treatment control system that will allow for the delivery of proton intensity modulation treatments. The proton accelerator will be a 250 MeV zero-gradient synchrotron with a slow extraction system. The facility is expected to open for patient treatments in the autumn of 2005. It is anticipated that 675 patients will be treated during the first full year of operation, while full capacity, reached in the fifth year of operation, will be approximately 3,400 patients per year. Treatments will be given up to 2-shifts per day and 6 days per week.
Incidence of Atypical Femur Fractures in Cancer Patients: The MD Anderson Cancer Center Experience.
Edwards, Beatrice J; Sun, Ming; West, Dennis P; Guindani, Michele; Lin, Yan Heather; Lu, Huifang; Hu, Mimi; Barcenas, Carlos; Bird, Justin; Feng, Chun; Saraykar, Smita; Tripathy, Debasish; Hortobagyi, Gabriel N; Gagel, Robert; Murphy, William A
2016-08-01
Atypical femoral fractures (AFFs) are rare adverse events attributed to bisphosphonate (BP) use. Few cases of AFF in cancer have been described; the aim of this study is to identify the incidence and risk factors for AFF in a large cancer center. This retrospective study was conducted at the MD Anderson Cancer Center. The incidence rate of AFF among BP users was calculated from January 1, 2004 through December 31, 2013. The control group (n = 51) included 2 or 3 patients on BPs matched for age (≤1 year) and gender. Logistic regression analysis was used to assess the relationship between clinical characteristics and AFF. Twenty-three AFF cases were identified radiographically among 10,587 BP users, the total BP exposure was 53,789 months (4482 years), and the incidence of AFF in BP users was 0.05 cases per 100,000 person-years. Meanwhile, among 300,553 patients who did not receive BPs there were 2 cases of AFF as compared with the 23 cases noted above. The odds ratio (OR) of having AFF in BP users was 355.58 times higher (95% CI, 84.1 to 1501.4, p < 0.0001) than the risk in non-BP users. The OR of having AFF in alendronate users was 5.54 times greater (OR 5.54 [95% CI, 1.60 to 19.112, p = 0.007]) than the odds of having AFF among other BP users. Patients who were on zoledronic acid (ZOL) had smaller odds of developing AFF compared with other BP users in this matched case control sample. AFFs are rare, serious adverse events that occur in patients with cancer who receive BP therapy. Patients with cancer who receive BPs for prior osteoporosis therapy or for metastatic cancer are at higher risk of AFF. © 2016 American Society for Bone and Mineral Research.
Kinetics of excitation in TL and OSL detectors
NASA Astrophysics Data System (ADS)
Mandowski, A.; Orzechowski, J.; Mandowska, E.
2010-10-01
Kinetic equations for the semi-localized transitions (SLT) model are presented describing charge carrier's kinetics for the excitation and fast relaxation stages. The formulation allows for dose dependence studies of thermoluminescence (TL) and optically stimulated luminescence (OSL) detectors based on the SLT model. The sets of equations were solved numerically demonstrating temporal evolution of all variables of the SLT model during excitation and fast relaxation. The influence of the dose rate on excitation kinetics is shown.
Localized and Extended States in a Disordered Trap
Pezze, Luca; Sanchez-Palencia, Laurent
2011-01-28
We study Anderson localization in a disordered potential combined with an inhomogeneous trap. We show that the spectrum displays both localized and extended states, which coexist at intermediate energies. In the region of coexistence, we find that the extended states result from confinement by the trap and are weakly affected by the disorder. Conversely, the localized states correspond to eigenstates of the disordered potential, which are only affected by the trap via an inhomogeneous energy shift. These results are relevant to disordered quantum gases and we propose a realistic scheme to observe the coexistence of localized and extended states in these systems.
Two-photon excitation fluorescence microscopy.
So, P T; Dong, C Y; Masters, B R; Berland, K M
2000-01-01
Two-photon fluorescence microscopy is one of the most important recent inventions in biological imaging. This technology enables noninvasive study of biological specimens in three dimensions with submicrometer resolution. Two-photon excitation of fluorophores results from the simultaneous absorption of two photons. This excitation process has a number of unique advantages, such as reduced specimen photodamage and enhanced penetration depth. It also produces higher-contrast images and is a novel method to trigger localized photochemical reactions. Two-photon microscopy continues to find an increasing number of applications in biology and medicine.
Non-equilibrium STLS approach to transport properties of single impurity Anderson model
Rezai, Raheleh Ebrahimi, Farshad
2014-04-15
In this work, using the non-equilibrium Keldysh formalism, we study the effects of the electron–electron interaction and the electron-spin correlation on the non-equilibrium Kondo effect and the transport properties of the symmetric single impurity Anderson model (SIAM) at zero temperature by generalizing the self-consistent method of Singwi, Tosi, Land, and Sjolander (STLS) for a single-band tight-binding model with Hubbard type interaction to out of equilibrium steady-states. We at first determine in a self-consistent manner the non-equilibrium spin correlation function, the effective Hubbard interaction, and the double-occupancy at the impurity site. Then, using the non-equilibrium STLS spin polarization function in the non-equilibrium formalism of the iterative perturbation theory (IPT) of Yosida and Yamada, and Horvatic and Zlatic, we compute the spectral density, the current–voltage characteristics and the differential conductance as functions of the applied bias and the strength of on-site Hubbard interaction. We compare our spectral densities at zero bias with the results of numerical renormalization group (NRG) and depict the effects of the electron–electron interaction and electron-spin correlation at the impurity site on the aforementioned properties by comparing our numerical result with the order U{sup 2} IPT. Finally, we show that the obtained numerical results on the differential conductance have a quadratic universal scaling behavior and the resulting Kondo temperature shows an exponential behavior. -- Highlights: •We introduce for the first time the non-equilibrium method of STLS for Hubbard type models. •We determine the transport properties of SIAM using the non-equilibrium STLS method. •We compare our results with order-U2 IPT and NRG. •We show that non-equilibrium STLS, contrary to the GW and self-consistent RPA, produces the two Hubbard peaks in DOS. •We show that the method keeps the universal scaling behavior and correct
Excitation Methods for Bridge Structures
Farrar, C.R.; Duffy, T.A.; Cornwell, P.J.; Doebling, S.W.
1999-02-08
This paper summarizes the various methods that have been used to excited bridge structures during dynamic testing. The excitation methods fall into the general categories of ambient excitation methods and measured-input excitation methods. During ambient excitation the input to the bridge is not directly measured. In contrast, as the category label implies, measured-input excitations are usually applied at a single location where the force input to the structure can be monitored. Issues associated with using these various types of measurements are discussed along with a general description of the various excitation methods.
Impurities and electronic localization in graphene bilayers
NASA Astrophysics Data System (ADS)
Ojeda Collado, H. P.; Usaj, Gonzalo; Balseiro, C. A.
2015-01-01
We analyze the electronic properties of bilayer graphene with Bernal stacking and a low concentration of adatoms. Assuming that the host bilayer lies on top of a substrate, we consider the case where impurities are adsorbed only on the upper layer. We describe nonmagnetic impurities as a single orbital hybridized with carbon's pz states. The effect of impurity doping on the local density of states with and without a gated electric field perpendicular to the layers is analyzed. We look for Anderson localization in the different regimes and estimate the localization length. In the biased system, the field-induced gap is partially filled by strongly localized impurity states. Interestingly, the structure, distribution, and localization length of these states depend on the field polarization.
Berg, Bernd A; Billoire, Alain; Janke, Wolfhard
2002-04-01
Recently, it has been conjectured that the statistics of extremes is of relevance for a large class of correlated systems. For certain probability densities this predicts the characteristic large x falloff behavior f(x) approximately exp(-ae(x)), a>0. Using a multicanonical Monte Carlo technique, we have measured the Parisi overlap distribution P(q) for the three-dimensional Edward-Anderson Ising spin glass at and below the critical temperature We find that a probability distribution related to extreme-order statistics gives an excellent description of P(q) over about 80 orders of magnitude.
Agrinskaya, N. V.; Berezovets, V. A.; Bouravlev, A.; Kozub, V. I.
2014-08-20
We present our results obtained for Mn-doped GaAs quantum wells where the evidences of the ferromagnetic transition at relatively high temperatures were found at unusually small Mn concentrations. The observed values of hopping resistance at small temperatures evidenced that the samples are deep in the insulating regime. Thus the corresponding estimates of the overlapping integrals can hardly explain the large values of Curie temperatures T{sub c} ≃ 100 K. We develop a theoretical model qualitatively explaining the experimental results basing on the concept of virtual Anderson transition.
NASA Astrophysics Data System (ADS)
Eskandari-asl, Amir
2016-09-01
We consider a single impurity Anderson model (SIAM) in which the quantum dot(QD) is strongly coupled to a phonon bath in polaron regime. This coupling results in an effective e-e attraction. By computing the self energies using a current conserving approximation which is up to second order in this effective attraction, we show that if the interaction is strong enough, in non particle-hole (PH) symmetric case, the system would be bi-stable and we have hysteresis loop in the I-V characteristic. Moreover, the system shows negative differential conductance in some bias voltage intervals.
Joint min-max distribution and Edwards-Anderson's order parameter of the circular 1/f-noise model
NASA Astrophysics Data System (ADS)
Cao, Xiangyu; Le Doussal, Pierre
2016-05-01
We calculate the joint min-max distribution and the Edwards-Anderson's order parameter for the circular model of 1/f-noise. Both quantities, as well as generalisations, are obtained exactly by combining the freezing-duality conjecture and Jack-polynomial techniques. Numerical checks come with significantly improved control of finite-size effects in the glassy phase, and the results convincingly validate the freezing-duality conjecture. Application to diffusive dynamics is discussed. We also provide a formula for the pre-factor ratio of the joint/marginal Carpentier-Le Doussal tail for minimum/maximum which applies to any logarithmic random energy model.
NASA Astrophysics Data System (ADS)
Monthus, Cécile
2016-07-01
For short-ranged disordered quantum models in one dimension, the many-body-localization is analyzed via the adaptation to the many-body context (Serbyn et al 2015 Phys. Rev. X 5 041047) of the Thouless point of view on the Anderson transition: the question is whether a local interaction between two long chains is able to reshuffle completely the eigenstates (delocalized phase with a volume-law entanglement) or whether the hybridization between tensor states remains limited (many-body-localized phase with an area-law entanglement). The central object is thus the level of hybridization induced by the matrix elements of local operators, as compared with the difference of diagonal energies. The multifractal analysis of these matrix elements of local operators is used to analyze the corresponding statistics of resonances. Our main conclusion is that the critical point is characterized by the strong-multifractality spectrum f(0≤slant α ≤slant 2)=\\fracα{2} , well known in the context of Anderson localization in spaces of effective infinite dimensionality, where the size of the Hilbert space grows exponentially with the volume. Finally, the possibility of a delocalized non-ergodic phase near criticality is discussed.
Proteins of Excitable Membranes
Nachmansohn, David
1969-01-01
Excitable membranes have the special ability of changing rapidly and reversibly their permeability to ions, thereby controlling the ion movements that carry the electric currents propagating nerve impulses. Acetylcholine (ACh) is the specific signal which is released by excitation and is recognized by a specific protein, the ACh-receptor; it induces a conformational change, triggering off a sequence of reactions resulting in increased permeability. The hydrolysis of ACh by ACh-esterase restores the barrier to ions. The enzymes hydrolyzing and forming ACh and the receptor protein are present in the various types of excitable membranes. Properties of the two proteins directly associated with electrical activity, receptor and esterase, will be described in this and subsequent lectures. ACh-esterase has been shown to be located within the excitable membranes. Potent enzyme inhibitors block electrical activity demonstrating the essential role in this function. The enzyme has been recently crystallized and some protein properties will be described. The monocellular electroplax preparation offers a uniquely favorable material for analyzing the properties of the ACh-receptor and its relation to function. The essential role of the receptor in electrical activity has been demonstrated with specific receptor inhibitors. Recent data show the basically similar role of ACh in the axonal and junctional membranes; the differences of electrical events and pharmacological actions are due to variations of shape, structural organization, and environment. PMID:19873642
NASA Technical Reports Server (NTRS)
Parcell, L. A.; Mceachran, R. P.; Stauffer, A. D.
1990-01-01
The differential and total cross section for the excitation of the 3s1P10 and 3p1P1 states of neon by positron impact were calculated using a distorted-wave approximation. The results agree well with experimental conclusions.
Asymmetric magnon excitation by spontaneous toroidal ordering
Hayami, Satoru; Kusunose, Hiroaki; Motome, Yukitoshi
2016-04-12
The effects of spontaneous toroidal ordering on magnetic excitation are theoretically investigated for a localized spin model that includes a staggered Dzyaloshinsky–Moriya interaction and anisotropic exchange interactions, which arise from the antisymmetric spin–orbit coupling and the multiorbital correlation effect. We show that the model exhibits a Néel-type antiferromagnetic order, which simultaneously accompanies a ferroic toroidal order. We find that the occurrence of toroidal order modulates the magnon dispersion in an asymmetric way with respect to the wave number: a toroidal dipole order on the zigzag chain leads to a band-bottom shift, while a toroidal octupole order on the honeycomb lattice gives rise to a valley splitting. These asymmetric magnon excitations could be a source of unusual magnetic responses, such as nonreciprocal magnon transport. A variety of modulations are discussed while changing the lattice and magnetic symmetries. Furthermore, the implications regarding candidate materials for asymmetric magnon excitations are presented.
Shear layer excitation, experiment versus theory
NASA Technical Reports Server (NTRS)
Bechert, D. W.; Stahl, B.
1984-01-01
The acoustical excitation of shear layers is investigated. Acoustical excitation causes the so-called orderly structures in shear layers and jets. Also, the deviations in the spreading rate between different shear layer experiments are due to the same excitation mechanism. Measurements in the linear interaction region close to the edge from which the shear layer is shed are examined. Two sets of experiments (Houston 1981 and Berlin 1983/84) are discussed. The measurements were carried out with shear layers in air using hot wire anemometers and microphones. The agreement between these measurements and the theory is good. Even details of the fluctuating flow field correspond to theoretical predictions, such as the local occurrence of negative phase speeds.
Nanoscale control of phonon excitations in graphene
Kim, Hyo Won; Ko, Wonhee; Ku, JiYeon; Jeon, Insu; Kim, Donggyu; Kwon, Hyeokshin; Oh, Youngtek; Ryu, Seunghwa; Kuk, Young; Hwang, Sung Woo; Suh, Hwansoo
2015-01-01
Phonons, which are collective excitations in a lattice of atoms or molecules, play a major role in determining various physical properties of condensed matter, such as thermal and electrical conductivities. In particular, phonons in graphene interact strongly with electrons; however, unlike in usual metals, these interactions between phonons and massless Dirac fermions appear to mirror the rather complicated physics of those between light and relativistic electrons. Therefore, a fundamental understanding of the underlying physics through systematic studies of phonon interactions and excitations in graphene is crucial for realising graphene-based devices. In this study, we demonstrate that the local phonon properties of graphene can be controlled at the nanoscale by tuning the interaction strength between graphene and an underlying Pt substrate. Using scanning probe methods, we determine that the reduced interaction due to embedded Ar atoms facilitates electron–phonon excitations, further influencing phonon-assisted inelastic electron tunnelling. PMID:26109454
Theory of elementary excitations in quasiperiodic structures
NASA Astrophysics Data System (ADS)
Albuquerque, E. L.; Cottam, M. G.
2003-03-01
The aim of this work is to present a comprehensive and up-to-date review of the main physical properties (such as energy profiles, localization, scale laws, multifractal analysis, transmission spectra, transmission fingerprints, electronic structures, magnetization curves and thermodynamic properties) of the elementary excitations that can propagate in multilayered structures with constituents arranged in a quasiperiodic fashion. These excitations include plasmon-polaritons, spin waves, light waves and electrons, among others. A complex fractal or multifractal profile of the energy spectra is the common feature among these excitations. The quasiperiodic property is formed by the incommensurate arrangement of periodic unit cells and can be of the type referred to as deterministic (or controlled) disorder. The resulting excitations are characterized by the nature of their Fourier spectrum, which can be dense pure point (as for the Fibonacci sequence) or singular continuous (as for the Thue-Morse and double-period sequences). These sequences are described in terms of a series of generations that obey particular recursion relations, and they can be considered as intermediate systems between a periodic crystal and the random amorphous solids, thus defining a novel description of disorder. A discussion is also included of some spectroscopic techniques used to probe the excitations, emphasizing Raman and Brillouin light scattering.
Yordy, John S.; Almond, Peter R.; Delclos, Luis
2012-03-15
Purpose: To provide historical background on the development and initial studies of the gynecological (gyn) applicators developed by Dr. Gilbert H. Fletcher, a radiation oncologist and chairperson from 1948 to 1981 of the department at the M.D. Anderson Hospital (MDAH) for Cancer Research in Houston, TX, and to acknowledge the previously unrecognized contribution that Dr. Leonard G. Grimmett, a radiation physicist and chairperson from 1949 to 1951 of the physics department at MDAH, made to the development of the gynecological applicators. Methods and Materials: We reviewed archival materials from the Historical Resource Center and from the Department of Radiation Physics at University of Texas M. D. Anderson Cancer Center, as well as contemporary published papers, to trace the history of the applicators. Conclusions: Dr. Fletcher's work was influenced by the work on gynecologic applicators in the 1940s in Europe, especially work done at the Royal Cancer Hospital in London. Those efforts influenced not only Dr. Fletcher's approach to the design of the applicators but also the methods used to perform in vivo measurements and determine the dose distribution. Much of the initial development of the dosimetry techniques and measurements at MDAH were carried out by Dr. Grimmett.
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.
Ellis, Margaret S.; Gunther, Gregory L.; Flores, Romeo M.; Ochs, Allen M.; Stricker, Gary D.; Roberts, Steven B.; Taber, Thomas T.; Bader, Lisa R.; Schuenemeyer, John H.
1998-01-01
The National Coal Resource Assessment (NCRA) project by the U.S. Geological Survey is designed to assess US coal with the greatest potential for development in the next 20 to 30 years. Coal in the Wyodak-Anderson (WA) coal zone in the Powder River Basin of Wyoming and Montana is plentiful, clean, and compliant with EPA emissions standards. This coal is considered to be very desirable for development for use in electric power generation. The purpose of this NCRA study was to compile all available data relating to the Wyodak- Anderson coal, correlate the beds that make up the WA coal zone, create digital files pertaining to the study area and the WA coal, and produce a variety of reports on various aspects of the assessed coal unit. This report contains preliminary calculations of coal resources for the WA coal zone and is one of many products of the NCRA study. Coal resource calculations in this report were produced using both public and confidential data from many sources. The data was manipulated using a variety of commercially available software programs and several custom programs. A general description of the steps involved in producing the resource calculations is described in this report.
Dynamical localization of coupled relativistic kicked rotors
NASA Astrophysics Data System (ADS)
Rozenbaum, Efim B.; Galitski, Victor
2017-02-01
A periodically driven rotor is a prototypical model that exhibits a transition to chaos in the classical regime and dynamical localization (related to Anderson localization) in the quantum regime. In a recent work [Phys. Rev. B 94, 085120 (2016), 10.1103/PhysRevB.94.085120], A. C. Keser et al. considered a many-body generalization of coupled quantum kicked rotors, and showed that in the special integrable linear case, dynamical localization survives interactions. By analogy with many-body localization, the phenomenon was dubbed dynamical many-body localization. In the present work, we study nonintegrable models of single and coupled quantum relativistic kicked rotors (QRKRs) that bridge the gap between the conventional quadratic rotors and the integrable linear models. For a single QRKR, we supplement the recent analysis of the angular-momentum-space dynamics with a study of the spin dynamics. Our analysis of two and three coupled QRKRs along with the proved localization in the many-body linear model indicate that dynamical localization exists in few-body systems. Moreover, the relation between QRKR and linear rotor models implies that dynamical many-body localization can exist in generic, nonintegrable many-body systems. And localization can generally result from a complicated interplay between Anderson mechanism and limiting integrability, since the many-body linear model is a high-angular-momentum limit of many-body QRKRs. We also analyze the dynamics of two coupled QRKRs in the highly unusual superballistic regime and find that the resonance conditions are relaxed due to interactions. Finally, we propose experimental realizations of the QRKR model in cold atoms in optical lattices.
Magnetostrictive resonance excitation
Schwarz, Ricardo B.; Kuokkala, Veli-Tapani
1992-01-01
The resonance frequency spectrum of a magnetostrictive sample is remotely determined by exciting the magnetostrictive property with an oscillating magnetic field. The permeability of a magnetostrictive material and concomitant coupling with a detection coil varies with the strain in the material whereby resonance responses of the sample can be readily detected. A suitable sample may be a magnetostrictive material or some other material having at least one side coated with a magnetostrictive material. When the sample is a suitable shape, i.e., a cube, rectangular parallelepiped, solid sphere or spherical shell, the elastic moduli or the material can be analytically determined from the measured resonance frequency spectrum. No mechanical transducers are required and the sample excitation is obtained without contact with the sample, leading to highly reproducible results and a measurement capability over a wide temperature range, e.g. from liquid nitrogen temperature to the Curie temperature of the magnetostrictive material.
Experiments on excitation waves
NASA Astrophysics Data System (ADS)
Müller, S. C.
Recent trends in the experimentation on chemical and biochemical excitation waves are presented. In the Belousov-Zhabotinsky reaction, which is the most suitable chemical laboratory system for the study of wave propagation in excitable medium, the efficient control of wave dynamics by electrical fields and by light illumination is illustrated. In particular, the effects of a feedback control are shown. Further new experiments in this system are concerned with three-dimensional topologies and boundary effects. Important biological applications are found in the aggregation of slime mould amoebae, in proton waves during oscillatory glycolysis, and in waves of spreading depression in neuronal tissue as studied by experiments in chicken retina. Numerical simulations with appropriate reaction-diffusion models complement a large number of these experimental findings.
NASA Astrophysics Data System (ADS)
Copelli, M.; Campos, P. R. A.
2007-04-01
When a simple excitable system is continuously stimulated by a Poissonian external source, the response function (mean activity versus stimulus rate) generally shows a linear saturating shape. This is experimentally verified in some classes of sensory neurons, which accordingly present a small dynamic range (defined as the interval of stimulus intensity which can be appropriately coded by the mean activity of the excitable element), usually about one or two decades only. The brain, on the other hand, can handle a significantly broader range of stimulus intensity, and a collective phenomenon involving the interaction among excitable neurons has been suggested to account for the enhancement of the dynamic range. Since the role of the pattern of such interactions is still unclear, here we investigate the performance of a scale-free (SF) network topology in this dynamic range problem. Specifically, we study the transfer function of disordered SF networks of excitable Greenberg-Hastings cellular automata. We observe that the dynamic range is maximum when the coupling among the elements is critical, corroborating a general reasoning recently proposed. Although the maximum dynamic range yielded by general SF networks is slightly worse than that of random networks, for special SF networks which lack loops the enhancement of the dynamic range can be dramatic, reaching nearly five decades. In order to understand the role of loops on the transfer function we propose a simple model in which the density of loops in the network can be gradually increased, and show that this is accompanied by a gradual decrease of dynamic range.
Harmonically excited orbital variations
Morgan, T.
1985-08-06
Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs.
Pulse excitation of bolometer bridges
NASA Technical Reports Server (NTRS)
Rusk, S. J.
1972-01-01
Driving bolometer bridge by appropriately phased excitation pulses increases signal-to-noise ratio of bolometer sensor which operates on a chopped light beam. Method allows higher applied voltage than is possible by conventional ac or dc excitation.
Apparatus for photon excited catalysis
NASA Technical Reports Server (NTRS)
Saffren, M. M. (Inventor)
1977-01-01
An apparatus is described for increasing the yield of photonically excited gas phase reactions by extracting excess energy from unstable, excited species by contacting the species with the surface of a finely divided solid.
Charge transfer excitations from excited state Hartree-Fock subsequent minimization scheme
Theophilou, Iris; Tassi, M.; Thanos, S.
2014-04-28
Photoinduced charge-transfer processes play a key role for novel photovoltaic phenomena and devices. Thus, the development of ab initio methods that allow for an accurate and computationally inexpensive treatment of charge-transfer excitations is a topic that nowadays attracts a lot of scientific attention. In this paper we extend an approach recently introduced for the description of single and double excitations [M. Tassi, I. Theophilou, and S. Thanos, Int. J. Quantum Chem. 113, 690 (2013); M. Tassi, I. Theophilou, and S. Thanos, J. Chem. Phys. 138, 124107 (2013)] to allow for the description of intermolecular charge-transfer excitations. We describe an excitation where an electron is transferred from a donor system to an acceptor one, keeping the excited state orthogonal to the ground state and avoiding variational collapse. These conditions are achieved by decomposing the space spanned by the Hartree-Fock (HF) ground state orbitals into four subspaces: The subspace spanned by the occupied orbitals that are localized in the region of the donor molecule, the corresponding for the acceptor ones and two more subspaces containing the virtual orbitals that are localized in the neighborhood of the donor and the acceptor, respectively. Next, we create a Slater determinant with a hole in the subspace of occupied orbitals of the donor and a particle in the virtual subspace of the acceptor. Subsequently we optimize both the hole and the particle by minimizing the HF energy functional in the corresponding subspaces. Finally, we test our approach by calculating the lowest charge-transfer excitation energies for a set of tetracyanoethylene-hydrocarbon complexes that have been used earlier as a test set for such kind of excitations.
Get excited: reappraising pre-performance anxiety as excitement.
Brooks, Alison Wood
2014-06-01
Individuals often feel anxious in anticipation of tasks such as speaking in public or meeting with a boss. I find that an overwhelming majority of people believe trying to calm down is the best way to cope with pre-performance anxiety. However, across several studies involving karaoke singing, public speaking, and math performance, I investigate an alternative strategy: reappraising anxiety as excitement. Compared with those who attempt to calm down, individuals who reappraise their anxious arousal as excitement feel more excited and perform better. Individuals can reappraise anxiety as excitement using minimal strategies such as self-talk (e.g., saying "I am excited" out loud) or simple messages (e.g., "get excited"), which lead them to feel more excited, adopt an opportunity mind-set (as opposed to a threat mind-set), and improve their subsequent performance. These findings suggest the importance of arousal congruency during the emotional reappraisal process.
Löhrer, L; Raschke, M J; Thiesen, D; Hartensuer, R; Surke, C; Ochman, S; Vordemvenne, T
2012-04-01
Although currently there are many different recommendations and strategies in the therapy of odontoid fractures in the elderly, there are still no generally accepted guidelines for a structured and standardised treatment. Moreover, the current opinion of spine surgeons regarding the optimal treatment of odontoid fractures Type II of the elderly is unknown. In order to have an objective insight into the diverging strategies for the management of Anderson Type II odontoid fractures and form a basis for future comparisons, this study investigated the current concepts and preferences of orthopaedic, neuro- and trauma surgeons. Spine surgeons from 34 medical schools and 8 hospitals in Germany, 4 university hospitals in Austria and 5 in Switzerland were invited to participate in an online survey using a 12-item 1-sided questionnaire. A total of 44 interviewees from 34 medical institutions participated in the survey, consisting of trauma (50%), orthopaedic (20.5%) and neurosurgeons (27.3%). Out of these, 70.5% treated 1-20 fractures per year; 63.6% favoured the anterior screw fixation as therapy for Type II odontoid fractures, the open posterior Magerl transarticular C1/C2 fusion, the posterior Harms C1/C2 fusion, and conservative immobilisation by cervical orthosis was preferred by 9.1% in each case. 59.1% preferred the anterior odontoid screw fixation as an appropriate treatment of Anderson Type II odontoid fractures in the elderly. 79.5% chose cervical orthosis for postsurgical treatment. Following operative treatment, nonunion rates were reported to be <10% and <20% by 40.9% and 70% of the surgeons, respectively. 56.8% reported changing from primary conservative to secondary operative treatment in <10% of cases. The most favoured technique in revision surgery of nonunions was the open posterior Magerl transarticular fusion technique, chosen by 38.6% of respondents. 18.2% preferred the posterior Harms C1/C2 fusion technique, 11.4% the percutaneous posterior Magerl
Universal role of quantum uncertainty in Anderson metal-insulator transition
NASA Astrophysics Data System (ADS)
Cheng, W. W.; Zhang, Z. J.; Gong, L. Y.; Zhao, S. M.
2016-07-01
We explore quantum uncertainty, based on Wigner-Yanase skew information, in various one-dimensional single-electron wave functions. For the power-law function and eigenfunctions in the Aubry-André model, the electronic localization properties are well-defined. For them, we find that quantum uncertainty is relatively small and large for delocalized and localized states, respectively. And around the transition points, the first-order derivative of the quantum uncertainty exhibits singular behavior. All these characters can be used as signatures of the transition from a delocalized phase to a localized one. With this criterion, we also study the quantum uncertainty in one-dimensional disorder system with long-range correlated potential. The results show that the first-order derivative of spectrum-averaged quantum uncertainty is minimal at a certain correlation exponent αm for a finite system, and has perfect finite-size scaling behaviors around αm. By extrapolating αm, the threshold value αc ≃ 1.56 ± 0.02 is obtained for the infinite system. Thus we give another perspective and propose a consistent interpretation for the discrepancies about localization property in the long-range correlated potential model. These results suggest that the quantum uncertainty can provide us with a new physical intuition to the localization transition in these models.
2015-02-03
N. Patwari, J. Ash, S. Kyperountas, A. Hero, R. Moses, and N. Correal, “Locating the nodes: cooperative localization in wireless sensor networks ...volume 2, pp. 750–754 vol.2 (Sept 2002), doi: 10.1109/PIMRC.2002.1047322. 5. G. Mao, B. Fidan, and B. D. Anderson, “ Wireless sensor network localization...on a Network of GNU Radio Sensors February 3, 2015 Approved for public release; distribution is unlimited. Andrew robertson sAstry KompellA Joe
BROADBAND EXCITATION IN NUCLEAR MAGNETIC RESONANCE
Tycko, R.
1984-10-01
Theoretical methods for designing sequences of radio frequency (rf) radiation pulses for broadband excitation of spin systems in nuclear magnetic resonance (NMR) are described. The sequences excite spins uniformly over large ranges of resonant frequencies arising from static magnetic field inhomogeneity, chemical shift differences, or spin couplings, or over large ranges of rf field amplitudes. Specific sequences for creating a population inversion or transverse magnetization are derived and demonstrated experimentally in liquid and solid state NMR. One approach to broadband excitation is based on principles of coherent averaging theory. A general formalism for deriving pulse sequences is given, along with computational methods for specific cases. This approach leads to sequences that produce strictly constant transformations of a spin system. The importance of this feature in NMR applications is discussed. A second approach to broadband excitation makes use of iterative schemes, i.e. sets of operations that are applied repetitively to a given initial pulse sequences, generating a series of increasingly complex sequences with increasingly desirable properties. A general mathematical framework for analyzing iterative schemes is developed. An iterative scheme is treated as a function that acts on a space of operators corresponding to the transformations produced by all possible pulse sequences. The fixed points of the function and the stability of the fixed points are shown to determine the essential behavior of the scheme. Iterative schemes for broadband population inversion are treated in detail. Algebraic and numerical methods for performing the mathematical analysis are presented. Two additional topics are treated. The first is the construction of sequences for uniform excitation of double-quantum coherence and for uniform polarization transfer over a range of spin couplings. Double-quantum excitation sequences are demonstrated in a liquid crystal system. The
Excitation entanglement entropy in two dimensional conformal field theories
NASA Astrophysics Data System (ADS)
Sheikh-Jabbari, M. M.; Yavartanoo, H.
2016-12-01
We analyze how excitations affect the entanglement entropy for an arbitrary entangling interval in a 2d conformal field theory (CFT) using the holographic entanglement entropy techniques as well as direct CFT computations. We introduce the excitation entanglement entropy ΔhS , the difference between the entanglement entropy generic excitations and their arbitrary conformal descendants denoted through h . The excitation entanglement entropy, unlike the entanglement entropy, is a finite quantity (independent of the cutoff), and hence a good physical observable. We show that the excitation entanglement entropy for any given interval is uniquely specified by a local second order differential equation sourced by the one point function of the energy momentum tensor computed in the excited background state, and two boundary and smoothness conditions. We analyze low and high temperature behavior of the excitation entanglement entropy and show that ΔhS grows as a function of temperature. We prove an "integrated positivity" for the excitation entanglement entropy, that although ΔhS can be positive or negative, its average value is always positive. We also discuss the mutual and multipartite information and (strong) subadditivity inequality in the presence of generic excitations and their conformal descendants.
Excitation mechanisms of Er optical centers GaN epilayers
NASA Astrophysics Data System (ADS)
Hawkins, Matthew; Jiang, Hongxing; Lin, Jingyu; Zavada, John; Vinh, Nguyen
We report direct evidence of two mechanisms responsible for the excitation of optically active Er3 + ions in GaN epilayers grown by metal-organic chemical vapor deposition. These mechanisms, resonant excitation via the higher-lying inner 4f shell transitions and band-to-band excitation of the semiconductor host, lead to narrow emission lines from isolated and the defect-related Er optical centers. However, these centers have different photoluminescence spectra, local defect environments, decay dynamics, and excitation cross sections. The photoluminescence at 1.54 micrometer from the isolated Er optical center which can be excited by either mechanism has the same decay dynamics, but possesses a much higher excitation cross-section under band-to-band excitation. In contrast, the photoluminescence at 1.54 micrometer from the defect-related Er optical center can only be observed through band-to-band excitation but has the largest excitation cross-section. These results explain the difficulty in achieving gain in Er doped GaN and indicate approaches for realization of optical amplification, and possibly lasing, at room temperature.
Search for Gluonic Excitations
Eugenio, Paul
2007-10-26
Studies of meson spectra via strong decays provide insight regarding QCD at the confinement scale. These studies have led to phenomenological models for QCD such as the constituent quark model. However, QCD allows for a much richer spectrum of meson states which include extra states such as exotics, hybrids, multi-quarks, and glueballs. First discussion of the status of exotic meson searches is given followed by a discussion of plans at Jefferson Lab to double the energy of the machine to 12 GeV, which will allow us to access photoproduction of mesons in search for gluonic excited states.
Search for Gluonic Excitations
Paul Eugenio
2007-10-01
Studies of meson spectra via strong decays provide insight regarding QCD at the confinement scale. These studies have led to phenomenological models for QCD such as the constituent quark model. However, QCD allows for a much richer spectrum of meson states which include extra states such as exotics, hybrids, multi-quarks, and glueballs. First discussion of the status of exotic meson searches is given followed by a discussion of plans at Jefferson Lab to double the energy of the machine to 12 GeV, which will allow us to access photoproduction of mesons in search for gluonic excited states.
Creveling, R.
1957-12-17
S> A shock-excited quartz crystal oscillator is described. The circuit was specifically designed for application in micro-time measuring work to provide an oscillator which immediately goes into oscillation upon receipt of a trigger pulse and abruptly ceases oscillation when a second pulse is received. To achieve the instant action, the crystal has a prestressing voltage applied across it. A monostable multivibrator receives the on and off trigger pulses and discharges a pulse through the crystal to initiate or terminate oscillation instantly.
Metastable Interactions: Dissociative Excitation.
1985-05-01
participate. The mercuric halide compounds HgBr2 , HgCl 2 , and HgI2 are of recent interest because of laser output achieved on the B2 E - X2 E transition in...the * respective mercuric halide radicals in the range of 400-600 nm. Population inversion has been obtained by photodissociation and electron impact...excitation in mixtures o the mercuric - halide compounds and the rare gases. Chang and -* Burnham (3) have noted Improved laser efficiency and improved
Not Available
1986-01-01
The committee recommends several amendments to H.R. 3653, a bill designed to improve nuclear insurance procedures. Among the amendments are the inclusion of storage, handling, transportation, treatment, or disposal of, or research and development on and changes dealing with reimbursement procedures and limits. The bill reauthorizes the Price-Anderson Act, but limits liability and creates industry-wide liability in the event of a major accident. The report covers background information and hearings, summarizes the 15 amendments and each section how the bill will effect relevant changes in the Atomic Energy Act of 1954. Dissenting views argue against setting a liability cap on nuclear waste accidents because it discourages safety consciousness on the part of contractors and because there is no precedent in liability insurance for limiting liability.
Sasaki, M; Hukushima, K; Yoshino, H; Takayama, H
2007-09-28
The stability of the spin-glass phase against a magnetic field is studied in the three- and four-dimensional Edwards-Anderson Ising spin glasses. Effective couplings J(eff) and effective fields H(eff) associated with length scale L are measured by a numerical domain-wall renormalization-group method. The results obtained by scaling analysis of the data strongly indicate the existence of a crossover length beyond which the spin-glass order is destroyed by field H. The crossover length well obeys a power law of H which diverges as H --> 0 but remains finite for any nonzero H, implying that the spin-glass phase is absent even in an infinitesimal field. These results are well consistent with the droplet theory for short-range spin glasses.
NASA Astrophysics Data System (ADS)
Chang, Cui-Zu; Zhao, Weiwei; Li, Jian; Jain, J. K.; Liu, Chaoxing; Moodera, Jagadeesh S.; Chan, Moses H. W.
2016-09-01
Fundamental insight into the nature of the quantum phase transition from a superconductor to an insulator in two dimensions, or from one plateau to the next or to an insulator in the quantum Hall effect, has been revealed through the study of its scaling behavior. Here, we report on the experimental observation of a quantum phase transition from a quantum-anomalous-Hall insulator to an Anderson insulator in a magnetic topological insulator by tuning the chemical potential. Our experiment demonstrates the existence of scaling behavior from which we extract the critical exponent for this quantum phase transition. We expect that our work will motivate much further investigation of many properties of quantum phase transition in this new context.
Gao, Jianjun; He, Qiuming; Subudhi, Sumit; Aparicio, Ana; Zurita-Saavedra, Amado; Lee, Da Hyun; Jimenez, Camilo; Suarez-Almazor, Maria; Sharma, Padmanee
2014-01-01
Targeting a T cell inhibitory checkpoint with the anti-CTLA-4 monoclonal antibody, ipilimumab, represents a scientific breakthrough in immunotherapy for the treatment of cancer. However, ipilimumab therapy is also associated with unique side effects, known as immune-related adverse events (irAEs), which need to be recognized and managed with immunosuppressive agents. To date, the majority of our knowledge regarding ipilimumab-associated side effects is based upon clinical studies in melanoma. Here, we provide a review of ipilimumab-induced irAEs and our experience in a cohort of 44 patients with prostate cancer who were treated at M. D. Anderson Cancer Center on two different clinical trial protocols. PMID:25659583
NASA Astrophysics Data System (ADS)
Aksu, H.; Goker, A.
2017-03-01
We invoke the nonequilibrium self-consistent GW method within the Anderson impurity model to investigate the dynamical effects occurring in a nanojunction comprised of two coupled molecules. Contrary to the previous single impurity model calculations based on the GW approximation, we observe that the density of states manages to capture both the Kondo resonance and the Breit-Wigner resonances associated with the HOMO and LUMO levels of the molecule. Moreover, the prominence of the Kondo resonance grows dramatically upon switching from the intermediate to the weak coupling regime involving large U / Γ values. The conductance is calculated as a function of the HOMO level and the applied bias across the molecular nanojunction. Calculated conductance curves deviate from the monotonic decay behaviour as a function of the bias when the half-filling condition is not met. The importance of the effect of the molecule-molecule coupling for the electron transport phenomena is also investigated.
Can 3D light localization be reached in ‘white paint’?
NASA Astrophysics Data System (ADS)
Sperling, T.; Schertel, L.; Ackermann, M.; Aubry, G. J.; Aegerter, C. M.; Maret, G.
2016-01-01
When waves scatter multiple times in 3D random media, a disorder driven phase transition from diffusion to localization may occur (Anderson 1958 Phys. Rev. 109 1492-505 Abrahams et al 1979 Phys. Rev. Lett. 42 673-6). In ‘The question of classical localization: a theory of white paint?’ Anderson suggested the possibility to observe light localization in TiO2 samples (Anderson 1985 Phil. Mag. B 52 505-9). We recently claimed the observation of localization effects measuring photon time of flight (ToF) distributions (Störzer et al 2006 Phys. Rev. Lett. 96 063904) and evaluating transmission profiles (TPs) (Sperling et al 2013 Nat. Photonics 7 48-52) in such TiO2 samples. Here we present a careful study of the long time tail of ToF distributions and the long time behavior of the TP width for very thin samples and different turbidities that questions the localization interpretation. We further show new data that allow an alternative consistent explanation of these previous data by a fluorescence process. An adapted diffusion model including an appropriate exponential fluorescence decay accounts for the shape of the ToF distributions and the TP width. These observations question whether the strong localization regime can be reached with visible light scattering in polydisperse TiO2 samples, since the disorder parameter can hardly be increased any further in such a ‘white paint’ material.
Excitability in Dictyostelium development
NASA Astrophysics Data System (ADS)
Schwab, David
2013-03-01
Discovering how populations of cells reliably develop into complex multi-cellular structures is a key challenge in modern developmental biology. This requires an understanding of how networks at the single-cell level, when combined with intercellular signaling and environmental cues, give rise to the collective behaviors observed in cellular populations. I will present work in collaboration with the Gregor lab, showing that the signal-relay response of starved cells of the amoebae Dictyostelium discoideum can be well modeled as an excitable system. This is in contrast to existing models of the network that postulate a feed-forward cascade. I then extend the signal-relay model to describe how spatial gradient sensing may be achieved via excitability. One potential advantage of relying on feedback for gradient sensing is in preventing ``cheaters'' that do not produce signals from taking over the population. I then combine these models of single-cell signaling and chemotaxis to perform large-scale agent-based simulations of aggregating populations. This allows direct study of how variations in single-cell dynamics modify population behavior. In order to further test this model, I use the results of a screen for mutant cell lines that exhibit altered collective patterns. Finally, I use an existing FRET movie database of starved cell populations at varying cell densities and dilution rates to study heterogeneity in repeated spatio-temporal activity patterns.
MacDermot, K; Holmes, A; Miners, A
2001-01-01
OBJECTIVES—To determine the natural history of Anderson-Fabry disease (AFD) as a baseline for efficacy assessment of potentially therapeutic drugs. DESIGN—The first large cross sectional study of a patient cohort from the AFD clinical and genetic register (UK), maintained for the last 15 years. MEASURES—Prevalence, mortality, frequency of AFD manifestations, and impact of disease on patient lives, assessed from the AFD register and the disease specific questionnaire. RESULTS—The median cumulative survival was 50 years (n=51), which represents an approximately 20 year reduction of life span. Neuropathic pain was present in 77% (n=93) with mean pain score of 5 (scale 0-10) despite treatment with anticonvulsants and opiates. Pain stopped in only 11%. Cerebrovascular complications developed in 24.2% and renal failure in 30%. The onset and progression of serious AFD manifestations was highly variable. The relationship of gastrointestinal manifestations on weight, using body mass index (BMI), was significant (p=0.01). High frequency sensorineural deafness was confirmed in 78% of audiograms. Neuropathic pain and angiokeratoma were absent in five adult males (~5%). Median age at diagnosis of AFD was 21.9 years (n=64). IMPACT OF DISEASE—Attendance at school, sports, and social activity were significantly affected by AFD. Only 56.6% (n=46) of patients were employed. Psychosexual effects of genital angiokeratoma, genital pain, and impotence were not previously recognised. CONCLUSION—The majority of males experience multiple disease manifestations and the duration of neuropathic pain was lifelong. The AFD register proved useful for the determination of baseline disease parameters in this cohort. Keywords: Anderson-Fabry disease; natural history; mortality; prevalence PMID:11694547
Howczak, Olga; Spałek, Jozef
2012-05-23
We apply the extended (statistically consistent, SCA) Gutzwiller-type approach to the periodic Anderson model (PAM) in an applied magnetic field and in the strong-correlation limit. The finite-U corrections are included systematically by transforming the PAM into the form with the Kondo-type interaction and the residual hybridization, both appearing at the same time and on equal footing. This effective Hamiltonian represents the essence of our Anderson-Kondo lattice model. We show that in ferromagnetic phases the low-energy single-particle states are strongly affected by the presence of the applied magnetic field. We also find that for large values of hybridization strength the system enters the so-called locked heavy fermion state introduced earlier. In this state the chemical potential lies in the majority-spin hybridization gap and, as a consequence, the system evolution is insensitive to further increase of the applied field. However, for a sufficiently strong magnetic field, the system transforms from the locked state to the fully spin-polarized phase. This is accompanied by a metamagnetic transition, as well as by a drastic reduction of the effective mass of the quasiparticles. In particular, we observe no effective mass enhancement in the fully polarized state. The findings are in overall agreement with experimental results for the Ce compounds in high magnetic fields. The mass enhancement for the spin-minority electrons may also diminish with the increasing field, unlike for the quasiparticle states in a single narrow band in the same limit of strong correlations.
Local quantum thermal susceptibility
De Pasquale, Antonella; Rossini, Davide; Fazio, Rosario; Giovannetti, Vittorio
2016-01-01
Thermodynamics relies on the possibility to describe systems composed of a large number of constituents in terms of few macroscopic variables. Its foundations are rooted into the paradigm of statistical mechanics, where thermal properties originate from averaging procedures which smoothen out local details. While undoubtedly successful, elegant and formally correct, this approach carries over an operational problem, namely determining the precision at which such variables are inferred, when technical/practical limitations restrict our capabilities to local probing. Here we introduce the local quantum thermal susceptibility, a quantifier for the best achievable accuracy for temperature estimation via local measurements. Our method relies on basic concepts of quantum estimation theory, providing an operative strategy to address the local thermal response of arbitrary quantum systems at equilibrium. At low temperatures, it highlights the local distinguishability of the ground state from the excited sub-manifolds, thus providing a method to locate quantum phase transitions. PMID:27681458
Electromagnetic toroidal excitations in matter and free space.
Papasimakis, N; Fedotov, V A; Savinov, V; Raybould, T A; Zheludev, N I
2016-03-01
The toroidal dipole is a localized electromagnetic excitation, distinct from the magnetic and electric dipoles. While the electric dipole can be understood as a pair of opposite charges and the magnetic dipole as a current loop, the toroidal dipole corresponds to currents flowing on the surface of a torus. Toroidal dipoles provide physically significant contributions to the basic characteristics of matter including absorption, dispersion and optical activity. Toroidal excitations also exist in free space as spatially and temporally localized electromagnetic pulses propagating at the speed of light and interacting with matter. We review recent experimental observations of resonant toroidal dipole excitations in metamaterials and the discovery of anapoles, non-radiating charge-current configurations involving toroidal dipoles. While certain fundamental and practical aspects of toroidal electrodynamics remain open for the moment, we envision that exploitation of toroidal excitations can have important implications for the fields of photonics, sensing, energy and information.
Percolation of optical excitation mediated by near-field interactions
NASA Astrophysics Data System (ADS)
Naruse, Makoto; Kim, Song-Ju; Takahashi, Taiki; Aono, Masashi; Akahane, Kouichi; D'Acunto, Mario; Hori, Hirokazu; Thylén, Lars; Katori, Makoto; Ohtsu, Motoichi
2017-04-01
Optical excitation transfer in nanostructured matter has been intensively studied in various material systems for versatile applications. Herein, we theoretically and numerically discuss the percolation of optical excitations in randomly organized nanostructures caused by optical near-field interactions governed by Yukawa potential in a two-dimensional stochastic model. The model results demonstrate the appearance of two phases of percolation of optical excitation as a function of the localization degree of near-field interaction. Moreover, it indicates sublinear scaling with percolation distances when the light localization is strong. Furthermore, such a character is maximized at a particular size of environments. The results provide fundamental insights into optical excitation transfer and will facilitate the design and analysis of nanoscale signal-transfer characteristics.
Electromagnetic toroidal excitations in matter and free space
NASA Astrophysics Data System (ADS)
Papasimakis, N.; Fedotov, V. A.; Savinov, V.; Raybould, T. A.; Zheludev, N. I.
2016-03-01
The toroidal dipole is a localized electromagnetic excitation, distinct from the magnetic and electric dipoles. While the electric dipole can be understood as a pair of opposite charges and the magnetic dipole as a current loop, the toroidal dipole corresponds to currents flowing on the surface of a torus. Toroidal dipoles provide physically significant contributions to the basic characteristics of matter including absorption, dispersion and optical activity. Toroidal excitations also exist in free space as spatially and temporally localized electromagnetic pulses propagating at the speed of light and interacting with matter. We review recent experimental observations of resonant toroidal dipole excitations in metamaterials and the discovery of anapoles, non-radiating charge-current configurations involving toroidal dipoles. While certain fundamental and practical aspects of toroidal electrodynamics remain open for the moment, we envision that exploitation of toroidal excitations can have important implications for the fields of photonics, sensing, energy and information.
Fractal superconductivity near localization threshold
Feigel'man, M.V.; Ioffe, L.B.; Kravtsov, V.E.; Cuevas, E.
2010-07-15
We develop a semi-quantitative theory of electron pairing and resulting superconductivity in bulk 'poor conductors' in which Fermi energy E{sub F} is located in the region of localized states not so far from the Anderson mobility edge E{sub c}. We assume attractive interaction between electrons near the Fermi surface. We review the existing theories and experimental data and argue that a large class of disordered films is described by this model. Our theoretical analysis is based on analytical treatment of pairing correlations, described in the basis of the exact single-particle eigenstates of the 3D Anderson model, which we combine with numerical data on eigenfunction correlations. Fractal nature of critical wavefunction's correlations is shown to be crucial for the physics of these systems. We identify three distinct phases: 'critical' superconductive state formed at E{sub F} = E{sub c}, superconducting state with a strong pseudo-gap, realized due to pairing of weakly localized electrons and insulating state realized at E{sub F} still deeper inside a localized band. The 'critical' superconducting phase is characterized by the enhancement of the transition temperature with respect to BCS result, by the inhomogeneous spatial distribution of superconductive order parameter and local density of states. The major new feature of the pseudo-gapped state is the presence of two independent energy scales: superconducting gap {Delta}, that is due to many-body correlations and a new 'pseudo-gap' energy scale {Delta}{sub P} which characterizes typical binding energy of localized electron pairs and leads to the insulating behavior of the resistivity as a function of temperature above superconductive T{sub c}. Two gap nature of the pseudo-gapped superconductor is shown to lead to specific features seen in scanning tunneling spectroscopy and point-contact Andreev spectroscopy. We predict that pseudo-gapped superconducting state demonstrates anomalous behavior of the optical
Strong correlation induced charge localization in antiferromagnets
Zhu, Zheng; Jiang, Hong-Chen; Qi, Yang; Tian, Chushun; Weng, Zheng-Yu
2013-01-01
The fate of a hole injected in an antiferromagnet is an outstanding issue of strongly correlated physics. It provides important insights into doped Mott insulators closely related to high-temperature superconductivity. Here, we report a systematic numerical study of t-J ladder systems based on the density matrix renormalization group. It reveals a surprising result for the single hole's motion in an otherwise well-understood undoped system. Specifically, we find that the common belief of quasiparticle picture is invalidated by the self-localization of the doped hole. In contrast to Anderson localization caused by disorders, the charge localization discovered here is an entirely new phenomenon purely of strong correlation origin. It results from destructive quantum interference of novel signs picked up by the hole, and since the same effect is of a generic feature of doped Mott physics, our findings unveil a new paradigm which may go beyond the single hole doped system. PMID:24002668