International Nuclear Information System (INIS)
Fredenhagen, K.; Joerss, M.
1994-10-01
Starting from a chiral conformal Haag-Kastler net on 2 dimensional Minkowski space we construct associated pointlike localized fields. This amounts to a proof of the existence of operator product expansions. We derive the result in two ways. One is based on the geometrical identification of the modular structure, the other depends on a ''conformal cluster theorem'' of the conformal two-point-functions in algebraic quantum field theory. The existence of the fields then implies important structural properties of the theory, as PCT-invariance, the Bisognano-Wichmann identification of modular operators, Haag duality and additivity. (orig.)
On the existence of pointlike localized fields in conformally invariant quantum physics
International Nuclear Information System (INIS)
Joerss, M.
1992-11-01
In quantum field theory the existence of pointlike localizable objects called 'fields' is a preassumption. Since charged fields are in general not observable this situation is unsatisfying from a quantum physics point of view. Indeed in any quantum theory the existence of fields should follow from deeper physical concepts and more natural first principles like stability, locality, causality and symmetry. In the framework of algebraic quantum field theory with Haag-Kastler nets of local observables this is presented for the case of conformal symmetry in 1+1 dimensions. Conformal fields are explicitly constructed as limits of observables localized in finite regions of space-time. These fields then allow to derive a geometric identification of modular operators, Haag duality in the vacuum sector, the PCT-theorem and an equivalence theorem for fields and algebras. (orig.)
Kholmetskii, A. L.; Missevitch, O. V.; Yarman, T.
2018-05-01
We point out that the known quantum phases for an electric/magnetic dipole moving in an electromagnetic (EM) field must be presented as the superposition of more fundamental quantum phases emerging for elementary charges. Using this idea, we find two new fundamental quantum phases for point-like charges, next to the known electric and magnetic Aharonov-Bohm (A-B) phases, named by us as the complementary electric and magnetic phases, correspondingly. We further demonstrate that these new phases can indeed be derived via the Schrödinger equation for a particle in an EM field, where however the operator of momentum is re-defined via the replacement of the canonical momentum of particle by the sum of its mechanical momentum and interactional field momentum for a system "charged particle and a macroscopic source of EM field". The implications of the obtained results are discussed.
String-localized quantum fields and modular localization
Energy Technology Data Exchange (ETDEWEB)
Mund, J. [Juiz de Fora Univ., MG (Brazil). Dept. de Fisica; Schroer, B. [FU-Berlin, Berlin (Germany). Inst. fuer Theoretische Physik; Yngvason, J. [Erwin Schroedinger Institute for Mathematical Physics, Vienna (Austria)
2005-12-15
We study free, covariant, quantum (Bose) fields that are associated with irreducible representations of the Poincare group and localized in semi-infinite strings extending to spacelike infinity. Among these are fields that generate the irreducible representations of mass zero and infinite spin that are known to be incompatible with point-like localized fields. For the massive representation and the massless representations of finite helicity, all string-localized free fields can be written as an integral, along the string, of point-localized tensor or spinor fields. As a special case we discuss the string-localized vector fields associated with the point-like electromagnetic field and their relation to the axial gauge condition in the usual setting. (author)
String-localized quantum fields and modular localization
International Nuclear Information System (INIS)
Mund, J.
2005-12-01
We study free, covariant, quantum (Bose) fields that are associated with irreducible representations of the Poincare group and localized in semi-infinite strings extending to spacelike infinity. Among these are fields that generate the irreducible representations of mass zero and infinite spin that are known to be incompatible with point-like localized fields. For the massive representation and the massless representations of finite helicity, all string-localized free fields can be written as an integral, along the string, of point-localized tensor or spinor fields. As a special case we discuss the string-localized vector fields associated with the point-like electromagnetic field and their relation to the axial gauge condition in the usual setting. (author)
Quantum effects in external fields determined by potentials with point-like support
International Nuclear Information System (INIS)
Mamev, S.G.; Trunov, N.N.
1982-01-01
Exact expressions are obtained for the vacuum expectation values of the energy-momentum tensor of a scalar field in external potentials of the delta-function type. The conditions for the onset of the vacuum instability are found and the properties of the resulting condensate are studied. Particle production in the field of a nonstationary delta potential is studied
Near-field interferometry of a free-falling nanoparticle from a point-like source
Bateman, James; Nimmrichter, Stefan; Hornberger, Klaus; Ulbricht, Hendrik
2014-09-01
Matter-wave interferometry performed with massive objects elucidates their wave nature and thus tests the quantum superposition principle at large scales. Whereas standard quantum theory places no limit on particle size, alternative, yet untested theories—conceived to explain the apparent quantum to classical transition—forbid macroscopic superpositions. Here we propose an interferometer with a levitated, optically cooled and then free-falling silicon nanoparticle in the mass range of one million atomic mass units, delocalized over >150 nm. The scheme employs the near-field Talbot effect with a single standing-wave laser pulse as a phase grating. Our analysis, which accounts for all relevant sources of decoherence, indicates that this is a viable route towards macroscopic high-mass superpositions using available technology.
Local fields and their extensions
Fesenko, I B
2002-01-01
This book offers a modern presentation of local fields whose spectacular development was initiated almost one hundred years ago by K. Hensel. The volume consists of nine chapters divided into four parts: arithmetic properties of local fields, class field theory for various types of local fields and generalizations, explicit formulas for the Hilbert pairing, and Milnor K-groups of fields and of local fields. The first three parts essentially simplify, revise, and update the first edition. This second edition contains about sixty additional pages reflecting several aspects of the developments in local number theory in the last ten years. Exercises point to many other paths for exploration. The book is designed for graduate students and research mathematicians interested in local number theory and its applications in arithmetic algebraic geometry.
String-localized quantum fields
International Nuclear Information System (INIS)
Mund, Jens; Santos, Jose Amancio dos; Silva, Cristhiano Duarte; Oliveira, Erichardson de
2009-01-01
Full text. The principles of physics admit (unobservable) quantum fields which are localized not on points, but on strings in the sense of Mandelstam: a string emanates from a point in Minkowski space and extends to infinity in some space-like direction. This type of localization might permit the construction of new models, for various reasons: (a) in general, weaker localization implies better UV behaviour. Therefore, the class of renormalizable interactions in the string-localized has a chance to be larger than in the point-localized case; (b) for certain particle types, there are no point-localized (free) quantum fields - for example Anyons in d = 2 + 1, and Wigner's massless 'infinite spin' particles. For the latter, free string-localized quantum fields have been constructed; (c) in contrast to the point-localized case, string-localization admits covariant vector/tensor potentials for fotons and gravitons in a Hilbert space representation with positive energy. We shall present free string-localized quantum fields for various particle types, and some ideas about the perturbative construction of interacting string-localized fields. A central point will be an analogue of gauge theories, completely within a Hilbert space and without ghosts, trading gauge dependence with dependence on the direction of the localization string. In order to discuss renormalizability (item (a)), methods from microlocal analysis (wave front set and scaling degree) are needed. (author)
Local fields in ionic crystals
International Nuclear Information System (INIS)
Claro, F.
1981-08-01
Local fields arising from the electronic distortion in perfect ionic crystals are described in terms of multipolar excitations. Field factors for the alkali halides and chalcogenide ions are found to differ significantly from the Lorentz value of 4π/3, the correction size following an exponential dependence on the difference in ionic radii. Local fields are only slightly modified by these corrections however, and together with the Clausius-Mossotti relation may be regarded as accurate to within 2% if the Lorentz value is adopted. (author)
The localized quantum vacuum field
International Nuclear Information System (INIS)
Dragoman, D
2008-01-01
A model for the localized quantum vacuum is proposed in which the zero-point energy (ZPE) of the quantum electromagnetic field originates in energy- and momentum-conserving transitions of material systems from their ground state to an unstable state with negative energy. These transitions are accompanied by emissions and re-absorptions of real photons, which generate a localized quantum vacuum in the neighborhood of material systems. The model could help resolve the cosmological paradox associated with the ZPE of electromagnetic fields, while reclaiming quantum effects associated with quantum vacuum such as the Casimir effect and the Lamb shift. It also offers a new insight into the Zitterbewegung of material particles
The localized quantum vacuum field
Energy Technology Data Exchange (ETDEWEB)
Dragoman, D [Physics Department, University of Bucharest, PO Box MG-11, 077125 Bucharest (Romania)], E-mail: danieladragoman@yahoo.com
2008-03-15
A model for the localized quantum vacuum is proposed in which the zero-point energy (ZPE) of the quantum electromagnetic field originates in energy- and momentum-conserving transitions of material systems from their ground state to an unstable state with negative energy. These transitions are accompanied by emissions and re-absorptions of real photons, which generate a localized quantum vacuum in the neighborhood of material systems. The model could help resolve the cosmological paradox associated with the ZPE of electromagnetic fields, while reclaiming quantum effects associated with quantum vacuum such as the Casimir effect and the Lamb shift. It also offers a new insight into the Zitterbewegung of material particles.
Interaction between two point-like charges in nonlinear electrostatics
Energy Technology Data Exchange (ETDEWEB)
Breev, A.I. [Tomsk State University, Tomsk (Russian Federation); Tomsk Polytechnic University, Tomsk (Russian Federation); Shabad, A.E. [P.N. Lebedev Physical Institute, Moscow (Russian Federation); Tomsk State University, Tomsk (Russian Federation)
2018-01-15
We consider two point-like charges in electrostatic interaction within the framework of a nonlinear model, associated with QED, that provides finiteness of their field energy. We find the common field of the two charges in a dipole-like approximation, where the separation between them R is much smaller than the observation distance r: with the linear accuracy with respect to the ratio R/r, and in the opposite approximation, where R >> r, up to the term quadratic in the ratio r/R. The consideration proposes the law a + bR{sup 1/3} for the energy, when the charges are close to one another, R → 0. This leads to the singularity of the force between them to be R{sup -2/3}, which is weaker than the Coulomb law, R{sup -2}. (orig.)
Interaction between two point-like charges in nonlinear electrostatics
Breev, A. I.; Shabad, A. E.
2018-01-01
We consider two point-like charges in electrostatic interaction within the framework of a nonlinear model, associated with QED, that provides finiteness of their field energy. We find the common field of the two charges in a dipole-like approximation, where the separation between them R is much smaller than the observation distance r : with the linear accuracy with respect to the ratio R / r, and in the opposite approximation, where R≫ r, up to the term quadratic in the ratio r / R. The consideration proposes the law a+b R^{1/3} for the energy, when the charges are close to one another, R→ 0. This leads to the singularity of the force between them to be R^{-2/3}, which is weaker than the Coulomb law, R^{-2}.
Indoor localization using magnetic fields
Pathapati Subbu, Kalyan Sasidhar
Indoor localization consists of locating oneself inside new buildings. GPS does not work indoors due to multipath reflection and signal blockage. WiFi based systems assume ubiquitous availability and infrastructure based systems require expensive installations, hence making indoor localization an open problem. This dissertation consists of solving the problem of indoor localization by thoroughly exploiting the indoor ambient magnetic fields comprising mainly of disturbances termed as anomalies in the Earth's magnetic field caused by pillars, doors and elevators in hallways which are ferromagnetic in nature. By observing uniqueness in magnetic signatures collected from different campus buildings, the work presents the identification of landmarks and guideposts from these signatures and further develops magnetic maps of buildings - all of which can be used to locate and navigate people indoors. To understand the reason behind these anomalies, first a comparison between the measured and model generated Earth's magnetic field is made, verifying the presence of a constant field without any disturbances. Then by modeling the magnetic field behavior of different pillars such as steel reinforced concrete, solid steel, and other structures like doors and elevators, the interaction of the Earth's field with the ferromagnetic fields is described thereby explaining the causes of the uniqueness in the signatures that comprise these disturbances. Next, by employing the dynamic time warping algorithm to account for time differences in signatures obtained from users walking at different speeds, an indoor localization application capable of classifying locations using the magnetic signatures is developed solely on the smart phone. The application required users to walk short distances of 3-6 m anywhere in hallway to be located with accuracies of 80-99%. The classification framework was further validated with over 90% accuracies using model generated magnetic signatures representing
International Nuclear Information System (INIS)
Miyagawa, Yuu; Ueta, Tsuyoshi
2008-01-01
The boundary element method (BEM) is so extended as to treat two-dimensional (2D) electron systems in the presence of pointlike islands of magnetic moment. In the present paper, the pointlike magnetic scatterer is modeled by a cylindrical barrier. The radius of the cylindrical barrier is assumed to be so small, keeping the volume definite, that the pointlike magnetic scatterer is approximated by a Dirac δ function. Then, we make an approximation on the BEM formulation, wherefore we derive a novel numerical method for electron transport in the presence of pointlike magnetic scatterers. In a numerical implementation of the method extended here, the numerical errors of probability conservation are less than 1% for any cases and the computational costs, that is, the required memory amount and CPU time, are much reduced. As examples, the proposed method is applied to transport problems through a quantum wire with four pointlike magnetic scatterers. It is clearly shown that magnetic scatterers, even pointlike magnetic moments, lead to spin flip-flop, localization and resonance
EMC effect, antishadowing, and pointlike configurations in nucleons
International Nuclear Information System (INIS)
Strikman, M.I.; Frankfurt, L.L.
1985-01-01
Antishadowing of valence-quark distributions in a nucleus is estimated for small x. It is shown that the probability of pointlike configurations is suppressed in a bound nucleon. The possible relation of these phenomena to the EMC effect is discussed. Experiments are proposed to search for pointlike configurations in hadrons. Indications are obtained of the existence of an effect analogous to the EMC effect for x>0.3 in near-threshold eD scattering studied at SLAC
Sigma models in the presence of dynamical point-like defects
International Nuclear Information System (INIS)
Doikou, Anastasia; Karaiskos, Nikos
2013-01-01
Point-like Liouville integrable dynamical defects are introduced in the context of the Landau–Lifshitz and Principal Chiral (Faddeev–Reshetikhin) models. Based primarily on the underlying quadratic algebra we identify the first local integrals of motion, the associated Lax pairs as well as the relevant sewing conditions around the defect point. The involution of the integrals of motion is shown taking into account the sewing conditions.
a Point-Like Picture of the Hydrogen Atom
Faghihi, F.; Jangjoo, A.; Khani, M.
A point-like picture of the Schrödinger solution for hydrogen atom is worked to emphasize that "point-like particles" may describe as "probability wave function". In each case, the three-dimensional shape of the |Ψnlm(rn, cosθ)|2 is plotted and the paths of the point-like electron (it is better to say reduced mass of the pair particles) are described in each closed shell. Finally, the orbital shape of the molecules are given according to the present simple model. In our opinion, "interpretations of the Correspondence Principle", which is a basic principle in all elementary quantum text, seems to be reviewed again!
Local eddy current measurements in pulsed fields
Energy Technology Data Exchange (ETDEWEB)
Espina-Hernandez, J.H. [SEPI-Electronica, ESIME-IPN, UPALM Edif. ' Z' . Zacatenco, Mexico DF 07738 (Mexico)], E-mail: jhespina@gmail.com; Groessinger, R. [Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, A-1040 Vienna (Austria); Hallen, J.M. [Departamento de Ingenieria Metalurgica, IPN-ESIQIE, UPALM Edif. 7, Zacatenco, Mexico DF 07738 (Mexico)
2008-07-15
This work presents new eddy current measurements in pulsed fields. A commercial point pick-up coil is used to detect the induction signal along the radius of Cu and Al samples with cylindrical shape and diameters between 5 and 35 mm. Local eddy current measurements were performed on the surface of conducting materials due to the small dimensions of the coil. A simple electrical circuit, used as a model, is proposed to describe the local eddy current effect in pulsed fields. The proposed model allows to calculate the phase shift angle between the signal proportional to eddy currents and the applied external field in a pulsed field magnetometer.
Local algebras in Euclidean quantum field theory
International Nuclear Information System (INIS)
Guerra, Francesco.
1975-06-01
The general structure of the local observable algebras of Euclidean quantum field theory is described, considering the very simple examples of the free scalar field, the vector meson field, and the electromagnetic field. The role of Markov properties, and the relations between Euclidean theory and Hamiltonian theory in Minkowski space-time are especially emphasized. No conflict appears between covariance (in the Euclidean sense) and locality (in the Markov sense) on one hand and positive definiteness of the metric on the other hand [fr
Non-local charges in local quantum field theory
International Nuclear Information System (INIS)
Buchholz, D.; Lopuszanski, J.T.; Rabsztyn, S.
1985-05-01
Non-local charges are studied in the general setting of local quantum field theory. It is shown, that these charges can be represented as polynomials in the incoming respectively outgoing fields with coefficients (kernels) which are subject to specific constraints. For the restricted class of models of a scalar, massive, self interacting particle in four dimensions, a more detailed analysis shows that all non-local charges of the generic type (genus 2) are products of generators of the Poincare group. This analysis, which is based on the macroscopic causality properties of the S-matrix, seems to indicate that less trivial examples of non-local charges can only exist in two dimensions. (orig.)
The quantum nonlinear Schroedinger model with point-like defect
International Nuclear Information System (INIS)
Caudrelier, V; Mintchev, M; Ragoucy, E
2004-01-01
We establish a family of point-like impurities which preserve the quantum integrability of the nonlinear Schroedinger model in 1+1 spacetime dimensions. We briefly describe the construction of the exact second quantized solution of this model in terms of an appropriate reflection-transmission algebra. The basic physical properties of the solution, including the spacetime symmetry of the bulk scattering matrix, are also discussed. (letter to the editor)
Local field in finite-size metamaterials
DEFF Research Database (Denmark)
Bordo, Vladimir
2018-01-01
The theory of the optical response of a metamaterial slab which is represented by metal nanoparticles embedded in a dielectric matrix is developed. It is demonstrated that the account of the reflections from the slab boundaries essentially modifies the local field in the slab and leads...
Propositional systems in local field theories
International Nuclear Information System (INIS)
Banai, M.
1980-07-01
The authors investigate propositional systems for local field theories, which reflect intrinsically the uncertainties of measurements made on the physical system, and satisfy the isotony and local commutativity postulates of Haag and Kastler. The spacetime covariance can be implemented in natural way in these propositional systems. New techniques are introduced to obtain these propositional systems: the lattice-valued logics. The decomposition of the complete orthomodular lattice-valued logics shows that these logics are more general than the usual two-valued ones and that in these logics there is enough structure to characterize the classical and quantum, non relativistic and relativistic local field theories in a natural way. The Hilbert modules give the natural inner product ''spaces'' (modules) for the realization of the lattice-valued logics. (author)
Supergauge symmetry in local quantum field theory
International Nuclear Information System (INIS)
Ferrara, S.
1974-01-01
The extension of supergauge symmetry to four-dimensional space-time allows to investigate the possible role of this symmetry in conventional local quantum field theory. The supergauge algebra is obtained by adding to the conformal group of space-time two Majorana spinor generators and the chiral charge. The commutation properties of the algebra are used to derive the most general form of the superfield. This field contains two Majorana spinors, two scalar fields, a chiral doublet, and a real vector field called the vector superfield. The covariant derivatives defined, together with the scalar and vector multiplets are the basic ingredients used in order to build up supergauge symmetric Lagrangians. It is shown that the only possible fields which can be considered as supergauge invariant Lagrangians are the F and D components of the scalar and vector multiplets respectively
Comparing Two Approaches for Point-Like Scatterer Detection
Directory of Open Access Journals (Sweden)
Angela Dell’Aversano
2015-01-01
Full Text Available Many inverse scattering problems concern the detection and localisation of point-like scatterers which are sparsely enclosed within a prescribed investigation domain. Therefore, it looks like a good option to tackle the problem by applying reconstruction methods that are properly tailored for such a type of scatterers or that naturally enforce sparsity in the reconstructions. Accordingly, in this paper we compare the time reversal-MUSIC and the compressed sensing. The study develops through numerical examples and focuses on the role of noise in data and mutual coupling between the scatterers.
Near-field Localization of Audio
DEFF Research Database (Denmark)
Jensen, Jesper Rindom; Christensen, Mads Græsbøll
2014-01-01
Localization of audio sources using microphone arrays has been an important research problem for more than two decades. Many traditional methods for solving the problem are based on a two-stage procedure: first, information about the audio source, such as time differences-of-arrival (TDOAs......) and gain ratios-of-arrival (GROAs) between microphones is estimated, and, second, this knowledge is used to localize the audio source. These methods often have a low computational complexity, but this comes at the cost of a limited estimation accuracy. Therefore, we propose a new localization approach......, where the desired signal is modeled using TDOAs and GROAs, which are determined by the source location. This facilitates the derivation of one-stage, maximum likelihood methods under a white Gaussian noise assumption that is applicable in both near- and far-field scenarios. Simulations show...
Measuring coseismic displacements with point-like targets offset tracking
Hu, Xie; Wang, Teng; Liao, Mingsheng
2014-01-01
Offset tracking is an important complement to measure large ground displacements in both azimuth and range dimensions where synthetic aperture radar (SAR) interferometry is unfeasible. Subpixel offsets can be obtained by searching for the cross-correlation peak calculated from the match patches uniformly distributed on two SAR images. However, it has its limitations, including redundant computation and incorrect estimations on decorrelated patches. In this letter, we propose a simple strategy that performs offset tracking on detected point-like targets (PT). We first detect image patches within bright PT by using a sinc-like template from a single SAR image and then perform offset tracking on them to obtain the pixel shifts. Compared with the standard method, the application on the 2010 M 7.2 El Mayor-Cucapah earthquake shows that the proposed PT offset tracking can significantly increase the cross-correlation and thus result in both efficiency and reliability improvements. © 2013 IEEE.
Point-like structure and off-shell dual strings
International Nuclear Information System (INIS)
Green, M.B.
1977-01-01
It is argued that in a consistent off-shell dual formalism the amplitude for the emission of a scalar off-shell state by a string consists of two components. One of these contains the particle poles in the off-shell leg and the other is intimately related to the insertion of a point-like energy density on the string. As a result, the amplitude for a string to emit a zero momentum scalar state into the vacuum (which may be relevant for spontaneous symmetry breaking) is described by the amplitude for a finite fraction of the energy in the string to collapse to a spatial point at some time (this fraction and its space-time position being integrated over). The off-shell amplitudes have an elegant formulation in terms of a set of 'confined modes' which can be assigned quark flavour quantum numbers to reproduce the Chan-Paton scheme. It is suggested that the dual model be modified by allowing for the coupling of scalar closed strings to the vacuum and the resulting effect on the space-time structure of dual Green functions is described. It is found that even the emission of a single zero-momentum closed string modifies the elastic amplitude in a significant manner, leading to a power-behaved fixed-angle cross section in contrast to the usual exponential decrease of the dual model. This arises from point-like scattering between energy densities accumulating in the colliding strings. The relationship between the fixed angle and Regge limits is discussed. The fixed angle behaviour is found to be the asymptotic limit in momentum transfer of a fixed pole that arises in the Regge limit. (Auth.)
D term and the structure of pointlike and composed spin-0 particles
Hudson, Jonathan; Schweitzer, Peter
2017-12-01
This work deals with form factors of the energy-momentum tensor (EMT) of spin-0 particles and the unknown particle property D term related to the EMT, and it is divided into three parts. The first part explores free, weakly and strongly interacting theories to study EMT form factors with the following findings. (i) The free Klein-Gordon theory predicts for the D term D =-1 . (ii) Even infinitesimally small interactions can drastically impact D . (iii) In strongly interacting theories one can encounter large negative D though notable exceptions exist, which include Goldstone bosons of chiral symmetry breaking. (iv) Contrary to common belief one cannot arbitrarily add "total derivatives" to the EMT. Rather the EMT must be defined in an unambiguous way. The second part deals with the interpretation of the information content of EMT form factors in terms of 3D densities with the following results. (i) The 3D-density formalism is internally consistent. (ii) The description is subject to relativistic corrections but those are acceptably small in phenomenologically relevant situations including nucleons and nuclei. (iii) The free-field result D =-1 persists when a spin-0 boson is not pointlike but "heuristically given some internal structure." The third part investigates the question of whether such "giving of an extended structure" can be implemented dynamically, and it has the following insights. (i) We construct a consistent microscopic theory which, in a certain parametric limit, interpolates between extended and pointlike solutions. (ii) This theory is exactly solvable which is rare in 3 +1 dimensions, admits nontopological solitons of Q -ball type, and has a Gaussian field amplitude. (iii) The interaction of this theory belongs to a class of logarithmic potentials which were discussed in the literature, albeit in different contexts including beyond-standard-model phenomenology, cosmology, and Higgs physics.
International Nuclear Information System (INIS)
Schroer, Bert; FU-Berlin
2012-02-01
Massive quantum matter of prescribed spin permits infinitely many possibilities of covariantization in terms of spinorial (undotted/dotted) pointlike fields, whereas massless nite helicity representations lead to large gap in this spinorial spectrum which for s=1 excludes vector potentials. Since the nonexistence of such pointlike generators is the result of a deep structural clash between modular localization and the Hilbert space setting of QT, there are two ways out: gauge theory which sacrifices the Hilbert space and keeps the pointlike formalism and the use of string like potentials which allows to preserve the Hilbert space. The latter setting contains also string-localized charge-carrying operators whereas the gauge theoretic formulation is limited to point-like generated observables. This description also gives a much better insight into the Higgs mechanism which leads to a revival of the more physical 'Schwinger-Higgs' screening idea. The new formalism is not limited to m=0, s=1, it leads to renormalizable inter- actions in the sense of power-counting for all s in massless representations. The existence of string like vector potentials is preempted by the Aharonov-Bohm effect in QFT; it is well-known that the use of pointlike vector potentials in Stokes theorem would with lead to wrong results. Their use in Maxwell's equations is known to lead to zero Maxwell charge. The role of string-localization in the problem behind the observed invisibility and confinement of gluons and quarks leads to new questions and problems. (author)
Local Field Potentials: Myths and Misunderstandings
Directory of Open Access Journals (Sweden)
Oscar Herreras
2016-12-01
Full Text Available The intracerebral local field potential (LFP is a measure of brain activity that reflects the highly dynamic flow of information across neural networks. This is a composite signal that receives contributions from multiple neural sources, yet interpreting its nature and significance may be hindered by several confounding factors and technical limitations. By and large, the main factor defining the amplitude of LFPs is the geometry of the current sources, over and above the degree of synchronization or the properties of the media. As such, similar levels of activity may result in potentials that differ in several orders of magnitude in different populations. The geometry of these sources has been experimentally inaccessible until intracerebral high density recordings enabled the co-activating sources to be revealed. Without this information, it has proven difficult to interpret a century’s worth of recordings that used temporal cues alone, such as event or spike related potentials and frequency bands. As such, a collection of biophysically ill-founded concepts have been considered legitimate, which can now be corrected in the light of recent advances. The relationship of LFPs to their sources is often counterintuitive. For instance, most LFP activity is not local but remote, it may be larger further from rather than close to the source, the polarity does not define its excitatory or inhibitory nature, and the amplitude may increase when source’s activity is reduced. As technological developments foster the use of LFPs, the time is now ripe to raise awareness of the need to take into account spatial aspects of these signals and of the errors derived from neglecting to do so.
Computing the Local Field Potential (LFP) from Integrate-and-Fire Network Models
Cuntz, Hermann; Lansner, Anders; Panzeri, Stefano; Einevoll, Gaute T.
2015-01-01
Leaky integrate-and-fire (LIF) network models are commonly used to study how the spiking dynamics of neural networks changes with stimuli, tasks or dynamic network states. However, neurophysiological studies in vivo often rather measure the mass activity of neuronal microcircuits with the local field potential (LFP). Given that LFPs are generated by spatially separated currents across the neuronal membrane, they cannot be computed directly from quantities defined in models of point-like LIF neurons. Here, we explore the best approximation for predicting the LFP based on standard output from point-neuron LIF networks. To search for this best “LFP proxy”, we compared LFP predictions from candidate proxies based on LIF network output (e.g, firing rates, membrane potentials, synaptic currents) with “ground-truth” LFP obtained when the LIF network synaptic input currents were injected into an analogous three-dimensional (3D) network model of multi-compartmental neurons with realistic morphology, spatial distributions of somata and synapses. We found that a specific fixed linear combination of the LIF synaptic currents provided an accurate LFP proxy, accounting for most of the variance of the LFP time course observed in the 3D network for all recording locations. This proxy performed well over a broad set of conditions, including substantial variations of the neuronal morphologies. Our results provide a simple formula for estimating the time course of the LFP from LIF network simulations in cases where a single pyramidal population dominates the LFP generation, and thereby facilitate quantitative comparison between computational models and experimental LFP recordings in vivo. PMID:26657024
Computing the Local Field Potential (LFP from Integrate-and-Fire Network Models.
Directory of Open Access Journals (Sweden)
Alberto Mazzoni
2015-12-01
Full Text Available Leaky integrate-and-fire (LIF network models are commonly used to study how the spiking dynamics of neural networks changes with stimuli, tasks or dynamic network states. However, neurophysiological studies in vivo often rather measure the mass activity of neuronal microcircuits with the local field potential (LFP. Given that LFPs are generated by spatially separated currents across the neuronal membrane, they cannot be computed directly from quantities defined in models of point-like LIF neurons. Here, we explore the best approximation for predicting the LFP based on standard output from point-neuron LIF networks. To search for this best "LFP proxy", we compared LFP predictions from candidate proxies based on LIF network output (e.g, firing rates, membrane potentials, synaptic currents with "ground-truth" LFP obtained when the LIF network synaptic input currents were injected into an analogous three-dimensional (3D network model of multi-compartmental neurons with realistic morphology, spatial distributions of somata and synapses. We found that a specific fixed linear combination of the LIF synaptic currents provided an accurate LFP proxy, accounting for most of the variance of the LFP time course observed in the 3D network for all recording locations. This proxy performed well over a broad set of conditions, including substantial variations of the neuronal morphologies. Our results provide a simple formula for estimating the time course of the LFP from LIF network simulations in cases where a single pyramidal population dominates the LFP generation, and thereby facilitate quantitative comparison between computational models and experimental LFP recordings in vivo.
Introduction to localization in quantum field theory
International Nuclear Information System (INIS)
Pestun, Vasily; Zabzine, Maxim
2017-01-01
This is the introductory chapter to this issue. We review the main idea of the localization technique and its brief history both in geometry and in QFT. We discuss localization in diverse dimensions and give an overview of the major applications of the localization calculations for supersymmetric theories. We explain the focus of the present issue. (topical review)
Localization of abelian gauge fields on thick branes
Energy Technology Data Exchange (ETDEWEB)
Vaquera-Araujo, Carlos A. [Universidad de Colima, Facultad de Ciencias, CUICBAS, Colima (Mexico); Corradini, Olindo [Universidad Autonoma de Chiapas, Ciudad Universitaria, Facultad de Ciencias en Fisica y Matematicas, Tuxtla Gutierrez (Mexico); Universita di Modena e Reggio Emilia, Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Modena (Italy)
2015-02-01
In this work, we explore a mechanism for abelian gauge field localization on thick branes based on a five-dimensional Stueckelberg-like action. A normalizable zero mode is found through the identification of a suitable coupling function between the brane and the gauge field. The same mechanism is studied for the localization of the abelian Kalb-Ramond field. (orig.)
Localized magnetic fields in arbitrary directions using patterned nanomagnets
DEFF Research Database (Denmark)
McNeil, Robert P G; Schneble, Jeff; Kataoka, Masaya
2010-01-01
Control of the local magnetic fields desirable for spintronics and quantum information technology is not well developed. Existing methods produce either moderately small local fields or one held orientation. We present designs of patterned magnetic elements that produce remanent fields of 50 mT (...
Topology optimization of nanoparticles for localized electromagnetic field enhancement
DEFF Research Database (Denmark)
Christiansen, Rasmus Ellebæk; Vester-Petersen, Joakim; Madsen, Søren Peder
2017-01-01
We consider the design of individual and periodic arrangements of metal or semiconductor nanoparticles for localized electromagnetic field enhancement utilizing a topology optimization based numerical framework as the design tool. We aim at maximizing a function of the electromagnetic field...
Local relativistic invariant flows for quantum fields
International Nuclear Information System (INIS)
Albeverio, S.; Hoeegh-Krahn, R.; Sirugue, M.
1983-01-01
For quantum fields with trigonometric interaction in arbitrary space dimension we construct a representation of the Lorentz group by automorphisms on a Banach space generated by the Weyl algebra. (orig.)
Shadow fields and local supersymmetric gauges
International Nuclear Information System (INIS)
Baulieu, L.; Bossard, G.; Sorella, S.P.
2006-01-01
To control supersymmetry and gauge invariance in super-Yang-Mills theories we introduce new fields, called shadow fields, which enable us to enlarge the conventional Faddeev-Popov framework and write down a set of useful Slavnov-Taylor identities. These identities allow us to address and answer the issue of the supersymmetric Yang-Mills anomalies, and to perform the conventional renormalization programme in a fully regularization-independent way
The loop I superbubble and the local interstellar magnetic field
International Nuclear Information System (INIS)
Frisch, Priscilla Chapman
2014-01-01
Recent data on the interstellar magnetic field in the low density nearby interstellar medium suggest a new perspective for understanding interstellar clouds within 40 pc. The directions of the local interstellar magnetic field found from measurements of optically polarized starlight and the very local field found from the Ribbon of energetic neutral atoms discovered by IBEX nearly agree. The geometrical relation between the local magnetic field, the positions and kinematics of local interstellar clouds, and the Loop I S1 superbubble, suggest that the Sun is located in the boundary of this evolved superbubble. The quasiperpendicular angle between the bulk kinematics and magnetic field of the local ISM indicates that a complete picture of low density interstellar clouds needs to include information on the interstellar magnetic field.
Energy Technology Data Exchange (ETDEWEB)
Schroer, Bert [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Freie Universitaet, Berlin (Germany). Inst. fuer Theoretische Physik
2010-02-15
The main topics of this second part of a two-part essay are some consequences of the phenomenon of vacuum polarization as the most important physical manifestation of modular localization. Besides philosophically unexpected consequences, it has led to a new constructive 'outside-inwards approach' in which the pointlike fields and the compactly localized operator algebras which they generate only appear from intersecting much simpler algebras localized in noncompact wedge regions whose generators have extremely mild almost free field behavior. Another consequence of vacuum polarization presented in this essay is the localization entropy near a causal horizon which follows a logarithmically modified area law in which a dimensionless area (the area divided by the square of dR where dR is the thickness of a light sheet) appears. There are arguments that this logarithmically modified area law corresponds to the volume law of the standard heat bath thermal behavior. We also explain the symmetry enhancing effect of holographic projections onto the causal horizon of a region and show that the resulting infinite dimensional symmetry groups contain the Bondi-Metzner-Sachs group. This essay is the second part of a partitioned longer paper. (author)
International Nuclear Information System (INIS)
Schroer, Bert; Freie Universitaet, Berlin
2010-02-01
The main topics of this second part of a two-part essay are some consequences of the phenomenon of vacuum polarization as the most important physical manifestation of modular localization. Besides philosophically unexpected consequences, it has led to a new constructive 'outside-inwards approach' in which the pointlike fields and the compactly localized operator algebras which they generate only appear from intersecting much simpler algebras localized in noncompact wedge regions whose generators have extremely mild almost free field behavior. Another consequence of vacuum polarization presented in this essay is the localization entropy near a causal horizon which follows a logarithmically modified area law in which a dimensionless area (the area divided by the square of dR where dR is the thickness of a light sheet) appears. There are arguments that this logarithmically modified area law corresponds to the volume law of the standard heat bath thermal behavior. We also explain the symmetry enhancing effect of holographic projections onto the causal horizon of a region and show that the resulting infinite dimensional symmetry groups contain the Bondi-Metzner-Sachs group. This essay is the second part of a partitioned longer paper. (author)
International Nuclear Information System (INIS)
Schroer, Bert
2010-01-01
The main topics of this second part of a two-part essay are some consequences of the phenomenon of vacuum polarization as the most important physical manifestation of modular localization. Besides philosophically unexpected consequences, it has led to a new constructive 'outside-inwards approach' in which the pointlike fields and the compactly localized operator algebras which they generate only appear from intersecting much simpler algebras localized in noncompact wedge regions whose generators have extremely mild almost free field behavior. Another consequence of vacuum polarization presented in this essay is the localization entropy near a causal horizon which follows a logarithmically modified area law in which a dimensionless area (the area divided by the square of dR where dR is the thickness of a light sheet) appears. There are arguments that this logarithmically modified area law corresponds to the volume law of the standard heat bath thermal behavior. We also explain the symmetry enhancing effect of holographic projections onto the causal horizon of a region and show that the resulting infinite dimensional symmetry groups contain the Bondi-Metzner-Sachs group. This essay is the second part of a partitioned longer paper. (author)
Response of an oscillating superleak transducer to a pointlike heat source
Directory of Open Access Journals (Sweden)
A. Quadt
2012-03-01
Full Text Available A new technique of superconducting cavity diagnostics has been introduced by D. L. Hartill at Cornell University, Ithaca, New York. It uses oscillating superleak transducers (OST which detect the heat transferred from a cavity’s quench point via Second Sound through the superfluid He bath, needed to cool the superconducting cavity. The localization of the quench point is done by triangulation. The observed response of an OST is a nontrivial, but reproducible pattern of oscillations. A small helium evaporation cryostat was built which allows the investigation of the response of an OST in greater detail. The distance between a pointlike electrical heater and the OST can be varied. The OST can be mounted either parallel or perpendicular to the plate that houses the heat source. If the artificial quench point releases an amount of energy compatible to a real quench spot on a cavity’s surface, the OST signal starts with a negative pulse, which is usually strong enough to allow automatic detection. Furthermore, the reflection of the Second Sound on the wall is observed. A reflection coefficient R=0.39±0.05 of the glass wall is measured. This excludes a strong influence of multiple reflections in the complex OST response. Fourier analyses show three main frequencies, found in all OST spectra. They can be interpreted as modes of an oscillating circular membrane.
Local freedom in the gravitational field revisited
International Nuclear Information System (INIS)
Pareja, Maria Jesus; MacCallum, Malcolm A H
2006-01-01
Maartens et al (1997 Class. Quantum Grav. 14 1927) gave a covariant characterization, in a (1 + 3) formalism based on a perfect fluid's velocity, of the parts of the first derivatives of the curvature tensor in general relativity which are 'locally free', i.e. not pointwise determined by the fluid energy-momentum and its derivative. The full decomposition of independent curvature derivative components given in earlier work on the spinor approach to the equivalence problem enables analogous general results to be stated for any order: the independent matter terms can also be characterized. Explicit relations between the two sets of results are obtained. The 24 Maartens et al locally free data are shown to correspond to the ∇Ψ quantities in the spinor approach, and the fluid terms are similarly related to the remaining 16 independent quantities in the first derivatives of the curvature
Local freedom in the gravitational field revisited
Energy Technology Data Exchange (ETDEWEB)
Pareja, Maria Jesus [Institute for Astronomy and Astrophysics, University of Tuebingen, Auf der Morgenstelle 10, D-72076 Tuebingen (Germany); MacCallum, Malcolm A H [School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom)
2006-08-07
Maartens et al (1997 Class. Quantum Grav. 14 1927) gave a covariant characterization, in a (1 + 3) formalism based on a perfect fluid's velocity, of the parts of the first derivatives of the curvature tensor in general relativity which are 'locally free', i.e. not pointwise determined by the fluid energy-momentum and its derivative. The full decomposition of independent curvature derivative components given in earlier work on the spinor approach to the equivalence problem enables analogous general results to be stated for any order: the independent matter terms can also be characterized. Explicit relations between the two sets of results are obtained. The 24 Maartens et al locally free data are shown to correspond to the {nabla}{psi} quantities in the spinor approach, and the fluid terms are similarly related to the remaining 16 independent quantities in the first derivatives of the curvature.
Impact of local electrostatic field rearrangement on field ionization
Katnagallu, Shyam; Dagan, Michal; Parviainen, Stefan; Nematollahi, Ali; Grabowski, Blazej; Bagot, Paul A. J.; Rolland, Nicolas; Neugebauer, Jörg; Raabe, Dierk; Vurpillot, François; Moody, Michael P.; Gault, Baptiste
2018-03-01
Field ion microscopy allows for direct imaging of surfaces with true atomic resolution. The high charge density distribution on the surface generates an intense electric field that can induce ionization of gas atoms. We investigate the dynamic nature of the charge and the consequent electrostatic field redistribution following the departure of atoms initially constituting the surface in the form of an ion, a process known as field evaporation. We report on a new algorithm for image processing and tracking of individual atoms on the specimen surface enabling quantitative assessment of shifts in the imaged atomic positions. By combining experimental investigations with molecular dynamics simulations, which include the full electric charge, we confirm that change is directly associated with the rearrangement of the electrostatic field that modifies the imaging gas ionization zone. We derive important considerations for future developments of data reconstruction in 3D field ion microscopy, in particular for precise quantification of lattice strains and characterization of crystalline defects at the atomic scale.
Miccio, Lisa; Merola, Francesco; Memmolo, Pasquale; Mugnano, Martina; Fusco, Sabato; Netti, Paolo A.; Ferraro, Pietro
2014-05-01
Guiding, controlling and studying cellular functions are challenging themes in the biomedical field, as they are fundamental prerequisites for new therapeutic strategies from tissue regeneration to controlled drug delivery. In recent years, multidisciplinary studies in nanotechnology offer new tools to investigate important biophysical phenomena in response to the local physical characteristics of the extracellular environment, some examples are the mechanisms of cell adhesion, migration, communication and differentiation. Indeed for reproducing the features of the extracellular matrix in vitro, it is essential to develop active devices that evoke as much as possible the natural cellular environment. Our investigation is in the framework of studying and clarifying the biophysical mechanisms of the interaction between cells and the microenvironment in which they exist. We implement an optical tweezers setup to investigate cell material interaction and we use Digital Holography as non-invasive imaging technique in microscopy. We exploit Holographic Optical Tweezers arrangement in order to trap and manage functionalized micrometric latex beads to induce mechanical deformation in suspended cells. A lot of papers in literature examine the dynamics of the cytoskeleton when cells adhere on substrates and nowadays well established cell models are based on such research activities. Actually, the natural cell environment is made of a complex extracellular matrix and the single cell behavior is due to intricate interactions with the environment and are strongly correlated to the cell-cell interactions. Our investigation is devoted to understand the inner cell mechanism when it is mechanically stressed by point-like stimulus without the substrate influence.
Influence of local field on spontaneous light emission by nanoparticles
DEFF Research Database (Denmark)
Keller, Ole; Lozovski, V.; Iezhokin, I.
2009-01-01
moment of transition that takes local-field effects into account. The effective dipole moment depends on the particle shape and size. Therefore, dipole radiation depends on those parameters too. The direction patterns of light emission by cubic particles have been calculated. The particles have been......A self-consistent approach based on the local-field concept has been proposed to calculate the direction patterns of light emission by nanoparticles with various shapes. The main idea of the method consists in constructing self-consistent equations for the electromagnetic field at any point...... of the system. The solution of the equations brings about relationships between the local field at an arbitrary point in the system and the external long-wave field via the local-field factor. The latter connects the initial moment of optical dipole transition per system volume unit and the effective dipole...
Asymptotic behavior of local dipolar fields in thin films
Energy Technology Data Exchange (ETDEWEB)
Bowden, G.J., E-mail: gjb@phys.soton.ac.uk [School of Physics and Astronomy, University of Southampton, SO17 1BJ (United Kingdom); Stenning, G.B.G., E-mail: Gerrit.vanderlaan@diamond.ac.uk [Magnetic Spectroscopy Group, Diamond Light Source, Didcot OX11 0DE (United Kingdom); Laan, G. van der, E-mail: gavin.stenning@stfc.ac.uk [ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom)
2016-10-15
A simple method, based on layer by layer direct summation, is used to determine the local dipolar fields in uniformly magnetized thin films. The results show that the dipolar constants converge ~1/m where the number of spins in a square film is given by (2m+1){sup 2}. Dipolar field results for sc, bcc, fcc, and hexagonal lattices are presented and discussed. The results can be used to calculate local dipolar fields in films with either ferromagnetic, antiferromagnetic, spiral, exponential decay behavior, provided the magnetic order only changes normal to the film. Differences between the atomistic (local fields) and macroscopic fields (Maxwellian) are also examined. For the latter, the macro B-field inside the film is uniform and falls to zero sharply outside, in accord with Maxwell boundary conditions. In contrast, the local field for the atomistic point dipole model is highly non-linear inside and falls to zero at about three lattice spacing outside the film. Finally, it is argued that the continuum field B (used by the micromagnetic community) and the local field B{sub loc}(r) (used by the FMR community) will lead to differing values for the overall demagnetization energy. - Highlights: • Point-dipolar fields in uniformly magnetized thin films are characterized by just three numbers. • Maxwell's boundary condition is partially violated in the point-dipole approximation. • Asymptotic values of point dipolar fields in circular monolayers scale as π/r.
Designing localized electromagnetic fields in a source-free space
International Nuclear Information System (INIS)
Borzdov, George N.
2002-01-01
An approach to characterizing and designing localized electromagnetic fields, based on the use of differentiable manifolds, differentiable mappings, and the group of rotation, is presented. By way of illustration, novel families of exact time-harmonic solutions to Maxwell's equations in the source-free space - localized fields defined by the rotation group - are obtained. The proposed approach provides a broad spectrum of tools to design localized fields, i.e., to build-in symmetry properties of oscillating electric and magnetic fields, to govern the distributions of their energy densities (both size and form of localization domains), and to set the structure of time-average energy fluxes. It is shown that localized fields can be combined as constructive elements to obtain a complex field structure with desirable properties, such as one-, two-, or three-dimensional field gratings. The proposed approach can be used in designing localized electromagnetic fields to govern motion and state of charged and neutral particles. As an example, motion of relativistic electrons in one-dimensional and three-dimensional field gratings is treated
Harmonic analysis on local fields and adelic spaces. I
International Nuclear Information System (INIS)
Osipov, D V; Parshin, A N
2008-01-01
We develop harmonic analysis on the objects of a category C 2 of infinite-dimensional filtered vector spaces over a finite field. This category includes two-dimensional local fields and adelic spaces of algebraic surfaces defined over a finite field. As the main result, we construct the theory of the Fourier transform on these objects and obtain two-dimensional Poisson formulae
Modeling of Local Magnetic Field Enhancements within Solar Flux Ropes
Romashets, E; Vandas, M; Poedts, Stefaan
2010-01-01
To model and study local magnetic-field enhancements in a solar flux rope we consider the magnetic field in its interior as a superposition of two linear (constant alpha) force-free magnetic-field distributions, viz. a global one, which is locally similar to a part of the cylinder, and a local torus-shaped magnetic distribution. The newly derived solution for a toroid with an aspect ratio close to unity is applied. The symmetry axis of the toroid and that of the cylinder may or may not coinci...
Non-Abelian monopole in the parameter space of point-like interactions
International Nuclear Information System (INIS)
Ohya, Satoshi
2014-01-01
We study non-Abelian geometric phase in N=2 supersymmetric quantum mechanics for a free particle on a circle with two point-like interactions at antipodal points. We show that non-Abelian Berry’s connection is that of SU(2) magnetic monopole discovered by Moody, Shapere and Wilczek in the context of adiabatic decoupling limit of diatomic molecule. - Highlights: • Supersymmetric quantum mechanics is an ideal playground for studying geometric phase. • We determine the parameter space of supersymmetric point-like interactions. • Berry’s connection is given by a Wu–Yang-like magnetic monopole in SU(2) Yang–Mills
Dynamical local field, compressibility, and frequency sum rules for quasiparticles
International Nuclear Information System (INIS)
Morawetz, Klaus
2002-01-01
The finite temperature dynamical response function including the dynamical local field is derived within a quasiparticle picture for interacting one-, two-, and three-dimensional Fermi systems. The correlations are assumed to be given by a density-dependent effective mass, quasiparticle energy shift, and relaxation time. The latter one describes disorder or collisional effects. This parametrization of correlations includes local-density functionals as a special case and is therefore applicable for density-functional theories. With a single static local field, the third-order frequency sum rule can be fulfilled simultaneously with the compressibility sum rule by relating the effective mass and quasiparticle energy shift to the structure function or pair-correlation function. Consequently, solely local-density functionals without taking into account effective masses cannot fulfill both sum rules simultaneously with a static local field. The comparison to the Monte Carlo data seems to support such a quasiparticle picture
Anisotropies in magnetic field evolution and local Lyapunov exponents
International Nuclear Information System (INIS)
Tang, X.Z.; Boozer, A.H.
2000-01-01
The natural occurrence of small scale structures and the extreme anisotropy in the evolution of a magnetic field embedded in a conducting flow is interpreted in terms of the properties of the local Lyapunov exponents along the various local characteristic (un)stable directions for the Lagrangian flow trajectories. The local Lyapunov exponents and the characteristic directions are functions of Lagrangian coordinates and time, which are completely determined once the flow field is specified. The characteristic directions that are associated with the spatial anisotropy of the problem, are prescribed in both Lagrangian and Eulerian frames. Coordinate transformation techniques are employed to relate the spatial distributions of the magnetic field, the induced current density, and the Lorentz force, which are usually followed in Eulerian frame, to those of the local Lyapunov exponents, which are naturally defined in Lagrangian coordinates
Relativistic local quantum field theory for m=0 particles
International Nuclear Information System (INIS)
Morales Villasevil, A.
1965-01-01
A method is introduced ta deal with relativistic quantum field theory for particles with m=0. Two mappings I and J, giving rise respectively to particle and anti particle states, are defined between a test space and the physical Hilbert space. The intrinsic field operator is then defined as the minimal causal linear combinations of operators belonging to the annihilation-creation algebra associated to the germ and antigerm parts of the element. Local elements are introduced as improper test elements and local field operators are constructed in the same way as the intrinsic ones. Commutation rules are given. (Author) 17 refs
Local and Nonlocal Parallel Heat Transport in General Magnetic Fields
International Nuclear Information System (INIS)
Castillo-Negrete, D. del; Chacon, L.
2011-01-01
A novel approach for the study of parallel transport in magnetized plasmas is presented. The method avoids numerical pollution issues of grid-based formulations and applies to integrable and chaotic magnetic fields with local or nonlocal parallel closures. In weakly chaotic fields, the method gives the fractal structure of the devil's staircase radial temperature profile. In fully chaotic fields, the temperature exhibits self-similar spatiotemporal evolution with a stretched-exponential scaling function for local closures and an algebraically decaying one for nonlocal closures. It is shown that, for both closures, the effective radial heat transport is incompatible with the quasilinear diffusion model.
The generally covariant locality principle - a new paradigm for local quantum field theory
International Nuclear Information System (INIS)
Brunetti, R.; Fredenhagen, K.; Verch, R.
2002-05-01
A new approach to the model-independent description of quantum field theories will be introduced in the present work. The main feature of this new approach is to incorporate in a local sense the principle of general covariance of general relativity, thus giving rise to the concept of a locally covariant quantum field theory. Such locally covariant quantum field theories will be described mathematically in terms of covariant functors between the categories, on one side, of globally hyperbolic spacetimes with isometric embeddings as morphisms and, on the other side, of *-algebras with unital injective *-endomorphisms as morphisms. Moreover, locally covariant quantum fields can be described in this framework as natural transformations between certain functors. The usual Haag-Kastler framework of nets of operator-algebras over a fixed spacetime background-manifold, together with covariant automorphic actions of the isometry-group of the background spacetime, can be re-gained from this new approach as a special case. Examples of this new approach are also outlined. In case that a locally covariant quantum field theory obeys the time-slice axiom, one can naturally associate to it certain automorphic actions, called ''relative Cauchy-evolutions'', which describe the dynamical reaction of the quantum field theory to a local change of spacetime background metrics. The functional derivative of a relative Cauchy-evolution with respect to the spacetime metric is found to be a divergence-free quantity which has, as will be demonstrated in an example, the significance of an energy-momentum tensor for the locally covariant quantum field theory. Furthermore, we discuss the functorial properties of state spaces of locally covariant quantum field theories that entail the validity of the principle of local definiteness. (orig.)
First all-flavor neutrino pointlike source search with the ANTARES neutrino telescope
Albert, A.; André, M.; Anghinolfi, M.; Anton, G.; Ardid, M.; Aubert, J.-J.; Avgitas, T.; Baret, B.; Barrios-Martí, J.; Basa, S.; Belhorma, B.; Bertin, V.; Biagi, S.; Bormuth, R.; Bourret, S.; Bouwhuis, M.C.; Brânzas, H.; Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr, J.; Celli, S.; Cherkaoui El Moursli, R.; Chiarusi, T.; Circella, M.; Coelho, J.A.B.; Coleiro, A.; Coniglione, R.; Costantini, H.; Coyle, P.; Creusot, A.; Díaz, A.F.; Deschamps, A.; De Bonis, G.; Distefano, C.; Di Palma, I.; Domi, A.; Donzaud, C.; Dornic, D.; Drouhin, D.; Eberl, T.; El Bojaddaini, I.; El Khayati, N.; Elsässer, D.; Enzenhöfer, A.; Ettahiri, A.; Fassi, F.; Felis, I.; Fusco, L.A.; Galatà, S.; Gay, P.; Giordano, V.; Glotin, H.; Grégoire, T.; Gracia-Ruiz, R.; Graf, K.; Hallmann, S.; van Haren, H.; Heijboer, A.J.; Hello, Y.; Hernández-Rey, J.J.; Hößl, J.; Hofestädt, J.; Hugon, C.; Illuminati, G.; James, C.W.; de Jong, M.; Jongen, M.; Kadler, M.; Kalekin, O.; Katz, U.; Kießling, D.; Kouchner, A.; Kreter, M.; Kreykenbohm, I.; Kulikovskiy, V.; Lachaud, C.; Lahmann, R.; Lefèvre, D.; Leonora, E.; Lotze, M.; Loucatos, S.; Marcelin, M.; Margiotta, A.; Marinelli, A.; Martinez-Mora, J.A.; Mele, R.; Melis, K.; Michael, T.; Migliozzi, P.; Moussa, A.; Navas, S.; Nezri, E.; Organokov, M.; Pavalas, G.E.; Pellegrino, C.; Perrina, C.; Piattelli, P.; Popa, V.; Pradier, T.; Quinn, L.; Racca, C.; Riccobene, G.; Sánchez-Losa, A.; Saldaña, M.; Salvadori, I.; Samtleben, D.F.E.; Sanguineti, M.; Sapienza, P.; Schüssler, F.; Sieger, C.; Spurio, M.; Stolarczyk, T.; Taiuti, M.; Tayalati, Y.; Trovato, A.; Turpin, D.; Tönnis, C.; Vallage, B.; Van Elewyck, V.; Versari, F.; Vivolo, D.; Vizzoca, A.; Wilms, J.; Zornoza, J.D.; Zúñiga, J.
2017-01-01
A search for cosmic neutrino sources using the data collected with the ANTARES neutrino telescope between early 2007 and the end of 2015 is performed. For the first time, all neutrino interactions --charged and neutral current interactions of all flavours-- are considered in a search for point-like
Effective electric and magnetic polarizabilities of pointlike spin-1/2 particles
Silenko, A. J.
2014-01-01
Effective electric and magnetic polarizabilities of pointlike spin-1/2 particles possesing an anomalous magnetic moment are calculated with the transformation of an initial Hamiltonian to the Foldy-Wouthuysen representation. Polarizabilities of spin-1/2 and spin-1 particles are compared.
Macroscopic local-field effects on photoabsorption processes
International Nuclear Information System (INIS)
Ma Xiaoguang; Gong Yubing; Wang Meishan; Wang Dehua
2008-01-01
The influence of the local-field effect on the photoabsorption cross sections of the atoms which are embedded in the macroscopic medium has been studied by a set of alternative expressions in detail. Some notes on the validity of some different local-field models used to study the photoabsorption cross sections of atoms in condensed matter have been given for the first time. Our results indicate that the local fields can have substantial and different influence on the photoabsorption cross section of atoms in condensed matter for different models. Clausius-Mossotti model and Onsager model have proved to be more reasonable to describe the local field in gas, liquid, or even some simple solid, while Glauber-Lewenstein model probably is wrong in these conditions except for the ideal gas. A procedure which can avoid the errors introduced by Kramers-Kronig transformation has been implemented in this work. This procedure can guarantee that the theoretical studies on the local field effects will not be influenced by the integral instability of the Kramers-Kronig transformation
Complementary bowtie aperture for localizing and enhancing optical magnetic field
Zhou, Nan; Kinzel, Edward C.; Xu, Xianfan
2011-08-01
Nanoscale bowtie antenna and bowtie aperture antenna have been shown to generate strongly enhanced and localized electric fields below the diffraction limit in the optical frequency range. According to Babinet's principle, their complements will be efficient for concentrating and enhancing magnetic fields. In this Letter, we discuss the enhancement of magnetic field intensity of nanoscale complementary bowtie aperture as well as complementary bowtie aperture antenna, or diabolo nanoantenna. We show that the complementary bowtie antenna resonates at a smaller wavelength and thus is more suitable for applications near visible wavelengths. The near-field magnetic intensity can be further enhanced by the addition of groove structures that scatter surface plasmon.
An anthology of non-local QFT and QFT on noncommutative spacetime
International Nuclear Information System (INIS)
Schroer, Bert; E-mail schroer@cbpf.br
2004-05-01
Ever since the appearance of renormalization theory there have been several differently motivated attempts at non-localized (in the sense of not generated by point-like fields) relativistic particle theories, the most recent one being at QFT on non-commutative Minkowski spacetime. The often conceptually uncritical and historically forgetful contemporary approach to these problems calls for a critical review of contemporary ideas in the light of previous results on this subject. (author)
An anthology of non-local QFT and QFT on non-commutative spacetime
Schroer, Bert
2005-09-01
Ever since the appearance of renormalization theory, there have been several differently motivated attempts at non-localized (in the sense of not generated by pointlike fields) relativistic particle theories, the most recent one being at QFT on non-commutative Minkowski spacetime. The often conceptually uncritical and historically forgetful contemporary approach to these problems calls for a critical review in the light of previous results on this subject.
An anthology of non-local QFT and QFT on non-commutative spacetime
International Nuclear Information System (INIS)
Schroer, Bert
2005-01-01
Ever since the appearance of renormalization theory, there have been several differently motivated attempts at non-localized (in the sense of not generated by pointlike fields) relativistic particle theories, the most recent one being at QFT on non-commutative Minkowski spacetime. The often conceptually uncritical and historically forgetful contemporary approach to these problems calls for a critical review in the light of previous results on this subject
Local-field refinement of neutron scattering lengths
Energy Technology Data Exchange (ETDEWEB)
Sears, V F
1985-06-01
We examine the way in which local field effects in the neutron refractive index affect the values of coherent scattering lengths determined by various kinds of neutron optical measurements. We find that under typical experimental conditions these effects are negligible for interferometry measurements but that they are significant for gravity refractometry measurements, producing changes in the effective scattering length of as much as two or three standard deviations in some cases. Refined values of the scattering length are obtained for the thirteen elements for which data are presently available. The special role of local field effects in neutron transmission is also discussed.
Local-field refinement of neutron scattering lengths
International Nuclear Information System (INIS)
Sears, V.F.
1985-01-01
We examine the way in which local field effects in the neutron refractive index affect the values of coherent scattering lengths determined by various kinds of neutron optical measurements. We find that under typical experimental conditions these effects are negligible for interferometry measurements but that they are significant for gravity refractometry measurements, producing changes in the effective scattering length of as much as two or three standard deviations in some cases. Refined values of the scattering length are obtained for the thirteen elements for which data are presently available. The special role of local field effects in neutron transmission is also discussed. (orig.)
Localized Electron Heating by Strong Guide-Field Magnetic Reconnection
Guo, Xuehan; Sugawara, Takumichi; Inomoto, Michiaki; Yamasaki, Kotaro; Ono, Yasushi; UTST Team
2015-11-01
Localized electron heating of magnetic reconnection was studied under strong guide-field (typically Bt 15Bp) using two merging spherical tokamak plasmas in Univ. Tokyo Spherical Tokamak (UTST) experiment. Our new slide-type two-dimensional Thomson scattering system documented for the first time the electron heating localized around the X-point. The region of high electron temperature, which is perpendicular to the magnetic field, was found to have a round shape with radius of 2 [cm]. Also, it was localized around the X-point and does not agree with that of energy dissipation term Et .jt . When we include a guide-field effect term Bt / (Bp + αBt) for Et .jt where α =√{ (vin2 +vout2) /v∥2 } , the energy dissipation area becomes localized around the X-point, suggesting that the electrons are accelerated by the reconnection electric field parallel to the magnetic field and thermalized around the X-point. This work was supported by JSPS A3 Foresight Program ``Innovative Tokamak Plasma Startup and Current Drive in Spherical Torus,'' a Grant-in-Aid from the Japan Society for the Promotion of Science (JSPS) Fellows 15J03758.
Non-local deformation of a supersymmetric field theory
Energy Technology Data Exchange (ETDEWEB)
Zhao, Qin [National University of Singapore, Department of Physics, Singapore (Singapore); Faizal, Mir [University of Lethbridge, Department of Physics and Astronomy, Lethbridge (Canada); University of British Columbia - Okanagan, Irving K. Barber School of Arts and Sciences, Kelowna, BC (Canada); Shah, Mushtaq B.; Ganai, Prince A. [National Institute of Technology, Department of Physics, Srinagar, Kashmir (India); Bhat, Anha [National Institute of Technology, Department of Metallurgical and Materials Engineering, Srinagar (India); Zaz, Zaid [University of Kashmir, Department of Electronics and Communication Engineering, Srinagar, Kashmir (India); Masood, Syed; Raza, Jamil; Irfan, Raja Muhammad [International Islamic University, Department of Physics, Islamabad (Pakistan)
2017-09-15
In this paper, we will analyze a supersymmetric field theory deformed by generalized uncertainty principle and Lifshitz scaling. It will be observed that this deformed supersymmetric field theory contains non-local fractional derivative terms. In order to construct such a deformed N = 1 supersymmetric theory, a harmonic extension of functions will be used. However, the supersymmetry will only be preserved for a free theory and will be broken by the inclusion of interaction terms. (orig.)
A course on quantum field theory and local observables
International Nuclear Information System (INIS)
Schroer, Bert
1997-03-01
A monograph on Quantum Field Theory and Local Observables is presented, aiming to unify two presently largely disconnected branches of QFT, as follows: the standard (canonical, functional) approach which is mainly perturbative in the sense of an infinitesimal 'deformation' of free fields; nonperturbative constructions of low-dimensional models as the form factor-bootstrap approach (which for the time being is limited to factorable models in d=1+1 spacetime dimensions) and the non-Lagrangian constructions of conformal chiral QFT's
Local field corrections in the lattice dynamics of chromium | Ndukwe ...
African Journals Online (AJOL)
This work extends the inclusion of local field corrections in the calculation of the phonon dispersion curves to the transition metal, chromium (Cr3+) using the formalism of lattice dynamics based on the transition metal model potential approach in the adiabatic and hatmonic approximations. The results obtained here have a ...
Localization of vector field on dynamical domain wall
Directory of Open Access Journals (Sweden)
Masafumi Higuchi
2017-03-01
Full Text Available In the previous works (arXiv:1202.5375 and arXiv:1402.1346, the dynamical domain wall, where the four dimensional FRW universe is embedded in the five dimensional space–time, has been realized by using two scalar fields. In this paper, we consider the localization of vector field in three formulations. The first formulation was investigated in the previous paper (arXiv:1510.01099 for the U(1 gauge field. In the second formulation, we investigate the Dvali–Shifman mechanism (arXiv:hep-th/9612128, where the non-abelian gauge field is confined in the bulk but the gauge symmetry is spontaneously broken on the domain wall. In the third formulation, we investigate the Kaluza–Klein modes coming from the five dimensional graviton. In the Randall–Sundrum model, the graviton was localized on the brane. We show that the (5,μ components (μ=0,1,2,3 of the graviton are also localized on the domain wall and can be regarded as the vector field on the domain wall. There are, however, some corrections coming from the bulk extra dimension if the domain wall universe is expanding.
Local Magnetic Fields in Ferromagnetics Studied by Positive Muon Precession
2002-01-01
Positive muons are used to study local magnetic fields in different materials. A polarized muon beam is employed with energies of 30-50 MeV, and the muons are stopped in the target being studied. During its lifetime the muon will precess in the magnetic fields present, and after the decay of the muon the emitted positron is detected in plastic scintillators. The time and angle of the detected positron is used to calculate the magnetic field at the position of the muon in the sample. \\\\ \\\\ The detector system consists of plastic scintillators. Most of the measurements are made in an applied magnetic field. A dilution cryostat is used to produce temperatures down to well below $ 1 ^0 $ K. \\\\ \\\\ The present line of experiments concern mainly: \\item a)~~~~Local magnetism in the paramagnetic state of the Lave's phase type REAl$_{2} $ and RENi$_{2} $ systems ~~~where RE is a rare-earth ion. \\item b)~~~~Local magnetic fields and critical behaviour of the magnetism in Gd metal. \\item c)~~~~Investigation of flux exclu...
Applicability of the local field concept for the electron gas
International Nuclear Information System (INIS)
Neilson, D.; Sjoelander, A.; Swierkowski, L.
1990-01-01
The static exchange-correlation hole surrounding an electron in an electron gas at metallic densities has been a highly successful and useful concept. The properties of the static exchange-correlation hole can be accurately reflected by the construction of a static local field. This field surrounds each electron and modifies it interaction with the other electrons in the system. An important limitation of the local field concept is that it does not handle the time-dependent relaxation of the surrounding electron cloud in a particularly transparent way. At metallic densities this is if no consequence since relaxation effects are only small corrections anyway, but at lower densities and in two-dimensional systems they become increasingly important. Approaches which attempt to address these problems are discussed. (author). 12 refs, 4 figs
Local conservation laws for principle chiral fields (d=1)
International Nuclear Information System (INIS)
Cherednik, I.V.
1979-01-01
The Beklund transformation for chiral fields in the two-dimensional Minkovski space is found. As a result an infinite series of conservation laws for principle chiral Osub(n) fields (d=1) has been built. It is shown that these laws are local, the infinite series of global invariants which do not depend on xi, eta, and which is rather rapidly decrease along xi (or along eta) solutions being connected with these laws (xi, eta - coordinates of the light cone). It is noted that with the help of the construction proposed it is possible to obtain conservation laws of principle chiral G fields, including G in the suitable ortogonal groups. Symmetry permits to exchange xi and eta. The construction of conservation laws may be carried out without supposition that lambda has a multiplicity equal to 1, however the proof of the locality applied does not transfer on the laws obtained
Local electric field screening in bi-layer graphene devices
Directory of Open Access Journals (Sweden)
Vishal ePanchal
2014-02-01
Full Text Available We present experimental studies of both local and macroscopic electrical effects in uniform single- (1LG and bi-layer graphene (2LG devices as well as in devices with non-uniform graphene coverage, under ambient conditions. DC transport measurements on sub-micron scale Hall bar devices were used to show a linear rise in carrier density with increasing amounts of 2LG coverage. Electrical scanning gate microscopy was used to locally top gate uniform and non-uniform devices in order to observe the effect of local electrical gating. We experimentally show a significant level of electric field screening by 2LG. We demonstrate that SGM technique is an extremely useful research tool for studies of local screening effects, which provides a complementary view on phenomena that are usually considered only within a macroscopic experimental scheme.
A systematic analysis of the Braitenberg vehicle 2b for point-like stimulus sources
International Nuclear Information System (INIS)
Rañó, Iñaki
2012-01-01
Braitenberg vehicles have been used experimentally for decades in robotics with limited empirical understanding. This paper presents the first mathematical model of the vehicle 2b, displaying so-called aggression behaviour, and analyses the possible trajectories for point-like smooth stimulus sources. This sensory-motor steering control mechanism is used to implement biologically grounded target approach, target-seeking or obstacle-avoidance behaviour. However, the analysis of the resulting model reveals that complex and unexpected trajectories can result even for point-like stimuli. We also prove how the implementation of the controller and the vehicle morphology interact to affect the behaviour of the vehicle. This work provides a better understanding of Braitenberg vehicle 2b, explains experimental results and paves the way for a formally grounded application on robotics as well as for a new way of understanding target seeking in biology. (paper)
Construction of local and non-local conservation laws for non-linear field equations
International Nuclear Information System (INIS)
Vladimirov, V.S.; Volovich, I.V.
1984-08-01
A method of constructing conserved currents for non-linear field equations is presented. More explicitly for non-linear equations, which can be derived from compatibility conditions of some linear system with a parameter, a procedure of obtaining explicit expressions for local and non-local currents is developed. Some examples such as the classical Heisenberg spin chain and supersymmetric Yang-Mills theory are considered. (author)
Microfocus x-ray imaging of traceable pointlike {sup 22}Na sources for quality control
Energy Technology Data Exchange (ETDEWEB)
Hasegawa, T.; Oda, K.; Sato, Y.; Ito, H.; Masuda, S.; Yamada, T.; Matsumoto, M.; Murayama, H.; Takei, H. [Allied Health Sciences, Kitasato University Kitasato 1-15-1, Minami-ku, Sagamihara-shi, Kanagawa 252-0373 (Japan); Positron Medical Center, Tokyo Metropolitan Institute of Gerontology Sakaecho 35-2, Itabashi-ku, Tokyo 173-0015 (Japan); Advanced Industrial Science and Technology (AIST) Central 2, Umezono 1-1-1, Tsukuba-shi, Ibaraki 305-8568 (Japan); Kanagawa Industrial Technology Center (KITC) Shimoimazumi 705-1, Ebina-shi, Kanagawa 243-0435 (Japan); Japan Radioisotope Association (JRIA) Komagome 2-28-45, Bunkyo-ku, Tokyo 113-8941 (Japan); Molecular Imaging Center, National Institute of Radiological Sciences Anagawa 4-9-1, Inage, Chiba 263-8555 (Japan); Graduate School of Medical Sciences, Kitasato University Kitasato 1-15-1, Minami-ku, Sagamihara-shi, Kanagawa 252-0373 (Japan)
2012-07-15
Purpose: The purpose of this study is to propose a microfocus x-ray imaging technique for observing the internal structure of small radioactive sources and evaluating geometrical errors quantitatively, and to apply this technique to traceable pointlike {sup 22}Na sources, which were designed for positron emission tomography calibration, for the purpose of quality control of the pointlike sources. Methods: A microfocus x-ray imaging system with a focus size of 0.001 mm was used to obtain projection x-ray images and x-ray CT images of five pointlike source samples, which were manufactured during 2009-2012. The obtained projection and tomographic images were used to observe the internal structure and evaluate geometrical errors quantitatively. Monte Carlo simulation was used to evaluate the effect of possible geometrical errors on the intensity and uniformity of 0.511 MeV annihilation photon pairs emitted from the sources. Results: Geometrical errors were evaluated with sufficient precision using projection x-ray images. CT images were used for observing the internal structure intuitively. As a result, four of the five examined samples were within the tolerance to maintain the total uncertainty below {+-}0.5%, given the source radioactivity; however, one sample was found to be defective. Conclusions: This quality control procedure is crucial and offers an important basis for using the pointlike {sup 22}Na source as a basic calibration tool. The microfocus x-ray imaging approach is a promising technique for visual and quantitative evaluation of the internal geometry of small radioactive sources.
Vector meson dominance and pointlike coupling of the photon in soft and hard processes
International Nuclear Information System (INIS)
Paul, E.
1990-05-01
Recent experimental results on photoproduction of hadrons probe the nature of the interacting photon over a wide kinematical range from soft to hard processes. Single inclusive spectra and energy flows of the final state charged particles are well described by assuming that photon production data are built up by an incoherent superposition of a soft Vector-Meson-Dominance component and a hard pointlike photon component. (orig.)
The Discovery of the Point-Like Structure of Matter
Energy Technology Data Exchange (ETDEWEB)
Taylor, Richard E
2000-09-28
The organizers of this workshop have invited me here to reminisce. The assigned subject is the proton and how it lost its identity as an elementary particle. In its youth, the proton was very much neglected. It was overweight and introverted, and all the attention went to its lighter and more gregarious companion, the electron. The electron was noticed first and was accepted as a constituent of all matter almost immediately. As a result, the chemical ''elements'' lost their elementary status. With Rutherford's discovery of the nuclear atom it became clear that there was something rather small inside the hydrogen atom with nearly 2000 times the mass of the electron, and equal but opposite charge. That something was called the ''positive electron'' or ''H-particle'' until 1930 or so. The Standard Model in those days had only two elementary particles with mass (whether light quanta might also be a particle was a subject of debate) and the only known forces were electromagnetic and gravitational. In the early days it was assumed that there were some extra positive electrons (each paired with a negative electron) inside nuclei other than hydrogen, to account for the observation that the atomic weight is equal to or greater than twice the atomic number. In 1914, Rutherford's group at Manchester turned its attention to alpha-particle scattering experiments on light nuclei. The group was intrigued by a calculation predicting that forward-scattered H-particles would have a much greater range than the incoming alpha particles. An experiment, the very first on the proton, verified the prediction experimentally and Marsden and Lantsberry concluded that the Coulomb field of the H particle could account for their results (at distances of closest approach that approximated 10{sup -13} cms.) World War I stopped most of the research in Rutherford's laboratory when many of the young scientists left to serve
Quantum field theory with infinite component local fields as an alternative to the string theories
International Nuclear Information System (INIS)
Krasnikov, N.V.
1987-05-01
We show that the introduction of the infinite component local fields with higher order derivatives in the interaction makes the theory completely ultraviolet finite. For the γ 5 -anomalous theories the introduction of the infinite component field makes the theory renormalizable or superrenormalizable. (orig.)
Local gauge invariant Lagrangeans in classical field theories
International Nuclear Information System (INIS)
Grigore, D.R.
1982-07-01
We investigate the most general local gauge invariant Lagrangean in the framework of classical field theory. We rederive esentially Utiyama's result with a slight generalization. Our proof makes clear the importance of the so called current conditions, i.e. the requirement that the Noether currents are different from zero. This condition is of importance both in the general motivation for the introduction of the Yang-Mills fields and for the actual proof. Some comments are made about the basic mathematical structure of the problem - the gauge group. (author)
A course on quantum field theory and local observables
Energy Technology Data Exchange (ETDEWEB)
Schroer, Bert [Frankfurt Univ., Berlin (Germany). Inst. fuer Theoretische Physik
1997-03-01
A monograph on Quantum Field Theory and Local Observables is presented, aiming to unify two presently largely disconnected branches of QFT, as follows: the standard (canonical, functional) approach which is mainly perturbative in the sense of an infinitesimal `deformation` of free fields; nonperturbative constructions of low-dimensional models as the form factor-bootstrap approach (which for the time being is limited to factorable models in d=1+1 spacetime dimensions) and the non-Lagrangian constructions of conformal chiral QFT`s
The local structure of a Liouville vector field
International Nuclear Information System (INIS)
Ciriza, E.
1990-05-01
In this work we investigate the local structure of a Liouville vector field ξ of a Kaehler manifold (P,Ω) which vanishes on an isotropic submanifold Q of P. Some of the eigenvalues of its linear part at the singular points are zero and the remaining ones are in resonance. We show that there is a C 1 -smooth linearizing conjugation between the Liouville vector field ξ and its linear part. To do this we construct Darboux coordinates adapted to the unstable foliation which is provided by the Centre Manifold Theorem. We then apply recent linearization results due to G. Sell. (author). 11 refs
Localization of effective actions in open superstring field theory
Maccaferri, Carlo; Merlano, Alberto
2018-03-01
We consider the construction of the algebraic part of D-branes tree-level effective action from Berkovits open superstring field theory. Applying this construction to the quartic potential of massless fields carrying a specific worldsheet charge, we show that the full contribution to the potential localizes at the boundary of moduli space, reducing to elementary two-point functions. As examples of this general mechanism, we show how the Yang-Mills quartic potential and the instanton effective action of a Dp/D( p - 4) system are reproduced.
International Nuclear Information System (INIS)
Efremova, S.A.; Tsarevskij, S.L.
1997-01-01
Magnetic field distribution in a unit cell of the Abrikosov vortex lattice near the surface of monoaxial anisotropic type-ii superconductors in inclined external magnetic field has been found in the framework of London model for the cases when the symmetry axis is perpendicular and parallel to the superconductor surface interface. Distribution of local magnetic field as a function of the distance from the superconductor interface surface and external field inclination angle has been obtained. Using high-Tc superconductor Y-Ba-Cu-O by way of examples, it has been shown that the study of local magnetic field distribution function, depending on external magnetic field inclination angle towards the superconductor symmetry axis and towards the superconductor surface, can provide important data on anisotropic properties of the superconductor [ru
Predicting local field potentials with recurrent neural networks.
Kim, Louis; Harer, Jacob; Rangamani, Akshay; Moran, James; Parks, Philip D; Widge, Alik; Eskandar, Emad; Dougherty, Darin; Chin, Sang Peter
2016-08-01
We present a Recurrent Neural Network using LSTM (Long Short Term Memory) that is capable of modeling and predicting Local Field Potentials. We train and test the network on real data recorded from epilepsy patients. We construct networks that predict multi-channel LFPs for 1, 10, and 100 milliseconds forward in time. Our results show that prediction using LSTM outperforms regression when predicting 10 and 100 millisecond forward in time.
Bi-local baryon interpolating fields with two flavors
Energy Technology Data Exchange (ETDEWEB)
Dmitrasinovic, V. [Belgrade University, Institute of Physics, Pregrevica 118, Zemun, P.O. Box 57, Beograd (RS); Chen, Hua-Xing [Institutos de Investigacion de Paterna, Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Valencia (Spain); Peking University, Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Beijing (China)
2011-02-15
We construct bi-local interpolating field operators for baryons consisting of three quarks with two flavors, assuming good isospin symmetry. We use the restrictions following from the Pauli principle to derive relations/identities among the baryon operators with identical quantum numbers. Such relations that follow from the combined spatial, Dirac, color, and isospin Fierz transformations may be called the (total/complete) Fierz identities. These relations reduce the number of independent baryon operators with any given spin and isospin. We also study the Abelian and non-Abelian chiral transformation properties of these fields and place them into baryon chiral multiplets. Thus we derive the independent baryon interpolating fields with given values of spin (Lorentz group representation), chiral symmetry (U{sub L}(2) x U{sub R}(2) group representation) and isospin appropriate for the first angular excited states of the nucleon. (orig.)
Globally and locally supersymmetric effective theories for light fields
Brizi, Leonardo; Scrucca, Claudio A
2009-01-01
We reconsider the general question of how to characterize most efficiently the low-energy effective theory obtained by integrating out heavy modes in globally and locally supersymmetric theories. We consider theories with chiral and vector multiplets and identify the conditions under which an approximately supersymmetric low-energy effective theory can exist. These conditions translate into the requirements that all the derivatives, fermions and auxiliary fields should be small in units of the heavy mass scale. They apply not only to the matter sector, but also to the gravitational one if present, and imply in that case that the gravitino mass should be small. We then show how to determine the unique exactly supersymmetric theory that approximates this effective theory at the lowest order in the counting of derivatives, fermions and auxiliary fields, by working both at the superfield level and with component fields. As a result we give a simple prescription for integrating out heavy superfields in an algebrai...
Instabilities in the flow past localized magnetic fields
International Nuclear Information System (INIS)
Beltran, Alberto; Cuevas, Sergio; Smolentsev, Sergey
2007-01-01
The flow in a shallow layer of an electrically conducting fluid past a localized magnetic field is analyzed numerically. The field occupies only a small fraction of the total flow domain and resemblances the magnetic field created by a permanent magnet located close to the fluid layer. Two different physical cases are considered. In the first one, the fluid layer is free from externally injected electric currents, therefore, only induced currents are present. In the second case, an external electric current is injected to the fluid layer, transversally to the main flow direction. It is shown that the Lorentz force created by the interaction of the electric currents with the non-uniform magnetic field acts as an obstacle for the flow and creates different flow patterns similar to those observed in the flow past bluff bodies. A quasi-two-dimensional model that takes into account the existence of the bottom wall through a linear Hartmann-Rayleigh friction term is considered. When inertial and magnetic forces are strong enough, the wake formed behind the zone of high magnetic field is destabilized and a periodic vortex shedding similar to the classical von Karman street is found. The effect of Hartmann-Rayleigh friction in the emergence of the instability is analyzed
Near-Field Source Localization by Using Focusing Technique
He, Hongyang; Wang, Yide; Saillard, Joseph
2008-12-01
We discuss two fast algorithms to localize multiple sources in near field. The symmetry-based method proposed by Zhi and Chia (2007) is first improved by implementing a search-free procedure for the reduction of computation cost. We present then a focusing-based method which does not require symmetric array configuration. By using focusing technique, the near-field signal model is transformed into a model possessing the same structure as in the far-field situation, which allows the bearing estimation with the well-studied far-field methods. With the estimated bearing, the range estimation of each source is consequently obtained by using 1D MUSIC method without parameter pairing. The performance of the improved symmetry-based method and the proposed focusing-based method is compared by Monte Carlo simulations and with Crammer-Rao bound as well. Unlike other near-field algorithms, these two approaches require neither high-computation cost nor high-order statistics.
Near-Field Source Localization by Using Focusing Technique
Directory of Open Access Journals (Sweden)
Joseph Saillard
2008-12-01
Full Text Available We discuss two fast algorithms to localize multiple sources in near field. The symmetry-based method proposed by Zhi and Chia (2007 is first improved by implementing a search-free procedure for the reduction of computation cost. We present then a focusing-based method which does not require symmetric array configuration. By using focusing technique, the near-field signal model is transformed into a model possessing the same structure as in the far-field situation, which allows the bearing estimation with the well-studied far-field methods. With the estimated bearing, the range estimation of each source is consequently obtained by using 1D MUSIC method without parameter pairing. The performance of the improved symmetry-based method and the proposed focusing-based method is compared by Monte Carlo simulations and with Crammer-Rao bound as well. Unlike other near-field algorithms, these two approaches require neither high-computation cost nor high-order statistics
Globally and locally supersymmetric effective theories for light fields
International Nuclear Information System (INIS)
Brizi, Leonardo; Gomez-Reino, Marta; Scrucca, Claudio A.
2009-01-01
We reconsider the general question of how to characterize most efficiently the low-energy effective theory obtained by integrating out heavy modes in globally and locally supersymmetric theories. We consider theories with chiral and vector multiplets and identify the conditions under which an approximately supersymmetric low-energy effective theory can exist. These conditions translate into the requirements that all the derivatives, fermions and auxiliary fields should be small in units of the heavy mass scale. They apply not only to the matter sector, but also to the gravitational one if present, and imply in that case that the gravitino mass should be small. We then show how to determine the unique exactly supersymmetric theory that approximates this effective theory at the lowest order in the counting of derivatives, fermions and auxiliary fields, by working both at the superfield level and with component fields. As a result we give a simple prescription for integrating out heavy superfields in an algebraic and manifestly supersymmetric way, which turns out to hold in the same form both for globally and locally supersymmetric theories, meaning that the process of integrating out heavy modes commutes with the process of switching on gravity. More precisely, for heavy chiral and vector multiplets one has to impose respectively stationarity of the superpotential and the Kaehler potential.
Reality, measurement and locality in Quantum Field Theory
International Nuclear Information System (INIS)
Tommasini, Daniele
2002-01-01
It is currently believed that the local causality of Quantum Field Theory (QFT) is destroyed by the measurement process. This belief is also based on the Einstein-Podolsky-Rosen (EPR) paradox and on the so-called Bell's theorem, that are thought to prove the existence of a mysterious, instantaneous action between distant measurements. However, I have shown recently that the EPR argument is removed, in an interpretation-independent way, by taking into account the fact that the Standard Model of Particle Physics prevents the production of entangled states with a definite number of particles. This result is used here to argue in favor of a statistical interpretation of QFT and to show that it allows for a full reconciliation with locality and causality. Within such an interpretation, as Ballentine and Jarret pointed out long ago, Bell's theorem does not demonstrate any nonlocality. (author)
Zhang, Senfu; Zhang, Junwei; Zhang, Qiang; Barton, Craig; Neu, Volker; Zhao, Yuelei; Hou, Zhipeng; Wen, Yan; Gong, Chen; Kazakova, Olga; Wang, Wenhong; Peng, Yong; Garanin, Dmitry A.; Chudnovsky, Eugene M.; Zhang, Xixiang
2018-01-01
Magnetic skyrmions are topologically protected nanoscale spin textures exhibiting fascinating physical behaviors. Recent observations of room temperature skyrmions in sputtered multilayer films are an important step towards their use in ultra-low power devices. Such practical applications prefer skyrmions to be stable at zero magnetic fields and room temperature. Here, we report the creation of skyrmion lattices in Pt/Co/Ta multilayers by a scanning local field using magnetic force microscopy tips. We also show that those newly created skyrmion lattices are stable at both room temperature and zero fields. Lorentz transmission electron microscopy measurements reveal that the skyrmions in our films are of Néel-type. To gain a deeper understanding of the mechanism behind the creation of a skyrmion lattice by the scanning of local fields, we perform micromagnetic simulations and find the experimental results to be in agreement with our simulation data. This study opens another avenue for the creation of skyrmion lattices in thin films.
Zhang, Senfu; Zhang, Junwei; Zhang, Qiang; Barton, Craig; Neu, Volker; Zhao, Yuelei; Hou, Zhipeng; Wen, Yan; Gong, Chen; Kazakova, Olga; Wang, Wenhong; Peng, Yong; Garanin, Dmitry A.; Chudnovsky, Eugene M.; Zhang, Xixiang
2018-03-01
Magnetic skyrmions are topologically protected nanoscale spin textures exhibiting fascinating physical behaviors. Recent observations of room temperature skyrmions in sputtered multilayer films are an important step towards their use in ultra-low power devices. Such practical applications prefer skyrmions to be stable at zero magnetic fields and room temperature. Here, we report the creation of skyrmion lattices in Pt/Co/Ta multilayers by a scanning local field using magnetic force microscopy tips. We also show that those newly created skyrmion lattices are stable at both room temperature and zero fields. Lorentz transmission electron microscopy measurements reveal that the skyrmions in our films are of Néel-type. To gain a deeper understanding of the mechanism behind the creation of a skyrmion lattice by the scanning of local fields, we perform micromagnetic simulations and find the experimental results to be in agreement with our simulation data. This study opens another avenue for the creation of skyrmion lattices in thin films.
Zhang, Senfu
2018-03-29
Magnetic skyrmions are topologically protected nanoscale spin textures exhibiting fascinating physical behaviors. Recent observations of room temperature skyrmions in sputtered multilayer films are an important step towards their use in ultra-low power devices. Such practical applications prefer skyrmions to be stable at zero magnetic fields and room temperature. Here, we report the creation of skyrmion lattices in Pt/Co/Ta multilayers by a scanning local field using magnetic force microscopy tips. We also show that those newly created skyrmion lattices are stable at both room temperature and zero fields. Lorentz transmission electron microscopy measurements reveal that the skyrmions in our films are of Néel-type. To gain a deeper understanding of the mechanism behind the creation of a skyrmion lattice by the scanning of local fields, we perform micromagnetic simulations and find the experimental results to be in agreement with our simulation data. This study opens another avenue for the creation of skyrmion lattices in thin films.
Vortex configuration in the presence of local magnetic field and locally applied stress
International Nuclear Information System (INIS)
Wissberg, Shai; Kremen, Anna; Shperber, Yishai; Kalisky, Beena
2017-01-01
Highlights: • We discuss different ways to determine vortex configuration using a scanning SQUID. • We determined the vortex configuration by approaching the sample during cooling. • We observed an accumulation of vortices when contact was made with the sample. • We show how we can manipulate local vortex configuration using contact. - Abstract: Vortex configuration is determined by the repulsive interaction, which becomes dominant with increasing vortex density, by the pinning potential, and by other considerations such as the local magnetic fields, currents flowing in the sample, or as we showed recently, by local stress applied on the sample. In this work we describe different ways to control vortex configuration using scanning SQUID microscopy.
Vortex configuration in the presence of local magnetic field and locally applied stress
Energy Technology Data Exchange (ETDEWEB)
Wissberg, Shai; Kremen, Anna; Shperber, Yishai; Kalisky, Beena, E-mail: beena@biu.ac.il
2017-02-15
Highlights: • We discuss different ways to determine vortex configuration using a scanning SQUID. • We determined the vortex configuration by approaching the sample during cooling. • We observed an accumulation of vortices when contact was made with the sample. • We show how we can manipulate local vortex configuration using contact. - Abstract: Vortex configuration is determined by the repulsive interaction, which becomes dominant with increasing vortex density, by the pinning potential, and by other considerations such as the local magnetic fields, currents flowing in the sample, or as we showed recently, by local stress applied on the sample. In this work we describe different ways to control vortex configuration using scanning SQUID microscopy.
Local field effects and metamaterials based on colloidal quantum dots
International Nuclear Information System (INIS)
Porvatkina, O V; Tishchenko, A A; Strikhanov, M N
2015-01-01
Metamaterials are composite structures that exhibit interesting and unusual properties, e.g. negative refractive index. In this article we consider metamaterials based on colloidal quantum dots (CQDs). We investigate these structures taking into account the local field effects and theoretically analyze expressions for permittivity and permeability of metamaterials based on CdSe CQDs. We obtain inequality describing the conditions when material with definite concentration of CQDs is metamaterial. Also we investigate how the values of dielectric polarizability and magnetic polarizability of CQDs depend on the dots radius and properties the material the quantum dots are made of. (paper)
On local field products in special Wightman theories
International Nuclear Information System (INIS)
Baumann, K.
1975-01-01
We shall try to define local field products under assumptions imposed only on the four-point-function. This idea is based on the work of Schlieder and Seiler. In our framework we shall prove that the two-point-function carries the strongest singularity whenever two arguments in a Wightman function coincide. This will be generalized to the case when more arguments coincide. We shall define 'regulated' n-point-functions and study their properties in detail. This will lead us to the definition of arbitrarily high powers of the field-operators as operator-valued distributions over D(R 4 ) in the center coordinate with a dense domain of definition. (orig.) [de
Near-Field Source Localization Using a Special Cumulant Matrix
Cui, Han; Wei, Gang
A new near-field source localization algorithm based on a uniform linear array was proposed. The proposed algorithm estimates each parameter separately but does not need pairing parameters. It can be divided into two important steps. The first step is bearing-related electric angle estimation based on the ESPRIT algorithm by constructing a special cumulant matrix. The second step is the other electric angle estimation based on the 1-D MUSIC spectrum. It offers much lower computational complexity than the traditional near-field 2-D MUSIC algorithm and has better performance than the high-order ESPRIT algorithm. Simulation results demonstrate that the performance of the proposed algorithm is close to the Cramer-Rao Bound (CRB).
MUSIC ALGORITHM FOR LOCATING POINT-LIKE SCATTERERS CONTAINED IN A SAMPLE ON FLAT SUBSTRATE
Institute of Scientific and Technical Information of China (English)
Dong Heping; Ma Fuming; Zhang Deyue
2012-01-01
In this paper,we consider a MUSIC algorithm for locating point-like scatterers contained in a sample on flat substrate.Based on an asymptotic expansion of the scattering amplitude proposed by Ammari et al.,the reconstruction problem can be reduced to a calculation of Green function corresponding to the background medium.In addition,we use an explicit formulation of Green function in the MUSIC algorithm to simplify the calculation when the cross-section of sample is a half-disc.Numerical experiments are included to demonstrate the feasibility of this method.
Energy Technology Data Exchange (ETDEWEB)
Neel, L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Faculte des Sciences de Grenoble, 38 (France)
1959-07-01
Initially, the present report outlines the work done by P. Weiss in the molecular field and spontaneous magnetization theory. It then stresses the success of the theory in the interpretation of the magnetic and energetic properties of ferro-magnetic bodies, and indicates recent progress: 'the energetic molecular field, and the corrective molecular field of the equation of state'. In the second part, the author reviews the difficulties encountered by the theory, and shows how they were overcome by the introduction of the notion of the 'local molecular field', thus supplying the key to the properties of anti-ferro and ferri-magnetic bodies. The present level of progress in the interpretation of the magnetic properties of pyrrhotite, which played a major part in the molecular field discoveries, is also discussed in paragraph 4 and appendices. (author) [French] Dans une premiere partie, l'auteur retrace l'historique des travaux de P. Weiss sur la theorie du champ moleculaire et l'aimantation spontanee; il en souligne les succes dans l'interpretation des proprietes magnetiques et energetiques des corps ferro-magnetiques et les perfectionnements ultimes: champ moleculaire energetique et champ moleculaire correctif de l'equation d'etat. Dans une deuxieme partie, apres avoir examine les difficultes auxquelles se heurtait la theorie, l'auteur montre qu'elles ont ete resolues en introduisant la notion de champ moleculaire local et en donnant ainsi la cle des proprietes des corps antiferro-et ferri-magnetiques. II etudie egalement (paragraphe 4 et Appendice) l'etat actuel de l'interpretation des proprietes magnetiques de la pyrrhotine qui a joue un grand role dans l'histoire du champ moleculaire. (auteur)
Time-localized projectors in string field theory with an E-field
International Nuclear Information System (INIS)
Maccaferri, C.; Scherer Santos, R.J.; Tolla, D.D.
2005-01-01
We extend the analysis of Bonora et al. [hep-th/0409063] to the case of a constant electric field turned on the world volume and on a transverse direction of a D-brane. We show that time localization is still obtained by inverting the discrete eigenvalues of the lump solution. The lifetime of the unstable soliton is shown to depend on two free parameters: the b parameter and the value of the electric field. As a by-product, we construct the normalized diagonal basis of the star algebra in the B μν -field background
Radiobiology at GANIL: local project and others fields studied
International Nuclear Information System (INIS)
Anon.
2001-01-01
This article reviews the research that is led in the field of radiobiology using heavy ions at Ganil. Our first studies with heavy ions were mainly focused on chromosome rearrangements induced in irradiated human cells. We analyzed R-banded chromosome rearrangements in human lymphocytes irradiated with several ions having a wide range of linear energy transfer (LET). Damage increased with the fluence and LET but at the higher LET, damage decreased for fluences above 10 7 particles/cm 2 . Chromosome rearrangements of high complexity involve several breaks. DNA strand breaks are concentrated in localized areas and their complexity is greatly increased by high-LET radiations. Our study was mainly qualitative and we showed a clear shift and dispersion of comet distribution towards high tail moments when particle LET and fluence increased. The higher the LET, the greater the level of DNA breaks observed for the same fluence. Gamma rays were more effective in producing DNA breaks than all the ions, at least in the lower dose range. In addition to early damage, high-LET irradiation also induces delayed lesions, and genomic instability occurs after many generations in the progeny of irradiated cells. We observed delayed chromosome instability on human dermis fibroblasts exposed to heavy ions, neon, argon, and lead but not after gamma rays. Various fields of radiobiology are now explored by different research groups. One of the studies aims to detect locally multiple damage sites (LMDS) formed in DNA after exposure to heavy ions. (A.C.)
On the connection between quantum fields and von Neumann algebras of local operators
International Nuclear Information System (INIS)
Driessler, W.; Summers, S.J.; Wichmann, E.H.
1986-01-01
The relationship between a standard local quantum field and a net of local von Neumann algebras is discussed. Two natural possibilities for such an association are identified, and conditions for these to obtain are found. It is shown that the local net can naturally be so chosen that it satisfies the Special Condition of Duality. The notion of an intrinsically local field operator is introduced, and it is shown that such an operator defines a local net with which the field is locally associated. A regularity condition on the field is formulated, and it is shown that if this condition holds, then there exists a unique local net with which the field is locally associated if and only if the field algebra contains at least one intrinsically local operator. Conditions under which a field and other fields in its Borchers class are associated with the same local net are found, in terms of the regularity condition mentioned. (orig.)
From neurons to circuits: linear estimation of local field potentials
Rasch, Malte; Logthetis, Nikos K.; Kreiman, Gabriel
2010-01-01
Extracellular physiological recordings are typically separated into two frequency bands: local field potentials (LFPs, a circuit property) and spiking multi-unit activity (MUA). There has been increased interest in LFPs due to their correlation with fMRI measurements and the possibility of studying local processing and neuronal synchrony. To further understand the biophysical origin of LFPs, we asked whether it is possible to estimate their time course based on the spiking activity from the same or nearby electrodes. We used Signal Estimation Theory to show that a linear filter operation on the activity of one/few neurons can explain a significant fraction of the LFP time course in the macaque primary visual cortex. The linear filter used to estimate the LFPs had a stereotypical shape characterized by a sharp downstroke at negative time lags and a slower positive upstroke for positve time lags. The filter was similar across neocortical regions and behavioral conditions including spontaneous activity and visual stimulation. The estimations had a spatial resolution of ~1 mm and a temporal resolution of ~200 ms. By considering a causal filter, we observed a temporal asymmetry such that the positive time lags in the filter contributed more to the LFP estimation than negative time lags. Additionally, we showed that spikes occurring within ~10 ms of spikes from nearby neurons yielded better estimation accuracies than nonsynchronous spikes. In sum, our results suggest that at least some circuit-level local properties of the field potentials can be predicted from the activity of one or a few neurons. PMID:19889990
The Local Stellar Velocity Field via Vector Spherical Harmonics
Markarov, V. V.; Murphy, D. W.
2007-01-01
We analyze the local field of stellar tangential velocities for a sample of 42,339 nonbinary Hipparcos stars with accurate parallaxes, using a vector spherical harmonic formalism. We derive simple relations between the parameters of the classical linear model (Ogorodnikov-Milne) of the local systemic field and low-degree terms of the general vector harmonic decomposition. Taking advantage of these relationships, we determine the solar velocity with respect to the local stars of (V(sub X), V(sub Y), V(sub Z)) (10.5, 18.5, 7.3) +/- 0.1 km s(exp -1) not corrected for the asymmetric drift with respect to the local standard of rest. If only stars more distant than 100 pc are considered, the peculiar solar motion is (V(sub X), V(sub Y), V(sub Z)) (9.9, 15.6, 6.9) +/- 0.2 km s(exp -1). The adverse effects of harmonic leakage, which occurs between the reflex solar motion represented by the three electric vector harmonics in the velocity space and higher degree harmonics in the proper-motion space, are eliminated in our analysis by direct subtraction of the reflex solar velocity in its tangential components for each star. The Oort parameters determined by a straightforward least-squares adjustment in vector spherical harmonics are A=14.0 +/- 1.4, B=13.1 +/- 1.2, K=1.1 +/- 1.8, and C=2.9 +/- 1.4 km s(exp -1) kpc(exp -1). The physical meaning and the implications of these parameters are discussed in the framework of a general linear model of the velocity field. We find a few statistically significant higher degree harmonic terms that do not correspond to any parameters in the classical linear model. One of them, a third-degree electric harmonic, is tentatively explained as the response to a negative linear gradient of rotation velocity with distance from the Galactic plane, which we estimate at approximately -20 km s(exp -1) kpc(exp -1). A similar vertical gradient of rotation velocity has been detected for more distant stars representing the thick disk (z greater than 1 kpc
Properties of field functionals and characterization of local functionals
Brouder, Christian; Dang, Nguyen Viet; Laurent-Gengoux, Camille; Rejzner, Kasia
2018-02-01
Functionals (i.e., functions of functions) are widely used in quantum field theory and solid-state physics. In this paper, functionals are given a rigorous mathematical framework and their main properties are described. The choice of the proper space of test functions (smooth functions) and of the relevant concept of differential (Bastiani differential) are discussed. The relation between the multiple derivatives of a functional and the corresponding distributions is described in detail. It is proved that, in a neighborhood of every test function, the support of a smooth functional is uniformly compactly supported and the order of the corresponding distribution is uniformly bounded. Relying on a recent work by Dabrowski, several spaces of functionals are furnished with a complete and nuclear topology. In view of physical applications, it is shown that most formal manipulations can be given a rigorous meaning. A new concept of local functionals is proposed and two characterizations of them are given: the first one uses the additivity (or Hammerstein) property, the second one is a variant of Peetre's theorem. Finally, the first step of a cohomological approach to quantum field theory is carried out by proving a global Poincaré lemma and defining multi-vector fields and graded functionals within our framework.
Probing N=2 superconformal field theories with localization
Energy Technology Data Exchange (ETDEWEB)
Fiol, Bartomeu [Departament de Física Fonamental i Institut de Ciències del Cosmos,Universitat de Barcelona,Martí i Franquès 1, 08028 Barcelona, Catalonia (Spain); Garolera, Blai [Escuela de Física, Universidad de Costa Rica,11501-2060 San José (Costa Rica); Torrents, Genís [Departament de Física Fonamental i Institut de Ciències del Cosmos,Universitat de Barcelona,Martí i Franquès 1, 08028 Barcelona, Catalonia (Spain)
2016-01-27
We use supersymmetric localization to study probes of four dimensional Lagrangian N=2 superconformal field theories. We first derive a unique equation for the eigenvalue density of these theories. We observe that these theories have a Wigner eigenvalue density precisely when they satisfy a necessary condition for having a holographic dual with a sensible higher-derivative expansion. We then compute in the saddle-point approximation the vacuum expectation value of 1/2-BPS circular Wilson loops, and the two-point functions of these Wilson loops with the Lagrangian density and with the stress-energy tensor. This last computation also provides the corresponding Bremsstrahlung functions and entanglement entropies. As expected, whenever a finite fraction of the matter is in the fundamental representation, the results are drastically different from those of N=4 supersymmetric Yang-Mills theory.
The local field potential reflects surplus spike synchrony
DEFF Research Database (Denmark)
Denker, Michael; Roux, Sébastien; Lindén, Henrik
2011-01-01
While oscillations of the local field potential (LFP) are commonly attributed to the synchronization of neuronal firing rate on the same time scale, their relationship to coincident spiking in the millisecond range is unknown. Here, we present experimental evidence to reconcile the notions...... of synchrony at the level of spiking and at the mesoscopic scale. We demonstrate that only in time intervals of significant spike synchrony that cannot be explained on the basis of firing rates, coincident spikes are better phase locked to the LFP than predicted by the locking of the individual spikes....... This effect is enhanced in periods of large LFP amplitudes. A quantitative model explains the LFP dynamics by the orchestrated spiking activity in neuronal groups that contribute the observed surplus synchrony. From the correlation analysis, we infer that neurons participate in different constellations...
Reconstructing the gravitational field of the local Universe
Desmond, Harry; Ferreira, Pedro G.; Lavaux, Guilhem; Jasche, Jens
2018-03-01
Tests of gravity at the galaxy scale are in their infancy. As a first step to systematically uncovering the gravitational significance of galaxies, we map three fundamental gravitational variables - the Newtonian potential, acceleration and curvature - over the galaxy environments of the local Universe to a distance of approximately 200 Mpc. Our method combines the contributions from galaxies in an all-sky redshift survey, haloes from an N-body simulation hosting low-luminosity objects, and linear and quasi-linear modes of the density field. We use the ranges of these variables to determine the extent to which galaxies expand the scope of generic tests of gravity and are capable of constraining specific classes of model for which they have special significance. Finally, we investigate the improvements afforded by upcoming galaxy surveys.
Local Field Response Method Phenomenologically Introducing Spin Correlations
Tomaru, Tatsuya
2018-03-01
The local field response (LFR) method is a way of searching for the ground state in a similar manner to quantum annealing. However, the LFR method operates on a classical machine, and quantum effects are introduced through a priori information and through phenomenological means reflecting the states during the computations. The LFR method has been treated with a one-body approximation, and therefore, the effect of entanglement has not been sufficiently taken into account. In this report, spin correlations are phenomenologically introduced as one of the effects of entanglement, by which multiple tunneling at anticrossing points is taken into account. As a result, the accuracy of solutions for a 128-bit system increases by 31% compared with that without spin correlations.
Decoupling Action Potential Bias from Cortical Local Field Potentials
Directory of Open Access Journals (Sweden)
Stephen V. David
2010-01-01
Full Text Available Neurophysiologists have recently become interested in studying neuronal population activity through local field potential (LFP recordings during experiments that also record the activity of single neurons. This experimental approach differs from early LFP studies because it uses high impendence electrodes that can also isolate single neuron activity. A possible complication for such studies is that the synaptic potentials and action potentials of the small subset of isolated neurons may contribute disproportionately to the LFP signal, biasing activity in the larger nearby neuronal population to appear synchronous and cotuned with these neurons. To address this problem, we used linear filtering techniques to remove features correlated with spike events from LFP recordings. This filtering procedure can be applied for well-isolated single units or multiunit activity. We illustrate the effects of this correction in simulation and on spike data recorded from primary auditory cortex. We find that local spiking activity can explain a significant portion of LFP power at most recording sites and demonstrate that removing the spike-correlated component can affect measurements of auditory tuning of the LFP.
Quantum field theory with infinite component local fields as an alternative to the string theories
Krasnikov, N. V.
1987-09-01
We show that the introduction of the infinite component local fields with higher-order derivatives in the interaction makes the theory completely ultraviolet finite. For the γ5-anomalous theories the introduction of the infinite component field makes the theory renormalizable or even superrenormalizable. I am indebted to J. Ambjōrn, P. Di Vecchia, H.B. Nielsen and L. Rozhansky for useful discussions. It is a pleasure to thank the Niels Bohr Institute (Copenhagen) where this work was completed for kind hospitality.
Non-local correlations within dynamical mean field theory
Energy Technology Data Exchange (ETDEWEB)
Li, Gang
2009-03-15
The contributions from the non-local fluctuations to the dynamical mean field theory (DMFT) were studied using the recently proposed dual fermion approach. Straight forward cluster extensions of DMFT need the solution of a small cluster, where all the short-range correlations are fully taken into account. All the correlations beyond the cluster scope are treated in the mean-field level. In the dual fermion method, only a single impurity problem needs to be solved. Both the short and long-range correlations could be considered on equal footing in this method. The weak-coupling nature of the dual fermion ensures the validity of the finite order diagram expansion. The one and two particle Green's functions calculated from the dual fermion approach agree well with the Quantum Monte Carlo solutions, and the computation time is considerably less than with the latter method. The access of the long-range order allows us to investigate the collective behavior of the electron system, e.g. spin wave excitations. (orig.)
Quantum dynamical simulations of local field enhancement in metal nanoparticles.
Negre, Christian F A; Perassi, Eduardo M; Coronado, Eduardo A; Sánchez, Cristián G
2013-03-27
Field enhancements (Γ) around small Ag nanoparticles (NPs) are calculated using a quantum dynamical simulation formalism and the results are compared with electrodynamic simulations using the discrete dipole approximation (DDA) in order to address the important issue of the intrinsic atomistic structure of NPs. Quite remarkably, in both quantum and classical approaches the highest values of Γ are located in the same regions around single NPs. However, by introducing a complete atomistic description of the metallic NPs in optical simulations, a different pattern of the Γ distribution is obtained. Knowing the correct pattern of the Γ distribution around NPs is crucial for understanding the spectroscopic features of molecules inside hot spots. The enhancement produced by surface plasmon coupling is studied by using both approaches in NP dimers for different inter-particle distances. The results show that the trend of the variation of Γ versus inter-particle distance is different for classical and quantum simulations. This difference is explained in terms of a charge transfer mechanism that cannot be obtained with classical electrodynamics. Finally, time dependent distribution of the enhancement factor is simulated by introducing a time dependent field perturbation into the Hamiltonian, allowing an assessment of the localized surface plasmon resonance quantum dynamics.
Batalin-Vilkovisky formalism in locally covariant field theory
International Nuclear Information System (INIS)
Rejzner, Katarzyna Anna
2011-12-01
The present work contains a complete formulation of the Batalin-Vilkovisky (BV) formalism in the framework of locally covariant field theory. In the first part of the thesis the classical theory is investigated with a particular focus on the infinite dimensional character of the underlying structures. It is shown that the use of infinite dimensional differential geometry allows for a conceptually clear and elegant formulation. The construction of the BV complex is performed in a fully covariant way and we also generalize the BV framework to a more abstract level, using functors and natural transformations. In this setting we construct the BV complex for classical gravity. This allows us to give a homological interpretation to the notion of diffeomorphism invariant physical quantities in general relativity. The second part of the thesis concerns the quantum theory. We provide a framework for the BV quantization that doesn't rely on the path integral formalism, but is completely formulated within perturbative algebraic quantum field theory. To make such a formulation possible we first prove that the renormalized time-ordered product can be understood as a binary operation on a suitable domain. Using this result we prove the associativity of this product and provide a consistent framework for the renormalized BV structures. In particular the renormalized quantum master equation and the renormalized quantum BV operator are defined. To give a precise meaning to theses objects we make a use of the master Ward identity, which is an important structure in causal perturbation theory. (orig.)
Local field in LiD polarized target material
Kisselev, Yu V; Baum, G; Berglund, P; Doshita, N; Gautheron, F; Görtz, S; Horikawa, N; Koivuniemi, J H; Kondo, K; Magnon, A; Meyer, Werner T; Reicherz, G
2004-01-01
We have experimentally studied the first and the second moments of D, **6Li and **7Li (I greater than 1/2) NMR lines in a granulated LiD- target material as a function of nuclear polarizations and the data has been compared with a theory elaborated by Abragam, Roinel and Bouffard for monocrystalline samples. The experiments were carried out in the large COMPASS twin-target at CERN. The static local magnetic field of the polarized nuclei was measured by frequency shift between the NMR-signals in the two oppositely polarized cells and lead to the first moment, whereas the investigation of the second moment was done through Gaussian approximation. The average field magnitude in granulated material was estimated 20% larger than the value given by the calculations for monocrystalline samples of cylindrical shape. The second moment shows a qualitative agreement with the theory but it is slightly larger at the negative than at the positive polarization. In a polarized mode, the moments depend on the saturated microw...
Batalin-Vilkovisky formalism in locally covariant field theory
Energy Technology Data Exchange (ETDEWEB)
Rejzner, Katarzyna Anna
2011-12-15
The present work contains a complete formulation of the Batalin-Vilkovisky (BV) formalism in the framework of locally covariant field theory. In the first part of the thesis the classical theory is investigated with a particular focus on the infinite dimensional character of the underlying structures. It is shown that the use of infinite dimensional differential geometry allows for a conceptually clear and elegant formulation. The construction of the BV complex is performed in a fully covariant way and we also generalize the BV framework to a more abstract level, using functors and natural transformations. In this setting we construct the BV complex for classical gravity. This allows us to give a homological interpretation to the notion of diffeomorphism invariant physical quantities in general relativity. The second part of the thesis concerns the quantum theory. We provide a framework for the BV quantization that doesn't rely on the path integral formalism, but is completely formulated within perturbative algebraic quantum field theory. To make such a formulation possible we first prove that the renormalized time-ordered product can be understood as a binary operation on a suitable domain. Using this result we prove the associativity of this product and provide a consistent framework for the renormalized BV structures. In particular the renormalized quantum master equation and the renormalized quantum BV operator are defined. To give a precise meaning to theses objects we make a use of the master Ward identity, which is an important structure in causal perturbation theory. (orig.)
Non-local correlations within dynamical mean field theory
International Nuclear Information System (INIS)
Li, Gang
2009-03-01
The contributions from the non-local fluctuations to the dynamical mean field theory (DMFT) were studied using the recently proposed dual fermion approach. Straight forward cluster extensions of DMFT need the solution of a small cluster, where all the short-range correlations are fully taken into account. All the correlations beyond the cluster scope are treated in the mean-field level. In the dual fermion method, only a single impurity problem needs to be solved. Both the short and long-range correlations could be considered on equal footing in this method. The weak-coupling nature of the dual fermion ensures the validity of the finite order diagram expansion. The one and two particle Green's functions calculated from the dual fermion approach agree well with the Quantum Monte Carlo solutions, and the computation time is considerably less than with the latter method. The access of the long-range order allows us to investigate the collective behavior of the electron system, e.g. spin wave excitations. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Dappiaggi, Claudio [Erwin Schroedinger Institut fuer Mathematische Physik, Wien (Austria); Pinamonti, Nicola [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Porrmann, Martin [KwaZulu-Natal Univ. (South Africa). Quantum Research Group, School of Physics; National Institute for Theoretical Physics, Durban (South Africa)
2010-01-15
In the framework of the algebraic formulation, we discuss and analyse some new features of the local structure of a real scalar quantum field theory in a strongly causal spacetime. In particular we use the properties of the exponential map to set up a local version of a bulk-to-boundary correspondence. The bulk is a suitable subset of a geodesic neighbourhood of any but fixed point p of the underlying background, while the boundary is a part of the future light cone having p as its own tip. In this regime, we provide a novel notion for the extended *-algebra of Wick polynomials on the said cone and, on the one hand, we prove that it contains the information of the bulk counterpart via an injective *-homomorphism while, on the other hand, we associate to it a distinguished state whose pull-back in the bulk is of Hadamard form. The main advantage of this point of view arises if one uses the universal properties of the exponential map and of the light cone in order to show that, for any two given backgrounds M and M{sup '} and for any two subsets of geodesic neighbourhoods of two arbitrary points, it is possible to engineer the above procedure such that the boundary extended algebras are related via a restriction homomorphism. This allows for the pull-back of boundary states in both spacetimes and, thus, to set up a machinery which permits the comparison of expectation values of local field observables in M and M{sup '}. (orig.)
International Nuclear Information System (INIS)
Dappiaggi, Claudio; Pinamonti, Nicola
2010-01-01
In the framework of the algebraic formulation, we discuss and analyse some new features of the local structure of a real scalar quantum field theory in a strongly causal spacetime. In particular we use the properties of the exponential map to set up a local version of a bulk-to-boundary correspondence. The bulk is a suitable subset of a geodesic neighbourhood of any but fixed point p of the underlying background, while the boundary is a part of the future light cone having p as its own tip. In this regime, we provide a novel notion for the extended *-algebra of Wick polynomials on the said cone and, on the one hand, we prove that it contains the information of the bulk counterpart via an injective *-homomorphism while, on the other hand, we associate to it a distinguished state whose pull-back in the bulk is of Hadamard form. The main advantage of this point of view arises if one uses the universal properties of the exponential map and of the light cone in order to show that, for any two given backgrounds M and M ' and for any two subsets of geodesic neighbourhoods of two arbitrary points, it is possible to engineer the above procedure such that the boundary extended algebras are related via a restriction homomorphism. This allows for the pull-back of boundary states in both spacetimes and, thus, to set up a machinery which permits the comparison of expectation values of local field observables in M and M ' . (orig.)
International Nuclear Information System (INIS)
Baseilhac, P.; Fateev, V.A.
1998-01-01
We calculate the vacuum expectation values of local fields for the two-parameter family of integrable field theories introduced and studied by Fateev (1996). Using this result we propose an explicit expression for the vacuum expectation values of local operators in parafermionic sine-Gordon models and in integrable perturbed SU(2) coset conformal field theories. (orig.)
Enhanced Soundings for Local Coupling Studies Field Campaign Report
Energy Technology Data Exchange (ETDEWEB)
Ferguson, Craig R [University at Albany, State University of New York; Santanello, Joseph A [NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Gentine, Pierre [Columbia Univ., New York, NY (United States)
2016-04-01
This document presents initial analyses of the enhanced radiosonde observations obtained during the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility Enhanced Soundings for Local Coupling Studies Field Campaign (ESLCS), which took place at the ARM Southern Great Plains (SGP) Central Facility (CF) from June 15 to August 31, 2015. During ESLCS, routine 4-times-daily radiosonde measurements at the ARM-SGP CF were augmented on 12 days (June 18 and 29; July 11, 14, 19, and 26; August 15, 16, 21, 25, 26, and 27) with daytime 1-hourly radiosondes and 10-minute ‘trailer’ radiosondes every 3 hours. These 12 intensive operational period (IOP) days were selected on the basis of prior-day qualitative forecasts of potential land-atmosphere coupling strength. The campaign captured 2 dry soil convection advantage days (June 29 and July 14) and 10 atmospherically controlled days. Other noteworthy IOP events include: 2 soil dry-down sequences (July 11-14-19 and August 21-25-26), a 2-day clear-sky case (August 15-16), and the passing of Tropical Storm Bill (June 18). To date, the ESLCS data set constitutes the highest-temporal-resolution sampling of the evolution of the daytime planetary boundary layer (PBL) using radiosondes at the ARM-SGP. The data set is expected to contribute to: 1) improved understanding and modeling of the diurnal evolution of the PBL, particularly with regard to the role of local soil wetness, and (2) new insights into the appropriateness of current ARM-SGP CF thermodynamic sampling strategies.
Geomagnetic Field Variation during Winter Storm at Localized ...
Indian Academy of Sciences (India)
that transports plasma and magnetic flux which create the geomagnetic field variation. Key words. Dst—vertical component of interplanetary magnetic field and geomagnetic field components. 1. Introduction. The magnetic field is one of the important properties of the earth. The main magnetic field originates from ...
Field investigation of mining-induced seismicity on local geohydrology
International Nuclear Information System (INIS)
Hsiung, S.M.; Chowdhury, A.H.; Philip, J.; Blake, W.
1993-01-01
Hydraulic response of the rock mass due to earthquakes is one of the concerns in the assessment of the long-term performance of a repository. Studies performed by other researchers indicated no systematic difference between natural earthquakes and mining-induced seismic events. The purpose of this field study at the Lucky Friday Mine is intended to obtain a better understanding regarding the local geohydrologic changes due to mining-induced seismicity and to evaluate analytical methods for simulation of these changes. Three saturated zones with faults and vein features were packed-off along a borehole drilled at approximately 20 degrees downward in a southerly direction from a depth about 1,737 m (5,700 ft) below surface for water pressure monitoring. The response of water pressure change to mine seismicity is found to be more pronounced in Zone 3, which contains the Lucky Friday Main Vein, than Zone 2, with the South Control Fault, and Zone 1, with the associated fractures parallel to the South Control Fault. The maximum observed pressure increase in Zone 3 was about 1.53 x 10 -2 MPa (2.22 psi) due to a seismic event of Richter drops in Zone 1 resulting from a number of seismic events are suspected to be related to slips along the associated fractures of the South Control Fault, or the South Control Fault itself, which initiated the seismic events. Water pressure increase in Zone 3 was found to be a function of event magnitude and distance
Nambu-Goto string with the Gauss-Bonnet term and point-like masses at the ends
Hadasz, Leszek; Róg, Tomasz
1996-02-01
We investigate classical dynamics of the Nambu-Goto string with Gauss-Bonnet term in the action and point-like masses at the ends in the context of effective QCD string. The configuration of rigidly rotating string is studied and its application to phenomenological description of meson spectroscopy is discussed.
Directory of Open Access Journals (Sweden)
Taisuke Murata
2016-10-01
Full Text Available Abstract Background The point spread function (PSF of positron emission tomography (PET depends on the position across the field of view (FOV. Reconstruction based on PSF improves spatial resolution and quantitative accuracy. The present study aimed to quantify the effects of PSF correction as a function of the position of a traceable point-like 22Na source over the FOV on two PET scanners with a different detector design. Methods We used Discovery 600 and Discovery 710 (GE Healthcare PET scanners and traceable point-like 22Na sources (<1 MBq with a spherical absorber design that assures uniform angular distribution of the emitted annihilation photons. The source was moved in three directions at intervals of 1 cm from the center towards the peripheral FOV using a three-dimensional (3D-positioning robot, and data were acquired over a period of 2 min per point. The PET data were reconstructed by filtered back projection (FBP, the ordered subset expectation maximization (OSEM, OSEM + PSF, and OSEM + PSF + time-of-flight (TOF. Full width at half maximum (FWHM was determined according to the NEMA method, and total counts in regions of interest (ROI for each reconstruction were quantified. Results The radial FWHM of FBP and OSEM increased towards the peripheral FOV, whereas PSF-based reconstruction recovered the FWHM at all points in the FOV of both scanners. The radial FWHM for PSF was 30–50 % lower than that of OSEM at the center of the FOV. The accuracy of PSF correction was independent of detector design. Quantitative values were stable across the FOV in all reconstruction methods. The effect of TOF on spatial resolution and quantitation accuracy was less noticeable. Conclusions The traceable 22Na point-like source allowed the evaluation of spatial resolution and quantitative accuracy across the FOV using different reconstruction methods and scanners. PSF-based reconstruction reduces dependence of the spatial resolution on the
Hasegawa, Tomoyuki; Oda, Keiichi; Wada, Yasuhiro; Sasaki, Toshiaki; Sato, Yasushi; Yamada, Takahiro; Matsumoto, Mikio; Murayama, Hideo; Kikuchi, Kei; Miyatake, Hiroki; Abe, Yutaka; Miwa, Kenta; Akimoto, Kenta; Wagatsuma, Kei
2013-05-01
To improve the reliability and convenience of the calibration procedure of positron emission tomography (PET) scanners, we have been developing a novel calibration path based on traceable point-like sources. When using (22)Na sources, special care should be taken to avoid the effects of 1.275-MeV γ rays accompanying β (+) decays. The purpose of this study is to validate this new calibration scheme with traceable point-like (22)Na sources on various types of PET scanners. Traceable point-like (22)Na sources with a spherical absorber design that assures uniform angular distribution of the emitted annihilation photons were used. The tested PET scanners included a clinical whole-body PET scanner, four types of clinical PET/CT scanners from different manufacturers, and a small-animal PET scanner. The region of interest (ROI) diameter dependence of ROI values was represented with a fitting function, which was assumed to consist of a recovery part due to spatial resolution and a quadratic background part originating from the scattered γ rays. The observed ROI radius dependence was well represented with the assumed fitting function (R (2) > 0.994). The calibration factors determined using the point-like sources were consistent with those by the standard cross-calibration method within an uncertainty of ±4 %, which was reasonable considering the uncertainty in the standard cross-calibration method. This novel calibration scheme based on the use of traceable (22)Na point-like sources was successfully validated for six types of commercial PET scanners.
Localization of bulk form fields on dilatonic domain walls
International Nuclear Information System (INIS)
Youm, Donam
2001-06-01
We study the localization properties of bulk form potentials on dilatonic domain walls. We find that bulk form potentials of any ranks can be localized as form potentials of the same ranks or one lower ranks, for any values of the dilaton coupling parameter. For large enough values of the dilaton coupling parameter, bulk form potentials of any ranks can be localized as form potentials of both the same ranks and one lower ranks. (author)
On local frame fields and fermion dynamics in space with nontrivial topologies
International Nuclear Information System (INIS)
Fomin, P.I.; Zemlyakov, A.T.
1991-01-01
The covariant operators of total angular momentum of fermion in spaces which possess Killing vector fields are defined. The classification of local frame fields in a closed world with S 3 topology is carried out. The vortex-type solution to Dirac equation in Minkowskii space is obtained by means of cylindrical local frame field. 7 refs. (author)
International Nuclear Information System (INIS)
Souza, Manoelito M. de
1997-01-01
We discuss the physical meaning and the geometric interpretation of implementation in classical field theories. The origin of infinities and other inconsistencies in field theories is traced to fields defined with support on the light cone; a finite and consistent field theory requires a light-cone generator as the field support. Then, we introduce a classical field theory with support on the light cone generators. It results on a description of discrete (point-like) interactions in terms of localized particle-like fields. We find the propagators of these particle-like fields and discuss their physical meaning, properties and consequences. They are conformally invariant, singularity-free, and describing a manifestly covariant (1 + 1)-dimensional dynamics in a (3 = 1) spacetime. Remarkably this conformal symmetry remains even for the propagation of a massive field in four spacetime dimensions. We apply this formalism to Classical electrodynamics and to the General Relativity Theory. The standard formalism with its distributed fields is retrieved in terms of spacetime average of the discrete field. Singularities are the by-products of the averaging process. This new formalism enlighten the meaning and the problem of field theory, and may allow a softer transition to a quantum theory. (author)
Energy Technology Data Exchange (ETDEWEB)
Morales Villasevil, A
1965-07-01
A method is introduced ta deal with relativistic quantum field theory for particles with m=0. Two mappings I and J, giving rise respectively to particle and anti particle states, are defined between a test space and the physical Hilbert space. The intrinsic field operator is then defined as the minimal causal linear combinations of operators belonging to the annihilation-creation algebra associated to the germ and antigerm parts of the element. Local elements are introduced as improper test elements and local field operators are constructed in the same way as the intrinsic ones. Commutation rules are given. (Author) 17 refs.
Mixed Far-Field and Near-Field Source Localization Algorithm via Sparse Subarrays
Directory of Open Access Journals (Sweden)
Jiaqi Song
2018-01-01
Full Text Available Based on a dual-size shift invariance sparse linear array, this paper presents a novel algorithm for the localization of mixed far-field and near-field sources. First, by constructing a cumulant matrix with only direction-of-arrival (DOA information, the proposed algorithm decouples the DOA estimation from the range estimation. The cumulant-domain quarter-wavelength invariance yields unambiguous estimates of DOAs, which are then used as coarse references to disambiguate the phase ambiguities in fine estimates induced from the larger spatial invariance. Then, based on the estimated DOAs, another cumulant matrix is derived and decoupled to generate unambiguous and cyclically ambiguous estimates of range parameter. According to the coarse range estimation, the types of sources can be identified and the unambiguous fine range estimates of NF sources are obtained after disambiguation. Compared with some existing algorithms, the proposed algorithm enjoys extended array aperture and higher estimation accuracy. Simulation results are given to validate the performance of the proposed algorithm.
Graphene as a local probe to investigate near-field properties of plasmonic nanostructures
Wasserroth, Sören; Bisswanger, Timo; Mueller, Niclas S.; Kusch, Patryk; Heeg, Sebastian; Clark, Nick; Schedin, Fredrik; Gorbachev, Roman; Reich, Stephanie
2018-04-01
Light interacting with metallic nanoparticles creates a strongly localized near-field around the particle that enhances inelastic light scattering by several orders of magnitude. Surface-enhanced Raman scattering describes the enhancement of the Raman intensity by plasmonic nanoparticles. We present an extensive Raman characterization of a plasmonic gold nanodimer covered with graphene. Its two-dimensional nature and energy-independent optical properties make graphene an excellent material for investigating local electromagnetic near-fields. We show the localization of the near-field of the plasmonic dimer by spatial Raman measurements. Energy- and polarization-dependent measurements reveal the local near-field resonance of the plasmonic system. To investigate the far-field resonance we perform dark-field spectroscopy and find that near-field and far-field resonance energies differ by 170 meV, much more than expected from the model of a damped oscillator (40 meV).
Localization from near-source quasi-static electromagnetic fields
Energy Technology Data Exchange (ETDEWEB)
Mosher, John Compton [Univ. of Southern California, Los Angeles, CA (United States)
1993-09-01
A wide range of research has been published on the problem of estimating the parameters of electromagnetic and acoustical sources from measurements of signals measured at an array of sensors. In the quasi-static electromagnetic cases examined here, the signal variation from a point source is relatively slow with respect to the signal propagation and the spacing of the array of sensors. As such, the location of the point sources can only be determined from the spatial diversity of the received signal across the array. The inverse source localization problem is complicated by unknown model order and strong local minima. The nonlinear optimization problem is posed for solving for the parameters of the quasi-static source model. The transient nature of the sources can be exploited to allow subspace approaches to separate out the signal portion of the spatial correlation matrix. Decomposition techniques are examined for improved processing, and an adaptation of MUtiple SIgnal Characterization (MUSIC) is presented for solving the source localization problem. Recent results on calculating the Cramer-Rao error lower bounds are extended to the multidimensional problem here. This thesis focuses on the problem of source localization in magnetoencephalography (MEG), with a secondary application to thunderstorm source localization. Comparisons are also made between MEG and its electrical equivalent, electroencephalography (EEG). The error lower bounds are examined in detail for several MEG and EEG configurations, as well as localizing thunderstorm cells over Cape Canaveral and Kennedy Space Center. Time-eigenspectrum is introduced as a parsing technique for improving the performance of the optimization problem.
Entanglement generation through local field and quantum dissipation
International Nuclear Information System (INIS)
Stockburger, Jürgen T; Schmidt, Rebecca; Ankerhold, Joachim
2015-01-01
Entanglement in a Gaussian two-mode system can be generated by local driving if additional non-local features are introduced to the dynamics. We demonstrate that weak to moderate ohmic friction arising from a dissipative environment can enable entanglement generation in a driven system. This synergy of driving and dissipation is highly sensitive to the pulse shape; several simple pulse shapes fail to produce this effect at all or deposit large amounts of energy in the system as a side effect. Complex pulse shapes, determined by optimal control techniques, however, are effective without detrimental side effects. (paper)
Scalar field localization on a brane with cosmological constant
International Nuclear Information System (INIS)
Ghoroku, Kazuo; Yahiro, Masanobu
2003-01-01
We investigate the localization of a massive scalar for both dS and AdS branes, where the scalar mass is varied from the massive-particle region to the tachyon region. We find that the eigenmass m of the localized mode satisfies a simple relation m 2 = cM 2 with a positive constant c for the dS brane, and m 2 = c 1 M 2 + c 2 with positive constants c 1 and c 2 for the AdS brane. We discuss the relation of these results to the stability of the brane and also some cosmological problems
Burov, V. A.; Morozov, S. A.
2001-11-01
Wave scattering by a point-like inhomogeneity, i.e., a strong inhomogeneity with infinitesimal dimensions, is described. This type of inhomogeneity model is used in investigating the point-spread functions of different algorithms and systems. Two approaches are used to derive the rigorous relationship between the amplitude and phase of a signal scattered by a point-like acoustic inhomogeneity. The first approach is based on a Marchenko-type equation. The second approach uses the scattering by a scatterer whose size decreases simultaneously with an increase in its contrast. It is shown that the retarded and advanced waves are scattered differently despite the relationship between the phases of the corresponding scattered waves.
Local central limit theorem for a Gibbs random field
Energy Technology Data Exchange (ETDEWEB)
Campanino, M; Capocaccia, D; Tirozzi, B [L' Aquila Univ. (Italy). Istituto di Matematica; Rome Univ. (Italy). Istituto di Matematica)
1979-12-01
The validity of the implication of a local limit theorem is extended from an integral one. The extension eliminates the finite range assumption present in the previous works by using the cluster expansion to analyze the contribution from the tail of the potential.
International Nuclear Information System (INIS)
Davari, Nazanin; Haghdani, Shokouh; Åstrand, Per-Olof
2015-01-01
A force field model for calculating local field factors, i.e. the linear response of the local electric field for example at a nucleus in a molecule with respect to an applied electric field, is discussed. It is based on a combined charge-transfer and point-dipole interaction model for the polarizability, and thereby it includes two physically distinct terms for describing electronic polarization: changes in atomic charges arising from transfer of charge between the atoms and atomic induced dipole moments. A time dependence is included both for the atomic charges and the atomic dipole moments and if they are assumed to oscillate with the same frequency as the applied electric field, a model for frequency-dependent properties are obtained. Furthermore, if a life-time of excited states are included, a model for the complex frequency-dependent polariability is obtained including also information about excited states and the absorption spectrum. We thus present a model for the frequency-dependent local field factors through the first molecular excitation energy. It is combined with molecular dynamics simulations of liquids where a large set of configurations are sampled and for which local field factors are calculated. We are normally not interested in the average of the local field factor but rather in configurations where it is as high as possible. In electrical insulation, we would like to avoid high local field factors to reduce the risk for electrical breakdown, whereas for example in surface-enhanced Raman spectroscopy, high local field factors are desired to give dramatically increased intensities
Local fields for asymptotic matching in multidimensional mode conversion
International Nuclear Information System (INIS)
Tracy, E. R.; Kaufman, A. N.; Jaun, A.
2007-01-01
The problem of resonant mode conversion in multiple spatial dimensions is considered. Using phase space methods, a complete theory is developed for constructing matched asymptotic expansions that fit incoming and outgoing WKB solutions. These results provide, for the first time, a complete and practical method for including multidimensional conversion in ray tracing algorithms. The paper provides a self-contained description of the following topics: (1) how to use eikonal (also known as ray tracing or WKB) methods to solve vector wave equations and how to detect conversion regions while following rays; (2) once conversion is detected, how to fit to a generic saddle structure in ray phase space associated with the most common type of conversion; (3) given the saddle structure, how to carry out a local projection of the full vector wave equation onto a local two-component normal form that governs the two resonantly interacting waves. This determines both the uncoupled dispersion functions and the coupling constant, which in turn determine the uncoupled WKB solutions; (4) given the normal form of the local two-component wave equation, how to find the particular solution that matches the amplitude, phase, and polarization of the incoming ray, to the amplitude, phase, and polarization of the two outgoing rays: the transmitted and converted rays
Continuous spin mean-field models : Limiting kernels and Gibbs properties of local transforms
Kulske, Christof; Opoku, Alex A.
2008-01-01
We extend the notion of Gibbsianness for mean-field systems to the setup of general (possibly continuous) local state spaces. We investigate the Gibbs properties of systems arising from an initial mean-field Gibbs measure by application of given local transition kernels. This generalizes previous
International Nuclear Information System (INIS)
Utrecht, R.; Hankiewicz, J.
1995-01-01
The local fields on 57 Fe nuclei in ferrite (BaFe 12 O 19 ) polycrystals have been investigated by means of spin echo amplitudes measurements at 4.2 and 77 K. The magnetic moment orientation and local field intensity have been determined for five different ferrite sublattices
Reconstructing the velocity field beyond the local universe
CSIR Research Space (South Africa)
Johnston, R
2014-10-01
Full Text Available an estimate of the velocity field derived from the galaxy over-density d(sub g) and the second makes use of the matter linear density power spectrum P(sub k). Using N-body simulations we find, with an SDSS-like sample (N(sub gal) 33 per deg(sup 2...
LOCALIZATION OF NMDA AND AMPA RECEPTORS IN RAT BARREL FIELD
JAARSMA, D; SEBENS, JB; KORF, J
1991-01-01
The aim of this study was to asses the distribution of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-S-methyl-4-isoxazole propionic acid (AMPA) receptors in the barrel field of rat primary somatosensory (SI) cortex using light-microscopic in vitro autoradiography. NMDA receptors were labeled
Measurements of weak localization of graphene in inhomogeneous magnetic fields
DEFF Research Database (Denmark)
Lindvall, N.; Shivayogimath, Abhay; Yurgens, A.
2015-01-01
attribute this to the inhomogeneous field caused by vortices in the superconductor. The deviation, which depends on the carrier concentration in graphene, can be tuned by the gate voltage. In addition, collective vortex motion, known as vortex avalanches, is observed through magnetoresistance measurements...
Sub-half-wavelength atom localization via two standing-wave fields
International Nuclear Information System (INIS)
Jin Luling; Sun Hui; Niu Yueping; Gong Shangqing
2008-01-01
We propose a scheme for sub-half-wavelength atom localization in a four-level ladder-type atomic system, which is coupled by two classical standing-wave fields. We find that one of the standing-wave fields can help in enhancing the localization precision, and the other is of crucial importance in increasing the detecting probability and leading sub-half-wavelength localization
Matter waves from localized sources in homogeneous force fields
Kramer, Tobias
2010-01-01
We derive a scattering theory in constant potentials based on the energy-dependent Green function. This approach enables us to formulate modern experiments in terms of Green function. One application discussed is the photodetachment of electrons in external electromagnetic fields. In this case an intricate currentdensity distributions exists, that can be explained in terms of interfering classical trajectories. We also derive analytically the two-dimensional Green function in perpendicular el...
Tang, Jian; Jiang, Xiaoliang
2017-01-01
Image segmentation has always been a considerable challenge in image analysis and understanding due to the intensity inhomogeneity, which is also commonly known as bias field. In this paper, we present a novel region-based approach based on local entropy for segmenting images and estimating the bias field simultaneously. Firstly, a local Gaussian distribution fitting (LGDF) energy function is defined as a weighted energy integral, where the weight is local entropy derived from a grey level distribution of local image. The means of this objective function have a multiplicative factor that estimates the bias field in the transformed domain. Then, the bias field prior is fully used. Therefore, our model can estimate the bias field more accurately. Finally, minimization of this energy function with a level set regularization term, image segmentation, and bias field estimation can be achieved. Experiments on images of various modalities demonstrated the superior performance of the proposed method when compared with other state-of-the-art approaches.
Olfactory source localization in the open field using one or both nostrils.
Welge-Lussen, A; Looser, G L; Westermann, B; Hummel, T
2014-03-01
This study aims to examine humans ́ abilities to localize odorants within the open field. Young participants were tested on a localization task using a relatively selective olfactory stimulus (2-phenylethyl-alcohol, PEA) and cineol, an odorant with a strong trigeminal component. Participants were blindfolded and had to localize an odorant source at 2 m distance (far-field condition) and a 0.4 m distance (near-field condition) with either two nostrils open or only one open nostril. For the odorant with trigeminal properties, the number of correct trials did not differ when one or both nostrils were used, while more PEA localization trials were correctly completed with both rather than one nostril. In the near-field condition, correct localization was possible in 72-80% of the trials, irrespective of the odorant and the number of nostrils used. Localization accuracy, measured as spatial deviation from the olfactory source, was significantly higher in the near-field compared to the far-field condition, but independent of the odorant being localized. Odorant localization within the open field is difficult, but possible. In contrast to the general view, humans seem to be able to exploit the two-nostril advantage with increasing task difficulty.
Localized damage in soft rock: experiments with field measurement techniques
International Nuclear Information System (INIS)
Nguyen, T.L.
2011-01-01
The research presented in this thesis concerns, firstly, an experimental study on the process of fracture in uniaxial compression of rock samples containing narrow, rectilinear notches inclined with respect to the axis of loading. Secondly, we study the evolution of shear strain localisation towards fracturing and failure in specimens of the same materials with a particular geometry, involving two rounded notches. This geometry, inspired by the work of Meuwissen et al. (1998) for tension tests on metals, promotes the localisation of shear strain in simple compression before fracture. Two different materials were studied: a natural rock of volcanic origin (Neapolitan Tuff) and an artificial 'roc' (CPIR09). In the studies presented, three full-field measurement techniques have been employed in combination: (i) the Digital Image Correlation (DIC), for measurement of kinematic fields at a sample's surface; (ii)acoustic Emission measurements (AE) and AE source location, to follow the evolution of damage in samples during loading; (iii) X-ray tomography (pre-and post-mortem studies), to characterise preexisting defects and discontinuities in the specimens and to better understand the fracturing in 3D. (author)
Interaction quench dynamics in the Kondo model in the presence of a local magnetic field.
Heyl, M; Kehrein, S
2010-09-01
In this work we investigate the quench dynamics in the Kondo model on the Toulouse line in the presence of a local magnetic field. It is shown that this setup can be realized by either applying the local magnetic field directly or by preparing the system in a macroscopically spin-polarized initial state. In the latter case, the magnetic field results from a subtlety in applying the bosonization technique where terms that are usually referred to as finite-size corrections become important in the present non-equilibrium setting. The transient dynamics are studied by analyzing exact analytical results for the local spin dynamics. The timescale for the relaxation of the local dynamical quantities turns out to be exclusively determined by the Kondo scale. In the transient regime, one observes damped oscillations in the local correlation functions with a frequency set by the magnetic field.
A hand-held sensor for analyses of local distributions of magnetic fields and losses
Krismanic, G; Baumgartinger, N
2000-01-01
The paper describes a novel sensor for non-destructive analyses of local field and loss distributions in laminated soft magnetic cores, such as transformer cores. It was designed for rapid information on comparative local degrees of inhomogeneity, e.g., for the estimation of local building factors. Similar to a magnifying glass with handle, the compact hand-held sensor contains extremely sharp needle electrodes for the detection of the induction vector B as well as double-field coils for the vector H. Losses P are derived from the Poynting law. Applied to inner -- or also outer -- core regions, the sensor yields instantaneous computer displays of local H, B, and P.
GROWTH OF A LOCALIZED SEED MAGNETIC FIELD IN A TURBULENT MEDIUM
International Nuclear Information System (INIS)
Cho, Jungyeon; Yoo, Hyunju
2012-01-01
Turbulence dynamo deals with the amplification of a seed magnetic field in a turbulent medium and has been studied mostly for uniform or spatially homogeneous seed magnetic fields. However, some astrophysical processes (e.g., jets from active galaxies, galactic winds, or ram-pressure stripping in galaxy clusters) can provide localized seed magnetic fields. In this paper, we numerically study amplification of localized seed magnetic fields in a turbulent medium. Throughout the paper, we assume that the driving scale of turbulence is comparable to the size of the system. Our findings are as follows. First, turbulence can amplify a localized seed magnetic field very efficiently. The growth rate of magnetic energy density is as high as that for a uniform seed magnetic field. This result implies that magnetic field ejected from an astrophysical object can be a viable source of a magnetic field in a cluster. Second, the localized seed magnetic field disperses and fills the whole system very fast. If turbulence in a system (e.g., a galaxy cluster or a filament) is driven at large scales, we expect that it takes a few large-eddy turnover times for the magnetic field to fill the whole system. Third, growth and turbulence diffusion of a localized seed magnetic field are also fast in high magnetic Prandtl number turbulence. Fourth, even in decaying turbulence, a localized seed magnetic field can ultimately fill the whole system. Although the dispersal rate of the magnetic field is not fast in purely decaying turbulence, it can be enhanced by an additional forcing.
Direct subwavelength imaging and control of near-field localization in individual silver nanocubes
Energy Technology Data Exchange (ETDEWEB)
Mårsell, Erik; Svärd, Robin; Miranda, Miguel; Guo, Chen; Harth, Anne; Lorek, Eleonora; Mauritsson, Johan; Arnold, Cord L.; L' Huillier, Anne; Mikkelsen, Anders; Losquin, Arthur, E-mail: arthur.losquin@fysik.lth.se [Department of Physics, Lund University, PO Box 118, 221 00 Lund (Sweden); Xu, Hongxing [Department of Physics, Lund University, PO Box 118, 221 00 Lund (Sweden); School of Physics and Technology and Institute for Advanced Studies, Wuhan University, Wuhan 430072 (China)
2015-11-16
We demonstrate the control of near-field localization within individual silver nanocubes through photoemission electron microscopy combined with broadband, few-cycle laser pulses. We find that the near-field is concentrated at the corners of the cubes, and that it can be efficiently localized to different individual corners depending on the polarization of the incoming light. The experimental results are confirmed by finite-difference time-domain simulations, which also provide an intuitive picture of polarization dependent near-field localization in nanocubes.
The lure of local SETI: Fifty years of field experiments
Ailleris, Philippe
2011-01-01
With the commemoration in October 2007 of the Sputnik launch, space exploration celebrated its 50th anniversary. Despite impressive technological and scientific achievements the fascination for space has weakened during the last decades. One contributing factor has been the gradual disappearance of mankind's hope of discovering extraterrestrial life within its close neighbourhood. In striking contrast and since the middle of the 20th century, a non-negligible proportion of the population have already concluded that intelligent beings from other worlds do exist and visit Earth through space vehicles popularly called Unidentified Flying Objects (UFOs). In light of the continuous public interest for the UFO enigma symbolized by the recent widely diffused media announcements on the release of French and English governmental files; and considering the approach of broadening the strategies of the "Active SETI" approach and the existence of a rich multi-disciplinary UFO documentation of potential interest for SETI; this paper describes some past scientific attempts to demonstrate the physical reality of the phenomena and potentially the presence on Earth of probes of extraterrestrial origin. Details of the different instrumented field studies deployed by scientists and organizations during the period 1950-1990 in the USA, Canada and Europe are provided. In conclusion it will be argued that while continuing the current radio/optical SETI searches, there is the necessity to maintain sustaining attention to the topic of anomalous aerospace phenomena and to develop new rigorous research approaches.
Refractive index dependent local electric field enhancement in cylindrical gold nanohole
International Nuclear Information System (INIS)
Zhu Jian
2011-01-01
We report on the local electric field characters in a long cylindrical gold nanohole. Theoretical calculation results based on quasi-static model show that the local environmental dielectric constant dependent electric field intensity and field distribution in the gold nanohole show quite unique properties, different from those in the thin gold nanotube. Because of the thick gold wall, no plasmon hybridization exists. So there is only one resonance frequency taking place, and the intense local field has been focused into the gold nanohole. Our main finding is that, the local field in the nanohole is largely dependent on the inner hole refractive index and outer environmental refractive index. The competition between inner hole and outer polarization leads to a non-monotonic change of the local field intensity with increasing the dielectric constant of the nanohole. This refractive index controlled local field enhancement in cylindrical gold nanohole presents a potential for tunable surface-enhanced fluorescence and novel nano-optical biosensing applications.
Sub-half-wavelength atom localization via phase control of a pair of bichromatic fields
International Nuclear Information System (INIS)
Xu Jun; Hu Xiangming
2007-01-01
We propose a scheme of atom localization based on the interaction of the atom in the Λ configuration with a strong bichromatic coupling field and a weak bichromatic probe field with equal frequency difference. One of the bichromatic coupling components is a standing-wave field, which imposes position information on the Rabi frequency. By varying the difference between the relative phases of the two bichromatic fields, the atom is localized in either of the two half-wavelength regions with 50% probability provided the population in the upper state is detected
Jeong, Samuel; Ito, Yoshikazu; Edwards, Gary; Fujita, Jun-ichi
2018-06-01
The visualization of localized electronic charges on nanocatalysts is expected to yield fundamental information about catalytic reaction mechanisms. We have developed a high-sensitivity detection technique for the visualization of localized charges on a catalyst and their corresponding electric field distribution, using a low-energy beam of 1 to 5 keV electrons and a high-sensitivity scanning transmission electron microscope (STEM) detector. The highest sensitivity for visualizing a localized electric field was ∼0.08 V/µm at a distance of ∼17 µm from a localized charge at 1 keV of the primary electron energy, and a weak local electric field produced by 200 electrons accumulated on the carbon nanotube (CNT) apex can be visualized. We also observed that Au nanoparticles distributed on a CNT forest tended to accumulate a certain amount of charges, about 150 electrons, at a ‑2 V bias.
Spontaneous symmetry breaking in local gauge quantum field theory; the Higgs mechanism
International Nuclear Information System (INIS)
Strocchi, F.
1977-01-01
Spontaneous symmetry breakings in indefinite metric quantum field theories are analyzed and a generalization of the Goldstone theorem is proved. The case of local gauge quantum field theories is discussed in detail and a characterization is given of the occurrence of the Higgs mechanism versus the Goldstone mechanism. The Higgs phenomenon is explained on general grounds without the introduction of the so-called Higgs fields. The basic property is the relation between the local internal symmetry group and the local group of gauge transformations of the second kind. Spontaneous symmetry breaking of c-number gauge transformations of the second kind is shown to always occur if there are charged local fields. The implications about the absence of mass gap in the Wightman functions and the occurrence of massless particles associated with the unbroken generators in the Higgs phenomenon are discussed. (orig.) [de
Search for point-like sources using the diffuse astrophysical muon-neutrino flux in IceCube
Energy Technology Data Exchange (ETDEWEB)
Reimann, Rene; Haack, Christian; Raedel, Leif; Schoenen, Sebastian; Schumacher, Lisa; Wiebusch, Christopher [III. Physikalisches Institut B, RWTH Aachen (Germany); Collaboration: IceCube-Collaboration
2016-07-01
IceCube, a cubic-kilometer sized neutrino detector at the geographic South Pole, has recently confirmed a flux of high-energy astrophysical neutrinos in the track-like muon channel. Although this muon-neutrino flux has now been observed with high significance, no point sources or source classes could be identified yet with these well pointing events. We present a search for point-like sources based on a six year sample of upgoing muon-neutrinos with very low background contamination. To improve the sensitivity, the standard likelihood approach has been modified to focus on the properties of the measured astrophysical muon-neutrino flux.
Directory of Open Access Journals (Sweden)
Abílio Amiguinho
2005-01-01
Full Text Available The process of socio-educational territorialisation in rural contexts is the topic of this text. The theme corresponds to a challenge to address it having as main axis of discussion either the problem of social exclusion or that of local development. The reasons to locate the discussion in this last field of analysis are discussed in the first part of the text. Theoretical and political reasons are there articulated because the question is about projects whose intentions and practices call for the political both in the theoretical debate and in the choices that anticipate intervention. From research conducted for several years, I use contributions that aim at discuss and enlighten how school can be a potential locus of local development. Its identification and recognition as local institution (either because of those that work and live in it or because of those that act in the surrounding context are crucial steps to progressively constitute school as a partner for development. The promotion of the local values and roots, the reconstruction of socio-personal and local identities, the production of sociabilities and the equation and solution of shared problems were the dimensions of a socio-educative intervention, markedly globalising. This scenario, as it is argued, was also, intentionally, one of transformation and of deliberate change of school and of the administration of the educative territoires.
Externally controlled local magnetic field in a conducting mesoscopic ring coupled to a quantum wire
International Nuclear Information System (INIS)
Maiti, Santanu K.
2015-01-01
In the present work, the possibility of regulating local magnetic field in a quantum ring is investigated theoretically. The ring is coupled to a quantum wire and subjected to an in-plane electric field. Under a finite bias voltage across the wire a net circulating current is established in the ring which produces a strong magnetic field at its centre. This magnetic field can be tuned externally in a wide range by regulating the in-plane electric field, and thus, our present system can be utilized to control magnetic field at a specific region. The feasibility of this quantum system in designing spin-based quantum devices is also analyzed
International Nuclear Information System (INIS)
Vasconcelos Dos Santos, R.J.; Coutinho, S.
1995-01-01
The effect of a local field acting on decorating classical D-vector bond spins of an antiferromagnetic Ising model on the square lattice is studied for both the annealed isotropic and the axial decorated cases. In both models the effect on the phase diagrams of the transversal and the longitudinal components of the local field acting on the decorating spins are fully analyzed and discussed
Local Electric Field Effects on Rhodium-Porphyrin and NHC-Gold Catalysts
2015-01-05
AFRL-OSR-VA-TR-2015-0023 (NII) - Local Electric Field Effects on Rhodium -Porphyrin and NHC-Gold Catalysts MATTHEW KANAN LELAND STANFORD JUNIOR UNIV...Effects on Rhodium -Porphyrin and NHC-Gold Catalysts Principal Investigator: Matthew W. Kanan Project Publications: 1. “An Electric Field–Induced Change...Stanford University Grant/Contract Title The full title of the funded effort. (NII)-Local Electric Field Effects on Rhodium -Porphyrin and NHC-Gold
Geometrical optics in the near field: local plane-interface approach with evanescent waves.
Bose, Gaurav; Hyvärinen, Heikki J; Tervo, Jani; Turunen, Jari
2015-01-12
We show that geometrical models may provide useful information on light propagation in wavelength-scale structures even if evanescent fields are present. We apply a so-called local plane-wave and local plane-interface methods to study a geometry that resembles a scanning near-field microscope. We show that fair agreement between the geometrical approach and rigorous electromagnetic theory can be achieved in the case where evanescent waves are required to predict any transmission through the structure.
Precise Localization and Control of Catalytic Janus Micromotors using Weak Magnetic Fields
Khalil, Islam S. M.; Magdanz, Veronika; Sanchez, Samuel; Schmidt, Oliver G.; Misra, Sarthak
2015-01-01
We experimentally demonstrate the precise localization of spherical Pt-Silica Janus micromotors (diameter 5 mu m) under the influence of controlled magnetic fields. First, we control the motion of the Janus micromotors in two-dimensional (2D) space. The control system achieves precise localization
Physical principles, geometrical aspects, and locality properties of gauge field theories
International Nuclear Information System (INIS)
Mack, G.; Hamburg Univ.
1981-01-01
Gauge field theories, particularly Yang - Mills theories, are discussed at a classical level from a geometrical point of view. The introductory chapters are concentrated on physical principles and mathematical tools. The main part is devoted to locality problems in gauge field theories. Examples show that locality problems originate from two sources in pure Yang - Mills theories (without matter fields). One is topological and the other is related to the existence of degenerated field configurations of the infinitesimal holonomy groups on some extended region of space or space-time. Nondegenerate field configurations in theories with semisimple gauge groups can be analysed with the help of the concept of a local gauge. Such gauges play a central role in the discussion. (author)
Anderson localization with second quantized fields in a coupled array of waveguides
International Nuclear Information System (INIS)
Thompson, Clinton; Vemuri, Gautam; Agarwal, G. S.
2010-01-01
We report a theoretical study of Anderson localization of nonclassical light in an array of waveguides in which neighboring waveguides are evanescently coupled and in which the disorder can be added in a controlled manner. We use squeezed light at the input to investigate the effects of nonclassicality and compare the results with those obtained by using conventional classical fields, such as a coherent field and a Gaussian field. Our results show that there is an enhancement in fluctuations of localized light due to the medium's disorder. We find superbunching of the localized light, which may be useful for enhancing the interaction between radiation and matter. Another important consequence of sub-Poissonian statistics of the incoming light is to quench the total fluctuations at the output. Finally, we show that as a result of the multiplicative noise in the problem, the output field is far from Gaussian even if the input is a coherent field.
Localization and the interface between quantum mechanics, quantum field theory and quantum gravity
Energy Technology Data Exchange (ETDEWEB)
Schroer, Bert [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]|[Freie Univ., Berlin (Germany). Institut fuer Theoretische Physik]. E-mail: schroer@cbpf.br
2007-07-01
We show that there are significant conceptual differences between QM and QFT which make it difficult to view QFT as just a relativistic extension of the principles of QM. The root of this is a fundamental distinction between Born-localization in QM (which in the relativistic context changes its name to Newton-Wigner localization) and modular localization which is the localization underlying QFT, after one liberates it from its standard presentation in terms of field coordinates. The first comes with a probability notion and projection operators, whereas the latter describes causal propagation in QFT and leads to thermal aspects. Taking these significant differences serious has not only repercussions for the philosophy of science, but also leads to a new structural properties as a consequence of vacuum polarization: the area law for localization entropy near the the causal localization horizon and a more realistic cutoff independent setting for the cosmological vacuum energy density which is compatible with local covariance. (author)
Localization and the interface between quantum mechanics, quantum field theory and quantum gravity
International Nuclear Information System (INIS)
Schroer, Bert; Freie Univ., Berlin
2007-01-01
We show that there are significant conceptual differences between QM and QFT which make it difficult to view QFT as just a relativistic extension of the principles of QM. The root of this is a fundamental distinction between Born-localization in QM (which in the relativistic context changes its name to Newton-Wigner localization) and modular localization which is the localization underlying QFT, after one liberates it from its standard presentation in terms of field coordinates. The first comes with a probability notion and projection operators, whereas the latter describes causal propagation in QFT and leads to thermal aspects. Taking these significant differences serious has not only repercussions for the philosophy of science, but also leads to a new structural properties as a consequence of vacuum polarization: the area law for localization entropy near the the causal localization horizon and a more realistic cutoff independent setting for the cosmological vacuum energy density which is compatible with local covariance. (author)
Stabilization of the Vertical Mode in Tokamaks by Localized Nonaxisymmetric Fields
International Nuclear Information System (INIS)
Reiman, A.
2007-01-01
Vertical instability of a tokamak plasma can be controlled by nonaxisymmetric magnetic fields localized near the plasma edge at the bottom and top of the torus. The required magnetic fields can be produced by a relatively simple set of parallelogram-shaped coils.
Covariance of time-ordered products implies local commutativity of fields
International Nuclear Information System (INIS)
Greenberg, O.W.
2006-01-01
We formulate Lorentz covariance of a quantum field theory in terms of covariance of time-ordered products (or other Green's functions). This formulation of Lorentz covariance implies spacelike local commutativity or anticommutativity of fields, sometimes called microscopic causality or microcausality. With this formulation microcausality does not have to be taken as a separate assumption
International Nuclear Information System (INIS)
Iannarella, L.; Guimaraes, A.P.; Silva, X.A. da.
1990-01-01
The magnetic behavior at T = O K of a system consisting of conduction electrons coupled to localized electrons, the latter submitted to an inhomogeneous crystal field distribution, is studied. The study implies that the inhomogeneity of the crystal field attenuates the quenching effects. The model is interesting to the study of disordered rare-earth intermetallic compounds. (A.C.A.S.) [pt
The Uncertainty of Local Background Magnetic Field Orientation in Anisotropic Plasma Turbulence
Energy Technology Data Exchange (ETDEWEB)
Gerick, F.; Saur, J.; Papen, M. von, E-mail: felix.gerick@uni-koeln.de [Institute of Geophysics and Meteorology, University of Cologne, Cologne (Germany)
2017-07-01
In order to resolve and characterize anisotropy in turbulent plasma flows, a proper estimation of the background magnetic field is crucially important. Various approaches to calculating the background magnetic field, ranging from local to globally averaged fields, are commonly used in the analysis of turbulent data. We investigate how the uncertainty in the orientation of a scale-dependent background magnetic field influences the ability to resolve anisotropy. Therefore, we introduce a quantitative measure, the angle uncertainty, that characterizes the uncertainty of the orientation of the background magnetic field that turbulent structures are exposed to. The angle uncertainty can be used as a condition to estimate the ability to resolve anisotropy with certain accuracy. We apply our description to resolve the spectral anisotropy in fast solar wind data. We show that, if the angle uncertainty grows too large, the power of the turbulent fluctuations is attributed to false local magnetic field angles, which may lead to an incorrect estimation of the spectral indices. In our results, an apparent robustness of the spectral anisotropy to false local magnetic field angles is observed, which can be explained by a stronger increase of power for lower frequencies when the scale of the local magnetic field is increased. The frequency-dependent angle uncertainty is a measure that can be applied to any turbulent system.
The Uncertainty of Local Background Magnetic Field Orientation in Anisotropic Plasma Turbulence
International Nuclear Information System (INIS)
Gerick, F.; Saur, J.; Papen, M. von
2017-01-01
In order to resolve and characterize anisotropy in turbulent plasma flows, a proper estimation of the background magnetic field is crucially important. Various approaches to calculating the background magnetic field, ranging from local to globally averaged fields, are commonly used in the analysis of turbulent data. We investigate how the uncertainty in the orientation of a scale-dependent background magnetic field influences the ability to resolve anisotropy. Therefore, we introduce a quantitative measure, the angle uncertainty, that characterizes the uncertainty of the orientation of the background magnetic field that turbulent structures are exposed to. The angle uncertainty can be used as a condition to estimate the ability to resolve anisotropy with certain accuracy. We apply our description to resolve the spectral anisotropy in fast solar wind data. We show that, if the angle uncertainty grows too large, the power of the turbulent fluctuations is attributed to false local magnetic field angles, which may lead to an incorrect estimation of the spectral indices. In our results, an apparent robustness of the spectral anisotropy to false local magnetic field angles is observed, which can be explained by a stronger increase of power for lower frequencies when the scale of the local magnetic field is increased. The frequency-dependent angle uncertainty is a measure that can be applied to any turbulent system.
Nature of the Diffuse Source and Its Central Point-like Source in SNR 0509–67.5
Energy Technology Data Exchange (ETDEWEB)
Litke, Katrina C.; Chu, You-Hua; Holmes, Abigail; Santucci, Robert; Blindauer, Terrence; Gruendl, Robert A.; Ricker, Paul M. [Astronomy Department, University of Illinois, 1002 W. Green Street, Urbana, IL 61801 (United States); Li, Chuan-Jui [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan, R.O.C. (China); Pan, Kuo-Chuan [Departement Physik, Universität Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Weisz, Daniel R., E-mail: kclitke@email.arizona.edu [Department of Astronomy, University of California, 501 Cambell Hall #3411, Berkeley, CA 94720-3411 (United States)
2017-03-10
We examine a diffuse emission region near the center of SNR 0509−67.5 to determine its nature. Within this diffuse region we observe a point-like source that is bright in the near-IR, but is not visible in the B and V bands. We consider an emission line observed at 6766 Å and the possibilities that it is Ly α , H α , and [O ii] λ 3727. We examine the spectral energy distribution (SED) of the source, comprised of Hubble Space Telescope B , V , I , J , and H bands in addition to Spitzer /IRAC 3.6, 4.5, 5.8, and 8 μ m bands. The peak of the SED is consistent with a background galaxy at z ≈ 0.8 ± 0.2 and a possible Balmer jump places the galaxy at z ≈ 0.9 ± 0.3. These SED considerations support the emission line’s identification as [O ii] λ 3727. We conclude that the diffuse source in SNR 0509−67.5 is a background galaxy at z ≈ 0.82. Furthermore, we identify the point-like source superposed near the center of the galaxy as its central bulge. Finally, we find no evidence for a surviving companion star, indicating a double-degenerate origin for SNR 0509−67.5.
Nature of the Diffuse Source and Its Central Point-like Source in SNR 0509–67.5
International Nuclear Information System (INIS)
Litke, Katrina C.; Chu, You-Hua; Holmes, Abigail; Santucci, Robert; Blindauer, Terrence; Gruendl, Robert A.; Ricker, Paul M.; Li, Chuan-Jui; Pan, Kuo-Chuan; Weisz, Daniel R.
2017-01-01
We examine a diffuse emission region near the center of SNR 0509−67.5 to determine its nature. Within this diffuse region we observe a point-like source that is bright in the near-IR, but is not visible in the B and V bands. We consider an emission line observed at 6766 Å and the possibilities that it is Ly α , H α , and [O ii] λ 3727. We examine the spectral energy distribution (SED) of the source, comprised of Hubble Space Telescope B , V , I , J , and H bands in addition to Spitzer /IRAC 3.6, 4.5, 5.8, and 8 μ m bands. The peak of the SED is consistent with a background galaxy at z ≈ 0.8 ± 0.2 and a possible Balmer jump places the galaxy at z ≈ 0.9 ± 0.3. These SED considerations support the emission line’s identification as [O ii] λ 3727. We conclude that the diffuse source in SNR 0509−67.5 is a background galaxy at z ≈ 0.82. Furthermore, we identify the point-like source superposed near the center of the galaxy as its central bulge. Finally, we find no evidence for a surviving companion star, indicating a double-degenerate origin for SNR 0509−67.5.
arXiv Stochastic locality and master-field simulations of very large lattices
Lüscher, Martin
2018-01-01
In lattice QCD and other field theories with a mass gap, the field variables in distant regions of a physically large lattice are only weakly correlated. Accurate stochastic estimates of the expectation values of local observables may therefore be obtained from a single representative field. Such master-field simulations potentially allow very large lattices to be simulated, but require various conceptual and technical issues to be addressed. In this talk, an introduction to the subject is provided and some encouraging results of master-field simulations of the SU(3) gauge theory are reported.
DEFF Research Database (Denmark)
List, Nanna Holmgaard; Jensen, Hans Jørgen Aagaard; Kongsted, Jacob
2016-01-01
chemical reference calculations. For the lowest π → π∗ transition in DsRed, inclusion of effective external field effects gives rise to a 1.9- and 3.5-fold reduction in the 1PA and 2PA cross-sections, respectively. The effective external field is, however, strongly influenced by the heterogeneity...... (1PA and 2PA, respectively) properties of PRODAN-methanol clusters as well as the fluorescent protein DsRed. Our results demonstrate the necessity of accounting for both the dynamical reaction field and effective external field contributions to the local field in order to reproduce full quantum...
Magnetic-field-driven localization of light in a cold-atom gas.
Skipetrov, S E; Sokolov, I M
2015-02-06
We discover a transition from extended to localized quasimodes for light in a gas of immobile two-level atoms in a magnetic field. The transition takes place either upon increasing the number density of atoms in a strong field or upon increasing the field at a high enough density. It has many characteristic features of a disorder-driven (Anderson) transition but is strongly influenced by near-field interactions between atoms and the anisotropy of the atomic medium induced by the magnetic field.
Fluctuating local field method probed for a description of small classical correlated lattices
Rubtsov, Alexey N.
2018-05-01
Thermal-equilibrated finite classical lattices are considered as a minimal model of the systems showing an interplay between low-energy collective fluctuations and single-site degrees of freedom. Standard local field approach, as well as classical limit of the bosonic DMFT method, do not provide a satisfactory description of Ising and Heisenberg small lattices subjected to an external polarizing field. We show that a dramatic improvement can be achieved within a simple approach, in which the local field appears to be a fluctuating quantity related to the low-energy degree(s) of freedom.
2D atom localization in a four-level tripod system in laser fields
Ivanov, Vladimir; Rozhdestvensky, Yuri
2012-01-01
We propose a scheme for two-dimensional (2D) atom localization in a four-level tripod system under an influence of two orthogonal standing-wave fields. Position information of the atom is retained in the atomic internal states by an additional probe field either of a standing or of a running wave. It is shown that the localization factors depend crucially on the atom-field coupling that results in such spatial structures of populations as spikes, craters and waves. We demonstrate a high-preci...
Local field theory on κ-Minkowski space, star products and noncommutative translations
International Nuclear Information System (INIS)
Kosinski, P.; Maslanka, P.; Lukierski, J.
2000-01-01
We consider local field theory on κ-deformed Minkowski space which is an example of solvable Lie-algebraic noncommutative structure. Using integration formula over κ-Minkowski space and κ-deformed Fourier transform, we consider for deformed local fields the reality conditions as well as deformation of action functionals in standard Minkowski space. We present explicit formulas for two equivalent star products describing CBH quantization of field theory on κ-Minkowski space. We express also via star product technique the noncommutative translations in κ-Minkowski space by commutative translations in standard Minkowski space. (author)
Energy Technology Data Exchange (ETDEWEB)
Meloni, A.; Di Mauro, D.; Mele, G.; Palangio, P. [Istituto Nazionale di Geofisica e Vulcanologia, Rome (Italy); Ernst, T.; Teisseyre, R. [Institute of Geophysics, Warszawa (Poland)
2001-04-01
Magnetotelluric data were collected at Collemeluccio (41.72{sup 0}N, 14.37{sup 0}E) in Central Italy from summer 1991 to spring 1998. Analyzed by means of tensor decomposition on the geoelectric potential and robust estimation on the geomagnetic field, this set of data allowed the investigation of the electromagnetic induction, is presented here in its time evolution and compared to local and regional seismic activity. Tecto magnetic field observations from absolute magnetic field level in Central Italy were also made on data simultaneously recorded at four magnetometer stations, using L'Aquila Geomagnetic Observatory as a reference for differentiation. Recent results gathered from a system of two VLF search coil wide-band antennas, installed in the L'Aquila Observatory, are also discussed in relation to local seismic activity.
International Nuclear Information System (INIS)
Hsu, J.Y.; Chan, V.S.; Harvey, R.W.; Prater, R.; Wong, S.K.
1984-01-01
The perpendicular heating in cyclotron waves tends to pile up the resonant particles toward the low magnetic field side with their banana tips localized to the resonant surface. A poloidal electric field with an E x B drift comparable to the ion vertical drift in a toroidal magnetic field may result. With the assumption of anomalous electron and neoclassical ion transport, density variations due to wave heating are discussed
Applications of the Local Algebras of Vector Fields to the Modelling of Physical Phenomena
Bayak, Igor V.
2015-01-01
In this paper we discuss the local algebras of linear vector fields that can be used in the mathematical modelling of physical space by building the dynamical flows of vector fields on eight-dimensional cylindrical or toroidal manifolds. It is shown that the topological features of the vector fields obey the Dirac equation when moving freely within the surface of a pseudo-sphere in the eight-dimensional pseudo-Euclidean space.
Prevention of brittle fracture of steel structures by controlling the local stress and strain fields
Directory of Open Access Journals (Sweden)
Moyseychik Evgeniy Alekseevich
Full Text Available In the article the author offers a classification of the methods to increase the cold resistance of steel structural shapes with a focus on the regulation of local fields of internal stresses and strains to prevent brittle fracture of steel structures. The need of a computer thermography is highlighted not only for visualization of temperature fields on the surface, but also to control the fields of residual stresses and strains in a controlled element.
Zhu, Hao; Xiao, Chong
2018-06-01
Thermoelectric materials provide a renewable and eco-friendly solution to mitigate energy shortages and to reduce environmental pollution via direct heat-to-electricity conversion. Discovery of the novel thermoelectric materials and optimization of the state-of-the-art material systems lie at the core of the thermoelectric society, the basic concept behind these being comprehension and manipulation of the physical principles and transport properties regarding thermoelectric materials. In this mini-review, certain examples for designing high-performance bulk thermoelectric materials are presented from the perspectives of both real objects and local fields. The highlights of this topic involve the Rashba effect, Peierls distortion, local magnetic field, and local stress field, which cover several aspects in the field of thermoelectric research. We conclude with an overview of future developments in thermoelectricity.
Properties of the localized field emitted from degenerate Λ-type atoms in photonic crystals
International Nuclear Information System (INIS)
Foroozani, N.; Golshan, M. M.; Mahjoei, M.
2007-01-01
The spontaneous emission from a degenerate Λ-type three-level atom, embedded in a photonic crystal, is studied. The emitted field, as a function of time and position, is calculated by solving the three coupled differential equations governing the amplitudes. We show that the spontaneously emitted field is characterized by three components (as in the case of two-level and V-type atoms): a localized part, a traveling part, and a t -3/2 decaying part. Our calculations indicate that under specific conditions the atoms do not emit propagating fields, while the localized field, having shorter localization length and time, is intensified. As a consequence, the population of the upper level, after a short period of oscillations, approaches a constant value. It is also shown that this steady value, under the same conditions, is much larger than its counterpart in V-type atoms
Kosevich, Yuriy A; Gann, Vladimir V
2013-06-19
We study the localization of magnon states in finite defect-free Heisenberg spin-1/2 ferromagnetic chains placed in an inhomogeneous magnetic field with a constant spatial gradient. Continuous transformation from the extended magnon states to the localized Wannier-Zeeman states in a finite spin chain placed in an inhomogeneous field is described both analytically and numerically. We describe for the first time the non-monotonic dependence of the energy levels of magnons, both long and short wavelength, on the magnetic field gradient, which is a consequence of magnon localization in a finite spin chain. We show that, in contrast to the destruction of the magnon band and the establishment of the Wannier-Stark ladder in a vanishingly small field gradient in an infinite chain, the localization of magnon states at the chain ends preserves the memory of the magnon band. Essentially, the localization at the lower- or higher-field chain end resembles the localization of the positive- or negative-effective-mass band quasiparticles. We also show how the beat dynamics of coherent superposition of extended spin waves in a finite chain in a homogeneous or weakly inhomogeneous field transforms into magnon Bloch oscillations of the superposition of localized Wannier-Zeeman states in a strongly inhomogeneous field. We provide a semiclassical description of the magnon Bloch oscillations and show that the correspondence between the quantum and semiclassical descriptions is most accurate for Bloch oscillations of the magnon coherent states, which are built from a coherent superposition of a large number of the nearest-neighbour Wannier-Zeeman states.
International Nuclear Information System (INIS)
Kosevich, Yuriy A; Gann, Vladimir V
2013-01-01
We study the localization of magnon states in finite defect-free Heisenberg spin-1/2 ferromagnetic chains placed in an inhomogeneous magnetic field with a constant spatial gradient. Continuous transformation from the extended magnon states to the localized Wannier–Zeeman states in a finite spin chain placed in an inhomogeneous field is described both analytically and numerically. We describe for the first time the non-monotonic dependence of the energy levels of magnons, both long and short wavelength, on the magnetic field gradient, which is a consequence of magnon localization in a finite spin chain. We show that, in contrast to the destruction of the magnon band and the establishment of the Wannier–Stark ladder in a vanishingly small field gradient in an infinite chain, the localization of magnon states at the chain ends preserves the memory of the magnon band. Essentially, the localization at the lower- or higher-field chain end resembles the localization of the positive- or negative-effective-mass band quasiparticles. We also show how the beat dynamics of coherent superposition of extended spin waves in a finite chain in a homogeneous or weakly inhomogeneous field transforms into magnon Bloch oscillations of the superposition of localized Wannier–Zeeman states in a strongly inhomogeneous field. We provide a semiclassical description of the magnon Bloch oscillations and show that the correspondence between the quantum and semiclassical descriptions is most accurate for Bloch oscillations of the magnon coherent states, which are built from a coherent superposition of a large number of the nearest-neighbour Wannier–Zeeman states. (paper)
International Nuclear Information System (INIS)
Bruzzo, V.
1986-01-01
This paper reports briefly on recent investigations concerning the formulation of field theories on supermanifolds. The usual formulations are unsatisfactory from a mathematical viewpoint, hence, this report. A variational theory for fields on a supermanifold is described where the action is a map between Banach spaces. The relationship between the field theory on the supermanifold and a suitably constructed field theory on space-time is also discussed. On-shell local supersymmetry are examined and the limit of global (rigid) supersymmetry is considered. A specific example is given which shows that the limit reproduces the known results
Determination of Intrinsic Magnetic Response from Local Measurements of Fringing Fields
Wen, Bo; Millis, Andrew J.; Pardo, Enric; Subedi, Pradeep; Kent, Andrew D.; Yeshurun, Yosi; Sarachik, Myriam P.
2014-01-01
Micron-sized Hall bars and micro-SQUIDs are now used routinely to measure the local static and dynamic magnetic response with micron-scale spatial resolution. While this provides a powerful new tool, determining the intrinsic magnetization presents new challenges, as it requires correcting for demagnetization fields that vary widely with position on a sample. In this paper we develop a method to correct for the demagnetization effect at local points of a rectangular prism shaped sample using ...
Localization of periodic orbits of polynomial vector fields of even degree by linear functions
Energy Technology Data Exchange (ETDEWEB)
Starkov, Konstantin E. [CITEDI-IPN, Av. del Parque 1310, Mesa de Otay, Tijuana, BC (Mexico)] e-mail: konst@citedi.mx
2005-08-01
This paper is concerned with the localization problem of periodic orbits of polynomial vector fields of even degree by using linear functions. Conditions of the localization of all periodic orbits in sets of a simple structure are obtained. Our results are based on the solution of the conditional extremum problem and the application of homogeneous polynomial forms of even degrees. As examples, the Lanford system, the jerky system with one quadratic monomial and a quartically perturbed harmonic oscillator are considered.
Localization of periodic orbits of polynomial vector fields of even degree by linear functions
International Nuclear Information System (INIS)
Starkov, Konstantin E.
2005-01-01
This paper is concerned with the localization problem of periodic orbits of polynomial vector fields of even degree by using linear functions. Conditions of the localization of all periodic orbits in sets of a simple structure are obtained. Our results are based on the solution of the conditional extremum problem and the application of homogeneous polynomial forms of even degrees. As examples, the Lanford system, the jerky system with one quadratic monomial and a quartically perturbed harmonic oscillator are considered
International Nuclear Information System (INIS)
Yu, Mina; Lee, Hyo Chun; Chung, Mi Joo; Kim, Sung Hwan; Lee, Jong Hoon; Jang, Hong Seok; Jeon, Dong Min; Cheon, Geum Seong
2013-01-01
To report the results of dosimetric comparison between intensity-modulated radiotherapy (IMRT) using Tomotherapy and four-box field conformal radiotherapy (CRT) for pelvic irradiation of locally advanced rectal cancer. Twelve patients with locally advanced rectal cancer who received a short course preoperative chemoradiotherapy (25 Gy in 5 fractions) on the pelvis using Tomotherapy, between July 2010 and December 2010, were selected. Using their simulation computed tomography scans, Tomotherapy and four-box field CRT plans with the same dose schedule were evaluated, and dosimetric parameters of the two plans were compared. For the comparison of target coverage, we analyzed the mean dose, Vn Gy, Dmin, Dmax, radical dose homogeneity index (rDHI), and radiation conformity index (RCI). For the comparison of organs at risk (OAR), we analyzed the mean dose. Tomotherapy showed a significantly higher mean target dose than four-box field CRT (p 0.001). But, V26.25 Gy and V27.5 Gywere not significantly different between the two modalities. Tomotherapy showed higher Dmax and lower Dmin. The Tomotherapy plan had a lower rDHI than four-box field CRT (p = 0.000). Tomotherapy showed better RCI than four-box field CRT (p = 0.007). For OAR, the mean irradiated dose was significantly lower in Tomotherapy than four-box field CRT. In locally advanced rectal cancer, Tomotherapy delivers a higher conformal radiation dose to the target and reduces the irradiated dose to OAR than four-box field CRT.
Energy Technology Data Exchange (ETDEWEB)
Yu, Mina; Lee, Hyo Chun; Chung, Mi Joo; Kim, Sung Hwan; Lee, Jong Hoon [Dept. of Radiation Oncology, St. Vincent' s Hospital, The Catholic University of Korea College of Medicine, Suwon (Korea, Republic of); Jang, Hong Seok; Jeon, Dong Min; Cheon, Geum Seong [Dept. of Radiation Oncology, Seoul St. Mary' s Hospital, The Catholic University of Korea College of Medicine, Seoul (Korea, Republic of)
2013-12-15
To report the results of dosimetric comparison between intensity-modulated radiotherapy (IMRT) using Tomotherapy and four-box field conformal radiotherapy (CRT) for pelvic irradiation of locally advanced rectal cancer. Twelve patients with locally advanced rectal cancer who received a short course preoperative chemoradiotherapy (25 Gy in 5 fractions) on the pelvis using Tomotherapy, between July 2010 and December 2010, were selected. Using their simulation computed tomography scans, Tomotherapy and four-box field CRT plans with the same dose schedule were evaluated, and dosimetric parameters of the two plans were compared. For the comparison of target coverage, we analyzed the mean dose, Vn Gy, Dmin, Dmax, radical dose homogeneity index (rDHI), and radiation conformity index (RCI). For the comparison of organs at risk (OAR), we analyzed the mean dose. Tomotherapy showed a significantly higher mean target dose than four-box field CRT (p 0.001). But, V26.25 Gy and V27.5 Gywere not significantly different between the two modalities. Tomotherapy showed higher Dmax and lower Dmin. The Tomotherapy plan had a lower rDHI than four-box field CRT (p = 0.000). Tomotherapy showed better RCI than four-box field CRT (p = 0.007). For OAR, the mean irradiated dose was significantly lower in Tomotherapy than four-box field CRT. In locally advanced rectal cancer, Tomotherapy delivers a higher conformal radiation dose to the target and reduces the irradiated dose to OAR than four-box field CRT.
Fast words boundaries localization in text fields for low quality document images
Ilin, Dmitry; Novikov, Dmitriy; Polevoy, Dmitry; Nikolaev, Dmitry
2018-04-01
The paper examines the problem of word boundaries precise localization in document text zones. Document processing on a mobile device consists of document localization, perspective correction, localization of individual fields, finding words in separate zones, segmentation and recognition. While capturing an image with a mobile digital camera under uncontrolled capturing conditions, digital noise, perspective distortions or glares may occur. Further document processing gets complicated because of its specifics: layout elements, complex background, static text, document security elements, variety of text fonts. However, the problem of word boundaries localization has to be solved at runtime on mobile CPU with limited computing capabilities under specified restrictions. At the moment, there are several groups of methods optimized for different conditions. Methods for the scanned printed text are quick but limited only for images of high quality. Methods for text in the wild have an excessively high computational complexity, thus, are hardly suitable for running on mobile devices as part of the mobile document recognition system. The method presented in this paper solves a more specialized problem than the task of finding text on natural images. It uses local features, a sliding window and a lightweight neural network in order to achieve an optimal algorithm speed-precision ratio. The duration of the algorithm is 12 ms per field running on an ARM processor of a mobile device. The error rate for boundaries localization on a test sample of 8000 fields is 0.3
An explicit formula for the Hilbert symbol for Honda groups in a multidimensional local field
International Nuclear Information System (INIS)
Vostokov, S V; Lorenz, F
2003-01-01
Based on the pairing on Cartier curves explicitly constructed in the previous paper of the authors, an explicit formula for the Hilbert symbol is constructed in a multidimensional local field of characteristic zero with residue field of positive characteristic on the formal module of a one-dimensional Honda formal group. In the proof a Shafarevich basis on the formal module is constructed, and so-called integer μ-modules in two-dimensional local rings of a special form ( μ-rings) are studied
Two-photon mapping of localized field enhancements in thin nanostrip antennas
DEFF Research Database (Denmark)
Beermann, I.; Novikov, S.M.; Søndergaard, Thomas
2008-01-01
scanning optical microscopy, in which two-photon-excited photoluminescence (TPL) excited with a strongly focused laser beam at the wavelength 745 nm is detected. We use TPL images to map the local field enhancements from individual nanostrips at a resolution of 0.35µm and compare results with theoretical......Resonant scattering and local field enhancements by 11-nm-thin gold nanostrip antennas due to constructive interference of counter propagating slow surface plasmon polaritons is investigated. We characterize nanostrips of widths between 50-530 nm using both reflection spectroscopy and nonlinear...
Local energy decay of massive Dirac fields in the 5D Myers-Perry metric
International Nuclear Information System (INIS)
Daudé, Thierry; Kamran, Niky
2012-01-01
We consider massive Dirac fields evolving in the exterior region of a five-dimensional Myers-Perry black hole and study their propagation properties. Our main result states that the local energy of such fields decays in a weak sense at late times. We obtain this result in two steps: first, using the separability of the Dirac equation, we prove the absence of a pure point spectrum for the corresponding Dirac operator; second, using a new form of the equation adapted to the local rotations of the black hole, we show by a Mourre theory argument that the spectrum is absolutely continuous. This leads directly to our main result. (paper)
Conformal quantum field theory: From Haag-Kastler nets to Wightman fields
International Nuclear Information System (INIS)
Joerss, M.
1996-07-01
Starting from a chiral conformal Haag-Kastler net of local observables on two-dimensional Minkowski space-time, we construct associated pointlike localizable charged fields which intertwine between the superselection sectors with finite statistics of the theory. This amounts to a proof of the spin-statistics theorem, the PCT theorem, the Bisognano-Wichmann identification of modular operators, Haag duality in the vacuum sector, and the existence of operator product expansions. Our method consists of the explicit use of the representation theory of the universal covering group of SL(2,R). A central role is played by a ''conformal cluster theorem'' for conformal two-point functions in algebraic quantum field theory. Generalizing this ''conformal cluster theorem'' to the n-point functions of Haag-Kastler theories, we can finally construct from a chiral conformal net of algebras a compelte set of conformal n-point functions fulfilling the Wightman axioms. (orig.)
International Nuclear Information System (INIS)
Vysotsky, V.S.; Takayasu, M.; Minervini, J.V.
1997-01-01
A new method has been developed to study Ramp Rate Limitation (RRL) phenomena. Samples of ITER-type cable-in-conduit (CICC) subcable were instrumented with local field sensors such as Hall probes and pick-up coils and then subjected to rapidly changing external magnetic field. The authors found that during fast field sweeps some discontinuous changes, or jumps occur in the local field. They believe that these jumps indicate a fast current redistribution processes inside CICC. Detailed information about local magnetic field jumps during changing field is presented. Possible origin of the jumps and their connection with RRL are discussed
Li, Duo-Jie; Li, Hong-Wei; He, Bin; Wang, Geng-Ming; Cai, Han-Fei; Duan, Shi-Miao; Liu, Jing-Jing; Zhang, Ya-Jun; Cui, Zhen; Jiang, Hao
2016-01-01
To retrospectively analyze the patterns of failure and the treatment effects of involved-field irradiation (IFI) on patients treated with locally advanced esophageal squamous cell carcinoma (ESCC) and to determine whether IFI is practicable in these patients. A total of 79 patients with locally advanced ESCC underwent three dimensional conformal (3D)CRT) or intensity modulated radiotherapy (IMRT) using IFI or elective nodal irradiation (ENI) according to the target volume. The patterns of failure were defined as local/regional, in-field, out)of)field regional lymph node (LN) and distant failure. With a median follow)up of 32.0 months, failures were observed in 66 (83.6%) patients. The cumulative incidence of local/regional failure (55.8 vs 52.8%) and in)field regional lymph node failure (25.6 vs 19.4%) showed no statistically significant difference between the IFI and the ENI group (p=0.526 and 0.215, respectively). Out)of)field nodal relapse rate of only 7.0% was seen in the IFI group. Three)year survival rates for the ENI and IFI group were 22.2 and 18.6%, respectively (p=0.240), and 3)year distant metastasis rates were 27.8 and 32.6%, respectively (p=0.180). The lung V10, V20, V30 and mean lung dose of the ENI group were greater than those of the IFI group, while the mean lung dose and V10 had statistically significant difference. The patterns of failure and survival rates in the IFI group were similar as in the ENI group; the regional recurrence and distant metastasis are the main cause of treatment failure. IFI is feasible for locally advanced ESCC. Further investigation is needed to increase local control and decrease distant metastasis in these patients.
Ferris, Kim; Jones, Dumont
2014-03-01
Local electric fields reflect the structural and dielectric fluctuations in a semiconductor, and affect the material performance both for electron transport and carrier lifetime properties. In this paper, we use the LOCALF methodology with periodic boundary conditions to examine the local electric field distributions and its perturbations for II-VI (CdTe, Cd(1-x)Zn(x)Te) semiconductors, containing Te inclusions and small fluctuations in the local dielectric susceptibility. With inclusion of the induced-field term, the electric field distribution shows enhancements and diminishments compared to the macroscopic applied field, reflecting the microstructure characteristics of the dielectric. Learning methods are applied to these distributions to assess the spatial extent of the perturbation, and determine an electric field defined defect size as compared to its physical dimension. Critical concentrations of defects are assessed in terms of defect formation energies. This work was supported by the US Department of Homeland Security, Domestic Nuclear Detection Office, under competitively awarded contract/IAA HSHQDC-08-X-00872-e. This support does not constitute an express or implied endorsement on the part of the Gov't.
International Nuclear Information System (INIS)
Choudhary, M.R.; Mustafa, U.S.
2009-01-01
Field tests were conducted to calibrate the existing SCS design equation in determining field border length using field data of different field lengths during 2nd and 3rd irrigations under local conditions. A single ring infiltrometer was used to estimate the water movement into and through the irrigated soil profile and in estimating the coefficients of Kostiakov infiltration function. Measurements of the unit discharge and time of advance were carried out during different irrigations on wheat irrigated fields having clay loam soil. The collected field data were used to calibrate the existing SCS design equation developed by USDA for testing its validity under local field conditions. SCS equation was modified further to improve its applicability. Results from the study revealed that the Kostiakov model over predicted the coefficients, which in turn overestimated the water advance length for boarder in the selected field using existing SCS design equation. However, the calibrated SCS design equation after parametric modification produced more satisfactory results encouraging the scientists to make its use at larger scale. (author)
Comment on the frequency dependence of the local field factor of an electron liquid
International Nuclear Information System (INIS)
Holas, A.; Singwi, K.S.
1981-08-01
We show that the reply of Rao et al. to the Letter of Brosens et al. regarding the existence of singularities in the local field factor G(k,ω) is in error. The function G indeed has logarithmic singularities at ωsub(s)=|(k 2 /2)+-k| as pointed out earlier by us. (author)
Near-field optical microscopy of localized excitations on rough surfaces: influence of a probe
DEFF Research Database (Denmark)
Bozhevolnyi, Sergey I.
1999-01-01
Starting from the general principles of near-field optical microscopy. I consider the influence of a probe when being used to image localized dipolar excitations and suggest a way of evaluating the perturbation thus introduced. Using the rigorous microscopic (electric) point-dipole description, I...
Measuring Earth's Local Magnetic Field Using a Helmholtz Coil
Williams, Jonathan E.
2014-01-01
In this paper, I present a low-cost interactive experiment for measuring the strength of Earth's local magnetic field. This activity can be done in most high schools or two-year physics laboratories with limited resources, yet will have a tremendous learning impact. This experiment solidifies the three-dimensional nature of Earth's…
DEFF Research Database (Denmark)
Wang, W.; Hanson, Steen Grüner; Miyamoto, Y.
2005-01-01
We present the first direct experimental evidence of the local properties of optical vortices in a random laser speckle field. We have observed the Berry anisotropy ellipse describing the anisotropic squeezing of phase lines close to vortex cores and quantitatively verified the Dennis angular mom...
Shibata, Naoya; Findlay, Scott D; Matsumoto, Takao; Kohno, Yuji; Seki, Takehito; Sánchez-Santolino, Gabriel; Ikuhara, Yuichi
2017-07-18
The functional properties of materials and devices are critically determined by the electromagnetic field structures formed inside them, especially at nanointerface and surface regions, because such structures are strongly associated with the dynamics of electrons, holes and ions. To understand the fundamental origin of many exotic properties in modern materials and devices, it is essential to directly characterize local electromagnetic field structures at such defect regions, even down to atomic dimensions. In recent years, rapid progress in the development of high-speed area detectors for aberration-corrected scanning transmission electron microscopy (STEM) with sub-angstrom spatial resolution has opened new possibilities to directly image such electromagnetic field structures at very high-resolution. In this Account, we give an overview of our recent development of differential phase contrast (DPC) microscopy for aberration-corrected STEM and its application to many materials problems. In recent years, we have developed segmented-type STEM detectors which divide the detector plane into 16 segments and enable simultaneous imaging of 16 STEM images which are sensitive to the positions and angles of transmitted/scattered electrons on the detector plane. These detectors also have atomic-resolution imaging capability. Using these segmented-type STEM detectors, we show DPC STEM imaging to be a very powerful tool for directly imaging local electromagnetic field structures in materials and devices in real space. For example, DPC STEM can clearly visualize the local electric field variation due to the abrupt potential change across a p-n junction in a GaAs semiconductor, which cannot be observed by normal in-focus bright-field or annular type dark-field STEM imaging modes. DPC STEM is also very effective for imaging magnetic field structures in magnetic materials, such as magnetic domains and skyrmions. Moreover, real-time imaging of electromagnetic field structures can
Particle localization in a double-well potential by pseudo-supersymmetric fields
International Nuclear Information System (INIS)
Bagrov, V. G.; Samsonov, B. F.; Shamshutdinova, V. V.
2011-01-01
We study properties of a particle moving in a double-well potential in the two-level approximation placed in an additional external time-dependent field. Using previously established property (J. Phys. A 41, 244023 (2008)) that any two-level system possesses a pseudo-supersymmetry we introduce the notion of pseudo-supersymmetric field. It is shown that these fields, even if their time dependence is not periodical, may produce the effect of localization of the particle in one of the wells of the double-well potential.
Quantum group structure and local fields in the algebraic approach to 2D gravity
Schnittger, Jens
1994-01-01
This review contains a summary of work by J.-L. Gervais and the author on the operator approach to 2d gravity. Special emphasis is placed on the construction of local observables -the Liouville exponentials and the Liouville field itself - and the underlying algebra of chiral vertex operators. The double quantum group structure arising from the presence of two screening charges is discussed and the generalized algebra and field operators are derived. In the last part, we show that our construction gives rise to a natural definition of a quantum tau function, which is a noncommutative version of the classical group-theoretic representation of the Liouville fields by Leznov and Saveliev.
Numerical forecast test on local wind fields at Qinshan Nuclear Power Plant
International Nuclear Information System (INIS)
Chen Xiaoqiu
2005-01-01
Non-hydrostatic, full compressible atmospheric dynamics model is applied to perform numerical forecast test on local wind fields at Qinshan nuclear power plant, and prognostic data are compared with observed data for wind fields. The results show that the prognostic of wind speeds is better than that of wind directions as compared with observed results. As the whole, the results of prognostic wind field are consistent with meteorological observation data, 54% of wind speeds are within a factor of 1.5, about 61% of the deviation of wind direction within the 1.5 azimuth (≤33.75 degrees) in the first six hours. (authors)
An unconventional canonical quantization of local scalar fields over quantum space-time
International Nuclear Information System (INIS)
Banai, M.
1985-12-01
An unconventional extension of the canonical quantization method is presented for a classical local field theory. The proposed canonical commutation relations have a solution in the A-valued Hilbert space where A is the algebra of the bounded operators of the Hilbert space Lsup(2) (IRsup(3)). The canonical equations as operator equations are equivalent formally with the classical field equations, and are well defined for interacting systems, too. This model of quantized field lacks some of the difficulties of the conventional approach. Examples satisfying the asymptotic condition provide examples for Haag-Kastler's axioms, however, they satisfy Wightman's axioms only partially. (author)
International Nuclear Information System (INIS)
Constantinescu, D.; Firpo, M.-C.
2012-01-01
Using Hamiltonian models for the magnetic field lines, we propose a methodology to improve their confinement through the creation of transport barriers. A local modification of the safety profile creating a low-shear zone is shown to be sufficient to locally enhance drastically the regularity of the magnetic field lines without requesting a reversed shear. The optimal benefits of low-shear are obtained when the value q 0 of the safety profile in the low-shear zone is sufficiently far from the main resonance values m/n with low m and n, in the case of large enough values of those (m, n) mode amplitudes. A practical implementation in tokamak plasmas should involve electron cyclotron current drive to locally modify the magnetic shear. (paper)
International Nuclear Information System (INIS)
Park, Byeolteo; Myung, Hyun
2014-01-01
With the development of unconventional gas, the technology of directional drilling has become more advanced. Underground localization is the key technique of directional drilling for real-time path following and system control. However, there are problems such as vibration, disconnection with external infrastructure, and magnetic field distortion. Conventional methods cannot solve these problems in real time or in various environments. In this paper, a novel underground localization algorithm using a re-measurement of the sequence of the magnetic field and pose graph SLAM (simultaneous localization and mapping) is introduced. The proposed algorithm exploits the property of the drilling system that the body passes through the previous pass. By comparing the recorded measurement from one magnetic sensor and the current re-measurement from another magnetic sensor, the proposed algorithm predicts the pose of the drilling system. The performance of the algorithm is validated through simulations and experiments. (paper)
Park, Byeolteo; Myung, Hyun
2014-12-01
With the development of unconventional gas, the technology of directional drilling has become more advanced. Underground localization is the key technique of directional drilling for real-time path following and system control. However, there are problems such as vibration, disconnection with external infrastructure, and magnetic field distortion. Conventional methods cannot solve these problems in real time or in various environments. In this paper, a novel underground localization algorithm using a re-measurement of the sequence of the magnetic field and pose graph SLAM (simultaneous localization and mapping) is introduced. The proposed algorithm exploits the property of the drilling system that the body passes through the previous pass. By comparing the recorded measurement from one magnetic sensor and the current re-measurement from another magnetic sensor, the proposed algorithm predicts the pose of the drilling system. The performance of the algorithm is validated through simulations and experiments.
Casimir Energy of the Nambu-Goto String with Gauss-Bonnet Term and Point-Like Masses at the Ends
Hadasz, Leszek
1999-09-01
We calculate the Casimir energy of the rotating Nambu-Goto string with the Gauss-Bonnet term in the action and point-like masses at the ends. This energy turns out to be negative for every values of the parameters of the model.
Casimir energy of the Nambu-Goto string with Gauss-Bonnet term and point-like masses at the ends
Hadasz, Leszek
1999-01-01
We calculate (using zeta function regularization) the Casimir energy of the rotating Nambu-Goto string with the Gauss-Bonnet term in the action and point-like masses at the ends. The resulting value turns out to be negative for all values of the parameters of the model.
Casimir Energy of the Nambu-Goto String with Gauss-Bonnet Term and Point-Like Masses at the Ends
International Nuclear Information System (INIS)
Hadasz, L.
1999-01-01
We calculate the Casimir energy of the rotating Nambu-Goto string with the Gauss-Bonnet term in the action and point-like masses at the ends. This energy turns out to be negative for every values of the parameters of the model. (author)
Bui, Huu Nguyen; Pham, Thanh Son; Ngo, Viet; Lee, Jong-Wook
2017-09-01
Controlling power to an unintended area is an important issue for enabling wireless power transfer (WPT) systems. The control allows us to enhance efficiency as well as suppress unnecessary flux leakage. The flux leakage from WPT can be reduced effectively via selective field localization. To realize field localization, we propose the use of cavities formed on a single metamaterial slab that acts as a defected metasurface. The cavity is formed by strong field confinement using a hybridization bandgap (HBG), which is created by wave interaction with a two-dimensional array of local resonators on the metasurface. This approach using an HBG demonstrates strong field localization around the cavity regions. Motivated by this result, we further investigate various cavity configurations for different sizes of the transmitter (Tx) and receiver (Rx) resonators. Experiments show that the area of field localization increases with the number of cavities, confirming the successful control of different cavity configurations on the metasurface. Transmission measurements of different cavities show that the number of cavities is an important parameter for efficiency, and excess cavities do not enhance the efficiency but increase unnecessary power leakage. Thus, there exists an optimum number of cavities for a given size ratio between the Tx and Rx resonators. For a 6:1 size ratio, this approach achieves efficiency improvements of 3.69× and 1.59× compared to free space and a uniform metasurface, respectively. For 10:1 and 10:2 size ratios, the efficiency improvements are 3.26× and 1.98× compared to free space and a uniform metasurface, respectively.
A simple model for localized-itinerant magnetic systems: crystal field effects
International Nuclear Information System (INIS)
Iannarella, L.; Silva, X.A. da; Guimarares, A.P.
1989-01-01
The magnetic behavior of a system consisting of localized electrons coupled to conduction electrons and submitted to an axial crystral field at T=0 K is ivestigated within the framework of the molecular field approximation. An analytical ionic magnetic state equation is deduced; it shows how the magnetization depends on the model parameters (exchange, crystal field, band occupation) and external magnetic field. A condition for the onset of spontaneous magnetic order is obtained and the ferro - and paramagnetic phases are studied. This study displays several features of real magnetic systems, including quenching or total suppression of the magnetic moments (depending on the relative value of the crystal field parameter) and exchange enhacement. The relevance of such model for the description of rare-earth intermetallic compounds is discussed. (author) [pt
Quasinormal modes of brane-localized standard model fields. II. Kerr black holes
International Nuclear Information System (INIS)
Kanti, P.; Konoplya, R. A.; Zhidenko, A.
2006-01-01
This paper presents a comprehensive study of the fundamental quasinormal modes of all standard model fields propagating on a brane embedded in a higher-dimensional rotating black-hole spacetime. The equations of motion for fields with spin s=0, 1/2 and 1 propagating in the induced-on-the-brane background are solved numerically, and the dependence of their QN spectra on the black-hole angular momentum and dimensionality of spacetime is investigated. It is found that the brane-localized field perturbations are longer-lived when the higher-dimensional black hole rotates faster, while an increase in the number of transverse-to-the-brane dimensions reduces their lifetime. Finally, the quality factor Q, that determines the best oscillator among the different field perturbations, is investigated and found to depend on properties of both the particular field studied (spin, multipole numbers) and the gravitational background (dimensionality, black-hole angular momentum parameter)
Theory of a gauge gravitational field at localization of the Einstein group
International Nuclear Information System (INIS)
Tunyak, V.N.
1985-01-01
Theory of a gauge gravitational field when localizing a group of movements of the Einstein homogeneous static Universe (the R x SO Einstein group (4)) has been formulated. Proceeding from tetrade components of the Einstein Universe the relation between the Riemann metrics and gauge fields of the Einstein group has been established. Metric coherence with torsion transforming to the Kristoffel coherence of the Einstein Universe has been found when switching out gauge fields. It is shown that within the limit of infinite radius of the Einstein Universe curvature the given Einstein-invariant gauge theory transforms to the tetrade gravitation theory with localized triade rotations. Exact solutions in the form of nonsingular cosmological models have been obtained
High-efficiency one-dimensional atom localization via two parallel standing-wave fields
International Nuclear Information System (INIS)
Wang, Zhiping; Wu, Xuqiang; Lu, Liang; Yu, Benli
2014-01-01
We present a new scheme of high-efficiency one-dimensional (1D) atom localization via measurement of upper state population or the probe absorption in a four-level N-type atomic system. By applying two classical standing-wave fields, the localization peak position and number, as well as the conditional position probability, can be easily controlled by the system parameters, and the sub-half-wavelength atom localization is also observed. More importantly, there is 100% detecting probability of the atom in the subwavelength domain when the corresponding conditions are satisfied. The proposed scheme may open up a promising way to achieve high-precision and high-efficiency 1D atom localization. (paper)
3D vector distribution of the electro-magnetic fields on a random gold film
Canneson, Damien; Berini, Bruno; Buil, Stéphanie; Hermier, Jean-Pierre; Quélin, Xavier
2018-05-01
The 3D vector distribution of the electro-magnetic fields at the very close vicinity of the surface of a random gold film is studied. Such films are well known for their properties of light confinement and large fluctuations of local density of optical states. Using Finite-Difference Time-Domain simulations, we show that it is possible to determine the local orientation of the electro-magnetic fields. This allows us to obtain a complete characterization of the fields. Large fluctuations of their amplitude are observed as previously shown. Here, we demonstrate large variations of their direction depending both on the position on the random gold film, and on the distance to it. Such characterization could be useful for a better understanding of applications like the coupling of point-like dipoles to such films.
RECONSTRUCTING THE INITIAL DENSITY FIELD OF THE LOCAL UNIVERSE: METHODS AND TESTS WITH MOCK CATALOGS
International Nuclear Information System (INIS)
Wang Huiyuan; Mo, H. J.; Yang Xiaohu; Van den Bosch, Frank C.
2013-01-01
Our research objective in this paper is to reconstruct an initial linear density field, which follows the multivariate Gaussian distribution with variances given by the linear power spectrum of the current cold dark matter model and evolves through gravitational instabilities to the present-day density field in the local universe. For this purpose, we develop a Hamiltonian Markov Chain Monte Carlo method to obtain the linear density field from a posterior probability function that consists of two components: a prior of a Gaussian density field with a given linear spectrum and a likelihood term that is given by the current density field. The present-day density field can be reconstructed from galaxy groups using the method developed in Wang et al. Using a realistic mock Sloan Digital Sky Survey DR7, obtained by populating dark matter halos in the Millennium simulation (MS) with galaxies, we show that our method can effectively and accurately recover both the amplitudes and phases of the initial, linear density field. To examine the accuracy of our method, we use N-body simulations to evolve these reconstructed initial conditions to the present day. The resimulated density field thus obtained accurately matches the original density field of the MS in the density range 0.3∼ –1 , much smaller than the translinear scale, which corresponds to a wavenumber of ∼0.15 h Mpc –1
THE NECESSITY OF IMPLEMENTING REFORMS IN THE FIELD OF LOCAL PUBLIC FINANCE
Directory of Open Access Journals (Sweden)
Vezure Oana Sabina
2013-06-01
Full Text Available The difficulties faced by local authorities as a result of the austerity conditions in which they work, the elements inherited from the previous regime, the need for additional resources to optimize public finance to meet the needs, optimally, if possible, citizens, require the design and continue the reform of public finances at the local level that correspond to these requirements. Optimization of the reform process in local public finances depend to a great extent on the use of financial levers of fiscal efficiency, fulfilment of the functions of public finance, the way resources are provided and how their administration for economic and social development. The uneven development of economic weakness of the assembly reflect and are unacceptable because, in their turn, become a source of economic and political instability. Responsibility for ensuring sufficient local revenue must not belong to a large measure, the central authorities, the context in which local authorities should prioritize finding solutions to supplement the local budget and obtain funds from the central budget. At the same time, cannot be intended directions of reform in the field of public administration without taking into account the financial implications reflected in the budgets for each level of Government, pyramid-shaped, from central to local level.
Effect of the local morphology in the field emission properties of conducting polymer surfaces
International Nuclear Information System (INIS)
De Assis, T A; Borondo, F; Benito, R M; Losada, J C; Andrade, R F S; Miranda, J G V; De Souza, Nara C; De Castilho, C M C; De B Mota, F
2013-01-01
In this work, we present systematic theoretical evidence of a relationship between the point local roughness exponent (PLRE) (which quantifies the heterogeneity of an irregular surface) and the cold field emission properties (indicated by the local current density and the macroscopic current density) of real polyaniline (PANI) surfaces, considered nowadays as very good candidates in the design of field emission devices. The latter are obtained from atomic force microscopy data. The electric field and potential are calculated in a region bounded by the rough PANI surface and a distant plane, both boundaries held at distinct potential values. We numerically solve Laplace’s equation subject to appropriate Dirichlet’s condition. Our results show that local roughness reveals the presence of specific sharp emitting spots with a smooth geometry, which are the main ones responsible (but not the only) for the emission efficiency of such surfaces for larger deposition times. Moreover, we have found, with a proper choice of a scale interval encompassing the experimentally measurable average grain length, a highly structured dependence of local current density on PLRE, considering different ticks of PANI surfaces. (paper)
Cui, Yong; Wang, Qiusheng; Yuan, Haiwen; Song, Xiao; Hu, Xuemin; Zhao, Luxing
2015-02-04
In the wireless sensor networks (WSNs) for electric field measurement system under the High-Voltage Direct Current (HVDC) transmission lines, it is necessary to obtain the electric field distribution with multiple sensors. The location information of each sensor is essential to the correct analysis of measurement results. Compared with the existing approach which gathers the location information by manually labelling sensors during deployment, the automatic localization can reduce the workload and improve the measurement efficiency. A novel and practical range-free localization algorithm for the localization of one-dimensional linear topology wireless networks in the electric field measurement system is presented. The algorithm utilizes unknown nodes' neighbor lists based on the Received Signal Strength Indicator (RSSI) values to determine the relative locations of nodes. The algorithm is able to handle the exceptional situation of the output permutation which can effectively improve the accuracy of localization. The performance of this algorithm under real circumstances has been evaluated through several experiments with different numbers of nodes and different node deployments in the China State Grid HVDC test base. Results show that the proposed algorithm achieves an accuracy of over 96% under different conditions.
Directory of Open Access Journals (Sweden)
Yong Cui
2015-02-01
Full Text Available In the wireless sensor networks (WSNs for electric field measurement system under the High-Voltage Direct Current (HVDC transmission lines, it is necessary to obtain the electric field distribution with multiple sensors. The location information of each sensor is essential to the correct analysis of measurement results. Compared with the existing approach which gathers the location information by manually labelling sensors during deployment, the automatic localization can reduce the workload and improve the measurement efficiency. A novel and practical range-free localization algorithm for the localization of one-dimensional linear topology wireless networks in the electric field measurement system is presented. The algorithm utilizes unknown nodes’ neighbor lists based on the Received Signal Strength Indicator (RSSI values to determine the relative locations of nodes. The algorithm is able to handle the exceptional situation of the output permutation which can effectively improve the accuracy of localization. The performance of this algorithm under real circumstances has been evaluated through several experiments with different numbers of nodes and different node deployments in the China State Grid HVDC test base. Results show that the proposed algorithm achieves an accuracy of over 96% under different conditions.
Field theoretic approach to dynamical orbital localization in ab initio molecular dynamics
International Nuclear Information System (INIS)
Thomas, Jordan W.; Iftimie, Radu; Tuckerman, Mark E.
2004-01-01
Techniques from gauge-field theory are employed to derive an alternative formulation of the Car-Parrinello ab initio molecular-dynamics method that allows maximally localized Wannier orbitals to be generated dynamically as the calculation proceeds. In particular, the Car-Parrinello Lagrangian is mapped onto an SU(n) non-Abelian gauge-field theory and the fictitious kinetic energy in the Car-Parrinello Lagrangian is modified to yield a fully gauge-invariant form. The Dirac gauge-fixing method is then employed to derive a set of equations of motion that automatically maintain orbital locality by restricting the orbitals to remain in the 'Wannier gauge'. An approximate algorithm for integrating the equations of motion that is stable and maintains orbital locality is then developed based on the exact equations of motion. It is shown in a realistic application (64 water molecules plus one hydrogen-chloride molecule in a periodic box) that orbital locality can be maintained with only a modest increase in CPU time. The ability to keep orbitals localized in an ab initio molecular-dynamics calculation is a crucial ingredient in the development of emerging linear scaling approaches
Localization and mass spectra of various matter fields on Weyl thin brane
Energy Technology Data Exchange (ETDEWEB)
Sui, Tao-Tao; Zhao, Li; Zhang, Yu-Peng [Lanzhou University, Institute of Theoretical Physics, Lanzhou (China); Xie, Qun-Ying [Lanzhou University, School of Information Science and Engineering, Lanzhou (China)
2017-06-15
It has been shown that the thin brane model in a five-dimensional Weyl gravity can deal with the wrong-signed Friedmann-like equation in the Randall-Sundrum-1 (RS1) model. In the Weyl brane model, there are also two branes with opposite brane tensions, but the four-dimensional graviton (the gravity zero mode) is localized near the negative tension brane, while our four-dimensional universe is localized on the positive tension brane. In this paper, we consider the mass spectra of various bulk matter fields (i.e., scalar, vector, and fermion fields) on the Weyl brane. It is shown that the zero modes of those matter fields can be localized on the positive tension brane under some conditions. The mass spectra of the bulk matter fields are equidistant for the higher excited states, and relatively sparse for the lower excited states. The size of the extra dimension determines the gap of the mass spectra. We also consider the correction to the Newtonian potential in this model and it is proportional to 1/r{sup 3}. (orig.)
Kimoto, Takuya; Yamazaki, Hideya; Suzuki, Gen; Aibe, Norihiro; Masui, Koji; Tatekawa, Kotoha; Sasaki, Naomi; Fujiwara, Hitoshi; Shiozaki, Atsushi; Konishi, Hirotaka; Nakamura, Satoaki; Yamada, Kei
2017-09-01
Radiotherapy is an effective treatment for the postoperative loco-regional recurrence of esophageal cancer; however, the optimal treatment field remains controversial. This study aims to evaluate the outcome of local field radiotherapy without elective nodal irradiation for postoperative loco-regional recurrence of esophageal cancer. We retrospectively investigated 35 patients treated for a postoperative loco-regional recurrence of esophageal cancer with local field radiotherapy between December 2008 and March 2016. The median irradiation dose was 60 Gy (range: 50-67.5 Gy). Thirty-one (88.6%) patients received concurrent chemotherapy. The median follow-up period was 18 months (range: 5-94 months). The 2-year overall survival was 55.7%, with a median survival time of 29.9 months. In the univariate analysis, the maximal diameter ≤20 mm (P = 0.0383), solitary lesion (P = 0.0352), and the complete remission after treatment (P = 0.00411) had a significantly better prognosis. A total of 27 of 35 patients (77.1%) had progressive disease (loco-regional failure [n = 9], distant metastasis [n = 7], and both loco-regional failure and distant metastasis [n = 11]). No patients had Grade 3 or greater mucositis. Local field radiotherapy is a considerable treatment option for postoperative loco-regional recurrence of esophageal cancer. © The Author 2017. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com
Spin dynamics under local gauge fields in chiral spin-orbit coupling systems
International Nuclear Information System (INIS)
Tan, S.G.; Jalil, M.B.A.; Fujita, T.; Liu, X.J.
2011-01-01
Research highlights: → We derive a modified LLG equation in magnetic systems with spin-orbit coupling (SOC). → Our results are applied to magnetic multilayers, and DMS and magnetic Rashba systems. → SOC mediated magnetization switching is predicted in rare earth metals (large SOC). → The magnetization trajectory and frequency can be modulated by applied voltage. → This facilitates potential application as tunable microwave oscillators. - Abstract: We present a theoretical description of local spin dynamics in magnetic systems with a chiral spin texture and finite spin-orbit coupling (SOC). Spin precession about the relativistic effective magnetic field in a SOC system gives rise to a non-Abelian SU(2) gauge field reminiscent of the Yang-Mills field. In addition, the adiabatic relaxation of electron spin along the local spin yields an U(1) x U(1) topological gauge (Berry) field. We derive the corresponding equation of motion i.e. modified Landau-Lifshitz-Gilbert (LLG) equation, for the local spin under the influence of these effects. Focusing on the SU(2) gauge, we obtain the spin torque magnitude, and the amplitude and frequency of spin oscillations in this system. Our theoretical estimates indicate significant spin torque and oscillations in systems with large spin-orbit coupling, which may be utilized in technological applications such as current-induced magnetization-switching and tunable microwave oscillators.
International Nuclear Information System (INIS)
Zekri, L.; Zekri, N.; Bouamrane, R.
1999-10-01
We present a new numerical method for determining exactly the effective conductivity and the local field for random RLC networks. This method is compared to a real space renormalization group method and the Frank and Lobb method. Although our method is slower than the Frank and Lobb method, it also computes exactly the local field for large size systems. We also show that the renormalization group method fails in determining the local field. (author)
International Nuclear Information System (INIS)
Watanabe, Tomohiko; Oya, Hiroshi; Watanabe, Kunihiko; Sato, Tetsuya.
1992-10-01
Extensive three-dimensional computer simulations of the magnetosphere-ionosphere (M-I) coupling are performed to study self-excitation of auroral arcs with special emphasis on 1) nonlinear evolution of the feedback instability in the M-I coupling system, 2) controlling mechanisms of the auroral arc structure, 3) formation of a field-aligned electric potential structure in association with the development of the feedback instability, and 4) effects of the parallel potential generation on auroral arc development. It is reconfirmed that the feedback instability produces a longitudinally elongated, latitudinally striated structure where the upward field-aligned current and the ionospheric density are locally enhanced. The following important new features are revealed. 1) The global distribution of the striation structure is primarily governed by the magnetospheric convection pattern and the ionospheric density distribution. 2) There appears a significant dawn-dusk asymmetry in the auroral arc formation, even though the apparent geometrical relationship is symmetric. 3) The recombination effect plays a significant role in the global, as well as local, development of the auroral arc structure. The nonlinearity of recombination, in conjunction with the closure of an arc-associated local field-aligned current system, acts to destroy an old arc and creates a new arc in a different but adjacent position. 4) A V-shaped field aligned potential structure is created in association with an auroral arc. Rapid increase in the electron density and the local upward field-aligned current of an arc arises as a result of enhanced ionization by precipitating electrons accelerated by the parallel potential. 5) A drastic oscillatory behavior of appearance and disappearance of auroral arcs is obtained when the ionization effect is strong. The period is primarily given by the Alfven bounce time. (J.P.N.)
3-Adic Cantor function on local fields and its p-adic derivative
International Nuclear Information System (INIS)
Qiu Hua; Su Weiyi
2007-01-01
The problem of 'rate of change' for fractal functions is a very important one in the study of local fields. In 1992, Su Weiyi has given a definition of derivative by virtue of pseudo-differential operators [Su W. Pseudo-differential operators and derivatives on locally compact Vilenkin groups. Sci China [series A] 1992;35(7A):826-36. Su W. Gibbs-Butzer derivatives and the applications. Numer Funct Anal Optimiz 1995;16(5 and 6):805-24. [2,3
Phase-Field Relaxation of Topology Optimization with Local Stress Constraints
DEFF Research Database (Denmark)
Stainko, Roman; Burger, Martin
2006-01-01
inequality constraints. We discretize the problem by finite elements and solve the arising finite-dimensional programming problems by a primal-dual interior point method. Numerical experiments for problems with local stress constraints based on different criteria indicate the success and robustness......We introduce a new relaxation scheme for structural topology optimization problems with local stress constraints based on a phase-field method. In the basic formulation we have a PDE-constrained optimization problem, where the finite element and design analysis are solved simultaneously...
3-Adic Cantor function on local fields and its p-adic derivative
Energy Technology Data Exchange (ETDEWEB)
Qiu Hua [Department of Mathematics, Nanjing University, Nanjing 210093 (China)]. E-mail: huatony@eyou.com; Su Weiyi [Department of Mathematics, Nanjing University, Nanjing 210093 (China)]. E-mail: suqiu@nju.edu.cn
2007-08-15
The problem of 'rate of change' for fractal functions is a very important one in the study of local fields. In 1992, Su Weiyi has given a definition of derivative by virtue of pseudo-differential operators [Su W. Pseudo-differential operators and derivatives on locally compact Vilenkin groups. Sci China [series A] 1992;35(7A):826-36. Su W. Gibbs-Butzer derivatives and the applications. Numer Funct Anal Optimiz 1995;16(5 and 6):805-24. [2,3
Stress fields and energy of disclination-type defects in zones of localized elastic distortions
Sukhanov, Ivan I.; Tyumentsev, Alexander N.; Ditenberg, Ivan A.
2016-11-01
This paper studies theoretically the elastically deformed state and analyzes deformation mechanisms in nanocrystals in the zones of localized elastic distortions and related disclination-type defects, such as dipole, quadrupole and multipole of partial disclinations. Significant differences in the energies of quadrupole and multipole configurations in comparison with nanodipole are revealed. The mechanism of deformation localization in the field of elastic distortions is proposed, which is a quasi-periodic sequence of formation and relaxation of various disclination ensembles with a periodic change in the energy of the defect.
Coulomb’s law corrections and fermion field localization in a tachyonic de Sitter thick braneworld
International Nuclear Information System (INIS)
Cartas-Fuentevilla, Roberto; Escalante, Alberto; Germán, Gabriel; Herrera-Aguilar, Alfredo; Mora-Luna, Refugio Rigel
2016-01-01
Following recent studies which show that it is possible to localize gravity as well as scalar and gauge vector fields in a tachyonic de Sitter thick braneworld, we investigate the solution of the gauge hierarchy problem, the localization of fermion fields in this model, the recovering of the Coulomb law on the non-relativistic limit of the Yukawa interaction between bulk fermions and gauge bosons localized in the brane, and confront the predicted 5D corrections to the photon mass with its upper experimental/observational bounds, finding the model physically viable since it passes these tests. In order to achieve the latter aims we first consider the Yukawa interaction term between the fermionic and the tachyonic scalar fields MF(T)ΨΨ-bar in the action and analyze four distinct tachyonic functions F(T) that lead to four different structures of the respective fermionic mass spectra with different physics. In particular, localization of the massless left-chiral fermion zero mode is possible for three of these cases. We further analyze the phenomenology of these Yukawa interactions among fermion fields and gauge bosons localized on the brane and obtain the crucial and necessary information to compute the corrections to Coulomb’s law coming from massive KK vector modes in the non-relativistic limit. These corrections are exponentially suppressed due to the presence of the mass gap in the mass spectrum of the bulk gauge vector field. From our results we conclude that corrections to Coulomb’s law in the thin brane limit have the same form (up to a numerical factor) as far as the left-chiral massless fermion field is localized on the brane. Finally we compute the corrections to the Coulomb’s law for an arbitrarily thick brane scenario which can be interpreted as 5D corrections to the photon mass. By performing consistent estimations with brane phenomenology, we found that the predicted corrections to the photon mass, which are well bounded by the experimentally
Coulomb’s law corrections and fermion field localization in a tachyonic de Sitter thick braneworld
Energy Technology Data Exchange (ETDEWEB)
Cartas-Fuentevilla, Roberto; Escalante, Alberto [Instituto de Física, Benemérita Universidad Autónoma de Puebla,Apdo. postal J-48, 72570 Puebla, Pue. (Mexico); Germán, Gabriel [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México,Apdo. Postal 48-3, 62251 Cuernavaca, Morelos (Mexico); Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road,Oxford, OX1 3NP (United Kingdom); Herrera-Aguilar, Alfredo [Instituto de Física, Benemérita Universidad Autónoma de Puebla,Apdo. postal J-48, 72570 Puebla, Pue. (Mexico); Institutode Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo,Edificio C-3, Ciudad Universitaria, CP 58040, Morelia, Michoacán (Mexico); Mora-Luna, Refugio Rigel [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México,Apdo. Postal 48-3, 62251 Cuernavaca, Morelos (Mexico)
2016-05-11
Following recent studies which show that it is possible to localize gravity as well as scalar and gauge vector fields in a tachyonic de Sitter thick braneworld, we investigate the solution of the gauge hierarchy problem, the localization of fermion fields in this model, the recovering of the Coulomb law on the non-relativistic limit of the Yukawa interaction between bulk fermions and gauge bosons localized in the brane, and confront the predicted 5D corrections to the photon mass with its upper experimental/observational bounds, finding the model physically viable since it passes these tests. In order to achieve the latter aims we first consider the Yukawa interaction term between the fermionic and the tachyonic scalar fields MF(T)ΨΨ-bar in the action and analyze four distinct tachyonic functions F(T) that lead to four different structures of the respective fermionic mass spectra with different physics. In particular, localization of the massless left-chiral fermion zero mode is possible for three of these cases. We further analyze the phenomenology of these Yukawa interactions among fermion fields and gauge bosons localized on the brane and obtain the crucial and necessary information to compute the corrections to Coulomb’s law coming from massive KK vector modes in the non-relativistic limit. These corrections are exponentially suppressed due to the presence of the mass gap in the mass spectrum of the bulk gauge vector field. From our results we conclude that corrections to Coulomb’s law in the thin brane limit have the same form (up to a numerical factor) as far as the left-chiral massless fermion field is localized on the brane. Finally we compute the corrections to the Coulomb’s law for an arbitrarily thick brane scenario which can be interpreted as 5D corrections to the photon mass. By performing consistent estimations with brane phenomenology, we found that the predicted corrections to the photon mass, which are well bounded by the experimentally
International Nuclear Information System (INIS)
Manoff, S.
1979-07-01
By utilization of the method of Lagrangians with covariant derivatives (MLCD) the different energy-momentum tensors (canonical, generalized canonical, symmetrical) and the relations between them are considered. On this basis, Einstein's theory of gravitation is studied as a field theory with a Lagrangian density of the type Lsub(g)=√-g.Lsub(g)(gsub(ij),Rsub(A)), (Rsub(A)=Rsub(ijkl)). It is shown that the energy-momentum tensors of the gravitational field can be defined for this theory. The symmetrical energy-momentum tensor of the gravitational field sub(gs)Tsub(k)sup(i), which in the general case is not a local conserved quantity (sub(gs)Tsub(k)sup(i)sub(;i) unequal 0) (in contrast to the material fields satisfying condition sub(Ms)Tsub(k)sup(i)sub(;i) = 0), is equal to zero for the gravitational field in vacuum (cosmological constant Λ = 0). Equations of the gravitational field of a new type are suggested, leading to equations of motion (sub(Ms)Tsub(k)sup(i) + sub(gs)Tsub(k)sup(i))sub(;i) = 0. The equations corresponding to the Lagrangian density Lsub(g)=(√-g/kappasub(o)) (R - lambda approximately), lambda approximately = const., are considered. The equations of Einstein Rsub(ij) = 0 are obtained in the case of gravitational field in vacuum. Some particular cases are examined as an illustration to material fields and the corresponding gravitational equations. (author)
Roy, Pratim; Ghosh, Tarun Kanti; Bhattacharya, Kaushik
2012-02-08
The present paper discusses magnetic confinement of the Dirac excitations in graphene in the presence of inhomogeneous magnetic fields. In the first case a magnetic field directed along the z axis whose magnitude is proportional to 1/r is chosen. In the next case we choose a more realistic magnetic field which does not blow up at the origin and gradually fades away from the origin. The magnetic fields chosen do not have any finite/infinite discontinuity for finite values of the radial coordinate. The novelty of the two magnetic fields is related to the equations which are used to find the excited spectra of the excitations. It turns out that the bound state solutions of the two-dimensional hydrogen atom problem are related to the spectra of graphene excitations in the presence of the 1/r (inverse-radial) magnetic field. For the other magnetic field profile one can use the knowledge of the bound state spectrum of a two-dimensional cutoff Coulomb potential to dictate the excitation spectra of graphene. The spectrum of the graphene excitations in the presence of the inverse-radial magnetic field can be exactly solved while the other case cannot be. In the later case we give the localized solutions of the zero-energy states in graphene.
Local probe (170Yb3+) measurements of magnetic fields in YBa2Cu3Ox
International Nuclear Information System (INIS)
Hodges, J.A.; Bonville, P.; Vincent, E.
1989-01-01
We introduce the technique of studying the field dependence of the electro-nuclear energy levels of a rare earth to measure the magnetic field present at the rare earth/yttrium site in YBa 2 Cu 3 O x . Measurements were made by 170 Yb spectroscopy. The hyperfine spectrum of the ground state Kramers doublet for Yb 3+ ions diluted into this matrix is sensitive to fields in the range 100 to 2000G. Flux penetration and trapping at the local site level have been measured in superconducting samples. A molecular field exists on the rare earth site in non superconducting samples suggesting that the ordered Cu2 magnetic moments are intrinsically non colinear
Education and Training Needs in the Field of Local Development in the Lower Danube Macro Region
Directory of Open Access Journals (Sweden)
Laurenţiu Tăchiciu
2010-11-01
Full Text Available The present paper is the result of an effort made by the authors to explore the needs of education and training in the field of local development, according to the situation in Romanian and Bulgarian Danube bordering regions, aiming at designing joint projects to address such needs between the universities to which authors are affiliated. Local development is here understood as a deliberately induced process of improving the welfare of local communities, which should be democratic, inclusive and sustainable, in particular with regard to creating competitive local economies, stimulating economic growth and ensuring better living conditions for the inhabitants. Local development is an important part of a governance process which involves complex interactions at various territorially defined levels: local, regional, national, cross-national, international. In the case of the regions considered in the present paper a historical opportunity is provided for them by the so called European Union Strategy for the Danube Region. In order to fully exploit this opportunity, the capacity to address local development issues should be strengthened in both countries, especially by well designed education and training programmes. This is why local development was considered a priority topic for the cooperation between the two universities. In the same framework, taking into consideration the challenges which are specific to the Lower Danube Region, other topics of interest were considered: logistics, tourism, consumer affairs or rural development. The authors of the present paper had to avoid overlapping with the work of the other teams. In particular, there are many common points between local development and rural development, because in both countries the regions on the border of Danube are predominately rural and significantly dependent on agriculture. Therefore, here, the needs for education and training are defined in strict correlation with the required
Local switching of two-dimensional superconductivity using the ferroelectric field effect
Takahashi, K. S.; Gabay, M.; Jaccard, D.; Shibuya, K.; Ohnishi, T.; Lippmaa, M.; Triscone, J.-M.
2006-05-01
Correlated oxides display a variety of extraordinary physical properties including high-temperature superconductivity and colossal magnetoresistance. In these materials, strong electronic correlations often lead to competing ground states that are sensitive to many parameters-in particular the doping level-so that complex phase diagrams are observed. A flexible way to explore the role of doping is to tune the electron or hole concentration with electric fields, as is done in standard semiconductor field effect transistors. Here we demonstrate a model oxide system based on high-quality heterostructures in which the ferroelectric field effect approach can be studied. We use a single-crystal film of the perovskite superconductor Nb-doped SrTiO3 as the superconducting channel and ferroelectric Pb(Zr,Ti)O3 as the gate oxide. Atomic force microscopy is used to locally reverse the ferroelectric polarization, thus inducing large resistivity and carrier modulations, resulting in a clear shift in the superconducting critical temperature. Field-induced switching from the normal state to the (zero resistance) superconducting state was achieved at a well-defined temperature. This unique system could lead to a field of research in which devices are realized by locally defining in the same material superconducting and normal regions with `perfect' interfaces, the interface being purely electronic. Using this approach, one could potentially design one-dimensional superconducting wires, superconducting rings and junctions, superconducting quantum interference devices (SQUIDs) or arrays of pinning centres.
Presnov, Denis E.; Bozhev, Ivan V.; Miakonkikh, Andrew V.; Simakin, Sergey G.; Trifonov, Artem S.; Krupenin, Vladimir A.
2018-02-01
We present the original method for fabricating a sensitive field/charge sensor based on field effect transistor (FET) with a nanowire channel that uses CMOS-compatible processes only. A FET with a kink-like silicon nanowire channel was fabricated from the inhomogeneously doped silicon on insulator wafer very close (˜100 nm) to the extremely sharp corner of a silicon chip forming local probe. The single e-beam lithographic process with a shadow deposition technique, followed by separate two reactive ion etching processes, was used to define the narrow semiconductor nanowire channel. The sensors charge sensitivity was evaluated to be in the range of 0.1-0.2 e /√{Hz } from the analysis of their transport and noise characteristics. The proposed method provides a good opportunity for the relatively simple manufacture of a local field sensor for measuring the electrical field distribution, potential profiles, and charge dynamics for a wide range of mesoscopic objects. Diagnostic systems and devices based on such sensors can be used in various fields of physics, chemistry, material science, biology, electronics, medicine, etc.
A note on the algebraic evaluation of correlators in local chiral conformal field theory
International Nuclear Information System (INIS)
Honecker, A.
1992-09-01
We comment on a program designed for the study of local chiral algebras and their representations in 2D conformal field theory. Based on the algebraic approach described by W. Nahm, this program efficiently calculates arbitrary n-point functions of these algebras. The program is designed such that calculations involving e.g. current algebras, W-algebras and N-Superconformal algebras can be performed. As a non-trivial application we construct an extension of the Virasoro algebra by two fields with spin four and six using the N=1-Super-Virasoro algebra. (orig.)
Atom localization via phase and amplitude control of the driving field
International Nuclear Information System (INIS)
Ghafoor, Fazal; Qamar, Sajid; Zubairy, M. Suhail
2002-01-01
Control of amplitude and phase of the driving field in an atom-field interaction leads towards the strong line narrowing and quenching in the spontaneous emission spectrum. We exploit this fact for the atom localization scheme and achieve a much better spatial resolution in the conditional position probability distribution of the atom. Most importantly the quenching in the spontaneous emission manifests itself in reducing the periodicity in the conditional position probability distribution and hence the uncertainty in a particular position measurement of the single atom by a factor of 2
Influence of plastic slip localization on grain boundary stress fields and microcrack nucleation
International Nuclear Information System (INIS)
Sauzay, Maxime; Vor, Kokleang
2013-01-01
Slip localization is widely observed in metallic polycrystals after tensile deformation, cyclic deformation (persistent slip bands) or pre-irradiation followed by tensile deformation (channels). Such strong deformation localized in thin slip bands induces local stress concentrations in the quasi-elastic matrix around, at the intersections between slip bands and grain boundaries where microcracks are often observed. Since the work of Stroh, such stress fields have been modeled using the dislocation pile-up theory which leads to stress singularities similar to the LEFM ones. The Griffith criterion has then been widely applied, leading usually to strong underestimations of the macroscopic stress for microcrack nucleation. In fact, slip band thickness is finite: 50-1000 nm depending on material, temperature and loading conditions. Then, many slip planes are plastically activated through the thickness. Stress fields have probably been overestimated using the pile-up theory which assumes that all dislocations are located on the same atomic plane. To evaluate more realistic stress fields, crystalline finite element (FE) computations are carried out using microstructure inputs (slip band aspect ratio and spacing). Slip bands (low critical resolved shear stress) are embedded in an elastic matrix. The following results are obtained concerning grain boundary normal stress fields: - strong influence of slip band thickness close to the slip band corner, which is not accounted for by the pile-up theory. But far away, the thickness has a negligible effect and the predicted stress fields are close to the one predicted by the pile-up theory, - analytical formulae are deduced from the numerous FE computation results which allows the prediction of surface/bulk slips as well as grain boundary stress fields. Slip band plasticity parameters, slip band length and thickness, Schmid factor and remote stress are taken into account. The dependence with respect to the various parameters can
Localizing gauge fields on a topological Abelian string and the Coulomb law
International Nuclear Information System (INIS)
Torrealba S, Rafael S.
2010-01-01
The confinement of electromagnetic field is studied in axial symmetrical, warped, six-dimensional brane world, using a recently proposed topological Abelian string-vortex solution as background. It was found, that the massless gauge field fluctuations follow four-dimensional Maxwell equations in the Lorenz gauge. The massless zero mode is localized when the thickness of the string vortex is less than 5β/4πe 2 v 2 and there are no other localized massless modes. There is also an infinite of nonlocalized massive Fourier modes, that follow four-dimensional Proca equations with a continuous spectrum. To compute the corrections to the Coulomb potential, a radial cutoff was introduced, in order to achieve a discrete mass spectrum. As a main result, a (R o /βR 2 ) correction was found for the four-dimensional effective Coulomb law; the result is in correspondence with the observed behavior of the Coulomb potential at today's measurable distances.
Squeezed bispectrum in the δ N formalism: local observer effect in field space
Energy Technology Data Exchange (ETDEWEB)
Tada, Yuichiro [Kavli Institute for the Physics and Mathematics of the Universe (WPI), UTIAS, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Vennin, Vincent, E-mail: yuichiro.tada@ipmu.jp, E-mail: vincent.vennin@port.ac.uk [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth, PO1 3FX (United Kingdom)
2017-02-01
The prospects of future galaxy surveys for non-Gaussianity measurements call for the development of robust techniques for computing the bispectrum of primordial cosmological perturbations. In this paper, we propose a novel approach to the calculation of the squeezed bispectrum in multiple-field inflation. With use of the δ N formalism, our framework sheds new light on the recently pointed out difference between the squeezed bispectrum for global observers and that for local observers, while allowing one to calculate both. For local observers in particular, the squeezed bispectrum is found to vanish in single-field inflation. Furthermore, our framework allows one to go beyond the near-equilateral ('small hierarchy') limit, and to automatically include intrinsic non-Gaussianities that do not need to be calculated separately. The explicit computational programme of our method is given and illustrated with a few examples.
Local-field correction in the lattice dynamics of b.b.c. transition metals
International Nuclear Information System (INIS)
Onwuagba, B.N.
1984-01-01
It is shown that the off-diagonal components of the inverse dielectric matrix which determine the local-field correction associated with s-d interactions, make contributions to the dynamical matrix for phonon dispersion in the body-centred cubic transition metals V, Nb and Ta which tend to cancel the Born-Mayer contribution, just as the diagonal components of the inverse dielectric matrix tend to cancel or screen the long-range (Coulombic) contribution. Numerical calculations show that the cancellation of the Born-Mayer contribution to the dynamical matrix by the local-field correction is such that the effective short-range interatomic potential turns out to be attractive rather than repulsive in these metals and accounts for some peculiar shapes of the major soft modes observed in these metals
Local field at an irradiated adatom on jellium: exact microscopic results
International Nuclear Information System (INIS)
Feibelman, P.J.
1980-01-01
The first microscopic correction to the image theory of the local field at an irradiated adatom has been calculated in the limit that the adatom is far from a jellium surface. The result of the calculation is the frequency-dependent position of the effective image plane in terms of the properties of semi-infinite jellium. The image plane position is found to be a complex number, reflecting the fact that the response of the surface electrons is lossy. Numerical calculations for r/sub s/=2 jellium suggest that the imaginary component of the image plane position is large enough to prevent large image enhancement of the local field at an adatom, casting doubt on the idea that such enhancement is responsible for the recently observed surface-enhanced Raman effect
The status and prospects of quantum non-local field theory
International Nuclear Information System (INIS)
Cornish, N.J.; Melbourne Univ., Parkville
1991-01-01
A critical review of the physical constraints on the form the non-locality can take is presented. The conclusion of this review is that non-locality must be restricted to interactions with the vacuum sea of virtual particles. A successful formulation of such a theory, Quantum Nonlocal Field Theory (QNFT), is applied to scalar electrodynamics and serves to illustrate how gauge invariance and manifest finiteness can be achieved. The importance of the infinite dimensional symmetry groups that occur in QNFT are discussed as an alternative to supersymmetry, the ability to generate masses by breaking the non-local symmetry with a non-invariant functional measure is given a critical assessment. To demonstrate some of the many novel applications QNFT may make possible, three disparate examples are mooted, the existence of electroweak monopoles, an mechanism for CP violation and the formulation of a finite perturbative theory of Quantum Gravity. 21 refs., ills
Convergence of solutions of a non-local phase-field system
Czech Academy of Sciences Publication Activity Database
Londen, S.-O.; Petzeltová, Hana
2011-01-01
Roč. 4, č. 3 (2011), s. 653-670 ISSN 1937-1632 R&D Projects: GA AV ČR(CZ) IAA100190606 Institutional research plan: CEZ:AV0Z10190503 Keywords : non-local phase-field systems * separation property * convergence to equilibria Subject RIV: BA - General Mathematics http://www.aimsciences.org/journals/displayArticles.jsp?paperID=5698
Liu, Ziyi; Gao, Junfeng; Yang, Guoguo; Zhang, Huan; He, Yong
2016-01-01
We present a pipeline for the visual localization and classification of agricultural pest insects by computing a saliency map and applying deep convolutional neural network (DCNN) learning. First, we used a global contrast region-based approach to compute a saliency map for localizing pest insect objects. Bounding squares containing targets were then extracted, resized to a fixed size, and used to construct a large standard database called Pest ID. This database was then utilized for self-learning of local image features which were, in turn, used for classification by DCNN. DCNN learning optimized the critical parameters, including size, number and convolutional stride of local receptive fields, dropout ratio and the final loss function. To demonstrate the practical utility of using DCNN, we explored different architectures by shrinking depth and width, and found effective sizes that can act as alternatives for practical applications. On the test set of paddy field images, our architectures achieved a mean Accuracy Precision (mAP) of 0.951, a significant improvement over previous methods. PMID:26864172
A novel full-field experimental method to measure the local compressibility of gas diffusion media
Energy Technology Data Exchange (ETDEWEB)
Lai, Yeh-Hung; Li, Yongqiang [Electrochemical Energy Research Lab, GM R and D, Honeoye Falls, NY 14472 (United States); Rock, Jeffrey A. [GM Powertrain, Honeoye Falls, NY 14472 (United States)
2010-05-15
The gas diffusion medium (GDM) in a proton exchange membrane (PEM) fuel cell needs to simultaneously satisfy the requirements of transporting reactant gases, removing product water, conducting electrons and heat, and providing mechanical support to the membrane electrode assembly (MEA). Concerning the localized over-compression which may force carbon fibers and other conductive debris into the membrane to cause fuel cell failure by electronically shorting through the membrane, we have developed a novel full-field experimental method to measure the local thickness and compressibility of GDM. Applying a uniform air pressure upon a thin polyimide film bonded on the top surface of the GDM with support from the bottom by a flat metal substrate and measuring the thickness change using the 3-D digital image correlation technique with an out-of-plane displacement resolution less than 0.5 {mu}m, we have determined the local thickness and compressive stress/strain behavior in the GDM. Using the local thickness and compressibility data over an area of 11.2 mm x 11.2 mm, we numerically construct the nominal compressive response of a commercial Toray trademark TGP-H-060 based GDM subjected to compression by flat platens. Good agreement in the nominal stress/strain curves from the numerical construction and direct experimental flat-platen measurement confirms the validity of the methodology proposed in this article. The result shows that a nominal pressure of 1.4 MPa compressed between two flat platens can introduce localized compressive stress concentration of more than 3 MPa in up to 1% of the total area at various locations from several hundred micrometers to 1 mm in diameter. We believe that this full-field experimental method can be useful in GDM material and process development to reduce the local hard spots and help to mitigate the membrane shorting failure in PEM fuel cells. (author)
A novel full-field experimental method to measure the local compressibility of gas diffusion media
Lai, Yeh-Hung; Li, Yongqiang; Rock, Jeffrey A.
The gas diffusion medium (GDM) in a proton exchange membrane (PEM) fuel cell needs to simultaneously satisfy the requirements of transporting reactant gases, removing product water, conducting electrons and heat, and providing mechanical support to the membrane electrode assembly (MEA). Concerning the localized over-compression which may force carbon fibers and other conductive debris into the membrane to cause fuel cell failure by electronically shorting through the membrane, we have developed a novel full-field experimental method to measure the local thickness and compressibility of GDM. Applying a uniform air pressure upon a thin polyimide film bonded on the top surface of the GDM with support from the bottom by a flat metal substrate and measuring the thickness change using the 3-D digital image correlation technique with an out-of-plane displacement resolution less than 0.5 μm, we have determined the local thickness and compressive stress/strain behavior in the GDM. Using the local thickness and compressibility data over an area of 11.2 mm × 11.2 mm, we numerically construct the nominal compressive response of a commercial Toray™ TGP-H-060 based GDM subjected to compression by flat platens. Good agreement in the nominal stress/strain curves from the numerical construction and direct experimental flat-platen measurement confirms the validity of the methodology proposed in this article. The result shows that a nominal pressure of 1.4 MPa compressed between two flat platens can introduce localized compressive stress concentration of more than 3 MPa in up to 1% of the total area at various locations from several hundred micrometers to 1 mm in diameter. We believe that this full-field experimental method can be useful in GDM material and process development to reduce the local hard spots and help to mitigate the membrane shorting failure in PEM fuel cells.
Action-at-a-distance metamaterials: Distributed local actuation through far-field global forces
Hedayati, R.; Mirzaali, M. J.; Vergani, L.; Zadpoor, A. A.
2018-03-01
Mechanical metamaterials are a sub-category of designer materials where the geometry of the material at the small-scale is rationally designed to give rise to unusual properties and functionalities. Here, we propose the concept of "action-at-a-distance" metamaterials where a specific pattern of local deformation is programmed into the fabric of (cellular) materials. The desired pattern of local actuation could then be achieved simply through the application of one single global and far-field force. We proposed graded designs of auxetic and conventional unit cells with changing Poisson's ratios as a way of making "action-at-a-distance" metamaterials. We explored five types of graded designs including linear, two types of radial gradients, checkered, and striped. Specimens were fabricated with indirect additive manufacturing and tested under compression, tension, and shear. Full-field strain maps measured with digital image correlation confirmed different patterns of local actuation under similar far-field strains. These materials have potential applications in soft (wearable) robotics and exosuits.
Action-at-a-distance metamaterials: Distributed local actuation through far-field global forces
Directory of Open Access Journals (Sweden)
R. Hedayati
2018-03-01
Full Text Available Mechanical metamaterials are a sub-category of designer materials where the geometry of the material at the small-scale is rationally designed to give rise to unusual properties and functionalities. Here, we propose the concept of “action-at-a-distance” metamaterials where a specific pattern of local deformation is programmed into the fabric of (cellular materials. The desired pattern of local actuation could then be achieved simply through the application of one single global and far-field force. We proposed graded designs of auxetic and conventional unit cells with changing Poisson’s ratios as a way of making “action-at-a-distance” metamaterials. We explored five types of graded designs including linear, two types of radial gradients, checkered, and striped. Specimens were fabricated with indirect additive manufacturing and tested under compression, tension, and shear. Full-field strain maps measured with digital image correlation confirmed different patterns of local actuation under similar far-field strains. These materials have potential applications in soft (wearable robotics and exosuits.
Dipolar local field in homogeneously magnetized quasi-two-dimensional crystals
International Nuclear Information System (INIS)
Leon, H; Estevez-Rams, E
2009-01-01
A formalism to calculate the dipolar local field in homogeneously magnetized quasi-two-dimensional (Q2D) crystals is comprehensively presented. Two fundamental tests for this formalism are accomplished: the transition from the Q2D quantities to the corresponding 3D ones; and the recovering of the macroscopic quantities of the 3D continuum theory. The additive separation between lattice and shape contributions to the local field allows an unambiguous interpretation of the respective effects. Calculated demagnetization tensors for square and circular lateral geometries of dipole layers show that for a single crystal layer an extremely thin film, but still with a finite thickness, is a better physical representation than a strictly 2D plane. Distinct close-packed structures are simulated and calculations of the local field at the nodes of the stacked 2D lattices allow one to establish the number of significantly coupled dipole layers, depending on the ratio between the interlayer distance and the 2D lattice constant. The conclusions drawn are of interest for the study of the dipolar interaction in magnetic ultrathin films and other nanostructured materials, where magnetic nanoparticles are embedded in non-magnetic matrices.
Reconstructing the Initial Density Field of the Local Universe: Methods and Tests with Mock Catalogs
Wang, Huiyuan; Mo, H. J.; Yang, Xiaohu; van den Bosch, Frank C.
2013-07-01
Our research objective in this paper is to reconstruct an initial linear density field, which follows the multivariate Gaussian distribution with variances given by the linear power spectrum of the current cold dark matter model and evolves through gravitational instabilities to the present-day density field in the local universe. For this purpose, we develop a Hamiltonian Markov Chain Monte Carlo method to obtain the linear density field from a posterior probability function that consists of two components: a prior of a Gaussian density field with a given linear spectrum and a likelihood term that is given by the current density field. The present-day density field can be reconstructed from galaxy groups using the method developed in Wang et al. Using a realistic mock Sloan Digital Sky Survey DR7, obtained by populating dark matter halos in the Millennium simulation (MS) with galaxies, we show that our method can effectively and accurately recover both the amplitudes and phases of the initial, linear density field. To examine the accuracy of our method, we use N-body simulations to evolve these reconstructed initial conditions to the present day. The resimulated density field thus obtained accurately matches the original density field of the MS in the density range 0.3 \\lesssim \\rho /\\bar{\\rho } \\lesssim 20 without any significant bias. In particular, the Fourier phases of the resimulated density fields are tightly correlated with those of the original simulation down to a scale corresponding to a wavenumber of ~1 h Mpc-1, much smaller than the translinear scale, which corresponds to a wavenumber of ~0.15 h Mpc-1.
Magnetic field in laser plasmas: non-local electron transport and reconnection
International Nuclear Information System (INIS)
Riquier, Raphael
2016-01-01
In the framework of the inertial confinement fusion, a pellet filled with the deuterium-tritium fuel is imploded, either through laser irradiation (direct drive, laser - low atomic number target interaction) or by the black body radiation from a cavity converting the laser radiation (indirect drive, laser - high atomic number target interaction). In both cases, a correct modeling of the electron transport is of first importance in order to have predictive hydro-radiative simulations. Nonetheless, it has been shown early on that the hypothesis of the linear transport are not valid in the framework of a solid target irradiated by a high power laser (I≅10 14 W/cm 2 ). This is due in part to very steep temperature gradients (kinetic effects, so-called 'non-local') and because of a magnetic field self-generated through the thermo-electric effect. Finally, the heat flux and the magnetic field are strongly coupled through two mechanisms: the advection of the field with the heat flux (Nernst effect) and the rotation and inhibition of the heat flux by the plasma's magnetization (Righi-Leduc effect).In this manuscript, we will first present the various electron transport models, particularly the non-local with magnetic field model included in the hydro-radiative code FCI2. Following, in order to validate this model, we will compare it first against a kinetic code, and then with an experiment during which the magnetic field has been probed through proton radiography. Once the model validated, we will use FCI2 simulations to explain the source and transport of the field, as well as its effect on the interaction. Finally, the reconnection of the magnetic field, during the irradiation of a solid target by two laser beams, will be studied. (author) [fr
Directory of Open Access Journals (Sweden)
J. C. K. Chow
2017-09-01
Full Text Available In the absence of external reference position information (e.g. surveyed targets or Global Navigation Satellite Systems Simultaneous Localization and Mapping (SLAM has proven to be an effective method for indoor navigation. The positioning drift can be reduced with regular loop-closures and global relaxation as the backend, thus achieving a good balance between exploration and exploitation. Although vision-based systems like laser scanners are typically deployed for SLAM, these sensors are heavy, energy inefficient, and expensive, making them unattractive for wearables or smartphone applications. However, the concept of SLAM can be extended to non-optical systems such as magnetometers. Instead of matching features such as walls and furniture using some variation of the Iterative Closest Point algorithm, the local magnetic field can be matched to provide loop-closure and global trajectory updates in a Gaussian Process (GP SLAM framework. With a MEMS-based inertial measurement unit providing a continuous trajectory, and the matching of locally distinct magnetic field maps, experimental results in this paper show that a drift-free navigation solution in an indoor environment with millimetre-level accuracy can be achieved. The GP-SLAM approach presented can be formulated as a maximum a posteriori estimation problem and it can naturally perform loop-detection, feature-to-feature distance minimization, global trajectory optimization, and magnetic field map estimation simultaneously. Spatially continuous features (i.e. smooth magnetic field signatures are used instead of discrete feature correspondences (e.g. point-to-point as in conventional vision-based SLAM. These position updates from the ambient magnetic field also provide enough information for calibrating the accelerometer bias and gyroscope bias in-use. The only restriction for this method is the need for magnetic disturbances (which is typically not an issue for indoor environments; however
Chow, J. C. K.
2017-09-01
In the absence of external reference position information (e.g. surveyed targets or Global Navigation Satellite Systems) Simultaneous Localization and Mapping (SLAM) has proven to be an effective method for indoor navigation. The positioning drift can be reduced with regular loop-closures and global relaxation as the backend, thus achieving a good balance between exploration and exploitation. Although vision-based systems like laser scanners are typically deployed for SLAM, these sensors are heavy, energy inefficient, and expensive, making them unattractive for wearables or smartphone applications. However, the concept of SLAM can be extended to non-optical systems such as magnetometers. Instead of matching features such as walls and furniture using some variation of the Iterative Closest Point algorithm, the local magnetic field can be matched to provide loop-closure and global trajectory updates in a Gaussian Process (GP) SLAM framework. With a MEMS-based inertial measurement unit providing a continuous trajectory, and the matching of locally distinct magnetic field maps, experimental results in this paper show that a drift-free navigation solution in an indoor environment with millimetre-level accuracy can be achieved. The GP-SLAM approach presented can be formulated as a maximum a posteriori estimation problem and it can naturally perform loop-detection, feature-to-feature distance minimization, global trajectory optimization, and magnetic field map estimation simultaneously. Spatially continuous features (i.e. smooth magnetic field signatures) are used instead of discrete feature correspondences (e.g. point-to-point) as in conventional vision-based SLAM. These position updates from the ambient magnetic field also provide enough information for calibrating the accelerometer bias and gyroscope bias in-use. The only restriction for this method is the need for magnetic disturbances (which is typically not an issue for indoor environments); however, no assumptions
Localized AdS_{5}×S^{5} Black Holes.
Dias, Óscar J C; Santos, Jorge E; Way, Benson
2016-10-07
According to heuristic arguments, global AdS_{5}×S^{5} black holes are expected to undergo a phase transition in the microcanonical ensemble. At high energies, one expects black holes that respect the symmetries of the S^{5}; at low energies, one expects "localized" black holes that appear pointlike on the S^{5}. According to anti-de Sitter/conformal field theory correspondence, N=4 supersymmetric Yang-Mills (SYM) theory on a 3-sphere should therefore exhibit spontaneous R-symmetry breaking at strong coupling. In this Letter, we numerically construct these localized black holes. We extrapolate the location of this phase transition, and compute the expectation value of the broken scalar operator with lowest conformal dimension. Via the correspondence, these results offer quantitative predictions for N=4 SYM theory.
Second-order Cosmological Perturbations Engendered by Point-like Masses
Energy Technology Data Exchange (ETDEWEB)
Brilenkov, Ruslan [Institute for Astro- and Particle Physics, University of Innsbruck, Technikerstrasse 25/8, A‐6020 Innsbruck (Austria); Eingorn, Maxim, E-mail: ruslan.brilenkov@gmail.com, E-mail: maxim.eingorn@gmail.com [North Carolina Central University, CREST and NASA Research Centers, 1801 Fayetteville St., Durham, NC 27707 (United States)
2017-08-20
In the ΛCDM framework, presenting nonrelativistic matter inhomogeneities as discrete massive particles, we develop the second‐order cosmological perturbation theory. Our approach relies on the weak gravitational field limit. The derived equations for the second‐order scalar, vector, and tensor metric corrections are suitable at arbitrary distances, including regions with nonlinear contrasts of the matter density. We thoroughly verify fulfillment of all Einstein equations, as well as self‐consistency of order assignments. In addition, we achieve logical positive results in the Minkowski background limit. Feasible investigations of the cosmological back-reaction manifestations by means of relativistic simulations are also outlined.
Quantum group structure and local fields in the algebraic approach to 2D gravity
Schnittger, J.
1995-07-01
This review contains a summary of the work by J.-L. Gervais and the author on the operator approach to 2d gravity. Special emphasis is placed on the construction of local observables — the Liouville exponentials and the Liouville field itself — and the underlying algebra of chiral vertex operators. The double quantum group structure arising from the presence of two screening charges is discussed and the generalized algebra and field operators are derived. In the last part, we show that our construction gives rise to a natural definition of a quantum tau function, which is a noncommutative version of the classical group-theoretic representation of the Liouville fields by Leznov and Saveliev.
Lubineau, Gilles
2015-03-01
We propose a domain decomposition formalism specifically designed for the identification of local elastic parameters based on full-field measurements. This technique is made possible by a multi-scale implementation of the constitutive compatibility method. Contrary to classical approaches, the constitutive compatibility method resolves first some eigenmodes of the stress field over the structure rather than directly trying to recover the material properties. A two steps micro/macro reconstruction of the stress field is performed: a Dirichlet identification problem is solved first over every subdomain, the macroscopic equilibrium is then ensured between the subdomains in a second step. We apply the method to large linear elastic 2D identification problems to efficiently produce estimates of the material properties at a much lower computational cost than classical approaches.
The canonical quantization of local scalar fields over quantum space-time
International Nuclear Information System (INIS)
Banai, M.
1983-05-01
Canonical quantization of a classical local field theory (CLFT) consisting of N real scalar fields is formulated in the Hilbert space over the sup(*)-algebra A of linear operators of L 2 (R 3 ). The canonical commutation relations (CCR) have an irreducible solution, unique up to A-unitary equivalence. The canonical equations as operator equations are equivalent to the classical (c) field equations. The interaction picture can be introduced in a well-defined manner. The main adventage of this treatment is that the corresponding S-matrix is free of divergences. The Feynman's graph technique is adaptable in a straightforward manner. This approach is a natural extension of the conventional canonical quantization method of quantum mechanics. (author)
A TEM method for analyzing local strain fields in irradiated materials
International Nuclear Information System (INIS)
Bennetch, J.I.; Jesser, W.A.
1983-01-01
Of great interest to the field of fracture mechanics is the strain field in front of a crack tip. In irradiated materials, cavities which naturally form as a result of radiation provide convenient internal markers. If a miniaturized irradiated tensile sample is pulled in situ in a transmission electron microscope (TEM), both the relative displacement of these cavities and their distortion in shape provide information on localized strain on a microscopic level. In addition, the TEM method allows direct correlation of active slip systems with crack propagation characteristics. To illustrate this method a strain field map was constructed about a crack propagating in a helium irradiated type 316 stainless steel sample containing large cavities. (orig.)
Field-aligned plasma-potential structure formed by local electron cyclotron resonance
International Nuclear Information System (INIS)
Hatakeyama, Rikizo; Kaneko, Toshiro; Sato, Noriyoshi
2001-01-01
The significance of basic experiments on field-aligned plasma-potential structure formed by local electron cyclotron resonance (ECR) is claimed based on the historical development of the investigation on electric double layer and electrostatic potential confinement of open-ended fusion-oriented plasmas. In the presence of a single ECR point in simple mirror-type configurations of magnetic field, a potential dip (thermal barrier) appears around this point, being followed by a subsequent potential hump (plug potential) along a collisionless plasma flow. The observed phenomenon gives a clear-cut physics to the formation of field-aligned plug potential with thermal barrier, which is closely related to the double layer formation triggered by a negative dip. (author)
Localization of electromagnetic field on the “Brouwer-island” and liquid metal embrittlement
Energy Technology Data Exchange (ETDEWEB)
Maksimenko, V.V.; Zagaynov, V.A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31, Kashirskoe shosse, 115409 Moscow (Russian Federation); Karpov Institute of Physical Chemistry, Vorontsovo Pole, 10, 105064 Moscow (Russian Federation); Agranovski, I.E., E-mail: I.Agranovski@griffith.edu.au [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31, Kashirskoe shosse, 115409 Moscow (Russian Federation); School of Engineering, Griffith University, Brisbane, 4111 QLD (Australia)
2015-03-01
Liquid metal embrittlement (LME) manifests itself as a sudden destruction of a metal sample if it is covered by a thin liquid film of eutectic mixture of specially selected metals. The proposed theoretical model of this phenomenon is based on an assumption related to the possibility of electromagnetic field localization in folds of interface between the phases or components of eutectic mixture filling cracks in solid metal surface (the typical example is In–Ga eutectic on Al-surface). Based on simultaneous presence of three different components in each space point of eutectic mixture (homogeneous In + Ga melt, solid In, and solid Ga), the system of interface folds could be simulated by the Brouwer surface – well known in topology. This surface separates three different components presented at each of its point. Such fractal surfaces posses by a finite volume. The volume occupied by the surface is defined as a difference between the eutectic mixture volume and the sum of volumes of its components. We investigate localization of external electromagnetic radiation in this system of folds. Due to very large magnitude of effective dielectric permeability of the considered system, at relative small volume change and fractal dimension of interface close to the value 3, the wave length of incident radiation inside the system is considerably decreased and multiscale folds are filled with localized photons. A probability of this process and the life time of the localized photons are calculated. The localized photons play crucial role in destruction of primary cracks in the metal surface. They are capable “to switch of” the Coulomb attraction of charge fluctuations on opposite “banks” of the crack filled with the eutectic. As a result, the crack could break down. - Highlights: • A new theoretical model of liquid metal embrittlement has been developed. • Light localization has a strong influence on liquid metal embrittlement. • Light is localized in folds at
Localization of electromagnetic field on the “Brouwer-island” and liquid metal embrittlement
International Nuclear Information System (INIS)
Maksimenko, V.V.; Zagaynov, V.A.; Agranovski, I.E.
2015-01-01
Liquid metal embrittlement (LME) manifests itself as a sudden destruction of a metal sample if it is covered by a thin liquid film of eutectic mixture of specially selected metals. The proposed theoretical model of this phenomenon is based on an assumption related to the possibility of electromagnetic field localization in folds of interface between the phases or components of eutectic mixture filling cracks in solid metal surface (the typical example is In–Ga eutectic on Al-surface). Based on simultaneous presence of three different components in each space point of eutectic mixture (homogeneous In + Ga melt, solid In, and solid Ga), the system of interface folds could be simulated by the Brouwer surface – well known in topology. This surface separates three different components presented at each of its point. Such fractal surfaces posses by a finite volume. The volume occupied by the surface is defined as a difference between the eutectic mixture volume and the sum of volumes of its components. We investigate localization of external electromagnetic radiation in this system of folds. Due to very large magnitude of effective dielectric permeability of the considered system, at relative small volume change and fractal dimension of interface close to the value 3, the wave length of incident radiation inside the system is considerably decreased and multiscale folds are filled with localized photons. A probability of this process and the life time of the localized photons are calculated. The localized photons play crucial role in destruction of primary cracks in the metal surface. They are capable “to switch of” the Coulomb attraction of charge fluctuations on opposite “banks” of the crack filled with the eutectic. As a result, the crack could break down. - Highlights: • A new theoretical model of liquid metal embrittlement has been developed. • Light localization has a strong influence on liquid metal embrittlement. • Light is localized in folds at
International Nuclear Information System (INIS)
Han, Yong; Lii-Rosales, A.; Zhou, Y.; Wang, C.-J.
2017-01-01
Theory and stochastic lattice-gas modeling is developed for the formation of intercalated metal islands in the gallery between the top layer and the underlying layer at the surface of layered materials. Our model for this process involves deposition of atoms, some fraction of which then enter the gallery through well-separated pointlike defects in the top layer. Subsequently, these atoms diffuse within the subsurface gallery leading to nucleation and growth of intercalated islands nearby the defect point source. For the case of a single point defect, continuum diffusion equation analysis provides insight into the nucleation kinetics. However, complementary tailored lattice-gas modeling produces a more comprehensive and quantitative characterization. We analyze the large spread in nucleation times and positions relative to the defect for the first nucleated island. We also consider the formation of subsequent islands and the evolution of island growth shapes. The shapes reflect in part our natural adoption of a hexagonal close-packed island structure. As a result, motivation and support for the model is provided by scanning tunneling microscopy observations of the formation of intercalated metal islands in highly-ordered pyrolytic graphite at higher temperatures.
International Nuclear Information System (INIS)
Choy, C.W.; Xiao, J.J.; Yu, K.W.
2007-01-01
The recent Green function formalism (GFF) has been used to study the local field distribution near a periodic interface separating two homogeneous media of different dielectric constants. In the GFF, the integral equations can be solved conveniently because of the existence of an analytic expression for the kernel (Greenian). However, due to a severe singularity in the Greenian, the formalism was formerly applied to compute the electric fields away from the interface region. In this work, we have succeeded in extending the GFF to compute the electric field inside the interface region by taking advantage of a sum rule. To our surprise, the strengths of the electric fields are quite similar in both media across the interface, despite of the large difference in dielectric constants. Moreover, we propose a simple effective medium approximation (EMA) to compute the electric field inside the interface region. We show that the EMA can indeed give an excellent description of the electric field, except near a surface plasmon resonance
Modular structure of local algebras associated with massless free quantum fields
International Nuclear Information System (INIS)
Hislop, P.D.
1984-01-01
The Tomita modular operators and the duality property for the local von Neumann algebras in quantum field models describing free massless particles with arbitrary helicity are studied. It is proved that the representation of the Poincare group in each model extends to a unitary representation SU(2,2), a covering group of the conformal group. An irreducible set of standard linear fields is shown to be covariant with respect to this representation. The von Neumann algebras associated with wedge, double-cone, and lightcone regions generated by these fields are proved to be unitarily equivalent. Using the results of Bisognano and Wichmann, the modular operators for these algebras are obtained in explicit form as conformal transformations and the duality property is proved. In the bose case, it is shown that the double-cone algebras constructed from any irreducible set of linear fields not including the standard fields do not satisfy duality and that any non-standard linear fields are not conformally covariant. A simple proof of duality, independent of the Tomita-Takesaki theory, for the double-cone algebras in the scalar case is also presented
PlumpyField – Network of local producers of RUF (contributed paper)
International Nuclear Information System (INIS)
Belete, Hilina
2014-01-01
Full text: Expanding coverage for the 35 million children in the world suffering from Moderate Acute Malnutrition (MAM) will require sustainably scaling up regional procurement of lipid-based RUSF products. Momentum is now building to achieve this aim through ten local ready-to-use food (RUF) producers in the PlumpyField Network, which was established by the French company Nutriset in 2005. These independently-owned factories, located in Sub-Saharan Africa, Asia, and the Caribbean, currently produce one-third of the world’s RUF supply. Overcoming substantial obstacles, they have achieved the same high quality standards of producers in Europe and the U.S., with increasingly competitive pricing. Being part of a mutually supportive and interactive network of RUF producers from around the world provides unique learning and partnership opportunities, from sharing insights on peanut supply chain development, increasingly complex quality challenges, to pooled procurement. This network system has been instrumental to the success of local production for the members of the PlumpyField Network. Historically, local producers achieving economies of scale and reliable local and international supply chains (i.e. for peanuts, oil, sugar, milk etc.) takes several years, making the cost of locally-procured products more expensive in the short term. However, there are numerous positive outcomes and externalities that cannot be ignored, such as decreased lead times (especially crucial to reach children with acute malnutrition), lower shipping costs, economic development, and maturation of the food processing and microbiological laboratory sectors. UNICEF and WFP have become leaders in local and regional procurement as they continually optimize their strategies to best meet global needs. Local production is often an important stimulant of public-private partnerships, including procurement of RUF by local governments for government-run acute malnutrition programs, furthering
MHODE: a local-homogeneity theory for improved source-parameter estimation of potential fields
Fedi, Maurizio; Florio, Giovanni; Paoletti, Valeria
2015-08-01
We describe a multihomogeneity theory for source-parameter estimation of potential fields. Similar to what happens for random source models, where the monofractal scaling-law has been generalized into a multifractal law, we propose to generalize the homogeneity law into a multihomogeneity law. This allows a theoretically correct approach to study real-world potential fields, which are inhomogeneous and so do not show scale invariance, except in the asymptotic regions (very near to or very far from their sources). Since the scaling properties of inhomogeneous fields change with the scale of observation, we show that they may be better studied at a set of scales than at a single scale and that a multihomogeneous model is needed to explain its complex scaling behaviour. In order to perform this task, we first introduce fractional-degree homogeneous fields, to show that: (i) homogeneous potential fields may have fractional or integer degree; (ii) the source-distributions for a fractional-degree are not confined in a bounded region, similarly to some integer-degree models, such as the infinite line mass and (iii) differently from the integer-degree case, the fractional-degree source distributions are no longer uniform density functions. Using this enlarged set of homogeneous fields, real-world anomaly fields are studied at different scales, by a simple search, at any local window W, for the best homogeneous field of either integer or fractional-degree, this yielding a multiscale set of local homogeneity-degrees and depth estimations which we call multihomogeneous model. It is so defined a new technique of source parameter estimation (Multi-HOmogeneity Depth Estimation, MHODE), permitting retrieval of the source parameters of complex sources. We test the method with inhomogeneous fields of finite sources, such as faults or cylinders, and show its effectiveness also in a real-case example. These applications show the usefulness of the new concepts, multihomogeneity and
Two-dimensional atom localization via two standing-wave fields in a four-level atomic system
International Nuclear Information System (INIS)
Zhang Hongtao; Wang Hui; Wang Zhiping
2011-01-01
We propose a scheme for the two-dimensional (2D) localization of an atom in a four-level Y-type atomic system. By applying two orthogonal standing-wave fields, the atoms can be localized at some special positions, leading to the formation of sub-wavelength 2D periodic spatial distributions. The localization peak position and number as well as the conditional position probability can be controlled by the intensities and detunings of optical fields.
International Nuclear Information System (INIS)
Smith, Roger J.
2008-01-01
A novel diagnostic technique for the remote and nonperturbative sensing of the local magnetic field in reactor relevant plasmas is presented. Pulsed polarimetry [Patent No. 12/150,169 (pending)] combines optical scattering with the Faraday effect. The polarimetric light detection and ranging (LIDAR)-like diagnostic has the potential to be a local B pol diagnostic on ITER and can achieve spatial resolutions of millimeters on high energy density (HED) plasmas using existing lasers. The pulsed polarimetry method is based on nonlocal measurements and subtle effects are introduced that are not present in either cw polarimetry or Thomson scattering LIDAR. Important features include the capability of simultaneously measuring local T e , n e , and B || along the line of sight, a resiliency to refractive effects, a short measurement duration providing near instantaneous data in time, and location for real-time feedback and control of magnetohydrodynamic (MHD) instabilities and the realization of a widely applicable internal magnetic field diagnostic for the magnetic fusion energy program. The technique improves for higher n e B || product and higher n e and is well suited for diagnosing the transient plasmas in the HED program. Larger devices such as ITER and DEMO are also better suited to the technique, allowing longer pulse lengths and thereby relaxing key technology constraints making pulsed polarimetry a valuable asset for next step devices. The pulsed polarimetry technique is clarified by way of illustration on the ITER tokamak and plasmas within the magnetized target fusion program within present technological means.
Ester carbonyl vibration as a sensitive probe of protein local electric field.
Pazos, Ileana M; Ghosh, Ayanjeet; Tucker, Matthew J; Gai, Feng
2014-06-10
The ability to quantify the local electrostatic environment of proteins and protein/peptide assemblies is key to gaining a microscopic understanding of many biological interactions and processes. Herein, we show that the ester carbonyl stretching vibration of two non-natural amino acids, L-aspartic acid 4-methyl ester and L-glutamic acid 5-methyl ester, is a convenient and sensitive probe in this regard, since its frequency correlates linearly with the local electrostatic field for both hydrogen-bonding and non-hydrogen-bonding environments. We expect that the resultant frequency-electric-field map will find use in various applications. Furthermore, we show that, when situated in a non-hydrogen-bonding environment, this probe can also be used to measure the local dielectric constant (ε). For example, its application to amyloid fibrils formed by Aβ(16-22) revealed that the interior of such β-sheet assemblies has an ε value of approximately 5.6. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Wan, Xiaoqing; Zhao, Chunhui
2017-06-01
As a competitive machine learning algorithm, the stacked sparse autoencoder (SSA) has achieved outstanding popularity in exploiting high-level features for classification of hyperspectral images (HSIs). In general, in the SSA architecture, the nodes between adjacent layers are fully connected and need to be iteratively fine-tuned during the pretraining stage; however, the nodes of previous layers further away may be less likely to have a dense correlation to the given node of subsequent layers. Therefore, to reduce the classification error and increase the learning rate, this paper proposes the general framework of locally connected SSA; that is, the biologically inspired local receptive field (LRF) constrained SSA architecture is employed to simultaneously characterize the local correlations of spectral features and extract high-level feature representations of hyperspectral data. In addition, the appropriate receptive field constraint is concurrently updated by measuring the spatial distances from the neighbor nodes to the corresponding node. Finally, the efficient random forest classifier is cascaded to the last hidden layer of the SSA architecture as a benchmark classifier. Experimental results on two real HSI datasets demonstrate that the proposed hierarchical LRF constrained stacked sparse autoencoder and random forest (SSARF) provides encouraging results with respect to other contrastive methods, for instance, the improvements of overall accuracy in a range of 0.72%-10.87% for the Indian Pines dataset and 0.74%-7.90% for the Kennedy Space Center dataset; moreover, it generates lower running time compared with the result provided by similar SSARF based methodology.
Vanishing of local non-Gaussianity in canonical single field inflation
Bravo, Rafael; Mooij, Sander; Palma, Gonzalo A.; Pradenas, Bastián
2018-05-01
We study the production of observable primordial local non-Gaussianity in two opposite regimes of canonical single field inflation: attractor (standard single field slow-roll inflation) and non attractor (ultra slow-roll inflation). In the attractor regime, the standard derivation of the bispectrum's squeezed limit using co-moving coordinates gives the well known Maldacena's consistency relation fNL = 5 (1‑ns) / 12. On the other hand, in the non-attractor regime, the squeezed limit offers a substantial violation of this relation given by fNL = 5/2. In this work we argue that, independently of whether inflation is attractor or non-attractor, the size of the observable primordial local non-Gaussianity is predicted to be fNLobs = 0 (a result that was already understood to hold in the case of attractor models). To show this, we follow the use of the so-called Conformal Fermi Coordinates (CFC), recently introduced in the literature. These coordinates parametrize the local environment of inertial observers in a perturbed FRW spacetime, allowing one to identify and compute gauge invariant quantities, such as n-point correlation functions. Concretely, we find that during inflation, after all the modes have exited the horizon, the squeezed limit of the 3-point correlation function of curvature perturbations vanishes in the CFC frame, regardless of the inflationary regime. We argue that such a cancellation should persist after inflation ends.
International Nuclear Information System (INIS)
Yamamoto, Atsushi; Yoshida, Shigeru; Okumura, Hiroshi; Inagaki, Masayo; Yamanishi, Hirokuni; Ito, Tetsuo; Furukawa, Michio
2015-01-01
The most effective and widespread method to decontaminate radioactive cesium from the Fukushima Daiichi Nuclear Power Plant Disaster was peeling topsoil. But the method had problems, such as large amounts of discarded soil and large-scale work. In nature, cyanobacteria formed biomats on the ground surface and facilitated peeling topsoil when the biomats dried. The cyanobacteria-facilitating peeling decontamination method utilized these cyanobacterial properties. Cyanobacteria are located all over Japan and 'local' cyanobacteria could be used for decontamination without introducing new species. Utilizing cyanobacteria could decrease the amount of discarded soil to about 30% and downsize the execution-scale to individual locations. Cyanobacterial biomats were easily cultivated, especially in rice fields, by maintaining wet conditions and exposure to 100 - 83% solar radiation. Shading by a thin net was helpful in maintaining an environment suitable for cyanobacteria. Nowadays, to prevent uptake of radioactive cesium into rice, K + is usually added to fertilizer in rice fields. The K + fertilization in rice fields might also enhance cyanobacterial capture of radioactive cesium, because high concentrations of K + enhanced cyanobacterial uptake of Cs + . Cyanobacteria could also mitigate the risk of radioactive cesium moving away from a decontaminating rice field. Therefore, the cyanobacteria-facilitating peeling decontamination method was proposed as an easy and safe 'D.I.Y.' method for both farmers and the environment. Besides, plowing rice fields with water before peeling improved the efficiency of this method, because plowing increased the radioactive cesium concentration in the topsoil. (author)
MgB_{2} nonlinear properties investigated under localized high rf magnetic field excitation
Directory of Open Access Journals (Sweden)
Tamin Tai
2012-12-01
Full Text Available The high transition temperature and low surface resistance of MgB_{2} attracts interest in its potential application in superconducting radio frequency accelerating cavities. However, compared to traditional Nb cavities, the viability of MgB_{2} at high rf fields is still open to question. Our approach is to study the nonlinear electrodynamics of the material under localized rf magnetic fields. Because of the presence of the small superconducting gap in the π band, the nonlinear response of MgB_{2} at low temperature is potentially complicated compared to a single-gap s-wave superconductor such as Nb. Understanding the mechanisms of nonlinearity coming from the two-band structure of MgB_{2}, as well as extrinsic sources of nonlinearity, is an urgent requirement. A localized and strong rf magnetic field, created by a magnetic write head, is integrated into our nonlinear-Meissner-effect scanning microwave microscope [T. Tai et al., IEEE Trans. Appl. Supercond. 21, 2615 (2011ITASE91051-822310.1109/TASC.2010.2096531]. MgB_{2} films with thickness 50 nm, fabricated by a hybrid physical-chemical vapor deposition technique on dielectric substrates, are measured at a fixed location and show a strongly temperature-dependent third harmonic response. We propose that several possible mechanisms are responsible for this nonlinear response.
Directory of Open Access Journals (Sweden)
Viljanen Ari
2015-01-01
Full Text Available Previous studies have demonstrated a close relationship between the time derivative of the horizontal geomagnetic field vector (dH/dt and geomagnetically induced currents (GIC at a nearby location in a power grid. Similarly, a high correlation exists between GIC and the local horizontal geoelectric field (E, typically modelled from a measured magnetic field. Considering GIC forecasting, it is not feasible to assume that detailed prediction of time series will be possible. Instead, other measures summarising the activity level over a given period are preferable. In this paper, we consider the 30-min maximum of dH/dt or E as a local activity indicator (|dH/dt|30 or |E|30. Concerning GIC, we use the sum of currents through the neutral leads at substations and apply its 30-min maximum as a regional activity measure (GIC30. We show that |dH/dt|30 at a single point yields a proxy for GIC activity in a larger region. A practical consequence is that if |dH/dt|30 can be predicted at some point then it is also possible to assess the expected GIC level in the surrounding area. As is also demonstrated, |E|30 and GIC30 depend linearly on |dH/dt|30, so there is no saturation with increasing geomagnetic activity contrary to often used activity indices.
Modular structure of the local algebras associated with the free massless scalar field theory
International Nuclear Information System (INIS)
Hislop, P.D.; Longo, R.
1982-01-01
The modular structure of the von Neuman algebra of local observables associated with a double cone in the vacuum representation of the free massless scalar field theory of any number of dimensions is described. The modular automorphism group is induced by the unitary implementation of a family of generalized fractional linear transformations on Minkowski space and is a subgroup of the conformal group. The modular conjugation operator is the anti-unitary impementation of a product of time reversal and relativistic ray inversion. The group generated by the modular conjugation operators for the local algebras associated with the family of double cone regions is the group of proper conformal transformations. A theorem is presented asserting the unitary equivalence of local algebras associated with lightcones, double cones and wedge regions. For the double cone algebras, this provides an explicitly realization of spacelike duality and establishes the known type III 1 factor property. It is shown that the timelike duality property of the lightcone algebras does not hold for the double cone algebras. A different definition of the von Neumann algebras associated with a region is introduced which agrees with the standard one for a lightcone or a double cone region but which allows the timelike duality property for the double cone algebras. In the case of one spatial dimension, the standard local algebras associated with the double cone regions satisfy both specelike and timelike duality. (orig.)
Magnetic field and contact resistance dependence of non-local charge imbalance
International Nuclear Information System (INIS)
Kleine, A; Baumgartner, A; Trbovic, J; Schoenenberger, C; Golubev, D S; Zaikin, A D
2010-01-01
Crossed Andreev reflection (CAR) in metallic nanostructures, a possible basis for solid-state electron entangler devices, is usually investigated by detecting non-local voltages in multi-terminal superconductor/normal metal devices. This task is difficult because other subgap processes may mask the effects of CAR. One of these processes is the generation of charge imbalance (CI) and the diffusion of non-equilibrium quasi-particles in the superconductor. Here we demonstrate a characteristic dependence of non-local CI on a magnetic field applied parallel to the superconducting wire, which can be understood by a generalization of the standard description of CI to non-local experiments. These results can be used to distinguish CAR and CI and to extract CI relaxation times in superconducting nanostructures. In addition, we investigate the dependence of non-local CI on the resistance of the injector and detector contacts and demonstrate a quantitative agreement with a recent theory using only material and junction characteristics extracted from separate direct measurements.
Precise Localization and Control of Catalytic Janus Micromotors Using Weak Magnetic Fields
Directory of Open Access Journals (Sweden)
Islam S. M. Khalil
2015-01-01
Full Text Available We experimentally demonstrate the precise localization of spherical Pt-Silica Janus micromotors (diameter 5 μm under the influence of controlled magnetic fields. First, we control the motion of the Janus micromotors in two-dimensional (2D space. The control system achieves precise localization within an average region-of-convergence of 7 μm. Second, we show that these micromotors provide sufficient propulsion force, allowing them to overcome drag and gravitational forces and move both downwards and upwards. This propulsion is studied by moving the micromotors in three-dimensional (3D space. The micromotors move downwards and upwards at average speeds of 19.1 μm/s and 9.8 μm/s, respectively. Moreover, our closed-loop control system achieves localization in 3D space within an average region-of-convergence of 6.3 μm in diameter. The precise motion control and localization of the Janus micromotors in 2D and 3D spaces provides broad possibilities for nanotechnology applications.
A local-to-global singularity theorem for quantum field theory on curved space-time
International Nuclear Information System (INIS)
Radzikowski, M.J.; York Univ.
1996-01-01
We prove that if a reference two-point distribution of positive type on a time orientable curved space-time (CST) satisfies a certain condition on its wave front set (the ''class P M,g condition'') and if any other two-point distribution (i) is of positive type, (ii) has the same antisymmetric part as the reference modulo smooth function and (iii) has the same local singularity structure, then it has the same global singularity structure. In the proof we use a smoothing, positivity-preserving pseudo-differential operator the support of whose symbol is restricted to a certain conic region which depends on the wave front set of the reference state. This local-to-global theorem, together with results published elsewhere, leads to a verification of a conjecture by Kay that for quasi-free states of the Klein-Gordon quantum field on a globally hyperbolic CST, the local Hadamard condition implies the global Hadamard condition. A counterexample to the local-to-global theorem on a strip in Minkowski space is given when the class P M,g condition is not assumed. (orig.)
Two-Photon Vibrational Spectroscopy using local optical fields of gold and silver nanostructures
Kneipp, Katrin; Kneipp, Janina; Kneipp, Harald
2007-03-01
Spectroscopic effects can be strongly affected when they take place in the immediate vicinity of metal nanostructures due to coupling to surface plasmons. We introduce a new approach that suggests highly efficient two-photon labels as well as two-photon vibrational spectroscopy for non-destructive chemical probing. The underlying spectroscopic effect is the incoherent inelastic scattering of two photons on the vibrational quantum states performed in the enhanced local optical fields of gold nanoparticles, surface enhanced hyper Raman scattering (SEHRS). We infer effective two-photon cross sections for SEHRS on the order of 10^5 GM, similar or higher than the best known cross sections for two-photon fluorescence. SEHRS combines the advantages of two-photon spectroscopy with the structural information of vibrational spectroscopy, and the high sensitivity and nanometer-scale local confinement of plasmonics-based spectroscopy.
Plasma and magnetic field characteristics of the distant polar cusp near local noon: The entry layer
International Nuclear Information System (INIS)
Paschmann, G.; Haerendel, G.; Sckopke, N.; Rosenbauer, H.; Hedgecock, P.C.
1976-01-01
Heos 2 plasma and magnetic field measurements in the distant polar cusp region reveal the existence of a plasma layer on day side field lines just inside the magnetopause. Density and temperature in this layer are nearly the same as they are in the adjacent magnetosheath, but the flow lacks the order existing both in the magnetosheath and in the plasma mantle. Flow directions toward and away from the sun but, in general, parallel to the field lines have been found. The magnetopause (as defined by a sudden rotation of the magnetic field vector) mostly coincides with the transition to ordered magnetosheath flow. The inner boundary of the layer is located just within the outer boundary of the hot ring current plasma. In the region of overlap the hot electrons have the signature of trapped particles, though often at reduced intensity. The magnetic field is strongly fluctuating in magnitude, while its orientation is more stable, consistent with a connection to the earth, but is systematically distorted out of the meridian plane. The layer is thought to be a consequence of the entry of magnetosheath plasma, which does not appear to be unobstructed, as has been claimed in the concept of a magnetospheric cleft. The magnetopause has a cusplike indentation which is elongated in local time. The existence of field-aligned currents (total strength approx. =10 6 A) and their location of flow in the inner part of the entry layer (into the ionosphere before noon and out of it after noon) are inferred from the systematic bending of field lines. It is proposed that the dynamo of the related current system is provided by the transfer of perpendicular momentum resulting from the plasma entry into the layer. The essential features of the entry layer might be compatible with the model of plasma flow through the magnetopause of Levy et al. (1964) if a 'dam' effect caused by the cusp geometry were added
International Nuclear Information System (INIS)
Schroer, Bert; Freie Universitaet, Berlin
2010-02-01
It is shown that there are significant conceptual differences between QM and QFT which make it difficult to view the latter as just a relativistic extension of the principles of QM. At the root of this is a fundamental distinction between Born localization in QM (which in the relativistic context changes its name to Newton- Wigner localization) and modular localization which is the localization underlying QFT, after one separates it from its standard presentation in terms of field coordinates. The first comes with a probability notion and projection operators, whereas the latter describes causal propagation in QFT and leads to thermal aspects of locally reduced finite energy states. The Born-Newton-Wigner localization in QFT is only applicable asymptotically and the covariant correlation between asymptotic in and out localization projectors is the basis of the existence of an invariant scattering matrix. In this first part of a two part essay the modular localization (the intrinsic content of field localization) and its philosophical consequences take the center stage. Important physical consequences of vacuum polarization will be the main topic of part II. The present division into two semi-autonomous essays is the result of a partition and extension of an originally one-part manuscript. (author)
International Nuclear Information System (INIS)
Schroer, Bert
2010-01-01
It is shown that there are significant conceptual differences between QM and QFT which make it difficult to view the latter as just a relativistic extension of the principles of QM. At the root of this is a fundamental distinction between Born-localization in QM (which in the relativistic context changes its name to Newton-Wigner localization) and modular localization which is the localization underlying QFT, after one separates it from its standard presentation in terms of field coordinates. The first comes with a probability notion and projection operators, whereas the latter describes causal propagation in QFT and leads to thermal aspects of locally reduced finite energy states. The Born-Newton-Wigner localization in QFT is only applicable asymptotically and the covariant correlation between asymptotic in and out localization projectors is the basis of the existence of an invariant scattering matrix. In this first part of a two part essay the modular localization (the intrinsic content of field localization) and its philosophical consequences take the center stage. Important physical consequences of vacuum polarization will be the main topic of part II. The present division into two semi-autonomous essays is the result of a partition and extension of an originally one-part manuscript. (author)
Energy Technology Data Exchange (ETDEWEB)
Schroer, Bert [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Freie Universitaet, Berlin (Germany). Inst. fuer Theoretische Physik
2010-02-15
It is shown that there are significant conceptual differences between QM and QFT which make it difficult to view the latter as just a relativistic extension of the principles of QM. At the root of this is a fundamental distinction between Born localization in QM (which in the relativistic context changes its name to Newton- Wigner localization) and modular localization which is the localization underlying QFT, after one separates it from its standard presentation in terms of field coordinates. The first comes with a probability notion and projection operators, whereas the latter describes causal propagation in QFT and leads to thermal aspects of locally reduced finite energy states. The Born-Newton-Wigner localization in QFT is only applicable asymptotically and the covariant correlation between asymptotic in and out localization projectors is the basis of the existence of an invariant scattering matrix. In this first part of a two part essay the modular localization (the intrinsic content of field localization) and its philosophical consequences take the center stage. Important physical consequences of vacuum polarization will be the main topic of part II. The present division into two semi-autonomous essays is the result of a partition and extension of an originally one-part manuscript. (author)
Optimal distribution of temperature points in μSR measurement of local field
International Nuclear Information System (INIS)
Pełka, R.; Zieliński, P.M.; Konieczny, P.; Wasiutyński, T.
2013-01-01
Three possible distributions of temperature points in the μSR measurement of local field (order parameter) are discussed. The least square method is applied to estimate the scale of the deviations of the fitted parameters from the true values. It indicates that the distribution corresponding to a uniform section of the order parameter values (uniform-in-signal) incurs the smallest errors. The distribution constructed on the basis of the zeros of the Chebyshev polynomials yields comparable uncertainties, while the uniform-in-temperature distribution turns out to be least effective incurring considerably larger errors. These findings can be useful while planning an order parameter measurement in the μSR experiment
Troiani, Filippo; Affronte, Marco; Carretta, Stefano; Santini, Paolo; Amoretti, Giuseppe
2005-05-20
We propose a scheme for the implementation of quantum gates which is based on the qubit encoding in antiferromagnetic molecular rings. We show that a proper engineering of the intercluster link would result in an effective coupling that vanishes as far as the system is kept in the computational space, while it is turned on by a selective excitation of specific auxiliary states. These are also shown to allow the performing of single-qubit and two-qubit gates without an individual addressing of the rings by means of local magnetic fields.
Energy Technology Data Exchange (ETDEWEB)
Dutta, Paramita; Karmakar, S. N. [Condensed Matter Physics Division, Saha Institute of Nuclear Physics, Sector-I, Block-AF, Bidhannagar, Kolkata-700 064 (India); Maiti, Santanu K., E-mail: santanu.maiti@isical.ac.in [Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 Barrackpore Trunk Road, Kolkata-700 108 (India)
2014-09-15
Electric field induced localization properties of a tight-binding ladder network in presence of backbone sites are investigated. Based on Green's function formalism we numerically calculate two-terminal transport together with density of states for different arrangements of atomic sites in the ladder and its backbone. Our results lead to a possibility of getting multiple mobility edges which essentially plays a switching action between a completely opaque to fully or partly conducting region upon the variation of system Fermi energy, and thus, support in fabricating mesoscopic or DNA-based switching devices.
International Nuclear Information System (INIS)
Lazzaro, E.; Comisso, L.; Valdettaro, L.
2010-01-01
In tokamaks magnetic islands arise from an unstable process of tearing and reconnecting of helical field lines across rational surfaces. After a linear stage the magnetic instability develops through three characteristic nonlinear stages where increasingly complex topological alterations occur in the form of the magnetic islands. The problem of response of reconnection process to the injection of an external current suitably localized is addressed using a four-field model in a plane slab plasma, with a novel extension to account consistently of the relevant neoclassical effects, such as bootstrap current and pressure anisotropy. The results found have implications on the interpretation of the possible mechanism of present day experimental results on neoclassical tearing modes as well as on the concepts for their control or avoidance.
Maximal locality and predictive power in higher-dimensional, compactified field theories
International Nuclear Information System (INIS)
Kubo, Jisuke; Nunami, Masanori
2004-01-01
To realize maximal locality in a trivial field theory, we maximize the ultraviolet cutoff of the theory by fine tuning the infrared values of the parameters. This optimization procedure is applied to the scalar theory in D + 1 dimensional (D ≥ 4) with one extra dimension compactified on a circle of radius R. The optimized, infrared values of the parameters are then compared with the corresponding ones of the uncompactified theory in D dimensions, which is assumed to be the low-energy effective theory. We find that these values approximately agree with each other as long as R -1 > approx sM is satisfied, where s ≅ 10, 50, 50, 100 for D = 4,5,6,7, and M is a typical scale of the D-dimensional theory. This result supports the previously made claim that the maximization of the ultraviolet cutoff in a nonrenormalizable field theory can give the theory more predictive power. (author)
International Nuclear Information System (INIS)
Hagelberg, F.; Das, T.P.; Speidel, K.
1993-01-01
The transient field phenomenon has been ascribed to a polarization transfer between the electrons of the ionic projectiles and the surplus of majority spin electrons of the ferromagnetic host over the minority spin electrons. Earlier attempts to explain this crucial process failed to account for the order of magnitude of the experimentally observed transient field strengths. A recent model which proposes spin exchange scattering between bound projectile electrons and quasifree host electrons as the mechanism of polarization transfer arrives at the correct orders of magnitude but is in conflict with the weak velocity dependence of the experimental polarization, exhibiting a strongly decreasing behavior with increasing velocity. The new model presented here proposes spin exchange between the ionic shell and localized electrons of the ferromagnet as a more adequate approach to the problem. It is shown that calculations involving hydrogenlike ions explain the size of the experimentally observed polarization effects as well as their velocity dependence for various ion probes traversing thin iron foils
String Chopping and Time-ordered Products of Linear String-localized Quantum Fields
Cardoso, Lucas T.; Mund, Jens; Várilly, Joseph C.
2018-03-01
For a renormalizability proof of perturbative models in the Epstein-Glaser scheme with string-localized quantum fields, one needs to know what freedom one has in the definition of time-ordered products of the interaction Lagrangian. This paper provides a first step in that direction. The basic issue is the presence of an open set of n-tuples of strings which cannot be chronologically ordered. We resolve it by showing that almost all such string configurations can be dissected into finitely many pieces which can indeed be chronologically ordered. This fixes the time-ordered products of linear field factors outside a nullset of string configurations. (The extension across the nullset, as well as the definition of time-ordered products of Wick monomials, will be discussed elsewhere).
Tissue heterogeneity as a mechanism for localized neural stimulation by applied electric fields
International Nuclear Information System (INIS)
Miranda, P C; Correia, L; Salvador, R; Basser, P J
2007-01-01
We investigate the heterogeneity of electrical conductivity as a new mechanism to stimulate excitable tissues via applied electric fields. In particular, we show that stimulation of axons crossing internal boundaries can occur at boundaries where the electric conductivity of the volume conductor changes abruptly. The effectiveness of this and other stimulation mechanisms was compared by means of models and computer simulations in the context of transcranial magnetic stimulation. While, for a given stimulation intensity, the largest membrane depolarization occurred where an axon terminates or bends sharply in a high electric field region, a slightly smaller membrane depolarization, still sufficient to generate action potentials, also occurred at an internal boundary where the conductivity jumped from 0.143 S m -1 to 0.333 S m -1 , simulating a white-matter-grey-matter interface. Tissue heterogeneity can also give rise to local electric field gradients that are considerably stronger and more focal than those impressed by the stimulation coil and that can affect the membrane potential, albeit to a lesser extent than the two mechanisms mentioned above. Tissue heterogeneity may play an important role in electric and magnetic 'far-field' stimulation
Tissue heterogeneity as a mechanism for localized neural stimulation by applied electric fields
Energy Technology Data Exchange (ETDEWEB)
Miranda, P C [Institute of Biophysics and Biomedical Engineering, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon (Portugal); Correia, L [Institute of Biophysics and Biomedical Engineering, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon (Portugal); Salvador, R [Institute of Biophysics and Biomedical Engineering, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon (Portugal); Basser, P J [Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD 20892-1428 (United States)
2007-09-21
We investigate the heterogeneity of electrical conductivity as a new mechanism to stimulate excitable tissues via applied electric fields. In particular, we show that stimulation of axons crossing internal boundaries can occur at boundaries where the electric conductivity of the volume conductor changes abruptly. The effectiveness of this and other stimulation mechanisms was compared by means of models and computer simulations in the context of transcranial magnetic stimulation. While, for a given stimulation intensity, the largest membrane depolarization occurred where an axon terminates or bends sharply in a high electric field region, a slightly smaller membrane depolarization, still sufficient to generate action potentials, also occurred at an internal boundary where the conductivity jumped from 0.143 S m{sup -1} to 0.333 S m{sup -1}, simulating a white-matter-grey-matter interface. Tissue heterogeneity can also give rise to local electric field gradients that are considerably stronger and more focal than those impressed by the stimulation coil and that can affect the membrane potential, albeit to a lesser extent than the two mechanisms mentioned above. Tissue heterogeneity may play an important role in electric and magnetic 'far-field' stimulation.
Sharma, Abhinav; Tiwari, Vijeet; Kumar, Vineet; Mandal, Tapas Kumar; Bandyopadhyay, Dipankar
2014-10-01
Strategic application of external electrostatic field on a pressure-driven two-phase flow inside a microchannel can transform the stratified or slug flow patterns into droplets. The localized electrohydrodynamic stress at the interface of the immiscible liquids can engender a liquid-dielectrophoretic deformation, which disrupts the balance of the viscous, capillary, and inertial forces of a pressure-driven flow to engender such flow morphologies. Interestingly, the size, shape, and frequency of the droplets can be tuned by varying the field intensity, location of the electric field, surface properties of the channel or fluids, viscosity ratio of the fluids, and the flow ratio of the phases. Higher field intensity with lower interfacial tension is found to facilitate the oil droplet formation with a higher throughput inside the hydrophilic microchannels. The method is successful in breaking down the regular pressure-driven flow patterns even when the fluid inlets are exchanged in the microchannel. The simulations identify the conditions to develop interesting flow morphologies, such as (i) an array of miniaturized spherical or hemispherical or elongated oil drops in continuous water phase, (ii) "oil-in-water" microemulsion with varying size and shape of oil droplets. The results reported can be of significance in improving the efficiency of multiphase microreactors where the flow patterns composed of droplets are preferred because of the availability of higher interfacial area for reactions or heat and mass exchange. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Radiofrequency Field Distribution Assessment in Indoor Areas Covered by Wireless Local Area Network
Directory of Open Access Journals (Sweden)
HELBET, R.
2009-02-01
Full Text Available Electromagnetic environment becomes day by day more congested. Radio communication systems in the short range are now part of everyday life, and there is a need to also assess the pollution level due to their emission if we take into account human health and protection. There is consistent scientific evidence that environmental electromagnetic field may cause undesirable biological effects or even health hazards. Present paper aims at giving a view on exposure level due to wireless local area networks (WLAN emission solely, as part of environmental radiofrequency pollution. Highly accurate measurements were made indoor by using a frequency-selective measurement system and identifying the correct settings for an error-minimum assessment. We focused on analysis of the electric flux density distribution inside a room, in the far field of the emitting antennas, in case of a single network communication channel. We analyze the influence the network configuration parameters have on the field level. Distance from the source and traffic rate are also important parameters that affect the exposure level. Our measurements indicate that in the immediate vicinity of the WLAN stations the average field may reach as much as 13% from the present accepted reference levels given in the human exposure standards.
Near-Field Sound Localization Based on the Small Profile Monaural Structure
Directory of Open Access Journals (Sweden)
Youngwoong Kim
2015-11-01
Full Text Available The acoustic wave around a sound source in the near-field area presents unconventional properties in the temporal, spectral, and spatial domains due to the propagation mechanism. This paper investigates a near-field sound localizer in a small profile structure with a single microphone. The asymmetric structure around the microphone provides a distinctive spectral variation that can be recognized by the dedicated algorithm for directional localization. The physical structure consists of ten pipes of different lengths in a vertical fashion and rectangular wings positioned between the pipes in radial directions. The sound from an individual direction travels through the nearest open pipe, which generates the particular fundamental frequency according to the acoustic resonance. The Cepstral parameter is modified to evaluate the fundamental frequency. Once the system estimates the fundamental frequency of the received signal, the length of arrival and angle of arrival (AoA are derived by the designed model. From an azimuthal distance of 3–15 cm from the outer body of the pipes, the extensive acoustic experiments with a 3D-printed structure show that the direct and side directions deliver average hit rates of 89% and 73%, respectively. The closer positions to the system demonstrate higher accuracy, and the overall hit rate performance is 78% up to 15 cm away from the structure body.
Locality for quantum systems on graphs depends on the number field
Hall, H. Tracy; Severini, Simone
2013-07-01
Adapting a definition of Aaronson and Ambainis (2005 Theory Comput. 1 47-79), we call a quantum dynamics on a digraph saturated Z-local if the nonzero transition amplitudes specifying the unitary evolution are in exact correspondence with the directed edges (including loops) of the digraph. This idea appears recurrently in a variety of contexts including angular momentum, quantum chaos, and combinatorial matrix theory. Complete characterization of the digraph properties that allow such a process to exist is a long-standing open question that can also be formulated in terms of minimum rank problems. We prove that saturated Z-local dynamics involving complex amplitudes occur on a proper superset of the digraphs that allow restriction to the real numbers or, even further, the rationals. Consequently, among these fields, complex numbers guarantee the largest possible choice of topologies supporting a discrete quantum evolution. A similar construction separates complex numbers from the skew field of quaternions. The result proposes a concrete ground for distinguishing between complex and quaternionic quantum mechanics.
Locality for quantum systems on graphs depends on the number field
International Nuclear Information System (INIS)
Hall, H Tracy; Severini, Simone
2013-01-01
Adapting a definition of Aaronson and Ambainis (2005 Theory Comput. 1 47–79), we call a quantum dynamics on a digraph saturated Z-local if the nonzero transition amplitudes specifying the unitary evolution are in exact correspondence with the directed edges (including loops) of the digraph. This idea appears recurrently in a variety of contexts including angular momentum, quantum chaos, and combinatorial matrix theory. Complete characterization of the digraph properties that allow such a process to exist is a long-standing open question that can also be formulated in terms of minimum rank problems. We prove that saturated Z-local dynamics involving complex amplitudes occur on a proper superset of the digraphs that allow restriction to the real numbers or, even further, the rationals. Consequently, among these fields, complex numbers guarantee the largest possible choice of topologies supporting a discrete quantum evolution. A similar construction separates complex numbers from the skew field of quaternions. The result proposes a concrete ground for distinguishing between complex and quaternionic quantum mechanics. (paper)
Cook, David O.; Kasliwal, Mansi; Van Sistine, Anglea; Kaplan, David; iPTF
2018-01-01
In this talk I introduce the Census of the Local Universe (CLU) galaxy survey. The survey uses 4 wavelength-adjacent, narrowband filters to search for emission-line (Hα) sources across ~3π (26,470 deg2) of the sky and out to distance of 200 Mpc. I will present an analysis of galaxy candidates in 14 preliminary fields (out of 3626) to assess the limits of the survey and the potential for finding new galaxies in the local Universe. We anticipate finding tens-of-thousands of new galaxies in the full ~3π survey. In addition, I present some interesting galaxies found in these fields, which include: newly discovered blue compact dwarfs (e.g., blueberries), 1 new green pea, 1 new QSO, and a known planetary nebula. The majority of the CLU galaxies show properties similar to normal star-forming galaxies; however, the newly discovered blueberries tend to have high star formation rates for their given stellar mass.
Local-Field Distribution of Two Dielectric Inclusions at Small Separation
Siu, Yuet-Lun; Yu, Kin-Wah
2001-03-01
When two dielectric inclusions approach to each other in a composite medium, significant mutual polarization effects must occur. These effects are multipolar in nature and are difficult to treat from first principles(J. D. Jackson, Classical Electrodynamics), 2nd edition, (Wiley, New York, 1975).. In this work, we employ the discrete-dipole theory(B. T. Draine and P. J. Flatau, J. Opt. Soc. Am. A 11) 1491 (1994). to account for the mutual polarization effects by dividing the inclusions into many small subparts. We begin the calculation at small inclusion sizes and large separation, where the point-dipole limit being valid, and proceed to larger inclusion sizes and small separation, for which the mutual polarization effect becomes important. Then, we apply the theory to determine the dipole moment of each subpart self-consistently. In this way, each dipole moment yields the local electric field, which in turn polarizes the neighboring dipoles. We also begin the calculation at small inclusion sizes and large separation, where the point-dipole limit being valid, and proceed to larger inclusion sizes and small separation. Our resluts indicate that convergence is achieved with moderate computational effects. The results produce valuable information about the local electric field distribution, which is relevant to optical absorption due to surface phonon-polaritons of ionic microcrystals.
Fault-tolerant design of local controller for the poloidal field converter control system on ITER
International Nuclear Information System (INIS)
Shen, Jun; Fu, Peng; Gao, Ge; He, Shiying; Huang, Liansheng; Zhu, Lili; Chen, Xiaojiao
2016-01-01
Highlights: • The requirements on the Local Control Cubicles (LCC) for ITER Poloidal Field Converter are analyzed. • Decoupled service-based software architecture is proposed to make control loops on LCC running at varying cycle-time. • Fault detection and recovery methods for the LCC are developed to enhance the system. • The performance of the LCC with or without fault-tolerant feature is tested and compared. - Abstract: The control system for the Poloidal Field (PF) on ITER is a synchronously networked control system, which has several kinds of computational controllers. The Local Control Cubicles (LCC) play a critical role in the networked control system for they are the interface to all input and output signals. Thus, some additional work must be done to guarantee the LCCs proper operation under influence of faults. This paper mainly analyzes the system demands of the LCCs and faults which have been encountered recently. In order to handle these faults, decoupled service-based software architecture has been proposed. Based on this architecture, fault detection and system recovery methods, such as redundancy and rejuvenation, have been incorporated to achieve a fault-tolerant private network with the aid of QNX operating system. Unlike the conventional method, this method requires no additional hardware and can be achieved relatively easily. To demonstrate effectiveness the LCCs have been successfully tested during the recent PF Converter Unit performance tests for ITER.
Fault-tolerant design of local controller for the poloidal field converter control system on ITER
Energy Technology Data Exchange (ETDEWEB)
Shen, Jun; Fu, Peng; Gao, Ge; He, Shiying; Huang, Liansheng, E-mail: huangls@ipp.ac.cn; Zhu, Lili; Chen, Xiaojiao
2016-11-15
Highlights: • The requirements on the Local Control Cubicles (LCC) for ITER Poloidal Field Converter are analyzed. • Decoupled service-based software architecture is proposed to make control loops on LCC running at varying cycle-time. • Fault detection and recovery methods for the LCC are developed to enhance the system. • The performance of the LCC with or without fault-tolerant feature is tested and compared. - Abstract: The control system for the Poloidal Field (PF) on ITER is a synchronously networked control system, which has several kinds of computational controllers. The Local Control Cubicles (LCC) play a critical role in the networked control system for they are the interface to all input and output signals. Thus, some additional work must be done to guarantee the LCCs proper operation under influence of faults. This paper mainly analyzes the system demands of the LCCs and faults which have been encountered recently. In order to handle these faults, decoupled service-based software architecture has been proposed. Based on this architecture, fault detection and system recovery methods, such as redundancy and rejuvenation, have been incorporated to achieve a fault-tolerant private network with the aid of QNX operating system. Unlike the conventional method, this method requires no additional hardware and can be achieved relatively easily. To demonstrate effectiveness the LCCs have been successfully tested during the recent PF Converter Unit performance tests for ITER.
Energy Technology Data Exchange (ETDEWEB)
Bhatia, Harsh [Univ. of Utah, Salt Lake City, UT (United States)
2015-05-01
This dissertation presents research on addressing some of the contemporary challenges in the analysis of vector fields—an important type of scientific data useful for representing a multitude of physical phenomena, such as wind flow and ocean currents. In particular, new theories and computational frameworks to enable consistent feature extraction from vector fields are presented. One of the most fundamental challenges in the analysis of vector fields is that their features are defined with respect to reference frames. Unfortunately, there is no single “correct” reference frame for analysis, and an unsuitable frame may cause features of interest to remain undetected, thus creating serious physical consequences. This work develops new reference frames that enable extraction of localized features that other techniques and frames fail to detect. As a result, these reference frames objectify the notion of “correctness” of features for certain goals by revealing the phenomena of importance from the underlying data. An important consequence of using these local frames is that the analysis of unsteady (time-varying) vector fields can be reduced to the analysis of sequences of steady (timeindependent) vector fields, which can be performed using simpler and scalable techniques that allow better data management by accessing the data on a per-time-step basis. Nevertheless, the state-of-the-art analysis of steady vector fields is not robust, as most techniques are numerical in nature. The residing numerical errors can violate consistency with the underlying theory by breaching important fundamental laws, which may lead to serious physical consequences. This dissertation considers consistency as the most fundamental characteristic of computational analysis that must always be preserved, and presents a new discrete theory that uses combinatorial representations and algorithms to provide consistency guarantees during vector field analysis along with the uncertainty
Worthmann, Brian M; Song, H C; Dowling, David R
2015-12-01
Matched field processing (MFP) is an established technique for source localization in known multipath acoustic environments. Unfortunately, in many situations, particularly those involving high frequency signals, imperfect knowledge of the actual propagation environment prevents accurate propagation modeling and source localization via MFP fails. For beamforming applications, this actual-to-model mismatch problem was mitigated through a frequency downshift, made possible by a nonlinear array-signal-processing technique called frequency difference beamforming [Abadi, Song, and Dowling (2012). J. Acoust. Soc. Am. 132, 3018-3029]. Here, this technique is extended to conventional (Bartlett) MFP using simulations and measurements from the 2011 Kauai Acoustic Communications MURI experiment (KAM11) to produce ambiguity surfaces at frequencies well below the signal bandwidth where the detrimental effects of mismatch are reduced. Both the simulation and experimental results suggest that frequency difference MFP can be more robust against environmental mismatch than conventional MFP. In particular, signals of frequency 11.2 kHz-32.8 kHz were broadcast 3 km through a 106-m-deep shallow ocean sound channel to a sparse 16-element vertical receiving array. Frequency difference MFP unambiguously localized the source in several experimental data sets with average peak-to-side-lobe ratio of 0.9 dB, average absolute-value range error of 170 m, and average absolute-value depth error of 10 m.
High-energy localized eigenstates in a Fabry-Perot graphene resonator in a magnetic field
Zalipaev, V. V.
2012-06-01
A semiclassical analysis of the high-energy eigenstates of Dirac fermions inside a graphene monolayer nanoribbon resonator of Fabry-Perot type in a magnetic field with zigzag boundary conditions is discussed. A semiclassical asymptotic method of construction of Maslov spectral series of energy spectrum and eigenfunctions, localized in an asymptotically small neighborhood of a periodic orbit, is developed for the graphene Dirac system. The isolated periodic orbit is confined between two flat boundaries. The analysis involves constructing a localized asymptotic solution to the Dirac system (electron-hole Gaussian beam). Then, the stability of a continuous family of periodic orbits (POs) confined between reflecting boundaries of the resonator is studied. The asymptotics of the eigenfunctions are constructed as a superposition of two Gaussian beams propagating in opposite directions between two reflecting points of the periodic orbit. The asymptotics of the energy spectrum are obtained by means of the generalized Bohr-Sommerfeld quantization condition only for stable POs. It provides two parts of semiclassical Maslov spectral series with positive and negative energies, for electrons and holes, correspondingly, with two different Hamiltonian dynamics and families of classical trajectories. The presence of electrostatic potential is vital as it makes a family of periodic orbit stable. For one subclass of lens-shaped periodic orbits, for a piecewise linear potential, localized eigenstates were computed numerically by the finite element method using COMSOL, and proved to be in very good agreement with the ones computed semiclassically.
Smith, Roger J
2008-10-01
A novel diagnostic technique for the remote and nonperturbative sensing of the local magnetic field in reactor relevant plasmas is presented. Pulsed polarimetry [Patent No. 12/150,169 (pending)] combines optical scattering with the Faraday effect. The polarimetric light detection and ranging (LIDAR)-like diagnostic has the potential to be a local B(pol) diagnostic on ITER and can achieve spatial resolutions of millimeters on high energy density (HED) plasmas using existing lasers. The pulsed polarimetry method is based on nonlocal measurements and subtle effects are introduced that are not present in either cw polarimetry or Thomson scattering LIDAR. Important features include the capability of simultaneously measuring local T(e), n(e), and B(parallel) along the line of sight, a resiliency to refractive effects, a short measurement duration providing near instantaneous data in time, and location for real-time feedback and control of magnetohydrodynamic (MHD) instabilities and the realization of a widely applicable internal magnetic field diagnostic for the magnetic fusion energy program. The technique improves for higher n(e)B(parallel) product and higher n(e) and is well suited for diagnosing the transient plasmas in the HED program. Larger devices such as ITER and DEMO are also better suited to the technique, allowing longer pulse lengths and thereby relaxing key technology constraints making pulsed polarimetry a valuable asset for next step devices. The pulsed polarimetry technique is clarified by way of illustration on the ITER tokamak and plasmas within the magnetized target fusion program within present technological means.
Improved iris localization by using wide and narrow field of view cameras for iris recognition
Kim, Yeong Gon; Shin, Kwang Yong; Park, Kang Ryoung
2013-10-01
Biometrics is a method of identifying individuals by their physiological or behavioral characteristics. Among other biometric identifiers, iris recognition has been widely used for various applications that require a high level of security. When a conventional iris recognition camera is used, the size and position of the iris region in a captured image vary according to the X, Y positions of a user's eye and the Z distance between a user and the camera. Therefore, the searching area of the iris detection algorithm is increased, which can inevitably decrease both the detection speed and accuracy. To solve these problems, we propose a new method of iris localization that uses wide field of view (WFOV) and narrow field of view (NFOV) cameras. Our study is new as compared to previous studies in the following four ways. First, the device used in our research acquires three images, one each of the face and both irises, using one WFOV and two NFOV cameras simultaneously. The relation between the WFOV and NFOV cameras is determined by simple geometric transformation without complex calibration. Second, the Z distance (between a user's eye and the iris camera) is estimated based on the iris size in the WFOV image and anthropometric data of the size of the human iris. Third, the accuracy of the geometric transformation between the WFOV and NFOV cameras is enhanced by using multiple matrices of the transformation according to the Z distance. Fourth, the searching region for iris localization in the NFOV image is significantly reduced based on the detected iris region in the WFOV image and the matrix of geometric transformation corresponding to the estimated Z distance. Experimental results showed that the performance of the proposed iris localization method is better than that of conventional methods in terms of accuracy and processing time.
Directory of Open Access Journals (Sweden)
Satyapriya Gupta
2018-03-01
Full Text Available The displacement discontinuity arising between crack surfaces is assigned to smooth densities of crystal defects referred to as disconnections, through the incompatibility of the distortion tensor. In a dual way, the disconnections are defined as line defects terminating surfaces where the displacement encounters a discontinuity. A conservation statement for the crack opening displacement provides a framework for disconnection dynamics in the form of transport laws. A similar methodology applied to the discontinuity of the plastic displacement due to dislocations results in the concurrent involvement of dislocation densities in the analysis. Non-linearity of the geometrical setting is assumed for defining the elastic distortion incompatibility in the presence of both dislocations and disconnections, as well as for their transport. Crack nucleation in the presence of thermally-activated fluctuations of the atomic order is shown to derive from this nonlinearity in elastic brittle materials, without any algorithmic rule or ad hoc material parameter. Digital image correlation techniques applied to the analysis of tensile tests on ductile Al-Cu-Li samples further demonstrate the ability of the disconnection density concept to capture crack nucleation and relate strain localization bands to consistent disconnection fields and to the eventual occurrence of complex and combined crack modes in these alloys.
Partnering Students, Scientists, and the Local Community in a Regionally-focused Field Campaign
McLaughlin, J. W.; Lemone, M. A.; Seavey, M. M.; Washburne, J. C.
2006-05-01
The GLOBE Program (www.globe.gov) involves students and scientists in a worldwide environmental data collection effort. The GLOBE ONE field campaign (www.globe.gov/globeone) represents a model for a focused implementation of GLOBE via a geographically-specific project. The campaign, which occurred in Black Hawk County, Iowa from February 2004 to February 2006, was developed by GLOBE Principal Investigators (PIs), the GLOBE Program Office, and GLOBE Iowa. The central scientific objective was to compare quantitatively the environmental effects of various soil tillage techniques. In addition, student research projects were supported that spanned a variety of Earth science topics. The campaign established a partnership between students and scientists to collect a structured, multidisciplinary data set and also increase GLOBE visibility. The fact that GLOBE ONE occurred in a focused geographic area made it necessary to form a network for local support. This started with choosing an active GLOBE partner, namely the Iowa Academy of Science, who had the ability to oversee the local implementation of such a project. Once this partner was chosen, additional local groups needed to be recruited to support the project. The local network included K-12 schools, the County Conservation Board, the University of Northern Iowa, Hawkeye Community College, and community volunteers. This network collected data via automated instrumentation, first-hand observations, and through special events organized with a focus on a specific measurement. The first major step in supporting student research was a teacher training workshop held in March of 2006 that helped to provide tools for, and increase comfort levels with, promoting scientific inquiry in the classroom. Student-scientists interactions were promoted via scientist visits, video conferences, letters, and email exchanges. The culminating event was a Student Research Symposium held in February 2006 which gave students and scientists a
Onyekuru, Bruno Uchenna
2015-01-01
This is a descriptive study that investigated the relationships among field dependence-field independence cognitive style and gender, career choice and academic achievement of secondary school students in Emohua Local Government Area of Rivers State, Nigeria. From the initial sample of 320 senior secondary school one (SS1) students drawn from the…
Non-solenoidal Startup with High-Field-Side Local Helicity Injection on the Pegasus ST
Perry, J. M.; Bodner, G. M.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Pachicano, J. L.; Pierren, C.; Richner, N. J.; Rodriguez Sanchez, C.; Schlossberg, D. J.; Reusch, J. A.; Weberski, J. D.
2017-10-01
Local Helicity Injection (LHI) is a non-solenoidal startup technique utilizing electron current injectors at the plasma edge to initiate a tokamak-like plasma at high Ip . Recent experiments on Pegasus explore the inherent tradeoffs between high-field-side (HFS) injection in the lower divertor region and low-field-side (LFS) injection at the outboard midplane. Trade-offs include the relative current drive contributions of HI and poloidal induction, and the magnetic geometry required for relaxation to a tokamak-like state. HFS injection using a set of two increased-area injectors (Ainj = 4 cm2, Vinj 1.5 kV, and Iinj 8 kA) in the lower divertor is demonstrated over the full range of toroidal field available on Pegasus (BT 0 = 10) attainable with LHI and the favorable stability of the ultra-low aspect ratio, low-li LHI-driven plasmas allow access to high βt-up to 100 % , as indicated by kinetically-constrained equilibrium reconstructions. Work supported by US DOE Grant DE-FG02-96ER54375.
International Nuclear Information System (INIS)
Hislop, P.D.
1988-01-01
The Tomita modular operators and the duality property for the local von Neumann algebras in quantum field models describing free massless particles with arbitrary helicity are studied. It is proved that the representation of the Poincare group in each model extends to a unitary representation of SU(2, 2), a covering group of the conformal group. An irreducible set of ''standard'' linear fields is shown to be covariant with respect to this representation. The von Neumann algebras associated with wedge, double-cone, and lightcone regions generated by these fields are proved to be unitarily equivalent. The modular operators for these algebras are obtained in explicit form using the conformal covariance and the results of Bisognano and Wichmann on the modular structure of the wedge algebras. The modular automorphism groups are implemented by one-parameter groups of conformal transformations. The modular conjugation operators are used to prove the duality property for the double-cone algebras and the timelike duality property for the lightcone algebras. copyright 1988 Academic Press, Inc
The influence of local electric fields on photoinduced absorption in dye-sensitized solar cells.
Cappel, Ute B; Feldt, Sandra M; Schöneboom, Jan; Hagfeldt, Anders; Boschloo, Gerrit
2010-07-07
The dye-sensitized solar cell (DSC) challenges conventional photovoltaics with its potential for low-cost production and its flexibility in terms of color and design. Transient absorption spectroscopy is widely used to unravel the working mechanism of DSCs. A surprising, unexplained feature observed in these studies is an apparent bleach of the ground-state absorption of the dye, under conditions where the dye is in the ground state. Here, we demonstrate that this feature can be attributed to a change of the local electric field affecting the absorption spectrum of the dye, an effect related to the Stark effect first reported in 1913. We present a method for measuring the effect of an externally applied electric field on the absorption of dye monolayers adsorbed on flat TiO(2) substrates. The measured signal has the shape of the first derivative of the absorption spectra of the dyes and reverses sign along with the reversion of the direction of the change in dipole moment upon excitation relative to the TiO(2) surface. A very similar signal is observed in photoinduced absorption spectra of dye-sensitized TiO(2) electrodes under solar cell conditions, demonstrating that the electric field across the dye molecules changes upon illumination. This result has important implications for the analysis of transient absorption spectra of DSCs and other molecular optoelectronic devices and challenges the interpretation of many previously published results.
International Nuclear Information System (INIS)
Nguyen Quoc Thang
2004-08-01
We show the validity of te Corestriction Principle for non-abelian cohomology of connected reductive groups over local ad global fields of characteristic p > 0 , by extending some results by Kneser and Douai. (author)
Group of local biholomorphisms of C/sup 1/ and conformal field theory on the operator formalism
Energy Technology Data Exchange (ETDEWEB)
Budzynski, R.J.; Klimek, S.; Sadowski, P.
1989-01-01
Motivated by the operator formulation of conformal field theory on Riemann surfaces, we study the properties of the infinite dimensional group of local biholomorphic transformations (conformal reparametrizations) of C/sup 1/ and develop elements of its representation theory.
Nozaki, Junji; Fukumura, Musashi; Aoki, Takaaki; Maniwa, Yutaka; Yomogida, Yohei; Yanagi, Kazuhiro
2017-04-05
Remarkable optical properties, such as quantum light emission and large optical nonlinearity, have been observed in peculiar local sites of transition metal dichalcogenide monolayers, and the ability to tune such properties is of great importance for their optoelectronic applications. For that purpose, it is crucial to elucidate and tune their local optical properties simultaneously. Here, we develop an electric field-assisted near-field technique. Using this technique we can clarify and tune the local optical properties simultaneously with a spatial resolution of approximately 100 nm due to the electric field from the cantilever. The photoluminescence at local sites in molybdenum-disulfide (MoS 2 ) monolayers is reversibly modulated, and the inhomogeneity of the charge neutral points and quantum yields is suggested. We successfully etch MoS 2 crystals and fabricate nanoribbons using near-field techniques in combination with an electric field. This study creates a way to tune the local optical properties and to freely design the structural shapes of atomic monolayers using near-field optics.
Quantum field theories coupled to supergravity. AdS/CFT and local couplings
International Nuclear Information System (INIS)
Grosse, J.
2006-01-01
This dissertation is devoted to the investigation of the interplay of supersymmetric Yang-Mills theories (SYM) and supergravity (SUGRA). The topic is studied from two points of view: Firstly from the point of view of AdS/CFT correspondence, which realises the coupling of four dimensional superconformal N=4 SYM theory and ten dimensional type IIB SUGRA in a holographic way. In order to arrive at theories that resemble quantum chromodynamics (QCD) more closely, fundamental fields are introduced using probe D7-branes and nontrivial background configuration are considered. In particular supergravity solutions that are only asymptotically anti-de Sitter and break supersymmetry are used. This allows the description of spontaneous chiral symmetry breaking. The meson spectrum is calculated and the existence of an associated Goldstone mode is demonstrated. Moreover it is shown that highly radially excited mesons are not degenerate. Additionally instanton configurations on the D7-branes are investigated, which lead to a holographic description of the dual field theory's Higgs branch. Finally a holographic description of heavy-light mesons is developed, which are mesons consisting of quarks with a large mass difference, such that a treatment of B mesons can be achieved. The second approach to the topic of this thesis is the technique of socalled space-time dependent couplings (also known as ''local couplings''), where coupling constants are promoted to external sources. This allows to explore the conformal anomaly of quantum field theories coupled to a classical gravity background. The technique is extended to the superfield description of N=1 supergravity, a complete basis for the anomaly is given and the consistency conditions that arise from a cohomological treatment are calculated. Possible implications for an extension of Zamolodchikov's c-theorem to four dimensional supersymmetric quantum field theories are discussed. (orig.)
Quantum field theories coupled to supergravity. AdS/CFT and local couplings
Energy Technology Data Exchange (ETDEWEB)
Grosse, J.
2006-08-03
This dissertation is devoted to the investigation of the interplay of supersymmetric Yang-Mills theories (SYM) and supergravity (SUGRA). The topic is studied from two points of view: Firstly from the point of view of AdS/CFT correspondence, which realises the coupling of four dimensional superconformal N=4 SYM theory and ten dimensional type IIB SUGRA in a holographic way. In order to arrive at theories that resemble quantum chromodynamics (QCD) more closely, fundamental fields are introduced using probe D7-branes and nontrivial background configuration are considered. In particular supergravity solutions that are only asymptotically anti-de Sitter and break supersymmetry are used. This allows the description of spontaneous chiral symmetry breaking. The meson spectrum is calculated and the existence of an associated Goldstone mode is demonstrated. Moreover it is shown that highly radially excited mesons are not degenerate. Additionally instanton configurations on the D7-branes are investigated, which lead to a holographic description of the dual field theory's Higgs branch. Finally a holographic description of heavy-light mesons is developed, which are mesons consisting of quarks with a large mass difference, such that a treatment of B mesons can be achieved. The second approach to the topic of this thesis is the technique of socalled space-time dependent couplings (also known as ''local couplings''), where coupling constants are promoted to external sources. This allows to explore the conformal anomaly of quantum field theories coupled to a classical gravity background. The technique is extended to the superfield description of N=1 supergravity, a complete basis for the anomaly is given and the consistency conditions that arise from a cohomological treatment are calculated. Possible implications for an extension of Zamolodchikov's c-theorem to four dimensional supersymmetric quantum field theories are discussed. (orig.)
Fluctuations of local electric field and dipole moments in water between metal walls.
Takae, Kyohei; Onuki, Akira
2015-10-21
We examine the thermal fluctuations of the local electric field Ek (loc) and the dipole moment μk in liquid water at T = 298 K between metal walls in electric field applied in the perpendicular direction. We use analytic theory and molecular dynamics simulation. In this situation, there is a global electrostatic coupling between the surface charges on the walls and the polarization in the bulk. Then, the correlation function of the polarization density pz(r) along the applied field contains a homogeneous part inversely proportional to the cell volume V. Accounting for the long-range dipolar interaction, we derive the Kirkwood-Fröhlich formula for the polarization fluctuations when the specimen volume v is much smaller than V. However, for not small v/V, the homogeneous part comes into play in dielectric relations. We also calculate the distribution of Ek (loc) in applied field. As a unique feature of water, its magnitude |Ek (loc)| obeys a Gaussian distribution with a large mean value E0 ≅ 17 V/nm, which arises mainly from the surrounding hydrogen-bonded molecules. Since |μk|E0 ∼ 30kBT, μk becomes mostly parallel to Ek (loc). As a result, the orientation distributions of these two vectors nearly coincide, assuming the classical exponential form. In dynamics, the component of μk(t) parallel to Ek (loc)(t) changes on the time scale of the hydrogen bonds ∼5 ps, while its smaller perpendicular component undergoes librational motions on time scales of 0.01 ps.
Nurbekyan, Levon
2017-03-11
Here, we study a one-dimensional, non-local mean-field game model with congestion. When the kernel in the non-local coupling is a trigonometric polynomial we reduce the problem to a finite dimensional system. Furthermore, we treat the general case by approximating the kernel with trigonometric polynomials. Our technique is based on Fourier expansion methods.
Nurbekyan, Levon
2017-01-01
Here, we study a one-dimensional, non-local mean-field game model with congestion. When the kernel in the non-local coupling is a trigonometric polynomial we reduce the problem to a finite dimensional system. Furthermore, we treat the general case by approximating the kernel with trigonometric polynomials. Our technique is based on Fourier expansion methods.
Earth Systems Field Work: Service Learning at Local and Global Scales
Moore, A.; Derry, L. A.
2016-12-01
The Earth & Environmental Systems (EES) Field Program engages students in hands-on exploration along the boundaries of the living earth, solid earth, ocean, and atmosphere. Based on Hawaíi Island, the semester-length program integrates scientific study with environmental stewardship and service learning. Each year EES students contribute 3000 hours of service to their host community. Throughout the semester students engage in different service activities. Most courses includes a service component - for example - study of the role of invasive species in native ecosystems includes an invasive species removal project. Each student completes a 4-week service internship with a local school, NGO, state or federal agency. Finally, the student group works to offset the carbon footprint of the program in collaboration with local conservation projects. This effort sequesters CO2 emissions while at the same time contributing to reforestation of degraded native ecosystems. Students learn that expertise is not confined to "the academy," and that wisdom and inspiration can be found in unexpected venues. Much of the service learning in the EES Program occurs in collaboration with local partners. Service internships require students to identify a partner and to design a tractable project. Students work daily with their sponsor and make a formal presentation of their project at the end of the internship period. This includes speaking to a non-technical community gathering as well as to a scientific audience. For many students the opportunity to work on a real problem, of interest in the real world, is a highlight of the semester. Beyond working in support of local community groups, the EES Prograḿs C-neutral project engages students with work in service to the global commons. Here the outcome is not measurable within the time frame of a semester, yet the intangible result makes the experience even more powerful. Students take responsibility for an important issue that is not
Hybrid Scheme for Modeling Local Field Potentials from Point-Neuron Networks
DEFF Research Database (Denmark)
Hagen, Espen; Dahmen, David; Stavrinou, Maria L
2016-01-01
on populations of network-equivalent multicompartment neuron models with layer-specific synaptic connectivity, can be used with an arbitrary number of point-neuron network populations, and allows for a full separation of simulated network dynamics and LFPs. We apply the scheme to a full-scale cortical network......With rapidly advancing multi-electrode recording technology, the local field potential (LFP) has again become a popular measure of neuronal activity in both research and clinical applications. Proper understanding of the LFP requires detailed mathematical modeling incorporating the anatomical...... and electrophysiological features of neurons near the recording electrode, as well as synaptic inputs from the entire network. Here we propose a hybrid modeling scheme combining efficient point-neuron network models with biophysical principles underlying LFP generation by real neurons. The LFP predictions rely...
Computationally efficient near-field source localization using third-order moments
Chen, Jian; Liu, Guohong; Sun, Xiaoying
2014-12-01
In this paper, a third-order moment-based estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm is proposed for passive localization of near-field sources. By properly choosing sensor outputs of the symmetric uniform linear array, two special third-order moment matrices are constructed, in which the steering matrix is the function of electric angle γ, while the rotational factor is the function of electric angles γ and ϕ. With the singular value decomposition (SVD) operation, all direction-of-arrivals (DOAs) are estimated from a polynomial rooting version. After substituting the DOA information into the steering matrix, the rotational factor is determined via the total least squares (TLS) version, and the related range estimations are performed. Compared with the high-order ESPRIT method, the proposed algorithm requires a lower computational burden, and it avoids the parameter-match procedure. Computer simulations are carried out to demonstrate the performance of the proposed algorithm.
International Nuclear Information System (INIS)
Muehlbauer, P.
1981-08-01
Experience is described gained with the application of computer code VELASCO in calculating the velocity field in fast reactor fuel assemblies taking into account configuration disturbances due to fuel pin displacement. Theoretical results are compared with the results of experiments conducted by UJV on aerodynamic models HEM-1 (model of the fuel assembly central part) and HEM-2 (model of the fuel assembly peripheral part). The results are reported of calculating the distribution of shear stress in wetted rod surfaces and in the assembly wall (model HEM-2) and the corresponding experimental results are shown. The shear stress distribution in wetted surfaces obtained using the VELASCO code allowed forming an opinion on the code capability of comprising local parameters of turbulent flow through a fuel rod bundle. The applicability was also tested of the code for calculating mean velocities in the individual zones, eg., in elementary cells. (B.S.)
Intrinsic dendritic filtering gives low-pass power spectra of local field potentials
DEFF Research Database (Denmark)
Lindén, Henrik; Pettersen, Klas H; Einevoll, Gaute T
2010-01-01
of contributions to the LFP from a single layer-5 pyramidal neuron and a single layer-4 stellate neuron receiving synaptic input. An intrinsic dendritic low-pass filtering effect of the LFP signal, previously demonstrated for extracellular signatures of action potentials, is seen to strongly affect the LFP power...... spectra, even for frequencies as low as 10 Hz for the example pyramidal neuron. Further, the LFP signal is found to depend sensitively on both the recording position and the position of the synaptic input: the LFP power spectra recorded close to the active synapse are typically found to be less low......The local field potential (LFP) is among the most important experimental measures when probing neural population activity, but a proper understanding of the link between the underlying neural activity and the LFP signal is still missing. Here we investigate this link by mathematical modeling...
THE CENTAURUS A ULTRAHIGH-ENERGY COSMIC-RAY EXCESS AND THE LOCAL EXTRAGALACTIC MAGNETIC FIELD
International Nuclear Information System (INIS)
Yüksel, Hasan; Kronberg, Philipp P.; Stanev, Todor; Kistler, Matthew D.
2012-01-01
The ultrahigh-energy cosmic-ray (UHECR) anisotropies discovered by the Pierre Auger Observatory provide the potential to finally address both the particle origins and properties of the nearby extragalactic magnetic field (EGMF). We examine the implications of the excess of ∼10 20 eV events around the nearby radio galaxy Centaurus A. We find that, if Cen A is the source of these cosmic rays, the angular distribution of events constrains the EGMF strength within several Mpc of the Milky Way to ∼> 20 nG for an assumed primary proton composition. Our conclusions suggest that either the observed excess is a statistical anomaly or the local EGMF is stronger than conventionally thought. We discuss several implications, including UHECR scattering from more distant sources, time delays from transient sources, and the possibility of using magnetic lensing signatures to attain tighter constraints.
Local-field enhancement effect on the nonlinear optical response of gold-silver nanoplanets.
Cesca, T; Calvelli, P; Battaglin, G; Mazzoldi, P; Mattei, G
2012-02-13
We report on the nonlinear optical properties of Au-Ag nanoplanets produced by ion implantation and irradiation in silica, experimentally investigated by means of the single beam z-scan technique. The measurements provided experimental evidence of the intense local-field enhancement effect theoretically demonstrated for these plasmonic nanosystems. In particular, this has a dramatic impact on their nonlinear absorption behavior and results in a tunable changeover from reverse saturable absorption to saturable absorption by slightly varying the pump intensity and in the possibility to activate and observe nonlinear phenomena of the electron dynamics otherwise unaccessible in the intensity range that can be employed to study these materials. Finally, for the nanoplanet configuration we found a dramatic decrease of the intensity-dependent absorption coefficient, which could be very promising for obtaining optical gain materials.
THE CENTAURUS A ULTRAHIGH-ENERGY COSMIC-RAY EXCESS AND THE LOCAL EXTRAGALACTIC MAGNETIC FIELD
Energy Technology Data Exchange (ETDEWEB)
Yueksel, Hasan; Kronberg, Philipp P. [Theoretical Division, MS B285, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Stanev, Todor [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Kistler, Matthew D. [Lawrence Berkeley National Laboratory and Department of Physics, University of California, Berkeley, CA 94720 (United States)
2012-10-10
The ultrahigh-energy cosmic-ray (UHECR) anisotropies discovered by the Pierre Auger Observatory provide the potential to finally address both the particle origins and properties of the nearby extragalactic magnetic field (EGMF). We examine the implications of the excess of {approx}10{sup 20} eV events around the nearby radio galaxy Centaurus A. We find that, if Cen A is the source of these cosmic rays, the angular distribution of events constrains the EGMF strength within several Mpc of the Milky Way to {approx}> 20 nG for an assumed primary proton composition. Our conclusions suggest that either the observed excess is a statistical anomaly or the local EGMF is stronger than conventionally thought. We discuss several implications, including UHECR scattering from more distant sources, time delays from transient sources, and the possibility of using magnetic lensing signatures to attain tighter constraints.
International Nuclear Information System (INIS)
Kuchinskii, E. Z.; Nekrasov, I. A.; Sadovskii, M. V.
2008-01-01
The DOS, the dynamic (optical) conductivity, and the phase diagram of a strongly correlated and strongly disordered paramagnetic Anderson-Hubbard model are analyzed within the generalized dynamical mean field theory (DMFT + Σ approximation). Strong correlations are taken into account by the DMFT, and disorder is taken into account via an appropriate generalization of the self-consistent theory of localization. The DMFT effective single-impurity problem is solved by a numerical renormalization group (NRG); we consider the three-dimensional system with a semielliptic DOS. The correlated metal, Mott insulator, and correlated Anderson insulator phases are identified via the evolution of the DOS and dynamic conductivity, demonstrating both the Mott-Hubbard and Anderson metal-insulator transition and allowing the construction of the complete zero-temperature phase diagram of the Anderson-Hubbard model. Rather unusual is the possibility of a disorder-induced Mott insulator-to-metal transition
Bamford, Simeon A; Murray, Alan F; Willshaw, David J
2010-02-01
A distributed and locally reprogrammable address-event receiver has been designed, in which incoming address-events are monitored simultaneously by all synapses, allowing for arbitrarily large axonal fan-out without reducing channel capacity. Synapses can change the address of their presynaptic neuron, allowing the distributed implementation of a biologically realistic learning rule, with both synapse formation and elimination (synaptic rewiring). Probabilistic synapse formation leads to topographic map development, made possible by a cross-chip current-mode calculation of Euclidean distance. As well as synaptic plasticity in rewiring, synapses change weights using a competitive Hebbian learning rule (spike-timing-dependent plasticity). The weight plasticity allows receptive fields to be modified based on spatio-temporal correlations in the inputs, and the rewiring plasticity allows these modifications to become embedded in the network topology.
Riker, J.; Watson, M.; Liu, E. J.; Chigna, G.; Purvis, M.; Naismith, A.
2016-12-01
For over ten years, the University of Bristol (U.K.) has run a field trip for masters students in Natural Hazards in the volcanically active areas of southern Guatemala, home to more than 13 million people. This trip has obvious benefits to its participants - it serves as an immersive and formative experience for students studying volcanic hazard, as well as a springboard for the work of the researchers who lead it. Over the years, it has helped to build strong collaborative ties between academic researchers at Bristol and Guatemala's geologic survey (INSIVUMEH) and emergency management agency (CONRED), facilitating the sharing of data, expertise, and monitoring equipment. The students' regular presence has also enabled infrastructure improvements at Fuego Volcano Observatory, which is itself hosted and partly staffed by the residents of Panimache, a small village just a few miles from the volcano's summit. This field trip does raise challenges, however - an influx of foreign students can draw questions from community members for whom the benefits are indirect (i.e., local job creation or infrastructure improvement) or intangible (i.e., incremental contributions to the body of knowledge regarding volcanic hazard). In this presentation, we'll share stories of our experiences of effective community collaboration in Guatemala. In the spirit of discussion, we would also like to explore the opportunities that exist to better utilise this trip, along with the energy and expertise of its participants, to maximise the positive impact on (and resilience of) local communities, particularly those in the small and largely indigenous villages that populate Fuego Volcano's flanks.
Directory of Open Access Journals (Sweden)
Gonzalo Martín-Vázquez
Full Text Available Fluctuations in successive waves of oscillatory local field potentials (LFPs reflect the ongoing processing of neuron populations. However, their amplitude, polarity and synaptic origin are uncertain due to the blending of electric fields produced by multiple converging inputs, and the lack of a baseline in standard AC-coupled recordings. Consequently, the estimation of underlying currents by laminar analysis yields spurious sequences of inward and outward currents. We devised a combined analytical/experimental approach that is suitable to study laminated structures. The approach was essayed on an experimental oscillatory LFP as the Schaffer-CA1 gamma input in anesthetized rats, and it was verified by parallel processing of model LFPs obtained through a realistic CA1 aggregate of compartmental units. This approach requires laminar LFP recordings and the isolation of the oscillatory input from other converging pathways, which was achieved through an independent component analysis. It also allows the spatial and temporal components of pathway-specific LFPs to be separated. While reconstructed Schaffer-specific LFPs still show spurious inward/outward current sequences, these were clearly stratified into distinct subcellular domains. These spatial bands guided the localized delivery of neurotransmitter blockers in experiments. As expected, only Glutamate but not GABA blockers abolished Schaffer LFPs when applied to the active but not passive subcellular domains of pyramidal cells. The known chemical nature of the oscillatory LFP allowed an empirical offset of the temporal component of Schaffer LFPs, such that following reconstruction they yield only sinks or sources at the appropriate sites. In terms of number and polarity, some waves increased and others decreased proportional to the concomitant inputs in native multisynaptic LFPs. Interestingly, the processing also retrieved the initiation time for each wave, which can be used to discriminate
Chromatic and Achromatic Spatial Resolution of Local Field Potentials in Awake Cortex.
Jansen, Michael; Li, Xiaobing; Lashgari, Reza; Kremkow, Jens; Bereshpolova, Yulia; Swadlow, Harvey A; Zaidi, Qasim; Alonso, Jose-Manuel
2015-10-01
Local field potentials (LFPs) have become an important measure of neuronal population activity in the brain and could provide robust signals to guide the implant of visual cortical prosthesis in the future. However, it remains unclear whether LFPs can detect weak cortical responses (e.g., cortical responses to equiluminant color) and whether they have enough visual spatial resolution to distinguish different chromatic and achromatic stimulus patterns. By recording from awake behaving macaques in primary visual cortex, here we demonstrate that LFPs respond robustly to pure chromatic stimuli and exhibit ∼2.5 times lower spatial resolution for chromatic than achromatic stimulus patterns, a value that resembles the ratio of achromatic/chromatic resolution measured with psychophysical experiments in humans. We also show that, although the spatial resolution of LFP decays with visual eccentricity as is also the case for single neurons, LFPs have higher spatial resolution and show weaker response suppression to low spatial frequencies than spiking multiunit activity. These results indicate that LFP recordings are an excellent approach to measure spatial resolution from local populations of neurons in visual cortex including those responsive to color. © The Author 2014. Published by Oxford University Press.
International Nuclear Information System (INIS)
Govorkov, A.B.
1988-01-01
It is shown that the local quantum field theory of free fields allows only the generalizations of the conventional quantizations (corresponding to the Fermi and Bose statistics) that correspond to the para-Fermi and para-Bose statistics and does not permit ''small'' violation of the Pauli principle
Lyu, Z.; Tran, N.; Boeck, T.; Karcher, C.
2017-07-01
Lorentz force velocimetry (LFV) is a non-contact electromagnetic flow measurement technique for electrically conductive liquids. It is based on measuring the flow-induced force acting on an external permanent magnet. Motivated by extending LFV to liquid metal two-phase flow measurement, in a first test we consider the free rising of a non-conductive spherical particle in a thin tube of liquid metal (GaInSn) initially at rest. Here the measured force is due to the displacement flow induced by the rising particle. In this paper, numerical results are presented for three different analytical solutions of flows around a moving sphere under a localized magnetic field. This simplification is made since the hydrodynamic flow is difficult to measure or to compute. The Lorentz forces are compared to experiments. The aim of the present work is to check if our simple numerical model can provide Lorentz forces comparable to the experiments. The results show that the peak values of the Lorentz force from the analytical velocity fields provide us an upper limit to the measurement results. In the case of viscous flow around a moving sphere we recover the typical time-scale of Lorentz force signals.
International Nuclear Information System (INIS)
Schlueter, P.
1985-05-01
In this work three topics related to the theory of positron creation in heavy ion collisions are investigated. The first of these is concerned with the local representation of the Dirac matrices. It consists of a space dependent similarity transformation of the Dirac matrices which is chosen in such a way that for certain orthogonal coordinate systems the Dirac equation assumes a simple standardized form. This form is well suited for analytical as well as numerical calculations. For all generally used coordinate systems the transformation can be given in closed form. The application of this idea is not restricted to the solution of the two-centre Dirac equation but may be used also for different electro-magnetic potentials. In the second of the above mentioned problems, the question is discussed, whether the recently observed peak structures in positron spectra from U-U collisions can originate from nuclear conversion processes. It is demonstrated that, taking this hypothesis at face value, in the photon or delta-electron spectrum corresponding structures should be observed. Moreover, rather large nuclear excitation probabilities in the order of percents are needed to make this explanation plausible. Finally, the third topic is concerned with a more fundamental question: May it be possible that the interaction of the strongly bound electrons in a critical electric field with the radiation field leads to an energy shift which is big enough to prevent the diving of the 1s-state into the negative energy continuum. (orig./HSI) [de
DEPENDENCE OF SOLAR-WIND POWER SPECTRA ON THE DIRECTION OF THE LOCAL MEAN MAGNETIC FIELD
International Nuclear Information System (INIS)
Podesta, J. J.
2009-01-01
Wavelet analysis can be used to measure the power spectrum of solar-wind fluctuations along a line in any direction (θ, φ) with respect to the local mean magnetic field B 0 . This technique is applied to study solar-wind turbulence in high-speed streams in the ecliptic plane near solar minimum using magnetic field measurements with a cadence of eight vectors per second. The analysis of nine high-speed streams shows that the reduced spectrum of magnetic field fluctuations (trace power) is approximately azimuthally symmetric about B 0 in both the inertial range and dissipation range; in the inertial range the spectra are characterized by a power-law exponent that changes continuously from 1.6 ± 0.1 in the direction perpendicular to the mean field to 2.0 ± 0.1 in the direction parallel to the mean field. The large uncertainties suggest that the perpendicular power-law indices 3/2 and 5/3 are both consistent with the data. The results are similar to those found by Horbury et al. at high heliographic latitudes. Comparisons between solar-wind observations and the theories of strong incompressible MHD turbulence developed by Goldreich and Sridhar and Boldyrev are not rigorously justified because these theories only apply to turbulence with vanishing cross-helicity although the normalized cross-helicity of solar-wind turbulence is not negligible. Assuming these theories can be generalized in such a way that the three-dimensional wavevector spectra have similar functional forms when the cross-helicity is nonzero, then for the interval of Ulysses data analyzed by Horbury et al. the ratio of the spectra perpendicular and parallel to B 0 is more consistent with the Goldreich and Sridhar scaling P perpendicular /P || ∝ ν 1/3 than with the Boldyrev scaling ν 1/2 . The analysis of high-speed streams in the ecliptic plane does not yield a reliable measurement of this scaling law. The transition from a turbulent MHD-scale energy cascade to a kinetic Alfven wave (KAW
Increase in local protein concentration by field-inversion gel electrophoresis
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Paulus Aran
2007-09-01
Full Text Available Abstract Background Proteins that migrate through cross-linked polyacrylamide gels (PAGs under the influence of a constant electric field experience negative factors, such as diffusion and non-specific trapping in the gel matrix. These negative factors reduce protein concentrations within a defined gel volume with increasing migration distance and, therefore, decrease protein separation efficiency. Enhancement of protein separation efficiency was investigated by implementing pulsed field-inversion gel electrophoresis (FIGE. Results Separation of model protein species and large protein complexes was compared between FIGE and constant field electrophoresis (CFE in different percentages of PAGs. Band intensities of proteins in FIGE with appropriate ratios of forward and backward pulse times were superior to CFE despite longer running times. These results revealed an increase in band intensity per defined gel volume. A biphasic protein relative mobility shift was observed in percentages of PAGs up to 14%. However, the effect of FIGE on protein separation was stochastic at higher PAG percentage. Rat liver lysates subjected to FIGE in the second-dimension separation of two-dimensional polyarcylamide gel electrophoresis (2D PAGE showed a 20% increase in the number of discernible spots compared with CFE. Nine common spots from both FIGE and CFE were selected for peptide sequencing by mass spectrometry (MS, which revealed higher final ion scores of all nine protein spots from FIGE. Native protein complexes ranging from 800 kDa to larger than 2000 kDa became apparent using FIGE compared with CFE. Conclusion The present investigation suggests that FIGE under appropriate conditions improves protein separation efficiency during PAGE as a result of increased local protein concentration. FIGE can be implemented with minimal additional instrumentation in any laboratory setting. Despite the tradeoff of longer running times, FIGE can be a powerful protein
Analysis of rainfall-induced slope instability using a field of local factor of safety
Lu, Ning; Şener-Kaya, Başak; Wayllace, Alexandra; Godt, Jonathan W.
2012-01-01
Slope-stability analyses are mostly conducted by identifying or assuming a potential failure surface and assessing the factor of safety (FS) of that surface. This approach of assigning a single FS to a potentially unstable slope provides little insight on where the failure initiates or the ultimate geometry and location of a landslide rupture surface. We describe a method to quantify a scalar field of FS based on the concept of the Coulomb stress and the shift in the state of stress toward failure that results from rainfall infiltration. The FS at each point within a hillslope is called the local factor of safety (LFS) and is defined as the ratio of the Coulomb stress at the current state of stress to the Coulomb stress of the potential failure state under the Mohr-Coulomb criterion. Comparative assessment with limit-equilibrium and hybrid finite element limit-equilibrium methods show that the proposed LFS is consistent with these approaches and yields additional insight into the geometry and location of the potential failure surface and how instability may initiate and evolve with changes in pore water conditions. Quantitative assessments applying the new LFS field method to slopes under infiltration conditions demonstrate that the LFS has the potential to overcome several major limitations in the classical FS methodologies such as the shape of the failure surface and the inherent underestimation of slope instability. Comparison with infinite-slope methods, including a recent extension to variably saturated conditions, shows further enhancement in assessing shallow landslide occurrence using the LFS methodology. Although we use only a linear elastic solution for the state of stress with no post-failure analysis that require more sophisticated elastoplastic or other theories, the LFS provides a new means to quantify the potential instability zones in hillslopes under variably saturated conditions using stress-field based methods.
Aerts, Sam; Deschrijver, Dirk; Verloock, Leen; Dhaene, Tom; Martens, Luc; Joseph, Wout
2013-10-01
In this study, a novel methodology is proposed to create heat maps that accurately pinpoint the outdoor locations with elevated exposure to radiofrequency electromagnetic fields (RF-EMF) in an extensive urban region (or, hotspots), and that would allow local authorities and epidemiologists to efficiently assess the locations and spectral composition of these hotspots, while at the same time developing a global picture of the exposure in the area. Moreover, no prior knowledge about the presence of radiofrequency radiation sources (e.g., base station parameters) is required. After building a surrogate model from the available data using kriging, the proposed method makes use of an iterative sampling strategy that selects new measurement locations at spots which are deemed to contain the most valuable information-inside hotspots or in search of them-based on the prediction uncertainty of the model. The method was tested and validated in an urban subarea of Ghent, Belgium with a size of approximately 1 km2. In total, 600 input and 50 validation measurements were performed using a broadband probe. Five hotspots were discovered and assessed, with maximum total electric-field strengths ranging from 1.3 to 3.1 V/m, satisfying the reference levels issued by the International Commission on Non-Ionizing Radiation Protection for exposure of the general public to RF-EMF. Spectrum analyzer measurements in these hotspots revealed five radiofrequency signals with a relevant contribution to the exposure. The radiofrequency radiation emitted by 900 MHz Global System for Mobile Communications (GSM) base stations was always dominant, with contributions ranging from 45% to 100%. Finally, validation of the subsequent surrogate models shows high prediction accuracy, with the final model featuring an average relative error of less than 2dB (factor 1.26 in electric-field strength), a correlation coefficient of 0.7, and a specificity of 0.96. Copyright © 2013 Elsevier Inc. All rights
Increase in local protein concentration by field-inversion gel electrophoresis.
Tsai, Henghang; Low, Teck Yew; Freeby, Steve; Paulus, Aran; Ramnarayanan, Kalpana; Cheng, Chung-Pui Paul; Leung, Hon-Chiu Eastwood
2007-09-26
Proteins that migrate through cross-linked polyacrylamide gels (PAGs) under the influence of a constant electric field experience negative factors, such as diffusion and non-specific trapping in the gel matrix. These negative factors reduce protein concentrations within a defined gel volume with increasing migration distance and, therefore, decrease protein separation efficiency. Enhancement of protein separation efficiency was investigated by implementing pulsed field-inversion gel electrophoresis (FIGE). Separation of model protein species and large protein complexes was compared between FIGE and constant field electrophoresis (CFE) in different percentages of PAGs. Band intensities of proteins in FIGE with appropriate ratios of forward and backward pulse times were superior to CFE despite longer running times. These results revealed an increase in band intensity per defined gel volume. A biphasic protein relative mobility shift was observed in percentages of PAGs up to 14%. However, the effect of FIGE on protein separation was stochastic at higher PAG percentage. Rat liver lysates subjected to FIGE in the second-dimension separation of two-dimensional polyarcylamide gel electrophoresis (2D PAGE) showed a 20% increase in the number of discernible spots compared with CFE. Nine common spots from both FIGE and CFE were selected for peptide sequencing by mass spectrometry (MS), which revealed higher final ion scores of all nine protein spots from FIGE. Native protein complexes ranging from 800 kDa to larger than 2000 kDa became apparent using FIGE compared with CFE. The present investigation suggests that FIGE under appropriate conditions improves protein separation efficiency during PAGE as a result of increased local protein concentration. FIGE can be implemented with minimal additional instrumentation in any laboratory setting. Despite the tradeoff of longer running times, FIGE can be a powerful protein separation tool.
Fewster, Christopher J
2015-08-06
The framework of locally covariant quantum field theory is discussed, motivated in part using 'ignorance principles'. It is shown how theories can be represented by suitable functors, so that physical equivalence of theories may be expressed via natural isomorphisms between the corresponding functors. The inhomogeneous scalar field is used to illustrate the ideas. It is argued that there are two reasonable definitions of the local physical content associated with a locally covariant theory; when these coincide, the theory is said to be dynamically local. The status of the dynamical locality condition is reviewed, as are its applications in relation to (i) the foundational question of what it means for a theory to represent the same physics in different space-times and (ii) a no-go result on the existence of natural states. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
Jiang, Xiangqian; Li, Jinjiang; Sun, Xiudong
2017-12-11
We study two-dimensional sub-wavelength atom localization based on the microwave coupling field controlling and spontaneously generated coherence (SGC) effect. For a five-level M-type atom, introducing a microwave coupling field between two upper levels and considering the quantum interference between two transitions from two upper levels to lower levels, the analytical expression of conditional position probability (CPP) distribution is obtained using the iterative method. The influence of the detuning of a spontaneously emitted photon, Rabi frequency of the microwave field, and the SGC effect on the CPP are discussed. The two-dimensional sub-half-wavelength atom localization with high-precision and high spatial resolution is achieved by adjusting the detuning and the Rabi frequency, where the atom can be localized in a region smaller thanλ/10×λ/10. The spatial resolution is improved significantly compared with the case without the microwave field.
International Nuclear Information System (INIS)
Schwadron, N A; Moebius, E; Adams, F C; Christian, E; Desiati, P; Frisch, P; Funsten, H O; Jokipii, J R; McComas, D J; Zank, G P
2015-01-01
The Interstellar Boundary Explorer (IBEX) observes enhanced Energetic Neutral Atoms (ENAs) emission in the keV energy range from a narrow (∼20° wide) ''ribbon'' in the sky that appears to be centered on the direction of the local interstellar (LIS) magnetic field. The Milagro collaboration, the Asγ collaboration and the IceCube observatory have recently made global maps of cosmic ray fluxes in the TeV energy range, revealing anisotropic structures ordered in part by the local interstellar magnetic field and the interstellar flow. This paper following from a recent publication in Science makes the link between these disparate observations by developing a simple model of the magnetic structure surrounding the heliosphere in the Local Interstellar Medium (LISM) that is consistent with both IBEX ENA fluxes and TeV cosmic ray anisotropies. The model also employs the revised velocity direction of the LIC derived from neutral He observations by IBEX. By modeling the propagation of cosmic rays through this magnetic field structure, we specifically show that (1) the large-scale TeV anisotropy provides a roughly consistent orientation for the local interstellar magnetic field at the center of the IBEX Ribbon and corroborates the ∼ 3 μG magnitude of the local interstellar magnetic field derived from IBEX observations of the global heliosphere; (2) and small-scale structures in cosmic rays (over < 30° angular scales) are influenced by the interstellar field interaction with the heliosphere at energies < 10 TeV. Thus, we provide a link between IBEX ENA observations, IBEX neutral observations of interstellar He, and TeV cosmic ray anisotropies, which are strongly influenced by the interactions between the local interstellar magnetic field, the flow of the local interstellar plasma, and the global heliosphere
Analysis of fracture patterns and local stress field variations in fractured reservoirs
Deckert, Hagen; Drews, Michael; Fremgen, Dominik; Wellmann, J. Florian
2010-05-01
independently estimated regional stress tensor is put as a boundary condition into the BE Model. The computed BE model allows to recognize local 3D stress tensor perturbations caused by the larger faults that act as mechanical inhomogeneities. The geometry of the fracture network from field work together with the local stress tensors derived from the 3D BE models allows examining normal and shear stresses on single fractures in different domains of the investigated area. This in turn is used to evaluate, which of the fractures might preferably act as fluid conduits by describing the dilation potential of single fractures. The combination of an improved understanding of the fracture network along with local stress tensors variations from mechanical models will provide a sound evaluation of fluid pathways in fractured reservoirs. In future applications the accurate investigation of large discontinuity pattern in outcrops might be used for a better mathematical definition of fracture networks which could be implemented into numerical simulations of fluid flow.
Directory of Open Access Journals (Sweden)
Abdullah N. Alkhalaf
2010-07-01
Full Text Available The objective of this study was to find out prevalence and types of avian influenza virus (AIV among broilers, native chickens, ducks and pigeons in Saudi Arabia. Field investigation was carried out in four localities including Al-Qassim, Hail, Al-Jouf and Northern Border regions. Serum sample, tracheal and cloacal swabs were collected from broilers (n=1561, layers (n=988, ducks (n=329 and pigeons (n=450 from these localities and tested for three different avian influenza viruses (H9, H5 and H3 using Enzyme linked immunosorbent (ELISA test, hamagglutination inhibition (HI test and polymerase chain reaction (PCR. All tested samples were negative for H5 and H3 viruses. In contrast, all positive results were found to be for H9 AI virus using PCR, ELISA and HI test. Chicken sera tested by ELISA for AIV revealed the highest positive samples in Northern Border regions (45.71%, followed by Al-Jouf (29.65%, Al-Qassim (23.98% and Hial (20.94% with non-significant difference (χ2=5.983; P=0.112. HI test carried out on duck sera revealed 35.90% prevalence of antibodies against AIV. PCR amplification resulted in 34.28 and 21.36% positive samples in ducks and chickens, respectively. The highest (45.71% PCR positive chicken samples were from Northern Border regions, followed by Al-Jouf (24.13%, Al-Qassim (19.30% and Hail (16.69% with significant difference (χ2=7.620; P=0.055. All tested pigeons samples were negative for the three virus serotypes included in the study.
International Nuclear Information System (INIS)
Halasah, Suleiman A.; Pearlmutter, David; Feuermann, Daniel
2013-01-01
In this study we employ Life-Cycle Assessment to evaluate the energy-related impacts of photovoltaic systems at different scales of integration, in an arid region with especially high solar irradiation. Based on the electrical output and embodied energy of a selection of fixed and tracking systems and including concentrator photovoltaic (CPV) and varying cell technology, we calculate a number of energy evaluation metrics, including the energy payback time (EPBT), energy return factor (ERF), and life-cycle CO 2 emissions offset per unit aperture and land area. Studying these metrics in the context of a regionally limited setting, it was found that utilizing existing infrastructure such as existing building roofs and shade structures does significantly reduce the embodied energy requirements (by 20–40%) and in turn the EPBT of flat-plate PV systems due to the avoidance of energy-intensive balance of systems (BOS) components like foundations. Still, high-efficiency CPV field installations were found to yield the shortest EPBT, the highest ERF and the largest life-cycle CO 2 offsets—under the condition that land availability is not a limitation. A greater life-cycle energy return and carbon offset per unit land area is yielded by locally-integrated non-concentrating systems, despite their lower efficiency per unit module area. - Highlights: ► We evaluate life-cycle energy impacts of PV systems at different scales. ► We calculate the energy payback time, return factor and CO 2 emissions offset. ► Utilizing existing structures significantly improves metrics of flat-plate PV. ► High-efficiency CPV installations yield best return and offset per aperture area. ► Locally-integrated flat-plate systems yield best return and offset per land area.
Wen, Xiao-Gang
2017-05-01
We propose a generic construction of exactly soluble local bosonic models that realize various topological orders with gappable boundaries. In particular, we construct an exactly soluble bosonic model that realizes a (3+1)-dimensional [(3+1)D] Z2-gauge theory with emergent fermionic Kramers doublet. We show that the emergence of such a fermion will cause the nucleation of certain topological excitations in space-time without pin+ structure. The exactly soluble model also leads to a statistical transmutation in (3+1)D. In addition, we construct exactly soluble bosonic models that realize 2 types of time-reversal symmetry-enriched Z2 topological orders in 2+1 dimensions, and 20 types of simplest time-reversal symmetry-enriched topological (SET) orders which have only one nontrivial pointlike and stringlike topological excitation. Many physical properties of those topological states are calculated using the exactly soluble models. We find that some time-reversal SET orders have pointlike excitations that carry Kramers doublet, a fractionalized time-reversal symmetry. We also find that some Z2 SET orders have stringlike excitations that carry anomalous (nononsite) Z2 symmetry, which can be viewed as a fractionalization of Z2 symmetry on strings. Our construction is based on cochains and cocycles in algebraic topology, which is very versatile. In principle, it can also realize emergent topological field theory beyond the twisted gauge theory.
Energy Technology Data Exchange (ETDEWEB)
Hasegawa, Tomoyuki [School of Allied Health Sciences, Kitasato University, 1-15-1, Kitasato, Minamiku, Sagamihara, Kanagawa, 252-0373 (Japan); Sato, Yasushi [National Institute of Advanced Industrial Science and Technology, 1-1-1, Umezono, Tsukuba, Ibaraki, 305-8568 (Japan); Oda, Keiichi [Tokyo Metropolitan Institute of Gerontology, 1-1, Nakamachi, Itabashi, Tokyo, 173-0022 (Japan); Wada, Yasuhiro [RIKEN Center for Molecular Imaging Science, 6-7-3, Minamimachi, Minatoshima, Chuo, Kobe, Hyogo, 650-0047 (Japan); Murayama, Hideo [National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage, Chiba, 263-8555 (Japan); Yamada, Takahiro, E-mail: hasegawa@kitasato-u.ac.jp [Japan Radioisotope Association, 2-28-45, Komagome, Bunkyo-ku, Tokyo, 113-8941 (Japan)
2011-09-21
The uncertainty of radioactivity concentrations measured with positron emission tomography (PET) scanners ultimately depends on the uncertainty of the calibration factors. A new practical calibration scheme using point-like {sup 22}Na radioactive sources has been developed. The purpose of this study is to theoretically investigate the effects of the associated 1.275 MeV {gamma} rays on the calibration factors. The physical processes affecting the coincidence data were categorized in order to derive approximate semi-quantitative formulae. Assuming the design parameters of some typical commercial PET scanners, the effects of the {gamma} rays as relative deviations in the calibration factors were evaluated by semi-quantitative formulae and a Monte Carlo simulation. The relative deviations in the calibration factors were less than 4%, depending on the details of the PET scanners. The event losses due to rejecting multiple coincidence events of scattered {gamma} rays had the strongest effect. The results from the semi-quantitative formulae and the Monte Carlo simulation were consistent and were useful in understanding the underlying mechanisms. The deviations are considered small enough to correct on the basis of precise Monte Carlo simulation. This study thus offers an important theoretical basis for the validity of the calibration method using point-like {sup 22}Na radioactive sources.
International Nuclear Information System (INIS)
Michmizos, K P; Nikita, K S; Sakas, D
2011-01-01
Studies on neurophysiological correlates of the functional magnetic resonance imaging (fMRI) signals reveal a strong relationship between the local field potential (LFP) acquired invasively and metabolic signal changes in fMRI experiments. Most of these studies failed to reveal an analogous relationship between metabolic signals and the spiking activity. That would allow for the prediction of the neural activity exclusively from the fMRI signals. However, the relationship between fMRI signals and spiking activity can be inferred indirectly provided that the LFPs can be used to predict the spiking activity of the area. Until now, only the LFP–spike relationship in cortical areas has been examined. Herein, we show that the spiking activity can be predicted by the LFPs acquired in a deep nucleus, namely the subthalamic nucleus (STN), using a nonlinear cascade model. The model can reproduce the spike patterns inside the motor area of the STN that represent information about the motor plans. Our findings expand the possibility of further recruiting non-invasive neuroimaging techniques to understand the activity of the STN and predict or even control movement
Directory of Open Access Journals (Sweden)
Mohammad S. Islam
2017-01-01
Full Text Available Decoding neural activities related to voluntary and involuntary movements is fundamental to understanding human brain motor circuits and neuromotor disorders and can lead to the development of neuromotor prosthetic devices for neurorehabilitation. This study explores using recorded deep brain local field potentials (LFPs for robust movement decoding of Parkinson’s disease (PD and Dystonia patients. The LFP data from voluntary movement activities such as left and right hand index finger clicking were recorded from patients who underwent surgeries for implantation of deep brain stimulation electrodes. Movement-related LFP signal features were extracted by computing instantaneous power related to motor response in different neural frequency bands. An innovative neural network ensemble classifier has been proposed and developed for accurate prediction of finger movement and its forthcoming laterality. The ensemble classifier contains three base neural network classifiers, namely, feedforward, radial basis, and probabilistic neural networks. The majority voting rule is used to fuse the decisions of the three base classifiers to generate the final decision of the ensemble classifier. The overall decoding performance reaches a level of agreement (kappa value at about 0.729±0.16 for decoding movement from the resting state and about 0.671±0.14 for decoding left and right visually cued movements.
Hybrid Scheme for Modeling Local Field Potentials from Point-Neuron Networks.
Hagen, Espen; Dahmen, David; Stavrinou, Maria L; Lindén, Henrik; Tetzlaff, Tom; van Albada, Sacha J; Grün, Sonja; Diesmann, Markus; Einevoll, Gaute T
2016-12-01
With rapidly advancing multi-electrode recording technology, the local field potential (LFP) has again become a popular measure of neuronal activity in both research and clinical applications. Proper understanding of the LFP requires detailed mathematical modeling incorporating the anatomical and electrophysiological features of neurons near the recording electrode, as well as synaptic inputs from the entire network. Here we propose a hybrid modeling scheme combining efficient point-neuron network models with biophysical principles underlying LFP generation by real neurons. The LFP predictions rely on populations of network-equivalent multicompartment neuron models with layer-specific synaptic connectivity, can be used with an arbitrary number of point-neuron network populations, and allows for a full separation of simulated network dynamics and LFPs. We apply the scheme to a full-scale cortical network model for a ∼1 mm 2 patch of primary visual cortex, predict laminar LFPs for different network states, assess the relative LFP contribution from different laminar populations, and investigate effects of input correlations and neuron density on the LFP. The generic nature of the hybrid scheme and its public implementation in hybridLFPy form the basis for LFP predictions from other and larger point-neuron network models, as well as extensions of the current application with additional biological detail. © The Author 2016. Published by Oxford University Press.
Decoding Pigeon Behavior Outcomes Using Functional Connections among Local Field Potentials.
Chen, Yan; Liu, Xinyu; Li, Shan; Wan, Hong
2018-01-01
Recent studies indicate that the local field potential (LFP) carries information about an animal's behavior, but issues regarding whether there are any relationships between the LFP functional networks and behavior tasks as well as whether it is possible to employ LFP network features to decode the behavioral outcome in a single trial remain unresolved. In this study, we developed a network-based method to decode the behavioral outcomes in pigeons by using the functional connectivity strength values among LFPs recorded from the nidopallium caudolaterale (NCL). In our method, the functional connectivity strengths were first computed based on the synchronization likelihood. Second, the strength values were unwrapped into row vectors and their dimensions were then reduced by principal component analysis. Finally, the behavioral outcomes in single trials were decoded using leave-one-out combined with the k -nearest neighbor method. The results showed that the LFP functional network based on the gamma-band was related to the goal-directed behavior of pigeons. Moreover, the accuracy of the network features (74 ± 8%) was significantly higher than that of the power features (61 ± 12%). The proposed method provides a powerful tool for decoding animal behavior outcomes using a neural functional network.
Local Electric Field Facilitates High-Performance Li-Ion Batteries.
Liu, Youwen; Zhou, Tengfei; Zheng, Yang; He, Zhihai; Xiao, Chong; Pang, Wei Kong; Tong, Wei; Zou, Youming; Pan, Bicai; Guo, Zaiping; Xie, Yi
2017-08-22
By scrutinizing the energy storage process in Li-ion batteries, tuning Li-ion migration behavior by atomic level tailoring will unlock great potential for pursuing higher electrochemical performance. Vacancy, which can effectively modulate the electrical ordering on the nanoscale, even in tiny concentrations, will provide tempting opportunities for manipulating Li-ion migratory behavior. Herein, taking CuGeO 3 as a model, oxygen vacancies obtained by reducing the thickness dimension down to the atomic scale are introduced in this work. As the Li-ion storage progresses, the imbalanced charge distribution emerging around the oxygen vacancies could induce a local built-in electric field, which will accelerate the ions' migration rate by Coulomb forces and thus have benefits for high-rate performance. Furthermore, the thus-obtained CuGeO 3 ultrathin nanosheets (CGOUNs)/graphene van der Waals heterojunctions are used as anodes in Li-ion batteries, which deliver a reversible specific capacity of 1295 mAh g -1 at 100 mA g -1 , with improved rate capability and cycling performance compared to their bulk counterpart. Our findings build a clear connection between the atomic/defect/electronic structure and intrinsic properties for designing high-efficiency electrode materials.
Long-term detection of Parkinsonian tremor activity from subthalamic nucleus local field potentials.
Houston, Brady; Blumenfeld, Zack; Quinn, Emma; Bronte-Stewart, Helen; Chizeck, Howard
2015-01-01
Current deep brain stimulation paradigms deliver continuous stimulation to deep brain structures to ameliorate the symptoms of Parkinson's disease. This continuous stimulation has undesirable side effects and decreases the lifespan of the unit's battery, necessitating earlier replacement. A closed-loop deep brain stimulator that uses brain signals to determine when to deliver stimulation based on the occurrence of symptoms could potentially address these drawbacks of current technology. Attempts to detect Parkinsonian tremor using brain signals recorded during the implantation procedure have been successful. However, the ability of these methods to accurately detect tremor over extended periods of time is unknown. Here we use local field potentials recorded during a deep brain stimulation clinical follow-up visit 1 month after initial programming to build a tremor detection algorithm and use this algorithm to detect tremor in subsequent visits up to 8 months later. Using this method, we detected the occurrence of tremor with accuracies between 68-93%. These results demonstrate the potential of tremor detection methods for efficacious closed-loop deep brain stimulation over extended periods of time.
Yubo Wang; Tatinati, Sivanagaraja; Liyu Huang; Kim Jeong Hong; Shafiq, Ghufran; Veluvolu, Kalyana C; Khong, Andy W H
2017-07-01
Extracranial robotic radiotherapy employs external markers and a correlation model to trace the tumor motion caused by the respiration. The real-time tracking of tumor motion however requires a prediction model to compensate the latencies induced by the software (image data acquisition and processing) and hardware (mechanical and kinematic) limitations of the treatment system. A new prediction algorithm based on local receptive fields extreme learning machines (pLRF-ELM) is proposed for respiratory motion prediction. All the existing respiratory motion prediction methods model the non-stationary respiratory motion traces directly to predict the future values. Unlike these existing methods, the pLRF-ELM performs prediction by modeling the higher-level features obtained by mapping the raw respiratory motion into the random feature space of ELM instead of directly modeling the raw respiratory motion. The developed method is evaluated using the dataset acquired from 31 patients for two horizons in-line with the latencies of treatment systems like CyberKnife. Results showed that pLRF-ELM is superior to that of existing prediction methods. Results further highlight that the abstracted higher-level features are suitable to approximate the nonlinear and non-stationary characteristics of respiratory motion for accurate prediction.
Khorasani, Abed; Heydari Beni, Nargess; Shalchyan, Vahid; Daliri, Mohammad Reza
2016-10-21
Local field potential (LFP) signals recorded by intracortical microelectrodes implanted in primary motor cortex can be used as a high informative input for decoding of motor functions. Recent studies show that different kinematic parameters such as position and velocity can be inferred from multiple LFP signals as precisely as spiking activities, however, continuous decoding of the force magnitude from the LFP signals in freely moving animals has remained an open problem. Here, we trained three rats to press a force sensor for getting a drop of water as a reward. A 16-channel micro-wire array was implanted in the primary motor cortex of each trained rat, and obtained LFP signals were used for decoding of the continuous values recorded by the force sensor. Average coefficient of correlation and the coefficient of determination between decoded and actual force signals were r = 0.66 and R 2 = 0.42, respectively. We found that LFP signal on gamma frequency bands (30-120 Hz) had the most contribution in the trained decoding model. This study suggests the feasibility of using low number of LFP channels for the continuous force decoding in freely moving animals resembling BMI systems in real life applications.
Energy Technology Data Exchange (ETDEWEB)
Aerts, Sam, E-mail: sam.aerts@intec.ugent.be; Deschrijver, Dirk; Verloock, Leen; Dhaene, Tom; Martens, Luc; Joseph, Wout
2013-10-15
In this study, a novel methodology is proposed to create heat maps that accurately pinpoint the outdoor locations with elevated exposure to radiofrequency electromagnetic fields (RF-EMF) in an extensive urban region (or, hotspots), and that would allow local authorities and epidemiologists to efficiently assess the locations and spectral composition of these hotspots, while at the same time developing a global picture of the exposure in the area. Moreover, no prior knowledge about the presence of radiofrequency radiation sources (e.g., base station parameters) is required. After building a surrogate model from the available data using kriging, the proposed method makes use of an iterative sampling strategy that selects new measurement locations at spots which are deemed to contain the most valuable information—inside hotspots or in search of them—based on the prediction uncertainty of the model. The method was tested and validated in an urban subarea of Ghent, Belgium with a size of approximately 1 km{sup 2}. In total, 600 input and 50 validation measurements were performed using a broadband probe. Five hotspots were discovered and assessed, with maximum total electric-field strengths ranging from 1.3 to 3.1 V/m, satisfying the reference levels issued by the International Commission on Non-Ionizing Radiation Protection for exposure of the general public to RF-EMF. Spectrum analyzer measurements in these hotspots revealed five radiofrequency signals with a relevant contribution to the exposure. The radiofrequency radiation emitted by 900 MHz Global System for Mobile Communications (GSM) base stations was always dominant, with contributions ranging from 45% to 100%. Finally, validation of the subsequent surrogate models shows high prediction accuracy, with the final model featuring an average relative error of less than 2 dB (factor 1.26 in electric-field strength), a correlation coefficient of 0.7, and a specificity of 0.96. -- Highlights: • We present an
International Nuclear Information System (INIS)
Aerts, Sam; Deschrijver, Dirk; Verloock, Leen; Dhaene, Tom; Martens, Luc; Joseph, Wout
2013-01-01
In this study, a novel methodology is proposed to create heat maps that accurately pinpoint the outdoor locations with elevated exposure to radiofrequency electromagnetic fields (RF-EMF) in an extensive urban region (or, hotspots), and that would allow local authorities and epidemiologists to efficiently assess the locations and spectral composition of these hotspots, while at the same time developing a global picture of the exposure in the area. Moreover, no prior knowledge about the presence of radiofrequency radiation sources (e.g., base station parameters) is required. After building a surrogate model from the available data using kriging, the proposed method makes use of an iterative sampling strategy that selects new measurement locations at spots which are deemed to contain the most valuable information—inside hotspots or in search of them—based on the prediction uncertainty of the model. The method was tested and validated in an urban subarea of Ghent, Belgium with a size of approximately 1 km 2 . In total, 600 input and 50 validation measurements were performed using a broadband probe. Five hotspots were discovered and assessed, with maximum total electric-field strengths ranging from 1.3 to 3.1 V/m, satisfying the reference levels issued by the International Commission on Non-Ionizing Radiation Protection for exposure of the general public to RF-EMF. Spectrum analyzer measurements in these hotspots revealed five radiofrequency signals with a relevant contribution to the exposure. The radiofrequency radiation emitted by 900 MHz Global System for Mobile Communications (GSM) base stations was always dominant, with contributions ranging from 45% to 100%. Finally, validation of the subsequent surrogate models shows high prediction accuracy, with the final model featuring an average relative error of less than 2 dB (factor 1.26 in electric-field strength), a correlation coefficient of 0.7, and a specificity of 0.96. -- Highlights: • We present an
Faye, Grégory; Rankin, James; Chossat, Pascal
2013-05-01
The existence of spatially localized solutions in neural networks is an important topic in neuroscience as these solutions are considered to characterize working (short-term) memory. We work with an unbounded neural network represented by the neural field equation with smooth firing rate function and a wizard hat spatial connectivity. Noting that stationary solutions of our neural field equation are equivalent to homoclinic orbits in a related fourth order ordinary differential equation, we apply normal form theory for a reversible Hopf bifurcation to prove the existence of localized solutions; further, we present results concerning their stability. Numerical continuation is used to compute branches of localized solution that exhibit snaking-type behaviour. We describe in terms of three parameters the exact regions for which localized solutions persist.
Energy Technology Data Exchange (ETDEWEB)
Kamble, Ramesh B., E-mail: rbk.physics@coep.ac.in [Department of Physics, Indian Institute of Science, Bangalore 560012, Karnataka (India); Department of Physics, College of Engineering, Pune 411005, Maharashtra (India); Tanty, Narendra; Patra, Ananya; Prasad, V. [Department of Physics, Indian Institute of Science, Bangalore 560012, Karnataka (India)
2016-08-22
We report the potential field emission of highly conducting metallic perovskite lanthanum nickelate (LaNiO{sub 3}) from the nanostructured pyramidal and whisker shaped tips as electron emitters. Nano particles of lanthanum nickelate (LNO) were prepared by sol-gel route. Structural and morphological studies have been carried out. Field emission of LNO exhibited high emission current density, J = 3.37 mA/cm{sup 2} at a low threshold electric field, E{sub th} = 16.91 V/μm, obeying Fowler–Nordheim tunneling. The DC electrical resistivity exhibited upturn at 11.6 K indicating localization of electron at low temperature. Magnetoresistance measurement at different temperatures confirmed strong localization in nanostructured LNO obeying Anderson localization effect at low temperature.
International Nuclear Information System (INIS)
Leznov, A.N.
1994-01-01
A general method for the construction of solutions of the d'Alamberian and double d'Alamberian (harmonic and bi-harmonic) equations with local dependence of arbitrary functions upon two independent arguments is proposed. The connection between solutions of this kind and self-dual configurations of gauge fields having no singularities is established. 5 refs
International Nuclear Information System (INIS)
Pham, Thanh Son; Ranaweera, Aruna Kumara; Ngo, Duc Viet; Lee, Jong-Wook
2017-01-01
To meet both safety and efficiency demands of future wireless power transfer (WPT) systems, field leakage to the nearby environment should be controlled below a certain level. Therefore, field localization is one of the key issues in advanced WPT systems. Recently, metamaterials have shown great potential for enhanced control of electromagnetic propagation in various environments. In this work, we investigate a locally modified metamaterial to create a two-dimensional (2D) cavity for field localization at a sub-wavelength scale. We also show that the field localization in the cavity can be explained using Fano-type interference. We believe that this is one of the first works demonstrating that Fano-type interference can be applied for resonance-coupled mid-range WPT. Using the proposed approach, we achieve a localized WPT in a region that is eight times smaller than that of a transmit coil. At a distance of 0.6 meters, the measured efficiency is 56.5%, which represents a six-fold and two-fold enhancement compared to free space and uniform metamaterial slabs, respectively. (paper)
Son Pham, Thanh; Kumara Ranaweera, Aruna; Viet Ngo, Duc; Lee, Jong-Wook
2017-08-01
To meet both safety and efficiency demands of future wireless power transfer (WPT) systems, field leakage to the nearby environment should be controlled below a certain level. Therefore, field localization is one of the key issues in advanced WPT systems. Recently, metamaterials have shown great potential for enhanced control of electromagnetic propagation in various environments. In this work, we investigate a locally modified metamaterial to create a two-dimensional (2D) cavity for field localization at a sub-wavelength scale. We also show that the field localization in the cavity can be explained using Fano-type interference. We believe that this is one of the first works demonstrating that Fano-type interference can be applied for resonance-coupled mid-range WPT. Using the proposed approach, we achieve a localized WPT in a region that is eight times smaller than that of a transmit coil. At a distance of 0.6 meters, the measured efficiency is 56.5%, which represents a six-fold and two-fold enhancement compared to free space and uniform metamaterial slabs, respectively.
Local field potential correlates of auditory working memory in primate dorsal temporal pole.
Bigelow, James; Ng, Chi-Wing; Poremba, Amy
2016-06-01
Dorsal temporal pole (dTP) is a cortical region at the rostral end of the superior temporal gyrus that forms part of the ventral auditory object processing pathway. Anatomical connections with frontal and medial temporal areas, as well as a recent single-unit recording study, suggest this area may be an important part of the network underlying auditory working memory (WM). To further elucidate the role of dTP in auditory WM, local field potentials (LFPs) were recorded from the left dTP region of two rhesus macaques during an auditory delayed matching-to-sample (DMS) task. Sample and test sounds were separated by a 5-s retention interval, and a behavioral response was required only if the sounds were identical (match trials). Sensitivity of auditory evoked responses in dTP to behavioral significance and context was further tested by passively presenting the sounds used as auditory WM memoranda both before and after the DMS task. Average evoked potentials (AEPs) for all cue types and phases of the experiment comprised two small-amplitude early onset components (N20, P40), followed by two broad, large-amplitude components occupying the remainder of the stimulus period (N120, P300), after which a final set of components were observed following stimulus offset (N80OFF, P170OFF). During the DMS task, the peak amplitude and/or latency of several of these components depended on whether the sound was presented as the sample or test, and whether the test matched the sample. Significant differences were also observed among the DMS task and passive exposure conditions. Comparing memory-related effects in the LFP signal with those obtained in the spiking data raises the possibility some memory-related activity in dTP may be locally produced and actively generated. The results highlight the involvement of dTP in auditory stimulus identification and recognition and its sensitivity to the behavioral significance of sounds in different contexts. This article is part of a Special
DEFF Research Database (Denmark)
Nerkararyan, Khachatur V.; Yezekyan, Torgom S.; Bozhevolnyi, Sergey I.
2018-01-01
electromagnetic field. Considering the QDE-field interactions in the regime of strong QDE-field coupling, we show that the feedback provided by the MNP on the QDE (due to the LSP excitation with the field generated by the dipole moment of the QDE transition) influences significantly the coherent process of Rabi...
Optical Implementation of Non-locality with Coherent Light Fields for Quantum Communication
Lee, Kim Fook
2008-01-01
Polarization correlations of two distant observers are observed by using coherent light fields based on Stapp's formulation of nonlocality. Using a 50/50 beam splitter transformation, a vertically polarized coherent light field is found to be entangled with a horizontally polarized coherent noise field. The superposed light fields at each output port of the beam splitter are sent to two distant observers, where the fields are interfered and manipulated at each observer by using a quarter wave...
International Nuclear Information System (INIS)
Binns, D.S.; O'Brien, T.J.; Murphy, M.; Cook, M.J.; Hicks, R.J.
1999-01-01
Full text: PET scanning is a useful ancillary technique in the localization of intractable partial epilepsy, but its widespread use has been limited by the high cost of traditional PET equipment and radioisotopes. The use of 3D-scanning mode with a large-field of-view PET scanner involves lower equipment costs and requires significantly lower doses of radioisotope. Our aim was to report our preliminary experience of the use of a 3-D, large-field-of-view scanner for FDG-PET studies in the localization of partial epilepsy. 31 patients (pts) with partial epilepsy were studied. The FDG-PET scans were reviewed blindly by a single reviewer without knowledge of seizure localization on structural imaging or ictal electroencephalographic (EEG) monitoring. The PET results were correlated with the localization by more traditional techniques and the results on surgery when available. A localized region of hypometabolism on FDG-PET scanning was reported in 26/31 (84%) patients (21 temporal, 5 extratemporal). This compared favourably with volumetric MRI on which 19/31 (61%) had a focal potentially epileptogenic abnormality, all of which were concordant with the PET localization. PET was concordant with ictal EEG onset in all 22 patients with localizing studies, including 5 pts with normal MRI. PET demonstrated localized hypometabolism in 4/5 pts with non-localizing ictal EEG and was concordant in both pts with abnormal MRI in this group. PET was considered normal in 4 pts, including 3 pts with normal MRI but localizing EEG and 1 pt without EEG or MRI abnormality. One pt with a localizing EEG and normal MRI was felt to have bitemporal hypometabolism. Five patients have subsequently had resective epilepsy surgery with 4 currently seizure-free and 1 significantly improved. Four patients are planned for surgery in the near future. In conclusion, FDG-PET using a 3-D, large-field-of view PET scanner provides sensitive and specific localization in partial epilepsy, and may provide a
Directory of Open Access Journals (Sweden)
Sebastian J Lehmann
Full Text Available The execution of reach-to-grasp movements in order to interact with our environment is an important subset of the human movement repertoire. To coordinate such goal-directed movements, information about the relative spatial position of target and effector (in this case the hand has to be continuously integrated and processed. Recently, we reported the existence of spatial representations in spiking-activity of the cortical fronto-parietal grasp network (Lehmann & Scherberger 2013, and in particular in the anterior intraparietal cortex (AIP. To further investigate the nature of these spatial representations, we explored in two rhesus monkeys (Macaca mulatta how different frequency bands of the local field potential (LFP in AIP are modulated by grip type, target position, and gaze position, during the planning and execution of reach-to-grasp movements. We systematically varied grasp type, spatial target, and gaze position and found that both spatial and grasp information were encoded in a variety of frequency bands (1-13Hz, 13-30Hz, 30-60Hz, and 60-100Hz, respectively. Whereas the representation of grasp type strongly increased towards and during movement execution, spatial information was represented throughout the task. Both spatial and grasp type representations could be readily decoded from all frequency bands. The fact that grasp type and spatial (reach information was found not only in spiking activity, but also in various LFP frequency bands of AIP, might significantly contribute to the development of LFP-based neural interfaces for the control of upper limb prostheses.
Observation of local fields in ZnO using the 111Cd probe
International Nuclear Information System (INIS)
Sato, W.; Komatsuda, S.; Imagawa, E.; Ohkubo, Y.; Yamada, Y.
2011-01-01
The authors prepared the ZnO sample ( 111m Cd-CZO) that contains totally 0.5 at.% of Cd including 111m Cd, and the ZnO sample ( 111m Cd-ICZO) made by doping with 0.5 at.% of In to 111m Cd-CZO, and measured γ-ray perturbed angular correlation (PAC) spectra. They compared these measurement results with the PAC spectra that were observed in the sample ( 111 In-IZO) made by doping with 0.5 at.% of stable In isotope in addition to ( 111 In→) 111 Cd probe, and examined the two characteristics of 111 In-IZO. As for 111 In-IZO, large electric field gradient and late effect due to remarkable EC decay was observed compared with the sample ( 111 In-UZO), where several ppt level of ( 111 In→) 111 Cd probe was solely doped into ZnO. This fact suggests that In atoms and 111 In atoms flocculate locally. When this flocculating condition is made of many In atom groups, several occupation positions of 111 In can be considered, and they cannot form the single frequency component as obtained in the PAC spectra. Therefore, the results of this experiment can be understood that In atoms themselves form the pairs in the nearest position while replacing the lattice positions of Zn. In is generally stable under the condition of three valence, but it can take one valence depending on compounds. Therefore, it can be considered that if In 3+ and In + mixture in this ratio replace Zn 2+ sites, this pairs can exist from the viewpoint of charge balance. (A.O.)
Directory of Open Access Journals (Sweden)
Rikkert Hindriks
Full Text Available Planar intra-cortical electrode (Utah arrays provide a unique window into the spatial organization of cortical activity. Reconstruction of the current source density (CSD underlying such recordings, however, requires "inverting" Poisson's equation. For inter-laminar recordings, this is commonly done by the CSD method, which consists in taking the second-order spatial derivative of the recorded local field potentials (LFPs. Although the CSD method has been tremendously successful in mapping the current generators underlying inter-laminar LFPs, its application to planar recordings is more challenging. While for inter-laminar recordings the CSD method seems reasonably robust against violations of its assumptions, is it unclear as to what extent this holds for planar recordings. One of the objectives of this study is to characterize the conditions under which the CSD method can be successfully applied to Utah array data. Using forward modeling, we find that for spatially coherent CSDs, the CSD method yields inaccurate reconstructions due to volume-conducted contamination from currents in deeper cortical layers. An alternative approach is to "invert" a constructed forward model. The advantage of this approach is that any a priori knowledge about the geometrical and electrical properties of the tissue can be taken into account. Although several inverse methods have been proposed for LFP data, the applicability of existing electroencephalographic (EEG and magnetoencephalographic (MEG inverse methods to LFP data is largely unexplored. Another objective of our study therefore, is to assess the applicability of the most commonly used EEG/MEG inverse methods to Utah array data. Our main conclusion is that these inverse methods provide more accurate CSD reconstructions than the CSD method. We illustrate the inverse methods using event-related potentials recorded from primary visual cortex of a macaque monkey during a motion discrimination task.
Theoretical analysis of the local field potential in deep brain stimulation applications.
Directory of Open Access Journals (Sweden)
Scott F Lempka
Full Text Available Deep brain stimulation (DBS is a common therapy for treating movement disorders, such as Parkinson's disease (PD, and provides a unique opportunity to study the neural activity of various subcortical structures in human patients. Local field potential (LFP recordings are often performed with either intraoperative microelectrodes or DBS leads and reflect oscillatory activity within nuclei of the basal ganglia. These LFP recordings have numerous clinical implications and might someday be used to optimize DBS outcomes in closed-loop systems. However, the origin of the recorded LFP is poorly understood. Therefore, the goal of this study was to theoretically analyze LFP recordings within the context of clinical DBS applications. This goal was achieved with a detailed recording model of beta oscillations (∼20 Hz in the subthalamic nucleus. The recording model consisted of finite element models of intraoperative microelectrodes and DBS macroelectrodes implanted in the brain along with multi-compartment cable models of STN projection neurons. Model analysis permitted systematic investigation into a number of variables that can affect the composition of the recorded LFP (e.g. electrode size, electrode impedance, recording configuration, and filtering effects of the brain, electrode-electrolyte interface, and recording electronics. The results of the study suggest that the spatial reach of the LFP can extend several millimeters. Model analysis also showed that variables such as electrode geometry and recording configuration can have a significant effect on LFP amplitude and spatial reach, while the effects of other variables, such as electrode impedance, are often negligible. The results of this study provide insight into the origin of the LFP and identify variables that need to be considered when analyzing LFP recordings in clinical DBS applications.
Phase Locking of Multiple Single Neurons to the Local Field Potential in Cat V1.
Martin, Kevan A C; Schröder, Sylvia
2016-02-24
The local field potential (LFP) is thought to reflect a temporal reference for neuronal spiking, which may facilitate information coding and orchestrate the communication between neural populations. To explore this proposed role, we recorded the LFP and simultaneously the spike activity of one to three nearby neurons in V1 of anesthetized cats during the presentation of drifting sinusoidal gratings, binary dense noise stimuli, and natural movies. In all stimulus conditions and during spontaneous activity, the average LFP power at frequencies >20 Hz was higher when neurons were spiking versus not spiking. The spikes were weakly but significantly phase locked to all frequencies of the LFP. The average spike phase of the LFP was stable across high and low levels of LFP power, but the strength of phase locking at low frequencies (≤10 Hz) increased with increasing LFP power. In a next step, we studied how strong stimulus responses of single neurons are reflected in the LFP and the LFP-spike relationship. We found that LFP power was slightly increased and phase locking was slightly stronger during strong compared with weak stimulus-locked responses. In summary, the coupling strength between high frequencies of the LFP and spikes was not strongly modulated by LFP power, which is thought to reflect spiking synchrony, nor was it strongly influenced by how strongly the neuron was driven by the stimulus. Furthermore, a comparison between neighboring neurons showed no clustering of preferred LFP phase. We argue that hypotheses on the relevance of phase locking in their current form are inconsistent with our findings. Copyright © 2016 the authors 0270-6474/16/362494-09$15.00/0.
Dynamic Neural State Identification in Deep Brain Local Field Potentials of Neuropathic Pain.
Luo, Huichun; Huang, Yongzhi; Du, Xueying; Zhang, Yunpeng; Green, Alexander L; Aziz, Tipu Z; Wang, Shouyan
2018-01-01
In neuropathic pain, the neurophysiological and neuropathological function of the ventro-posterolateral nucleus of the thalamus (VPL) and the periventricular gray/periaqueductal gray area (PVAG) involves multiple frequency oscillations. Moreover, oscillations related to pain perception and modulation change dynamically over time. Fluctuations in these neural oscillations reflect the dynamic neural states of the nucleus. In this study, an approach to classifying the synchronization level was developed to dynamically identify the neural states. An oscillation extraction model based on windowed wavelet packet transform was designed to characterize the activity level of oscillations. The wavelet packet coefficients sparsely represented the activity level of theta and alpha oscillations in local field potentials (LFPs). Then, a state discrimination model was designed to calculate an adaptive threshold to determine the activity level of oscillations. Finally, the neural state was represented by the activity levels of both theta and alpha oscillations. The relationship between neural states and pain relief was further evaluated. The performance of the state identification approach achieved sensitivity and specificity beyond 80% in simulation signals. Neural states of the PVAG and VPL were dynamically identified from LFPs of neuropathic pain patients. The occurrence of neural states based on theta and alpha oscillations were correlated to the degree of pain relief by deep brain stimulation. In the PVAG LFPs, the occurrence of the state with high activity levels of theta oscillations independent of alpha and the state with low-level alpha and high-level theta oscillations were significantly correlated with pain relief by deep brain stimulation. This study provides a reliable approach to identifying the dynamic neural states in LFPs with a low signal-to-noise ratio by using sparse representation based on wavelet packet transform. Furthermore, it may advance closed-loop deep
Local Fields in Human Subthalamic Nucleus Track the Lead-up to Impulsive Choices
Directory of Open Access Journals (Sweden)
John M. Pearson
2017-11-01
Full Text Available The ability to adaptively minimize not only motor but cognitive symptoms of neurological diseases, such as Parkinson's Disease (PD and obsessive-compulsive disorder (OCD, is a primary goal of next-generation deep brain stimulation (DBS devices. On the basis of studies demonstrating a link between beta-band synchronization and severity of motor symptoms in PD, the minimization of beta band activity has been proposed as a potential training target for closed-loop DBS. At present, no comparable signal is known for the impulsive side effects of PD, though multiple studies have implicated theta band activity within the subthalamic nucleus (STN, the site of DBS treatment, in processes of conflict monitoring and countermanding. Here, we address this challenge by recording from multiple independent channels within the STN in a self-paced decision task to test whether these signals carry information sufficient to predict stopping behavior on a trial-by-trial basis. As in previous studies, we found that local field potentials (LFPs exhibited modulations preceding self-initiated movements, with power ramping across multiple frequencies during the deliberation period. In addition, signals showed phasic changes in power around the time of decision. However, a prospective model that attempted to use these signals to predict decision times showed effects of risk level did not improve with the addition of LFPs as regressors. These findings suggest information tracking the lead-up to impulsive choices is distributed across multiple frequency scales in STN, though current techniques may not possess sufficient signal-to-noise ratios to predict—and thus curb—impulsive behavior on a moment-to-moment basis.
Bakken, M. R.; Burke, M. G.; Fonck, R. J.; Lewicki, B. T.; Rhodes, A. T.; Winz, G. R.
2016-10-01
A new diagnostic measuring local E-> (r , t) fluctuations is being developed for plasma turbulence studies in tokamaks. This is accomplished by measuring fluctuations in the separation of the π components in the Hα motional Stark spectrum. Fluctuations in this separation are expected to be Ẽ / ẼEMSE 10-3EMSE 10-3 . In addition to a high throughput, high speed spectrometer, the project requires a low divergence (Ω 0 .5°) , 80 keV, 2.5 A H0 beam and a target plasma test stand. The beam employs a washer-stack arc ion source to achieve a high species fraction at full energy. Laboratory tests of the ion source demonstrate repeatable plasmas with Te 10 eV and ne 1.6 ×1017 m-3, sufficient for the beam ion optics requirements. Te and ne scalings of the ion source plasma are presented with respect to operational parameters. A novel three-phase resonant converter power supply will provide 6 mA/cm2 of 80 keV H0 at the focal plane for pulse lengths up to 15 ms, with low ripple δV / 80 keV 0.05 % at 280 kHz. Diagnostic development and validation tests will be performed on a magnetized plasma test stand with 0.5 T field. The test chamber will utilize a washer-stack arc source to produce a target plasma comparable to edge tokamak plasmas. A bias-plate with programmable power supply will be used to impose Ẽ within the target plasma. Work supported by US DOE Grant DE-FG02-89ER53296.
Directory of Open Access Journals (Sweden)
Clinton B McCracken
Full Text Available High-frequency electrical stimulation of specific brain structures, known as deep brain stimulation (DBS, is an effective treatment for movement disorders, but mechanisms of action remain unclear. We examined the time-dependent effects of DBS applied to the entopeduncular nucleus (EP, the rat homolog of the internal globus pallidus, a target used for treatment of both dystonia and Parkinson's disease (PD. We performed simultaneous multi-site local field potential (LFP recordings in urethane-anesthetized rats to assess the effects of high-frequency (HF, 130 Hz; clinically effective, low-frequency (LF, 15 Hz; ineffective and sham DBS delivered to EP. LFP activity was recorded from dorsal striatum (STR, ventroanterior thalamus (VA, primary motor cortex (M1, and the stimulation site in EP. Spontaneous and acute stimulation-induced LFP oscillation power and functional connectivity were assessed at baseline, and after 30, 60, and 90 minutes of stimulation. HF EP DBS produced widespread alterations in spontaneous and stimulus-induced LFP oscillations, with some effects similar across regions and others occurring in a region- and frequency band-specific manner. Many of these changes evolved over time. HF EP DBS produced an initial transient reduction in power in the low beta band in M1 and STR; however, phase synchronization between these regions in the low beta band was markedly suppressed at all time points. DBS also enhanced low gamma synchronization throughout the circuit. With sustained stimulation, there were significant reductions in low beta synchronization between M1-VA and STR-VA, and increases in power within regions in the faster frequency bands. HF DBS also suppressed the ability of acute EP stimulation to induce beta oscillations in all regions along the circuit. This dynamic pattern of synchronizing and desynchronizing effects of EP DBS suggests a complex modulation of activity along cortico-BG-thalamic circuits underlying the therapeutic
International Nuclear Information System (INIS)
Zahnd, G.; Pham, V.T.; Marty, A.; Jamet, M.; Beigné, C.; Notin, L.; Vergnaud, C.; Rortais, F.; Vila, L.; Attané, J.-P.
2016-01-01
We study domain wall injection in 100 nm wide NiFe nanowires, followed by domain wall propagation and pinning on 50 nm wide constrictions. The injection is performed using local and external magnetic fields. Using several nucleation pad geometries, we show that at these small dimensions the use of an external field only does not allow obtaining a reproducible injection/pinning process. However, the use of an additional local field, created by an Oersted line, allows to nucleate a reversed domain at zero external applied field. Then, an external field of 5 mT enables the domain wall to propagate far from the Oersted line, and the pinning occurs reproducibly. We also show that notwithstanding the reproducibility of the pinning process, the depinning field is found to be stochastic, following a bimodal distribution. Using micromagnetic simulation we link two different DW configurations, vortex and transverse, to the two typical depinning fields. - Highlights: • Magnetic domain wall introduction and pinning in Permalloy nanowires with 50 nm wide constrictions. • Magnetic domain nucleation at zero external applied field. • Bimodal distribution of the domain wall configuration in the constriction.
Feature selectivity of the gamma-band of the local field potential in primate primary visual cortex
Directory of Open Access Journals (Sweden)
Philipp Berens
2008-12-01
Full Text Available Extra-cellular voltage fluctuations (local field potentials; LFPs reflecting neural mass action are ubiquitous across species and brain regions. Numerous studies have characterized the properties of LFP signals in the cortex to study sensory and motor computations as well as cognitive processes like attention, perception and memory. In addition, its extracranial counterpart – the electroencelphalogram (EEG – is widely used in clinical applications. However, the link between LFP signals and the underlying activity of local populations of neurons remains largely elusive. Here, we review recent work elucidating the relationship between spiking activity of local neural populations and LFP signals. We focus on oscillations in the gamma-band (30-90Hz of the local field potential in the primary visual cortex (V1 of the macaque that dominate during visual stimulation. Given that in area V1 much is known about the properties of single neurons and the cortical architecture, it provides an excellent opportunity to study the mechanisms underlying the generation of the local field potential.
International Nuclear Information System (INIS)
Yuan Yi; Lu Cheng-Biao; Li Xiao-Li
2015-01-01
Local field potential (LFP) signals of the rat hippocampus were recorded under noninvasive focused ultrasound stimulation (FUS) with different ultrasonic powers. The LFP mean absolute power was calculated with the Welch algorithm at the delta, theta, alpha, beta, and gamma frequency bands. The experimental results demonstrate that the LFP mean absolute power at different frequency bands increases as the ultrasound power increases. (paper)
DEFF Research Database (Denmark)
Jalaal, M.; Soleimani, Soheil; Domairry, G.
2011-01-01
In this paper the meshless Local Multi Quadrics-based Differential Quadrature (MQ-DQ) method is applied to obtain the electric field distribution for different applicable irregular geometries. This method is the combination of Differential Quadrature approximation of derivatives and function...
Verhagen, R.; Zwartjes - de Klerk, D.G.M; Heida, Tjitske; Contarino, M.F.; de Bie, R.M.A.; van den Munckhof, P; Schuurman, P.R.; Martens, H.C.F.; Veltink, Petrus H.; Bour, L.J.
2013-01-01
To evaluate the nature of oscillatory activity in the subthalamic nucleus (STN) by means of intraoperative local field potential (LFP) recordings, its relationship with microelectrode recordings (MER) and its potential use to locate the STN and its sensorimotor sub-area in patients with Parkinson’s
International Nuclear Information System (INIS)
Gasparian, Vladimir; Cahay, Marc; Jodar, Esther
2011-01-01
A two-dimensional δ-potential Kronig-Penney model for quasi-one-dimensional (Q1D) disordered systems is used to study analytically the influence of a constant electric field on the inverse localization length (LL). Based on the Green's function formalism we have calculated LL as a function of the incoming energy E, electric field F, length L of the Q1D sample, number of modes M in the transverse direction and the amount of disorder w. We show that, for large L in Q1D systems, states are weakly localized, i.e. we deal with power-law localization. With increasing electric field in Q1D mesoscopic systems a transition from exponential to a power-law behavior takes place, as in 1D systems. We note that the graphs showing the inverse LL change significantly with increasing F (for fixed M) rather than with increasing M (for fixed F). We also show that the graphs representing the ratio of the corresponding localization length without and with electric field collapse for all modes M into a universal curve in the Q1D strip model.
International Nuclear Information System (INIS)
Fateev, V.; Lukyanov, S.; Zamolodchikov, A.; Zamolodchikov, A.
1998-01-01
Exact expectation values of the fields e aφ in the Bullough-Dodd model are derived by adopting the ''''reflection relations'''' which involve the reflection S-matrix of the Liouville theory, as well as a special analyticity assumption. Using this result we propose explicit expressions for expectation values of all primary operators in the c 1,2 or Φ 2,1 . Some results concerning the Φ 1,5 perturbed minimal models are also presented. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Matukhin, V. L.; Pogoreltsev, A. I.; Gavrilenko, A. N., E-mail: ang-2000@mail.ru; Garkavyi, S. O.; Shmidt, E. V. [Kazan State Power University (Russian Federation); Babaeva, S. F. [All-Russia Research Institute of Geology and Mineral Resources of the World Ocean “VNIIOkeangeologiya” (Russian Federation); Sukhanova, A. A. [Saint-Petersburg Mining University (Russian Federation); Terukov, E. I. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)
2017-01-15
The results of investigating natural samples of chalcopyrite mineral CuFeS{sub 2} from massive oceanic sulfide ores of the Mid-Atlantic ridge by the {sup 63}Cu nuclear magnetic resonance (NMR {sup 63}Cu) in a local field at room temperature are presented. The significant width of the resonance lines found in the {sup 63}Cu NMR spectrum directly testifies to a wide distribution of local magnetic and electric fields in the investigated chalcopyrite samples. This distribution can be the consequence of an appreciable deviation of the structure of the investigated chalcopyrite samples from the stoichiometric one. The obtained results show that the pulsed {sup 63}Cu NMR can be an efficient method for studying the physical properties of deep-water polymetallic sulfides of the World Ocean.
Martin, Thomas B.; Drissen, Laurent; Melchior, Anne-Laure
2018-01-01
We present a detailed description of the wavelength, astrometric and photometric calibration plan for SITELLE, the imaging Fourier transform spectrometer attached to the Canada-France-Hawaii telescope, based on observations of a red (647-685 nm) data cube of the central region (11 arcmin × 11 arcmin) of M 31. The first application, presented in this paper is a radial-velocity catalogue (with uncertainties of ∼2-6 km s-1) of nearly 800 emission-line point-like sources, including ∼450 new discoveries. Most of the sources are likely planetary nebulae, although we also detect five novae (having erupted in the first eight months of 2016) and one new supernova remnant candidate.
Tullis, T.
2003-04-01
Rotary shear friction experiments on layers of simulated gouge and on bare surfaces of rock that generate gouge, with displacements up to several meters, show that in some situations slip becomes localized. The two constitutive parameters that control whether slip localizes are the displacement and the velocity dependence of the shear strength. When slip-weakening and velocity-weakening both occur, slip localizes, since the overall resistance is reduced and less energy is dissipated. Similarly, when slip- and velocity-strengthening both occur, slip delocalizes, again because less energy is dissipated. If the variation of shear resistance with slip and velocity are of opposite sign, then the magnitude of the slip and rate dependencies and the amount and rate of slip determine whether localization or delocalization occur. In most laboratory experiments, the displacement dependence of the strength is minimal and the velocity dependence controls the tendency for localization. However, some experiments illustrate the situation in which the displacement dependence dominates. Regardless of their underlying causes, slip- and velocity-weakening result in unstable slip in compliant systems. Consequently unstable slip and localization are linked through these constitutive properties. This connection between unstable slip, displacement/velocity-weakening, and localization suggests that slip on faults that occurs primarily via earthquakes will be localized. However, localization is more complicated on natural faults because laboratory faults are geometrically simpler than natural ones. Laboratory faults are smooth at long wavelengths, whereas natural faults have approximately a self-similar surface roughness, the amplitude of irregularities being proportional to their wavelength. Thus, slip on a localized surface in a laboratory fault can continue indefinitely, whereas slip on natural faults is likely to require fracture of new wall rock as sufficient slip brings higher
Reggiani, M.; Christiaens, V.; Absil, O.; Mawet, D.; Huby, E.; Choquet, E.; Gomez Gonzalez, C. A.; Ruane, G.; Femenia, B.; Serabyn, E.; Matthews, K.; Barraza, M.; Carlomagno, B.; Defrère, D.; Delacroix, C.; Habraken, S.; Jolivet, A.; Karlsson, M.; Orban de Xivry, G.; Piron, P.; Surdej, J.; Vargas Catalan, E.; Wertz, O.
2018-03-01
Context. Transition disks offer the extraordinary opportunity to look for newly born planets and to investigate the early stages of planet formation. Aim. In this context we observed the Herbig A5 star MWC 758 with the L'-band vector vortex coronagraph installed in the near-infrared camera and spectrograph NIRC2 at the Keck II telescope, with the aim of unveiling the nature of the spiral structure by constraining the presence of planetary companions in the system. Methods: Our high-contrast imaging observations show a bright (ΔL' = 7.0 ± 0.3 mag) point-like emission south of MWC 758 at a deprojected separation of 20 au (r = 0.''111 ± 0.''004) from the central star. We also recover the two spiral arms (southeast and northwest), already imaged by previous studies in polarized light, and discover a third arm to the southwest of the star. No additional companions were detected in the system down to 5 Jupiter masses beyond 0.''6 from the star. Results: We propose that the bright L'-band emission could be caused by the presence of an embedded and accreting protoplanet, although the possibility of it being an asymmetric disk feature cannot be excluded. The spiral structure is probably not related to the protoplanet candidate, unless on an inclined and eccentric orbit, and it could be due to one (or more) yet undetected planetary companions at the edge of or outside the spiral pattern. Future observations and additional simulations will be needed to shed light on the true nature of the point-like source and its link with the spiral arms. The reduced images (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A74
International Nuclear Information System (INIS)
Stafford, Jason; Walsh, Ed; Egan, Vanessa
2011-01-01
Highlights: ► Velocity field and local heat transfer trends of centrifugal fans. ► Time-averaged vortices are generated by flow separation. ► Local vortex and impingement regions are evident on surface heat transfer maps. ► Miniature centrifugal fans should be designed with an aspect ratio below 0.3. ► Theory under predicts heat transfer due to complex, unsteady outlet flow. - Abstract: Scaled versions of fan designs are often chosen to address thermal management issues in space constrained applications. Using velocity field and local heat transfer measurement techniques, the thermal performance characteristics of a range of geometrically scaled centrifugal fan designs have been investigated. Complex fluid flow structures and surface heat transfer trends due to centrifugal fans were found to be common over a wide range of fan aspect ratios (blade height to fan diameter). The limiting aspect ratio for heat transfer enhancement was 0.3, as larger aspect ratios were shown to result in a reduction in overall thermal performance. Over the range of fans examined, the low profile centrifugal designs produced significant enhancement in thermal performance when compared to that predicted using classical laminar flow theory. The limiting non-dimensional distance from the fan, where this enhancement is no longer apparent, has also been determined. Using the fundamental information inferred from local velocity field and heat transfer measurements, selection criteria can be determined for both low and high power practical applications where space restrictions exist.
Phase space properties of charged fields in theories of local observables
International Nuclear Information System (INIS)
Buchholz, D.; D'Antoni, C.
1994-10-01
Within the setting of algebraic quantum field theory a relation between phase-space properties of observables and charged fields is established. These properties are expressed in terms of compactness and nuclarity conditions which are the basis for the characterization of theories with physically reasonable causal and thermal features. Relevant concepts and results of phase space analysis in algebraic qunatum field theory are reviewed and the underlying ideas are outlined. (orig.)
Directory of Open Access Journals (Sweden)
Heike Mónika Greschke
2007-09-01
Full Text Available This article aims to introduce an ethnic group inhabiting a common virtual space in the World Wide Web (WWW, while being physically located in different socio-geographical contexts. Potentially global in its geographical extent, this social formation is constituted by means of interrelating virtual-global dimensions with physically grounded parts of the actors' lifeworlds. In addition, the communities' social life relies on specific communicative practices joining mediated forms of communication with co-presence based encounters. Ethnographic research in a pluri-local and computer-mediated field poses a set of problems which demand thorough reflection as well as a search for creative solutions. How can the boundaries of the field be determined? What does "being there" signify in such a case? Is it possible to enter the field while sitting at my own desk, just by visiting the respective site in the WWW, simply observing the communication going on without even being noticed by the subjects in the field? Or does "being in the field" imply that I ought to turn into a member of the studied community? Am I supposed to effectively live with the others for a while? And then, what can "living together" actually mean in that case? Will I learn enough about the field simply by participating in its virtual activities? Or do I have to account for the physically grounded dimensions of the actors' lifeworlds, as well? Ethnographic research in a pluri-local and computer-mediated field in practice raises a lot of questions regarding the ways of entering the field and being in the field. Some of them will be discussed in this paper by means of reflecting research experiences gained in the context of a recently concluded case study. URN: urn:nbn:de:0114-fqs0703321
The current algebra on the circle as a germ of local field theories
International Nuclear Information System (INIS)
Buchholz, D.; Mack, G.; Todorov, I.; Bylgarska Akademiya na Naukite, Sofia. Inst. za Yadrena Izsledvaniya i Yadrena Energetika)
1988-01-01
Methods of algebraic quantum field theory are used to classify all field- and observable algebras, whose common germ is the U(1)-current algebra. An elementary way is described to compute characters of such algebras. It exploits the Kubo-Martin-Schwinger condition for Gibbs states. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Hirotani, Kouichi [Academia Sinica, Institute of Astronomy and Astrophysics (ASIAA), P.O. Box 23-141, Taipei, Taiwan (China)
2015-01-10
We investigate the particle accelerator that arises in a rotating neutron-star magnetosphere. Simultaneously solving the Poisson equation for the electro-static potential, the Boltzmann equations for relativistic electrons and positrons, and the radiative transfer equation, we demonstrate that the electric field is substantially screened along the magnetic field lines by pairs that are created and separated within the accelerator. As a result, the magnetic-field-aligned electric field is localized in higher altitudes near the light cylinder and efficiently accelerates the positrons created in the lower altitudes outward but does not accelerate the electrons inward. The resulting photon flux becomes predominantly outward, leading to typical double-peak light curves, which are commonly observed from many high-energy pulsars.
Bone metastasis: review and critical analysis of random allocation trials of local field treatment
International Nuclear Information System (INIS)
Ratanatharathorn, Vaneerat; Powers, William E.; Moss, William T.; Perez, Carlos A.
1999-01-01
Purpose: Compare and contrast reports of random allocation clinical trials of local field radiation therapy of metastases to bone to determine the techniques producing the best results (frequency, magnitude, and duration of benefit), and relate these to the goals of complete relief of pain and prevention of disability for the remaining life of the patient. Methods and Materials: Review all published reports of random allocation clinical trials, and perform a systematic analysis of the processes and outcomes of the several trial reports. Results: All trials were performed on selected populations of patients with symptomatic metastases and most studies included widely diverse groups with regard to: (a) site of primary tumor, (b) location, extent, size, and nature of metastases, (c) duration of survival after treatment. All trial reports lack sufficient detail for full and complete analysis. Much collected information is not now available for reanalysis and many important data sets were apparently never collected. Several of the variations in patient and tumor characteristics were found to be much more important than treatment dose in the outcome results. Treatment planning and delivery techniques were unsophisticated and probably resulted in a systematic delivery of less than the assigned dose to some metastases. In general the use and benefit of retreatment was greater in those patients who initially received lower doses but the basis and dose of retreatment was not documented. Follow-up of patients was varied with a large proportion of surviving patients lost to follow-up in several studies. The greatest difference in the reports is the method of calculation of results. The applicability of Kaplan-Meier actuarial analysis, censoring the lost and dead patients, as used in studies with loss to follow-up of a large number of patients is questionable. The censoring involved is 'informative' (the processes of loss relate to the outcome) and not acceptable since it
Star Formation, Quenching And Chemical Enrichment In Local Galaxies From Integral Field Spectroscopy
Belfiore, Francesco
2017-08-01
Within the currently well-established ΛCDM cosmological framework we still lack a satisfactory understanding of the processes that trigger, regulate and eventually quench star formation on galactic scales. Gas flows (including inflows from the cosmic web and supernovae-driven outflows) are considered to act as self-regulatory mechanisms, generating the scaling relations between stellar mass, star formation rate and metallicity observed in the local Universe by large spectroscopic surveys. These surveys, however, have so far been limited by the availability of only one spectrum per galaxy. The aim of this dissertation is to expand the study of star formation and chemical abundances to resolved scales within galaxies by using integral field spectroscopy (IFS) data, mostly from the ongoing SDSS-IV MaNGA survey. In the first part of this thesis I demonstrate the ubiquitous presence of extended low ionisation emission-line regions (LIERs) in both late- and early-type galaxies. By studying the Hα equivalent width and diagnostic line ratios radial profiles, together with tracers of the underlying stellar population, I show that LIERs are not due to a central point source but to hot evolved (post-asymptotic giant branch) stars. In light of this, I suggest a new classification scheme for galaxies based on their line emission. By analysing the colours, star formation rates, morphologies, gas and stellar kinematics and environmental properties of galaxies with substantial LIER emission, I identify two distinct populations. Galaxies where the central regions are LIER-like, but show star formation at larger radii are late types in which star formation is slowly quenched inside-out. This transformation is associated with massive bulges. Galaxies dominated by LIER emission at all radii, on the other hand, are red-sequence galaxies harbouring a residual cold gas component, acquired mostly via external accretion. Quiescent galaxies devoid of line emission reside in denser
Directory of Open Access Journals (Sweden)
Jorje Ignacio Zalles
2017-09-01
Full Text Available From a natural sciences perspective, efforts directed at the conservation of biodiversity are based upon what is known as conservation biology. Given its epistemological assumptions, conservation biology faces obstacles in the incorporation of wisdom originating in local ecological knowledge, that which a local population has gained about the local environment which it is surrounded by and due to its direct contact with this local environment, instead of the result of a product of a positivist scientific inquiry. Post-normal science has emerged in recent decades as an alternative for public management that aims to complement the search for knowledge by means of empirical approaches through the inclusion of understandings based on the everyday experiences and the subjective interpretation of natural phenomena, transcending the compartmentalization associated with scientific traditions born out of modernity. This article discusses the integration of local ecological knowledge and conservation biology from the perspective of post normal science, illustrating different forms of intercultural communication that would make the requisite dialogue of knowledges possible.
Wei, Hong; Li, Zhipeng; Tian, Xiaorui; Wang, Zhuoxian; Cong, Fengzi; Liu, Ning; Zhang, Shunping; Nordlander, Peter; Halas, Naomi J; Xu, Hongxing
2011-02-09
We show that the local electric field distribution of propagating plasmons along silver nanowires can be imaged by coating the nanowires with a layer of quantum dots, held off the surface of the nanowire by a nanoscale dielectric spacer layer. In simple networks of silver nanowires with two optical inputs, control of the optical polarization and phase of the input fields directs the guided waves to a specific nanowire output. The QD-luminescent images of these structures reveal that a complete family of phase-dependent, interferometric logic functions can be performed on these simple networks. These results show the potential for plasmonic waveguides to support compact interferometric logic operations.
Wu, L Y; Wang, K L; Jiang, T; Kang, L; Yang, S Z; Wu, P H
2002-01-01
In this paper, we present our approach to probe the local microwave properties of superconducting thin films by using the microwave near-field scanning technique. We have employed a coaxial cavity together with a niobium tip as the probe and established a scanning sample stage cooled by liquid nitrogen to study thin film devices at low temperature in our scanning microwave near-field microscope. Nondestructive images have been obtained on the inhomogeneity of the YBaCuO superconducting thin films at microwave frequency. We believe that these results would be helpful in evaluating the microwave performance of the devices.
International Nuclear Information System (INIS)
Suzuki, Takahiro; Mori, Chizuo
2005-01-01
We, high school teachers, collaborated with a local organization, Chubu Atomic Power Conference (partly in co-operation with The Radiation Education Forum), in the education on the subjects of energy and radiation fields. In addition to the subjects concerned with radiations, cloud chamber and personal radiation-monitor, we developed a few new subjects, which are not directly connected themselves with radiations, for the purpose to widen the fields and to bring the high acceptability of the subjects in high school side. (author)
Self-consistent-field calculations of atoms and ions using a modified local-density approximation
International Nuclear Information System (INIS)
Liberman, D.A.; Albritton, J.R.; Wilson, B.G.; Alley, W.E.
1994-01-01
Local-density-approximation calculations of atomic structure are useful for the description of atoms and ions in plasmas. The large number of different atomic configurations that exist in typical plasmas leads one to consider the expression of total energies in terms of a Taylor series in the orbital occupation numbers. Two schemes for computing the second derivative Taylor-series coefficients are given; the second, and better one, uses the linear response method developed by Zangwill and Soven [Phys. Rev. A 21, 1561 (1980)] for the calculation of optical response in atoms. A defect in the local-density approximation causes some second derivatives involving Rydberg orbitals to be infinite. This is corrected by using a modified local-density approximation that had previously been proposed [Phys. Rev. B 2, 244 (1970)
A simple localized-itinerant model for PrAl3: crystal field and exchange effects
International Nuclear Information System (INIS)
Ranke, P.J. von; Palermo, L.
1990-01-01
We present a simple magnetic model for PrAl sub(3). The effects of crystal field are treated using a reduced set of levels and the corresponding wave functions are extracted from the actual crystal field levels of Pr sup(+3) in a hexagonal symmetry. The exchange between 4f- and conduction electrons are dealt within a molecular field approximation. An analytical magnetic state equation is derived and the magnetic behaviour discussed. The parameters of the model are estimated from a fitting of the inverse susceptibility of PrAl sub(3) given in the literature. (author)
Continuous spins in 2D gravity: Chiral vertex operators and local fields
International Nuclear Information System (INIS)
Gervais, Jean-Loup; Schnittger, Jens
1994-01-01
We construct the exponentials of the Liouville field with continuous powers within the operator approach. Their chiral decomposition is realized using the explicit Coulomb-gas operators we introduced earlier. From the quantum group viewpoint, they are related to semi-infinite highest- or lowest-weight representations with continuous spins. The Liouville field itself is defined, and the canonical commutation relations are verified, as well as the validity of the quantum Liouville field equations. In a second part, both screening charges are considered. The braiding of the chiral components is derived and shown to agree with an ansatz of a parallel paper of Gervais and Roussel. ((orig.))
Directory of Open Access Journals (Sweden)
B. Miao
2009-03-01
Full Text Available Field-aligned ion beams (FABs originate at the quasi-perpendicular Earth's bow shock and constitute an important ion population in the foreshock region. The bulk velocity of these FABs depends significantly on the shock normal angle, which is the angle between shock normal and upstream interplanetary magnetic field (IMF. This dependency may therefore be taken as an indicator of the local structure of the shock. Applying the direct reflection model to Cluster measurements, we have developed a method that uses proton FABs in the foreshock region for remote sensing of the local shock structure. The comparison of the model results with the multi-spacecraft observations of FAB events shows very good agreement in terms of wave amplitude and frequency of surface waves at the shock front.
Uchida, Emi; Swallow, Stephen K; Gold, Arthur; Opaluch, James; Kafle, Achyut; Merrill, Nathaniel; Michaud, Clayton; Gill, Carrie Anne
2018-04-01
Innovative market mechanisms are being increasingly recognized as effective decision-making institutions to incorporate the value of ecosystem services into the economy. We present a field experiment that integrates an economic auction and a biophysical water flux model to develop a local market process consisting of both the supply and demand sides. On the supply side, we operate an auction with small-scale livestock owners who bid for contracts to implement site-specific manure management practices that reduce phosphorus loadings to a major reservoir. On the demand side, we implement a real money, multi-unit public good auction for these contracts with residents who potentially benefit from reduced water quality risks. The experiments allow us to construct supply and demand curves to find an equilibrium price for water quality improvement. The field experiments provide a proof-of-concept for practical implementation of a local market for environmental improvements, even for the challenging context of nonpoint pollution.
International Nuclear Information System (INIS)
Shah, Ronak; Mandge, Deepak; Rathod, Vipal; Parmar, Rajvi; Dilip, E. Sharan; Yadav, Amit; Sharma, Anjali; Rao, S.L.
2017-01-01
High power RF sources such as a Gyrotron system are operated at required output parameter by using various auxiliary power supplies, High voltage power supplies, auxiliary services and a dedicated Local Control Unit (LCU). These sub-systems must be operated in synchronous and safe way to control the gyrotron output parameters. The LCU performs remote, synchronous and safe operation of the all the gyrotron sub-systems. Broadly the LCU functions are operational control, data acquisition, protection and safety of the gyrotron system. At ITER-India gyrotron Test Facility (IIGTF) a local control unit (LCU) is being developed to operate the complete gyrotron system. This paper presents the design, development and various features of the field simulator. It also discuss LCU functionality test cases and results obtained using field simulator
H0, q0 and the local velocity field. [Hubble and deceleration constants in Big Bang expansion
Sandage, A.; Tammann, G. A.
1982-01-01
An attempt is made to find a systematic deviation from linearity for distances that are under the control of the Virgo cluster, and to determine the value of the mean random motion about the systematic flow, in order to improve the measurement of the Hubble and the deceleration constants. The velocity-distance relation for large and intermediate distances is studied, and type I supernovae are calibrated relatively as distance indicators and absolutely to obtain a new value for the Hubble constant. Methods of determining the deceleration constant are assessed, including determination from direct measurement, mean luminosity density, virgocentric motion, and the time scale test. The very local velocity field is investigated, and a solution is preferred with a random peculiar radial velocity of very nearby field galaxies of 90-100 km/s, and a Virgocentric motion of the local group of 220 km/s, leading to an underlying expansion rate of 55, in satisfactory agreement with the global value.
Komorowski, P A
2000-01-01
The localization of possible electrical faults in superconducting accelerator magnets may, in most cases, be a complex, expensive and time-consuming process. In particular, inter-turn short circuits and failures of the ground insulation are well detectable when the magnet is collared, but often disappear after disassembly for repair due to the release of the pre-stress in the coils. The fault localization method presented in this paper is based on the measurement and analysis of the magnetic field generated inside the magnet aperture by a high voltage pulse. The presence of the fault modifies the distribution of the current in the coils and produces a distortion of the magnetic field. The described method aims at locating both the longitudinal and azimuthal position of the fault-affected area. The test method, the transient case FEM models and the implemented experimental set-up are presented and discussed for the LHC dipole models.
Comsa, Daria Craita
2008-10-01
There is a real need for improved small animal imaging techniques to enhance the development of therapies in which animal models of disease are used. Optical methods for imaging have been extensively studied in recent years, due to their high sensitivity and specificity. Methods like bioluminescence and fluorescence tomography report promising results for 3D reconstructions of source distributions in vivo. However, no standard methodology exists for optical tomography, and various groups are pursuing different approaches. In a number of studies on small animals, the bioluminescent or fluorescent sources can be reasonably approximated as point or line sources. Examples include images of bone metastases confined to the bone marrow. Starting with this premise, we propose a simpler, faster, and inexpensive technique to quantify optical images of point-like sources. The technique avoids the computational burden of a tomographic method by using planar images and a mathematical model based on diffusion theory. The model employs in situ optical properties estimated from video reflectometry measurements. Modeled and measured images are compared iteratively using a Levenberg-Marquardt algorithm to improve estimates of the depth and strength of the bioluminescent or fluorescent inclusion. The performance of the technique to quantify bioluminescence images was first evaluated on Monte Carlo simulated data. Simulated data also facilitated a methodical investigation of the effect of errors in tissue optical properties on the retrieved source depth and strength. It was found that, for example, an error of 4 % in the effective attenuation coefficient led to 4 % error in the retrieved depth for source depths of up to 12mm, while the error in the retrieved source strength increased from 5.5 % at 2mm depth, to 18 % at 12mm depth. Experiments conducted on images from homogeneous tissue-simulating phantoms showed that depths up to 10mm could be estimated within 8 %, and the relative
DEFF Research Database (Denmark)
Christensen, Dennis; Bjørk, Rasmus; Nielsen, Kaspar Kirstein
2010-01-01
The magnetocaloric eﬀect causes a magnetic material to change temperature upon application of a magnetic ﬁeld. Here, spatially resolved measurements of the adiabatic temperature change are performed on a plate of gadolinium using thermography. The adiabatic temperature change is used to extract...... the corresponding change in the local magnetic ﬁeld strength. The measured temperature change and local magnetic ﬁeld strength are compared to results obtained with a numerical model, which takes demagnetization into account and employs experimental data....
International Nuclear Information System (INIS)
Karlsson, Joakim; Sjögren, Torsten; Snis, Anders; Engqvist, Håkan; Lausmaa, Jukka
2014-01-01
Additive manufacturing, or 3D-printing as it is often called, build parts in a layer-by-layer fashion. A common concern, regardless of the specific additive manufacturing technique used, is the risk of inadequate fusion between the adjacent layers which in turn may cause inferior mechanical properties. In this work, the local strain properties of titanium parts produced by Electron Beam Melting (EBM ® ) were studied in order to gain information about the quality of fusion of the stock powder material used in the process. By using Digital Image Correlation (DIC) the strain fields in the individual layers were analyzed, as well as the global strain behavior of the bulk material. The results show that fully solid titanium parts manufactured by EBM are homogenous and do not experience local deformation behavior, neither on local nor on a global level
Energy Technology Data Exchange (ETDEWEB)
Karlsson, Joakim, E-mail: Joakim.karlsson@sp.se [SP Technical Research Institute of Sweden, Box 857, SE-501 15, Borås (Sweden); Division of Applied Materials Science, Department of Engineering Sciences, Ångström Laboratory, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden); Sjögren, Torsten [SP Technical Research Institute of Sweden, Box 857, SE-501 15, Borås (Sweden); Snis, Anders [Arcam AB, Krokslätts fabriker 27 A, SE-431 37, Mölndal (Sweden); Engqvist, Håkan [Division of Applied Materials Science, Department of Engineering Sciences, Ångström Laboratory, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden); Lausmaa, Jukka [SP Technical Research Institute of Sweden, Box 857, SE-501 15, Borås (Sweden)
2014-11-17
Additive manufacturing, or 3D-printing as it is often called, build parts in a layer-by-layer fashion. A common concern, regardless of the specific additive manufacturing technique used, is the risk of inadequate fusion between the adjacent layers which in turn may cause inferior mechanical properties. In this work, the local strain properties of titanium parts produced by Electron Beam Melting (EBM{sup ®}) were studied in order to gain information about the quality of fusion of the stock powder material used in the process. By using Digital Image Correlation (DIC) the strain fields in the individual layers were analyzed, as well as the global strain behavior of the bulk material. The results show that fully solid titanium parts manufactured by EBM are homogenous and do not experience local deformation behavior, neither on local nor on a global level.
Khandaker, Mohammad Moneruzzaman; Boyce, Amru Nasrulhaq; Osman, Normaniza; Golam, Faruq; Rahman, M. Motior; Sofian-Azirun, M.
2013-01-01
This study investigated the effects of gibberellin (GA3) on the fruit development, pigmentation and biochemical properties of wax apple. The wax apple trees were rubbing treated with 0, 20, 50 and 100 mgGA3/l under field conditions. The localized application (rubbing) of 50 mg GA3/l significantly increased the fruit set, fruit length and diameter, color development, weight and yieldcompared to the control. In addition, GA3 treatments significantly reduced the fruit drop. With regard to the fr...
Tartakoff, David S.
1994-01-01
We prove global analytic hypoellipticity on a product of tori for partial differential operators which are constructed as rigid (variable coefficient) quadratic polynomials in real vector fields satisfying the H\\"ormander condition and where $P$ satisfies a `maximal' estimate. We also prove an analyticity result that is local in some variables and global in others for operators whose prototype is $$ P= \\left({\\partial \\over {\\partial x_1}}\\right)^2 + \\left({\\partial \\over {\\partial x_2}}\\righ...
Tyu, N. S.; Ekhilevsky, S. G.
1992-07-01
For the perfect molecular crystals the equations of the local field method (LFM) with the account of spatial dispersion are formulated. They are used to derive the expression for the crystal polarizability tensor. For the first time within the framework of this method the formula for the gyrotropy tensor of an arbitrary optically active molecular crystal is obtained. This formula is analog of well known relationships of Lorentz-Lorenz.
van Beurden, M.C.; Setija, Irwan
2017-01-01
We present two adapted formulations, one tailored to isotropic media and one for general anisotropic media, of the normal vector field framework previously introduced to improve convergence near arbitrarily shaped material interfaces in spectral simulation methods for periodic scattering geometries.
The extended local gauge invariance and the BRS symmetry in stochastic quantization of gauge fields
International Nuclear Information System (INIS)
Nakazawa, Naohito.
1989-05-01
We investigate the BRS invariance of the first-class constrained systems in the context of the stochastic quantization. For the first-class constrained systems, we construct the nilpotent BRS transformation and the BRS invariant stochastic effective action based on the D+1 dimensional field theoretical formulation of stochastic quantization. By eliminating the multiplier field of the gauge fixing condition and an auxiliary field, it is shown that there exists a truncated BRS transformation which satisfies the nilpotency condition. The truncated BRS invariant stochastic action is also derived. As the examples of the general formulation, we investigate the BRS invariant structure in the massless and massive Yang-Mills fields in stochastic quantization. (author)
ON A PROLONGATION CONSTRUCTION FOR LOCAL NON-DIVERGENT VECTOR FIELDS ON Rn
Directory of Open Access Journals (Sweden)
A. M. Lukatsky
2015-01-01
Full Text Available The problem of a prolongation of non-divergent vector field, defined in a vicinity of zero in Rn t, to a finite non-divergent vector field on Rn is considered. Explicit formulas for the elements of the simple Lie algebra of non-divergent vector from the well-known Cartan series are obtained. This construction allows to move from the Euler equations for the ideal incompressible fluid to the Euler equations on finite-dimensional Lie groups.
Motional Stark Effect measurements of the local magnetic field in high temperature fusion plasmas
Wolf, R. C.; Bock, A.; Ford, O. P.; Reimer, R.; Burckhart, A.; Dinklage, A.; Hobirk, J.; Howard, J.; Reich, M.; Stober, J.
2015-10-01
The utilization of the Motional Stark Effect (MSE) experienced by the neutral hydrogen or deuterium injected into magnetically confined high temperature plasmas is a well established technique to infer the internal magnetic field distribution of fusion experiments. In their rest frame, the neutral atoms experience a Lorentz electric field, EL = v × B, which results in a characteristic line splitting and polarized line emission. The different properties of the Stark multiplet allow inferring, both the magnetic field strength and the orientation of the magnetic field vector. Besides recording the full MSE spectrum, several types of polarimeters have been developed to measure the polarization direction of the Stark line emission. To test physics models of the magnetic field distribution and dynamics, the accuracy requirements are quite demanding. In view of these requirements, the capabilities and issues of the different techniques are discussed, including the influence of the Zeeman Effect and the sensitivity to radial electric fields. A newly developed Imaging MSE system, which has been tested on the ASDEX Upgrade tokamak, is presented. The sensitivity allows to resolve sawtooth oscillations. A shorter version of this contribution is due to be published in PoS at: 1st EPS conference on Plasma Diagnostics
Tai, Tamin
2011-03-01
Niobium Superconducting Radio Frequency (SRF) cavities are very sensitive to localized defects that give rise to quenches at high accelerating gradients. In order to identify these defects via scanning microscopy, and to further understand the origins of the quench under high radio frequency excitation (1-3 GHz), a scanning probe with localized and up to ~ 200 mT RF magnetic field is required for low temperature microscopy to achieve sub-micron resolution. For this purpose, we developed a micro loop probe on silicon substrate with outer diameter 20 μ m and inner diameter 17 μ m and successfully fabricated it by lithography. The probe has been used to identify a signal arising from the nonlinear Meissner effect in a Nb thin film. In addition, a magnetic write head is another promising candidate to achieve this goal of understanding localized defect behavior under high RF magnetic field at low temperatures. We will discuss and compare both types of probe for nonlinear scanning microscopy and RF defect localization in superconductors. We acknowledge the support of DOE/HEP.
Goossens, Sander Johannes; Ishihara, Yoshiaki; Matsumoto, Koji; Sasaki, Sho
2012-01-01
We present a method with which we determined the local lunar gravity field model over the South Pole-Aitken (SPA) basin on the farside of the Moon by estimating adjustments to a global lunar gravity field model using SELENE tracking data. Our adjustments are expressed in localized functions concentrated over the SPA region in a spherical cap with a radius of 45deg centered at (191.1 deg E, 53.2 deg S), and the resolution is equivalent to a 150th degree and order spherical harmonics expansion. The new solution over SPA was used in several applications of geophysical analysis. It shows an increased correlation with high-resolution lunar topography in the frequency band l = 40-70, and admittance values are slightly different and more leveled when compared to other, global gravity field models using the same data. The adjustments expressed in free-air anomalies and differences in Bouguer anomalies between the local solution and the a priori global solution correlate with topographic surface features. The Moho structure beneath the SPA basin is slightly modified in our solution, most notably at the southern rim of the Apollo basin and around the Zeeman crater
Directory of Open Access Journals (Sweden)
Goran Marošević
2011-12-01
Full Text Available Introduction: The aim of this paper is to study the distribution of the therapy dosage applied by a modified conventional “field in field” technique and compare it to the distribution of the dosage applied by the standard conventional technique.Methods: The study included ten patients with right side breast cancer, after they were exposed to radical mastectomy and chemotherapy. Radiotherapy dosage of TD 50 Gy in 25 fractions was applied to the anterolateral side of the right thoracic wall, with two opposite conventional tangential fields by the linear accelerator Elekta Synergy and the energy of 6 megavolts (MV. A delineation of the target volume (CTV – Clinical Target Volume was done within conventional fields. At the XiO system for planning we included additional fields within the existing conventional fields, which was the so called “field in field” technique. On the basis of CTV the Dose Volume Histogram (DVH was calculated for conventional and “field in field” plans. VD90%, VD95%, VD107%, VD115%, CI and HI were calculated for both techniques. Means were pared with the paired Student's t-test. The results were considered significantly different if p<0.05.Results: VD90% and VD 95% were significantly higher for the “field in field” technique. Therefore, CI also favored the “field in field” technique (p=0.02. There was no difference in VD107% and VD115% between the compared groups. Consequently, there was no statistically significant difference in HI (1.13±0.03 vs.1.13±0.03, p=0.06.Conclusion: Conventional postoperative radiotherapy of localized right side breast cancer by “field in field” technique provides excellent coverage of the target volume by radiotherapy isodose.
The energy-momentum spectrum in local field theories with broken Lorentz-symmetry
International Nuclear Information System (INIS)
Borchers, H.J.; Buchholz, D.
1984-05-01
Assuming locality of the observables and positivity of the energy it is shown that the joint spectrum of the energy-momentum operators has a Lorentz-invariant lower boundary in all superselection sectors. This result is of interest if the Lorentz-symmetry is (spontaneously) broken, such as in the charged sectors of quantum electrodynamics. (orig.)
International Nuclear Information System (INIS)
Osborn, H.
1991-01-01
A local renormalisation group equation which realises infinitesimal Weyl rescalings of the metric and which is an extension of the usual Callan-Symanzik equation is described. In order to ensure that any local composite operators, with dimensions so that on addition to the basic lagrangian they preserve renormalisability, are well defined for arbitrarily many insertions into correlation functions the couplings are assumed to depend on χ. Local operators are then defined by functional differentiation with respect to the couplings just as the energy-momentum tensor is given by functional differentiation with respect to the metric. The local renormalisation group equation contains terms depending on derivatives of the couplings as well as the curvature tensor formed from the metric, constrained by power counting. Various consistency relations arising from the commutativity of Weyl transformations are derived, extending previous one-loop results for the trace anomaly to all orders. In two dimensions the relations give an alternative derivation of the c-theorem and similar extensions are obtained in four dimensions. The equations are applied in detail to general renormalisable σ-models in two dimensions. The Curci-Paffuti relation is derived without any commitment to a particular regularisation scheme and further equations used to construct an action for the vanishing of the β-functions are also obtained. The discussion is also extended to σ-models with a boundary, as appropriate for open strings, and relations for the additional β-functions present in such models are obtained. (orig.)
Mycorrhizal Symbiosis and Local Adaptation in Aster amellus: A Field Transplant Experiment
Czech Academy of Sciences Publication Activity Database
Pánková, Hana; Raabová, J.; Münzbergová, Zuzana
2014-01-01
Roč. 9, č. 4 (2014), s. 1-7, e93967 E-ISSN 1932-6203 R&D Projects: GA ČR GAP504/10/1486 Institutional support: RVO:67985939 Keywords : mycorrhizal symbiosis * local adaptation * Aster amellus Subject RIV: EF - Botanics Impact factor: 3.234, year: 2014
Energy Technology Data Exchange (ETDEWEB)
Haelg, Roger A., E-mail: rhaelg@phys.ethz.ch [Institute for Radiotherapy, Radiotherapie Hirslanden AG, Hirslanden Medical Center, Rain 34, CH-5000 Aarau (Switzerland); Besserer, Juergen [Institute for Radiotherapy, Radiotherapie Hirslanden AG, Hirslanden Medical Center, Rain 34, CH-5000 Aarau (Switzerland); Boschung, Markus; Mayer, Sabine [Division for Radiation Safety and Security, Paul Scherrer Institut, CH-5232 Villigen (Switzerland); Clasie, Benjamin [Department of Radiation Oncology, Massachusetts General Hospital, 30 Fruit Street, Boston, MA 02114 (United States); Kry, Stephen F. [Department of Radiation Physics, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030 (United States); Schneider, Uwe [Institute for Radiotherapy, Radiotherapie Hirslanden AG, Hirslanden Medical Center, Rain 34, CH-5000 Aarau (Switzerland); Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 204, CH-8057 Zurich (Switzerland)
2012-12-01
In order to quantify the dose from neutrons to a patient for contemporary radiation treatment techniques, measurements inside phantoms, representing the patient, are necessary. Published reports on neutron dose measurements cover measurements performed free in air or on the surface of phantoms and the doses are expressed in terms of personal dose equivalent or ambient dose equivalent. This study focuses on measurements of local neutron doses inside a radiotherapy phantom and presents a field calibration procedure for PADC track etch detectors. An initial absolute calibration factor in terms of H{sub p}(10) for personal dosimetry is converted into neutron dose equivalent and additional calibration factors are derived to account for the spectral changes in the neutron fluence for different radiation therapy beam qualities and depths in the phantom. The neutron spectra used for the calculation of the calibration factors are determined in different depths by Monte Carlo simulations for the investigated radiation qualities. These spectra are used together with the energy dependent response function of the PADC detectors to account for the spectral changes in the neutron fluence. The resulting total calibration factors are 0.76 for a photon beam (in- and out-of-field), 1.00 (in-field) and 0.84 (out-of-field) for an active proton beam and 1.05 (in-field) and 0.91 (out-of-field) for a passive proton beam, respectively. The uncertainty for neutron dose measurements using this field calibration method is less than 40%. The extended calibration procedure presented in this work showed that it is possible to use PADC track etch detectors for measurements of local neutron dose equivalent inside anthropomorphic phantoms by accounting for spectral changes in the neutron fluence.
Directory of Open Access Journals (Sweden)
G. V. Bezprozvannych
2016-12-01
Full Text Available Introduction. Reliability of high voltage power cables in the process of long-term operation is largely due to the intensity of polymeric insulation aging. It is now established that the aging of polyethylene, which is the main material for the insulation of high voltage power cables, under the action of the electric field is determined primarily by the presence of structural heterogeneity arising both during cable production and during use. The cable is always there deviations from the ideal structure, which manifest in a deviation of diameters of conductors from nominal values; in the arrangement of the conductor and the insulation is not strictly coaxially and eccentrically; in elliptic (oval core and insulation; change in relative dielectric constant and thickness of insulation on cable length force the formation of low molecular weight products (including water in the flow at the manufacturing stage crosslinked polyethylene insulation and moisture during operation. Such defects are structural, technological and operational irregularities, which lead to a local change in the electric field. Purpose. Analysis of the influence of the eccentricity, elliptic and spherical inclusions in the electric field distribution in the power cable of a coaxial design with cross-linked polyethylene insulation, based on numerical simulation. Methodology. The bases of the numerical method of calculation of the electrical field strength are Fredholm integral equations of the first and second kind (method of secondary sources for an axially symmetric field. Analysis of the influence of irregularities, including water treeing, the shape of the sounding signal is made using the method of discrete resistive circuit inductance and capacitance of substitution with the initial conditions. Solving systems of linear algebraic equations nodal analysis performed by the sweep method. Results. The presence of the eccentricity and ellipticity in the construction of cable has
International Nuclear Information System (INIS)
Lennernaes, B.; Rikner, G.; Letocha, H.; Nilsson, S.
1995-01-01
The purpose of the present study was to identify factors of importance in the planning of external beam radiotherapy of prostatic adenocarcinoma. Seven patients with urogenital cancers were planned for external radiotherapy of the prostate. Four different techniques were used, viz. a 4-field box technique and four-, five- or six-field conformal therapy set-ups combined with three different margins (1-3 cm). The evaluations were based on the doses delivered to the rectum and the urinary bladder. A normal tissue complication probability (NTCP) was calculated for each plan using Lyman's dose volume reduction method. The most important factors that resulted in a decrease of the dose delivered to the rectum and the bladder were the use of conformal therapy and smaller margins. Conformal therapy seemed more important for the dose distribution in the urinary bladder. Five- and six-field set-ups were not significantly better than those with four fields. NTCP calculations were in accordance with the evaluation of the dose volume histograms. To conclude, four-field conformal therapy utilizing reduced margins improves the dose distribution to the rectum and the urinary bladder in the radiotherapy of prostatic adenocarcinoma. (orig.)
The stress energy tensor of a locally supersymmetric quantum field on a curved spacetime
International Nuclear Information System (INIS)
Koehler, M.
1995-04-01
For an analogon of the free Wess-Zumino model on Ricci flat spacetimes, the relation between a conserved 'supercurrent' and the point-separated improved energy momentum tensor is investigated and a similar relation as on Minkowski space is established. The expectation value of the latter in any globally Hadamard product state is found to be a priori finite in the coincidence limit if the theory is massive. On arbitrary globally hyperbolic spacetimes the 'supercurrent' is shown to be a well defined operator valued distribution on the GNS Hilbertspace of any globally Hadamard product state. Viewed as a new field, all n-point distributions exist, giving a new example for a Wightman field on that manifold. Moreover, it is shown that this field satisfies a new wave front set spectrum condition in a nontrivial way. (orig.)
Effect of the local electric field on the formation of an ordered structure in porous anodic alumina
Lazarouk, S. K.; Katsuba, P. S.; Leshok, A. A.; Vysotskii, V. B.
2015-09-01
Experimental data and a model are presented, and the electric field that appears in porous alumina during electrochemical anodic oxidation of aluminum in electrolytes based on an aqueous solution of oxalic acid at a voltage of 90-250 V is calculated. It is found that the electric field in the layers with a porosity of 1-10% in growing alumina reaches 109-1010 V/m, which exceeds the electric strength of the material and causes microplasma patterns emitting visible light at the pore bottom, the self-organization of the structure of porous alumina, and the anisotropy of local porous anodizing. Moreover, other new effects are to be expected during aluminum anodizing under the conditions that ensure a high electric field inside the barrier layer of porous oxide.
Directory of Open Access Journals (Sweden)
K.J.B. Ghosh
2018-01-01
Full Text Available We consider four-dimensional chiral gauge theories defined over a spacetime manifold with topology R3×S1 and periodic boundary conditions over the compact dimension. The effective gauge-field action is calculated for Abelian U(1 gauge fields Aμ(x which depend on all four spacetime coordinates (including the coordinate x4∈S1 of the compact dimension and have vanishing components A4(x (implying trivial holonomies in the 4-direction. Our calculation shows that the effective gauge-field action contains a local Chern–Simons-like term which violates Lorentz and CPT invariance. This result is established perturbatively with a generalized Pauli–Villars regularization and nonperturbatively with a lattice regularization based on Ginsparg–Wilson fermions.
Ghosh, K. J. B.; Klinkhamer, F. R.
2018-01-01
We consider four-dimensional chiral gauge theories defined over a spacetime manifold with topology R3 ×S1 and periodic boundary conditions over the compact dimension. The effective gauge-field action is calculated for Abelian U (1) gauge fields Aμ (x) which depend on all four spacetime coordinates (including the coordinate x4 ∈S1 of the compact dimension) and have vanishing components A4 (x) (implying trivial holonomies in the 4-direction). Our calculation shows that the effective gauge-field action contains a local Chern-Simons-like term which violates Lorentz and CPT invariance. This result is established perturbatively with a generalized Pauli-Villars regularization and nonperturbatively with a lattice regularization based on Ginsparg-Wilson fermions.
Localization in presence of magnetic field in 2-D disordered binary alloys
International Nuclear Information System (INIS)
Brezini, A.; Zekri, N.
1993-08-01
The conductance fluctuations in the presence of a magnetic field B for a disordered binary alloy are numerically examined. The Hamiltonian is quite different from the Anderson model. We calculate the participation ration for finite systems in the whole range spectrum to discriminate the nature of eigenstates. We then evaluate the conductivity from the usual Kubo Greenwood formula. The fluctuations are therefore extracted as a function of energy for a given value of B and system size L. The data predict a delocalization of the eigenstates due to the magnetic field and a factor of 2 reduction of the universal conductance fluctuations in agreement with the theory. (author). 28 refs, 3 figs
Estimation of local and regional components of drain - flow from an irrigated field
International Nuclear Information System (INIS)
Eching, S.O.; Hopmans, J.W.; Wallender, W.W.; Macyntyre, J.L.; Peters, D.
1995-01-01
The contribution of regional ground water and deep percolation from a furrow irrigated field to total drain flow was estimated using salt load analysis. It was found that 64% of the drain flow comes from regional ground water flow. The electrical conductivity of the drain water was highly correlated with the drain flow rate. From the field water balance with deep percolation as estimated from the salt load analysis, using yield function derived evapotranspiration, and measured changes in root zone water storage, it was shown that 14% of the crop evapotranspiration comes from ground water during the study period. 8 figs; 5 tabs; 15 refs ( Author )
Computing the Local Field Potential (LFP) from Integrate-and-Fire Network Models
DEFF Research Database (Denmark)
Mazzoni, Alberto; Linden, Henrik; Cuntz, Hermann
2015-01-01
Leaky integrate-and-fire (LIF) network models are commonly used to study how the spiking dynamics of neural networks changes with stimuli, tasks or dynamic network states. However, neurophysiological studies in vivo often rather measure the mass activity of neuronal microcircuits with the local f...... in cases where a single pyramidal population dominates the LFP generation, and thereby facilitate quantitative comparison between computational models and experimental LFP recordings in vivo....
Path integral for spinning particle in the plane wave field: Global and local projections
International Nuclear Information System (INIS)
Boudiaf, N.; Boudjedaa, T.; Chetouani, L.
2001-01-01
The Green function related to the problem of a Dirac particle interacting with a plane wave is calculated via the path integral formalism proposed recently by Alexandrou et al. according to the two so-called global and local projections. With the help of the incorporation of two simple identities, it is shown that the contribution to the calculation of the integrals comes essentially from classical solutions projected along the direction of wave propagation. (orig.)
The Gravity of Dark Vortices: Effective Field Theory for Branes and Strings Carrying Localized Flux
Burgess, C P; Williams, M
2015-01-01
A Nielsen-Olesen vortex usually sits in an environment that expels the flux that is confined to the vortex, so flux is not present both inside and outside. We construct vortices for which this is not true, where the flux carried by the vortex also permeates the `bulk' far from the vortex. The idea is to mix the vortex's internal gauge flux with an external flux using off-diagonal kinetic mixing. Such `dark' vortices could play a phenomenological role in models with both cosmic strings and a dark gauge sector. When coupled to gravity they also provide explicit ultra-violet completions for codimension-two brane-localized flux, which arises in extra-dimensional models when the same flux that stabilizes extra-dimensional size is also localized on space-filling branes situated around the extra dimensions. We derive simple formulae for observables such as defect angle, tension, localized flux and on-vortex curvature when coupled to gravity, and show how all of these are insensitive to much of the microscopic detail...
Energy Technology Data Exchange (ETDEWEB)
Stafford, Jason, E-mail: jason.stafford@ul.ie [Stokes Institute, Mechanical, Aeronautical and Biomedical Engineering Department, University of Limerick, Limerick (Ireland); Walsh, Ed; Egan, Vanessa [Stokes Institute, Mechanical, Aeronautical and Biomedical Engineering Department, University of Limerick, Limerick (Ireland)
2011-12-15
Highlights: Black-Right-Pointing-Pointer Velocity field and local heat transfer trends of centrifugal fans. Black-Right-Pointing-Pointer Time-averaged vortices are generated by flow separation. Black-Right-Pointing-Pointer Local vortex and impingement regions are evident on surface heat transfer maps. Black-Right-Pointing-Pointer Miniature centrifugal fans should be designed with an aspect ratio below 0.3. Black-Right-Pointing-Pointer Theory under predicts heat transfer due to complex, unsteady outlet flow. - Abstract: Scaled versions of fan designs are often chosen to address thermal management issues in space constrained applications. Using velocity field and local heat transfer measurement techniques, the thermal performance characteristics of a range of geometrically scaled centrifugal fan designs have been investigated. Complex fluid flow structures and surface heat transfer trends due to centrifugal fans were found to be common over a wide range of fan aspect ratios (blade height to fan diameter). The limiting aspect ratio for heat transfer enhancement was 0.3, as larger aspect ratios were shown to result in a reduction in overall thermal performance. Over the range of fans examined, the low profile centrifugal designs produced significant enhancement in thermal performance when compared to that predicted using classical laminar flow theory. The limiting non-dimensional distance from the fan, where this enhancement is no longer apparent, has also been determined. Using the fundamental information inferred from local velocity field and heat transfer measurements, selection criteria can be determined for both low and high power practical applications where space restrictions exist.
X-RAY CIRCULAR-DICHROISM AND LOCAL MAGNETIC-FIELDS
CARRA, P; THOLE, BT; ALTARELLI, M; WANG, XD
1993-01-01
Sum rules are derived for the circular dichroic response of a core line (CMXD). They relate the intensity of the CMXD signal to the ground-state expectation value of the magnetic field operators (orbital, spin, and magnetic dipole) of the valence electrons. The results obtained are discussed and
Nonlinear microscopy of localized field enhancements in fractal shaped periodic metal nanostructures
DEFF Research Database (Denmark)
Beermann, I.; Evlyukhin, A.; Boltasseva, Alexandra
2008-01-01
Fractal shaped periodic nanostructures formed with a 100 nm period square lattice of gold nanoparticles placed on a gold film are characterized using far-field nonlinear scanning optical microscopy, in which two-photon photoluminescence (TPL) excited with a strongly focused femtosecond laser beam...
Moisture convergence using satellite-derived wind fields - A severe local storm case study
Negri, A. J.; Vonder Haar, T. H.
1980-01-01
Five-minute interval 1-km resolution SMS visible channel data were used to derive low-level wind fields by tracking small cumulus clouds on NASA's Atmospheric and Oceanographic Information Processing System. The satellite-derived wind fields were combined with surface mixing ratios to derive horizontal moisture convergence in the prestorm environment of April 24, 1975. Storms began developing in an area extending from southwest Oklahoma to eastern Tennessee 2 h subsequent to the time of the derived fields. The maximum moisture convergence was computed to be 0.0022 g/kg per sec and areas of low-level convergence of moisture were in general indicative of regions of severe storm genesis. The resultant moisture convergence fields derived from two wind sets 20 min apart were spatially consistent and reflected the mesoscale forcing of ensuing storm development. Results are discussed with regard to possible limitations in quantifying the relationship between low-level flow and between low-level flow and satellite-derived cumulus motion in an antecedent storm environment.
Localization of supersymmetric field theories on non-compact hyperbolic three-manifolds
Energy Technology Data Exchange (ETDEWEB)
Assel, Benjamin; Martelli, Dario; Murthy, Sameer; Yokoyama, Daisuke [Department of Mathematics, King’s College London,The Strand, London WC2R 2LS (United Kingdom)
2017-03-17
We study supersymmetric gauge theories with an R-symmetry, defined on non-compact, hyperbolic, Riemannian three-manifolds, focusing on the case of a supersymmetry-preserving quotient of Euclidean AdS{sub 3}. We compute the exact partition function in these theories, using the method of localization, thus reducing the problem to the computation of one-loop determinants around a supersymmetric locus. We evaluate the one-loop determinants employing three different techniques: an index theorem, the method of pairing of eigenvalues, and the heat kernel method. Along the way, we discuss aspects of supersymmetry in manifolds with a conformal boundary, including supersymmetric actions and boundary conditions.
A Genealogy of Convex Solids Via Local and Global Bifurcations of Gradient Vector Fields
Domokos, Gábor; Holmes, Philip; Lángi, Zsolt
2016-12-01
Three-dimensional convex bodies can be classified in terms of the number and stability types of critical points on which they can balance at rest on a horizontal plane. For typical bodies, these are non-degenerate maxima, minima, and saddle points, the numbers of which provide a primary classification. Secondary and tertiary classifications use graphs to describe orbits connecting these critical points in the gradient vector field associated with each body. In previous work, it was shown that these classifications are complete in that no class is empty. Here, we construct 1- and 2-parameter families of convex bodies connecting members of adjacent primary and secondary classes and show that transitions between them can be realized by codimension 1 saddle-node and saddle-saddle (heteroclinic) bifurcations in the gradient vector fields. Our results indicate that all combinatorially possible transitions can be realized in physical shape evolution processes, e.g., by abrasion of sedimentary particles.
Some consequences of the law of local energy conservation in electromagnetic field
International Nuclear Information System (INIS)
Beshtoev, Kh.M.
2001-01-01
At electromagnetic interactions of particles there arise defects of masses, i.e. the energy is liberated since the particles of the different charges are attracted. It is shown that this change of the effective mass of a particle in the external electric field (of a nucleus) results in displacement of atomic levels of electrons. The expressions describing these velocity changes and displacement of energy levels of electrons in the atom are obtained
Exact expectation values of local fields in the quantum sine-Gordon model
International Nuclear Information System (INIS)
Lukyanov, S.; Rossijskaya Akademiya Nauk, Chernogolovka; Zamolodchikov, A.; Rossijskaya Akademiya Nauk, Chernogolovka
1997-01-01
We propose an explicit expression for vacuum expectation values left angle e iaφ right angle of the exponential fields in the sine-Gordon model. Our expression agrees both with semi-classical results in the sine-Gordon theory and with perturbative calculations in the massive Thirring model. We use this expression to make new predictions about the large-distance asymptotic form of the two-point correlation function in the XXZ spin chain. (orig.)
Near-Field Cosmology with Resolved Stellar Populations Around Local Volume LMC Stellar-Mass Galaxies
Carlin, Jeffrey L.; Sand, David J.; Willman, Beth; Brodie, Jean P.; Crnojevic, Denija; Forbes, Duncan; Hargis, Jonathan R.; Peter, Annika; Pucha, Ragadeepika; Romanowsky, Aaron J.; Spekkens, Kristine; Strader, Jay
2018-06-01
We discuss our ongoing observational program to comprehensively map the entire virial volumes of roughly LMC stellar mass galaxies at distances of ~2-4 Mpc. The MADCASH (Magellanic Analog Dwarf Companions And Stellar Halos) survey will deliver the first census of the dwarf satellite populations and stellar halo properties within LMC-like environments in the Local Volume. Our results will inform our understanding of the recent DES discoveries of dwarf satellites tentatively affiliated with the LMC/SMC system. This program has already yielded the discovery of the faintest known dwarf galaxy satellite of an LMC stellar-mass host beyond the Local Group, based on deep Subaru+HyperSuprimeCam imaging reaching ~2 magnitudes below its TRGB, and at least two additional candidate satellites. We will summarize the survey results and status to date, highlighting some challenges encountered and lessons learned as we process the data for this program through a prototype LSST pipeline. Our program will examine whether LMC stellar mass dwarfs have extended stellar halos, allowing us to assess the relative contributions of in-situ stars vs. merger debris to their stellar populations and halo density profiles. We outline the constraints on galaxy formation models that will be provided by our observations of low-mass galaxy halos and their satellites.
International Nuclear Information System (INIS)
Lopes, F; Barbosa, S M; Silva, H G; Bárias, S
2015-01-01
The atmospheric electric field near the Earth's surface is dominated by atmospheric pollutants and natural radioactivity, with the latter directly linked to radon ( 222 Rn) gas. For a better comprehension on the temporal variability of both the atmospheric electric field and the radon concentration and its relation with local atmospheric variables, simultaneous measurements of soil-emitted gamma radiation and potential gradient (defined from the vertical component of the atmospheric electric field) were taken every minute, along with local meteorological parameters (e.g., temperature, atmospheric pressure, relative humidity and daily solar radiation). The study region is Amieira, part of the Alqueva lake in Alentejo Portugal, where an interdisciplinary meteorological campaign, ALEX2014, took place from June to August 2014. Soil gamma radiation is more sensitive to small concentrations of radon as compared with alpha particles measurements, for that reason it is more suited for sites with low radon levels, as expected in this case. Preliminary results are presented here: statistical and spectral analysis show that i) the potential gradient has a stronger daily cycle as compared with the gamma radiation, ii) most of the energy of the gamma signal is concentrated in the low frequencies (close to 0), contrary to the potential gradient that has most of the energy in frequency 1 (daily cycle) and iii) a short-term relation between gamma radiation and the potential gradient has not been found. Future work and plans are also discussed. (paper)
Tenke, Craig E.; Kayser, Jürgen
2012-01-01
The topographic ambiguity and reference-dependency that has plagued EEG/ERP research throughout its history are largely attributable to volume conduction, which may be concisely described by a vector form of Ohm’s Law. This biophysical relationship is common to popular algorithms that infer neuronal generators via inverse solutions. It may be further simplified as Poisson’s source equation, which identifies underlying current generators from estimates of the second spatial derivative of the field potential (Laplacian transformation). Intracranial current source density (CSD) studies have dissected the “cortical dipole” into intracortical sources and sinks, corresponding to physiologically-meaningful patterns of neuronal activity at a sublaminar resolution, much of which is locally cancelled (i.e., closed field). By virtue of the macroscopic scale of the scalp-recorded EEG, a surface Laplacian reflects the radial projections of these underlying currents, representing a unique, unambiguous measure of neuronal activity at scalp. Although the surface Laplacian requires minimal assumptions compared to complex, model-sensitive inverses, the resulting waveform topographies faithfully summarize and simplify essential constraints that must be placed on putative generators of a scalp potential topography, even if they arise from deep or partially-closed fields. CSD methods thereby provide a global empirical and biophysical context for generator localization, spanning scales from intracortical to scalp recordings. PMID:22796039
Directory of Open Access Journals (Sweden)
B. Aouizerats
2011-08-01
Full Text Available High resolution simulation of complex aerosol particle evolution and gaseous chemistry over an atmospheric urban area is of great interest for understanding air quality and processes. In this context, the CAPITOUL (Canopy and Aerosol Particle Interactions in the Toulouse Urban Layer field experiment aims at a better understanding of the interactions between the urban dynamics and the aerosol plumes. During a two-day Intensive Observational Period, a numerical model experiment was set up to reproduce the spatial distribution of specific particle pollutants, from the regional scales and the interactions between different cities, to the local scales with specific turbulent structures. Observations show that local dynamics depends on the day-regime, and may lead to different mesoscale dynamical structures. This study focuses on reproducing these fine scale dynamical structures, and investigate the impact on the aerosol plume dispersion. The 500-m resolution simulation manages to reproduce convective rolls at local scale, which concentrate most of the aerosol particles and can locally affect the pollutant dispersion and air quality.
Shi, Zhaoyue; Wu, Ruiqi; Yang, Pai-Feng; Wang, Feng; Wu, Tung-Lin; Mishra, Arabinda; Chen, Li Min; Gore, John C
2017-05-16
Although blood oxygenation level-dependent (BOLD) fMRI has been widely used to map brain responses to external stimuli and to delineate functional circuits at rest, the extent to which BOLD signals correlate spatially with underlying neuronal activity, the spatial relationships between stimulus-evoked BOLD activations and local correlations of BOLD signals in a resting state, and whether these spatial relationships vary across functionally distinct cortical areas are not known. To address these critical questions, we directly compared the spatial extents of stimulated activations and the local profiles of intervoxel resting state correlations for both high-resolution BOLD at 9.4 T and local field potentials (LFPs), using 98-channel microelectrode arrays, in functionally distinct primary somatosensory areas 3b and 1 in nonhuman primates. Anatomic images of LFP and BOLD were coregistered within 0.10 mm accuracy. We found that the point spread functions (PSFs) of BOLD and LFP responses were comparable in the stimulus condition, and both estimates of activations were slightly more spatially constrained than local correlations at rest. The magnitudes of stimulus responses in area 3b were stronger than those in area 1 and extended in a medial to lateral direction. In addition, the reproducibility and stability of stimulus-evoked activation locations within and across both modalities were robust. Our work suggests that the intrinsic resolution of BOLD is not a limiting feature in practice and approaches the intrinsic precision achievable by multielectrode electrophysiology.
International Nuclear Information System (INIS)
Moeller, R.; Tschoeke, H.
1980-01-01
The operating reliability of nuclear reactors calls for a reliable strength analysis of the highly loaded core elements, one of its prerequisites being the reliable determination of the three-dimensional velocity and temperature fields. To verify thermohydraulics computer programs, extensive local temperature measurements in the rod claddings of the critical bundle zone were performed on a heated 19-rod bundle model with sodium flow and provided with spacer grids (P/D = 1.30; W/D = 1.19). The essential results are: - Outside the spacer grids, the azimuthal temperature variations of the side and corner rods are approximately 10-fold those of rods in the central bundle zone. - The spacer grids investigated give rise to great local temperature peaks and correspondingly great temperature gradients in the axial and azimuthal directions immediately around the support points. - Continuous reduction of a subchannel by rod bowing results in substantial rises of temperature which, however, are limited to adjacent cladding tubes. (orig.)
Local fields in Co and Mn Co-doped ZnO
Energy Technology Data Exchange (ETDEWEB)
Sato, W., E-mail: wsato@se.kanazawa-u.ac.jp [Kanazawa University, Institute of Science and Engineering (Japan); Kano, Y.; Suzuki, T.; Nakagawa, M. [Kanazawa University, Graduate School of Natural Science and Technology (Japan); Kobayashi, Y. [The University of Electro-Communications, Department of Engineering Science (Japan)
2016-12-15
The magnetic properties of ZnO co-doped with 5 at. % Co and 5 at. % Mn(Zn{sub 0.90}Co{sub 0.05}Mn{sub 0.05}O) synthesized by a solid-state reaction were investigated by means of {sup 57}Co emission Mössbauer spectroscopy. The majority of the probe ions (80 %) residing in defect-free substitutional Zn sites take the oxidation state of {sup 57}Fe {sup 2+}, and the others presumably form local defects taking the state of {sup 57}Fe {sup 3+} at room temperature. Both components show doublets, and RT ferromagnetism was thus absent in the sample. For the measurement at 10 K, spectral broadening was observed, implying a possible presence of a weak magnetic component.
One-Dimensional Stationary Mean-Field Games with Local Coupling
Gomes, Diogo A.; Nurbekyan, Levon; Prazeres, Mariana
2017-01-01
A standard assumption in mean-field game (MFG) theory is that the coupling between the Hamilton–Jacobi equation and the transport equation is monotonically non-decreasing in the density of the population. In many cases, this assumption implies the existence and uniqueness of solutions. Here, we drop that assumption and construct explicit solutions for one-dimensional MFGs. These solutions exhibit phenomena not present in monotonically increasing MFGs: low-regularity, non-uniqueness, and the formation of regions with no agents.
One-Dimensional Stationary Mean-Field Games with Local Coupling
Gomes, Diogo A.
2017-05-25
A standard assumption in mean-field game (MFG) theory is that the coupling between the Hamilton–Jacobi equation and the transport equation is monotonically non-decreasing in the density of the population. In many cases, this assumption implies the existence and uniqueness of solutions. Here, we drop that assumption and construct explicit solutions for one-dimensional MFGs. These solutions exhibit phenomena not present in monotonically increasing MFGs: low-regularity, non-uniqueness, and the formation of regions with no agents.
Some consequences of the law of local energy conservation in the gravitational field
International Nuclear Information System (INIS)
Beshtoev, Kh.M.
2001-01-01
At gravitational interactions of bodies and particles there appears the defect of masses, i.e. the energy yields since the bodies (or particles) are attracted. It is shown that this changing of the effective mass of the body (or the particle) in the external gravitational field leads to changes of the measurement units: velocity and length (relative to the standard measurement units). The expression describing the advance of the perihelion of the planet (the Mercury) has been obtained. This expression is mathematically identical to Einstein's equation for the advance of the perihelion of the Mercury
Global and Local Gravity Field Models of the Moon Using GRAIL Primary and Extended Mission Data
Goossens, Sander; Lemoine, Frank G.; Sabaka, Terence J.; Nicholas, Joseph B.; Mazarico, Erwan; Rowlands, David D.; Loomis, Bryant D.; Chinn, Douglas S.; Neumann, Gregory A.; Smith, David E.;
2015-01-01
The Gravity Recovery and Interior Laboratory (GRAIL) mission was designed to map the structure of the lunar interior from crust to core and to advance the understanding of the Moon's thermal evolution by producing a high-quality, high-resolution map of the gravitational field of the Moon. The mission consisted of two spacecraft, which were launched in September 2011 on a Discovery-class NASA mission. Ka-band tracking between the two satellites was the single science instrument, augmented by tracking from Earth using the Deep Space Network (DSN).
Local measurement of error field using naturally rotating tearing mode dynamics in EXTRAP T2R
Sweeney, R. M.; Frassinetti, L.; Brunsell, P.; Fridström, R.; Volpe, F. A.
2016-12-01
An error field (EF) detection technique using the amplitude modulation of a naturally rotating tearing mode (TM) is developed and validated in the EXTRAP T2R reversed field pinch. The technique was used to identify intrinsic EFs of m/n = 1/-12, where m and n are the poloidal and toroidal mode numbers. The effect of the EF and of a resonant magnetic perturbation (RMP) on the TM, in particular on amplitude modulation, is modeled with a first-order solution of the modified Rutherford equation. In the experiment, the TM amplitude is measured as a function of the toroidal angle as the TM rotates rapidly in the presence of an unknown EF and a known, deliberately applied RMP. The RMP amplitude is fixed while the toroidal phase is varied from one discharge to the other, completing a full toroidal scan. Using three such scans with different RMP amplitudes, the EF amplitude and phase are inferred from the phases at which the TM amplitude maximizes. The estimated EF amplitude is consistent with other estimates (e.g. based on the best EF-cancelling RMP, resulting in the fastest TM rotation). A passive variant of this technique is also presented, where no RMPs are applied, and the EF phase is deduced.
Suran, Swathi; Bharadwaj, Krishna; Raghavan, Srinivasan; Varma, Manoj M
2016-04-26
Most methods for optical visualization beyond the diffraction limit rely on fluorescence emission by molecular tags. Here, we report a method for visualization of nanostructures down to a few nanometers using a conventional bright-field microscope without requiring additional molecular tags such as fluorophores. The technique, Bright-field Nanoscopy, is based on the strong thickness dependent color of ultra-thin germanium on an optically thick gold film. We demonstrate the visualization of grain boundaries in chemical vapour deposited single layer graphene and the detection of single 40 nm Ag nanoparticles. We estimate a size detection limit of about 2 nm using this technique. In addition to visualizing nano-structures, this technique can be used to probe fluid phenomena at the nanoscale, such as transport through 2D membranes. We estimated the water transport rate through a 1 nm thick polymer film using this technique, as an illustration. Further, the technique can also be extended to study the transport of specific ions in the solution. It is anticipated that this technique will find use in applications ranging from single-nanoparticles resolved sensing to studying nanoscale fluid-solid interface phenomena.
Kushch, Volodymyr I.; Sevostianov, Igor; Giraud, Albert
2017-11-01
An accurate semi-analytical solution of the conductivity problem for a composite with anisotropic matrix and arbitrarily oriented anisotropic ellipsoidal inhomogeneities has been obtained. The developed approach combines the superposition principle with the multipole expansion of perturbation fields of inhomogeneities in terms of ellipsoidal harmonics and reduces the boundary value problem to an infinite system of linear algebraic equations for the induced multipole moments of inhomogeneities. A complete full-field solution is obtained for the multi-particle models comprising inhomogeneities of diverse shape, size, orientation and properties which enables an adequate account for the microstructure parameters. The solution is valid for the general-type anisotropy of constituents and arbitrary orientation of the orthotropy axes. The effective conductivity tensor of the particulate composite with anisotropic constituents is evaluated in the framework of the generalized Maxwell homogenization scheme. Application of the developed method to composites with imperfect ellipsoidal interfaces is straightforward. Their incorporation yields probably the most general model of a composite that may be considered in the framework of analytical approach.
DEFF Research Database (Denmark)
Wangel, Arne
2003-01-01
While the epistemological aspects of cross-cultural research are extensively discussed in general terms by ethnographers and other social scientists, little attention is paid to the specific patterns of interests and expectations involved. Drawing upon previous field work in Malaysia and also upo...... universally applicable. Their purpose is to inspire a discussion on how to develop new approaches in relating to respondents and local colleagues, by which the negotiation of co-operation based on mutual interest and shared benefits is given priority....
NMR investigation of the effect of hydrostate pressure on the local magnetic fields in Y6Fe23
International Nuclear Information System (INIS)
Vasil'kovskij, V.A.; Bartashevich, M.I.; Gorlenko, A.A.; Kovtun, N.M.; Kupriyanov, A.K.
1990-01-01
The local magnetic fields at the Y 89 and Fe 57 nuclei in the intermetallic compound Y 6 Fe 23 and their shift induced by pressure are investigated by the NMR technique. The results are discussed on the basis of a model in which the atomic magnetic moment for iron includes the moment of polarized collectivized electrons responsible for the chemical bond between yttrium and iron. It is shown that with decreasing concentration of yttrium in the Y x Fe y compounds delocalization of the iron magnetic electrons occurs
International Nuclear Information System (INIS)
Souza, P E N de; Oliveira, L M de; Ortiz, W A; Camargo, P C de; Oliveira, A J A de
2005-01-01
In this work we present magnetic susceptibility results for Cr-x at.% Nb alloys (x = 0.2, 0.6, 0.7, 1.4, and 2.0), showing that a local short-range order spin-density wave (L-SDW) appears at a characteristic temperature (T loc ) above the Neel temperature. The evidence for L-SDW is based on a Curie-Weiss-like behaviour, which is suppressed when large magnetic fields are applied or for alloys with Nb concentration above x = 2.0 at.%
International Nuclear Information System (INIS)
Nalesso, G.; Jacobson, A.R.
1984-01-01
Using a ten-chord interferometer, we have measured a field-aligned (k/sub parallel/roughly-equal2 m -1 ; k/sub perpendicular/> or approx. =25 m -1 ) plasma-density disturbance propagating along B with a speed in the ion acoustic range. The propagation is purely in the electron drift direction and is observed only when the drift parameter (electron drift speed/electron thermal speed)> or approx. =0.1. A novel spatial-filter technique resolves this localized mode, which otherwise would be hidden by more robust global disturbances present along the lines of sight
Particle-like representation for the field of a moving point charge in nonlinear electrodynamics
International Nuclear Information System (INIS)
Gitman, D M; Shabad, A E; Shishmarev, A A
2017-01-01
In a simple nonlinear model stemming from quantum electrodynamics wherein the pointlike charge has finite field-self-energy, we demonstrate that the latter can be presented as a soliton with its energy–momentum vector satisfying the standard mechanical relation characteristic of a free moving massive relativistic particle. (paper)
International Nuclear Information System (INIS)
Lyuboshits, V.L.
1991-01-01
Interference correlations introduced between identical particles with close momenta by the effect of Bose or Fermi statistics are discussed. Relations describing two- and three-particle correlations of identical bosons and fermions with arbitrary spin and arbitrary spin polarization are obtained on the basis of the model of independent single-particle point-like sources. The general structure of the dependence of narrow two- and three-particle correlations on the difference of the four-momenta in the presence of several groups of single-particle sources with different space-time distributions is analyzed. The idea of many-particle point sources of identical bosons is introduced. The suppression of two- and three-particle interference correlations between identical π mesons under conditions when one or several many-particle sources are added to a system of randomly distributed independent single-particle sources is studied. It is shown that if the multiplicities of the particles emitted by the sources are distributed according to the Poisson law, the present results agree with the relations obtained by means of the formalism of coherent states. This agreement also holds in the limit of very large multiplicities with any distribution laws
DEFF Research Database (Denmark)
Sun, Baozhou; Yang, Deshan; Esthappan, Jackie
2015-01-01
-field intensity-modulated radiation therapy (IMRT) and image-guided BT in locally advanced cervical cancer. METHODS AND MATERIALS: Thirty-three patients treated with split-field-IMRT to 45.0-51.2 Gy in 1.6-1.8 Gy per fraction to the elective pelvic lymph nodes and to 20 Gy to the central pelvis region were...... included in this study. Patients received six weekly fractions of high-dose rate BT to 6.5-7.3 Gy per fraction. A dose tracker software was developed to compute the equivalent dose in 2-Gy fractions (EQD2) to gross tumor volume (GTV), organs-at-risk and point A. Total dose-volume histogram parameters were...
International Nuclear Information System (INIS)
Blau, M.; Thompson, G.
1995-01-01
We review localization techniques for functional integrals which have recently been used to perform calculations in and gain insight into the structure of certain topological field theories and low-dimensional gauge theories. These are the functional integral counterparts of the Mathai-Quillen formalism, the Duistermaat-Heckman theorem, and the Weyl integral formula respectively. In each case, we first introduce the necessary mathematical background (Euler classes of vector bundles, equivariant cohomology, topology of Lie groups), and describe the finite dimensional integration formulae. We then discuss some applications to path integrals and give an overview of the relevant literature. The applications we deal with include supersymmetric quantum mechanics, cohomological field theories, phase space path integrals, and two-dimensional Yang-Mills theory. (author). 83 refs
International Nuclear Information System (INIS)
Eberhard, Jens
2004-01-01
We focus on transport parameters in heterogeneous media with a flow modelled by an ensemble of periodic and Gaussian random fields. The parameters are determined by ensemble averages. We study to what extent these averages represent the behaviour in a single realization. We calculate the centre-of-mass velocity and the dispersion coefficient using approximations based on a perturbative expansion for the transport equation, and on the iterative solution of the Langevin equation. Compared with simulations, the perturbation theory reproduces the numerical results only poorly, whereas the iterative solution yields good results. Using these approximations, we investigate the self-averaging properties. The ensemble average of the velocity characterizes the behaviour of a realization for large times in both ensembles. The dispersion coefficient is not self-averaging in the ensemble of periodic fields. For the Gaussian ensemble the asymptotic dispersion coefficient is self-averaging. For finite times, however, the fluctuations are so large that the average does not represent the behaviour in a single realization
Roman, D. C.
2003-12-01
A complete understanding of the initiation, evolution, and termination of volcanic eruptions requires reliable monitoring techniques to detect changes in the conduit system during periods of activity, as well as corresponding knowledge of conduit structure and of magma physical properties. Case studies of stress field orientation prior to, during, and after magmatic activity can be used to relate changes in stress field orientation to the state of the magmatic conduit system. These relationships may be tested through modeling of induced stresses. Here I present evidence from case studies and modeling that horizontal rotation of the axis of maximum compressive stress at an active volcano indicates pressurization of a magmatic conduit, and that this rotation, when observed, may also be indicative of the physical properties of the ascending magma. Changes in the local stress field orientation during the 1992 eruption sequence at Crater Peak (Mt. Spurr), Alaska were analyzed by calculating and inverting subsets of over 150 fault-plane solutions. Local stress tensors for four time periods, corresponding approximately to changes in activity at the volcano, were calculated based on the misfit of individual fault-plane solutions to a regional stress tensor. Results indicate that for nine months prior to the eruption, local maximum compressive stress was oriented perpendicular to regional maximum compressive stress. A similar horizontal rotation was observed beginning in November of 1992, coincident with an episode of elevated earthquake and tremor activity indicating intrusion of magma into the conduit. During periods of quiescence the local stress field was similar to the regional stress field. Similar horizontal rotations have been observed at Mt. Ruapehu, New Zealand (Miller and Savage 2001, Gerst 2003), Usu Volcano, Japan (Fukuyama et al. 2001), Unzen Volcano, Japan (Umakoshi et al. 2001), and Mt. St. Helens Volcano, USA (Moran 1994) in conjunction with eruptive
Hackstein, S.; Vazza, F.; Brüggen, M.; Sorce, J. G.; Gottlöber, S.
2018-04-01
We simulate the propagation of cosmic rays at ultra-high energies, ≳1018 eV, in models of extragalactic magnetic fields in constrained simulations of the local Universe. We use constrained initial conditions with the cosmological magnetohydrodynamics code ENZO. The resulting models of the distribution of magnetic fields in the local Universe are used in the CRPROPA code to simulate the propagation of ultra-high energy cosmic rays. We investigate the impact of six different magneto-genesis scenarios, both primordial and astrophysical, on the propagation of cosmic rays over cosmological distances. Moreover, we study the influence of different source distributions around the Milky Way. Our study shows that different scenarios of magneto-genesis do not have a large impact on the anisotropy measurements of ultra-high energy cosmic rays. However, at high energies above the Greisen-Zatsepin-Kuzmin (GZK)-limit, there is anisotropy caused by the distribution of nearby sources, independent of the magnetic field model. This provides a chance to identify cosmic ray sources with future full-sky measurements and high number statistics at the highest energies. Finally, we compare our results to the dipole signal measured by the Pierre Auger Observatory. All our source models and magnetic field models could reproduce the observed dipole amplitude with a pure iron injection composition. Our results indicate that the dipole is observed due to clustering of secondary nuclei in direction of nearby sources of heavy nuclei. A light injection composition is disfavoured, since the increase in dipole angular power from 4 to 8 EeV is too slow compared to observation by the Pierre Auger Observatory.
Bao, Zhihua; Okubo, Takashi; Kubota, Kengo; Kasahara, Yasuhiro; Tsurumaru, Hirohito; Anda, Mizue; Ikeda, Seishi; Minamisawa, Kiwamu
2014-08-01
In a previous study by our group, CH4 oxidation and N2 fixation were simultaneously activated in the roots of wild-type rice plants in a paddy field with no N input; both processes are likely controlled by a rice gene for microbial symbiosis. The present study examined which microorganisms in rice roots were responsible for CH4 oxidation and N2 fixation under the field conditions. Metaproteomic analysis of root-associated bacteria from field-grown rice (Oryza sativa Nipponbare) revealed that nitrogenase complex-containing nitrogenase reductase (NifH) and the alpha subunit (NifD) and beta subunit (NifK) of dinitrogenase were mainly derived from type II methanotrophic bacteria of the family Methylocystaceae, including Methylosinus spp. Minor nitrogenase proteins such as Methylocella, Bradyrhizobium, Rhodopseudomonas, and Anaeromyxobacter were also detected. Methane monooxygenase proteins (PmoCBA and MmoXYZCBG) were detected in the same bacterial group of the Methylocystaceae. Because these results indicated that Methylocystaceae members mediate both CH4 oxidation and N2 fixation, we examined their localization in rice tissues by using catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). The methanotrophs were localized around the epidermal cells and vascular cylinder in the root tissues of the field-grown rice plants. Our metaproteomics and CARD-FISH results suggest that CH4 oxidation and N2 fixation are performed mainly by type II methanotrophs of the Methylocystaceae, including Methylosinus spp., inhabiting the vascular bundles and epidermal cells of rice roots. Copyright © 2014, American Society for Microbiology. All Rights Reserved.
Suspended and localized single nanostructure growth across a nanogap by an electric field
International Nuclear Information System (INIS)
Lee, Chung-Hoon; Schneider, Susan C; Josse, Fabien; Han, Jun Hyun
2011-01-01
Direct growth of a suspended single nanostructure (SSN) at a specific location is presented. The SSN is grown across a metallic nanoscale gap by migration in air at room temperature. The nanogap is fabricated by industrial standard optical lithography and anisotropic wet chemical silicon etching. A DC current bias, 1 nA, is applied across the metallic gap to induce nanoscale migration of Zn or ZnO. The history of the voltage drop across the gap as a function of time clearly indicates the moment when migration begins. The shape of SSNs grown across the nanogap by the migration is asymmetric at each electrode due to the asymmetric electric field distribution within the nanogap. An SSN can be used as the platform for two-terminal active or passive nanoscale electronics in optoelectronics, radio frequency (RF) resonators, and chemical/biological sensors.
Fortin, Guillaume; LeBlanc, Mélanie; Schiavone, Sophie; Chouinard, Omer; Utzschneider, Anouk
2015-01-01
Erosion and sedimentation in water courses represent a major and costly problem everywhere on the planet. Perception of local actors of the state of the river can be a useful source of information to document the river's changes. The main objective of this study consists of understanding how multiple data sources can be used for identifying the most sensitive areas subject to erosion and sedimentation in a watershed. To achieve our objective we combined three complementary methods: conducting interviews, estimating the most sensitive soil loss areas using the Revised Universal Soil Loss Equation for Application in Canada (RUSLEFAC) and taking measurements of environmental variables (turbidity, deposition rate, particle size, water quality, rainfall). The information gathered from the interviews allowed us to determine which areas were the most affected (e.g., either erosion or deposition). However, we observed that there were some differences between the areas identified by the participants and those obtained from the RUSLEFAC and in situ measurements. Among these differences, participants identified sites which were the results of misuse or bad practices (e.g., ATV). By contrast sensitive sites for erosion, as identified using RUSLEFAC, are instead areas of steep slopes, located near the river without forest cover. The in situ measurements were very helpful in establishing background values for turbidity but also for comparing quantitative information (e.g., particle size) with what was reported in the interviews.
Directory of Open Access Journals (Sweden)
Daniel C. Orey
2015-07-01
Full Text Available The acquisition of both emic (local and etic (global knowledge is an alternative goal for the implementation of ethnomodeling research. Emic knowledge is essential for an intuitive and empathic understanding of mathematical ideas, procedures, and practices developed by the members of distinct cultural groups. It is essential for conducting effective ethnographic fieldwork. Furthermore, emic knowledge is a valuable source of inspiration for etic hypotheses. Etic knowledge is essential for cross-cultural comparisons, which are based on the components of ethnology. In this regard, such comparisons demand standard units and categories to facilitate communication. Dialogical (glocal is a third approach for ethnomodeling research that makes use of both emic and etic knowledge traditions through processes of dialogue and interaction. Ethnomodeling is defined as the study of mathematical phenomena within a culture because it is a social construct and is culturally bound. Finally, the objective of this article is to show how we have come to use a combination of emic, etic and dialogical (glocal approaches in our work in the area of ethnomodeling, which contributes to the acquisition of a more complete understanding of mathematical practices developed by the members of distinct cultural groups.
International Nuclear Information System (INIS)
Flueckiger, E.O.; Smart, D.F.; Shea, M.A.
1983-01-01
We have investigated the effect of local perturbations of the geomagnetic field on the vertical cosmic ray cutoff rigidities at Jungfraujoch and Kiel as representative mid-latitude neutron monitor stations. The main, effective, and Stoermer vertical cutoff rigidities and their changes were determined by utilizing the trajectory-tracing technique in a magnetic field which is modeled as a simple dipole field to which the disturbance field is superposed. It was found that the cosmic ray cutoff rigidities are most sensitive to variations of the z component of the geomagnetic field at geomagnetic latitudes -20 0 0 and at longitudes within 90 0 to the east of these northern hemisphere stations. Furthermore, cutoff rigidity variations at Kiel are predominantly due to changes of the geomagnetic field within geocentric distances 2.5R/sub E/< r<6R/sub E/, whereas at Jungfraujoch changes in cutoff rigidities are caused almost exclusively by magnetic disturbances within 1R/sub E/< r<4.5R/sub E/. For both locations the dependence of the main, effective, and Stoermer vertical cutoff rigidities on the radial, latitudinal and longitudinal structure of the magnetic perturbations is given explicitly. The results are discussed with respect to the theory by Treiman (1953) describing the effect of a ring current on cosmic ray cutoff rigidities. It is also shown that for the analysis of the characteristic properties of the correlation between cutoff rigidity variations and specific geomagnetic perturbations the rigidity corresponding to the first ''discontinuity band'' of the rigidity spectrum is an extremely useful parameter
International Nuclear Information System (INIS)
Apsimon, R.J.; Flower, P.S.; Hallewell, G.; Morris, J.A.G.; Morris, J.V.; Paterson, C.N.; Sharp, P.H.; Atkinson, M.; Brook, N.; Coyle, P.; Dickinson, B.; Donnachie, A.; Doyle, A.T.; Ellison, R.J.; Foster, J.M.; Hughes-Jones, R.E.; Ibbotson, M.; Kolya, S.D.; Lafferty, G.D.; McCann, H.; McManus, C.; Mercer, D.; Ottewell, P.J.; Reid, D.; Thompson, R.J.; Waterhouse, J.; Baake, M.; Diekmann, B.; Gapp, C.; Gebert, F.; Heinloth, K.; Hoeger, C.; Holzkamp, A.; Holzkamp, S.; Jakob, H.P.; Joseph, D.; Kingler, J.; Koersgen, G.; Oedingen, R.; Paul, E.; Rotscheidt, H.; Soeldner-Rembold, S.; Weigend, A.S.; Bagdasarian, L.S.; Danagulian, S.; Galumian, P.I.; Oganesian, A.G.; Barberis, D.; Davenport, M.; Eades, J.; McClatchey, R.; Brodbeck, T.J.; Charity, T.; Clegg, A.B.; Henderson, R.C.W.; Hickman, M.T.; Keemer, N.R.; Newton, D.; O'Connor, A.; Wilson, G.W.; Danaher, S.; Galbraith, W.; Thacker, N.A.; Thompson, L.
1990-01-01
Energy-flow distributions for charged hadrons from interactions of photons, pions and kaons on hydrogen are presented as functions of Σp T 2 in the event plane. Data cover the range 0.0 T 2 in 2 and 0.0 F T 2 in for the photon-induced data. Using the hadron-induced data to parameterise the hadronic behaviour of the photon, the differences between cross sections are used to measure the contribution of the point-like photon interactions. Quantitative calculations of the point-like photon interactions using the Lund Monte-Carlo program LUCIFER, based on QCD, are in agreement with the data. (orig.)